Patent Abstract:
An article, method, and related apparatus for a novel hook and loop lock stitch. The lock stitch is embodied in a stitched article that includes a workpiece including a series of stitch holes, or a seam, therethrough and further including a back side surface composed of a hook material including hooks therein. The lock stitch is provided through each stitch hole, and includes an upper thread extending down through each stitch hole, forming a loop underneath the workpiece, and extending back up through each stitch hole. A lower thread, or strip, is composed of a hook material including hooks therein. The loop is spread out amongst the hooks of the lower thread and interlocks therewith. The lower thread is thus entrapped between and within the loop and the back side surface of the workpiece. The workpiece can include the back side surface being composed of a loop material including loops therein for interlocking with the hooks of the lower thread. The stitched article can also include an underlining applied to the back side of the workpiece and over the lower thread. The underlining can be composed of a loop material including loops therein interlocking with the hooks of the hook material of the lower thread to retain the underlining to the workpiece.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to methods and apparatus of sewing and stitching. More specifically, this invention relates to a lock stitch, wherein a novel “hook and loop” style lower thread is interlocked with a conventional upper thread. 
     2. Description of the Prior Art 
     Until now, the two-thread lock stitch has been among the most widely used methods of joining fabric. Conventionally, and as shown in FIGS. 1 and 2, a two-thread lock stitch  32 P includes two threads: a needle or upper thread  24 , and a bobbin or lower thread  50 P. The upper thread is typically wound on a spool system (not shown) to provide a continuous feed of thread. In contrast, the lower thread  50 P is typically wound on a bobbin  54 P to provide a predetermined feed of thread. The two-thread lock stitch  32 P is considered an efficient stitch that does not unravel easily and has a “both-sides equal” aesthetic appearance. In order to maintain the aesthetic appearance, the upper and lower threads  24  and  50 P must typically be composed of nearly identical size and strength material to enable stitch conformance. 
     Stitch conformance relates to the relative position of the upper and lower threads  24  and  50 P in the stitch as shown in FIGS. 1 and 2. Conventional lock stitch practice requires a balance of stitching force on either side of a workpiece  10 P being sewn, so that the lower thread  50 P is not completely pulled up through the workpiece  10 P. FIGS. 1 and 2 illustrate how the upper thread  24  and lower thread  50 P must properly entwine at a midpoint  16 P of the workpiece  10 P. 
     Referring to FIG. 1, in operation, a needle  20  penetrates the workpiece  10 P from a front side  12 P thereof, carrying with it the upper thread  24  that is fed through an eyelet  22  of the needle  20 . The needle  20  reaches the bottom of its stroke on a back side  14 P of the workpiece  10 P and starts to retract, thus forming a loop  26  from the slack upper thread  24 . Referring now to FIGS. 1 and 2, and as is well known in the art, the bobbin  54 P and the entire supply of lower thread  50 P is encircled by the loop  26  in order to interlock the upper and lower threads  24  and  50 P, thus forming the locking portion of the lock stitch  32 P. The size of the bobbin  54 P and quantity of lower thread  50 P is necessarily relatively small to enable them to be encircled by the loop  26 . Therefore, the bobbin  54 P is exhausted of its lower thread  50 P at extremely frequent intervals, resulting in downtime of the sewing operation, and, often, stopping and restarting of the sewing operation in the middle of the workpiece  10 P. 
     Several alternative methods and associated devices of the prior art have been directed at mitigating the problem of the limited supply of lower thread. For example, U.S. Pat. No. 4,117,789 to Rovin et al. teaches a method of automatically loading a bobbin in situ. Rovin et al. disclose a highly complex apparatus that is capable of reloading an empty bobbin in between workpiece cycles and as an operator positions a new workpiece to the sewing machine. The apparatus refills the empty bobbin, in situ, with a precisely measured length of thread. 
     U.S. Pat. No. 4,140,069 to Laursen teaches a sewing method and associated apparatus for forming a double backstitch seam. The double backstitch seam is formed similarly to previous versions of two-thread lock stitches with one exception. The upper thread is fed through the workpiece and a loop thereof is formed as usual. The lower thread, however, is processed much differently than those of the prior art. The supply of lower thread is not passed entirely through the loop as usual, but instead is passed through the loop in individual thread sections equal in length to several stitches. The lower thread is fed from a relatively large continuous spool, similar to the upper thread. As the loop is formed, a free end of the lower thread is fed and sucked through the loop by a suction nozzle. As the loop is tightened by the needle retracting back through the workpiece, a looper simultaneously grabs the lower thread section near its middle and a free end of a previous lower thread section. The looper then pulls back and tightens the lower thread sections against the loop, thus completing a lock stitch. 
