GB1351178A - Hydraulic jacks - Google Patents

Abstract

1351178 Hydraulic jacks or pit props J HAAMANN 5 May 1971 [8 May 1970] 13177/71 Heading F1D An hydraulic jack or pit prop comprises a ram 2, 21 slidable in a cylinder 1 and a ram head 3 containing a valve assembly, the valve assembly comprising a relief valve 57, a non-return ball valve, and a release valve 6 operable either manually or by fluid pressure. To raise the jack a throttle valve 7 is first unscrewed. This allows liquid to flow from a line 75 past the non-return ball valve and thence through passages 81, 82, 31 into the cylinder 1. Should an excess pressure occur, liquid displaces the relief valve 57 and escapes through a line 87, 33, 76. The release of liquid from the jack is effected by leftward movement of the release valve 6 away from its seat 82 to open a flow path 31, 9, 15, 34, 74 into the line 75, the line 75 being connected to return by a valve (not shown) during this operation. Leftward movement of the valve 6 is effected by manually pivoting a lever 13 or by pressurizing an annular chamber 14 through the line 76. The valve 7 may be constructed to open the line 76 while closing the line 75 and vice versa.