GB2036105A - Controlling Sewing Machines - Google Patents

Abstract

A device enabling rapid disengagement of a foot pedal controlling the clutch/brake control of an industrial sewing machine is in the form of a two-part control rod in which one part is fixed to a coupling 3 and the other part 2 can be engaged by a spring-biased latching bolt 8. The bolt 8 is moved out of engagement by a solenoid or a pneumatic cylinder 11, 12 actuable by a control apparatus which includes sensing devices detecting the presence or absence of thread or trim at various points on the machine and an electronic control circuit which provides the actuating signal when any sensing device signals. One of the sensing devices may be in the form of a presser foot having a switch mounted thereon, operated by the top thread of a lockstitch sewing machine when the under-thread fails. <IMAGE>

Description

SPECIFICATION Controlling Sewing Machines This invention relates to apparatus for controlling sewing machines, particularly industrial sewing machines.

In industrial sewing machines such as are used in garment manufacture, breakage or other failure in the supply of thread or trim to a needle may not be noticed by an operator until the workpiece being sewn has travelled an appreciable distance unsewn. This is especially likely in a multi-needle machine where, for example, four, or more rows of stitching have to be monitored by the operator.

The presence of an unsewn length may necessitate re-sewing of the workpiece, or possibly rejection of the workpiece, which may be a complete garment, thus wasting time or materials or both.

It is possible to provide detectors which will signal failure of a thread in an operator-controlled sewing machine, but to minimise waste it is important that the machine should be stopped as quickly as possible when a failure is signalled.

Many industrial sewing machines have a continuously-running electric (or other) motor and a clutch control between the motor and the sewing machine drive, the machine being operated by depressing a foot-control pedal to operate the clutch to engage the motor with the drive. The pedal or clutch control will be springloaded so that when pressure is released the clutch is released and the drive and motor disengaged. A brake may be applied simultaneously to the sewing machine drive. The pedal will be linked to the clutch control by a rigid control rod, referred to as a "Pitman rod", or possibly by a flexible cable linkage. To disengage the drive rapidly it is desirable to provide means which will over-ride the operation of the footcontrol pedal.

According to a first aspect of the invention, there is provided a control rod for linking a foot pedal to drive controlling means in a sewing machine, which comprises a coupling linking two parts of the rod, the coupling being fixed to a first part of the rod and including latching means engageable on the second part of the rod to hold the second part in a first position in the coupling, and means operable to disengage the latching means from the rod.

The second part of the rod may have a circumferential groove therein adjacent to one end thereof the latching means being arranged to engage in the groove. Preferably, the coupling includes a socket into which the second part of the rod may be inserted, and the latching means comprises a bolt slidable in the coupling in a direction normal to the axis of the socket, the bolt being biased to extend into the socket to engage the second part of the rod.

The bolt may be spring biased and may be disengaged from the second part of the rod by a solenoid or pneumatically-operated piston.

The coupling may be arranged to retain the second part of the rod, effectively extending the overall length of the rod sufficiently to prevent any movement of the pedal being transmitted to the clutch or other control of the sewing machine, or it may completely release the second part.

Ths control rod may itself form a rigid link between the foot-pedal and the sewing machine control means, or it may form a link in a flexible cable linking the foot-pedal to the control means.

The control rod may be caused to operate by any suitable control apparatus detecting faults.

Thread failure detectors are known in which a thread sensor is used to signal the machine to stop when the thread fails, but such detectors are typically installed in new machines during manufacture, and to modify an existing machine can be both time-consuming and costly, and gives only single-function control. It is difficult to provide thread-failure control for all needles of a multi-needle machine, and it is particularly important that failure should be detected immediately in such machines.

A further disadvantage with known detectors using microswitches is that unless a relatively high current is used, relays responding to the closure of the microswitch and serving to control stoppage of the machine will be slow to operate and thus delay will be experienced between thread breakage and the machine stopping.

A second aspect of the invention provides a control apparatus for use with a sewing machine, comprising a plurality of sensing devices arranged to signal an interruption in the supply of thread, fabric, or trim, to the sewing needle of the machine, and detector means generating an actuating signal when a signal is received from any of the sensing devices.

The apparatus may include an audible and/or visible warning device and preferably has a display to indicate, for example numerically, which sensing device is signalling, and therefore what part of the thread or trim supply requires attention. A multiple-segment light-emitting diode display is suitable, or simply a plurality of indicator lights, suitably labelled.

