GB1306371A - - Google Patents

Abstract

1306371 Hoists with extensible towers D WICKHAM & CO Ltd 3 March 1970 [4 March 1969] 11523/69 Heading B8H An extendable hoist comprises a mast 15 on which a cage 11 is slidable on outer guides 13, 14, and a wire cable 12 which is secured to a drum 17 passes over a return pulley 30, under a lower travelling pulley 19, over a cathead pulley 24 and under a pulley 28 attached to the cage 11 to an anchorage on the cathead pulley 24. The pulley 24 is mounted on a support 25 and the travelling pulley 19 on a cross-bar 21, both of which can slide on inner guides 20. In order to extend the hoist the cage 11 is lowered to the ground and a metal frame section 16 is lifted on to the top of the cage using a jib 31 which is mounted on the cage 11, and the cage is then raised to the upper limit of its travel where the mast section 16 is handled into position on the top of mast 15. The cage 11 is then locked to the mast by spraggs 29, the drum 17 is rotated to unwind cable which is taken up by the pulley 19 which descends until the associated bar 21 contacts a switch 23 thus stopping the unwinding. The cathead 24 and support 25 are raised to a point on the added mast section 16 (shown in dotted lines) by the jib 31, the travelling pulley 19 simultaneously returning to its upper position. The cage 11 can then be raised or lowered over the entire mast height, including the extended portion 16.