The essential elements of the automatic electric reciprocating compressor type of refrigerating unit for cooling household refrigerators are combined in this old machine. It consists of a small, motor-driven, 1-cylinder, air-cooled compressor, mounted inside of the coils of a so-called “cage” condenser, which is a continuous, rectangular coil of copper tubing. Compressor cylinder and condenser are cooled by a stream of air from the fanlike spokes of the compressor flywheel-pulley. The cooling coils are contained in a zinc brine chamber provided with openings to take ice freezing trays of muffin-pan design. The operation of the motor is controlled by a thermostat switch designed to hold the temperature of the brine at an approximately even temperature.
In operation a refrigerant gas, SO2, is compressed in the cylinder of the compressor and delivered to the condenser, where it is cooled to approximately the temperature of the air that is blown over the condenser. The compressed and cooled SO2 then passes through a reducing valve, which permits it to expand to a low pressure in the cooling coils in the brine tank. As it is a physical property of gas that in expanding it absorbs heat, the expanding SO2 takes heat from the surrounding brine and thus lowers the temperature of the chamber. The SO2 then returns to the compressor where it is again compressed and the process continues. When the brine is cold enough the thermostat switch turns off the motor until the temperature rises a few degrees when it starts the motor again.
The unit is said to be the one that Edmund J. Copeland, then chief engineer of the Kelvinator Corporation, believed to be the first one of his designs to approach successful, automatic, dependable operation. It contains parts taken from earlier machines and now includes parts of later dates.
This description comes from the 1939 Catalog of the Mechanical Collections of the Division of Engineering United States Museum Bulletin 173 by Frank A. Taylor.
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