Patent GB-266447-A (GB)
Title: Improvements in or relating to hoisting mechanism
IPC: B66C13/00
Filed: 1925-11-24
Abstract: 266,447. Fitch, B. F. Nov. 24, 1925. Overhead travellers; load, engaging and depositing.-An overhead traveller, particularly suitable for handling removable vehicle bodies is provided with means acting automatically to cause the lifting frame to grip the load on hoisting. The traveller is constructed so as to require a minimum of headroom and comprises a turntable to permit swinging of the load through a complete revolution. The crane is actuated by electric motors, and cut-out switches automatically stop the hoisting motor when the load is raised and lowered to given points. The frame 15 of the traveller runs upon the rails 10, 11 and carries a turntable 16 actuated by an electric motor 63 through a clutch, gearing 73, 74 and a spur pinion engaging the rack 64. In another position of the clutch, the motor 63 drives the wheels 17, 18 for traversing. Hoisting mechanism on the turntable comprises a screwed shaft 32 actuated by an electric motor 35 and engaging a nut 33 which moves in guides 93 and hauls four-load ropes 55 which pass over horizontal and vertical guide sheaves 56, 57 and support the longitudinals 50 of the lifting frame. The hoisting, traversing and turning mechanisms are housed within the height of the frame of the traveller. The bars 50 of the lifting frame are provided with hooks 49 to engage beneath shoulders on the vehicle body. The ends of the bars 50 are connected to arms 51 hinged together at 52 and supported by cables 93 through springs 111. When the cables 93 are slack, the weight of the parts bring the arms 51 to the position shown in broken lines in Fig. 3 with the hooks 49 disengaged from the load. The cables 93 are actuated automatically by the nut 33 so that on hoisting, the lifting frame engages the load, and after the load has been set down the frame is free to disengage by its own weight. For this purpose the cables 93 are connected to an arm 94, shown in plan in Fig. 11, pivoted at 95 and normally held by a spring against a stop 105 with the frame disengaged. On hoisting, a pin 99 on the nut 33 engages a latch lever 100 which is pivoted on the arm 94 so as to be free to swing one way only. When the nut 33 moves for raising the lifting frame, the pin 99 moves the arms 100 and 94, as shown in Fig. 11, and the cables 93 are hauled in faster than the lifting cables. the frame being thus brought, into engagement with the load. On further hoisting, the pin 99 passes the end of the latch 100, and the cables 93 become slack, the arms 100 and 94 returning to the original position. On lowering, the pin 99 passes the latch 100 without moving the arm 94. When the load rests upon the vehicle, the cables 93 are still slack and the frame disengages by its own weight. A hand line 133 is used to prevent reengagement of the frame when the latter is being raised clear of the load. The travelling nut 33 may be of bronze to reduce friction, and for safety a steel nut 190 is threaded on the rod 32 in position to support the main nut and sustain the load if necessary. Spring-closed limit switches 151, 152, Fig. 13, in the circuit of the hoisting motor are opened by the travelling nut 33 at each end of its run, and the motor is re-started in the, reverse direction by throwing over the controller, indicated generally at A. The controller comprises two sets of contacts 7-9, Fig. 13, and 160-163, Fig. 16, arranged for reversing the direction of the current through the armature. In Fig. 18, the motor runs in the direction to move the nut 33 to the right for hoisting, and the circuit through the armature includes the limit switch 152. In Fig. 16, the controller is set for lowering, the switch 152 has been opened at the end of the hoisting run, and the circuit through the armature includes the limit switch 151. The positions of the switches 151, 152 may be adjusted to vary the lift..