GB2059636A - Sewing machines - Google Patents

Description

SPECIFICATION Apparatus for making up textile articles The present invention relates to apparatus for making up textile articles, and more particularly to such apparatus including automatic control devices.

One device used to make up textile articles is commonly called a sewing machine but within the trade there are specific sewing machines for different operations although a number of similar operations may be carried out on a single machine. The present specification will use the term sewing machine generically to cover all stitching devices used in the textile trade.

In addition to the sewing machine, there have been available for many years additional pieces of equipment such as cutters, usually called knives, and stackers for assisting the machine operator to increase her production.

These are usually manually activated by the machine operator at the appropriate time although they may be power assisted, usually pneumatically.

In certain operations, such as the addition of lace or elastic or the like to a garment, it is conventional that the operator will produce a number of articles one immediately after the other with adjacent articles joined together by the lace or elastic. The lace or elastic is usually fed to the sewing head or the machine automatically by well known feeding means. It has been found that on occasion the operator will leave very large amounts of lace or elastic between garments. This is wasteful and on occasion expensive. Other operations require some considerable skill from the operator if they are to be carried out efficiently.

The present invention provides control apparatus designed to be associated with a sewing machine for improving the efficiency of the operator.

Two embodiments will be described in detail, one in which waste is reduced to a minimum and the other in which the operation is carried out more efficiently than can the average operator.

In order that the present invention be more readiiy understood, embodiments thereof will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows diagrammatically a sewing machine modified to accomodate control apparatus according to the present invention; Figure 2 shows an electrical circuit diagram of a first embodiment of the present invention; Figure 3 shows a pneumatic circuit diagram for use with the electrical circuit of Fig. 2; Figure 4 shows an electrical circuit diagram of a second embodiment of the present invention; and Figure 5 shows a pneumatic circuit diagram for use with the electrical circuit of Fig. 2.

In both the embodiments to be described, a sewing machine is provided with sensors for providing signals for controlling the operation of the machine as well as associated apparatus. The signals are electrical signals which are operated upon to produce output electrical control signals. These control signals are used to control pneumatic equipment which actually controls the machine and/or the ancilliary apparatus. Thus, the electrical circuit is the "brains" and the pneumatic circuit is the "muscle".

Turning now to the drawings, Fig. 1 shows a sketch of a sewing machine 10 with parts broken away for clarity. The machine 10 has a sewing head 1 Oa provided with one or more work piece presence detectors for detecting the position of the work piece. In this case, the machine 10 has detectors before and after a needle 11 in the sewing head. The detectors may be of any convenient type but in this embodiment they are optical detectors 12, 1 3 working on a reflective principal, light from a light source being reflected from a reflective surface 1 2a, 1 3a in the absence of a work piece.

The sewing machine may also have a revolution sensor in the form of a detector for detecting rotation of a flywheel 14. Again the detector may be of convenient type and again it is preferred to use an optical detector 1 5 working on a reflective principal, light being reflected from reflective marks on the flywheel 14.

Turning now to Figs. 2 and 3, these show the electrical and pneumatic circuit diagrams of control apparatus for controlling the machine 10 so as to increase the number of stitches per inch at one or more selected places in the work piece. This will be called stitch cramming.

In this embodiment only one sensor at the sewing head is required, that being the sensor 12 in front of the needle 11. The sensor 12 is represented in Fig. 2 by a phototransistor the emitter of which is connected to ground via a variable resistor 20. Stitch cramming at the start of the work piece will be described first.

A signal is developed across the resistor 20 when there is no work present. When a work piece is fed under the sewing head 1 0a the signal across the resistor 20 disappears and the output of a first trigger circuit 21 goes high which means that the output of a following trigger circuit 22 goes low. This low output is fed to one input of a NOR gate 23 whose output is connected to both inputs of a further NOR gate 24 whose output is connected to a reset input of a binary counter 25.

Thus, when work is present at the sewing head, the reset signal is removed from the binary counter 25 and so it can count the number of stitching motions made by the machine by counting pulses developed by the sensor 1 5 adjacent the flywheel of the machine. The pulses developed by the sensor 1 5 are shaped by the trigger circuits 26 and the flip-flop 27 before being divided by 4 by dividing circuit 28 and fed to a counter 25.