     Finally, U.S. Pat. No. 4,366,765 to Hoekstra teaches use of a combination single thread chain and lock stitch. Hoekstra discloses a stitch formation having a first loop passing through the workpiece thus forming the first half of a chain stitch. A second loop passes through the workpiece and, with the first loop, forms the second half of the chain stitch. A locking thread passes through the closed end of the second loop to form a lock stitch. The chain and lock stitches thus formed are continuously alternated for the entire length of the stitch. 
     In addition to the problem of a limited supply of lower thread, thread breakage is a frequent problem when generating the conventional lock stitch. If either the upper or lower thread breaks during a stitch cycle, the entire process must be stopped and the sewing machine re-threaded. Additionally, the article being sewn must be scrapped, or the stitch removed and restarted, since the stitch cannot be stopped and restarted in mid-stitch. 
     Therefore, what is needed is a lock stitch, method, and related apparatus that is inexpensive, efficient, does not require a bobbin having a limited supply of lower thread, that uses a method and apparatus that are relatively simple compared to the prior art, and that is not so susceptible or sensitive to thread breakage. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided a novel lock stitch that does not require use of a bobbin nor other complex thread feeding mechanisms, thereby avoiding the shortcomings of the prior art—particularly that of thread breakage and a limited supply of lower thread. 
     In one form of the invention, an article is provided in the form of a workpiece having a novel lock stitch. Preferably, the stitched article includes the workpiece having upper and lower layers or plies, and a series of needle-made stitch holes extending from a front side through to a back side thereof. A stitch is provided through each stitch hole, and includes an upper thread and a lower thread. The upper thread extends down through each stitch hole, forms a loop underneath the workpiece, and extends back up through each stitch hole. The lower thread is composed of discrete cut-off segments of a hook material, having hooks therein, wherein the lower thread interlocks with the upper thread, and extends transversely through the loop and is entrapped between the loop and the back side surface of the workpiece. 
     Alternatively, the lower thread can take the form of a hook material composed of discrete cut-off segments that are each aligned with a respective stitch hole. The upper thread extends down through the workpiece and the hook material. The upper thread forms a loop underneath the workpiece and the loop is interlocked with the hooks. Optionally, the workpiece can include the back side surface that is composed of a loop material having loops therein for interlocking with the hooks of the lower thread. Further still, the stitched article can also include an underlining applied to the back side of the workpiece and over the lower thread. The underlining can be composed of a loop material having loops therein interlocking with the hooks of the hook material of the lower thread to retain the underlining to the workpiece. 
     An apparatus is provided for producing the lock stitch of the present invention wherein the apparatus includes a needle, with an eyelet therethrough, for penetrating the workpiece to a back side thereof. A loop spreader mechanism is provided on the back side of the workpiece for spreading a loop of the upper thread, as is well known in the art. A feeder mechanism and conduit is provided for feeding a portion of the lower thread through the loop of the upper thread, wherein a portion of the lower thread is entrapped between the loop and the back side of the workpiece to complete the lock stitch. 
     An assembly method is provided for using the apparatus of the present invention to make the stitched article of the present invention. The method includes penetrating a workpiece with a needle that carries an upper thread therethrough, wherein a loop of the upper thread is formed on a back side of the workpiece. Next, the loop of the upper thread is enlarged by a loop spreader and a portion of a lower thread is fed through the loop of the upper thread. The lower thread is fed in a direction transverse to the travel of the upper thread, and the lower thread is composed of a hook material having hooks therein. Finally, the needle is retracted back through the workpiece and thus the upper thread is pulled back through the workpiece, the loop is pulled tightly against the lower thread and the lower thread is in turn pulled against a back side surface of the workpiece. During the retracting step, the upper thread interlocks with the hooks of the lower thread to securely lock the stitch in place. 
     Accordingly, it is an object of the present invention to reduce overall process time by eliminating the need to use a bobbin of limited lower thread supply. The present invention provides an unlimited length of lower thread such that interrupting the sewing cycle to resupply the bobbin is unnecessary. Stitch cycle time is also reduced, since the upper thread need not make the long travel around the bobbin. 
     It is another object to provide improved locking action between an upper and lower thread of a lock stitch via interlocking action between hook and loop material used for the lower thread and back side of the workpiece. 
