Sewing – Method of sewing – Stitch forming
Reexamination Certificate
1999-10-08
2001-01-09
Izaguirre, Ismael (Department: 3741)
Sewing
Method of sewing
Stitch forming
C112S235000
Reexamination Certificate
active
06170419
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a presser foot for a sewing machine.
The mass-production garment industry is now heavily mechanised, and one technique that is commonly used for assembling together two or more garment parts is to use a stitching jig. Such jigs comprise a lower plate and an upper plate between which the garment parts may be held, and fulling means may also be present between the upper and lower plates in order that “fullness” may be introduced into required areas of the fabric. The lower plate of the jig has a guide track which, in use, is engaged with a guide member on the base plate of a sewing machine, with the fabric parts to be stitched together overlying the guide track. The guide member has an opening for the needle of a sewing machine and an elongated opening adjacent to the needle opening through which a trimming knife may be reciprocated. In use, the loaded jig is driven so that it moves beneath the needle and the trimming knife, with the guide track following the guide member. A line of stitching between the garment parts is effected along the line defined by the guide track, and unwanted material lying outside the stitch line is cut away by the trimming knife. The resulting composite garment part can then be removed from the jig for further processing.
It will be appreciated that the trimming knife cuts simultaneously through all the fabric layers, and thus that the distance from the stitch line to the free edge of each layer will be substantially identical.
In the manufacture of some high quality garments, a so-called “feathered edge” (or step-back edge) is required, and in order to form such an edge it is a requirement that the trimmed edges of the respective layers of fabric should not be equidistant from the stitch line, but that a further layer of fabric should extend beyond a second layer by a predetermined distance along the whole of the trimmed edge. Thus, the edge of the second layer is substantially uniformly stepped back from the edge of the first layer. The resultant single layer strip of first fabric is necessary in forming the feathered edge. This type of edge can be hand made, but has proved difficult to automate.
Our prior patent GB-B-2201694 relates to a presser foot for a sewing machine which is capable of automatically effecting a stepped back edge as fabric is fed through the machine. Although successful on some fabrics, the presser foot disclosed therein did not always give good results with all fabrics, and it was also necessary to trim more fabric than had previously been conventional, thereby leading to more waste. The present invention provides a presser foot which seeks to avoid these disadvantages.
SUMMARY OF THE INVENTION
According to the invention there is provided a presser foot.
In use of a presser foot according to the invention, a stitching jig loaded with the fabric parts to be joined together is presented to the presser foot, in which a guide track of the jig has already been engaged with a guide member on the base plate of the sewing machine. In the region where stitching is to commence, a free edge of the uppermost ply of fabric in the jig is separated from the lower ply or plies and presented to the fulling rod so that the uppermost ply lies above the fulling rod and the remaining ply or plies lie below the rod. As the jig is advanced past the needle, it will be seen that a degree of “fullness” is introduced into the upper ply, and that the plies are stitched together on one side of the fulling rod. On the other side of the fulling rod, the fabric plies are trimmed by a trimming knife which reciprocates synchronously with the needle, and with the knife moving to a top position lying above both fabric plies so that it can reliably trim the plies without puckering the fabric. Once the stitched parts have been removed from the jig and the stitched and trimmed edge has been smoothed so that the plies lie flat one on the other, it will be seen that the uppermost ply into which fullness was introduced will project beyond the cut edge of the lower ply or plies so that the cut edge of the lower ply or plies is stepped back from the cut edge of the uppermost ply. The stitched assembly can thus be used in the formation of a feathered edge.
In the presser foot described in GB-B-2201694, the fabric was overlain by the presser foot for a substantial distance to each side of the fulling rod. This tended to cause “puckering” or pleating of the fabric, which is avoided with the presser foot of the invention. With the earlier construction, it was necessary to provide a substantial width of fabric beneath the presser foot, with the result that more fabric than usual was removed as waste by the trimmer knife. Such extra waste fabric is not necessary with the presser foot of the invention.
Correct presentation of the fabric to the presser foot may be assisted, particularly for lightweight fabrics, if the presser foot includes an air supply means opening into a second surface of the presser foot to direct air away from that surface and above the fulling rod. An air flow of this type will tend to fold the top ply around the fulling rod, and hold it in a horizontal position, rather than possibly extending in a diagonally upward direction from that rod.
The fulling rod is desirably spaced from the second surface of the presser foot by a distance of about 2 to 4 mm, and preferably about 3 mm. The rod may have a rounded surface, or it may have a substantially flattened surface facing towards and substantially parallel to the second surface of the presser foot.
The second surface of the presser foot extends generally at an angle to the horizontal which is preferably from about 20 to 45°, and with an angle of 30 to 35° being particularly suitable. The second surface may be planar, but more preferably is inwardly curved to co-operate with the surface of the fulling rod.
The fulling rod may conveniently be secured to the base section by an extension of the fulling rod, with the extension lying clear of the groove. The shape of the extension may be such as to accommodate the fabric shapes that are to be stitched.
The cross-section and dimensions of the fulling rod will be designed to produce the desired degree of step back between the fabric plies. In addition to the flattened section of the fulling rod that faces towards the second surface of the presser foot, it is preferred that the lower surface of the fulling rod be flat and substantially horizontal in order to facilitate turning of the jig as corners of the guide track are reached.
REFERENCES:
patent: 1300184 (1919-01-01), Mittleberg
patent: 3370559 (1968-02-01), Longcore
patent: 3669049 (1972-06-01), Marforio
patent: 4527492 (1985-07-01), Gill
patent: 4644885 (1987-02-01), Bennison
patent: 4928610 (1990-05-01), Akutsu
patent: 497861 (1970-12-01), None
patent: 978872 (1964-12-01), None
patent: 2201694 (1988-09-01), None
Prout Jason
Raven Neil
AMF Reece, Inc.
Izaguirre Ismael
Madson & Metcalf
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