U.S. patent application number 12/572985 was filed with the patent office on 2010-04-15 for vending machine and method for defrosting.
This patent application is currently assigned to Dixie-Narco, Inc.. Invention is credited to Jose G. Avendano, Talbert J. Black, JR., Joseph C. Fontecchio.
Application Number | 20100089081 12/572985 |
Document ID | / |
Family ID | 42073926 |
Filed Date | 2010-04-15 |
United States Patent
Application |
20100089081 |
Kind Code |
A1 |
Fontecchio; Joseph C. ; et
al. |
April 15, 2010 |
VENDING MACHINE AND METHOD FOR DEFROSTING
Abstract
A method includes sensing an exposure of a refrigerated
compartment of a vending machine to ambient air and, in response,
sensing an initial temperature of the refrigerated compartment. The
method also includes, responsive to sensing the exposure to ambient
air, selecting a procedure from a plurality of procedures according
to the sensed initial temperature, and controlling a refrigeration
system of the vending machine using the selected procedure during
an initial period. The method may include sensing a current
temperature of the vending machine and, once the refrigerated
compartment reaches a second predetermined temperature, controlling
the refrigeration system according to the sensed current
temperature, monitoring an operational characteristic of a
compressor of the refrigeration system, and performing a defrost
procedure according to the monitored operational
characteristic.
Inventors: |
Fontecchio; Joseph C.; (St.
Peters, MO) ; Black, JR.; Talbert J.; (Lexington,
SC) ; Avendano; Jose G.; (Springfield, IL) |
Correspondence
Address: |
DOCKET CLERK
P.O. DRAWER 800889
DALLAS
TX
75380
US
|
Assignee: |
Dixie-Narco, Inc.
Williston
SC
|
Family ID: |
42073926 |
Appl. No.: |
12/572985 |
Filed: |
October 2, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61195160 |
Oct 3, 2008 |
|
|
|
Current U.S.
Class: |
62/155 ; 62/156;
62/234 |
Current CPC
Class: |
F25B 2600/112 20130101;
F25D 2600/02 20130101; F25B 2600/0251 20130101; F25B 2700/2117
20130101; F25D 2700/02 20130101; A47F 3/0482 20130101; F25D 21/006
20130101; G07F 9/105 20130101 |
Class at
Publication: |
62/155 ; 62/234;
62/156 |
International
Class: |
F25D 21/06 20060101
F25D021/06; F25B 49/00 20060101 F25B049/00; F25D 21/00 20060101
F25D021/00 |
Claims
1. A method, comprising: sensing an exposure of a refrigerated
compartment of a vending machine to outside air; and responsive to
sensing the exposure of a refrigerated compartment to outside air,
sensing an initial temperature of the refrigerated compartment,
according to the sensed initial temperature, selecting a procedure
from a plurality of procedures, and controlling a refrigeration
system of the vending machine using the selected procedure during
an initial period.
2. The method of claim 1, wherein the step of sensing an exposure
of a refrigerated compartment of a vending machine to ambient air
comprises sensing an opening of a door of the refrigerated
compartment.
3. The method of claim 1, wherein the procedure is selected
according to whether the initial temperature of the vending machine
is above a first predetermined temperature.
4. The method of claim 1, wherein the step of controlling the
refrigeration system during the initial period further comprises:
activating a compressor of the refrigeration system for a first
predetermined length of time; and deactivating the compressor for a
second predetermined length of time, where the first and second
predetermined lengths of time are selected according to the sensed
initial temperature.
5. The method of claim 1, further comprising: sensing a current
temperature of the vending machine; and during a second period:
controlling the refrigeration system according to the sensed
current temperature, monitoring an operational characteristic of a
compressor of the refrigeration system, and performing a defrost
procedure according to the monitored operational
characteristic.
6. The method of claim 5, wherein the defrost procedure is
performed according to one of an accumulated length of time the
compressor has been activated and a number of activations of the
compressor.
7. The method of claim 5, wherein the second period begins when a
second predetermined temperature of the vending machine is
sensed.
