Refrigerator defrost control with control of time interval between defrost cycles

• US 4,297,852 A
• Filed: 07/17/1980
• Issued: 11/03/1981
• Est. Priority Date: 07/17/1980
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Brooks, Robert B.
• Primary Examiner(s): Wayner, William E.
• Assistant Examiner(s): Tanner, Harry
• Application Number:
  US06/169,570
• Time in Patent Office: 474 Days
• Field of Search: 62/153, 62/154, 62/155, 62/156, 62/157, 62/158, 62/234
• US Class Current: 62/153
• CPC Class Codes: F25B 2600/23 Time delays
• CPC Class Codes: F25D 21/006 with electronic control circuits
• CPC Class Codes: F25D 2700/02 Sensors detecting door opening
• CPC Class Codes: F25D 2700/12 Sensors measuring the inside temperature
• CPC Class Codes: F25D 2700/122 of freezer compartments

Abstract

Door open time in an automatic defrost refrigerator is accumulated in the memory of a microcomputer. Normal cycling of defrost is delayed by inactivating the defrost timer during periods of light usage of the refrigerator until a minimum predetermined accumulated door open time is reached. Provision is made for sensing interior refrigerator temperature to override the delaying effect of the door open measurement when a sensed over-temperature condition indicates an abnormal build-up of frost on the evaporator coils even though the refrigerator is experiencing relatively light usage. A maximum compressor run time interval between defrost cycles is provided for when no door openings occur, as during vacation periods.

Claims

1. In a self-defrosting refrigerator having at least one food storage compartment with an access door thereto and a refrigerant system including a motor-operated compressor, an evaporator for cooling the food storage compartments, thermostatic means for turning the compressor on and off to maintain a desired temperature in the food compartments, and defrost heater means for periodically removing frost build-up from the evaporator, the combination comprising:

timer operated switch means responsive to the thermostatic means (a) during the compressor-on periods to establish a minimum compressor run time between defrost cycles and (b) during the defrost cycle to activate the defrost heater means for a predetermined maximum defrost period;

means for accumulating total compressor run time during the entire elapsed time between defrost cycles;

a door open sensor;

means responsive to the door open sensor for accumulating the amount of time the door is open at least up to a predetermined amount of door-open time;

decision means for providing a first control effect representative of when the accumulation of compressor run time reaches the minimum run time of the timer means and a second control effect representative of when the predetermined amount of accumulated door-open time is reached;

and timer control switch means coupled in electrical circuit with the timer means and effective in response to the decision means to interrupt operation of the timer means in response to the sole presence of the first control effect, and to initiate or continue operation of the timer means in response to the simultaneous presence of both the first and second control effects;

whereby elapsed time between defrost cycles is extended beyond a minimum compressor run time during relatively light usage of the refrigerator wherein usage is measured by door open time.

2. The combination of claim 1 including means for sensing interior compartment temperature, the decision means being operative in response to a higher than normal compartment temperature after reaching the minimum compressor run time to provide a third control effect operative to initiate or continue operation of the timer means even in the absence of the second control effect representative of having reached the minimum predetermined accumulated door open time.

3. The combination of claim 1 in which the minimum predetermined accumulated door open time is approximately 400 seconds.