Gripper loom including weft insertion system and automatic control method

Abstract

The present invention relates to a loom and a control method thereof comprising an optical device for monitoring the wear of a gripper belt. A gripper loom comprising a weft insertion system comprises an optical device for monitoring the wear condition of at least one of the gripper belts, a memory unit and a comparison unit, the optical device comprising: a light source having a predetermined wavelength and emitting optical radiation to the surface of the gripper belt when the gripper belt moves, a sensor detecting the intensity of the optical radiation reflected by the gripper belt during the movement and emitting a corresponding sequence of electrical signals, and an acquisition device and a buffer memory for acquiring the sequence of electrical signals and transmitting the electrical signals converted into digital signals to a central control unit of the loom, in the memory unit the digital signals are stored as a historical sequence of optical profiles of the gripper belt at the wavelength at subsequent times, the comparison unit comparing the processed latest optical profile with the stored historical sequence of optical profiles and providing an evaluation of the progressive wear condition of the gripper belt.

Description

Technical Field

[0001] The present invention relates to a loom comprising an optical device for monitoring the wear of a flexible strap driving two grippers for weft insertion in a gripper loom (hereinafter simply referred to as "gripper strap"). In particular, the present invention relates to a control device for continuously monitoring the wear of the gripper strap and sending an alarm signal to a central control system of the loom before the gripper strap wear reaches a level that endangers its mechanical strength.

[0002] The invention also relates to an automatic control method of the loom. Background Art

[0003] It is known to those skilled in the art and Figure 1 As shown schematically in FIG. 1 , in a gripper loom, the alternating movement of the weft-sending gripper and the weft-taking gripper is controlled by means of two flexible gripper belts T, to which the weft-sending gripper or the weft-taking gripper is respectively fixed at one end, so as to introduce the weft yarn into the shed formed by the warp yarn. The alternating movement of each of the two gripper belts is generated by a respective gear W, the teeth of which mesh with a series of continuous eyelets F formed along the central part of the gripper belt T. Thus, in operation, the gripper belt T behaves as a flexible rack controlled by a gear; in fact, a pair of metal guide slides S forces the gripper belt T to bend, adheres to a sector of the gear W, the sector being wide enough to transmit the movement to the belt T without causing excessive local stress on the eyelets F, and guides the gripper belt T to the area below the loom when the gripper is in a position outside the shed.

[0004] The deformation of the gripper belt around the gear W caused by the guide slide S results in a continuous dragging friction between the surface of the guide slide S and the outer surface of the belt T, since the belt tends to maintain its original rectilinear shape. Further friction phenomena then occur between the outer side edge of the gripper belt T and the metal guide hooks arranged along the shed, which allow the gripper belt T to be pulled back and maintain its rectilinear shape, thus driving the gripper belt T through the shed in the desired direction. The friction generated by the rapid drag of the gripper belt T in the guide slide S and the guide hooks results in a progressive wear of the surface of the gripper belt T until it becomes no longer usable in a safe condition.

[0005] The flexible gripper belt is actually made by stacking several layers of material with different compositions and functions. The surface of the gripper belt that is subject to friction and thus the wear phenomenon is the outermost layer, which consists of a layer of plastic material (e.g. polyamide) to which PTFE-based fillers are added in order to reduce the friction coefficient. Immediately below the outermost layer, there are additional layers that form the structure of the gripper belt and determine its mechanical characteristics (such as flexibility, dimensional stability and strength). When the outermost layer is completely worn, the friction coefficient of the gripper belt increases sharply, which greatly accelerates the wear phenomenon and requires the gripper belt to be replaced within a short period of time.

[0006] However, gripper band wear is not a regular phenomenon as it is governed by several concurrent factors which together determine the gripper band wear rate including:

[0007] - loom operating speed;

[0008] - operating temperature;

[0009] - the gap between the gripper belt and the guide slide;

[0010] - incorrect assembly of the gripper strap;

[0011] - Incorrect loom adjustment.

[0012] Thus, predicting the optimal time to replace the gripper belt is currently a rather tricky operation, which requires the intervention of specialized weavers who know how to correctly assess the remaining usable life of the gripper belt based on its appearance. Indeed, replacing the gripper belt too early obviously leads to a waste of resources and economic losses, while using excessively worn gripper belts for a long time carries a serious risk of failure of the gripper belt, which may cause damage to the textile being processed and to the same parts of the weaving machine.

