GB1153812A - Improvements in or relating to Devices for Controlling and Adjusting the Tension of a Web Fed from a Roll - Google Patents

Abstract

1,153,812. Feeding webs. CHAMBON Ltd. 1 June, 1967 [7 June, 1966], No. 25257/67. Heading B8R. A tension control device for a web 1 passing from a supply roll 2, through a first pair of feed rollers 3, 4 and a second pair of feed rollers 5, 6, comprises a looping roller 9 between a pair of rollers 7 and 8, the looping roller 9 being connected to a relatively heavy cylinder 13 adapted to roll on an inclined plane 14. The angle of inclination of the plane 14 is varied either manually or automatically, so as to vary the force exerted on the roller 9 by the cylinder 13, thereby varying the web tension. Feed rollers 3 and 4 are driven by a power shaft 21, via a differential 22, the output of which is controlled by a servomotor 23. The motor 23 is in turn controlled by photo-electric cells 24 and 25 detecting the length of the web loop formed by the roller 9. In the embodiment illustrated, the rollers 5 and 6 are printing cylinders, and registration marks m, on the pre-printed web are compared with a registration mark m 2 on the printing cylinder 5 by photo-electric cells 35 and 36. The error signal produced is used to control firstly the differential gear 32 driving the cylinder 5, and secondly the angle of indication of the plane 14 by means of a servomotor 15 to which energizing current is supplied from an integrating unit 39 connected to the output of a comparator gate 37. As an alternative, the looping roller 9 may be positioned above rollers 8 and 7 (Fig. 2). As a further alternative, the cylinder 13 is connected by a link (26, Fig. 3) to the roller 9 instead of the chain 11 passing over the sprocket 12.