Abstract:
A yarn tensioning apparatus is supplied with a yarn clamping position and a positive yarn engaging position to precisely meter yarns to tufting machine needles and especially to more uniformly advance pneumatically supplied yarns to hollow needles.

Description:
The present application claims priority to the Jul. 21, 2008 filing date of U.S. provisional patent application Ser. No. 61/082,311. 
    
    
     FIELD OF THE INVENTION 
     The present invention is addressed to more precisely feeding yarns for sewing fabrics, and is especially adapted to the feeding of yarns that are pneumatically supplied for tufting, as via a hollow needle. 
     BACKGROUND OF THE INVENTION 
     In most hollow needle tufting machines, as typified by Kile, U.S. Pat. No. 4,549,496; Davis, et al., U.S. Pat. No. 5,588,383 and Ingram, U.S. Pat. No. 7,318,383, yarns are selectively fed to hollow needles by pneumatic pressure. Where the yarn being fed to a particular needle is changed, Kile and Davis found it necessary to retract the previously fed yarn from the hollow needle and to pneumatically urge the newly selected yarn to extend through the hollow needle to the appropriate length for tufting. Due to the characteristics of yarns and the imprecise nature of pneumatically supplied yarn, the lengths of yarns tufted are generally not uniform and the resulting fabrics not only require tip shearing but also result in the waste of substantial amounts of yarn. 
     Accordingly, the need exists to obtain more uniform stitch height with pneumatically fed yarns. Due to the elasticity of yarns, when tension is released from a yarn being fed for tufting, there is a contraction of yarn length. Different yarns have differing elasticities so the contraction is not precisely controllable. Furthermore, the amount of contraction varies with the length of yarn that has been placed under tension. Therefore, a need exists to provide for the provide for the feeding of yarns, and particularly the pneumatic feeding of yarns, in a fashion where only a relatively short length of yarn is placed under tension when the yarn is fed. In this fashion, the contraction of the yarn will be limited when the tension is released. 
     Additionally, even in the case of yarns fed by conventional means, varying yarn elasticity contributes to less uniform output. For instance, varying tension in pulling yarns from a yarn supply, and the release of tension after yarns are cut or otherwise released from a hook or looper, may cause different yarns to produce yarn bights of different heights. 
     Furthermore, some pneumatic yarn feeds are designed to constantly urge yarns to their associated hollow needles. In the absence of a tensioning device, the yarns will be fed at an incremental rate toward the hollow needle. Therefore, a need exists to prevent the slippage of yarns that are not selected for the current stitch. 
     SUMMARY OF THE INVENTION 
     In order to accomplish these and other objects of the invention, an improved yarn feed control is provided with the teethed yarn puller wheels to positively grip and feed yarns. A yarn tensioning and clamping device is also provided that serves to keep yarns under tension while those yarns are being fed for tufting and that clamps the yarns when yarn feed tension is relaxed so that only a limited length of yarn may contract, and so that there is no slippage of yarns that are not selected for tufting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings in which: 
         FIG. 1  is a perspective view of a gear housing assembly with yarn clamping and yarn feed control components. 
         FIG. 2  is a partially exploded perspective view of the gear housing assembly of  FIG. 1 . 
         FIG. 3  is a side plan view of the gear housing assembly of  FIG. 1  mounted to the head of a tufting machine and engaged with a driven yarn feed roll. 
         FIG. 4  is a side plan view of the gear housing assembly of  FIG. 1  mounted to the head of a tufting machine in a position clamping a yarn against a tension bar. 
         FIG. 5  is a side sectional view of an array of gear housing assemblies attached to a tufting machine head. 
         FIG. 6  is a perspective view of a pattern control yarn feed system comprising an array of gear housing assemblies and driven yarn feed rolls. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIGS. 1 and 2  a gear housing assembly  10  designed to provide precise yarn feed and yarn tensioning control is illustrated. The principal elements of gear housing assembly  10  are coupling pins  24 , weight block  20 , mounting bar  11 , and teethed yarn roll  36 . These elements are carried in a structure comprising first side plate  16  and second side plate  17  with fasteners  31  that are received in fastener openings  30  located in top fastening block  25 , second fastening block  26 , third fastening block  27 , and bottom fastening block  28 . In addition, some fasteners  31  are received within openings  30   a  in bearing support  35 . 
