Note: Descriptions are shown in the official language in which they were submitted.
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COIN DISCRIMINATION APPARATUS AND METHOD
The present invention relates to an apparatus and method for sensing coins and
other
small discrete objects, and in particular to an apparatus which may be used in
coin counting
or handling.
BACKGROUND INFORMATION
A number of devices are intended to identify and/or discriminate coins or
other small
discrete objects. One example is coin counting or handling devices, such as
those described
in U.S. Patent 5564546; U.S. Patent 7028827; U.S. Patent 5620079; U.S. Patent
5799767;
and U.S. Patent 5746299. Other examples include vending machines, gaming
devices such
as slot machines, bus or subway coin or token "fare boxes," and the like.
Preferably, for such
purposes, the sensors provide information which can be used to discriminate
coins from non-
coin objects and/or which can discriminate among different coin denominations
and/or
discriminate coins of one country from those of another.
Previous coin handling devices, and sensors therein, however, have suffered
from a
number of deficiencies. Many previous sensors have resulted in an undesirably
large
proportion of discrimination errors. At least in some cases this is believed
to arise from an
undesirably small signal to noise ratio in the sensor output. Accordingly, it
would be useful
to provide coin discrimination sensors having improved signal to noise ratio.
Many previous coin handling devices, and associated sensors, were configured
to
receive only one coin at a time, such as a typical vending machine which
receives a single
coin at a time through a coin slot. These devices typically present an easier
coin handling and
sensing environment because there is a lower expectation for coin throughput,
an avoidance
of the deposit of foreign material, an avoidance of small inter-coin spacing
(or coin overlap),
and because the slot naturally defines maximum coin diameter and thickness.
Coin handlers
and sensors that might be operable for a one-at-a-time coin environment may
not be
satisfactory for an environment in which a mass or plurality of coins can be
received in a
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single location, all at once (such as a tray for receiving a mass of coins,
poured into the tray
from, e.g., a coin jar). Accordingly it would be useful to provide a coin
handler and/or sensor
which, although it might be successfully employed in a one-coin-at-a-time
environment, can
also function satisfactorily in a device which receives a mass of coins.
Many previous sensors and associated circuitry used for coin discrimination
were
configured to sense characteristics or parameters of coins (or other objects)
so as to provide
data relating to an average value for a coin as a whole. Such sensors and
circuitry were not
able to provide information specific to certain regions or levels of the coin
(such as core
material vs. cladding material). In some currencies, two or more denominations
may have
average characteristics which are so similar that it is difficult to
distinguish the coins. For
example, it is difficult to distinguish U.S. dimes from pre-1982 U.S. pennies,
based only on
average differences, the main physical difference being the difference in
cladding (or absence
thereof). In some previous devices, inductive coin testing is used to detect
the effect of a coin
on an alternating electromagnetic field produced by a coil, and specifically
the coin's effect
upon the coil's impedance, e.g. related to one or more of the coin's diameter,
thickness,
conductivity and permeability. In general, when an alternating electromagnetic
field is
provided to such a coil, the field will penetrate a coin to an extent that
decreases with
increasing frequency. Properties near the surface of a coin have a greater
effect on a higher
frequency field, and interior material have a lesser effect. Because certain
coins, such as the
United States ten and twenty-five cent coins, are laminated, this frequency
dependency can
be of use in coin discrimination, but, it is believed, has not previously been
used in this
manner.. Accordingly, it would further be useful to provide a device which can
provide
information relating to different regions of coins or other objects.
Although there are a number of parameters which, at least theoretically, can
be useful
in discriminating coins and small objects (such as size, including diameter
and thickness),
mass, density, conductivity, magnetic permeability, homogeneity or lack
thereof (such as
cladded or plated coins), and the like, many previous sensors were configured
to detect only a
single one of such parameters. In embodiments in which only a single parameter
is used,
discrimination among coins and other small objects was often inaccurate,
yielding both
misidentification of a coin denomination (false positives), and failure to
recognize a coin
denomination (false negatives). In some cases, two coins which are different
may be
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identified as the same coin because a parameter which could serve to
discriminate between
the coins (such as presence or absence of plating, magnetic non-magnetic
character of the
coin, etc.) is not detected by the sensor. Thus, using such sensors, when it
is desired to use
several parameters to discriminate coins and other objects, it has been
necessary to provide a
plurality of sensors (if such sensors are available), typically one sensor for
each parameter to
be detected. Multiplying the number of sensors in a device increases the cost
of fabricating,
designing, maintaining and repairing such apparatus. Furthermore, previous
devices typically
required that multiple sensors be spaced apart, usually along a linear track
which the coins
follow, and often the spacing must be relatively far apart in order to
properly correlate
sequential data from two sensors with a particular coin (and avoid attributing
data from the
two sensors to a single coin when the data was related, in fact, to two
different coins). This
spacing increases the physical size requirements for such a device, and may
lead to an
apparatus which is relatively slow since the path which the coins are required
to traverse is
longer.
Furthermore, when two or more sensors each output a single parameter, it is
typically
difficult or impossible to base discrimination on the relationship or profile
of one parameter
to a second parameter for a given coin, because of the difficulty in knowing
which point in a
first parameter profile corresponds to which point in a second parameter
profile. If there are
multiple sensors spaced along the coin path, the software for coin
discrimination becomes
more complicated, since it is necessary to keep track of when a coin passes by
the various
sensors. Timing is affected, e.g., by speed variations in the coins as they
move along the coin
path, such as rolling down a rail.
Even in cases where a single core is used for two different frequencies or
parameters,
many previous devices take measurements at two different times, typically as
the coin moves
through different locations, in order to measure several different parameters.
For example, in
some devices, a core is arranged with two spaced-apart poles with a first
measurement taken
at a first time and location when a coin is adjacent a first pole, and a
second measurement
taken at a second, later time, when the coin has moved substantially toward
the second pole.
It is believed that, in general, providing two or more different measurement
locations or
times, in order to measure two or more parameters, or in order to use two or
more
frequencies, leads to undesirable loss of coin throughput, occupies
undesirably extended
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space and requires relatively complicated circuits and/or algorithms (e.g. to
match up sensor
outputs as a particular coin moves to different measurement locations).
Some sensors relate to the electrical or magnetic properties of the coin or
other object,
and may involve creation of an electromagnetic field for application to the
coin. With many
previous sensors, the interaction of generated magnetic flux with the coin was
too low to
permit the desired efficiency and accuracy of coin discrimination, and
resulted in an
insufficient signal-to-noise ratio.
Many previous coin handling devices and sensors had characteristics which were
undesirable, especially when the devices were for use by untrained users. Such
previous
devices had insufficient accuracy, short service life, had an undesirably high
potential for
causing user injuries, were difficult to use, requiring training or extensive
instruction, failed,
too often, to return unprocessed coins to the user, took toe long to process
coins, had an
undesirably low throughput, were susceptible to frequent jamming, which could
not be
cleared without human intervention, often requiring intervention by trained
personnel, could
handle only a narrow range of coin types, or denominations, were overly
sensitive to wet or
sticky coins or foreign or non-coin objects, either malfunctioning or placing
the foreign
objects in the coin bins, rejected an undesirably high portion of good coins,
required frequent
and/or complicated set-up, calibration or maintenance, required too large a
volume or
footprint, were overly-sensitive to temperature variations, were undesirably
loud, were hard
to upgrade or retrofit to benefit from new technologies or ideas, and/or were
difficult or
expensive to design and manufacture
Accordingly, it would be advantageous to provide a coin handler and/or sensor
device
having improved discrimination and accuracy, reduced costs or space
requirements, which is
faster than previous devices, easier or less expensive to design, construct,
use and maintain,
and/or results in improved signal-to-noise ratio.
SUMMARY OF THE INVENTION
The present invention provides a device for processing and/or discriminating
coins or
other objects, such as discriminating among a plurality of coins or other
objects received all
at once, in a mass or pile, from the user, with the coins or objects being of
many different
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sizes, types or denominations. The device has a high degree of automation and
high
tolerance for foreign objects and less-than-pristine objects (such as wet,
sticky, coated, bent
or misshapen coins), so that the device can be readily used by members of the
general public,
requiring little, if any, training or instruction and little or no human
manipulation or
intervention, other than inputting the mass of coins.
According to one embodiment of the invention, after input and, preferably,
cleaning,
coins are singulated and move past a sensor for discrimination, counting
and/or sorting. In
general, coin slowing or adhesion is reduced by avoiding avoiding extensive
flat regions in
surfaces which contact coins (such as making such surfaces curved, quilted or
dimpled).
Coin paths are configured to flare or widen in the direction of coin travel to
avoid jamming.
A singulating bin pickup assembly is preferably provided with two or more
concentrically-mounted disks, one of which includes an integrated exit ledge.
Movable
paddles flex to avoid creating or exacerbating jams and deflect over the coin
exit ledge.
Vertically stacked coins tip backwards into a recess and slide over supporting
coins to
facilitate singulation. At the end of a transaction, coins are forced along
the coin path by a
rake, and debris is removed through a trap door. Coins exiting the coin pickup
assembly are
tipped away from the face-support rail to minimize friction.
According to one embodiment of the present invention, a sensor is provided in
which
nearly all the magnetic field produced by the coil interacts with the coin
providing a
relatively intense electromagnetic field in the region traversed by a coin or
other object.
Preferably, the sensor can be used to obtain information on two different
parameters of a coin
or other object. In one embodiment, a single sensor provides information
indicative of both
size, (diameter) and conductivity. In one embodiment, the sensor includes a
core, such as a
ferrite or other magnetically permeable material, in a curved (e.g., torroid
or half-torroid)
shape which defines a gap. The coin being sensed moves through the vicinity of
the gap, in
one embodiment, through the gap. In one embodiment, the core is shaped to
reduce
sensitivity of the sensor to slight deviations in the location of the coin
within the gap (bounce
or wobble). As a coin or the object passes through the field in the vicinity
of the gap, data
relating to coin parameters are sensed, such as changes in inductance (from
which the
diameter of the object or coin, or portions thereof, can be derived), and the
quality factor (Q
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factor), related to the amount of energy dissipated (from which conductivity
of the object or
coin, or portions thereof, can be obtained).
In one embodiment, data relating to conductance of the coin (or portions
thereof) as a
function of diameter are analyzed (e.g. by comparing with conductance-diameter
data for
known coins) in order to discriminate the sensed coins. Preferably, the
detection procedure
uses several thresholds or window parameters to provide high recognition
accuracy.
According to one aspect of the invention, a coin discrimination apparatus and
method
is provided in which an oscillating electromagnetic field is generated on a
single sensing
core. The oscillating electromagnetic field is composed of one or more
frequency
components. The electromagnetic field interacts with a coin, and these
interactions are
monitored and used to classify the coin according to its physical properties.
All frequency
components of the magnetic field are phase-locked to a common reference
frequency. The
phase relationships between the various frequencies are locked in order to
avoid interference
between frequencies and with any neighboring cores or sensors and to
facilitate accurate
determination of the interaction of each frequency component with the coin.
In one embodiment, low and high frequency coils on the core form a part of
oscillator
circuits. The circuits are configured to maintain oscillation of the signal
through the coils at a
substantially constant frequency, even as the effective inductance of the coil
changes (e.g. in
response to passage of a coin). The amount of change in other components of
the circuit
needed to offset the change in inductance (and thus maintain the frequency at
a substantially
constant value) is a measure of the magnitude of the change in the inductance
caused by the
passage of the coin, and indicative of coin diameter.
In addition to providing information related to coin diameter, the sensor can
also be
used to provide information related to coin conductance, preferably
substantially
simultaneously with providing the diameter information. As a coin moves past
the coil, there
will be an amount of energy loss and the amplitude of the signal in the coil
will change in a
manner related to the conductance of the coin (or portions thereof). For a
given effective
diameter of the coin, the energy loss in the eddy currents will be inversely
related to the
conductivity of the coin material penetrated by the magnetic field.
Preferably, the coin pickup assembly and sensor regions are configured for
easy
access for cleaning and maintenance, such as by providing a sensor block which
slides away
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from the coin path and can be re-positioned without recalibration. In one
embodiment, the
diverter assembly is hinged to permit it to be tipped outward for access.
Preferably, coins
which stray from the coin path are deflected, e.g. via a ramped sensor housing
and/or bypass
chutes, to a customer return area.
Coins which are recognized and properly positioned or spaced are deflected out
of the
default (gravity-fed) coin path into an acceptance bin or trolley. Any coins
or other objects
which are not thus actively accepted travel along a default path to the
customer return area.
Preferably, information is sensed which permits an estimate of coin velocity
and/or
acceleration so that the deflector mechanism can be timed to deflect a coins
even though
1o different coins may be traveling at different velocities (e.g. owing to
stickiness or adhesion).
In one embodiment, each object is individually analyzed to determine if it is
a coin that
should be accepted (i.e. is recognized as an acceptable coin denomination),
and, if so, if it is
possible to properly deflect the coin (e.g. it is sufficiently spaced from
adjacent coins). By
requiring that active steps be taken to accept a coin (i.e. by making the
default path the
"reject" path, it is more likely that all accepted objects will in fact be
members of an
acceptable class, and will be accurately counted.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. IA depicts a coin handling apparatus that may he used in connection with
an
embodiment of the present invention;
Fig. lB depicts a coin handling apparatus according to an embodiment of the
present
invention;
Fig. 2A is a front elevational view of a sensor and adjacent coin, according
to an
embodiment of the present invention;
Figs. 2B and 2C are perspective views of sensors and a coin-transport rail
according
to embodiments of the present invention;
Fig. 2D depicts a two-core configuration according to an embodiment of the
present
invention;
Fig. 3 is a front elevational view of a sensor and adjacent coin, according to
another
embodiment of the present invention;
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Fig. 4 is a top plan view of the sensor of Fig. 3;
Fig. 5 is a block diagram of a discrimination device according to an
embodiment of
the present invention.
Fig. 6 is a block diagram of a discrimination device according to an
embodiment of
the present invention;
Fig. 7 depicts various signals that occur in the circuit of Figs. 8A-C;
Figs. 8A-8D are block and schematic diagrams of a circuit which may be used in
connection with an embodiment of the present invention;
Fig. 9 depicts an example of output signals of a type output by the circuit of
Figs. 8A-
D as a coin passes the sensor;
Figs. 10A and 10B depict standard data and tolerance regions of a type that
may be
used for discriminating coins on the basis of data output by sensors of the
present invention;
Fig. 11 is a block diagram of a discrimination device, according to an
embodiment of
the present invention;
Fig. 11A is a block diagram of a two-core discrimination device, according to
an
embodiment of the present invention;
Fig. 12 is a schematic and block diagram of a discrimination advice according
to an
embodiment of the present invention;
Fig. 13 depicts use of in-phase and delayed amplitude data for coin
discriminating
according to one embodiment;
Fig. 14 depicts use of in-phase and delayed amplitude data for coin
discriminating
according to another embodiment;
Figs. 15A and 15B are front elevational and top plan views of a sensor, coin
path and
coin, according to an embodiment of the present invention;
Figs. 16A and 16B are graphs showing D output from high and low frequency
sensors, respectively, for eight copper and aluminum disks of various
diameters, according to
an embodiment of the present invention;
Fig. 17 is a perspective view of a coin pickup assembly, rail, sensor and
chute system,
according to an embodiment of the present invention;
Fig. 18 is an exploded view of the system of Fig. 17;
Fig. 19 depicts the system of Fig. 17 with the front portion pivoted;
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Fig. 20 is a cross-sectional view taken along line 20-20 of Fig. 17;
Fig. 21 is a front elevational view of the coin rail portion of Fig. 17;
Fig. 22 is a perspective view of the system of Fig. 17, showing an example of
coin
locations;
Figs. 23A through 23G are cross sectional views taken along lines 23A-23A
through
23G-23G, respectively, of Fig. 21;
Fig 24 is a cross sectional view taken along line 24-24 of Fig. 22;
Fig. 25 is a rear elevational view of the system of Fig. 1.7;
Fig. 25A is a partial view corresponding to Fig. 25, but showing the rake in
the
downstream position;
Figs. 26 and 26A are cross-sectional views taken along lines 26-26 and 26A-26A
of
Figs. 25 and 26A;
Fig. 26 is a top plan view of a portion of the system of Fig. 17, showing a
rail rake;
Figs. 27A and 27B are front and rear perspective views of a sensor and sensor
board
according to an embodiment of the present invention;
Figs. 28A and 28 B are front and side elevational views of a sensor core
according to
an embodiment of the present invention;
Fig. 29 is a block diagram of functional components of a sensor board,
according to
an embodiment of the present invention;
Fig. 30 is a graph of an example of sensor signals according to an embodiment
of the
present invention;
Fig. 31 is a schematic diagram of a sensor board, according to an embodiment
of the
present invention;
Fig. 32 is a block diagram of hardware for a coin discrimination device,
according to
an embodiment of the present invention;
Fig. 33 is a graph of a hypothetical example of sensor signals, according to
an
embodiment of the present invention;
Fig. 34 is a flow chart of a coin signature calculation process, according to
an
embodiment of the present invention;
Fig. 35 is a state diagram for a coin discrimination process according to an
embodiment of the present invention;
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Fig. 36 is a state diagram for a categorization process according to an
embodiment of
the present invention;
Fig. 37 is a block diagram for a categorization process according to an
embodiment of
the present invention;
Fig. 38 is a state diagram of a Direct Memory Access process according to an
embodiment of the present invention;
Fig. 39 is a timing diagram of a Direct Memory Access process according to an
embodiment of the present invention;
Fig. 40 is a flowchart showing a coin discrimination process, according to an
embodiment of the present invention;
Fig. 41 is a block diagram showing components of a coin discrimination system
according to an embodiment of the present invention;
Fig. 42 is a flowchart showing a leading and trailing gap verification
procedure; and
Fig. 43 is a partial cross sectional view showing a coin return path according
to an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The sensor and associated apparatus described herein can be used in connection
with
a number of devices and purposes. One device is illustrated in Fig. IA. In
this device, coins
are placed into a tray 120, and fed to a sensor region 123 via a first ramp
230 and coin pickup
assembly 280. In this sensor region 123, data is collected by which coins are
discriminated
from non-coin objects, and different denominations or countries of coins are
discriminated.
The data collected in the sensor area 123 is used by the computer 290 to
control movement of
coins along a second ramp 125 in such a way as to route the coins into one of
a plurality of
bins 210. The computer may output information such as the total value of the
coins placed
into the tray, via a printer 270, screen 130, or the like. In the depicted
embodiment, the
conveyance apparatus 230, 280 which is upstream of the sensor region 123
provides the coins
to the sensor area 123 serially, one at a time.
The embodiment depicted in Fig. I B generally includes a coin counting/sorting
portion 12 and a coupon/voucher dispensing portions 14a,b. In the depicted
embodiment, the
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coin counting portion 12 includes an input tray 16, a voucher dispensing
region 18, a coin
return region 22, and customer I/O devices, including a keyboard 24,
additional keys 26, a
speaker 28 and a video screen 32. The apparatus can include various indicia,
signs, displays,
advertisement and the like on its external surfaces. A power cord 34 provides
power to the
mechanism as described below.
Preferably, when the doors 36a, 36b are in the open position as shown, most or
all of
the components are accessible for cleaning and/or maintenance. In the depicted
embodiment,
a voucher printer 23 (Fig. 41) is mounted on the inside of the door 36a. A
number of printers
can be used for this purpose. In one embodiment, a model KLDS0503 printer,
available from
io Axioh is used. The right-hand portion of the cabinet includes the coupon
feeder 42 for
dispensing, e.g., pre-printed manufacturer coupon sheets through a chute 44 to
a coupon
hopper on the outside portion of the door 36b. A computer 46, in the depicted
embodiment,
is positioned at the top of the right hand portion of the cabinet in order to
provide a relatively
clean, location for the computer. An I/O board 48 is positioned adjacent the
sheet feeder 42.
