GB419730A - Improvements in or relating to web roll controlling mechanism for printing or other machines - Google Patents

Abstract

419,730. Feeding webs. HOE & CO., Ltd., R., 109, Borough Road, London.- (Hoe & Co., Inc., R. ; 138th Street, New York, U.S.A.) May 15, 1933, No. 14100. [Class 100 (i).] Web-tensioning mechanism for printing &c. machines comprises friction means engaging the surface of the web roll, means operating independently of the tension of the web to cause the friction means to apply a normal pressure on the roll surface, to provide a normal running tension to the web, and a member held in a normal position by the web and adapted, when moved from its normal position by decrease of web tension, e.g. when the web breaks or the machine suddenly stops, to operate means acting mechanically to cause the friction means to press more strongly against the roll. In one form, Fig. 2, the roll R is controlled by four belts 10-13 anchored at their lower ends and wound upon drums 17-20 loose upon a fixed shaft 21 and urged by springs 23-26 in a direction to wind the belts thereon. The normal web tension may be provided only by the end belts 10, 13, the springs 24, 25 serving only to hold the belts 11, 12 taut. The additional tension is applied to the belts 11, 12 upon stoppage of the press or breakage of the web, by the falling of a drop roller 27, Fig. 4, normally supported by the web. The roller 27 is carried by a pair of arms 29 fast to a rockshaft 30 to which is secured a pair of brake sheaves 31, one for each belt 11, 12. Loosely mounted adjacent to each sheave 31 is a brake arm 34 to which the ends of a brake band 35 encircling the sheave are secured, one end by a spring rod 39. A link 44 connects the arm 34 with a pawl arm 45 loose on the shaft 21 and carrying a pawl 48 adapted to engage a ratchet wheel 50 fast with the drum of the belt 11 or 12. A stop screw 46 on the arm 45 normally holds the pawl disconnected from the ratchet wheel 50. When the roller 27 drops, the sheaves 31 are turned and, through the brake bands, arms 34, and links 44, turns the arms 45 to allow the pawls 48 to engage and turn the ratchet wheels 50, thus applying an increased pressure to the belts 11, 12. The movement of the shaft 30 may be controlled by a dash pot, and the weight of the roller 27 may be partly counterbalanced by an adjustable weight 62 on an arm 60 secured to the shaft 30. In a modification, Figs. 6 and 8, the normal tension is applied by belts 63 and spring drums 65 and the additional tension is applied by gripping devices adapted to grip and exert a pull upon the belts 63. Each gripping device comprises an arm 79 loose upon the rock-shaft 78 carrying the drop roller 72, and an arm 80 slidably guided on the arm 79 and having a slot engaged by a pin 83 on an arm fast to the shaft 78. When the roller 72 drops, the arm 80 moves along the arm 79 to grip the belt 63 and both arms move about the shaft 78 to exert a pull upon the belt. In a further modification, Figs. 12 and 14, normal tension is applied by one or more belts 851 actuated by spring drums 101, and the additional tension by one or more belts 85 actuated by a double spring drum device. The belt 85 is wound on a drum 108 containing a heavy spring 107 attached at its ends to the drum and to a sleeve 106 loose upon the shaft 95 and integral with a drum 105 containing a light spring 104 attached to the drum and to a sleeve 103 fixed to the shaft 95. The spring 104 normally holds the belt 85 taut. The rock-shaft 88 carrying the drop roll 86 has an arm 92 connected by a link 93 to an arm 94 carrying a pawl 98 adapted to engage ratchet teeth 100 on the drum 105. A stop 96 on the arm 94 normally holds the pawl disengaged from the teeth 100. When the roll 86 drops, the arm 92 operates the link 93 and arm 94 allowing the pawl to engage the teeth 100 and turn the drum 105 which thereby acts quickly through the heavy spring 107 to apply tension to the belt 85. An adjustable weight 111 is provided to partly counterbalance the weight of the roll 86.