Feed for sewing machine

Abstract

A sewing machine has a pair of superposed workpiece guides which conduct a pair of workpieces one atop the other to a stitching location with the edges of the workpieces lying directly over one another so that the machine can form a line of stitching parallel to the workpiece edges. A pair of rollers lying in a common plane inclined to the transport direction is provided immediately upstream of the stitching location and their plane intersects the guide edges downstream of these rollers, so that they exert a biasing force on the two workpieces toward the guide edges. The upper roller at least is displaceable transverse to the transport direction out of the path of the upper workpiece so as to allow loading of the machine. FIELD OF THE INVENTION The present invention relates to a workpiece feed for a sewing machine. More particularly this invention concerns such a feed for a sewing machine adpated to stitch together a pair of overlying textile workpieces parallel to one of the edges thereof. BACKGROUND OF THE INVENTION It is known to provide a sewing machine at the stitching plate thereof with a pair of superposed laterally opening guides having guide edges which extend parallel to the stitching direction. A workpiece is introduced into each of these guides with its edge running along the respective guide edge so that the machine can form a line of stitching parallel to the edges of the workpiece. Thereafter the two fabric edges can be over stitched with a zigzag or united in a French or flat fell seam. These workpiece guides are generally constituted by a stack of four plates with the first and third plates up from the stitching plate forming the guide edges and the second and fourth plates serving to hold down and flatten the workpieces. It is absolutely essential that the edges of the two workpieces remain continuously on contact with the guide edges. To this end it is known to form the stitching plate with a plurality of ridges which are inclined in the transport direction toward the guide edges so as to urge the fabric workpieces toward these guide edges. It is also known to form a bump or the like on the stitching plate to one side of the stitching location so as similarly to bias the fabric toward the guide edges. The principal difficulty with both of these arrangements is that they are effective only on the lowermost workpiece, that is the workpiece lying directly on the surface of the stitching plate. A guide for the uppermost workpiece has been dispensed with because of the difficulty it would create in setting up the machine. OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide an improved workpiece feed for a sewing machine. Yet another object is the provision of such a feed for a machine adapted to sew together of a pair of workpieces along a line parallel to their edges. A further object is to provide a workpiece feed for a sewing machine having a pair of laterally open guides next to a stitching plate with a guide edge in each of the guides extending parallel to the stitching direction. Yet another object is the provision of such a feed which is effective both on the upper workpiece and the lower workpiece, the terms upper and lower here merely referring to position relative to the stitching plate which traditionally underlies the workpieces. These objects are attained according to the present invention in a system wherein a pair of rollers are provided as the feed means, one of these rollers engaging from above on the upper workpiece and the other roller engaging from below on the lower workpiece. According to the present invention these rollers are rotatable about axes which are parallel to each other and inclined to the feed direction. The rollers are arranged upstream of the stitching location and lie generally in planes which cross the stitching direction and intersect the guide edges downstream of the rollers so that these rollers exert a biasing effect on the workpiece toward the guide edges. Such rollers need not be driven, in fact simple idler rollers function admirably to maintain the two workpieces snugly against their guide edges. The apparatus is simple in the extreme and effective on both workpieces. In accordance with another feature of this invention the two rollers lie directly opposite one another so that absent workpieces between them they would engage each other. Means is provided for varying the pressure which the upper and/or lower roller exerts on the workpieces. In addition means is provided for varying the angle of attack of these rollers so as to alter the force which these idler rollers exert on the workpiece perpendicular to the stitching direction. In accordance with yet another feature of this invention means is provided for displacing the upper and/or lower roller laterally out of the way for loading of workpieces into the guides. This means can comprise a slider on the stitching plate which is displaceable orthogonally to the stitching direction and which automatically lifts the respective roller upwardly away from the workpiece as it is displaced laterally.

Description

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features and advantages will become more readily apparent from the following, reference being made to the accompanying drawing in which:

FIG. 1 is a section through a sewing machine equipped with a feed according to the present invention in operative position;

FIG. 2 is a top view of the feed shown in FIG. 1;

FIG. 3 is a view similar to FIG. 2 illustrating the feed in inoperative position; and

FIG. 4 is a section taken along line IV--IV of FIG. 3.

SPECIFIC DESCRIPTION

As shown in FIGS. 1 and 2 a sewing machine has a base surface 1 on which is mounted an arm 2 carrying a vertically reciprocal needle 3. The machine has a stitch plate 4 formed with a needle hole 5 through which a feed foot 6 or the machine engages so as to define a transport direction D (FIG. 2).

A pair of superposed steel plates 7 and 8 have edges 7' and 8' which extend parallel to the direction D adjacent the stitch plate 4 and curve back away from the direction D upstream of the plate 4. These two edges 7' and 8' are vertically in line and form a guide edge 11 parallel to direction D. A pair of plates 9 and 10 separate the plates 7 and 8. The plate 9 extends parallel to the base surface 1 across the stitching direction D so as to form a narrow gap adapted to receive a lower workpiece N1. The plate 10 overlies the upper guide plate 8 like the plate 9 and again forms a gap adapted to receive a respective upper workpiece N2.

