Abstract:
A method is disclosed of producing an RFID tag assembly including an associated antenna and attachment means suitable for attaching the tag assembly to a material. The material may be flexible such as fabric or relatively rigid such as cardboard. The method includes forming the associated antenna and the attachment means as a unitary conductive frame. An RFID tag assembly produced by the method is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to an RFID tag assembly and method for producing the tag assembly. The tag assembly includes an associated antenna and an attachment means for attaching the assembly to a material. The material may be flexible such as fabric or it may relatively rigid such as cardboard. In a preferred embodiment the invention may include a rivet containing a radio frequency identification (RFID) tag. In some embodiments the tag may be applied to the material in the vicinity of a structure present on the material which structure may function as a secondary antenna. 
       THE PRIOR ART 
       [0002]    Use of a generic RFID tag on material such as fabric typically involves stitching the tag directly to the fabric or enclosing it within a patch to provide an enclosure for the tag. However this often leads to a bulky and inflexible solution particularly with a clothing garment that may be uncomfortable to wear. 
         [0003]    In one prior art solution, a conductive thread is used to provide a secondary antenna and a plastic encapsulated RFID tag in the form of a traditional clothing button is stitched to the fabric in order to couple to the secondary antenna to form a larger overall tag system. While this solution is flexible and comfortable the thread link holding the button to the fabric loosens over time with repeated washing cycles and the button can rock about or tilt, deteriorating electromagnetic coupling between a primary antenna on the RFID tag and the secondary antenna associated the fabric. 
         [0004]    An object of the present invention is to at least alleviate the disadvantages of the prior art. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention may provide a two part tag solution, namely an RFID tag assembly including an associated or primary antenna formed with means for attaching the assembly to a material such as fabric or cardboard. In some embodiments the primary antenna may couple to a secondary antenna provided on or with the material. This solution may be particularly useful since use of ultra high frequency (UHF) as a carrier frequency for RFID tags has become more widespread following introduction of international UHF RFID standards. Although RFID protocols have converged, allowed regional UHF carrier frequencies have not. A separate secondary antenna may be useful for longer range operation because it may allow itself and thus the overall tag be optimised for an operating region, using a common and economically manufacturable generic tag which may account for most of the total cost. 
         [0006]    The present invention may address the problems of the prior art by providing an RFID assembly such as a rivet to replace the unstable button. The rivet may be held firmly in place to maintain a relatively consistent electromagnetic coupling between the primary antenna associated with RFID tag and a secondary antenna associated with a flexible material such as a fabric item. The coupling may be substantially maintained throughout many washing cycles of the service life of the fabric item. 
         [0007]    The body of the rivet may be constructed from plastics such as polyamide (e.g. Nylon), a fluoropolymer (e.g. polytetrafluoroethylene (PTFE) or Teflon), a urethane, or acrylonitrile butadiene styrene (ABS), all which may exhibit desirable working properties such as molding or machining and may be relatively soft for comfortable wearing on a clothing garment. 
         [0008]    The RFID assembly may include a rivet and an RFID tag including a primary antenna. The RFID tag may include a substrate and an integrated circuit chip. The substrate may include a flexible film such as a polyester (e.g. polyethyleneterephthalate (PET)) for its ball bonding suitability for flip chip attachment of the RFID chip. Other substrates such as a polyamide or epoxy glass (e.g. FR4) are stiffer and thus less suited for reliable ball bonding assembly but are easier to die cut for small tag sizes and may make assembly easier to a plug part associated with the rivet. 
         [0009]    The conductor of the primary antenna associated with the RFID tag is preferably aluminium for its low cost and resistance to corrosion, not only in end use but also in a manufacturing process. Other embodiments may include direct application of conductor to the rivet plug part, e.g. via sputtering, vapour deposition or printing, and subsequent bonding of the RFID chip to the conductor. 
         [0010]    The RFID tag may be held in place on apart of a rivet such as a plug part with a potting material such as a urethane or epoxy resin which may fully surround the RFID tag for good seal against liquids and steam, and may remain relatively flexible for durable use on the fabric item. 
