US2705466A - Electrical apparatus - Google Patents

Description

April 5, 1955 J. A. SARGROVE ET AL 2,705,466

ELECTRICAL APPARATUS Filed Oct. 16, 1950 4g;- M W United States Patent ELECTRICAL APPARATUS John A. Sargrove, Shepperton-on-Thames, and Denis A.

Ball, Tolworth, England, assignors to Sargrove Electronics Limited, Tolworth, England, a British company Application October 16, 1950, Serial No. 190,336

Claims priority, application Great Britain October 28, 1949 7 Claims. (Cl. 112-252 The present invention relates to electrical apparatus adapted for use in conjunction with the progressive treatment of lengths of material.

One such progressive treatment with which the invention is concerned is the application of a continuous thread, tape or the like to a length of material such as cloth forming part of a garment, for example by means of a sewing machine. The rate at which such treatment can be performed on a number of ditferent lengths of material is often seriously reduced by the necessity for stopping the machine after each treatment and hand cutting the portions of thread, tape or the like which extend from either end of a length.

One object of the present invention is to provide electrical apparatus adapted for use in conjunction with the progressive treatment of lengths of material for automatically performing a desired operation associated with that treatment.

A further object is to provide electrical apparatus for use in the above process of applying thread, tape or the like to a length of material, whereby there is effected automatic cutting of the portions of thread, tape or the like which extend from each end of a length after the treatment.

According to the present invention there is provided apparatus for use in conjunction with the progressive treatment of a length of material, comprising first means for performing a desired operation associated with the treatment of said material, detector means for detecting the progress of the treatment of said material, and means controlled by said detector means for automatically effecting operation of said first means before and after said treatment.

Thus in the application of thread, tape or the like to a length of material such as cloth, the desired operation may be the cutting of the thread, tape or the like in front of the leading edge of the length and behind the trailing edge thereof, the means for performing this operation being, for example, a guillotine cutter.

For such a purpose there is provided according to the invention apparatus adapted for use in conjunction with sewing and like machines in which a continuous length of thread, tape, elastic or the like is applied to a length of material, comprising cutting means for severing said thread, tape, elastic or the like, detector means responsive to the progress of said material out of the work field in which said thread, tape, elastic or the like is secured relative to said material, and means controlled by said detector means for automatically operating said cutting means to cut said thread or the like at a predetermined distance in front of the leading edge and behind the trailing edge of said length of material.

The detector means may comprise a photo-cell and associated light projector positioned near the outlet end of the working field, and arranged so that material leaving the working field obscures the photo-cell. To discriminate against relatively narrow width material, such as tape, being applied to the main material two photo-cells spaced apart and connected in parallel may be used. The action of obscuring the photo-cell or photo-cells may be arranged to cause direct operation of the cutting means, whilst the action of uncovering them may be arranged to cause operation of the cutting means after the material has traveled for a further predetermined distance. This delay may be governed by movement of a reciprocating or rotating member forming part of the machine which may be arranged to operate contacts, for example,

2,705,466 Patented Apr. 5, 1955 at each stitching action. Thus each action may be arranged to add a charge to a capacitor until the potential developed across the capacitor is sufiicient to cause a triggering action which results in operation of the cutting means.

Suitable means may be provided for disabling the automatic control and replacing it by hand control and for preventing operation of the cutting means when the material is stationary.

One embodiment of the present invention will now be described, by way of example, as applied to electrical apparatus for use in conjunction with sewing machines whereby the threads extending from each end of a length of material after treatment are automatically cut off at a predetermined distance from the appropriate end.

The embodiment will be described with reference to the accompanying drawing, the single view illustrated being a combined electrical and mechanical schematic presentation which shows the cutting means, its associated detector means and control circuits for effecting operation of the cutting means.

The electrical apparatus in this embodiment is intended for use with a so-called Flat lock sewing machine having four needles and with five threads in the' top working foot and four threads in the bottom work arm producing in the working field a fiat plaited thread structure termed a chain. While the sewing machine is correctly operating it forms this chain irrespective of whether there is any material to sew or not. Thus if the machine is started before the material to be sewn is inserted in the working field a short piece of chain precedes the material, also a piece of chain follows the emerging end of the piece of sewn material. Both these ends are usually cut or trimmed off by hand during which period of time the machine is inoperative.

Mounted near the outlet end of the working field is a thread-cutting guillotine constructed so that it is capable of cutting off the protruding threads which precede the leading edge, and follow the trailing edge, of the material coming from the working field, the cutting taking place at a predetermined position from those edges. The electrical apparatus to be described is designed to control automatically the operation of this guillotine, and comprises detector means responsive to the presence or absence of material adjacent to the outlet end of the working field and control circuits fed from the detector means and controlling the operation of the guillotine.

