Abstract: An electronic control system for a variable displacement pump comprises apparatus for sensing the actual position of the displacement determinative element and the actual rotational speed of the pump cylinder block, and for producing representative signals which are combined to produce a signal indicative of actual output flow rate. The displacement determinative elements position and the cylinder rotational speed are sensed directly by sensors mounted within the housing of the pump. The speed sensor is disposed in close proximity to, and aligned with marks inscribed on, the outer surface of the rotatable cylinder block. The volumetric efficiency of the pump is also sensed by and used to determine the actual flow rate.

Abstract: A method and an apparatus are disclosed for reducing operating noise in axial piston pumps and motors. An elongated passage (88, 98) connects the outlet plenum (86) of the apparatus directly with each cylinder (30) during its discharge stroke, the passage being positioned between the point (68) at which the discharge stroke begins and the leading edge (78) of the discharge port (74) of the apparatus and the length and cross-section of the passage being sufficient to permit gradual attenuation of any pressure differential between each cylinder and the outlet plenum before the cylinder opens to the discharge port leading to the outlet plenum. See FIGS. 1 and 2.

Abstract: A hydraulic control system for regulating the distribution of fluid from a variable displacement pump to a plurality of fluid actuated devices is disclosed. The control system includes at least first and second control valves, each of which valves regulates the flow of fluid to a fluid actuated device. Each of the first and second control valves includes, respectively, a first means for developing a first pressure signal and a second means for developing a second pressure signal. A selector means senses the first and second pressure signals and transmits a control pressure signal which is the smaller of the two pressure signals to a fluid actuated displacement control means which regulates the displacement of the pump in response to the magnitude of the control pressure signal.

Abstract: An hydraulic control system is disclosed which comprises a fluid reservoir (14), a variable displacement pump (12) having a fluid input connected to the reservoir and a fluid output, and a fluid pressure actuated displacement of the pump. A control valve (18) is connected to the fluid output of the variable displacement pump and to the reservoir and is adapted to control the flow of fluid to a fluid actuated device. The control valve includes means (44, 50, 52, 54, 56) for regulating flow of a signal fluid provided either by a constant displacement pump (46) or a pressure actuated flow control valve (47).

Abstract: A hydraulic control system is provided including a fluid reservoir, a variable displacement pump having a fluid input in fluid communication with the reservoir and having a fluid output, and a fluid actuated displacement control mechanism for controlling the displacement of the pump. A control valve is placed in fluid communication with the fluid output of the variable displacement pump and with the reservoir and is adapted to control the flow of fluid to a fluid actuated device. The control valve includes means for developing a control pressure signal.