GB412981A - Improvements in safe load indicators for jib cranes - Google Patents

Abstract

412,981. Jib cranes. BAKER, G., Greno House, Swinton, near Rotherham. Jan. 4, 1933, No. 300. [Class 78 (iv).] In a safe-load indicating device for a luffing crane, the hoisting or derricking rope passes over a pulley C which is mounted on a pivoted frame and is movable towards and away from the pivot of the frame under the control of a spring or equivalent device. The movement of the pulley under varying load and radius is transmitted to an indicator which gives the same reading when the crane is under maximum safe load at all positions of the jib. As shown in Fig. 1, the hoisting rope B between the jib-head pulley and the hoisting drum passes over the pulley C journalled in a frame E<1> having slots H which pivot upon and slide over a spindle G on the mast A. The frame E<1> turns about the spindle G so as to lie in the direction of the resultant of the forces in the parts B, B<1> of the hoisting rope, and it moves longitudinally against the resistance of a spring K until the resultant force due to the load is balanced by the spring. An extension M of the pulley spindle engages a quadrant N pivoted at O and connected to the indicator, and the quadrant is shaped so that the maximum safe load, varying with the radius, brings the pointer to the same position. The movement may be transmitted to the indicator from any suitable point of the frame E <1>, and in a modification, Fig. 5 (not shown), this point is to the right of the spindle G. In a modification, Fig. 4, the pivoted frame comprises a pair of toggle links E<2>, E<3> connected by a spring K<1>. In another modification, Fig. 6, the pivoted member N is replaced by a member N<2> fixed on the frame E<1> and engaging a lever N<3> connected with the indicator. Specification 405,653 is referred to.