CN110656427A

CN110656427A - Optical device for detecting short weft in weaving machine

Info

Publication number: CN110656427A
Application number: CN201910571356.3A
Authority: CN
Inventors: L·安德烈; N·法比奥; W·詹
Original assignee: Itema SpA
Current assignee: Itema SpA
Priority date: 2018-06-29
Filing date: 2019-06-28
Publication date: 2020-01-07
Also published as: JP3238799U; IT201800006835A1; JP2020002519A; EP3587639A1

Abstract

The present invention provides an optical device for detecting short weft yarns in a weaving machine, the weaving machine control system stopping the operation of the weaving machine upon receiving a signal corresponding to the absence of weft yarns at least one predetermined weft yarn detection position, the optical device comprising: a. at least one base optical unit provided with a light emitter and a light receiver, which transmits a light signal emitted by the light emitter and received by the light receiver to the processing unit; b. at least one respective optical fiber sensor comprising two prongs supporting respective optical fibers, each optical fiber being housed in its own seat, the optical fibers converging at one end towards the weft detection position and being connected at the opposite ends respectively to the optical emitter and to the optical receiver of the base optical unit; c. a processing unit for detecting the signal, the processing unit verifying the presence or absence of a weft thread in at least one weft thread detection position for a set length of time and transmitting a warning of the absence of a weft thread to the loom control system.

Description

Optical device for detecting short weft in weaving machine

Technical Field

The present invention relates to an optical device for detecting short weft yarns in shuttleless looms such as projectile looms, air jet looms and rapier looms. As used herein, the term "short weft yarns" as used herein refers to those weft yarns which, due to the inherent elasticity of the yarn or dynamic effects in the weft insertion, attempt to return to the shed after the weft insertion is completed (even only partially), thus producing uneven flash of the weft yarn end or making the fabric significantly defective.

In particular, the optical device for detecting short weft yarns according to the invention finds an effective application whenever necessary to verify the actual presence of the weft in the different weft-holding devices (fixed or movable grippers, waste selvedges, or spreader nozzles), which may be used in the various types of weaving machines listed above, to keep the weft fully extended outwards during the period from the full insertion of the weft into the shed to the beating up of the fabric being formed by the reed.

A particularly complete and efficient application of the optical device for detecting short weft yarns according to the invention is in connection with weaving methods in which, upon introduction of a weft into a shed, the holding device of said weft consists of two grippers arranged at opposite ends of the shed, moving together with the weft towards the reed beat-up line, and thus being movable in the same direction as the reed and slightly forward.

As is known, the weaving methods described above are generally used in gripper weaving looms and therefore, in the following description, reference will be conveniently made exclusively to this type of loom, but it should be understood that this is only an illustrative and non-limiting example of a possible broader field of application of the optical device for detecting short weft yarns according to the invention, which can in fact be interestingly embodied also in other types of shuttleless looms.

Background

In a gripper weaving machine, the introduction of the weft thread into the shed formed by warp threads is currently carried out according to the general diagram shown in figure 1, which comprises a succession of different steps, reported from top to bottom, each identified by a progressive number 1 to 4. In step 1, the gripper P passes through the shed, completes the weft insertion of the weft thread T and then stops in the brake, thus moving back to the coupling position of the gripper return system which returns the gripper to the side of the loom where the weft thread T is inserted (left side in fig. 1). During the gripper return movement, while the weft thread is still stably retained by it, the weft thread tensioner is activated, which is reset in the direction indicated by the arrow towards the left of the just inserted weft thread T in the loom, to avoid slackening caused by the backward movement of the gripper P and to give the weft thread the desired tension.

In step 2, while the weft thread T still maintains tension between the weft thread-tensioner and the gripper P in the direction indicated by the arrow, two selvedge grippers Gs and Gd, which are arranged on the left and right sides of the loom, respectively, advance toward the weft thread T to hook and block the weft thread T. At the same time, the gripper P is opened, releasing the free end of the weft thread T just inserted and allowing the return movement of the gripper P from the right to the left of the loom to take place.

In step 3, the selvedge grippers Gs and Gd are simultaneously moved towards the beating-up position, moving in the direction indicated by the arrow together with the gripped weft thread T, while shed closure is started by the weaving machine (dobby) and reed R. The reed advances towards the beat-up position.

