GB190825712A - An Improved Luffing Gear for Cranes. - Google Patents

Abstract

25,712. Wylie, H. N. Nov. 28. cranes.-Relates to jib cranes in which the length of the jib is at least two and a half times the height of the crane-post, and comprises means for ensuring horizontal traverse of the load. Fig. 1 is a diagram. matic view of a crane constructed according to the invention. The jib B is pivoted to the crane post at O, and its outer end is supported by an arrangement of ropes shown diagrammatically in Fig. 5. One end of the hoisting-rope H is secured to the jib head as shown in Fig. 4, the arrangement ensuring that the pull of the load always passes through the axis of the jib pulley P. The hoisting- rope passes around the load pulley R, the jib pulley P, a pulley F and one of the pulleys M down to the jib pivot and the hoisting-drum S. The luffing- line L is fastened to the pulley F, and passes around another of the pulleys M to the pivot 0 and the luffing-drum D. A line Q is attached to a pulley N, and passes around the pulleys M, N and is secured to' the pulley F. The arrangement of ropes is such that the pull in the tension member always bears the same ratio to the weight of the load (three in this case) as the ratio of the length of the jib to the height of the crane post. The pulley N is connected to the crane post by a rope which passes over a rigid curve E constructed so that the resultant force on the jib passes through the jib pivot. Hence, no work is done when the jib is luffed, and the load therefore travels in an horizontal line. The movement of the jib about the pivot is balanced by a constant pull in the luffing-line, effected by a counterweight C. A geometric method of constructing the curve E is described in the Specification.