Patent Publication Number: US-6666157-B1

Title: Flatbed sewing machine conversion for sewing the rim of a molded sole to an upper

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The very wide acceptance of sports oriented molded rubber sole footwear over the past few decades has prompted the shoe production industry to expand the involved technology to a broader range of shoe products. Appealing features of the molded soles are, for instance, their comfort, their enhanced frictional engagement with walking surfaces and their immunity from deterioration when they become wet. Comfort is established by molding the interior of the sole with lower durometer and thus softer material which is 3-dimensionally contoured to support the foot with a shaped heel cradle, arch support and toe grip. Outside portions of the molded soles then are formed with a stiffer, higher durometer value material to establish desired strength or robustness. The resultant molded sole typically will exhibit a maximum thickness of about ⅝ inch at the heel-arch region, such thickness diminishing or tapering non-uniformly toward the toe region to a thickness of about ⅜ inch or less. To assemble the shoe products, for example, fashioned as slippers, it is necessary for sewing machine operators to sew a preassembled cloth upper to the molded relatively thick soles. Attachment of the upper is made at an integrally molded continuous rim extensible outwardly from either the top or bottom of the molded sole. Such sewing attachment may be carried out directly or using such fabrication procedures as “stitch and turn”. 
     Heretofore, the requisite sewing attachment procedure has posed a fabrication cost barrier for a variety of reasons. Basic ubiguitous flatbed industrial sewing machines available in essentially all factories have sewing surfaces which will be located below the necessarily elevated molded sole rim. Thus, without more, they are incapable of carrying out the sewing task. Somewhat specialized sewing machines such as cylinder or post machines are incapable of performing this necessary task inasmuch as the operator is unable to hold and align the work pieces for sewing and the stitching will be improperly positioned due to the inherent design of the machines. Further, the cost of providing the factory floor with customized sewing machines would be prohibitive both in terms of machine cost and operator training. 
     To produce these new shoe products at acceptable costs, it is necessary that a custom retrofit of the basic flatbed sewing machine be achieved at a practical cost level. In the latter regard, the retrofit must be carried out without altering the camming mechanisms or stroke of the machines and the machines must be easily reconvertible to their initial basic status. This alteration to the original structuring of the machines is necessary, inasmuch as the products may be produced on the production floor for relatively shorter intervals, for example, about three months. Following those intervals, then the machines are returned to fabrication of more conventional products. 
     Efficiencies of production also are predicated upon the type of task required of the machine operators. In this regard, the hand aligned molded sole and cloth upper must be held together and advanced through the sewing station. This generally calls for holding the entire assemblage with two hands as the bottom of the sole is slid over a flat support surface. It is necessary that the operator assert a slight downward pressure during this sliding maneuver and not be called upon to support the assemblage entirely with the hands. Lack of such full hand support not only results in relatively poor quality stitching but also induces unacceptable operator fatigue. The noted necessity of sliding the sole over a support surface also poses the inherent problem that the molded sole will have been structured to resist sliding activity. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is addressed to method and apparatus wherein a basic flatbed sewing machine design is converted for sewing through a thick workpiece such as a molded rubber sole having a sewing rim extending from either its top or bottom surface. To connect such a sole with an upper by a stitching procedure, the design facilitates the operational tasks of the sewing machine operator, permitting the holding of the two pieces to be joined with both hands and permitting the thus joined and aligned assemblage to be held down against a work surface as well as an upstanding guide surface. This arrangement achieves both accurate and desirably positioned stitching and results in less operator fatigue and substantial minimization of any opportunity for “kick-out” of the workpieces being joined together. 
     With the approach of the invention, preexisting basic sewing machines can be retrofitted very simply, for example, using a screwdriver, at relatively low cost inasmuch as the drive mechanisms of the basic machine, for example, incorporating cam actuation and the like are not altered. Correspondingly, the stroke of the machine is not altered. Thus, sewing machines with which operators are already familiar may be retrofitted for the production of footwear such as slippers or the like with relatively thick molded rubber soles and cloth uppers for a given production interval, for example, three months. Following that interval, the machines readily are converted back to their original structuring for production of a next product. As a consequence of the resultant low cost tooling for these specific products, cost of the products themselves are substantially reduced to the extent that superior products are cost competitive with preexisting inferior ones. 