The general coin path for the embodiment depicted in Fig. 1B is from the input
tray
16, down first and second chutes to a trommel 52, to a coin pickup assembly
54, along a coin
rail 56 and past a sensor 58. If, based on sensor data, it is determined that
the coin can and
should be accepted, a controllable deflector door 62 is activated to divert
coins from their
gravitational path to coin tubes 64a, b for delivery to coin trolleys 66a, b.
If it has not been
determined that a coin can and should be accepted, the door 62 is not
activated and coins (or
other objects) continue down their gravitational or default path to a reject
chute 68 for
delivery to a customer-accessible reject or return box 22.
Devices that may be used in connection with the input tray are described in
U.S.
Patent 5564546, U.S. Patent 5620079, supra.
Devices that may be used in connection with the coin trolleys 66a, 66b are
described
in U.S. Patent 6,082,519.
Devices that may be used in connection with the coin chutes and the trommel 52
are
described in PCT/US97/03136 Feb 28, 1997 published as WO 97/33257.
Briefly, and as described more thoroughly below and in the above-noted
applications,
a user is provided with instructions such as on computer screen 32. The user
places a mass of
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coins, typically of a plurality of denominations (typically accompanied by
dirt or other non-
coin objects) in the input tray 16. The user is prompted to push a button to
inform the
machine that the user wishes to have coins discriminated. Thereupon, the
computer causes an
input gate 17 (Fig. 41) to open and illuminates a signal to prompt the user to
begin feeding
coins. The gate may be controlled to open or close for a number of purposes,
such as in
response to sensing of a jam, sensing of load in the trommel or coin pickup
assembly, and the
like. In one embodiment, signal devices such as LEDs can provide a user with
an indication
of whether the gate is open or closed (or otherwise to prompt the user to feed
or discontinue
feeding coins or other objects). Although instructions to feed or discontinue
may be provided
on the computer screen 32, indicator lights are believed useful since users
often are watching
the throat of the chute, rather than the computer screen, during the feeding
of coins or other
objects. When the gate is open, a motor 19 (Fig. 41) is activated to begin
rotating the trommel
assembly 52. The user moves coins over the peaked output edge 72 of the input
tray 16,
typically by lifting or pivoting the tray by handle 74, and/or manually
feeding coins over the
peak 72. The coins pass the gate (typically set to prevent passage of more
than a
predetermined number of stacked coins, such as by defining an opening equal to
about 3.5
times a typical coin thickness). Instructions on the screen 32 may be used to
tell the user to
continue or discontinue feeding coins, can relay the status of the machine,
the amount
counted thus far, provide encouragement or advertising messages and the like.
First and second chutes (not shown) are positioned between the output edge 72
of the
input tray 16 and the input to the trommel 52. Preferably, the second chute
provides a
funneling effect by having a greater width at its upstream edge than its
downstream edge.
Preferably, the coins cascade or "waterfall" when passing from the first chute
to the second
chute, e.g. to increase momentum and tumbling of the coins.
Preferably, some or all of the surfaces that contact the coin along the coin
path,
including the chutes, have no flat region large enough for a coin to contact
the surface over
all or substantially all of one of the faces of the coin. Some such surfaces
are curved to
achieve this result, such that coins make contact on, at most, two points of
such surfaces.
Other surfaces may have depressions or protrusions such as being provided with
dimples,
quilting or other textures. Preferably, the surface of the second chute is
constructed such that
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it has a finite radius of curvature along any plane normal to its longitudinal
axis, and
preferably with such radii of curvature increasing in the direction of coin
flow.
In one embodiment, the chutes are formed from injected molded plastic such as
an
acetal resin e.g. Delrin , available from E.L. DuPont de Nemours & Co., or a
polyamide
polymer, such as a nylon, and the like. Other materials that can be used for
the chute include
metals, ceramics, fiberglass, reinforced materials, epoxies, ceramic-coated or
-reinforced
materials and the like. The chutes may contain devices for performing
additional functions
such as stops or traps, e.g., for dealing with various types of elongate
objects.
The trommel 52, in the depicted embodiment is a perforated-wall, square cross-
section, rotatably mounted container. Preferably, dimples protrude slightly
into the interior
region of the trommel to avoid adhesion and/or reduce friction between coins
and the interior
surface of the trommel. The trommel is rotated about its longitudinal axis.
Preferably,
operation of the device is monitored, such as by monitoring current draw for
the trommel
motor using a current sensor 21. A sudden increase or spike in current draw
may be
considered indicative of an undesirable load and/or jam of the trommel. The
system may be
configured in various ways to respond to such a sensed jam such as by turning
off the
trommel motor to stop attempted trommel rotation and/or reversing the motor,
or altering
motor direction periodically, to attempt to clear the jam. In one embodiment,
when a jam or
undesirable load is sensed, coin feed is stopped or discouraged, e.g., by
closing the gate
and/or illuminating a "stop feed" indicator. As the trommel motor 19 rotates
the trommel,
one or more vanes protruding into the interior of the trommel assist in
providing coin-
lifting/free-fall and moving the coins in a direction towards the output
region. Objects
smaller than the smallest acceptable coin (about 17.5 mm, in one embodiment)
pass through
the perforated wall as the coins tumble. In one embodiment, the holes have a
diameter of
about 0.61 inches (about 1.55 cm) to prevent passage of U.S. dimes. An output
chute directs
the (at least partially) cleaned coins exiting the trommel towards the coin
pickup assembly
54. The depicted horizontal disposition of the trommel, which relies on vanes
rather than
trommel inclination for longitudinal coin movements, achieves a relatively
small vertical
space requirement for the trommel. Preferably the trommel is mounted in such a
way that it
may be easily removed and/or opened or disassembled for cleaning and
maintenance, as
described, e.g., in PCT Application US97/03136, supra.
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CA 02426411 2003-05-07
As depicted in Fig. 17, coin pickup assembly 54 includes a hopper 1702 for
receiving
coins output from the trommel 52. The hopper 1702 may be made at relatively
low cost such
as by vacuum forming. In one embodiment, the hopper 1702 is formed of a
plastic material,
such as polyethylene, backed with sound-absorbing foam for reducing noise.
Without being
bound by any theory, it is believed that polyethylene is useful to reduce coin
sticking. Other
features which may be provided for the hopper include shaping to provide a
curvature
sufficient to avoid face-to-face contact between coins and the hopper surface
and/or
providing surface texture (such as embossing, dimpling, faceting, quilting,
ridging or ribbing)
on the hopper interior surface. The hopper 1702 preferably has an amount of
flexibility,
rather than being rigid, which reduces the occurrence of jams and assists in
clearing jams
since coins are not forced against a solid, unyielding surface.
As described below, the coins move into an annular coin path defined, on the
outside,
by the edge of a circular recess 1802 (Fig. 18) and, on the inside, by a ledge
1804 formed on
a rail disk 1806. The coins are moved along the annular path by paddles 1704a,
b, c, d for
delivery to the coin rail 56.
A circuit board 1744 for providing certain control functions, as described
below, is
preferably mounted on the generally accessible front surface of the chassis
1864. An
electromagnetic interference (EMI) safety shield 1746 normally covers the
circuit board 1744
and swings open on hinges 1748a,b for easy service access.
In the embodiment depicted in Fig. 17 and 18, the coin rail 56 and the recess
1808 for
the disks are formed as a single piece or block, such as the depicted base
plate 1810. In one
embodiment, the base plate 1810 is formed from high density polyethylene
(HDPE) and the
recess 1808 and coin rail 56, as well as the various openings depicted, are
formed by
machining a sheet or block of HDPE. HDPE a useful material because, among
other reasons,
components may be mounted using self-tapping screws, reducing manufacturing
costs.
Furthermore, use of a non-metallic back plate is preferred in order to avoid
interference with
the sensor. In one embodiment, electrically conductive HDPE may be used, e.g.
to dissipate
static electricity.
The base plate 1810 is mounted on a chassis 1864 which is positioned within
the
cabinet (Fig. 1B) such that the base plate 1810 is disposed at an angle 1866
with respect to
vertical 1868 of between about 0 and about 45 , preferably between about 0
and about 15 ,
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CA 02426411 2003-05-07
more preferably about 20 . Preferably, the diverter cover 1811 is pivotally
coupled to the
base plate 1810, e.g. by hinges 1872a, 1872b, so that the diverter cover 1811
may be easily
pivoted forward (Fig. 19) e.g. for cleaning and maintenance.
A rotating main disk 1812 is configured for tight (small clearance) fit
against the edge
1802 of recess 1808. Finger holes 1813a, b, c, d facilitate removal of the
disk for cleaning or
maintenance. Relatively loose (large clearance) fit is provided between disk
holes 1814a, b,
c, d and hub pins 1816a, b, c, d and between central opening 1818 and motor
hub 1820. The
loose fit of the holes and the tight fit of the edge of disk 1812 assist in
reducing debris
entrapment and motor jams. Because the main disk is received in recess 1802,
it is free to
flex and/or tilt, to some degree, e.g. in order to react to coin jams.
A stationary rail disk 1806 is positioned adjacent the main disk 1812 and has
a central
opening 1824 fitting loosely with respect to the motor hub 1820. In one
embodiment, the rail
disk is formed of graphite-filled phenolic.
The ledge 1804 defined by the rail disk 1806 is preferably configured so that
the
annular coin path flares or widens in the direction of coin travel such that
spacing between
the ledge and the recess edge near the bottom or beginning of the coin path
(at the eight
o'clock position 1876) is smaller. (such as about 0.25 inches, or about 6 mm
smaller) than the
corresponding distance 1827 at the twelve o'clock position 1828. In one
embodiment, the rail
disk 1806 (and motor 2032) are mounted at a slight angle to the plane formed
by the
attachment edge 2042 of the hopper 1702 such that, along the coin path, the
coin channel
generally increases in depth (i.e. in a direction perpendicular to the face of
the rail disk).
As the coins travel counterclockwise from approximately a twelve o'clock
position
1828 of the rail disk, the ledge is thereafter substantially linear along a
portion 1834 (Fig. 19)
extending to the periphery of the rail disk 1806 and ending adjacent the coin
backplate 56 and
rail tip 1836. A tab-like protrusion 1838 is engaged by rail tip 1836, holding
the rail disk
1806 in position. The rail disk is believed to be more easily manufactured and
constructed
than previous designs, such as those using a coin knife. Furthermore, the
present design
avoids the problem, often found with a coin knife, in which the tip of the
knife was
susceptible to prying outward by debris accumulated behind the tip of the coin
knife.
A tension disk 1838 is positioned adjacent the rail disk. The tension disk
1838 is
mounted on the motor hub 1820 via central opening 1842 and threaded disk knob
1844. As
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the knob 1844 is tightened, spring fingers 1846a, b, c, d apply force to keep
the disks 1838,
1806, 1812 tightly together, reducing spaces or cracks in which debris could
otherwise
become entrapped. Preferably, the knob 1844 can be easily removed by hand,
permitting
removal of all the disks 1812, 1806, 1838 (e.g., for maintenance or cleaning)
without the need
for tools.
In one embodiment, the tension disk 1838 and main disk 1812 are formed of
stainless
steel while the rail disk 1806 is formed of a different material such as
graphite-filled
phenolic, which is believed to be helpful in reducing galling. The depicted
coin disc
configuration, using the described materials, can be manufactured relatively
easily and
inexpensively, compared to previous devices. Paddles 1704a, b, c, d are
pivotally mounted
on tension disk pins 1848a, b, c, d so as to permit the paddles to pivot in
directions 1852a,
1852b parallel to the tension disk plane 1838. Such pivoting is useful in
reducing the
creation or exacerbation of coin jams since coins or other items which are
stopped along the
coin path will cause the paddles to flex, or to pivot around pins 1848a, b, c,
d, rather than
requiring the paddles to continue applying full motor-induced force on the
stopped coins or
other objects. Springs 1854a, b, c, d resist the pivoting 1852a, 1852b, urging
the paddles to a
position oriented radially outward, in the absence of resistance e.g. from a
stopped coin or
other object.
Preferably, sharp or irregular surfaces which may stop or entrap coins are
avoided.
Thus, covers 1856a, b, c, d are placed over the springs 1854a, b, c,, d and
conically-shaped
washers 1858a, b, c, d protect the pivot pins 1848a, b, c, d. In a similar
spirit, the edge of the
tension disk 1862 is angled or chamfered to avoid coins hanging on a disk
edge, potentially
causing jamming.
As depicted in Fig. 25, a number of components are mounted on the rear surface
of
the chassis 1864. A motor, such as model 2032 drives the rotation of disks
1812, 1838 via
motor drive hub 1820. An actuator such as solenoid 2014 controls movement of
the trap door
1872 (described below). A sensor assembly, including sensor printed circuit
board (PCB)
2512 is slidably mounted in a shield 2514.
The lower edge of the recess 1808 is formed by a separate piece 1872 which is
mounted to act as a trap door. The trap door 1872 is configured to be moved
rearwardly 2012
(Fig. 20) by actuator 2014 to a position 2016 to enable debris to fall into
debris cup 2018.
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CA 02426411 2003-05-07
Solenoid 2014 is actuated under control of a microcontroller as described
below. Preferably,
the trap door 1872 retracts substantially no further than the front edge of
the coin rail disk, to
avoid catching, which could lead to a failure of the trap door to close.
Preferably, a sensor
switch provides a signal to the microcontroller indicating whether the trap
door has
completely shut. Preferably the trap door is resiliently held in the closed
position in such a
manner that it can be manually opened if desired.
Coins which fall into the hopper 1702 from the trommel 52 are directed by the
curvature of the hopper towards the six o'clock position 1877 (Fig. 19) of the
annular coin
path. In general, coins traveling over the downward-turning edge 2024 of the
hopper 1702
are tipped onto edge and, partially owing to the backward inclination 1866 of
the apparatus,
tend to fall into the annular space 1801. Coins which are not positioned in
the space 1801
with their faces adjacent the surface of the rail disk (such as coins that may
be tipped outward
2026a or may be perpendicular to the rail disk 2026b) will be struck by the
paddle 1704 as it
rotates, agitating the coins and eventually correctly positioning coins in the
annular space
1801 with their faces adjacent the face 1801 of the annular space defined by
the rail disk
1806. It is believed that the shape of the paddle head 2028a, 2028c, in
particular the rounded
shape of the radially outmost portion 2206 of the head, assists in agitating
or striking coins in
such a manner that they will assume the desired position.
Once coins are positioned along the annular path, the leading edge of the
paddle heads
2028 contact the trailing edge of the coins, forcing them along the coin path,
e.g. as depicted
in Fig. 17. Preferably each paddle can move a plurality of coins, such as up
to about 10
coins. The coins are thus eventually forced to travel onto and along the
linear portion 1834 of
the rail disk ledge 1804 and are pushed onto the coin rail tip 1836. Some
previous devices
were provided with an exit gate for coins exiting the coin pickup assembly
which, in some
cases, was susceptible to jamming. According to an embodiment of the present
invention,
such jamming is eliminated because no coin pickup assembly exit gate is
provided.
As the paddle heads 2028 continue to move along the circular path, they
contact the
linear portion 1834 (Fig. 19) of the ledge 1804 and flex axially outward 2032,
facilitated by a
tapered shape of the radially inward portion of the paddle pad 2028 to ride
over (i.e. in front
of) a portion 1884 of the rail disk. In one embodiment, openings or holes 1708
are provided
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CA 02426411 2003-05-07
in this portion to reduce frictional drag and to receive e.g. trapped debris,
which is thus
cleared from the annular coin path.
As seen in Fig. 21, the ledge 1804 as defined by the rail disk 1806 is
displaced
upwardly 2102 with respect to the ledge 2104 of the coin rail tip 1836. The
distance 2102
may be, for example, about 0.1 inches (about 2.5 mm). The difference in height
2102 assists
in gravitationally moving coins from the rail disk ledge 1804 over the upper
portion of the
"V" gap (described below) and onto the ledge of coin rail tip 1836.
The terminal point 2105 of the rail disk ledge is laterally spaced a distance
2107 from
the initial edge of the coin rail ledge 2104 to define a "V" gap therebetween.
This gap, which
1o extends a certain distance 2109 circumferentially, as seen in Fig. 21,
receives debris which
may be swept along by the coin paddles. The existence of the gap 2107, and its
placement,
extending below the rail ledge, by providing a place for debris swept up by
the paddles,
avoids a problem found in certain previous devices in which debris tended to
accumulate
where a disk region met a linear region, sometimes accumulating to the point
of creating a
bump or obstruction which could cause coins to hop or fly off the ledge or
rail.
The coin rail 56 functions to receive coins output by the coin pickup assembly
54, and
transports the coins in a singulated (one-at-a-time) fashion past the sensor
58 to the diverting
door 62. Singulation and separation of coins is of particular use in
connection with the
described sensor, although other types of sensors may also benefit from coin
singulation and
spacing. In general, coins are delivered to the coin rail 56 rolling or
sliding on their edge or
rim along the rail ledge 2104. The face of the coins as they slide or roll
down the coin rail are
supported, during a portion of their travel, by rails or stringers 2106a, b,
c. The stringers are
positioned (Fig. 23A), respectively, at heights 2108a, b, c (with respect to
the height of the
ledge 2104) to provide support suitable for the range of coin sizes to be
handled while
providing a relatively small area or region of contact between the coin face
and the stringers.
Although some previous devices provide for flat-topped or rounded-profile
rails or ridges, the
present invention provides ridges or stringers which at least in the second
portion, 2121b,
have a triangular or peaked profile. This is believed to be easier to
manufacture (such as by
machining into the baseplate 1810) and also maintains relatively small area of
contact with
the coin face despite stringer wear.
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The position and shape of the stringers and the width of the rail 2104 are
selected
depending on the range of coin sizes to be handled by the device. In one
embodiment, which
is able to handle U.S. coins in the size range between a U.S. dime and a U.S.
half-dollar, the
ledge 2104 has a depth 2111 (from the backplate 2114) of about 0.09 inches
(about 2.3 mm).
The top stringer 2106a is positioned at a height 2108a (above the ledge 2104)
of about 0.825
inches (about 20 mm), (the middle stringer 2106b is positioned at a height
2108b of about
0.49 inches (about 12.4 mm), and the bottom stringer 2106c is positioned at a
height of about
0.175 inches (about 4.4 mm). In one embodiment, the stringers are about 0.8
inches (about 2
mm) wide 2109 (Fig. 23C) and protrude about 0.05 inches (about 1.3 mm) 2112
above the
back plate 2114 of the coin rail.
As seen in Fig. 22, as the coins enter the coin rail 56, the coins are
typically
horizontally singulated, i.e., coins are in single file, albeit possibly
adjacent or touching one
another. The singulated configuration of the coins can be contrasted with
coins which are
horizontally partially overlapped 2202a, b as shown in Fig. 22A. Fig. 22A also
illustrates a
situation in which some coins are stacked on top of one another vertically
2202c, d. A
number of features of the coin rail 56 contribute to changing the coins from
the bunched
configuration to a singulated, and eventually separated, series of coins by
the time they move
past the sensor 58. One such feature is a cut-out or recess 2116 provided in
or adjacent the
top portion of the rail along a first portion of its extent. As seen in Fig.
24, when coins which
are vertically stacked such as coins 2202c, b, illustrated in Fig. 22, reach
the cut-out portion
2116, the top coin, aided by the inclination 1866 of the rail, tips backward
2402 an amount
sufficient that it will tend to slide forward 2404 in front of the lower coin
2202, falling into
the hopper extension 2204 which is positioned beneath the cut-out region 2116,
and sliding
back into the main portion of the hopper 1702 to be conveyed back on to the
coin rail.
