Field of invention

The present invention is related to automated bag making operation or operations where a fabric or a bag made from it is stitched or heat-seamed or seamed otherwise in an automated manner. In particular the invention is related to a device for pulling the article being stitched or seamed after the stitching or seaming operation.

Background of Invention

Polly Olefin fabrics are usually very flexible. During sewing or seam making operation of any fabric, or any article made using such fabric, the quality of stitching improves if the fabric is in a taut state as it passes through the sewing or seaming zone.

In the conventional sewing operations deployed in the automated bag making devices, there are no special measures adopted to keep the fabric in a taut state while it is being stitched. This results in inferior quality seams that potentially suffer from defects such as pleating. In some circumstances the fabric could get caught in the sewing area and gather together which could potentially lead to machine breakdown.

There is a need for a device that would keep the fabric in a taut state while it passes through the sewing or seaming zone of a sewing or seaming machine used in industrial bag making devices.

Objects and advantages of the invention:

Accordingly one of the objects of the present invention is to provide a device that would keep the fabric in a taut state while it passes through the sewing or seaming zone of a sewing or seaming machine used in industrial bag making devices

Summary of the invention

The device uses a set of pulleys and belt drives to apply pulling force to the fabric advancing through the sewing zone of a sewing machine. As the pulling device is linked to the feeder mechanism that feeds the article needing stitching to the sewing area, the fabric pulling speed is synchronised with the feeding speed of the advancing fabric. This ensures that there's no undesirable or excessive pulling while at the same time the article being stitched is kept in a desirably taut state so that the seam formed is without any flaws such as pleat formation. Brief description of figures

Figure 1 shows the device of the present invention

Figure 2 shows an alternative arrangement of the present invention

List of parts

1 - Sewing machine 7 - Bag pulling pulley

2 - Pressure plate 8 - Belt drive pulley

3 - Needle 8A - tension adjustment mechanism

4 - Fabric; 4a - direction of fabric 9 - First Belt (9) advance 10 - Second belt

5 - Sewing platform 11 - Lever

6 - Driver pulley 11 - Lever

Description of the invention

Figure 1 shows the device of the invention. A typical sewing machine (1) uses a needle (3) for stitching operation, while a pressure plate (2) holds the fabric (4) in place on top of a sewing platform (5).

The device of the present invention operates in the post-stitch zone, which is the zone in which the bag or the fabric (4) which is being stitched enters after stitching. A driver pulley (6) is connected, preferably fixedly, to a belt drive pulley (8) of the fabric feeding assembly (not shown). The fabric feeding assembly is the machinery that feeds the bag or the fabric (4) which is to be stitched to the sewing machine (1). It normally comprises a conveyor belt type arrangement that continuously feeds the fabric (4) to the stitching zone in a direction (4a) indicated in Figure 1. The belt drive pulley (8) is connected to the feeding assembly, preferably through a first belt (9). As the bag or the fabric (4) is fed automatically to the stitching zone, the driver pulley (6) rotates in synchronisation with the belt drive pulley (8). For the purpose of this description the word bag here onward is used to mean either a bag or a fabric (4) that needs stitching. A bag pulling pulley (7) is connected to the driver pulley (6), preferably using a second belt (10) or similar mechanism. As seen in the Figure 2, a tension adjustment mechanism (8A) is provided to ensure that the upper leg of the second belt (10) is kept taut for its proper functioning. A number of alternatives are available known to a person skilled in the art to maintain tautness in the upper part of the second belt (10).

The bag pulling pulley (7) is preferably of a smaller diameter than the driver pulley (6). The diameters of the driver pulley (6) and the bag pulling pulley (7), are so maintained that the second belt operates at a desirable speed without slipping over the pulleys. The speed of the second belt is maintained within the range between 4m/min to 60 m/min depending on the application for which the device is used. At the same time, the surface speed of the bag pulling pulley (7) is maintained somewhat higher than the fabric (4) speed to ensure a positive drag force on the seam in the direction of the fabric (4) advance after the stitching operation is complete. The bag pulling pulley (7) is preferably provided with a coating, preferably rubber or similar material, to improve the grip between the pulley (7) and the fabric (4).

A mechanical arrangement, preferably to include a lever (11) and a spring, is provided to press the bag pulling pulley (7) down such that adequate pressure is applied on the advancing fabric (4) so that the fabric (4) doesn't uplift during the post-stitch stage. The lever (11) is preferably connected to the hub of the bag pulling pulley (7) through a suitable arrangement, preferably a welded connection. The lever (11) is provided a means to support adjustable weights (12) so that a desired amount of load may be applied at the point of contact of the bag pulling pulley (7) with the fabric (4). The amount of load should not be so high that the fabric doesn't get jammed due to pressure and it should not be so low that the fabric slips under the pulling force. These values will vary depending on the application, the type of fabric, among other things, however, these will be known to person skilled in the art.