[0013] The problem addressed by the present invention is thus to automate the assessment of the actual wear condition of the gripper band, with the aim on the one hand of optimizing the full use of the gripper band, avoiding excessive pre-replacement of the gripper band, and on the other hand of avoiding any risk of unexpected gripper band failure during the weaving process.

[0014] In solving this problem, a first object of the present invention is to define a technique for detecting the condition of wear of a gripper band, on the basis of which the condition of progressive wear of the gripper band can be effectively and continuously evaluated, said detection not being affected by unpredictable variables attributable to the inherent properties of the individual gripper bands used, as well as by possible surface modifications of the gripper band that may occur during the weaving process (such as different coloring of the gripper band caused by color transfer of the processed yarn).

[0015] A second object of the invention is then to provide a device for monitoring the wear condition of a gripper belt which can be mounted on a weaving machine without creating additional bulk and which is not affected by variable external conditions of the weaving environment, such as light and dust.

[0016] Finally, a third object of the present invention is to integrate the device for monitoring the wear condition of the clamp belt into the overall control system of the loom so that the wear state detected on the clamp belt can be used to directly act on the working condition of the loom, usually by reducing the operating speed to ensure the safe progress of the weaving operation while waiting for the worn clamp belt to be replaced. Summary of the invention

[0017] The above problems are solved and the above purposes are achieved by means of the following technical solutions:

[0018] A gripper loom comprising a weft insertion system, wherein, in a shed formed by warp yarns, a weft delivery gripper and a weft joining gripper are driven by alternating motion by means of a pair of gears (W) with the aid of corresponding flexible gripper belts (T), said corresponding flexible gripper belts (T) carrying said weft delivery gripper and said joining gripper, respectively, at one end, said gripper belt (T) being engaged with said gears (W) through a series of holes formed longitudinally in the body of said gripper belt (T) and being kept attached to a sector of said gears (W) by means of a guide slide (S), the operation of said system being controlled by a central control unit (LCU) of the loom, said loom further comprising:

[0019] An optical monitoring device for monitoring the wear condition of at least one of the gripper strips (T), the optical monitoring device comprising

[0020] at least one light source (2) having a predetermined wavelength and emitting light radiation towards the surface of the gripper belt (T) when the gripper belt (T) moves,

[0021] at least one sensor (3) which detects the intensity of the light radiation reflected by the gripper belt (T) during the movement of the gripper belt (T) and emits a corresponding sequence of electrical signals,

[0022] It is characterized in that it also includes

[0023] an acquisition and buffer memory device, which acquires the electrical signal sequence and transmits the electrical signal converted into a digital signal to the central control unit (LCU) of the loom,

[0024] a memory unit, wherein said digital signal is saved as a historical sequence of optical profiles of said gripper strip (T) at said wavelength at subsequent times, and

[0025] A comparison unit that compares the latest optical profile processed with a historical sequence of saved optical profiles and provides an assessment of the progressive wear condition of the gripper strip (T).

[0026] Further preferred features of the device for monitoring the wear condition of the gripper strip are defined in the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Other features and advantages of a weaving machine including a device for monitoring the wear condition of a gripper belt according to the invention will become more apparent from the following detailed description of a preferred embodiment of the invention, provided purely as a non-limiting example, and illustrated in the accompanying drawings, in which:

[0028] Figure 1 is a schematic front view of a gripper loom showing the basic elements of the yarn delivery system described in the background section of this specification;

[0029] Figure 2 is a plan view of a portion of a gripper belt;

[0030] Figure 3 is a perspective top view of an optical detector of the upper surface of a gripper belt as part of an apparatus for monitoring the wear condition of a gripper belt according to the present invention;

[0031] Figure 4 yes Figure 3 A bottom view of an optical detector;

[0032] Figure 5 is a block diagram showing the electronic infrastructure of the monitoring device of the present invention. DETAILED DESCRIPTION