The sensing devices may be of conventional form, for example micro-switches or opto electronic devices, and the apparatus may include an amplifier, thus enabling the sensing devices to operate on a very low current, increasing safety and reliability. Optical sensors may be arranged near the needle, or other moving parts of the machine, to stop the machine if a hand, for example, is brought too near the needle or moving part.

One form of sensing device suitable for use with the control apparatus is that in accordance with a third aspect of the invention. This is a sensing device for detecting the presence or absence of an underthread at a needle of a lockstitch sewing machine during sewing, and comprises a presser foot for the machine, the foot including an electrical switch and being adapted so that the top thread from the needle engages the switch to open or close the switch when the underthread is absent.

Preferably the presser foot has an aperture through which the needle passes during sewing, and a slot extending forward of the aperture in the direction of travel relative to the foot of the fabric being sewn, whereby the top thread is drawn from the aperture along the slot and into contact with the switch when the fabric is advanced after the underthread fails.

Two alternative preferred forms of the device have respectively an electrically-conducting and an electrically-insulating presser foot. Where the foot is electrically-conducting, the switch may comprise an electrically-conducting member mounted on but electrically insulated from the foot and having a resilient portion extending therefrom which can be engaged by the top thread and deflected into contact with the foot, the foot and said member respectively serving as opposite poles of the switch. Where the foot is insulating, for example of a plastics material, the switch may comprise a pair of electrically conducting members mounted on the foot, one member being resiliently deflectable into contact with the other member by engagement with the top thread.

It has been found that for commonly available presser feet the length of the slot should be about 8 mm to operate satisfactorily for a full range of stitch lengths. Where the slot is not open upwards, the roof of the slot should extend at about 300 from the lower leading edge thereof.

Reference is made to the drawings, in which: Figure 1 is a persepctive view of a control rod in accordance with the first aspect of the invention; Figure 2 is a block diagram of a control apparatus according to the second aspect of the invention; Figure 3 is a circuit diagram of one form of control apparatus; Figure 4 is a partially cross-sectioned side elevation of a presser foot showing a sensing device in accordance with the third aspect of the invention; Figure 5 is a perspective view corresponding in part to Figure 4; Figure 6 is a top plan view of the electrical connector of the device shown in Figure 4, the cap having been removed; Figure 7 is a section on line 7-7 in Figure 7, but with the cap in place; and Figure 8 is a partially cross-sectioned side elevation corresponding to Figure 4 showing an alternative form of sensing device.

Figure 1 shows part of a control rod having a first part 2 connected to the clutch/brake control of an industrial sewing machine (also not shown), and a coupling 3 between the first and second parts. The coupling consists of a block 4 containing a first bore 5 therethrough, into which the second part 2 can be inserted. The first bore 5 is threaded at its lower end to receive the threaded end of the first part 1 of the rod. The second part 2 of the rod has at its lower end a circumferential groove 6 and a frusto-conical portion 7 below the groove. A bolt 8 slides in a transverse slot 9 in the block 4, the slot 9 intersecting with the bore 5 so that the bolt 8 can engage the groove 6 in the second part 2 of the rod.The frusto-conical portion 7 engages a chamfered edge portion 10 on the bolt 8 and serves to force the bolt 8 back into its groove as the second part 2 of the rod is pushed along the bore. The bolt 8 is biased towards the first bore 5 by a spring 100.

A second bore 11 extends partially through the block 4 parallel with the first bore 5 and forms a pneumatic cylinder in which a piston 12 is slidably mounted. The upper end of the second bore 11 is threaded and receives a threaded plug 13 containing a suitable tapping 14 for connecting a compressed air line linking the cylinder to a pneumatic controller. The piston 12 carries an actuating rod 1 5 which extends through a third bore 16, of smaller diameter than and co-axial with the second bore 11, and into engagement with a longitudinal slot 1 7 in the bolt 8. A frusto-conical end 18 of the actuating rod 1 5 bears against one end of the slot 17 so that downward movement of the rod 1 5 displaces the bolt 8 in its slot 9 out of the circumferential groove 6 in the second part 2 of the rod.A return spring 19 bears on the underside of the piston 12.

The second part 2 of the rod carries a transversely extending retaining pin 20 which moves in an elongate retaining slot 21 provided in the block 4. Engagement of the pin 20 with the ends of the slot 21 limits the travel of and retains the second part 2 in the block 4.

Although reference is made for convenience to upwards, downwards, top, and bottom, in the aforegoing description, it will be understood that the control rod will operate satisfactorily in any position or attitude.

