US3688958A

US3688958A - Device for sensing thread passage to control machine operation

Info

Publication number: US3688958A
Application number: US89811A
Authority: US
Inventors: Sten-Ake Olaus Rydborn
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-11-16
Filing date: 1970-11-16
Publication date: 1972-09-05
Anticipated expiration: 1989-09-05

Abstract

A thread supervising device preferably for use in a shuttleless looms having a sensing element for producing an electric signal in accordance with an intermittent withdrawal of a thread from a thread supply, the signal in turn being supervised at least during a predetermined period of the withdrawal of the thread by an electronic device for filtering and amplifying and for rendering a thread withdrawing means inoperative upon breakage of the thread, the supervising period being determined by electrical switch means.

Description

United States Patent Rydborn Sept. 5, 1972 [54] DEVICE FOR SENSING THREAD [56] References Cited P A C NTROL A 0 M CHINE UNITED STATES PATENTS 2,578,620 12/1951 Wilhelm ..3l0/8.l X [72] Invent z Rydbm" Almhult 3,361,314 l/l968 Gith ..226/45 x [22] Filed: Nov. 16, 1970 Primary Examine rRichard A. Schacher pp No 89 811 Att0rney-Waters, Roditi, Schwartz & Nissen Related US. Application Data I [57] ABSTRACT [63] Continuatiomimpan of SeL'NO. 882,766 Dec. A thread supervising device preferably for use in a 18 1969 abandoned which is a continuation shuttleless looms having asensmg element for producing an electric signal in accordance with an intermitof Sept' 1967 abandoned' tent withdrawal of a thread from a thread supply, the signal in turn being supervised at least during a [52] 2 32 5 342 predetermined period of the withdrawal of the thread I t Cl B65h 25/32 by an electronic device for filtering and amplifying 58 d 310 8 and for rendering a thread withdrawing means in- 1 0 operative upon breakage of the thread, the supervising period being determined by electrical switch means.

13 Claims, 17 Drawing Figures PATEmmsEP m I 3.688.958

I SHEET 2 BF 5 25 I R J 3 g Q x V M L. Q) F5 8 8 a w w PKTE'N'TEDsEP 51922 SHEET 3 BF 5 FIGS) PIC-3.4

DEVICE FOR SENSING THREAD PASSAGE TO CONTROL MACHINE OPERATION CROSS-RELATED APPLICATION This is a continuation-in-part of my earlier application Ser. No. 882,766 filed Dec. 18, I969 now abandoned, which in turn is a streamlined continuation of my still earlier application Ser. No 665,791 filed Sept. 6, 1967 and now abandoned.

BRIEF SUMMARY OF THE INVENTION In the textile industry it is of extreme importance that a running thread be supervised and operation of the machine be instantly discontinued after a thread has broken.

The prior art stop motion devices are of electromechanical construction including mechanical arms or rotating magnetic fields. These stop motion devices usually react in response to the tension maintained in the thread, and after breaking of a thread, a relatively long period of time passes before the operation of the machine is interrupted. These, prior art stop motion devices do not sense the thread motion but the tension in the thread and also interrupt the machine operation in response to a temporary slackening of the moving thread. These devices require a certain force between the thread and the means by which it is engaged, and it cannot therefore be used for supervising thin threads which must be subjected to low tensile stress only.

These shortcomings and inconveniences of the prior art stop motion devices are eliminated by the present invention, according to which a sensing element is positioned in contact with the thread and adapted, in response to irregularities in the thread or the friction thereof, to produce an electrical signals; an input portion of an electronic device is connected to the sensing element and is adapted to filter and amplify the signal produced by the sensing element; and a supervising portion of the electronic device, after having been rendered operative by means of mechanical and/or electronic switches, is adapted in response to the signal obtained from the input portion to release a relay circuit which is adapted after release to interrupt the operation of the thread withdrawing means.

Several practical embodiments of the invention will be described in more detail with reference to the accompanying drawing, in which:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a circuit diagram of the device according to the invention;

FIGS. 2A-2G schematically illustrate the mode of operation of the device;

FIGS. 3-7 illustrate different basic constructions of a sensing element in the device according to the invention;

FIG. 8 is a cross-section of a sensing element;

FIG. 9A is an elevation view diagrammatically illustrating a further embodiment of sensing element; and

FIG. 9B is a perspective view partly broken away and in section of another embodiment of sensing element.