[0033] As a result of numerous studies by the Applicant on monitoring the wear condition of gripper strips, it was eventually discovered that the only detection technology that allows achieving the desired goal of continuously and efficiently measuring the condition of the gripper strips is a detection technology based on optical measurements. In fact, these experiments demonstrated that the optical measurement of the reflectivity variations of the gripper strip surface affected by wear - both in terms of the spectral content and the intensity of the reflected radiation - relative to the intact surface of the same gripper strip allows an objective, reliable and reproducible assessment of the wear condition of the gripper strip. The optical measurements can also be performed smoothly on a moving gripper strip, thus allowing the exploration of wide surfaces of the gripper strip subject to wear phenomena; they require a limited installation volume and lend themselves to being subsequently processed automatically in order to obtain an optical profile of the gripper strip - here "optical profile" means an ordered sequence of information about the intensity of the reflected radiation detected at different wavelengths along a test face of a gripper strip of predetermined width and length - which the Applicant found to be a good representation of the wear condition of different portions of the gripper strip, especially in a comparative analysis of historical sequences of optical profiles detected of the same gripper strip. These optical profiles are then automatically compared at predetermined intervals with predetermined reference thresholds of reflected radiation, thereby enabling automatic assessment of the most correct time to replace a worn gripper strip.Based on the results of this successful experiment, a device for monitoring the wear condition of a gripper strip according to the invention was conceived.

[0034] In the preferred embodiment described herein, the monitoring device comprises two separate optical detectors 1, each arranged on a respective gripper strip T, and an electronic infrastructure 10 for processing the electrical signals coming from the optical detectors 1. Conceptually, and also physically, the electronic infrastructure 10 comprises three different components: a FE front end for the acquisition and digitization of the signals, a BE back end for the control and transmission of the signals, and finally a central control unit LCU of the loom, within which the synchronization and planning of the signal acquisition, the storage and processing of the detected optical profiles, and the evaluation of the gripper strip wear condition are carried out.

[0035] Optical detector

[0036] Each optical detector 1 comprises at least one LED light source 2 and a sensor 3, which are oriented to each other in such a way that the light emitted by the light source 2 and reflected by the surface of the gripper strip T is mainly focused on the sensor 3. According to the invention, the optical detector 1 is advantageously placed adjacent to the relative guide slides S in order to minimize the overall volume. As mentioned above, each gripper strip T is usually equipped with two guide slides S ( Figure 1), it is therefore desirable that the optical detector 1 is placed in the immediate vicinity of the guide slide 8 arranged in the upper part of the loom. This position is desirable because it is easier to access and because the optical detector 1 can here control the subsequent entry into the shed, thus the entire portion of the gripper belt T to which the friction forces formed by the guide slide S, the guide hooks and the warp yarns exert the greatest stress. In order to further reduce the overall volume, the optical detector 1 can also be incorporated into the upper guide slide S so that a single device must be installed.

[0037] The optical detector 1 is fixed to the guide rail R of the gripper strip T in a manner known per se, by means of a fixing plate P and suitable screws. The optical detector 1 comprises a light source 2 emitting radiation incident on the gripper strip T, and a sensor 3 detecting radiation reflected by said gripper strip T, the light source 2 and the sensor 3 being arranged immediately behind a window formed in the lower surface of the optical detector 1, facing the channel 4 in which the gripper strip T slides, and being closed by a sheet of glass or another suitable material transparent to the wavelength of interest, such as Figure 4 Thus, the illumination of the gripper strip T by the light source 2 and the detection of the radiation reflected by the gripper strip T by means of the sensor 3 take place at a location completely shielded from light conditions and ambient dust by the same body of the optical detector 1 .

[0038] For the light source 2, according to the invention, LEDs with different very narrow band wavelengths are used both in the visible radiation range (RGB) and in the infrared radiation range (IR). The analysis of the reflected radiation of the multiple radiations emitted at different wavelengths makes it possible in practice to minimize disturbances, such as those caused by the deposition of colored substances on the gripper tape by the processed yarn, or by different types of gripper tapes available on the market or by color variants of the same type of gripper tape; in fact, the color variations of the gripper tape that follow will only disturb the reflected radiation for some of the wavelengths of the emitted radiation, while the reflected radiation for the other wavelengths will remain unchanged, so that it is always possible to elaborate a significant optical profile based on the reflected radiation of said other wavelengths, and then to carry out an analysis of the wear condition of the gripper tape T on this basis.

