Ericsson Steam Engine, Patent Model

This model was filed with the application to the U.S. Patent Office for Patent Number 41,612 issued to John Ericsson of New York, New York on February 16, 1864. The patent was for an improvement in reciprocating steam engines that would reduce the destructive vibration effects of then current designs.

Many marine steam engines were mounted transversely in the vessel in order to facilitate operating crank arms to turn the propeller. With each successive cycle of the engine the oscillating masses of the engine’s pistons produced high concussive forces on the engine mounts and hull of the vessel. This was more serious for engines directly driving the ship’s propeller without gearing; the engine needed to run at higher speeds thereby making the vibrations more damaging.

Mr. Ericsson’s patent design provided a rolling counter balance weight that moved in the opposite direction as the motion of the of the engine’s piston. The weight would be matched to the combined weight of the piston and its pushrods and other oscillating masses. He provided for a crank lever mechanism that would translate the motion of the piston to that of the counter balance weight.

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. The Monitor engine was based on his Patent Number 20,782 of July 6, 1858 . In that patent he began to address design issues that would reduce stresses on the engine’s components and its bed. In this patent, Number 41,612, he addressed the issue of concussive force effect of that engine and showed how his counterbalancing weight concept could be applied.

The patent model is shown in the image. It is constructed of wood and brass and illustrates the major elements of the patent. A brass plate on the model is engraved “J. Ericsson, Inventor, 1863.” A spring motor causes the model to simulate actual operation with the piston moving and the counterbalancing weight moving within a hollow space in the wooden base of the model. Diagrams showing the complete design of the engine can be found in the patent document online (www.USPTO.gov).

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This page was imported from Smithsonian National Museum of American History. Released by the Smithsonian Institution under CC0 through Smithsonian Open Access.

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