GB953133A - Improvements in hydraulic ram units - Google Patents

Abstract

953,133. Hydraulic rams; lifting machines. E. TEN KATE. Nov. 7, 1962 [Aug. 11, 1961], No. 29022/61. Headings B8H and B8J. A lifting device which is actuated upon application of mechanical pressure to a ram 38 comprises a piston 22 slidable within a cylinder 15 surrounded by a further cylinder 13 to form a space 21. The piston includes a resilient seal 23 held in position by a plug 24 which has a bore 42. A spring 26 bears on the plug 24 and urges the stem 28 of a piston valve upwardly. The head 31 of the valve is a close fit in a bore 32 in the piston, the bore constituting a valve chamber. Valve ports 33 in the piston open to the top of the piston via bores 34 or longitudinal flutes or passages around the periphery of the upper portion of the piston. A ram 38 is supported by a spring 36 resting on the piston and has a portion 39 adjacent the valve head 31. A sleeve 35 also rests on the piston. Outlets 40 provide communication between the inner cylinder 15 and the space 21 between the cylinders 13, 15. In operation, hydraulic pressure liquid enters the inner cylinder 15 through passages 12, 41, passes through the piston via bores 42, 32 and passages 33, 34 and thence into the upper portion of the cylinder 15 from which it escapes through the outlet 40 into the space 21. The liquid is drawn from this space by a pump (not shown). If a load is placed on a platform fixed or connected to the ram, the spring 36 is compressed and the ram portion 39 depresses the valve head 31. The valve ports 33 are thus closed, the flow of liquid through the piston is stopped and the ram and its load are raised. When the load is removed, the spring 36 lifts the ram, the valve 31 is allowed to rise and the ports 33 are again uncovered. The piston then descends under the weight of the ram and its platform. If, for some reason the load is not removed, the ram continues to move upwardly until the upper end of the sleeve 35 reaches a stop (not shown). The resulting increase in pressure within the cylinder causes a relief valve 17 to blow and the hydraulic liquid escapes through a passage 20 into the space 21. The hydraulic pressure may be provided by a power driven pump mounted together with the lifting device, on a wheeled chassis. The load platform may be connected to the ram by a hoisting cable, linkage or the like.