Apparatus for blind stitching an S-shaped hem
FIELD OF THE INVENTION 
     The present invention relates to sewing machines, and more particularly, to a sewing apparatus capable of blind stitching an S-shaped hem in the marginal edge of a tubular workpiece. 
     BACKGROUND OF THE INVENTION 
     Devices for sewing the edge of tubular workpieces are known in different forms of embodiments. An example of such is U.S. Ser. No. 372,366 filed Apr. 27, 1982. In that device, a support assembly and a positioning assembly cooperate in moving a workpiece edge to and through the sewing station of the machine. With such an apparatus, however, there is only a single turn of the workpiece edge. It is heretofore been difficult, without continuous operator interference, to automatically and mechanically perform the type of finish sewing operation wherein a looped or tubular article has the free end folded in an S-shaped fold and secured with an overedge stitch. The problem with such a sewing operation is enhanced because the needle may penetrate only one half of a ply of material being sewn. Moreover, when the hem has traversed substantially 360° of rotation, it must again be presented to the stitch forming instrumentalities with substantially the same lateral disposition as before or an imperfect seam will result. But, when the beginning of the sewn and hemmed seam again approaches the sewing machine, the transition, from the outstretched, to the folded and sewn edge of the material, causes the edge to proceed in an uncertain manner. In such operations, there is no assurance that the folded but unsewn edge will remain in its folded state. It may unfold under the tension provided by the tensioning apparatus. Because of this lack of control, faults in the seam occur at the end of the seam. To add to this already difficult situation, the control apparatus governing machine operation may error unless the workpiece edge is properly controlled. In summary, to automate this type of sewing operation has heretofore been a very difficult task to accomplish. 
     SUMMARY OF THE INVENTION 
     Because of the above, and in accordance with the present invention, there is provided an automatic sewing apparatus capable of blind stitching an S-shaped hem in the marginal edge of a tubular workpiece. With the apparatus according to this invention, continual intervention by the operater should no longer be required or necessitated. 
     The present invention includes an overedge sewing machine and workpiece support means disposed on opposite side of the machine&#39;s stitch forming instrumentalities. The support means serve to arrange the open end of the workpiece edge in a tensioned, closed loop configuration. The support means are adapted to concomitantly advance the workpiece edge through the machine in synchronized timed relation with the rate of workpiece advancement imparted by the feed mechanism of the machine. 
     The support means, on the downstream side of the sewing machine, is provided with a guiding portion. The guiding portion is adapted to receive and controllably guide the sewn and hemmed edge of the tubular workpiece as it exits the sewing machine. Preferably, the guide portion of the support is formed by two coaxial annular upstruck members having a channel or groove arranged therebetween. It is into this groove or channel that the sewn workpiece hem depends upon its emergence from the sewing machine. The hem depends into this channel because of the circumferential tension being applied on the workpiece by the work support means. One of the upstruck members is provided with an abutment flange extending radially outward from the bottom of the channel and against which the hem is controllably guided. The abutment flange is laterally disposed relative to the support means in the same vertical plane as that traversed by the needle. In this manner, the wall or flange forms a guiding surface which prevents the lateral movement of the workpiece edge toward the needle. Accordingly, and after substantially 360° of rotation, the beginning of the sewn hem is automatically again presented to the stitching point with substantially the same lateral disposition relative to the needle as when the hem exited the stitch forming instrumentalities thereby producing a satisfactory or acceptable blind stitch hem. 
     In line with the above, a primary object of this invention is to reduce the onus on an operator of a stitching machine in the above mentioned stitching operation. 
     Another object of this invention is to provide an automatic apparatus in which an S-shaped hem is formed in the edge of a tubular workpiece and is secured automatically, in a regular manner, without the operator having to intervene. 
     Another object of this invention is to provide an apparatus wherein a tubular article may be provided with a blind stitch hem in a fully automatic operation rather than by the customary manual operation. 
     Still a further object of this invention is to provide an apparatus wherein such a sewing operation can be preformed at high efficiency. 
     Yet a further object of this invention is to provide a method of sewing an S-shaped hem along the edge of a tubular article whereby the hem is rotated 360° and presented again to the sewing station with substantially the same lateral disposition as when that hem exited the stitch forming instrumentalities. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Having in mind the above objects and other attendent advantages that would be evident from an understanding of this disclosure, the invention comprises the devices, combination, and arrangement of parts as illustrated in the presently preferred embodiment of the invention which are hereinafter set forth in detail to enable those skilled in the art to readily understand the function, operation, construction and advantages of same when read in conjunction with the accompanying drawings in which: 
     FIG. 1 is a schematic showing of the present invention; 
     FIG. 2 is a schematic showing of the tubular workpiece arrangement prior to sewing; and 
     FIG. 3 is a schematic showing, similar to FIG. 2, but showing the orientation of the sewn hem and apparatus for maintaining such orientation. 
