GB656083A - Improvements in or relating to safe-load indicators for cranes - Google Patents

Abstract

656,083. Safe load indicators for cranes. HAUSSER, P. C. G., JAMES, R...T., and AITKEN, R. L. Jan. 3, 1949, No. 112. [Class 78 (iv)] In a safe load indicator for a crane, a cable 11 tensioned according to the load passes from a pulley at the end of the jib over pulleys 12, 13 to an anchorage. The pulleys 12, 13 are mounted in carriers 9, 14 of which the former is pivoted at 17 to a fixed mast 10 of the crane while the latter 14 is pivoted at 18 to the former. Pivotal movement together of the carriers 9, 14 is resisted by the yielding member 19 of an indicating mechanism, while upward pivotal movement of the device as a whole about pivot 17 is limited by an abutment 30 on the carrier 9 which engages the mast 10. Downward pivotal movement of the device about the pivot 17 is restrained by the abutment of the spindle' 29 of pulley 13 on a pair of links 21 pivoted at 22 on a member 19 secured to the carrier 9 and abutting at 24 on the mast 10. Thus when the jib lies above a predetermined angle, the carrier 14 is pressed upwardly towards the carrier 9 by the cable 11 and a force which is independent of the elevation of the jib is applied to the member 19. When, however, the jib is at a lower elevation, the cable 11 applies to the pulley 12 a force tending to turn it downwardly about the pivot 17 and this force is dependent upon the angle at which the cable 11 meets the pulley 12; the resultant force on the member 19 depends also upon the position of the abutment 24. To enable the characteristics of the device to be altered, the abutment 24 is mounted on a plate 26 slidable along the links 21 and secured in any desired position by a bolt 27. In an alternative construction the links 21 are pivoted at their lower ends to a clevis bolt projecting from the mast 10, the abutment 24 being omitted, and, instead of the spindle 29, an abutment capable of sliding adjustment on the carrier 14 bears against the edges of the links 21. In this construction the abutment 30 is replaced by a stop which limits the pivotal movement of the links 21 relatively to the carrier 9.