GB1308581A - Crane safety device - Google Patents

Abstract

1308581 Crane safety devices KATO SEISAKUSHO KK 18 May 1971 [18 May 1970] 15521/71 Heading B8B A control device for a safety device of a crane having a boom 7 of variable length and inclination angle comprises a three-dimensional cam 1 mounted for sliding movement along a shaft 19 in response to the length of the boom 7 sensed by a wire 15 wound on a spring drum 14 and attached to the jib head. Rotation of the drum 14 sets the position of the cam 1 along the shaft 19 through gearing 22, 21, shaft 20 and yoke 23. The angular setting of the cam 1 about the shaft 19 is by a pendulum 27 operating through gears 28, 29 integral with 30, and 31 (which can slide along the gear 30). The control device is contained in a housing 13 mounted on the boom 7 by a plate 18, so that inclination of the boom 7 causes the angular movement of the cam 1. The shape of the cam 1 is so determined by actual measurement that the cross-sectional shape at which a cam-follower 2 contacts the cam 1 is such that, at the maximum allowable load the displacement of the cam-follower 2 and the strain in the base of the boom 7 sensed by a bellows (42), Fig. 1 (not shown), are in appropriate correspondence and actuate a microswitch (5), Fig. 4 (not shown), in the crane safety device control circuit (not shown) operating an automatic circuit breaker or alarm. A second cam-follower 2a co-operates with a part of the cam 1 corresponding to the use of an auxiliary jib boom (not shown) detachably mounted in the extremity of the main boom 7.