     It is yet another object to provide a simplified machine and method for producing a lock stitch. 
     It is a further object of the present invention to reduce or eliminate the instances of thread breakage, as is prevalent in the prior art. 
     These objects and other features, aspects, and advantages of this invention will be more apparent after a reading of the following detailed description, taken in conjunction with the appended claims and accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a seam being sewn according to a two-thread lock stitch of the prior art, wherein a lower thread wound on a bobbin is being passed through a loop in an upper thread to produce the lock stitch; 
     FIG. 2 is a perspective view of the seam of FIG. 1, wherein the upper thread is being pulled upwards to tighten against the lower thread to complete the lock stitch; 
     FIG. 3 is a partially cutaway perspective view of a seam being sewn into a workpiece according to one embodiment of the present invention; 
     FIG. 3A is a perspective view of three examples of a lower thread composed of hook material; 
     FIG. 3B is the workpiece of FIG. 3, further illustrating an underlining being applied underneath; 
     FIG. 4 is a partially cutaway perspective view of the stitching apparatus used for carrying out the method of the present invention; 
     FIG. 5 is a partially cutaway perspective view of the stitching apparatus of FIG. 4 illustrating a loop spreading step; 
     FIG. 6 is a partially cutaway perspective view of the stitching apparatus of FIG. 5, wherein a lower thread in the form of a strip is being fed through a loop in an upper thread; 
     FIG. 7 is a partially cutaway perspective view of the stitching apparatus of FIG. 6, wherein the loop of the upper thread is being pulled against the lower thread to complete the lock stitch; 
     FIG. 8A is a partial bottom perspective view of a seam being sewn according to another embodiment of the present invention; 
     FIG. 8B is a partial sectional view of an alternative workpiece and hook material of FIG. 8A; 
     FIG. 8C is a partial sectional view of another alternative workpiece and hook material of FIG. 8A; 
     FIG. 8D is a partial sectional view of yet another alternative workpiece and hook material of FIG. 8A; 
     FIG. 9 is a partially cutaway perspective view of the seam of FIG. 8A, wherein a loop of an upper thread is being flattened against a bottom thread hook material; 
     FIG. 10 is a perspective view of an alternative lower thread conduit and loop spreader device initially engaging the upper thread; 
     FIG. 11 is a top view of the device of FIG. 10 illustrating a quill fully inserted into the loop of the upper thread; 
     FIG. 12 is an end view of the device of FIG. 10 showing the loop of the upper thread initially engaged; and 
     FIG. 13 is an end view of the device of FIG. 11 showing the loop of the upper thread fully enlarged. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 3 through 7 illustrate partially cutaway sectional views in order to more clearly show the stitching operation. Additionally, the term back side may mean, in general, the area underneath the workpiece as the workpiece is being sewn. Back side may also refer specifically to the actual surface on the back side of the workpiece. This characterization applies analogously to the term front side. 
     Referring now in detail to the Figures and specifically to FIG. 3, there is shown an article or workpiece  10  undergoing a process of stitching according to an embodiment of the present invention. The workpiece  10  is shown as a combination of upper and lower plies  18 U and  18 L of material that are penetrable by a needle  20  from a top or front side  12  of the workpiece  10 . On a bottom or back side  14  of the workpiece  10 , a loop sheet  19  is preferably included in the form of an additional layer, but may instead take the form of individual patches or strips. As such, the loop sheet  19  establishes a back side surface  14 S of the workpiece  10 . The loop sheet  19  is consistent with hook and loop fastener material otherwise known under the trademark of VELCRO®. Thus, the loop sheet  19  includes a pattern of loops  19 L therein. Alternatively, the loop sheet  19  may be formed of loop material composed of DACRON® polyester scrim or mesh, or have an integral loop laminate. For example, automobile interior material, such as simulated leather, typically includes a woven backing layer that could be replaced by a woven or non-woven material having loop characteristics. 
     An upper thread  24  is shown along a seam  30  having four lock stitches  32  completed within four stitch holes  34  in the workpiece  10 . The upper thread  24  is preferably composed of any standard strand-like thread, but may also be composed of any other material including, for example, a monofilament line for limited applications, or a loosely stranded wire. The upper thread  24  includes a loop  26  that is formed underneath the workpiece  10  after the needle  20  penetrates the upper and lower plies  18 U and  18 L, and the loop sheet  19 . A lower thread  50  is caused to move inside the loop  26  such that when the needle  20  is withdrawn from the workpiece  10  the lower thread  50  resides between the loop  26  of the upper thread  24  and the back side  14  of the workpiece  10 , as the upper thread  24  is pulled upwards to tighten the loop  26 , thus establishing the lock stitch  32 . The lower thread  50  is preferably composed of material consistent with hook and loop fastener material, and, thus, includes a pattern of hooks  52  therein. 