DETAILED DESCRIPTION In the electronic circuitry illustrated in FIG. I, a sensing element (FIGS. 3-7) which, upon passage of a high-frequency signal, the frequency of which is approximately 30 kilocycles per second when the sensing element illustrated in FIGS. 3 and 8 is utilized. 7

For a better understanding of the circuit diagram shown in FIG. 1, the parts of the electronic circuitry which are connected to the terminal block, will be explained in more detail. Connected to the contacts 1 and 2 is a supply transformer 7 which can be set for different incoming voltages which are applied to contacts 1 and 2 from an external source. Connected to contacts 3-8 are relay contacts which are operated by a relay coil 2 and the operating circuit for the thread withdrawing means. A switch for resetting relay 2 after a release is connected to contacts 9 and 10. Connected to contacts 11-14 are a switch unit 3,4 and secondary windings of the transformer 7.

The input portion of the electronic circuitry comprises an amplifier having three steps, each with one transistor TRl, TR2, TR3. This amplifier is frequencybalanced and thus filters off the -cyclesignal component of the input signal, the remaining components of which are amplified. The signal form in the last amthrough a capacitor C8 whereby the transistor TR4 is rendered conductive and complete charge of the capacitor C10 is prevented by the varying character of the signal at B.

If the signal fails, the capacitor'Cl0 will be charged through resistor R15 and the transistor TRS will be conducting and permit the signal shown in insert F to pass to a relay or release circuit, if the electronic switch 4 and the mechanical switch are both open. The relay circuit receives the signal at G from the transistor TRS and interrupts continued operation of the machine or the thread withdrawing means.

In this connection, it is pointed out that the signal derived from the input portion through C8 is not used for charging C10 but for controlling, through TR4, the charge on capacitor C10. As C10 must be charged to a predetermined value to enable a signal to pass through TRS, the time which passes from the moment the signal from C8 ceases until the signal at G occurs in the relay circuit, will always be constant and independent of the appearance of the signal derived from C8. The reaction period of the device will thus not be influenced by different types and different running speeds, and this is an indispensable condition, for example, in gripping looms where it is desired that one can establish exactly where and when the gripper releases the thread at the selvage.

The relay circuit preferably consists of the relay 2 which is controlled by a thyristor TR6 and of which only the symbol of the operating coil in the circuit is shown in FIG. 1. Because it is controlled by a thyristor, the relay will always be operative as long as the thyristor is conductive. The thyristor is rendered conductive after the signal G has been applied to the resonance circuit C11, R18, and will remain conductive even if signal G fails. Thus, relay 2 is operative until reset by closing of contacts 9 and 10, whereby it is rendered inoperative through the transistor TR7. The relay 2 is preferably connected to the operating circuit of the thread withdrawing machine, which circuit is interrupted when the relay 2 is rendered operative, and closed when relay 2 is rendered inoperative. Connecte in parallel with relay 2 is a protective diode D2.

The entire electronic circuitry is connected, through a rectifier portion comprising the diode D1 and a conventional transformer 7 to a current source (not shown) which is connected to contacts 1 and 2 of the terminal block.

In the first instance, it is desired, during certain phases of the machine operation, to render the electronic circuitry inoperative so that the machine operation is not interrupted when no signal is produced by the sensing element 1. The oscillator R15 C and TRS must thus be prevented from oscillating and delivering signal G, and this is done preferably by short-circuiting the voltage normally charging C10 through R during the desired operational phases or periods of time.

This short-circuiting is done quite simply be means of a conventional switch or circuit breaker. If, as is the case especially in looms, it is desired to establish the time of the short-circuiting with great exactitude, special steps must be taken. It is especially important to establish the end of a supervising period, which corresponds to the time at which e.g. a gripper arm releases the thread drawn through the fabric at the selvage.

If the above-desired electronic circuitry is to be used for supervising breakage of a running thread in a shuttlelcss loom, the transistor gate TR4 is opened and closed on the one hand by a mechanical cam-actuated circuit breaker or switch 3 and, on the other hand, by

an electronic circuit breaker or switch 4. The mechanical circuit breaker 3 is connected in parallel with the electronic switch 4, and this parallel circuit is con nected in the electronic circuitry to the transistor gate TR4. The mechanical switch 3 is opened and closed by a member operating the gripper arm of the loom or operated by said arm.

In this case, the electronic switch is photoelectrical, although it may, of course, be of some other similar construction. The photoelectrical switch 4 is controlled by a member 50 attached to the gripper arm and interrupting the path of the radiation between the light source 60 and a light-sensitive transistor TR8. The signal derived from transistor TR8 upon interruption of said radiation path is amplified by means of transistor TR9 and supplied through rectifier D3 to the control electrode of thyristor TR10. The signal derived from transistor TR8 causes the thyristor to become conductive and to short-circuit the voltage supplied through R15 to the transistor gate TR4. The thyristor remains conductive as long as the mechanical switch remains open, and thus thyristor TR10 will be rendered nonconductive when mechanical switch 3 is closed.

