Patent GB-1005679-A (GB)
Abstract: 1,005,679. Hydraulic reciprocating motors and pumps; engine turning gear. NEW YORK AIR BRAKE CO. Jan. 13, 1964 [Feb. 7, 1963], No. 1357/64. Headings F1A and F1K. [Also in Division F2] In a swash plate unit I for operation as a motor for starting an I.C. engine 3 and then as a pump driven by the engine, movement of the swash plate is automatically controlled by motor assemblies 19 and 41 according to the pressure in the system. Motor assembly 19 comprises a piston 23 having an area greater than piston 44 of motor 41, so that when both are pressurized, piston 23 of motor 24 prevents movement of the swash plate into its motoring position. Piston 23 is coupled to a motor 28 acting with spring 29 to move the swash plate into its pumping position. Swash plate motors 24 and 28 are controlled by a selector valve 72 and motor 41 by a control valve 47. The motorpump unit 1 is supplied by an accumulator 4 to start auxiliary engine 3 which then drives unit 1 to supply hydraulic motor 5 to start a main engine 7 and to supply a hydraulic circuit at 14d. When auxiliary engine start valve 15 is opened accumulator 4 is connected to motorpump unit 1 and to control valve assembly 47 to set the valve 47 to the lowest of three reference pressures and to vent swash plate control motors 24 and 28. The accumulator pressure acting in inlet chamber 49 of valve 47 and on actuating motor 67 moves valve plunger 53 to supply pressure to swash plate control motor 41 to move the swash plate to its maximum displacement motoring position against .spring 29. The accumulator capacity is sufficient to supply motor-pump unit 1 until engine 3 reaches cutout speed, whereupon the system pressure drops below said lowest reference pressure so that control valve spring 62 moves valve plunger 53 to exhaust control motor 41. Spring 29 then moves the swash plate to a small displacement pumping position so that the system pressure is raised above said lowest reference pressure and valve plunger 53 is moved rightwards to a lap position and hydraulically locks motor 41. The pump now acts to maintain the system at said lowest reference pressure. Start valve 15 is then closed, thereby venting control valve piston 67 so that spring 62 moves valve plunger 53 to its vent position. Pressure in valve inlet chamber 49 then moves valve piston 68 to connect swash plate control motors 24, 28 to delivery pressure, piston 23 being moved to abut shoulder 38 to move assembly 19 to its pumping position, and pressure acting on piston 26 via bore 39 acting with spring 29 to move the swash plate to its maximum pumping displacement position, as defined by control motor 41. A stop 33 on assembly 19 prevents movement of the swash plate into its motoring position during pumping. Venting 6, valve piston 67 automatically sets valve 53 for an intermediate reference pressure, which is then maintained by motor-pump unit 1 for starting the main engine and re-charging the accumulator. Variation in pressure in the system is compensated by the action of valve plunger 53 controlling swash plate control motor 41 so that the pumping displacement under equilibrium conditions equals the rate of leakage from the system. To start main engine 7, start valve 15<SP>1</SP> is opened to connect motorpump unit 1 to starter motor 5. The resulting drop in system pressure causes valve plunger 53 to move to is vent position for control motor 28 and spring 29 to move .the swash plate to its maximum pumping position. Valve 15<SP>1</SP> also acts to connect system pressure to valve spring seat 63 to increase the loading on spring 62 and thereby raise the reference pressure of control valve 47 to its highest value. When engine 7 reaches cut-out speed, start valve 15<SP>1</SP> is closed and spring seat 63 is vented to reduce the reference pressure to its intermediate value. The system pressure then acts to move valve plunger 53 to connect pressure to swash plate control motor 41 to move the swash plate to a reduced displacement position equal to the system rate of leakage, the motor-pump unit then being available to supply the hydraulic circuit connected to conduit 14d at the selected reference pressure. Specification 1,005,678 is referred to.