In use, a signal is transmitted to the coupling in the form of a pulse of compressed air which drives the piston 12 against the return spring 19 and urges the actuating rod 1 5 into engagement with the end of the slot 17 in the bolt 8. The bolt is deflected out of engagement with the second part 2 of the control rod, allowing it to slide.

Under the influence of the spring in the sewing machine brake/clutch control the clutch is thus disengaged and the brake applied regardless of the position of the foot pedal. To re-set the coupling when the fault causing its operation has been rectified, the two parts of the rod are simply pushed towards each other until the bolt 8 engages the circumferential groove 6 again.

Referring to Figure 2, the control apparatus has a plurality of sensing devices which are mounted on or in a sewing machine, or equipment anciliary thereto such as a trim supply, to sense the presence or absence of the thread or trim or the fabric being sewn. Sensing devices for such duties are well-known and will therefore not be described in detail. The devices will typically be of the microswitch type or opto-electronic, in which light passing from an emitter to a detector is interrupted by the presence of body between them.

Trim is understood to mean herein any material, other than thread or the fabric being sewn, which is delivered to the needle during sewing.

The wires 31 from the sensing devices are led to a queueing circuit 32 which passes on signals from the sensing devices to the display decoder 33 in the order in which they are received. The display decoder 33 controls a display 34 which indicates which sensing device is signalling, and thus what part of the machine requires attention.

The display 34 may be a simple seven-segment light-emitting diode display, which can indicate 10 numerals (0 to 9), or a more elaborate display indicating pictorially or verbally the location of the "fault" or its nature.

The display decoder 33 also passes all the signals separately to an input commoning stage 35, at which the signals pass to a common line 36 via diodes to isolate the display 34. The common line 36 leads to a relay drive 37, which includes an amplifier to ensure a relatively high current to operate a relay 38 quickly, the relay 38 controlling, for example, a control rod device as described hereinbefore with reference to Figure 1.

Other inputs controlled by different functional parts of the apparatus may be connected to the relay drive 37.

The relay may be electrical or electro-pneumatic, an electrical signal switching an air supply, or possibly electro-hydraulic, or electro-mechanical.

The sub-circuit formed by the first four components 31 to 34 may be repeated in the apparatus to provide for any number of sensing devices desired.

Figure 3 shows a more detailed circuit diagram of the control apparatus, in which individual lightemitting diodes are used to identify the fault being signalled. The sensing devices are connected between a common ground and separate inputs 300 to the display detector stage in which light-emitting diodes (LED) 301 are separately connected to each input line 302 so that a signal on any line will cause the respective LED to illuminate. The LED's are isolated from each other on the input side by diodes 303.

The input lines 302 are joined and lead to one input of a NAND gate NAND 1 of conventional form whose output is connected to a relay RLA 1 and to one input of a second NAND gate NAND 2.

The output from NAND 2 is connected to one input of a NOR gate and also to the input of NAND 1. The second input to NAND 2 is linked to a reset switch RS which leads to ground.

A third NAND gate NAND 3 has one input connected to ground through a mute switch M and the other input connected to the input of a fourth NAND gate NAND 4. The output from NAND 3 is connected to a warning lamp W, to one input of NAND 4, and to the second input of the NOR gate. The second input to NAND 4 is also connected to the reset switch RS. The output from the NOR gate is connected to a solid-state warning buzzer SSB.

The operation of the circuit is as follows. A low input (0) to any of the detector inputs 300 caused, for example, by closure of a microswitch, thus dropping the input to ground potential, causes the potential on the input line 302 to drop below 5V, allowing current to flow through the respective LED. The common input to NAND 1 will drop to low (0) giving a high (1) output which energizes the relay RLA 1. The resulting high input (1) to NAND 2 will give a low (0) output to the input of the NOR gate. This gives a high (1) output which causes the buzzer SSB to sound a warning.

The operator can cancel the buzzer SSB by closing the mute switch M, which will be a pushbutton switch. This grounds the input to NAND 3, giving a low (0) input, which results in a high output fed to the second input of the NOR gate, resulting in turn in a low output (0), muting the buzzer. The high output also causes the lamp W to light.

When the fault has been rectified, so that all the inputs are returned to high (1), the reset switch RS is pressed giving a low (O) on the second input to NAND 2 and NAND 4, thus resetting the outputs of NAND 1, NAND 3 and NOR to low. Thus, the relay RLA 1 is deenergized.

