Patent Publication Number: US-2005133653-A1

Title: Tension controlled thread feeding system

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application is a continuation-in-part of U.S. patent application Ser. No. 10/722,261, filed Nov. 25, 2003. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a thread feeding system or fiber unwinding device, and more specifically to a system or device that minimizes average tension levels and tension variations of a plurality of elastomeric threads or fibers being transported to a downstream thread or fiber processing operation.  
      2. Description of Background Art  
      The most common method of unwinding thread or fiber from a cylindrical mandrel (or “package”) in manufacturing processes is referred to as “rolling takeoff”. It should be noted that the terms “thread” or “fiber” are used interchangeably throughout this document. When the package is exhausted the empty mandrel must be removed and a new package installed. This operation requires shutting down the manufacturing line causing unproductive downtime.  
      Another method often utilized, the over end takeoff (OETO) method, allows continuous operation, because the terminating end of the thread or fiber wound on an active package can be attached to the leading end of the thread or fiber wound on a standby package. This allows the active package to be fully exhausted at which point the standby package becomes the active package, all without any process interruption. However, unacceptable variations in threadline tension are common with OETO.  
      Research Disclosure, p. 729, November 1995, item #37922, discloses an OETO system in which elastomeric thread or fiber is passed through a system comprising a relaxation section and motor driven nip rolls, before being fed to the manufacturing line. The relaxation section, extending between the package and the nip rolls, is stated to suppress tension variations. However, threads or fibers that exhibit high cohesive forces (generally referred to as “tack”) display unusually high variations in frictional forces and tension levels as the package unwinds. The slackness of the thread line in the relaxation region can vary and can result in temporarily excessive amounts of filament being unwound from the package. This excess thread or fiber can be drawn into the nip rolls and wound up on itself leading to entanglement or breakage of the threadline requiring the manufacturing line to be stopped. The high level of tack contributes to the possibility of the excess fiber adhering to it and to the nip rolls. The OETO device can also be configured such that the thread or fiber horizontally traverses the relaxation section. In this case, the fiber then travels through nip rolls whose axes are vertical. However, in this configuration, the thread or fiber in the region between the package and the nip rolls can sag. This sagging allows the threadline position on the nip rolls to become unstable and can result in interference between adjacent threadlines.  
      U.S. Pat. Nos. 3,797,767; 3,999,715 and 6,158,689 disclose the use of spirally grooved rolls in thread or fiber winding machines in order to impart a specified pitch angle to a fiber as it is wound on a package. The use of grooved rolls for maintaining positional stability among a plurality of thread lines on a single roll is not described.  
      U.S. Pat. No. 5,566,574 (Tiziano) discloses a method for feeding a thread or fiber to a textile machine by utilizing a braking member and actuator to adjust the tension and feed rate of the thread or fiber. However, Tiziano does not disclose the concept of utilizing a variable speed electrical motor for a driven roll, where the speed of the motor is determined based on a range of desired thread tensions, is not disclosed. In addition, an elastomeric thread or fiber like Spandex, which has a unique inherent finish texture that differs from threads or fibers used in the textile industry, requires an electrical motor feeding device that allows the Spandex to remain in contact with the driven feed roll attached to the motor. Further, Spandex has a higher tensile strength specification and other characteristics that differ from fibers used in the textile industry. For example, threads or fibers typically used in the textile industry are specified in the range of 50-100 decitex(decigrams per kilometer) and tend to operate at lower rotation speeds of 1-50 feet/minute when being unwound from a package as compared to those used for elastomeric threads which typically are specified in the range of 600-1500 decitex and with higher rotation speeds of 300-400 feet/minute. Moreover, Tiziano is not directed to operate with or feed systems that require high tack, elastomeric threads such as Spandex.  
      The aforementioned problems make the processing of high tack, elastomeric threads or fibers particularly problematic. Fiber tack and its associated problems have been addressed by using topical fiber additives (prior to winding) or by unwinding the package and re-winding it on a new mandrel. However, both approaches add additional expense. Furthermore some applications (e.g., manufacturing of diapers and other personal care products) require the use of as-spun thread or fiber that is substantially finish-free and, consequently, exhibits high tack. Therefore, a fast and reliable method of unwinding and feeding high tack elastomeric thread or fiber from a package to a thread processing system is still needed in the art.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  schematically illustrates the fiber unwinding test equipment used to obtain the data in Examples 1-4.  
       FIG. 2  shows a perspective drawing of a preferred embodiment of an OETO unwinding device/thread feeding system.  
       FIG. 3  illustrates a perspective view of a portion of an unwinding device/thread feeding system of the invention including some of the packages, threadline guides and the first driven roll.  
       FIG. 4  is a top view of an unwinding device/thread feeding system of the invention.  
       FIGS. 5A and 5B  are back and side views, respectively, of an unwinding device/thread feeding system of the invention.  
       FIG. 6  is a schematic top plan view of a diaper making thread processing system and the thread feeding system of the invention.  
       FIG. 7  is a front elevational view of the thread feeding system showing four feed roll packages, a support frame and a drive and tension control apparatus.  
       FIG. 8  is a top plan view of thread feeding system shown in  FIG. 7 .  
       FIG. 9  is an exemplary enlarged front elevational view of a four thread drive and tension control apparatus.  
       FIG. 10  is a top plan view of the four thread drive and tension control apparatus shown in  FIG. 9 .  
       FIG. 11  is a right side elevational view of the four thread drive and tension control apparatus shown in  FIG. 9  and  FIG. 10 .  
       FIG. 12  is an exemplary perspective view showing a single thread drive and tension control apparatus.  
       FIG. 13  is a front elevational view showing two drive and tension control apparatus, each having four active feed roll packages.  
       FIG. 14  is an exemplary perspective view showing another drive and tension control apparatus.  
       FIG. 15  is a top plan view of the drive and tension control apparatus shown in  FIG. 14 .  
       FIG. 16  is another exemplary embodiment of thread feeding system with multiple drive and tension control apparatuses.  
       FIG. 17  is another exemplary perspective view showing a single thread drive and tension control apparatus.  
       FIG. 18  is an exemplary enlarged front elevational view of a second embodiment of a single thread drive and tension control apparatus.  
       FIG. 19  is a right side elevational view of the single thread drive and tension control apparatus shown in  FIG. 18 .  
       FIG. 20  is a top plan view of the single thread drive and tension control apparatus shown in  FIG. 18 .  
       FIG. 21  an exemplary enlarged front elevational view of a third embodiment of a single thread drive and tension control apparatus.  
       FIG. 22  is a top plan view of the third embodiment of the single thread drive and tension control apparatus shown in  FIG. 21 .  
       FIG. 23  shows a flow diagram of the method of monitoring thread tension of the present invention. 
    
    
     SUMMARY OF THE INVENTION  
      The present invention is a system, apparatus and method for tension control in a thread feeding system that provides a fast and reliable method for feeding high tack elastomeric thread or fiber from a package to a thread processing system.  
      In a first embodiment, the present invention provides a thread feeding system comprising: a support frame; a package holder affixed to said support frame for holding a package of thread about a rotational axis such that at least one thread can unwind from the package in a direction defining an acute angle (θ) with the rotational axis of the package; a driven take-off roll for unwinding thread from the package at a predetermined take-off rate: a first static guide for directing thread unwound from the package, said first static guide positioned on said frame such that; a distance (d) from the first static guide to the end of the package facing the first static guide, measured on the line defined by the rotational axis of the package, is equal to: at least about 0.41 meter for thread with tack of greater than about 2 grams OETO and less than about 7.5 grams OETO; or from about 0.71 meter to about 0.91 meter for fiber with tack greater than about 7.5; an angle (θ), defined by the intersection of imaginary lines corresponding, respectively, to the rotational axis of the package and the central axis of the first static guide inlet orifice that is equal to: 0° to about 30° for threads with tack greater than about 2 grams OETO and less than about 7.5 grams OETO; or 0° to about 10° for threads with tack levels greater than about 7.5 grams OETO; and a drive and tension control apparatus for sensing and controlling the speed of the driven take-off roll, wherein the drive and tension control apparatus controls the speed of a variable-speed motor for the driven take-off roll by determining whether at least one of the mean tension and maximum tension is within a predetermined range of thread tension values.  