For better illustration of its operation, the stop motion device will be described in more detail with reference to FIG. 2 and the withdrawal of a thread by means of a gripper arm in a shuttleless loom. The first and second vertical full lines in FIG. 2 delimit the width of the fabric and the third vertical full line (as seen from the left in FIG. 2) is the point where thyristor TR10 is rendered conductive. The arrow shown at the top of FIG. 2 shows the direction of the thread run. The functions of the mechanical and electronic switches are shown at 2D. (The mechanical switch is opened at 10 and the electronic switch is closed or rendered conduc tive at 10A). After the gripper arm has picked up a thread and withdrawn it from the thread supply, the signal shown at 2A is produced and applied to the input portion of the electronic device, and is filtered and amplified to the signal shown at 2B. 2C shows the signal upon thread breakage which is applied to the transistor gate TR4 through capacitor C8. When the gripper arm has drawn the thread a certain distance into the fabric, the mechanical switch 3 is opened at 10 when the actual supervising operation starts. To the transistor gate TR4 is now applied the signal derived from the input portion and produced by the sensing element, and holds the gate closed. If the signal fails at 11, the transistor gate TR4 opens and the oscillator C10, TR5 and R15 will oscillate and after a given period of time determine by the charge period of the capacitor C10, the signal 2G will occur in the relay circuit, whereby operation of the loom is interruped after a constant period of time, after signal 2C has ceased and a thread breakage thus has occurred. At D, E and F in FIG. 1 are shown the signals occurring in the outputs of transistor gate TR4. The signal at D is obtained when the mechanical or electronic switch is closed, the signal at E when the switches are open and the signal at B is applied to TR4, and the signal at F is obtained when the switches are open and the signal at B has ceased after breakage of a thread.

As the gripper arm, upon leaving the fabric, must release the thread so that signal 28 ceaces, this signal must be replaced at a very exactly determined point of time 10A which must be located within the latter part of the period required for charging the capacitor C10 and beginning at the point where the gripper arm releases the thread at the selvage. At this point, the electronic switch 40 is closed by the member 50 mounted on the gripper arm. The electronic switch 40 is closed until the mechanical switch 3 is closed and opens the electronic switch. FIG. 2 shows at 2E the signal pattern at theselvage when the gripper arm has released the thread and signal 28 has failed. After the release, signal 2E will thus occur in the output of transistor gate TR4, but not so long that the capacitor is completely charged or sufficiently long for resetting TRS since the electronic switch is closed at 10A and signal 28 thus is replaced. FlGS. 2C and 2F show the signal pattern upon thread breakage at a point ll adjacent the selvage. In this case, signal 2F will be present in the output of transistor TR7 as long as is required for the charging of C10 and thus the production of the signal shown at 2G, and loom operation is interrupted by rendering relay 2 operative by means of signal 4 in insert C through TR6 and TR7.

The sensing element used in the present invention may be of several different designs. The main requirement is that the sensing element respond to irregularities in the thread and to the friction of the thread against the sensing element, while the thread exerts very little force on the sensing element. Moreover, the sensing element must be adequately damped against surrounding mechanical oscillation since it is desired to attain a quick return to standstill after breakage of a thread. FIGS. 3-7 illustrate a number of different constructions satisfying these requirements. These constructions consist of a piezoelectric signal device of ceramic type (FIG. 3), a photoelectric signal device (FIG. 4), a piezoelectric signal device of crystal type (FIG. 5), a resistance signal device (FIG. 6), and a capacitor signal device (FIG. 7).

FIG. 8 is a detailed illustration of a piezoelectric signal device of ceramic type for a sensing element for use with the device of the invention. This signal device has a substantially cylindrical housing 20 with one end open and the other end substantially closed and provided with a slot 21 to facilitate threading. Bushings 22 which preferably are of porcelain and serve to guide the thread through the housing 20 are provided at the ends of the slot 21 in the housing wall. A sensing body 23 is located at right angles to the thread path through the housing and in such a way relative to said bushings 22 that the thread will engage the sensing-body 23 which is in the form of a cylindrical rod and made from piezoelectric ceramic material. The sensing body 23 is clamped between two essentially S-shaped and opposed contact springs 24 and 25, the upper parts of which are bent to engage the end surfaces of the sensing body 23. The sensing body is held in position in the contact springs 24 and 25 by means of a rod 26 of suitable insulating material such as nylon. The rod 26 is clamped between the contact springs and rests against the waist portions thereof. A ring 27 of suitable insulating material, such as nylon, is provided in the lower parts of contact springs 24 and 25.

