GB702596A - Improvements in hydraulic pumps and motors and hydraulic power transmission devices - Google Patents

Abstract

702,596. Hydraulic pumps. BORG-WARNER CORPORATION. July 5, 1950 [July 15, 1949], No. 16778/50. Class 102 (1). [Also in Group XXIX] In a hydraulic pump or motor of the type comprising a cylinder block having an annular series of cylinders and ports therein co-operating with a ported valve member, the flow of pressure liquid to and from the cylinders' being controlled by relative rotation between the valve member and the cylinder block and the consequential relative movement between the co-operating ports in these parts, the ports in the valve member are arcuate in outline and each comprises an intermediate portion of substantially uniform width merging immediately at its opposite ends into uniformly tapered end portions of substantial arcuate length, these end portions and the intermediate portion of each port being so dimensioned that the volumetric rate of flow through the ports is at all times approximately proportional to the velocity of the piston reciprocable in the associated cylinder. The Figures show a revolving cylinder swash plate type motor forming part of an hydraulic transmission. The supply of liquid to and from cylinders 20 is controlled by rotation of the cylinder block 21, cylinder ports 22 co-operating with inlet and outlet ports 50, 51 in a stationary valve plate 43. The ends of each port 50, 51 comprise tapered extensions 50a, 51a as shown which ensure that pressure is applied gradually and released gradually and that there is no undue increase of pressure in each cylinder as the piston approaches the end of the. working stroke. It is stated that the amount of taper of the extensions can be calculated to some extent but the final design must be worked out by experiment. In order to enable the inclination of the swash plate to be adjusted even though a port 22 is in a position in which it registers with the part of the manifold plate between the inlet and outlet ports, each cylinder contains a bore 66 which registers in this position of the cylinder port with a slot 67 connected to the sump. The inclination is variable by turning a shaft 37. A constant velocity universal joint 31 is connected between the shaft 14 and the swash plate 32. The pressure in each cylinder acts on an area 22a which is greater than an area 22b and thus urges the cylinder block into contact with the manifold plate. Grooves 22c are connected to the sump by a groove 22d. A gear pump or other pressure generator supplies the motor, the outlet side of the pump being connected to a chamber 40 and the inlet side being connected to a chamber 41.