Note: Descriptions are shown in the official language in which they were submitted.
2148316
CANADIAN PATENT APPLICATION
TITLE: ELECTRONICALLY CONTROLLED BEVERAGE DISPENSER
FIELD OF THE INVENTION:
The present invention relates to beverage dispensers and in particular
electronically
controlled beverage dispensers of the ice bank type.
BACKGROUND OF THE BVVENTTON:
Beverage dispensers are well known in the art and are typically used to
dispense
carbonated beverages consisting of a combination of syrup and carbonated
water.
Beverage dispensers of the ice bank variety use refrigeration equipment
including a
compressor, condenser and evaporator to form an ice bank around the evaporator
coils.
The ice bank is suspended in a tank of cold water and provides a cooling
reserve for the
carbonated water and syrup beverage constituents.
A major problem with the ice banks concerns the regulation of the size
thereof.
Mechanical and electro-mechanical controls are known, however such controls
can be slow
to respond and therefore result in wider than desired fluctuation in the size
of the ice bank.
Electronic controls are known whereby a pair of probes determine the presence
of ice or
water as a function of the conductivity thereof. However, early electronic
controls
suffered from reliability problems, and the probes over time can become
corroded and
therefore provide unreliable information. Furthermore, both mechanical and
electronic
controls have the problem of hysteresis management wherein undesirable short
cycling of
the refrigeration compressor can occur. Such prior art controls have not been
able to
determine with a high degree of certainty if ice is present, and if so is
there is sufficient
thickness that further ice production should be terminated.
A similar problem exists in current art beverage dispensers with respect to
the carbonator.
The carbonator, of course, is the vessel wherein plain water and carbon
dioxide are
combined to produce the carbonated water. Typically, a carbonator includes a
probe
21~$~~,6
positioned therein having high and low probe contact points for electronically
determining
the level of water within the carbonator. Specifically, the probes determine
the presence
of water or air with respect to the difference in electrical resistance there
between. Prior
art level controls of this type, as with ice bank controls, suffer with the
problem of
accuracy. The interior of the carbonator is a dynamic environment where water
and
carbon dioxide are being combined causing turbulation and spray. Thus, it has
always
been difficult to know if the water is in fact sufficiently low to require
water to be
pumped to the carbonator. Since it is difficult to know the level of the water
in the tank,
it is also difficult to build in any form of hysteresis control so that the
pump is not short
cycled
A further problem with prior art dispensers of the ice bank type concerns the
control of
the agitator motor. The agitator motor is used to circulate water within the
water tank in
which the ice bank resides to enhance heat exchange between the ice and the
water and
ultimately the beverage constituents. In such prior art dispensers agitator
motors are
generally operated continuously. However, such use of electrical power is
wasteful,
especially during periods of time wherein the dispenser is not in use. Thus,
it would be
desirable to operate the agitator motor more in accordance with the actual
need thereof.
It is also known that the carbonator can become less effective at carbonating
plain water
over time. This can occur as a result of oxygen and other gases entrained in
the water
being released therefrom within in the carbonator. Eventually, the air space
within the
carbonator that is ideally totally carbon dioxide, can include a substantial
percentage of
oxygen, nitrogen, and so forth. Thus, various strategies have been proposed to
use a
solenoid operated valve to periodically vent air from the carbonator air space
and replace
it with carbon dioxide. However, such devices typically purge air from the
carbonator
based upon a predetermined time Iapse. It would be more desirable to purge the
carbonator based more directly upon the actual presence of contaminating gases
as
opposed to the lapse of a predetermined period of time where such purging may
occur
needlessly.
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SUMMARY OF THE INVENTION
The present invention is an electronic control for use with a beverage
dispenser, and
particular a beverage dispenser of the ice bank type. Such a beverage
dispenser includes a
water tank for holding a volume of water. The water is refrigerated by an
evaporator
suspended therein and connected to a compressor and a condenser. A fan motor
is used to
cool the condenser. A plurality of syrup lines extend through the tank for
cooling thereof
and are connected to a plurality of beverage dispensing valves secured to the
beverage
dispenser. In the preferred embodiment, a carbonator is positioned within the
water tank
to provide for direct cooling thereof. The carbonator includes a level sensor
having low
and high sensing contact points and includes a solenoid operated safety valve.
The
carbonator has a plurality of carbonated water lines extending therefrom for
connection to
the plurality of beverage dispensing valves. An agitator motor is secured to
the dispenser
and includes a shaft and an agitating plate for providing movement of the
water in the
water bath. An ice bank sensor is positioned within the water bath with
respect to the
evaporator coils to provide for the formation of the desired sized ice bank on
the
evaporator coils. The ice bank sensor includes two probes across which an
electrical pulse
can be generated. A temperature sensing probe is positioned with respect to
the
evaporator coils so that it exists centrally within the ice bank. A water pump
provides for
pressurized delivery of plain water to the carbonator tank.
The electronic control of the present invention includes a microprocessor
connected to and
receiving information from the ice bank sensor, the temperature sensor and the
carbonator
level sensor. In turn, the microprocessor is connected to and provides for the
control, of
the solenoid safety valve, the agitator motor, the water pump and the
compressor. Of
course, the ice bank sensor, the temperature sensor, the carbonator level
sensor, the
solenoid safety valve, the agitator motor, the water pump and the compressor
all have
specific circuitry associated therewith through which the microprocessor
exercises control
and receives information. Power is supplied to the microprocessor by a
regulated supply
and further input is provided thereto by a zero crossing circuit. A constant
reference
voltage circuit is supplied to the microprocessor and to the ice bank probe
and carbonator
probe.
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The microprocessor is programmed to control the ice bank sensor and related
circuitry
wherein a DC signal is alternately permitted to flow in opposite directions
between the
two probes thereof.
The microprocessor is programmed to control the ice bank sensor and related
circuitry
wherein the presence or not of ice is determined by the change in resistance
to electrical
flow between the probes thereof. However, unlike the prior art a DC signal is
alternately
permitted to flow in opposite directions between the two probes thereof.
