Patent Abstract:
The present invention provides a double end yarn drive pattern attachment for tufting machines characterized by independent servo-motor control of yarn feed rolls capable of increased torque to carry multiple yarn ends on a single feed roll, thereby economically retaining many advantages of a single end pattern attachment. The improved attachment utilizes an intermediate gear to provide a relatively high torque drive adaptable between single and plural yarn pattern attachments.

Full Description:
This application is a continuation in part of U.S. Ser. No. 10/227,376 filed Aug. 23, 2002, issued as U.S. Pat. No. 6,550,407. 

   BACKGROUND OF THE INVENTION 
   This invention relates to a yarn feed mechanism for a tufting machine and more particularly to a scroll-type pattern controlled yarn feed where about two to five yarns may be wound on a separate yarn feed roll, and each yarn feed roll is driven by an independently controlled servo motor; or for providing a high torque single end yarn feed roll drive. 
   Pattern control yarn feed mechanisms for multiple needle tufting machines are well known in the art and may be generally characterized as either roll-type or scroll-type pattern attachments. Roll type attachments are typified, by J. L. Card, U.S. Pat. No. 2,966,866 which disclosed a bank of four pairs of yarn feed rolls, each of which is selectively driven at a high speed or a low speed by the pattern control mechanism. All of the yarn feed rolls extend transversely the entire width of the tufting machine and are journaled at both ends. There are many limitations on roll-type pattern devices. Perhaps the most significant limitations are: (1) as a practical matter, there is not room on a tufting machine for more than about eight pairs of yarn feed rolls; (2) the yarn feed rolls can be driven at only one of two, or possibly three speeds, when the traditional construction utilizing clutches is used—a wider selection of speeds is possible when using direct servo motor control, but powerful motors and high gear ratios are required and the shear mass involved makes quick stitch by stitch adjustments difficult; and (3) the threading and unthreading of the respective yarn feed rolls is very time consuming as yarns must be fed between the yarn feed rolls and cannot simply be slipped over the end of the rolls, although the split roll configuration of Watkins, U.S. Pat. No. 4,864,946 addresses this last problem. 
   Scroll-type pattern attachments are disclosed in J. L. Card, U.S. Pat. No. 2,862,465, and are shown projecting transversely to the row of needles, although subsequent designs have been developed with the yarn feed rolls parallel to the row of needles as in Hammel, U.S. Pat. No. 3,847,098. Typical of scroll type attachments is the use of a tube bank to guide yarns from the yarn feed rolls on which they are threaded to the appropriate needle. In this fashion yarn feed rolls need not extend transversely across the entire width of the tufting machine and it is physically possible to mount many more yarn feed rolls across the machine. Typically, scroll pattern attachments have between 36 and 120 sets of rolls, and by use of electrically operated clutches each set of rolls can select from two, or possibly three, different speeds for each stitch. The use of yarn feed tubes introduces additional complexity and expense in the manufacture of the tufting machine; however, the greater problem is posed by the differing distances that yarns must travel through yarn feed tubes to their respective needles. Yarns passing through relatively longer tubes to relatively more distant needles suffer increased drag resistance and are not as responsive to changes in the yarn feed rates as yarns passing through relatively shorter tubes. Accordingly, in manufacturing tube banks, compromises have to be made between minimizing overall yarn drag by using the shortest tubes possible, and minimizing yarn feed differentials by utilizing the longest tube required for any single yarn for every yarn. Tube banks, however well designed, introduce significant additional cost in the manufacture of scroll-type pattern attachments. 
   One solution to the tube bank problems, which also provides the ability to tuft full width patterns is the full repeat scroll invention of Bradsley, U.S. Pat. No. 5,182,997, which utilizes rocker bars to press yarns against or remove yarns from contact with yarn feed rolls that are moving at predetermined speeds. Yarns can be engaged with feed rolls moving at one of two preselected speeds, and while transitioning between rolls, yarns are briefly left disengaged, causing those yarns to be slightly underfed for the next stitch. 
   Another significant limitation of scroll-type pattern attachments is that each pair of yarn feed rolls is mounted on the same set of drive shafts so that for each stitch, yarns can only be driven at a speed corresponding to one of those shafts depending upon which electromagnetic clutch is activated. Accordingly, it has not proven possible to provide more than two, or possibly three, stitch heights for any given stitch of a needle bar. 
