Abstract:
An apparatus and method for unwinding yarns with: (1) a drive roll with a polished metal finish to ensure good fiber/metal contact; (2) a drive roll/separator roll combination that enables multiple wraps of yarn on the drive roll; (3) pivoting yarn holding arms for the active and standby packages that provide for easier access to the packages on a frame; and (4) in combination with the pivoting yarn holding arms, one or more pivoting legs extending from a frame so that the apparatus has a relatively small footprint and simplified yarn threading/string-up as compared to background art OETO apparatus.

Description:
FIELD OF THE INVENTION 
     The present invention relates to yam unwinding devices, and more specifically to a method and apparatus designed to continuously deliver as-spun over-end-take-off yarn to manufacturing equipment. 
     BACKGROUND OF THE INVENTION 
     A background art example of a method for unwinding of yarns from a creel is the over-end-take-off (OETO) method. The OETO method allows for continuous operation of the unwinding process since the terminating end of the yarn of an active package is attached to the leading end of the yarn of a standby package. In the OETO method, after the active package is fully exhausted, the standby package becomes the active package. However, a drawback of the OETO method is that unacceptable yarn tension variations can occur during the unwinding process. 
     A background art example of a system and apparatus that implements the OETO method was disclosed in Research Disclosure, p. 729, November 1995, item #37922. In particular, the disclosure describes an OETO system that elastomeric fibers are passed through before being fed to a manufacturing line. The OETO system of the disclosure has a rack structure that holds the creels of active packages and standby packages, a relaxation section and motor driven nip rolls. The relaxation section is located between an active package and the nip rolls of the OETO system. The relaxation section helps to suppress the unacceptable yarn tension variations discussed above by providing some slack in the yarn being unwound. 
     However, background art OETO systems that include such a relaxation section have problems with fibers or yarns that exhibit high levels of tack (i.e., yarns having particularly high cohesive forces). Moreover, yarns with high levels of tack also display unusually high variations in frictional forces and yarn tension levels as the active package is unwound from the creel. 
     In addition, the slack in the yarn provided by the relaxation section can vary, and excess yarn can be unwound from the active package. This excess yarn can be drawn into the nip rolls and wound upon itself leading to entanglement or breakage of the yarn. Use of yarns with high levels of tack further contributes to the possibility of the excess yarn adhering to itself and to the nip rolls. The entanglement or breakage of yarns during the unwinding process requires the manufacturing line to be stopped, delays the unwinding process and increases the cost of manufacturing. 
     Background art OETO apparatus are typically configured such that the yarn horizontally traverses the relaxation section. In this configuration, the yarn travels through nip rolls with axes that are vertical. However, with such a vertical configuration for the axes of the nip rolls, the yarn located in the relaxation section between the active package and the nip rolls tends to sag. As a result, the yarn position on the nip rolls can become unstable, and interference and entanglement can occur between adjacent yarns. Each of these problems would require the manufacturing line to be stopped. 
     Furthermore, some manufacturing applications (e.g., diaper manufacturing) require the use of as-spun fiber that is substantially finish-free. Such finish-free yarns also exhibit the problems associated with high levels of tack discussed above. 
     The problems discussed above make applying OETO methods and apparatus particularly difficult when processing yarn with a high level of tack. Background art OETO apparatus have attempted to address these problems in the unwinding process by: (1) using yarns with anti-tack additives applied prior to winding; and/or (2) using rewound packages, where an active package is unwound and then rewound on a different creel to create a rewound package. Both of these approaches add additional expense to the manufacturing and unwinding processes. 