A preselected count number representative of the length of garment to have stitch cramming is determined by selector circuit 29 connected to the counter 25 and when the counter reaches the preselected count a flip flop 30 is operated to produce a high signal at the Q output which in turn produces a reset signal to reset the counter to zero. Simultaneously, the Q output of the flip flop 30 which was previously high goes low and, assuming that a switch 30 is connecting the Q output to a drive transistor 32, the transistor 32 turns off which de-energises relay coil 33 to reduce the number of stitches per inch made by the apparatus by, in this case reducing the speed at which the work piece is fed through the sewing head.

Stitch cramming only at the back of the work piece will now be described. In this case the switch 31 is arranged so that the base of the transistor 32 is connected to only the output from the trigger circuit 22. Thus, although the part of the circuit previously described may operate, it does not control or cause any stitch per inch change. Thus the machine will function normally until the work piece leaves the detector 12, which it will be recalled is in front of the needle. Hence there is still a length of work piece to be sewn by the machine, which length is determined by the distance between the detector 1 2 and the needle 11. if desired, this distance can be made adjustable.

Now, when the work piece clears the detector 12, the output of the trigger 22, which was previously low, becomes high thus driving transistor 32 on to energise relay 33 and increase the number of stitches per inch.

By ensuring that switch 31 connects both the Q output from flip flop 30 and the output from inverter 22 simultaneous to the transistor 32 stitch cramming can be achieved at both the front and the back of the work piece.

An additional feature of this circuit is that it also controls the operation of a stacker for stacking finished work pieces. This is done by a timer circuit 35 which is activated by the signal from the detector 1 2. The arrangement is such that after a work piece clears the sewing head, the timer circuit 35 holds a flip floo 36 in an existing condition for a time sufficient for the thread to be cut by conventional automatic cutting apparatus. Thereafter, the timer circuit 35 causes the flip flop 36 to change state which causes a high signal to be present at the Q output of the flip flop 36.

This high signal is used to reset the flip flop 30 and is also used to operate a one-shot circuit 37 which in turn energises a relay 38 associated with stacker operating apparatus.

The sewing machine and its electrical control circuit are now ready to sew the next garment.

The above apparatus allows stitch cramming to take place at an optimum speed and the length of the cramming to be accurately defined and regularly maintained.

For completness, the pneumatic circuit as sociated with the electrical circuit is shown in Fig. 3. The coils shown are the coils of the relays referred to in Fig. 2 and are therefore allocated identical numbers. The pneumatic circuit is in two separate parts; one which operates change of feed length to effect stitch cramming and is operated by the coil 33; and the other which operates the stacker under the control of the coil 38. As shown, the stacker could be operated manually using a knee press 39, and because of this a shuttle valve 40 is required. Operation of the knee press 39 automatically disengages the coil 38 by operating a further valve 39a.

Turning now to a second embodiment of the invention, this is primarily designed to add lace or elastic to a garment and is arranged to automatically start and stop the machine as well as automatically cut the lace or elastic joining together adjacent work pieces. This embodiment utilises a front and a back detector at the sewing head and does not require the detector 15.

The second embodiment will now be described with reference to Figs. 4 and 5. The front detector 1 2 provides a signal when no work piece is present and this is inverted and shaped by a trigger circuit 41. In the presence of a work piece, there is a signal present at the output of the circuit 41 and this is fed via a resistor to a motor energisation circuit in the form of a transistor 42 and a relay 43. Thus, when a work piece is present at the sewing head and the motor is provided with power, the machine is started. Absence of the work piece at the sewing head will automatically stop the machine. The output of the circuit 42 is also fed to one terminal 44a of a switch 44.

The back detector 1 3 and a trigger circuit 45 are similar in operation to detector 1 2 and circuit 41. Thus, when a work piece is present there is a signal present at the output of the circuit 45. This signal is fed via a diode and a switch 46 the resistor in the base circuit of the motor drive transistor 42. Thus, with switch 46 open the machine is started and stopped under the control of only the front detector 1 2. With switch 46 closed, the machine will start under the control of the front detector 1 2 but will be stopped under the control of the back detector 1 3.

The output of the circuit 45 is also fed to one input of a NOR gate, the other input of which is taken from the centre terminal of the switch 44 which has a further terminal 44b connected to the negative supply rail. The output from the NOR gate 47 is fed via an inverter to a one shot circuit 48 which is used to operate a relay 49 to control a cutting device for cutting the lace or elastic and thus separating adjacent work pieces. By correct positioning of the switch 44, the cutter will operate and cut when the material clears the back detector with the switch 44 arranged to connect the terminal 44b to one input of the NOR gate 47. With the terminal 44a connected to one input of the NOR gate 47 the cutter will operate and cut only when both the front and the back detectors are cleared.

