GB743351A - Improvements in or relating to web tension control means - Google Patents

Abstract

743,351. Feeding webs. GOSS PRINTING PRESS CO. May 19, 1953 [Feb. 9, 1953], No. 14073/53. Class 100 (1). In a_tension control system for maintaining a desired tension in a running web 11 fed from a paper roll 12, a braking force is applied to the roll by a belt 20 peripherally engaging the roll and tension is applied to the belt by a fluid pressure actuator 21 supplied by a variable pressure regulator 40 having a control rod 41 and a control spring 42 therefor, the control rod being operatively coupled to a floating roller 50 which engages a loop 51 of the web and is biased for bodily movement in a direction to increase the size of the loop, a compensating cylinder 80 being connected to the output of the regulator to apply to the control rod a force equal and opposite to that exerted by the control spring. As shown in Fig. 1, the roll 12 is mounted on a spider 13 and the web 11 passes over rollers 15, 50, 54 prior to going into a printing press 10. The roller 50 is mounted on arms 52 pivoted at 53. Movements of the roller 50 in response to changes in web tension are transmitted to the control rod 41 of the pressure regulator 40 the output pressure of which is applied through a line 43 to the actuator 21 of the belt brake 20. The latter is anchored at its lower end to a spring 87. The force on the roller 50 due to the tension in the web 11 is opposed by the pneumatic pressure in a loading cylinder 55 acting on the arms 52 through a plunger 56. Compressed air from a line 30 is supplied to the regulator 40 and to the cylinder 55 through a constant pressure regulator 31. A further pressure regulator 60 and a gauge 62 calibrated in terms of web tension is arranged in the pipe 63 between the cylinder 55 and the outlet of the regulator 31. The pipes 34, 63 are provided with accumulators 35, 64 respectively. A restricted orifice 66 is arranged in the inlet to the cylinder 55 so that the movement of the floating roller 50 takes place at a controlled rate. The pressure regulator 40, Fig. 3, comprises an inlet valve 75 and an exhaust valve 72 operated by a diaphragm 70 loaded by the control spring 42 the force of which is adjusted by the control rod 41. The inlet valve 75 is connected to a balancing piston 78. The outlet chamber leading to the line 43 is normally connected to a diaphragm chamber 71 through pipes 68, 69 and a passage 67a in an emergency valve 67, Fig. 7. In an emergency, a solenoid 98 is energized either manually through an emergency switch 99 or automatically through a web break detector and the valve 67 is moved to a position in which the chamber 71 is cut off from the line 43 and connected to atmosphere through a valve passage 67b. The reaction of the control rod 41, Fig. 1, on the floating roller 50 and arms 52 is eliminated by the compensating cylinder 80 having a plunger 81 operative on the arms 52. The output pressure of the regulator 40 is applied to the cylinder 80 and the movement of the plunger 81 is arranged to counterbalance that of the spring 42 acting through the control rod 41. The movements of the floating roller 50 are limited by stops 85, 86. Means are provided for rapidly taking up the decrease in tension when the speed of the press is reduced. Such means comprise a spring 90 which on energization of a solenoid 91 is moved towards the arms 50 and is fully effective when the latter are in the lefthand portion of their range of-movement and progressively less effective as the arms 50 are moved to the right. The effect of the spring 90 is therefore to move the control rod 41 rapidly to a position in which the output pressure of the regulator 40 is increased and so also the braking action of the belt 20. The solenoid 91 is energized on closure of a spring-opened switch 96, Fig. 6, operated by the press motor controller 92 through rack and pinion mechanism 93 and a dashpot 94.