[0039] As mentioned in the background section, wear of the gripper strip T occurs over the entire upper surface of the gripper strip T due to friction with the guide slide S, wear of the gripper strip T occurs on the upper and lower surfaces of the gripper strip due to friction with the warp threads, and wear of the gripper strip T occurs mainly on the side edges of the gripper strip due to friction with the guide hooks in the shed. Thus, the side areas U of the upper surface of the gripper strip T adjacent to the eyelets F are undoubtedly the areas that are more susceptible to wear. For this reason, according to the invention, the optical analysis of the wear condition is carried out precisely in said area U, so that in order to monitor these two areas simultaneously, in the preferred embodiment of the invention illustrated in the figure, the optical detector 1 is equipped with a corresponding side area U of the gripper strip ( Figure 2 A pair of sensors 3 are arranged precisely (schematically indicated by dashed lines in FIG. 1 ), each sensor 3 being coupled to two respective light sources 2, namely an infrared LED 2r emitting infrared radiation and a visible light LED 2v emitting visible light radiation in the three primary colors of the RGB color model. Both the infrared LED 2r and the visible light LED 2v are mounted in the optical detector 1 in an orientation that directs most of the radiation reflected by the clamper strip T in the direction of the corresponding sensor 3.

[0040] The optical detector 1 then illuminates the gripper strip T at predetermined intervals by each light source 2 in a corresponding independent operation of the gripper strip T and acquires, by means of the sensor 3, the intensity of the radiation reflected by the gripper strip T. From these data, a complete optical profile of the intensity of the reflection along the gripper strip is extracted and saved, said optical profile comprising all four frequencies of the radiation emitted by the light source 2. In fact, the Applicant has found by experiment that any possible worn portion of the gripper strips, due to their different reflectivities, causes a recognizable alteration of the reflected radiation localized to well-defined locations of the optical profile. These locations are then matched by equally well-defined areas of the gripper strip T, since the process of acquiring the radiation reflected by the gripper strip T is precisely synchronized with the movement of the loom.

[0041] Typically, the analysis of the wear condition of the gripper strip T is divided into the following stages:

[0042] 1. With respect to a new holder tape T or a holder tape T without any obvious signs of wear, acquiring and storing an initial reference optical profile;

[0043] 2. Obtaining an optical profile of the length of the gripper tape T undergoing optical inspection at regular intervals;

[0044] 3. comparing the values ​​of the current optical profile corresponding to various areas of the gripper belt that experience different wear conditions;

[0045] 4. Compare the current optical profile with the initial optical reference profile and with a historical sequence of previously acquired optical profiles;

[0046] 5. Evaluate the average wear condition of the clamp belt T in use;

[0047] 6. Identify any areas of the gripper band T that show a wear condition different from the average wear condition due to localized wear.

[0048] Electronic infrastructure for optical signal processing

[0049] front end

[0050] The front end FE is mounted in duplicate on two identical electronic boards associated with the two optical detectors 1, as described above. Each front end FE comprises the following functions.

[0051] Gripper with light

[0052] The gripper strip T is illuminated by a pair of light sources 2 formed by an RGB LED and an IRLED for each sensor 3. The relative positioning between the sensors 3 and the light sources 2 is such as to maximize the convergence of the radiation reflected by the gripper strip T on the sensors 3 and thus the sensitivity of the system. For the same reason, the wavelength of the radiation emitted by the light source 2 is chosen at the peak of the sensitivity of the sensors 3. Thanks to the above-mentioned positioning of the light sources 2 and the sensors 3, the body of the optical detector 1 prevents ambient light from reaching the gripper strip T and thus changing the readings of the sensors 3, which makes it possible to avoid laborious modulation and filtering techniques of the reflected radiation.

[0053] Acquisition and digitization of radiation reflected by the holder strip T

[0054] As sensor 3, preferably an analog phototransistor or photodiode is used, since they are characterized by a high acquisition rate of the reflected radiation; this allows the detection of the reflected radiation to be carried out in fact under normal weaving conditions, without then having to interrupt the process or wait for the loom to stop. Of course, it is also possible to use a digital sensor, which however generally offers a much lower acquisition rate; in this case, then, the detection of the reflected radiation must be carried out during production stops and by moving the loom at a low speed using the so-called "slow motion weaving" function.