The parts provided in the housing 20 are retained therein by means of a base plate 28 secured to the housing by screws (not shown). When the base plate 28 is screwed to the housing, the parts therein will be urged against the closed end wall by the contact springs 24 and 25. Owing to the shape of the upper parts of the contact springs, these springs will be urged against the sensing body 23. Contact spring 24 is insulated from the base plate 28 by a member 29 of insulating material which covers the base of the contact spring. Screwed against the base plate 28 by a screw 31 is a plate 30 which preferably is of brass. The brass plate 30 and the base plate 28 both have a lead-through for a cable 32 which preferably is a coaxial cable, the inner conductor of which is connected to one contact spring and the screw of which is connected to the other contact spring. The cable 32 extends to the terminal block and is connected to contacts and 16. The housing and its base plates 28 and 30 are secured in a mounting ring 33 by means of foam rubber damper rings 34 clamped between flanges of said mounting ring, the base plate 28 and a flange of housing 20. Also provided on the mounting ring is a fastening bolt 36 by which the entire sensing element can be mounted at a suitable location for sensing the thread.

When a thread engaging the sensing body is moved at a given speed, a signal will be produced by the sensing body and supplied through cable 32 to the electronic circuitry where the signal will be processed in the manner described before. It is pointed out that the frequency of the resulting signal is approximately 30 kilocycles per second when the sensing body is of piezoelectric ceramic material.

If several threads are to be withdrawn, one signal device may be provided for each thread, and all the signal devices can be connected in parallel. This parallel circuit is connected to the input portion of the electronic circuitry.

In FIG. 9A, two

ceramic bushings

50, 51 are mounted in electrically insulating housing 60 of rubber, or the like, so as to be pressed against opposite sides of a plate 52 of piezoelectric ceramic material. The threads pass through and rub against the ceramic bushings and the irregularities of the thread are transmitted to the piezoelectric plate 52, thus producing an electrical signal. Contact strips 53, 54 are mounted in the housing and engage the piezoelectric plate 52 and a coaxial cable 55 connected to the contact strips extends from the housing and the leads thereof are connected to the input portion of the electronic circuit.

The housing 60 is constructed in two parts and is provided with recesses for the bushings, the piezoelectric elements and the contact strips. The parts of the housing are secured together by screws or like fasteners. The housing 60 is mounted in an aluminum holder 61 which serves to connect the housing in its place of operation. The holder may also serve to connect a number of sensing devices in side-by-side relation and in such case, the contact strips are all connected in parallel to the input portion of the electronic circuitry via their coaxial cables.

FIG. 9B shows another embodiment of sensing device for several threads. Herein a ceramic bushing is pressed against a rod 71 of piezoelectric ceramic material by means of a wire 72 twisted around the bushing and the rod. Connecting wires 73, 74 are soldered to both ends of the piezoelectric rod 71. The assembly of the bushing, the rod, the wire and the conducting wires is moulded in silicone rubber 75 in a casing 76 made of aluminum. The silicone rubber serves as both dampingmaterial and protecting material. This signal device can be made with any number of ceramic bushings and can be connected either in parallel or separately for each thread.

Naturally, the above described embodiments of the present invention are not limited to use in a loom, but can be used in any machine whatever where a stop motion is required.

The following Table gives the values of the components in FIG. 1 for a preferred embodiment of the electronic circuitry of the invention, but the invention must not be regarded as limited to a device having precisely the components according to this Table.

TABLE R1 56 kohm R19 ohm C10 0.047 mfd D3 BAY87 R2 22 kohm R20 2.2 kohmCll 1.6 mfd D4 B2Yl8 R3 5.6 kohm R21 47 ohm C12 l0 mfd R4 1 kohm R22 390 ohm C13 100 mfd R5 33 kohm R23 10 kohmC14 l.6 mfd R6 12 kohm R24 100 kohmClS 0.22