     As a result of the problems discussed above, OETO apparatus of the background art have been designed to take into account the difficulties due to the relaxation section, high levels of tack and breakage in yarns unwound with the OETO method. As an example, U.S. Pat. No. 6,676,054 (Heaney et al.) discloses an OETO method and apparatus for unwinding elastomeric fiber packages with high levels of tack from a package. In particular, the OETO apparatus of Heaney et al. requires that a minimum distance exists between a fiber guide and the fiber package. In accordance with Heaney et al., minimum distances less than 0.41 meter can result in undesirably large tension variations. These variations can cause process control difficulties and can also lead to yarn breakages. Further, in accordance to Heaney et al, distances longer than 0.91 meter make the unwinding equipment less compact and ergonometrically less favorable. As the level of tack exhibited by the fiber increases, the minimum allowable distance, d, increases. For yams with tack levels greater than about 2 grams and less than about 7.5 grams, d is preferably at least about 0.41 meter; and for fibers with tack levels greater than about 7.5 grams, d is preferably at least about 0.71 meter. 
     However, due to such minimum distance and other requirements for high tack yarns, OETO apparatus typically requires a frame with a large footprint that can take up significant floor space in a manufacturing environment. 
     Therefore, there is a need in the art for an OETO apparatus for unwinding yarns with high levels of tack that avoids the problems of entanglement, breakage and increased manufacturing costs of the methods and apparatus of the background art. Moreover, there is a need in the art for an OETO apparatus for unwinding yarns with anti-tack additives that can be implemented in a relatively small footprint. 
     SUMMARY OF THE INVENTION 
     The present invention is an apparatus for unwinding yarns with: (1) a drive roll with a polished metal finish to ensure good fiber/metal contact; (2) a drive roll/separator roll combination that enables multiple wraps of yarn on the drive roll; (3) pivoting yarn holding arms for the active and standby packages that provide for easier access to the packages on a frame; and (4) in combination with the pivoting yarn holding arms, one or more pivoting legs extending from a frame so that the apparatus has a relatively small footprint and simplified yam threading/string-up as compared to background art OETO apparatus. 
     One embodiment of the present invention is an apparatus for continuously unwinding yarns that has a frame with at least one pivoting leg connected to the frame; a drive control assembly, preferably attached to the frame and configured to continuously unwind yarns from one or more active packages; an electrical control box preferably attached to the frame and electrically connected to the drive control assembly; two or more pivoting yam holding arms attached to each pivoting leg; and first yarn guides attached to the frame. The pivoting legs of the frame are located at acute angles relative to the frame so that they may be adjusted to provide a small apparatus footprint to take up less space in a manufacturing area. The first yam guides are separated from the active packages by a minimum distance, preferably at least 0.34 meters. 
     Another embodiment of the present invention is a method for unwinding yarns continuously comprising: (a) holding an active package on a pivoting arm such that at least one yarn can unwind from the active package in a direction defining an acute angle with the rotational axis of the active package; (b) unwinding yarn from the active package of step (a) at a controlled predetermined rate; (c) controlling the direction of said yarn of step (a) by passing the yarn through first yam guides; and (d) controlling the minimum distance (d) from said first yarn guides to the end of said active package facing said first yam guides, measured on a line defined by the rotational axis of the active package, such that said distance (d) is equal to:
         i. at least about 0.34 meter for yarns with tack of greater than about 2 grams OETO and less than about 7.5 grams OETO; or   ii. from about 0.71 meter to about 0.91 meter for yarns with tack greater than about 7.5; (e.) controlling an angle (θ), defined by the intersection of imaginary lines corresponding, respectively, to the rotational axis of the active package and the central axis of said first yarn guide that is perpendicular to the plane of the orifice, such that said angle (θ) is equal to:   i. 0° to about 30° for yarns with tack greater than about 2 grams OETO and less than about 7.5 grams OETO; or   ii. 0° to about 10° for yarns with tack levels greater than about 7.5 grams OETO.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Several embodiments of the invention will now be further described in the following more detailed description of the specification when read with reference to the accompanying drawings in which: 
