GB177586A - Improvements in and relating to cranes and lifting machinery of like nature - Google Patents

Abstract

177,586. Arrol & Co., Ltd., Sir W., and Huntley, J. H. Dec. 22, 1920. Jib cranes.-A jib in the form of a two-armed lever pivoted at a<4> is luffed by a force applied to the short arm or tail at a point that varies with the position of the jib. Means are provided such that the load travels horizontally or in some other predetermined path as the jib is raised, the dead-weight of the jib is approximately balanced in all positions, continued movement of the luffing mechanism moves the jib to and fro between determined limits, and luffing is effected without the use of ropes or chains. The tail of the jib forms a runway a<2> for two trollies b, c. The balancing trolley c carries a counterweight and is moved along the tail of the jib by the luffing-link m, which is pivoted to the frame at a point m<1> below and to the rear of its point of attachment m<2> to the trolley. The link m is raised and lowered successively by continued rotation of a crank k. The compensating trolley b is controlled by rollers d which run in guides e in the framework of the crane. The load rope g runs from the hoisting-drum h over sheaves i, b<1>, i<1>, b<2>, to the head sheave, the sheaves b<1>, b<2> being mounted on the trolley b. As the jib is raised from the position shown, the sheaves b<1>, b<2> approach the fixed sheaves i, i<1>, shortening the loop g<1> and paying out the load rope at the jib head, to an extent determined by the contour of the guides e.