      In another embodiment of the present invention is a drive and tension control apparatus comprising: guide rolls configured to guide at least one thread through a thread path of the drive and tension control apparatus; a driven take-off roll configured to move the at least one thread through the drive and tension control apparatus; a variable-speed motor configured to drive the driven take-off roll; a tension sensor configured to determine the tension on the at least one thread; a tension controller device configured to at least one of increment, maintain and decrement a speed of the variable-speed motor, wherein the guide rolls are located before and after the driven take-off roll, the tension sensor is located after the driven take-off roll, and wherein the speed of the variable-speed motor is maintained within a predetermined range of thread tension values by the tension controller device.  
      The above embodiments of the present invention preferably further include a second thread guide positioned between the package and the first thread guide for directing thread unwound from the package. More preferably, the present invention further comprises a third thread guide positioned between the first thread guide and the driven take-off roll. Further, this embodiment of the present of invention may also include a fourth thread guide positioned between the third thread guide and the driven take-up roll. Furthermore, at least one of the thread guides may be a grooved roll or the driven take-off roll may be a grooved roll.  
      Moreover, in a preferred embodiment, at least one thread guide is a static circular guide having a wear-resistant surface for contacting the thread. The static circular thread guide preferably has a wear-resistant inner surface such that the wear-resistant surface is the inner surface of an annulus.  
      In yet another embodiment, the present invention is a method for controlling thread tension in a thread feeding system, comprising: determining whether threads are broken; determining whether threads are moving; measuring the tension of the moving threads; determining whether any of the moving threads have a tension that is out-of-range relative to predetermined tension values; at least one of incrementing and decrementing the speed of a driven take-off roll when the tension is out of range and at least one of the number of increments and decrements is below a correction threshold; 
          determining whether an average tension for the moving threads is out-of-range relative to the predetermined tension values for the threads; at least one of incrementing and decrementing the speed of a driven take-off roll when the tension is out of range and at least one of the number of increments and decrements is below a correction threshold; and setting an alarm when the threads are at least one of broken, not moving and out-of-range and above a correction threshold, wherein the value that determines that the tension is out-of-range are in accordance with predetermined tension values for the threads.        

     DETAILED DESCRIPTION OF THE INVENTION  
      With reference to  FIG. 1 , a package  10  is maintained in a desired orientation by a cylindrical rod (not shown). The diameter of the rod is smaller than the diameter of the open core of the package such that the package can be slid over the suitably positioned rod and such that the thread or fiber can be unwound from the package by over end takeoff. The thread or fiber is then directed, in sequence, through a static guide  20  having a substantially circular orifice; a driven roll  30  around which the fiber is wrapped 360°, or less; and a second, driven take-up roll or set of rolls  50 . The static guide is typically an orifice whose inner surface can be a highly polished ceramic material. Such a surface can provide excellent wear resistance and low friction. The take-up roll or rolls  50  representing that part of the manufacturing process equipment to which the thread or fiber is being supplied, is/are rotated at a speed relatively higher than the first motor-driven roll  30 , so as to provide the desired draft. A distance (d) between the package and the static guide  20 , which is at least about 0.43 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 package 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. Means for stabilizing the position of the threadline on the first driven roll can be provided by, for example, use of one or more additional guides  60 ,  70 ,  80  and/or a plurality of grooves in the surface of the first driven roll  30  wherein said grooves are substantially perpendicular to the roll  30  axis and substantially parallel to the direction of travel of the threadline.  
      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 thread line breakages. 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 fibers with tack levels greater than about 2 and less than about 7.5, d is preferably at least about 0.41 meter; and for fibers with tack levels greater than about 7.5, d is preferably at least about 0.71 meter.  
      As the level of tack exhibited by the fiber increases, the maximum allowable angle, θ, decreases. The directional change of the threadline, as it passes through the first static guide, as measured in terms of θ, is preferably limited to between 0° and about 30° for fibers 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 threadline breakage.  
      The desired thread line positional stability can be assured by providing grooves in the surface of the first driven roll  30 . Such grooves also allow closer spacing of the threadlines, thereby minimizing the dimensions of the equipment. The resulting stability of the threadline position also allows operator intervention to correct a threadline problem, while the process is running, with less risk of disturbing adjacent thread lines.  
      Threadline guides can be used in addition to, or instead of, grooved rolls to impart thread line stability and to direct the threadline along a desired path. Of the various threadline guides available, captive, rolling guides are preferred. The use of a single, first motor-driven roll described above is found to give outstanding process performance without the need for employing the more mechanically complex and expensive nip rolls described in Research Disclosure, item 37922, cited above. A wrap of 360° or less of the thread line around the roll  30  minimizes fiber-on-fiber contact and the possibility of fiber damage associated with such contact. Less than 360° contact between the thread line and roll can be achieved by the appropriate positioning of a threadline guide placed immediately after the roll to lift the fiber off the roll surface short of a complete 360° wrap.  
      The process by which the unwinder of this invention can be operated involves the following steps, with reference to  FIGS. 2, 3 ,  4 ,  5 A and  5 B: a) placing the fiber packages on their respective mounting rods; b) tying the leading end of fiber from each standby package  300 ′ or  400 ′ to the trailing fiber end of its corresponding active package  300  or  400 , respectively; c) directing the leading fiber end of each active package through its respective static guide  100  or  100 ′, then through a wrap of 360° or less around the first driven roll  800  and then causing it to be engaged by a take-up device not shown in  FIGS. 2-5  (identified as  50  in  FIG. 1 ) (this device, typically a driven roll or set of driven rolls, represents that element of the manufacturing process which first engages the fiber as it exits the unwinder); d) initiating rotation of the first driven roll  800  and take-up device (not shown); while e) controlling the surface speeds of each such that the surface speed of roll(s) (not shown) exceeds that of roll  800  by the percentage corresponding to the desired fiber elongation (or draft); f) replacing each active package  300  or  400 , as it becomes exhausted, with what now becomes a standby package  300 ′ or  400 ′; and g) tying the leading fiber end of this new standby package  300  or  400  with the trailing end of the now, active package  300 ′ or  400 ′. Repeating steps f and g (or b), as required, allows uninterrupted operation.  
      As previously described, positional stabilization of the threadlines can be achieved by the use of a grooved roll  800 , and/or additional threadline guides. In the event that a grooved roll is employed, step c, above, also includes placing each fiber in its corresponding groove. In the event that additional threadline guides are employed, additional steps must be added to the above procedure to thread each fiber through its respective, additional guides in the sequence that such guides are encountered.  
      FIGS.  2 - 5 A&amp;B illustrate a preferred embodiment of an OETO unwinding device for high tack spandex fiber. For the purpose of improved clarity, the threadlines are not shown. As presented in  FIGS. 2, 3  and  4 , the OETO fiber unwinding system has the capacity to feed a manufacturing line with eight (8) threadlines, requiring a capacity to accommodate sixteen (16) packages. Each threadline supplied from an active package to the first static guide  100  or  100 ′ is kept in the horizontal plane. The packages are mounted in vertical tiers  200 , each tier holding four (4) packages  300 ,  300 ′,  400  and  400 ′. The four packages are arranged in pairs, each pair consisting of one active  300  or  400  and one standby  300 ′ or  400 ′ package.  
      With reference to  FIGS. 3, 4 ,  5 A and  5 B, each threadline leads from an active package  300  or  400  through a first static guide  100  or  100 ′ and then through a captive rolling guide  500 , at the horizontal center of the unwinding device. All three of these elements are located substantially on the same horizontal plane.  
      In particular, referring to  FIG. 3 , the threadline is then turned up or down, depending upon the tier from which it originated, to the vertical center of the unwinding device. At the vertical center of the unwinding device, each threadlines is fed through its respective captive rolling guide  600  and then directed horizontally through its respective static guide  700 . Finally, the threadlines are wrapped 360°, or less, around a horizontal driven roll  800 . The driven roll  800  (shown in  FIG. 3 ) is illustrated with eight grooves  900 , through which the threadlines run. The groove depths are 0.38 mm and the spacing between the grooves is 15 mm. Grooves are an optional feature of horizontal driven roll  800 ; the driven roll may alternatively have a smooth surface.  
