GB500496A - Improvements in and relating to mechanism for registering intermittently advanced web by means of markings thereon - Google Patents

Abstract

500,496. Photo-electric control of webfeeding mechanism. INTERNATIONAL CIGAR MACHINERY CO. Aug. 17, 1937, No. 22559. Convention date, April 21. [Class 40 (iii)] Relates to machines for feeding strips or webs of paper or the like, particularly for wrapping articles with such material provided with recurrent designs or printed matter thereon, and consists in improvements in devices for controlling the intermittent feeding of the web by means of successive markings on the web co-operating with a detecting device such as photo-electric apparatus. According to the invention, there is provided a detecting device which, when it detects a marking on the web as it passes a predetermined point during a forward feeding movement of the web, causes or controls the operation of means separate from the detecting device, which means, after the completion of the forward feeding movement of the web, effects a backward movement to restore the marking to the saidpoint. The web W is fed by intermittentlydriven rollers 5, 6 which are geared together and driven by a shaft 7. A pinion 8, oscillated by a reciprocating rack 9, Fig. 1, or by an internally geared segment 36, Fig. 2, is integral with a disc 42 carrying driving pawls 43 which engage with a ratchet-wheel 44 keyed to the shaft 7. By this mechanism an intermittent forward drive of the web is obtained, the forward steps being equal and greater than the distance between successive markings provided on the web. The ratchet-wheel 44 is integral with a clutch disc 45, normally engaging a clutch disc 46, the latter being integral with a disc 50 adapted to be attracted to and held by a magnet 14 when this is energized. The disc 45 carries a laterally extending pin 52, connected by a spring 55 to a pin 54 on the disc 46, and normally held by the spring against a. second pin 53 on 46. Adjacent to the web is a detecting device 15, Fig. 1, comprising a casing containing a lamp 18 and a photoelectric cell 17. Below an aperture in the casing, markings M arranged, on the web at regular intervals pass, and in turn cause variations in the light reflected on to the cell. Each time a marking passes the aperture, the cell is affected so as to operate through an amplifier 22 a relay 23, which closes a circuit through the magnet 14, provided that cam-actuated contacts 24 have been closed. The action of the cam, which is driven by gearing from a shaft 13, is timed to close 24 shortly before a marking M arrives at the detector 15. When the marking causes operation of the relay 23, the magnet 14 is energized and a holding relay 27 is actuated to keep the magnet circuit closed until the contacts 24 are opened by the cam 25. Attraction of the disc 50 by the magnet, at the moment a marking M passes the device 15, disengages the clutch 45, 46, and the spring 55 is stretched during the continued forward feeding of the web which occurs as the disc 45 continues to rotate with the ratchet-wheel 44. At the end of this forward movement of the web, it is severed by a cutter 16, whereupon the pinion 8 and pawls 43 are reversed by the rack 9 or segment 36. The spring 55 then causes the disc 45 and ratchet-wheel 44 to follow this movement until the pin 52 is again in contact with the pin 53, backward movement of the parts 50 and 46 being prevented by a pawl 56. By this means the web is fed backwardly until the marking which had just passed the device 15 has been brought back beneath the aperture therein. At the end of the return movement of the pinion 8, the cam 25 allows contacts 24 to open, the magnet 14 is de-energized, and the cycle recommences. A one-way friction-brake 57 .. 60 prevents over-running of the shaft 7 at the end of each forward stroke.