[0055] The intensity of the reflected radiation is detected by the sensor 3 and converted directly into an amplified analog electrical signal suitable for digitization in an analog-to-digital converter by the sensor 3. The selection of the channels to be converted, the conversion rate and the order of the channels are completely managed by the back end.

[0056] Send digital signal to the backend

[0057] The digitized signal is sent to the back end through a high-speed serial interface on a differential channel to improve anti-interference capabilities.

[0058] rear end

[0059] The rear end BE is mounted on an electronic board. This board is connected on one hand to the two electronic front end FE boards and on the other hand to the central control unit LCU ( Figure 5 ). The backend BE includes the functions shown below.

[0060] LED lighting dimming and other front-end controls

[0061] The power supply of the light-emitting diodes constituting the light sources 2r and 2v is a constant current modulated at a different specific value for each of the four emission wavelengths. This allows obtaining, at different wavelengths of incident light, for each frequency of the emitted optical radiation, the amount of light required to compensate for the nonlinearity of the sensitivity of the sensor 3, so as to obtain, for each identical illuminated area of ​​the gripper strip T, a detection signal of the reflected radiation with a constant intensity, whatever the wavelength of the incident light. In a similar manner, the above-described modulation of the constant supply current of the LEDs makes it possible to simultaneously compensate for the nonlinearity of different types of LEDs, in terms of the emitted light intensity / supply current ratio.

[0062] Within certain limits, as described more fully below, modulation of the constant current of the power supply also makes it possible to compensate for the degradation of the detection signal caused by accumulation of dust on the transparent window protecting the light source 2 and the sensor 3 .

[0063] The back end also controls other front end FE functions, in particular the management of the analog to digital converters.

[0064] Receives digital signals from the front end and transmits these signals to the central control unit of the loom

[0065] The differential signals from the two front ends FE, representing the intensity of the radiation reflected along the sweep area of ​​the two gripper strips T, are converted in common mode and provided as input to the DSP of the back end BE for subsequent transmission to the central control unit LCU of the loom.

[0066] The back end BE acquires this data sequence in a buffer memory at a high transmission rate (bit rate) substantially corresponding to the acquisition rate; it then briefly keeps the last acquired data sequence available to the central control unit LCU of the loom until the acquisition of the next sequence using a different light source 2.

[0067] This delay allows to optimize the transmission speed of the communication between the back end BE and the central control unit LCU of the loom at a value much lower than the rate at which the sensor 3 acquires the data of the radiation reflected by the gripper strip T, thus avoiding unnecessary blocking of the communication channel towards said central control unit LCU of the loom, while keeping intact the original detected data sequence without the need for subsampling or decimation. The transmission is carried out with serialized data sent by a dedicated protocol and through a high-speed serial interface on differential channels, in order to improve its immunity to interference.

[0068] Once the transmission of the data sequence to the central control unit of the weaving machine has been completed, the buffer memory is emptied and the DSP of the BE backend is ready to receive new acquisitions with a different light source 2 .

[0069] Central control unit for weaving machines

[0070] A dedicated software module is integrated into the software of the central control unit LCU of the loom to process the data obtained from the back end BE and ultimately evaluate the gripper belt wear condition. The main functions of this software module are as follows.

[0071] Acquired angle synchronization

[0072] Firstly, the acquisition of data from the front end FE is synchronized with the angular position of the loom, so as to limit the acquisition only to the periods of the weft insertion cycle in which the gripper tape T actually moves under the sensor 3, and only to the areas of the gripper tape whose detection is of interest. Furthermore, a high degree of consistency of the synchronization between successive different acquisitions is also indispensable in order to make the detected data correspond exactly one-to-one to the different sweeping areas of the gripper tape T, and in order to be able to make a significant comparison between the optical profiles of the gripper tape T acquired in subsequent time periods.

