CATALOG OF THE MECHANICAL COLLECTIONS I77 



The model represents a high-pressure hot-air engine employing 

 two vertical transfer (called generating) cylinders and a horizontal 

 work cylinder. The upper walls of the transfer cylinders are heated 

 by hot water from a separate tubular boiler, while the lower walls 

 are cooled by cold water from a separate tubular refrigerator. In 

 operation the transfer cylinders move the air alternately from the hot 

 to the cold walls, causing it to expand and contract. Each transfer 

 cylinder is connected to one end of the work cylinder. They are 

 timed somewhat as the valves of a steam engine so that the work 

 piston moves alternately from end to end of the work cylinder as 

 the air in each transfer cylinder expands and contracts. The work 

 piston is connected to the crankshaft of the engine as in a steam 

 engine. The transfer pistons are raised and lowered by plunger 

 rods, which are racks meshing with tooth segments that are rocked 

 by levers worked by cams on the crankshaft. 



The novel features of the engine are claimed to be the use of 

 glass, which is relatively nonconducting, in rods and tubes as tha 

 heat-storing or regenerative surfaces (see the Ericsson engine of 

 1855, next below) ; the use of large passages between the working 

 and transfer cylinders; and use of water and oil to seal the working 

 surfaces. Comparison with the engines of Stirling and Ericsson 

 and suggestions for the use of liquid carbonic acid instead of air 

 are made in the patent. 



ERICSSON HOT-AIR ENGINE, 1855 



Plate 35, Figuee 1 



U.S.N.M. no. 251279 ; original patent model ; transferred from the United States 

 Patent Office; photograph no. 30369. 



This model was filed with the application for Patent no. 13348, 

 issued to Jolm Ericsson, July 31, 1855. 



This model shows a 2-cylinder, horizontal engine, in each cylinder 

 of which are two pistons so connected that cold air is drawn into the 

 cylinder, compressed, transferred to the heater, returned to the same 

 cylinder, and then expanded. It includes the regenerator that 

 Ericsson developed in 1833 to utilize the heat in the exhausted air 

 to heat the new supply of air. From this design were developed most 

 of the commercial hot-air engines used in this country. 



The operation within each cylinder is the same though the pistons 

 move always in opposite directions. "When the pistons in a cylinder 

 are at the end nearest the crank the two are close together, but wlien 

 they start away from the crank the inner or transfer piston moves 

 faster than the other (the work piston) and draws air into the cylin- 

 der between the two. When they approach the other end of the 

 stroke they close up again and the air is compressed between them. 