Moreover, this
energizing of the probes only occurs when readings are to be taken, otherwise
there is no
potential there between. Furthermore, it was found that if each sampling
occurs for a
period of time of less than 4 milliseconds, corrosive deposition from one
probe to the
other can be avoided. Also, the alternating of the direction of the current
flow further
serves to negate any deposition that could occw over time as well as permit
the use of DC
current which allows for simpler and less costly circuitry than with the use
of AC current
as seen in the prior art. The sampling is controlled by software wherein 8
readings are
taken after which the two highest and two lowest readings are thrown out and
the
remaining four are averaged. The resulting reading is compared to high and low
set points
that have been experimentally determined based upon the known range of water
qualities
as well as the particular dimensions of the ice sensor, its specific
performance in water of
varying ionic and particulate content and so forth. Thus, the compressor will
be signaled
to turn on to build the ice bank if the sensed resistance is below the low set
point, and
conversely will be turned off if the averaged reading is above the high set
point. No
change in the current state, whether it be make ice or not make ice, will
occur if the
averaged reading is between the low and high set points. The high and low set
points
therefore provide for hysteresis management so that the determination of the
existence of
ice or not over the probes can be done with a high degree of reliability. In
addition, a
reading of the temperature probe is also taken simultaneously with the
determination of the
resistance between the ice bank probes. If the determination is that ice is
present over the
probes, an increment, in the present case 0.9 degrees F as experimentally
determined, is
subtracted from the current ice bank temperature reading. Rather than
immediately turning
off the compressor, it is left running until the ice bank temperature probe
reads this lower
temperature. As is understood by those of skill, to increase the size of an
ice bank
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requires the refrigeration system to work progressively harder. Thus, there is
a correlation
between the temperature within the ice bank and its overall size or thickness.
Therefore,
by permitting the compressor to run based upon the temperature of the ice
bank, a further
desired amount of ice can be safely and accurately added to the ice bank
beyond the
physical position of the probes. In addition, ambient load proportionally
affects the
amount of ice which is added to the ice bank. The product of the refrigeration
system
cooling rate and the ice thickness forms the basis for determining the amount
of ice added.
As the ambient load increases, the refrigeration cooling rate decreases,
forming increased
or additional ice reserve compared to nominal ambient loads. The increased ice
reserve is
beneficial to provide additional cooling reserve when needed in higher
ambients. The
reverse also hold true wherein lower than nominal ambients will produce less
ice when
additional cooling is not needed. It can be seen that such an approach further
protects
against undesirable short cycling of the compressor as is not turned off at
the first
indication of ice at the ice sensing probes, which particularly during a
period of high
volume beverage dispensing, could very quickly result in melting of that ice
and a
determination that ice should again be produced.
The carbonator probes also use a DC signal, but, unlike the ice bank sensor
probes. since
the current flow is not between the high and low water level probes but
between each
probe and the grounded carbonator tank, reversal of such flow is not
necessary. However,
in the carbonator level sensing circuit , like that of the ice bank sensing
circuit, current is
not present at the high and low probes unless readings are being taken. The
microcontroller software then directs the sampling of each probe 64 times in
time spans of
less than 4 milliseconds to prevent any corrosive degradation. The 64 samples
provide for
determining with high reliability that each probe is either in air or water. I
f they are both
in air the water pump is turned on, if they are both in water the pump is
turned off. If the
high and low water level probes disagree, that is, one is in air and the other
in water, then
no change is made to the current pump operation.
The carbonator safety valve is operated periodically based upon an
accumulation of pump
run time. Thus, unwanted gases are released from the carbonator based upon a
factor that
relates directly to the presence of those unwanted gases therein.
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The agitator motor is operated as a function of the temperature sensed by the
temperature
probe during initial start up of the dispenser when no ice is present on the
evaporator
coils. Also, the agitator is operated on the basis of whether or not the
compressor and/or
the carbonator pump have been running during a predetermined time period.
Thus, if no
drinks have been drawn during the predetermined time period, as indicated by
no running
of the water pump, or the compressor has not been running during that time
period, also
indicating no drink dispensing requiring ice bank replenishment, the agitator
is fumed off.
Such agitator control was found to decrease the amount of time needed for and
initial pull
down forming a full ice bank, and to save energy by not running the agitator
motor and
not running the compressor to replace ice needlessly eroded by constant
running of the
agitator.
DESCRIPTION OF THE DRAWINGS
A further understanding of the structure, operation, and objects and
advantages of the
present invention can be had by referring to the following detailed
description which refers
to the following figures, wherein:
Fig. 1 shows a perspective view of a carbonator.
Fig. 2 shows a top plan view along lines 2-2 of figure 1.
Fig. 3 shows a partial cross-sectional side plan view along Iines 3-3 of
figure Z.
Fig. 4 shows an end plan view long lines 4-4 of Fig. 3.
Fig. 5 shows a cross-sectional view along lines 5-5 of Fig. 3.
Fig. 6 shows a side plan partial cross-sectional view of an ice bank cooled
beverage
dispenser.
Fig. 7 shows a top plan view along lines 7-7 of figure 6.
Fig. 8 shows an enlarged exploded view of the ice bank probe, temperature
probe and
evaporator coil mounting plate.
Fig. 9 shows an enlarged front plan view of the ice bank probe secured to the
evaporator
coil mounting plate.
Fig. 10 shows a side plan view along lines 10-10 of Fig. 9.
Fig. 11 shows an enlarged cross-sectional view of the solenoid operated safety
valve.
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Fig. 12 is an overall schematic diagram of the electronic control of the
present invention.
Fig. 13 shows a schematic view of a plain water connection to a dispensing
valve.
Fig. 14 is a schematic diagram of the ice bank probe control circuitry.
Fig. 15 is a schematic diagram of the carbonator probe control circuitry.
