GB744032A - An improved web tension controlling means for use in association with printing machines - Google Patents

Abstract

744,032. Feeding webs. HALLEY & SONS, Ltd., J., and HALLEY, A. M. Dec. 13, 1954 [Dec. 14, 1953], No. 31630/53. Class 100 (1). Apparatus for tensioning a web a comprises a tensioning roll e (Fig. 1) bearing upon a portion of the web between two positively driven rolls around which the web passes, the roll e being movable in accordance with the length of the web between the two positively driven rolls to determine the setting of an arm n which in turn determines the rotation of a control disc v (Figs. 4 and.5) for varying the speed of one of the positively driven rolls. The web a passes around a positively driven roll c, under the roll e, around idler rolls f, f<SP>1</SP> to the positively rotated feed rolls of a printing or like machine. The roll e is mounted in bearing blocks g adapted to slide up and down parallel guide tubes h. The blocks g are connected to a chain j. running round sprocket wheels k, k<SP>1</SP> and provided with variable weights j<SP>1</SP>. A pin g<SP>1</SP> on the block g is adapted to co-operate with one or other of a pair of contacts m, m<SP>1</SP> mounted on the arm n which is pivoted at n<SP>1</SP>. The upper end of the arm n operates a switch mechanism o and through a circuit determines the position of the armature of a solenoid p, the armature being linked to a rocker arm r. The roll c is driven from a V- pulley through a V-belt connection which also runs over a variable pulley t formed in two parts t, t<SP>1 </SP>which may be moved axially relative to each other so as to vary the effective diameter of the pulley. The pulley t is driven through a constant speed pulley u. The distance apart of the parts t, t<SP>1</SP> is determined by a rotatable screw threaded disc v which engages an externally threaded portion w<SP>1</SP> of the pulley shaft w. The disc v is adapted to be rotated by the action of a pawl x, oscillated by a lever y from the main machine drive, on ratchet teeth v<SP>2</SP> formed on the disc. The pawl x is controlled by the arm r. In operation, assuming that the roll c is rotating faster than the main machine drive rolls, the roll e on a block g will descend until the pin g<SP>1</SP> actuates the contact ml of the arm n so that the switch o is operated to position the arm r so that the pawl x rotates the disc v in a direction to decrease the effective diameter of the pulley t and thereby also drives the roll c. As the speed of the roll c slows down the roll c will rise until the contact m is actuated and the arm r operated to cause the pawl x to start increasing the effective diameter of the pulley t and thereby speed up the roll c. During operation the roll e continually rises and falls between the contacts m and m<SP>1</SP>.