Movement 278

278. C. R. Otis’s safety-stop for the platform of a hoisting apparatus. A are the stationary uprights, and B is the upper part of the platform working between them. The rope, a, by which the platform is hoisted, is attached by a pin, b, and spring, c, and the pin is connected by two elbow levers with two pawls, d, which work in ratchets secured to the uprights, A. The weight of the platform and the tension of the rope keep the pawls out of gear from the ratchets in hoisting or lowering the platform, but in case of the breakage of rope the spring, c, presses down the pin, b, and the attached ends of the levers, and so presses the pawls into the ratchets and stops the descent of the platform.