8. The method of claim 7, wherein the step of controlling a
refrigeration system according to the sensed current temperature
further comprises activating an evaporator fan of the refrigeration
system for a third predetermined length of time after the
temperature of the vending machine reaches the second predetermined
temperature.
9. The method of claim 8, wherein the step of controlling a
refrigeration system according to the sensed current temperature
further comprises, after the third predetermined length of time,
deactivating the evaporator fan when the compressor is
deactivated.
10. A vending machine, comprising: a controller; a temperature
probe communicatively coupled to the controller; and a
refrigeration system communicatively coupled to the controller,
wherein the controller is adapted to: sense an exposure of a
refrigerated compartment of a vending machine to outside air; and
responsive to sensing the exposure of a refrigerated compartment to
outside air, sense an initial temperature of the refrigerated
compartment, according to the sensed initial temperature, select a
procedure from a plurality of procedures, and control a
refrigeration system of the vending machine using the selected
procedure during an initial period.
11. The vending machine of claim 10, wherein the controller is
further adapted to select the procedure according to whether the
initial temperature of the vending machine is above a first
predetermined temperature.
12. The vending machine of claim 10, wherein the controller is
further adapted to, during the initial period: activate a
compressor of the refrigeration system for a first predetermined
length of time; deactivate the compressor for a second
predetermined length of time; and select the first and second
predetermined lengths of time according to the sensed initial
temperature.
13. The vending machine of claim 10, wherein the controller is
further adapted to: sense a current temperature of the vending
machine; and during a second period: control the refrigeration
system according to the sensed current temperature, monitor an
operational characteristic of a compressor of the refrigeration
system, and perform a defrost procedure according to the monitored
operational characteristic.
14. The vending machine of claim 13, wherein the controller is
further adapted to perform the defrost procedure according to one
of an accumulated length of time the compressor has been activated
and a number of activations of the compressor.
15. The vending machine of claim 13, wherein the controller is
further adapted to begin the second period when a second
predetermined temperature of the vending machine is sensed.
16. The vending machine of claim 15, wherein the controller is
further adapted to, when the second period begins, activate an
evaporator fan of the refrigeration system for a third
predetermined length of time.
17. The vending machine of claim 16, wherein the controller is
further adapted to, during the second period, after the third
predetermined length of time, deactivate the evaporator fan when
the compressor is deactivated.
18. A method, comprising: sensing an opening of a door of a
refrigerated compartment of a vending machine; and responsive to
sensing the opening of the door, sensing an initial temperature of
the refrigerated compartment, and during an initial period,
operating a compressor of a refrigeration system of the vending
machine in a plurality of cycles of activation and deactivation,
where the compressor is activated and deactivated for predetermined
lengths of time selected according to whether the initial
temperature of the vending machine is above a first predetermined
temperature.
19. The method of claim 18, further comprising: sensing a current
temperature of the vending machine; and during a second period that
begins when a second predetermined temperature of the vending
machine is sensed: controlling the refrigeration system according
to the sensed current temperature, monitoring an operational
characteristic of a compressor of the refrigeration system, and
performing a defrost procedure according to the monitored
operational characteristic.
20. The method of claim 19, wherein the defrost procedure is
performed according to one of an accumulated length of time the
compressor has been activated and a number of activations of the
compressor.
21. The method of claim 19, wherein the step of controlling the
refrigeration system according to a sensed current temperature
further comprises: activating an evaporator fan of the
refrigeration system for a predetermined length of time after the
second predetermined temperature is sensed; and subsequently,
activating the evaporator fan when the compressor is activated and
deactivating the fan when the compressor is deactivated.
Description
CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY
[0001] The present application is related to U.S. Provisional
Patent Application No. 61/195,160, filed Oct. 3, 2008, entitled
"DEFROST STRATEGY". Provisional Patent Application No. 61/195,160
is assigned to the assignee of the present application and is
hereby incorporated by reference into the present application as if
fully set forth herein. The present application hereby claims
priority under 35 U.S.C. .sctn.119(e) to U.S. Provisional Patent
Application No. 61/195,160.