Fig. 16 is a schematic diagram of the solenoid operated safety valve and the
temperature
sensing control circuitry.
Fig. 17 is a schematic diagram of the agitator motor, the carbonator and the
compressor
control circuitry.
Fig. 18 is a schematic diagram of the boost pumping circuitry and of the
microprocessor
and connections thereto.
Fig. 19 is a schematic diagram of the power and zero crossing circuitry.
Fig. 20 is a schematic diagram of the voltage regulating and voltage reference
circuitry.
Fig. 21 is a flow diagram of the microprocessor control of the ice bank probe
and the data
received therefrom.
Fig. 22 is a flow diagram of the microprocessor control of compressor.
Fig. 23 is a flow diagram of the microprocessor control of carbonator probe
and the data
received therefrom.
Fig. 24 is a flow diagram of the microprocessor control of plain water pump.
Fig. 25 is a flow diagram of the microprocessor control of agitator motor.
Fig. 26 is a flow diagram of the microprocessor control of solenoid operated
carbonator
safety valve.
DETAILED DESCRIPTTON
A carbonator is seen in figures 1-5 and generally is referred to by the
numeral 10. As
seen therein, carbonator 10 includes a first half 12 and a second half 14.
Halves 12 and
14 are made from a suitable sheet metal such as 18 gauge stainless steel. In
particular,
they are cold drawn to form an alternating pattern of seams 16 and ridges 18.
Halves 12
and 14 are welded together around their respective perimeter edges having top
and bottom
perimeter edge portions 20 and 21 respectively and side edge portions 22, and
along
corresponding seams 16, to form the carbonator tank 22. It can be seen that
tank 23
includes a top tank volume area 24, a bottom area 26 and a plurality of
vertical column
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214~~~.~
areas 28. The top and bottom areas 24 and 26 provide for fluid communication
between
the columns 28. A top end 29 of tank includes a solenoid operated pressure
relief valve
30, a carbon dioxide inlet fitting 32, a water inlet fitting 34 and a level
sensor fitting 36
for retaining a water Level sensor 38. Sensor 38 includes a high level sensing
contact 38a,
and a low level sensing contact 38b that are connected by a pair of wires 40
to control
means described in greater detail below. A J-tube 41 is secured to fitting 34
and extends
within a column 28.
A plurality of carbonated water lines 42 extend from a bottom end 43 of tank
23 and
include vertical portions 42a that travel upwardly closely along and adjacent
first half 12
and then extend with horizontal portions 42b over end 29 and outwardly
therefrom in a
direction towards side 14 and terminate with beverage valve fittings 44.
As is seen by refernng to Fig.'s 6 and 7, carbonator 10 is shown in an ice
bank type of
beverage dispenser 50. As is known in the art, dispenser 50 includes an
insulated water
bath tank 51 having a bottom surface 51 a, a front surface 51 b, and rear
surface 51 c and
two side surfaces Sld. A plurality of evaporator coils 52 are held
substantially centrally
within tank 51 and substantially below a surface level W of water held in tank
51 for
producing an ice bank 53 thereon. Carbonator 10 is located within tank 50 and
adjacent a
front end 54 of dispenser 50. In particular, dispenser 50 includes a plurality
of beverage
dispensing valves 55 secured to the front end 54. It can be understood that
carbonated
water fittings 44 allow lines 42 to be hard-plumbed directly to each valve S5.
A
transformer marked TR is connected to an AC line voltage supply and provides
24VAC
current to the valves 55. Dispenser 50 also includes a removable plate 56 that
provides
access to a space 57 between plate and tank 50. A water delivery line 58 is
connected to
a source of potable water and routed through space 57 to a water pump 59. Pump
59
pumps water through a line 60 to carbonator 10. The majority of the length of
line 60
consists of a serpentine coil 60a submerged in tank 50 to provide for cooling
of the water
flowing there through. Coil 60a is arranged in four convoluted or serpentine
portions
centrally of evaporator coils 53. Evaporator coils 53 are, as is known in the
art, connected
to a refrigeration system. Specifically, the refrigeration system main
components include,
a refrigeration compressor 61 secured to a top deck floor 62, a condenser 63
held by a
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2~.48~~.~
support and air directing shroud 64 above a cooling fan 64a operated by a
motor 64b. An
agitator motor 65 includes a shaft 65a and a turbulator blade 65b on an end
thereof, and is
secured at an angle to floor 62 by an angled support 65c. A carbon dioxide gas
delivery
line 66 is routed through space 57 and is connected to gas inlet 32. Each
valve 55 is
connected to a syrup line 67. Lines 67 are each connected to a source of syrup
and are
also initially routed through space 57 and then consist of a plurality of
loops positioned
closely adjacent carbonator 10 in tank 51. Lines 67 then terminate by direct
hard
plumbing to valves 55 as the ends thereof come up and over carbonator top end
29. Tank
51 includes a front ridge 68, and a U-shaped ridge 69, integrally molded into
bottom
surface 51 a thereof. Ridge 68 includes an angled surface 68a, and extends
across the
width of tank 51 from one side Sld to the other. Ridge 69 has two parallel
components
69a extending in a direction from dispenser front end 56 to the rear end
opposite
therefrom, and a component 69b perpendicular thereto and extending there
between
forming the "U" shape. Ridge portion 69a and 69b each include a portion 69c
that
extends transversely to tank bottom 51 a.
As seen in Fig. 8, an ice bank sensor 70 and a temperature sensor 72 are
secured to a
retaining bracket 74 which in turn is releasably securable to evaporator coils
52. As seen
by also refernng to Figs. 8, 9 and 10, bracket 74 includes a pair of lower
coil retaining
arms 76 and a flexible coil engaging tab 78. Bracket 74 also includes a
temperature probe
guide arm 80 having a guide hole 81 therein, and three ice bank sensor
retaining holes 82
extending through a flat vertical surface 83 thereof. Hole 81 provides for
slideably
receiving the body 84 of temperature sensor 72. Sensor 72 also includes an
upper plate 86
for securing to deck 62 and includes a pair of wires 88 for connection to a
control means.