         FIG. 1  is an exemplary perspective view showing an OETO apparatus for continuous unwinding of yarns; 
         FIG. 2  is an exemplary top plan view of the apparatus for unwinding yarns shown in  FIG. 1 ; 
         FIG. 3  is an exemplary detailed view of the drive control assembly; 
         FIG. 4  is an exemplary detailed perspective view of the path of the yarn through a guiding system that passes the yarn from the active or standby packages to the drive roll; 
         FIG. 5A  is an exemplary exterior view of the electrical control box; 
         FIG. 5B  is an exemplary interior of the electrical control box; 
         FIG. 5C  is an exemplary schematic diagram of the electrical control box; 
         FIG. 6A  is an exemplary perspective view showing an OETO apparatus for continuous unwinding of yarns; 
         FIG. 6B  is an exemplary top plan view of the apparatus for unwinding yarns shown in  FIG. 6A ; 
         FIG. 7  is an exemplary graph showing test results of tension measurements on a yarn without anti-tack additives using the OETO apparatus of the present invention; 
         FIG. 8  is another exemplary graph showing test results of tension measurements on a yarn without anti-tack additives using the OETO apparatus of the present invention; 
         FIG. 9  is an exemplary graph showing test results of tension measurements on a yarn with anti-tack additives using the OETO apparatus of the present invention; 
         FIG. 10  is another exemplary graph showing test results of tension measurements on a yarn with anti-tack additives using the OETO apparatus of the present invention; 
         FIG. 11  is an exemplary graph showing tension measurement test results on a yarn on a rewound package using the OETO apparatus of the present invention; and 
         FIG. 12  is an exemplary graph showing tension measurement test results on an as-spun with anti-tack OETO yarn package that is unwound with the OETO apparatus of the present invention. 
         FIG. 13  illustrates how a desired angular orientation θ is maintained between the active package and the central leg of the frame of the apparatus of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The apparatus for unwinding yarns of the present invention allows for the cost efficient use of an OETO method with rewound yarn and/or as-spun OETO yarn with anti-tack additives. In particular, the apparatus of the present invention continuously unwinds as-spun OETO yarns and delivers a relatively constant yarn tension in a relatively small footprint. This provides for improved efficiency in manufacturing processes. 
       FIG. 1  is an exemplary perspective view showing one embodiment of the apparatus of the present invention for continuous unwinding of yarns.  FIG. 1  shows a frame  110  with two pivoting legs  111 ,  113  that are connected to a central leg portion  109  shown in  FIG. 1  as two parallel posts with bridging supports therebetween. Central leg  109  thus extends from one side of frame  110  in the embodiment shown in  FIG. 1 . 
     The pivoting legs  111 ,  113  contain pivoting yarn holding arms  120  ( FIG. 2 ). The pivoting yarn holding arms  120  hold creels for up to eight packages  105  on each of the pivoting legs  111 ,  113 . The packages  105  may be either active packages or standby packages. The pivoting legs  111 ,  113  of the frame  110  are set at acute angles (α 1 ,α 2 ) relative to the central leg  109  in order to provide a versatile and small footprint for the frame  110 . The acute angles (α 1 ,α 2 ) are in the range of 0° to 90°. As a result, the frame can be configured with various orientations of the two pivoting legs  111 ,  113  to optimize space on a manufacturing floor. 
     In addition,  FIG. 1  shows first yarn guides  117  and a drive control assembly  107  that are attached to the central leg  109  of frame  110 . The drive control assembly  107 , as shown in  FIG. 1 , further comprises a drive motor  112 , a drive roll  114 , an electrical control box  118 , a separator roll  122 , second yarn guides  126 , break sensors  128 , and third yarn guides  132 . A non-limiting value for the number of first yarn guides  117 , second yarn guides  126 , break sensors  128  and third yarn guides  132  is eight. The drive control assembly  107  is shown in greater detail  FIG. 3  below. 
     A non-limiting example of an active and a standby package  105  is a full 3 kg creel package of a wound fiber or yarn. While not wishing to be limited, an exemplary yarn for OETO unwinding is spandex (segmented polyurethane), such as LYCRA® sold by INVISTA (formerly DuPont). The active and standby packages  105  typically occupy either of two adjacent pivoting yarn holding arms  120  positions on the small footprint frame  110 . The pivoting yarn holding arms  120  pivot for easy access to the active and standby packages  105 . The pivoting yarn holding arms  120  hold regular yarn tube cores (e.g., as-spun OETO material). 