TECHNICAL FIELD OF THE INVENTION
[0002] The present application relates generally to refrigerated
vending machines and, more specifically, to an apparatus and method
for vending machine defrosting.
BACKGROUND OF THE INVENTION
[0003] During operation of a refrigeration system of a refrigerated
vending machine, water vapor in the air may condense on the cooling
elements (or coils) within the vending machine cabinet. Such
condensation may freeze on the coils, and the resulting ice may
inhibit the heat transfer from the cooling system to products
contained within the vending machine. This reduced heat transfer
may increase operating costs and decrease efficiency, and reduce
product cooling. Moreover, if ice builds up within the unit, it may
interfere with other components of the refrigeration system or
vending machine and lead to mechanical failure.
[0004] Defrosting may be performed by temporarily removing all
products from the vending machine cabinet, turning off power to the
unit, leaving the doors to the unit open, and waiting for the ice
to melt, and draining it appropriately. The defrosting process may
be sped up by mechanical removal of ice, or by the introduction of
gentle heat into the cabinet. For example, placing a pan of hot
water in the vending machine and closing the vending machine may be
an effective method. In addition, using a fan to blow room
temperature air over the built-up ice may also speed up the melting
process, as well as help to evaporate moisture from damp
surfaces.
[0005] This process can be time consuming and labor intensive.
Perishable products may require refrigeration during such a
defrosting process. Determining when a defrost cycle is needed may
require regular physical inspection of the machine.
SUMMARY
[0006] In one embodiment, a method includes sensing an exposure of
a refrigerated compartment of a vending machine to ambient air. In
response, the method further includes sensing an initial
temperature of the refrigerated compartment, selecting a procedure
from a plurality of procedures according to the sensed initial
temperature, and controlling a refrigeration system of the vending
machine using the selected procedure during an initial period.
[0007] In another embodiment, a vending machine includes a
controller, a temperature probe, and a refrigeration system. The
temperature probe and the refrigeration system are communicatively
coupled to the controller. The controller senses an exposure of a
refrigerated compartment of a vending machine to ambient air. In
response, the controller also senses an initial temperature of the
refrigerated compartment, selects a procedure from a plurality of
procedures according to the sensed initial temperature, and
controls a refrigeration system of the vending machine using the
selected procedure during an initial period.
[0008] In yet another embodiment, a method includes sensing an
opening of a door of a refrigerated compartment of a vending
machine and, in response, sensing an initial temperature of the
refrigerated compartment. The method also includes, in response to
sensing the opening of the door and during an initial period,
operating a compressor of a refrigeration system of the vending
machine in cycles of activation and deactivation, where the
compressor is activated and deactivated for predetermined lengths
of time that are selected according to whether the initial
temperature of the vending machine is above a predetermined
temperature.
[0009] Before undertaking the DETAILED DESCRIPTION below, it may be
advantageous to set forth definitions of certain words and phrases
used throughout this patent document: the terms "include" and
"comprise," as well as derivatives thereof, mean inclusion without
limitation; the term "or," is inclusive, meaning and/or; the
phrases "associated with" and "associated therewith," as well as
derivatives thereof, may mean to include, be included within,
interconnect with, contain, be contained within, connect to or
with, couple to or with, be communicable with, cooperate with,
interleave, juxtapose, be proximate to, be bound to or with, have,
have a property of, or the like; and the term "controller" means
any device, system or part thereof that controls at least one
operation, such a device may be implemented in hardware, firmware
or software, or some combination of at least two of the same. It
should be noted that the functionality associated with any
particular controller may be centralized or distributed, whether
locally or remotely. Definitions for certain words and phrases are
provided throughout this patent document, those of ordinary skill
in the art should understand that in many, if not most instances,
such definitions apply to prior, as well as future uses of such
defined words and phrases.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For a more complete understanding of the present disclosure
and its advantages, reference is now made to the following
description taken in conjunction with the accompanying drawings, in
which like reference numerals represent like parts:
[0011] FIG. 1 illustrates a block diagram of a vending machine
according to an embodiment of the disclosure;
[0012] FIG. 2 is a state diagram of initial refrigeration control
of a vending machine according to an exemplary embodiment of the
disclosure; and
[0013] FIG. 3 is a state diagram of refrigeration control for
temperature maintenance and defrosting of a vending machine
according to an exemplary embodiment of the disclosure.
