GB683996A - Hydraulic control system with automatic stop - Google Patents

Abstract

683,996. Hydraulic machines. BENDIX AVIATION CORPORATION. March 27, 1951 [March 27, 1950], No. 7137/51. Class 69 (ii). In a hydraulic control system comprising a motor, valve, and a control handle each having a movable element, the three elements are coupled together differentially so that motion of any element applies forces to the other elements to move that one of the other two elements offering the least resistance to motion. The motor 10 comprises a cylinder pivotally mounted at 18 and a piston 14 having a rod 15 connected to an arm 16 which extends to the device to be actuated. Fluid is supplied to the motor via conduits 21, 22 through a valve 11 having a grooved piston 27 held in the neutral position shown in Fig. 1 by a spring 29, in which position ports 19 and 20 leading to the conduits 21, 22 are blocked and ports 26 and 23 are connected and hence fluid supplied by a pump 12 flows via these latter ports and a conduit 24 back to the reservoir 25. The differential mechanism comprises a lever arm 42 pivotally connected to the piston rod 15 and by links 43 and 44 to the valve piston 27 and handle 13 respectively. To move the piston 14 to the right a predetermined distance corresponding to the setting of an adjustable stop 47, the handle 13 is given a push to the right and released. This movement shifts the valve piston 27 to the left where it is held by a garter spring 36 engaging a groove 40. Fluid flows via port 26, passage 30, port 19 and conduit 21 to move the piston 14 to the right, the displaced fluid flowing via conduit 22, ports 20 and 23 and conduit 24 to the reservoir 25. As the valve piston 27 is held by the spring 36, movement of the rod 15 rotates the arm 42 clockwise about the link 43 and moves the handle 13 to the right in synchronism with the piston 14 until the handle is held by the stop 47. The arm 42 then rotates about the lefthand pivot of the link 44, the valve piston being moved to the right to force the spring 36 out of the groove 40 so that the spring 29 returns the piston 27 to its neutral position wherein further movement of the piston 14 is arrested. Similarly the piston 14 may be moved a predetermined distance to the left by pushing the handle 13 to a stop 48 to cause the spring 36 to engage a groove 41. The valve 11 contains a relief valve 35. Either or both of the stops 47 and 48 may be omitted and the handle 13 moved continuously by hand to a desired position corresponding to that to which it is desired to move the piston 14.