       FIG. 2  is a top plan view of the apparatus for unwinding yarns shown in  FIG. 1 . As can be seen in  FIG. 2 , the frame  110  is designed to provide a versatile configuration and a small footprint by placing the two pivoting legs  111 ,  113  of the frame  110  that hold the packages  105  at acute angles acute angles (α 1 ,α 2 ) relative to the central leg  109 . Because the two legs  111 ,  113  can be moved and because the frame  110  has a small footprint, the present invention takes up less floor space in a manufacturing environment. 
       FIG. 3  shows a more detailed view of the drive control assembly  107 . In this embodiment, the drive roll  114  is mounted below the separator roll  122 . The second yarn guides  126  are mounted on either side of the separator roll  122 . The second yarn guides  126  are mounted before the separator roll  122 , and before and lateral to the drive roll  114 . The break sensors  128  are mounted above and to the right of the drive roll  114 . The third yarn guides  132  are mounted above and after each of the separator roll  122 , drive roll  114  and break sensors  128 . The third yarn guides  132  may be mounted on the drive control assembly front panel  130  or on the small foot print frame  110 . The position of the third yarn guides  132  relative to the separator roll  122 , drive roll  114  and break sensors  128 , is as discussed above. 
     In addition,  FIG. 3  shows multiple wraps of yarn around the drive roll  114 . The multiple wraps of yarn around the drive roll  114  ensure positive feeding without yarn slippage. This helps to avoid entanglement and breakage that occurred with background art OETO apparatus. 
       FIG. 4  shows the details of the path of the yarn through a guiding system that passes the yarn/fiber  125  from the active or standby packages  105  to the drive roll  114 . Pivoting guide brackets  117  are mounted on sleeves  119  that allow the pivoting guide brackets  117  to pivot on the central leg  109  of the frame  110 . The pivoting guide brackets  117  are secured in a particular position with a securing screw  121 . The pivoting guide brackets  117  are adjusted in accordance with the acute angles at which the pivoting legs  111 ,  113  are set. The pivoting brackets  117  include, but are not limited to, a pigtail guide  115  and yarn guides  116 ,  118  that direct the yam to the second yarn guides  126  attached to the drive control assembly panel  130 . The use of pigtail guides  115  in this path increases the ease of loading/stringing-up the active and standby packages in comparison to the use of eyelets in the background art apparatus. Horizontally mounted yarn guide  116  is positioned closest to the pigtail guide  115  and vertically mounted yarn guide  118  is positioned on a vertical surface of the bracket on a vertical surface of the bracket  117 . 
     Preferably, the yarn/fiber  125  is selected from those referred to as spandex or segmented polyurethane. A particularly preferred spandex is offered under the Lycra® trademark and can be obtained from INVISTA® INCORPORATED, 4417 Lancaster Pike, Wilmington, Del. 19805. Preferred grades of Lycra® spandex include, but are not limited to: Type 151 and Type 262P. 
     The fabricated parts for the frame (e.g., pivoting holding arms  120  pivoting bracket  117 ) can be obtained, for example, from Industrial Machine Works, 444 North Bayard Avenue, Waynesboro, Va. USA. The motor and electrical control box  118  cabinet can be obtained, for example, from MSC Industrial Supply Company, 75 Maxess Road, Melville, N.Y. USA. The components comprising the electrical control box  118  can be purchased, for example, from Control Corporation of America, 1255 Trapper Circle NW, Roanoke, Va. 24012. 
       FIG. 5A  is a front view of the electrical control box  118 . In particular,  FIG. 5A  shows a drive access panel  140 , power disconnect switch  142  and mode selector switch  143  that are mounted on the access door  144  of the electrical control box  118 . 