In step 4, the weft thread T is finally beaten up by the reed R and incorporated into the fabric C being formed. Thus, shortly after the weft thread T is cut on the left side of the weaving machine, the weft insertion cycle can be started again and the selvedge grippers Gs and Gd are opened in view of their continuous advancement (at the beginning of step 2) towards the insertion position of the new weft thread T.

From the above brief description, it should therefore be apparent that in a gripper weaving machine of the known type, the correct position of the weft thread T inserted last, after the weft thread has been released from the gripper P and until the beating-up step by the reed R has been completed and the shed closed, is ensured only by the correct operation of the selvedge grippers Gs and Gd, while, after the shed is closed, the weft thread is held in its correct position by the pressure exerted thereon by the crossing warp threads. However, in the known weaving machines, it is currently not possible to verify the correct operation of the selvedge grippers Gd and Gs and therefore to prevent fabric defects due to any possible failure thereof.

Selvedge gripper failure may occur in two main modes:

the selvedge gripper cannot hold the weft: this inconvenience occurs when the selvedge gripper is not correctly adjusted or it has been damaged;

the weft thread slips out of the selvedge gripper prematurely: this inconvenience occurs when the selvedge gripper wears out or becomes dirty.

Whatever the mode of failure of the selvedge gripper, in both cases the defects produced (commonly known as "short wefts") can exhibit different levels of importance:

i. the weft tail does not correctly position the weft tail in the selvage protector, so that the correct operation of a subsequent cutting device is hindered;

the weft loses a portion of the applied tension, resulting in a defect in the selvedge area of the fabric;

the weft moves back into the shed due to its own elasticity, thus creating a significant defect in the fabric.

Therefore, against the background of the prior art, the present invention has the problem of providing a weft detection device which makes it possible to verify on a gripper loom the actual presence of the weft inserted last at the left and right ends of the shed during the time period between the weft insertion and the weft beating-up by the reed, i.e. during the time the selvedge gripper is active, so that in the event of detection of the absence of a weft, the loom operation can be stopped and the weft removal cycle for the wrong weft can be started.

However, the usual optical devices for detecting the weft thread cannot be directly used to solve this problem, since these devices are too large to be installed in narrow areas (the area between the fabric edge and the selvedge gripper) where the detection of the weft thread must be carried out, since they are also very susceptible to damage by the weaving waste and therefore do not provide a reliable detection of the weft thread in sufficiently long uninterrupted times, since they must be installed in working areas which are particularly exposed to such waste. Furthermore, the operation of the known optical devices is strongly influenced by the actual lighting conditions and above all by their variations. Therefore, the sensitivity of the detection device is not as stable as desired.

Disclosure of Invention

Therefore, seeking a solution to the above-mentioned problems, a first object of the present invention is to provide an optical device for detecting a weft thread which has a very small bulk in the transverse direction of the loom (i.e. in the weft insertion direction of the weft thread).

Another object of the present invention is to provide an optical device for detecting weft threads which is less susceptible to weaving waste and therefore capable of operating uninterruptedly for a sufficiently long time before cleaning interventions are required.

Another object of the present invention is to provide an optical device for detecting weft threads provided with an alarm system apt to promptly give an alarm when a critical condition of the optical signal is reached, which requires a cleaning operation of the optical equipment due to the accumulation of knitting waste.

Finally, it is a further object of the invention to provide an optical device for detecting weft threads which is independent of any variation of the actual lighting conditions.

This problem is solved and these objects are achieved by an optical device for detecting short weft yarns, comprising the features defined in claim 1. Further preferred features of the optical device are defined in the dependent claims.

Drawings

Further characteristics and advantages of the optical device for detecting short weft yarns according to the present invention will become more apparent from the following detailed description of a preferred embodiment of the invention, given as a mere and non-limiting example and illustrated in the accompanying drawings, wherein:

FIG. 1 is an operational diagram of a gripper weaving machine of known type, showing the progressive weft insertion and beating-up;

FIG. 2 is a perspective view of a fiber optic sensor and associated support, which are part of an optical device for short weft yarns according to the invention mounted at the right end of the shed;

FIG. 3 is a side view of an end portion of the fiber optic sensor of FIG. 2; and

fig. 4 is a side view of the fiber sensor of fig. 2 without its support and taken from the opposite side with respect to the side shown in fig. 2, i.e. the side where the optical fibers are accommodated.

