184 BULLETIN 173, U. S. NATIONAL MUSEUM 



expansion or cooling chamber. This ball in the original installation 

 turned in a tank of brine, which was chilled thereby and circulated 

 where needed. 



These machines were charged with the necessary refrigerant (SO2) 

 and lubricating oil at the factory and usually required little attention 

 during years of service. This machine operated for 22 years with 

 the same oil and refrigerant and only one adjustment in that period. 



FROST-MAKER REFRIGERATING UNIT, c. 1914 

 Plate 37, Figuke 2 



U.S.N.M. no. 311358; original; gift of W. W. Stuart, photograph uo. 33065A. 



This is a small, direct-drive, water-cooled, gear-pump type of do- 

 mestic refrigerating unit. It used SO2 as a refrigerant and had a 

 rated capacity equivalent to the heat absorbed by the melting of 300 

 pounds of ice per day (I. M. E.). It is of the type of machine 

 variously marketed as the Frost-maker, Isko, and Jack Frost during 

 the early period of domestic refrigerating machines. 



In the machine a condenser chamber enclosing the condenser coil 

 and a reservoir for liquid sulphur dioxide is supported upon a cylin- 

 der containing the compressor and oil-cooling coil. These are bolted 

 to a base with an electric motor directly connected to the compressor 

 shaft. The compressor is a herringbone gear pump. The compressed 

 gas entered the top of the condenser chamber and passed over the 

 nest of coils through which the cooling water circulated. The cooled 

 liquid sulphur dioxide collected at the bottom of the chamber from 

 %vhich it discharged to the refrigerator. 



The name plate reads : "Frost-Maker, Patented July 22, 1913, Feb. 

 10, 1914. Frost-maker Ice Machine Co., 140 S. Dearborn St. Chi- 

 cago, 111. Capacity 300#, hp. I/2, serial no. 156." 



DOMESTIC ELECTRIC REFRIGERATING UNIT, c. 1918 



U.S.N.M. no. 310729; original; gift of Winslow-Baker-Meyering Corporation; 

 not illustrated. 



The essential elements of the automatic electric reciprocating com- 

 pressor 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 fly- 

 wheel-pulley. The cooling coils are contained in a zinc brine chamber 

 provided with openings to take ice freezing trays of muffin-pan de- 

 sign. The operation of the motor is controlled by a thermostat switch 