     Successful conversion is achieved inter alia, through the utilization of a conversion feed dog assembly incorporating a conventional workpiece advancing component which performs at the original flatbed level but also includes an upstanding thread sequestering channel through which the needle of the machine passes in which, in particular, during a down stroke extending through the workpieces being sewn together avoids thread breakage by maintaining the lock-stitch forming thread loop at a size avoiding thread breakage when operationally associated with a rotating sewing hook. The cover plate is reconfigured such that it incorporates a platform-like structure with an outwardly disposed guide surface and an upwardly disposed elevated sewing surface carrying a needle receiving slot. Thus beneath or adjacent to this slot resides the needle receiving opening of the conversion feed dog thread sequestration channel. Accordingly, where the platform height corresponds with the bottom of rim to opposite side of a molded sole at its maximum thickness, the side of the sole opposite the rim may be advanced against friction by the workpiece advancing component of the feed dog while the rim is advanced at the elevated sewing surface by the top feed mechanism of the machine. To aid the operator in holding the aligned workpieces together and in proper position at the sewing station of the machine, an auxiliary working surface component is provided which is mounted upon the sewing machine outwardly from the conversion cover plate. This surface is slightly canted upward as it extends outwardly to aid in positioning the workpiece against the upwardly extending cover plate guide surface. The original stroke of the sewing machine is maintained through the utilization of a needle of a type wherein the eyelet is spaced quite closely to the tip as compared to a more conventional needle. Additionally, an edge guide may be installed inwardly of the sewing station of the machine to engage the outer periphery of the rim of the molded sole to thus position the stitching line or locus uniformly from that periphery. For molded sole structures having the rim extending from a bottom surface, an alignment guide, again installed inwardly of the sewing station may be provided which engages the rim to align it with the level of the elevated sewing surface prior to its advancement thereon. 
     In one aspect, the invention provides a method of converting a sewing machine having a flatbed sewing surface, a sewing station with given stroke, a needle, a lower disposed bobbin and sewing hook, compound feed components having a given extent of reciprocal travel including a reciprocal feed dog, a cover plate, an upper feed and a presser foot for sewing the rim of a molded sole of given rim to bottom thickness to an upper which comprises the steps of: 
     Providing a cover plate conversion assembly having a lower plate portion with a dog receiving slot, an edge guide having a guide surface extending upwardly and generally normally to the lower plate portion to an elevated sewing platform surface generally parallel to the lower plate portion and having a needle or receiving slot formed therein; 
     providing a conversion dog assembly having a workpiece advancing component configured for reciprocal movement within the dog receiving slot and a thread sequestering channel component adjacent to and extending upwardly from the advancing component to a needle receiving opening located for reciprocal movement adjacent the needle receiving slot of the conversion cover plate assembly; 
     removing the cover plate; 
     removing the feed dog; 
     installing the conversion feed dog assembly in place of the feed dog; and 
     installing the conversion cover plate assembly in place of the cover plate, the edge guide surface being located in the spaced adjacency with the thread sequestering channel component and the needle receiving opening being located adjacent the needle receiving slot. 
     Another feature and object of the invention is to provide a kit for converting a sewing machine of a variety having a flatbed sewing surface, a sewing station with a given stroke, a presser foot, a top feed mechanism, a needle, a lower disposed bobbin and sewing hook, a feed dog drive mechanism with a removably connected feed dog, and a removable cover plate, such conversion providing for carrying out the sewing together of first and second workpieces, the first workpiece having a thickness portion of at least about ¼ inch between top and bottom surfaces and further having a rim extending outwardly from one of the top and bottom surfaces, the second workpiece having a peripherally disposed portion for sewing attachment with the rim. The kit comprises: 
     A conversion cover plate assembly configured for mounting in place of the removable cover plate, having a lower plate portion locatable in alignment with the flatbed sewing surface, having a feed dog workpiece advancement component receiving slot, an edge guide having a guide surface generally extending upwardly normally to the lower plate portion a distance corresponding with the first workpiece thickness portion to an elevated sewing surface configured for operation with the top feed mechanism and presser foot of the sewing machine and being generally parallel with the lower plate portion and including a needle receiving slot; and 
     a conversion feed dog assembly configured for mounting upon the feed dog drive mechanism in place of the removably connected feed dog, including the workpiece advancing component and a thread sequestering channel component adjacent to the workpiece advancing component and extending upwardly a distance generally corresponding with the guide surface distance to a needle receiving opening and located for operably associating the needle and the sewing hook of the sewing machine. 
