U.S. patent application number 09/766045 was filed with the patent office on 2001-11-01 for compressor control mechanism and method.
Invention is credited to Nelson, William G., Weber, Paul R..
Application Number | 20010035016 09/766045 |
Document ID | / |
Family ID | 27373416 |
Filed Date | 2001-11-01 |
United States Patent
Application |
20010035016 |
Kind Code |
A1 |
Weber, Paul R. ; et
al. |
November 1, 2001 |
Compressor control mechanism and method
Abstract
The present invention is a mechanical refrigeration system and
method of operation thereof including a compressor, a condenser, an
expansion valve an evaporator, a hot gas bypass line and a hot gas
valve. A control regulates the operation of the compressor and the
hot gas valve and, upon determining that the compressor is to be
shut off, first opens the hot gas valve for a predetermined time
period to reduce any pressure differential between the high and low
pressure sides of the compressor. This pressure reduction providing
for reducing or eliminating any destructive compressor movement
that would otherwise occur at shut down as the momentum of the
moving parts of the compressor operate against a pressure
differential. A similar method can be used to avoid such unwanted
movement at start-up of the compressor.
Inventors: |
Weber, Paul R.; (Ham Lake,
MN) ; Nelson, William G.; (South Haven, MN) |
Correspondence
Address: |
Sten Erik Hakanson
Patent Attorney
IMI Cornelius Inc.
One Cornelius Place
Anoka
MN
55303-6234
US
|
Family ID: |
27373416 |
Appl. No.: |
09/766045 |
Filed: |
January 19, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09766045 |
Jan 19, 2001 |
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09639868 |
Aug 16, 2000 |
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09639868 |
Aug 16, 2000 |
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09079063 |
May 14, 1998 |
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5914537 |
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09079063 |
May 14, 1998 |
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08987395 |
Dec 9, 1997 |
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6163095 |
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Current U.S.
Class: |
62/210 |
Current CPC
Class: |
A23G 9/045 20130101;
A23G 9/163 20130101; H02K 2207/03 20130101; A23G 9/46 20130101;
H02K 1/2753 20130101; A23G 9/224 20130101 |
Class at
Publication: |
62/210 |
International
Class: |
F25B 041/00 |
Claims
1. A refrigeration system comprising: a compressor fluidly
connected to a high pressure line extending between a high pressure
outlet side of the compressor and a condenser, the condenser in
fluid communication with an expansion valve for regulating a flow
of condensed and cooled refrigerant to an evaporator and the
evaporator fluidly connect to a low pressure inlet side of the
compressor, and a bypass line having a hot gas valve therein for
directing refrigerant from the high pressure outlet side of the
compressor to the inlet side of the compressor, and a control
mechanism for operating the expansion valve, the compressor and the
hot gas valve for closing the expansion valve and at substantially
the same time opening the hot gas valve for a first predetermined
period of time prior to a desired shut off of the compressor.
2. The system as defined in claim 1 and the first predetermined
period of time elapsing substantially at the time of shut off of
the compressor whereupon the hot gas valve is closed.
3. The system as defined in claim 1 and the first predetermined
period of time elapsing after the turn off of the compressor
whereupon the hot gas valve is closed.
4. A refrigeration system comprising: a compressor fluidly
connected to a high pressure line extending between a high pressure
outlet side of the compressor and a condenser, the condenser in
fluid communication with an expansion valve for regulating a flow
of condensed and cooled refrigerant to an evaporator and the
evaporator fluidly connect to a low pressure inlet side of the
compressor, and a bypass line having a hot gas valve therein for
directing refrigerant from the high pressure outlet side of the
compressor to the inlet side of the compressor, and a control
mechanism for operating the expansion valve, the compressor and the
hot gas valve for closing the expansion valve and at substantially
the same time opening the hot gas valve for a first predetermined
period of time prior to a desired shut off of the compressor and
the control closing the hot gas valve after the lapse of a second
predetermined period of time following the shut off of the
compressor.
Description
[0001] The present application is a co-pending continuation-in-part
of U.S. patent application Ser. No. 09/639,868, filed Aug. 16,
2000, which was a co-pending continuation in part of U.S. Ser. No.
09/079,063, filed May 15, 1998, which was a co-pending
continuation-in-part of U.S. patent application Ser. No.
08/987,395, filed Dec. 9, 1997.
FIELD OF THE INVENTION
[0002] The present invention relates to refrigeration compressor
controls and in general to such controls and methods designed to
relieve mechanical strain on the compressor.
BACKGROUND
[0003] Mechanical refrigeration systems are well known and are used
in a wide variety of products including, air conditioning and
refrigeration equipment. It has long been understood that upon
shut-off of a compressor, the compressing mechanism, such as the
piston and crankshaft, continue to rotate for a few revolutions due
to the momentum thereof. However, there can exist a considerable
pressure differential between the high and low sides of the
compressor that the piston must work against. This pressure
difference can result in shaking of the compressor as the piston
comes to a stop there against. As a result, it has long been known
to have a spring mounting for the compressor so as to absorb this
undesired movement in a way that safely dissipates that energy and
eliminates mechanical damage to the compressor and its associated
components. However, it has been found that in applications where
the compressor is required to endure frequent on/off cycles, a
spring mounting may not suffice to protect the compressor assembly
from metal fatigue and subsequent failure.
[0004] An example of an application where frequent on/off
refrigeration cycles are required is found in frozen carbonated
beverage (FCB) making and dispensing machines. FCB machines are
well known in the art and generally utilize a freezing cylinder for
producing a flavored slush ice beverage therein. An evaporator coil
is wrapped around the exterior of the cylinder for cooling the
contents thereof. The proper ratio of water and a syrup flavoring
is introduced into the cylinder and a scraper mechanism extends
along the central axis of the cylinder and is rotated to scrape
thin iced or frozen layers of the beverage or food product from the
internal surface of the cylinder. Mechanisms for maintaining the
slush at the desired consistency and include an electronic control
mechanism that sense the viscosity of the slush. Thus, the
compressor is automatically turned on to cool the cylinder and
cause more freezing of the beverage if the viscosity is considered
too low, and conversely shuts off the compressor once the viscosity
has attained a predetermined high level, thereby discontinuing the
cylinder cooling. However, the slush is desirably held within a
rather narrow viscosity range which in itself requires frequent
compressor on/off cycling. In addition, the amount of beverage
dispensed overtime greatly influences this cycling as new beverage
must be introduced into the cylinder to make up for the volume
dispensed, and this newly introduced beverage must be cooled and
turned into the desired slush state. Furthermore, increases in
ambient temperature can also shorten the time between the
attainment of the desired viscosity and the time the compressor
must again be started due to warming of the cylinder contents.
Accordingly, it would be desirable to minimize any undesired
compressor movement during the operation thereof.
