Note: Descriptions are shown in the official language in which they were submitted.
MULTI-VOLTAGE DISINFECTOR TIMING CIRCUIT
ABSTRACT OF THE DISCLOSURE
. . ~ . _ _
A contact lens disinfector unit having mul-ti-voltage
capabilities includes a timing circuit for controlling
the duration of operation of a contact lens disinfector
heater. The circuit is particularly suitable for use
with a heater consisting of a positive tempera-ture
coefficient thermistor. In the preferred forml -the
con-tact lens disinfector units are suitable for use
regardless of the voltage value at an electrical outlet
receptacle providing power to such a disinfector uni-t.
Depending upon the country in which the device is used,
voltages can vary generally anywhere from 95 AC volts to
256 vol-ts AC. Positive temperature coefficient (PTC)
thermistors are capable of operation irrespective of
such variable voltage range and the unique control
circuit disclosed is capable of timing control and
operation where the inpu-t voltage has such a wide value range.
BACKGROUND OF THE INVENTION
1. Field of the Invention
~ _ . _ . . .
This invention relates to a contact lens
disinfecting unit timing control circuit and more
particularly to a timing control circuit for a contact
lens disinfector capable of operation under a variable
voltage range.
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2. Brief Description of the Prior Art:
Heretofore, disinfecting devices for contact
lenses have been rather bulky and have required the
operators of such devices to perform multiple ~perations
5 in the process of disinfecting their contac-t lenses.
Typically, the units have been designed for use only with
a voltage source of a given value. Those units which
have adaptability to multiple voltages require that the
operator perform additional manual operations and have
necessitated the incorporation of separate circuitry,
including separate heating elements to accommodate the
different voltage values. These considerations add
additional cost and bulk to the individual units.
Further, the opera-tor must be especially mindful and
knowledgeable of the value of the voltage source being
utilized.
U.S. Patent 4,165,359 for inventor M.D. Thomas et
al, for example, discloses a circuit at FIGURE 7 for use
with voltages of two given values. The circuit illustrates
a manually operable switch~ separate from the start
switch, which must be positioned by the operator and is
dependent upon the value of the ~oltage source. The
circuit also illustrates that two separate heating
elements are necessary in order to accommodate each of the
two voltage values. Additional resistive elements must
be incorporated, as illustrated thereat, to balance the
needs of the actuator switch and indicator lamp. The
-timer or star-ter unit is schematically shown as a switch
Z
and is simultaneously energized when the actuator
switch is operated, although no preferred embodiment
of the starter unit and no explanation of its
simultaneous actuation is provided.
SUMMARY OF THE INVENTION
This invention provides a timing circuit for a
contact lens disinfector capable of operation under a
wide range of voltages available for powering such units
regardless of the country of use particularly where such
a disinfecting unithas a positive temperature coefficient
thermistor heater equally capable of satisfactory
operation under a wide range of voltage inputs. The
circuit requires only that the operator perform a single
step to start the operation of the unit. This is true
regardless of the value of the voltage souxce. Afterwards,
the unit completes a full disinfecting cycle without
need for further operator assistanceO
The circuit operates to generate a single capable
of closing and keeping closed an electronic gate for a
period of time sufficient to disinfect contac-t lenses
heated by the heating device. A multistage binary
counter provides the timing capability within an
integrated circuit (IC3 of a programmable timer. The
timer is programmed to time for a cycle having a
duration which is a function of the period of time
necessary to disinfect contact lenses. An oscillating
circuit associated with the IC is pr~vided for clocking.
The t:iming circuit is capable of manual initialization
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either by the disinfector heating unit being plugged
into the voltage source or by providing a mechanical
interruption of the powercircuit by a swi-tch to be
manually and momentarily depressed to initialize the
counter.
The multi-voltage aspect can be applied to
circuitry where variable, but selectable, timing is
provided for operation of loads, including contact lens
disinfector heaters, but not limited to such loads.