   As the use of servo motors to power yarn feed pattern devices has evolved, it has become well known that it is desirable to use many different stitch lengths in a single pattern. Prior to the use of servo motors, yarn feed pattern devices were powered by chains or other mechanical linkage with the main drive shaft and only two or three stitch heights, in predetermined ratios to the revolutions of the main drive shaft, could be utilized in an entire pattern. With the advent of servo motors, the drive shafts of yarn feed pattern devices may be driven at almost any selected speed for a particular stitch. 
   Thus a servo motor driven pattern device might run a high speed drive shaft to feed yarn at 0.9 inches per stitch if the needle bar does not shift, 1.0 inches if the needle bar shifts one gauge unit, and 1.1 inches if the needle bar shifts two gauge units. Other slight variations in yarn feed amounts are also desirable, for instance, when a yarn has been sewing low stitches and it is next to sew a high stitch, the yarn needs to be slightly overfed so that the high stitch will reach the full height of subsequent high stitches. Similarly, when a yarn has been sewing high stitches and it is next to sew a low stitch, the yarn needs to be slightly underfed so that the low stitch will be as low as the subsequent low stitches. Therefore, there is a need to provide a pattern control yarn feed device capable of producing scroll-type patterns and of feeding the yarns from each yarn feed roll at an individualized rate. 
   Commonly assigned U.S. Pat. No. 6,224,203, invented by Morgante et. al., incorporated herein by reference, addressed many of these concerns by creating a single-end servo attachment. This servo-scroll attachment allowed each end of yarn across the entire width of a full-size tufting machine to be independently controlled. By providing each end of yarn with an independently driven yarn feed roll, the use of the tube bank was eliminated, while allowing the creation of patterns that do not repeat across the entire width of a broadloom tufting machine. Despite the advances associated with a single-end servo scroll attachments, the cost of the single end attachment makes its use for generic or commodity carpeting financially disadvantageous. In addition, for tufting at high speeds with bulky yarns, it is desirable to have more torque than is provided by the relatively small servo motors that can be positioned on the single-end servo attachment disclosed in the U.S. Pat. No. 6,224,203. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of this invention to provide in a multiple needle tufting machine a pattern controlled yarn feed mechanism incorporating a plurality of individually driven yarn feed rolls carrying at least two yarn ends. 
   The yarn feed mechanism made in accordance with this invention includes a plurality of yarn feed rolls, each being directly driven by a servo motor up to approximately twenty yarn feed rolls with attached servo motors, may be mounted upon an arched mounting arm which is attached to the tufting machine. A plurality of mounting arms extend across the tufting machine. Each yarn feed roll is driven at a speed dictated by its corresponding servo motor and each servo motor can be individually controlled. 
   It is a further object of this invention to provide a pattern controlled yarn feed mechanism with many of the benefits of a single-end motor driven yarn feed attachment at reduced cost. 
   It is yet another object of the invention to provide additional torque for the rotation of the yarn feed rolls, without using unnecessarily large servo motors, for use with both single and multiple yarn feed rolls. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevation view of the multiple-needle tufting machine incorporating an embodiment the double-end pattern control yarn feed mechanism made in accordance with the invention; 
       FIG. 2  is a side elevation view of a similar embodiment of an arched support for a pattern control yarn feed mechanism according to the invention, shown in isolation; 
       FIG. 3  is a top elevation view of a segment of a support bar with four servo driven yarn feed rolls, two on each side; 
       FIG. 4  is a rear elevation view of a section of a support holding two stepped down yarn feed rolls, two servo motors that control yarn feed roll rotation, and yarn guide plate; 
       FIG. 5A  is a side elevation view of a double-end pattern control yarn feed mechanism utilizing a geared drive system. 
       FIG. 5B  is a rear elevation view of the invention of  FIG. 5A , taken along a section of the support bar and showing two yarn drives and a yarn guide plate. 
       FIGS. 6A and 6B  illustrate the tufting pattern dictated by double-end servo scroll attachments showing identical tufting heights for each needle pair fed by a given servo motor. 
