Patent GB-769134-A (GB)
Title: Improvements in or relating to web tension control systems
Inventor: JR WILLIAM BAUMRUCKER
IPC: B65H23/08
Filed: 1955-04-29
Abstract: 769,134. Feeding webs, RESEARCH CORPORATION. April 29, 1955, No. 12481/55. Class 100(1) A web tension control system including a web roll and drive therefor comprises braking means between the web roll and a processing apparatus for controlling web tension between the braking: means and processing apparatus, loop-forming means disposed between the web roll and braking means which compensates for small sudden fluctuations in web tension, and means actuated by variations in web tension between the loop-forming means and braking means to vary the speed of the web roll drive. As shown, a supply roll 10, Fig. 1, supported for rotation on a shaft 12, is driven by at least one driving belt 14. The belt engages a driven pulley 16 and idler pulleys 18 and 20, the pulley 20 being pressed towards the roll 10 to maintain contact therewith upon reduction of roll diameter. The pulley 16 is coaxial with and driven by a V-belt pulley 22 driven by a V-belt 24 engaging a variable speed stepped pulley 26 on a driven shaft 28, preferably driven by a motor, not shown, which drives the machine being fed, e.g., a printing machine. A bell-crank lever 34, biased by springs 40, has a roller 38 engaging the web and a pulley 42 engaging the belt 24. Variation in web tension effects variation in tension of the belt 24, such that the belt either runs on a larger or smaller diameter portion of the pulley 26, thus altering the speed of the belt or belts 14. Small fluctuations in web tension, e.g. those caused by a non-circular supply roll 10, are compensated for by a loop formed in the web by vacuum, within an apertured U-shaped plate 50 over which the passes. The plate 50 is slightly longer than the web width and has smooth lateral edges. A conduit 54 having a control valve 56 communicates with a trough 48 secured to the plate 50. Tension in the web is indicated visually by a lever arm 68 co-operating with a scale 72; the arm 68 is counterbalanced by springs 70 and carries a roller 66 around which the web passes. The web is tensioned by passage over a suction box 76 communicating with a conduit 82, the top 78 of the box 76 being polished to reduce drag and provided with a slot 86 (Fig. 5, not shown) of chevron formation. As the web is drawn, by the machine, over the box 76 the web is held to the top 78 thus creating longitudinal tension proportional to the suction, while the chevron formation of the slot smooths the web laterally. Alternatively, the web may be tensioned by a pair of rollers driven through a variable speed drive by the machine. In a modification, the speed of a driving belt 14<SP>11</SP> Fig. 6, is controlled by a variable speed drive 216 having a hydraulically actuated control 220 operated by a lever 224 carrying a roller 38<SP>11</SP> engaging the web. In this case, the web is tensioned prior to entry into the machine, by air jets 248 directed on to a plate 242 over which the web passes, the tension imposed on the web being adjustable by valves 250. In a further embodiment (Fig. 7, not shown) a web-engaging roller 270 controls valves 292 and 294 through levers, these valves controlling the flow of fluid to a control motor 296. The motor 296 controls a variable speed drive for web roll-engaging belts, thus variations in web tension, as sensed by the roller 270, effect compensating variations in speed of the web supply roll.