      The following examples include experiments with Lycra® XA® fibers having no topically applied finish.  
     EXAMPLE 1  
      The test equipment used in obtaining the data for this and the following examples, could be configured in various ways, such as optionally including or excluding certain design elements and changing the sequence of certain elements. The equipment configuration employed for this example, with reference to  FIG. 1 , was comprised of the following elements, listed in the order in which they were encountered by the moving threadline: fiber package  10 , static guide  20 , first, driven roll  30 , tension sensor  40 , and driven take-up rolls  50 .  
      The test equipment geometry and other experimental test conditions are summarized below:  
      The distances between the static guide  20  and the first driven roll  30 , between the first driven roll  30  and the tension sensor  40  and between the first driven roll  30  and the take-up roll  50  were 0.22, 1.94 and 2.1-3.4 meters, respectively. In this example, the first driven roll  30 , having a diameter of 8.89 cm. was not grooved. The threadline was maintained in the horizontal plane (relative to ground), and its directional change within that horizontal plane as it passed through the static guide, was maintained constant at 0° θ. The distance between the package  10  and first guide  20  was varied. The threadline was wrapped 360° around the first driven roll  30 . The threadline draft was controlled at 2.15×. by maintaining the surface speeds of the first roll  30  at 93.4 meter/min, and the surface speed of the take-up rolls  50  at 294.3 meters/min.  
      Tension data (expressed in grams) were collected with a Model PDM-8 data logger, and a Model TE-200-C-CE-DC sensor (Electromatic Equipment Co.). All tension measurements were averaged over five-minute run time using a data sampling frequency of approximately 82 samples/sec.  
      “Mean range tension” was determined as follows: within every 1.25-second interval of the tension measurement, the minimum and maximum tension levels were recorded (yielding 103 data points). Mean range tension was calculated by averaging the differences (between the minimum and maximum values) over the 5-min run.  
      The fiber evaluated in this test was as-spun Lycra® XA® spandex (a registered trademark of E.I. du Pont de Nemours and Company) having a linear density of 620 dtex (decigram per kilometer).  
      Table 1 shows the thread line tension variations, as measured at the sensor, as the distance, d, between the package and the static guide was varied over a distance between about 0.25 and 0.81 meter.  
                       TABLE 1                       Distance   Means Range   Max. Tension       (meter)   Tension (grams)   (grams)                                            0.27   16.90   50.00       0.28   17.60   50.00       0.30   17.80   50.00       0.33   16.30   50.00       0.36   1630   49.00       0.38   14.50   50.00       0.41   13.70   48.40       0.43   13.30   38.00       0.46   12.40   37.10       0.48   12.20   44.70       0.51   11.60   36.30       0.53   11.60   36.70       0.56   11.60   30.40       0.58   11.80   32.60       0.61   10.00   28.80       0.64   10.60   34.30       0.66   10.60   25.30       0.69   10.40   34.30       0.71   10.60   29.80       0.74   10.00   28.40       0.76   10.40   29.40       0.79   10.80   27.80       0.80   10.80   34.50                  
 
      Table 1 demonstrates that thread line tension (expressed either as the mean range or the maximum tension) decreases as the distance between the package and the static guide is increased. Minimum tensions, not shown in the table ranged from about 0.6 to 1.4 grams. Unexpectedly, it has been discovered that there is a minimum distance of about 0.41 meter below which the absolute level of tension and the tension variability (as observed by plotting, for example, maximum tension versus distance) rises to an unacceptably high level identifiable by the occurrence of threadline breakages which are usually preceded by a relatively abrupt increase in mean range tension.  
     EXAMPLE 2  
      The same test equipment as described in Example 1, but configured to more closely correspond to the preferred embodiment of the OETO unwinder design was utilized. With reference to  FIG. 1 , the equipment had the following elements in the order in which they were encountered by the moving threadline: fiber package  10 , captive rolling guide  60 , static guide  20 , captive rolling guide  70 , first, driven roll  30 , captive rolling guide  80 , tension sensor  40 , and driven take-up rolls  50 .  
      The distances between the static guide  20  and the first driven roll  30 , between the first driven roll  30  and the tension sensor  40 , and between the first driven roll  30  and the take-up rolls  50  were 0.43, 0.51 and 2.43 meters, respectively. The first driven roll  30  was a single roll having a single groove with a depth of 0.38 mm. The threadline was again maintained in the horizontal plane. The distance between the package and the static guide  20  was held constant at 0.65 meter while the angle, θ, was varied. Threadline draft was maintained at 4× by controlling the first driven roll  30  and the take-up rolls  50 , respectively, at surface speeds of 68.6 and 274.3 meters/min.  
      In addition to monitoring threadline tension as in Example 1, tension spikes were also recorded. “Tension spikes” are the average number of sudden increases in tension greater than 25 grams above baseline tension in a 5-min period.  
      Various as-spun Lycra® XA® spandex fibers, exhibiting different levels of tack, were evaluated. Tack levels were characterized by measuring the OETO tension (in grams) by the following method: The fiber package and a ceramic pig tail guide were mounted 0.61 meter apart, such that the axes of each were directly in line. The fiber is pulled off the package over end at a threadline speed of 50 meters/min, through the guide, and through a tension sensor.  
      Table 2 shows the threadline tension variations as the angle θ increased; where θ is defined as the acute angle made by the intersection of the imaginary lines corresponding, respectively, to the rotational axis of the package and the central axis of the static guide orifice that is perpendicular to the plane of the orifice.  
                                   TABLE 2                               Mean   Max.                   Angle   Range   Tension   Tension       Fiber   (decree)   Tension (g)   (grams)   Spikes   Tack                                                        T-127   0   38.4   174.9   56           620 dtex   5   40.8   176.5   85       Lot 9291   11   BROKE       Merge 1Y331   22   BROKE           45   BROKE       T-127   0   16.5   118.4   0       620 dtex   5   17.3   119.2   0       Lot 0211   11   17.3   122.4   0       Merge 16398   22   18.8   124.7   0           45   20.4   131.8   0           57   25/1   138.0   1           67   29.0   149.0   9           77   30.6   156.9   11           90   35.3   167.9   14       T-162B   22   32.9   171.8   16   11.368       800 dtex   45   40.8   198.4   53   ″       Lot 0205   57   44.7   &gt;200   72   ″       Merge 16525       T-162C   22   25.9   159.2   0   7.02       800 dtex   45   29.8   176.5   4   ″       Lot 0020   57   31.4   169.4   24   ″       Merge 16600                  
 
      Examination of the data in the above table reveals an unexpected relationship between threadline tension and the angle between the centerlines of the package  10  and the static guide  20 . As the angle increases so does thread line tension, and tension spikes occur more frequently. At sufficiently large angles, thread line breakage can occur. The sensitivity of thread line tension to the angle traversed by the thread line as it passes through the guide is dependent upon the properties of the fiber. The data of Table 2 indicates that fibers characterized by higher tack exhibit higher sensitivity of thread line tension with respect to this angle. For some fibers that exhibit an exceptionally high level of tack, the angle above which thread line breakage cannot be avoided is less than about 10°.  
     EXAMPLE 3  
      This series of runs, using the test equipment described previously and configured as in Example 2, evaluated the effect of angle on threadline tension for fibers of different tack levels. The distance, d, between the package and the static guide  20  was maintained constant at 0.65 meter. Threadline draft was maintained at 4× by controlling the first driven roll  30  and the take-up rolls  50 , respectively, at surface speeds of 68.6 and 274.3 meters/min. All other experimental conditions were as described for Example 2. The data are summarized in Table 3.  
