GB2164366A - Sewing machines - Google Patents

Abstract

Apparatus comprising detection means and electronic control circuitry for monitoring the inclusion and correct alignment of one piece of cloth with respect to another piece of cloth. The electronic control circuitry on receipt of signals from the detectors is operative to stop the operation of the sewing machine if the one piece of cloth is absent or it is incorrectly aligned. <IMAGE>

Description

SPECIFICATION Improvements in or relating to sewing machines The present invention relates to sewing machines and more particularly to apparatus for use with sewing machines for monitoring the correct sewing of two pieces of cloth to each other.

A particular problem is encountered during the inclusion of, for example, the leg portions of a pair of jeans into the waistband. The waistband is normally formed by folding a ribbon of cloth, turning the edges inwards and the leg portions are sewn into the centre of the fold formed from the ribbon of cloth. If the leg portions are not correctly positioned with respect to the waistband then portions of the waistband may not be correctly sewn to the leg portions resulting in the finished garment being a reject.

It is an object of the present invention to provide apparatus for monitoring the correct sewing together of two pieces of cloth and it is a further object to provide apparatus for monitoring the correct inclusion of one piece of cloth into another.

Though, for purposes of simplicity the term "cloth" is used, any similar material such as rubber, plastics or thin metal is considered to be included.

According to the present invention there is provided apparatus for use with sewing machines for monitoring the sewing together of a first piece of cloth with a second piece of cloth including guide means for guiding the first piece of cloth, first and second detection means associated with the guide means, the first detection means being for the detection of the presence of the second piece of cloth and the second detection means being for the accurate detection of the position of the second piece of cloth relative to the guide means.

The sewing machine preferably includes means for automatically feeding at least the first piece of cloth past a sewing needle to enable the second piece of cloth to be sewn to the second piece of cloth.

The apparatus preferably includes means for monitoring the position and presence of the first piece of cloth and for monitoring the movement of the first piece of cloth.

Embodiments of the present invention will now be described, by way of example with reference to the accompanying drawings, in which: Figure 1 shows a piece of cloth in an unfolded condition; Figure 2 shows the piece of cloth of Figure 1 folded once; Figure 3 shows the piece of cloth of Figure 1 folded twice; Figure 4 shows the piece of cloth of Figure 3 together with a further piece of cloth for inclusion therewith; Figure 5 shows a first variation of the folded type; Figure 6 shows a second variation of the folded type; Figure 7shows the apparatus according to the present invention for monitoring the inclusion of one piece of cloth with respect to another; Figure 8 shows an alternative sensing arrangement to that shown in Figure 7; Figure 9 shows block diagrammatically the control system of the present invention;; Figure 10 shows the amplification and threshold detection circuit for a sensor; Figure 11 shows the amplification and threshold circuitry associated with the other sensor; Figure 12 shows the logic circuit associated with Figures 10 and 11; Figure 13 shows the mid rail voltage level circuitry associated with the circuit of Figures 10 and 11; and Figure 14 shows a possible oscillating source feed circuit for the emitters.

With reference to the drawings,-a piece of cloth 10 (see Figure 1) in "ribbon" form is introduced into a first folding apparatus 12 (Figure 7) to form at its exit 14 a first folded form 16 (Figure 2). The folded form 16 is fed into a second folding apparatus 18 in which two further folds are introduced to form the second folded form 20 (Figure 3).

A piece of cloth 22 to be included within the second folded form 20 at a sewing station 24 is shown in Figures 4 and 5.

Variations on the folded form are shown in Figures 5 and 6, the needle direction being indicated by a dotted arrow and the stitch line being indicated as a dotted line. A further possible variation is to use the form shown in Figure 2, again the needle and stitch line being indicated by dotted lines.

The apparatus can also be used with a fabric guide where it is required to stitch together two single pieces of material with an accurate overlap as indicated by the dotted lines in Figure 1.