Another feature contributing to singulation is the change in inclination of
the coin rail
from a first portion 2121a which is inclined, with respect to a horizontal
plane 2124 at an
angle 2126 of about 0 to about 30 , preferably about 0 to about 15 and more
preferably
about 10 , to a second portion 2121b which is inclined with respect to a
horizontal plane
2124 by an angle 2128 of about 30 to about 60 , preferably between about 40
and about 50
and more preferably about 45 . Preferably, the coin path in the transitional
region 2121c
between the first portion 2121a and second portion 2121b is smoothly curved,
as shown. In
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CA 02426411 2003-05-07
one embodiment, the radius of curvature of the ledge 2104 in the transition
region 2121c is
about 1.5 inch (about 3.8 cm).
One feature of singulating coins, according to the depicted embodiment, is to
primarily use gravitational forces for this purpose. Use of gravity force is
believed to, in
general, reduce system cost and complexity. This is accomplished by
configuring the rail so
that a given coin, as it approaches and then enters the second portion 2121b,
will be
gravitationally accelerated while the next ("following") coin, on a shallower
slope, is being
accelerated to a much smaller degree, thus allowing the first coin to move
away from the
following coin, creating a space therebetween and effectively producing a gap
between the
to singulated coins. Thereafter, the following coin moves into the region
where it is, in turn,
accelerated away from the successive coin. As a coin moves from the first
region 2121a
toward and into the second region 2121b, the change in rail inclination 2126,
2318 (Fig. 21)
causes the coin to accelerate, while the following coins, which are still
positioned in the first
region 2121a, have a relatively lower velocity.
In one embodiment, acceleration of a coin as it moves into the second rail
region
2121b is also enhanced by placement of a short, relatively tall auxiliary
stringer 2132
generally in the transition region 2121c. The auxiliary stringer 2132 projects
outwardly from
the back surface 2114 of the coin tail, a distance 2134 (Fig. 23B) greater
than the distance
2112 of projection of the normal stringers 2106a, b, c. Thus, as a coin moves
into the
transition region 2121c, the auxiliary stringer 2132 tips the coin top outward
2392, away from
contact with the normal stringers 2106a, b, c so that it tends to "fly" (roll
or slide on its edge
or rim along the coin rail ledge 2104 without contact with the normal
stringers 2106a, b, c)
and, for at least a time period following movement past the auxiliary stringer
2132, continues
to contact the coin rail only along the ledge 2104, further minimizing or
reducing friction and
allowing the coin to accelerate along the second region 2121b of the coin
rail. In one
embodiment, the coin-contact portion of the stringers in the first portion
2121 a are somewhat
flattened (Fig. 23A) to increase friction and exaggerate the difference in
coin acceleration
between the first section 2121a and the second section 2121b, where the
stringer profiles are
more pointed, such as being substantially peaked (Fig. 23C).
Another feature of the coin rail contributing to acceleration is the provision
of one or
more free-fall regions where coins will normally be out of contact with the
stringers and thus
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CA 02426411 2003-05-07
will contact, at most, only the ledge portion 2104 of the rail. In the
depicted embodiment, a
first free-fall region is provided at the area 2136a wherein the auxiliary
stringer 2132
terminates. As noted above, coins in this region will tend to contact the coin
rail only along
the ledge 2104. Another free-fall region occurs just downstream of the
upstream edge 2342
of the door 62. As seen in Fig. 23E, the door 62 is preferably positioned a
distance 2344
(such as about 0.02 inches, about 0.5 mm) from the surface 2114 of the rail
region. This
setback 2344, combined with the termination of the stringers 2106, provides a
free-fall region
adjacent the door 62. If desired, another free-fall region can be provided
downstream from
the door 62, e.g., where the reject coin path 1921 meets the (preferably
embossed) surface of
the reject chute or reject chute entrance which may be set back a distance
such as about 1/8
inch (about 3 mm).
Another free-fall region may be defined near the location 2103 where coins
exit the
disks 1812, 1806 and enter the rail 56, e.g., by positioning the disk 1812 to
have its front
surface in a plane slightly forward (e.g., about 0.3 inches, or about 7.5 mm)
of the plane
defined by rail stringers 2106. This free-fall region is useful not only to
assist the transition
from the disk onto the rail but makes it more likely that coins which may be
slowed or
stopped on the rail near the end of a transaction will be positioned
downstream of the retract
position (Fig. 21) of the rake 2152 such that when the rake operates (as
described below), it is
more likely to push slowed or stopped coins down the rail than to knock such
coins off the
tail. Providing periods of coin flying reduces friction, contributes to coin
acceleration and
also reduces variation in coin velocity since sticky or wet coins behave
similarly to pristine
coins when both are in a flying mode. Producing periods of flying is believed
to be
particularly useful in maintaining a desired acceleration and velocity of
coins which may be
wet or sticky.
The sensor 58 is positioned a distance 2304 (Fig. 23D) away from the surface
of the
stringers 2106a, b, c sufficient to accommodate passage of the thickest coin
to be handled.
Although certain preferred sensors, and their use, are described more
thoroughly below, it is
possible to use features of the present invention with other types of sensors
which may be
positioned in another fashion such as embedded in the coin rail 56.
The leading surface of the sensor housing is preferably ramped 2306 such that
coins
or other objects which do not travel into the space 2304 (such as coins or
other objects which
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CA 02426411 2003-05-07
are too large or have moved partially off the coin path) will be deflected by
the ramp 2306
onto a bypass chute 1722 (Fig. 17), having a deflector plane 1724 and a trough
1726 for
delivery to the coin return or reject chute 68 where they may be returned to
the user. The
sensor housing also performs a spacer function, tending to hold any jams at
least a minimum
distance from the sensor core, preferably sufficiently far that the sensor
reading is not
affected (which could cause misdetection). If desired, the sensor housing can
be configured
such that jams may be permitted within the sensing range of the sensor (e.g.,
to assist in
detecting jam occurrence).
In the depicted configuration, the sensor 58 is configured so that it can be
moved to a
position 2142 away from the coin rail 56, for cleaning or maintenance, such as
by sliding
along slot 2144. Preferably, the device is constructed with an interference
fit so that the
sensor 58 may be moved out of position only when the diverter cover 1811 has
been pivoted
forward 1902 (Fig. 19) and such that the diverter cover 1811 may not be
repositioned 1904 to
its operating configuration until the sensor 2142 has been properly positioned
in its operating
location (Fig. 21). Preferably, the sensor apparatus is configured so that it
will seat reliably
and accurately in a desired position with respect to the coin rail such as by
engagement of a
retention clip 2704 (Fig. 21). Such seating, preferably combined with a
relatively high
tolerance for positional variations of coins with respect to the sensor
(described below),
means that the sensor may be moved to the maintenance position 2142 and
returned to the
operating position repeatedly, without requiring recalibration of the device.
As noted above, in the depicted embodiment, a door 62 is used to selectively
deflect
coins or other objects so the coins ultimately travel to either an acceptable-
object or coin bin
or trolley, or a reject chute 68.
In the embodiment depicted in Fig. 43, a coin return ramp 4312 extends from
the coin
return region 1921, through the opening 1813 of the diverter cover 1811 and
extends a
distance 4314 outward and above the initial portion of the coin return chute
68. Thus, coins
which are not deflected by the door 62 travel down the ramp 4312 and fly off
the end 4316 of
the ramp in a "ski jump" fashion before landing on the coin return chute
surface 68. Even
though preferably, coin contact surfaces such as the ramp 4312 and coin return
chute 68 are
embossed or otherwise reduce facial contact with coins, providing the "ski
jump" flying
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CA 02426411 2003-05-07
region further reduces potential for slowing or adhesion of coins (or other
objects) as they
travel down the return chute towards the customer return box.
Preferably the device is configured such that activation of the door deflects
coins to an
acceptable coin bin and non-activation allows a coin to move along a default
path to the reject
chute 68. Such "actuate-to-accept" technique not only avoids accumulation of
debris in the
exit bins but improves accuracy by accepting only coins that are recognized
and, further,
provides a configuration which is believed superior during power failure
situations. The
actuate-to-accept approach also has the advantage that the actuation mechanism
will be
operating on an object of known characteristics (e.g. known diameter, which
may be used,
e.g. in connection with determining velocity and/or acceleration, or known
mass, which may
be used, e.g. for adjustment of forces, such as deflection forces). This
affords the opportunity
to adjust, e.g. the timing, duration and/or strength of the deflection to the
speed and/or mass
of the coin. In a system in which items to be rejected are actively deflected,
it would be
necessary to actuate the deflection mechanism with respect to an object which
may be
unrecognized or have unknown characteristics.
Although in one embodiment the door 62 is separately actuated for each
acceptable
coin (thus reducing solenoid 2306 duty cycle and heat generation), it would
also be possible
to configure a device in which, when there are one or two or more sequential
accepted coins,
the door 62 is maintained in its flexed position continuously until the next
non-accepted coin
(or other object) approaches the door 62.
An embodiment for control and timing of the door 62 deflection will be
described
more thoroughly below. In the depicted embodiment, the door 62 is deflected by
activation
of a solenoid 2306. The door 62, in one embodiment, is made of a hard
resilient material,
such as 301 full hard stainless steel which may be provided in a channel shape
as shown. In
one embodiment, the back surface of the coin-contact region of the door 2308a
is
substantially covered with a sound-deadening material 2334 such as a foam tape
(available
from 3M Company). Preferably the foam tape has a hole 2335 adjacent the region
where the
solenoid 2306 strikes the door 62.
In one embodiment, the door 62 is not hinged but moves outwardly from its rest
position (Fig. 23E) to its deflected position (Fig. 23F) by bending or
flexing, rather than
pivoting. Door 62, being formed of a resilient material, will then deflect
back 2312 to its rest
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CA 02426411 2003-05-07
position once the solenoid 2306 is no longer activated. By relying on
resiliency of an
unhinged door for a return motion, there is no need to provide a door return
spring.
Furthermore, the resiliency of the door, in general, provides a force greater
than the solenoid
spring return force normally provided with a solenoid, so that the door 62
will force the
solenoid back to its rest position (Fig. 23E) (after cessation of the
activation pulse), more
quickly than would have been possible if relying on the force of the solenoid
return spring.
As a result, the effective cycle time for the solenoid/door system is reduced.
In one
embodiment, a solenoid is used which has a normal cycle time of about 24
milliseconds but
which is able to achieve a cycle time of about 10 milliseconds when the
resilient-door closing
1o feature is used for solenoid return, as described. In one embodiment, a
solenoid is used
which is rated at 12 volts but is activated using a 24-volt pulse.
In some situations, particularly at the end of a coin discrimination cycle or
transaction, one or more coins, especially wet or sticky coins, may reside on
the first portion
2121 a of the rail such that they will not spontaneously (or will only slowly)
move toward the
sensor 58. Thus, it may be desirable to include a mechanical or other
transducer for
providing energy, in response to a sensed jam, slow-up or other abnormality.
According to
one embodiment for providing energy, a coin rake 2152, normally retracted into
a rake slot
2154 (Fig. 23A), may be activated to extend outward 2156 from the slot 2154
and move
lengthwise 2156 down the slot 2154 to push slow or stopped coins down the coin
path, such
as onto the second portion 2121b of the coin rail, or off the rail to be
captured by the hopper
extension 2204. An embodiment for timing and control of the rake is described
more
thoroughly below. In one embodiment, rake movement is achieved by activating a
rake
motor 2502 (Fig. 19) coupled to a link arm 2504 (Fig. 25). This link 2504 is
movably
mounted to the rear portion of the chassis 1864 by a pin and slot system
2506a,b, 2507a,b. A
plate section 2509 of the link 2504 is coupled via slot 2511 to an eccentric
pin of motor 2502.
A slot 2513 of the link arm 2504 engages a rear portion of the rake 2152.
Activation of the
motor 2502 rotates eccentric pin 2515 and causes link 2504 to move
longitudinally 2517. A
slot 2513 of the link arm 2504, forces the rake 2152 to move 2519 along the
inclined slot
2154 toward a downstream position 2510 (Fig. 26A). The function of causing the
rake to
protrude or extend outward 2156 from the slot 2154 can be achieved in a number
of fashions.
In one embodiment, the link arm 2504 is shaped so that when the rake is
positioned down the
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CA 02426411 2003-05-07
slot 2154, the rake 2152 is urged outwardly 2156 bu the shape of the resilient
link arm 2504.
As the rake is moved upstream 2525 toward the normal operating location, a cam
follower
formed on the free end 2527 of the link arm is urged rearwardly by a cam 2529
carrying the
rake 2152 with it, rearwardly to the retracted position (Fig. 23A, Fig. 26).
Preferably, the rake position is sensed or monitored, such as by sensing the
position of
the rake motor 2502, in order to ensure proper rake operation. Preferably the
system will
detect (e.g. via activity sensor 1754) if the coin rake knocked coins off the
rail or, via coin
sensor 58, if the coin rake pushed coins down the coin rail to move past the
sensor 58. In one
embodiment if activation of the coin rake results in coins being knocked off
the rail or moved
down the tail, the coin rake will be activated at least a second time and the
system may be
configured to output a message indicating that the system should be cleaned or
requires
maintenance.
Between the time that a coin passes beneath the sensor 58 and the time it
reaches the
deflection door 62 (typically a period of about 30 milliseconds), control
apparatus and
software (described below) determine whether the coin should be diverted by
the door 62. In
general, it is preferred to make the time delay between sensing an object and
deflecting the
object (i.e., to make the distance between the sensor and the deflection door)
as short as
possible while still allowing sufficient time for the recognition and
categorization processes
to operate. The time requirements will be at least partially dependent on the
speed of the
processor which is used. In general, it is possible to shorten the delay by
employing a higher-
speed processor, albeit at increased expense. Shortening the path between the
sensor and the
deflector not only reduces the physical size of the device but also reduces
the possibility that
a coin or other object may become stuck or stray from the coin path after
detection and before
disposition (potentially resulting in errors, e.g. of a type in a coin is
"credited" but not
directed to a coin bin). Furthermore, shortening the separation reduces the
chance that a
faster following coin will "catch up" with a previous slow or sticky coin
between the sensor
and the deflector door. Shortening the separation additionally reduces the
opportunity for
coin acceleration or velocity to change to a significant degree between the
sensor 58 and the
door 62. Since the door, in one embodiment, is controlled based on velocity or
acceleration
measured or (calculated using data measured) at the sensor, a larger
separation (and
consequently larger rail length with potential variations is, e.g. friction)
between the sensor
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CA 02426411 2003-05-07
58 and the door 62 increases the potential for the measured or calculated coin
velocity or
acceleration to be in error (or misleading).
Because the coin deflector requires a certain minimum cycle time (i.e., the
time from
activation of the solenoid until the door has returned to a rest state and is
capable of being
reactivated), it is impossible to successfully deflect two coins which are too
close together.
Accordingly, when the system determines that two coins are too close together
(e.g. by
detecting successive "trail" times which are less than a minimum period
apart), the system
will refrain from activating the deflector door upon passage of one or both
such coins, thus
allowing one or both such coins to follow the default path to the reject
chute, despite the fact
1o that the coins may have been both successfully recognized as acceptable
coins.
If a coin is to be diverted, when it reaches the door 62, solenoid 2306 is
activated.
Typically, because of the step 2136b and/or other flying-inducing features, by
the time a coin
reaches door 62 it will be spaced a short distance 2307 (such as 0.08 inches,
or about 2 mm)
above the door plane 62 and the door, as it is deflected to its activated
position (Fig. 23F),
will meet the flying coin and knock the coin in an outward direction 2323 to
the common
entrance 1728 of acceptable-coin tubes 64a, 64b. Preferably all coin contact
surfaces of the
return chute and coin tube are provided with a surface texture such as an
embossed surface
which will reduce friction and/or adhesion. Additionally, such surfaces may be
provided
with a sound-deadening material and/or a kinetic energy-absorbing material (to
help direct
coins accurately into the accept bins).
In one embodiment, the timing of deflection of the door 62 is controlled to
increase
the likelihood that the door will strike the coin as desired in such a fashion
as to divert it to
entrance to the coin tubes 1728. The preferred striking position may be
selected empirically,
if desired, and may depend, at least partially, on the diameter and mass of
the coins and the
coin mix expected in the machine as well as the size and characteristics of
the door 62. In
one embodiment, the machine is configured to, on average, strike the coin when
the leading
edge of the coin is approximately 3 mm upstream ("upstream" indicating a
direction opposite
the direction of coin flow 2332) of the downstream edge 2334 of the actuator
door 62 (Fig.
23E). In one embodiment, this strike position is the preferred position
regardless of the
diameter of the coin.
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CA 02426411 2003-05-07
Preferably, there is a gap between coins as they stream past the door 62. The
preferred gap between adjacent coins which have different destinations (i.e.,
when adjacent
coins include an accepted coin and a not-accepted coin) depends on whether the
accepted
coin is before or after the non-accepted coin (in which the "accepted coin" is
a coin which
will be diverted by the door and the not-accepted coin will travel past the
door without being
diverted). The gap behind a not-accepted coin (or other object) which reaches
the door 62
before an accepted coin is referred to herein as a "leading gap". The gap
behind an accepted
coin is referred to herein as a "trailing gap". In one embodiment, the
preferred leading gap is
described by the following equation:
GAPlead.min = AdStoh.lead + Errorplus + a (l )
where:
Odstoajead represents the change in the actual inter-coin gap from the time
the coins pass the
sensor 58 to the time when the coins reach the door 62 (approximately 3 mm);
Errorpins represents the distance error due to compensation uncertainties,
assuming leading
gap worst conditions of maximum initial velocity and a frictionless rail
(approximately 6 mm); and
a represents the dimension from the downstream edge of the actuator door 2334
to
the leading edge of the coin at the preferred strike position (approximately 3
mm).
The preferred minimum leading gap of approximately 12 mm applies when a non-
accepted coin (or other object) precedes an accepted coin. In the common case
of a string of
consecutive accepted coins, this constraint need not be enforced after the
first coin in the
stream.
In one embodiment, the preferred trailing gap is described by the following
equation:
GAPtr.min = AdSto7,..trail + Adontime + Errorminus + b - a - Dcoin.mi (2)
where:
Adsto;..uail represents the change in actual inter-coin gap between the sensor
58 and the door
62 (approximately 2 mm);
4dontime represents the distance the coins travel during the time the actuator
door is
extended (approximately 5 mm);
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CA 02426411 2003-05-07
Errorminus represents the error due to compensation uncertainties, assuming
trailing gap
worst conditions of zero initial velocity and a sticky or high-friction rail
(approximately 6 mm);
b represents the length 2336 of the door 62; and
Dco;n.m; represents the diameter of the accepted coin (in the worst case for a
common U.S.
coin mix, 17.5 mm).
This results in a preferred minimum trailing gap of 5.2 mm.
A process for verifying the existence of preferred leading and trailing gaps,
in
appropriate situations, and/or selecting or controlling the activation of the
door 62 to strike
coins at the preferred position, is described below.
In the depicted embodiment, the region of the common entrance 1728 (Fig. 17)
is
provided with a flapper movable from a first position 1732a which guides the
coins into the
first coin tube 64a for delivery, ultimately, to a first coin trolley 66a, to
a second position
1732b for deflection to the second coin tube 64b for delivery to the second
coin trolley 66b.
In one embodiment, the flapper 1732 is made of plastic to reduce noise and the
tendency to
bind during operation. A solenoid actuator 1734, via link arm 1736, is used to
move the
flapper between the positions 1732a,17326, e.g. in response to control signals
from a
microcontroller (described below). The flapper 1732 may also be rapidly cycled
between its
extreme positions to self-clean material from the mechanism.. In one
embodiment, such self-
cleaning is performed after each transaction. In one embodiment, coin
detectors such as
paired LEDs and optical detectors 1738a, b output signals to the
microcontroller whenever
passage of a coin is detected. These signals may be used for various purposes
such as
verifying that a coin deflected by the door 62 is delivered to a coin tube,
verifying that the
flapper 1732 is in the correct position, and detecting coin tube blockages
such as may result
from backup of coins from an over-filled coin bin. Thus, the sensor 1738a,
1738b at the end
of each tube provides data used for performing two or more functions, such as
verifying
accepted-coin delivery, verifying flapper placement, and verifying and
detecting coin bin
overfill.