Referring now to the drawings, the detector means comprises a pair of photo-electric cells 10 mounted adjacent to each other in the bottom work arm of the machine, both at the same distance from the needles (not shown) but spaced apart at substantially the same distance as the width of the thread chain. These photocells 10 co-operate with a small light projector 11 mounted close to the top working foot. The arrangement is such that material emerging from the working field will prevent the light from the projector 11 illuminating the photo-cells 10, the chain due to its limited width not being able to obscure both photocells 10 at the same time. The two photo-cells 10 are connected in parallel across a common high resistance load R1, and the light intensity is arranged to be such as to bring the standing voltage of the cells 10 beyond the bend in their output characteristic so that the output voltage is substantially independent of Whether one or both cells 1.0 is or are illuminated; thus obscuring of a single cell by the chain will have no effect.

The photo-cells load resistance R1 is connected in the input circuit of a three stage direct-coupled amplifier 12 forming part of the control circuits. The anode circuit of the last stage contains a relay A/2, which has two moving contacts a1 and a2 each co-operating with a single fixed contact. With at least one of the photo-cells 10 illuminated the output from the amplifier 12 is arranged to be suliicient to operate relay A/Z. The control circuits include a fourth triode amplifier valve V4 (which as shown is one section of a double triode valve), the other section of which forms the last valve in the amplifier 12. The anode circuit of V4 includes a relay B/2, which has two moving contacts b1 and b2 each movable between two fixed contacts.

The fixed front contact co-operating with moving contact bz is commoned to the fixed back contact co-operating with the moving contact b1 and these commoned fixed contacts are joined to the positive terminal of a rectifying and smoothing circuit 13 which supplies the high tension for the valves and is itself supplied from mains terminals 20 through a constant voltage transformer 9. The other two fixed contacts are commoned and joined to the negative earthed terminal of the supply. The moving contact be is connected in series with a capacitor C2 of, for example, one micro-farad, and a relay C/l to the moving contact hr. The effect of this arrangement is that a change of state of operation of relay B/2 causes a reversal of the polarity of the voltage applied across the relay C/1 and capacitor C2, so that a pulse of current passes through the relay C/1 energising it for a short period. Thus the relay C/l is energised for a short period at every change of state of operation of the relay B/2. The relay C/1 has a pair of contacts 01 included in the circuit of a solenoid 14, the contacts 01 being closed on energisation of the relay C/ 1. The solenoid armature 15 is coupled mechanically to the moving blade of the thread-cutting guillotine 16.

The grid of the valve V4 is connected to earth through the moving contact a1 when relay A/2 is not energised. The cathode of the valve V4 is connected to a point of positive potential on a potentiometer formed by resistors R2, R3 and R4 which are connected across the high tension supply, the potential being sufficient to cut off the anode current when the grid is earthed. The potential can be adjusted over a limited range by movement of the slider of resistor R2. The grid of valve V4 is also connected to earth through a capacitor C3 of relatively large capacity, for example one micro-farad, which is fed through a resistor R5 of relatively high resistance, for example ten megohms, from a point 17 of higher POSI- tive potential than that to which the cathode is connected. The potential at the point 17 is derived from a bridge rectifier 26 supplied from a secondary winding of a transformer 27 whose primary winding is connected to the mains terminals 20. A further secondary winding of the transformer 27 provides the heater current for the valves V1 to V4. This means that if relay A/2 is energised so that the grid of valve V4 is disconnected from earth the capacitor C3 will ,charge up in a predetermined time and raise the grid potentral to render valve V4 conductive. The capacitor C3 is also connected through the moving contact a2, when relay A/2 is energised, to the back contact associated with a moving contact d1 controlled by a relay D/1. The moving contact d1 is connected to earth through a capacitor C4 which is of approximately one tenth of the capacity of the capacitor C3. When the relay D/1 is unenergised the moving contact d1 rests on a front contact connected to the point 17 of positive potential from which the capacitor C3 is charged so that the capacitor C4 is charged when relay D/l is unenergised. The relay D/l is preferably of the high speed type and has an actuating contact 18 arranged to be operated by a cam 19 mounted on a rotating component in the head of the sewing machine so that the relay D/l is pulsed every time a stitch is made by the sewing machine. The arrangement is such that immediately after the relay A/2 is energised the capacitor C of large capacity is uncharged and the capacitor C4 of small capacity will be connected across the large capacitor C3 once per stitch and transfer a charge to it, thus charging-up the capacitor C3 more quickly than it would be charged through the resistance R5 provided that the stitches occur fairly rapidly. With the small capacitor C4 having one tenth of the capacity of that of the capacitor C3, the latter will be fully charged after approximately ten stitches and the valve V4 thereupon rendered conductive. The number of stitches required can, of course, be varied by varying the ratio of the capacity of the two capacitors C and C4. It will be seen that provided the stitches occur sufficiently rapidly for the capacitor C3 to be charged from the small capacitor C4 rather than through the large resistor R5, the time at which the valve V4 becomes conductive will be dependant only upon the time in which the predetermined number of stitches occur after the energisation of relay A/2.