SUMMARY OF THE INVENTION
[0005] The present invention serves to greatly reduce any unwanted
compressor movement. An application of the present invention can be
understood in the context of a FCB machine wherein a freeze
cylinder includes an evaporator coiled around an exterior perimeter
thereof. The freeze cylinder evaporator is connected on an inlet en
to a pulsed type refrigeration expansion valve and on its opposite
or low pressure end to a compressor. As is well understood the
compressor has a discharge tube on its high pressure side connected
to a condenser with the condenser, in turn, completing the
refrigerant circuit and fluidly connected to the expansion valve. A
scraping mechanism within the cylinder provides for scraping frozen
beverage from the inner surface of the cylinder. A control
mechanism provides for controlling the operation of the
refrigeration system and hence the cooling of beverage within the
freeze cylinder. A defrost valve is positioned in a refrigerant
line extending between the discharge line and the expansion valve.
As is understood, the control mechanism operates the defrost valve
to open to flood the evaporator with hot refrigerant from the
compressor high side. Typically, this is done in what is known as a
defrost mode where the slush beverage is purposefully and
periodically melted to remove unwanted large ice particles that
have a tendency to form over time.
[0006] In operation, the control of the present invention includes
programming that opens the hot gas defrost valve for a
predetermined short period of time before the shut off of the
compressor is required and holds it open for a predetermined period
of time after shut off of power to the compressor is sensed. In
this manner, those of skill can understand that such action serves
to significantly reduce the pressure differential between the high
a low sides of the compressor before and during the shut off
period. As a result thereof, any shaking of the compressor at
shut-off is greatly reduced by not having to come to a stop against
this high pressure difference. Conversely, and for basically the
same reason, those of skill will readily understand that it is also
possible to have the control herein open the hot gas valve just
prior to and/or extending to just after start up as a means to also
equilibrate any unwanted pressure differential that may exist at
that point.
DESCRIPTION OF THE DRAWINGS
[0007] A better and further understanding of the structure,
function and the objects and advantages of the present invention
can be had by reference to the following detailed description which
refers to the following figures, wherein:
[0008] FIG. 1 shows a perspective view of a frozen food product
dispensing machine.
[0009] FIG. 2 shows an exploded view of a frozen food product
cylinder assembly in conjunction with a first drive mechanism of
the present invention.
[0010] FIG. 3 shows a plan view of the frozen food product cylinder
assembly including the first drive mechanism of the present
invention.
[0011] FIG. 4 shows a cross-sectional view along lines 4-4 of FIG.
3.
[0012] FIG. 5 shows a cross-sectional view along lines 5-5 of FIG.
2.
[0013] FIG. 6 shows an electrical schematic for the first drive
mechanism.
[0014] FIG. 7 shows a cross-sectional view of a frozen food product
cylinder assembly including a second drive mechanism of the present
invention.
[0015] FIG. 8 shows a surface plan view of a magnetic drive disk of
the present invention.
[0016] FIG. 9 shows a cross-sectional view along lines 9-9 of FIG.
7
[0017] FIG. 10 shows a perspective view of a frozen food product
dispensing machine.
[0018] FIG. 11 shows an enlarged cross-sectional view of the driven
disk.
[0019] FIG. 12 shows a perspective view of the present
invention.
[0020] FIG. 13 shows a further perspective view of the present
invention.
[0021] FIG. 14 shows a perspective view of the present invention
having the panels removed therefrom.
[0022] FIG. 15 shows a partial cut away view of the water bath
tank.
[0023] FIG. 16 shows a cross-sectional plan view of a
carbonator/blending bottle.
[0024] FIG. 17 shows a top plan view of the a carbonator/blending
bottle.
[0025] FIG. 18 shows a schematic diagram of the refrigeration
system.
[0026] FIG. 19 shows a schematic diagram of the fluid beverage
system.
[0027] FIG. 20 shows a schematic diagram of the electronic
control.
[0028] FIG. 21 shows a perspective view of the dual ice bank
control sensor.
[0029] FIG. 22 shows a end plan view along lines 21-21 of FIG.
20.
[0030] FIG. 23 shows a flow diagram of the viscosity monitoring
control logic.
[0031] FIG. 24 shows a flow diagram of the viscosity control
logic
[0032] FIG. 25 shows a flow diagram of the ice bank forming control
logic.
[0033] FIG. 26 shows a flow diagram of the expansion valve control
logic.
[0034] FIG. 27 shows a partial cross-sectional view of a further
embodiment of a carbonator/blending bottle.
[0035] FIG. 28 shows a top plan view of the carbonator of FIG.
27.
[0036] FIG. 29 shows a perspective view of the internal baffle
plate of the carbonator of FIG. 27.
[0037] FIG. 30 shows a perspective view of the combined level
sensor and water inlet of the carbonator of FIG. 27.
[0038] FIG. 31 shows a schematic of the compressor pressure
equilibrating mechanism of the present invention.
[0039] FIG. 32 shows a flow diagram of the software control of the
pressure equilibrating method of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] A frozen food product making and dispensing machine is seen
in FIG. 1, and generally referred to by the number 10. Machine 10
is illustrative of the type wherein the present invention can be
applied. As seen by also referring to FIGS. 2-4, a stainless steel
cylinder 12 includes a cylindrical wall 14 and a stainless steel
plate 16 welded to one end thereof forming a closed end surface and
defining a cylinder interior 18. A three phase stator 20 includes a
ring portion 22 made of multiple lamination layers 22a to which
three electrical windings 23 are wound and braided there around.
Stator 20 is positioned on the end of cylinder 12 adjacent end wall
16 with cylinder wall 14 extending through the center thereof.
[0041] A plastic spacer disk 24 is located within cylinder 12 and
is positioned against end wall 16. Disk 24 is made of a suitable
food grade plastic and includes a bearing 26 mounted centrally
thereof. As understood by also referring to FIG. 5, a rotor 30
includes a metal tube ring section 32 having eight permanent
magnets 34 secured equidistantly around a perimeter thereof wherein
the North and South polarities thereof alternate. Ring 32 and
magnets 34 are encased in a food grade plastic 35, such as
Delrin.RTM., molded there around and leaving a central shaft hole
36.
[0042] A scraper mechanism 40, also made of a suitable food grade
plastic, includes a central shaft 42 having a plurality of mixing
rods 44 and scraper blade supports 46 extending therefrom. A pair
of scraper blades 48 are mounted on supports 46 wherein holes 50
thereof receive pin portions 52 of supports 46. Shaft end portion
54 extends through hole 36 and is received in hole 28 of bearing
26. Shaft 42 also includes an attachment skirt 56 for securing
thereof to rotor disk 30. An opposite end 58 of shaft 42 is
received in a short support section 60 integral with extending from
a plastic end cover 62. Cover 62 includes an O-ring 64 extending
around a cylinder inserting portion 66 thereof. Cover 62 is secured
to cylinder 12 by a plurality of bolts 67a and nuts 67b. Flange 68,
as with plate 16, is also made of stainless steel and welded to
cylinder 12. As is known in the art, cover 62 includes a hole 70
for receiving a dispensing valve 72.