                                   TABLE 3                               Mean   Max.                   Angle   Range   Tension   Tension       Fiber   (decree)   Tension (g)   (grams)   Spikes   Tack                                                        T-162C   0   25.1   164.7   2   7.02        800 dtex   5   25.1   157.7   0   ″       Merge 16600   11   27.5   156.9   0   ″       Lot 0020   22   28.2   160.0   0   ″           45   36.9   182.8   16   ″           57   42.4   196.1   59   ″           67   47.8   &gt;200.0   127   ″           77   BROKE       T-162C   0   18.8   150.6   0   1.408       As-spun   5   15.7   142.8   0   ″       840 den   11   17.3   143.5   0   ″       Merge 16795   22   14.9   140.4   0   ″       Lot 1019   45   14.9   138.8   0   ″           57               ″           67   15.7   140.4   0   ″           90   17.3   145.1   0   ″       T-162 B   0   29.0   171.8   13   11.368        800 dtex   5   32.2   172.6   10   ″       Merge 16525   11   36.1   184.3   42   ″       Lot 0205   22   39.2   &gt;200.0   43   ″           45   52.6   &gt;200.0   126   ″           57   BROKE           ″                  
 
      The high tack fibers tested in this series of runs are the same as two of the fibers tested in Example 2. Comparison of the data for these same fibers in Tables 2 and 3, shows that thread line tension increases with increasing angle, and thread line breakage may occur at excessively high angles. (In contrast, fibers containing finish can be run at angles of up to and including 90° with no increase in thread line tension, no occurrence of tension spikes and no thread line breaks. When Lycra® XA® T-162C fiber, 924 dtex den, merge 16795(lot 1019), finish, having a tack of 1.406, was run at angles of 0-90°, there was no threadline tension increase and no tension spikes.)  
      These data demonstrate that limiting the angle the thread line traverses as it passes through the first static guide provides uninterrupted manufacturing processing even for high tack fiber threadlines.  
     EXAMPLE  4   
      This series of runs using the test equipment described previously and configured as in Example 2, evaluated the effect of the distance, d, between the package and the static guide on threadline tension for fibers of different tack levels. The angle, θ, was maintained constant at 22°. The threadline draft was controlled at 4× and the take-up speed at 274.3 meters/min.  
                               TABLE 4                               Mean Range   Max. Tension   Tack       Fiber   Distance (meter)   Tension (g)   (grams)   (grams)                                                    T-162 C   0.20   56.5   &gt;200   7.02       As-spun   0.30   44.7   200.0   ″       720 den   0.41   32.2   182.0   ″       Merge 16600   0.51   32.2   174.9   ″       Lot 0020   0.61   31.4   181.2   ″           0.71   29.0   173.3   ″           0.81   29.8   178.8   ″           0.91   32.2   173.3   ″           1.02   29.0   167.9   ″       T-162 B   0.20   BROKE   BROKE   11.368       As-spun   0.30   57.3   &gt;200   ″       720 den   0.41   56.5   &gt;200   ″       Merge 16525   0.51   55.7   &gt;200   ″       Lot 0205   0.61   56.5   200.0   ″           0.71   56.5   200.0   ″           0.81   48.6   200.0   ″           0.91   50.2   200.0   ″           1.02   52.6   200.0   ″                  
 
      The test results for these fibers show the minimum distance between the package and the fixed guide below which the threadline tension and mean range tension increase unacceptably. The value of this minimum depends upon the tack level of the fiber being tested. In contrast, there is essentially no effect of package-to-static guide distance on the lower tack Lycra® spandex. These results reinforce the difficulty in maintaining smoothly running process conditions with high tack fibers. The present invention allows successful control of processes utilizing such fibers.  
     EXAMPLE 5  
      A test of the operation of the unwinder system of this invention, as pictured in  FIGS. 2-5 , was conducted under commercial production conditions using fibers that were characterized by different levels of tack. Table 5 summarizes these test results. Data were obtained as in previous examples, except that each of the tension measurements reported is the average of a minimum of 4 separate measurements, each measurement consisting of one tube running for a 10-min period. Similarly, each number of tension spikes, as reported in Table 5, is the average number of spikes greater than 25 grams above baseline tension in a 10-min period. Measurements were made on packages that were nearly full (surface) or nearly empty (core). Core measurements are those with about 1.6-cm thickness of thread or fiber remaining on the tube. Of the 5 as-spun fibers run, 4 ran with no operational problems. One fiber sample, Merge 1Y331, did result in an unacceptable occurrence of tension spikes. That fiber demonstrated an unusually high level of tack, even for as-spun fiber, as evidenced by the fact that the mean range tension was over 60% higher than that of the fiber exhibiting the next highest level of tack.  
                                           TABLE 5                                           Mean                   Linear       Fiber       Range   Max.           Density   Location   Speed   Fiber   Tension   Tension   Tension       Fiber   (dtex)   on Tube   (ft/min)   Draft   (grams)   (grams)   Spikes                                                                Merge 16398   620   Surface   274.3   4X   12.3   10016   0       Merge 16398   620   Surface   121.9   4X   12.5   96.1   0       Merge 16398   620   Core   274.3   4X   17.5   110.7   0       Merge 16398   620   Core   121.9   4X   16.3   104.1   0       Merge 1Y331   620   Surface   274.3   4X   28.6   151.4   18                  
 
       FIG. 6  is a exemplary schematic top plan view of a thread processing  101  and the thread feeding system  103  of the invention. According to an exemplary application, as thread exits the thread feeding system  103 , the thread engages a take-up device (not shown) of the thread processing system  101 . The take-up device is commonly a driven roll or a set of driven rolls that pull the thread from thread feeding system  103 . The movement of the take-up device of the thread processing system  101 , discussed in detail below, causes the thread to unwind from an active package  105 . As the thread unwinds from an active package  105 , the thread follows a predetermined thread path before reaching a drive and tension control apparatus  110 . Preferably the thread path is configured, as discussed above, to minimize the addition of unintended tension to the elastomeric thread before reaching the drive and tension control apparatus  110  whenever practically possible.  
       FIG. 7  is a front elevational view of the thread feeding system  103  showing a support frame  109  with four feed roll packages  105 ,  106 ,  107 ,  108 , a guide system  112 A,  112 B and a drive and tension control apparatus  110  mounted on the support frame  109 .  FIG. 8  is a top plan view of the thread feeding system  103  shown in  FIG. 6  and  FIG. 7 . Thread feeding system  103  is preferably configured as a single unit, as shown. In alternative embodiments, thread feeding system  103  may not include each of support frame  109 , guide system  112 A,  112 B drive and tension control apparatus  110  as a single unit, but instead may comprise any combination of separate units that define a thread feeding system. In all embodiments of the present invention, support frame  109 , guide system  112 A,  112 B, drive and tension control apparatus  110  cooperate to provide the thread feeding system  103  with a method for monitoring and adjusting the net tension of a thread group or the tension of a single thread by at least one of increasing, maintaining or decreasing the thread tension of the thread group or thread; and providing uniformity and increased efficiency to the operation of the thread feeding system.  
      Referring to  FIG. 7  and  FIG. 8 , support frame  109  is a structure functioning as a creel to support and position the thread that is fed to a thread processing system ( FIG. 6, 101 ) by the thread feeding system  103 . Elastomeric thread is generally placed on support frame  109  in the form of active packages  105 ,  106 ,  107 ,  108  and standby packages ( FIG. 8 ,  105 ′,  106 ′ and  107 ′, 108 ′ (not shown)). As used herein, the term “package” is used to describe elastomeric fabric that has been wound around an object. “Active package” refers to the package that is currently being unwound. “Standby package” refers to a package that is connected to the end of the active package and will be unwound when the thread on the active package is exhausted. Preferably, all packages are spools of elastomeric threads or fibers and have been wound around a hollow cylindrical object or core. The configuration of packages, as shown in  FIG. 7  and  FIG. 8 , is not intended to be limiting and is illustrated for exemplary purposes only. As can be appreciated, the present invention is applicable with elastomeric fibers or threads provided in any configuration.  
      The support frame  109  shown in  FIG. 7  and  FIG. 8  is a frame-like structure designed to support active packages  105 ,  106 ,  107 ,  108  and standby packages ( FIG. 8 ,  105 ′,  106 ′ and  107 ′,  108 ′ (not shown)). Support frame  109  preferably includes at least one end frame member  122 , each having at least one projection  124  located on opposite ends of each of the frame members to support the active and standby packages. Preferably, the projections  124  are cylindrical rods having a cross-section smaller than the cross section of the opening of the hollow cylindrical object or core of the active packages  105 ,  106 ,  107 ,  108  and standby packages  105 ′,  106 ′ and  107 ′,  108 ′.  