The relay RLA 1, when energized, can operate any suitable electrical or electro-pneumatic or hydraulic device for stopping the sewing machine.

The relay may operate a control rod coupling such as hereinbefore described, the output from the relay opening an electropneumatic valve, supplying compressed air to the piston in the coupling.

A presser foot sensing device, for detecting the absence of the underthread at the fabric, is shown in Figures 4 and 5. The device 40, has in common with commonly available presser feed, a sole plate 41 fixedly or pivotally mounted, via a pin 42 and slide plates 43, to a support bracket 44 which is connected to the foot bar 45 of a sewing machine by a screw 46. A thread slot 47 leads to an aperture or needle hole 48 through which the needle passes during sewing.

In addition to these standard features, the device 40 has a further slot 49 extending from the needle hole 48 forwardly, in the normal direction of travel of fabric being sewn, for a distance of about 8 mm from the forward edge of the hole.

Where the slot 49 passes under the bracket 44 it is angled upwardly from the leading lower edge 50 thereof by an angle of 300 to the horizontal.

The device also has mounted on one face 51 of the bracket 44 a plastics block 52 through which passes an electrical contact plate 53 which extends downwardly to a position below the upper edge 54 of the mouth 55 of the slot 49, and spaced therefrom by a distance of about 1.6 mm. This feature is omitted from Figure 4 for clarity, but is shown in Figure 5.

The contact plate 53 will have a thickness of from about 0.13 mm to about 0.52 mm, depending upon the sewing conditions, for example thread tension and thickness. The plate extends on the upper surface 56 of the plastics block 52 to form a contact surface 57. A collar 60, described hereinafter in more detail with reference to Figure 6 and 7, is secured to the foot bar 45. The collar 60 has a spring loaded ball contact 61 which engages the contact surface 57.

In use, when the underthread breaks or runs out, the top thread will no longer be held in the fabric being sewn but will lift and lie in a straight line from the last complete stitch to the needle.

As the fabric advances, this last stitch moves away from the needle until the thread engages the lower edge of the plate 53 bringing it into contact with the foot at each side of the mouth 55 of the slot 49. This closes the circuit of which the sensing device forms part, sending a signal which can, via an apparatus of the type hereinbefore described, stop the sewing machine.

Thus, only a short distance is travelled by the fabric without stitching, before the machine is stopped.

The connecting collar 60 (Figures 6 and 7 ) is formed of plastics material and has a hole 62 therethrough by which it is attached to the foot bar 45, locking screws being passed through threaded holes 63 on opposite sides of the hole 62. The hole 62 also has on its wall a contact plate 64 which can be connected to a wire which is grounded. The ball contact 61 is spring loaded and a wire leads through an inset beneath the cap 65 to be connected to a suitable detector apparatus, for example that previously described.

By suitably positioning the collar 60 on the foot bar 45, when the presser foot is changed contact is automatically made between the contact surface 57 and the ball contact 61 when the new foot is secured in place.

Where an electrically insulating plastics presser foot is used, or where isolation from the body of the machine is required to avoid the risk of false signals being sent to the detector, the form illustrated in Figure 8 is used.

The switch takes the form of an attachment which can be fixed on the presser foot, which is modified in the manner described with reference to Figures 4 and 5, having a slot extending from the needle aperture. A plastics block 81 has a slotted fixing bracket which overlies the support bracket 44 of the presser foot and is held by the same screw 46. The block 81 contains two metallic conductor strips 82 and 83 which terminate in connector pins 84 extending from the ends of the fixing bracket. One strip 82 extends downwardly generally following the surface of the presser foot, while the second strip 83 extends downwardly from the block overlying, but spaced from the first strip 82.The second strip 83 can be engaged by a thread 85 from the needle 86 and drawn against the first strip 82, closing the switch, when the thread is pulled along the slot 49 (Figure 5). A connector plug 87 is provided with connecting wires 88, by which the switch is linked to control apparatus, and with sockets 89 receiving the pins 84 extending from the block.

The configuration shown in Figure 8 can also be used with a metal presser foot, where electrical isolation from the machine frame is required. In this case, an insulating strip is provided between the first strip 82 and the foot.

In a further modification of the arrangement of Figure 8, the two strips 82 and 83 may carry contacts spaced from the ends, the strips being arranged so that a small closing movement is required at the contacts, and this is generated by a relatively large movement of the free ends of the second strip 83 contacted by the top thread. This reduces the risk of false signals being generated by vibrations, for example.