     Moreover, upon retraction of the needle  20  from the workpiece  10 , the loop  26  of the upper thread  24  does not only encircle the lower thread  50 , but forces engagement of the hooks  52  to the loops  19 L on the loop sheet  19  to further secure the lock stitch. The hooks  52  of the lower thread  50  interlock with the loops of the loop sheet  19  underneath the workpiece  10  to secure the lock stitch. Those skilled in the art will recognize that the lower thread  50  preferably includes a cross-sectional area greater than the cross-sectional area of the stitch hole  34 , thereby preventing the lower thread  50  from being pulled through the stitch hole  34  by the upper thread  24 . The lower thread  50  is preferably formed as shown in FIG. 3 of discrete cut-off segments, cut from a continuous strip fed along the back side  14  of the workpiece  10 . As shown in FIG. 3A, the lower thread  50  preferably takes the form of a cylindrical shape  50 C. Alternatively, a laminate  50 A, or a folded laminate  50 B, could be used. 
     FIG. 3B illustrates an alternative application of the present invention with an underlining  70 . The underlining  70  is shown as being secured to a side of the lower thread  50  that is opposite the side that interlocks with the loop sheet  19 . The underlining  70  is also composed of a loop type material having loops  72  therein for interlocking with the hooks  52  of the lower thread  50 . Such an underlining  70  is preferably an individual sheet or patch of material, but may also take the form of a component attached to a larger assembly such as a seat (not shown). Accordingly, the hooks  52  of the lower thread  50  of the workpiece  10  can be quickly and easily interlocked to corresponding VELCRO® loops of a seat, a headliner, a dashboard, etc. 
     FIG. 4 illustrates the portion of a sewing apparatus  80  that is preferably used to produce the stitched article of FIG.  3 . Note that the direction of travel of the workpiece  10  in FIGS. 4 through 7 is exactly opposite that of FIG. 3, in order to more clearly show the loop  26  and lower thread  50  interaction. Located preferably underneath the workpiece  10 , is a base  82  that supports an upright loop spreader  84  and conduit  86 . The loop spreader  84  is moveably mounted with respect to the base  82  and includes a finger  88  as is consistent with such prior art devices. The conduit  86  is preferably fixed to the base  82 , or alternatively can be moveable with respect to the base  82 . A loop guard  90  extends parallel to but offset from the needle  20  and a blade  92  extends in the same direction as the needle  20  and abuts an exit end  86 E of the conduit  86 . 
     In operation, the needle  20  reciprocates down and up and carries in its eyelet  22  the upper thread  24  into and out of the workpiece  10  along the seam. As shown in FIG. 4, the needle  20  is carrying the upper thread  24  to the back side  14  of the workpiece  10  and has reached the bottom of its stroke. As the needle  20  begins its return, or upward stroke, the upper thread  24  becomes slack, thereby widening the loop  26 , as is well known in the art. The loop guard  90  is aligned closely to one side of the needle  20  in order to push the slack in the upper thread  24  to the opposite side of the needle  20  for enlarging the loop  26 , as is consistent with the prior art. Simultaneously, the loop spreader  84  begins to move toward the needle  20  as shown by arrow  84 A from its home position as shown in FIG.  4 . 
     The lower thread  50  is continuously fed through the conduit  86  in a direction transverse—preferably normal—to the direction of travel of the upper thread  24 . The lower thread  50  can be fed in any convenient method, but is preferably fed in a similar manner to that which is well known in the prior art and best exemplified by U.S. Pat. No. 4,920,904 to Frye, which is incorporated by reference herein. The blade  92 , in its up position as shown, temporarily blocks the lower thread  50  from advancing toward the loop  26 . 
