GB172761A - Improvements in grabs - Google Patents

Abstract

172,761. Smith, W. Sept. 27, 1920. Grab-buckets. -Comprises means for manipulating gravity locking- catches in grabs of the kind in which a lower fall block moves hetween the head of the grab and the bucket hinge during the operations of opening and closing. In the illustrated form applied to a singlechain grab, the operating rope p is wound round an upper block a4 fixed on the framework of the g r a b and also round pulleys on shafts e' carried by the lower fall-block which slides on telescopic frame members f, and is guided by rollers e<3> during its sliding movement. When the open grab rests on the ground at the loading station, further paying out of the rope lowers the fall-block on the guides. The fallblock carries two swinging gravity catches g, linked by interengaging teeth to act in unison, and forced inwards towards each other by weighted levers m so that they pass freely into a casing associated with the bucket pivots, during the descent. At the lower limit of the movement the levers m are raised by stops n on the buckets to free the catches g and allow them to swing outwards by gravity into engagement with notches in the casing. Hauling on the rope then raises the fall-block and the bucket pivots to close the grab, and eventually hoists it after the fall-block has reached its upper limit. The levers mare released from the stops during this process, but the weight of the load prevents the catches from being disengaged. The raised grab is swung over and lowered on to the dump heap. Slackening of the rope then lowers the catches relatively to the notches in the casing and. allows the levers m to disengage them. Hauling on the rope then first raises the fall-block and finally raises the whole framing, leaving the unsupported bucket pivots free to fall and open the grab. The opened grab is then lowered on to the loading heap for a. fresh operation. The grab may be made into a doublechain grab by adding a supporting chain to take the weight of the load when desired. This enables the grab to be opened when suspended. In a modified form the catches g act inwardly instead of outwardly and engage a collar on a central bolt instead of a casing.