[0043] As is understood by those of skill, an evaporator coil 74
extends around the exterior of cylinder 12 and includes an inlet
fitting 74a and an outlet fitting 74b. Fittings 74a and 74b are
connected to high pressure line 76 and low pressure line 78
respectively of a mechanical refrigeration system including a
compressor 80 and a condenser 82. Insulation 84 extends around
cylinder 12 and evaporator 74. A beverage inlet line 86 is
connected to a cylinder inlet fitting 88 and a beverage reservoir
or mixing tank 90. A pair of cylinders 12 can be secured within the
housing of dispenser 10 and supported therein by a framework 92
thereof.
[0044] As seen in the schematic of FIG. 6, a power supply 94
includes an inverter 96 for converting 220 VAC to a three phase DC
current. This three phase current is connected to the three winding
23 of stator 20. Thus, those of skill will understand that stator
20 and rotor 30 comprise a DC motor. In operation, therefore, the
three phase current induces movement of rotor 30 which, in turn,
rotates scraper mechanism or assembly 40. Thus, with a beverage,
for example, delivered within cylinder 12 through line 86 and
cooling thereof by evaporator 74 and its associated refrigeration
system, frozen beverage can be produced by scraping thereof from
the interior surface of cylinder 12. The use of a rotor around
which a food grade plastic has been molded permits that part of the
DC drive motor to be internal of the cylinder and in contact with
the food product. In general, all the components of the present
invention are made of or coated with a suitable food grade
material. Thus, the present invention comprises a drive mechanism
for a frozen food product machine utilizing an internally scraped
cylinder wherein the drive motor therefore is an integral part of
the cylinder assembly. As a result, no dynamic seal or external
shaft bearing is needed for the scraper mechanism. Thus, the
traditional external motor, dynamic seal, external shaft bearing
and transmission can be eliminated.
[0045] In one example of the integral DC motor drive embodiment of
the present invention, the drive motor is used in a cylinder that
is approximately 15 inches long with a diameter of approximately
4.5 inches. The drive motor in such an application is designed to
produce a torque of approximately 110 inch/lbs. at 100 RPM's.
[0046] In a second embodiment of the present invention, as seen in
FIGS. 7-9, a cylinder 100 has a cylinder wall 102 and an end plate
104 defining a cylinder end surface 106. An AC motor 108 is secured
to a transmission 110 which is in turn secured to a plastic collar
112 attached to plate 104. Transmission 110 includes a drive shaft
114 to which is attached a magnetic drive disk 116. As seen in FIG.
8, disk 116 includes six permanent magnets 118 secured thereto
around a perimeter of one side or face thereof wherein the North
and South polarities thereof alternate. Magnets 118 are positioned
to face and be held closely adjacent end surface 106.
[0047] Within cylinder 100 a food grade plastic spacer 120 is
positioned against the interior surface of end wall 106. Spacer 120
includes a central bearing 122 and includes an annular wall portion
124 defining a disk retaining space 126. A food grade plastic
collar 128 is received in stainless steel bearing 122 and on one
end thereof has a driven magnetic disk 130 secured thereto. As seen
by also referring to FIG. , a stainless steel disk 130 includes a
plurality of permanent magnets 131 arranged on a metal ring 132.
Ring 132 is secured to disk 130 within an annular groove 134
thereof as defined by walls 135. A plastic collar or ring cover
ring 136 is secured to walls 135 around a top perimeter thereof for
sealably enclosing magnets 131 and ring 132 within annular groove
134. Magnets 131 of disk 130 are positioned to face and lie closely
adjacent the interior surface of end wall 106.
[0048] As with the first drive embodiment described above, the
second drive embodiment also includes a scraper mechanism 40 having
a central shaft 42 having a plurality of mixing rods 44 and scraper
blade supports 46 extending therefrom. A pair of scraper blades 48
are mounted on supports 46 wherein holes 50 thereof receive pin
portions 52 of supports 46. A shaft end portion 140 is shaped as
seen in FIG. 9, to provide for driving receiving thereof in a
similarly shaped bore 142 of collar 128. As with the previously
described embodiment, an opposite end 144 of shaft 42 is received
in support 60 extending from plastic end cover 62. Flange 68, as
with plate 104, is also made of stainless steel and welded to
cylinder 100.
[0049] As with the previously described DC motor embodiment,
cylinder 100 includes an evaporator coil 74 extending there around
that includes an inlet fitting 74a, an outlet fitting 74b and a
food product/beverage inlet 88 for connection as stated above.
Insulation 84 also extends around cylinder 100 and evaporator 74. A
pair of cylinders 100 can be secured within the housing of
dispenser 10 and supported therein by a framework 92 thereof.
[0050] In operation, motor 108 operates through transmission 110 to
rotate magnetic disk 116. Due to the magnetic coupling between disk
116 and 130 as they face each other on opposite sides of end wall
106, rotation of disk 116 results in the rotation of disk 130, and
hence, rotation of scraper mechanism or assembly 40. Thus, with
beverage or food product delivered within cylinder 100 through line
86 and cooling thereof by evaporator 74 and its associated
refrigeration system, frozen beverage can be produced by scraping
thereof from the interior surface of cylinder 100. This magnetic
drive embodiment, as with the DC motor embodiment herein,
eliminates the need for a dynamic seal and an external bearing with
respect to the shaft 42 of the scraper mechanism 40. Also, plate
having an annular groove for receiving the magnets and ring wherein
those components are sealed therein by a food grade plastic ring,
permit the driven disk 130 to be in contact with food product, i.e.
permits a magnetic drive approach or mechanism that is food
compatible.
[0051] A further embodiment of the present invention is seen in
FIGS. 12 and 13 and generally referred to by the numeral 200.
Machine 200 has an outer housing having removable panels, including
side panels 201, a top panel 202 and a display door 203 having a
transparency window 204. Panels 201 and 202 include louvers 205 and
an air flow grate 206, respectively. A plurality of light fixtures
208 are secured door 203, and are used for back lighting a
transparency 210. Door 203 is hinged to a front surface of machine
200, and as seen in FIG. 13, can be swung to an open position for
facilitating access to fixtures 208 and to user interface 212.
[0052] As seen by also referring to FIG. 14, machine 200 includes a
framework 213 for supporting various internal components as well as
the various portions of the exterior housing including housing
panels 201 and 202, and access door 203. A pair of freeze cylinder
assemblies 214 are held within separate insulated housings 216.
