Patent GB-616270-A (GB)
Title: A combination hoisting, jacking and wire-stretching tool
IPC: B66D3/14
Filed: 1945-09-26
Abstract: 616,270. Strainers. COFFING, F. W. Sept. 26, 1945. No. 24951. [Class 45] [Also in Group XXX] A combination hoisting, jacking and wirestretching tool comprises a body 12 housing a sprocket 22 supporting a load chain 14, the teeth of the sprocket projecting through the chain for engagement by a driving pawl 28 pivoted at 27 to an operating handle 25, and by a holding pawl 30 pivoted at 31 to the body 12. The two pawls 28 and 30 are inter-connected by a spring 33 which is subject to the control of a finger lever 36 pivoted to the body and providing a means for adjusting the mechanism alternatively for raising and lowering the load by reciprocation of the handle 25. Each pawl, moreover, has two operative faces 40, 41 and 43, 44 which come into action successively upon successive strokes of the handle, the chain moving half a link at each stroke. For raising, the finger lever is turned to the position of Fig. 1 with its nose 37 bearing continuously on the spring 33 and maintaining the holding pawl 30 permanently up to the sprocket 22. For lowering, the finger lever 36 is turned to the position of Fig. 5, its side edge then coming opposite the spring 33 which is then less-stressed and runs clear at certain parts of the operative cycle. Thus, as the driving pawl 28 moves upwardly, pawl 30 is moved clear of the sprocket to allow it to follow the driving pawl 28, but re-engages 'the sprocket at the upper limit to hold it for the downward stroke of the driving pawl which then moves clear of the sprocket. In a slightly modified construction, Figs. 8 to 10 (not shown), the holding pawl is located above the driving pawl and operating lever. The finger control for raising and lowering is mounted on the operating handle and is slidable instead of pivoted. In the construction of Fig. 13 the finger control lever 336 is pivoted to the operating handle 325 concentrically with the driving pawl 328, and is adapted to act on the spring 333 connecting the driving pawl with the' holding pawl 330 through a reinforcing spring 351. This construction also has provision for free-running of the chain : a second control lever 371 is pivoted on the handle and is connected by a spring 372 with the driving pawl, so that the two pawls can be pulled clear of the sprocket 323 by rocking this control lever. A still further construction, Fig. 19, has a three-position control lever 455 which can be set for raising, free-running or lowering. The lever 455 is secured to a shaft 490 journalled in the body 410, and the shaft 490 has a cam-like part with three flats for alternative engagement with a spring 469 which is held up to it by a compression spring 477. The spring 469 is taken round, and is engageable with the spring 467 inter-connecting the driving and holding pawls 463, 460 and its free end has a lostmotion connection with the holding pawl 460 through a link 468. Fig. 19 shows the apparatus set for raising. In the free-running and lowering positions, the corresponding flats on the shaft 490 hold the spring 469 and its link 468 in such positions as to control the pawls 460 and 463 in the appropriate manner. The body 12 (Fig. 1) has a hook 20 by which it can be suspended from a support A when used as a hoist, or attached to a fixture for fence-wire stretching. To increase the load-handling capacity, the chain may be taken round a sprocket in a receiving block carrying the load hook 16, the free end of the chain being attached to the body. For bale-tying, the chain is taken round the bale, and the load hook'attached to the hook 20. To convert the appliance into a lifting-jack, a spigot 13 on the body is inserted into a tubular column 11 on a base 10. The column may be in jointed sections to enable its height to be adjusted to requirements. In a modified mounting, Figs. 27 to 30 (not shown), the base plate has sockets for two such columns side-by-side, and the hoist body is mounted on them through the intermediary of a bridge member.