GB1192311A - Web Tensioning Mechanism - Google Patents

Abstract

1,192,311. Feeding webs. HARRIS-INTERTYPE CORP. 8 April, 1968 [13 April, 1967], No. 16785/68. Heading B8R. Apparatus for maintaining constant the tension of a web W being fed to a printing, cutting, folding, or other machine comprises a driven feed roller 30 around which the web passes, a driving roller 28 rotated, e.g. by a motor, and a drive-transmitting roller 36 between the rollers 28, 30, the roller 36 having a resilient deformable covering 38 and being moved under the control of web-tension sensing means to vary the pressure between it and the rollers 28, 30 and thus vary the speed of the roller 30 to maintain the tension constant. The web passes from a supply roll 12 over an idler roller 25, around the roller 30 and a pinch roll 32 held against the roller 30 by its weight and the web tension, over an idler roller 26, a dancer roller 22 and an idler roller 27, to the machine. The journals 84 of the roller 22 are carried by resilient brackets 24. Each journal 84 is connected by a link 88 to a flap 80 situated between a pair of bleed nozzles 68b, 70b associated respectively with conduits 68, 70, the flap, link and nozzle arrangement being duplicated at each end of the roller 22. Pressure air is supplied from a source 62 to the conduits 68, 70 which are connected to chambers 44, 46 respectively on opposite sides of a diaphragm 50 in a casing 42. A rod 52 connects the diaphragm 50 to a lever 54 movement of which rotates an eccentric bearing 56 for the roller 36 so as to vary the pressure between the roller 36 and the rollers 28, 30. With a normal web tension, the roller 22 holds the flaps 80 centrally between the nozzles 68b, 70b so that the pressure in the conduits 60, 70 and chambers 44, 46 remains the same and no movement of roller 36 occurs. If the web tension increases, roller 22 moves to the right, Fig. 1, thus causing the flaps 80 to reduce the airpressure escape from nozzles and to increase the air pressure in the conduit 68 and chamber 44. At the same time, movement of the flaps 80 away from the nozzles 70b causes the pressure in the chamber 46 to be reduced. The consequent movement of the diaphragm 50 rotates the eccentric 56 so that the pressure between rollers 28, 36 decreases and that between rollers 30, 36 increases, thus increasing the speed of the roll 30 to compensate for the increased tension. A decrease in web tension causes leftward movement of the dancer roll 22 to increase the pressure in the chamber 46 and decrease the pressure in the chamber 44 to effect a movement of the eccentric 56 which will decrease the web speed. The duplication of link 88, flap 80 and nozzles 68b, 70b at each end of roller 22 is to ensure that, if the web tension is not uniform across the width of the web, the device operates in accordance with the average tension. The casing 42, the eccentric bearings 56 and a mounting for the roller 32 are carried by arms which can be pivoted upwardly for threading the web through the feeding arrangement.