GB987855A - Improvements in or relating to the synchronised operation of a number of hydraulic rams - Google Patents

Abstract

987,855. Fluid-pressure servomotor systems. PLESSEY CO. Ltd. Jan. 23, 1962 [Dec. 2, 1960], No. 41499/60. Heading G3P. A pump 2, Fig. 1, draws liquid from a reservoir 1 and supplies it through a relief valve or an accumulator 4 with a pressure or level switch, to a manifold 5 having four branches, each including a double-acting ram 6-9, pipes 14, 15 leading to a rotary valve 10-13 and connections to a line 16 returning to the reservoir. Each ram cylinder 6, Fig. 2, is open at each end to both the manifold 5 via restrictor 17, 18, and with its valve 10 through lines 19, 20; the latter lead to ports 19a, 20a in the rotary closure 21 while the seat 22 contains a port 23 open to the line 16. The seat 22 is attached to the ram rod 27 by a helical cam 25 which provides a rotary "follow-up" movement to the seat. The shaft 29 of the rotary closure 21 carries a sprocket 30, Fig. 3, which is coupled by a chain 34 to sprockets on the other valve shafts 31-33 and to a further sprocket 35 which is connected by a lost-motion device to a manual control whereby the rams are controlled each occupying an identical position at any one time. The ports 19a, 20a may be arranged with an overlap relative to the port 23 so that some liquid passes into both lines 19, 20 when the valves are in the neutral position. In a modification, the outlet from the ends of each ram cylinder 6a, Fig. 5, is controlled by a piston valve 38 having ports 39, 40 which lead to the line 16 via a restrictor 41; the valve casing is attached to the cylinder 6a, the ram 28a of which is fixed while the cylinder is movable. Each valve is connected by a rod 44 to a bar 45 joined by linkage and a lost-motion device to a manual control.