     A further feature and object of the invention is to provide a sewing machine for stitching together first and second workpieces, the first workpiece have a thickness portion of at least about ¼ inch between top and bottom surfaces and having a rim extending outwardly from one of the top and bottom surfaces, the second workpiece having a peripherally disposed portion for sewing attachment with the rim. The sewing machine comprises a flatbed defining a first work surface, an arm extending outwardly over the flatbed to a compound sewing mechanism including a compound reciprocating needle and top feed mechanism and a height adjustable presser foot. A bobbin and sewing hook are mounted for actuation below the first work surface for operational association of bobbin fed thread with needle carrying thread to define a sewing station. The cover plate assembly is provided having a lower plate portion at the first work surface with a feed dog workpiece advancing component receiving slot, an edge guide having a guide surface generally extending upwardly normally to the lower plate portion a distance corresponding with the first workpiece thickness portion to an elevated second work surface operable with the top feed mechanism and presser foot and which is generally parallel with the first work surface and includes a needle receiving slot. A feed dog assembly including the workpiece advancing component is provided, the latter component being extensible through the receiving slot of the cover plate assembly and a thread sequestering channel component is provide adjacent to the workpiece advancing component which extends upwardly to a needle receiving opening located for reciprocatory movement adjacent the needle receiving slot at the second working surface. A sewing drive mechanism is provided for carrying out the actuation of the needle, top feed mechanism, bobbin, sewing hook and feed dog assembly. 
     Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter. The invention, accordingly, comprises the method and apparatus possessing the construction, combination of elements, arrangement of parts and steps which are exemplified in the following detailed description. 
    
    
     For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in connection with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a flatbed basic sewing machine having been converted according to the invention and illustrating its operation in sewing a cloth slipper upper to a molded rubber sole; 
     FIG. 2 is an exploded perspective view of the slipper shown in FIG. 1 illustrating a molded rubber sole and a cloth upper; 
     FIG. 3 is a partial perspective view of the sewing station and a slanted auxiliary work surface associated therewith, the components of the sewing station being represented in a mode wherein the needle is moving upwardly and in a recovery orientation horizontally; 
     FIG. 4 is a sectional view taken through the plane  4 — 4  shown in FIG. 3; 
     FIG. 5 is a partial perspective view in the manner of FIG. 3 showing an orientation wherein the needle is moving downwardly in a stitch-forming motion; 
     FIG. 6 is a sectional view taken through the plane  6 — 6  shown in FIG.  5  and illustrating two phantom workpieces being joined; 
     FIG. 7 is a perspective view of a conversion feed dog according to the invention; and 
     FIGS. 8A-8E schematically illustrate a sequence of operations of a sewing station as modified according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The sewing machine retrofit feature of the invention functions, in effect, to elevate the sewing or working surface of a conventional, flatbed, basic sewing machine without incurring excessive costs. In this regard, there is no alteration of the stroke of the machine as would involve camming changes and the like. With the elimination of such complexity, the basic sewing machine can be returned, for example after three months working with molded soles, to other products not requiring the elevated surface, again at minimal cost and, in general, through the simple utilization of a screwdriver. In concert with this working or sewing surface elevation the retrofit achieves solution to a resultant operational defect otherwise evoking thread breakage and solves the workpiece retention difficulties otherwise encountered with molded rubber soles. 