The last valve V3 in the amplifier 12 and the valve V4, which control co-operating relays A/2 and B/2 respectively, are preferably the two portions of a double triode valve as shown or are connected with their filaments in series in order to fail simultaneously. This also applies to the first two valves V1 and V2.

The solenoid 14 is fed from an alternating current supply, connected to the terminals 20, through an energising circuit which includes the contacts 01, a safety switch 21 of the microswitch kind which is open when the sewing machine is stationary and is operated with the machine clutch through the wire 22 which raises the lever 23 when the clutch is engaged, and an isolator switch 24 by which the automatic operation can be stopped but which keeps the valves in a stand-by condition with the cathode heaters alight. There is also an alternative solenoid operating circuit provided by a hand impulsing switch 25 by which the guillotine 16 can be operated even when the machine is stationary.

A preferred sequence of operation will now be described. With the machine stationary and no material in it the photo-cells 10 are exposed to light. Relay A/2 is energised and the grid of the valve V4 is disconnected from earth, so that the large capacitor C3 can be charged slowly through the high value resistor R5 until it attains a voltage at which the valve V4 conducts and relay B/2 is energised. This latter results in the relay C/l being pulsed, but the guillotine operating solenoid 14 is not energised as the safety switch 21 is open. If now the machine is started and material is placed in the machine, the photo-cells 10 will remain exposed until the leading edge of the treated material emerges from the working field, when relay A/ 2 becomes unenergised. The grid of the valve V4 is thus earthed and relay B/2 becomes unenergised causing relay C/1 to be pulsed. This completes the guillotine solenoid circuit to pass a large A. C. pulse through the solenoid 14 and operate the guillotine 16 for a short period thus cutting off the thread chain protruding from the leading edge of the material. The guillotine 16 being further from the working field than the photo-cells 10 can be arranged to cut the chain in the required place ahead of the leading edge. As the material proceeds through the machine the photo-cells 10 remain obscured so that relays A/2, B/2 and C/1 are unenergised. Only the relay D/1 is energised once per stitch but the small capacitor C4 cannot transfer its charge to the large capacitor C3 as the circuit is broken by the unoperated movable contact a2. When the trailing edge of the material emerges from the working field the photo-cells 10 are again exposed to light, relay A/2 is energised and the earth is removed from the grid of the valve V4. The small capacitor C4 now transfers its charge to the large capacitor C2 until the predetermined number of stitches have been made when the potential of the large capacitor C3 is sufiicient for anode current to pass in the valve V4 and thereby operate the relay B/2. Or to put the matter somewhat differently, the time that valve V4 becomes conductive depends not upon time as such but rather upon the number of stitches which takes place as measured by a corresponding number of revolutions of the shaft on which cam 19 is mounted. The means for counting the number of revolutions of that shaft are the cam 19, contacts 18, relay D/1 and capacitors C3, C4. As before this results in operation of the guillotine 16 which cuts the thread chain behind the trailing edge, provided that the machine is still running and the safety switch 21 is thus closed. The control circuit is now in the same condition as first described so that if the machine continues to run and if further material is fed in, the automatic thread cutting will continue as desired. It will be seen that the arrangement by which the guillotine 16 operates on the chain succeeding the trailing edge is such that the operation of the guillotine 16 depends only upon the number of stitches made after the trailing edge leaves the working field and uncovers the photo-cells 10, provided that the machine is operating at a reasonable speed. The number of stitches which cause operation can be varied by adjustment of the slider of resistor R2. A simple time delay circuit would not be suitable as it would be dependant upon a constant operating speed of the machine. This would be diflicult to guarantee, particularly as the second cut is made at a time when the operator is instinctively tending to slow up the machine, particularly when the operators attention is directed to inserting a fresh piece of material into the machine. With a simple time delay circuit a considerable slow-down might lead to cutting of the mate rial itself. Moreover, such a delay circuit would have to be switched for operation on the trailing edge cut only. The safety switch 21 prevents automatic operation of the guillotine 16 when the machine is stationary so that operation cannot occur whilst material is being inserted into the working field from any direction, thus protecting both the material and the'operator.

n sewing machines adapted for the insertion of tape or elastic it is advantageous in addition to the above features to arrange a towing device for extracting the material from the sewing machine in a flat and orderly manner. In the absence of this the tape or elastic would contract on emergence and bend and deform the material so that the photo-cells could not correctly sense the edges of the material and the guillotine 16 would not operate correctly.