Ice bank sensor 70 includes a sensor retaining clip 90 having a wire retaining
portion 92a
and a protective portion 92b. Protective portion 92b is secured to retaining
portion 92a by
a live hinge 94. Retaining portion 92a includes elevated end portions 96a and
96b.
Portion 96a includes a wire retaining recessed area 98 and return receiving
cavities 99, and
portion 96b includes a pair of probe end retaining holes 100. Portion 92a also
includes
three legs I02 for providing snap fitting retaining thereof with bracket holes
82. Portion
92b includes two flexible clip arms 104 having returns 104a thereon and a pair
of probe
protectors 105. Dual wires W, as seen in Figs. 8 and 9, are partially
separated and have
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214831
some insulation removed therefrom thereby creating probes 106 and 108. Each
probe 106
and 108 include bent ends 106a and 108a respectively for inserting into probe
holes 100.
It can be understood that wires W are retained within clip 90 wherein after
insertion of
probe ends 106a and 108a into holes 100, and an insulated portion of wires W
is placed
within recessed area 98, portion 92b can be secured to portion 92a.
Specifically, as seen
in Fig. 10, clip arms 104 provide for snap fitting securing where returns 104a
of clip arms
104 provide for snap fitting securing to end portion 96a wherein the return
retaining slots
99 thereof hold returns 104x. Clip 90 can then be secured to bracket 74 by
insertion of
the legs thereof into holes 82. Bracket 74 is secured to evaporator coils 52
by first
receiving an individual coil 52 in arms 76 and then snap fitting flexible tab
78 over a
further coil 52. Temperature sensor 72 is secured to dispenser 50 wherein
probe body 84
is guided through hole 81 thereof and plate 86 is secured to deck 62.
Protectors 105 serve
to prevent physical disruption or contact with probes 106 and 108.
As seen in Fig. l I, solenoid valve 30 includes a solenoid 110 and operating
arm 112.
Arm 112 is connected to a valve arm I14 which includes a valve end 114a. Valve
end
114a provides for sealable seating with seat 116. Valve arm 114 is secured to
solenoid
arm I12 by a pin 118. A spring 120 extends around arm 114 and provides for
biasing
seat end 114a against seat 116. Valve arm 114 and spring 120 are retained
within a lower
valve housing portion 122. Housing portion 122 includes a lower hole 124 and a
plurality
of perimeter holes 126. Arm 112 is also secured to a manual actuating ring
128.
Solenoid 110 includes electrical contacts 130 for connection by wires 132 to
control means
and power circuitry therefore.
As seen in Fig. 12, the present invention includes a microcontroller 140 for
providing
electronic control of the safety valve 30, ice bank temperature sensor 72,
carbonator probe
38, ice bank sensor 70, agitator motor 65, pump 59, and compressor 61. Valve
30, ice
bank temperature sensor 72, carbonator probe 38, ice bank probe 72, agitator
motor 65,
water pump 59, and compressor 61 each include particular control circuits 142,
144, 146,
148, 150, 152, and 154 respectively associated therewith. Power is supplied to
the present
invention by power supply circuit I56 having a +Svolt Vcc circuit 157 and a
zero crossing
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circuit 158. The control of the present invention also includes a boost pump
circuit 160
and reference and threshold voltage circuits 162 and 164.
Fig. 13 shows a schematic diagram of the situation where a beverage valve 55
is
connected to a plain water line L coming off a T-fitting marked T. Plain water
is supplied
to line L by pump 59. Line 60 provides water to carbonator 10, and as is known
in the
art, a check valve CV is used to prevent carbonated water from exiting back
from
carbonator 10 into line 60. If the plain water supply is of a low pressure,
such as below
30 PSI, pump 59 is turned on by circuit 160 as controlled by microcontroller
140 to
provide additional pressure. Transformer TR provides the 24VAC to each
solenoid SSa of
each valve 55. The 24 VAC is provided to connector JS of boost circuit 160,
seen in
Fig.l8 , and as described in further detail below, for operating pump 59. This
connection
is made at installation of dispenser 50 if the water supply pressure is low.
Thus, pump 59
will be operated when a beverage valve 55 using plain water is activated. The
water will
then flow to that valve 55. Check valve CV along with the pressure in
carbonator 10 will
prevent the plain water from flowing therein.
A detailed view of the control circuitry 148 for ice bank sensor 70 is seen by
refernng to
Fig. 14. Circuit 144 includes a line 166 for providing a known reference
voltage to a pair
of pull-up resistors Rl l and R13. Probe wires 106 and 108 are connected by
wires W to
resistors Rl l and R13 respectively. A pair of open collector inverting
buffers UlA and
U1B are connected via lines 168 and 170 to probes 106 and 108 and resistors
Rll and
R13 respectively. Lines 168 and 170 in turn provide for connection to a logic
ground as
represented by microprocessor pins PC4 and PCS, as seen in Fig. 18. A pair of
non
inverting unity gain op-amps U2B and U2A are connected by lines 172 and 174 to
probes
106 and 108 respectively. Each op-amp UZA and U2B include input protection as
provided by resistors Rl and R2 diode D3 and D1 and capacitors C7 and C6
respectively.
Op-amps U2A and U2B are, in turn, connected to microprocessor 140 along lines
176 and
178.