R7 5.6 kohm R25 4.7 kohmTRI BCl3lC R8 l.8 kohm R26 560 ohm TR2 BCI30B R9 39 kohm R27 3.3 kohmTR3 BCI3OA R10 6.8 kohm Cl 0.22 mfd TR4 BC130A R11 1 kohm C2 100 mfd TR5 TlS43 R12 4.7 kohm ca 0047 mfd TR6 Cl06Y2 R13 2.2 kohm C4 L6 mfd TR7 BC107A R14 1 kohm C5 0.047 mfd TR8 OCP70 R15 is kohm C6 1.6 mfd TR9 2N3702 R16 2.2 kohm 07 1.6 mfdTRlO Cl06Y2 R17 680 ohm ca 2200 pfd D1 BAY87 R19 68 ohm c9 250 mfd D2 BAY87 What is claimed is:

l. A stop motion device for a thread comprising means for intermittently withdrawing thread from a thread supply, sensing means in contact with said thread for sensing said thread and for producing an electrical signal in response to the friction of said thread against said sensing means during the period of withdrawal of said thread from said thread supply, said sensing means including a sensing body of piezoelectric material, and electrical contact means engaging said body, electronic means connected to the electrical contact means engaging the body for stopping the thread withdrawing means upon a breakage of said thread, said electronic means including a first portion for filtering and amplifying said electrical signal, a second portion connected to the first portion for supervising the said signal during at least a period of intermittent withdrawal of said thread, electrical switch means for determining said supervising period, and relay means which is operative, upon the disappearance of said supervised signal during the supervising period when the thread breaks, to stop the thread withdrawing means.

2. A device as claimed in claim 1, wherein said first portion of the electronic means comprises a frequencybalanced amplifier.

3. A device as claimed in claim 1, wherein said second portion of the electronic means comprises a transistor gate means and an oscillator means connected to the relay means.

4. A device as claimed in claim 3, wherein said oscillator means comprises a capacitor connected to said transistor gate means and a switch transistor of unijunction type connected to said capacitor, said capacitor being incompletely charged for operation of said switch transistor means for producing a signal to operate the relay means for stopping the thread withdrawing means upon breakage of the thread unless said gate is opened.

5. A device as claimed in claim 3, wherein said electronic means comprises a mechanical switch means and an electronic switch means connected with said transistor gate means, said mechanical switch means being opened at the beginning of said supervising period and said electronic switch means being closed at the end of said supervising period, whereby said transistor gate means is closed by said electrical signal and opened if the signal disappears upon a breakage of the thread.

6. A device as claimed in claim 4, wherein said mechanical switch means comprises a limit switch and a cam disk operatively coupled to said limit switch and driven by the thread withdrawing means.

7. A device as claimed in claim 4, wherein said electronic switch means is of photoelectric type and operable by means which is provided on the thread withdrawing means.

8. A device as claimed in claim 7, wherein said mechanical switch means comprises a limit switch, said electronic switch means comprising a thyristor which on rece'vin a lse from ot e1 c tric elemen is conductive mtil t he limit sw 'it ii whi h is connecte 1n parallel with the thyristor and the electronic switch means is closed.

9. A device as claimed in claim 1, wherein said sensing means further comprises guiding means for guiding a plurality of threads and in separate contact with said sensing body.

10. A device as claimed in claim 9, wherein said guiding means comprises ceramic bushings, said sensing body comprising a plate, said bushings being pressed against opposite surfaces of said plate.

11. A device as claimed in claim 9, wherein said electrical contact means comprises a pair of contact strips for said sensing body.

12. A device as claimed in claim 1, wherein said sensing body is a rod, said sensing means further comprising means for guiding the thread disposed on said rod, and a wire twisted around said rod and the guiding means to fix the same together.

13. A device as claimed in claim 12, comprising a body of silicone rubber, said rod, guiding means and wire being moulded into said body of silicone rubber, and conducting wires each connected to one end of the rod and extending out of the body of silicone rubber.

Claims

1. A stop motion device for a thread comprising means for intermittently withdrawing thread from a thread supply, sensing means in contact with said thread for sensing said thread and for producing an electrical signal in response to the friction of said thread against said sensing means during the period of withdrawal of said thread from said thread supply, said sensing means including a sensing body of piezoelectric material, and electrical contact means engaging said body, electronic means connected to the electrical contact means engaging the body for stopping the thread withdrawing means upon a breakage of said thread, said electronic means including a first portion for filtering and amplifying said electrical signal, a second portion connected to the first portion for supervising the said signal during at least a period of intermittent withdrawal of said thread, electrical switch means for determining said supervising period, and relay means which is operative, upon the disappearance of said supervised signal during the supervising period when the thread breaks, to stop the thread withdrawing means.

2. A device as claimed in claim 1, wherein said first portion of the electronic means comprises a frequency-balanced amplifier.

8. A device as claimed in claim 7, wherein said mechanical switch means comprises a limit switch, said electronic switch means comprising a thyristor which on receiving a pulse from a photoelectric element is conductive until the limit switch which is connected in parallel with the thyristor and the electronic switch means is closed.