GB2206360A - Sewing apparatus - Google Patents

Abstract

Sewing apparatus includes a sewing machine 12, a supply of fabric strip 15 to be sewn, in one or more layers, and a store for sewn strips, a guide 17 being provided between the supply and a sewing position to direct the or each layer towards the sewing position. Rollers 23, 24 feed strip(s) and tension them. The guide has a slot (S) with a fixed guide edge and a movable guide edge. The strip is biassed so that one edge is in engagement with the fixed edge. The rollers and sewing machine are driven off the same drive motor, the rollers being driven via a gearbox. Take-up roll 26 is driven by motor 27 which is switched on and off by weighted arm 28 engaging switches 30 and 31 respectively, to maintain a linear take-up rate by the roller. <IMAGE>

Description

SEWING APPARATUS This invention relates to apparatus for sewing strips of fabric.

In manufacturing textile articles such as clothing, bedding and furnishings, strips of fabric, which may be, for example, from 5Omm to 200mm wide are used as trims, edgings, frills and the like. The free edge of each such strips has to be treated to prevent unravelling. Hemming is very complicated and thus expensive of operative time. It is usual, therefore, to use overlock stitching along the free fabric edge to prevent fraying and to improve the appearance.

Zig-zag overlock stitching in a colour contrasting with the fabric colour can enhance the appearance of an article.

Strips of fabric for this purpose are usually sewn manually by a machinist. However, this is generally unsatisfactory in that although a sewing machine can maintain a high speed, the guiding and manipulation of the strip by the machinist makes the actual production rate much lower than the potential rate if set by the sewing machine. Also, edges tend to be irregular because of human error. As the task is very repetitive and tedious, attention can easily wander leading to irregularities and waste.

It is an object of the present invention therefore to provide sewing apparatus whereby the above disadvantages can be obviated or reduced.

Accordingly the invention provides sewing apparatus comprising: a supply for fabric strip; a sewing maching; a guide upstream of the sewing machine for guiding fabric strip from the supply towards the sewing machine; tension means for drawing sewn fabric from the sewing machine; and take up means for accumulating and storing sewn fabric strip.

The fabric strip can have a single layer of fabric in which case the sewing machine will operate to produce an overlock edging on the one layer, or spaced from the fabric edges, for example along the central part of the strip.

Alternatively, the fabric strip can have two or more layers and the sewing machine can operate to unite the layers with simple chain or decorative stitching, centrally or at edges.

The guide upstream of the sewing machine preferably includes, for each layer of fabric in the strip, a slot with ample thickness for the fabric, a fixed guide edge for a reference edge of the fabric and a movable guide edge securable at different differences from the fixed guide edges to accommodate different fabric widths. Strip feed is preferably such as to bias one edge of the fabric slightly towards the fixed guide edge, for example by placing the supply on that side of the guide, or by having means for engaging the fabric to urge it gently towards the fixed guide edge.

The tension means can be constituted by a puller nip between either a pair of rollers (one or both driven) or between a driven roller and a smooth slide surface, or between a pair of facing belts. The puller nip can be driven from the same motor as the sewing machine, preferably via a variable ratio gearbox which enables the speed of the puller nip to be varied to closely follow the fabric speed which is determined by the stitch length set on the sewing machine.

The take-up means can include a store roll driven intermittently in response to slack in sewn strip between the roll and the puller nip. The slack can be sensed by a movable member mounted to travel with the strip between the puller mip and the take-up roll and arranged to trigger the take up roll to wind on when slack reaches a high value and switch off when slack reaches a low value.

On its way to the sewing machine the strip, or each layer thereof, can pass a "break" switch capable of detecting the absence of fabric and, in that event, such as the end of a roll, switching off the machine.

When the apparatus is used for stitching two layers of fabric within a strip there can be a guide slot for each layer of fabric and a "break switch for each layer.

The invention will be described further, by way of example, with reference to the accompanying drawing, wherein Fig. 1 is a side elevation of a preferred sewing apparatus of the invention; Fig. 2 is a view of a guide of the apparatus of Fig. 1; Fig. 3 is a view, similar to that of Fig. 1, showing a modified apparatus; and Fig. 4 is an elevation of a guide for the apparatus of Fig. 3.

A preferred sewing apparatus 10 has a table 11 whereon is mounted an overlock sewing machine 12 driven from a motor 13. A supply roll 14 is mounted below the table and a strip 15 of fabric (in this case a strip having only one layer of fabric) passes upwardly to the surface of table 11 via a "break" switch 16. Switch 16 is connected to stop the apparatus when the end of a roll of fabric is reached.

On the surface of table 11 upstream of machine 12 is a guide 17 best seen in Fig. 2. Guide 17 has a fixed guide edge 18 aligned to direct the fabric to the sewing maching to be stitched in the correct position, usually in a band along the right hand edge in Fig. 2 to form a decorative edge formation preventing unravelling. However sewing between the edges may be desirable in some applications.

The guide 17 has a pair of plates 19 which with edge 18 define a slot therebetween. A movable guide edge 20 is secured in any desired position by fixing screws 21 movable along slots 22.

Downstream of sewing machine 10 the seam strips 15a is drawn towards a puller nip defined between rollers 23, 24 the former being driven from motor 13 via a variable gearbox 25. The puller nip should run at exactly the same speed as the sewing machine fabric feed mechanism. As the fabric travel rate from the sewing machine varies with stitch length, the variable gearbox allows this variation to be accommodated.

