Patent GB-719359-A (GB)
Title: Improvements relating to pumps
IPC: F04C2/10
Filed: 1952-12-05
Abstract: 719,359. Rotary pumps. HOBOURN-EATON MANUFACTURING CO., Ltd. Dec. 5, 1952 [Dec. 14, 1951], No. 30899/52. Class 110(2) A rotary pump comprises a housing 10, having therein the pump chamber 18, intake and discharge means for the working fluid, a delivery passage 45, valve means 40 to by-pass the fluid from the discharge to the intake, a means defining a permanently open flow orifice 60 through which the delivery passage is connected to the discharge, the operation of the valve means being responsive to the fluid pressure differential across the orifice. In Figs. 1, 3 and 5 the pump is associated with a fluid reservoir 12 and an external closed loop circuit 13 comprising conduits 15 and 16 leading to and-from a power steering device 14 of a motor vehicle. The pump includes internally meshing toothed rotors 22, 23, of which the outer one 22 is supported for rotation by an annular wire 29 in the chamber 18, and the inner one is keyed to a driving shaft 21. The pump casing comprises a body 17a, and cover 17b formed with arcuate intake ports 19a, 19b and discharge ports 20a, 20b. As shown in Fig. 5, the liquid passes from the discharge ports to the valve chamber 41 in which the valve means is arranged, such means including a hollow valve 48 on which a spring 54 acts, and a valve member 49 which is slidable within the valve 48, is urged forwards by a spring 57, and provides the orifice 60. In normal running the valves remain in the position shown under the action of the springs and pressures of the fluids, the valve 48 being prevented from moving further to the left by a retaining ring 58. Should the speed of the pump increase. the resultant higher rate of flow will increase the difference of pressure across the orifice 60, and the valve assembly 40 as the result of the relatively lower pressure to its left will move to the right. Such movement brings the annular-edge 50a of the plunger portion 50 of the valve past the edge 42a of the valve seat 42, thus establishing communication between the discharge port 20b and intake port 19b. By this means the volume of fluid pumped to the external circuit is maintained substantially constant. The inner valve 49, which presents a smaller area upstream than downstream, will move to the right when pressure in the passage 45 and external circuit increases beyond a given value. This movement serves to uncover ports 52 in the valve member 48, and fluid is thus enabled to pass from the discharge to the intake port. In a modification, Fig. 7, (not shown) the orifice is provided in the member 48 adjacent the discharge port 20b. In other modifications the two valve devices are separate. Thus in Fig. 19 the pressure relief valve member 175 is moved upwards against the action of spring 170, when excessive pressures are produced, thereby establishing communication between delivery passage 153 and intake port 140. In this construction the volume control valve member 159 works in chamber 150 which soans the space between intake ports 140 and discharge ports 142. The orifice 154 connects the valve chamber as shown to the delivery passage 153, and the latter communicates with a space above member 159 bv means of a passage 157. In use the member 159 is normally maintained in the position shown by a spring 165, but at excessively high speeds the pressure differential across the orifice is such that the valve will be lifted to establish communication with the discharge end inlet ports. In this and the other modifications dashpots such as 161, 167 are used to prevent undesired oscillations of the valve members.