| 摘要 |
1469142 Step-by-step jacks ENOR NOMINEES PTY Ltd 1 March 1974 [7 March 1973 (2)] 15536/75 Divided out of 1469141 Heading B8J A climbing jack comprises a jack tube 10 with a plurality of evenly spaced apertures 11 along its length adapted to receive reversible pawl sets 12a, 12b in an upper pawl supporting section 16 of a jack assembly 13 and similar pawl sets 12c, 12d in a similar lower pawl supporting section 17. As shown the pawls 12a, 12b and 12c, 12d are biased by oppositely acting pairs of springs 42a, 43a and 43a, 43b so that their lower ends bear against the tube 10 and, at various times during operation, engage the apertures 11. The sections 16, 17 are separated, and connected together, by a pair of hydraulic rams 18 operation of which in conventional manner causes the sections 16, 17 to climb the tube 10, the lower section 17 being attached to a load to be lifted. Reversal of the bias of the pawls by shifting a plate 41 vertically so that their upper ends bear towards the tube 10 is provided in order that, when the rams 18 are operated, the jack assembly 13 being held at a fixed position, the tube 10 is pushed up through the jack assembly 13, step-by-step. Pneumatic rams, or other force applying means may be used in place of the hydraulic rams 18, while the apertures 11 may be replaced by projections (not shown). |
