GB958779A - Improvements in gear type hydraulic pumps and motors - Google Patents

Abstract

958,779. Rotary pumps and motors. R. W. BRUNDAGE. May 19, 1960, No. 17721/60. Heading F1F. In a hydraulic pump or motor of the internally-toothed gear meshing with an externallytoothed gear type, the bearing 17 supporting the internally toothed gear 12 is mounted with a limited freedom of radial movement in the housing H such that the resultant force due to the hydraulic pressures within the working chambers of the pump or motor acts about a point of contact between the bearing and the housing so as to maintain the working chambers hydraulically sealed. The bearing 17 has an inner cylindrical surface mounting the gear 12 and an eccentric outer surface provided with a bead 66, there being a clearance c between the bead 66 of the housing H. The gear members 11, 12 engage a manifold member 14 provided with an inlet port 43 and an outlet cut out 46. The neutral axis A, B through the centres of the inner and outer surfaces of the bearing 17 is angularly off-set from the land mid-line of the manifold member 14 so that trapping occurs in the pumping chambers. Chambers in which liquid is trapped are in communication with ports 70 which are interconnected by a restricted passage 71. The eccentricity of the bearing member 17, the clearance c and the spacing of the axis of rotation of the internally and externally toothed gears 11, 12 are so chosen that the eccentric bearing member engages the housing at a point 102 a distance d from the resultant m of the hydraulic forces so that a moment is applied to the bearing member 17 and thus the gear 12, tending to rotate these members so as to bias the open mesh gear teeth into engagement. As the speed of the pump increases the effect of the trapped hydraulic fluid increases due to the restricted passage 71 and modifies the resultant of the hydraulic forces such that the closing force on the open mesh gear teeth no longer exists. The end sealing member 13 is an interference fit or is welded to the drive shaft 16 and is mounted in a bearing 54; it is biased axially by means of a sealing member 75 the internal surfaces of which are subjected to low pressure through a passage 19 and the external shoulder 87 to high pressure existing in the housing H. Specification 958,780 is referred to.