Abstract:
A tension device is utilized for equalizing, or at least reducing differentials in tension across strands in a web. The device utilizes an overfeed roll which rotates faster than the speed of feeding the web. Strands at the desired tension, or less, slip about the exterior surface of the overfeed roll. Strands which are greater than the desired tension have sufficient friction to be rotated, at least temporarily, by the overfeed roll to thereby create slack in the higher tension strands to equalize the tension relative to the other strands. Feedback from feed rolls, support rolls, and/or the overfeed roll may be utilized to adjust the speed of the overfeed roll.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus which equalizes, or at least reduces differences in tension, among a web comprising a multiplicity of strands, and more particularly to an apparatus designed to overfeed tighter strands in order to loosen those strands with an overfeed roll. 
     Many industry segments utilize multiple strands of elongated elements in various processes. In some processes, multiple strands are preferably fed at a substantially uniform tension to reduce or prevent unwanted effects. Various industries including the carpet industry, textile industry, tire cord industry, and others have processes where multiple strands are preferably fed at substantially the same tension. In fact, some problems can occur when particular strands in a web are at a significantly higher tension than others. 
     In the carpet industry, a tufting machine is generally utilized to tuft yarn into a backing to produce carpet having pile extending from a surface. The tufting machine generally has a multiplicity of needles, each fed with a strand of yarn. The yarn strands are typically fed to the tufting machine from a creel. When fed from a creel, some of the yarn strands are closer to the tufting machine than others. Other yarn strands travel through a more tortuous path than others. Accordingly, the resistance to movement is greater among some strands than others. 
     When yarn strands are fed to a tufting machine, those which have a higher resistance typically exhibit a higher tension than some others. Additionally, resistance may vary at different times on strands for many different reasons. When a higher tension yarn is run through the tufting machine, undesired effects could include the tufting of loops which are not the same height as those from “looser” yarn ends. If one were attempting to tuft a particular level over a section of carpet, the presence of a higher or a lower loop could be noticeable and cause the carpet product to be rejected. In cut pile carpets such an effect could require excessive tip shearing. Accordingly a need exists to equalize tension across multiple yarn ends. 
     The typical approach in the carpet industry has been to try to control tension in the individual strands which are slack, or exhibit a low tension. Many patents are believed to be directed to devices which apply tension to lower tension yarn strands. For instance U.S. Pat. No. 908,255 shows a braking system which increases tension on lower tension strands. 
     Other tension control devices utilize two successive wheels where yarn is completely wrapped around both wheels. U.S. Pat. No. 5,957,359 provides yarn to a first wheel which has a greater diameter than a second wheel, about which the yarns then pass. The first wheel “supplies more length of fibre to the space between the wheels” than which passes over the second wheel (Col. 3, lines 23-35). Thus, all the tensions are raised at the first wheel, and then lowered between the first and second wheel due to the slightly slower speed of the second wheel. U.S. Pat. No. 4,087,956 appears to have somewhat similar double roll wrapped structure. 
     While many attempts have been made to equalize the tension, none are believed to be simple and effective. Accordingly, a need exists for an improved tension equalization device. 
     SUMMARY OF THE INVENTION 
     Consequently, it is an object of the present invention to provide a tension equalizing device for equalizing, or at least reducing the difference in tension, between multiple strands fed as a web. 
     It is a further object of the invention to utilize an overfeed roll to equalize tension by feeding tighter, or higher tension strands faster to thereby create slack in those strands. 
     It is another object of the invention to utilize gravity to assist with an overfeed roll to equalize tension across multiple strands. 
     Yet another object of the invention is to utilize an overfeed roll which contacts yarn along an arc of contact at the bottom half of the overfeed roll so that gravity and friction may assist in equalizing tension across a web. 
     Accordingly, an overfeed roll is positioned laterally to the direction of feeding of multiple strands. The strands contact the overfeed roll along a bottom portion of the circumference of the overfeed roll. Additionally, the arc which the strands contact the overfeed roll is preferably less than about two hundred and seventy degrees. As tighter strands are fed about the overfeed roll, the overfeed roll feeds these strands at a higher rate until they have similar slip characteristics as the looser strands. This is believed to be opposite of how almost every prior art device operates. Gravity may assist in pulling the strands away from the overfeed roll when the appropriate amount of slack is achieved in a high tension strand. 
    
    
     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 side plan view of a preferred embodiment of the tension device of the present invention; 
     FIG. 2 is a schematic of a second embodiment of a tension device; and 
     FIG. 3 is an electrical schematic for use with the second embodiment of FIG.  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a first embodiment of a tension device  10  such as may be utilized in conjunction with a tufting machine  12  and a creel  14 . While the tension device  10  illustrated is utilized to work with tufting machines, it is believed to have a wide range of applications including other textile industries, tire cord industries, fiber optic industries, and others. 
     The tension device  10  is comprised of an overfeed roll  16  having a circumference with an exterior surface  18 . Strands  20 , illustrated as yarn, are directed about a portion of the exterior surface  18  of the overfeed roll  16 . The overfeed roll  16  has a higher speed at its exterior surface than the speed at which the strands  20  are fed into the tufting machine  12  of course, for other industries, the tufting machine  12  would be replaced with another device, and the strands  20 , may or may not, be yarn. 
