US20060218950A1

US20060218950A1 - Damper door control from adaptive defrost control

Info

Publication number: US20060218950A1
Application number: US11/388,035
Authority: US
Inventors: Leonard Jenski; Robert Alvord; Gary Ashurst; Thomas Donahue
Original assignee: Robertshaw Controls Co
Current assignee: Robertshaw Controls Co
Priority date: 2005-03-31
Filing date: 2006-03-23
Publication date: 2006-10-05
Also published as: CA2602448A1; WO2006104936A3; WO2006104936A8; WO2006104936A2; KR20070113291A; MX2007010796A

Abstract

An adaptive defrost control method and device for controlling a damper door during a defrost cycle is provided. Before entering the defrost cycle, the adaptive defrost control logic determines if the damper door is open. If the damper door is open, the defrost cycle is suspended until the door is closed. If the damper door is closed, the adaptive defrost control logic activates a barrier between the damper door motor and a power supply so that the damper door may not be opened during the defrost cycle. After the defrost cycle is completed, the adaptive defrost control logic removes the barrier between the damper door motor and a power supply. The damper door may then be opened and closed as necessary. Accordingly, warm moist air from the defrost cycle does not enter the fresh food compartment.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application claims the benefit of U.S. Provisional Patent Application No. 60/666,682 filed Mar. 31, 2005, the teachings and disclosure of which are hereby incorporated in their entireties by reference thereto.

FIELD OF THE INVENTION

The invention relates generally to refrigerators and, more particularly, to controlling the air flow between a freezer compartment and a fresh food compartment in a refrigerator.

BACKGROUND OF THE INVENTION

Many modern refrigeration units include a fresh food compartment for storing food above a freezing temperature. The fresh food compartment is normally isolated from a main or freezer compartment for storing food below the freezing temperature. Often, the temperatures of the fresh food and freezer compartments can be separately controlled. To provide cooling to the fresh food compartment, the fresh food compartment is typically equipped with an active damper door controlled by a damper motor. When the damper door is open, typically the evaporator fan is energized to move cooling air from inside of the freezer compartment into the fresh food compartment. When the damper door is closed, the fresh food compartment is isolated from the freezer compartment and its temperature can change separately from the freezer compartment.
In a typical refrigeration unit, the fresh food compartment is equipped with its own thermostatic switch to permit thermostatic control of the temperature of the fresh food compartment. This thermostatic switch detects when the temperature of the fresh food compartment exceeds a threshold, indicating that cool air from the freezer compartment must be introduced into the fresh food compartment. When the thermostatic switch detects this condition, the thermostatic switch changes state to its “hot” condition, in which it delivers electrical power to the damper motor to open the damper. When the fresh food compartment cools, the thermostatic switch again changes state to its “cool” condition, in which it delivers electrical power to the damper motor to close the damper.
It is further known that the efficiency of the typical refrigeration unit can be enhanced by reducing the amount of frost that builds up on the heat exchanger within the freezer compartment. Modern systems, therefore, are generally of the self-defrosting type. To this end, they employ a heater specially positioned and controlled to slightly heat the heat exchanger to cause melting of frost build-up on the heat exchanger. These defrost heaters are controlled pursuant to defrost cycle algorithms and configurations. As a result, these refrigerator-freezers undergo two general cycles or modes, a cooling cycle or mode and a defrost cycle or mode. During the cooling cycle, a compressor is connected to a line voltage and the compressor is cycled on and off by means of a thermostat, i.e., the compressor is actually run only when the enclosure becomes sufficiently warm to require cooling. During the defrost cycle, the compressor is disconnected from the line voltage and a defrost heater is connected to the line voltage. The defrost heater is turned off by means of a temperature sensitive switch in proximity to the heat exchanger after the frost has been melted away, or otherwise by programmatic control.
Unfortunately, conventional refrigeration systems do nothing to prevent the damper door from being open during the defrost cycle if the refrigerator compartment calls for cooling while the freezer compartment is in a defrost cycle. Accordingly, warm moist air is permitted to flow through the damper door duct into the fresh food compartment. It is not desirable to have warm moist air in a compartment where food is meant to be kept cool and fresh. Accordingly, there is a need in the art to prevent the damper door from opening during the defrost cycle.