     FIG. 1 reveals the salient features of the ubiguitous flatbed industrial sewing machine as it is converted or modified according to the invention. The sewing machine is depicted in general  10  as it is in the process of producing a slipper  12 . Illustrated machine  10  is, for example, a model LU-562 produced by Tokyo Juki Industrial Co., Ltd. of Tokyo, Japan. The machine  10  is seen to have a flatbed  14  over which is supported an arm represented generally at  16 . Rearwardly, the machine  10  incorporates a hand wheel  18  and a feed graduation plate  20 . Forwardly on the arm  16  is a thread guide bar  22 , thread pressure nut  24 , spring guide disc  26 , and a take-up lever  28 . The sewing station for the compound form of sewing activity of machine  10  is represented by the arrow  30  and, in the instant figure, reveals a needle  32 , presser foot  34  and L-shaped upper feed  36  through which the needle  32  is extensible. A bobbin cover plate is shown at  38  upon which are mounted a rim edge guide shown generally at  40  and a retractable rim alignment guide  41  which is pivotally mounted to plate  38  at  42  and includes a generally L-shaped rim engagement and aligning plate  44 . Alignment guide  41  may be retracted from involvement at the sewing station  30  by rotation about the pivot  42 . The guide  41  is employed in particular with rim and molded sole structures wherein the rim extends from the bottom surface of the sole and therefore is flexed for alignment with a sewing platform prior to sewing. 
     Looking additionally to FIG. 2, the slipper  12  is illustrated in perspective and exploded fashion. The slipper model  12  is seen to be formed with a molded rubber sole represented generally at  46  to which is sewn a prefabricated cloth upper represented generally at  48 . Molded sole  46  is formed with two rubber components of differening durometer. In this regard, sole  46  incorporates a somewhat outwardly disposed higher durometer outer portion  50  within which there is formed a softer, lower durometer honeycomb format formed interior part  52 . Note, that for the present embodiment, the molded sole  46  at its upward surface is configured with an integrally formed outwardly extending rim  54 . Typically, the bottom or ground engaging surface of the sole  46  as shown at  56  will extend varying distances below the corresponding bottom surface  58  of rim  54 . The molded sole typically will be thicker, for example, about ⅝″ in the heel and arch region and will taper to about ¼″ in thickness toward the toe region. Cloth upper  12  is seen having a continuous connector ledge  58  extending about its lower surface. It is the function of the retrofitted sewing machine  10  to sew the ledge  58  to the rim  54  while holding the upper  48  in alignment with the sole  46 . This procedure is generally represented in FIG. 1 wherein a slight gap  60  is shown between the unsewn upper  48  and sole  46  as the slipper  12  is being maneuvered through sewing station  30 . Note that the sole  46  bottom surface  56  is in adjacency with the working surface level of the bed  14  while the conjoined rim  54  and ledge  58  are elevated above that surface. 
     Looking to FIG. 3, flatbed  14  is illustrated in conjunction with the sewing station  30 ; rearwardly extending plate cover  38 ; and a forwardly extending and inwardly sloping auxiliary working surface component represented generally at  70 . The figure reveals the orientation of needle  32  and upper feed  36  as the needle  32  is moving upwardly, as represented at arrow  72 , and toward the operator as represented at arrow  74 . Needle  32  is shown removably connected to needle drive member  76 . For the retrofit at hand, the needle  32 , while a typical one, is selected having a foreshortened shank portion to provide a shaft length increase of about ⅛″. Note additionally, that the center of the needle eye  78  through which spool supplied thread  80  passes is closer to the tip or point than needles employed for the conventional use of the sewing machine  10 . This achieves a maximum utilization of the available stroke of the mechanism of the device. Such needles may be type 135X16 or 175X3. The tip of the needle  32  is shown poised above the aperture  82  within the horizontal leg of upper feed  36 . Note, additionally, that using conventional machine adjustment procedures, the presser foot  34  has been elevated as earlier illustrated in connection with FIG.  1 . Mounted in the manner of a conventional cover plate between the inward edge  84  of working surface  70  and the forward or outward edge  86  of cover plate  38  is an elevated sewing surface cover plate assembly represented generally at  90 . 
     Attached to the bed  14  with two machine screws  92  and  94  the assembly  90  is formed having a lower plate portion  96 , the upward surface of which is substantially coplanar with the upper surface of cover plate  38  and bed  14 . Within that lower plate portion are two elongate dog receiving slots  98  and  100  through which protrude the multi-tooth or serrated gripper or workpiece advancing components  102  and  104  of a customized feed dog. Not shown are the blocking teeth components formed within cover plate  90  and which perform in concert with workpiece advancing components  102  and  104 . 
