Yarn tensioning device
[ Apr. 1,1975  
 [ YARN TENSIONING DEVICE [75] Inventor: Joseph John Hurley, Paisley,  
 1 Scodand [73] Assignee: J &amp; P Coats Limited, Glasgow,  
 Scotland 22 Filed: July 31,1973  
  21 Appl. No.: 384,308  
 [30] Foreign Application Priority Data 5/1956 Vila Reyes 242/150 FOREIGN PATENTS OR APPLICATIONS 242,775 11/1925 United Kingdom 242/154 Primary Examiner-Stanley N. Gilreath Attorney, Agenhor Firm-John Lezdey [57] ABSTRACT An automatic yarn tensioning mechanism incorporates a yarn tensioning device which is arranged to apply a biasing force as a retarding force to a yarn. A yarn package carrier-is mounted in such a way and coupled to the yarn tensioning device that at least part of the total weight of the carrier and a yarn package carried thereon is applied as a control force opposing the biasing force of the yarn tensioning device. The yarn tensioning device&#39;and the yarn package carrier may incorporate pivoted levers connected by a link. Means for providing the biasing force may be a weight or a SpI&#39;lIlg. 1  
 31 C1aims,8 Drawing Figures YARN TENSIONING DEVICE The subject of this invention is a yarn tensioning mechanism for automatically tensioning yarn being withdrawn from a yarn package to compensate for changes in the force required to pull the yarn from the package so that the total tension in the yarn follows a predetermined pattern, for example, the tension may be required to remain constant as the package in unwound or may require to have arising or a falling characteristic as the package is unwound.  
  In drawing yarn from a cop-wound package the effort required to pull the yarn from the package increases progressively as the yarn is pulled from the package. This is because in the cop winding of yarn the yarn is laid on a core starting from one end in a series of superimposed cone-shaped layers. The layers first laid thus become compressed by the subsequently laid layers as the core becomes filled. There may also be other factors contributing to the variations in the force required. For example where the package has been previously wetted the normal natural drying action causes the moisture content of the yarn to become reduced progressively as yarn is removed from the package with consequent increase in the stiffness of the yarn. Also where as is customarily done yarn is withdrawn axially from the end of the package at which winding terminated the increase in the ballooning effect as the point of yarn withdrawal from the package moves towards the other end of the package increases the tension resulting from centrifugal force acting on the yarn. To maintain constant the tension in the yarn being withdrawn from a package, or to cause the tension to rise or fall progressively according to a predetermined pattern it is necessary to add some additional tension which varies in such a fashion that the total tension follows the desired pattern.  
  It is an object of the invention to provide an automatic yarn tensioning mechanism capable of sensing the amount of yarn on a package from which yarn is being withdrawn and applying to the yarn an additional tension which varies as necessary to provide the required pattern of total tension in the yarn.  
  An automatic yarn tensioning mechanism according to the invention incorporates a yarn tensioning device operative by application of a biasing force to it to apply a retarding force to a yarn passing therethrough, biasing means arranged to apply a predetermined biasing force to the yarn tensioning means, a yarn package carrier so mounted on a fixed support that at least part of the total weight of the yarn package carrier and a yarn package carried thereon is available as an unbalanced force, and means coupling the yarn package carrier to the tensioning device and arranged to transmit the unbalanced force available from the yarn package carrier to the tensioning device as a control force opposing the biasing force.  
  The biasing means may consist of a weight connected to the tensioning device. Alternatively the biasing means may consist of a spring connected to the tensioning device.  
  The weight or the spring may be connected directly to the tensioning device or may be connected by a lever system to the tensioning device.  
  The yarn package carrier may incorporate a lever mounted on a fulcrum and carrying means for mounting a yarn package on the lever, the lever being linked to the tensioning device. The lever may be counterbalanced so that the unbalanced force available from the yarn package carrier is constituted solely by the weight of a yarn package mounted on the carrier.  
  Alternatively at least part of the weight of the yarn package carrier is unbalanced so that the unbalanced force available from the yarn package carrier is derived from the unbalanced part of the weight of the yarn package carrier and the weight of a yarn package mounted on the yarn package carrier.  
  The biasing means may be arranged to tend to cause the tensioning device to tend to exert a predetermined maximum retarding force on yarn passing through the tensioning device or may be arranged to cause the tensioning device to tend to exert a minimum retarding force, which may be zero, on yarn passing through the tensioning device.  
  In one practical embodiment the yarn tensioning device includes a lever mounted on a fixed pivot, the lever being so operatively connected to the biasing means and the tensioning device that the biasing force exerted by the biasing means influences the retarding force applied by the tensioning device to a yarn passing therethrough, and the yarn package carrier incorporates a lever mounted on a fixed pivot, a link connecting the lever of the yarn package carrier to the lever of the yarn tensioning device, and means for carrying a yarn package fitted to the lever of the yarn package carrier. In this practical embodiment the yarn tensioning device and the fulcra for the two levers may be mounted on a common bracket attachable to the frame of a machine with which the mechanism is to be used.  
  Various embodiments of the invention are illustrated in the accompanying drawings in which:  
  FIG. 1 is a side elevation of the yarn tensioning mechanism of this invention;  
  FIGS. 2-6 are diagrammatic illustrations of various arrangements of the yarn tensioning mechanism and biasing means according to this invention; 1  
  FIGS. 7 and 8 are diagrammtic illustrations of further arrangements of the yarn package carrier according to this invention.  
