GB420921A - Improvements in safe load indicators for jib cranes - Google Patents

Abstract

420,921. Jib cranes. BAKER, G., Greno House, Swinton, near Rotherham. June 28, 1933, No. 18414. [Class 78 (iv)] Relates to a safe-load indicator responsive to variation in the load and in the inclination of the job interposed as a unit in the derricking rope or other member of the derricking gear in which the tension varies with the load and with the inclination of the jib. As shown in Fig. 1, the device comprises a stirrup B and rod D connected with the tie-bar system at C and G, so as to compress a spring A between collars B<1>, D<1>. A dial.plate 1 weighted at W is pivoted at 8 on the stirrup B and carries a pointer 6 pivoted at 6<1> and connected by a link 5 with a lever 3 pivoted on the plate 1 at 2. One arm of this lever is formed as a quadrant bearing against a pin or roller 7 on the rod D, and the arrangement is such that the pointer 6 reaches the same position on the plate 1 when the specified maximum safe loads are on the crane at different inclinations of the jib. In a modification, Fig. 2, the dial plate 1 is rigid with the stirrup B and a lever 10 weighted at W is pivoted on the plate at 81 and is connected by a link 11 with a quadrantplate 31 pivoted to the pointer 6 at 2<1>, the pointer being pivoted on the dial-plate 1 at 6<1>. The quadrant plate 3<1> bears against a roller 7<1> on the rod D. In these forms an audible signal may be given by an alarm on the plate 1 or lever 10. In another modification, Fig. 3, the stirrup B and rod D are replaced by a pair of levers H, J pivoted together at K and forced apart against the action of the spring S by the tension on the derricking rope P which passes from the dead end O around a fixed guide N on the lever H, a sleeve L or a fixed guide on the pivot K, and a sleeve M on the lever J. Alternatively, the levers H, J, may be connected to the two parts of a divided derricking rope. In another modification, Fig. 4, the parts 10, 11, 31 of Fig. 2 are replaced by a pendulum W<1> pivoted on the stirrup B, a link 111, and a quadrant-plate 31 pivoted on the rod D and engaging a roller 7<1> on the pointer. The stirrup B, Figs. 1, 2 and 4, may be tubular and the indicator may be mounted on a frame free to turn on the stirrup and weighted to keep in one plane while the rope twists. The dial-plate 1, Fig. 3, pivoted on the lever H may co-operate with a pointer or a scale on the lever H or J to act as a radius indicator. Specification 405,653 is referred to.