     As shown in FIG. 5, the loop spreader  84  advances toward the needle  20  to its fully advanced position so that the finger  88  enters the loop  26 . The blade  92  remains in its up position and the loop spreader  84  begins to move sideways as shown by arrow  84 B. As shown in FIG. 6, the loop spreader  84  sweeps sideways to its fully open position away from the needle  20  in order to further enlarge the loop  26 . Simultaneously, the blade  92  drops away from the conduit  86  as shown by arrow  92 A to permit the lower thread  50  to feed forward through the enlarged loop  26  and stop against the loop spreader  84 . Accordingly, a portion of the lower thread  50  is fed through the loop  26 . As shown in FIG. 7, the blade  92  returns upward to its home position as shown by arrow  92 B to sever the lower thread  50  into a discrete segment  50 S of predetermined length. The needle  20  proceeds upward as shown by arrow  20 A, thereby pulling and entrapping the discrete segment  50 S of lower thread  50  in the loop  26  and forcing it against the back side  14  of the workpiece  10 . Alternatively, and not shown, the conduit  86  advances through the loop  26  with the lower thread  50  housed therein to an advanced position. The conduit  86  would then retract back out of the loop  26  while the lower thread  50  maintains the advanced position within the loop  26 . In this way, the conduit  86  would further ensure a proper feed of the lower thread  50  through the loop  26 . 
     As shown in FIGS. 8A and 9, an alternative article and method of sewing is presented. In FIG. 8A, a workpiece  110  includes upper and lower plies  118 U and  118 L, and a lower thread or hook material  150  establishing a back side surface  114  thereof. The hook material  150  preferably takes the form of a strip as shown, but can also take the form of patches or an entire sheet layer. The hook material  150  is preferably loosely applied to the back side of the workpiece  110 , but may be permanently attached thereto. As shown in FIG. 8A, the needle  20  carries the upper thread  24  down and up through the workpiece  110 . As discussed above, the loop  26  is formed along the back side surface  114  of the workpiece  110 , as is well known in the art. 
     In contrast with the previous embodiment, however, only a hook portion  152  of the lower thread  150  is fed into engagement or interlocks with the loop  26 . Here, the loop  26  is flattened against a portion of the hooks  152  of the hook material such that the loop  26  is spread out along the back side surface  114  amongst the hooks  152  for interlocking the upper thread  24  to the hooks  152  of the back side surface  114  of the workpiece  110 . Accordingly, the loop  26  of the upper thread  24  is maintained and secured by the hooks  152  along the back side surface  114  of the workpiece  110  and will not pull through the stitch hole (not shown). 
     FIGS. 8B and 8C respectively show standard hooks  152 B for use with a stranded upper thread  24 , and shanked cones  152 C for use with a monofilament thread (not shown). FIG. 8D illustrates a dual locking combination of standard hooks  152 B and shanked cones  152 C that are particularly suited for use with stranded types of thread. With this dual locking arrangement, the shanked cones  152 C provide a positive transverse lock and maintain position of the upper thread  24  until the loop  26  is forced into engagement with the hooks  152 B along the back side surface  114  of the workpiece  110 . Additionally, the stranded upper thread  24  may be slightly unraveled so as to be more receptive to being interlocked with the standard hooks  152 B and shanked cones  152 C of the lower thread. Accordingly, the standard hooks  152 B and shanked cones  152 C are sufficiently rigid and sharp in order to interlock with strands of the stranded upper thread  24 . 
     FIG. 9 illustrates one approach for flattening the standard loop  26  of the workpiece  110  of FIGS. 8A through 8C. FIG. 9 illustrates the workpiece  110  as a partial cutaway to better show the loop  26 . A hammer tool  95  is advanced upward into engagement with the loop  26  and perpendicular to the back side surface  114  of the workpiece  110 , so that the loop  26  flattens against the back side surface  114  of the workpiece  110 . The loop  26  thus engages the hooks (not shown) of the back side surface  114  to retain the loop  26  from pulling back through the workpiece  110 . A back side surface  114  combination of hooks  152 B and shanked cones  152 C, as shown in FIG. 8D, effects a situation where the upper thread (not shown) cleats around the shanked cones  152 C thereby being securely positioned and then locked in that position by the hooks  152 B. The hammer tool  95  is preferably advanced by a pneumatic cylinder located below the loop guard  90  and loop spreader apparatus (shown in FIG.  4 ). The hammer tool  95  also preferably includes a head  95 H composed of a resilient and conformable material such as rubber. Additionally, the head  95 H may have a predetermined surface configuration, such as one with projections, in order to more effectively force the loop  26  into interlocking engagement with the hooks. 
