GB232043A - Improvements relating to grab dredgers - Google Patents

Abstract

232,043. Priestman, S. H. April 26, 1924. Grab machines. - A grab dredger adapted to leave a flat surface has check ropes attached to the lower axis of the grab and to a sliding weight working in fixed guides, preferably part of or secured to the framework of the crane, so that the dredger excavates to a predetermined depth. In Fig. 1, an opening rope 37 is connected to the grab and a hoisting rope 1 passes over a pulley 2 to a drum 5, ropes 8 passing oppositelv round smaller drums and being fixed to the grab head; the grab closes when the hoisting rope is drawn in, owing to winding of the ropes 8 on their drums, while when the load is taken by the rope 37 the grab opens. Check ropes 10 pass from the lower axle of the grab over a jib pulley 3 and pulleys 15 on a structure 17, then over pulleys 23 on a weight 22 sliding in the structure 17, and then over pulleys coaxial with the pulleys 15 to ratchet-controlled drums 27; on lowering the grab, the weight rises, descent of the grab being limited by contact of spring buffers on the weight 22 with buffer stops in the structure 17. A scale and pointer are provided. in a modification, the weight slides along the jib 14 and the ratchet drums 27 are mounted in the weight. In Fig. 5, the check ropes pass round drums 38, 39 on the grab to be wound on during closing of the grab and thereby lift the grab, so providing a wider and shallower cut; this effect is increased by providing long hinge arms 43 on the grab.