Ericsson Hot-Air Engine, Patent Model

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This model was submitted to the U.S. Patent Office with the application for the patent issued to John Ericsson, October 9, 1860, no. 30306.
This engine employs two “equilibrium" pistons in connection with two cylinders and a work piston to prevent diminution of the working pressure during the stroke of the work piston.
The engine consists of two “equilibrium” cylinders placed in line end to end and a short distance apart. Within each cylinder is a hollow equilibrium piston, both connected by a long piston of relatively small diameter, called the working piston, which passes through airtight stuffing boxes in the heads of the equilibrium cylinders. The cylinders are connected to a heater and to a water-cooled chamber, through suitable valves and passages, so that both ends of one equilibrium cylinder are simultaneously in communication with the cooler. The pressure being higher in the heater than in the cooler, the effect is to force the working piston out of the cylinder in communication with the heater into the other. The equilibrium pistons move with the work piston and circulate the air in the cylinders to the heater or cooler and back to the respective cylinders, maintaining a constant pressure in each cylinder throughout the stroke. When the piston has completed its stroke the valves are reversed and a continuous motion is produced. This engine includes the regenerator or “heat deposit vessel,” which was a feature of most of Ericsson’s engines. In this construction it is a vessel filled with disks of wire cloth, which are heated by the hot air passing from the cylinders to the cooler and, in turn, give up this heat to the air passing from the cooler to the heater.
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.
Currently not on view
date made
patent date
Ericsson, John
place made
United States: New York
associated place
United States: New York, New York
overall: 7 3/4 in x 10 3/4 in x 6 in; 19.685 cm x 27.305 cm x 15.24 cm
ID Number
accession number
catalog number
patent number
Patent Models
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Work and Industry: Mechanical and Civil Engineering
Industry & Manufacturing
Bulletin 173
Patent Models
Engineering, Building, and Architecture
Data Source
National Museum of American History


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