     FIGS. 10 through 13 illustrate a portion of the preferred embodiment of the apparatus of the present invention. As shown in FIG. 10, a quill  184  replaces the stationary conduit  86  of FIGS. 4 through 7. The quill  184  includes a hollow housing  186  and a hollow spreader  188  that is slidingly disposed within the hollow housing  186 . A spear portion  188 S pointedly terminates a hollow body portion  188 B of the spreader  188 . 
     As shown in FIGS. 10 and 12, the spreader  188  and lower thread  50  advance from a home position within the housing  186  toward the needle  20 . In this way, the spear portion  188 S begins to run through the loop  26  of the upper thread  24  in an initial engagement position as shown. Beyond this initial engagement position, the spreader  188  and lower thread  50  continue to advance through the loop  26  until they reach an advanced position. 
     The advanced position is set by a stopper  189 , that locates on the end of the lower thread  50  to prevent it from advancing any further, as shown in FIG.  11 . As best shown in FIGS. 11 and 13, as the spreader has advanced transversely through the loop  26 , the loop  26  has gradually enlarged as it transitions from, or ramps over, the spear portion  188 S to the body portion  188 B of the spreader  188 . Accordingly, the loop  26  directly circumscribes the body portion  188 B that, in turn, circumscribes the lower thread  50 . As a result, the lower thread  50  is now circumscribed by the loop  26  in the advanced position. 
     From this advanced position, the spreader  188  fully retracts back into the housing  186  to the home position, while the lower thread  50  remains in the advanced position circumscribed by the loop  26 . Finally, at or near the same time the needle  20  and upper thread  24  are retracted back upward, the blade  92  advances upward to sever the lower thread  50  and complete the stitch cycle. 
     From the above, it can be appreciated that a significant advantage of the present invention is that the sewing process need not be interrupted to supply more lower thread to a bobbin, either due to thread breakage or limited thread supply. In fact, the present invention provides for continuity of lower thread supply, where the sewing cycle need not be interrupted to add additional lower thread. 
     An additional advantage is that the thread locking action is improved because the pull-up force of the upper thread causes the hooks of the lower thread to penetrate, entwine, encircle, interlock, and otherwise mesh with the upper thread strands and the back side loop material. Accordingly, the stitched seam will have a higher than traditional shear strength and will be more resistant to being ripped apart. 
     Another advantage is that the size of the upper thread can be varied without affecting the conformance of the stitch. Stitch conformance is therefore guaranteed since regardless of the upper thread pull-up force, the lower thread cannot be pulled up through the workpiece. Therefore, any tension adjustment of the upper thread is much less sensitive and easier to control than with current lock stitches. 
     Yet another advantage is that thread damage will not migrate beyond the stitch that is damaged. Each discrete segment of lower thread locked with the upper thread against the hooks on the back side surface ensures that damage to the continuous upper thread will not migrate beyond the adjacent damaged stitch. This is because of the inherently high shear and locking strength associated with hook and loop joining. Similarly, threading can be terminated without the need for multiple end stitches to prevent unraveling of the seam. 
     Still another advantage is that the stitches will be more moisture resistant since each discrete segment of lower thread effectively blocks off the stitch hole on one side. Hooks on the lower thread interlocking with loops on the back side surface of the workpiece even further ensure moisture resistance. 
     A further advantage is that the hooks of the lower thread provide an attachment base for any underlining material having loops therein, such that the workpiece has inherent fastening capability. Accordingly the workpiece can be removably secured to another object having such an underlining material. Alternatively, an independent underlining material can be removably secured to the lower threads of the workpiece until it can be permanently secured thereto, similar to a basting thread attachment. 
     Still a further advantage is that the stitch of the present invention is not as susceptible to thread wear as stitches of the prior art. Interlocked stranded threads of the prior art tend to failure prematurely due to rubbing action between relatively small surface areas on the threads. This is particularly true for stitches in seat cushions that typically bear heavy dynamic loads. With the present invention, the surface area between the threads is much larger since the lower thread is much larger than lower thread of the prior art. Accordingly, the stitch is more capable of distributing load per unit area between the threads, and therefore more robust against failure due to thread wear. 
     Yet a further advantage is that the length of the lower thread segments can be varied in order to increase strength and rigidity of the workpiece. 
     While the present invention has been described in terms of a preferred embodiment, it is apparent that other forms could be adopted by one skilled in the art. For example the location of the hooks and loops could be reversed, such that the lower thread has loops and the back side of the workpiece has hooks. Accordingly, the scope of the present invention is to be limited only by the following claims.

Technology Classification (CPC): 3