         [0011]    The fabric item to which the rivet is applied may or may not include a hole. In a case where the fabric item includes a hole an assembled rivet may be relatively flat on the surface of the fabric as is preferable for a worn garment. During application of the rivet, the hole may facilitate easy alignment of the primary antenna associated with the RFID tag to the secondary antenna associated with the fabric. The secondary antenna may be formed by stitching a suitable antenna pattern using conductive thread around the hole such that the secondary antenna is flexible and relatively comfortable for a garment wearer. 
         [0012]    In a case wherein the fabric item does not include a hole, a version of the rivet may be provided with larger tolerance on the rivet plug part such that an associated snap locking mechanism may accommodate the fabric in the locking mechanism. Although more bulky, this may be more suitable for fabrics such as linen (e.g. in a hotel, hospital, or restaurant), wherein no secondary antenna may be required or a larger secondary antenna (or the region close by the rivet) may be used to compensate for more tolerance on positioning of the RFID tag in the rivet relative to the secondary antenna on the fabric. 
         [0013]    According to one aspect of the present invention there is provided an RFID tag assembly including as associated antenna and attachment means suitable for attaching the tag assembly to a material wherein said antenna and said attachment means comprise a unitary conductive frame. The material may be flexible such as fabric or it may be relatively rigid such as cardboard. The associated antenna may include a loop antenna. 
         [0014]    The frame may be formed with a plurality of like frames by die stamping from a continuous roll of conductive material. The conductive material may include stainless steel or aluminium. 
         [0015]    The attachment means may include a plurality of legs connected to the associated antenna. The free end of each leg may include a sharpened lead to penetrate the material. The tag assembly may include a backing plate for receiving the plurality of legs. The backing plate may include apertures on plural pitch circles to accommodate various thicknesses of material. The tag assembly may include means for short circuiting the associated antenna during assembly at least temporarily. 
         [0016]    The material may be flexible and may include a secondary antenna. The tag assembly may be adapted to be attached to the flexible material such that the associated or primary antenna substantially maintains electromagnetic coupling with the secondary antenna when the flexible material flexes in use or is subject to repeated physical manipulation such as may take place during washing cycles. 
         [0017]    The present invention may be embodied as a rivet including a tag assembly as described above. The rivet may include an RFID tag. The attachment means may be adapted to attach the rivet to a flexible material such that it may withstand repeated physical manipulation without detaching of the rivet. The flexible material may include fabric or an item of clothing. In some embodiments the secondary antenna may include a conductive thread stitched into the flexible material in the vicinity of the primary antenna. 
         [0018]    According to a further aspect of the present invention there is provided a method of producing an RFID tag assembly including an associated antenna and attachment means suitable for attaching the tag assembly to a material including forming the antenna and the attachment means as a unitary conductive frame. The material may be flexible or relatively rigid. 
         [0019]    The method may include forming the frame with a plurality of like frames by die stamping from a continuous roll of conductive material. The conductive material may include stainless steel or aluminium. The attachment means may include a plurality of legs connected to the antenna. The method may further include attaching an RFID chip to the antenna on the conductive frame. The method may further include encapsulating the RFID chip and the antenna on the conductive frame. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  shows a rivet plug and rivet ring; 
           [0021]      FIG. 2  shows an RFID tag including an RFID chip bonded to a conductive track on an insulating substrate; 
           [0022]      FIG. 3  shows the RFID tag placed onto the rivet plug; 
           [0023]      FIG. 4  shows potting material added to hold and seal the RFID tag in place on the rivet plug to form an RFID rivet plug; 
           [0024]      FIG. 5  shows a fabric with a hole around which a secondary antenna is stitched with conductive thread; 
           [0025]      FIG. 6  shows the rivet ring placed into the hole in the fabric which facilitates alignment of the rivet to a secondary antenna; 
           [0026]      FIG. 7  shows placement of a rivet plug and RFID tag which snap locks to the rivet ring to complete the RFID rivet; 
           [0027]      FIGS. 8 to 10  show an alternative embodiment with a one piece rivet plug; 