DETAILED DESCRIPTION
[0014] FIGS. 1 through 3, discussed below, and the various
embodiments used to describe the principles of the present
disclosure in this patent document are by way of illustration only
and should not be construed in any way to limit the scope of the
disclosure. Those skilled in the art will understand that the
principles of the present disclosure may be implemented in any
suitably arranged vending machine.
[0015] FIG. 1 illustrates a block diagram of a vending machine 100
according to an embodiment of the disclosure. The vending machine
100 includes a vending machine controller (VMC) 102 that operates
to control functions of the vending machine 100. Such functions may
include vending, payment, and refrigeration functions. In some
embodiments, the control functions of the controller 102 may be
implemented in a single microcontroller or microprocessor. In other
embodiments, the control functions of the controller 102 may be
distributed across a plurality of microcontrollers or
microprocessors.
[0016] The vending machine includes a temperature probe 104 that is
communicatively coupled to the VMC 102. The temperature probe 104
is located in a position within the vending machine 100 that
enables the temperature probe 104 to sense a temperature that is
representative of the temperature of products stored in the vending
machine 100. For example, such a location may be in a product
compartment of the vending machine 100 in which products are
stored, or in a return air duct for air returning from the
compartment to be chilled.
[0017] The vending machine 100 also includes a refrigeration system
106 that controls the temperature of the product compartment of the
vending machine 100, in which products are stored. In the
refrigeration system 106, a refrigerant is compressed in a
compressor 108. The compressed refrigerant is cooled in condenser
coils and then passes through an expansion device. The low pressure
refrigerant flows through evaporator coils before returning to the
compressor. An evaporator fan 110 pulls air from the product
compartment over the evaporator coils and pushes chilled air back
into the product compartment. The compressor 108 and the evaporator
fan 110 are communicatively coupled to the VMC 102, which controls
their operation. In some embodiments, the temperature probe 104 may
be located in a position that that enables the temperature probe
104 to sense a temperature of the evaporator coils.
[0018] Typically, the product compartment of the vending machine
100 is accessible via a door for restocking products. The vending
machine 100 further includes a door sensor communicatively coupled
to the VMC 102. The door sensor 112 provides an indication of
whether the door is open or closed.
[0019] The vending machine 100 also includes a cumulative clock 114
that is communicatively coupled to the VMC 102. The VMC 102
controls the cumulative clock 114 by resetting its value to zero,
starting it without changing its value, stopping it, and reading
its current value. The VMC 102 may use the cumulative clock 114 to
determine a cumulative length of time that the compressor 108 has
been activated by starting and stopping the cumulative clock 114
whenever the VMC 102 activates and deactivates, respectively, the
compressor 108.
[0020] FIG. 2 illustrates a state diagram 200 of initial
refrigeration control of a vending machine according to an
exemplary embodiment of the disclosure. Often, the door that
provides restocking access to the product compartment of the
vending machine 100 comprises an entire sidewall of the
compartment. As a result, a significant quantity of unchilled
outside air may enter the compartment when the door is opened.
[0021] The introduction of outside air and unchilled products to
the product compartment during restocking may cause the temperature
within the compartment to rise. Furthermore, condensation may build
up on products and surfaces inside the product compartment that are
below the dew point. Similarly, when power is turned off to the
vending machine 100, the refrigeration system 106 stops functioning
and the temperature within the product compartment increases.
