Allen Cut-Off Valve Gear, Patent Model

This model was submitted to the U.S. Patent Office with the application for the patent issued to Horatio Allen, of New York, New York, August 29, 1848, no. 5745.
This is an adjustable drop cut-off valve gear in which a poppet valve is raised by a lift rod but is permitted to return to its seat sooner or more rapidly than the lift rod returns.
The model represents a poppet steam valve raised from its seat by an arm fixed at right angles to a lift rod, which works vertically and parallel to the valve stem. Upon the face of the arm is a moveable block a part of the upper surface of which is parallel to the face of the arm and a part of which is a steep curve. All the movement of the valve is transmitted to it through a roller on its stem, which rolls on the surface of this block. The block is so linked with a vibratory rod, which receives its motion from the cross head of the engine, that the block will move along the face of the lift rod arm and bring different points of its surface under the roller of the valve stem. By proper adjustment the roller will rest upon the flat part of the block and move with the lift rod as it is rising and the valve is opening, then the block moves so that the roller comes to the edge of the inclined portion and rolls down the incline permitting the valve to drop more quickly than the lift rod. The movement of the block on the arm and consequently the point of cut-off are fully adjustable.
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, steam engine, model
date made
patent date
Physical Description
wood (overall material)
on walnut board - from catalog card: 16 in x 16 in; 40.64 cm x 40.64 cm
overall: 16 in x 15 5/8 in x 2 1/2 in; 40.64 cm x 39.6875 cm x 6.35 cm
place made
United States: New York
ID Number
catalog number
accession number
patent number
Engineering, Building, and Architecture
Industry & Manufacturing
Bulletin 173
See more items in
Work and Industry: Mechanical and Civil Engineering
Bulletin 173
Data Source
National Museum of American History, Kenneth E. Behring Center
Related Publication
Frank A. Taylor. Catalog of the Mechanical Collections of the Division of Engineering United States National Museum, Bulletin 173

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