           [0028]      FIGS. 11 to 15  show a further embodiment of an RFID tag assembly with an extended tube section; 
           [0029]      FIG. 16  shows a sew-on tag, wherein a primary antenna is held by conductive thread in proximity to a secondary antenna also constructed from conductive thread; 
           [0030]      FIG. 17  shows a tag wherein a primary tag package is formed from two halves, one half having a relief slot such that an assembled primary tag package forms a tube through which part of the secondary antenna conductor passes; 
           [0031]      FIG. 18  shows a rivet tag wherein a major part containing a primary antenna and an RFID chip is attached to the fabric by pushing metal legs through the fabric and folding the legs over against a minor retaining part; 
           [0032]      FIGS. 19A to 19D  show a conductive frame of the major part of  FIG. 18 ; 
           [0033]      FIG. 20  shows a circular variation of the rivet tag of  FIG. 18 . which may be further used as an RFID press-stud; 
           [0034]      FIG. 21  shows an inline process for producing a conductive frame and associated attachment parts; 
           [0035]      FIGS. 22 to 27  show production steps  212  to  217  respectively of the inline process; 
           [0036]      FIG. 28  shows an alternative form of loop antenna; 
           [0037]      FIG. 29  shows a further form of loop antenna; 
           [0038]      FIG. 30  shows an RFID press stud button and a backing plate; 
           [0039]      FIGS. 31 to 34  show an RFID press stud button and backing plate being attached to fabric; and 
           [0040]      FIG. 35  shows a modified version of the backing plate. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0041]    Referring to  FIG. 1  an RFID rivet is formed in two parts, a disc part or rivet plug  10  which snap locks into a rectangular toroid part or rivet ring  11 . The rivet plug  10  includes a smaller diameter raised tubular part  12  with an external barb  13  which mates to an internal barb recess  14  of a larger diameter raised tubular section of rivet ring  11  to provide a snap locking mechanism. 
         [0042]    Referring to  FIG. 2 , RFID tag  20  includes a primary antenna and RFID chip  21  bonded to a conductive track  22  formed on an insulating substrate  23 . Insulating substrate  23  comprises a rectangular toroid shape and may be die cut from a continuous web of complete RFID tags. 
         [0043]    Referring to  FIG. 3 , RFID tag  20  is placed over the raised tubular part  12  of rivet plug  10  and into an annular recess  15  of rivet plug  10  which is on the same side as raised tubular part  12 , the recess  15  having larger outside and smaller inside diameters than the corresponding diameters of RFID tag  20 . RFID tag  20  has one flat side facing or contacting the base of recess  15  in rivet plug  10  and the other flat side is exposed. The side of the RFID tag  20  facing the base of recess  15  in rivet plug  10  may have adhesive between itself and the base of recess  15  in rivet plug  10  to hold it in position before a potting step. 
         [0044]    Referring to  FIG. 4 , potting material  40  is poured into recess  15  of rivet plug  10  and flows to surround RFID tag  20  to hold and seal the RFID tag  20  to rivet plug  10 . The potting material  40  at least contacts part of upper regions of outer and inner diameter walls of recess  15  in rivet plug  10  and the exposed flat side of the RFID tag  20  in order to cap recess  15  and seal the RFID tag  20  to form a complete RFID rivet plug  41 . 
         [0045]    A preferable situation is when potting material  40  contacts all outer and inner diameter walls of recess  15  in rivet plug  10 , and hence inner and outer walls of insulating substrate  23  of RFID tag  20 , and the exposed flat side of RFID tag  20 . This may occur if adhesive is used between RFID tag  20  and rivet plug  10 . 
         [0046]    A more preferable situation is when potting material  40  contacts all outer and inner diameter walls of recess  15  in rivet pug  10 , and hence inner and outer walls of insulating substrate  23  of RFID tag  20 , and both the exposed flat side and side facing the base of recess  15  in rivet plug  10  of RFID tag  20 . In this situation RFID tag  20  may be totally sealed within potting material  40  and there may be no reliance on a seal created between potting material  40  and walls of recess  15  in rivet plug  10  permitting the rivet to flex more in use, or permitting use of difficult-to-bond materials for the rivet. 
         [0047]    Referring to  FIGS. 5 to 7 , fabric  50  is prepared with hole  51  around which a secondary antenna  52  is stitched with conductive thread. Hole  51  is preferably not button-holed or over-lock stitched to maintain an associated rivet flat or firm against fabric  50 . In severe duty use, such as industrial garments, an adhesive may be used between the two halves of a rivet in the region of hole  51  to prevent fraying of fabric  50  when stretched in use. 