Units of manufacture according to the principles of
this invention can be made less costly. Additionally,
they can be of minimum size and enjoy the luxury of
outward ornamental design which is appealing to the
eye and thus highly marketable. Further, the circuit
features provided are such that the operation of the
unit is practically self explanatory. Minimal
instruction is necessary and the operator, for all
practicalpurposes, need not be concerned about the
value of the voltage at the receptacle outlet. Thus,
the unit is universal for use on the North American
continent and as well in Europe and in all countries
where receptacle voltage value is substantially between
95 and 256 volts.
:BRIEF DE5CRIPTION OF THE DRAWINGS
_ _ .. . .
FIGURE 1 is a schematic block diagram of a circuit
for a contact lens disinfecting unit according to the
principles of the present invention.
7'~2
FIGURE 2 is a detailed schematical ilLustration oE
a contact lens disinfecting unit circuit in -accordance
with FIGURE 1.
FIGU~E 3 is an alternate embodiment o~ the voltage
control circuitry according to FIGURE 1.
EIGURE 4 is an alternate embodiment oE the circuit
control system in accordance with FIG[JRE 1.
FIG~RE 5 is a further alternate embodiment oE the
circuit control system in accordance with FIGURE 1.
FIGURE 6 is yet another alternate embodiment of
the circuit control system in accordance with FIGURE 1
FIGURE 7 is a schematic circuit of an alternative
embodiment for the circuit and timer control of FIGURE 1
according to the principles of the present invention.
FIGURE 8 is a schematic block diagram of a circuit
having multiple voltage capabilities with select timing
features.
FIGURE 9 is a schematic diagram of an exemplary circuit
for use in the selectable timers of FIGURE 80
FIGURE 10 is a schematic circuit diagram of -the
time switching mechanism of FIGURE 9.
FIGURE 11 is a schematic diagram oE an exemplary
switching circuit for use when the present invention is
connected to a DC electrical power source.
DETAILED DESCRIPTION OF THE PREFERRED E'MBODIMENTS
rrhe circuits illustrated in FIGS. 1-6 are suitable
for use with various types of loads including the
preferred embodiments of disinfectors having heating
element~s made from positive temperature coefficient
resistance material. A heating device of this material
will hereinafter be referred to as a PTC heater. PTC
6~72
heaters have been used, for example, as self-regulating
heaters. An example of one is illustrated in ~.S.
Patent 3,489,976. This type of heater ls self limiting
and thus has little need fo:r control devices :Eor
regulating the amount of cu:rrent received by the PTC
heater.
Although in heating devices PTC hea-ters are
generally preferred, the descri~ed circui-t is equally
as suitable for use with heaters well known in the art
including the full array of resistive type heating
devices. In FIG. 1 a circuit 10 having a unit for
disinfecting contact lenses is illustrated. ~lthough for
practical purposes, the circuit is shown as including a
voltage source 12, it is anticipated that in most instances
the circuit will terminate at an electrical supply cord
suitable ~or accommodation to an electrical receptacle.
This circuit 10 is ideally suited for use with multiple
voltages and specifically for voltages which are
nominally identified as 100, 110, 220 and 2~0 volts.
The voltage values are typically those found in general use
in Japan, the United States, and in European states and
countries, respectively, The illustrated unit, according
to ~he principles of the invention, is operationally
independent of the ~requency of the voltage source.
Circuit 10 has a heating device 14 which, as
hereinbefore stated, is preferably a PTC heater serially
connected to a switching circuit 16. The heater 14 is
operative to heat contact lenses, in a suitable carrying
case, placed in close proximity thereto when the switching
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circuit 16 is operated and a closed path is -therefore
provided for current to flow. A heating device, of
PTC material, can readily accommodate mu].tiple voltages
such as 110 volt or 220 volt. However, in addition it
can operate effectively when the voltage source provides
an alternating current (A.C.) voltage value anywhere
appro~imately from 90 to 260 volts. So, in effect, the
circuit system 10 is operative in a disinfecting unit
for variable voltage sources coverin~ a wide range, as
distinctive from selec.ted individual multi voltage
sources. Further, the invention is broad enough in
concept to only be limited by the load. Any voltage
level AC or DC suitable to be used directly or indirectly
to operate a selected loadcan be used to function the
timer.
