GB687489A - Improvements in or relating to block-and-tackle lifting devices - Google Patents

Abstract

687,489. Pulley hoists. DIDSBURY ENGINEERING CO., Ltd., and FRANKS, A. L. Nov. 27, 1950..[Nov. 28, 1949] No. 30392/49. Class 78 (v). In a portable block and tackle lifting-device of the kind in which a standing block suspended from an overhead support is united to the upper end of a column having at its lower end a manually rotatable member for pulling the running end of the tackle, the running end of a roller chain tackle engages with a winding sprocket and the surplus chain is accommodated in a spill tank united to the said column with its open end adjacent the standing block. The sprockets are arranged as shown in Fig. 9. The sprockets 21 and 37 are mounted in a standing block 19, and the sprockets 17 within the running block. The chain passes over two jockey pulleys 35, 36. The free ends of the chain are anchored at 22 and 41. The chain 18 passes through a guide tube 40 into a spill tube 24 which is integral with a tube 40 into a spill tube 24 which is integral with a tube 12 along which the chain passes. At the lower end of the spill tube spaced plates 28 are bolted within an outer casing 23. The chain passes round a sprocket 34, which is driven through reduction gearing from any of the shafts 32, 45 or 50. A brake drum 55 is mounted on the shaft 50. Internally expanding shoes mounted on the shaft are held together by springs and operated through linkage connected to a lever 66. A set of rollers 69 act between a shoulder 70, and a ratchet ring 71 fixed to the sprocket 51 so that the drum can free wheel. The rate of descent when the brake is off is governor controlled. Two arcuate shoes 74 connected by springs 75 are mounted on pins 73 on a back plate 72 and at the critical speed, move radially and angularly to engage a drum fixed to the side plate.