An override switch 50 is included for considering the automatic start/stop of the machine.

The pneumatic circuit for this embodiment is shown in Fig. 5. Again it is in two distinct parts, the upper part being the motor control part under the control of the relay 43, and the lower part being primarily the cutter control under the operation of the relay 49.

Returning to the upper part of Fig. 5, associated with the stop start control is a pneumatic piston and cylinder arrangement 51 at the side of the sewing machine for holding the work piece while it is being cut and stacked.

Turning now to the bottom of Fig. 5, there is a more complicated pneumatic arrangement which controls a stacker and a further work piece holding device as well as the cutter. The whole arrangement at the bottom of Fig. 5 may be automatically controlled by signals derived from the sewing machine using the relay 49 or it may be manually controlled by operating a knee press 52. If the automatic function is to be overriden, a switch 53 is operated to isolate the pneumatic switch associated with the relay 49. The automatic operation will be described and it will be appreciated that the manual operation using the knee press is identical.

When the relay 49 is energised, the switch 49a associated therewith is operated to connect a source of either vacuum or positive pressure to a further valve 54 provided with two outlets which are connected to opposite ends of a piston and cylinder device 55 for driving the piston thereof in either direction.

The piston is connected to a guard of the cutter and the guard is arranged to have an actuator 56 which will activate the cutting biade only when the guard is in position. This is done by the actuator 56 operating a limit switch 57 to connect a piston and cylinder device 58 associated with the cutting blade with a pressure source. It is apparent that the guard and the cutting blade are mechanically separate and are both powered down to the cutting position and up from the cutting position. Thus, the cutting operation is accomplished quickly and safely. In fact, so quick is the cutting operation that the cut can be made while the next work piece is being sewn.

A work piece holding device 59 is also activated by the relay 49. This device 59 holds the already sewn work piece during the cutting operation.

A stacker 60 is also activated by the relay 49 to stack the already sewn work piece after it has been separated from the workpiece being sewn. If required, the stacker can be isolated from the rest of the apparatus using the manually operated switch 61.

From the above two embodiments it will be apparent that by using the control apparatus as shown, a sewing machine can be operated in such a manner that it is run at maximum speed for the maximum time while ensuring that waste is kept to a minimum. A further advantage is that the sewn work pieces are of a consistent quality.

Claims (9)

1. Sewing apparatus for making up textile articles comprising a work station provided with a sewing head, sensing means for sensing the presence of a workpiece at the work station, a control circuit for producing a control signal in response to an output from the sensing means and fluid power operating means responsive to the control signal from the control circuit for controlling an operation of the apparatus.

2. Sewing apparatus according to Claim 1, and comprising a cutting device arranged to be operated by said fluid power operating means.

3. Sewing apparatus according to Claim 1 or 2, and comprising a further sensing means for producing a signal indicative of the number of stitches per unit length of article being fed through the work station, the control circuit being responsive to both the first-mentioned and further sensing means whereby to produce a control signal for controlling the number of stitches per unit length.

4. Sewing apparatus according to Claim 3, wherein the apparatus is provided with an automatic article feeding device and the fluid power operating means is arranged to alter the rate of feed of said feeding device whereby to alter the number of stitches per unit length of article.

5. Sewing apparatus according to Claim 4, wherein the control circuit comprises a timing circuit for controlling the length of time said fluid power operating means is in operation.

6. Sewing apparatus according to Claim 3, 4 or 5, and comprising a second sensing means for sensing the presence of a work piece at the work station, the first-mentioned and second sensing means being arranged to detect an article entering and leaving the work station, and the control means being arranged to provide control signals whereby the number of stitches per unit length of article is in creased at the beginning and end of an article with respect to the number of stitches per unit length in the remained of the length of the article.

7. Sewing apparatus according to any one of the preceding claims and comprising stacking apparatus for collecting articles from the work station, the stacking apparatus being operated at the appropriate time under the control of the control circuit and fluid power operating means.

8. Sewing apparatus according to any one of the preceding claims wherein the fluid power operating means are pneumatic.

9. Sewing apparatus substantially as herein before described with reference to the accompanying drawings.