US3818236A

US3818236A - Apparatus for detecting broken threads or other disturbances in a fibre web

Info

Publication number: US3818236A
Application number: US00281424A
Authority: US
Inventors: B Lind; M Mansson
Original assignee: Nordiska Maskinfilt AB
Current assignee: Nordiska Maskinfilt AB
Priority date: 1971-08-23
Filing date: 1972-08-17
Publication date: 1974-06-18
Anticipated expiration: 1991-06-18
Also published as: FR2150357B1; FR2150357A1; SE355608B; GB1388588A; DE2240112B2; DE2240112A1; CH553270A; IT964166B

Abstract

An apparatus for the supervision of fibrous webs, or other sheet-like material, particularly within the textile and paper industries, with the purpose of detecting faults in webs. An emitter is positioned at one side of the web and arranged to give off a beam of light essentially at right angles to the web extension. A receiver, positioned at the opposite side of the web, receives the beam of light. In accordance with the invention, the beam is imparted a particular movement covering an area of the web where faults are likely to arise and the immediate vicinity of said area. Evaluation means register any disturbances and compare them with a predetermined value, and upon excess of said predetermined value an impulse is emitted to a warning and/or stopping mechanism.

Description

United States Patent [191 Lind et a1.

[ APPARATUS FOR DETECTING BROKEN THREADS OR OTHER DISTURBANCES IN A FIBRE WEB [75] Inventors: Bjorn Ivar Lind, Goteborg; Mans Gunnar Ove Mansson, Killeberg, both of Sweden [73] Assignee: Nordiska Maskinfilt Aktiebolaget,

I-Ialmstad, Sweden [22] Filed: Aug. 17, 1972 [21] Appl. No.: 281,424

[30] Foreign Application Priority Data Aug. 23, 1971 Sweden 10637/71 [52] U.S. C1 250/561, 28/51, 139/353 [51] Int. Cl. G0ln 21/30 [58] Field of Search... 250/219 S, 219 NE, 219 DF;

[56] References Cited UNITED STATES PATENTS 3,124,289 3/1964 Lynch 28/51 3,345,812 10/1967 Pickering 3,401,267 9/1968 Engle 3,447,213 6/1969 Dost 28/51 3,536,926 10/1970 Friedrich 250/219 S 3,543,360 12/1970 Fertig 28/51 June 18, 1974 3,677,307 7/1972 Fiorucci 139/353 3,717,771 2/1973 Abilock 250/219 DF FOREIGN PATENTS OR APPLICATIONS 691,069 5/1953 Great Britain Primary Examiner-James W. Lawrence Assistant ExaminerD. C. Nelms Attorney, Agent, or Firm-Kane, Dalsimer, Kane, Sullivan, Kurucz & Goldstein ABSTRACT An apparatus for the supervision of fibrous webs, or other sheet-like material, particularly within the textile and paper industries, with the purpose of detecting faults in webs. An emitter is positioned at one side of the web and arranged to give off a beam of light essentially at right angles to the web extension. A receiver, positioned at the opposite side of the web, receives the beam of light. In accordance with the invention, the beam is imparted a particular movement covering an area of the web where faults are likely to arise and the immediate vicinity of said area. Evaluation means register any disturbances and compare them with a predetermined value, and upon excess of said predetermined value an impulse is emitted to a warning and/or stopping mechanism.

12 Claims, 3 Drawing Figures PATENIEU JUN 1 8 m:

SHEU 1 BF 2 PATENTEDJUNIBIW 3.818.236

SHEET 2 OF 2 l; 2O CLOCK 21 I9\ 2/ COUNTING DE VICE LEVEL SENSOR 22 I8 T COMPARATOR FILTER SWITCH CONTROL AMPLIFIER 24 ALARIVI SIGNAL RECEIVER-- Q 25 MOTOR APPARATUS FOR DETECTING BROKEN THREADS OR OTHER DISANCES IN A FIBRE WEB BACKGROUND OF THE INVENTION In order to avoid as much as possible weaving faults caused by breakage of one or several warp threads during weaving, it is necessary to supervise the threads continuously throughout the weaving procedure. Since each individual weaver handles a large number of weaves, manual supervision of the condition of the warp threads naturally is completely insufficient to de tect defects of this kind to effect stoppage of the machine before long stretches of faulty material webs have already been woven.