         [0048]    Embodiments without hole  51  are possible if the diameter of raised tubular section  15  which provides the snap locking mechanism between rivet plug  10  and rivet ring  11  is increased to accommodate fabric  50 . Various rivets or at least one of the rivet halves can be made with locking mechanisms adapted or sized to cater for varying fabric thickness. It may be preferable to provide a common complete RFID rivet plug  41  and varying rivet rings  11 . In such an arrangement rivet ring  11  may be sized to suit hole  51  to fit common complete RFID rivet plug  41 . 
         [0049]    Versions of a rivet to be used with a hole may be used on smaller patches of fabric which may be subsequently stitched onto a main fabric item such that the main fabric item is without a hole. The advantages of good RFID tag to secondary antenna alignment and a simple RFID tag assembly may thereby be maintained. 
         [0050]    Referring to  FIG. 6 , raised tubular section  12  of rivet ring  11  fits into hole  51  in fabric  50  which facilitates easily achievable and good alignment of the rivet to secondary antenna  52 . 
         [0051]    Referring to  FIG. 7 , a complete RFID rivet plug  41  is pushed into rivet ring  11  such that the respective barbs  13 ,  14  of the snap locking mechanism hold the complete rivet together. The arrangement may allow relatively good coupling between the primary antenna associated with the RFID tag and the secondary antenna to be maintained when the rivet is knocked about such as in a laundry process. 
         [0052]    An alternative embodiment is shown in  FIG. 8  wherein a rivet plug  80  is in one piece, which may be simpler to manufacture, and RFID tag assembly  82  is retained in a groove of rivet ring  81  by epoxy  83 . 
         [0053]      FIG. 9  shows an addition to the alternative embodiment of  FIG. 8  wherein a retaining boss  90  is pressed from the outer side of the rivet ring  81  to lock the assembly.  FIG. 10  shows the RFID rivet of the alternative embodiment fully locked by retaining boss  90 . 
         [0054]    A further embodiment is shown in  FIG. 11  wherein a rivet plug  110  contains a RFID tag assembly  112 , retained by epoxy  113  in a groove of rivet plug  110 . The rivet plug  110  includes an extended tube section  115  which after assembly on fabric  114  is flared into and against a recess  116  on the outer face of rivet ring  111 .  FIG. 12  shows initial assembly of parts of the embodiment shown in  FIG. 11 .  FIG. 13  shows an early stage of locking the RFID rivet of the embodiment with addition of a heated die  130  which flares the tube section of the rivet plug. The heated die  130  is pressed down against the extended tube section of the rivet plug which flares the extended tube outwards, and the heated die is pressed down until the extended tube section of the rivet plug is fully flared into the recess of the rivet ring. 
         [0055]      FIG. 14  shows a last stage of locking the RFID rivet of the further embodiment wherein the heated die  130  has fully flared the tube section  115  of the rivet plug  110  into and against recess  116  in rivet ring  111 .  FIG. 15  shows the RFID rivet of the further embodiment fully seated. 
         [0056]    A sew-on embodiment is shown in  FIG. 16  wherein RFID tag  160  includes a primary antenna  161  formed by conductor on substrate  162  and RFID chip  163 . Tag  160  is held by conductive thread  167  which is sewn through holes  166  in the tag  160  such that tag  160  is held in proximity to secondary antenna  164  also constructed from conductive thread sewn to fabric  165 . Alternate embodiments may use a semi-flexible substrate such as polyvinyl chloride (PVC) which may be directly sewn to the fabric without a need for pre-existing holes in the substrate. 