This innovative arrangement of a rotating bag pulling pulley (7) with the downward load applied through the lever (11) ensures that a sufficient pulling force exerted on the fabric (4) ensuring that the fabric (4) is not unduly stretched yet keeping it sufficiently taut at all times during the stitching operation. The various parameters such as the drive ratio, the adjustable weights, the length of the lever, are so maintained that amount of pulling force should not be so low that the fabric doesn't get jammed as soon as it comes out from the stitching zone, and it should not be so high that the fabric slips under the pulling force which could affect the seam quality. The required pulling force will vary depending on the application, the type of fabric, among other things, however, these will be known to person skilled in the art. This eliminates any possibility of the fabric gathering together after the seam has been formed thereby removing the related possibility of machine breakdown.

In an embodiment of the present invention, the bag pulling pulley (7) has a serrated surface so that the pulley gets further grip on the fabric(4).

In another embodiment of the present invention, the fabric (4) or the bag is being provided a heat joint rather than a sewing machine stitch.

It is evident from the foregoing discussion that the present invention comprises the following items: 1. A post stitch bag seam pulling mechanism on automatic bag cutting and sewing machine or a heat joint-making machine, said sewing machine provided with a fabric feeding assembly which feeds the fabric (4) to the stitching zone of said sewing machine, said feeding assembly typically incorporates a conveyor belt arrangement that feeds said fabric (4) to said stitching zone, and wherein the advancing fabric (4) which is being stitched is continually pulled in the post-stitch zone, such that said fabric (4) is not unduly stretched yet kept sufficiently taut at all times during said stitching operation.

2. A fabric pulling mechanism as described in item 1, wherein said mechanism comprises a driver pulley (6), a belt drive pulley (8), a first belt (9), a bag pulling pulley (7), a second belt (10), a lever (11), and a set of adjustable weights (12), further wherein said driver pulley (6) is connected, preferably fixedly, to said belt drive pulley (8) of said fabric feeding assembly; said conveyor belt type arrangement continuously feeds the fabric (4) to the stitching zone; said belt drive pulley (8) is connected to said feeding assembly, preferably through a first belt (9); and wherein as said fabric (4) is fed automatically to the stitching zone, said driver pulley (6) rotates in synchronisation with said belt drive pulley (8); said bag pulling pulley (7) is connected to said driver pulley (8), preferably using a second belt (10) or similar mechanism; and wherein while said fabric (4) is being pulled, said bag pulling pulley (7) presses said fabric (4) down using a mechanical arrangement, preferably including a lever (11) and a spring, wherein said lever (11) is provided with a facility to accommodate adjustable weights (12) such that through said bag pulling pulley (7) adequate pressure is applied on the advancing fabric (4) so that the fabric (4) doesn't uplift during the post-stitch stage.

3. A fabric pulling mechanism as described in item 2, wherein said lever (11) is preferably connected to the hub of the bag pulling pulley (7) through a suitable arrangement, preferably a welded connection.

4. A fabric pulling mechanism as described in item 3, wherein said bag pulling pulley (7) is preferably of a smaller diameter than said driver pulley (6) and the relative diameters of the said driver pulley (6) and said bag pulling pulley (7) are so provided that the second belt (10) operates at a predetermined speed without slipping over the pulleys, preferably moving at a speed in the range between

4m/min to 60m/min.

5. A fabric pulling mechanism as claimed in claim 4, wherein surface speed of said bag pulling pulley (7) is higher than the speed of fabric advance.

6. A fabric pulling mechanism as described in item 5 wherein said bag pulling pulley (7) is preferably provided with a coating, preferably rubber or similar material. 7. A fabric pulling mechanism as described in item 6 wherein said bag pulling pulley (7) has a serrated surface of the type such said bag pulling pulley (7) gets further grip on the fabric (4).

8. A fabric pulling mechanism as described in item 7, wherein said mechanism is used on the machines used for heat-formed joints.

9. A fabric pulling mechanism as claimed in claim 2, further wherein a tension adjustment mechanism is provided to keep said second belt in taut state.

10. A method of pulling fabric in post-stitch zone of a automated fabric feeding and stitching apparatus, said method comprising the steps of: a. providing a fabric pulling mechanism in post-stitch area of an advancing fabric. b. synchronising speeds of said driver pulley, bag pulling pulley and belt drive pully, c. adjusting the weight on said lever (11), d. auto-feeding said fabric (4) to stitching zone e. continually pulling the stitched fabric using said mechanism.

11. A method of pulling as described in item 10, wherein said mechanism of step a is as described in item 1. 12. A method of pulling fabric in post-stitch zone of a automated fabric feeding and stitching apparatus as described in item 10, wherein said mechanism of step a is as described in item 2.

13. A method of pulling fabric in post-stitch zone of a automated fabric feeding and stitching apparatus as described in item 10, wherein said mechanism of step a is as described in any of items 3 to 8.

While the above description contains much specificity, these should not be construed as limitation in the scope of the invention, but rather as an exemplification of the preferred embodiments thereof. It must be realized that modifications and variations are possible based on the disclosure given above without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.