As best seen in Figs. 27A and 278, the sensor 58 is preferably directly
mounted on the
sensor PCB 2512 and communicates, electrically, therewith via a header 2702
with leads
2704 soldered onto the board 2512. Providing the sensor and the sensor board
as a single
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CA 02426411 2003-05-07
integrated unit reduces manufacturing costs and eliminates cabling and
associated signal
noise. The sensor 58 is made of a core 2802 (Figs. 28A, 28B) with a low-
frequency 2804 and
high frequency 2806 windings on the core. Polarity of the windings should be
observed so
that they are properly synchronized. Providing a winding in a reverse
direction can cause
signal cancellation.
The core 2802, in the depicted embodiment, is generally U-shaped with a lower
annular, semicircular, rectangular cross-sectioned portion 2808 and an upper
portion defining
two spaced-apart legs 2812a, 2812b. The core 2802, in the depicted embodiment,
has a
thickness 2814 of less than about 0.5 inches, preferably about 0.2 inches
(about 5 mm), a
1o height 2816 of about 2.09 inches (about 53 mm) and a width 2818 of about
1.44 inches
(about 3.65 cm).
Because the sensor 58 is preferably relatively thin, 2814, the magnetic field
is
relatively tightly focused in the longitudinal (stream wise) direction. As a
result, the coin or
other object must be relatively close to the sensor before the coin will have
significant effect
on sensor output. For this reason, it is possible to provide relatively close
spacing of coins
without substantial risk of undesirable influence of a leading or following
coin on sensor
output.
The facing surfaces 2822a, b of the legs 2812a, bare, in the depicted
embodiment,
substantially parallel and planar and are spaced apart a distance 2824 of
about 0.3 inches
(about 8 mm). The interior facing surfaces 2822a, b have a height at least
equal to the width
of the coin rail 2826, such as about 1.3 inches (about 33 mm). With the sensor
positioned as
depicted in Fig. 21 in the operating configuration, the upper leg 2812a of the
core is spaced
from the lower leg 2812b of the core (see Fig. 23D) by the inter-face gap 2824
to define a
space 2304 for coin passage through the inter-leg gap. The core 2802 may be
viewed as
having the shape of a gapped torroid with extended legs 2812a, 2812b with
parallel faces
2822a, b. In one embodiment, the legs 2812a, b are substantially parallel. In
another
embodiment, the legs 2812a, b are slightly inclined with respect to one
another to define a
tapered gap. Without wishing to be bound by any theory, it is believed that
extended faces
which are inclined to define a gap which slightly tapers vertically downward
yields somewhat
greater sensitivity near the rail (where the majority of the coins or other
items will be located)
but is relatively insensitive to the vertical 2828 or horizontal 2832 position
of coins therein
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CA 02426411 2003-05-07
(so as to provide useful data regardless of moderate coin bounce and/or
wobble) as a coin
passes through the gap 2824. In the depicted embodiment, the faces 2822a,b
extend across
the entire path width, to sense all metallic objects that move along the path
in the region of
the sensor.
It is believed that providing a core with a larger gap (i.e. with more air
volume) is
partially responsible for decreasing the sensitivity to coin misalignments but
tends to result in
a somewhat lower magnetic sensitivity and an increase in cross-talk. In one
embodiment, the
sensor can provide reliable sensor output despite a vertical displacement
("bounce") of about
0.1 inch (about 2.5 mm) or more, and a sideways (away from the stringers)
displacement or
"wobble" of up to 0.015 inches (about 0.4 mm).
In the depicted embodiment the low frequency winding 2804 is positioned at the
bottom of the semicircular portion 2808 and the high frequency winding is
positioned on each
leg 2806a, b of the semicircular portion. In one embodiment the low frequency
winding is
configured to have an inductance (in the driving and detection circuitry
described below) of
about 4.0 millihenrys and the high frequency winding 2806a, b to have an
inductance of
about 40 microhenrys. These inductance values are measured in the low
frequency winding
with the high frequency winding open and measured in the high frequency
winding with the
low frequency winding shorted together. The signals on the windings are
provided to printed
circuit board via leads 2704.
Fig. 29 depicts the major functional components of the sensor PCB 2512. In
general,
the sensor or transducer 58 provides a portion of a phase locked loop which is
maintained at a
substantially constant frequency. Thus, the low frequency coil leads are
provided to a low
frequency PLL 2902a and the high frequency leads are provided to high
frequency sensor
PLL 2902b.
Fig. 40 provides an overview of a typical transaction. The transaction begins
when a
user presses a "go" or start button 4012. In response, the system opens the
gate, and begins
the trommel and coin pickup assembly disk motors 4014. As coins begin passing
through the
system, a sensor (not shown) is used to determine if the hopper is in an
overfill condition, in
which case the gate is closed 4018. The system is continuously monitored for
current peaks
in the motors 4022 e.g. using current sensors 21,4121 (Fig. 41) so that
corrective action such
as reversing either or both of the motors for dejamming purposes 4024 can be
implemented.
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CA 02426411 2003-05-07
During normal counting operations, the system will sense that coins are
streaming
past the sensor 4026. The system is able to determine 4028 whether coins are
being sent to
the reject chute or the coin trolley. In the latter case, the system proceeds
normally if the
sensor in the coin tube outputs an intermittent or flickering signal. However,
if the coin tube
sensor is stuck on or off, indicating a jam upstream or downstream (such as an
overfilled bin),
operations are suspended 4036.
In one embodiment, the flow of coins through the system is managed and/or
balanced.
As shown in Fig. 41, coin flow can be managed by, e.g., controlling any or all
of the state of
the gate 17, state or speed of the trommel motor 19 and/or state or speed of
the coin pickup
1o assembly motor 2032 e.g. to optimize or otherwise control the amount of
coins residing in the
trommel and/or coin pickup assembly. For example, if a sensor 1754 indicates
that the coin
pickup assembly 54 has become full, the microcontroller 3202 can turn off the
trommel to
stop feeding the coin pickup assembly. In one embodiment, a sensor 4112,
coupled to or
adjacent the trommel 52, senses the amount (and/or type) of debris falling out
of the trommel
during a particular transaction or time period and, in response, the
microcontroller 3202
causes the coin pickup assembly motor 2032 to run in a different speed and/or
movement
pattern (e.g. to accommodate a particularly dirty batch of coins), possibly at
the expense of a
reduction in throughput.
When the coin sensor 58 (and associated circuitry and software) are used to
measure
or calculate coin speed, this information may be used not only to control the
deflector door 62
as described herein, but to output an indication of a need for maintenance.
For example as
coin speeds decrease, a message (or series of messages) to that effect may be
sent to the host
computer 46 so that it can request preventive maintenance, potentially thereby
avoiding a jam
that might halt a transaction.
Once the system senses that coins are no longer streaming past the sensor, if
desired a
sensor may be used to determine whether coins are present e.g. near the bottom
of the hopper
4042. If coins are still present, the motors continue operating 4044 until
coins are no longer
detected near the bottom of the hopper. Once no more coins are detected near
the bottom of
the hopper 4046, the system determines that the transaction is complete. The
system will
then activate the coin rake, and, if coins are sensed to move past the coin
sensor 58 or into the
hopper, the counting cycle is preferably repeated. Otherwise, the transaction
will be
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CA 02426411 2003-05-07
considered finished 4028, and the system will cycle the trap door and output
e.g. a voucher of
a type which may be exchanged for goods, services or cash.
The coin sensor phase locked loop (PLL), which includes the sensor or
transducer 58,
maintains a constant frequency and responds to the presence of a coin in the
gap 2824 by a
change in the oscillator signal amplitude and a change in the PLL error
voltage. The phase
locked loop shown in the depicted embodiment requires no adjustments and
typically settles
in about 200 microseconds. The system is self-starting and begins oscillating
and locks phase
automatically. The winding signals (2 each for high frequency and low
frequency channels)
are conditioned 2904 as described below and sent to an analog-to--digital
(A/D) converter
2906. The A/D converter samples and digitizes the analog signals and passes
the information
to the microcontroller 3202 (Fig. 32) on the Control Printed Circuit Board
Assembly (PCBA)
(described below) for further manipulation to identify coins.
As a coin passes through the transducer 58, the amplitude of the PLL error
voltage
2909 a,b (sometimes referred to herein as a "D" signal) and the amplitude of
the PLL
sinusoidal oscillator signal (sometimes referred to as a "Q" signal) decrease.
The PLL error
voltage is filtered and conditioned for conversion to digital data. The
oscillator signal is
filtered, demodulated, then conditioned for conversion to digital data. Since
these signals are
generated by two PLL circuits (high and low frequency), four signals result as
the "signature"
for identifying coins. Figure 30 shows a four channel oscilloscope plot of the
change in the
four signals (LF-D 3002, LF-Q 3004, HF-D 3006, and HF-Q 3008) as a coin passes
the
sensor. Information about the coin is represented in the shape, timing and
amplitude of the
signal changes in the four signals. The Control PCBA, which receives a
digitized data
representation of these signals, performs a discrimination algorithm to
categorize a coin and
determine its speed through the transducer, as described below.
The coin sensor phase locked loop, according to one embodiment, consists of a
voltage controlled oscillator, a phase comparator, amplifier/filter for the
phase comparator
output, and a reference clock. The two PLL's operate at 200 KHz and 2.0 MHZ,
with their
reference clocks synchronized. The phase relationship between the two clock
signals 3101 a,
b is maintained by using a divided-down clock rather than two independent
clock sources
3102. The 2 MHZ clock output 3101a is also used as the master clock for the
A/D converter
2906.
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CA 02426411 2003-05-07
As a coin passes through the transducer's slot, there is a change in the
magnetic
circuit's reluctance: This is seen by circuitry as a decrease in the
inductance value and results
in a corresponding decrease in the amplitude of the PLL error voltage,
providing a first coin-
identifying factor. The passing coin also causes a decrease in the amplitude
of the sinusoidal
oscillator waveform, depending on its composition, e.g. due to an eddy current
loss, and this
is measured to provide a second coin-identifying factor.
The topology of the oscillators 2902a, b relies on a 180 degree phase shift
for
feedback to its drive circuitry and is classified as a Colpitts oscillator.
The Colpitts oscillator
is a symmetric topology and allows the oscillator to be isolated from ground.
Drive for the
oscillator is provided by a high speed comparator 3104a, b. The comparator has
a fast
propagation to minimize distortion due to phase delay, low input current to
minimize loss,
and remains stable while operating in its linear region. In the depicted
embodiment, the plus
and minus terminals of the inductors go directly to a high-speed comparator
which autobiases
the comparator so that signals convert quickly and are less susceptible to
oscillation and so
that there is no need to bias the comparator to a central voltage level. By
tying the plus and
minus terminals of the inductor to the plus and minus terminals of the
comparator, the
crossing of the terminals' voltage at any arbitrary point in the voltage
spectrum will cause a
switch in the comparator output voltage so that it is autobiasing. This
achieves a more nearly
even (50%) duty cycle.
The output of the comparator drives the oscillator through resistors 3106a, b.
The
amplitude of the oscillating signal varies and is correlated to the change in
"Q" of the tuned
circuit. Without wishing to be bound by any theory, this change is believed to
be due to
change in eddy current when a coin passes through the transducer gap.
Resistors 3108 a, b, c,
d work with the input capacitance of the comparator 3104a, b to provide
filtering of unwanted
high frequency signal components.
Voltage control of the oscillator frequency is provided by way of the
varactors 3112a,
b, c, d, which act as voltage controlled capacitors (or tuning diodes). These
varactors change
the capacitive components of the oscillator. Use of two varactors maintains
balanced
capacitance on each leg of windings 2804,2806. As the reverse diode voltage
increases,
capacitance decreases. Thus by changing the Voltage Controlled Oscillator
(VCO) input
voltage in accordance with the change in inductance due to the presence of a
coin, the
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CA 02426411 2003-05-07
frequency of oscillation can be maintained. This VCO input voltage is the
signal used to
indicate change of inductance in this circuit.
The phase/frequency detector 3114a, b performs certain control functions in
this
circuit. It compares the output frequency of the comparator 3106a, b to a
synchronized
reference clock signal and has an output that varies as the two signals
diverge. The output
stage of the device amplifies and filters this phase comparator output signal.
This amplified
and filtered output provides the VCO control signal used to indicate change of
inductance in
this circuit.
In addition, the depicted device has an output 3116a, b which, when
appropriately
1o conditioned, can be used to determine whether the PLL is "in lock". In one
embodiment, a
lock-fail signal is sent to the microprocessor on the Control PCBA as an error
indication, and
an LED is provided to indicate when both high and low frequency PLL are in a
locked state.
Because the sensor 58 receives excitation at two frequencies through two coils
wrapped on the same ferrite core, there is a potential for the coupling of
signals which may
result in undesired amplitude modulation on the individual signals that are
being monitored.
Filters 2912a, b remove the undesired spectral component while maintaining the
desired
signal, prior to amplitude measurement. In this way, the measured amplitude of
each signal
is not influenced by an independent change in the amplitude of the other
oscillator circuit
signals.
The filtered output signals are level-shifted to center them at 3.0 VDC in
order to
control the measurement of the signal amplitude by downstream circuitry.
In the depicted embodiment, the active highpass and lowpass filters are
implemented
as Sallen-Key Butterworth two-pole filter circuits 2916a, b. DC offset
adjustment of the
output signals is accomplished by using a buffered voltage divider as a
reference. Input
buffers 2914a, b are provided to minimize losses of the oscillator circuit by
maintaining a
high input impedance to the filter stage.
The lowpass filter 2916a is designed to provide more than 20dB of attenuation
at 2
MHZ while maintaining integrity of the 200 KHz signal, with less that 0.1 dB
of loss at that
frequency. The cutoff frequency is 530 KHz. Highpass filtering of the output
from the
lowpass filter is provided 2918a with a cutoff frequency of 20 KHz. Tying to a
DC reference
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CA 02426411 2003-05-07
2922a provides an adjusted output that centers the 200 KHz signal at 3.0 VDC.
This output
offset adjustment is desired for subsequent amplitude measurement.
The highpass filter 2916b is designed to provide more than 20dB of attenuation
at 200
KHz while maintaining integrity of the 200 MHZ signal, with less than 0.1 dB
of loss at that
frequency. The cutoff frequency is 750 KHz.
Amplitude measurement of the sinusoidal oscillator waveform is accomplished by
demodulating the signal with a negative peak detecting circuit, and measuring
the difference
between this value and the DC reference voltage at which the sinusoidal signal
is centered.
This comparison measurement is then scaled to utilize a significant portion of
the A/D
lo converter's input range. The input to the circuit is a filtered sinusoidal
signal centered at a
known DC reference voltage output of the highpass or lowpass active filter.
The input signal is demodulated by a closed-loop diode peak detector circuit.
The
time constant of the network, e.g. 33 cosec, is long compared to the period of
the sinusoidal
input, but short when compared to the time elapsed as a coin passes through
the sensor. This
relationship allows the peak detector to react quickly to a change in
amplitude caused by a
coin event. The circuit is implemented as a negative peak detector rather than
a positive peak
detector because the comparator is more predictable in its ability to drive
the signal to ground
than to drive it high. Comparators 3126a, b, such as model LT1016CS8,
available from
Linear Technology, provide a high slew rate and maintain stability while in
the linear region.
The analog closed-loop peak detector avoids the potential phase error problems
that filter-
stage phase lag and dynamic PLL phase shifts might create for a sample-and-
hold
implementation, and eliminates the need for a sampling clock.
The negative peak detector output is compared to the DC reference voltage,
then
scaled and filtered, by using an op amp 3124a, b implemented as a difference
amplifier. The
difference amp is configured to subtract the negative peak from the DC
reference and
multiply the difference by a scaling factor. In one embodiment, for the low
frequency
channel, the scaling factor is 4.02, and the high frequency channel scales the
output by 5.11.
The output of the difference amplifier has a lowpass filter on the feedback
with a corner
frequency at approximately 600 Hz. In the depicted embodiment, there is a
snubber at the
output to filter high frequency transients caused by switching in the A/D
converter.
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CA 02426411 2003-05-07
The error voltage measurement, scaling, and filtering circuit 3128a, b is
designed to
subtract 2.5 VDC from the PLL error voltage and amplify the resulting
difference by a factor
of two. The PLL error voltage input signal will be in the 2.5-4.5 VDC range,
and in order to
maximize the use of the A/D converter's input range, the offset voltage is
subtracted and the
signal is amplified.
The input signal is pre-filtered with a lowpass corner frequency of 477 Hz,
and the
output is filtered in the feedback loop, with a cut-off frequency of 2.3 KHz.
A snubber at the
output filters high frequency transients caused by switching in the A/D
converter.
In an interface circuit, 2922 data and control signals are pulled up and pass
through
1o series termination resistors. In addition, the data signals DATA-DATA15 are
buffered by bi-
directional registers. These bi-directional buffers isolate the A/D converter
from direct
connection to the data bus and associated interconnect cabling.
The A/D converter 2906 is a single supply, 8-channel, 12-bit sampling
converter
(such as model AD7859AP available from Analog Devices). The A/D transactions
are
directly controlled by the microprocessor on the Control PCBA.
An overview of control provided for various hardware components is depicted in
Fig.
32. In Fig. 32, the control hardware is generally divided into the coin sensor
hardware 3204
and the coin transport hardware 3206. A number of aspects of hardware 3204,
3206 are
controlled via a microcontroller 3202 which may be any of a number of
microcontrollers. In
one embodiment, AM186ES, available from Advanced Micro Devices, is provided.
The microcontroller 3202 communicates with and is, to some degree, controlled
by,
the host computer 46. The host computer 46 can be any of 'a number of
computers. In one
embodiment, computer 46 is a computer employing an Intel 486 or Pentium
processor or
equivalent. The host computer 46 and microcontroller 3202 communicate over
serial line
3208 via respective serial ports 3212,3214. The microcontroller 3202, in the
depicted
embodiment, has a second serial port 3216 which may be used for purposes such
as
debugging, field service 3218 and the like.
During normal operation, programming and data for the microcontroller are
stored in
memory which may include normal random access memory (RAM) 3222, non-volatile
random access memory such as flash memory, static memory and the like 3224,
and read-
only memory 3226 which may include programmable and/or electronically erasable
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CA 02426411 2003-05-07
programmable read-only memory (EEPROM). In one embodiment, microprocessor
firmware
can be downloaded from a remote location via the host computer.
Applications software 3228 for controlling operation of the host computer 46
may be
stored in, e.g., hard disk memory, nonvolatile RAM memory and the like.
Although a number of items are described as being implemented in software, in
general it is also possible to provide a hardware implementation such as by
using hard wired
control logic and/or an application specific integrated circuit (ASIC).
An input/output (1/0) interface on the microcontroller 3232 facilitates
communication
such as bus communication, direct I/O, interrupt requests and/or direct memory
access
(DMA) requests. Since, as described more thoroughly below, DMA is used for
much of the
sensor communications, the coin sensor circuitry includes DMA logic circuitry
3234 as well
as circuitry for status and control signals 3236. Although, in the described
embodiment, only
a single sensor is provided for coin sensing, it is possible to configure an
operable device
having additional sensors 3238.
In addition to the motors 2502, 2032, solenoids 2014, 1734, 2306 and sensors
1738,
1754 described above in connection with coin transport, controlling latches,
gates and drivers
of a type that will be understood by those of skill in the art,, after
understanding the present
invention, are provided 3242.