     As shown in FIG. 1, the strands  20  contact the exterior surface  18  of the overfeed roll  16  along a bottom portion of the overfeed roll  16 . The arc of contact is preferably less than two hundred seventy degrees, such as approximately one hundred and eighty degrees or the two hundred degrees illustrated in FIG.  1 . The arc of contact is also positioned so that very little, if any, of the contact is above the equator axis  22  illustrated. In FIG. 1, about five degrees of contact is illustrated at the left of the overfeed roll  16  above the equator axis  22  and about fifteen degrees of contact is illustrated at the right above the equator axis  22 . A limited, if any, amount of contact above the equator axis  22  is believed to assist in preventing yarn which is successfully overfed by the overfeed roll  16 , to continue to be overfed such as to create a significant amount of slack above the equator axis  22 . Specifically, it would be very undesirable for slack to accumulate on the top portion of the overfeed roll  16  and then continue around the top to make a complete loop as the strands  20  would then get caught up in one another. The exterior surface  18  is preferably a polished metal surface having relatively low friction as opposed to a surface such as sandpaper which would exhibit relatively high friction. 
     Gravity and friction are believed to play a part in the successful operation of the overfeed roll  16 . As the incoming yarn end  24  contacts the exterior surface  18  of the overfeed roll  16 , it remains in contact until it leaves as exiting yarn end  26 . If a particular yarn end, or strand  20 , is at, or below, the desired tension it will slip about the exterior surface of the overfeed roll. However, if the strand  20  is above the desired tension, the friction against the exterior surface pulls that strand  20  at a higher rate until the tension is at, or below, the desired tension. Gravity is believed to assist the process in acting downwardly, or pulling the strands  20  away from the bottom half of the overfeed roll  16 . Accordingly, any particular strand  20  can&#39;t be overfed significantly, since it will begin to slip off of the overfeed roll  16  as it is overfed and then will be at a lower tension. As the outgoing yarn end  26  is fed into machine  12 , even if the strand  20  had slipped completely off of the overfeed roll  16 , which is not believed to be likely, it would then be brought back into contact as it is pulled by a feed roll. 
     In order to facilitate operation of the overfeed roll  16 , support rolls  28 , 30  have been found helpful. The support rolls  28 , 30  have top portions  32 , 34  which are located at a higher elevation than the bottom portion  36  of the overfeed roll  16 . As illustrated in FIGS. 1 and 2, the support rolls are located completely above the overfeed roll  16 , but this need not be the arrangement in all embodiments. 
     Frame  38  may be utilized to support the overfeed roll  16  as well as one or more support rolls  32 . The support roll  32  may also be a feed roll, or a separate feed roll  40  may be utilized and/or connected to the frame  38 . A director  42  may receive stands  20  from the creel  14 . A load cell  44  may be placed upstream and/or downstream of the overfeed roll  16 . 
     FIG. 2 shows a schematic of a second embodiment of a tension device  50 . Once again, an overfeed roll  52  is positioned below two support rolls  54 , 56 . Downstream of the second support roll  56  are the feed rolls  58 , 60  which pull the web  62  of strands (similar as shown in FIG. 1) for further processing. Load cell  64  is illustrated as being connected to the second support roll  56 , but the load cell  64  could be connected to another roll or other object up against any, or all, of the strands in the web  62 . 
     The load cell  64  may measure the tension on any, or all, of the stands in the web  62 . The load cell  64  is illustrated as downstream of the overfeed roll  52  which has been found helpful in controlling, such as through controller  66  the speed of the overfeed roll  52 . Specifically, if the total tension experienced at the load cell  64  exceeds a selected value, the controller  66  may send a signal to increase the speed of the overfeed roll  52 . Conversely, if the tension at the load cell  64  is below a selected value, the controller  64  may send a signal to the overfeed roll  52  to slow down. 
     The controller  64  is also illustrated as communicating with one of the feed rolls  60 . This may be performed utilizing an encoder or tack feedback unit receiving a signal from the feed roll drive, such as at feed roll  60 . This has been found helpful for a number of situations including when the speed of the feed roll  60  is adjusted such as when starting, stopping, or other speed change event. Specifically, the overfeed roll  52  may be maintained at a set percentage, such as one hundred, twenty five percent, of the speed of the feed roll  60  during and through a speed change. 
     In the second embodiment, the tension device  50  has the overfeed roll  52  in contact with the web  62  only below the equator axis  68  at bottom portion  78  of overfeed roll  52 . It is illustrated as spanning an arc of less than about one hundred eighty degrees. Depending on the size of the overfeed roll selected, the amount of contact may be less than about one hundred degrees, less than about sixty degrees, or even about thirty degrees of contact. The arc of contact is primarily confined to the bottom portion of the overfeed roll  62 , and preferably does not extend above the equator axis  68  as illustrated in FIG.  2 . 
     FIG. 3 is second diagram which shows more of the electronic circuitry used with the tension device  50  of FIG.  2 . Specifically, the load cell  64  provides a signal, such as feedback, to controller  66 . Additional inputs to the controller  66  include a signal  70  from feed roll  60  shown in FIG.  2  and feedback signal  72  from the overfeed roll  52 . From the controller  66 , a signal is sent to the overfeed roll inverter  74 , which may physically be located with the controller or separate therefrom. Finally, a signal is sent to the overfeed roll motor  76  to drive the overfeed roller  52  at a desired speed. Desired speeds are greater than the speed of the feed roll  60 , preferably by at least ten, and more preferably at about twenty five percent faster than the speed of the feed roll  60  which is the speed of the web  62  as it is sent to a machine for processing with substantially equal tension across the web  62 . 
     Numerous alternations of the structure herein disclosed will suggest themselves to those skilled in the art. However, it is to be understood that the present disclosure relates to the preferred embodiment of the invention which is for purposes of illustration only and not to be construed as a limitation of the invention. All such modifications which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims.