Sickels Drop Cut-Off Valve Gear, Patent Model

Sickels Drop Cut-Off Valve Gear, Patent Model

This model was part of the application to the U.S. Patent Office for the patent issued to Frederick E. Sickels, of New York, New York, May 20, 1842, no. 2631.
The Sickels valve gear is generally considered to be the first successful and practical drop cut-off. It was widely used on the engines of the side-wheel steamboats up to the beginning of the 20th century and was the forerunner of the many subsequent designs of drop cut-off valve gears. This valve gear provides a means of rapidly cutting off the admission of steam to the cylinder of the engine at any point in the stroke of the piston. It accomplishes this by tripping or disengaging the valve from the valve gear and permitting it to drop to its seat under the impulse of a spring. A plunger operating in a water chamber gradually retards the falling valve and brings it to rest without shock.
The Sickels valve is of the conical or poppet type, working vertically with the valve stem directed upward. Motion is transmitted to the valve through a lift rod working up and down continuously parallel to the valve stem. Spring clips on the lift rod engage with the projections on the valve stem and lift and open the valve, until the clips come into contact with wedge-shaped blocks, which spread the clips and permit the valve to fall back to its closed position. The wedge-shaped disengaging block can be placed so as to cause the valve to disengage and close at any desired instant during the up or down movement of the lift rod. A spring bearing upon the top of the valve stem causes it to close rapidly, while a plunger or piston attached to the underside of the valve and working in a chamber of water retards the valve gradually and permits it to close without shock. The lift rod may be actuated by an eccentric or, as was more usually the case, by cam and follower of the “alligator” jaw or steamboat type of gear.
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
Object Name
valve gear, steam engine
valve gear, balanced, steam engine, model
Object Type
Patent Model
date made
patent date
place made
United States: Missouri
Physical Description
brass (overall material)
wood (overall material)
overall: 14 1/4 in x 5 1/2 in x 7 in; 36.195 cm x 13.97 cm x 17.78 cm
ID Number
catalog number
accession number
patent number
See more items in
Work and Industry: Mechanical and Civil Engineering
Industry & Manufacturing
Bulletin 173
Engineering, Building, and Architecture
Data Source
National Museum of American History
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