US3844101A

US3844101A - Thread monitor device for textile machinery

Info

Publication number: US3844101A
Application number: US00394936A
Authority: US
Inventors: H Schwartz
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-10-11
Filing date: 1973-09-06
Publication date: 1974-10-29
Anticipated expiration: 1991-10-29
Also published as: CH542296A; FR2203373A5; GB1379720A; IT995364B; DE2344068A1; DE7331739U

Abstract

To check the presence of thread close to thread handling apparatus in which the thread is apt to balloon, two hook shaped metallic thread guides, together, form a thread guiding eye; the hook shaped guides are spaced from each other in the direction of thread travel, so that they are electrically insulated. The guides act, electrically, as separate electrodes and mechanically to, conjointly, form the guiding eye. The guide-electrodes are connected over high impedance input to a differential amplifier which responds to presence of or absence of the thread which, due to the ballooning tendency, alternately contacts the one and the other of the hook-shaped guide-electrodes, to transmit pulses due to electrostatic charge on the thread to the differential amplifier or, if the thread is conductive due to moisture and low resistance material, or the presence of metallic threads, connects, alternately, a source of potential to the differential amplifier. Absence of pulses is an indication of thread breakage. An integrator delays initial sensing to permit start-up.

Description

United States Patent 1 Schwartz 1 THREAD MONITOR DEVICE FOR TEXTILE MACHINERY [75] Inventor: Hermann Schwartz, Pfaffikon, Switzerland [73] Assignee: Siegfried Peyer, Bach, Switzerland [22] Filed: Sept. 6, 1973 [21] Appl. No.: 394,936

[30] Foreign Application Priority Data Oct. 11, 1972 Switzerland 14843/72 [52] US. Cl 57/81, 57/34 R, ZOO/61.13, ZOO/61.18 [51] Int. Cl D0lh 13/16 [58] Field of Search 57/78, 80, 81, 106, 34 R; ZOO/61.13, 61.18; 242/157 R, 157 C [56] References Cited UNITED STATES PATENTS 3,010,273 11/1961 Bailey 57/81 3,043,991 7/1962 Schneider et al.. 57/81 X 3,114,233 12/1963 Guri 57/81 3,132,466 5/1964 Preisser 57/81 3,158,852 ll/l964 Schacher 57/81 X 3,701,247 10/1972 Rehn et al. 57/81 3,772,524 11/1973 Erbstein 57/81 X [451 Oct. 29, 1974 Primary Examiner.lohn Petrakes Attorney, Agent, or Firm-Flynn & Frishauf 57 ABSTRACT To check the presence of thread close to thread handling apparatus in which the thread is apt to balloon, two hook shaped metallic thread guides, together, form a thread guiding eye; the hook shaped guides are spaced from each other in the direction of thread travel, so that they are electrically insulated. The guides act, electrically, as separate electrodes and mechanically to, conjointly, form the guiding eye. The guide-electrodes are connected over high impedance input to a differential amplifier which responds to presence of or absence of the thread which, due to the ballooning tendency, alternately contacts the one and the other of the hook-shaped guide-electrodes, to transmit pulses due to electrostatic charge on the thread to the differential amplifier or, if the thread is conductive due to moisture and low resistance material, or the presence of metallic threads, connects, alternately, a source of potential to the differential amplifier. Absence of pulses is an indication of thread breakage. An integrator delays initial sensing to permit start-up.

10 Claims, 3 Drawing Figures PATENTEDumzs 1974 3.344.101

SHEEI 1 [IF 2 PATENTEDnm 29 I974 SHEET 2 0F 2 Hu k PDnCIDO JOMFZOU The present invention relates to a thread monitoring and detection device, and particularly such a device which is adapted to cooperate with thread handling apparatus in which the thread balloons outwardly, when the device is in operation.

Various types of textile machinery require accurate monitoring of the presence of threads, and apparatus which, upon absence of thread, provide an alarm signal. Such thread monitor devices utilize various mechanical, electrical, and electronic and systems. Some electronic systems check axial, or radial movement of the thread and obtain a signal for the presence, or absence of the thread.

