GB489663A - Improvements in or relating to hydraulic rams - Google Patents

Abstract

489,663. Hydraulic rams ; lifting- jacks. CLAYTON DEWANDRE CO., Ltd., CALLA, W. M., and WILLETT, S. E. Feb. 1, 1937, No. 2905. [Class 69 (ii)] [Also in Groups XXX and XXXII] A hydraulic ram wherein an escape valve is adapted to be opened automatically when the ram reaches the end of its outward stroke is arranged so that the excess pressure fluid passes through a passage leading from the front of the piston to an annular space formed behind it, the outlet being at the outer end of the cylinder and controlled by a valve in the piston. A telescopic hydraulic ram for use in tipping bodies of motor vehicles is mounted on trunnions 2, 3 and consists of a central ram 5 and piston 8 in a cylinder 4 having at its lower end a piston 6 movable within an outer cylinder 1 carried by the trunnions. Supply of fluid is by the hollow trunnion 2 and pipe 10 and the exhaust is by way of telescopic tubes 24, 26 with ports 29 leading to the other trunnion 3. The piston 8 of the ram proper carries a ball valve 14 which is disposed beneath a projection 17 on a cross bar 19 and when the piston is at the outward end of its stroke the bar 19 contacts with the end of a sleeve 21 fixed in the cylinder, thereby opening the valve and permitting escape of excess fluid through the passage 22 to an annular space 23 which is under valve control 25 to the inner tube 24. Fluid from 24 passes out at openings in the bottom end into the outer tube 26 and thence away through the ports 29. In order to prevent accumulations of pressure behind the second piston there is also provided a valve 27 controlling a passage 28 leading to the outer tube 26.