A pair of smaller plates 12 and 13 lying in the same plane as the plates 9 and 10, respectively extend up to the stitching location at the stitching plate 4.

A slide 14 secured to plates 12 and 13 and displaceable in a transverse direction T orthogonal to the direction D is carried on one end of an arm 16 operated by the piston rod of a small pneumatic cylinder 15. The other end of this arm 16 is pivoted on a link 30 which itself is pivoted fixedly on the sewing machine. Thus extension of the cylinder 15 pushes the slide 14 into the position illustrated in FIG. 2 and retraction of this cylinder 15 pulls it back into the positions of FIG. 3 and 4.

A rod 17 is secured at one end in a fork 31 pivotal about an axis a on the slide 14 and is formed at its other end with a collar 26 in which is fitted a crank 18. A screw 32 secures the crank 18 fixedly in the socket 26. The end of this crank 18 pivotally carries a roller 19 defining a roller plane P and rotatable about an axis A orthogonal to the plane P and inclined to the direction D, intersecting the guide edge 11 upstream of the center of the roller 19. The surface of this roller 19 formed with a plurality of ridges and the roller 19 is freely rotatable on the end of the crank 18. A leaf spring 20 secured at one end of the slide 24 is pressed against the rod 17 by a set screw 21 threaded into an arm 22 on the slide 14 and provided with a lock nut 23. Thus screwing the adjustment screw 21 in and out by means of its knurled head allows the spring force downwardly on the crank 18 and rod 17 to be varied.

The plate 13 is formed with an oval hole 27 in line with the roller 19. The slide 14 is displaceable in a base 24 provided with a ridge 25 having a head engageable with the collar 26. Thus when the slide 14 is pulled back in the direction T away from the stitching station 4 the roller is pivoted up about axis a by engagement of the element 25 with the collar 26.

In addition under the surface 1 and the stitching plate 4 there is provided another roller 28 lying in the roller plane P and rotatable on a respective pivot rod 29 parallel to the axis A. A hole 33 (FIG. 3) is formed in the stitching plate 4 in order to permit this roller 28 to engage through the stitching plate 4 with the under workpiece N1.

In operation the cylinder 15 is first actuated to withdraw the slide 14 and plate 13 back into the position of FIG. 3, automatically lifting the roller 19. A lower workpiece N1 is loaded between the surface 1 and the plates 9 and 12 and an upper workpiece is loaded between the plates 9 and 12 on one side and 10 and 13 on the other side. The cylinder is then actuated so as to displace the upper roller 19 back into the positions of FIGS. 1 and 2 and thereby dropping this roller 19 down onto the upper workpiece N2 so as to press it against the lower workpiece and press the lower workpiece against the lower roller 28. The stitching operation is commenced and the workpieces rotate the rollers 19 and 28, thereby imparting to themselves a coefficient of force in the direction of arrow T toward the guide edge 11.

The surface of the rollers 19 and 28 is shown to be formed of a plurality of small ridges to aid in engagement with the workpieces N1 and N2. It is also within the scope of this invention to provide these rollers with a friction coating such as a rubber layer. In addition the plates, 7, 8, 9, 12, and 13 are coated with polytetrofluorethylene, a synthetic-resin having a very low coefficient of friction. In particular the edges 7' and 8' are so coated so as to reduce friction with the workpieces.

Such an arrangement has been found extremely effective for holding the workpieces against the guide edges of the sewing machine. This insures a line of stitching exactly parallel to the edges of the workpieces without requiring constant close attention by the machine operator.

Claims

We claim:

1. A workpiece feed for a sewing machine having a pair of laterally open guides provided on a stitching surface adjacent a stitching location thereon and having a pair of guide edges offset from the stitching location and parallel to the machine stitching direction, said feed comprising:

a pair of rollers to either side of the stitching surface downstream from said stitching location and each rotatable in a roller plane intercepting said guide edges downstream of said rollers; and

a pair of axles defining respective rotation axes transverse to said direction supporting said rollers.

2. The feed defined in claim 1 further comprising means for displacing one of said rollers and the respective axis transverse to said direction.

3. The feed defined in claim 2 further comprising means for pressing said one roller down toward said surface.

4. The feed defined in claim 3, wherein said rollers both lie in the same roller plane.

5. The feed defined in claim 4, wherein each of said rollers is provided with a friction surface engageable with said workpieces.

6. The feed defined in claim 4 wherein said surface is formed with a hole, the other of said rollers engaging through said hole with one of said workpieces and said one roller engaging the other workpiece.

7. The feed defined in claim 4, further comprising means for lifting said one roller away from said surface on displacement thereof transverse to said stitching direction away from said location.

8. The feed defined in claim 7, further comprising means for displacing said plane relative to said direction.

9. The feed defined in claim 8 wherein said means comprises a crank constituting said axle and a socket receiving said crank, whereby rotation of said crank in said socket displaces said plane relative to said direction.

10. The apparatus defined in claim 6, wherein said guides include a stack of plates, two of which are formed with said edges and two of which extend transverse to said direction across the pass of said workpieces, the uppermost of the latter two plates being formed with a hole through which said one roller is engageable with the respective workpiece.