       FIG. 7  illustrates that the thread path is defined by the positioning of the packages  105 - 108 ,  105 ′- 108 ′ and the configuration of guide system  112 A,  112 B. According to a preferred embodiment, the distance between the packages  105 - 108 ,  105 ′- 108 ′ and drive and tension control apparatus  110  should be minimized when practically possible. Parameters for optimum configurations of an unwinding device/thread feeding system in terms of both the distance and angle of the packages have been discussed above. A substantial distance between the packages  105 - 108 ,  105 ′- 108 ′ and the drive and tension control apparatus  110  may undesirably add tension to the thread before reaching drive and tension control apparatus  110 . However, in alternative embodiments, it may be preferable not to minimize the distance between the packages  105 - 108 ,  105 ′- 108 ′ and the drive and tension control apparatus  110  in accordance with the parameters discussed above.  
      As shown in  FIG. 8 , packages  105 ,  105 ′,  106 ,  106 ′ are positioned on the projections  124  in such a manner that the thread can be unwound and supplied to the drive and tension control apparatus  110 . According to a preferred embodiment, the thread feeding system  103  is an “over end take off” (OETO) thread feeding system. The OETO method involves tying the tail end of the thread of the active packages  105 ,  106  to the lead end of the thread of standby packages  105 ′,  106 ′, as shown in  FIG. 8 . The OETO method is intended to allow the active packages to become fully exhausted of thread and to then allow for a continuous transition to the standby package without requiring the thread feeding system to be shut down. As can be appreciated, the present invention is not limited to thread feeding systems utilizing the OETO method, and includes any other take off methods that are generally known or otherwise appropriate.  
      Thread feeding system  103 , as shown in  FIG. 7  and  FIG. 8 , may include more than one active package  105 ,  106 ,  107 ,  108  and is configured to supply multiple elastomeric fibers or threads  104  to a thread processing system ( FIG. 6, 101 ) as a thread group. Preferably, thread feeding system  103  is configured to supply multiple thread groups for more than one application. For example, in a diaper manufacturing system, it is generally known to include an elastic band feature near the open end of each leg to help retain moisture in the diaper and for a snug fit around the legs. The elastic band feature for each leg may be provided by using one or more elastomeric fibers or threads.  
      As shown in  FIG. 8 , the multiple elastomeric fibers or threads  104  supplied to each leg constitute a thread group and hence two threads groups could be provided to a diaper manufacturing system (i.e., one thread group for each leg). For example, as shown in the  FIG. 8 , thread feeding system  103  is configured to supply two thread groups, each having two elastomeric threads per thread group to a thread processing system. In alternative embodiments, thread feeding system  103  may be configured to supply any number of thread groups each having any number of threads per thread group. Support frame  109  may be configured to meet such demands.  
       FIG. 9  is an exemplary enlarged front elevational view of a four thread drive and tension control apparatus  110  mounted on the support frame  109 . The drive and tension control apparatus  110  comprising a driven take-off or driven take-off roll  111 , guide rolls  113 A- 113 A′″ to  113 E- 113 E′″, a tension sensors  115 ′- 115 ′″, motion sensors  116 - 116 ′″, breakage sensors  117 - 117 ′″ and a tension controller device  119 . The tension controller device  119  further comprises a graphical display  121 , a keyboard  123  for data entry and control, and alarm lights  125  to indicate alarm conditions to the operator. Static guides  128  and captive rolling guides  129  that are external to the drive and tension control apparatus  110  are also shown in  FIG. 9 .  
      As shown in  FIG. 9 , guide system  112 A,  112 B are used to direct the thread towards the drive and tension control apparatus  110 . In particular, when the thread feeding system  103  is feeding multiple threads, the multiple guide systems  112 A,  112 B may be needed to direct the threads to drive and tension control apparatus  110  so that the threads do not tangle. Preferably the thread path for each thread is isolated relative to the other threads, other than the time that the threads are in contact with the driven take-off roll  111  as will be discussed below.  
      In addition, it has been contemplated that the use of guide systems  112 A,  112 B, as most clearly shown in  FIG. 10 , may be required for safety reasons. Further guide systems (not shown) may be used to direct the thread to the take-up device of the thread processing system ( FIG. 6, 101 ) after passing through drive and tension control apparatus  110 .  
      However, in alternative embodiments, the use of guide systems is preferably minimized. As shown in  FIG. 9 , guide system  112 A,  112 B includes a series of contact points. Given the possible high tack level of the elastomeric fiber or thread, contact points are likely to undesirably add tension to the thread before reaching drive and tension control apparatus  110 . As can be appreciated by those having ordinary skill in the art, it is generally preferable to stretch the thread with drive and tension control apparatus  110  before tension is added to the thread since tension added to the thread before the thread reaches drive and tension control apparatus  110  gets amplified by the drive and tension control apparatus  110 .  
      The following paragraphs give exemplary details of the operation of the drive and tension control apparatus in terms of guide rolls  113 A- 113 E, tension sensor  115 , motion sensor  116 , and break sensor  117 . It is understood that these same details of operation are also applicable to guide rolls  113 A′- 113 A′″ to  113 E′- 113 E′″, tension sensors  115 ′- 115 ′″, motion sensors  116 ′- 116 ′″, and break sensors  117 ′- 117 ′″.  
      According to a preferred embodiment, as shown in  FIG. 9 , guide systems  112 A,  112 B include a combination of static guides  128  and captive rolling guides  129 . In addition,  FIG. 9  shows guide rolls  113 A- 113 E of the drive and tension control apparatus  110  direct the thread through the feeding system  103 . Alternatively, any of the guide rolls  113 A- 113 E may be eliminated from the drive and tension control apparatus  110  if an application performance can be improved through the use of fewer guide rolls.  
      The guide system  112 A,  112 B is typically attached to a central frame member  125 . According to a particularly preferred embodiment, as the thread comes off the packages  105 - 108 ,  105 ′- 108 ′, the thread is directed by static guides  128 . If multiple threads are being used, multiple static guides  128  may be provided for each thread. Static guide  128  is preferably an orifice through which the thread passes. According to a preferred embodiment, the static guides  128  are substantially circular orifices. However, static guides  128  are not limited to having a circular orifice for directing the thread. As can be appreciated, alternative embodiments may use any known or appropriate guide device for directing the thread.  
      After the thread passes through the static guides  128  and the captive rolling guides  129 , the thread engages a guide roll  113 A- 113 A′″ configured to direct the thread to the drive and tension control apparatus  110 . Again, if multiple threads are being used, a first guide roll  113 A may be provided for each thread. Further, as most clearly shown in  FIG. 13 , if the thread feeding system  103  is supplying multiple thread groups to the thread processing system, multiple drive and tension control apparatus  110  and corresponding first guide roll  113 A may be added.  FIG. 10  shows first guide rolls  113 A,  113 A′,  113 A″,  113 A′″ are free-spinning idler rolls. According to a preferred embodiment, if a thread group having more than one thread is being directed to the drive and tension control apparatus  110 , the first guide rolls  113 A′,  113 A″,  113 A′″ for each thread spins independently of the other first guide roll  113 A.  
      The tension controller device  119 , as best shown in  FIG. 10 , is preferably a programmable device that implements a tension trimming algorithm in accordance to programs and parameters entered into the device. A non-limiting example of such a tension controller device is manufactured by Best Technologies Study and Research (BSTR), 21057 Olglate Olona, ITALY. In an alternative embodiment, the tension controller can be provided by Dover Flexo Electronics, Inc., 217 Pickering Road, Rochester. The tension controller  119  may include, but is not limited to, a digital display or readout  121  that provides information on the controller operation and measurements, input means  123  such as buttons, keyboard, or a touch panel for inputting information, and indicator lights  125 , such as light-emitting diodes, that represent the status of the device and alarms.  
      Multiple tension sensors  115 ,  115 ′,  115 ″,  115 ′″ may be used to determine a net tension value for a group of threads. Multiple break sensors  117 ,  117 ′,  117 ″,  117 ′″ determine whether there is a break in any individual thread or fiber. In addition, multiple motion sensors  116 ,  116 ′,  116 ″,  116 ′″ may be added to determine whether the individual thread or fibers are moving. Non-limiting examples of tension, breakage and motion sensors are also available from BTSR.  