In many instances it is possible to locate the thread sensing device in a region where the thread is longitudinally guided, that is, where it has relatively small radial movement. In some textile machinery, however, such as spooling machines, and spinning machines, and thread winding machines, reliable thread sensing is only obtained if the thread is sensed after all machine elements have been passed thereby, that is, if the presence or absence of thread is sensed preferably immediately in advance of it being wound on the spool. The sensing element must then be located in the free space between the operating elements of the machine and the subsequent winding device. In this region, however, the

thread is free and not guided. Such apparatus, often,

utilizes a spooling arrangement in which the thread balloons radially outwardly due to centrifugal force, and is subjected to circular motion, the size of which depends on the winding speed and the spool diameter at any time. This circular motion is commonly referred to as ballooning.

Various physical arrangements have been proposed to electronically control the presence or absence of a thread at this stage. Some apparatus utilize photoelectric, capacitative or piezoelectric systems. The static charge on the thread can also be detected. For static charge detection, the thread is either electrically charged, by application of an electric charge thereto, or the thread is subjected to friction which causes an electric charge build-up. The surface of the thread, however, has only low capacity and a certain time is required for the thread to pass from the charge point to the sensing device. The thread, as a removing charge carrier therefore must have an extremely high electrical resistance if the charge is to be maintained for any period of time. Textile threads of natural fibers require, however, a relatively high degree of moisture for machine handling; synthetic threads frequently are treated with chemicals which prevent acceptance of static charges during production of the thread. Electrical resistance of the thread is substantially reduced in these systems, so that electrostatic charge cannot be ensured. Textile threads which are mixed with metallic fibers cannot be used as charge carriers for static charges at all. Thus, known thread sensing or monitoring devices can be used only selectively.

It is an object of the present invention to provide a thread sensing element which permits sensing of a running thread independent of its physical characteristics, and within the region where the thread is apt to balloon.

Subject matter of the present invention Briefly, two hook-shaped thread guides are located, spaced from each other, in the thread running direction, such that, together, in projection they form a thread eye with their free ends. The hook-shaped guide elements are metallic, and are connected over resistors with a source of direct current in order to provide a voltage drop between the two elements, if connected by a metallic thread; they are coupled over capacitors with an input, each, of a differential amplifier in order to provide an output signal depending on the presence of thread and motion of the thread within the eye formed by the two guides. The guides thus act, to define the thread eye and electrically as separate electrodes, and may be termed guide-electrodes.

The invention will be described by way of example with reference to the accompanying drawings, wherein:

FIG. 1 is a top view of the thread guiding eye formed by the two elements;

FIG. 2 is a front view of the elements, highly schematic, and illustrating the position of a thread applied to a spooling device; and

FIG. 3 is a circuit diagram of the arrangement in accordance with the present invention.

The thread sensing device, see FIGS. 1 and 2, includes two similar hook-shaped metal elements 1' and 1". They are made, preferably, of steel wire about 3 to 4 mm diameter, and coated with a hard chrome finish. Each end of the thread guide is bent over hook-shaped, and the two hook-shaped guide elements are located to be offset with respect to each other by so that they, together, form, in projection, a thread guiding eye 2. The hook-shaped elements are spaced from each other by about 2 3 mm, in the direction of thread movement. This permits easy threading of a thread F (FIG. 2) and further separates the hook-shaped elements electrically from each other. The thread guide eye, that is, the two elements, are located so that they are placed in the balloon formed by the thread when it is wound on a spool 8 (see FIG. 2), in such a manner that, as the thread forms its circular rotation, it is constantly in contact with the limiting surfaces defining the eye 2. Thus, the thread alternately contacts the one or the other element 1' or 1'', respectively; upon transition from one to the other, both elements may be contacted together. These different contact zones of the threads, with the respective elements, are essential for the operation of the system, as will be described below. FIG. 2 illustrates, in solid line, the thread when wound on the left side of the spool 8, at which point it contacts only thread guide element 1", and in chain dotted line the position of the thread when the spool has revolved 180, and the thread contacts the element 1'.

The thread guide element 1" is connected over a high resistance resistor R1 with the positive terminal of a voltage source (FIG. 3), for example +24V; the other element 1 is connected to the negative terminal of the source over a resistor R2. A voltage, therefore, of 24 volts is applied between the two elements 1', 1". The two guide elements form electrodes, which are connected over coupling capacitors C1, C2 to two high resistance inputs of a differential amplifier 3. The resistors R1, R2 must be high resistors, and resistances of about 10 megohms are suitable. The output of the differential amplifier 3 is connected to an integrator 4 which, in turn, is connected to a trigger circuit 5, the output of which is connected to an alarm 6 and to a monostable multivibrator 7, to initiate further control functions.