       FIG. 7  is a schematic view of the electrical flow diagram for a multiple needle tufting machine incorporating a yarn feed mechanism made in accordance with the present invention. 
       FIG. 8  is a side elevation view of a preferred embodiment of a double-end pattern control yarn feed mechanism according to the invention. 
       FIG. 9  is a rear elevation view of a section of a support bar with a servo driver yarn feed roll and intermediate reducing gear on each side. 
       FIG. 10  is another rear elevation view with some detail removed to better illustrate the gear interfaces. 
       FIG. 11  is a rear elevation view of a single end servo scroll adapted to the same servo motor and gearing arrangement as the double end scroll. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings in more detail,  FIG. 1  discloses a multiple needle tufting machine  10  upon the front of which is mounted a pattern control yarn feed attachment  11  in accordance with this invention. It will be understood that it is possible to mount pattern control yarn feed attachments  11  on both sides of a tufting machine  10  when desired. The machine  10  includes a housing  12  and a bed frame  13  upon which is mounted a needle plate, not shown, for supporting a base fabric adapted to be moved through the machine  10  from front to rear in the direction of the arrow  14  by front and rear fabric rollers. The bed frame  13  is in turn mounted on the base  15  of the tufting machine  10 . 
   A main drive motor drives a rotary main drive shaft  17  mounted in the head  18  of the tufting machine. Drive shaft  17  in turn causes push rods  19  to move reciprocally toward and away from the base fabric. This causes needle bar  20  to move in a similar fashion. Needle bar  20  supports a plurality of preferably uniformly spaced needles  21  aligned transversely to the fabric feed direction  14 . 
   In operation, yarns  22  are fed through tension bars  23 , into the pattern control yarn feed device  11 . After exiting the yarn feed device  11 , yarns  22  are guided in a conventional manner through yarn puller rollers  24 , and yarn guides  25  to needles  21 . A looper mechanism, not shown, in the base  15  of the machine  10  acts in synchronized cooperation with the needles  21  to seize loops of yarn  22  and form cut or loop pile tufts, or both, on the bottom surface of the base fabric in well known fashions. 
   In order to form a variety of yarn pile heights, a pattern controlled yarn feed mechanism  11  incorporating a plurality of yarn feed rolls adapted to be independently driven at different speeds has been designed for attachment between the tensioning bars  23  and the yarn puller rollers  24 . As best disclosed in  FIGS. 1 and 2 , an array of yarn drives  35  is assembled on an arching support bar  26  extending across the front of the tufting machine  10  and providing opposing vertical mounting surfaces  71 ,  72  on each of its sides and an upward facing top surface  73  (shown in FIG.  3 ). On the opposing side-facing surfaces  71 ,  72  are preferably mounted a total of twenty servo motors  31  and driven yarn feed rolls  39 , ten on each side, shown in isolation in FIG.  3 . It will be understood that the number of rolls on each support bar  26  may be varied for many reasons, especially in proportion to the gauge of the needles  21  on the needle bar  20 . For instance, in the case of ⅛ gauge needle spacing (8 needles per inch) and support bars spaced every three inches, it would be desirable to carry twelve independently driven double end yarn feed rolls on each support bar  26 . In practice, the support bars  26  should carry at least about six, and preferably at least about twelve, double end servo driven yarn feed rolls  39 . Typically, each support bar  26  will carry a complement of twenty servo motor driven yarn feed rolls  39 , and the spacing of the support bars will be adjusted to suit the needle gauge. 
   As shown in FIG.  1  and in detail in  FIG. 3 , the arching support bar  26  accommodates the wiring bundle  53  from the motors via the wiring path  43 , shown in  FIG. 4 , built into the arching support bar  26 , which facilitates the wiring of the motors. Wiring plugs  54   a  and  54   b  join the wiring bundle  53  to leads connected to the motors  31  and allow for easy servicing. Wiring bundle  53  is in turn connected to servo motor controller board, which may be in a central cabinet or installed on an arching support  26 . 