The operation of circuit 148 can be understood wherein a current coming in
along line 166
will normally flow to resistors Rl l and R13 to a logic ground through buffers
UlA and
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U1B. When a reading of the conductivity of the water existing between probes
106 and
108 is desired for determining whether or not water or ice is present,
electrically current is
induced to flow between probe wires 106 and 108 by, for example, the signaling
of buffer
UlA to switch from ground to an open circuit. Thus, the current will flow
through
resistor Rl l to probe 106 and after a period of time a voltage and current
flow equilibrium
will reached wherein current will now flow from probe 106 to probe 108 and to
logic
ground represented by buffer U1B. As this current flow is DC, the direction of
current
flow between probe wires 106 and 108 is periodically reversed so as to
minimize any
corrosive effects as a result of the DC current. The specific manner of
reversing of such
current flow and the sensing thereof by micrcontroller 140 will be described
in greater
detail herein below. Thus, it will be apparent to those of skill, that such a
reversal of flow
will occur wherein buffer U1B is switched from ground to an open state and
conversely
buffer UlA is switched from an open state to ground. Thus, current will flow
along
resistor R13 in the direction from probe 108 to probe 106. It can also be
understood that
when current is flowing in the direction from probe 106 to 108 op-amp U2B will
be able
to detect the magnitude of such and report such analog information to
microcontroller 140.
Microcontroller 140 includes an analog to digital converter which converts the
signal from
op-amp U2B to a scale of zero to 255 wherein zero represents OV and 255
represents
Z.SV. In the same manner, op-amp U2A provides an analog signal proportional to
the
magnitude of current flow in the direction of probe 108 to probe 106. As
stated, an
advantage of the present ice bank detecting circuit of the present invention
concerns the
ability to reverse the direction of flow to minimize any corrosion of either
of the probes.
Moreover, it can be seen that there is no potential at the probes other than
when readings
are to be taken, and such readings within a two millisecond window to further
prevent any
corrosive deposits. It was found that a 4 millisecond threshold current flow
time must
occur before any corrosive deposition occurs. Thus, keeping such reading time
below that
threshold will serve to prevent any corrosive deposition on either of the
probes.
The carbonator probe circuitry 146 is seen in greater detail in Fig. 15. Lines
180 provide
reference voltage to resistors R9 and R10. A high level water level sensor
probe 38a is
connected via line 182 to resistor R9 and a lower water level sensor probe 38b
is
connected via line 184 to resistor R10. Open collector inverting buffers UlE
and U1F are
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connected by lines 186 and 188 to lines 184 and 182 respectively. Buffers UlE
and UlF
are connected to a logic ground via line 190. A comparator U6a is connected to
line 182
and to a threshold voltage along line I92. Similarly, a second comparator U6b
is
connected to line 184 and connected to the same threshold voltage via line
194. Both
comparators U6a and U6b include resistors RS and R4, diodes D2 and D4, and
capacitors
C8 and C9 respectively for providing input protection as is understood by
those of skill.
Comparators U6a and U6b have outputs connected to microcontroller inputs AS
and
carbonator level sensor also includes a contact 196 connected by jumper 197 to
a ground
198 through the carbonator tank 23 which is connected to ground. As an
integral part of
the level sensor, when the sensor connector is removed from the control, the
contact 196 is
connected by line 199 to VCC which can be detected by the microcontroller 140.
This
will prevent the pump operation when no carbonator level sensor is connected
to the
control.
The operation of the carbonator probe level sensing circuitry is similar to
that of ice bank
control circuitry 144. In particular, buffers UlE and U1F are generally held
at logic
ground wherein current flows along lines 180 through resistors R9 and R10
through
buffers UlE and U1F of line 190. If a reading of upper level probe 38a is to
occur, buffer
UIF is changed to an open state wherein current will now flow from upper probe
38a to
the grounded carbonator tank 23. Similarly, if a reading of lower probe 38b is
to take
place, buffer U1B is signaled to change to an open state wherein potential
will now form
between 38b and the grounded tank 23. As with prior art carbonator level
sensing probe,
sensing of air or water is determined by the difference in resistance to flow
there between.
However, unlike the situation just described for sensing the presence of water
or ice where
such differences are proportionately smaller and more subject to variability
with respect to
purity, or lack thereof, in the water forming the ice bank, the difference in
resistance of
flow between water and air is quite dramatic. Thus, comparators U6a and U6b
can be
used to send a digital signal to microcontroller 140 wherein a high reading
will indicate a
presence of air and a low reading will indicate the presence of water. Thus,
comparators
U6a and U6b only need a threshold of voltage supplied thereto along lines 192
and 194 to
which to compare the signals from probes 38a and 38b. Microcontroller 140 will
therefore
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signal the operation of pump 59 based upon the inputs from circuit 144. A more
detailed
understanding of the air level probe control logic will be discussed herein
below.
Referring to Fig. 18, single chip microcontroller 140 is seen. In the present
invention,
controller 140 is a model MC68HC05 made by Motorola having a microprocessor,
RAM ,
an onboard A to D converter and the particular programming of the present
invention
contained in the permanent memory thereof. Crystal X1, capacitors C10 and C11,
and
resistor R13 form the clock oscillator for microcontroller 140, and capacitor
C20 provides
power input filtering therefor. The output port pins of microcontroller output
directly
control the AC outputs to compressor 61, carbonator water pump 59, and
agitator motor
65. The low voltage outputs thereof control ice bank sensor 70, carbonator
level sensor
38 and their associated circuitry 148 and 146. Two status LEDs (D15 and D16)
are
directly under software control.
As also seen in Fig. 18, resistor R30, diode D7 and the opto-coupled
darlington transistor
(ISO1) form a carbonator pump boosting input to the microcontroller. A 24V AC
signal
applied to pin 3 of JS will activate pump 59.
As seen in Fig.'s 18 and 19, 24V AC input power is supplied to connector JS
pins 1 and 2.
Diode D12, capacitors C19 and C21, voltage regulator U4 and resistors R36 and
R38 form
a half wave rectified +12V DC power supply. The +12V DC supply has dual use as
a
pre-regulator for +SV DC "VCC" power supply 158 and the power for the a relay
coil T90
seen in Fig. 16. The pre-regulator is necessary to provide reliable operation
over a wide
input voltage range. Resistor R34 and zener diode D14 are provided for
operation at the
high limit of input voltages. Diode D13 and capacitor C18 are included as
noise filter
elements to protect the power regulators from transient voltages developed
when switching
the compressor relay coil Kl . The metal oxide varistor RV 1 is included to
protect the
circuit board from power line transient voltages. Resistor R37 and capacitor
C22 provide
some additional power dissipation for the +SV DC regulator (LTS) to allow
operation
without a heat sink.
