Patent GB-1437413-A (GB)
Title: Pump power governor
IPC: F04B49/00
Filed: 1973-08-06
Abstract: 1437413 Fluid-pressure servomotor systems POCLAIN 6 Aug 1973 [4 Aug 1972 19 April 1973] 37262/73 Heading G3P The power output of a variable displacement pump is controlled by a system comprising first and second members movable along rectilinear guides in response respectively to delivery flow and pressure, the members being linked by a variable length connecting rod joined also to a valve controlling flow of fluid from an auxiliary pump to a double-acting ram of the displacement varying mechanism. In one arrangement, Fig. 1, the output pipe 9 of variable displacement pump 7 is connected to duct 9a within a fixed piston rod 12 which forms a guide for movable cylinder 10. Duct 9a constitutes a restriction, the upstream and downstream ends of which are connected via passages 15, 16 respectively to the chambers 13, 14 on opposite sides of piston 11. The position of cylinder 10 depends on the pressure drop through duct 9a and is thus a function of the pump delivery flow. Output pipe 9 is also connected via passage 25 in a fixed piston-rod 23 to chamber 24 on one side of piston 22. The latter guides a movable cylinder 21 which is thus positioned in dependence upon delivery pressure in pipe 9. Cylinders 10, 21 are connected by the slidable engagement of pins 32, 27 within respective slots 31, 28 in rod 29. Point 34 on the latter is pivotally connected to rod 35 of a valve 36 controlling flow from an auxiliary pump 37 to drain 43 or to one or other side of a double-acting ram 40 connected to the displacement varying mechanism 8 of pump 7. In the equilibrium condition, point 34 is disposed at the intersection of lines normal to guide rods 12, 23 and passing respectively through the theoretical zero flow positions 32', 27' of pins 32, 27. Any departure of the sensed flow or pressure from the desired values causes movement of cylinders 10 or 21 and connecting rod 29 with consequent adjustment of valve 36 to alter the displacement of pump 7 to restore desired conditions. The pump power which is a function of flow and pressure is thus maintained constant. To compensate for viscosity variations of the working fluid with temperature a material having an appropriate coefficient of thermal expansion is used for piston-rod 12. The latter is fixed at its lower end but is slidably connected to pipe 9 at its opposite end. In a modification, Fig. 3 (not shown) the desired power of pump 7 can be varied by the attachment to cylinder 10 of a transverse arm (18) having a slot (19) in which pin 32 can be fixed at any position. Alternatively pin 32 can be movable in slot (19) during operation in response to the output power of a constant flow pump to enable power control of a group of pumps comprising both constant and variable flow types. In another arrangement, Fig. 2 the flow of pump 7 is sensed as the inclination of swash-plate 54, the latter having an extension 54b having a slot 54c engaging pin 55 slidable in fixed guide 56. Pin 55 also engages slot 31 in connecting rod 29. In a modification of this arrangement, Fig. 4 (not shown) guide 56 can itself be moved transversely in a guide (59) to enable the set power to be adjusted. In this case an auxiliary connecting rod (58) is provided between rod 29 and extension 54b. As in a previously described arrangement the guide 56 can be moved during operation in response to the power of another pump. In another modification Fig. 5 (not shown) a V-shaped connecting rod 29 is used. The slotted rods &c. may be replaced by telescopic members. The piston-rods may be movable and the cylinders fixed.