Abstract: A proportional force amplifier having a cylinder separated by a piston assembly into a pressure chamber, a control chamber and a reservoir chamber, a spool valve mounted for axial movement within a bore in said piston assembly to selectively connect the control chamber to either the pressure chamber or the reservoir chamber, the piston assembly moving in response to the change in pressure between the pressure chamber and the control chamber a distance equal to the distance of movement of the spool valve, the spool valve being connected for actuation by a resilient compensating rod and being pressure balanced.

Abstract: A servo mechanism for a prime mover interconnected to a hydrostatic transmission includes a source of pressurized fluid, a fluid reservoir, an actuator having a piston operatively connected to the hydrostatic transmission and being provided with large and small hydraulic receiving areas which are exposed to first and second hydraulic chambers, respectively within the actuator housing, a first passage for connecting the pressurized fluid source to the second chamber, a second passage for connecting the pressurized fluid source to the first chamber, a third passage for connecting the first chamber to the reservoir, and a pair of spool valve means disposed, respectively, within the second and third passages and responsive to a signal indicative of the power required of the prime mover and an actual speed or feedback signal of the prime mover.

Abstract: A throttle actuator for accelerating and decelerating the speed of an internal combustion engine in response to work demand where the engine drives the pump of a hydraulic system. In one aspect, the invention is directed to a throttle actuating piston and rod arrangement for operating the throttle of the engine and a pulsation intensifier for sensitively controlling the piston's movement. The pulsation intensifier is connected in a pressure line from the pump and comprises a free spring biased floating piston of configuration such that there is a differential in area across the piston for fluid pressure intensification purposes. The intensifier piston in one embodiment also has an axial passage therethrough and an orifice communicating with the throttle actuating piston. Both pistons are slidably mounted in housings which have springs to normally position the pistons in directions to cause the engine to return to idle speed when there is no work demand.