Claims (25)

Claims

1. A control rod for linking a foot pedal to drive controlling means in a sewing machine, which comprises a coupling linking two parts of the rod, the coupling being fixed to a first part of the rod and including latching means engageable on the second part of the rod to hold the second part in a first position in the coupling, and means operable to disengage the latching means from the rod.

2. A contol rod according to claim 1, wherein the second part of the rod has a circumferential groove therein adjacent to one end thereof and the latching means is arranged to engage in the groove.

3. A control rod according to claim 1 or 2, wherein the coupling includes a socket into which the second part of the rod may be inserted, and the latching means comprises a bolt slidable in the coupling in a direction normal to the axis of the socket, the bolt being biased so as to extend into the socket to engage the second part of the rod.

4. A control rod according to claim 3, wherein the bolt is spring-biased.

5. A control rod according to any preceding claim, wherein the means operable to disengage the latching means comprises a solenoid.

6. A control rod according to any of claims 1 to 4, wherein the means operable to disengage the latching means comprises a pneumatic piston.

7. A control rod according to any preceding claim, wherein the second part of the rod slides in the coupling between the first position and a second position, the distance between the two positions being selected to be greater than the maximum distance through which the rod can move in operating the sewing machine control means.

8. A control rod according to claim 7, wherein the coupling has an elongate slot extending transversely therethrough, and a retaining pin which extends transversely from the second part of the rod into the slot, engagement of the pin with opposite ends of the slot defining the first and second positions.

9. A control rod for linking a foot pedal to drive controlling means for a sewing machine, substantially as described herein with reference to or as shown in Figure 1 of the drawings.

10. A control apparatus for use with a sewing machine, comprises a plurality of sewing devices arranged to signal an interruption in the supply of thread, fabric, or trim, to the sewing needle of the machine, and detector means generating an actuating signal when a signal is received from any of the sewing devices.

11. An apparatus according to claim 10, wherein audible and/or visible warning means are provided operating when an actuating signal is generated.

12. An apparatus according to claim 10 or 11, comprising an indicator device to indicate which sensing device is signalling.

13. An apparatus according to claim 10, 11 or 12, wherein the sensing devices include electrical devices operating at a very low current, and the detector means includes an amplifier to amplify signals received from the sensing devices.

14. An apparatus according to claim 13, wherein at least some of the sensing devices are opto-electronic devices.

1 5. An apparatus according to any of claims 10 to 14, wherein the actuating signal is used to actuate the disengaging means of a control rod according to any of claims 1 to 9.

1 6. An apparatus according to claim 15, wherein the actuating signal operates an electropneumatic valve controlling the compressed air supply to the disengaging means in the form of a pneumatic piston.

17. A control apparatus for use with a sewing machine, substantially as described with reference to Figure 2 or Figure 3 of the drawings.

1 8. A sensing device for detecting the presence or absence of an underthread at a needle of a lockstitch sewing machine during sewing, comprising a presser foot for the machine, the foot including an electrical switch and being adapted so that the top thread from the needle engages the switch to open or close the switch when the underthread is absent.

1 9. A device according to claim 18, wherein the foot has an aperture through which the needle passes during sewing, a slot extending forward of the aperture in the direction of travel relative to the foot of the fabric being sewn, whereby the top thread is drawn from the aperture along the slot and into contact with the switch when the fabric is advanced after the underthread fails.

20. A device according to claim 19, wherein the slot extends for at least 8 mm from the aperture.

21. A device according to claim 19 or 20, wherein those parts of the slot which do not open upwardly have an inner roof surface opening towards the aperture at an angle of about 300 to the horizontal.

22. A device according to any of claims 1 8 to 21, wherein the foot is formed of an electrically conducting material and the switch comprises an electrically conducting member mounted on but electrically insulated from the foot and having a resilient portion extending therefrom which can be engaged by the top thread and deflected into contact with the foot, the foot and said member respectively serving as opposite poles of the switch.

23. A device according to any of claims 1 8 to 21, wherein the foot is formed of an electrically insulating material and the switch comprises a pair of electrically conducting members mounted on the foot, one member being resiliently deflectable into contact with the other member by engagement with the top thread.

24. A sensing device for detecting the presence or absence of an underthread at a needle of a lockstitch sewing machine during sewing, substantially as described with reference to or as shown in Figures 4 to 7 or Figure 8 of the drawings.

25. An apparatus according to any of claims 10 to 17, wherein at least one of the sensing devices is as claimed in any of claims 1 8 to 24.