Patent GB-1005678-A (GB)
Title: Hydraulic device
IPC: F02N7/08
Filed: 1963-06-25
Abstract: 1,005,678. Reciprocating pumps and motors. NEW YORK AIR BRAKE CO. June 25, 1963 [Aug. 10, 1962], No. 25200/63. Headings F1A and F1K. [Also in Division F2] In a hydraulic starting system having a unit which functions as a motor to start an auxiliary engine and then, when that engine is running and driving the unit, functions as a pump supplying liquid to one or more hydraulic motors for starting one or more main engines and for operating various hydraulically actuated devices, a valve arrangement is provided for maintaining the discharge pressure of the unit at three pressure levels, namely a low level when the unit is functioning as a pump and there is no demand for liquid, an intermediate pressure for operating the hydraulically actuated devices, and a high pressure for starting a main engine. As shown the unit 1 functions as a motor to start an auxiliary engine 3 and is supplied by an accumulator 4 under the control of an auxiliary starter valve 15. The engine 3 then drives the unit 1 as a pump which supplies auxiliary devices through a conduit 14e and a hydraulic motor 5 for starting a main engine 7 under the control of a starter valve 15<SP>1</SP>. A control valve 68 controls supply of liquid to a motor 65 moving the units swash plate 11 to its minimum displacement position against the pressure of a spring 43, and the valve spool 76 of valve 68 is subject to the discharge pressure of the pump supplied through conduits 14h, 14i to a chamber 84 to tend to move the spool to the right against the pressure of a spring 83. Liquid is also supplied to an inlet chamber 71 of the valve, and in the vent position to which the plunger 76 is biased, a land 81 isolates the inlet chamber 71 from a chamber 72 leading to the motor 65 and connects the chamber 72 to an exhaust chamber 73 communicating with a reservoir 13 through a passage 74 and a chamber 75. The plunger 76 is shifted to the right, first to a lap position in which land 81 isolates outlet chamber 72 from chambers 71, 73, and then to a supply position in which a groove 77 interconnects chambers 71, 72 by the pressure in chamber 84 acting upon the left-hand end of the plunger. The pressure in chamber 84 required to shift valve plunger 76 to the lap position is termed the reference pressure, and the valve 68 includes two devices for raising and lowering this reference pressure. In order to raise the reference pressure, pressure is supplied to a chamber 87 to shift a movable seat 85 for the spring 83 which is then shifted to a high spring-load position abutting a stop 86. The reference pressure is lowered by supplying pressure to a chamber 93 to act on a piston 91 abutting the left end of the plunger 76. Operation. Initially the components of the system assume their illustrated positions and accumulator 4 is charged by a hand pump 19. To start auxiliary engine 3, interconnected switches 42, 64 are closed thereby energizing solenoids 39, 63 to shift valves 34, 53 to the left against spring bias. Valve 34 now admits pressure from the accumulator 4 to a chamber 29 to shift a valve 24 to the left to supply liquid from the accumulator 4 through conduits 14 to the unit 1 which is driven as a motor to start the auxiliary engine 3. Simultaneously the valve 53 vents a motor 49, and fluid under pressure is delivered through a conduit 94 to the chamber 93 to set the control valve 68 to its lowest reference pressure and the valve spool 76 is shifted to the right so that pressure is supplied to the motor 65 which moves swash plate 11 clockwise to its maximum displacement position on the motor side of neutral. As engine 3 accelerates, the pressure delivered by accumulator 4 progressively decreases to the low reference pressure, and when the engine 3 starts and drives the unit faster than it is supplied by the accumulator the pressure decreases momentarily below the reference pressure and spring 83 shifts spool 76 to its vent position to exhaust chamber 67 so that spring 43 moves swash plate 11 counterclockwise beyond its zero displacement position. Unit 1 then functions as a pump and commences to discharge fluid from the high pressure port 8. When the system pressure is restored to the low reference pressure, while the valve spool 76 is moved to its lap position, and the switches 42, 64 are then opened so that chamber 93 is vented and valve 68 is set to give the intermediate reference pressure, the spool 76 being shifted to its vent position until the intermediate pressure is attained. Valve 53 now admits pressure to the motor 49 which positions a stop 47 to prevent the swash plate 11 moving beyond its zero stroke position. The unit 1 will now function to charge the accumulator up to the intermediate reference pressure. In order to start the main engine 7 a switch 42<SP>1</SP> is closed to energize a solenoid 39<SP>1</SP> actuating a valve 34<SP>1</SP> which then admits liquid from conduits 14, 14a to a chamber 29<SP>1</SP> to actuate a valve 24<SP>1</SP> which then admits liquid from conduit 14a to the motor 5 to start the main engine. The valve 34<SP>1</SP> also admits pressure through a conduit 88 to the chamber 87 to move the control valve 68 to its high reference pressure position.