   Each double end yarn drive  35  consists of a yarn feed roll  39  and a servo motor  31 . In one embodiment, the servo motor  31  directly drives the yarn feed roll  39 , which may be advantageously attached concentrically about the servo motor  31 , as shown in FIG.  3 . Preferably a yarn  22  is directed by yarn guide plates  27  and other conventional designs so that the yarn wrapped around nearly 180° of the circumference of the yarn feeding surface  28  of the yarn feed roll, and at least about 135° of said circumference. As shown in  FIG. 4 , yarn guide posts  34  may protrude from the yarn guide plates  27  in the general direction of the yarn feed, and help ensure the proper placement of two or more yarns  22  on yarn feed rolls  39 . 
   It will also be noted in  FIGS. 2 and 4  that yarns  22  from the yarn supply are fed through apertures  29  on the support yarn guides  27 ,  37 . Specifically, a pair of yarns  22  for a yarn feed drive  35  on the support  26  distal from the tufting machine are fed through apertures  29   a ,  29   b  near the bottom of guides  37  until the yarns reach their associated yarn drive  35 , and are fed around approximately 180° of the yarn feed roll  39  on its associated yarn drive  35 , and those yarns then continue through lower apertures  29   a ,  29   b  of the remaining support yarn guides  37 . Because two ends of yarn are wrapped around each of the ten yarn feed rolls  28  on one side of the attachment  11 , twenty apertures  29  are required on each of the left and right sides of the yarn guide plate  37  to accommodate the yarns. Yarns  22  being wrapped and driven by a contacting yarn feed roll  39  distal from the tufting machine  10  enter the apertures  29   a ,  29   b  with each of the two yarns to a particular yarn feed roll  39  threaded through adjacent apertures. For example apertures  29   a  and  29   b  could have yarns driven by the same yarn feed roll  39 . Yarns from a yarn feed roll  39  quite proximal to the tufting machine  11  would occupy apertures  29   c  and  29   d . The apertures  29  are arranged in parallel, diagonally offset rows. The arrangement allows all the yarn ends for each of the yarn feed rolls  39  to be directed through the attachment  11  to the proper needles without introducing unwanted friction between individual yarns. 
   It will also be seen in  FIG. 4  that the servo motors  31  are advantageously set on base plates  30  of greater diameter than the yarn feed rolls  39 , which permits the base plate  30  and attached motors  31  to be mounted on the support bar  26  with several motor mount bolts  38 . Additional fasterns  41  are used to secure covers  44 ,  45  or circuit board assemblies over support  26 , thereby defining wiring path  43 . 
   Each feed roll  39  has a yarn feeding surface  28  formed of a sand-paper like or other high friction material upon which the yarns are fed. As shown in  FIG. 3  end caps  46  help ensure the yarns  22  remain on the feeding surface  28 , and may protect motors  31  from dust or other contamination. Each of the yarn feed rolls  39  may be loaded with two yarns, which is a light load providing little resistance compared to the hundred or more yarns that might be carried on a roll-type yarn feed attachment, the hundreds of individual yarns typically driven by a single scroll drive shaft, or even the dozen yarns typically driven in the commonly assigned servo-scroll patent, U.S. Pat. No. 6,244,203. Because of the lighter loads involved in feeding only a very few yarns, the present design permits the use of small servo motors that can mount inside or outside of the yarn feed rolls  39 . For instance, a typical motor for a double end yarn would be a 24-28 volt motor using 3 amps of power. This motor would be able to generate 5 lb-in of torque at 3 amps, having a maximum no load speed of 650 RPM. A representative motor of this type is the Full Repeat Scroll Motor by Moog, Inc. (C22944), which meets these general specifications. A motor of this type is sufficiently powerful to turn the associated yarn feed roll without the need for any gearing advantage in most situations. Thus the preferred ratio of servo motor revolutions to yarn feed roll revolutions is 1:1. 
   However, in some applications, especially utilizing heavy and irregular yarns with frequent low stitch height to high stitch height yarn feed changes, additional torque may be preferred, whether a single or several yarns are being driven. Accordingly, modified yarn feed rolls  49  are shown in FIG.  4 . These yarn feed rolls  49  have a mounting section  48  that fits over and engages servo motors  31 , a stepped down diameter yarn feeding surface  28 , and an end cap portion  46 . The associated yarn guide plate  37  is also modified to a wider structure than that used with conventional yarn feed rolls  39 , shown in  FIG. 3 , so that the apertures  29  for feeding yarns are generally aligned beneath the yarn feeding surfaces  28 . By reducing the diameter of the yarn feed surface portion  28  of the yarn feed rolls, a single revolution of servo motor  31  feeds less yarn, effectively reducing the maximum yarn feed rate and increasing the torque of the yarn feed drive  35 . 
