Patent GB-745728-A (GB)
Title: Improvements in or relating to speed governing apparatus
Inventor: EMERSON REGINALD STANLEY
IPC: G05D13/00
Filed: 1952-08-01
Abstract: 745,728. Fluid-pressure servomotor-control systems. NAPIER & SON, Ltd., D. Oct. 14, 1953 [Aug. 1, 1952], No. 19574/52. Class 135. A hydraulic speed-governing apparatus for internal combustion and other engines comprises a displacement type liquid pump 8 arranged to be driven at a speed proportional to engine speed, a flow-control orifice in the pump circuit, means such as the pressure-stabilizing valve 29 for maintaining a predetermined pressure drop across and hence a predetermined flow through the orifice, control means, such as the piston assembly 41, 42, 43, 44, responsive to changes in hydraulic pressure in the circuit between the pump and the flow control device for actuating the speed-control mechanism of the engine, and master control means for controlling the governed speed of the engine by varying the flow through the flow control orifice. Such flow variation may be effected by varying the effective area of the flow control orifice or by varying the predetermined pressure drop which is to be maintained across it, or by varying both. Means are also provided (1) to give an adjustable " run up," (2) to limit the output torque for a given speed, and (3) to shut off the engine in an emergency. As shown, a pump 8 of the rotary vane type has inlet and discharge chambers 6, 7 and discharges liquid past a valve 13 into a gallery 14 communicating with a valve bore 16 and a stepped bore 15 for a differential working piston 41, 42, 43, 44. The bore 16 contains a pressurizing valve 17 loaded to close by springs 23 and formed with circumferential slots 18 and spaced lands 20. The lands 20 have longitudinal passages 19 and co-operate with annular outlet grooves 21 leading into one or more longitudinal passages 22 in the wall of the valve bore. Liquid leaves the passage or passages 22 by annular grooves 31 controlled by a piston type pressure stabilising valve 29 generally similar to the valve 17 and loaded by a spring 28 which tends to open the valve against the outlet pressure in a chamber 32. Liquid passes from the chamber 32 back to the pump inlet 6 via a passage 33 and a chamber 34 containing the flow control orifice. The latter is constituted by co-operating ports into two interengaging screw-threaded sleeves 35, 36 the inner 35 of which is rotated by a shaft 37 from an external manual speed selector lever 38. The pump delivery pressure acts directly on the small end 42 of the working piston and the pressure in the passage 22 is communicated to the larger end 44 by a passage 40. The central part 41 of the working piston is connected by an arm 56 to a shaft 55 adapted to control the fuel injection pumps of the engine. To give an adjustable " run up " a bleed is provided between the passage 22 and the pump inlet and this is controlled in dependence on the position of the working piston. Thus liquid in the passage 40 passes through passages 46 in the working piston past a spring-loaded valve 48 which maintains a constant pressure in an annular chamber 49. The larger bore of the working piston contains a series of circumferentially spaced tapering grooves 51 which are progressively uncovered to connect the chamber 49 with a chamber 52 leading to relief or the pump inlet. The effective areas of the grooves may be adjusted by eccentric portions 54 on rotatably adjustable rods 53. This arrangement of grooves provides for adjustable " run up," i.e. an increase of governed speed with a decrease in load. To limit the output torque for any particular speed, the valve 13 is provided. It consists of a disc 60 loaded by a spring 63 and moving with clearance in a tapered bore 61 communicating with the pump delivery. The spring 63 acts on an abutment 64 carried by a movable guide 62 for the disc 60. One end 65 of the guide is connected to the pump inlet, and the other is open to pressure fluid admitted through co- . operating ports 70, 71 in the guide 62 and a stationary piston-like member 69 respectively. The pressure in the chamber 68 of the guide 62 thus balances the spring 63 and varies with engine speed. This pressure is supplied through a connection 73 to a spring-loaded piston 75 coaxial with the working piston and having a hollow stem 78 closed at one end. The stem 78 has ports 80 co-operating with a part 79 of the working piston and serving to connect the smaller part of the bore 15 with a connection 83 when the working piston moves in the speed increasing direction beyond a position representing the instantaneous speed of the engine defined by the piston 75. In such a case the connection 83 admits pressure behind a spring- pressed plunger 85 which co-operates with the valve 29 to lower the pressure in the chamber 32. Pressure therefore rises in the passage 22 and the working piston moves to close the ports 80 again and reduce the fuel supply. To facilitate the shut-off of the engine in an emergency, the gallery 14 may be connected with the pump inlet 6 at any time by a valve opened by a hand-operated cam and maintained open by fluid pressure until the pressure in the gallery drops. Further movement of the lever which operates the cam may move the fuel control mechanism to the shut-off position directly or separate manually operated means for this purpose may be provided.