GB301202A - Improvements in luffing jib cranes - Google Patents

Abstract

301,202. Baker, G., Holliday, H., and Booth & Bros., Ltd., J. Nov. 28, 1927. Jib cranes.-In cranes in which the jib is balanced by a weight J on a lever H connected by a link G to the inner end E<1> of the luffing link D, approximately horizontal movement of the load during luffing is effected by passing the load rope M round sheaves 0 on the superstructure and P on the luffing arm as shown in Fig. 1. The guides for the slide E may be vertical, inclined, or curved. Luffing is effected by a crank disc K driven preferably by worm gearing. In modifications, the compensating pulley is carried by a radius rod pivoted on the crane structure and connected by a link to the luffing gear, and the point E<1> may move in a curved path. As shown in Fig. 2 the load rope passes over a pulley Q on an arm R pivoted at R<1> and moved by a link T pivoted at E' forming a toggle linkage with the luffing links D, G. The pulley Q may be at the point T' or any other point on the arm R, or on the link T. In Fig. 3 (not shown) the pivot R<1> is arranged low down on the crane structure and the link T is connected with the point G<1> instead of E<1>. In Fig. 4 (not shown) the inner end of the luffing link D moves in a curved guide, and in Fig. 5 (not shown), the pin E' is guided by a radius link. The balance weight J may be adjustable on the lever H. By suitably guiding the slide or roller E, the jib may be balanced approximately in all positions, but when the guides are vertical, Fig. 1, the jib is balanced only in an intermediate position to which it always tends to return.