Both cylinder assemblies 214 are of the type disclosed above in
FIGS. 2-6 herein and have DC drive motors 217 as also shown and
described therein. However, unlike dispenser 10, embodiment 200
includes a water bath tank 218. Tank 218 includes sides 219 for
retaining a volume of water therein. As seen by also referring to
FIG. 15, tank 218 includes an ice bank forming evaporator 220.
Evaporator 220 is held therein by support means 222 and positioned
thereby adjacent three of the four interior surfaces of sides
219.
[0053] A pair of specialized carbonator/blender bottles 224 are
retained in tank 218. Bottles 224 are seen in greater detail in
FIGS. 16 and 17 and are essentially the same as the carbonator
disclosed in co-pending U.S. patent application Ser. 08/761,191,
filed Dec. 5, 1996, which application is incorporated herein by
reference thereto. Bottles 224 each include a cylindrical stainless
steel body 226 having a bottom end 228 and a top open end 230. A
plastic disk 232 is sized to fit within open end 230 and sealed
there against by an O-ring 234. Disk 232 is releasably retained in
open end 230 by means of a wire spring or clip 238. Clip 238 can be
grasped by ends 238a thereof to remove from or insert into slots
240, cut through cylinder 226, through which radiused comers 238b
are inserted. Disk top surface 242 is designed to cooperate with
clip 238 to minimize any accidental disengagement thereof with disk
232. In addition, disk 232 includes a fluid inlet 244, a gas inlet
246 for receiving pressurized carbon dioxide gas and a fluid outlet
248. Disk 232 also includes a safety release pressure valve 250 and
a liquid level sensor 252. Sensor 252 includes a rod 254 that is
positioned within bottle 224 having a movable float 256 free to
slide there along. Rod 254 includes one or more magnetically
actuated switches 258 therein and along the length thereof, and
float 256 includes a magnet 260. As is understood in the art sensor
252 operates whereby float 256 is carried by the level of liquid
within 224. As magnet 258 moves adjacent one of the switches 258
turning it on, then a level can be indicated. Inlet 244 is fluidly
connected to a J-tube 262, and outlet 248 is fluidly connected to a
tube 264 extending to a point adjacent bottle end 228.
[0054] Water bath tank 218 also includes a two serpentine coils of
heat exchange stainless steel tubing 262 positioned together and
adjacent a fourth or remaining interior surface side against which
evaporator 220 is not positioned. An agitator motor 264 is secured
to a top cover panel 266 and includes a shaft and attached agitator
blade, not shown, for agitating the water within bath 218.
[0055] As understood by also referring to FIG. 18, the
refrigeration system used in machine 200 includes a refrigeration
compressor 270 connected by refrigerant high pressure and low
pressure lines 271a and 271b, respectively, to a condenser 272. As
is well understood in the art, line 271b includes a discharge line
portion 271b' that emanates directly from compressor 270. Each
cylinder assembly 214 includes an evaporator coil 274 and each
evaporator coil has associated there with an electronically pulsed
expansion valve 276 and a hot gas defrost valve 278. Hot gas valves
278 are fluidly connected to a refrigerant bypass line 278a and
expansion valves 276 are provided refrigerant from condenser 272
along line 276a. Also, each coil 274 includes an inlet temperature
sensor 277a and an outlet temperature sensor 277b. The ice bank
forming evaporator 220 is also connected to compressor 270 by high
and low pressure lines 271a and 271b. Evaporator 220 also has
refrigerant metered therein by an electronically pulsed expansion
valve 280. Evaporator 220 also includes an inlet temperature sensor
282 and an outlet temperature sensor 284.
[0056] An ice bank 286 forms on evaporator 220 and, as further
understood by referring to FIGS. 21 and 22, the size thereof is
regulated by a pair of ice bank sensors 288a and 288b. Sensors 288a
and 288b each include a housing 290 wherein a pair of wire probes
291 extend. Probes 291 are connected to wires 292 that provide
connection to the control of the present invention, further
described below. Each housing 290 is secured to an attachment plate
293. Sensor 288a is secured to a first level surface 293a of plate
293 and sensor 288b is secured to a second outer level surface 293b
thereof. Thus, a differential distance D, as indicated by the
dashed lines of FIG. 21, is created between the probes 291 of each
of the sensors 288a and 288b. A flange 294 and hook 295 provide for
attachment of plate 293 to a suitable support means within ice bath
218 at a suitable distance from evaporator 220.
[0057] A schematic of the beverage fluid delivering system used in
the present invention can be understood by referring to FIG. 19. A
seen therein, an inlet water line 300 is connected to a source of
potable water for delivering the water, first to a T-fitting 302
and then to a brixing or ratioing valve 304. A second line 306
extends from fitting 302 to a float operated valve 308 positioned
within water bath tank 218. A third line 310 is connected to a
source of beverage syrup, such as a bag-in-box 312. Line 310
includes a fluid flow sensor 314 and is fluidly connected to a
further brixing valve 316. Sensor 314 is of the piston fluid
contact type as, for example, model FS-3, as manufactured by Gems
Sensors, of Plainville, Conn. Valves 304 and 316 provide for mixing
the water and syrup at a ratio of typically 5 to 1 respectively.
The fluid components flow to a Y-fitting 318 and are mixed
together. A pump 320 pumps the properly ratioed, but as yet
noncarbonated beverage, to a test valve 322 and from there to one
of the heat exchange serpentine coils located in tank 218. Valve
322 normally directs the beverage to a coil 262, but can be
manually operated to divert and deliver a test sample of the
beverage along line 324 to an outlet point. In this manner the
beverage can be easily tested to check for the proper ratioing
thereof by valves 304 and 316. The beverage flows from a coil 262
to inlet 244 of the associated blender/carbonator bottle 224. A
pressurized source of carbon dioxide gas 326 provides carbon
dioxide first to a valve 328. Valve 328 provides for diverting
carbon dioxide gas to bag-in-box 312 in the example where a carbon
dioxide pump 327 is used to move syrup therefrom. Those of skill
will realize that other means, such as electric pumps can be used
to pump the syrup whereby valve 328 would not be required. Or,
carbon dioxide gas can be used to propel the syrup from a rigid
stainless syrup tank. Regulator valves 330a and 330b provide the
carbon dioxide at a desired pressure to the gas inlets 246 of each
blender/carbonator 224 positioned in tank 218. It will be
appreciated that FIG. 18 shows a schematic of one of the beverage
fluid systems, there being one for each cylinder assembly 214.
Thus, in a machine 200 having two cylinders 214, there are two
brixing valves 304, two brixing valves 316, two coils 262, tow
pumps 320, two flow sensors 314, and two carbonator/blenders 224.
The outlets of each blender/carbonator 224 are connected to outlet
lines 332 that are connected first to manual valves 234 and then to
inlets 236 of each of the cylinders 214. Valves 234 provide for
manually stopping the flow of carbonated beverage to cylinders 214,
primarily for the purpose of facilitating servicing thereof.
