GB179663A - Improvements in grabs, excavators and similar apparatus - Google Patents

Abstract

179,663. Richardson, H. Feb. 11, 1921. Grab-buckets.-A grab comprises a frame A with vertical guide-bars a for sliding blocks b, c, the upper block b being attached to the hoisting- chain H and the lower block c being connected by links d to the buckets. For closing the buckets and holding them closed while lifting, the two blocks are locked together by levers e on the lower block which project through a central opening in the upper block and may be spread apart by a weighted discharging-lever g pivoted on the upper block. When used as a double chain grab, a bell-crank lever l operated by a chain K, is provided on the grab head for actuating the lever g against the resistance of a spring, or the opening chain may be attached directly to the lever g for hand dumping. When used as a single-chain grab, the lever g is provided with a hook for engaging the suspension ring; a counterweight k holds the lever with the hook clear of the ring for lowering open grab. The singlechain-grab may be discharged by dumping; when the closed grab rests on the ground the upper block b is relieved of the weight, the lever g is freed from the grip of the members e, e and is turned by the weight k into the discharging position shown in chain lines in Fig. 1, so that the grab is free to open on hauling in the lifting chain grab may be discharged by dumping; when charged by a hand line attached to the lever g. The operation of closing the grab is the same whether operating on the single or double-chain principle. When the open grab is grounded the upper block b falls in the guides a, and passes over the members e, e. At the same time the weight k rests on the bottom of its guides, and the lever g is free to fall by gravity into the horizontal or locking position, where it is held by the grip of the members e, e as soon as the weight is taken by the upper block.