The operation and duration of operation of the
switching circuit 16 and accordingly heater device 14
is principally controlled by a timer control unit 18.
Control of the operation of the total circuit is
accomplished by means of a circuit control system 20
which initializes the timer control circuit 18 and
provides a current path for the continued operation of
the timer control circuit 18. A voltage control circuit
22 is incorporated to provide a suitable volta~e level
2~ for operation of the circuit control 20 and -the timer
control 18 regardless of the value at the voltage source
].2. The timer control circuit 18, once initialized,
operates independently o~ any control by the control
circuit 20 ~or a period of time which is a function of
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its own circuit. In the environment preferably intended
for use by the present circuit the time period selected
is -that which is necessary :Eor disinfecting contact
lenses. This period of opexation is more fully
described in "The May 1980 (,uidelines for Contact Lenses
(May, 1980 Revision)" issuecl June 9, 1980 by H.E.W.
As long as switching ci.rcuit 16 is in a closed mode
and influenced by an existing signal ~rom the timer
control 18, current not only will pass through the heater
14 but al50 through a lamp circuit 24 to provide a
visual indication that the dlsinfecting cycle of the
contact lenses is in progress.
In FIG. 2 a specific embodiment of the disinfecting
heating circuit 10 of FIG. 1 is illustrated. As before,
voltage source 12 is illustrated and is bridged by a
resistor voltage divider network comprising resistors 30
and 32 having connected to their common terminal a diode
34 for providing a direct current (D.C.) level voltage
to the circuit control 20 and timer control 18 of the
control circuit 10. A selected capacitor 36 is applied
across the output of the diode 34 to ground to act as a
filter to remove ripple due to any instability of the
voltage at source 12 which may occur in the ~oltage
signal appearing at that point.
In the preferred form, a switch 38 is illustrated
as being connected directly to initialization pin 6 of
an IC unit 40 incorporating the time control circuit 18.
The switch 38 is of the variety known as momentary switches
which r~turn to a normal circuit condition of being open
36~7~2
when the actuating force applied by the operator is
removed. The IC 40 is a programmable timer as more
fully described hereinafter. The input sicle of the
switch 38 is connected to a programmable unijunction
transistor (PUT) 42. The equivalent circuitry of the
PIJT comprises a NPN/PNP transistor ne-twork where the
base of the ~PN transistor is connected to the collector
of the PNP transistor. Momentary depression of the
switch provides a negative pulse which turns on the IC
40 at pin 6 and resets it to commence its oscillator
timing operation as soon as the switch 38 is open. A
current is thereby caused to flow from the base of the
NPN to the col]ector of the PNP of the PVT 42 to provide
circuit operation between the anode and the cathode of
the PUT. Once the regenerative condition starts, the
equivalent circuitry of the PUT remains in operation
until the load drops off, i.e., when ~he IC 40 timing
cycle is completed. In order to preven-t the anode to
gate voltage of the PUT from floating, a bleed resistor
44 is connected across those points with a capacitor 46
applied to filter out any noise.
The frequency of the oscillator circuit of IC 40
is determined by an ~C network comprising two resistors
48 and 50 and a capacitor 51 connected at pins, 1, 2 and 3
of the IC and valued according to the manufacturer's
recommendations. Likewise, to get the proper timing
period, pins 12 and 13 of the IC 40 are high. Selecting
the proper logic of the IC 40 to provi~e a signal or
high value output at pin 8 requires pin 9 also being
kept high. Accordingly, pin 9 is common to pins 1~,
13, and 14. Pin 14 is the power connection to the IC
unit 40. Auto reset pin 5 of IC 40 is connected to
the power pin 14 and functions as does a signal at pin
6 to reset the logic.
Resistive element 53 is effective :in decreasing
the sensitivity of pin 6 so that it is not affected by
spuxious signal glitches. A resistor 54 sets -the current
at a level to turn on a silicon controlled rectifier (SCR)
56 to provide for current flow through the heater 14.