     Turning then to the principal features of the gear housing assembly  10 , the coupling pins  24  extend upwards and operate in conjunction with a clevis  47  and clevis pin  48  illustrated in  FIGS. 3 and 4  to apply pressure at the top of the gear housing assembly on coupling pins  24 . Mounting bar  11  has vertical openings  12  which, as shown on  FIGS. 3 and 4 , receive fasteners  32  to mount the gear housing assembly  10  on the manifold beam  40  which, as shown in  FIGS. 5 and 6 , is in turn mounted in a frame  61  of pattern control yarn feed attachment  60  that is mounted to the head  62  of a tufting machine. At the end of the mounting bar  11  opposite the vertical openings  12  is a rounded end  13  and a lateral opening  14  that receives bearing pin  15  extending between the first side plate  16  and second side plate  17  and being received in plate opening  18  on the first side plate  16  and a similar opening in second side plate  17  as shown in  FIGS. 1 and 2 . The rounded end  13  permits the structure held by the first side plate  16  and second side plate  17  to rotate about 10 degrees in either direction. The slots  19  in cooperation with the lateral pins  21  permit the weight block  20  to move slightly forward and rearward relative to the first side plate  16  and second side plate  17 . The weight block  20  has at one end a yarn clamping area such as notch  23 . The gear housing assembly  10  also has a series of yarn guiding features such as apertures  29  in fastening blocks  25 ,  26 ,  27 ,  28  and yarn guide pins  22  on weight block  20 . 
     In  FIG. 3 , the gear housing assembly  10  is illustrated in operation to provide precise increments of yarn to associated needles. On support manifold  40  at the bottom is secured the mounting bar  11  of gear housing assembly  10 . Within the manifold are pressurized air conduits  49  that convey pressurized air to electronically controlled valves, not shown, that selectively supply air pressure to ports  43 ,  44  of air cylinder  42 . On the top of support manifold  40  is L bracket  41  which has an opening to receive the forward end of cylinder  42 . The forward end of cylinder  42  is threaded and fastened in place by securing bolt  45  on the opposite face of L bracket  41 . Air cylinder  42  is preferably a double acting cylinder with air supplied to port  44  to retract the cylinder shaft  46 , shown in  FIG. 4 . Conversely, pressurized air is supplied to port  43  to drive the cylinder shaft  46  forward. 
     In  FIG. 3 , the gear housing assembly  10  is shown with pressurized air having been supplied to port  44  so that cylinder shaft  46  is entirely retracted and clevis  47  is in proximity to cylinder mounting bolt  45 . Clevis pin  48  is positioned between coupling pins  24  and has moved the top portion of gear housing assembly  10  closer to the tufting machine head  62  while the bottom portion of gear housing assembly  10  carrying yarn roll  36  has pivoted about bearing pin  15  to extend outward and engage its teeth with the teeth of driven yarn roll  37  mounted on drive shaft  38 . The yarn  34  being fed from yarn supply, not shown, through vertical yarn guide openings  29  in fastening blocks  25 ,  26 ,  27  and  28  is carried between the interfitting teeth of yarn roll  36  and driven yarn roll  37  and securely gripped. In this fashion, a precise increment of yarn is advanced by the rotation of drive shaft  38  and corresponding driven yarn roll  37 . 
     It will also be seen that a stationary clamping member such as tension bar  51  is mounted with fastener  52  to angle  50  that connects back to support beam  40 . When the upper portion of gear housing assembly  10  is retracted toward the tufting machine head  62  as illustrated in  FIG. 3 , the lateral pins  21  of weight block  20  are positioned in intermediate portions of slots  19  so that the yarn  34  passing through notch  23  is tensioned only by the weight of block  20 . This allows the yarn to advance, when pulled by driven yarn roll  37  but the yarn advances in a tensioned state so that the longitudinal elasticity of the yarn is slightly expanded. Furthermore, in the course of feeding yarn from the yarn supply, there are occasional variations in tension as when yarn unwinding from a spool snags and then releases suddenly. The sudden release of tension sends a wave of excess yarn from the yarn supply to the pattern control yarn mechanism. The pressure provided by weight block  20  is sufficient to prevent the excess yarn  34  from feeding prematurely toward the needles. 
     In  FIG. 4 , pressurized air is supplied to port  43  of double acting air cylinder  42  so that cylinder shaft  46  is extended and the top portion of gear housing assembly  10  is moved away from the tufting machine head. The lower portion of gear housing assembly  10  carrying yarn roll  36  is pivoted about bearing pin  15  to move closer to tufting machine and out of engagement with driven yarn roll  37  so that yarn  34  is no longer advanced. However, it can be seen at the upper end of gear housing assembly  10  that the lateral pins  21  of weight block  20  are at the upper most pins of slots  19  in first side plate  16  so that the pressure brought on yarn  34  as it passes through notch  23  is not merely the weight of block  20 , but is instead the pressure applied by the action of pressurized gas through port  43  in air cylinder  42 . The yarn can thereby be pinched relatively securely between tension bar  51  and the yarn clamping portion of weight block  20 , namely in the notch  23  of the illustrated embodiment. 
