The invention relates to a device as an integrated part of or as an accessory of a sewing machine for straightening the edge portion of fabric which is to be sewn.

At industrial sewing of knitted fabric on indus¬ trial sewing machines it is a problem to straighten the curling edge portions of the fabric, i.e. the edge of the fabric curls up due to different circumstances such as material properties, or the manner in which the fabric is knitted or cut. To be sewn the edge should be so straightened out that it easily can be conveyed across the top of the sewing machine and down under the presser foot. The operator of the sewing machine shall be able to work at a relatively high rate, and it is a delaying circumstance all the time- having to straighten the curling edge by hand. It is both about straightening the curling edge of a single layer of fabric, where the edge shall be listed, and about the curling edge of two layers of fabric, which is to be sewn together, such as front and rear portion for a T-shirt or sewing sleeves on. Two layers fabric can be sewn together such that the edges curl opposite each other onto the outer side, or they curl with each other in between the two layers of fabric. With woven fabrics such as cotton fabric and fabric of synthetic fibres the phenomena with curling edges is not so distinct, so with these fabrics the edges can be straightened by fixed abutment and by pas¬ sage under the presser foot. The woven fabrics are usu¬ ally also thinner than the knitted fabrics dealt with. It has not as a matter of course proved possible to straighten the curling edges of knitted fabric with fixed abutment.

The object of the invention is to provide a mechan-

ical device as an integrated part of or as an accessory to a sewing machine, which can be used to straighten the curling edges on knitted fabric which should be sewn industrially. This object is achieved by a device ac¬ cording to the invention which is characterized in that it comprises at least one driven roller placed in the vicinity of the presser foot of the sewing machine at the feeding end of the fabric and transversely to the presser foot in the feeding direction of the fabric. By a suitable choice of the dimension of the roller, speed rotation direction and relative positioning in relation to the sewing machine top and presser foot, it appears that the device according to the invention is able to straighten the curling edges of knitted fabric as the fabric is fed during sewing.

Due to the sewing operator's general view of the sewing area, i.e. the area around the presser foot, it is important that the proportions of the device are as small as possible and besides are placed such that they do not disturb the general view appreciably.

For simultaneous straightening of the the curling edges of two fabric pieces, which are to be sewn to¬ gether, the device is designed such that it comprises two parallel and above each other placed rollers which can be counter driven and designed such that the direc¬ tion of rotation can be changed. Compared with an offset positioning in the longitudinal direction a positioning of the rollers above each other implies obvious advan¬ tages such as the curling edges are straightened simul¬ taneously, smaller proportions in the longitudinal di¬ rection as well as a simple mechanical construction. If the fabric has outwardly curling edges, then these are guided between the rollers which are driven against the feeding direction of the fabric, and if the fabric has inwardly curling edges, then these are guided on the outer side of the rollers. One piece of the fabric is

then guided between the lower roller and the top of the sewing machine and the other piece is guided above the upper roller, above which preferably a retaining roller is placed such that the fabric is guided between the roller and the retaining roller. In relation to the situation with outwardly curling edges the rotation direction of the rollers is changed such that they also in this situation rotate against the feeding direction of the fabric.

It appears that the most reliable and smooth straightening of the curling edges is achieved when the rollers are driven such that the rotation direction is against the feeding direction of the fabric.

To ease the insertion of the fabric the device is designed such that the rollers can be raised and lowered in relation to the top of the sewing machine and with two rollers such that they are displaceable away and towards each other in the vertical direction. A vertical displacement of the rollers is preferred for a pivoting movement as with a vertical movement a slight pressure on the fabric can be allowed. If the device also has a retainer roller, then it is mounted on a swivel arm, such that it lifts itself when the rollers are dis¬ placed, thereby admitting free entrance for unobstructed placing of the fabric.

A design of the device according to the invention which is especially preferable is characterized in that the rollers are embedded in separate vertical beams, at each end guided by guiding stands and that the lower beam is connected to a compressed-air cylinder situated below the beam, and that the upper beam likewise is connected to a compressed-air cylinder situated under the lower beam as there is a cutting herefor in said beam. This construction gives a compact unit which can be designed as an accessory to existing sewing machines. The travel of the horizontal beams is determined by the

stroke of the compressed-air cylinders. The variations which may occur in the thickness of the fabric are ab¬ sorbed in the resilience of the compressed-air cylin¬ ders.

By this design the retainer roller can be mounted on the upper beam in a simple manner and arranged such that it cooperates with a fixed impact on the guide stand nearby, such that the roller swivels up when the beam is displaced towards its upper position. Besides, the roller is spring loaded to the start position and can have the same shape as the driven rollers. The re¬ tainer roller can of course be driven, if this is con¬ sidered advantageous.

The rollers can be driven in different ways, but preferably an electrical gear motor is used where the rotation direction can be changed and thereby changing the direction of rotation of the rollers. The drive shafts can be flexible e.g. cables such that complicated gears are avoided to raise and lower the beams. The gear motor can drive a gear wheel which drives two other gear wheels connected to the driving cables. Hereby the rol¬ lers will always be counter driven despite the rotation direction.

