GB1432194A - Hyeraulic installation more particularly for driving warping and retaining winches on bulk cargo ships - Google Patents

Abstract

1432194 Hydrostatic transmission control FRIEDRICH KOCKS GmbH 12 Oct 1973 [14 Oct 1972 20 July 1973] 47882/73 Heading F2W In a hydrostatic drive in which a plurality of variable displacement motors 15 are supplied from a constant pressure network fed by a pump (13) (Fig. 1, not shown) each motor has a regulating valve 18 and adjusted in dependance on the motor 15 adjusting member 16, or vice versa valve 18 controlling flow rate substantially independent of pressure. In the embodiment shown in Fig. 2 the valve 18 is adjusted by a cam 23 on rotation of a wheel 21, the wheel 21 also rotating a crank 24 to adjust the adjusting means 16 of the motor 15. The shape of the cam 23 is such that initial movement of wheel 21 adjusts the means 16 away from the neutral position whilst maintaining valve 18 closed to prevent flow, further rotation moving cam follower 25 along portion 27 or 28 to gradually open the valve 18 whilst increasing pump displacement, the valve 18 being fully open when follower 25 reaches the outer periphery of the cam 23. A hydrostatic braking valve 72 is provided downstream of motor 15 and adjusted in dependance on the motor input pressure P<SP>1</SP> 1 to vary braking in dependance on the speed of the motor 15. The valve 18 is shown in the flow line 11a to the motor 15, but it may alternatively be in the return line 12a. A different embodiment is shown in Fig. 7, the valve 18 here being in the return line 12a and variable to adjust the pressure p 2 downstream of the motor, which pressure is communicated to a chamber 36 of a servo 34 whose other chamber 37 receives a constant pressure p 3 from the flow line 11a via a pressure reducing valve 45. The servo 34 adjusts the motor adjusting member 16 away from its lowest displacement position (one third maximum displacement in the embodiment shown) as valve 18 is adjusted to reduce p 2 to below p 3 , the motor running at its lowest displacement until p 2 equals p 3 . As the motor displacement is increased p 2 again falls to equalize the pressures in a follow-up action. A throttle valve 50 and check valve 49 prevent sudden increase of pump displacement, but allow a fast decrease thereof. A piston and cylinder device 52 in the connection between servo 34 and member 16 adjusts between its extreme positions on switching over of reversing valves 59 and 43 so that the minimum displacement is maintained for either direction of rotation of the motor. The adjustment of the member 16 in dependance on the motor output pressure prevents overspeeding of the motor and increases the displacement thereof to accommodate increased torque. The piston and cylinder 52 can be replaced by mechanical stops, moved by the operation of the reversing valve 43 (Fig. 5, not shown) and the constant pressure p 3 can be replaced by a spring device acting against pressure p 2 (Fig. 8, not shown). It is also possible to modify the characteristics of the regulating valve 18 by having a further throttle valve in series with it, both valves being operated together but the further valve being fully open before valve 18 (Fig. 10, not shown). The system shown in Fig. 7 will apparently maintain a constant speed of motor 15 for any single setting of valve 18.