       FIG. 10  is a top plan view of the four threads drive and tension control device shown in  FIG. 9 .  FIG. 10  shows the motor  127  for the driven take-off roll  111  and the connection between the motor  127  and the tension controller device  119 . Cable  120  is used to make the electrical connection for the control signals transmitted between the tension controller device  119  and the variable speed motor  127 . A variety of electrical interfaces including but not limited to, serial bus, parallel bus, PMCIA bus and USB bus interfaces may be transmitted using cable  120 . Signals from the tension controller device  119  are used to increment, maintain or decrement the speed of the variable speed motor  127 .  FIG. 11  is a right side elevational view of the tensioning trim module shown in  FIG. 9  and  FIG. 10 .  
      As shown in  FIG. 10 , thread feeding system  103  includes a drive and tension control apparatus  110  that is used to increment, maintain or decrease the amount of tension in the elastomeric thread. The drive and tension control apparatus  110  includes a variable-speed motor  127  having a drive shaft attached to a driven take-off roll ( FIG. 9, 111 ). Each thread of a thread group is wrapped around the same driven take-off roll ( FIG. 9, 111 ). The surface of the driven take-off roll  111  may be relatively smooth, or in alternative embodiments, the surface may include one or more grooves extending substantially parallel to the thread path to further guide the thread  102 ,  102 ′,  102 ″,  102 ′″ while on the driven take-off roll  111 .  
      The motor  127  shown in  FIG. 9  and  FIG. 10  is a variable speed motor. This is in contrast to the constant speed motors typically used in background art unwinding devices/thread feeding systems. The thread is wrapped around driven take-off roll  111  at an angle sufficient to minimize slippage and low enough to avoid tangling. The angle at which the thread is wrapped around driven take-off roll  111  is referred to as a “first wrap angle.” Preferably the first wrap angle (θ 1 ) is approximately between 2 degrees and 360 degrees. The first wrap angle (θ 1 ) may vary depending on the type of elastomeric thread of fiber being used and the corresponding level of tack. According to a particularly preferred embodiment, the thread is wrapped around driven take-off roll  111  at the first wrap angle (θ 1 ) of approximately 270 degrees.  
      As shown most clearly in  FIG. 9 , a second guide roll  113 B engages the thread after coming off driven take-off roll  111  and cooperates with first guide roll  113 A to define the first wrap angle (θ 1 ) of the thread around driven take-off roll  111 . First guide roll  113 A and second guide roll  113 B may be selectively positioned to achieve the desired first wrap angle (θ 1 ).  
      As shown in  FIG. 9 , the drive and tension control apparatus  110  further includes a tension controller device  119  that is provided after driven take-off roll  111  to monitor the tension of the thread coming off driven take-off roll  111  and to alter the speed of motor  127  to control the tension of the thread  102 ,  102 ′,  102 ″,  102 ′″. The tension controller  119  is connected to a tension sensor  115 . The tension sensor  115  determines a measure of the tension of the thread as the thread comes off driven-take-off roll  111  and generates a signal representative of that tension.  
      As shown in  FIG. 9 , the tension sensor  115  is positioned after driven take-off roll  111  and in the thread path. The distance the thread travels between the driven take-off roll  111  and tension sensor  115  is preferably minimized. Reducing the distance the thread travels between driven take-off roll  111  and tension sensor  115  enables the drive and tension control apparatus  110  to better account for tension variations occurring at the point where the correction is being made (i.e., at the driven take-off roll  111 ). A substantial distance between driven take-off roll  111  and tension sensor  115  may add additional tension variations not seen at the driven take-off roll  111 .  
      As shown in  FIG. 10 , tension controller device  119  that is operably coupled to both tension sensor  115  and the variable speed motor  127 . The tension controller device  119  is capable of recognizing the signal generated by tension sensor  115  indicating a variation in thread tension, and providing an output signal for maintaining the current speed, increasing the current speed, or decreasing current speed of motor  127  in response to such recognition. This output signal is communicated to the motor via interface cable  120 , as shown in  FIG. 10 . The interface between the motor  127  and sensor may use any standard electronic interfaces. Examples of such standard electronic interfaces include, but are not limited to, serial bus, parallel bus, PCIbus, PMCIA and USBbus.  
      According to a preferred embodiment, tension sensor  115  is a strain gauge type sensor that provides an output voltage signal to tension controller device  119  that is representative of thread tension. According to a particularly preferred embodiment, a MagPower CL 1-5 tension sensor  115 , from Magnetic Power Systems, Inc., 1626 Manufacturers Drive, Fenton, Mo., may be used. Alternatively a BTSR TS4 Series or a Dover Flexo Electronics, Inc. Model LT may also be used. As can be appreciated, the present invention may include any sensor suitable to provide an output signal representative of thread tension. As yet another alternative a load cell type sensor may also be used.  
      Guide rolls  113 C,  113 D and tension sensor  115  define a second wrap angle (θ 2 ) in the range of 0 to 180 degrees of circumference for the thread around the tension sensor  115 . Preferably, the thread is wrapped over the range of 45 degrees to 180 degrees. Directing the thread through tension sensor  115  at the second wrap angle (θ 2 ) enables the tension sensor  115  to more easily be calibrated based on the type of thread and the number of threads being used. A predetermined second wrap angle (θ 2 ), at a predetermined tension, will provide a resultant force on the tension sensor  115  in the vertical direction. This resultant force is detected by tension sensor  115  and converted into an output signal that can be recognized by tension controller device  119 .  
      According to a preferred embodiment, tension sensor  115  is calibrated to have a tension detection range between 0 grams and 500 grams. According to an alternative embodiment, tension sensor  115  is calibrated to have a range of detection between 0 grams and 1000 grams. As can be appreciated, tension sensor  115  may be calibrated to have a variety of ranges of tension detection depending on the application. In addition, alternative embodiments may utilize additional tension sensors variously located throughout the thread feeding system. However, as can be appreciated, these tension sensors may include a variety of characteristics and calibrations.  
      In addition, the tension sensor  115  supplies an output signal in the form of a voltage to then tension controller device  119  that is dependent on the thread tension. According to a preferred embodiment, tension sensor  115  provides an output voltage signal ranging from 0 volts to 10 volts that is representative of thread tension. However, as can be appreciated, in alternative embodiments, these tension sensors may utilize a variety of voltage, current, magnetic or other representative signals and a variety of ranges for these representative signals.  
      According a particularly preferred embodiment, the variable speed motor  127  is a servomotor and the tension controller device  119  is a servo driver having a built in PID controller. One vendor providing such controllers is Emerson Control Techniques, 12005 Technology Drive, Eden Prairie, Minn. 55344. A non-limiting example of such a variable speed motor is the Emerson Control Techniques Unimotor Series, Model 75EZB301CACAA, which may use a Emerson Control Techniques Undrive Series, Model SP1201, Drive Controller. This variable speed motor drive system includes an internal tension PID so that an external PLC or other motor controller is not required. The system has an approximate update time of 250 microsecond (μs) on the tension input. Another example of such a system is the BTSR Model SMDIN/RW Controller and KTF/100RW Feeder Motor. Variable-speed motor drive systems are well known, as are the corresponding control systems. Accordingly, further details of their operation will not be provided here. However, it should be understood that the thread speed in the present invention may be driven and controlled by any suitable or otherwise appropriate drive and control system.  
      The thread feeding system  103 , as shown in  FIG. 6  to  FIG. 11 , provides for net tension control of a thread group being supplied to an application of the thread processing system. In addition, thread feeding system  103  may provide for a separate net tension control of a second thread group being supplied to a second application of the thread processing system. As used herein, net tension refers to the resultant tension of the group of threads passing over the same driven take-off roll  111 . By controlling the net tension of a first thread group, and separately controlling the net tension of a second thread group, tension variations for each thread group may be corrected where background art unwinding devices/thread feeding systems typically could not make such a correction.  
       FIG. 12  is an exemplary enlarged front elevational view of a single thread drive and tension control apparatus  110 . The drive and tension control apparatus  110  comprising a driven take-off or driven take-off roll  111 , guide rolls  113 A- 113 E, a tension sensor  115 , breakage sensors  117 , motor  127  and a tension controller device  119 . Optionally, a motion sensor (not shown) may also be included. The tension controller device  119  further comprises a graphical display, a keyboard, and alarm lights.  