     Therefore, in operation, a gear housing assembly  10  is provided for each yarn that is being fed to a needle on the associated tufting machine. In the case of a hollow needle tufting machine, this generally means that six or eight gear housing assemblies are provided for each needle to feed the yarns downward into funnel slots such as are disclosed in Ingram, U.S. Pat. No. 7,318,383. To provide adequate space for this number of gear housing assemblies, yarns may be supplied from both the front and rear side of the tufting machine. In the case of a hollow needle tufting machine with eight yarns supplied to each of the funnel slots, it would typically be advantageous to mount four gear housing assemblies  10  on each side of the tufting machine. When the tufting machine is in operation, only one of the eight gear housing assemblies will be in the yarn advancing position illustrated in  FIG. 3  and the remaining seven gear housing assemblies would be in the yarn clamping position illustrated in  FIG. 4 . When it is desired to switch the yarn being supplied to the associated needle, the gear housing assembly  10  in the yarn supplying configuration of  FIG. 3  is operated by the application of air pressure to port  43  of air cylinder  42  to disengage yarn  34  and yarn roll  36  from the driven yarn roll  37  and to simultaneously clamp the yarn  34  between the tension bar  51  and weight block  20 . The action of the weight block  20  and the clamping action performs two functions that appear to improve the preciseness of the yarn feed: (1) to prevent the elasticity of the yarn between the yarn supply and the yarn clamping area  23  to substantially alter the length of yarn that has already passed between the position of the yarn rolls; and (2) to prevent the unintended advancement of yarns either by the reciprocating motion of the hollow needle assemblies or by the pneumatic urgings applied to the yarns generally so that they feed freely from the yarn supply to the needles. 
     When the yarn being supplied to needles is changed, just as the gear housing assembly  10  of the previously supplied yarn is rotated out of the supplying position of  FIG. 3 , the gear housing assembly  10  of the newly selected yarn is rotated from the clamping position of  FIG. 4  to the yarn supplying position of  FIG. 3  by the application of pneumatic pressure through port  44  of double acting cylinder  42 . The yarn  34  is unclamped and advanced by the positive cooperation of driven yarn roll  37  and yarn roll  36 . Due to the clamping action between tension bar  51  and notch  23  of weight block  20 , the only length of yarn not already tensioned when the yarn advancement begins is the length of yarn between the yarn clamping point  23  and the mating gear teeth of yarn rolls  36 ,  37 . In this fashion, the operation of gear housing assembly  10  facilitates relatively precise metering of yarns to hollow needles and minimizes height irregularities in the resulting tufted fabrics. This results in less wasted yarn and the ability to produce a finished product with limited tip shearing so that the tufting height of the yarns can be only slightly greater than the intended height of the finished tufted carpets. 
     Furthermore, the effectiveness of the present yarn control system is such that in the context of a tufting machine with yarns fed by pneumatic pressure to hollow needles, in step of yarn retraction is not required. Instead, the leading end of the yarn after being cut is allowed to remain within the hollow needle. Due to the elasticity of the yarn, there may be a slight retraction of the leading end of yarn from the open tip of the hollow needle after the fed yarn is cut, however, the secure clamping of unfed yarns allows the leading ends of those yarns to remain within the hollow needle without resulting in subsequent underfeeding or overfeeding of the yarns. 
     In  FIGS. 5 and 6 , an array of gear housing assemblies  10  are illustrated in a frame  61  optimized to supply six yarns to each hollow needle. The frame  61  is mounted to the head  62  of a tufting machine. A manifold  82  is provided to convey pressurized gas across the width of the tufting machine. The pressurized gas is provided from ports  81  of manifold  82  to ports  83  of the support manifolds  40  and thence through electronically activated valves to air supply ports  43 ,  44 . To complete the array of  FIG. 6 , preferably independently operable servo motors would be associated with each drive shaft  38  for the driven yarn rolls  37 . Both the servo motors and electronically activated air valves are controlled by an electronic controller interpreting pattern data and supplying control commands via electronic signals distributed across an appropriate controller network 
     All publications, patent, and patent documents mentioned herein, and particularly Davis, et al., U.S. Pat. No. 5,588,383 and Ingram, U.S. Pat. No. 7,318,383, are incorporated by reference herein as though individually incorporated by reference. Although preferred embodiments of the present invention have been disclosed in detail herein, it will be understood that various substitutions and modifications may be made to the disclosed embodiment described herein without departing from the scope and spirit of the present invention as recited in the appended claims.