A method for deriving, from the four sensor signals (Fig. 30) a set of values
or a
"signature" indicative of a coin which has passed the sensor, is described in
connection with
the graphs of Fig. 33 which show a hypothetical example of the four signals
LFD 3302, LFQ
3304, HFD 3306 and HFQ 3308 during a period of time in which a coin passes
through the
arms of the sensor. Units of Fig. 33 are arbitrary since Fig. 33 is used to
illustrate the
principles behind this embodiment. A baseline value 3312, 3314, 3316, 3318 is
associated
with each of the sensor signals, representing a value equal to the average or
mean value for
that signal when no coins are adjacent the sensor. Although, in the depicted
embodiment, the
LFD signal is used to define a window of time 3322 during which the minimum
values for
each of the four signals 3302, 3304, 3306, 3308 will be determined and other
threshold-
crossing events, (at least in part because this signal typically has the
sharpest peak), it would
be possible to use other signals to define any or all of the various crossing
events, or it may
be possible to define the window separately for each signal.
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CA 02426411 2003-05-07
In the depicted embodiment, the base line value 3312 associated with the LFD
signal
3302 is used to define a descent threshold 3324 (equal to the LFD baseline
3312 minus a
predefined descent offset 3326, and a predefined gap threshold 3328 equal to
the LFD
baseline 3312 minus a gap offset 3332).
In one embodiment, the system will remain in an idle loop 3402 (Fig. 34) until
the
system is placed in a ready status (as described below) 3404. Once the system
is in ready
status, it is ready to respond to passage of a coin past the sensor.
In the depicted embodiment, the beginning of a coin passage past the sensor is
signaled by the LFD signal 3302 becoming less 4212 than the descent threshold
3324 (3406)
1o which, in the embodiment of Fig. 33, occurs at time tl 3336. When this
event occurs 3338, a
number of values are initialized or stored 3408. The status is set to a value
indicating that the
window 3322 is open 4214. Both the "peak" time value and the "lead" time value
are set
equal to the clock value, i.e., equal to tI 3336. Four variables LFDMIN 3342,
LFQMIN 3344, HFDMIN 3346 and HFQMIN 3348, are used to hold a value indicating
the
minimum signal values, for each of the signals 3302, 3304, 3306, 3308, thus-
far achieved
during the window 3322 and thus are initialized at the Tl values for each of
the variables
3302, 3304, 3306, 3308. In the illustration of Fig. 33, the running minimum
values 3342,
3344, 3346, 3348 are depicted as dotted lines, slightly offset vertically
downward for clarity.
During the time that the window is open 3322, the minimum-holding variables
LFDMIN, LFQMIN, HFDMIN and HFQMIN will be updated, as needed, to reflect the
minimum value thus-far achieved. In the depicted embodiment, the four values
are updated
serially and cyclically, once every clock signal. Updating of values can be
distributed in a
different fashion if it is desired, for example, to provide greater time
resolution for some
variables than for others. It is believed that, by over sampling specific
channels, recognition
and accuracy can be improved. As the LFD value is being tested and, if
necessary, updated, a
value for an ascent threshold 3336 (which will be used to define the end of
the window 3322,
as described below) is calculated or updated 3414. The value for the ascent
threshold 3336 is
calculated or updated as a value equal to the current value for LFDMIN 3342
plus a
predefined ascent hysteresis 3352.
Whenever the LFDMIN value 3342 must be updated (i.e., when the value of LFD
descends below the previously-stored minimum value 3412), the "peak" time
value is also
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CA 02426411 2003-05-07
updated by being made equal to the current clock value. In this way, at the
end 4226 of the
window 3322, the "peak" variable will hold a value indicating the time at
which LFD 3302
reached its minimum value within the window 3322.
As a coin passes through the arms of a sensor, the four signal values 3302,
3304,
3306, 3308 will, in general, reach a minimum value and then begin once more to
ascend
toward the baseline value 3312, 3314, 3316, 3318. In the depicted embodiment,
the window
3322 is declared "closed"` when the LFD value 3302 raises to a point that it
equals the current
value for the ascent value threshold 3336. In the illustration of Fig. 33,
this event 3354
occurs at time T3 3356. Upon detection 3418 of this event, the current value
for the clock
(i.e., the value indicating time T3) is stored in the 'trail" variable. Thus,
at this point, three
times have been stored in three variables: "lead" holds a value indicating
time T1, i.e., the
time at which the window was opened; "peak" holds a value indicating time T2,
i.e., the
minimum value for variable LFD 3302; and variable "trail" holds a value
indicating time T3,
i.e., the time when the window 3322 was closed.
The other portion of the signature for the coin which was just detected (in
addition to
the three time variables) are values indicating the minimum achieved, within
the window
3332, for each of the variables 3302, 3304, 3306, 3308. These values are
calculated 3422 by
subtracting the minimum values at time T3 3342, 3344, 3346, 3348 from the
respective
baseline values 3312, 3314, 3316, 3318 to yield four difference or delta
values, ALFD 3362,
ALFQ 3364, AHFD 3366 and AHFQ 3368. Providing output which is relative to the
baseline
value for each signal is useful in avoiding sensitivity to temperature
changes.
Although, at time t3 3356, all the values required for the coin signature have
been
obtained, in the depicted embodiment, the system is not yet placed in a
"ready" state. This is
because it is desired to assure that there is at least a minimum gap between
the coin which
was just detected and any following coin. It is also desirable to maintain at
least a minimum
distance or gap from any preceding coin. In general, it is believed useful to
provide at least
some spacing between coins for accurate sensor reading, since coins which are
touching can
result in eddy current passing between coins. Maintaining a minimum gap as
coins move
toward the door 62 is useful in making sure that door 62 will strike the coin
at the desired
time and location. Striking too soon or too late may result in deflecting an
accepted coin
other than into the acceptance bin, degrading system accuracy.
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CA 02426411 2003-05-07
Information gathered by the sensor 58 may also be used in connection with
assuring
the existence of a preferred minimum gap between coins. In this way, if coins
are too closely
spaced, one or more coins which might otherwise be an accepted coin, will not
be deflected
(and will not be "counted" as an accepted coin). Similarly, in one embodiment,
a coin having
an acceleration less than a threshold (such as less than half a maximum
acceleration) will not
be accepted.
Accordingly, in order to assure an adequate leading gap, the system is not
placed in a
"ready" state until the LFD signal 3302 has reached a value equal to the gap
threshold 3328.
After the system verifies 3424 that this event 3372 has occurred, the status
is set equal to
"ready" 3326 and the system returns to an idle state 3401 to await passage of
the next coin.
To provide for a minimum preferred trailing gap, in one embodiment, the
software
monitors the LFD signal 3302 for a short time after the ascending hysteresis
criterion has
been satisfied 4236. If the signal has moved sufficiently back towards the
baseline 3312
(measured either with respect to the baseline or with respect to the peak)
after a
predetermined time period, then an adequate trailing gap exists and the door,
if the coin is an
accepted coin, will be actuated 4244. If the trailing gap is not achieved, the
actuation pulse is
canceled 4244, and normally the coin will be returned to the user. In all
cases, software
thresholds are preferably calibrated using the smallest coins (e.g., a U.S.
dime in the case of a
U.S. coin mix).
Because the occurrence of events such as the crossing of thresholds 3338,
3354, 3372
are only tested at discrete time intervals 3411 a, 341 lb, 3411c, 3411d, in
most cases the event
will not be detected until some time after it has occurred. For example, it
may happen that,
with regard to the ascent-crossing event 3354, the previous event-test at time
T4 3374 occurs
before the crossing event 3354 and the next event-test occurs at time T5, a
period of time
3378 after the crossing event 3354. Accordingly, in one embodiment, once a
test determines
that a crossing event has occurred, interpolation such as linear
interpolation, spline-fit
interpolation or the like, is used to provide a more accurate estimate of the
actual time of the
event 3354.
As noted above, by time t3 3356, all the values required for the coin
signature have
been obtained. Also, by time t3, the information which can be used for
calculating the time at
which the door 62 should be activated (assuming the coin is identified as an
accepted coin) is
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CA 02426411 2003-05-07
available. Because the distance from the sensor to the door is constant and
known, the
amount of time required for a coin to travel to the preferred position with
respect to the door
can be calculated exactly if the acceleration of the coin along the rail is
known (and constant)
and a velocity, such as the velocity at the sensor is known. According to one
method,
acceleration is calculated by comparing the velocity of the coin as it moves
past the sensor 58
with the velocity of the coin as it passes over the "knee" in the transition
region 2121C. In
one embodiment, the initial "knee" velocity is assumed to be a single value
for all coins, in
one case, 0.5 meters/second. Knowing the velocity at two locations (the knee
2121C and the
sensor location 58) and knowing the distance from the knee 2121C to the sensor
location 58,
lo the acceleration experienced by the coin can be calculated. Based on this
calculated
acceleration, it is then possible to calculate how long it will be, continuing
at that
acceleration, before the coin is positioned at the preferred location over the
actuator. This
system essentially operates on a principle of assuming an initial velocity and
using
measurements of the sensor to ultimately calculate how friction (or other
factors such as
surface tension) affects the acceleration being experienced by each coin.
Another approach
might be used in which an effective friction was assumed as a constant value
and the data
gathered at the sensor was used to calculate the initial ("knee") velocity.
In any case, the calculation of the time when the coin will reach the
preferred position
can be expected to have some amount of error (i.e., difference between
calculated position
and actual position at the door activation time). The error can arise from a
number of factors
including departures from the assumption regarding the knee velocity, non-
constant values
for friction along the rail, and the like. In one embodiment it has been found
that, using the
described procedure, and for the depicted and described design, the worst-case
error occurs
with the smallest coin (e.g., amount 17.5 mm in diameter) and amounts to
approximately 6
mm in either direction. It is believed that, in at least some environments, an
error window of
6 mm is tolerable (i.e., results in a relatively low rate of misdirecting
coins or other objects).
In order to implement this procedure, data obtained at the sensor 58 is used
to
calculate a velocity. According to one scheme, time Tl 3336 is taken as the
time when the
coin first enters the sensor and time tt (the "peak" time) is taken as the
time when the coin is
centered on the sensor, and thus has traveled a distance approximately equal
to a coin radius.
Because, once the coin has been recognized (e.g. as described below in
connection with Figs.
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CA 02426411 2003-05-07
36 and 37), the radius of the coin is known (e.g. using a look-up table), it
is possible to
calculate velocity as radius divided by the difference (t2 -t1).
The procedure illustrated in Figs. 33 and 34 is an example of one embodiment
of a
detection process 3502. As seen in Fig. 35, a number of processes, in addition
to detection,
should be performed between the time data is obtained by the sensor 58 and the
time a coin
reaches the door 62. In general, processes can be considered as being either
recognition
processes 3504 relating to identifying and locating objects which pass the
sensor, and
disposition processes 3506, relating to sending coins to desired destinations.
Once the
detection process has examined the stream of sensor readings and has generated
signatures
corresponding to the coin (or other object) passing the sensor, the signatures
are passed 4228
to a categorization process 3508. This process examines the signatures
received from the
detection process 3502 and determines, if possible, what coin or object has
passed the sensor.
Referring to Fig. 32, the recognition and disposition processes 3504, 3506 are
preferably
performed by the microcontroller 3202.
Fig. 36 provides an illustration of one embodiment of a categorization
process. As
shown in Fig. 36, in one embodiment a calibration mode may be provided in
which a
plurality of known types of coins are placed in the machine and these coins
are used to define
maximum and minimum LFD, LFQ, HFD and I IFQ values for that particular
category or
denomination of coin. In one embodiment, timing parameters are also
established and stored
during the calibration process. According to the embodiment of Fig. 36, if the
system is
undergoing calibration 3602, the system does not attempt to recognize or
categorize the coins
and, by convention, the coins used for calibration are categorized as
"unrecognized" 3604.
As illustrated in Fig. 37, in one embodiment, a coin signature 3702 is used to
categorize an object by performing a comparison for each of a number of
different potential
categories, starting with the first category 3606 and stepping to each next
category 3608 until
a match is found 3612 or all categories are exhausted 3614 without finding a
match 3616, in
which case the coin is categorized 4220 as unrecognized 3604. During each test
for a match
3618, each of the four signal peaks 3362, 3364, 3366, 3368 is compared,
(successively for
each category 3704a, 3704b, 3704n) with minimum and maximum ("floor" and
"ceiling")
values defining a "window" for each signature component 3712a, 3712b, 3714a,
b, 3716a, b,
3718a, b. A match is declared 3612 for a given category only if all four
components of the
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CA 02426411 2003-05-07
signature 3362, 3364, 3366, and 3368 fall within the corresponding window for
a particular
category 3704a, b, c, n.
In the embodiment of Fig. 36, the system may be configured to end the
categorization
process 3622 whenever the first category 3624 resulting in a match has been
found, or to
continue 3626 until all n categories have been tested. In normal operation,
the first mode
3624 will typically be used. It is believed the latter mode will be useful
principally for
research and development purposes.
The results of the categorization 3508 are stored in a category buffer 3512
and are
provided to the relegator process 3514. The difference between categorization
and relegation
relates, in part, to the difference between a coin category and a coin
denomination. Not all
coins of a given denomination will have similar structure, and thus two coins
of the same
denomination may have substantially different signatures. For example, pennies
minted
before 1982 have a structure (copper core) substantially different from that
of pennies minted
after that date (zinc core). Some previous devices have attempted to define a
coin
discrimination based on coin denomination, which would thus require a device
which
recognizes two physically different types of penny as a single category.
According to one embodiment, coins or other objects are discriminated not
necessarily on the basis of denomination but on the basis of coin categories
(in which a single
denomination may have two or more categories). Thus, according to one
embodiment,
pennies minted before 1982 and pennies minted after 1982 belong to two
different coin
categories 3704. This use of categories, based on physical characteristics of
coins (or other
objects), rather than attempting to define on the basis of denominations, is
advantageous
since it is believed that this approach leads to better discrimination
accuracy. In particular,
by defining separate categories e.g. for pre-1982 and post-1982 pennies, it
becomes easier to
discriminate all pennies from other objects, whereas if an attempt was made to
define a single
category embracing both types of pennies, it is believed that the recognition
windows or
thresholds would have to be so broadly defined that there would be a
substantial risk of mis-
discrimination. By providing a system in which coin categories rather than
coin
denominations are recognized, coin destinations may be easily configured and
changed.
Furthermore, in addition to improving discrimination accuracy, the present
invention
provides an opportunity to count coins and sort coins or other objects on a
basis other than
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CA 02426411 2003-05-07
denomination. For example, if desired, the device could be configured to place
"real silver"
coins in a separate coin bin so that the machine operator can benefit from
their potentially
greater value.
Once a relegator process 3514 receives information from a category buffer
regarding
the category of a coin (or other object), the relegator outputs a destination
indicator,
corresponding to that coin, to a destination buffer 3516. The data from the
destination buffer
is provided to a director process 3518 whose function is to provide
appropriate control signals
at the appropriate time in order to send the coin to a desired destination,
e.g. to provide
signals causing the deflector door to activate at the proper time if the coin
is destined for an
acceptance bin. In the embodiment of Fig. 25, the director procedure outputs
information
regarding the action to be taken and the time when it is to be taken to a
control schedule
process 3522 which generates a control bit image 3524 provided to
microprocessor output
ports 3526 for transmission to the coin transport hardware 3206.
In one embodiment, the solenoid is controlled in such a manner as to not only
control
the time at which the door is activated 4234,4244 but also the amount of force
to be used
(such as the strength and/or duration of the solenoid activation Volts). In
one embodiment,
the amount of force is varied depending on the mass of the coin, which can be
determined,
e.g., from a look-up table, based on recognition of the coin category.
Preferably, information from the destination buffer 3516 is also provided to a
counter
3528 which retains a tally of at least the number of coins of each
denomination sent to the
coin bins. If desired, a number of counters can be provided so that the system
can keep track
not only of each coin denomination, but of each coin category and/or, which
coin bin the coin
was destined for.
In general, the flow of data depicted in Fig. 35 represents a narrowing
bandwidth in
which a relatively large amount of data is provided from the A/D converter
which is used by
the detector 3502 to output a smaller amount of data (as the coin signature),
ultimately
resulting in a single counter increment 3528. According to one embodiment of
the present
invention, the system is configured to use the most rapid and efficient means
of information
transfer for those information or signal paths which have the greatest volume
or bandwidth
requirements. Accordingly, in one embodiment, a direct memory access (DMA)
procedure is
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CA 02426411 2003-05-07
used in connection with transferring sensor data from the converter 2906 to
the
microcontroller reading buffer 3500.
As depicted in Fig. 38, a two-channel DMA controller (providing channels DMAO
and DMAI) is used 3802. In the depicted embodiment, one of the DMA channels is
used for
uploading the program from one of the serial ports to memory. After this
operation is
completed, both DMA channels are used in implementing the DMA transfer. DMAO
is used
to write controller data 3804 to the A-to-D converter 2906, via a control
register image buffer
3806. This operation selects the analog channel for the next read, starts the
conversion and
sets up the next read for the A-to-D converter output data register. DMAI then
reads the
output data register 3808. DMAO will then write to the controller register
3806 and DMAI
will read the next analog channel and so forth.
In the preferred embodiment, the DMA interface does not limit the ability of
the
software to independently read or write to the A-to-D converter. It is
possible, however, that
writing to the control register of the A-to-D converter in the middle of a DMA
transfer may
cause the wrong channel to be read.
Preferably the DMA process takes advantage of the DMA channels to configure a
multiple word table in memory with the desired A-to-D controller register
data. Preferably
the table length (number of words in the table) is configurable, permitting a
balance to be
struck between reducing microcontroller overhead (by using a longer table),
and reducing
memory requirements (by using a shorter table). The DMA process sets up DMAO
for
writing these words to a fixed I/O address. Next, DMAII is set up for reading
the same
number of words from the same I/O address to a data buffer in memory, DMAI is
preferably
set up to interrupt the processor when all words have been read 3812.
Preferably hardware
DMA decoder logic controls the timing between DMAO and DMA1.
Fig. 39 depicts timing for DMA transfer according to an embodiment of the
present
invention. In this embodiment, a PIO pin will be used to enable or disable the
timer output
3902. If the timer enable signal 3904 is low, the hardware will block the
timer output 3902
and conversions can only be started by setting the start conversion bit in the
control register
of the A-to-D converter 3906. If the timer enable signal 3904 is high, the A/D
conversions
start at the rising edge of the timer output 3902, and write cycles will be
allowed only after
the following edge of the timer output 3902 with read cycles only being
allowed after the
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CA 02426411 2003-05-07
busy signal 3912 goes low while the timer output signal 3902 is high. The
described design
provides great flexibility with relatively small overhead. There is a single
interrupt (DMA
interrupt) event once the buffer is filled with data from the A-to-D converter
are read and put
into memory. Preferably, software can be configured to change the DMA
configuration to
read any or all analog channels, do multiple reads in some channels, read the
channels in any
order and the like. Preferably, the A-to-D converter is directly linked to the
microprocessor
by a 16-bit data bus. The microprocessor is able to read or write to the A-to-
D converter bus
interface port as a single input or output instruction to a fixed I/O address.
Data flow between
the A-to-D converter and the microprocessor is controlled by the busy 3912,
chip select, read
3914 and write 3908 signals. A conversion clock 3902 and clock enable 3904
signals provide
control and flexibility over the A-to-D conversion rate.