         [0057]    A further sew-on embodiment is shown in  FIG. 17  wherein a primary tag package is formed from two halves. A major substrate half  170  with primary antenna conductor  171  and RFID chip  172 , may have a relief slot  173  such that when a second minor substrate half  174  is bonded to the major substrate half  170 , the assembled primary tag package forms a tube through which part of the secondary antenna conductor  175  passes. The relief slot  173  may alternatively be made on the minor substrate half  170 . The secondary antenna conductor  175  is sewn using conductive thread to the base fabric and has a loop section formed by lifting the needle after some stitching and shifting the fabric before resuming stitching to form a loop section of the secondary around which the two primary tag package halves  170 ,  174  may be assembled. The looping step may be repeated to increase thickness of the secondary antenna conductor in the coupling region, for reasons such as strength or conductivity. The loop may also be in the form of a wick which is sewn across a break in the secondary antenna conductor, or this wick may be already inserted into the tube formed by the two halves of the primary tag package and the assembly stitched across a break in the secondary. The assembled primary tag package may pivot on the secondary antenna which allows fabric surrounding the coupling vicinity to move relative to the primary tag package hence preventing fabric tearing or strain on the thread used to attach the primary tag. This may be the case when the fabric is subjected to bending wherein the fabric surface away from the primary tag has a larger bending radius than the primary tag, and the primary tag being rigid and held only at one edge slips relative to the fabric. Variations in construction may include a paper minor half such as a retail product label with a semi-circular cross sectioned crease as the slot, and a flexible major substrate half which includes an adhesive on one side such that when stuck onto the paper forms a tube wherein a product label may be attached to the product via a tie with a barbed push-together-clasp, wherein at least part of the tie is conductive to form the secondary antenna. 
         [0058]    An embodiment of a rivet shown in  FIG. 18  is based on dual in-line packaging (DIL packaging or DIP) wherein encapsulating material may be plastics or ceramic for extreme use such as in high temperature and pressure laundry applications. A major part  180  containing a primary antenna which is part of a conductive frame  181  and an RFID chip is sandwiched between a package top half  183  and package bottom half  184 . The major part  180  may be attached to the fabric by pushing the part  180  with a top die so that metal legs  182  push through the fabric and through holes  187  in a minor retaining part  186 , and folding the legs  182  over against a bottom die with curved slots which positions the minor retaining part  186  against the fabric and directs the ends of the legs  182  into recesses  188  of the minor retaining part  186 . Package bottom half  184  may include a recess  185  to provide clearance for the conductive thread. The minor retaining part  186  may be supplied on a reel to match the major part  180  on a separate reel for automated attachment. 
         [0059]      FIGS. 19A and 19B  shows a conductive frame  190  which is constructed from metal such as stainless steel, typically by die stamping, in a roll with legs  191  attached to a rectangular loop antenna  192  and to adjacent feeding frames (not shown). A small loop  193 , short circuits terminals  194 ,  195  which are nickel-gold flashed to prepare a surface wherein RFID chip  196  is connected by bond wires  197 ,  198  or is otherwise connected. Once RFID chip  196  is attached to conductive frame  190 , the two halves of the major part packaging may be bonded together sandwiching the conductive frame  190  therebetween with the short circuit loop  193  extending out beyond the packaging of the major part. Alternatively conductive frame  190  and RFID chip  196  may be encapsulated using an injection molding process known as overmolding. The packaged assembly may be left on the roll for automated assembly wherein it may later be die stamped out from the roll. The stamping process may form each leg  191  with a sharp lead in the form of tapered edge  199  and may also remove the short circuit loop  193  leaving small ends  200 ,  201  as shown in  FIG. 19B . The short circuit  193  is desirable during assembly to eliminate static electricity which could otherwise destroy the RFID chip during assembly. 
         [0060]      FIG. 19C  show an alternative example of a conductive frame  190  including sharpened leads in the form of barbs  202 .  FIG. 19D  shows a further example of a conductive frame  190  including sharpened leads in the form of tapered edges  203 . Tapered edges  203  may be similar to the edges formed on the legs of a staple. 
         [0061]    Variations of the design may include a circular loop and associated parts for the major part  204  of an RFID tag assembly as shown in  FIG. 20 . An RFID press-stud button, as shown may be formed using a circular variation of the major part  204  and insulating materials for the minor part  205  of the RFID tag assembly which forms the stud part of the press-stud on the opposite side of material  206 . 
         [0062]      FIG. 21  shows inline steps for producing a conductive frame  210  including associated parts for the major part  211  of the RFID tag assembly as shown in  FIG. 21 . The production steps include steps  212  to  217  which may be carried out at respective production stations as described below. Conductive frame  210  is constructed from metal such as stainless steel strip, typically by die stamping in a roll with legs  218  attached to circular loop antenna  219  and to peripheral border  220  of conductive frame  210 . Loop antenna  219  is short circuited via tracks  221 ,  222  as described below. In one form conductive frame  210  may be formed from strip material approximately 35 mm wide. 