To solve this problem automated supervision or inspection systems have been developed, these systems comprising an emitter giving off a beam of light at an angle essentially normal to the warp threads, which beam of light is received by a receiver positioned at the opposite side of the weave and arranged to measure the change of intensity of the beam of light occurring when the the light beam path is disturbed or interrupted by a warp thread. Means are connected to said receiver to emit, at a predetermined disturbance, an impulse providing an alarm signal and/or stopping the weaving.

In these known systems both the emitter and the receiver are fixed to the reed in such a way that the emitter gives off a beam of light which in response to the movement of the reed describes an arcuate motion path lying completely within the shed, i.e., between the warp threads of the upper and the lower part of the warp. When a break occurs of a thread of the upper part of the warp, this broken thread will hang down within the shed and thus interrupt the beam of light when the latter travels to the receiver. This disturbance, caused by the pendant thread, will cause a decrease of intensity of the light reaching the receiver, this intensity decrease causing the means connected to the receiver to start functioning and thus stop the weaving. If, on the other hand, a thread of the lower part of the warp breaks, this thread will hang down below the area scanned by the beam and the weaving operation will continue, resulting in a deficient product.

Mounting of the supervisory components directly on the reed has the effect that the maximum number of scanning movements that may be performed is two for each working stroke of the reed. In addition, both emitter and receiver will be exposed to strong vibrations and considerable stress on account of the heavy acceleration movements of the reed and its thrust-like deceleration movements.

The emitter of these earlier systems operates with a beam of light which originally has a diameter of between 2 and 3 centimeters and which diverges to a diameter of up to between 5 and 6 centimeters, dependent on the width of the weave. In the receiver, only a smaller amount of this light is used for detecting purposes and the result is that disturbances occur as shadows in the receiver. However, following the laws of optics, the shadowing caused by a broken thread positioned adjacent the emitter is much less than that caused by a broken thread having the same dimensions but positioned close to the receiver, and as a result great variations of shadowing will arise for the same degree of disturbance at different areas of the warp. This is clearly unsatisfactory as the receiver then must be made particularly sensitive in order to be able to register thread breakages at the emitter side of the warp, and this hightened sensitivity has the effect that also smaller particles, such as grains of dust passing the beam of the light at the receiver side will release an impulse to stop the apparatus.

In case of failure of the receiver of these earlier systems for one reason or another, the weaving furthermore will continue also at the occurrence of thread breaks which normally would bring about stoppage.

SUMMARY OF THE INVENTION In order to provide for supervision of web in an effi cient manner, an apparatus is suggested in accordance with the present invention which is essentially characterised in that the emitter, which is positioned at one side of the web, is arranged to give off an essentially coherent light beam to which means impart such a movement that the light beam travels within an area of the web where disturbances are likely to arise, and in that the means connected to the receiver are arranged both to register the number of disturbances per time unit, to compare the number of registered disturbances per time unit with a predetermined value, and also, in case of deviation of the registered value from the predetermined value, to emit said impulse.

This apparatus thus provides supervision while making use of the emitted light fully for the scanning activity which embraces all warp threads. As a result is obtained in the receiver a decrease of intensity which is proportional to the dimension of the disturbing object, irrespective of the distance between the receiver and the disturbing object. In addition, the apparatus does not suffer from any one of the disadvantages mentioned previously.

BRIEF DESCRIPTION OF THE DRAWINGS The structure and function of the apparatus will be described more in detail in the following with reference to the accompanying drawings, wherein FIG. 1 illustrates in a highly schematic view from above the apparatus as applied to a weaving loom,

FIG. 2 is a side view of the loom of FIG. 1, and

FIG. 3 is a diagrammatic basic circuit diagramme showing the underlying principle of the receiver part of the apparatus.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT The loom illustrated in FIGS. 1 and 2 comprises generally a warp beam 1 on which warp threads 2 are wound. Only a small number of these threads 2 is shown in FIG. 1. The warp threads 2 pass through healds 3 where, with the aid of shafts, they form an aperture 4 the shed through which weft threads are inserted and compacted with 'the aid of a weave reed 5, the latter having been excluded from FIG. 1 in order not to clutter the drawing and being shown only in FIG. 2. The fabric web 6 formed during weaving is thereafter wound onto a fabric beam 7.