The invention will now be described with reference to the inclusion of a piece of material into the folded form of Figure 4 using the apparatus shown in Figure 7 as modified by Figure 8. It is to be understood however that the folder 12,18 of Figure 7 could be of a modified form to produce the folded forms shown in Figures 2,5 and 6 or a fabric guide for use with the single fabric form of Figure 1. The invention relies only on a piece of material of a desired shape emerging along a defined path relative to the detectors, as shown by arrow 26.

In normal operation the folded form of cloth, which may be a waistband for a garment, is pulled in the direction shown by arrow 26 by, for example, a mechanism (not shown) associated with and driven in synchronism with the main drive motor of the sewing machine which also operates the sewing action at station 24. Station 24 may comprise more than one needle to provide, for example, a double row of stitches.

The piece of material 22 which is to be included may, for example, comprise the complex leg portions of a pair of jeans or trousers. Often the material is relatively stiff and the complex shape makes the problem of handling the piece of material 22 very difficult for the operator of the sewing machine. This often results in the material 22 being wrongly positioned with respect to the material 20 and for the sewing action to fail to sew the two pieces of material together accurately. In many cases the stitches miss the material 22 for short lengths resulting in the pulling apart of the legs from the waistband in a pair of jeans or trousers during wear or during a testing operation. Since the stitching operation takes place when the material 22 is "included" within the material 20 it is difficult for the operator to monitor the correct alignment of the two pieces of material.

The present invention provides monitoring apparatus for ensuring the correct alignment of the two pieces of material and thereby the correct inclusion to form a good seam between the pieces of material.

The apparatus comprises first and second light emitters 28, 30 mounted on a platform 32 which may form part of the folding means 12,18. The system may, as shown, be of the reflective type in which detectors A and B are incorporated in the same mounting as the sources 28, 30, using the reflection of light from the material 22 to detect its presence or may be of the transmission type as shown in Figure 8 wherein detectors A and B are situated on the opposite side to the light sources 28, 30. The detectors and light sources may be situated either above or below the path of material 22 as shown by Figures 7a and 8.

The first detector A is used to detect the presence of the material 22 and the second detector B is used to determine the position of the material 22 relative to the folding apparatus 18 and hence relative to the folds formed in the material.

The platform 32 may be movable relative to the folding apparatus 18 by clamping screws 33,35 to enable adjustment of the amount of material 22 included in the folded form 20, for example when a double row of stitches is required.

In operation detector A first detects the material 22 as it is inserted into the sewing machine by the operator. Detector B is operative to detect the correct positioning of the edge 34 of material 22 relative to the folding apparatus 18. If the edge 34 of material 22 does not cover the detector B then the sewing machine will be rendered non-operative by electronic logic and solenoid operated means shown in Figures 10 to 14. Equally, if during a sewing operation edge 34 fails to cover the detector B the main sewing machine drive will be de-energised and the sewing operation will cease until detector B is again covered by edge 34.The ability of modern electric sewing machines to stop within one or two stitch lengths means that there is enough distance between detector B and the sewing station 24to enable a correction to be made by pushing edge 34 in towards the folding apparatus 18 such that at the sewing station 24 a correct seam will be obtained.

For the purpose of completing a sewing action at station 24 a logic function is required since at the comp!etion of a garment the leg portion will pass the detector 30 and uncover this detector. Normally, the sewing machine will be de-energised. However, priorto detector 30 being uncovered detectorAwill be uncovered and this can be used to inhibit operation of detector Bto allow the garment to be completed.

With reference now to Figure 9 the outputs from sensors A and B are fed via a logic decoder and motor control panel 40 to control the operation of the sewing machine motor 42.

The general operational sequence is as follows: 1. Sensor A: senses the presence of fabric and via logic decoder (Figures lotto 14) ensures the motor 42 is in the stop position.

- 2. Sensor B: upon presenting fabric 22 directly in the path of sensor B the motor is enabled by the logic decoder.