       FIG. 13  is a front elevational view showing two drive and tension control apparatus  110 , each having four feed roll packages  105 - 108 ,  125 - 128  mounted vertically on a support frame  109 .  FIG. 14  is an exemplary perspective view showing another support frame configuration  109  for a thread feeding system  103  that supports a set of active packages  105 ,  106  and standby packages  105 ′,  106 ′.  FIG. 15  is a top plan view of the thread feeding system  103  shown in  FIG. 14 .  
      The concept of net tension control for a thread group may be further explained using the diaper manufacturing as thread processing system example. According to a preferred embodiment, as shown in  FIG. 13 , thread feeding system  103  includes two thread groups  104 ,  104 ′ having two threads per group. Each thread group is driven by a separate drive and tension control apparatus  110  with a separate driven take-off roll  111 . Both thread groups may be supplied to a diaper manufacturing process to provide the elastic band features near the open end of the legs. A first thread group may provide the elastic feature for the right leg portion, and a second thread group may provide the elastic feature for the left leg portion. During manufacturing, the tension of the elastic feature for the right or left leg portion may no longer be at an acceptable level due to tension variations in the thread. Thread feeding system  103  enables the tension of the first thread group or the second thread group to be adjusted independently of the other thread group in order to correct any such variations.  
      In operation, a thread processing system is likely to provide a signal to the tension controller  119  of the drive and tension control apparatus  110  indicating what speed motor  127  should operate at to provide the necessary elongation to achieve a desired tension. The signal from the thread processing system is typically based on industry standards that have been created indicating the theoretical amount of elongation necessary to achieve a desired tension. This input signal from the thread processing system is referred to as the tension set point and initially dictates the speed of the driven take-off roll  111  of the drive and tension control apparatus  110 .  
      According to a preferred embodiment, a user enters a desired tension range that is to be maintained for the thread group directly into tension controller device  119 . The tension controller device receives input signals from the tension sensor  115  representative of the thread tension. Tension controller device  119  uses these input signals to determine whether the tension level of the thread coming off driven take-off roll  111  can be maintained because it is within the desired tension range, or whether the tension needs to be increased or decreased. Variable-speed motor  127  of the drive and tension control apparatus  110  will maintain a speed until tension controller device  119  outputs a signal indicating that the net tension is outside the desired range based on a signal received from the tension sensor  115 . The output signal from tension sensor  115  will override an input signal from the thread processing system and change the speed of the variable speed motor  127  of the drive and tension control apparatus  110  until the speed is within the desired range. That is, the speed of motor  127  will be adjusted to correct for variations in tension that occur during unwinding or the thread feeding process.  
      If the tension controller device  119  determines that the thread tension after driven take-off roll  111  is too high, the tension controller device  119  will increase the speed of motor  127 . Alternatively, if the tension controller device  119  determines that the thread tension after driven take-off roll  111  is too low, the tension controller device  119  will decrease the speed of motor  127 .  
      As described above, thread feeding system  103  may be configured to look at a signal from the thread processing system as well as a signal from the tension sensor  115  in determining the appropriate speed for motor  127 . In alternative embodiments, the drive and tension control apparatus  110  of thread feeding system  103  may be configured to look only at a signal from tension sensor  115  (i.e., a tension feedback signal) in determining the appropriate speed for motor  127 . Further, thread feeding system  103  may include multiple sensors positioned throughout the system that determine the appropriate speed of motor  127 .  
      According to another alternative embodiment, as shown in  FIG. 16 , thread feeding system  203  may be configured with separate drive and tension control apparatus  210  to control the tension of each thread separately. Controlling the tension of each thread separately may advantageously be used to correct variations in each active package. Junction boxes  219 A and  219 C contain cabling and power connections to the tension control apparatus  210 . Junction box  219 B contains, for example, the BTSR Model SMDIN/RW Controller, as the tension controller device  219  for each drive and tension control apparatus  210 . Controlling the thread tension for each thread separately is in contrast to the apparatus shown in  FIG. 9  and  FIG. 10 , where the thread feeding system  103  controlled the net thread tension of a thread group. Controlling the net thread tension of a thread group tension corrects overall variability in the combined packages, but does not separately correct for variability for individual active packages in the thread group.  
      As shown in  FIG. 17 , drive and tension control apparatus  210  includes a separate variable-speed motor  227  and a corresponding separate tension sensor  215  for each individual thread. While such a system may advantageously correct variations in each active package, use of such a system may not be cost efficient considering the costs of motors, tension sensors, and tension controller devices.  
      According to a preferred embodiment, the speed of motor  227  is controlled without receiving input from a thread processing system. That is, the motor speed is based solely on tension feedback detected by tension sensor  215  and recognized by tension controller device  219 .  
      When only a single thread is being driven by driven take-off roll  211 , the guide system for a thread feeding system may be simplified as compared to a system using multiple threads wherein thread paths must be kept separate. For example, thread feeding system  203 , as shown in  FIG. 16 , may use a guide system  212  having only a static guide  212 A, such as a ceramic eye, through which the thread passes after coming off package  205 , and a first guide roller  213 A to direct the thread towards driven take-off roll  211 .  
      In the single thread configuration shown in  FIG. 16 , the control of the speed of motor  227  is based solely on tension feedback. In this case, the changes in speed are likely to occur more frequently and in larger increments/decrements than a thread feeding system controlled by a tension set point provided by a thread processing system in combination with tension feedback, as discussed above. In particular, a large decrement in the speed of motor  127  may cause slack in the thread before reaching driven take-off roll  211  which may lead to a subsequent slippage of the thread around driven take-off roll  211 .  
      To reduce the likelihood of such slack in the thread before reaching driven take-off roll  211 , a pretensioner may be used in the first guide roll  213 A. Background art pretensioners rely on friction between the thread and the pretensioner to maintain tension in the thread feeding system and avoid slack in the thread. However, such friction-type pretensioners are not applicable to elastomeric threads where tack is an issue. Accordingly, pretensioner guide roll  213 A uses a pretensioner which otherwise hinders the speed of rotation of the guide roll. In a preferred embodiment for pretensioner guide roll  213 A, a magnet is positioned adjacent to pretensioner guide roll  213 A and a material that is coupled to the guide roll. The material to be coupled to the guide roll is, for example, a ferrous metal such as steel. The magnetic force slows the rotational speed of the pretensioner guide roll  213 A and thereby maintains the tension and eliminates slack in the thread without relying on friction.  
      As shown in  FIG. 17 , after the thread is directed around pretensioner guide roll  213 A, the thread is wrapped around driven take-off roll  211 . A tension sensor  215  is positioned after driven take-off roll  211 . The guide roll  213 B is located after driven take-off roll  211 . In addition, the tension sensor  215  may also be simplified because only a single thread is being used.  
       FIG. 18  is an exemplary enlarged front elevational view of a second embodiment of a single threads drive and tension control apparatus  210 . As shown in  FIG. 18 , after the thread is directed around pretensioner guide roll  213 A, the thread is wrapped around driven take-off roll  211 . In particular, the thread is wrapped around driven take-off roll  211  at an angle sufficient to minimize slippage and low enough to avoid tangling. The angle at which the thread is wrapped around driven take-off roll  211  is referred to as a “first wrap angle.” Preferably the first wrap angle (θ 1 ) is approximately between 2 degrees and 360 degrees. The first wrap angle (θ 1 ) may vary depending on the type of elastomeric thread of fiber being used and the corresponding level of tack. According to a particularly preferred embodiment, the thread is wrapped around driven take-off roll  211  at the first wrap angle (θ 1 ) of approximately 270 degrees. The first wrap angle (θ 1 ) can be obtained by the proper positioning of guide rolls  213 A, driven take-off roll  211 , and tension sensor  215 .  
      The tension sensor  215  is positioned after driven take-off roll  211 . The guide roll  213 B is located after driven take-off roll  211 . The thread maintains a second wrap angle (θ 2 ) across tension sensor  215  that provides an accurate and consistent measurement of the thread tension in the range of 0 to 180 degrees of circumference. The thread is pressed against the thread guides before and after the tension sensor to guarantee a consistent second wrap angle (θ 2 ). The second wrap angle (θ 2 ) can be obtained by the proper positioning of guide rolls  213 B, driven take-off roll  211 , and tension sensor  215 . A tension controller device  219  monitors the thread tension measured by tension sensor  215  and at least one of increments, maintains or decrements the speed of the variable-speed motor  227 .  