[0022] When the door is closed or the power is turned back on, the
vending machine 100 enters an initial mode during which the VMC 102
operates the refrigeration system 106 to quickly bring the
temperature within the product compartment to a desired operating
temperature. This initial mode is illustrated in FIG. 2. From any
state of the state diagram 200, when the door is opened, the VMC
102 enters a Door Open/Power Off state 202. Similarly, when power
is first applied to the vending machine, the VMC 102 enters the
Door Open/Power Off state 202.
[0023] When the door sensor 112 indicates that the door is closed,
the VMC 102 moves from state 202 to either a Reload state 204 or an
Initial Pulldown state 206, according to an initial temperature in
the product compartment, as sensed by the temperature probe 104. If
the initial temperature is less than 73 degrees Fahrenheit, the
state of VMC 102 changes to the Reload state 204. If the initial
temperature is greater than or equal to 73 degrees Fahrenheit, the
state of VMC 102 changes to the Initial Pulldown state 206.
[0024] In both the Reload state 204 and the Initial Pulldown state
206, the VMC 102 controls the refrigeration system 106 according to
scripted actions that include cycles of activating and deactivating
the compressor 108, which are explained in more detail below. In
either the Reload state 204 or the Initial Pulldown state 206, if
the VMC 102 determines that the temperature probe 104 has reached a
predetermined temperature set point, the state of the VMC 102
changes to a Steady State Temperature state 210.
[0025] In some embodiments, the predetermined temperature set point
is 35 degress Fahrenheit. In other embodiments, the predetermined
temperature set point is 37 degress Fahrenheit. While particular
predetermined temperature set points have been described, it will
be understood that in still other embodiments, other predetermined
temperature set points may be utilized. In yet other embodiments,
the predetermined temperature set point may be set by an operator
of the vending machine 100.
[0026] If the VMC 102 completes the scripted actions in the Reload
state 204 and the temperature probe 104 has not reached the
predetermined temperature set point, then the state of the VMC 102
changes to a Reload Pulldown state 208. In the Reload Pulldown
state 208, the VMC 102 again controls the refrigeration system 106
according to scripted actions, which are explained in more detail
below. While in the Reload Pulldown state 208, if the VMC 102
determines that the temperature probe 104 has reached the
predetermined temperature set point, the state of the VMC 102
changes to the Steady State Temperature state 210.
[0027] In the Reload State 204, the VMC 102 controls the
refrigeration system 106 according to the following script of
actions. As indicated above, if at any time during the performance
of this script the VMC 102 determines that the temperature probe
104 has reached the predetermined temperature set point, the state
of the VMC 102 changes to the Steady State Temperature state
210.
[0028] Reload state 204 Script: [0029] 1. Activate (turn on) the
evaporator fan 110. [0030] 2. Wait two minutes. [0031] 3. Activate
(start) the compressor 108. [0032] 4. Wait forty-five (45) minutes.
[0033] 5. Deactivate (stop) the compressor 108. The evaporator fan
110 stays activated (running). [0034] 6. Wait three minutes. [0035]
7. Start the compressor 108. [0036] 8. Wait forty-five (45)
minutes. [0037] 9. Stop the compressor 108. The evaporator fan 110
stays running. [0038] 10. Wait two minutes. [0039] 11. Start the
compressor 108. [0040] 12. Wait forty-five (45) minutes. [0041] 13.
Stop the compressor 108. The evaporator fan 110 stays running.
[0042] 14. Wait two minutes.
[0043] Initial Pulldown state 206 Script: [0044] 1. Turn on the
evaporator fan 110. [0045] 2. Activate (start) the compressor 108.
[0046] 3. Wait FirstIPCompressorOnTime. [0047] 4. Deactivate (stop)
the compressor 108. The evaporator fan 110 stays activated
(running). [0048] 5. Wait four minutes. [0049] 6. Start the
compressor 108. [0050] 7. Wait SecondIPCompressorOnTime. [0051] 8.
Stop the compressor 108. The evaporator fan 110 stays running.
[0052] 9. Wait ten minutes. [0053] 10. Start the compressor 108.
[0054] 11. Wait SecondIPCompressorOnTime. [0055] 12. Stop the
compressor 108. The evaporator fan 110 stays running. The
evaporator fan 110 stays running. [0056] 13. Wait twenty
minutes.