Another embodiment of a gapped torroid sensor, and its use, is depicted in
Figs 2A
through 16B. As depicted in Fig. 2A, a sensor, 212 includes a core 214 having
a generally
curved shape and defining a gap 216, having a first width 218. In the depicted
embodiment,
the curved core is a torroidal section. Although "torroidal" includes a locus
defined by
rotating a circle about a non-intersecting coplanar line, as used herein, the
term "torroidal"
generally means a shape which is curved or otherwise non-linear. Examples
include a ring
shape, a U shape, a Y shape or a polygon. In the depicted embodiment both the
major cross
section (of the shape as a whole) and the minor cross section (of the
generating form) have a
circular shape. However, other major and minor cross-sectional shapes can be
used,
including elliptical or oval shapes, partial ellipses, ovals or circles (such
as a semi-circular
shape), polygonal shapes (such as a regular or irregular hexagon/octagon,
etc.), and the like.
The core 214 may be made from a number of materials provided that the material
is
capable of providing a substantial magnetic field in the gap 216. In one
embodiment, the
core 214 consists of, or includes, a ferrite material, such as formed by
fusing ferric oxide with
another material such as a carbonate hydroxide or alkaline metal chloride, a
ceramic ferrite,
and the like. If the core is driven by an alternating current, the material
chosen for the core of
the inductor, should be normal-loss or low-loss at the frequency of
oscillation such that the
"no-coin" Q of the LC circuit is substantially higher than the Q of the LC
circuit with a coin
adjacent the sensor. This ratio determines, in part, the signal-to-noise ratio
for the coin's
conductivity measurement. The lower the losses in the core and the winding,
the greater the
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CA 02426411 2003-05-07
change in eddy current losses, when the coin is placed in or passes by the
gap, and thus the
greater the sensitivity of the device. In the depicted embodiment, a
conductive wire 220 is
wound about a portion of the core 214 so as to form an inductive device.
Although Fig. 2A
depicts a single coil, in some embodiments, two or more coils may be used,
e.g. as described
below. In the depicted embodiment, the coin or other object to be
discriminated is positioned
in the vicinity of the gap (in the depicted embodiment, within the gap 216).
Thus, in the
depicted embodiment the gap width 218 is somewhat larger than the thickness
222 of the
thickest coin to be sensed by the sensor 212, to allow for mis-alignment,
movement,
deformity, or dirtiness of the coin. Preferably, the gap 216 is as small as
possible, consistent
with practical passage of the coin. In one embodiment, the gap is about 4 mm.
Fig. 2B depicts a sensor 212', positioned with respect to a coin conveying
rail 232,
such that, as the coin 224 moves down the rail 234, the rail guides the coin
214 through the
gap 216 of the sensor 212'. Although Fig. 28 depicts the coin 214 traveling in
a vertical (on-
edge) orientation, the device could be configured so that the coin 224 travels
in other
orientations, such as in a lateral (horizontal) configuration or angles
therebetween. One of
the advantages of the present invention is the ability to increase speed of
coin movement
(and thus throughput) since coin discrimination can be performed rapidly. This
feature is
particularly important in the present invention since coins which move very
rapidly down a
coin rail have a tendency to "fly" or move partially and/or momentarily away
from the rail.
The present invention can be configured such that the sensor is relatively
insensitive to such
departures from the expected or nominal coin position. Thus, the present
invention
contributes to the ability to achieve rapid coin movement not only by
providing rapid coin
discrimination but insensitivity to coin "flying." Although Fig. 2B depicts a
configuration in
which the coin 224 moves down the rail 232 in response to gravity, coin
movement can be
achieved by other unpowered or powered means such as a conveyor belt. Although
passage
of the coin through the gap 216 is depicted, in another embodiment the coin
passes across,
but not through the gap (e.g. as depicted with regard to the embodiment of
Fig. 4).
Fig. 3 depicts a second configuration of a sensor, in which the gap 316,
rather than
being formed by opposed faces 242a, 242b, of the core 214 is, instead, formed
between
opposed edges of spaced-apart plates (or "pole pieces") 344a, 344b, which are
coupled to the
core 314. In this configuration, the core 314 is a half-torus. The plates
344a, 344b, may be
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CA 02426411 2003-05-07
coupled to a torroid in a number of fashions, such as by using an adhesive,
cement or glue, a
pressfit, spot welding, or brazing, riveting, screwing, and the like. Although
the embodiment
depicted in Fig. 3 shows the plates 344a, 344b attached to the torroid 314, it
is also possible
for the plates and torroid to be formed integrally. As seen in Fig. 4, the
plates 344a, 344b,
may have half-oval shapes, but a number of other shapes are possible,
including semi-
circular, square, rectangular, polygonal, and the like. In the embodiment of
Figs. 3 and 4, the
field-concentrating effect of ferrite can be used to produce a very localized
field for
interaction with a coin, thus reducing or eliminating the effect of a touching
neighbor coin.
The embodiment of Figs. 3 and 4 can also be configured to be relatively
insensitive to the
1o effects of coin "flying" and thus contribute to the ability to provide
rapid coin movement and
increase coin throughput. Although the percentage of the magnetic field which
is affected by
the presence of a coin will typically be less in the configuration of Figs. 3
and 4, than in the
configuration of Fig. 2, satisfactory results can be obtained if the field
changes are
sufficiently large to yield a consistently high signal-to-noise indication of
coin parameters.
Preferably the gap 316 is sufficiently small to produce the desired magnetic
field intensity in
or adjacent to the coin, in order to expose the coin to an intense field as it
passes by and/or
through the gap 316. In the embodiment of Fig. 4, the length of the gap 402 is
large enough
so that coins with different diameters cover different proportions of the gap.
The embodiment of Fig., 3 and 4 is believed to be particularly useful in
situations in
which it is difficult or impossible to provide access to both faces of a coin
at the same time.
For example, if the coin is being conveyed on one of its faces rather than on
an edge (e.g.,
being conveyed on a conveyor belt or a vacuum belt). Furthermore, in the
embodiment of
Figs. 3 and 4, the gap 316 does not need to be wide enough to accommodate the
thickness of
the coin and can be made quite narrow such that the magnetic field to which
the coin is
exposed is also relatively narrow. This configuration can be useful in
avoiding an adjacent or
"touching" coin situation since, even if coins are touching, the magnetic
field to which the
coins are exposed will be too narrow to substantially influence more than one
coin at a time
(during most of a coin's passage past the sensor).
When an electrical potential or voltage is applied to the coil 220, a magnetic
field is
created in the vicinity of the gap 216, 316 (i.e. created in and near the gap
216, 316). The
interaction of the coin or other object with such a magnetic field (or lack
thereof) yields data
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which provides information about parameters of the coin or object which can be
used for
discrimination, e.g. as described more thoroughly below.
In one embodiment, current in the form of a variable or alternating current
(AC) is
supplied to the coil 220. Although the form of the current may be
substantially sinusoidal as
used herein "AC" is meant to include any variable (non-constant) wave form,
including ramp,
sawtooth, square waves, and complex waves such as wave forms which are the sum
of two or
more sinusoidal waves. Because of the configuration of the sensor, and the
positional
relationship of the coin or object to the gap, the coin can be exposed to a
significant magnetic
field, which can be significantly affected by the presence of the coin. The
sensor can be used
1o to detect these changes in the electromagnetic field, as the coin passes
over or through the
gap, preferably in such as way as to provide data indicative of at least two
different
parameters of the coin or object. In one embodiment, a parameter such as the
size or
diameter of the coin or object is indicated by a change in inductance, due to
the passage of
the coin, and the conductivity of the coin or object is (inversely) related to
the energy loss
(which may be indicated by the quality factor or "Q.")
Figs. 15A and 15B depict an embodiment which provides a capability for
capacitive
sensing, e.g. for detecting or compensating for coin relief arid/or flying. In
the embodiment
of Figs. 15A and 15B, a coin 224 is constrained to move along a substantially
linear coin path
1502 defined by a rail device such as a polystyrene rail 1504. At least a
portion of the coin
path is adjacent a two-layer structure having an upper layer which is
substantially non-
electrically conducting 1506 such as fiberglass and a second layer 1508 which
is substantially
conductive such as copper. The two-layer structure 1506, 1508 can be
conveniently provided
by ordinary circuit board material 1509 such as 1/23 inch thick circuit board
material with the
fiberglass side contacting the coin as depicted. In the depicted embodiment, a
rectangular
window is formed in the copper cladding or layer 1508 to accommodate
rectangular ferrite
plates 1512a, 1512b which are coupled to faces 1514a, 1514b of the ferrite
torroid core 1516.
A conductive structure such as a copper plate or shield 1518 is positioned
within the can 1520
formed between the ferrite plates 1512a, 1512b. The shield is useful for
increasing the flux
interacting with the coin. Without wishing to be bound by any theory, it is
believed that such
a shield 1518 has the effect of forcing the flux to go around the shield and
therefore to bulge
out more into the coin path in the vicinity of tle gap 1520 which is believed
to provide more
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flux interacting with the coin than without the shield (for a better signal-to-
noise ratio). The
shield 1518 can also be used as one side of a capacitive sensor, with the
other side being the
copper backing/ground plane 1508 of the circuit board structure 1509.
Capacitive changes
sensed between the shield 1518 and the ground plane 1508 are believed to be
related to the
relief of the coin adjacent the gap 1520 and the distance to the coin.
In the embodiment of Fig. 5, the output of signal 512 is related to change in
inductance, and thus to coin diameter which is termed "D." The configuration
of Fig. 6
results in the output of a signal 612 which is related to Q and thus to
conductivity, termed, in
Fig. 6, "Q." Although the D signal is not purely proportional to diameter
(being at least
somewhat influenced by the value of Q) and Q is not strictly and linearly
proportional to
conductance (being somewhat influenced by coin diameter) there is a sufficient
relationship
between signal D 512 and coin diameter and between signal Q 612 and
conductance that
these signals, when properly analyzed, can serve as a basis for coin
discrimination. Without
wishing to be bound by any theory, it is believed that the interaction between
Q and D is
substantially predictable and is substantially linear over the range of
interest for a coin-
counting device.
Many methods and/or devices can be used for analyzing the signals 512, 612,
including visual inspection of an oscilloscope trace or graph (e.g. as shown
in Fig. 9),
automatic analysis using a digital or analog circuit and/or a computing device
such as a
microprocessor-based computer and/or using a digital signal processor (DSP).
When it is
desired to use a computer, it is useful to provide signals 512 and 612 (or
modify those
signals) so as to have a voltage range and/or other parameters compatible with
input to a
computer. In one embodiment, signals 512 and 612 will be voltage signals
normally lying
within the range 0 to +5 volts.
In some cases, it is desired to separately obtain information about coin
parameters for
the interior or core portion of the coin and the exterior or skin portion,
particularly in cases
where some or all of the coins to be discriminated may be cladded, plated or
coated coins.
For example, in some cases it may be that the most efficient and reliable way
to discriminate
between two types of coins is to determine the presence or absence of cladding
or plating, or
compare a skin or core parameter with a corresponding skin or core parameter
of a known
coin. In one embodiment, different frequencies are used to probe different
depths in the
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thickness of the coin. This method is effective because, in terms of the
interaction between a
coin and a magnetic field, the frequency of a variable magnetic field defines
a "skin depth,"
which is the effective depth of the portion of the coin or other object which
interacts with the
variable magnetic field. Thus, in this embodiment, a first frequency is
provided which is
relatively low to provide for a larger skin depth, and thus interaction with
the core of the coin
or other object, and a second, higher frequency is provided, high enough to
result in a skin
depth substantially less than the thickness of the coin. In this way, rather
than a single sensor
providing two parameters, the sensor is able to provide four parameters: core
conductivity;
cladding or coating conductivity; core diameter; and cladding or coating
diameter (although it
is anticipated that, in many instances, the core and cladding diameters will
be similar).
Preferably, the low-frequency skin depth is greater than the thickness of the
plating or
lamination, and the high frequency skin depth is less than, or about equal to,
the plating or
lamination thickness (or the range of lamination depths, for the anticipated
coin population).
Thus the frequency which is chosen depends on the characteristics of the coins
or other
objects expected to be input. In one embodiment, the low frequency is between
about 50
KHz and about 500 KHz, preferably about 200 KHz and the high frequency is
between about
0.5 MHZ and about 10 MHZ, preferably about 2 MHZ.
In some situations, it may be necessary to provide a first driving signal
frequency
component in order to achieve a second, different frequency sensor signal
component. In
particular, it is found that if the sensor 212 (Fig. 2) is first driven at the
high frequency using
high frequency coil 242 and then the low frequency signal 220 is added, adding
the low
frequency signal will affect the frequency of the high frequency signal 242.
Thus, the high
frequency driving signal may need to be adjusted to drive at a nominal
frequency which is
different from the desired high frequency of the sensor such that when the low
frequency is
added, the high frequency is perturbed into the desired value by the addition
of the low
frequency.
Multiple frequencies can be provided in a number of ways. In one embodiment, a
single continuous wave form 702 (Fig. 7), which is the sum of two (or more)
sinusoidal or
periodic waveforms having different frequencies 704,706, is provided to the
sensor. As
depicted in Fig. 2C, a sensor 214 is preferably configured with two different
coils to be
driven at two different frequencies. It is believed that, generally, the
presence of a second
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coil can undesirably affect the inductance of the first coil, at the frequency
of operation of the
first coil. Generally, the number of turns of the first coil may be
correspondingly adjusted so
that the first coil has the desired inductance. In the embodiment of Fig. 2C,
the sensor core
214 is wound in a lower portion with a first coil 220 for driving with a low
frequency signal
706 and is wound in a second region by a second coil 242 for driving at a
higher frequency
704. In the depicted embodiment, the high frequency coil 742 has a smaller
number of turns
and uses a larger gauge wire than the first coil 220. In the depicted
embodiment, the high
frequency coil 242 is spaced 242a, 242b from the first coil 220 and is
positioned closer to the
gap 216. Providing some separation 242a, 242b is believed to help reduce the
effect one coil
1o has on the inductance of the other and may somewhat reduce direct coupling
between the low
frequency and high frequency signals.
As can be seen from Fig. 7, the phase relationship of the high frequency
signal 704
and low frequency signal 706 will affect the particular shape of the composite
wave form
702. Signals 702 and 704 represent voltage at the terminals of the high and
low frequency
coils, 220, 242. If the phase relationship is not controlled, or at least
known, output signals
indicating, for example, amplitude and/or Q in the oscillator circuit as the
coin passes the
sensor may be such that it is difficult to determine how much of the change in
amplitude or Q
of the signal results from the passage of the coin and how much is
attributable to the phase
relationship of the two signals 704 and 706 in the particular cycle being
analyzed.
Accordingly, in one embodiment, the phases of the low and high signals 704,
706 are
controlled such that sampling points along the composite signal 702 (described
below) are
taken at the same phase for both the low and high signals 704, 706. A. number
of ways of
assuring the desired phase relationship can be used including generating both
signals 704,
706 from a common reference source (such as a crystal oscillator) and/or using
a phase
locked loop (PLL) to control the phase relationship of the signals 704, 706.
By using a phase
locked loop, the wave shape of the composite signal 702 will be the same
during any cycle
(i.e., during any low frequency cycle), or at least will change only very
slowly and thus it is
possible to determine the sampling points (described below) based on, e.g., a
pre-defined
position or phase within the (low frequency) cycle rather than based on
detecting
characteristics of the wave form 702.
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Figs. 8A - 8D depict circuitry which can be used for driving the sensor of
Fig. 2C and
obtaining signals useful in coin discrimination. The low frequency and high
frequency coils
220, 242, form portions of a low frequency and high frequency phase locked
loop,
respectively 802a, 802b. Details of the clock circuits 808 are shown in Fig.
8D. The details
of the high frequency phase locked loop are depicted in Fig. 8B and, the low
frequency phase
locked loop 802a may be identical to that shown in Fig. 8B except that some
components
may be provided with different values, e.g., as discussed below. The output
from the phase
locked loop is provided to filters, 804, shown in greater detail in Fig. 8C.
The remainder of
the components of Fig. 8A are generally directed to providing reference and/or
sampling
pulses or signals for purposes described more fully below.
The crystal oscillator circuit 806 (Fig. 8D) provides a reference frequency
808 input
to the clock pin of a counter 810 such as a Johnson "divide by 10" counter.
The counter
outputs a high frequency reference signal 812 and various outputs Q0-Q9 define
10 different
phase positions with respect to the reference signal 812. In the depicted
embodiment, two of
these phase position pulses 816a, 816b are provided to the high frequency
phase locked loop
802b for purposes described below. A second counter 810' receives its clock
input from the
reference signal 812 and outputs a low frequency reference signal 812' and
first and second
low frequency sample pulses 816a' 816b' which are used in a fashion analogous
to the use of
the high frequency pulses 816a and 816b described below.
The high frequency phase locked loop circuit 802b, depicted in Fig. 8B,
contains five
main sections. The core oscillator 822 provides a driving signal for the high
frequency coil
242. The positive and negative peak samplers 824 sample peak and trough
voltages of the
coil 242 which are provided to an output circuit 826 for outputting the high
frequency Q
output signal 612. The high frequency reference signal 812 is converted to a
triangle wave
by a triangle wave generator 828. The triangle wave is used, in a fashion
discussed below, by
a sampling phase detector 832 for providing an input to a difference amplifier
834 which
outputs an error signal 512, which is provided to the oscillator 822 (to
maintain the frequency
and phase of the oscillator substantially constant) and provides the high
frequency D output
signal 512.
Low frequency phase locked loop circuit 802a is similar to that depicted in
Fig. 8B
except for the value of certain components which are different in order to
provide appropriate
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low frequency response. In the high frequency circuit of Fig. 8B, an inductor
836 and
capacitor 838 are provided to filter out low frequency, e.g. to avoid duty
frequency cycling
the comparator 842 (which has a low frequency component). This is useful to
avoid driving
low frequency and high frequency in the same oscillator 822. As seen in Fig.
8B, the
inductor and capacitor have values, respectively, of 82 microhenrys and 82
picofarads. The
corresponding components in the low frequency circuit 802A have values,
respectively, of
one microhenry and 0.1 microfarads, respectively (if such a fitter is provided
at all). In high
frequency triangle wave generator, capacitor 844 is shown with a value of 82
picofarads
while the corresponding component in the low frequency circuit 802a has a
value of 0.001
microfarads.
Considering the circuit of Fig. 8B in somewhat greater detail, it is desired
to provide
the oscillator 822 in such a fashion that the frequency remains substantially
constant, despite
changes in inductance of the coil 242 (such as may arise from passage of a
coin past the
sensor). In order to achieve this goal, the oscillator 822 is provided with a
voltage
controllable capacitor (or varactor diode) 844 such that, as the inductance of
the coil 242
changes, the capacitance of the varactor diode 844 is adjusted, using the
error signal 512 to
compensate, so as to maintain the LC resonant frequency substantially
constant. In the
configuration of Fig. 8B, the capacitance determining the resonant frequency
is a function of
both the varactor diode capacitance and the capacitance of fixed capacitor
846. Preferably,
capacitor 846 and varactor die 844 are selected so that the control voltage
512 can use the
greater part of the dynamic range of the varactor diode and yet the control
voltage 512
remains in a preferred range such as 0-5 volts (useful for outputting directly
to a computer).
Op amp 852 is a zero gain buffer amplifier (impedance isolator) whose output
provides one
input to comparator 842 which acts as a hard limiter and has relatively high
gain. The hard-
limited (square wave) output of comparator 842 is provided, across a high
value resistor 844
to drive the coil 242. The high value of the resistance 844 is selected such
that nearly all the
voltage of the 4uare wave is dropped across this resistor and thus the
resulting voltage on the
coil 242 is a function of its Q. In summary, a sine wave oscillation in the LC
circuit is
converted to a constant amplitude square wave signal driving the LC circuit so
that the
amplitude of the oscillations in the LC circuit are directly a measure of the
Q of the circuit.