BRIEF SUMMARY OF THE INVENTION

The invention provides an adaptive defrost control method and device for controlling a damper door during a defrost cycle. Before entering the defrost cycle, the adaptive defrost control logic determines if the damper door is open. If the damper door is open, the defrost cycle is suspended until the door is closed. If the damper door is closed, the adaptive defrost control logic prevents the opening of the damper door.
In one embodiment of the present invention, the system of the present invention activates an electronic barrier between the damper door motor and a power supply so that the damper door may not be opened during the defrost cycle. In one embodiment the barrier is a triac located between the main power supply and a thermostatic switch for controlling the temperature of the fresh food compartment. In another embodiment of the invention, the barrier is a triac located between the main power supply and the damper door motor. After the defrost cycle is completed, the adaptive defrost control logic removes the barrier to allow operation of the damper door motor. The damper door may then be opened and closed as necessary.
Other aspects, objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:
FIG. 1 is a schematic diagram of a refrigeration unit in accordance with the present invention;
FIG. 2 is a schematic diagram of a control circuit for controlling the refrigeration unit in accordance with one embodiment of the present invention;
FIG. 3 is a schematic diagram of a control circuit for controlling the refrigeration unit in accordance with a second embodiment of the present invention; and
FIG. 4 is a flow diagram illustrating a control logic method in accordance with the present invention.
While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the major electrical components of a refrigeration unit 100 such as, for example, a commercial or domestic refrigerator-freezer are schematically illustrated. As will be more fully explained below, the present invention prevents warm moist air from passing into a fresh food compartment from a freezer compartment when the refrigeration unit 100 undergoes a defrost cycle. As such, food within the fresh food compartment is advantageously maintained in a fresh condition for a longer period of time.
Still referring to FIG. 1, the refrigeration unit 100 includes a first or main compartment such as a freezer compartment 101 and a second fresh food compartment 102. The first and second compartments 101, 102 are separately thermostatically controlled. Under thermostatic control, the freezer and fresh food compartments 101, 102 are coupled together by opening a damper door 104 to uncover an opening or passage interposed between the two compartments 101, 102. When the damper door 104, which is moveable by a damper motor 105, is driven or otherwise biased opened, a flow of air is permitted to pass between the two adjacent compartments 101, 102. When the damper door 104 is closed, air is inhibited or prevented from flowing between the two neighboring compartments 101, 102. In other words, the damper door 104 regulates the flow of air between the compartments 101, 102 to control the temperature of the fresh food compartment 101.
The damper door 104 is generally coupled to and driven by an electric damper motor 105. The damper door 104 is, in some situations, also driven closed by the electric damper motor 105. In other situations, the damper door 104 is simply resiliently biased closed as well known in the art.
Inside of the freezer compartment 101 is a main thermostat 106 that has as a primary component a thermostatic switch 107. In a typical application, the thermostat 106 is adjustable so that the temperature of the freezer compartment 101 is maintainable at different selected temperatures. Inside of the fresh food compartment 102 is a fresh food thermostat 108 that has as a primary component a second thermostatic switch 109. In a typical application, the thermostat 108 is also adjustable so that the temperature of the fresh food compartment 102 is maintainable at different selected temperatures.
Refrigeration unit 100 is cooled by a heat transfer engine that facilitates heat transfer from the freezer compartment 101 by the cyclical compression, condensation, decompression and evaporation of a thermally coupled refrigerant captured in a thermodynamic loop. The thermodynamic loop includes an evaporator 110, compressor 111, and condenser 112. As the refrigerant passes through evaporator 110, which is located inside of the freezer compartment 101, the refrigerant evaporates from a liquid to a gaseous state, absorbing heat transferred from the freezer compartment 101 into the refrigerant. The primarily gaseous refrigerant is delivered at the outlet of evaporator 110 to compressor 111.
