GB1246307A - Improvements in or relating to rotary positive displacement pumps - Google Patents

Abstract

1,246,307. Rotary pumps. BRONZAVIA. Nov.22, 1968 [Nov.28, 1967], No.55483/68. Heading F1F. A rotary positive displacement pump comprising a housing having at least one rotary element therein and two side-wall members within the housing, one on either side of the rotary element, with at least one movable axially with respect to the housing and the rotary element, wherein the movable side-wall member is subjected at least on part of its face adjacent the rotary element to a pressure close to delivery pressure and wherein means are provided to apply to at least part of the other face of the movable side-wall a regulated back-pressure whose magnitude determines the lateral clearance between the rotary element and the side-wall members. As described, the invention is applied to a gear pump having a pair of inter-meshing gears 30, Figs.1, 2 rotatably mounted in a two-port housing 1a, 1b with each disposed between a fixed side-wall member 24 and an axially-movable side-wall member 6 mounted in stepped bores 5, 4 in the housing parts. Each side-wall member 6 is stepped and with the bore 4 and a fixedly located ring member 7 defines annular chambers C 1 , C 2 , C 3 , communicating with the pumping chamber midway between the inlet 2 and outlet 3. The chamber C 1 through a passage 19, the chamber C 2 through a passage 16 and an arcuate recess 14 and the chamber C 3 through a passage 17 and the arcuate recess 14. The chamber C 2 also communicates with the passage 17 through a restricted passage 18 and the chamber C 3 with a chamber 12 connected to the pump inlet by a jet passage 11 the size of which determines the pressure in the chambers C 2 , C 3 and hence the clearance between the side-wall member 6 and the side face of the gear 30 which is sufficient to preclude excessive leakage without excessive friction. Arcuate recesses 13, 15 on either side of the recess 14 enables a pressure of constant magnitude to be maintained. The recesses 13, 14, 15 are matched by corresponding recesses 25, 26, 27 in the sidewall member 24 and inter-connected by balancing passages 31, 32 through the gears and spaces between the gear teeth. The passages 32 are connected by radial passages 33 to the roots of the gear teeth. In a modification, the jet passage 11 is replaced by a perforated spring-loaded washer located at that end of the chamber C 3 remote from the gear 30 which co-operates with an adjustable screw-threaded plug having a central bore through which leakage occurs to again determine the pressure in the chambers C 2 , C 3 .