GB1395901A - Hydraulic engine starting systems - Google Patents

Abstract

1395901 Hydraulic engine starting; reciprocating pumps and motors JOSEPH LUCAS (INDUSTRIES) Ltd 20 April 1972 [20 April 1971] 10311/71 Headings F1A and F1K An hydraulic engine starting system comprises an accumulator 23 or 24, a pump 28, Fig.3, for charging the accumulator and connected thereto by a non-return valve 80 or 81, a clutch 29 for driving by connecting the pump to motive means when charging of the accumulator is required, an engine starting motor 22 and valve means 26 centralling connection of the engine starting motor 22 to the accumulator so that on actuation of the valve means liquid is discharged from the accumulator into the motor, the clutch being fluid-pressure actuated and being connected to an hydraulic circuit 21 associated with the engine 20 such that hydraulic pressure is normally present in the circuit when the engine is running the clutch being disengaged when the pressure in the circuit is below a predetermined value. During the charging of the accumulators 23, 24 pressurized liquid from the circuit 21 is supplied to the inlet of the motor 22 and pressure is applied to engage the clutch 29 so that the motor 22 can drive the pump 28. A plunger which forms the maximum stroke stop for the motor is urged to a slightly withdrawn position. The speed at which the motor 22 drives the pump 28 is determined by the servo 25 in combination with the restrictor 79. As the accumulators 23, 24 become fully charged the pressure at the outlet of the pump 28 rises to a value such that the force applied by a plunger of the shut-off valve 30 to a spool thereof can overcome the spring-loading of the spool and thereby disconnect the motor inlet from the circuit 21. The motor 22 thus stops rotating. In fact the valve 30 will take up a slightly open position. When it is desired to start the engine 20 the pilot device 27 is operated. Liquid is discharged from one of the accumulators 23 or 24 via the selector valve 26 to the motor and to the servovalve 25 for varying the stroke of the motor. The clutch 29 is disengaged because of the absence of pressure in the hydraulic circuit 21, for charging the accumulator 23, 24. The motor 22 and pump 28 comprise radial pistons engaging eccentric track rings, the motor track rings 36 having opposite eccentricities adjustable by a piston 44 in a cylinder connected to valve 25, a spring-loaded piston 43 biasing the track rings into their maximum stroke positions. When no pressure is available in the hydraulic circuit 21 there is provided an auxiliary pump 32, Fig.13, which is manually operated through an epicyclic gear 105. Pump 32 has radial pistons engaging eccentric track rings 111 which are spring-loaded into their maximum stroke positions and automatically destroke as the pump cylinder pressure rises.