  The arrangements illustrated in FIGS. 2-6 are not exhaustive of the possible arrangements of the yarn tensioning device and its biasing means falling within the scope of the invention.  
  In the drawings 1 denotes a fixed support clamped to a suitable part 2 of a machine with which the mechanism is to be used and 3 denotes a yarn package carrier incorporating a lever 4 pivoted at 5 to the fixed support 1 and connected by a link 6 to a point 6A on a lever 7 pivoted at 8 to the fixed support 1, the lever 7 carrying at the end remote from the connection of the link 6 a biasing weight 9 and at the end adjacent the connection of the link 6 the movable member 10 of a yarn tensioning device 11. The fixed member 12 of the yarn tensioning device 11 is supported on a bracket 13 clamped to the fixed support 1. The bracket 13 also carries the pivot 8. 14 denotes a yarn package carrier mounted on the lever 4 at a point between the pivot 5 and the connection of the link 6. In the practical construction illustrated in FIG. 1 the lever 4 is a lever of the third order and corresponds with that shown in the diagram of FIG. 7 while the lever 7 corresponds with that shown in the diagram of FIG. 2 and is a lever of the first order.  
  The diagram of FIG. 3 shows an arrangement in which the biasing weight 9 tends to reduce the tension provided by the tensioning device. The diagram of FIG. 4 shows a construction in which a spring 15 acts directly on the movable member of the tensioning device. The diagram of FIG. 5 shows a construction in which the spring operates through the lever 7 to increase the tension provided by the yarn tensioning device ll while the diagram of FIG. 6 shows an arrangement in which the spring 15 operates through the lever 7 to reduce the tension provided by the yarn tensioning device 11. The arrows l6 and 17 in FIGS. 2, 3, 5 and 6 corresponding with the arrows l6 and 17 in FIGS. 7 and 8 and show how the lever 4 of the yarn package carrier 3 can be arranged either as a lever of the third order or as a lever of the first order and applied to any of the constructions of FIGS. 2, 3, 5 and 6 to operate according to the invention.  
  In practice, the biasing means constituted by the weight 9 or the spring 15 applies a biasing force tending to cause the yarn tensioning device 11 to exert a predetermined maximum or minimum retarding force on yarn passing through the device. The weight of the yarn package 14 reduces as yarn is removed from the package so that the control force available to oppose the biasing force and exerted through the link 6 diminishes also as yarn is removed from the package. Referring to FIGS. 1, 2, 4 and 5 which show constructionsin which the biasing means tends to cause a maximum retarding force to be applied to yarn passing through the tensioning device 11, a reduction in the control force opposing the biasing force results in an increase in the retarding force exerted by the tensioning device 11.  
  Referring now to FIGS. 3 and 6 which show constructions in which the biasing means tends to cause a minimum, e.g., zero retarding force to be applied to yarn passing through the tensioning device 11, a reduction in the control force opposing the biasing force results in a decrease in the retarding force exerted by the tensioning device because in this construction the retarding force is obtained mainly or wholly from the control force.  
  As the retarding force exerted by the yarn tensioning device 11 on yarn passing through the device causes a tension in the yarn additional to that existing in the yarn resulting from the pull necessary to remove yarn from the yarn package 14 any desired pattern of tension can be arranged to occur in the yarn as withdrawal of yarn from the yarn package proceeds. For example as the pull necessary to remove yarn from the package increases progressively as yarn is removed from the package a constant tension in the yarn can be achieved by arranging the mechanism, e.g., by changing the weight 9 and/or altering the position of the point 6A, to reduce the tension generated by the tensioning device in such a way as to compensate more or less exactly for that resulting from the increasing pull required for withdrawal of yarn from the package. Alternatively the mechanism can be arranged to undercompensate or overcompensate to any desired extent for the increasing pull required for withdrawal of the yarn from the package thus providing a predetermined rising tension or reducing tension characteristic as yarn withdrawal proceeds.  
 What is claimed is:  
  1. An automatic yarn tensioning device incorporating a yarn tensioning means operative by application of a biasing force to it so as to apply a retarding force to a yarn passing therethrough, biasing means arranged for applying a predetermined biasing force to said yarn tensioning means, said yarn tensioning device including a first lever, a fixed pivot on which said first lever is mounted, said first lever being operatively connected to said biasing means and said tensioning means so that the force exerted by the biasing means tends to swing said first lever so as to apply a constant biasing force to the tensioning device, a second lever, a fixed pivot on which said second lever is mounted, a link connecting said first lever to said second lever, a yarn package carrier mounted on said second lever so that at least part of the total weight of said yarn package carrier and a yarn package carried thereon is available as an unbalanced force tending to swing said second lever so as to transmit the variable unbalanced force available from the yarn package carrier to said first lever as a variable control force opposing the biasing force generated by the biasing means.  
  2. A mechanism as claimed in claim 1 in which the fixed pivot on which said first lever is mounted is located between the ends of said first lever, the biasing means being connected to one end of said first lever and the tensioning device being connected to the other end of said first lever, and the fixed pivot on which said second lever is pivoted is located at one end of said second lever, the other end of said second lever is connected to said first lever of the yarn tensioning device, and the means for carrying the yarn package is located between the ends of said second lever.  
  3. A mechanism as claimed in claim 1 in which a common bracket carries the yarn tensioning device and the pivots on which said two levers are mounted, the common bracket being attachable to the frame of a machine with which the mechanism is to be used.