Detailed Description

According to the invention, in order to solve the above-mentioned problems, the application of an optical device for detecting weft threads is proposed, which comprises three distinct elements, namely a base optical unit, an optical fiber sensor and a processing unit of the detection signal. The base optical unit comprises an optical transmitter and an optical receiver for generating and receiving signals, for converting the signals into suitably filtered electrical signals (i.e. detection signals), and for analog transmission of the signals. On the other hand, the optical fiber sensor, which provides the transmission of the optical signal from the base optical unit to the weft detection position and vice versa, consists of a plate having two prongs, each provided with an optical fiber housed in a respective seat, said optical fibers converging at one end towards the weft detection position and being connected at the opposite ends respectively to said optical emitter and optical receiver. Finally, the processing unit of the analog signals coming from the photoreceiver comprises a Digital Signal Processor (DSP) which performs an analog-to-digital conversion of the analog signals coming from the photoreceiver and then a logical interpretation of the converted digital signals to verify the presence or absence of weft threads and also communicates with the loom control system.

Thanks to this structure, the optical fiber sensor can therefore be easily and efficiently arranged in a narrow area of the weft channel (housed in a less important position in case of bulk) that needs to be monitored by using the optical signal coming from a nearby elementary optical unit (not shown in the figures), then the optical signal is transmitted back to the elementary optical unit again to be converted into an electrical signal, and the subsequent digital conversion and signal analysis are carried out by the processing unit that detects the signal.

Optical fiber sensor

In the drawings, there is shown a preferred embodiment of a fibre-optic sensor of the present invention. As can be clearly seen in fig. 2, the optical fiber sensor simply consists of a plate 2 with two prongs, having a small thickness in the weft insertion direction, in which the

optical fibers

3 and 4 are firmly accommodated. The plate 1 is arranged laterally with respect to the warp W and the fabric being formed, in the gaps between the warp W and the fabric being formed and the selvedge grippers Gs and Gd on both sides of the loom, respectively.

In fig. 4, which shows the side of the plate 1 opposite to the plate 1 shown in fig. 2 and 3, it can be seen that the plate comprises an upper prong 1T and a lower prong 1b separated by a cavity 2, and the free ends 1e of said prongs face each other at a sufficient distance to allow passage of a weft thread T into the cavity 2. Longitudinal grooves are further formed in the thickness of said

prongs

1t and 1b, which provide housing seats for the respective

optical fibres

3 and 4. The housing seats extend from the free ends 1e of the

prongs

1t and 1b up to the opposite end of the plate 1 and are formed so as to be perfectly aligned at the free ends of the prongs and, moreover, to conform in the curved portion thereof to a minimum permitted radius of curvature which does not compromise the integrity of the

optical fibres

3 and 4 housed in the curved portion. Thus, the correct positioning of the

optical fibres

3 and 4 on the plate 1, in particular their optical alignment at the free end 1e, is therefore very simple, making it possible to form a detection beam L with high efficiency from the optical fibre 3 to the optical fibre 4, the optical fibre 3 being connected to the optical transmitter of the elementary optical unit and the optical fibre 4 being connected to the optical receiver of the same elementary optical unit. In order to provide the above-described optical fibre sensor with the required structural rigidity, the plate 1 is preferably formed from a suitable metal material and is fixed to a support base 5 integral with the loom, for example by screws housed in holes 6, despite its thin thickness.

The shape of the cavity 2 provided inside the plate 1 is not particularly restricted, but only needs to be long enough and wide enough to prevent any possible contact between said prongs 1T and 1b and the weft thread T (carried by the selvedge grippers Gd, Gs and reed R) sliding inside the cavity 2, moving along the line F between a weft insertion position Ti and a weft beating-up position Tb in which the weft thread is beaten up against the fabric C being formed.

As shown in fig. 3, the optical device for detecting a weft thread of the invention in fact verifies the presence of the weft thread T during the return movement of the selvedge grippers Gs, Gd from the weft insertion position Ti, in which the weft thread is gripped by said selvedge grippers Gs, Gd, towards the weft beat-up position Tb (against the fabric C being formed), and therefore just before the shed is closed. In fact, any weft thread that may be lost by the selvedge gripper after the shed has closed is irrelevant, since such a weft thread does not in any case lead to defects in the fabric.

The optical device for detecting weft threads according to the invention performs an optical control of the barrier type: the light beam generated by the light emitter of the base optical unit is transmitted practically along the optical fiber 3 up to the free end of the prong 1t, where it is transmitted to the optical fiber 4 housed in the prong 1b, forming a light beam L for detecting the weft thread passing through the free space between the opposite free ends of the two

prongs

1t and 1 b. The optical signal is then carried by the optical fibre 4 to an optical receiver housed in the base optical unit, which converts the optical signal into an electrical signal. The electrical signal is then converted to a digital signal and monitored by a Digital Signal Processor (DSP) disposed within the processing unit that detects the signal.