The compressor 111 compresses the primarily gaseous refrigerant received from evaporator 110 and delivers the compressed refrigerant to condenser 112. The compressed refrigerant is generally delivered by the application of a mechanical force generated by an electric motor integrated within the compressor 111. After leaving the compressor 111, the compressed, high pressure refrigerant passes through condenser 112. While passing through the condenser 112, heat is transferred from the refrigerant to the environment external to freezer compartment 101 as the refrigerant condenses from a primarily gaseous state to a primarily liquid state. The primarily liquid refrigerant then passes back into the inlet of evaporator 110 to complete the cycle.
To facilitate and promote heat transfer between the refrigerant in the coils of the evaporator 110 and the air within the freezer compartment 101, a fan 113 is included in the refrigeration unit 100. Specifically, an evaporator fan 113 is disposed in the freezer compartment 101 to circulate the air in the freezer. The evaporator fan 113 is specifically able to produce a flow of air that passes over and around the coils of the evaporator 110. This flow of air past the coils of the evaporator 110 encourages the exchange of heat from the air in freezer compartment 101 to the refrigerant. As such, the refrigerant in the coils is able draw heat out of, and absorb heat from, the air within the freezer compartment 101.
As the fresh food compartment 102 warms, the fresh food thermostat 108 senses higher temperatures. When the sensed temperature reaches or exceeds a high temperature limit, the fresh food thermostat 108 closes thermostatic switch 109 to send a signal to damper motor 105 to open the damper door 104. With the damper door 104 open, colder air from the freezer compartment 101 is passed or circulated into the fresh food compartment 102. The temperature in the fresh food compartment 101 is lowered by the inflow of colder air from the freezer compartment 101 until the temperature falls to a temperature that is at or below the high temperature limit of the fresh food thermostat 108. At that point, the fresh food thermostat 108 opens the thermostatic switch 109 to send a signal to the damper motor 105 to close damper door 104.
To ensure that frost build up on the condenser 112 does not reduce the effectiveness of the cooling cycle, refrigeration unit 100 further includes a defrost heater 120. The defrost heater 120 is situated near the evaporator 110 to melt frost from the evaporator during a defrost cycle. Operation of the defrost heater 120 is controlled by an adaptive defrost control logic unit 121 as commonly known in the art.
As previously described, in the conventional refrigeration unit the damper door may be left open or permitted to open during the defrost cycle thereby allowing heat and moisture into the fresh food compartment 102. In an embodiment of the present invention, the damper door 104 is closed or forced to remain closed during the defrost cycle. As such, heat and moisture are prevented from entering the fresh food compartment 102. As schematically illustrated in FIG. 2, a control circuit 200 for closing the damper door during a defrost cycle is shown.
With reference to FIG. 2, an adaptive defrost controller (ADC) 203 coordinates the operation of a compressor motor 205, a condenser motor 206, a defrost heater 204, and a triac 201. In the illustrated embodiment, the compressor motor 205 is connected between terminal T6 of the ADC 203 and a ground line N and is actuated by the ADC during a cooling cycle when cooling of the freezer compartment is required. Condenser motor 206 is connected between terminal T7 of the ADC 203 and the ground line N and is actuated by the ADC during a cooling cycle. Evaporator fan motor 207 is connected between terminal T8 of the ADC 203 and the ground line N and is actuated by the ADC during a cooling cycle. Heater 204 is connected to terminal T4 of the ADC 203 and is actuated by the ADC during a defrost cycle. The triac 201 is connected between power line L1 and contact “a” of switch S1 (e.g., such as switch 109 in FIG. 1) and is actuated by the ADC 203 via a control line connected to terminal T3 of the ADC. The triac 201 is actuated by ADC 203 during a defrost cycle to deny current to contact “a” of switch S1. The ADC 203 is further connected to power line L1 at terminal T1 and ground line N at terminal T4.