       FIG. 19  is a right side elevational view of the drive and tension control apparatus  210  shown in  FIG. 18 . As shown in  FIG. 19 , after the thread is directed around the driven take-off roll  211  which is driven by motor  227 , the thread passes through the tension sensor  215  and out of the apparatus via guide roll  213 B.  
       FIG. 20  is a top plan view of the single threads drive and tension control apparatus shown in  FIG. 18 . As shown in  FIG. 20 , after the thread is directed around pretensioner guide roll  213 A, the thread is wrapped around driven take-off roll  211 . A tension sensor  215  is positioned after driven take-off roll  211 . The guide roll  213 B is located after driven take-off roll  211   
       FIG. 21  an exemplary enlarged front elevational view of a third embodiment of a single thread drive and tension control apparatus  210 . As shown in  FIG. 21 , after the thread is directed around pretensioner guide roll  313 A, the thread is wrapped around driven take-off roll  311  which is driven by motor  327 . In particular, the thread is wrapped around driven take-off roll  311  at an angle sufficient to minimize slippage and low enough to avoid tangling. The angle at which the thread is wrapped around driven take-off roll  311  is referred to as a “first wrap angle.” Preferably the first wrap angle (θ 1 ) is approximately between 2 degrees and 360 degrees. The first wrap angle (θ 1 ) may vary depending on the type of elastomeric thread of fiber being used and the corresponding level of tack. According to a particularly preferred embodiment, the thread is wrapped around driven take-off roll  311  at the first wrap angle (θ 1 ) of approximately 270 degrees. The first wrap angle (θ 1 ) can be obtained by the proper positioning of guide rolls  313 A, driven take-off roll  311 , and tension sensor  315 .  
      A tension sensor  315  is positioned after driven take-off roll  311 . The guide roll  313 B is located after driven take-off roll  311 . The thread maintains a second wrap angle (θ 2 ) across tension sensor  315  that provides an accurate and consistent measurement of the thread tension in the range of 0 to 180 degrees of circumference. The thread is pressed against the thread guides before and after the tension sensor to guarantee a consistent second wrap angle (θ 2 ). The second wrap angle (θ 2 ) can be obtained by the proper positioning of guide roll  313 B, driven take-off roll  311  and tension sensor  315 . A tension controller device  319  monitors the thread tension measured by tension sensor  315  and at least one of increments, maintains or decrements the speed of the variable-speed motor  327 .  
       FIG. 22  is a top plan view of the third embodiment of the single threads drive and tension control apparatus  310  shown in  FIG. 21 . As shown in  FIG. 21 , after the thread is directed around pretensioner guide roll  313 A, the thread is wrapped around driven take-off roll  311 . A tension sensor  315  is positioned after driven take-off roll  311 . The guide roll  313 B is located after driven take-off roll  311 . A tension controller device  319  monitors the thread tension measured by tension sensor  315  and at least one of increments, maintains or decrements the speed of the variable-speed motor  327 .  
       FIG. 23  shows a flow diagram for the tension trim algorithm  2301  of the method of monitoring threads or fiber tension of the present invention. In step  2303  of  FIG. 23 , the method determines whether any of the threads or fibers is broken. When a broken thread or fiber is detected, a BREAK ALARM is set in step  2305  and the tension trim algorithm  2301  is stopped at step  2327 A.  
      When no broken threads or fibers are detected in step  2303 , the method determines whether the threads or fibers are moving in step  2304  of  FIG. 23 . When the threads or fibers are not moving, a MOTION ALARM is set in step  2309  and the tension trim algorithm  2301  is stopped at step  2327 B. When the threads or fibers are moving, a measurement of the tension of the moving threads or fibers occurs in step  2311 .  
      In step  2312  of  FIG. 23 , the method determines whether any of the individual thread or fibers has a tension that is outside of a predetermined range. The predetermined range is preferably defined by at least one of the mean range tension and maximum tension as disclosed in TABLE 1 to TABLE 5 above. Alternatively, any acceptable predetermined range of tensions may be used with the thread feed processing system. When an out-of-range value of tension is detected, a TENSION ALARM is set in step  2313 .  
      In accordance with whether the out-of-range tension is above or below the predetermined range, the motor speed is decremented or incremented, respectively, in step  2314 . The number of increments and decrements in the motor speed over the course of the algorithm are stored in step  2320 . When an individual thread or fiber tension has a value that is out-of-range, the method determines whether the number of increment/decrement steps that is stored in step  2320  exceeds a correction threshold in step  2318 .  
      When no out-of-range tension values are detected for the individual threads or fibers, the method determines an average value for the tension of multiple threads or fibers in step  2315  of  FIG. 23 . In addition, the average value for the threads or fiber tension is stored in step  2317 .  
      In step  2318  of  FIG. 23 , the method determines whether the average value for the threads or fiber tension is outside of a predetermined range. The predetermined range is preferably defined by at least one of the mean range tension and maximum tension as disclosed in TABLE 1 to TABLE 5 above. When an average value for the thread or fiber tension has a value that is out-of-range, the method determines whether the number of increment decrement steps, previously stored in step  2320 , exceeds a correction threshold in step  2323 .  
      The correction threshold is a predetermined value that is entered in the trim tension algorithm  2301  at initialization and may be updated in real-time. The predetermined value is a maximum number of corrections that are to be allowed by the algorithm before operator intervention is suggested. The values for the predetermined value of the correction threshold may be different in terms of the number of decrements and the number of increments that are determined to exceed the threshold.  
      When the correction threshold has been exceeded, by either or both the number of increments or decrements, a TENSION UPDATE alarm is set in step  2325  and the tension trim algorithm  2301  is stopped at step  2327 C. When the tension trim algorithm  2301  is stopped at either of steps  2327 A,  2327 B or  2327 C, as discussed above, the operator can read the alarm status of the equipment and take the appropriate steps to intervene and correct the process.  
      When the average value of the thread or fiber tension is not out-of-range, the method maintains the motor speed, as indicated in step  2321  and returns to step  2303  to repeat the above discussed trim tension monitoring algorithm.  
      The foregoing description of the present invention provides illustration and description, but is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The scope of the invention is defined by the claims and their equivalents.  
      The foregoing figures (FIG.) show particular unwinder systems used to feed elastomeric threads to a thread processing system. However, it should be understood that the present invention is not limited to the configuration of the unwinder systems shown. Alternative unwinder systems also fall within the scope of the present invention even if they vary from the unwinder systems shown in a variety of ways not limited to but at least including: (1) number of threads being fed; (2) types of packages supported; (3) positioning and use of guide members; and (4) number and type of drive systems. In particular, the present invention is suitable for use with any unwinder system where it would be desirable to monitor and control the tension of elastomeric or other types of thread in order to minimize tension variations in the thread from being introduced into a thread processing system.  
      In addition, though the figures illustrate a particular unwinder system that uses the OETO method for unwinding a package, it should be understood that the present invention is equally suitable for use with unwinder systems that do not use the OETO method. In particular, the present invention applies to all unwinder systems where a tension monitoring and tension adjusting system can be used to enhance efficiency and/or quality of thread processing systems using elastomeric or other types of threads.  
      Further, the written description of the preferred and other exemplary embodiments discusses the applicability of the present invention for providing elastomeric thread to a thread processing system in the form of a diaper manufacturing system. In particular, the application is preferably directed at the task of supplying elastomeric thread to be used for the elastic band features present near the open end of the legs of the diaper. While the present invention is shown in a diaper manufacturing environment, such illustration is not intended to be limiting and is included for exemplary purposes only. It will be understood by those skilled in the art after reading the description that the present invention is equally suitable for use for any other manufacturing process that utilizes an elastomeric thread.  
      Further, though only a few exemplary embodiments of the present invention have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible in these embodiments (e.g., types of rack systems, guide systems, drive systems, and control systems; sizes, structures, shapes and proportions of the various elements and mounting arrangements; and use of materials in terms of combinations and shapes) without materially departing from the novel teachings and advantages of the present invention.  
      Furthermore, the order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating configuration and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the inventions as expressed herein.