Patent GB-545722-A (GB)
Title: Improvements in or relating to a web feeding mechanism
IPC: G03B21/32
Filed: 1941-09-19
Abstract: 545,722. Automatic control systems. KODAK, Ltd. Sept. 19, 1941, No. 12144. Convention date, May 22. [Class 38 (iv)] [Also in Groups XVI and XXIV] A photographic film or other web feeding or winding mechanism comprises a disc connected to the feeding or winding roller and a driving wheel frictionally engaging a face of the disc and movable laterally upon a change of tension in the web so that its plane is at an angle to the tangent to the driving circle of the disc through the point of contact of the disc and wheel, whereby the wheel is caused to move axially to a position nearer to or further from the axis of the disc to vary its speed and thus restore the tension to normal. In one form, Fig. 5, the web on its passage over guide rollers to a winding core 32, passes in horizontal loop form round a roller 20 which can move in a guide slot 21 in the frame 22. The normal tension of the web is determined by a weight 84 connected by a cable 85 to a block 81 which carries the roller 20 and is fixed to the upper end of a square section shaft 51 on which a driving wheel 50, frictionally engaging a disc 25 fixed to the spindle of the core 32, is slidably mounted. The shaft 51 is driven by bevel gearing from the shaft 77 of an electric motor and the shaft 51 can turn about the axis of the shaft 77 upon movement in either direction of the roller 20. As shown, the disc 25 is driven anti-clockwise. Upon an increase in web tension the shaft 51 is turned to the right and the plane of the wheel 50 is at an angle to the tangent to the circle on the disc 25 through the point of contact of the wheel and disc and a component of the driving force moves the wheel along the shaft towards the periphery of the disc to decrease the speed of the latter and thus decrease the web tension and allow the shaft 51 to return to its normal position. A similar action occurs if the web tension is reduced and in this case the shaft 51 turns to the left and the component of the driving force axially of the shaft 51 moves the wheel 50 towards the axis of the disc to increase the speed of the disc and the tension of the web. The wheel 50 comprises a rubber tyre 52 on a body part having a square bore engaging the shaft 51 and a tubular extension 54, Fig. 3, surrounding the shaft. To this extension is fixed a semi-circular block 55 to which is adjustably clamped a block 57 carrying a roller 62 engaging a face of the shaft 51. To resist the inward axial movement of the wheel on the shaft due to the weight of the wheel, rollers 65 are mounted in cam recesses 66 in the block 57 and engage the spindle 61 of the roller 62, the recesses acting to lock the rollers 65, 62 upon inward movement of the wheel, but allowing free rotation of those rollers upon onward movement of the wheel. The core 32 is mounted on a tubular shaft 38, Fig. 2, provided with a flange 39 having a pin 40 in driving engagement with a hole in the core. This shaft 38 is slidable, by means of a key and slot connection 42, on a stub shaft 35 having a flange 36 mounted in a recess in the disc 25 and operatively connected thereto by a one-way clutch device 45 which permits manual rotation of the core independently of the disc 25. A spring 43 holds the shaft 38 in normal position on the shaft 35 in which position the core is held by a spring ball 41. In a modification, Fig. 7, the web passes round a floating roller 102 carrying a finger 108 which, upon variation of the web tension, closes one or the other of two normally open switches 99, 99<SP>1</SP> in the circuits of two electromagnets 97. The block 81 on the upper end of the shaft 51 is provided with armatures 95 opposite to the magnets 97 so that the shaft 51 is turned towards the excited magnet, to act, as in the first construction, to restore the tension of the web to normal. When both switches are open, the shaft 51 is held in the normal position by springs 98. Specification 534,443, [Group VIII], is referred to.