GB802084A - Improvements relating to load handling tongs - Google Patents

Abstract

802,084. Lifting tongs. HEPPENSTALL CO. Nov. 28, 1955 [July 11, 1955], No. 34014/55. Classes 78 (2) and 78 (4). The lifting arms 63, 65, Fig. 5, of a lifting tong are moved through a linkage 54, 55, 58, 59, 67, 68 by vertical movement of a cross head 18 carried by spaced guides 13. In the construction illustrated the crosshead 18 is carried by slides 17 sliding on the guides 13 and is raised and lowered by a pair of chains 28 passed round sprockets 24 on the shaft 21 and sprockets 25 on a lower shaft 26. The shaft 21 is turned by a chain 19, Fig. 4, and chain wheel 20 through gearing and an irreversible coupling. The coupling includes a yoke 46, Fig. 8, which can transmit drives in either direction to a block 49 carried by a plate 50 fast on the shaft 21. A floating brake band 47 normally engages a drum 53 to prevent the block 49 from moving but is pulled inwardly by the yoke 46 as it turns to engage the block 49. An external contracting brake band may be employed in place of the internal expanding brake band illustrated. Counter balances (not shown) sliding within the guides 13 may be connected by a pulley 78, Fig. 4, passing over suitably disposed pulleys to the crosshead 18. In an alternative construction the chains 28 raising and lowering the crosshead 18 may be replaced by a screw driven by an electric motor carried by the frame of the tongs. The lifting arms 63 may be joined by rails 71, 72 or, in a construction for engaging inside a coil resting with its axis horizontal, the linkages carrying the lifting arms 63 and the lifting arms themselves may converge to provide on each side of the tongs a single member for engaging within the coil. An arcuate saddle carried by the frame of the tongs may guide the tongs into correct relation with the coil. The middle portions of a stack of plates supported by the tongs illustrated may be held against sagging by shoes 82, Fig. 4, suspended from cables 86 which are passed to spring drums 88 by which the cables are normally retracted. Extension of the cable 86 is normally prevented by a ratchet mechanism which can be released by pulling a control wire. The shoes 82, when not in use, are retained by pins 85 on brackets 84 as shown to the right of Fig. 4.