The conditions such as the shape of the rollers, position, rotation direction, speed influencing on the ability to straighten the curling edge of a fabric are determined from experience gained. It appears that a good straightening is achieved by long thin rollers in relation to the presser foot of the sewing machine. The length of the rollers can be in the range of seven times the diameter. It also appears to have a favourable in¬ fluence on the straightening when the rollers are ar¬ ranged at an angle in relation to the feeding direction of the fabric under the presser foot, such that the rollers point rearwards against the feeding direction. The angle can be approximately 15-55°, preferably ap-

proximately 35°. If the device shall be perpendicular to the sewing machine, the angle can be provided by giving the outer portion of the beams a bend, such that the rollers get the intended angle when pointing perpen¬ dicularly out from the bend. Further it appears advan¬ tageous if the rollers are smooth.

Preferably the device is a unit arranged displace¬ able in and out of the feeding direction of the fabric, preferably by being arranged link motioned on a hori¬ zontal compressed-air cylinder. This is a simple solu¬ tion ensuring that the sewing machine can easily be used for other purposes.

In the following the invention shall be explained further in connection with the accompanying drawing, which among others shows an embodiment of the device according to the invention in the nature of an accessory to existing sewing machines.

In the drawing is shown:-

Fig. 1: A schematically partial view of a sewing machine with an embodiment of the device according to the invention and with two pieces of fabric with out¬ wardly curling edge portions, which shall be sewn to¬ gether and where the retaining roller is not shown for the sake of clearness.

Fig. 2: The device in Fig. 1 in its entirety and shown in more detail.

Fig. 3: A schematical view of two pieces of fabric with outwardly curling edges which are fed perpendicu¬ larly into the picture and with an indication of the rotation direction of the rollers, and

Fig. 4: Same as Fig. 3 but with two pieces of fabric with inwardly curling edge portions.

The device shown in the drawing comprises two hori¬ zontal beams la, lb above each other and each end guided by two vertical guiding stands 2a, 2b as there are through bores herefor in the beams in connection with dowel bushes 3a-3d mounted to the beams. The guiding stands 2 are fixed in a base 4 comprising two plate halves, in which there are shaped air channels for two air cylinders 5a, 5b mounted on the base below the beam lb. In the sides of the base there are connections for compressed air 6a-6d, to the air cylinders. By its piston rod one cylinder 5a is connected to the upper beam la, as in the lower beam lb there is a hollow for free movement of the piston rod. The lower beam lb is connected to the piston rod of the other cylinder 5b, as in the upper bean there is a hollow for the nut with which the rod is fastened, such that the two beams can lie closely against each other.

In the outer portion of the beams 1 two longitu¬ dinal smooth rollers 7a, 7b are embedded. The outer portion of the beams has an angle of approximately 55° in relation to the longitudinal direction of the beams, and such that the rollers in the working position of the device point approximately 35° rearwards towards the feeding direction of the fabric.

The rollers 7 are driven by an electrical gear motor 8 mounted on a console on the base. The console contains a gear transmission and two couplings for each bowden-cable 10a, 10b connected to the rollers 7, which are passed through the beams. The transmission is such that the rollers are counter driven despite the rotation direction, which can be changed on the gear motor.

The base is slidably mounted on a vertically linear compressed-air cylinder 12, as the piston with piston rods 13 is secured to an end piece 14, which at its side is secured to the base. When the device is mounted in connection with a sewing machine 15, the rollers can be

slid in just above the top 16 of the machine in the path of the fabric immediately at the feeding end of the presser foot 17 of the sewing machine, and pulled free of the machine when not in use. The device is placed such that the rollers 7 are at a distance of 10-15 mm from the presser foot.

In Fig. 3 of the drawing two pieces of fabric 18a, 18b are shown schematically having outwardly curling edges 19a, 19b. The fabric pieces are thus placed be¬ tween the rollers for straightening the curling edges cf. also Fig. 1. The rotation direction of the rollers is also indicated. In Fig. 4 two pieces of fabric 18c, 18d are indicated having inwardly curling edges 20a, 20b which are straightened by guiding the fabric pieces on the outer sides of the rollers 7. In that situation the upper fabric 18 is kept in contact with the upper driven roller 17 by a retaining roller 21, which is pivoted hinged on the upper side of the upper beam la. The con¬ sole, in which the non-driven retaining roller is em¬ bedded, has a fork member 22, which is snugly fitted around the top of the guiding stand 2a. The retaining roller is kept in engagement by a spring 23 around the guiding stand and which extends between the upper face of the beam and the underside of the fork member. The retaining roller is swivelled upwards when the fork member engages a fixed ring stop 24 on the upper part of the guiding stand 2a, which takes place when the upper beam la is displaced upwardly. The retaining roller is then lifted and eases the feeding of the fabric.

It is obvious that the concrete embodiment of the device according to the invention is adapted to whether it is designed as an accessory to an existing sewing machine and further individually to the different brands and models, or whether the invention is integrated in new sewing machines. Despite this, it is within the scope of the present invention.