The weft thread T passes through a light beam L formed between the two opposite free ends of the prongs 1T and 1b, intercepting it partially or totally, generating an electrical signal of repeatable variation in amplitude, shape, length and time with respect to the work cycle of the loom. As will be described in more detail below, the DSP is programmed according to a suitable algorithm which makes it possible to identify the presence or absence of such varying electrical signals and thus verify the actual passage of the weft thread. When no electrical signal is detected that there is such a change, the DSP will send a warning signal to the loom control system to stop it, allowing the usual manual or automatic intervention to repair the short weft yarns.

Electronic infrastructure

From a logical point of view, the electronic infrastructure of the optical device for detecting short weft yarns according to the invention comprises two distinct parts: controlling analog front ends of the optical transmitter and the optical receiver; and a digital back end that provides analog to digital conversion of the signal, processing of the digitized signal, and any communication with the loom control system. From the point of view of the physical components of the device, the optical device for detecting short weft yarns according to the invention comprises: two electronic cards comprising analog front ends arranged on both sides of the loom; and a main electronic card including a pair of digital back-ends and associated wiring.

The analog front end supervises the following functions:

-directing a light emitter

The transmitter is directed by a PWM modulated square wave current having a constant and known frequency and duty cycle. The current intensity during the phase in which the square-wave current is switched on is defined and set by the digital back-end.

-processing the signal from the optical receiver

The received signal has the same harmonic content as the transmitted signal. The signal is amplified, filtered and demodulated to extract its information content useful to the digital back end. The optical device of the invention is rendered insensitive to any possible continuous or alternating components of the signal having a different frequency than the pilot frequency (such as those related to ambient lighting) due to the respective filtering operations of the pilot and received signals of the square wave current.

Analog interface to the backend

The input and output analog stages provide an interface between the analog front end and the digital signal processing back end.

The digital back end supervises the following functions:

-supply of electricity

All necessary voltage levels for the front and back ends are generated locally starting from the main power supply of the loom at a low voltage (standard 24V voltage). Overcurrent and short circuit protection is typically provided for the supply phase.

-generating a reference signal for the front-end

The desired current level of the optical transmitter is processed by the back-end and transmitted to the front-end via the buffered analog reference.

-digital processing of the signal from the front end

The analog signals received by the front end are converted to digital signals and then processed by the back end through special control algorithms running on the DSP.

-communicating with a loom control system

The operation of the optical device for detecting short weft yarns according to the invention must be perfectly synchronized with the various operating steps of the loom. The exchange of information between the back-end and the weaving machine takes place via a field bus (CANBUS) and suitable digital signals.

DSP control algorithm

Two copies of the same control algorithm are run simultaneously on two DSPs, one for the right side of the loom and one for the left side of the loom.

By analyzing the digital signal in the DSP, it is made possible for the algorithm verifying the presence of a weft thread to comprise three different subsequent operating steps, which are closely related to the three different periods of each individual weft insertion cycle in the weaving machine.

1. Wait for

In this first operating step, which corresponds approximately to the period of time running between the weft beat-up and the subsequent weft presentation, the algorithm monitors only the digital signal coming from the front end to adjust its amplitude and confirm the absence of noise.

2. Alignment of

The second operating step is activated between two well-defined working positions of the loom, which can be set as desired during the weaving cycle in which weft thread presentation takes place; before the weft insertion starts, the second operating step ends in any case. Thus, during this alignment step, there is no weft channel corresponding to the optical fiber sensor, so the signal from the optical receiver of each sensor is analyzed to identify its different characteristics, such as amplitude, signal-to-noise ratio, and other possible characteristics, which is then stored by the algorithm as a standard reference signal for the subsequent detection step of the weft.

3. Detection of

This step is activated at the end of the preceding step, i.e. before the start of weft insertion, and ends at the time of weft beating-up, which can be set as desired in a well-defined working position of the weaving machine. In this step, the DSP analysis identifies each variation in the characteristics of the detected signal, in particular the digital signal duration and amplitude and the background noise level caused by the passage of the weft thread, with respect to the standard reference signal detected in the alignment step. The analysis of said variations comprises their comparison with the predefined and parameterized acceptable ranges of the characteristics reported above, in order to verify the presence or absence of a weft thread in the expected detection position. The parameters defining the acceptable ranges mentioned above may be set by the user or may be calculated by the algorithm itself by a self-learning program. When the analyzed result is that no weft thread exists, the DSP sends out a warning to a loom control system to stop the machine.