     Cover plate  90  further is configured supporting a generally tower or platform-like structure shown generally at  106 . Structure  106  is configured having an outwardly disposed edge guide  108  with a surface  110  extending upwardly and generally normally to the lower plate portion  96 . Edge guide  108  forms a portion of the support of an elevated sewing platform  112  the upper surface of which at  114  is disposed generally in parallel with the upper surface of lower plate portion  96 . An elongate, rectangular needle receiving slot  116  is shown formed within the platform  112 . 
     The feed dog assembly for the instant application is customized for utilization with the elevated sewing surface and is shown partially in phantom at  118  as not only supporting the workpiece advancing components  102  and  104 , but also supporting and reciprocally actuating a tube-like thread sequestering chamber component shown partially in phantom at  120  which is seen to extend into adjacency with slot  116  at upper surface  122 . A cylindrical opening extends as a channel fully through the tube-like thread sequestering component  120 , the upward aperture or opening thereof being seen in the figure at  124 . Note that bobbin supplied thread  126  is shown emerging from the upward opening  124 . 
     Looking momentarily to FIG. 7, the one piece feed dog assembly  118  is revealed in perspective fashion. Assembly  118  includes an angle-form base  128  functioning to support the grippers  102  and  104  as well as the overlapping support of thread sequestering component  120 . This provides clearance for the internal channel, the upward opening of which is seen at  124 . Feed dog  118  is attached to the cam actuated drive mechanism of the sewing machine  10  through conventionally spaced machine screws, the openings therefore being revealed at  130  and  132 . 
     The channel or passageway within thread sequestering component  120  for use in fabricating shoe products as described in conjunction with FIG. 2 will have a width-wise extent of about {fraction (3/32)} inch and a principal diametric extent of about ⅛ inch. Structure  120  itself can be employed with a square cross-sectional dimension of about {fraction (5/16)} inch and the forward or outward edge of the opening  124  will be spaced from the forward surface  134  about {fraction (13/64)} inch. In general, the upstanding height or lengthwise extent of component  120  will be about {fraction (7/16)} inch, again for the application represented in FIG.  2 . That dimension in general will correspond with the distance from the bottom surface  56  of molded sole  46  to the underside surface  58  of rim  54  as that distance is of maximum value for the sole, for example, in the heel-arch region. 
     Turning to FIG. 4, a sectional portrayal of the feed dog assembly  180 , cover plate assembly  90  and auxiliary working surface component  70  is provided in conjunction with a cross-sectional representation of the molded sole  46  and upper  48  of slipper  12 . In the figure, a bobbin assembly  136  is revealed at  136  in an orientation wherein bobbin rotation is about a vertical axis. Associated operationally with the bobbin  136  is a sewing hook  138  and the bobbin thread again is shown at  126  extending through the interior channel  140  of thread sequestering component  120 . Rim edge guide  40  is connected to cover plate  38  by machine screws  142  and  144  and is seen having a upwardly depending angular portion  146  extending over and supporting a guide roll  148 . Guide roll  148  is seen to be positioned adjacent the upper surface  114  of tower-like structure  106 . As the operator, using two hands, maneuvers the two-component workpiece through sewing station  30 , presser foot  34  and upper feed  36 , when engaged, will tend to distort or flatten out the continuous connector ledge  58  of upper  48 . The operators&#39; two hands in pushing down on the two-component work piece will urge that portion of the molded sole  46  at  150  extending between bottom  56  and the ridge bottom  58  into engagement against surface  110  of edge guide  108 . This task is aided, as is apparent, by the inwardly sloping surface  152  of auxiliary working surface component  70 . As this is occurring, the lower surface  58  of rim  54  is positioned over the upper or elevated sewing surface  114 . Note that the guide roll  148  is in contact with the outer-periphery of ledge  58  and functions to orient ledge  58  with respect to the needle  32  in a consistent inward spacing manner. Typical spacing will provide a final product wherein stitching is about ¼ inch inward from the edge of ledge  58 . FIG. 4 also reveals the cam actuated mechanical drive  154  to which the feed dog  118  is attached by machine screws extending through openings  130  and  132  (FIG.  7 ). 
