GB531213A - Improvements in devices for protecting metal-drawing presses - Google Patents

Abstract

531,213. Machinery guards. OPEL AKT.-GES., A. July 14, 1939, No. 20525. Convention date, Aug. 12, 1938. [Class 80 (iv)] Stamping presses are provided with a safety device to prevent injury to the dies in the event of the metal fracturing during the operation in which case compressed air escaping through the crack lowers the pressure in the supply pipe and movement of a spring-loaded piston causes the operation of a visible or audible signal and may stop the press. The escaping air may actuate a siren. In the form shown the metal is most likely to crack at 6 and air is fed to this part of the punch by conduits 7 fed from a distribution channel 10, supplied at 8 with compressed air through a valve 9. A branch port 19 supplies a cylinder with a spring-loaded piston. Whenever air escapes at 7 the resulting drop of pressure enables the spring 16 to close switch 15, and if this occurs during the drawing stroke the drop B, C in a cam 23 rotating synchronously with the press shaft has also enabled a switch 22 to release and a signalling device such as a lamp 11 is actuated. The high part A of the cam opens the switch 22 and prevents the signal from being actuated during the up-stroke of the press on the down-stroke before the draw is sufficiently advanced to close the conduits 7. The switches are double acting and in the positions in which the signal circuit is broken they close the circuit through a solenoid 26 that maintains a switch 28 closed. The two solenoid switches are in parallel and consequently the switch 28 is maintained closed except when the alarm signal 11 operates. The press then stops and can be packed to remove the defective work before damage occurs to the dies.