[0058] Sensors 314 provide a major advantage in that they are able
to sense when the syrup has sun out whether the syrup is delivered
from a bag-in-box or from a stainless tank. Prior art machines
required that there be two sensor systems, one for either syrup
containing source. A pressure sensor was required for the
bag-in-box as, when the bag became empty, there would be no
pressure, and that would indicate a sold out condition. However, if
a tank was used the carbon dioxide gas used to propel the syrup
would indicate to the pressure sensor that syrup was present, when
in fact, it was not. Thus, a tank syrup reservoir required a float
sensor that would only be affected by actual liquid syrup.
Therefore, sensor 314 eliminates having redundant systems and the
associated cost and complexity thereof.
[0059] It can be appreciated that the present invention provides
for the cooling of a volume of beverage within coils 262 prior to
introduction thereof into each blender/carbonator 224. Thus, the
beverage will have reached a temperature of approximately 36
degrees Fahrenheit prior to the introduction thereof into a
corresponding container 224. In addition, each blender/carbonator
is also held at the same temperature being immersed in the cold
water bath. Therefore, the carbonation of the beverage that occurs
therein can reach a desired level of saturation at much lower
carbon dioxide gas pressures than if the mixing were occurring in a
bottle held at a much warmer room ambient temperature. In addition,
the present invention has a much greater beverage production
capacity, as an ice bank presents a large cooling reserve that
would otherwise not be available unless an exceedingly large
refrigeration system is used. Thus, as the beverage is presented to
the freeze cylinder at a very low temperature, the cooling required
of the freeze cylinder evaporators is much lower so that overall,
the present invention works much more efficiently than do
comparable prior art machines that produce semi-frozen beverages or
food products from beverage delivered to the cylinders at ambient
temperatures.
[0060] As seen in FIG. 20, the present invention uses a distributed
electronic control having a product delivery control board 340 for
the control of each cylinder 214. A main logic board 342 is
connected to each control board 340, and there is one inverter
board 344 for each of the two cylinders 214. The boards communicate
as is generally indicated by the arrows of FIG. 19. Main board 342
receives inputs from the user interface 212, and from each of the
product delivery board (340) on the system, as well from the
CO.sub.2 pressure sensor, an H.sub.2O pressure sensor, high/low
line voltage, ice bank thickness (min), ice bank thickness (max.),
ice bank evaporator input temperature and ice bank evaporator
output temperature. Main board 342 controls the operation of
compressor 27- on/off, ice bank agitator motor and ice bank pulse
valve. Each product delivery board receives inputs from its
associated syrup flow sensor 314, level sensor 252, evaporator
input temperature sensor, evaporator output temperture sensor,
product viscosity sensor and beater motor error, and controls the
operation of its associated beater motor on/off, defrost valve
on/off, pulse valve on/off, syrup valve on/off, H.sub.2O valve
on/off, disp. Valve lockout, product status light and blendonator
pump 320. The inverter board 344 provides for inverting the 240 VAC
supplied current to the 340 VDC current used by motors 217. In
addition, it senses the current draw being placed on each motor 217
and runs them at a constant 120 revolutions per minute (RPM).
[0061] A distributed control is used to better accommodate machines
having more than two cylinders 214. Thus, the main board 342 can be
designed to work with more than two product delivery boards. In
this manner, a cost saving can be had as opposed to having a main
control board having to be designed specifically for each machine
having a particular number of cylinders. The main board receives
the commands from the operator interface, and distributes this
information to the appropriate board. For instance, if the operator
wants to turn on cylinder #1, the main board will send the "on"
command to the product delivery board on cylinder #1. The PDB will
then tell the inverter board to apply power to stator #1, as well
as request the compressor to come on and begin pulsing the pulse
valve for cylinder #1.
[0062] A better understanding of the control logic utilized by the
control of the present invention to monitor the viscosity of the
beverage, control the viscosity of the beverage and to regulate the
ice bank can be had by referring to the flow diagrams thereof shown
in FIGS. 23-26. Viscosity is monitored as a function of the current
draw of the DC drive motor for the particular cylinder. In
addition, each motor 217, as stated above, is controlled to operate
at a constant 120 RPM rate. Thus, the more viscous the beverage the
greater load and current draw on the motor 217 to maintain the set
point rotational speed. Since the motors 217 are directly driving
the cylinder scraper mechanisms, and the RPM's are kept constant,
there exists a very direct correlation between the current draw of
the motors and the viscosity of the food product. Each product
delivery board has look up tables that correlate the current draw
to an arbitrary viscosity number scale, which scale is utilized by
each board to indicate a level of viscosity of the beverage within
the cylinder. As seen in FIG. 23, a start point is indicated by
block 350. The viscosity is monitored by each board 340, wherein at
block 351 it is determined if the viscosity is below a preset
viscosity minimum. If the viscosity is below that minimum, and it
has been below that minimum for greater than one second, block 352,
then at block 354, it is determined if compressor 270 is on. If
compressor 270 is on, then the viscosity is controlled at block
356. A more detailed description of the viscosity control is
contained below with reference to FIG. 24. If compressor 270 is not
on, then the control inquires if it has been off for more than two
minutes, block 358. If it has, then compressor 270 is turned on at
block 360 and viscosity is controlled at block 356. At block 361,
it is determined if the desired viscosity has attained a
predetermined desired level. If it has, the compressor is turned
off at block 362 and the control goes to return at block 364 and
monitors the viscosity. If at blocks 351, 352 or 358 it is
determined, respectively, that the viscosity is not below viscosity
minimum or the viscosity minimum was not maintained for more than
one second or that the compressor has been off for less than two
minutes, then the control, at block 366, determines if the float
sensor 252 of the associated bottle 224 has been activated to
signal for more beverage to be pumped therein, i.e. has beverage
been drawn from the associated cylinder whereby further beverage
must be replaced therein, and in its associated carbonator/blender
224. If the float has been activated, then further beverage is
added to the cylinder by control of pump 320 and operation of
valves 304 and 316. The control then inquires, at block 368, if the
compressor is on, and turns the compressor on as needed or proceed
directly to viscosity control, block 356. If the sensor 252 has not
been activated to deliver more beverage within its associated
bottle 224, block 366, then the control determines if 5 minutes has
elapsed since the last refrigeration cycle, block 370. If less than
the 5 minutes has elapsed, the control goes to return, block 372
where viscosity is monitored. If more than 5 minutes have elapsed
since the last operation of the compressor, the control then
inquires, at block 368, if the compressor is on, and turns the
compressor on as needed, block 360, or proceeds directly to
viscosity control, block 356. The viscosity control of the present
invention can be better understood in terms of the flow diagram of
FIG. 24. At the start block 380 the control moves to blocks 381 and
382, where the board determines the inlet and outlet temperatures,
respectively, of the particular evaporator coil 274, and at block
384, measures the barrel viscosity. At block 386 it is determined
if the viscosity is greater than a pre-selected viscosity maximum.