[0057] In some embodiments the FirstIPCompressorOnTime is 7 hours
and the SecondIPCompressorOnTime is 6 hours. In other embodiments,
which may be used with a smaller vending machine, the
FirstIPCompressorOnTime and the SecondIPCompressorOnTime are both 5
hours.
[0058] Reload Pulldown state 208 Script: [0059] 1. Turn on the
evaporator fan 110. [0060] 2. Activate (start) the compressor 108.
[0061] 3. Wait RPCompressorOnTime. [0062] 4. Deactivate (stop) the
compressor 108. The evaporator fan 110 stays activated (running).
[0063] 5. Wait FirstRPCompressorOffTime. [0064] 6. Start the
compressor 108. [0065] 7. Wait RPCompressorOnTime. [0066] 8. Stop
the compressor 108. The evaporator fan 110 stays running. [0067] 9.
Wait SecondRPCompressorOffTime. [0068] 10. Start the compressor
108. [0069] 11. Wait RPCompressorOnTime. [0070] 12. Stop the
compressor 108. The evaporator fan 110 stays running. [0071] 13.
Wait ThirdRPCompressorOffTime.
[0072] In some embodiments: [0073] the RPCompressorOnTime is six
hours, [0074] the FirstRPCompressorOffTime is eight minutes, [0075]
the SecondRPCompressorOffTime is twelve minutes, and [0076] the
ThirdRPCompressorOffTime is twenty minutes.
[0077] In other embodiments, which may be used with a smaller
vending machine: [0078] the RPCompressorOnTime is five hours,
[0079] the FirstRPCompressorOffTime is twelve minutes, [0080] the
SecondRPCompressorOffTime is twelve minutes, and [0081] the
ThirdRPCompressorOffTime is twenty minutes.
[0082] While particular compressor on times and compressor off
times for two embodiments have been described, it will be
understood that in still other embodiments, other compressor on
times and compressor off times may be utilized. While three
compressor on-off cycles have been described for the two
embodiments shown, it will be understood that more or fewer
compressor on-off cycles may be used in any or all of the Reload
state 204, the Initial Pulldown state 206, or the Reload Pulldown
state 208.
[0083] FIG. 3 illustrates a state diagram 300 of the Steady State
Temperature state 210, which provides refrigeration control for
temperature maintenance and defrosting of a vending machine
according to an exemplary embodiment of the disclosure. In some
embodiments, while in the Steady State Temperature state 210, the
VMC 102 maintains a temperature of the product compartment of the
vending machine 100 within a range of temperatures. As described
with reference to FIG. 3, the Steady State Temperature state 210 is
entered when the temperature probe 104 has reached a predetermined
temperature set point. Upon entering the Steady State Temperature
state 210, the VMC 102 enters a state 302, deactivating the
compressor 108, setting the cumulative clock 114 to zero, and
leaving the evaporator fan 110 activated.
[0084] After two minutes, the VMC 102 enters a state 304. In the
state 304, the temperature probe 104 is monitored and the
compressor 108 is started and stopped according to the current
temperature as sensed by the temperature probe 104. Specifically,
when the compressor 108 is stopped and the temperature probe
exceeds the predetermined temperature set point by a predetermined
hysteresis amount, the compressor 108 and the cumulative clock 114
are started. In some embodiments, the hysteresis amount is 2.7
degrees Fahrenheit. When the compressor 108 is running and the
temperature probe falls below the predetermined temperature set
point, the compressor 108 and the cumulative clock 114 are stopped.
In the state 302, the evaporator fan 110 is running both when the
compressor 108 is activated and deactivated.