The timing operation of the IC 40, as no-ted, is a
function of the oscillator frequency cixcuit at pins 1,
2 and 3 and the bit capacity preference is dictated by
the values at pins 12 and 13. For the duration of the
timing or disinfecting cycle, pin 8 is kept high and
current to the SCR 56 continues to cause the SCR to
provide a path for current flow from the voltage source
12 through the PTC 58 until the disinfecting cycle is
timed out.
As an indicator of the operation of the unit during
the disinfecting cycle, a lamp 60 is connected in
parallel across the PTC 58. The resistor 62 has its
value selected dependent upon the indicator lamp and
the illumirlation brilliance desired during its operation.
In FIG. 3 there is illustrated an alternate voltage
control CirCuI t 22. A zener diode 64 comprises one of
the legs of the voltage divider network and sets a
constant level of ~oltage at the input side to the PUT.
The other leg of the voltage divider network includes a
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resistor 66 and diode 68. Similarly, a capacitor 70
is provided to control ripple. This alternate
embodiment is more costly but can provide a ~ery stable
influence to the operation of the PUT 42.
FIGS. 4, 5 and 6 illustrate alternate embodiments
for the circuit control 20 a In FIG. 4 a momentary
switch 72 is illustrated as being connected across pins
5 and 6 of the IC 40. If the circuit of FIG. 4 is
incorporated into the circuit of FIG.2, the IC 40
starts its timing cycle when power is applied initially,
such as when the unit is connected to its power source.
When the disinfecting cycle is completed, and if the
unit remains directly connected to -the power source,
the cycle can be initiated again by momentary depression
of the switch 72. As hereinbefore explained, a capacitor
36 is connected for practical purposesO When the
capacitor 36 is incorporated, recycling of the unit may
be delayed due to a residual charge on the capacitor
which prevents the IC 40 from being reset immediately
following disconnection of the power cord. In this
case the residual charge must be allowed to dissipate.
A resistor 73, not unlike resistor 53, provides for
desensitizing signals at pin 6 of the IC 40.
The circuit of FIG. 5 differs slightly from that
of FIG. 4 in that there is no momentary switching
incorporated. With this particular embodiment, starting
of the timer in each case is accomplished by plugging in
the unit. As before, the charge on the capacitor 36
must be dissipated before operation can be effected.
11 -
In FIG. 6 a single pole single throw switch 74 is
incorporated. When the switch 74 is manually closed,
the timer of the IC 40 is initiali~ed. Act~ation of
the switch 7~ takes the place of inserting and removing
and reinserting the cord as ~or the circuit of FIG. 5.
~ccordingly, switch 74, a~ter the timer of [C ~0 has
timed out and before it can be reset, must be opened
and then closed and then the timer of IC ~0 wil:L start
up again.
In the preferred embodiment oE FIG~ 2 actual
reductions to practice have included the incorporation
of a MCR 72-6 SC~ at SCR 56 and a MC 145~1 BCP
programmable timer at IC 40 both manufactured by Motorola.
Further, a 2N6027 PUT unijunction transistor ~2
manufactured by General Electric was included. These
devices and their equivalent are acceptable. The
remaining elements and their values can be arrived at
without undue difficulty and are a function of the
particular elements selected for use elsewhere in the
circuit~
As hereinbefore stated, the inven-tion is suitable
for use with a DC power source. When modified to
operate with a DC electrical source the switching circuit
can be, for example as seen in Fig. 11, an NPN silicon
powered transistor 57 directly replacing the SCR 56 where
the gate, anode and cathode of the SCR is equivalent to the
base, collector and emitter of the transistor 57.
An alternate circuit is illustrted in E`IG~ 7.