If it is, the control queries if the particular coil 274 is in the
"top off mode", block 388. If not, the top off mode is begun at
block 390. The top off mode is a sequence that permits a relatively
accurate determination of the beverage viscosity. Thus, at block
392 a 3 second timer is started during which the associated pulse
valve 276 is closed, block 393. Further refrigeration is stopped
for this time period, however the scraper mechanism continues to
turn. At block 394 pulse valve 280 is operated to provide for
building of the ice bank. A further understanding of the control of
the ice bank will be had below in reference to FIG. 25. At block
396, the maximum viscosity sensed during the top off period is
recorded. If the 3 second timer has timed out, block 398, then the
control determines if the difference between the present viscosity
and the maximum viscosity currently sensed during top off is lesser
or greater than a pre-selected viscosity delta or difference, block
400. The delta is contained in a look-up table and is an
experimentally derived number. If the delta is not exceeded, this
means that the viscosity of the beverage is at the desired level
and refrigeration of the cylinder can be stopped, block 402, and
the control can go to return 404. If the measured delta is too
large, i.e. in excess of the preset delta, this indicates that the
beverage is not viscous enough. Then the control goes to block 406
ending top off and continuing refrigeration and goes to return 404.
Ice can not be built on evaporator 220 during refrigeration of
either coil 274. Only when both cylinders are satisfied and/or are
otherwise not being cooled. Thus, if the other cylinder evaporator
274 is being cooled, cooling of evaporator 220 is not permitted.
Therefore, ice can be formed during top off if the other coil 274
is not being cooled or if both are in top off. As a consequence
thereof, if top off has ended as the delta was too large, block
400, further cylinder cooling is required and cooling of evaporator
220 is stopped, if one or both cylinders 214 are in a refrigeration
sequence. At block 386, if the viscosity is below the preset
viscosity maximum, then at block 408 the temperature of the
particular inlet of the associated coil 274, as measured by sensor
277a, is determined. If that temperture is greater than 40 degrees
Fahrenheit, then a proportional/integral/differential "PID"
calculation is made to control the temperature down to 40.degree.
F., block 410. As is understood in the control art, PID control
generally follows the equation PID=E.sub.c(Kp)+(E.sub.p1, E.sub.p2
. . . E.sub.c)K.sub.i+((d)E/(d)t)K.su- b.d. where Ec is the current
error, K.sub.p is a proportional proportionality constant, E.sub.p1
. . . represent previous error values, K.sub.i is the integral
proportionality constant, (d)E/(d)t is the rate of change of the
error and K.sub.d is the associated differential proportionality
constant. The value (E.sub.p1, E.sub.p2 . . . E.sub.c) represents
an equation, such as the averaging of the E values, that,
multiplied by K.sub.i represents the portion of the PID valve that
is based on the size the error over time. The E.sub.c(K.sub.p)
value represents the portion of the PID valve that is based on the
size of the currently measured error. All three variables can be
used produce a very accurate understanding of how a particular
target point is being approached. In the present invention, PID
control is used to control to a 40 degree F. set point with a high
degree of accuracy. The particular pulse valve 276 is operated
accordingly, block 412, as per the PID output. If at block 408 the
temperature of the inlet is less than 40 degrees F., then it is
determined if the outlet temperature, as determined by sensor 277b,
is greater than 46 degrees F., block 414. If that temperature is
greater than 46 degree F., then the logic control returns to blocks
410 and 412 and controls the temperature of the inlet to 40 degrees
F. Thus, the control is first seeking to establish a delta T of six
degrees between the coil 274 inlet and outlet temperatures at a
particular starting point where the inlet temperature is 40 degree
F. and an outlet temperature is 46 degrees. When that is
accomplished, then, at block 416, the PID control can be used to
simply control the delta T to 6 degrees F. whereby the inlet and
outlet temperatures can fall below 40 and 46 respectively, as long
as the delta T of 6 degrees between them is accurately
maintained.
[0063] A better understanding of the ice bank control herein can be
has with reference to FIG. 25. At the start point 420, the control
then starts a 30 second ice measure timer, block 421. During that
30 second interval ice sensors 288b and 288a are measured,
respectively, blocks 422 and 423. After the 30 second timer has
timed out, block 424, the control determines if either cylinder 214
is calling for refrigeration, block 425. If either cylinder is
calling for refrigeration then it is determined if the compressor
270 is running, block 426. The compressor is then turned on, block
427, or the control goes directly to block 428. At block 428 it is
determined if either cylinder is in a normal operate mode, i.e. not
in top off and requiring refrigeration. If either cylinder is in a
normal operating mode, then no refrigeration of the ice bank can
occur and the control goes to return, block 429. If one or both are
not in normal mode, i.e. in top off mode, then the particular pulse
valve 276 is pulsed at the top off rate, block 430 and the control
goes to return 431 the rate that is determined to maintain a 20
degree F. temp. If, at block 425, neither cylinder 214 is calling
for refrigeration, then ice bank sensor 288b is polled to determine
if ice is present, block 432. If sensor 288b senses ice, then no
more building of ice is desirable so, if the compressor is running,
block 434, it is turned off, block 435 and valve 280 is opened for
5 seconds to equalize pressure, block 436, and the control goes to
return, 438. If sensor 288b does not sense ice, then at block 440,
the control looks at sensor 288a to see if it senses ice. If sensor
288a so indicates, then the control follows blocks 434, 435, 436
and 438. If sensor 288a does not sense ice, then ice can and should
be added to the ice bank, it having eroded to a point that a
greater cooling reserve is desirable. Thus, at block 444, if the
compressor is running, pulse valve 280 is operated to cool
evaporator 220 and build ice thereon, block 445. If the compressor
is not running, it is turned on, block 446. Pulse valve 280 is
operated as per the flow diagram valve control loop delineated in
FIG. 26 below.
[0064] As can be understood by referring to FIG. 26, at a start
point 450, the control measures evaporator 220 inlet temperature
using sensor 282a, block 452 and then measures the outlet
temperature thereof using outlet sensor 282b, block 454. The delta
T of evaporator 220 is controlled in substantially the same manner
as previously described for the cylinders 214. Thus, the inlet
temperature is first sensed, block 456, and moved down using a PID
control, block 458, and a valve pulse timer as per that PID
calculation, block 460, to a preset temperature of 20 degrees F.
Once that value is attained, the control goes to return, block 462.
If the inlet temperature is less than 20, then the control
determines if the outlet temperature is greater than 40 degrees,
block 464. If it is then the control returns to blocks 458 and 460
to move the inlet temperature to 20 degrees F. Once the inlet
temperature is equal to 20 degrees F. and the outlet temperature is
equal to -40 degrees F., then at block 464, the control then moves
to block 466. At block 466 a PID control is utilized to maintain a
delta T of 20 degrees F. The pulse valve 280 is set accordingly,
block 468, and the control goes to return, block 270.