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2148316
As seen in Fig. 19, a zero-cross circuit 158 consisting of R31, C12, D6, R32,
R33 and
transistor Q3 provides pulse outputs to an input port pin of microcontroller
140 to indicate
when the input AC power is near zero volts. This signal is used to synchronize
a
compressor relay T90 with the input power to minimize current surges at turn-
on and
electrical noise spikes at turn-off of the compressor.
As seen in Fig. 20, circuit 157 includes regulator IC (US) for providing a +SV
DC output
from the pre-regulated +12V DC input. Capacitors C15, C4 and C1 provide
electrical
noise filtering for reliable operation of the control. Regulator US also
monitors the +SV
DC power through "sense" input and provides a logical reset signal to
microcontroller 140
when power is below the safe operating limit. Capacitor C23 provides
additional reset
pulse filtering to microcontroller 140.
The ice bank temperature, ice bank continuity and carbonator level detect
circuits 144, 148
and 146 require a stable voltage reference to measure their respective
parameters. As seen
in Fig. 20, circuit 162 includes resistive divider R35 and R14 with capacitor
C3 to divide
the +SV DC in half to +2.SV DC. An operational amplifier (U2C) buffers the
+Z.SV
signal with a low-impedance driver to isolate the off board components from
the on-board
components to minimize electrical noise interference on the control board.
The carbonator circuit comparators U6A and U6B need a voltage threshold to
compare
against the input signals to make a logic level decision whether the probes
are in "air" or
"water". Resistors R16 and R17 divide the +SV DC "VCC" to provide the
threshold
signal. Since the signal does not leave the circuit board, no additional
buffering with an
op-amp is needed.
As seen in Fig. 16, the ice bank temperature thermistor sensor circuit 144
forms a voltage
divider circuit with resistor R7 and filter capacitor C2. The operational
amplifier U2D
provides all the signal conditioning needed to expand the sensor usable signal
range to
cover the expected ice bank temperature range. Resistors R3, R6 and R8 provide
the
needed gain and offset.
-15-
~~~s~~s
As seen in Fig. 17 with respect to agitator control circuit 150,
microcontroller output port
pin controls the LED half of an optically coupled triac driver IS04. In
addition, when the
agitator output is active, LED D10 will also be illuminated. The output power
for agitator
motor 65 is directly switched through triac Q4. Resistors R20, R21 and
capacitor C14
form a "snubber" circuit to provide reliable "switching" operation.
As seen in Fig. 17 with respect to carbonator pump circuit 152, a
microcontroller output
port pin controls the LED half of an optically coupled triac driver IS03. In
addition,
when the carbonator output is active, LED D9 will also be illuminated. The
output power
for carbonator motor 59 is directly switched through a heavy duty triac Q1,
which is
attached to a heat sink to dissipate heat when pump 59 is running. Resistors
R18, R19
and capacitor C17 form a "snubber" circuit to provide reliable "switching"
operation. Fuse
F1 is included in the output to protect the circuit components if pump motor
59 becomes
stalled, since motor 59 has no internal overcurrent protection.
As seen in Fig. 17 with respect to compressor control circuit 154, a
microcontroller output
port pin controls a transistor switch formed by Q2 and resistors R39 and R40.
In addition,
when the compressor output is active, LED D8 will also be illuminated. Diode
D5
protects the transistor switch from electrical transients which occur when the
relay is
switched off. The output power for compressor 61 is directly switched through
the relay
contacts. Resistor R12 and capacitor C13 form a "snubber" circuit to provide
long reliable
contact life while reducing electrical noise interference.
As seen by referring to Fig. 16 with respect to safety valve control circuit
142, a
microcontroller output port pin controls the LED half of an optically coupled
triac driver
IS02. In addition, when the safety valve output is active, LED D11 will also
be
illuminated. The output power for valve 30 is directly switched through triac
Q5.
Resistors R22, R23 and capacitor C16 form a "snubber" circuit to provide
reliable
"switching" operation.
An understanding of the operation of the present invention can be had by
refernng to the
flow diagrams contained in Fig.'s 21 through 26. It will be understood, by
those of skill,
-16-
21~831~
that microcontroller 140 includes specific progamming for operating the
various
components of a beverage dispenser. Such flow diagams being illustrative of
the control
of such components as exercised by microcontroller 140 as a function of its
specific
progamming.
A more detailed understanding of the operation of ice sensor 70 and related
circuit 148
can be had by referring to Fig. 21. As seen therein, current is made to flow
from probe
106 to 108 by energizing of buffer UlA. Four individual readings are taken
wherein
buffer U1B is switched between an open state and logic ground four times with
a suitable
wait period there between to provide for the voltage and current flow to
stabilize. At
block 204 buffer UlA is switched to logic Bound after which buffer U1B at
block 206 is
switched to an open state. Block 208 four readings are taken by op-amp U2A
current
flow from probe 108 to 106 as a result of the cycling between an open state
and logic
ground by buffer U1B. At block 210 both buffers UlA and U1B are held to a
logic
Bound. At block 212 there now exists eight individual conductivity readings
wherein the
highest two and lowest two such readings are thrown out and the remaining four
readings
are averaged. Decision block 214 the microcontroller determines whether or not
a make
ice mode is set. Thus, if microcontroller 140 has previously determined that
ice should be
made, the make ice mode will have been set as will become more clear in the
following
flow diagam. If the make ice mode is not set, then at decision block 216 it is
determined
as calculated by block 212, is below a low set point. The low set point is a
resistance
level that has been chosen therein if the resistance determined by sensor 90
is below this
level then water is indicated and a change to a make ice state occurs at block
218 then
LED 1 is turned on at block 220. If however, at decision block 216 the average
is greater
than the low set point, no change in state is indicated and this routine is
exited. If at
decision block 214 the make ice mode is set, then at decision block 222 it is
determined if
the average resistance value calculated at block 212 is greater than a high
set point. The
high set point is a resistance level selected as being indicative of ice being
present
covering probes 106 and 108. If the average calculated at block 212 is greater
than the
high set point, then the microprocessor changes to a stop make ice state after
which LED
1 is turned off at block 226. If at decision block 222 the average determined
at block 212
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2148~~.~
is less than the high set point, then no change in the ice mode is made and
the routine is
exited
The programmed control of compressor 61 can be understood by referring to Fig.
