GB1431793A - Servomechanisms - Google Patents

Abstract

1431793 Fluid-pressure servomotor systems DBA 4 April 1973 [4 April 1972 15 Nov 1972] 16005/73 Heading G3P A step by step controlled servo-mechanism comprises a movable member dividing a fixed cylinder into two chambers, the movable member having a series of receiver ports and the cylinder having at least three transmitting or supply ports which can be connected selectively in succession and in pairs respectively to sources of low and high-pressure to provide step by step control of the movable member. The servo-mechanism may be a rotary hydraulic motor or, as shown in Figs. 1a, 1b, a piston 1 and cylinder 2 arrangement having a straight axis. The latter arrangement comprises a chamber 4 in constant communication with high-pressure, and a chamber 3 communicating via axial duct 5 in piston 1 with radial receiver ports 6, 6a, 6b. The cylinder wall is provided with supply or transmitting ports 7, 7', 7" of the same width as ports 6, a, b and which can be selectively connected in pairs to low and highpressure ducts 13, 14 in the barrel 10 of rotary cock 9. When barrel 10 is moved through 120 degrees in a clockwise direction from the stable state shown in Fig. 1a then piston 1 moves one step leftwards into the position shown in Fig. 1b, and vice versa. In a modification, Fig. 3, rotary cock 9 is replaced by valves 22, 23 which respectively provide reversal and step control of piston 1. Ball check valves 20, 20 , 21, 21' are provided in this arrangement. Numerous other arrangements are described, e.g. axially overlapping transmitting ports Fig. 7 (not shown), and double-acting arrangements Fig. 8 (not shown). Relationships are specified between the port sizes and spacing to satisfy requirements of hydraulic locking, continuity of piston movement and no fluid shortcircuiting.