[0065] Those of skill will understand that the present invention
provides for the production of a semi-frozen food product in a
manner that maximizes the efficiency of operation of the
refrigeration system thereof. The life of the compressor is
extended as refrigerant gas can be alternately directed to either
of the cylinder evaporators 274 or the ice bank evaporator 220. In
particular, the two ice bank sensors provide for an incremental
area between an ice bank maximum size and an ice bank minimum size
where the ice bank can be grown to prevent the compressor from
running and building pressure after both the valves 276 are closed.
In this manner the compressor is not short cycled or presented with
damaging high pressures when an expansion valve is closed. Since
the erosion of the ice bank generally occurs at a faster rate than
it is built up, it is contemplated that there will be very few or
no occasions where the refrigerant can not be diverted to
evaporator 220 so as to protect the compressor.
[0066] Furthermore, as an ice bank is used, a large cooling reserve
can be built up during the times that neither cylinder 214 is
calling for refrigeration, such as when the beverage therein is of
sufficient viscosity, or where the cylinders have been shut down
entirely during a "sleep mode", well known in the art, where no
drinks will be dispensed. Also, as the PID control permits a much
smaller delta T to be maintained in a safe manner, better
efficiency of cooling is obtained from evaporators 274 and
evaporator 220. Dispenser 200 therefore has a substantial advantage
over comparable prior art machines in terms of refrigeration system
design parameters. Dispenser 200 can use a much smaller compressor
to do the work of a larger compressor in a prior art machine, or
obtain more cooling from the same sized system.
[0067] As seen by again referring to FIG. 3, framework 213 defines
three areas 500, 502 and 504. Top area 500 will be understood to
retain water bath 218, condenser 272 and compressor 270. Middle
area 502 retains cylinder packs 216, and the expansion valves 276
and 280 and the defrost valves 278. Lower section 504 includes
beverage pumps 320 and ratio valves 304 and 316. As is known in the
art, defrost valves 278 serve to provide hot gas defrost of each
cylinder 214. Such defrost is periodically required to remove large
particles of ice that can periodically form within a cylinder. A
filter grate, not shown, is secured to condenser 272 on the
exterior side of beverage machine 200 opposite from the fan 273
thereof.
[0068] As seen by referring to FIGS. 27 and 28, a further improved
and preferred embodiment of a carbonator of the present invention
is seen and generally indicated by the numeral 600. Carbonator 600
is of the same general design as previously described carbonator
224 and includes a cylinder 602 having an bottom end 604, a
perimeter side wall 606 and a top open end defined by a perimeter
edge 608. As with carbonator 224, a plastic disk or plug 610 is
retained in the top end of cylinder 602 by a spring wire 612 and
sealed therein by an O-ring 613 extending around a perimeter
thereof. Further, as with carbonator 224, a retaining wire 612 is
bent into a rectangular configuration that is retained in grooves
614 of disk 610, and includes four comer portions 612a for
insertion through holes 616 extending through side wall 606
adjacent edge 608. Also, as previously described with respect to
carbonator 224, wire 612 includes two vertical ends 612b for
effecting release of disk 610 from carbonator 600.
[0069] Disk 224 includes an outlet tube 620 having an upper end
620a and a lower end 620b, and a carbon dioxide gas inlet tube 622
having an upper end 622a and a lower end 622b. A plastic tube 624
is fluidly connected to end 620b of tube 620 and extends within
cylinder 602 and terminates therein adjacent bottom end 604. A
further plastic tube section 626 is fluidly connected on its
proximal end to bottom end 622b of inlet 622 and on its distal end
to an adapter fitting 628. Adapter fitting 628 permits fluid tight
securing of tube 626 to plastic diffuser 630. Diffuser 630 has a
larger diameter than tube 626 and has a perimeter side wall 630a
and a bottom end 630b defining a closed interior space 632.
Diffuser 630 is preferably made of a porous plastic material such
as a microporous polyethylene as manufactured by Porex Corporation
of Fairburn, Ga.
[0070] As understood by also referring to FIG. 29, carbonator 600
includes a metal baffle plate 634. Plate 634 is round and sized to
fit within cylinder 602. Plate 634 includes a plurality of primary
flow holes 636, a larger hole 638 for receiving tube 624 there
through, and a secondary flow hole 640. Plate 634 is supported at a
level within cylinder 602 above end 604 approximately one quarter
of the distance between bottom end 604 and disk 610. Plate 634 is
so supported by a pair of U-shaped legs 642 secured thereto and
that rest on bottom end 604.
[0071] Carbonator 600 includes a combined level sensor and beverage
mixture inlet 644 as seen by also referring to FIG. 30. Sensor 644
includes a singularly molded plastic body having a top end portion
644a and a bottom end portion 644b. Top end 644a includes threads
646 for providing threaded screw securing thereof to disk 610 in a
corresponding threaded hole 646 therein. A mixture inlet tube 648
is integral with end portion 644a and includes a top end 648a and a
bottom end 648b. Level sensor bottom portion 644b includes shaft
portion 652 terminating in a flow disk 654. A further shaft 656 is
secured to a proximal end of shaft portion 652 and includes a
buoyant float 658 slideably secured thereto. As is understood,
float 658 includes a magnet 660 for interacting with a switch 662
within shaft 652. Wires 664 provide for connection of switch 662
with a control mechanism, not shown.
[0072] In operation, an outlet line, such as line 232 seen in FIG.
19, is connected to end 620a of tube 620 and provides for delivery
of carbonated beverage to a cylinder, such as cylinder 214 of FIG.
14. A source of pressurized carbon dioxide gas, such as 326 shown
in FIG. 19, is connected to end 622a of inlet 622. and a mixture
line, as also depicted in FIG. 19 and indicated by the numeral 262,
is secured to end 648a of inlet tube 648. As is understood a pump,
such as pump 320 of FIG. 19, is operated by a electronic control as
a function of the level of the beverage mixture within cylinder
602. Such level is determined by the level of float 658 as it is
carried up and down shaft 656 by the level of the fluid beverage
mixture. Thus, pump 320 is turned on when float 658 drops to a
level wherein magnet 660 is no longer sufficiently close to switch
662 to maintain it in a closed non conducting position, which
signals the need to replenish cylinder 602 with beverage mixture.
Such minimum level is indicated by the horizontal line in FIG. 27
as marked by the letter M.
[0073] Specifically, it can be understood that the beverage mixture
is delivered to tube 648 and exits end 648b thereof. As end 648b is
positioned centrally of and above deflection disk 654, the mixture
impacts disk 654 and is deflected thereby, as indicated by the
arrows of FIG. 27, in various directions transverse to the initial
downward flow. It can be appreciated that disk 654 protects float
658 from any disruption thereof and any false level readings that a
direct flow impact thereon may cause. Thus, disk 654 permits a
combination of the mixture inlet and level sensing elements thereby
permitting cost savings in terms of parts reduction and assembly
time.
