safety-stop

Century Dictionary and Cyclopedia

1. n. On an elevator or other hoisting-apparatus, an automatic device designed to prevent the machine from falling in case the rope or chain breaks. In the accompanying cut, a is the hoisting-rope; b, bar or link by which the attachment of the rope to the elevator-frame g is made through the intervening bell-cranks c, carrying the sliding catches or pawls e; d, spring which, when the rope breaks, forces the inner ends of the bellcranks downward, and the catches e outward into engagement with the ratches f, thus immediately stopping the descent of the elevator.
2. n. In firearms, a device to lock the hammer in order to prevent an accidental discharge.
3. n. On a pulley or sheave, a stop to prevent running backward.
4. n. In a spinning-machine, loom, etc., a device for arresting the motion in case of the breakage of a yarn, thread, or sliver.
5. n. In a factory or mill, an apparatus by which the power can be shut off at the prime mover in case of accident in any department. In steam-plants the throttle may be closed by the fall of a weight, the weight being normally held up by a detent or catch which can be released by an electromagnet when a push-button or switch is thrown in any department. A brake may also be applied at the engine to shorten the time of the stop.
6. n. A device to shut off power from the engine in case the governing mechanism should fail or break and the engine start to run at excessive speed.
7. n. In sheet-metal work, an attachment to a press designed to arrest its motion by throwing the clutch, through which it receives power, out of gear in case the hand of the operator, in feeding the shells or blanks to the press, comes too near the dies for safety, or in case a shell chokes or jams the feed-motion or is wrongly presented to the dies. Safety-stops are also used in presses to prevent the descent of the plungers while the dies are being changed. Compare dial-feed.