When a thermostat 106 senses that a temperature in the freezer compartment 101 has risen above a specified level, the thermostat instructs the refrigeration unit 100 to enter a cooling cycle. During the cooling cycle, the thermostat 106 commands the switch S2 (e.g., such as switch 107 in FIG. 1) to close such that current is permitted to flow from contact “d” of switch S2 to contact “e” of switch S2 and, in turn, to terminal T2 of the ADC 203. When the ADC 203 receives this current signal at the terminal T2, the ADC 203 actuates the compressor motor 205, the condenser fan motor 206, and the evaporator fan motor 207. When the thermostat 106 senses that the temperature in the freezer compartment 101 has been cooled to a specified level, the thermostat 106 instructs the switch S2 to once again open. With the switch S2 open, a current no longer flows into the terminal T2 of the ADC 203. Based on the lack of current signal at the terminal T2, the ADC 203 deactivates the compressor motor 205, the condenser fan motor 206, and the evaporator fan motor 207 and the cooling cycle is generally competed.
When a thermostat 108 senses that a temperature in the fresh food compartment 102 has risen above a specified level, the thermostat 108 instructs the refrigeration unit 100 to enter a cold air transfer cycle. The thermostat 108 causes the switch S1 to move from an initial position, where the contacts “a” and “b” are coupled, to a secondary position, where the contacts “a” and “c” are coupled. The secondary position of the switch S1 permits current to flow from the power line L1, through the closed triac 201, through the switch S1, and to contact “f” of switch S3 and contact “i” of switch S4. The switch S3 is in a position to connect contact “f” to contact “h” and the switch S4 is in a position to connect contact “i” to contact “k”. As such, current is permitted to flow into and energize or actuate the damper motor 202. The energized damper motor 202 is adapted to drive the damper door 104 (FIG. 1) open such that cold air is transferred from the freezer compartment 110 to the fresh food compartment 102 through the opening 103.
Because the damper door 104 is mechanically coupled to the switch S3, as commonly known in the art, when the damper door 104 has attained an open position the switch S3 is manipulated to connect contact “g” to contact “h” and the switch S4 is manipulated to connect contact “j” to contact “k”. Since terminal “b” of switch S1 is not coupled to the power line L1, the flow of current to the damper motor 202 ceases after the damper door 104 has achieved the open position. Notably, switch S3 and switch S4 are redundant and open and close one at a time to prevent stalling of the damper door 104 in a partially-open position upon a loss of power.
When the thermostat 108 senses that the temperature in the fresh food compartment 102 has appropriately dropped, the thermostat instructs the switch S1 to open. With the switch S1 open, the damper motor 202 no longer receives a current and the damper door 104 is able to close. To close, the damper door 104 is generally drawn away from the open position by a biasing member such as, for example, a spring or other resilient member.
In accordance with the adaptive control logic, the refrigeration unit 100 is occasionally instructed to enter a defrost cycle to melt away any frost (i.e., ice) that has accumulated on or around the coils of the evaporator 110. During the defrost cycle, the ADC 203 activates the defrost heater 204 to melt the frost from the evaporator 110. Operation of the heater 120 produces warm and moist air (e.g., air that is at a temperature above freezing and has a relative humidity higher than normally found in conventional freezers) such that any ice or condensation adhered to the coils is removed or reduced. Due to the melting ice and evaporating condensation, the air in the freezer compartment 101 becomes warm and moist as the temperature inside the compartment 101 rises.
In addition to activating the defrost heater 120, the ADC 203 also ensures that the compressor motor 205, the condenser motor 206, and the evaporator fan motor 207 are inactive. Since defrost cycle is producing heat, and the cooling cycle is absorbing heat, the two cycles are controlled and activated in a mutually exclusive fashion by the ADC 203. As a result, even if the switch S2 is instructed to close by thermostat 106 in an attempt to activate the cooling cycle, the ADC 203 ignores the closure of the switch. Therefore, until the completion of the defrost cycle, the components 205, 206, 207 remain deactivated regardless of the position of switch S2. In other words, the heat absorbing (or exchanging) process remains idle in favor of the defrost cycle.