         [0063]      FIG. 22  shows step  212  being carried out at a production station. Step  212  includes terminals  223 ,  224  being spot nickel gold flash metallized to prepare surfaces wherein an RFID chip is attached at a subsequent station. Terminals  223 ,  224  are short circuited via tracks  221 ,  222  which are severed in a subsequent step. The short circuit serves to eliminate static electricity during assembly as described above. 
         [0064]      FIG. 23  shows step  213  being carried out at a production station. Step  213  includes depositing a spot of conductive adhesive  230  to terminal  223  for attaching an RFID chip  240  as described below. 
         [0065]      FIG. 24  shows step  214  being carried out at a production station. Step  214  includes attaching RFID chip  240  to terminal  223  of frame  210  via adhesive  230 . 
         [0066]      FIG. 25  shows step  215  being carried out at a production station. Step  215  includes bonding wires  250 ,  251  between terminals associated with chip  240  and terminals  223 ,  224  of conductive frame  210  known as wedge bonding. Alternatively chip  240  may be surface mounted to terminals  223 ,  224  known as ball bonding (not shown). 
         [0067]      FIG. 26  shows step  216  being carried out at a production station. Step  216  includes encapsulation of antenna loop  219  on frame  210  via plastics packaging  260  using an injection molding process known as overmolding. The complete plastics package may be formed in one piece and in one molding step. 
         [0068]      FIG. 27  shows step  217  being carried out at a production station. Step  217  includes severing of encapsulated antenna loop  219  and legs  218  from peripheral border  220 . Step  217  also includes severing of tracks  223 ,  224  to open circuit antenna loop  219  and testing of the assembly. Step  217  may also include turning of legs  218  to form the major part  211 . 
         [0069]      FIG. 28  shows an alternative form of primary loop antenna  280  that may be formed with conductive frame  210  in place of loop antenna  219  shown in  FIGS. 21 to 27 . Loop antenna  280  is formed with spiral or arc extensions  281  and legs  282  which correspond to legs  191  in the previously described embodiment. However, unlike loop antenna  219  which is open circuit, loop antenna  280  is closed circuit and includes cruciform conductors  283  that are adapted to interface with two ports (two RF inputs) of a modified version of chip  240 . 
         [0070]      FIG. 29  shows a further form of primary loop antenna  290  that may be formed with conductive frame  210  in place of loop antenna  219  shown in  FIGS. 21 to 27 . Loop antenna  290  is formed with serpentine extensions  291  and legs  292  which correspond to legs  191  in the previously described embodiment. Loop antenna  291  includes cruciform conductors  293  which perform a similar function to conductors  283  described above. 
         [0071]      FIG. 30  shows the major part  211  of the RFID tag assembly comprising an RFID press stud button and a minor part  284  comprising a backing plate formed from an insulating material such as plastics. Minor part  284  includes recesses  285  for receiving respective legs  218  and a through aperture  286  located on a circle associated with each recess  285 . 
         [0072]      FIG. 31  shows the major part  211  positioned above a secondary antenna  294  stitched into fabric  295  with conductive thread. Minor part  284  is positioned under the fabric  295  for mating with major part  211  as described below. 
         [0073]      FIG. 32  shows the underside of the fabric  295  after legs  218  of major part  211  have penetrated fabric  295 . Minor part  284  is positioned so that each leg  218  is adjacent a respective recess  285  which extends to the underside of minor part  284 . 
         [0074]      FIG. 33  shows the underside of the fabric  295  after legs  218  are bent towards the centre of minor part  284  so that each leg  218  lies in a respective recess  285  and the tip  310  of each leg  218  over lies a respective aperture  286  in minor part  284 . 
         [0075]      FIG. 34  shows the underside of the fabric  295  after the tip  310  of each leg  218  is bent into a respective aperture  286  to provide for parts  211  and  284  to be securely held together after repeated washing cycles. 
         [0076]      FIG. 35  shows a modified version of minor part  284  including a further set of through apertures  330 . The further set of apertures  330  are located on a pitch circle that is larger in diameter relative to the circle on which apertures  286  are located. This is, apertures  330  are spaced further out from the centre of minor part  284  and are adapted to accommodate attachment of parts  211  and  284  to fabric  295  that is proportionately thicker. 
         [0077]    Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention.