GB618369A - Improvements in or relating to safety devices for machinery guards or the like - Google Patents

Abstract

618,369. Machinery safety devices. WEBSTER, C. J., and ANSON, W. E. Oct. 28, 1946, No. 31936. [Class 80 (iv)] The guard or door of a machine is adapted to be locked in a closed position by the end 10a of a sliding bolt 10, Fig. 2, movement of which at the same time operates an electric switch or hydraulic valve 19 through a cam recess 15 and plunger 16 to close the power circuit of the machine ready for starting by the normal starting gear. The bolt is adapted to be operated by a handle 39 with a portion 39a sliding on a rod 40 and engaging behind an abutment 14 on the bolt 10, and in the closed position of the bolt the handle 39 is rotated slightly on the rod 40 to engage in a recess 41a in a rod 41 to lock the bolt in this position. When the machine is to be shut off the handle 39 is returned to its " off " position and the bolt 10 is returned to its unlatched position by a spring 13 under control of a delay device so that its initial movement opens the power circuit of the machine through the switch or valve 19 whilst a predetermined period of time elapses before the guard or door is released, to allow the machinery time to come to rest. The delay device comprises a train of gears 29-32, Fig. 3, controlled by an escapement device 33-36 and driven from the bolt 10 by a lever 25 and pawl 30 engaging a ratchetwheel 28, the drive being inoperative on the forward movement of the bolt. The delay device may alternatively comprise a hydraulic or pneumatic dashpot. A switch operable by the guard may also be arranged in series with the bolt switch to ensure that the guard is closed before the machine is started or a cam attached to the guard may engage the bolt when the guard is open to prevent it being latched.