This model was filed with the application to the U.S. Patent Office for Patent Number 226,052 issued to John Ericsson of New York, New York on March 30, 1880. The patent was for an improvement in air engines.
In this type of engine a charge of air is repeatedly heated and cooled as it is transferred from one end to the other of a single cylinder. One end of the cylinder is surrounded by a furnace, the other end of is water jacketed. The air expands and contracts beneath a work piston that travels through a short stroke near the upper end of the cylinder. The air is displaced from end to end of the cylinder at the proper time by a large loosely fitting transfer piston independently connected to the crankshaft.
Mr. Ericsson claimed his design improved the method of connecting the short stroke of the work piston so as to magnify the length of its stroke at the crankshaft. This also produced a longer stroke for the exchange piston in order to properly time its movement. He also made provisions for a water pump that was operated by the engine. It circulated water into the jacket surrounding the engine’s cylinder in order to more rapidly cool the hot air in the upper part of the cylinder.
Mr. Ericsson was a prolific inventor; his inventions included many types of steam engines and associated apparatus as well as hot air engines. He was the designer of the USS Monitor for the North during the Civil War, and that vessel included one of his then new marine steam engine designs.
The patent model is shown in the image. It is made of brass, steel and wood. All of the key elements of the patent are illustrated by the model including the crank mechanism and the water pump. The upper cylinder is cut away to illustrate the motion of the two pistons. Diagrams showing the complete design can be found in the patent document online (www.USPTO.gov).
National Museum of American History