In the alignment and detection steps, usual data filtering techniques are applied to make the algorithm less sensitive to any noise, whether optical or electromagnetic. In each of the previous operating steps, the algorithm also monitors the quality of the signal in view of amplitude and noise, and if necessary, generates an alarm message to the loom control system.

In addition to the above-described operating steps, the control algorithm of the optical device for detecting short weft yarns according to the invention accomplishes other control and supervision tasks that are performed after a strictly predetermined time schedule. The main tasks among these are as follows:

-adjusting the pilot current

The guiding current of the optical transmitter is not a constant current but is continuously adjusted based on the signal detected by the optical receiver from time to time. Continuous adjustment of the pilot signal by the PID adjuster allows the detected signal to be maintained within a desired operating range despite the presence of external factors that reduce the optical efficiency of the device. These elements can be dirt and wear on the end portions of the

optical fibres

3 and 4, possible mechanical misalignment between the opposite ends of the optical fibres, and finally also loss of light emitter efficiency over time.

-quality assessment of the detection signal

A range of values corresponding to a satisfactory quality of the detection signal is predefined and stored in the DSP based on the output/input ratio of the signal itself. The predefined range of these values allows to set warning and alarm thresholds, which, if reached, are activated by the operator to restore correct operability. This evaluation of the signal quality also makes it possible to quickly evaluate the suitability of the optical device for first installation.

Remote configurability and data communication

The optical means can be adjusted by communication of some parameters of the loom control system, which can be changed, if necessary, according to the different weft threads being processed. This two-way communication occurs on the field bus and is independent for each side of the loom. Similarly, the back end communicates with the loom, controlling the basic operating parameters of the optical device to allow monitoring thereof. The same communication channel is used for real-time communication of the latitude detection result.

Optimization of detection parameters by self-learning

In addition to the direct parameterization of the optical means driven by the loom control system, the optical means of the invention are also able to activate a self-learning program to identify the optimal parameters for the detection algorithm. Such a self-learning procedure may even be applied to only some of the different types of weft threads being processed on the weaving machine, if desired.

From the foregoing description it is clear how the optical device for detecting short weft threads of the present invention fully achieves the intended objects. In fact, thanks to the use of an optical fiber sensor separate from the optical unit for sending and receiving optical signals, it is possible that the optical sensor has a flat and thin shape which allows to easily insert the optical sensor in narrow areas where the presence of weft threads has to be detected. Moreover, the sheet shape of the optical fiber sensor makes such a sensor less prone to the accumulation of textile waste and therefore able to provide satisfactory performance for a sufficiently long uninterrupted period of time between two subsequent cleaning interventions. Furthermore, due to the quality evaluation function of the detection signal included in the DSP control algorithm, it is possible to perform such cleaning interventions in a targeted manner and only when such interventions are really needed for restoring the optical signal efficiency. Finally, it should be noted that, thanks to the particular square-wave current guidance of the light emitters and the corresponding filtering operation of the received signals with the same frequency and duty cycle, the optical device of the invention is completely insensitive to the particular ambient light conditions and their variations, thus keeping the sensitivity of the weft detection constant.

It is to be understood, however, that the invention is not to be considered limited to the particular arrangements shown above, which are merely exemplary embodiments of the invention, and that various modifications are possible, all within the ability of those skilled in the art, without departing from the scope of the invention, which is limited only by the claims appended hereto.

Claims

1. An optical device for detecting short weft yarns in a loom in which a weft yarn (T) is subsequently inserted into a shed formed between warp yarns and is therefore beaten up by a reed (R) against the fabric (C) being formed, in which a loom control system stops loom operation upon receiving a signal corresponding to the absence of a weft yarn in a predetermined at least one weft detection position, characterized in that it comprises:

a. at least one base optical unit provided with an optical transmitter and an optical receiver, wherein,

a1. the optical transmitter is directed by a pulse width modulated square wave current having a constant frequency and duty cycle to transmit an optical signal towards the optical receiver;

a2. the optical signal is received by an optical receiver and converted into an analog electrical signal;

a3. the analog electric signal is processed in a filter with the same frequency as the current frequency of the guide light emitter, so that the filtered analog electric signal is used as a detection signal;

a4. transmitting the detection signal to a processing unit;

b. at least one respective optical fiber sensor comprising two prongs (1t, 1b) supporting respective optical fibers (3, 4), each fiber being housed in its own seat, said optical fibers (3, 4) converging at one end towards said weft detection position and being connected at the opposite ends respectively to said light emitter and light receiver of said elementary optical unit;

c. a processing unit of the detection signal, the processing unit verifying the presence or absence of a weft thread within a set length of time in the at least one weft thread detection position.

