Movement 253

253. Centrifugal check-hooks, for preventing accidents in case of the breakage of machinery which raises and lowers workmen, ores, etc., in mines. A is a frame-work fixed to the side of the shaft of the mine, and having fixed studs, D, attached. The drum on which the rope is wound is provided with a flange, B, to which the checkhooks are attached. If the drum acquires a dangerously rapid motion, the hooks fly out by centrifugal force, and one or other or all of them catch hold of the studs, D, and arrest the drum and stop the descent of whatever is attached to the rope. The drum ought besides this to have a spring applied to it, otherwise the jerk arising from the sudden stoppage of the rope might produce worse effects than its rapid motion.