22. As
seen therein at block 228 it is first determined whether or not compressor 61
is running.
If the answer is yes, at decision block 230 it is determined whether or not
the program is
in the make ice mode. If the compressor and it is the make ice mode then a
stop flag is
cleared at block 232 after which at block 234 the ice bank temperature probe
70 is read
and at decision block 236 it is determined if the temperature is below a fail
safe level.
This fail safe temperature is experimentally determined as a temperature
indicating that the
ice bank, for whatever reason, has grown too large, thereby indicating some
sort of
mechanical and/or electronic failure. Thus, at block 238 the compressor is
shut down,
failure is indicated. The compressor startup is locked out wherein the
compressor can
only be restarted by a manual reset. If at decision block 230 the routine is
not in the
make ice mode at decision block 240 the decision is made whether or not the
stop flag is
set. If it has not been set at block 240 it is set and the routine flows
through to return.
On a subsequent time through at decision block 240 the decision will be that
the stop flag
is set. The reason for the stop flag is that the sensing of the presence of
ice by ice bank
sensor 90 and as per the flow diagram of Fig. 21 and the ruining of the
present
compressor control regime occur every 30 seconds. Thus, requiring stop flags
ensures that
at least two measurements are taken 30 seconds apart with respect to the
decision of
whether to turn off compressor 61. This approach provides for added assurance
that ice
bank probes 106 and 108 indeed are covered with ice as opposed to a transient
situation.
Continuing, at decision block 244 routine asks is this the first time through.
In the present
case since this will be the first time through and at decision block 246 ice
bank
temperature probe 72 is read and 0.9°F is subtracted from that
currently sensed
temperature and stored as a set point. The next time through, assuming the
compressor is
running, make ice mode is yes, stop flag is set at decision block 246, this
will now be the
second time through, for purposes of this discussion, after which at block 248
the current
temperature is read and compared with the previous stored set point. If at
decision block
250 the read temperature is greater than the set point then the compressor is
left running
and again cycles through blocks 234, 236, and 238. If the sensed temperature
is less than
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21~83~.~
the set point then at block 2S2 turn off the compressor and clear a two minute
timer. The
reason for the "first time" question block 246 is to provide a set temperature
point for
determining when the compressor should be turned off. It was experimentally
determined
that the 0.9°F increment that must be reached at decision block 250
before compressor 61
can be turned off. Thus, compressor 61 is not turned off immediately when ice
is
determined to be covering probes 106 and 108, but is allowed to run and
develop
additional ice beyond probes 106 and 108. In the particular embodiment
described herein,
the 0.9°F was found to provide for the desired additional amount of ice
bank deposition.
It can be appreciated by those with skill that decision block 246 permits a
fixing of that
ice temperature set point so that the routine can subsequently flow to block
248.
Otherwise, the set point would be changed each time and the compressor would
not turn
off. If at block 228 it is determined that the compressor is not running, at
decision block
2S3 it is first determined if the compressor is in lock up. If it is the
routine goes to return
and compressor can not be started. If it is not in lock up, at decision block
2S4 it is
determined whether or not the two minute timer has expired. If not, the
routine flows to
the return and repeats. If subsequently it is determined that the two minute
timer had
expired then at decision block 2S6 it is determined whether or not we are in
the make ice
mode. If it is not in the make ice mode at block 258 a start flag is cleared.
If at block
256 it is the make ice mode, then at decision block 260 it is determined if
this is the
second time through. If it is not, the start flag is set; if it is, the
compressor is turned on
at block 262 the start flag is set. An understanding of the foregoing wherein
at block 2S4
a two minute timer must expire from the last time compressor 61 was turned off
before it
can be turned on. This, of course, provides for a short cycling protection.
Moreover,
compressor 61 is not turned on at block 264 until at block 260 it is
determined that this is
the second time through the routine. Thus, at least two determinations 30
seconds apart
must confirm that probes 106 and 108 are sensing water.
The control of the carbonator probes can be understood by referring to Fig.
23. At block
270 high and low probe 38a and 38b are turned on and the logical signal is
sent along line
192 to buffers UlE and U1F. Though both probes are turned on simultaneously,
unlike
the situation with ice bank probes 106 and 108, there is not need to reverse
current flow
that would result in flow from carbonator tank 23 to the probes. However, as
with probes
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21483~.G
106 and 108 each probe 38a and 38b is read individually although there will be
a potential
at both. Thus, at block 272 after a suitable delay period at block 274 probe
38a is read 64
times during a total on time of less than 4 milliseconds and generally
approximately 2
milliseconds. The signal along line 192 then provides for turning off buffers
UlE and
U1F at block 276. The probes are then turned on again at block 278 after a
suitable delay
time to allow the voltages to stabilize at block 280 probe 38b is read 64
times, again
within the same time frame as the readings occurnng at probe 38a. At block 284
the
probes are again turned off. At block 286 the 64 samples of probe 38a are read
and if a
majority indicate the probe is in air then that status is set at block 288. Or
if the majority
of readings indicate that the probe is in water, that particular set is set at
block 288. At
block 290 the same procedure occurs for the readings taken with respect to
sensor 38b.