The sewn strip 15a now passes to a take-up roll 26 driven by its own motor 27. Roll 26 cannot run at a steady speed as a linear take-up rate is desired. Accordingly a pivoted arm 28 has a guide 29 connected to follow the loop in strip 15a between puller nip and take-up roll. Arm 28 is weighted and tends to fall. At a lower limit arm 28 contacts a switch 30 which starts motor 27. At an upper limit arm 28 contacts a switch 31 which stops motor 17.

The apparatus of the invention can be operated automatically without supervision except occasionally.

Initially an operator loads the machine, threads up and aligns the strip to be sewn and then presses a treadle 32 which switches on the motor 13. Thereafter motor 13 stays on until the apparatus is stopped by the operator or by switch 16. The operator will check initially, and from time to time, that the stitching is being placed correctly. One operative can supervise two or more apparatuses. The output of two such apparatuses is equal in volume to the output of five machinists, and the quality of the work is superior, because once set up the machine will run true under most circumstances.

The sewing machine 12 shown in Figs. I and 2 is an overlock machine, normally used for applying an edging to a strip of fabric. However, the apparatus 32 of Fig. 3 operates on the same principle to unite two or more layers of fabric in a strip. Most parts of the apparatus are similar to those of the Fig. 1 apparatus and therefor the same reference numerals have been used. The main differences are that a simple chain stitch machine 33 is used and that there is a second supply roll 34 for a second layer 35b of fabric as well as a first key 35a from roll 14. Each layer passes a 'break' switch 16, 16a and the two layers then pass a double guide 36 (Fig. 4). After guide 36 the strip 35 made up of two layers 35a, 35b passes to the machine 33 is sewn and passes as a sewn strip 35c to the puller nip. Thereafter apparatus operation is the same as in the Fig. 1 embodiment.

The guide 36 has three plates 37, 38, 39 and two fixed stops 40, 41 which are in line (if two layers are to be sewn with their edges not in line the fixed stops can be other than in-line vertically (in fact each slot can have two movable stops if desired). Each slot has a movable stop 42, 43. The screws 44 of the stop 43 are accessible by a tool passing through slots in plate 37. The guide 36 operates in a manner similar to guide 16 but for two layers in a strip.

Operation of the machine of Fig. 3 is comparable to operation of the machine of Fig. 1, save that a two layer strip is being treated. The apparatus could be easily modified to sew three or more layers if desired.

Claims (18)

1. Sewing apparatus comprising: a supply for fabric strip; a sewing machine; a guide upstream of the sewing machine for guiding fabric strip from the supply towards the sewing machine; tension means for drawing sewn fabric from the sewing machine; and take up means for accumulating and storing sewn fabric strip.

2. Sewing apparatus as claimed in claim 1, wherein the fabric strip has a single layer of fabric and the sewing machine operates to produce an overlock edging on the one layer, or spaced from the fabric edges, for example along a central part of the strip.

3. Sewing apparatus as claimed in claim 1, wherein the fabric strip has two or more layers and the sewing machine operates to unite the layers with stitching, centrally or an edge or edges.

4. Sewing apparatus as claimed in claims 1, 2 or 3 wherein the guide upstream of the sewing machine includes, for each layer of fabric in the strip, a slot with ample thickness for the fabric, a fixed guide edge for a reference edge of the fabric and a movable guide edge securable at different differences from the fixed guide edges to accommodate different fabric widths.

5. Sewing apparatus as claimed in claim 4, wherein strip feed is such as to bias one edge of the fabric slightly towards the fixed guide edge.

6. Sewing apparatus as claimed in claim 5, wherein this is achieved by placing the supply on that side of the guide.

7. Sewing apparatus as claimed in claim 5, wherein means is provided for engaging the fabric to urge it towards the fixed guide edge.

8. Sewing apparatus as claimed in any preceding claim, wherein the tension means is constituted by a puller nip.

9. Sewing apparatus as claimed in claim 8 wherein the pulley nip is between a pair of rollers (one or both driven).

10. Sewing apparatus as claimed in claim 8, wherein the puller nip is between a driven roller and a smooth slide surface.

11. Sewing apparatus as claimed in claim 8, wherein the puller nip is between a pair of facing belts.

12. Sewing apparatus as claimed in claims 8 to 11 wherein the puller nip is driven from the same motoe as the sewing machine.

13. Sewing apparatus as claimed in claim 12, wherein the nip is driven via a variable ratio gearbox which enables the speed of the puller nip to be varied to closely follow the fabric speed which is determined by the stitch length set on the sewing machine.

14. Sewing apparatus as claimed in any preceding claim, wherein the take-up means includes a store roll driven intermittently in response to slack in sewn strips between the roll and the puller nip.

15. Sewing apparatus wherein slack can be sensed by a movable member mounted to travel with the strip between the puller nip and the take-up roll and arranged to trigger the take-up roll to wind on when slack reaches a high value and switch off when slack reaches a low value.

16 Sewing apparatus as claimed in any preceding claim wherein on its way to the sewing machine the strip, or each layer thereof, passes a "break" switch capable of detecting the absence of fabric and, in that event, such as the end of a roll, switching off the machine.

17. Sewing apparatus as claimed in any of claims 1 to 15, wherein the apparatus is used for stitching two layers of fabric and there is a guide slot for each layer of fabric and a "break" switch for each layer.

18. A fabric strip sewn by the apparatus of any preceding claim.