Patent GB-694392-A (GB)
Title: Improvements in or relating to hydraulic power transmission systems
Inventor: ZISKAL JOSEPH FRANK
IPC: F15B11/20
Filed: 1951-05-25
Abstract: 694,392. Fluid-pressure servomotor-control systems. INTERNATIONAL HARVESTER CO. May 25, 1951, No. 12313/51. Class 135 In a servomotor control system comprising a control valve movable from a neutral position in either direction to place either of two alternative reversible flow conduits in communication with a source of hydraulic pressure and the one not so connected with a return conduit, a servomotor having its piston connected to the movable valve element to reset it in its neutral position, and a ram hydraulically connected in series with the servomotor, the ram is made interchangeable with other rams of differing diameter and stroke, the arrangement being such that the rod ends of the ram cylinders are of equal capacity and the same as that of that end of the servomotor cylinder to which they are connected so that movement of any of the ram pistons corresponds to movement of the servomotor piston. As shown, the system comprises a control valve 14 operable through a floating lever 17, link 10 and a hand control member 15 to supply and exhaust pressure liquid serially to and from a servomotor 16 and a ram 19..The control valve comprises a plunger 26 slidable in a casing 27 to control an inlet port 48 from a pump 29, exhaust ports 38, 46, 39, 46<SP>1</SP> to a reservoir R, and motor ports 49, 74. The motor port 49 is connected through a reversible flow conduit 51 and a piston-actuated check valve 52 to the left end of the servomotor cylinder 45, whilst the motor port 74 is connected through a reversible flow conduit 71 and a manually-actuated cock 91 to the left end of the ram cylinder 61. A branch 78 from the conduit 71 supplies pressure liquid to the piston 81 of the check valve 52, and a branch 57 from the conduit 51 supplies pressure liquid to the piston 55 of a piston-actuated check valve 53 controlling through the cock 91 communication between the piston-rod ends of the servomotor and the ram. In the neutral position of the system shown, flow through the control valve 14 is blocked and outlet flow from the pump passes through a conduit 32 having a restriction 47 to the back of a piston 41 to open a pump by-pass valve 42. On movement of the control member 15, e.g., towards A, the port 38 is opened to relieve pressure behind the piston 41 to close the by-pass valve 42 and port 49 is opened to direct pump pressure to the conduit 51 and its branch 57 to directly open the check valve 52 and indirectly the check valve 53. Pressure liquid then flows to the left end of the motor cylinder to urge its piston 18 rightwards to operate through levers 22a, 25 any desired equipment and through the lever 17 return the plunger 26 towards its neutral position. Liquid expelled from the piston-rod end of the motor cylinder passes through the check valve 53 to the piston-rod end of the ram cylinder to move the piston 21 thereof leftwards which through its rod 92 may operate another piece of equipment. Liquid expelled from the non-rod end of the ram cylinder passes through the conduit 71, port 74, passage 75 through the plunger 26, and a conduit 13 to the reservoir R. On moving the control member 15 from its neutral position towards C, the ports and passages are connected to move the ram piston rightwards and the motor piston leftwards. The amount of movement of both the motor and ram pistons in each case corresponding to the amount of movement of the control member 15. On rotating the cock 91 through 90 degrees, the conduit 71 may be connected through the check valve 53 to the pistonrod end of the motor cylinder and the two ends of the ram cylinder are interconnected so that the ram is isolated and only the servomotor operable. The ram 19 may be replaced by a ram 19<SP>1</SP>, Fig. 2, having a larger diameter cylinder and a shorter stroke. The piston rod in this case is shrouded by a member 92<SP>1</SP> so that the volume of the ram cylinder 611 on its piston-rod side at any stroke position is equal to the volume of the ram cylinder 61 at its corresponding stroke position and to the piston-rod side of the motor cylinder at the same corresponding stroke position. The ram may be made of any diameter and stroke provided the above relationship holds.