Then at block 292 if the majority of readings indicate air or water, that
particular status is
set. It will be apparent to those with skill that the readings of the
carbonator level probes
will be received by microcontroller 140 as digital information rather than the
analog
information provided by ice bank probes circuit 148. So, at blocks 288 and 292
the probe
status will remain the same as it previously was if the number of readings for
water or air
at any one probe are equal.
An understanding of the control of water pump 59 as a function of the
determination of
the water level sensor 38 it can be had by refernng to Fig. 24. At decision
block 300 it is
first determined if the plain water boost is active. As previously described
the plain water
boost is activated if incoming plain water pressure is not sufficient for
providing flow of
plain water to one of the valves. Thus, we are not concerned at this point
whether or not
the carbonator needs water as pump 59 is being operated to provide plain water
to one of
the valves. At decision block 302 we must first determine if pump 59 is in a
lockup
mode. If it is not, at block 304 we turn on pump 59. At decision block 306 we
determine
if the maximum run time of pump 59 has been exceeded. If it has we indicate
failure at
block 308, shut off pump 59 at block 310 and lockup the operation of pump 59
at block
312 so that restarting must require service personnel. If at decision block
306 the
maximum run time has not been exceed then we can go to return. It can be
appreciated
by those with skill that decision block 306 provides a safety measure wherein
if pump 59
has been running for a continuous period of time, for example, more than five
minutes the
-20-
21483~f
failure is indicated such as a ruptured line for which the operation pump 59
should be
terminated. If at decision block 300 plain water boost is not active, then the
set values for
probes 38a and 38b are reviewed. If at block 314 both probes are determined to
be in air,
then the pump will be turned on provided it is not in lockup. If at block 316
it is
determined that both probes are in water and block 318 pump 59 is turned off
and the
maximum run time timer is reset at block 320. If at decision block 322, which
we have
reached because probes 38a and 38b do not agree, that is they are not both in
water or
both in air, it is determined if the pump is on. If it is it is allowed to run
unless at block
306 the actual run time is exceeded. If the pump is not on, it is Left off.
Thus, if probes
38a and 38b are indicating the opposite condition, either air or water, from
the other, then
the current state is not changed and the pump is allowed to either run or not
run
depending on that current state.
Appreciation of agitator motor 65 can be understood by refernng to the diagram
of Fig.
25. At decision block 330 it is determined if compressor 61 is on. If it is on
at decision
block 332 it is determined by temperature probe 72 if the ice bank temperature
is above
65°. If it is, agitator 65 is turned off at block 324. If the ice bank
temperature is below
65° at decision block 326 it is determined if the ice bank temperature
is below 60°F. If
the temperature is between 65° and 60°F, no change is made to
the current operation of
the agitator, whether it be on or off. If, however, temperature at block 326
is determined
to be below 60°F, then agitator 65 is turned on at block 328. Blocks
322 through 328
provide for control of agitator 65 at initial pull down, that is startup of
dispenser 50
wherein no ice bank has of yet formed. Typically, in an initial pull down
situation a
compressor would run until it trips off because of the great cooling demand.
This demand
of course was exacerbated by the fact that, to quote prior art, dispenser the
agitator motor
would be running continuously. It was found that if the agitator motor were
turned off in
situations where the temperature was sensed to be above 65° compressor
61 would not
have to run as much and would not run until it would trip off as a result of a
safety in the
compressor motor itself. Thus, agitator 65 would only be run if the
temperature reached a
lower value such as 60°F. Of course, the 5° range between
60° and 65° provides for a
hysteresis of management. It was found that this strategy provides for initial
pull down to
a full formation of a desirable ice bank in a shorter period of time than if
the agitator
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2~.~8~1~
motor were allowed to run constantly. If at black 330 the compressor is found
to be off at
decision block 340 is determined whether or not a carbonator 10 is located
within the ice
bank. If it is not, the agitator is turned on and left running. Thus, in a non-
integral
carbonator situation, that is a remote carbonator, the agitator motor run
continuously. If,
however, the carbonator is located within the ice bank then at decision block
342 it is
determined if water pump 59 and compressor 61 have both been off for a period
of time
greater than ten minutes. If both have been off for a period of time greater
than ten
minutes, then at block 344 agitator motor 65 is turned off. If, however, both
pump 59 and
compressor 61 had been not been off for a period of time greater than ten
minutes then
agitator motor 65 is turned on. In this manner, it can be appreciated that
agitator motor 65
is only run in situations where pump 59 and/or compressor 61 had been running.
In other
words, the operation of agitator 65 is correlated to the drawing of drinks
and/or the
building of ice banks which is directly indicative of dispensing of drinks.
Where in both
situations cooling of beverage constituents is required. However, if pump 59
and/or
compressor 61 had not been active for a period greater than ten minutes, this
indicates that
no drinks are being drawn and the operation of agitator 65 is unneeded. This
is especially
true of tong periods of non-use such as overnight, where continuous operation
of agitator
65 would result in erosion of the ice bank which would have to be replaced by
operation
of the compressor. Thus, not only is some energy saved by not running the
agitator, a
significant amount of energy is saved by not having to run the compressor to
replace
needless erosion caused by the agitator during periods of non-use.
The control of safety valve 30 can be understood by the flow diagram seen in
Fig. 26. At
decision block 350 it is determined if water pump 59 is running. If it is,
that total run
time is accumulated at block 352. If the pump is not running at decision 354
it is
determined if the pump run time accumulated at block 352 has exceeded a
predetermined
set point. If it has not, the pump is allowed to continue running. If it has,
then the
accumulation of run time is reset at decision block 356 and the solenoid of
safety valve 30
is operated to release gases from carbonator 10. In particular, valve 30 is
pulsed rapidly
rather than held open so that the gases in carbonator 10 are allowed to be
released in small
amounts. In this manner, the release of such gas does not cause undesirable
noise.
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