At the level of the shed 4, an emitter 8 is arranged at one longitudinal side of the loom, said emitter giving off an essentially coherent beam of light 9 and being mounted essentially immovably relative to the machine frame of the loom, either by being attached directly on the frame or in order to avoid machine vibrations on the machine base. At the opposite side of the shed, a receiver it) is positioned in a similar manner, said receiver being provided with a collecting input screen corresponding to the path of movement of the light, and preferably comprising a photoelectric cell arranged to measure the intensity of the incoming beam of light.

Adjacent the emitter 8 there is a device 11 which is arranged to impart a definite movement to the beam of light 9 from the emitter. The device 11 comprises in accordance with the illustrated, preferred embodiment a hollow shaft 12 which is orientated in alignment with the direction of issue of the beam of light 9 in such a manner that the beam of light passes through the shaft. At the shaft end remote from the emitter the shaft is provided with a nonrotational optical element 13 which may consist of mirrors, lenses or prisms and is arranged to effect a parallel movement of the beam of light over a short distance. The shaft 12 is rotatably mounted and driven at a high speed by a motor 14, whereby the beam of light 9 is imparted a rapid rotational movement in a plane perpendicular to the warp threads 2.

Below the lower part of the warp catcher means 15 are provided, these means extending essentially normally to the extension of the warp threads and consisting in their most simple version of wires suspended beneath the shed in a manner permitting a thread of the lower warp, when breaking, to remain in a pending position within the area being scanned by the moving beam of light 9 whereas the wires themselves are orientated in a way preventing them from interfering with or interrupting the rotational path of the beam of light at any point.

FIG. 2 illustrates in a more detailed manner the position of the catcher means 15 as also the extent of the path of movement 16 along which the beam of light 9 carries out its scanning action. This Figure also shows the position of the reed 5 whereas the detecting apparatus is not illustrated here in order to give a clearer view of the scanned path 16.

FIG. 3 is a basic circuit diagramme showing the underlying principle of the construction of the receiver portion of the apparatus.

To the receiver it) proper is coupled an amplifier 17 which amplifies the input pulses. Thereafter is connected a filter 18 which forwards pulses having a determined frequency to a level-sensing unit 19. The latter is adjustable such that pulses exceeding a predetermined value are permitted passage to a clock 20 determining the measuring interval and providing the measuring time to a counting device 21 counting the number of pulses per time unit. This number is compared in a comparator 22 to a predetermined value which is dependent on the speed at which the shaft 12 is rotated and on the measuring time. Upon occurrence of deviations of the measured value from the predetermined one, the comparator 22 emits an impulse to a means 23 arranged to control a switch 24 in the supply line to the loom drive motor 25. The switch 24 is preferably arranged to close a circuit for an alarm signal apparatus 26 in connection with breaking the circuit of the drive motor 25.

As long as the weaving continues without faults the beam of light 9 will, in accordance with the shown embodiment, be exposed to disturbance by warp threads 2 four times for each rotational revolution. Each sequence of measuring thus comprises a large number of revolutions and the number is determined by the clock 20 in addition to which each measuring sequence lasts a comparatively short time in relation to the duration of the loom working stroke, i.e., the reciprocating movement of the reed. The photo-electric cell of the receiver then receives a number of signals corresponding to the number of revolutions multiplied by four. Analogy is thus obtained in the comparator 22 between the predetermined value and the one registered by the counter. In this situation, the comparator does not issue an impulse to the breaking means 23.

Upon occurrence of a warp thread break, irrespective of whether the break occurs in the upper or lower part of the warp, the light beam will be disturbed or interrupted one time in excess of the four normal times per revolution. This creates a discrepancy between the predetermined value and the registered value and the comparator will find that analogy is missing and thus emit an impuise to stop the motor 25. Since each measuring sequence has a duration which is brief in comparison with the reed working stroke, any break of a warp thread will very rapidly have the effect of stopping the weaving machine, and in case an alarm signal device 26 is incorporated in the receiver, stopping of the machine will likewise be detected very quickly.

In case any one of the details in the receiver portion up to the comparator and including the receiver proper should fail and stop functioning in the intended manner, the comparator will likewise bring about stopping. The probability that too low a disturbance impulse value caused by apparatus failure could be evened out by one or several thread breaks occurring simultaneously is negligible.

The movement which the coherent light beam 9 is imparted has been described in the aforegoing as a rotating movement. This motion pattern is comparatively easy to achieve but what is essential to the functioning of the detecting apparatus is that the light beam 9 moves in such a way that the shed, the upper warp and the lower warp and the area closest to the lower warp are scanned, and for this reason it is also possible to use a very simple movement such as a rectilinear one.

