GB1262673A - Safe load monitoring system for material handling apparatus - Google Patents

Abstract

1,262,673. Safety devices for cranes. GROVE MFG. CO. 16 July, 1969 [19 Dec., 1968], No. 35921/69. Heading B8B. [Also in Divisions G4-G6] A safe load indicating system for a crane of the kind having an extensible boom pivoted on a supporting structure and an hydraulic ram for moving the boom vertically about its pivot, comprises a selector switch 52, Fig. 12, rotated through a worm gear and cable reel as the boom is extended to select one of twelve selector switches Al-A12, the wipers of which rotate together as the boom is raised and lowered, a further group of switches P is controlled by a pressure responsive mechanism connected to the hydraulic ram so as to be operated by different pressure ranges, the switches P connecting outputs of the selector switches A1-A12 to an indicating circuit in such a way that a lamp indicates when the moment of force, at a particular boom length and angle exceeds a safe level. A cam 59, Fig. 3, rotating with the boom is so shaped that the cable 62 running over it moves an equal distance for each increment of horizontal displacement of the end of the boom for different boom elevation angles. The other end of cable 62 is wrapped round a pulley, spring loaded against it. Shafts on the pulley carry the wipers 72. The pressure responsive mechanism comprises a spring loaded cylinder 80, Fig. 6, connected by a lever 95 and link 98 to a slider 100 acting as a cam to operate a series of the switches Pl-P24. The safe pressures for each angle and length of boom are calculated and connections such as 78, Fig. 12, made to these switches so that relay 108 is energized to light green lamp 117. If the safe pressure is exceeded the relay drops out and red lamp 121 is lit. A buzzer 122 may also sound and solenoid-operated valves 123-126 are actuated which prevent the crane being operated to move further beyond the safe limits. Specification 1,126,727 is referred to.