GB817373A - Improvements in or relating to pneumatic jacks - Google Patents

Abstract

817,373. Pneumatic jacks. REGIE NATIONALE DES USINES RENAULT. Oct. 21, 1955 [May 13, 1955], No. 30192/55. Class 8(2). A pneumatic jack comprises a differential piston 27, 28, 29, Fig. 2, a hollow piston rod 31 having a port 56 open to the cylinder space 57 below the piston, an axial tube 37 within and spaced from the rod 31 and open to the cylinder space 58 above the piston, a non-return valve 22 carried by the exterior wall of the cylinder for maintaining a supply of compressed air to the cylinder space 57 and a reversing distributor e.g. a rotary slide valve 48 carried by the projecting end of the piston rod 31 and serving to connect the axial tube and hence the cylinder space 58 either to atmosphere to effect the inward stroke of the piston or to the annular conduit 38 and hence the cylinder space 57 for effecting the outward stroke of the piston by virtue of the area of its upper face being greater than that of the lower face. The non-return valve 22 is connected by a rigid tube 24 to a flexible hose; neither of the supply tubes participating in the movement of the jack. Cushioning near the end of the inward stroke and when the piston member 27 enters a cylinder space 8 is effected by a screw 11 which regulates the escaped compressed air from the space 58 through bores 10, 9 to the space 8 and hence the tube 37 to atmosphere. A similar constructions is provided at the outer end of the cylinder. In a modification cushioning at or near the end of the inward stroke and when the piston 68, Fig. 4 enters a cylinder chamber 76 is effected by a yieldable packing ring 69 of the piston allowing air trapped between the piston and the cylinder end 76 to pass to an annular chamber 75. A similar packing ring 70 yields near the end of the outward stroke of the piston. Specifications 815,971 (Group XXIX), and 815,972 are referred to.