The differential amplifier will accept surrounding noise voltages due to the high input impedance, which are applied by capacitative or inductive coupling to the elements 1', 1". These noise voltages are primarily at power supply frequency, and are derived from usual power supply cables, for drive motors, supplies for supervisory equipment and the like. A differential amplifier having an input sensitivity of 50 millivolts would be rapidly blocked by'noise frequencies, particularly since the rotational frequency of thread balloons, from experience, falls in the region of 50 200 Hz, that is, within the range of power line frequencies and the third harmonic thereof. Thus, filters cannot be used. If both thread guides are exactly equal, and have the same input capacitance to the differential amplifier, then noise signals will be induced in both hook-shaped elements with equal amplitude and phase, which will be transmitted with equal amplitude and phase to the differential amplifier so that it willnot provide an output signal.

Let it be assumed that the thread is of high resistance, and thus capable of holding a static charge, at least for a short period of time. It is not necessary to provide a specific static charge to the.thread-,,or to utilize any auxiliary charging devices. If the thread has received any charge, for example due to friction with some element of machinery, then this static charge is alternately applied to the hook-

shaped elements

1 and 1" respectively, and transmitted to the respective amplifier inputs in the form of pulses. If the thread has not received any charge as yet, then friction with the hook-shaped elements, which are, respectively, connected to positive and negative terminals of the supply, will apply an electrostatic charge thereto, which charge will be alternately exchanged between the guide elements 1', 1" thus likewise providing pulse type signals to the amplifier 3.

Let it be assumed that, under other conditions, a thread is used which has low electrical resistance, for example due to moisture, application of chemicals, or the like, or that the thread-includes metallic filaments or fibers,so that its resistance is 0. Under those conditions no static charge can be transferred. The thread, however, contacts the two

elements

1, 1, alternately, as it forms the thread balloon. For each rotation within the balloon, the thread touches both

elements

1, 1" simultaneously, although only instantaneously; for each rotation of the thread, therefore, the electrical resistance of the thread is twice placed over the thread guides l, 1" between the resistors R1 and R2. This leads to a change of voltage at the two resistors'Capacitor C1 then transmits negative pulses, and capacitor C2 transmits positive pulses to amplifier 3. Assuming input impedance and sensitivity as above given, a thread resistance of 10,000 Megohms per centimeter of thread would already provide a sufficient signal to the amplifier.

'Thesystem,"therefore, utilizes a signal which is obtained by electrostatic charge on the thread, or by thread resistance, and it is independent of the material, or of its electrical characteristics.

The output signal from differential amplifier 3 is rectified in a rectifier (not shown) and applied to an integrator '4. integrator 4 integrates for a short period of time, for example for about 2 seconds, if a signal is present. Then a pulse is applied to set the trigger circuit 5, which may be an ordinary flip-flop. The delay prevents generation of a control signal upon threading of the thread or due to momentary manual contact with the thread guides. lf a thread signal is present for two seconds, then the circuit 5 changes state, and the system is in monitor or thread sensing condition. If the thread is missing, or if there is no thread motion, then the flip-flop 5 automatically switches back, immediately, which provides an alarm on a lamp 6, for example, and additionally a trigger pulse to a monostable multivibrator 7, which provides an output control pulse to control further alarm apparatus, or which is available as a trigger pulse for other control functions.

The flip-flop 5, thus, is a l-input flip-flop which is held its set position by a signal from integrator 4 that changes to reset immediately upon cessation of this signal. The time delay of the combined circuits 4, 5, thus is unilateral.

Various changes and modifications may be made within the scope of the inventive concept.

The

guide elements

1, 1" may be insulated at their facing surfaces and then actually brought in contact with each other, so long as they are electrically insulated by high quality insulation without leakage paths which might detract from sensing of the thread. The separation of these elements, then, will be that determined by the thickness of the separating, insulating layer.

1 claim: 1. Thread monitor-device, particularly for thread handling apparatus in which the thread forms a ballon comprising two hook-shaped thread guides (1', 1") of electrically conductive material, having their hooks located to be spaced from each other, in the direction of thread travel electrically insulated from each other to form, electrically two electrodes, said guides forming mechanically, in the projection of thread travel, a thread guide eye (2);

a source of electrical energy (V);

high impedance means R1, R2) connecting the respective thread guide-electrodes (1', 1") to said source;

a differential amplifier (3);

and means (C1, C2) coupling the

thread guideelectrodes

1, 1") to a respective input, each, of the differential amplifier, said differential amplifier providing an output signal representative of motion of thread through the thread guide eye (2) formed by said thread guide-electrodes 1', 1").