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In order to obtain a measure of the amplitude of the voltage, it is necessary
to sample
the voltage at a peak and a trough of the signal. In the embodiment of Fig.
8B, first and
second switches 854a, 854b provide samples of the voltage value at times
determined by the
high frequency pulses 816a, 816b. In one embodiment, the timing is determined
empirically
by selecting different outputs 814 from the counter 810. As seen in Fig. 8A,
the [empirically
selected] outputs used for the high frequency circuit may be different from
those used for the
low frequency circuit, e.g., because of differing delays in the two circuits
and the like.
Switches 854 and capacitors 855 form a sample and hold circuit for sampling
peak and
trough voltages and these voltages are provided to differential amplifier 856
whose output
612 is thus proportional to the amplitude of the signal in the LC circuit and,
accordingly is
inversely proportional to Q (and thus related to conductance of the coin).
Because the phase
locked loops for the low and high frequency signals are locked to a common
reference, the
phase relationship between the two frequency components is fixed, and any
interference
between the two frequencies will be common mode (or nearly so), since the wave
form will
stay nearly the same from cycle to cycle, and the common mode component will
be
subtracted out by the differential amplifier 856.
In addition to providing an output 612 which is related to coin conductance;
the same
circuit 802b also provides an output 512 related to coin diameter. In the
embodiment of Fig.
8B, the high frequency diameter signal HFD 512 is a signal which indicates the
magnitude of
the correction that must be applied to varactor diode 844 to correct for
changes in inductance
of the coil 242 as the coin passes the sensor. Fig. 7 illustrates signals
which play a role in
determining whether correction to the varactor diode 844 is needed. If there
has been no
change in the coil inductance 242, the resonant frequency of the oscillator
822 will remain
substantially constant and will have a substantially constant phase
relationship with respect to
the high frequency reference signal 812. Thus, in the absence of the passage
of a coin past
the sensor (or any other disturbance of the inductance of the coil 242) the
square wave output
signal 843 will have a phase which corresponds to the phase of the reference
signal 812 such
that at the time of each edge 712a, 712b, 712c of the oscillator square wave
signal 843, the
reference signal 812 will be in a phase midway between the wave peak and wave
trough.
Any departure from this condition indicates there has been a change in the
resonant frequency
of the oscillator 822 (and consequent phase shift) which needs to be
corrected. In the
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embodiment of Fig. 8B, in order to detect and correct such departures, the
reference signal
812 is converted, via triangle wave generator 828, to a triangle wave 862
having the same
phase as the reference signal 812. This triangle wave 862 is provided to an
analog switch 864
which samples the triangle wave 862 at times determined by pulses generated in
response to
edges of the oscillator square wave signal 843, output over line 866. The
sampled signals are
held by capacitor 868. As can be seen from Fig. 7, if there has been no change
in the
frequency or phase relationship of the oscillator signal 843, at the times of
the square wave
edges 712a, 712b, 712c, the value of the square wave signal 862 will be half
way between the
peak value and the trough value. In the depicted embodiment, the triangle wave
862 is
1o configured to have an amplitude equal to the difference between VCC
(typically 5 volts) and
ground potential. Thus, difference amplifier 834 is configured to compare the
sample values
from the triangle wave 862 with one-half of VCC 872. If the sampled values
from the
triangle wave 862 are half way between ground potential and VCC, the output
512 from
comparator 834 will be zero and thus there will be no error signal-induced
change to the
capacitance of varactor diode 844. However, if the sampled values from the
triangle wave
862 are not halfway between ground potential and VCC, difference amplifier 834
will output
a voltage on line 512 which is sufficient to adjust the capacitance of
varactor diode 844 in an
amount and direction needed to correct the resonant frequency of the
oscillator 822 to
maintain the frequency at the desired substantially constant value. Thus
signal 512 is a
measure of the magnitude of the changes in the effective inductance of the
coil 242, e.g.,
arising from passage of a coin past the sensor. As shown in Fig. 8A, outputs
612, 512 from
the high frequency PLL circuit as well as corresponding outputs 612' 512' from
the low
frequency PLL are provided to filters 804. The depicted filters 804 are low
pass filters
configured for noise rejection. The pass bands for the filters 804 are
preferably selected to
provide desirable signal to noise ratio characteristic for the output signals
882a, 882b, 882a',
882b'. For example, the bandwidth which is provided for the filters 804 may
depend upon the
speed at which coins pass the sensors, and similar factors.
In one embodiment, the output signals 88a, 882b, 882a', 882b' are provided to
a
computer for coin discrimination or other analysis. Before describing examples
of such
analysis, it is believed useful to describe the typical profiles of the output
signals 882a, 882b,
882a', 882b'. Fig. 9 is a graph depicting the output signals, e.g., as they
might appear if the
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output signals were displayed on a properly configured oscilloscope. In the
illustration of
Fig. 9, the values of the high and low frequency Q signals 882a, 882a' and the
high and low
frequency D signals 882b, 882b' have values (depicted on the left of the graph
of Fig. 9) prior
to passage of a coin past the sensor, which change as indicated in Fig. 9 as
the coin moves
toward the sensor, and is adjacent or centered within the gap of the sensor at
time T1,
returning to substantially the original values as the coin moves away from the
sensor at time
T2.
The signals 882a, 882b, 882a', 882b' can be used in a number of fashions to
characterize coins or other objects as described below. The magnitude of
changes 902a,
902a' of the low frequency and high frequency D values as the coin passes the
sensor and the
absolute values 904, 904' of the low and high frequency Q signals 882a', 882a,
respectively,
at the time t1 when the coin or other object is most nearly aligned with the
sensor (as
determined e.g., by the time of the local maximum in the D signals 882b,
882b') are useful in
characterizing coins. Both the low and high frequency Q values are useful for
discrimination.
Laminated coins show significant differences in the Q reading for low vs. high
frequency.
The low and high frequency "D" values are also useful for discrimination. It
has been found
that some of all of these values are, at least for some coin populations,
sufficiently
characteristic of various coin denominations that coins can be discriminated
with high
accuracy.
In one embodiment, values 902a, 902a', 904, 904' are obtained for a large
number of
coins so as to define standard values characteristic of each coin
denomination. Figs. 1 OA and
lOB depict high and low frequency Q and D data for different U.S. coins. The
values for the
data points in Figs. 10A and 10B are in arbitrary units. A number of features
of the data are
apparent from Figs. 10A and 10B. First, it is noted that the Q, D data points
for different
denominations of coins are clustered in the sense that a given Q, D data point
for a coin tends
to be closer to data points for the same denomination coin than for a
different denomination
coin. Second, it is noted that the relative position of the denomination for
the low frequency
data (Fig. l0B) are different from the relative positions for corresponding
denominations in
the high frequency graph Fig. I OA.
One method of using standard reference data of the type depicted in Figs. 10A
and
10B to determine the denomination of an unknown coin is to define Q, D regions
on each of
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the high frequency and low frequency graphs in the vicinity of the data
points. For example,
in Figs. 10A and 10B, regions 1002a-1002e, 1002a'-1002e' are depicted as
rectangular areas
encompassing the data points. According to one embodiment, when low frequency
and high
frequency Q and D data are input to the computer in response to the coin
moving past the
sensor, the high frequency Q, D values for the unknown coin are compared to
each of the
regions 1002a -1002e of the high frequency graph and the low frequency Q, D
data compared
to each of the regions 1002a'-1002e' of the low frequency graph Fig. 10B. If
the unknown
coin lies within the predefined regions corresponding to the same denomination
for each of
the two graphs Fig. IOA Fig. I OB, the coin is indicated as having that
denomination. If the
Q, D data falls outside the regions 1002a-1002e, 1002a'-1002e' on the two
graphs or if the
data point of the unknown coin or object falls inside a region corresponding
to a first
denomination with a high frequency graph but a different denomination with low
frequency
graph, the coin or other object is indicated as not corresponding to any of
the denominations
defined in the graphs of Figs. 1OA and 1OB.
As will be apparent from the above discussion, the error rate that will occur
in regard
to such an analysis will partially depend on the size of the regions 1002a-
1002e, 1002a'-
1002e' which are defined. Regions which are too large will tend to result in
an unacceptably
large number of false positives (i.e., identifying the coin as being a
particular denomination
when it is not) while defining regions which are too small will result in an
unacceptably large
number of false negatives (i.e., failing to identify a legitimate coin
denomination). Thus, the
size and shape of the various regions may be defined or adjusted, e.g.
empirically, to achieve
error rates which are no greater than desired error rates. In one embodiment,
the windows
2002a -2002e, 2002a'-2002e' have a size and shape determined on the basis of a
statistical
analysis of the Q, D values for a standard or sample coin population, such as
being equal to 2
or 3 standard deviations from the mean Q, D values for known coins. The size
and shape of
the regions 1002a-1002e, 1002a'-1002e' may be different from one another,
i.e., different for
different denominations and/or different for the low frequency and high
frequency graphs.
Furthermore, the size and shape of the regions may be adjusted depending on
the anticipated
coin population (e.g., in regions near national borders, regions may need to
be defined so as
to discriminate foreign coins, even at the cost of raising the false negative
error rate whereas
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such adjustment of the size or shape of the regions may not be necessary
locations in the
interior of a country where foreign coins may be relatively rare).
If desired, the computer can be configured to obtain statistics regarding the
Q, D
values of the coins which are discriminated by the device in the field. This
data can be useful
to detect changes, e.g., changes in the coin population over time, or changes
in the average Q,
D values such as may result from aging or wear of the sensors or other
components. Such
information may be used to adjust the software or hardware, perform
maintenance on the
device and the like. In one embodiment, the apparatus in which the coin
discrimination
device is used may be provided with a communication device such as a modem 25
(Fig. 41)
and may be configured to permit the definition of the regions 1002a-1002e,
1002a'-1002e' or
other data or software to be modified remotely (i.e., to be downloaded to a
field site from a
central site). In another embodiment, the device is configured to
automatically adjust the
definitions of the regions 1002a-1002e, 1002a'-1002e' in response to ongoing
statistical
analysis of the Q, D data for coins which are discriminated using the device,
to provide a type
of self calibration for the coin discriminator.
In light of the above description, a number advantages of the present
invention can be
seen. Embodiments of the present invention can provide a device with increased
accuracy
and service life, ease and safety of use, requiring little or no training and
little or no
instruction, which reliably returns unprocessed coins to the user, rapidly
processes coins, has
a high throughput, a reduced incidence of jamming, in which some or all jams
can be reliably
cleared without human intervention, which has reduced need for intervention by
trained
personnel, can handle a broad range of coin types, or denominations, can
handle wet or sticky
coins or foreign or non-coin objects, has reduced incidence of malfunctioning
or placing
foreign objects in the coin bins, has reduced incidence of rejecting good
coins, has simplified
and/or reduced requirements for set-up, calibration or maintenance, has
relatively small
volume or footprint requirements, is tolerant of temperature variations, is
relatively quiet,
and/or enhanced ease of upgrading or retrofitting.
In one embodiment, the apparatus achieves singulation of a randomly-oriented
mass
of coins with reduced jamming and high throughput. In one embodiment, coins
are
effectively separated from one another prior to sensing and/or deflection. In
one
embodiment, deflection parameters, such as force and/or timing of deflection
can be adjusted
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to take into account characteristics of coins or other objects, such as mass,
speed, and/or
acceleration, to assist in accuracy of coin handling. In one embodiment, slow
or stuck coins
are automatically moved (such as by a pin or rake), or otherwise provided with
kinetic
energy. In one embodiment items including those which are not recognized as
valuable,
acceptable or desirable coins or other objects are allowed to follow a non-
diverted, default
path (preferably, under the force of gravity), while at least some recognized
and/or accepted
coins are diverted from the default path to move such items into an acceptance
bin or other
location.
In one embodiment, the device provides for ease of application (e.g. multiple
measurements done simultaneously and/or at one location), increased
performance, such as
improved throughput and reduced jams (that prematurely end transactions and
risk losing
coins), more accurate discrimination, and reduced cost and/or size. One or
more torroidal
cores can be used for sensing properties of coins or other objects passing
through a magnetic
field, created in or adjacent a gap in the torroid, thus allowing coins,
disks, spherical, round
or other objects, to be measured for their physical, dimensional, or metallic
properties
(preferably two or more properties, in a single pass over or through one
sensor). The device
facilitates rapid coin movement and high throughput. The device provides for
better
discrimination among coins and other objects than many previous devices,
particularly with
respect to U.S. dimes and pennies, while requiring fewer sensors and/or a
smaller sensor
region to achieve this result. Preferably, multiple parameters of a coin are
measured
substantially simultaneously and with the coin located in the same position,
e.g., multiple
sensors are co-located at a position on the coin path, such as on a rail. In a
number of cases,
components are provided which produce more than one function, in order to
reduce part
count and maintenance. For example, certain sensors, as described below, are
used for
sensing two or more items and/or provide data which are used for two or more
functions.
Coin handling apparatus having a lower cost of design, fabrication, shipping,
maintenance or
repair can be achieved. In one embodiment, a single sensor exposes a coin to
two different
electromagnetic frequencies substantially simultaneously, and substantially
without the need
to move the coin to achieve the desired two-frequency measurement. In this
context,
"substantially" means that, while there may be some minor departure from
simultaneity or
minor coin movement during the exposure to two different frequencies, the
departure from
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simultaneity or movement is not so great as to interfere with certain purposes
of the
invention such as reducing space requirements, increasing coin throughput and
the like, as
compared to previous devices. For example, preferably, during detection of the
results of
exposure to the two frequencies, a coin will move less than a diameter of the
largest-diameter
coin to be detected, more preferably less than about 3/4 a largest-coin
diameter and even
more preferably less than about 1/2 of a coin diameter.
The present invention makes possible improved discrimination, lower cost,
simpler
circuit implementation, smaller size, and ease of use in a practical system.
Preferably, all
parameters needed to identify a coin are obtained at the same time and with
the coin in the
same physical location, so software and other discrimination algorithms are
simplified.
Other door configurations than those depicted can be used. The door 62 may
have a
laminated structure, such as two steel or other sheets coupled by, e.g.,
adhesive foam tape.
A number of variations and modifications of the invention can be used. It is
possible
to use some aspects of the invention without using others. For example, the
described
techniques and devices for providing multiple frequencies at a single sensor
location can be
advantageously employed without necessarily using the sensor geometry
depicted. It is
possible to use the described torroid-core sensors, while using analysis,
devices or techniques
different from those described herein and vice versa. It is possible to use
the sensor and or
coin rail configuration described herein without using the described coin
pickup assembly.
For example it is possible to use the sensor described herein in connection
with the coin
pickup assembly described in U.S. Patent 6,168,001. It is possible to use
aspects of the
singulation and/or discrimination portion of the apparatus without using a
trommel.
Although the invention has been described in the context of a machine which
receives a
plurality of coins in a mass, a number of features of the invention can be
used in connection
with devices which receive coins one at a time, such as through a coin slot.
Although the sensors have been described in connection with the coin counting
or
handling device, sensors can also be used in connection with coin activated
devices, such as
vending machines, telephones, gaming devices, and the like. In addition to
using information
about discriminated coins for outputting a printed voucher, the information
can be used in
connection with making electronic funds transfers, e.g. to the bank account of
the user (e.g. in
accordance with information read from a bank card, credit card or the like)
and/or to an
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account of a third party, such as the retail location where the apparatus is
placed, to a utility
company, to a government agency, such as the U.S. Postal Service, or to a
charitable, non-
profit or political organization (e.g. as described in U.S. Patent 5,909,794).
In addition to
discriminating among coins, devices can be used for discriminating and/or
quality control on
other devices such as for small, discrete metallic parts such as ball
bearings, bolts and the
like. Although the depicted embodiments show a single sensor, it is possible
to provide
adjacent or spaced multiple sensors (e.g., to detect one or more properties or
parameters at
different skin depths). The sensors of the present invention can be combined
with other
sensors, known in the art such as optical sensors, mass sensors, and the like.
In the depicted
embodiment, the coin 242 is positioned on both a first side 244a of the gap
and a second side
244b of the gap. It is believed that as the coin 224 moves down the rail 232,
it will be
typically positioned very close to the second portion 244b of the coil 242. If
it is found that
this close positioning results in an undesirably high sensitivity of the
sensor inductance to the
coin position (e.g. an undesirably large variation in inductance when coins
"fly" or are
otherwise somewhat spaced from the back wall of the rail 232), it may be
desirable to place
the high frequency coil 242 only on the second portion 244a (Fig. 2C) which is
believed to be
normally somewhat farther spaced from the coin 242 and thus less sensitive to
coin positional
variations. The gap may be formed between opposed faces of a torroid section,
or formed
between the opposed and spaced edges of two plates, coupled (such as by
adhesion) to faces
of a section of a torroid. In either configuration, a single continuous non-
linear core has first
and second ends, with a gap there between.
Although it is possible to provide a sensor in which the core is driven by a
direct
current, preferably, the core is driven by an alternating or varying current.
In one embodiment two or more frequencies are used. Preferably, to reduce the
number of sensors in the devices, both frequencies drive a single core. In
this way, a first
frequency can be selected to obtain parameters relating to the core of a coin
and a second
frequency selected to obtain parameters relating to the skin region of the
coin, e.g., to
characterize plated or laminated coins. One difficulty in using two or more
frequencies on a
single core is the potential for interference. In one embodiment, to avoid
such interference
both frequencies are phase locked to a single reference frequency. In one
approach, the
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sensor forms an inductor of an L-C oscillator, whose frequency is maintained
by a Phase-
Locked Loop (PLL) to define an error signal (related to Q) and amplitude which
change as
the coin moves past the sensor.
As seen in Figs. 2A, 2B, 3 and 4, the depicted sensor includes a coil which
will
provide a certain amount of inductance or inductive reactance in a circuit to
which it is
connected. The effective inductance of the coil will change as, e.g. a coin
moves adjacent or
through the gap and this change of inductance can be used to at least
partially characterize the
coin. Without wishing to be bound by any theory, it is believed the coin or
other object
affects inductance in the following manner. As the coin moves by or across the
gap, the AC
magnetic field lines are altered. If the frequency of the varying magnetic
field is sufficiently
high to define a "skin depth" which is less than about the thickness of the
coin, no field lines
will go through the coin as the coin moves across or through the gap. As the
coin is moved
across or into the gap, the inductance of a coil wound on the core decreases,
because the
magnetic field of the direct, short path is canceled (e.g., by eddy currents
flowing in the coin).
Since, under these conditions no flux goes through any coin having any
substantial
conductivity, the decrease in inductance due to the presence of the coin is
primarily a
function of the surface area (and thus diameter) of the coin.
A relatively straightforward approach would be to use the coil as an inductor
in a
resonant circuit such as an LC oscillator circuit and detect changes in. the
resonant frequency
of the circuit as the coin moved past or through the gap. Although this
approach has been
found to be operable and to provide information which may be used to sense
certain
characteristics of the coin (such as its diameter) a more preferred embodiment
is shown, in
general form, in Fig. 5 and is described in greater detail below.
In the embodiment of Fig. 5, a phase detector 506 compares a signal indicative
of the
frequency in the oscillator 508 with a reference frequency 510 and outputs an
error signal 512
which controls a frequency-varying component of the oscillator 514 (such as a
variable
capacitor). The magnitude of the error signal 512 is an indication of the
magnitude of the
change in the effective inductance of the coil 502. The detection
configuration shown in Fig.
5 is thus capable of detecting changes in inductance (related to the coin
diameter) while
maintaining the frequency of the oscillator substantially constant. Providing
a substantially
constant frequency is useful because, among other reasons, the sensor will be
less affected by
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interfering electromagnetic fields than a sensor that allows the frequency to
shift would be. It
will also be easier to prevent unwanted electromagnetic radiation from the
sensor, since
filtering or shielding would be provided only with respect to one frequency as
opposed to a
range of frequencies.