2. Optical device according to claim 1, wherein the prongs (1t, 1b) of the optical fiber sensor are formed in a plate (1) having a small thickness along the weft insertion direction, the plate (1) being arranged laterally to the warp (W) and to the fabric being formed.

3. Optical device according to claim 2, wherein the plate (1) comprises an upper prong part (1T) and a lower prong part (1b) separated by a cavity (2), the free ends (1e) of the prong parts (1T, 1b) ending facing each other with a sufficient distance to allow passage of the weft thread (T) inside the cavity (2) during the beating-up movement of the reed (R).

4. Optical device according to claim 3, wherein a longitudinal groove is formed in the thickness of the prongs (1t, 1b), which provides a housing seat for the optical fibres (3, 4), said longitudinal groove extending from the free ends (1e) of the prongs (1t, 1b) up to the opposite ends of the plate (1), being perfectly aligned at the free ends (1e) of the prongs, and also having, in their curved portion, a minimum radius of curvature not less than a minimum radius which allows the integrity of the optical fibres (3, 4).

5. Optical device according to claim 4, wherein said plate (1) is made of a metallic material and is fixed by screws to a supporting base (5) integral with said loom structure.

6. Optical device according to claim 1, wherein the current intensity during the phase of switching on a square wave current is defined and set by the processing unit detecting the signal.

7. The optical apparatus according to any one of the preceding claims, wherein the processing unit of the detection signals performs the following functions: supplying power; generating a standard reference signal for controlling the intensity of the pilot current of the light emitter; performing analog-to-digital conversion on the filtered electrical signal from the base optical element; obtaining digital processing of the digital signal by a control algorithm running on a Digital Signal Processor (DSP); communicating with a loom control system.

8. The optical apparatus of claim 7, wherein the control algorithm comprises:

a. a first operating step, which substantially corresponds to the period of time running between the weft beat-up and the subsequent weft presentation, in which the signal coming from the base optical unit is monitored to adjust the amplitude of the signal and verify the absence of noise;

b. a second operating step, which substantially corresponds to the period of time during which the presence of the weft thread occurs, in which the signal coming from the base optical unit is analyzed in order to identify its different characteristics, said signal being considered as a standard reference signal with respect to the subsequent third operating step;

c. a third operating step, which substantially corresponds to the period of weft insertion and beating-up, wherein any variations in the duration and amplitude of the digital signal detected and in the level of background noise caused by the passage of the weft at the weft detection position are analyzed by comparison with respective predefined and parameterized acceptable ranges, with respect to the standard reference signal detected in the preceding second operating step; based on said comparison, the presence or absence of a weft thread in the weft thread detection position is thus verified, and, in the absence of a weft thread, a warning of the absence of a weft thread is sent to the textile machine control system.

9. Optical device according to claim 8, wherein the working steps of the algorithm start and end at predetermined working positions of the loom.

10. The optical apparatus of claim 8, wherein the algorithm further performs the following control and supervisory tasks: adjusting a pilot current of the light emitter; performing quality evaluation on the detection signal; and (5) self-learning optimization of detection parameters.

11. Optical device according to any one of the preceding claims, in which the weaving loom is a gripper weaving loom and the optical fibre sensors are arranged on both sides of the gripper weaving loom in the gap between the warp W and the fabric being formed on one side and the selvedge grippers (Gs, Gd) on the other side.

12. Optical device according to any one of claims 1 to 10, in which the weaving loom is a gripper loom and the optical fiber sensors are arranged on both sides of the weaving loom in the gap between the warp W and the fabric being formed on one side and the retaining means of the free end of the weft tail on the other side.

13. The optical device according to any one of claims 1 to 10, wherein the loom is an air loom and the optical fiber sensor is arranged on a weft insertion side in a gap between a warp W located on one side and a fabric being formed and a weft holding gripper located on the other side.