Patent GB-621109-A (GB)
Title: Improvements in hoisting apparatus
IPC: B66C11/20
Filed: 1945-05-28
Abstract: 621,109. Overhead traveller; balancing apparatus. SOC. FRANCAISE DE CONSTRUCTION DE BENNES AUTOMATIQUES. May 28, 1945, No. 13357. Convention date, Feb. 4, 1944. [Classes 78 (ii) and 78 (iv)] Hoisting apparatus comprising a substantially horizontal runway for a trolley from which is suspended a grab bucket or the like and which is displaced in one direction by an electric motor controlling the hoisting cable of the grab and in the opposite direction by a counter-weight which becomes preponderant as soon as the bucket is raised and suspended from its head or crown and the hoisting cable ceases to exert traction on the trolley, an abutment being provided to stop the trolley at the filling point, is characterised in that a spring or springs is or are associated with the abutment so as to be compressed by the trolley or its counter-weight and to relax as soon as the hoisting cable is slackened so as to assist the starting of the trolley in the reverse direction. In Figs. 1, 2 a grab bucket 4 is suspended on a cable 3 from a trolley 1 which is moved in one direction along a runway 2 by the cable 3 under the control of an electric motor (not shown) and in the opposite direction towards dumping points by a cable 5 connected to a counter-weight 7. This counter-weight moves between guides 13, 14 and its upward movement is limited by an abutment 15 on a rod 16 which extends through the counter-weight and a tie 17 and is formed at its lower end with a head 30 between which latter and the tie are springs 31, 32. When, after dumping, the bucket is moved towards its filling point by the cable 3, the counter-weight rises until it engages the abutment 15 and then compresses the spring 31. The bucket is then lowered and after being filled, raised again by the cable 3 so as to be supported in its crown 8. The cable 3 is now slackened and under the action of the counter-weight and the spring 31, the trolley returns to its dumping point. If for any reason the bucket is impeded during its upward movement and the hoisting effort becomes excessive, the spring 31 becomes fully compressed and compression of the spring 32 is also effected whereby the head 30 engages a switch 34 to stop the hoisting motor. Changing of the filling point of the bucket is effected by providing a second abutment 15a on the rod 16 at right-angles to the abutment 15. The slot in the counter-weight to receive the rod 16 is shaped to correspond with these abutments so that by turning the rod, the appropriate abutment is perpendicular to the slot in the counter-weight and serves to limit the upward movement of the counter-weight. In a modification, the filling point is varied at each operation by providing one abutment on the rod 16 and rotating the rod continuously through gearing by an electric motor, such rotation being reversed automatically by switches provided at both ends of the trolley run. In the embodiment shown in Fig. 6, the abutment 36 co-operates directly with the trolley and the springs 31, 32 are threaded on a rod 37 adapted to slide in a support 38 and operate a switch 34.