This model was submitted to the U.S. Patent Office with the application for the patent issued to Thomas Richards, of Lansingburg, New York, May 22, 1866, no. 54959.
This model represents a slightly conical plug valve fitted within a conical valve housing, which is provided with eight equally spaced steam ports so arranged that diametrically opposite ports are connected together in pairs. The result is that the pressure on the valve due to the steam or exhaust pressure in each pair of ports is perfectly balanced.
Three adjoining ports in the valve housing are continued through the housing, which is provided at that point with a flat surface that permits the valve to be placed against the ordinary valve seat of a D-slide valve engine, the three ports registering with the steam passages to the ends of the cylinder and with the exhaust passage at the center of the seat. The valve is constructed with four equally spaced longitudinal recesses with four alternate bands. The valve is operated by rocking it a part of a turn in each direction from the center.
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.
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