    
    
     DETAILED DESCRIPTION OF THE PRESENT INVENTION 
     Referring now to the drawings, wherein like reference numerals indicate like parts throughout the several views, there is shown in FIG. 1 a sewing machine 1, for instance a conventional chainstitch overedging machine. The machine 1 is supported on a work table or frame. Suffice it to say, the machine is provided with stitch forming instrumentalities including the usual reciprocatory needle means 14 driven towards and away from the stitch forming location, a presser foot, a work support means and a conventional feed mechanism for advancing the workpiece edge through the stitch forming location. The work table also supports a well known sewing machine drive motor 2 and control mechanism. As it&#39;s name implies, the control mechanism is adapted to govern the course of machine operation including machine deactivization, lifting of the presser foot and severing of the threads. Arranged immediately forward of the stitch forming location, in the direction of feed, is a hem former assembly or folder device 15 through which the workpiece edge passes on its way to the sewing machine. The folder device is adapted to arrange the workpiece edge into an S-shaped fold. 
     Arranged proximate the stitch forming location of the machine is a tensioning device. The tensioning device includes a pair of roller support means or cylinders 3 and 4. The roller support means are spaced apart, one on each side of the stitching location. The spacing being such that an open end of a tubular workpiece 11 to be hemmed may be trained over the rollers, with an ample space being provided therebetween to receive the necessary sewing machine and other associated mechanisms. One of the roller supports, i.e. roller 4 in the embodiment shown, is movable with respect to the other roller support such that the endless loop or annular formation of the workpiece edge may be subjected to a light tension. By this construction, the distance between the rollers and thus the peripheral tension on the workpiece edge is adapted to the particular diameter the circumferential cloth presently being sewn. The rotational axes of the roller support means are parallel and they are disposed in a plane extending substantially parallel to the work support surface of the machine. Moreover, the rotational axes of the rollers extend generally perpendicular to the workpiece advancing movement. Preferably, each of the roller support means are driven by a motor 6 at the sewing speed so as to impart a concomitant advancing motion to the open end or edge of the workpiece. In the preferred embodiment, a positioning element, driven by motor 7, operates in conjunction with the roller support means 3. The positioning element or assembly engages the workpiece adjacent one end thereof and is adapted to influence the positioning of the workpiece edge in a direction transverse or lateral to the feeding direction without affecting the feed in the sewing direction. For a more complete understanding of the construction and working of the roller assemblies and positioning element, the readers attention is directed to U.S. Ser. No. 372,366 filed Apr. 27, 1982; the full disclosure of which is incorporated herein by reference. 
     As best seen in FIGS. 2 and 3, the support roller 4 includes a work engageable guide means at one end thereof. As will be subsequently described, the work engageable guide means cooperates with the tensioning of the workpiece edge in controlling the lateral disposition of the S-shaped hem or workpiece edge relative to the stitch forming instrumentalities. In the preferred embodiment, the work engageable guide means comprises two upstruck annular surfaces 8 and 9 having a groove or channel 12 disposed therebetween. The two upstruck surfaces are disposed a predetermined distance from the rollers inner end and are arranged coaxially with the support means. Preferably, the periphery of surface 9 defines a rounded rim which, amongst other things, enhances the drawing in of the folded edge of the workpiece into the groove or channel 12. Depending from the upstruck annular surface 8 is an abutment flange 13 serving to guide the hem sewn into the workpiece. The abutment flange or wall 13 extends radially outward from the channel&#39;s bottom, substantially perpendicular to the axis of rotation of the support roller 4. Moreover, the guiding surface of the abutment flange is disposed a predetermined distance from the desirous path of the workpiece edge and is in vertical alignment with the reciprocal path of the needle means 14. In this manner, the wall 13 forms a stop which prevents the lateral movement of the workpiece edge toward the needle. 
     To carry out a hem folding operation by means of the apparatus as described, a tubular article is arranged such that its open end is trained about the roller support means 3 and 4. The workpiece edge is initially positioned, by the operator, as shown in FIG. 2 over both upstruck surfaces 8 and 9. The support roller 4 is thereafter caused to controllably move away from the stitch forming zone. The workpiece edge is thereby placed under a controlled amount of circumferential tension. Next, the workpiece edge is advanced through the hemmer 15 toward the stitch forming instrumentalities. Accordingly, the marginal portion or edge of the article changes into a curved or S-shaped configuration. As seen in FIG. 3, the workpiece edge&#39;s curved configuration is formed by a triple thickness fold. Then, when the sewing operation is commenced, the edge is sewn and the upper edge is trimmed to form the hem shown in FIG. 3. The edge continues to be folded mechanically and automatically during the sewing operation. As the sewn hem exits the stitch forming zone and as it approaches the roller support means 4, the hem in drawn into the channel or groove 12 as a result of the circumferential tension being applied to the workpiece by the roller support means 3 and 4. Thereafter, the triple thickness of material comprising the S-shaped hem workpiece edge is guided by the abutment flange 13. In this manner, and after substantially 360° rotation, the sewn hem is presented to the stitching point or location in substantially the same lateral disposition relative to the needle means as when the hem exited the stitch forming instrumentalities thus producing a satisfactorily formed blind stitch seam. 
     Thus, there has been provided an Apparatus For Blind Stitching An S-Shaped Hem that fully satisfies the objects, aims, and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.