Microprocessor controlled defrost termination

Abstract

An apparatus and method are disclosed for terminating a refrigeration unit's defrost function. The refrigeration unit comprises an evaporator, a temperature sensor to measure the temperature of the evaporator during a defrost function, and a controller configured to calculate the rate of temperature change and terminate the defrost function when the rate meets a specified criteria, such as a predetermined rate or a sharp increase in the rate after the evaporator temperature has increased above the freezing point of water.

What is claimed is: 
     
         1 . A refrigeration unit comprising:
 an evaporator;   defrost means for defrosting said evaporator;   at least one temperature sensor in measurable connection with said evaporator; and   at least one controller communicatively connected to said at least one temperature sensor, wherein said at least one controller is configured to calculate a rate of temperature rise and to terminate operation of said defrost means when said rate exhibits a predetermined criteria.   
     
     
         2 . The refrigeration unit of  claim 1 , wherein said predetermined criteria is a predetermined rate. 
     
     
         3 . The refrigeration unit of  claim 1 , wherein said predetermined criteria is a significant increase. 
     
     
         4 . The refrigeration unit of  claim 1 , wherein said at least one controller is further configured to determine a point in time at which said temperature has risen to a freezing point of water. 
     
     
         5 . The refrigeration unit of  claim 4 , wherein said predetermined criteria is a predetermined rate after said point in time. 
     
     
         6 . The refrigeration unit of  claim 4 , wherein said predetermined criteria is a significant increase after said point in time. 
     
     
         7 . The refrigeration unit of  claim 4 , wherein said predetermined criteria is a lack of significant increase after a specified length of time starting at said point in time. 
     
     
         8 . The refrigeration unit of  claim 1 , wherein said predetermined criteria is a significant increase after a significant decrease. 
     
     
         9 . A method for terminating a refrigerator defrost function, the method comprising:
 initiating a function to defrost an evaporator in a refrigeration unit;   measuring the temperature of said evaporator during said function to defrost said evaporator;   calculating a rate of temperature change of said evaporator, said calculation based on said measured temperature; and   terminating said function to defrost when said rate of temperature change exhibits a specified criteria.   
     
     
         10 . The method of  claim 9 , further comprising the step of determining a first point in time at which said temperature of said evaporator reaches approximately the freezing temperature of water. 
     
     
         11 . The method of  claim 10 , wherein said point in time is determined by a significant decline in said rate of temperature change 
     
     
         12 . The method of  claim 9 , wherein said specified criteria is a predetermined value. 
     
     
         13 . The method of  claim 9 , wherein said specified criteria is a significant increase. 
     
     
         14 . The method of  claim 10 , wherein said specified criteria is a lack of significant increase after a specified duration of time starting at said point in time. 
     
     
         15 . The method of  claim 9 , wherein said step of measuring occurs at continuous intervals over a length of time. 
     
     
         16 . The method of  claim 9 , wherein said step of calculating occurs at continuous intervals over a length of time. 
     
     
         17 . A method for terminating a refrigerator defrost function, the method comprising:
 operating a defrost function in a refrigeration unit;   measuring the rate of temperature increase of an evaporator during said defrost function; and   terminating said defrost function based on said rate of temperature change.   
     
     
         18 . The method of  claim 17 , the terminating step occurring when a significant increase is detected in said rate of temperature change. 
     
     
         19 . The method of  claim 17 , said terminating step occurring when a said rate of temperature change exceeds a predetermined rate value.