2. Device according to claim 1 wherein the coupling means comprises coupling capacitors C1, C2).

3. Device according to claim 1 wherein the thread guide-electrodes 1', 1") have approximately bent-over ends and are offset by about 180 with respect to each other.

4. Device according to claim 1 wherein the thread guides (1', 1"), each, are made of steel wire with a hardened surface.

5. Device according to claim 1 wherein the thread guides (1', l") are made of steel wire with a hard chrome surface.

6. Device according to claim 1 further comprising an integrator (4) connected to the differential amplifier and a bistable flip-flop (5) connected to the integrator and changing state when the integrator integrates an output signal from the differential amplifier in a direction representative of presence of a signal.

7. Device according to claim 6 wherein the integrator (4) and the monostable flip-flop 5) provide a unidirectional delay of the output signal from the differentiator, the flip-flop responding immediately upon change of direction of output from the differential amplifier.

8. Device according to claim 6 further comprising a monostable multivibrator triggered by change of state of said flip-flop and providing an output control pulse.

9. Device according to claim 1 wherein said thread guide-electrodes (1', 1") are similar, and spaced from each other in the direction of travel of the thread by a distance sufficient to electrically insulate said guideelectrodes (1, 1) from each other, in the absence of a conductive thread, but insufficient to cause changes in phase or amplitude of stray noise signals induced therein.

10. Device according to claim 1 wherein the thread guides (1', 1") are steel wires with a hardened surface of approximately 3 to 4 mm diameter, and are spaced from each other, in the direction of thread travel, by a distance which is sufficient to provide electrical insulation between said guide-electrodes l, l"), in the absence of a thread, and not more than about the diameter of the wires forming said thread guides 1, 1").

Claims

1. Thread monitor-device, particularly for thread handling apparatus in which the thread forms a ballon comprising two hook-shaped thread guides (1'', 1'''') of electrically conductive material, having their hooks located to be spaced from each other, in the direction of thread travel electrically insulated from each other to form, electrically two electrodes, said guides forming mechanically, in the projection of thread travel, a thread guide eye (2); a source of electrical energy (V); high impedance means (R1, R2) connecting the respective thread guide-electrodes (1'', 1'''') to said source; a differential amplifier (3); and means (C1, C2) coupling the thread guide-electrodes (1'', 1'''') to a respective input, each, of the differential amplifier, said differential amplifier providing an output signal representative of motion of thread through the thread guide eye (2) formed by said thread guide-electrodes (1'', 1'''').

2. Device according to claim 1 wherein the coupling means comprises coupling capacitors (C1, C2).

3. Device according to claim 1 wherein the thread guide-electrodes (1'', 1'''') have approximately 180* bent-over ends and are offset by about 180* with respect to each other.

4. Device according to claim 1 wherein the thread guides (1'', 1''''), each, are made of steel wire with a hardened surface.

5. Device according to claim 1 wherein the thread guides (1'', 1'''') are made of steel wire with a hard chrome surface.

6. Device according to claim 1 further comprising an integrator (4) connected to the differential amplifier (3); and a bistable flip-flop (5) connected to the integrator and changing state when the integrator integrates an output signal from the differential amplifier in a direction representative of presence of a signal.

7. Device according to claim 6 wherein the integrator (4) and the monostable flip-flop (5) provide a unidirectional delay of the output signal from the differentiator, the flip-flop responding immediately upon change of direction of output from the differential amplifier.

9. Device according to claim 1 wherein said thread guide-electrodes (1'', 1'''') are similar, and spaced from each other in the direction of travel of the thread by a distance sufficient to electrically insulate said guide-electrodes (1'', 1'''') from each other, in the absence of a conductive thread, but insufficient to cause changes in phase or amplitude of stray noise signals induced therein.

10. Device according to claim 1 wherein the thread guides (1'', 1'''') are steel wires with a hardened surface of approximately 3 to 4 mm diameter, and are spaced from each other, in the direction of thread travel, by a distance which is sufficient to provide electrical insulation between said guide-electrodes (1'', 1''''), in the absence of a thread, and not more than about the diameter of the wires forming said thread guides (1'', 1'''').