   In commercial operation, it is anticipated that a typical two meter, rug size tufting machine will utilize pattern controlled yarn feed devices  11  according to the embodiments of  FIGS. 1-4  with approximately fourteen support bars  26 , each bar bearing twenty yarn feed drives  35  thereby providing about 280 independently controlled yarn feed rolls  28 . This provides the capacity to feed 560 yarns in the double end drive configuration, without the necessity of a tube bank. If any yarn feed roll  39  or associated servo motor  31  should become damaged or malfunction, the arched support bar  26  can be pivoted downward for ease of access. A replacement yarn drive  35  already fitted with a yarn feed roll  39  or  49  and a servo motor  31  can be quickly installed. This allows the tufting machine to resume operation while repairs to the damaged or malfunctioning yarn feed rolls and motor are completed, thereby minimizing machine down time. 
   In a typical configuration, the double end yarn drives  11  are longitudinally spaced at about four to seven inch intervals along the support bar. This spacing is necessary to ensure proper yarn travel and minimal yarn resistance and stretching while still allowing enough space between the yarn feed rolls  39  or  49  to allow minor adjustments. The distance between support bar centers carrying double end drives  35  is typically about six to eight inches but may vary. This variability is necessary because of differences in the needle gauge that may be used. For instance, a larger needle gauge will require the needles to be spread at further intervals allowing more space between the support bars. However, for smaller needle gauges, the support arms will need to be closer together due to the increased proximity of the needles. As a result of the greater spacing between support bars in this embodiment in comparison to the single end drives of U.S. Pat. No. 6,283,053, yarn spreaders may be used to disperse the yarns from pattern attachment  11  to the yarn puller rollers  24  and guides  25 . 
     FIGS. 5A and 5B  illustrates an alternative preferred embodiment of a double end servo yarn feed pattern attachment  11 . In this embodiment, only about five servo motors  31  are mounted on each of the opposed surfaces  71 ,  72  of support bar  26 . The greater longitudinal spacing between servo motors  31 , now on the order of about eight to fifteen inches, permits the mounting of geared yarn feed rolls  59 . On servo motors  31  is mounted a drive gear  55 , having gear teeth  56  that mesh with teeth  57  of yarn feed roll  59 . The overall diameter of the servo motor  31  is only about three inches, and the drive gear  55  adds little additional diameter. The overall diameter of the teethed section  58  of the geared yarn drive roll  59  may be between about six to nine inches. The diameter of the yarn feeding surface portion  28  on rolls  59  remains at about three inches. Thus, it now requires two or three revolutions of servo motors  31  to feed the same lengths of yarn that would have been fed by a single servo motor revolution in the embodiment of FIG.  3 . The result is that the maximum yarn feed rate has been diminished and the effective torque of yarn feed drives  35  has been increased by a factor of about two or three. Unlike the extended yarn feed rolls  49  of  FIG. 4 , the geared rolls do not require additional lateral spacing between support bars, and about twenty-five to thirty such support bars  26  might be placed on a two meter tufting machine, with as little as 3¼ inch spacing between bar centers. Because the support bars  26  as illustrated in  FIG. 5  are spaced just as single end drive support bars, no changes are necessary to spread the yarns  22  as they exit the pattern attachment  11  and proceed to the yarn puller rollers  24 , guides  25  and needles  21 . 
   It will be understood that the geared portion  56  of drive gear  55  and the teethed section  58  of geared yarn feed roll  59 , are adjacent to the support bar  26 , so as not to interfere with placement of yarns over end cap  46  and on the yarn feeding surfaces  28 . This embodiment provides the enhanced torque desired for feeding a plurality of yarns, however, it does introduce a linkage between the geared wheels  55 ,  59 , and a slight loss in yarn feed precision in comparison to a direct yarn drive. 
