This model was submitted to the U.S. Patent Office with the application for the patent issued to Junius Judson and William A. Cogswell, of Rochester, New York, November 9, 1875, no. 169815.
The model represents a flyball governor in which the driving pulley is fitted loosely to the driving shaft and connected to it by a spiral spring, which allows a free turning of the pulley on the shaft to an extent sufficient to counteract the jerks or impulses, which are transmitted to the governor by the uneven operation of the engine.
The inventor states that the ordinary crank motion of a steam engine results in an unequal operation that is not always equalized by the flywheel of the engine. This irregularity, though not always perceptible, is transmitted to the governor, which, when operated unevenly, would exaggerate the variations. This device is designed to prevent the jerks being transmitted to the governor.
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.