Without wishing to be bound by any theory, it is believed that the presence of
the coin
affects energy loss, as indicated by the Q factor in the following manner. As
noted above, as
the coin moves past or through the gap, eddy currents flow causing an energy
loss, which is
related to both the amplitude of the current and the resistance of the coin.
The amplitude of
the current is substantially independent of coin conductivity (since the
magnitude of the
current is always enough to cancel the magnetic field that is prevented by the
presence of the
coin). Therefore, for a given effective diameter of the coin, the energy loss
in the eddy
currents will be inversely related to the conductivity of the coin. The
relationship can be
complicated by such factors as the skin depth, which affects the area of
current flow with the
skin depth being related to conductivity.
Thus, for a coil 562 driven at a first, e.g. sinusoidal, frequency, the
amplitude can be
determined by using timing signals 602 (Fig. 6) to sample the voltage at a
time known to
correspond to the peak voltage in the cycle, using a first sampler 606 and
sampling at a
second point in the cycle known to correspond to the trough using a second
sampler 608. The
sampled (and held) peak and trough voltages can be provided to a differential
amplifier 610,
the output of which 612 is related to the conductance. More precisely
speaking, the output
612 will represent the Q of the circuit. In general, Q is a measure of the
amount of energy
loss in an oscillator. In a perfect oscillator circuit, there would be no
energy loss (once
started, the circuit would oscillate forever) and the Q value would be
infinite. In a real
circuit, the amplitude of oscillations will diminish and Q is a measure of the
rate at which the
amplitude diminishes. In another embodiment, data relating to changes in
frequency as a
function of changes in Q are analyzed (or correlated with data indicative of
this functional
relationship for various types of coins or other objects).
In one embodiment, the invention involves combining two or more frequencies on
one core by phase-locking all the frequencies to the same reference. Because
the frequencies
are phase-locked to each other, the interference effect of one frequency on
the others becomes
a common-mode signal, which is removed, e.g., with a differential amplifier.
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In one embodiment, a coin discrimination apparatus and method is provided in
which
an oscillating electromagnetic field is generated on a single sensing core.
The oscillating
electromagnetic field is composed of one or more frequency components. The
electromagnetic field interacts with a coin, and these interactions are
monitored and used to
classify the coin according to its physical properties. All frequency
components of the
magnetic field are phase-locked to a common reference frequency. The phase
relationships
between the various frequencies are fixed, and the interaction. of each
frequency component
with the coin can be accurately determined without the need for complicated
electrical filters
or special geometric shaping of the sensing core. In one embodiment.. a sensor
having a core,
preferably ferrite, which is curved (or otherwise non-linear), such as in a U-
shape or in the
shape of a section of a torus, and defining a gap, is provided with a wire
winding for
excitation and/or detection. The sensor can be used for simultaneously
obtaining data
relating to two or more parameters of a coin or other object, such as size and
conductivity of
the object. Two or more frequencies can be used to sense core and/or cladding
properties.
In the embodiment depicted in Figs. 8A-8C, the apparatus can be constructed
using
parts which are all currently readily available and relatively low cost. As
will be apparent to
those of skill in the art, other circuits may be configured for performing
functions useful in
discriminating coins using the sensor of Figs. 2-4. Some embodiments may be
useful to
select components to minimize the effects of temperature, drift, etc. In some
situations,
particularly high volume situations, some or all of the circuitry may be
provided in an
integrated fashion such as being provided on an application specific
integrated circuit
(ASIC). In some embodiments it may be desirable to switch the relative roles
of the square
wave 843 and triangle wave 862. For example, rather than obtaining a sample
pulse based on
a square wave signal 843, a circuit could be used which would provide a pulse
reference that
would go directly to the analog switch (without needing an edge detect). The
square wave
would be used to generate a triangular wave.
The phase locked loop circuit described above uses a very high (theoretically
infinite)
DC gain such as about 100 dB or more on the feedback path, so as to maintain a
very small
phase error. In some situations this may lead to difficulty in achieving phase
lock up, upon
initiating the circuits and thus it may be desirable to relax, somewhat, the
small phase error
requirements in order to achieve initial phase lock up more readily.
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Although the embodiment of Figs. 8A-8C provides for two frequencies, it is
possible
to design a detector using three or more frequencies, e.g. to provide for
better coin
discrimination.
Additionally, rather than providing two or more discrete frequencies, the
apparatus
could be configured to sweep or "chirp" through a frequency range. In one
embodiment, in
order to achieve swept-frequency data it would be useful to provide an
extremely rapid
frequency sweep (so that the coin does not move a large distance during the
time required for
the frequency to sweep) or to maintain the coin stationary during the
frequency sweep.
In some embodiments in place of or in addition to analyzing values obtained at
a
single time (t1 Fig. 9) to characterize coins or other objects, it may be
useful to use data from
a variety of different times to develop a Q vs. profile or D vs. t profile
(where t represents
time) for detected objects. For example, it is believed that larger coins such
as quarters, tend
to result in a Q vs. t profile which is flatter, compared to a D vs. t
profile, than the profile for
smaller coins. It is believed that some, mostly symmetric, waveforms have dips
in the middle
due to an "annular" type coin where the Q of the inner radius of the coin is
different from the
Q of the outer annulus. It is believed that, in some cases, bumps on the
leading and trailing
edges of the Q waveforms may be related to the rim of the coin or the
thickness of plating or
lamination near the rim of the coin.
In some embodiments the output data is influenced by relatively small-scale
coin
characteristics such as plating thickness or surface relief. In some
circumstances it is
believed that surface relief information can be used, e.g., to distinguish the
face of the coin,
(to distinguish "heads" from "tails") to distinguish old coins from new coins
of the same
denomination and the like. In order to prevent rotational orientation of the
coin from
interfering with proper surface relief analysis, it is preferable to construct
sensors to provide
data which is averaged over annular regions such as a radially symmetric
sensor or array of
sensors configured to provide data averaged in annular regions centered on the
coin face
center.
Although Fig. 5 depicts one fashion of obtaining a signal related to Q, other
circuits
can also be used. In the embodiment depicted in Fig. 5, a sinusoidal voltage
is applied to the
sensor coil 220, e.g., using an oscillator 1102. The waveform of the current
in the coil 220,
will be affected by the presence of a coin or other object adjacent the gap
216, 316, as
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described above. Different phase components of the resulting current wave form
can be used
to obtain data related to inductance and Q respectively. In the depicted
embodiment, the
current in the coil 220 is decomposed into at least two components, a first
component which
is in-phase with the output of the oscillator 1102, and a second component
which is delayed
by 90 degrees, with respect to the output of the oscillator 1102. These
components can be
obtained using phase-sensitive amplifiers 1104, 1106 such as a phase locked
loop device and,
as needed, a phase shift or delay device of a type well known in the art. The
in-phase
component is related to Q, and the 90 degree lagging component is related to
inductance. In
one embodiment, the output from the phase discriminators 1104, 1106, is
digitized by an
analog-to-digital converter 1108, and processed by a microprocessor 1110. In
one
implementation of this technique, measurements are taken at many frequencies.
Each
frequency drives a resistor connected to the coil. The other end of the coil
is grounded. For
each frequency, there is a dedicated "receiver" that detects the I and Q
signals. Alternatively,
it is possible to analyze all frequencies simultaneously by employing, e.g., a
fast Fourier
transform (FFT) in the microprocessor. In another embodiment, it is possible
to use an
impedance analyzer to read the Q (or "loss tangent") and inductance of a coil.
In another embodiment, depicted in Fig. 12, information regarding the coin
parameters is obtained by using the sensor 1212 as an inductor in an LC
oscillator 1202. A
number of types of LC oscillators can be used as will be apparent to those of
skill in the art,
after understanding the present disclosure. Although a transistor 1204 has
been depicted,
other amplifiers such as op amps, can be used in different configurations. In
the depicted
embodiment, the sensor 1212 has been depicted as an inductor, since presence
of a coin in the
vicinity of the sensor gap will affect the inductance. Since the resonant
frequency of the
oscillator 1202 is related to the effective inductance (frequency varies as
(l/LC-Y'): as the
diameter of the coin increases, the frequency of the oscillator increases. The
amplitude of the
AC in the resonant LC circuit, is affected by the conductivity of objects in
the vicinity of the
sensor gap. The frequency is detected by frequency detector 1205, and by
amplitude detector
1206, using well known electronics techniques with the results preferably
being digitized
1208, and processed by microprocessor 1210. In one embodiment the oscillation
loop is
completed by amplifying the voltage, using a hard-limiting amplifier (square
wave output),
which drives a resistor. Changes in the magnitude of the inductance caused the
oscillator's
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frequency to change. As the diameter of the test coin increases, the frequency
of the
oscillator increases. As the conductivity of the test coin decreases, the
amplitude of the AC
voltage and the tuned circuit goes down. By having a hard-limiter, and having
a current-
limiting resister that is much larger than the resonant impedance of the tuned
circuit, the
amplitude of the signal at the resonant circuit substantially accurately
indicates, in inverse
relationship, the Q of the conductor.
Although one manner of analyzing D and Q signals using a microprocessor is
described above, a microprocessor can use the data in a number of other ways.
Although it
would be possible to use formulas or statistical regressions to calculate or
obtain the
numerical values for diameter (e.g., in inches) and/or conductivity (e.g., in
mhos), it is
contemplated that a frequent use of the present invention will be in
connection with a coin
counter or handler, which is intended to 1) discriminate coins from non-coin
objects, 2)
discriminate domestic from foreign coins and/or 3) discriminate one coin
denomination from
another. Accordingly, in one embodiment, the microprocessor compares the
diameter-
indicating data, and conductivity-indicating data, with standard data
indicative of
conductivity and diameter for various known coins. Although it would be
possible to use the
microprocessor to convert detected data to standard diameter and conductivity
values or units
(such as inches or mhos), and compare with data which is stored in memory in
standard
values or units, the conversion step can be avoided by storing in memory, data
characteristic
of various coins in the same values or units as the data received by the
microprocessor. For
example, when the detector of Fig. 5 and/or 6 outputs values in the range of
e.g., 0 to +5
volts, the standard data characteristic of various known coins can be
converted, prior to
storage, to a scale of 0 to 5, and stored in that form so that. the comparison
can be made
directly, without an additional step of conversion.
Although in one embodiment it is possible to use data from a single point in
time,
such as when the coin is centered on the gap 216, (as indicated, e.g., by a
relative maximum,
or minimum, in a signal), in another embodiment a plurality of values or a
continuous signal
of the values obtained as the coin moves past or through the gap 216 is
preferably used.
An example of a single point of comparison for each of the in-phase and
delayed
detector, is depicted in Fig. 13. In this Figure, standard data (stored in the
computer),
indicates the average and/or acceptance or tolerance range of in-phase
amplitudes (indicative
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of conductivity), which has been found to be associated with U.S. pennies,
nickels, dimes and
quarters, respectively 1302. Data is also stored, indicating the average
and/or acceptance or
tolerance range of values output by the 90 degree delayed amplitude detector
406 (indicative
of diameter) associated with the same coins 1304. Preferably, the envelope or
tolerance is
sufficiently broad to lessen the occurrence of false negative results, (which
can arise, e.g.,
from worn, misshapen, or dirty coins, electronic noise, and the like), but
sufficiently narrow
to avoid false positive results, and to avoid or reduce substantial overlap of
the envelopes of
two or more curves (in order to provide for discrimination between
denominations).
Although, in the figures, the data stored in the computer is shown in
graphical form, for the
sake of clarity of disclosure, typically the data will be stored in digital
form in a memory, in a
manner well-known in the computer art. In the embodiment in which only a
single value is
used for discrimination, the digitized single in-phase amplitude value, which
is detected for a
particular coin (in this example, a value of 3.5) (scaled to a range of 0 to 5
and digitized), is
compared to the standard in-phase data, and the value of 3.5 is found (using
programming
techniques known in the art) to be consistent with either a quarter or a dime
1308. Similarly,
the 90-degree delayed amplitude value which is detected for this same coin
1310 (in this
example, a value of 1.0), is compared to the standard in-phase data, and the
value of 1.0 is
found to be consistent with either a penny or a dime 1312. Thus, although each
test by itself
would yield ambiguous results, since the single detector provides information
on two
parameters (one related to conductivity and one related to diameter), the
discrimination can
be made unambiguously since there is only one denomination (dime) 1314 which
is
consistent with both the conductivity data and the diameter data.
As noted, rather than using single-point comparisons, it is possible to use
multiple
data points (or a continuous curve) generated as the coin moves past or
through the gap 216,
316. Profiles of data of this type can be used in several different ways. In
the example of
Fig. 14, a plurality of known denominations of coins are sent through the
discriminating
device in order to accumulate standard data profiles for each of the
denominations 1402a, b,
c, d, 1404a, b, c, d. These represent the average change in output from the in-
phase
amplitude detector 1104 and a 90-degree delay detector for (shown on the
vertical axes) 1403
and acceptance ranges or tolerances 1405 as the coins move past the detector
over a period of
time, (shown on the horizontal axis). In order to discriminate an unknown coin
or other
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object, the object is passed through or across the detector, and each of the
in-phase amplitude
detector 1104 and 90-degree delayed amplitude detector 1106, respectively,
produce a curve
or profile 1406, 1410, respectively. In the embodiment depicted in Fig. 8, the
in-phase
profile 1406 generated as a coin passes the detector 212, is compared to the
various standard
profiles for different coins 1402a, 1402b, 1402c, 1402d. Comparison can be
made in a
number of ways. In one embodiment, the data is scaled so that a horizontal
axis between
initial and final threshold values 1406a equals a standard time, for better
matching with the
standard values 1402a through 1402d. The profile shown in 1406 is then
compared with
standard profiles stored in memory 1402a through 1402d, to determine whether
the detected
1o profile is within the acceptable envelopes defined in any of the curves
1402a through 1402d.
Another method is to calculate a closeness of fit parameter using well known
curve-fitting
techniques, and select a denomination or several denominations, which most
closely fit the
sensed profile 1406. Still another method is to select a plurality of points
at predetermined
(sealed) intervals along the time axis 1406a (1408a, b, c, d) and compare
these values with
corresponding time points for each of the denominations. In this case, only
the standard
values and tolerances or envelopes at such predetermined times needs to be
stored in the
computer memory. Using any or all these methods, the comparison of the sensed
data 1406,
with the stored standard data 1402a through 1402d indicates, in this example,
that the in-
phase sensed data is most in accord with standard data for quarters or dimes
1409. A similar
comparison of the 90-degree delayed data 1410 to stored standard 90-degree
delayed data
(1404a through 1404d), indicates that the sensed coin was either a penny or a
dime. As
before, using both these results, it is possible to determine that the coin
was a dime 1404.
In one embodiment, the in-phase and out-of-phase data are correlated to
provide a
table or graph of in-phase amplitude versus 90-degree delayed amplitude for
the sensed coin
(similar to the Q versus D data depicted in Figs I OA and I OB), which can
then be compared
with standard in-phase versus delayed profiles obtained for various coin
denominations in a
manner similar to that discussed above in connection with Figs I OA and l OB.
Although coin acceptance regions are depicted (Figs. 1OA, 1 OB) as
rectangular, they
may have any shape.
In both the configuration of Fig. 2 and the configuration of Figs. 3 and 4,
the presence
of the coin affects the magnetic field. It is believed that in some cases,
eddy currents flowing
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in the coin, result in a smaller inductance as the coin diameter is larger,
and also result in a
lower Q of the inductor, as the conductivity of the coin is lower. As a
result, data obtained
from either the sensor of Figs. 2A and 2B, or the sensor of Figs. 3 and 4, can
be gathered and
analyzed by the apparatus depicted in Figs. 5 and 6, even though the detected
changes in the
configuration of Figs. 3 and 4 will typically be smaller than the changes
detected in the
configuration of Figs. 2A and 2B.
Although certain sensor shapes have been described herein, the techniques
disclosed
for applying multiple frequencies on a single core could be applied to and of
a number of
sensor shapes, or other means of forming an inductor to subject a coin to an
alternating
lo magnetic field.
Although an embodiment described above provides two AC frequencies to a single
sensor core at the same time, other approaches are possible. One approach is a
time division
approach, in which different frequencies are generated during different, small
time periods, as
the coin moves past the sensor. This approach presents the difficulty of
controlling the
oscillator in a "time-slice" fashion, and correlating time periods with
frequencies for
achieving the desired analysis. Another potential problem with time-
multiplexing is the
inherent time it takes to accurately measure Q in a resonant circuit. The
higher the Q, the
longer it takes for the oscillator's amplitude to settle to a stable value.
This will limit the rate
of switching and ultimately the coin throughput. In another embodiment, two
separate sensor
cores (1142 a,b Fig. 11A) can be provided, each with its own winding 1144a, b
and each
driven at a different frequency 1146a, b. This approach has not only the
advantage of
reducing or avoiding harmonic interference, but provides the opportunity of
optimizing the
core materials or shape to provide the best results at the frequency for which
that core is
designed. When two or more frequencies are used, analysis of the data can be
similar to that
described above, with different sets of standard or reference data being
provided for each
frequency. In one embodiment, multiple cores, such as the two cores 1142a, b
of Fig. 11 A,
along the coin path 1148 are driven by different frequencies 1146a, b that are
phase-locked
1152a, b to the same reference 1154, such as a crystal or other reference
oscillator. In one
embodiment, the oscillators 1154a, b that provide the core driving frequencies
11 46a, b are
phase-locked by varactor tuning (e.g. as described above) the oscillators
1154a, b using the
sensing inductor 1154 a, b as part of the frequency determination.
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In one embodiment, a sensor includes first and second ferrite cores, each
substantially
in the shape of a section of a torus 282a, b (Fig. 2D), said first core
defining a first gap 284a,
and said second core defining a second gap 284b, said cores positioned with
said gaps aligned
286 so that a coin conveyed by said counting device will move through said
first and second
gaps; at least first and second coils 288a, b of conductive material wound
about a first portion
of each of said first and second cores, respectively; an oscillator 292 a
coupled to said first
coil 288a configured to provide current defining at least a first frequency
defining a first skin
depth less than said cladding thickness and wherein, when a coin is conveyed
past said first
gap 282a, the signal in said coil undergoes at least a first change in
inductance and a change
in the quality factor of said inductor; an oscillator 292b coupled to said
second coil 288b
configured to provide current defining at least a second frequency defining a
second skin
depth greater than said first skin depth wherein, when said coin is conveyed
past said second
gap 284b, the signal in said coil undergoes at least a second change in
inductance and a
second change in the quality factor of said inductor; and a processor 294
configured to
receive data indicative of said first and second changes in inductance and
changes in quality
factor to permit separate characterization of said cladding and said core.
In another embodiment, current provided to the coil is a substantially
constant or DC
current. This configuration is useful for detecting magnetic (ferromagnetic)
v. non-magnetic
coins. As the coin moves through or past the gap, there will be eddy current
effects, as well
as permeability effects. As discussed above, these effects can be used to
obtain, e.g.,
information regarding conductivity, such as core conductivity. Thus, in this
configuration
such a sensor can provide not only information about the ferromagnetic or non-
magnetic
nature of the coin, but also regarding the conductivity. Such a configuration
can be combined
with a high-frequency (skin effect) excitation of the core and., since there
would be no low-
frequency (and thus no low-frequency harmonics) interference problems would be
avoided.
It is also possible to use two (or more) cores, one driven with DC, and
another with AC. The
DC-driven sensor provides another parameter for discrimination (permeability).
Permeability
measurement can be useful in, for example, discriminating between U.S. coins
and certain
foreign coins or slugs. Preferably, computer processing is performed in order
to remove
"speed effects."
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Although the invention has been described by way of a preferred embodiment and
certain variations and modifications, other variations and modifications can
also be used, the
invention being defined by the following claims.
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