GB416993A - Improvements in or relating to web tensioning devices - Google Patents

Abstract

416,993. Feeding webs. IGRANIC ELECTRIC CO., Ltd., 147, Queen Victoria Street, London, and MACKLEY, A. H., 15, Waterloo Road, Bedford. April 28, 1933, No. 12393. [Class 100 (i).] In a device for regulating the tension of webs drawn from web reels which are supported by a plurality of web-roll mountings provided with respective brake drums and brakes and each capable of being moved selectively to a given working position at which the web is to be drawn off, a common source of mechanical power other than that by which the web is drawn off is provided which is adapted to become operatively connected to the brake of each roll mounting only when the latter is moved to the working position. The spindles 1 of the reels 2 are mounted in a rotatable support 3 whereby any of the reels may be brought to a given web-supplying position in which the brake mechanism carried by each spindle is rendered operative under control of the web tension. The brake mechanism provided on each spindle comprises a pair of brake shoes 6, adapted to engage a drum 7 on the spindle but held therefrom by spring means ; each brake shoe is pivoted at 8 to a lever 9 pivoted at 10 to the support 3 and the ends of the levers 9 are pivoted to struts 11, the ends of which are pivoted together and carry a roller 13. The struts 11 are in the form of telescopic rods pressed apart by springs 12, so that when the roller 13 is moved towards the spindle 1, the compression of the springs 12 causes the brake shoes to be applied with a corresponding pressure. The roller 13 is engaged in the operative position of the spindle 1 by a Common cam 14 rotatably mounted on the axis 4 of the support 3, and biassed about the axis in such a direction as to apply the shoes 6 to the spindle 1 under the action of a torque motor 15, the action of which varies inversely as the tension of the web 5. Rheostats 16, 19 in the circuit of the motor 15 are provided with arms 17, each connected to one of the end bearings of a roller 18 which is spring-pressed against the web 5 so that as the tension varies the effective resistance in the motor circuit is suitably adjusted ; the two arms 17 are provided to compensate for non-central running of the web relatively to the roller 18, particularly when a narrow web is employed. The cam 14 is mounted on a toothed disc 20 freely supported on the axis 4 and in engagement with a pinion 21 on the motor shaft. A weight adjustably mounted on the disc 20 normally maintains the cam in a non-braking position but on starting the web feed, the motor 15 rotates the disc 20 in a clockwise direction to the position shown, when the brake is suitably applied and is thereafter automatically controlled. The cam 14 may be collapsed to an inoperative position when necessary and for this purpose it is composed of two curved links pivoted together, the end 21 of one link being pivoted to the disc 20, while the end of the other link is connected by a pin 22 through a link 23 to a lever 24, the pin 22 moving in a slot 27 in the disc 20. By moving the lever 24 to the dotted position, the cam is collapsed. The initial braking can be adjusted by varying the operative position of the spindle 1 and a paper-break switch may be incorporated serving to shortcircuit the resistance in the motor circuit and thus apply the maximum braking. According to the Provisional Specification, a slightly different form of brake mechanism is provided comprising brake-shoe carrying levers moving about a common pivot under the control of springs attached to pivoted arms which are spread to a greater or less extent by a cam surface mounted between them and rotated by a cam such as 14.