Also during the defrost cycle, the ADC 203 instructs the triac 201 to close. As illustrated in FIG. 2, the deactivated triac 201 restricts current from flowing to the damper motor 202. Therefore, even if switch S1 is instructed to close by thermostat 108 in an attempt to begin the cold air transfer cycle, no current can flow to the damper motor 202. As such, the position of the switch S1 becomes meaningless during the defrost cycle. Resultantly, the opening 103 remains impeded by the damper door 104 and the warm moist air that is generated in the freezer compartment 101 during the defrost cycle is not permitted to escape into the fresh food compartment 102.
As schematically illustrated in FIG. 3, another embodiment of a control circuit 300 for retaining the damper door in a closed position during a defrost cycle is shown. With reference to FIG. 3, an adaptive defrost controller (ADC) 303 coordinates the operation of a compressor motor 305, a condenser motor 306, a defrost heater 304, and a triac 301. The compressor motor 305 is connected between terminal T6 of the ADC 303 and a ground line N and is actuated by the ADC during a cooling cycle. The condenser motor 306 is connected between terminal T7 of the ADC 303 and the ground line N and is actuated by the ADC during a cooling cycle. The evaporator fan motor 307 is connected between terminal T8 of the ADC 303 and the ground line N and is actuated by ADC 303 during a cooling cycle. The heater 304 is connected to terminal T5 of the ADC 303 and is actuated by the ADC during a defrost cycle. The triac 301 is connected between power line L1 and damper motor 302 and is actuated by the ADC 303 via a control line connected to terminal T3 of the ADC 303. The triac 301 is actuated by the ADC 303 during a defrost cycle to restrict current from flowing to the damper motor 302. In other words, the triac 301 prevents the damper motor 302 from being activated or operating during the defrost cycle. The ADC 303 is further connected to the power line L1 at terminal T1 and the ground line N at T4.
When a thermostat 106 senses that a temperature in the freezer compartment 101 has risen above a specified level, the thermostat 106 instructs the refrigeration unit 300 to enter a cooling cycle. During the cooling cycle, the switch S2 closes to permit current to flow from contact d of switch S2 to contact e of switch S2 and, in turn, to terminal T2 of ADC 303. When the ADC 303 receives this current signal at terminal T2, the ADC actuates the compressor motor 305, the condenser motor 306, and the evaporator fan motor 307. When the thermostat 106 senses that the temperature in the freezer compartment 101 has been cooled to a specified level, the thermostat instructs the switch S2 to once again open. With the switch S2 open, a current no longer flows into the terminal T2 of the ADC 303. Based on the lack of current signal at T2, the ADC deactivates the compressor motor 305, the condenser motor 306, and the evaporator fan motor 307 and the cooling cycle is generally completed.
When a thermostat 108 senses that a temperature in the fresh food compartment 102 has risen above a specified level, the thermostat causes the switch S5 to move to from an initial (i.e., open) position, where the contacts “m” and “n” are uncoupled, to a secondary (i.e., closed) position, where the contacts “m” and “n” are coupled, to enter a cold air transfer cycle. The secondary switch position completes a circuit between terminal T11 and terminal T9 of the ADC 303. Upon detection of this completed circuit, the ADC 303 opens triac 301 to permit current to flow to the damper door motor 302. The energized damper motor 302 resultantly drives the damper door 104 open to allow cold air from the freezer compartment 101 to flow into the fresh food compartment 102 through the opening 103.
Because the damper door 104 is mechanically coupled to the switch S6, as commonly known in the art, when the damper door 104 has attained an open position, the switch S6 is manipulated to uncouple and disconnect contacts “q” and “r.” With the switch S6 opened, the circuit between terminal T9 and terminal T10 of the ADC 303 is broken and the ADC is resultantly notified that the damper door is in an open position.
When the thermostat 108 senses that the temperature in the fresh food compartment 102 has cooled to an acceptable level, the thermostat instructs the switch S5 to open. As such, the connection between terminal T11 and terminal T9 is broken. When this connection is broken, the ADC 303 recognizes this condition and closes the triac 301. With the triac closed, the damper motor 302 is no longer energized and the damper door 104 is permitted to close. The closing of the damper door 104 causes the switch S6, which is mechanically coupled to the damper door, to close. As such, the circuit between terminal T9 and terminal T10 is reestablished and the ADC 303 is advised that the damper door has been closed.