       FIG. 5B  shows a view of the interior of the electrical control box  118 . In particular,  FIG. 5B  shows terminal blocks  152 ,  156  that provide an interface connection for signals for the components of the electrical control box  118 . Non-limiting examples of the major components of the electrical control box  118  include, but are not limited to, a master encoder  150  (not shown), power supply  154 , drive motor controller  153 , relay  157 , break detector interface  158  (not shown) and digital converter  160 . A schematic diagram showing the interconnection of these components is set out in  FIG. 5C . The break detector interface  158  and the drive motor controller  153  are electrically connected to the break detectors  128  and the drive motor  112 , respectively, of the drive control assembly  107 . The master encoder  150  may be provided externally and the break detector interface  158  may be a part of the break detectors  128 . 
     The motor and electrical control box  118  cabinet can be obtained, for example, from MSC Industrial Supply Company, 75 Maxess Road, Melville, N.Y. USA. The components comprising the electrical control box  118  can be purchased, for example, from Control Corporation of America, 1255 Trapper Circle NW, Roanoke, Va. 24012. The electrical control cabinet 
     An alternative configuration (not shown) for the frame  110  would mount a second yarn holding arm, located at an angle of 180° relative to each of the existing pivoting yarn holding arms, on the frame. This alternative configuration would permit one to hand additional yarn creels on the small footprint frame  110 , thus providing more active and standby packages  105  ready for use in the manufacturing process. 
       FIG. 6A  is another exemplary perspective view showing an OETO apparatus for continuous unwinding of yarns.  FIG. 6B  is an exemplary top plan view of the apparatus for unwinding yarns shown in  FIG. 6A . 
     The fabricated parts for  FIG. 6A  can be obtained, for example, from Industrial Machine Works, 444 North Bayard Avenue, Waynesboro, Va. USA. The motor and electrical control box cabinet of  FIG. 6A  can be obtained, for example, from MSC Industrial Supply Company, 75 Maxess Road, Melville, N.Y. USA. The components comprising the electrical control box can be purchased, for example, from Control Corporation of America, 1255 Trapper Circle NW, Roanoke, Va. 24012. 
       FIG. 7  to  FIG. 12  are exemplary graphs of test results using the OETO apparatus of the present invention. The yarn/fiber used for tests is selected from those referred to as spandex or segmented polyurethane. A particularly preferred spandex is offered under the LYCRA® trademark and can be obtained from INVISTA S.àr.l., Wichita, Kans. Preferred grades of LYCRA® spandex include, but are not limited to: Type 151 and Type 262P. For  FIG. 9 ,  FIG. 10  and  FIG. 12 , the concentration of anti-tack additives is in the range of 0.05% to 1%. The legend of each figures gives parameters particular to the test such as unwind and take-up speed in feet-per-minute (FPM). The legend of each figure also indicates the lot number of the yarns, test date and the age of the yarns-under-test. 
       FIG. 7  is an exemplary graph showing test results of tension measurements on a yarn without anti-tack additives using the OETO apparatus of the present invention. As can be seen in  FIG. 7 , the yam tension  701  starts out at about 95 grams and climbs to about 140 grams at the end of the test cycle. This corresponds to an increase of about 47% in the yam tension. 
       FIG. 8  is an exemplary graph showing test results of tension measurements on a yarn without anti-tack additives using the OETO apparatus of the present invention. As can be seen in  FIG. 8 , the yarn tension  801  starts out at about 95 grams and climbs to about 150 grams at the end of the test cycle. This corresponds to an increase of about 58% in the yarn tension. 
     In addition, the graph of  FIG. 8  shows brief spikes in the yarn tension up to the maximum measurement value of 180 grams. Moreover, the yarn could not be unwound to the core of the creel. 
       FIG. 9  is an exemplary graph showing test results of tension measurements on a yarn with a low level of anti-tack additives using the OETO apparatus of the present invention. As can be seen in  FIG. 9 , the yam tension  901  starts out at about 100 grams and climbs to about 120 grams at the end of the test cycle. This corresponds to an increase of about 20% in the yarn tension. Though this is a relatively constant value for yarn tension, there were still breaks in the yarn during the unwinding method, as illustrated in  FIG. 9 . 