     Referring to FIG. 5, another stage in the compound sewing maneuvers at sewing station  30  is revealed. In the figure, the needle  32  is being driven downwardly as represented at arrow  170  while the needle, upper feed  36  and feed dog  118  are also being driven horizontally in a material advancing direction as represented at arrow  172 . Note that the tip of needle  32  is within the thread sequestering component  120  channel and the orientation of workpiece advancing components  102  and  104 , as well as connected chamber component  120  are located in a region of commencement of a stitch. 
     FIG. 6 reveals a sectional detail of this orientation of FIG. 5 in conjunction with a phantom cross-sectional representation of the sole  46  and upper  48 . At this juncture in the procedure, the friction enhancing bottom  56  of molded sole  46  is engaging upper surface  158  of auxiliary working surface component  70 . Additionally, it may be recalled that the operator, using both hands, is pushing down and inwardly on the assemblage of molded sole  46  and upper  48  such that the sole lower outer surface  156  beneath the ridge lower surface  60  is in contact with surface  110  of edge guide  108 . The frictional engagement of the sole bottom  56  with surface  158  is overcome, however, to provide movement in the noted direction represented by arrow  172  by virtue of the material advancement components  102  and  104 , as well as the corresponding movement of forward feed  36  as thinner portions and a lesser height of the side surface  156  are encountered, the sole bottom  56  in the vicinity of advancing components  102  and  104  tends to lift off of them but with a concomitant reduction in overall surface contact with surface  158 . Thus, operator fatigue continues to be avoided. It may be observed that with the emergence of the tip of needle  76  below the thread sequestering component  120  a loop in thread  80  will be formed as represented at  80   a . Loop  80   a  is of correct size for engagement by sewing hook  138  because of the presence of component  120 . Without the presence of that component, the loop would be much too large and engaged not once but twice by the sewing hook  138  to break thread. 
     FIGS. 8A through 8E schematically portray a lock-stitch forming sequence carried out with the conversion or adaptation of a standard flat bed machine as described in the discourse above. For clarity of presentation, the bobbin  136  and sewing hook  138  are shown as rotating about a horizontal as opposed to a vertical axis. Depicted in the drawing is the particularly selected needle  32 , the feed forward component  36 , thread sequestering component  120 , thread  180  and one of the workpiece advancing components as at  104 . The stitch is shown being formed within the abutting rim  54  and ledge  58 . 
     In FIG. 8A needle  32  is represented as descending toward the workpiece as represented at arrow  174 . Bobbin thread  126  extends through the channel of component  120  to the next previous stitch as does the needle carrying thread  80 . 
     FIG. 8B shows an orientation of needle  32  wherein the tip and the eyelet  78  have descended through the channel of the sequestration component  120  into the vicinity of sewing hook  138 . Note that a loop has been formed in thread  80  as represented at  80   a  and that sewing hook  138  has rotated in a counterclockwise fashion and is about to encounter and pass through the loop  80   a . In developing the retrofit or conversion arrangement of the invention, it was found that the component  120  is quite necessary to avoid forming too large a sewing loop. In effect, the sewing hook  138  would pass through such a large loop twice and break the thread. The loop  80   a  being of proper size, as shown in FIG.  8 C and arrow  176 , needle  32  has commenced to move upwardly with some tension on the thread  80 . At the same time, the leading edge of sewing hook  138  has engaged or passed through loop  80   a.    
     Looking to FIG. 8D, it may be observed, as represented at arrow  178 , that the tip of needle  32  has emerged from the opening  82  in forward feed  36  and sewing hook  138  is releasing from the thread loop  80   a  and has caused the bobbin thread  126  to pass through loop  80   a.    
     Finally, looking to FIG. 8E, as represented at arrow  180 , needle  32  has moved more fully upwardly and the needle thread  80  is being pulled tight by a lever on the sewing machine  10  to form the stitch. 
     Since certain changes may be made in the above-described apparatus and method without departing from the scope of the invention herein involved, it is intended that all matter contain in the description thereof or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.