Wylain, Inc.

Friedrich Air Conditioning & Refrigeration Co.

Friedrich Refrigerators Inc.

Roger C Ansted

Gerald L Rodgers

Roger W Dougan

A method and apparatus for initiating the defrost of refrigeration equipment on demand. A defrost clock which normally controls the conventional refrigeration and defrost modes of a refrigeration system includes an auxiliary switch to cease operation of the clock motor a predetermined time prior to normal defrost initiation. The defrost clock thus remains in the refrigeration mode until the demand defrost sensor switch, or an optional demand switch, initiates a defrost cycle of the refrigeration equipment. The closure of the demand defrost switch or the optional switches causes the defrost clock motor to run for a predetermined short period of time. The defrost clock switch subsequently closes slightly prior to initiation of a defrost to guarantee that the clock runs throughout the defrost mode. Thereafter, the defrost clock controls the length of the defrost and will terminate defrost upon a signal from a thermostat, or by a time signal, or a pressure signal. The auxiliary switch remains closed after termination to allow the defrost clock to repeat the previous sequence of operation.

Demand defrost time clock control circuit

Foam plastic is injected into a hollow space between the inner and outer skin of a refrigeration unit. Contained in the foam plastic are metal plates positioned at points where walls, dividers or shelves may be attached to the refrigeration unit. The foam plastic hardens around the metal plates. Self taping screws drill through the skin, foam plastic and plate to rigidly attach structure being supported to the plate with a minimum amount of heat transfer through the foam plastic and metal plates.

Foam plastics display unit

The electrical control panel for a refrigeration unit using single or three phase power. The control portion has an oil pressure safety switch, defrost timer, temperature controls and perhaps a refrigerant pressure control in conjunction with the normal internal overload circuit breakers for the compressor. After operation of the refrigeration unit for a period of time, a defrost control device cuts off the compressor and turns on the electric defrost heaters. As the evaporator coils are defrosted, defrost thermostats open the defrost heater supply circuits. When the current sensing relay senses that all the defrost heaters have been shut off via the defrost thermostats, a time delay relay will return the refrigeration unit to the normal refrigeration cycle. The same current sensing relay will prevent false triggering by the oil pressure safety switch if the compressor's internal overload circuit breaker opens.

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San Antonio, TX, United States of America

Roger C Ansted