It is important to ensure the accurate positioning and alignment of the blades of the guillotine 16. The bottom blade is desirably a solid fixture though adjustable whilst the top blade should be adjustable as well as flexible.

A desired arrangement may also contain two or more guillotine blades each operated separately or jointly according to desired combinations. The blades may be at different angles and combined with different combinations of photo-cells. Moreover instead of employing direct electrical operation the guillotine may be mechanically operated and merely have an electrically operated release.

The indication as to whether the sewing machine is operating can also be monitored by using the impulses from the stitch counter or a rotary centrifugal governor type of switch instead of the clutch operated safety switch.

Many other modifications may be made to the detailed arrangement described; thus for example it may be more convenient to use photo-cells and a light source mounted in the same housing and provide a light reflector on the opposite side of the path which the material takes, or the stitch counter may take the form of a commutator.

It will be seen that by using apparatusof the kind specified when applying thread, tape or the like to successive lengths of material, production can be continuous as there is no requirement either during or after the process to cut by hand the thread, tape or the like.

What we claim is:

1. In combination with a sewing machine adapted to produce a plaited chain of thread and to sew the same onto a length of material fed through the machine, means for cutting said thread chain, detector means adapted to be responsive to the passage of the trailing edge of material from the stitching position of said machine, and means responsive to the stitching action of the machine and initialed by said detector means for effecting operation of said cutting means a predetermined number of stitching actions behind the trailing edge of the material, the means responsive to the stitching action of the machine comprising a first capacitor, a second capacitor having a relatively larger capacitance than said first capacitor, means for charging said first capacitor, means operable by the stitching mechanism of said sewing machine for transferring the charge on said first capac1tor to said second capacitor at each stitching action, the minimum interval between the transference of charge being such that said first capacitor is fully charged before each transference, and means connected to said second capacitor and responsive to the attainment thereby of a predetermined charge for effecting cutting of said chain, said predetermined charge being a multiple of the full charge of said first capacitor, said multiple being substantially equal to said predetermined number of stitching actions.

2. Apparatus according to claim 1, in which the means for transferring the charge comprises a movable contact member connected to said first capacitor and movable between a contact connected to said means for charging the first capacitor and a contact connected to said second capacitor.

3. In a sewing machine having means for feeding material therethrough and simultaneously sewing it, the combination comprising a cutting device mounted on the machine for cutting the material after it has been sewn, and spaced light source means and co-operating photocell means having a light path between them that is in the path of movement of the material when it is moved through the sewing machine, means responsive when the material fed through the machine reduces the light transmitted from the light source means to the photocell means for operating said cutting device, and means responsive when the light transmitted to the photo-cell means increases due to further feeding of the material for again operating said cutting device after a predetermined delay, said delay being determined by the material feed of said machine and corresponding to the passage of a predetermined length of material through said machine.

4. Apparatus according to claim 3, in which said photo-cell means comprises a pair of photo-cells spaced apart, the distance between said photo-cells being less than the width of the material being treated.

5. Apparatus according to claim 3, in which means are provided for preventing operation of said cutting device when said sewing machine is stationary.

6. In combination with a sewing machine adapted to continuously produce a plaited chain of thread and sew the same onto a length of material fed through the machine, detector means for detecting the departure of the trailing edge of the material from the stitching position of said machine, a moving portion on said machine actuated in accordance with the material feed of said machine, means connected to said moving portion and controlled thereby for measuring a predetermined distance traveled by the trailing edge of the material from the stitching position of said machine, said measuring means being initiated by said detector means, and means controlled by said measuring means for cutting said thread chain.

7. The combination as defined in claim 6 wherein the moving portion of said machine actuated] in accordance with the material feed thereof is constituted by a rotary shaft, and said means controlled by said moving portion for measuring the passage of a predetermined length of the material from the treatment zone .includes means initiated by said detector means for counting the revolutions of said rotary shaft.

References Cited in the file of this patent UNITED STATES PATENTS

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