The circuit oE FIG, 7 provides a circuit oE equivalence
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for the functional operation described for con-trol
circuit 20 and timer contro:l 18 of FIG. 1. An
oscillator comprising a PUT transistor 76, a capacitor
78 and resistors 80, 82 and 8~ provides the timing for
a counter 86. Switch 92 acts similarl~ to those
hereinbefore described to initiate the actuation of
the timing circuit. The counter 86 counts the negative
pulses of the oscillator. The logic le~el for the
counter is out of pin 11 and pin 10 of the counter 86
is -the output. NOR gates 88 and 90 act as a latch to
control the output to the switching circuit 16. The
latch of the NOR gates 88 and 90 is essentially the
circuit control 20 of FIG. 1 and ~hen the latch goes
high the SCR is turned on and when the latch goes low
the SCR is turned offO A diode 104 is incorporated to
stabilize the DC signal level into the latch. Resistor
94 sets the output current level from the latch.
Resistor 102 further controls the current level of the
signal passed into the switching circui-t 16 so as, for
example, not to overdrive the SCR 56. Resistors 96, 98
and 100 are provided to stabilize signals in the circuit
respec~ive to their locations. The counter 86 of FIG.
7 can comprise a CMOS MSI 14 bit counter and, for
example, can be a MC14020B element available from
Mo-torola Corporation.
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i7tf 2
In the embodiment for the invention illustrated
in FIG. 8 there is disclosed a circuit fox use with
load 106, which load can be variable and selected by
the user. Such a selected load can be disposed in the
circuit path in any manner commercially suitable. This
can be accomplished, :Eor example, by a receptacle being
disposed to receive a mating plug connected directly or
indirectly with the load selected. It will be
appreciated that other methods are available to switch
loads into and out of the circuit.
Like elements of this circuit to previously
discussed elements of other figures are identified by
like re~erence characters which have been heretofore
disclosed. The circuit control 108 is modi~ied
from the circuit controls previously described with
respect to FIGS. 2, 4, 5, 6 and 7 by providing a
manually operable switch 110 outside the balance of the
previously described circuit control circuits. Switch
110 is i]lustrated in this manner for the convenience
of identifying that the alternate circuit of EIG. 8
becomes operational by the actuation of a switch. The
operator will select by means of a schematically
illustrated time select switching circuit 112 a specific
time period desired for operation of the load 106. Each
of the illustrated time blocks 114, 116~ , 120 and 122
identi~iecl by letter designations Tl, T2~ T3, T4 and T5,
respectively, when connected through the time select
switch 112 provided a fixed period of time fox operation
14
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of the circuit of FIG. 9. Each time period can
differ in length. During the timing operation master
timer control 124 provides for a signal to be passed
to the switching circuit 16. It will be appreciated
that timer control 124 incorF)orates the baslc elements
of the timer control 18 as shown in FIG. 1 as explained
in more detail with respect particularly ko FIGS. 2
and 7. This is more fully explained hereinafter with
respect to FIG. 10.
Depending upon the type of load 106, the circuit
of switching circuit 16 can be operator or desiyn
selected to incorporatel for example, a SCR like SCR 56
for a half wave or purely resistive load or a triac device
for a load requiring full wave or an NPN transistor
where the voltage source is of a DC type as hereinbefore
explained.
FIG. 9 illustrates an exemplary circuit for the
timers 114, 116, 118, 120 and 122 where, as appreciated,
values for resistors 126 and 128, as well as the value
for capacitor 130, are selected to provide the desired
ti.me period.
FIG. 10 schematically illustrates in part the time
select switch 112 and includes switches 132, 134 and 136
and the IC 138 of the master timer control 124. It will
be noted that the time select switch 112 is a 3 pole
variable throw type switch, as is best appreciated from
FIG. 10 ancl mi~ht, for example, be a rotary type switch.
The variable throw is dependent upon the number of time
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blocks and for the illustraled circui.t of FIG. 8 the
throw is 5~ The IC of FIG. lO, for example~ can be
the Motorola Corporation element MCl4541B.
While there have been described and preEerred
embodiments of this invention at the present time, it
should be obvious to those skilled in the art that
chan~es and modificat.ions can be made thereto without
departing from the spirit and scope of -the invention.
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