The clock 20 is programmed to release measuring sequences at predetermined intervals and to prevent starting of measure sequences during exchange of the reeds.

The coherent beam of light 9 given off by the emitter 8 preferably is of laser type although it is also possible to use other kinds of light.

The emitter described above gives off a beam of light which is essentially normal to the threads to be supervised. This does not, however, necessarily mean that the emitter must be positioned at right angles to the warp but the beam of light may be forwarded to its point of departure via so called fibre optics. The same technique may also be used to supervise several points with the aid of the very same emitter. The clock 20 which decides the measuring intervals may also have the form of several clocks which connect and disconnect their individual counter for the registration of the situation at the various portions of the area within which the light beam moves. This makes possible emit tance of several kinds of impulses for disturbances occurring within different portions of the area of move ment of the light beam.

The apparatus in accordance with the invention has been described in connection with use in a particular application but the possibilities of modifications are numerous within the scope of the appended claims.

The invention thus is not limited to use in connection with looms to detect broken warp threads. Within the textile industry there are numerous processes where webs of threads or filaments run in one and the same plane. As examples may be mentioned spinning and twisting machines, winding machines, warping machines and knitting machines. Also within the paper industry the invention may find applications such as for instance to scan or continuously supervise the paper web of a paper machine. On the whole, the apparatus in accordance with the invention may be used to scan any regular systems for detecting and registering disturbances.

What we claim is:

1. An improved apparatus for detecting disturbances of a fibrous web, such as broken threads, comprising an emitter giving off a beam of light directed essentially at right angles to the threads, a receiver positioned at the opposite side of the threads and arranged to measure a change of intensity to which said beam of light is subjected when the path of said beam of light is interrupted, e.g., by a thread, means connected to said receiver for emitting, in response to a predetermined disturbance, an impulse capable of providing circuit response, the improvement comprising the emitter giving off an essentially coherent beam of light, a device provided to impart to said beam of light a movement of travel within an area where disturbances are expected to occur, said means connected to said receiver including counting means to count the number of disturbances per time unit and comparatory means to compare said number of disturbances per time unit with a predetermined number, and to emit said impulse in case of any discrepancy between said number of disturbances per time unit and said predetermined number.

2. The improved apparatus as claimed in claim 1 utilized for detection of broken upper and lower warp 3. The improved apparatus as claimed in claim 1, wherein a predetermined number of scanning operations of said area defines a measuring sequence.

4. The improved apparatus as claimed in claim 3, wherein said beam movement imparting device is arranged to give to said beam of light a particular movement a plurality of times per measuring sequence.

5. The improved apparatus as claimed in claim 1, wherein said beam movement imparting device consists of a hollow shaft, being rotated, through which hollow shaft passes said beam of light from the emitter, an optical element being provided on said shaft to give said beam of light a back and forth movement of adjustable width.

6. The improved apparatus as claimed in claim 1, wherein said beam of light emitted by said emitter is a laser beam.

7. The improved apparatus as claimed in claim 1, wherein both said emitter and said receiver are mounted rigidly relative to each other.

8. The improved apparatus as claimed in claim 1, comprising catcher means positioned beneath the threads to prevent broken threads from hanging down, this arrangement retaining said threads within said area being scanned by said beam of light without causing any disturbance to said beam of light by said catcher means themselves.

9. The improved apparatus as claimed in claim 1, comprising clock means connected between said receiver and said counting means and programmed to connect and disconnect said counting means.

10. The improved apparatus as claimed in claim 1, comprising breaking means, switch means connected between said receiver and said breaking means and programmed to carry out measurings at predetermined occasions.

11. The improved apparatus as claimed in claim 10, comprising means to interrupt measurings upon shift of weaving harness.

12. The improved apparatus as claimed in claim 1, comprising a unit coupled between the receiver and said counting means to emit an impulse to said counting means only upon change of intensity exceeding a predetermined value.

Claims

2. The improved apparatus as claimed in claim 1 utilized for detection of broken upper and lower warp threads in weaving, wherein said movement imparted to said beam of light by said device is effected within an area lying between the upper and the lower warp threads and above and beneath these threads.

3. The improved apparatus as claimed in claim 1, wherein a predetermined number of scanning operations of said area defines a measuring sequence.