GB1053557A - - Google Patents

Abstract

1,053,557. Photo-electric machinery guards. VICTORY-KIDDER PRINTING MACHINE CO. Ltd. Oct. 15, 1963 [Oct. 15, 1962], No. 38965/62. Heading F2J. The correct working of a photo - electric guard for a guillotine is checked automatically during each working cycle of the machine. A light curtain provided in front of the guillotine blade 2 by lamps 5 shining on to photo-electric devices 6 is so located that it will not be interrupted by e.g. a stack of paper positioned for cutting beneath the blade 2. A power supply 10b energizes the lamps 5 through a transformer 27, and the devices 6 through a transformer 18 and a rectifying and smoothing circuit 19. A transistor 20 is in series with the devices 6 and in parallel with a relay 21. A control relay 13 is energized to close a holding switch 13a and to cause the release of a brake and engagement of a clutch to drive the machine, from a supply 10a through push-button starter switches 11 and a stop switch 12, the holding switch 13a and a micro-switch 14, which is opened to stop the machine when the blade 2 reaches top dead centre, being in parallel with the switches 11. Closure of the switches 11 also closes contacts 16a and opens contacts 16b of a switch 16. Interruption of the light curtain causes at least one device 6 to become non-conducting, upon which the relay 21 is energized to move a switch 21a out of the position shown in Fig. 4 to deenergize a relay 24, allowing switches 15, 16a to open to de-energize the relay 13, stopping the machine. The switch 16 can be reset only by a key-holder, e.g. a foreman. Testing of the photo-electric devices takes place preferably with the blade 2 at rest at top dead centre, under the control of three rotary cams 7a-7c. The cam 7a closes a switch 8a to maintain energization of the relay 24. The cam 7b opens a switch 8b to deenergize the lamps 5, which should cause the devices 6 to become non-conducting and the relay 21 to be energized, to move the switch 21a to the position in which it energizes a relay 23, in parallel with a switch 8c, which latter is then opened by the cam 7c. If the switch 21a has not been moved to hold energization of the relay 23-indicating a fault in the protecting circuit-the resultant de-energization of the relay 23 opens contacts 23a to de-energize the relay 24, to stop the machine. If the switch 21a has been correctly operated, the cams complete their rotation, returning to their starting positions the switches 7c, 7b, 7a, in that order.