In accordance the adaptive control logic, the refrigeration unit 300 is occasionally instructed to enter a defrost cycle to melt away any frost (i.e., ice) that has accumulated on or around the coils of the evaporator 110. During the defrost cycle, the ADC 303 activates the defrost heater 304 to melt the frost from the evaporator 110. As before, the heat and warm air produced by the heater 120 are permitted to flow over and around the coils of the evaporator 110 such that any ice or condensation adhered to the coils is removed or reduced. Due to the melting ice and evaporating condensation, the air in the freezer compartment 101 becomes warm and moist as the temperature inside the compartment 101 rises.
In addition to activating the defrost heater 120, the ADC 303 also ensures that the compressor motor 305, the condenser motor 306, and the evaporator fan motor 307 are inactive. Since defrost cycle is producing heat, and the cooling cycle is absorbing heat, the two cycles are controlled and activated in a mutually exclusive fashion by the ADC 303. As a result, even if the switch S2 is instructed to close by thermostat 106 in an attempt to activate the cooling cycle, the ADC 303 ignores the closure of the switch. Therefore, until the completion of the defrost cycle, the components 305, 306, 307 remain deactivated regardless of the position of switch S2. In other words, the heat absorbing (or exchanging) process remains idle in favor of the defrost cycle.
Also during the defrost cycle, the ADC 303 instructs the triac 301 to close. As illustrated in FIG. 3, the closed triac 301 forms an electronic barrier to the flow of current to the damper motor 302. Therefore, even if switch S5 should be instructed to close by thermostat 108 in an attempt to initiate the cold air transfer cycle, no current can flow to the damper motor 302. As such, the position of switch S5 is irrelevant during the defrost cycle. Resultantly, the opening 103 remains impeded by the damper door 104 and the warm moist air that is generated in the freezer compartment 101 during the defrost cycle is not permitted to escape into the fresh food compartment 102.
In light of the above embodiments of the invention and as will be appreciated by those skilled in the art, when the refrigeration unit 100 is in the defrost cycle, closure of the switches S1 and S5 by the thermostat 108, which would normally begin the cold air transfer cycle, has no effect since the current path to the damper motor 202, 302 is cut off by the deactivation of the triac 201, 301. With no actuating or energizing current, the damper door 104 cannot be driven open and the warm, moist air that generated during the defrost cycle cannot, no matter what happens to switches S1 and S5, pass from the freezer compartment 101 to the fresh food compartment 102. Furthermore, those skilled in the art will recognize that while the triacs 201, 301 are described in detail and illustrated in both FIGS. 2 and 3, different types and varieties of devices and/or switches are employable within the control circuits 200, 300 to prevent a current from flowing.
In addition to the conventional known adaptive defrost control logic, the flow diagram of FIG. 4 illustrates additional logic for ensuring that the damper door 104 is closed during the defrost cycle. When the control circuit 200, 300 in the refrigeration unit 100 is started 399, the adaptive defrost control logic determines 400 if the damper door is open before entering the defrost cycle. If the damper door is open, the defrost cycle is suspended until the door is closed. If the damper door is closed, the adaptive defrost control logic cuts power 401 to the damper door motor (e.g., provides a barrier between the damper door motor and a power supply) so that the damper door cannot be opened during the defrost cycle. With the damper door disengaged from the power supply, the defrost cycle is performed 402. After the defrost cycle is completed, the adaptive defrost control logic removes the barrier from between the damper door motor and a power supply such that the damper motor is once again permitted to run 403. With the damper motor once again free to drive the damper door, the protection cycle is ended 404 and the damper door can open and closed as necessary to transfer colder air from the freezer compartment to the fresh food compartment during normal operation of the appliance until the next defrost cycle is begun.
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

