Abstract: An internal combustion engine overspeed protection system utilizes a spring-actuated expandable overspeed link in the fuel control linkage to shut off fuel independently of governor or throttle action. The link is normally latched in a contracted condition and positioned in the fuel linkage between a manual fuel lever and the fuel cranks for the respective cylinders of the engine. An automatically resetable hydraulic actuating device unlatches the link in high speed response to an engine overspeed condition. A spring coupling in the fuel linkage permits relatching of the overspeed link by manipulation of the fuel lever.

Abstract: A movable member, including a first piston in a hydraulic cylinder, is biased toward a first position by a reset spring and toward a second position by a trip spring which is compressed between the first piston and a second piston in the same cylinder. The second piston is disposed for limited floating movement relative to said movable member. Hydraulic fluid under pressure is admitted into a first chamber between the first piston and the adjacent end of the cylinder, and a constricted fluid passage in the movable member enables the hydraulic fluid to flow between the first chamber and a second chamber defined by the second, floating piston and the other end of the cylinder. With equal, relatively high fluid pressure in both chambers, the trip spring is charged and the movable member is held by the reset spring in its first position.