Patent GB-862810-A (GB)
Title: Hydro-pneumatic power mechanism
IPC: F15B11/076
Filed: 1959-09-10
Abstract: 862,810. Hydraulic apparatus. HARTFORD SPECIAL MACHINERY CO. Sept. 10, 1959 [Nov. 7, 1958], No. 30895/59. Class 69 (2). [Also in Group XXVIII] Restriction at a valve 65, Fig. 4, of flow of hydraulic fluid from one side to the other of a piston 44 secured to a coaxial compressedair actuated piston 33 (see Group XXVIII) serves to control the speed of said piston 33 during the end portion of its forward stroke within a cylinder 28 ; both pistons being secured to a spindle 18 to effect axial displacement thereof. Said spindle 18 is rotatably mounted in a carrier 11 which forms the connection between pistons 33, 44 and in respect of which the spindle is prevented from relative axial movement by shoulders 22, 23, Fig. 1, engaging bearings 19, 20. The spindle 18 is splined to a tube 25 over a length equal to the maximum displacement of the pistons 33, 44, the carrier 11  and hence of the spindle 18, and the tube 25 is rotatably driven from a power source 26. Forward movement of the carrier 11 is limited when an adjustable nut 73 threaded to the interior of the carrier 11 and keyed to a stoptube 70 rotatably supported by the carrier frame 10 abuts a ring 71 secured to the free end of tube 70. In operation the forward stroke is effected by allowing compressed air from a supply 49 to traverse a line 110, a valve spool 113 and a line 51 leading to the pressure side of piston 33 ; the discharge side being vented to atmosphere through a line 52 and a port 120 of the main valve 50. Simultaneously hydraulic fluid is forced by forward movement of the piston 44 from one side to the other thereof through a line 62 past the centrally-located spool of a main valve 60 which by-passes the control valve 65 and through a line 61 until a dog 100 carried by a rod 95 secured to the carrier 11 opens a poppet valve 101 to vent one side 121 of the spool of valve 60. The latter is thus forced to its closed position whereon hydraulic fluid traverses a filter 130 and the control valve 65, a check-valve 131 and the line 61 during which time the forward speed of connected pistons 33, 44 and spindle 18 is continued at a lower rate. The return stroke is initiated automatically on breaking a switch 82 which de-energizes a solenoid valve 53 and allows access of compressed air to the face 118  of a piston 115 of the valve 50 to displace the spool thereof to its other position whereby compressed air from the source 49 gains access to line 52 and cylinder 28 ; the other side of piston 33 being vented to atmosphere through line 51 and a port. 120a of valve 50. The hydraulic fluid now being driven through line 61 traverses an unimpeded path through a check-valve 127 to the other side of piston 44 which is permitted a rapid return stroke near the end of which a dog 96 opens a poppet valve 98 to vent the other side of the spool of 60 which is then returned to its central position. Re-energization of solenoid valve 53 results in another cycle by venting a line 116 through a port 48 so as to move spool 113 of valve 50 to the right against a stop 117. A slow instead of rapid return stroke may be effected by manually closing check-valve 127, thereby forcing the hydraulic fluid to traverse a restrictor valve 140. In a modification, a pump 155, Fig. 6 (not shown), draws from a sump and discharges to the hydraulic cylinder 40 to assist forward displacement of piston 44 during the slow portion of the stroke.