GB906553A - Improvements in hydraulic ball pumps and motors - Google Patents

Abstract

906,553. Reciprocating pumps. NATIONAL RESEARCH DEVELOPMENT CORPORATION. June 27, 1960 [June 27, 1959 (3)], No. 22147/59, 22148/59 and 22149/59. Class 102(1). [Also in Groups XXVI and XXIX]. In a revolving cylinder pump or motor, comprising ball pistons 3, Fig. 1, reciprocable in radially disposed cylinders in a rotary cylinder block 1 by means of a cam ring 4 having radial clearance between it and the block, each cylinder is fitted with a liner 30, Fig. 3, of hard low-friction material such as tungsten carbide to reduce wear between the ball pistons and the cylinders. The liner has an external diameter at its inner end 32, greater than at its outer end to form an intermediate shoulder 31. The enlarged diameter of the inner end 32 is such that on the liner being cooled in a refrigerator and the cylinder block being heated to a relatively high temperature the liner may be inserted in the cylinder bore 29. The axial lengths of the inner end 32 and the corresponding undercut in the cylinder bore are such that when the parts return to normal temperature the end 32 is securely locked in the undercut by axial compression of the end 32. A fixed pintle 14 having longitudinal ducts 15, 16, Fig. 2, connected to transverse upper and lower grooves, 17, 18 through suitably arranged ports 20, 23 distributes the hydraulic operating fluid to and from the cylinders in the usual manner through cylinder ports 19. The pintle 14 may be angularly adjusted with respect to the ports 19 to promote smooth running of the pump by means of an eccentric pin 24 carried on a stud 25 and working in a longitudinal groove 27 in the flanged end 28 of the pintle. The instant of cutoff of the ports 19 being delayed at the ends of the delivery (pump) or power (motor) strokes of their respective pistons so as to allow the pistons to commence their suction or exhaust strokes before the ports are opened to the oil at inlet or exhaust pressure, as the case may be. The pump or motor is shown with four rings of pistons and cylinders each with its own cam ring pivotedly mounted on a shaft 7 which carries four eccentric sheaves 8 snugly lying between horns 9. The eccentricities of the sheaves are alternately arranged at 180 degrees with respect to each other, the throws being equal so that when the shaft is rotated by means of a rack 11 and pinion 10, adjacent cams 4 are adjusted equally in opposite senses. The shaft 7 may be rotated manually or automatically so that the stroke of each ball is dependent upon the load demand of the machine being driven. The axis of each cylinder is set at a slight angle to the radius of the cylinder block to reduce the lateral forces between the balls and the cylinder bores. The track of each cam ring 4 is grooved at 34, Fig. 7, to reduce the Hertzian stresses set up in the ball by the fluid pressure during each pumping or power stroke to further reduce rate of wear.