Patent GB-1460466-A (GB)
Title: Method and winding unit for making a yarn package of cheese form
IPC: B65H54/52
Filed: 1974-02-06
Abstract: 1460466 Controlling pressure of yarn package against driving roll TOYODA JIDOSHOKKI SEISAKUSHO and DIAWA BOSEKI KK 6 Feb 1974 [9 Feb 1973 17 July 1973] 05405/74 Heading D1J A method of driving a yarn package by a friction roller comprises gradually decreasing the contact pressure from an initial value when commencing the winding operation to a final value when completing the winding operation, said contact pressure following a substantially exponential variation curve wherin the rate of pressure change is gradually reduced. In a first embodiment Fig. 6 the package 4 is mounted in a cradle 7a, 7b pivoted at 10. The cradle has a projection 11 acted on by two compression springs 6a, 6b. As the package increases in diameter the spring 6a first exerts a decreasing downward force on the package 4, this force reducing to zero when the package 4 reaches a size that causes the spring 6a to lie along the line Xa-Xa; and thereafter on the package continues to grow the spring 6a causes an increasing upward force on the package 4. Spring 6b, on the other hand, when the bobbin is empty, lies on the line Xb-Xb and exerts zero force on the bobbin. As the package increases in size the spring 6b exerts an increasing lift and thereafter a decreasing lift that reduces to zero as the package reaches completion. The strength of the springs 6a, 6b is such that their combined effect taken in association with the increasing weight of the package, is such as to produce a decreasing contact pressure between the package 4 and friction drive roller 2, the pressure following a substantially exponential variation curve with a rate of pressure change that is gradually reduced. Fig. 9 shows a modified embodiment in which a single spring 26 acts on a pivoted cam plate 21. The pivoted cradle 7a, 7b carries a roller 17 that rests on the cam plate 21. The cam plate 21 is so shaped that when the bobbin 3 is empty the contact pressure between the friction drive roller 2 and the bobbin 3 is supplemented by the force exerted by the spring 26. As the package commences to increase in diameter the effective supplementary force decreases until such time as a line connecting the pivot 10 and roller 18 is at right angles to the cam surface of the plate 21. At this stage the effective force of the spring 26 on the package 4 is zero. As the package continues to grow, the upward thrust of the spring 26 on the plate 21 commences to exert a lifting influence on the cradle 7a, 7b. The spring 6 and cam plate 21 are such as to produce the aforesaid rate of pressure change between the package 4 and drive roller 2. In a third embodiment, Figs. 17, 18, 19 a cradle 5 pivoted at 10 carries at 30 a bracket 31. A compression spring 36, pivoted at 34, is coupled to the bracket 31 at 29. Rigid with the cradle 5 is a circular cam 27 co-axial with the shaft 10. The bracket 31 carries a roller 33 on which the cam 27 rests. At the start of a winding operation, Fig. 17, the position of the cam 27 and bracket 31 is such that a downward thrust is exerted on the package 4, this thrust decreasing on the package increases in diameter until the parts assume the setting shown in Fig. 18 at which stage the effect of the spring 36 on the package is zero. Further increase in the size of the package causes the parts to move to a setting such as in Fig. 19 wherein the effect of the spring 36 is to exert an upward force on the cradle 5. The shape of the cam 27 and the plate 31 is such as to produce the aforesaid rate of pressure change between the package 4 and drive roller 2.