       FIG. 10  is an exemplary graph showing test results of tension measurements on a yarn with anti-tack additives using the OETO apparatus of the present invention. As can be seen in  FIG. 10 , the yam tension  1001  starts out at about 100 grams and climbs to about 120 grams at the end of the test cycle. This corresponds to an increase of about 20% in the yam tension. In addition, there were step-like jumps in the yarn tension during the unwinding method as a result of the transfer from an active package to a standby package. 
       FIG. 11  is an exemplary graph showing tension measurement test results on a yarn on a rewound package using the OETO apparatus of the present invention.  FIG. 11  shows both the package side yarn tension  1101  and the machine side yarn tension  1103 . In particular,  FIG. 11  shows a package side yarn tension  1101  for a typical rewound package. The package side yarn tension starts out at about 80 grams and climbs to about 140 grams at the end of the test cycle. This corresponds to an increase of about 75% in the yarn tension. 
       FIG. 12  is an exemplary graph showing tension measurements test results on an as-spun OETO with anti-tack yarn package that is unwound with the method and apparatus of the present invention.  FIG. 12  demonstrates the desired relatively constant yarn tension.  FIG. 12  also shows both the package side yarn tension  1201  and the machine side yarn tension  1203 . In particular, the graph of  FIG. 12  shows a package side tension  1201  that starts out at about 110 grams and only climbs to a maximum of 125 grams at the end of the test cycle. In contrast to the test results of  FIG. 11 , which showed a 75% increase in yarn tension, these test results indicate that the method and apparatus for unwinding of the present invention experiences an increase of only a 14% in yarn tension. 
       FIG. 13  shows a configuration of the active package relative to the central leg  109  of the frame  110  of the invention. In  FIG. 13 , active packages  105  are maintained in a desired orientation by pivoting yarn holders  120  ( FIG. 2 ). The diameter of the pivoting yarn holders  120  is smaller than the diameter of the open core of the active package  105  such that the active packages  105  can be slid over the suitably positioned pivoting yam holder  120  and such that the yarn  125  ( FIG. 4 ) can be unwound from the active package  105  by the OETO apparatus of the present invention. The yarn  125  ( FIG. 4 ) is then directed to the drive control assembly  107  for the unwinding process. A distance (d) between the active packages  105  and the first yarn guides  117 , which is at least about 0.34 meter and preferably not more than about 0.91 meter, can be maintained for operation with high tack fibers. An acute angle (θ), defined by the intersection of the imaginary lines corresponding, respectively, to the rotational axis of the active packages  105  and the central axis of the static guide orifice that is perpendicular to the plane of the orifice, is preferably maintained between 0 and about 30° for operation with high tack fibers. 
     As the level of tack exhibited by the fiber increases, the maximum allowable angle, θ, decreases. The directional change of the yarn  125 , as it passes through a first yarn guide  117 , as measured in terms of θ, is preferably limited to between 0° and about 30° for yarns with tack levels greater than about 2 and less than about 7.5, and between 0° and about 10° for fibers with tack levels greater than about 7.5. Larger angles can result in excessive variations in thread line tension and draft, or even yarn breakage. 
     Therefore, as demonstrated by the above test results, the method and apparatus of the present invention provides an OETO method and apparatus for unwinding yarns with anti-tack additives that can be implemented in a relatively small footprint and avoids the problems of entanglement, breakage and increased manufacturing costs of the background art. 
     The foregoing description illustrates and describes the present invention. Additionally, the disclosure shows and describes only the preferred embodiments of the invention, but, as mentioned above, it is to be understood that the invention is capable of use in various other combinations, modifications, and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein, commensurate with the above teachings and/or the skill or knowledge of the relevant art. The embodiments described hereinabove are further intended to explain best modes known of practicing the invention and to enable others skilled in the art to utilize the invention in such, or other, embodiments and with the various modifications required by the particular applications or uses of the invention. Accordingly, the description is not intended to limit the invention to the form or application disclosed herein. Also, it is intended that the appended claims be construed to include alternative embodiments.