1. An apparatus for preventing warm air generated in a freezer compartment during a defrost cycle from flowing through an opening regulated by a damper door and into a fresh food compartment, comprising:

a damper motor adapted to drive the damper door;

a thermostatic switch operatively coupled to the damper motor, the thermostatic switch adapted to actuate the damper motor;

an electronic barrier interposed between the thermostatic switch and a power supply; and

a controller operatively coupled to the electronic barrier, the controller adapted to open the electronic barrier during the defrost cycle thereby prohibiting the damper motor from operating.

2. The apparatus of claim 1, wherein the electronic barrier is a triac.

3. The apparatus of claim 1, wherein the thermostatic switch is disabled when the electronic barrier has been opened by the controller.

4. The apparatus of claim 1, further comprising an additional thermostatic switch interposed between the power supply and the controller, the controller initiating operation of one or more of a compressor motor; a condenser motor, and an evaporator fan upon activation of the additional thermostatic switch.

5. The apparatus of claim 4, wherein the controller is configured to prevent operation of the compressor motor, the condenser motor, and the evaporator fan during the defrost cycle.

6. The apparatus of claim 1, further comprising a defrost heater energized during the defrost cycle.

7. The apparatus of claim 1, wherein the apparatus further comprises one or more redundant switches interposed between the thermostatic switch and the damper motor, the redundant switches configured to prevent the damper door from remaining in an open position during a loss of power.

8. The apparatus of claim 1, wherein the apparatus further comprises a damper door switch, the damper door switch operatively coupled to the controller such that the controller is informed of a position of the damper door.

9. An apparatus for preventing warm air generated in a freezer compartment during a defrost cycle from flowing through an opening regulated by a damper door and into a fresh food compartment, the apparatus comprising:

a damper motor adapted to drive the damper door;

a thermostatic switch operatively coupled to the damper motor, the thermostatic switch adapted to actuate the damper motor to open the damper door;

a switch interposed between the damper motor and a power supply; and

a controller operatively coupled to the switch, the controller programmed to open the switch during the defrost cycle thereby disabling the damper motor to prevent the damper door from opening during the defrost cycle.

10. The apparatus of claim 9, wherein the switch is a triac.

11. The apparatus of claim 9, wherein the thermostatic switch is disabled when the switch has been opened by the controller.

12. The apparatus of claim 9, further comprising an additional thermostatic switch operatively coupled to the controller, the controller configured to initiate operation of a compressor motor; a condenser motor, and an evaporator fan upon actuation of the additional thermostatic switch.

13. The apparatus of claim 12, wherein the controller is configured to prevent operation of the compressor motor, the condenser motor, and the evaporator fan during the defrost cycle.

14. The apparatus of claim 9, further comprising a defrost heater positioned in the freezer compartment.

15. The apparatus of claim 9, further comprising one or more redundant switches interposed between the thermostatic switch and the damper motor, the redundant switches preventing the damper door from remaining in an open position during a loss of power.

16. The apparatus of claim 9, wherein the apparatus further comprises a damper door switch, the damper door switch operatively coupled to the controller such that the controller is informed of a position of the damper door.

17. A method of preventing warm air from flowing through an opening in a freezer compartment into a fresh food compartment during a defrost cycle, comprising the steps of:

disabling operation of a damper door;

performing the defrost cycle; and

enabling operation of the damper door after completion of the step of performing the defrost cycle.

18. The method of claim 17, further comprising the step of sensing a state of the damper door, and wherein the steps of disabling and performing are performed when the step of sensing the state of the damper door indicates that the damper door is closed.

19. The method of claim 17, wherein the step of disabling the operation of the damper door comprises the step of preventing a flow of current to a damper motor.

20. The method of claim 17, wherein the step of disabling the operation of the damper door comprises the step of preventing a flow of current through a thermostatic switch.