[0074] It can be understood that the level of beverage mixture in
cylinder 602 is determined by level sensor 644 to always be
maintained well above the level of plate 634. Generally, the
beverage mixture tends to exist as a gradient of less carbonated to
more carbonated in a direction from a top possible level thereof to
the fraction thereof residing closely adjacent bottom end 604.
Thus, outlet tube 624 tends to desirably extract the most
carbonated mixture from the cylinder due to its distal end position
closely adjacent cylinder end 604. However, it is believed that
such gradient is easily disrupted by the inflow of beverage mixture
and/or carbon dioxide gas resulting in some inadequately carbonated
beverage product being dispensed to cylinder 214. Also, where a
carbon dioxide gas inlet tube, such as tube 262 of FIG. 16,
terminates within a carbonator cylinder, the efficiency of mixture
of the gas with the beverage component is not optimized. Thus,
diffuser 630 serves to introduce the gas into the beverage as very
finely divided bubbles providing for a much increased surface area
of mixture there between. In this manner it is thought that the
carbon dioxide gas is more rapidly put into solution in the
beverage.
[0075] It was also found that plate 634 serves to partially
separate the beverage mixture into two regions, one above the plate
and one below. This separation appears to provide for both a
preferential carbonating of the beverage in the upper region as the
diffuser 630 is located therein, and provides for a preferential
dispensing of the lower portion. It is though that plate 634
prevents disruption of the aforementioned carbonation gradient
permitting more orderly and efficient carbonation of the beverage,
which enhances the overall rate and efficiency of carbonation. In
addition, the use of the diffuser 530, as mentioned above, further
contributes to carbonation speed and efficiency. Thus, carbonator
600 provides for the ability to fully carbonate a large volume of
beverage mixture rapidly under high draw and/or high ambient
temperature conditions. The primary holes 636 permit beverage flow
there through under conditions of low or normal dispense demand in
a direction from the upper region t the lower region. The large
flow hole 638 insures against starving of outlet tube 620 under
conditions of high dispense demand.
[0076] As seen by referring to FIG. 31, a simplified schematic of a
refrigeration system generally designated 700 is shown. A
compressor 701 is fluidly connected by a high pressure side
refrigerant line 702 to a condenser 704. Condenser 704 is cooled by
a fan 705 and is fluidly connected by a refrigerant line 706 to an
expansion valve 708. Valve 708 serves to meter compressed and
cooled refrigerant into an evaporator 710 as determined by a
microprocessor based electronic control 712. Control 712 also
controls the on/off operation of compressor 701 and the operation
of fan 703. Evaporator 710 is fluidly connected to compressor 701
at a low pressure side 714 thereof. A hot gas defrost valve 716 is
fluidly connected to a bypass line 718 that extends between
refrigerant line 702 and evaporator 710. Control 712 also controls
the on/off operation of valve 716.
[0077] The method of control of the foregoing refrigeration system
700 is seen by referring to the flow diagram of FIG. 32. At a
start-up block 720 it will be assumed that compressor 701 is
running to provide cooling of evaporator 710 in the conventional
manner well known in the art. At block 722 control 712 determines
if the cooling of evaporator 710 should stop. If the answer is no,
compressor 701 is allowed to continue to run, if the answer is yes,
compressor 701 is to be shut off. The shut off procedure is
commenced at block 724 where expansion valve 708 is first closed
and hot gas valve 716 is subsequently opened for a predetermined
period of time. At block 726 it is determined if that predetermined
period of time has timed out. Once the answer at block 726 is yes,
control 712 shuts off the current to compressor 701 at block 728.
Once the current to compressor 701 is shut off, a second
predetermined period of time is counted at block 730. When that
second time period has elapsed, i.e. "yes" at block 730, hot gas
valve 716 is closed at block 732 and the system returns to the run
mode at block 720.
[0078] It will be appreciated by those of skill that the first and
second time periods surrounding the shut-off of electrical power to
compressor 701 permit the refrigerant pressure differential at
compressor 701 as between the high and low pressures sides, to move
towards a state of equilibration. As a result of this pressure
leveling, the rotating internal components of compressor 701, not
shown, can come to a smooth stop that eliminates or greatly reduces
any destructive shaking of compressor 701. It has been found that
the high pressure line 702, and in particular the discharge portion
thereof that line that directly emanates from compressor 701 can be
especially sensitive to any shaking. Such movement can result in
metal fatigue failure thereof causing loss of refrigerant and
subsequent failure of the refrigeration system. Those of skill will
understand that a variation on the above strategy could be used
where, for example, there could be a single predetermined time
period that occurs and that is timed to exist for a predetermined
period of time commencing before compressor shut-down and
terminating substantially at the same time as power is shut-off
thereto.
[0079] It will be clear to those of skill that the refrigeration
system depicted in FIG. 31 can be adapted for use in an FCB machine
as generally shown and described herein with respect to FIGS. 1-30.
In particular compressor 701, high pressure line 702, condenser
704, refrigerant line 706, expansion valve 708, evaporator 710, hot
gas valve 716 and bypass line 718 could be substituted for
compressor 270, high pressure line 271b, and in particular
discharge line portion 271b', condenser 273, refrigerant line 276a,
pulse valve 276, evaporator 274, hot gas valve 278 and bypass line
278a, respectively and seen, for example, in FIG. 18. Control 712
could likewise consist of the distributed electronic control seen
in FIG. 20 controlling compressor 270 and motors 217. Thus, the
determination that a predetermined viscosity level had been reached
or gone below would signal the shutting off or on, respectively, of
compressor 270. Thus, hot gas valve 278 could be opened in a manner
to reduce any unwanted pressure differential that exists at shut
down of compressor 270 as per the method shown in FIG. 32 or that
exists at start up as per the above described procedure that is
analogous to that seen in FIG. 32.
[0080] Although some warm gas is directed into the evaporator as a
result of the method of FIG. 32, it was found that the amount
required to obtain the advantages of that method of the invention
herein does not unduly heat the evaporator. In an FCB machine as
shown and described herein wherein compressor 270 is sized at
approximately 3 horsepower and where five pounds of 404a
refrigerant is used, the first predetermined time period can be
approximately 1.5 seconds in duration and the second predetermined
time period can be of approximately 1.0 second in duration. It can
be understood that bypass line 718 and hot gas valve 716 generally
comprise a mechanism that permits equilibration of pressures
between the high and low pressure sides of a refrigeration
compressor. Thus, bypass line 718 can extend directly between the
high and low sides of the compressor bypassing the evaporator 710,
as indicated by the dashed line 718a.
* * * * *