| 摘要 |
833,525. Feeding webs. SPOONER DRYER ENGINEERING CO. Ltd. Nov. 12, 1957 [Feb. 9, 1957], No. 4498/57. Class 100(1) [Also in Group XXXIV] An apparatus for tensioning webs comprises a roller frictionally engaging a length of web, a shaft carrying the roller, one end of the roller being freely rotatable relatively to the shaft, a driving connection between the other end of the roller and the shaft, either the driving connection or the shaft being resilient, whereby the transmission of torque between the roller and the shaft adjacent the one end of the roller @ses a relative angular displacement between the one end of the roller and the adjacent shaft portion, and means for applying braking torque to the shaft to cause the angular displacement. As shown, a braked tensioning roller 19, Fig. 6, is supported at each end by end members 33, 36a freely rotatable on a shaft 30. The end member 36a is connected to one end 37 of a spring 38 attached to a collar 39 keyed to the shaft 30. A disc 34a carrying a pair of electrical contacts 40, 41, Fig. 7, is keyed to the shaft 30. Solenoids 46, 47 operating normally closed, valves 52, 51 respectively are connected through slip rings 45, 44 to the contacts 41, 40, respectively. Variations in tension exerted on web material, not shown, passing around the roller 19 causes relative rotation of the roller 19 and shaft 30, thereby causing a contact 42 on the roller to engage either contact 40 or thereby energizing solenoid 46 or 47. Energization of solenoid 46, as a result of an increase in web tension, causes valve 52 to open, thereby releasing air from a cylinder 50 having a piston which actuates a bell-crank lever 49 attached to a brake strap 28 engaging a brake drum 27 to decrease the braking action. Similarly, energization of the valve 51, as a result of a decrease in tension, causes valve 51 to open to admit air to the cylinder 50, thereby increasing the braking action applied by the strap 28. The cylinder 50 may be permanently connected to a reservoir vessel 53 so that large quantities of air have to be admitted or discharged from the cylinder 50 to effect a given movement of piston in cylinder 50. If the braking torque applied to the shaft 30 is high and the speed of the web 13, Fig. 3, passing around the roller 19 is low, the brake drum is connected to the shaft 30 by step up gearing 68 so that the drum 27 rotates faster than the shaft 30, thereby reducing brake snatch. The web 13 may be initially tensioned by reversely rotating the shaft 30 through worm and wheel gearing 70, a oneway clutch 69 being interposed be tween the brake drum 27 and its carrying shaft to permit this rotation. In a modification, Figs. 4 and 5 (not shown) intended for use when high web tensions apply, the spring 38 may be dispensed with; in this case torsional displacement of the shaft is magnified by a system of levers and gearing which is connected between the roller and disc on the roller shaft. The disc may be graduated for cooperation with a pointer fixed to the roller.
|
