Patent GB-1078696-A (GB)
Title: Improvements relating to tension sensing devices
IPC: B65H59/34
Filed: 1964-09-21
Abstract: 1,078,696. Automatic tension control. S. HEIM. Sept. 21, 1964 [Sept. 21, 1963; March 20, 1964], No. 38495/64. Heading G3R. [Also in Division D1] A device for sensing the tension in a yarn comprises three guides over which the yarn passes to form two sides of a triangle, Fig. 1. The centre guide can move transversely of the yarn and is subject to a force derived from the tension of the yarn which tends to move the guide to increase the angle between the two sides of the triangle and which decreases as the angle increases. The guide is also subject to an electromagnetic force which opposes the force derived from the tension. The geometric, mechanical and electromagnetic characteristics of the arrangement are such that for a given tension on the yarn, the guide is in equilibrium over a range of positions. The device may be used to keep the tension in a running yarn constant, or to relate it to the growth of a take-up package. To this end, it may regulate the speed at which the yarn travels, or it may regulate a brake which may be of the grid or disc type or be of the kind when the yarn wraps a driven member, the speed of the drive being varied according to the degree of braking required. In Fig. 1 the electromagnetic force acting on the centre guide is derived from an armature of a solenoid 15 which, for a given current in the solenoid, exerts a force varying according to the extent to which the armature is withdrawn from the winding. As the guide moves with changes of tension, a member 17 moves to obscure to a greater or less extent a light-sensitive cell 18. Instead of a light-sensitive control, a heatsensitive or capacitative or inductive device or a potentiometer may be employed. According to its condition the cell 18 regulates, through a transistorized amplifier circuit Fig. 10 (not shown) the current in a solenoid, the armature of which is connected through leaf springs Fig. 9 (not shown) to the movable part of a yarn-brake. When the yarn brake is actuated to correct for a change in tension, the correction applied wholly covers that necessary to restore the tension to its proper value, in the sense that it does not include an element corresponding to the force necessary to maintain the guide in equilibrium, as would be the case if the arrangement were not such as to provide a range of positions over which the guide is in equilibrium. The amplifying circuit is such as to establish a minimum tension at start-up and to damp vibrations of the amplifier output. Damping means are also provided for the guide and the yarn-brake. The working-tension may be established from a central point for a number of working positions by a potentiometer Fig. 10 (not shown) which is adjustable to vary the current in the solenoid (15). Where it is desired to vary the tension during the winding-up of the yarn, the laying-guide is mounted on an arm pivoted to a shaft which is rotated slowly as the guide moves with the growth of the package, and through gearing moves the contact of a potentiometer Figs. 6, 12 (not shown) controlling the current in the solenoid 15.