Earle S Pittman
Electrician at Claremont Dr, Boulder, CO

4187093, Feb 5, 1980

Feb 1, 1978

5/874258

James P. Boratgis - Boulder CO
Earle S. Pittman - Boulder CO

F25B 4900

62126

Electronic control apparatus is disclosed for automatically controlling the operation of refrigeration units on truck-drawn trailers and providing a signal to the truck driver in the event there is a malfunction in the refrigeration unit that could result in damage to the cargo. An electronic automatic temperature control circuit includes solid state comparators which are responsive to a temperature sensor and to a temperature selector. The comparators provide output signals that selectively actuate solid state control elements which in turn control the actuation of the various load devices in the refrigeration unit to maintain the temperature in the refrigerated chamber within a selected temperature range. When the temperature in the refrigerated chamber is above a selected temperature setting to the extent that damage to the cargo might be caused, a solid state malfunction circuit controls the actuation of a solid state relay and in turn a malfunction indicator. A solid state defrost cycle control circuit is responsive to a defrost cycle sensor indicating defrosting is taking place, which overrides the actuation of the malfunction circuit for a few minutes during each multiple-hour time interval and, if the defrost cycle sensor fails, the defrost cycle control circuit is arranged to insure that the defrosting operation is still carried out.

4313308, Feb 2, 1982

Sep 8, 1980

6/184965

James P. Boratgis - Boulder CO
Earle S. Pittman - Boulder CO

F25B 4900, F25B 2900

62126

Electronic control apparatus is disclosed for automatically controlling the operation of refrigeration units on truck-drawn trailers which includes an undercool comparator (240) connected to a resistor (239) in a voltage divider including a temperature selector (13) and having its output in parallel with an overcool comparator (44), either of which will actuate a malfunction indicator (15) in the event of undercooling or overheating conditions during a chilled food setting for the temperature selector (13). An overcool comparator (91) that is turned on when the selector (13) is moved to a frozen food mode operates a control element in the form of a transistor (99) that serves to disable the output of overcool comparator (240) and prevent the actuation of the heat load device (23) by effecting grounding connections in the circuit.