GB853589A - Improvements in pneumatic web control device - Google Patents

Abstract

853,589. Band brakes; fluid-pressure brakes. WOOD NEWSPAPER MACHINERY CORPORATION. April 8, 1958 [Jan. 15, 1958], No. 11038/58. Class 103 (1). [Also in Group XVI] A pneumatic web-tensioning apparatus for controlling the tension of a web running from a supply roll comprises a floating roller engaged by the web, a variable-pressure control-valve actuated by the floating roller, a pressure chamber in the control valve, a reaction chamber in the control valve communicating with the pressure chamber, pressure-operated braking means in communication with the pressure chamber for braking the supply roll, and rate control means for varying the rate at which pressure is built up in the reaction chamber upon actuation of the floating roller. As shown, the tension of a web 4 is controlled by a roller 10 carried by arm 11, the arm being urged counterclockwise by a piston 12 within a cylinder supplied with air under pressure by a valve, the setting of which determines the initial web tension. The arm 11 rocks a lever 21 carrying a roller 32 through a link 20. The roller 32 engages a piston 30 slidable. inwardly of a housing 31 of a control-valve 9 against a spring 42 engaging-a diaphragm 40 secured to a tube 41. The spring 42 balances the weights of the roller 10 and arm 11 when the arm is inclined. A reaction chamber 44 is connected by a pipe 46 to a cylinder, not shown, which varies the force applied to a tension belt, not shown, engaging the periphery of a web roll. A valve 47 controls the rate of build-up of pressure, in the reaction chamber 44. Tube 41 has an exhaust valve seat 50 co-operating with a valve 51 on a stem 52 also carrying an inlet valve 53 cooperating with a seat 54, the valves being closed by a spring 55. The inlet valve supplies air under pressure from a pipe 57 via a pressurechamber 56 to a pipe 8 leading to the brake operating cylinder, not shown. A sudden increase in web tension causes the arm 21 to move clockwise thus allowing the piston 30 to move outwardly, while the tube 41 is also moved to the left by the diaphragm 40, thus opening exhaust valve 50 connected both to the brakeoperating cylinder and to atmosphere through the tube 41. Thus, the tension belt effects a reduction in braking effect and so web tension. Should the machine being supplied with web make an emergency stop, the roller 10 moves to the left, thus moving piston 30 inwardly against spring 42, thereby moving diaphragm 40 and tube 41 to the right. The inlet valve 53 opens to cause the brake-operating cylinder to increase the braking effect on the web roll. After a delay, dependent on the setting of valve 47, the pressure in reaction chamber 44 increases, thereby moving diaphragm 40 and tube 41 to the left to shut the valve 53. Specification 838,892 is referred to.