     FIGS. 6A and 6B  illustrate the resolution characteristics of a simple carpet pattern manufactured with five double end yarn drives. Each of the yarn feed rolls A-E sends two yarn ends to adjacent needles. The yarns can be tufted with a plurality of heights, but for the sake of clarity stitch heights have been restricted to High (H), Medium (M), and Low (L). The use of double end drives restricts yarns on needle pairs  1 - 2 ,  3 - 4 ,  5 - 6 ,  7 - 8  and  9 - 10  to the same stitch height, creating double stitch groupings. In practical terms the finest resolution achievable with a double end yarn feed attachment is limited to the width of two contiguous needles. However, the stitch density is not affected. In other words fabrics with the same number of stitches per inch are produced as in products manufactured using single end yarn drives. The double end yarn drives can change stitch heights for a pair of needles just as stitch heights are changed for a single needle in a single end yarn drive. However, because both adjacent needles fed by a double end yarn drive must change to the same stitch height resulting in less definition on the finished fabric. The result is a patterned fabric having conventional stitch density, a wide range of variances in stitch height, but only half the resolution of single end yarn feed designs. A double end drive attachment permits tufting of fabrics with only half the yarn drives of a single end attachment without sacrificing any stitch count in the fabric. Double end attachments are therefore cheaper to manufacture, easier to maintain, and allow high resolution tufting to enter lower margin tufting markets. With appropriate modifications in the yarn guides  27 ,  37 , triple end and even quadruple end yarn feed attachments are also practicable, With a corresponding further loss in pattern definition. It must also be noted that the pattern design software used for tufting machines equipped with single end yarn feed attachments must be slightly modified for use with double end yarn feed attachments. Specifically, the software must be altered to require the stitches of paired needles to always be at the same heights. 
   Turning now to  FIG. 7 , a general electrical diagram of the invention is shown in the context of a computerized tufting machine with main drive motor  19  and drive shaft  17 . A personal computer  60  is provided as a user interface, and this computer  60  may also be used to create, modify, display and install patterns in the tufting machine  10  by communication With the tufting machine master controller  42 . 
   Due to the very complex patterns that can be tufted when individually controlling each end of yarn, many patterns will comprise large data files that are advantageously loaded to the master controller by a network connection  61 ; and preferably a high bandwidth network connection. 
   Master controller  42  preferably interfaces with machine logic  63 , so that various operational interlocks will be activated if, for instance, the controller  42  is signaled that the tufting machine  10  is turned off, or if the “jog” button is depressed to incrementally move the needle bar, or a housing panel is open, or the like. Master controller  42  may also interface with a bed height controller  62  on the tufting machine to automatically effect changes in the bed height when patterns are changed. Master controller  42  also receives information from encoder  68  relative to the position of the main drive shaft  17  and preferably sends pattern commands to and receives status information from controllers  76 ,  77  for backing tension motor  78  and backing feed motor  79  respectively, Said motors  78 , 79  are powered by power supply  70 . Finally, master controller  42 , for the purposes of the present invention, sends ratiometric pattern information to the servo motor controller boards  65 . The master controller  42  will signal particular servo motor controller board  65  that it needs to spin its particular servo motors  31  at given revolutions for the next revolution of the main drive shaft  17  in order to control the pattern design. The servo motors  31  in turn provide positional control information to their servo motor controller board  65  thus allowing two-way processing of positional information. Power supplies  67 ,  66  are associated with each servo motor controller board  65  and motor  31 . 
   Master controller  42  also receives information relative to the position of the main drive shaft  17 . Servo motor controller boards  65  process the ratiometric information and main drive shaft positional information from master controller  42  to direct servo motors  31  to rotate yarn feed rolls  28  the distance required to feed the appropriate yarn amount for each stitch. 
     FIGS. 8-10  present an improved double end yarn feed. The structure of  FIG. 8  can also be easily modified by the simple substitution of yarn feed rolls and yarn guide plates to operate as a single end servo scroll pattern attachment.  FIG. 8  shows an array of yarn drives  135  assembled on an arching support bar  126  which would be mounted across the front and in some instances also the back of tufting machine  10 . Support bars  126  have opposed mounting surfaces  171  and opposite surface  172  (shown in FIG.  9 ). On the opposing side facing surfaces  171 , 172 , are preferably mounted a total of twenty servo motors  131  and driven yarn feed rolls  139 , ten on each side. In addition, intermediate gear wheels  140  are placed in communication between servo motors  131  and yarn feed rolls  139 . The number of servo motors and yarn feed rolls on each support bar  126  may be varied as discussed in connection with previously described embodiments. 
