GB551193A - Improvements in, or relating to, hoists, cranes, lifts and the like lifting apparatus - Google Patents

Abstract

551,193. Load-limiting devices. ASEA ELECTRIC, Ltd., and BAYNES, S. Nov. 3, 1941, No. 14138. [Classes 78 (iv) and 78 (v)] In hoists, cranes, lifts &c., in which the load is supported by two duplicate hoisting ropes 16, 17 anchored to a swinging equalising link 1, means is provided for cutting off the power motor in case of excessive load. The ropes 16, 17, which may be in one piece, are fixed each to a grooved wheel 5 journalled on the link 1 and carrying each an arm 12 the lower ends of which are connected by a tensioning device. Against each of the wheels 5 there may be arranged friction discs which can be adjustably pressed against the wheels to take the initial twist of a temporary load due to inertia. The tensioning device may comprise a spring 33 simply pulled against an abutment 34 by a. connecting rod 24, or, in the more elaborate form shown, may include a fluid friction control. In this form a cylinder 22 is attached to the arm link 21 and adjustably screws into the cap 34 through a packing gland 36 in which the rod 24 slides. To the rod 24 is fixed a piston 28 squeezing the spring 33 on to the cap 34. In the piston are two bleed valves 29 opening one on each side and the head of the rod 24 is bored at 25 and has a side inlet 26 to the cylinder below the piston 28. The bored end of the rod 24 takes over a small central projection 27 in the cylinder head. A heavy load, if of short duration, will be held from rapid opening of the arms 12 by the slow leakage through the head valve 29. If of sufficiently long duration to permit the head of the rod 24 leaving the projection 27, a rapid flow through the bore 25 will be permitted and the bight 37 will rise to turn a switch lever 38. The grooves in the wheel rims are set at an angle to enable the hanging portions of the ropes 16, 17 to clear the bight 37. In a modification the cylinder 22 is connected to further links pivoted to one another and to the arms 12, and in one form these links may be scissors crossed and the cylinder 22 and piston work against outer compression.