3. If at any time during the sewing process fabric 22 is moved out of the path of sensor B the motor 42 stops.

The circuitry in the panel 40 is shown in greater detail in Figures lotto 14to which reference is now made. In Figure 10 sensor B is connected as the input to complex amplifier 44. The output of amplifier 44 is connected to a threshold detection circuit 46 which provides via an inverter 48 output R for the logic circuit of Figure 12 and also an output to light a green LED 50 which provides an indication of the correct presence and positioning of fabric edge 34 relative to the edge of guide 18 to cover sensor B and also indicates the correct functioning of the sensor B detection system.

With reference now to Figure 11 sensor A is connected to an exactly similar amplifier 44 (not shown) and provides an output to a similarthreshold circuit 46' the output of which provides a signal S for the logic circuit of Figure 12 and via inverter 52 provides power for illumination of a second green LED 54. This LED gives an indication to the operator of the presence of fabric 22 and also is useful for indicating the correct functioning of the sensor A detection system.

Thus in both Figures 10 and 11 the design of amplifier 44 is identical. Amplifier 44 comprises a three stage amplifier/rectifier. The first stage 56 amplifies the oscillating output from the detectors which is rectified by the second precision rectifier stage 58 the D.C. output of which is buffer amplified by the third stage 60 to provide the threshold detectable input for detector 46. In stages 58, 60 of amplifier 44 a 3 volt "mid rail" voltage input is used in the differential amplifiers to enable the operation of the amplifier with a single 12 volt rail and earth.

Thus the oscillation is detectable about the 3 volt level. Resistor 62 in arnplifier stage 58 is shown as 1K n but should be chosen to suit the detector type such that V = 6V + 2 VOLTS.

The 3 volt mid rail voltage is provided by the circuit of Figure 13 the operation of which is considered to be self explanatory.

The emitters are powered by an oscillating voltage which is supplied as shown by the circuit of Figure 14. The emitters 28,30 are connected as shown in series and emit an alternating light wave. Sensors A and B are not sensitive to ordinary light from other sources e.g. bright inspection lamps and amplifiers 44 are tuned to receive light of the correct frequency.

The logic and control circuitry shown in Figure 12 comprises an input gate 64 the output of which controls a transistor 66. When transistor 66 turns on, which occurs when sensor A is covered but sensor B is uncovered, relay coil 68 is energised to cause the relay contacts (not shown) to open and the motor 42 to be rapidly stopped. The logic function for the sensors to stop the motor 42 is therefore A AND NOT B. A red LED 70 is also illuminated to indicate that the fabric edge 34 is not correctly positioned so that the machine operator can correct the positioning of the fabric edge 34 and continue with the sewing operation.

Claims (8)

1. Apparatus for use with sewing machines for monitoring the sewing together of a first piece of cloth with a second piece of cloth including guide means for guiding the first piece of cloth, first and second detection means associated with the guide means, the first detection means being for the detection of the presence of the second piece of cloth and the second detection means being for the accurate detection of the position of the second piece of cloth relative to the guide means.

2. Apparatus as claimed in Claim 1 including electronic control circuitry connected to receive the outputs from the first and second detecton means and being operative to provide a first output signal to the main motor of the sewing machine to stop the sewing machine when the second detection means detects a wrong position of the second piece of cloth relative to the guide means.

3. Apparatus as claimed in Claim 2 in which the electronic circuitry includes logic means for inhibiting the operation of the main motor of the sewing machine until the first sensor detects the presence of the second piece of cloth.

4. Apparatus as claimed in Claim 3 in which the logic means includes means to allow the main motor of the sewing machine to remain operative after the first sensor detects the absence of the second piece of cloth to allow a garment to be completed.

5. Apparatus as claimed in any one of Claims 1 to 4 in which the guide means comprises a folder and in which a second guide is provided to guide the second piece of cloth the detectors being mounted on the second guide means and the second guide means being movable relative to the first guide means.

6. Apparatus as claimed in Claim 5 in which the first and second detection means each comprise a light source and detector.

7. Apparatus as claimed in Claim 6 in which the first detection means is situated to be covered by the second piece of cloth prior to the second detection means during normal operation.

8. Apparatus for use with sewing machines for monitoring the sewing together of a first piece of cloth with a second peice of cloth substantially as described with reference to the accompanying drawings.