   Each double end yarn drive  135  on pattern attachment  111  consists of a yarn feed roll  139  and intermediate gear  140  and a servo motor  131 . Preferably, yarns are directed by yarn guide plates  127  so that yarn is wrapped around a substantial portion of the yarn feeding surface  128  of the yarn feed rolls  139  (as shown in FIG.  9 ). The improved pattern attachment  111  in  FIG. 8  is designed to increase the torque applied by servo motors  131  to yarn feed rolls  139 . This is accomplished by mounting a drive gear  155  having gear teeth  156  that mesh with large circumference portion gear teeth  132  of intermediate gear  140 . When servo motor  131  rotates and correspondingly causes drive gear  155  (which is held in place by clamp  142 ) to similarly rotate, the result is that intermediate gear  140  rotates in the opposite direction and at a slightly higher rate of rotation due to the slightly smaller diameter and fewer gear teeth  132  in comparison to diameter of gear  155  and number of gear teeth  156 . However, intermediate gear  140  has a second smaller diameter section with substantially fewer gear teeth  133  that interface with gear teeth  157  on the very large diameter at gear portion  158  of yarn feed roll  139 . Because the smaller diameter section teeth  133  are only between ½ to ¼ as numerous as the larger diameter section teeth  132 , the effect of intermediate gear  140  is to require about two or three times as many revolutions of servo motor  131  to accomplish a revolution of yarn feed roll  139 . The result of employing the intermediate gear is that the maximum yarn feed rate is diminished and the effective torque of yarn feed drives  131  is increased by a factor of more than 2. Because the larger geared portion  138  of yarn feed rolls  139  and the smaller diameter teeth  133  of intermediate gear  140  are recessed into support  126  while yarn drive gear  155  and larger diameter section  132  at intermediate gear  140  are raised upon surfaces  171 , 172  of supports  126 , it is possible to arrange a compact array of ten yarn feed drives  135  on each opposed surface  171 , 172  of support  126 .  FIG. 9  is a sectional view taken along  9 — 9  in FIG.  8 . In this view the apertures  129  of yarn guide plate  137  as well as the opposed position of a pair of yarn feed drives  135  are illustrated. A particular advantage of this construction with a servo motor driven gear  155  and intermediate gear  140  to drive yarn feed roll  139  is that the yarn feed roll  139  rotates in the same direction as the servo motor  131 . In this fashion the programming utilized in connection with the pattern attachments shown in  FIGS. 1-4  where the servo motors directly drive yarn feed rolls, does not require adjustment. In the alternative construction of  FIG. 5  the servo motors rotate in the opposite direction of the yarn feed rolls, and it is necessary to utilize different programming to compensate for this characteristic. 
   A further advantage of the embodiment of  FIG. 8  is that in order to convert an attachment from a double end yarn feed drive to a single end yarn feed drive, the only changes required are the replacement of yarn feed rolls  139  with relatively wide yarn feeding surfaces  128  and the replacement of relatively guides  137 .  FIG. 11  illustrates the pattern attachment of  FIG. 8  in which single end yarn feed rolls  239  and narrower single end yarn guide plates  237  have been substituted. The resulting high torque single end yarn drive can be constructed with very few modifications to components utilized in the improved double end yarn feed drive. While the use of an intermediate gear  140  does introduce the possibility of some lost motion in driving yarn feed rolls  139 , bolts  175  permit yarn feed roll  139  to be adjusted in the direction of the axis of intermediate yarn feed roll  140  and thereby minimize any play or slack in the gears. 
   While preferred embodiments of the invention have been described above, it is to be understood that any and all equivalent realizations of the present invention are included within the scope and spirit thereof. Thus, the embodiments depicted are presented by way of example only and are not intended as limitations upon the present invention. While particular embodiments of the invention have been described and shown, it will be understood by those skilled in the art that the present invention is not limited thereto since many modifications can be made. Therefore, it is contemplated that any and all such embodiments are included in the present invention as may fall within the scope or equivalent scope of the appended claims.

Technology Classification (CPC): 3