GB681249A - Improvements in or relating to safety guards for power presses - Google Patents

Abstract

681,249. Machinery guards. BLISS (ENGLAND), Ltd., E. W., SMITH, W. J., VALLANCE, A. H. M., and UDAL, J. D. June 20, 1950 [March 21,1949], No. 7607 /49. Class 80 (iv). The starting of a power press by means of a fluid-pressure actuated clutch having an actuating cylinder 34, Fig. 3, controlled by a starting valve 36, which may be actuated electrically under control of a suitable push button, is further controlled by a switch 15, Fig. 2, in the electrical starting circuit and a pilot valve 29 which controls pressure fluid to a cylinder 31 to actuate inlet and exhaust valves 37, 38 to the clutch cylinder 34. The switch 15 and valve 29 are actuated through linkage 18, 17, 13, 12 and 9 from a cam groove 7, 8 on a vertically moving guard 1 so that unless the guard is fully closed the switch 15 is held open and the valve 29 actuated to exhaust the clutch cylinder 34 to prevent operation of the press. When the guard is closed the switch 15 is closed and lever 18 is moved longitudinally to allow a plunger 23 of the valve 29 to move into a hole 40 which conditions the system for starting on operation of the valve 36. The hole 40 in the lever 18 being engaged by the plunger 23 also prevents the guard being opened during the working stroke of the press. In order however to allow the guard to be raised before the press slide actually reaches its top position on the return stroke when it is stopped by the usual limit switch operated from the crankshaft the lever 18 is also controlled by a cam disc 20 on the crankshaft having low and high portions acting on a roller 19 on the lever. When the high portion is acting the lever 18 is raised and the plunger 23 is either raised to prevent actuation of the press or engaged in the hole 40 to prevent raising of the guard. When the roller 19 drops onto the low portion which is arranged to correspond to the return movement of the slide the lever 18 falls to release itself from the plunger 18 and thus allow the guard to be opened although the slide may not be quite at rest. The starting valve 36 may be directly operated by hand and the stopping of the press effected by the actuation of a valve by the cam device. The switch 15 is also replaced by a valve in this case.