Patent GB-951313-A (GB)
Title: Hydraulic systems and methods for starting engines
IPC: F16H39/00
Filed: 1962-02-27
Abstract: 951,313. Hydraulic starting devices; liquid pressure engines; hydraulic pumps. NEW YORK AIR BRAKE CO. Feb. 27, 1962 [March 27, 1961; May 22, 1961; Feb. 1, 1962], No. 7628/62. Headings F1A and F1K. [Also in Division G3] An hydraulic starting system comprises a variable displacement hydraulic motor 9, Fig. 1, supplied with fluid from an accumulator 39, Fig. 3, with a decaying pressure characteristic, and pressure responsive means 20, 23, which hold the displacement control element 13 in the maximum displacement position when the supply pressure is above a predetermined value and move it towards its minimum displacement position when the pressure drops below that value. In Fig. 1 the pump shaft 3 carries gear wheels 131, 132, which mesh with gear wheels 123, 124, which are connected to an engine driven shaft 120 through one-way clutches 128, 129, operative so that when the hydraulic unit 9 acts as a motor, the shaft 120 is driven from shaft 3 through gear wheels 131, 123, to start the engine whilst when the engine is running the shaft 3 is driven from shaft 120 through gear wheels 124,132. Starting. The accumulator 39, Fig. 3, is normally charged at 3000 p.s.i. and opening of the start valve 41 at starting supplies fluid through pipes 43c, 43b, Fig. 3, to servomotor 20 and simultaneously through pipe 75 to move valve 51 to the right to connect motor 23 to exhaust whereby the displacement control member 13 is moved to maximum displacement position in which the hydraulic unit is driven as a motor at maximum torque by the pressure fluid supplied to the high pressure port 6 of the hydraulic motor and the engine is turned over. As the hydraulic motor rotates, the supply pressure from accumulator 39 continuously decreases and when it has dropped to 1500 p.s.i. valve 51 is moved back to its original position by spring 52 to connect motor 23 to supply pressure, whereby the displacement member 13 returns to neutral position in which the hydraulic motor idles. Pumping. When the engine speed reaches a predetermined value a governor 67, Fig. 5, moves valve 65 to the right to connect motor 20 to exhaust, whereby motor 23 moves control member 13 over dead-centre position to set the hydraulic unit to act as a variable displacement pump to recharge the accumulator 39 to charge pressure of 3000 p.s.i. and to maintain the pressure in a hydraulic system 151 for operating accessories. The pump output is controlled by a servomotor 30, under the control of a pressure responsive valve 92, Fig. 5, actuated by the primer-pipe 76 connected to the pump outlet 6. Under cold weather conditions a solenoid operated valve 115 is energized to transmit the supply pressure through pipe 111 to a piston 86 which increases the spring load on valve 92, whereby the accumulator is charged to a higher pressure e.g. 4000 p.s.i. In a modification, Fig. 7, the displacement control member 215 of the hydraulic unit is biased towards its maximum displacement pumping position (broken lines, Fig. 7) by a spring 223 and is movable over dead centre position to its maximum displacement motoring position by a servomotor 231 which is supplied with pressure fluid from the accumulator 240 under the control of a spring loaded valve 255. When start valve 242 is opened, the pressure fluid at 3000 p.s.i. is supplied to the pressure port 208 of the hydraulic motor and through line 248 to valve 255 which is moved to the left against loading spring 264 to enable fluid to flow through pipe 251 to servomotor 231. The control member 215 is thereby moved to the maximum displacement motoring position and the hydraulic motor is driven at maximum torque to turn the engine over. When the fluid pressure from accumulator 240 drops below 1500 p.s.i. spring 264 moves valve 255 back to the right whereby motor 231 is connected to exhaust 253 and the displacement control member 215 returns to neutral position, by which time the engine has started and is driving the hydraulic motor with the displacement control 215 in neutral position. When the engine is capable of operating under power, a switch 291 is opened to de-energize a solenoid 288 whereby a valve 283 is moved to the right by spring 257 to connect chambers 224, 263a, to the pressure supply. Piston 226 is thereby moved to the left to increase the load of spring 223 on the control member 215 and move it to maximum pumping position and piston 263 is moved to the right to increase the load of spring 264 on valve 255. The hydraulic unit then acts as a pump to restore the pressure in chamber 240 to 3000 p.s.i. at which it is maintained by the valve 255 and motor 231. In a modification of this system the biasing of springs 223, 264 is arranged so that the control member 215 remains in the maximum displacement motoring position until the engine reaches about 50 % of the starter cut-out speed and the displacement member 215 then moves towards neutral position as the engine speed approaches starter cut-out speed.