[0085] As described in the state 302, the predetermined temperature
set point and the hysteresis amount define a range of temperatures
where the temperature set point is at the low end of the range. In
other embodiments, the VMC 102 may start the compressor 108 when
the temperature probe 104 exceeds the temperature set point and
stop the compressor 108 when the temperature probe falls below the
temperature set point by more than the hysteresis amount. In such
embodiments, the temperature set point is at the high end of the
range of temperatures defined by the predetermined temperature set
point and the hysteresis amount. In still other embodiments, the
predetermined temperature set point and the hysteresis amount may
be combined to define a range with the temperature set point in any
desired position relative to the range. In still further
embodiments, the hysteresis amount may be larger or smaller than
2.7 degrees Fahrenheit.
[0086] After thirty-six (36) hours, the VMC 102 enters a state 308.
In the state 308, the temperature probe 104 is monitored and the
evaporator fan 110 is started and stopped along with the compressor
108, according to the current temperature as sensed by the
temperature probe 104. Control of the compressor 108 and the
cumulative clock 114 according to the current value of the
temperature probe 104 is the same as that described for the state
304.
[0087] In either the state 304 or the state 308, if a predetermined
defrost trigger is reached, the VMC 102 will enter a state 306 or a
state 310, respectively. In both the state 306 and the state 310,
the VMC 102 performs a defrost function by turning off the
compressor 108, while leaving the evaporator fan 110 running. After
fifteen minutes, the VMC 102 returns from the state 306 to the
state 304, or from the state 310 to the state 308.
[0088] In some embodiments, the defrost trigger is a total
accumulated time that the compressor 108 has been activated since a
last previous defrost cycle or since last entering the Steady State
Temperature state 210. While in the state 304 or the state 306, the
VMC 102 starts and stops the cumulative clock 114 when starting and
stopping, respectively, the compressor 108. When the length of time
measured by the cumulative clock 114 exceeds 180 minutes, the
defrost trigger is reached and either the state 306 or the state
310 is entered to perform a defrost cycle. When the defrost cycle
is completed, the VMC 102 resets the cumulative clock 114 to zero,
returns to the state 304 or the state 306, and resumes starting and
stopping the cumulative clock 114 when starting and stopping,
respectively, the compressor 108.
[0089] In other embodiments, the defrost trigger is a number of
activations of the compressor 108 since a last previous defrost
cycle or since last entering the Reload state 204. While in the
state 304 or the state 306, the VMC 102 increments a counter each
time the compressor 108 is started. When the counter value reaches
20, the defrost trigger is reached and either the state 306 or the
state 310 is entered to perform a defrost cycle. When the defrost
cycle is completed, the VMC 102 resets the counter to zero, returns
to the state 304 or the state 306, and resumes counting activations
of the compressor 108.
[0090] In still other embodiments, both the total accumulated time
that the compressor 108 has been activated and the number of
activations of the compressor 108 are monitored. The defrost
trigger may be reached when the first of 180 minutes of activation
or 20 activations is reached, and a defrost cycle performed. When
the defrost cycle is completed, both the cumulative clock 114 and
the activation counter are reset to zero.
[0091] It the embodiment described with reference to FIG. 2 and
FIG. 3, the cumulative clock 114 tallies only time that the
compressor 108 is activated while in the Maintain Temperature mode
210. In another embodiment, the cumulative clock 114 also tallies
time that the compressor 108 is activated while in one or more of
the Reload state 204, the Initial Pulldown state 206, or the Reload
Pulldown state 208. In such an embodiment, the cumulative clock 114
is reset to zero each time the compressor 108 is stopped when the
temperature probe 104 is above the predetermined temperature set
point. When the compressor 108 is started, the cumulative clock 114
is started. Thus, if the temperature probe 104 reaches the
predetermined temperature set point VMC 102 and changes to the
Maintain Temperature mode 210, any final period that the compressor
108 was running will be included in the total time count
accumulated by the cumulative clock 114.
[0092] Although the present disclosure has been described with an
exemplary embodiment, various changes and modifications may be
suggested to one skilled in the art. It is intended that the
present disclosure encompass such changes and modifications as fall
within the scope of the appended claims. For example, while
temperatures have been expressed in Fahrenheit in this disclosure,
it will be understood that in other embodiments temperature
measurements may be made in Centigrade or another suitable
temperature scale.
* * * * *