[0073] Plan acquisition

[0074] The frequency of data acquisition for each side of the loom, and thus for each of the two gripper strips T, and also the sequence of wavelengths used to illuminate the gripper strips T in each of said acquisitions is defined by the program. For example, the data acquisition sequences concerning the various light sources 2r and 2v mentioned above are separated by short intervals of the order of seconds, so that for wear detection, four acquisitions are carried out almost simultaneously, while a short time interval is kept between two consecutive acquisitions in order to allow the completion of the data transmission to the central control unit LCU of the loom, and to empty the buffer memory of the back end BE. Considering that wear is a rather slow phenomenon, much larger intervals, for example of the order of hours, are usually kept instead between a data acquisition group and the next one.

[0075] Creation and storage of gripper belt optical profiles and assessment of gripper belt wear

[0076] A sequence of digital data representing a set of four subsequent acquisitions of reflected radiation intensity at the above mentioned different wavelengths is formatted in a single holder strip optical profile and the subsequent optical profiles are stored in a memory unit so that they can be compared at certain intervals which can be adjusted at will.

[0077] The historical sequence of optical profiles of each of the two gripper strips thus saved is then automatically analyzed by a programmable comparison unit installed on the central control unit LCU of the weaving machine in order to extract information about the progression of wear of the gripper strips. In fact, wear is represented by a gradual decay of the intensity of the reflected radiation relative to the wear condition initially detected on a new gripper strip at at least one of four different incident radiations, which can be detected by the intensity of the reflected signal (which decreases with increasing wear depth) and by the extent in terms of width and length of the gripper strip area where signs of wear appear (which increases with the development of wear). This method thus makes it possible to make color differences between gripper strips belonging to different batches irrelevant, since only the trend of the reflected radiation signal extracted from the same gripper strip is evaluated. In fact, based on this trend, the comparison unit can automatically evaluate the wear condition of the gripper strip (extension and depth of the worn area).

[0078] Manage user messages and loom control

[0079] Based on the evaluation of the wear condition of the gripper strips with reference to predefined threshold values, and possibly also based on other monitoring systems of the loom, a warning message is sent to the user via the display device V, or a blocking signal is sent directly to the central control unit LCU of the loom. Such a warning message can then, for example, prompt the operator to reduce the weaving speed, replace a damaged gripper strip, or verify the mechanical adjustment of the gripper strips. In the case of severe wear, i.e. when the evaluation of the wear condition of at least one gripper strip (T) of the loom exceeds a predetermined threshold value, the central control unit of the loom is programmed according to the automatic control method of the invention to impose a limitation of the weaving speed at a first threshold value, or to prevent the loom from restarting for any other reason after a first stop at a second threshold value, or finally to force a stop of the loom operation when a third threshold value is reached.

[0080] Algorithm for assessing gripper belt wear

[0081] A possible algorithm for evaluating the wear of the gripper strip that can be implemented in the software of the central control unit LCU of the weaving machine is now briefly described. This algorithm is represented here in order to better illustrate the preferred embodiment of the invention, but it must be clear that the optical profile of the gripper strip created and saved using the device disclosed above can of course also be further processed with other algorithms without thereby departing from the scope of protection of the present invention.

[0082] First, two areas are identified along the clamper belt T, specifically, area A where the clamper belt T is worn only at the edge because it does not pass under the guide slide S or only passes there at a low speed when the clamper belt is inserted, and area B which is an area that constantly passes under the guide slide S and is therefore more worn.

[0083] Due to the possibility of synchronizing the acquisition with the angular position of the weaving machine, the radiation reflected in the two areas A and B is acquired separately.

[0084] The data acquired in region A of the gripper strip is used to:

[0085] a. Modulating the intensity of the constant current supplied to the LED light sources 2r and 2v to obtain a predetermined signal level that is considered optimal;

[0086] b. defining the level of the "base signal" of the reflected radiation in the absence of wear, which is characteristic of the particular gripper strip being inspected and is considered to be the initial reference value for that gripper strip;

[0087] c. before starting each data acquisition group, compensating for the above-mentioned non-linearities in the operation of the light source 2 and the sensor 3 and, in addition, for the presence of dirt on the relative protection window and, moreover, for color variations between gripper strips from different batches, until the same initial reference values ​​according to point b above are obtained for the reflected radiation in the area A;

[0088] d. in the event that it is not possible to reach this initial reference value of the reflected radiation by compensation, an error message is sent to the operator in order to clean the protective sheet of the light source 2 and the sensor 3 and / or to check the correct operation of the optical detector 1;

[0089] The data acquired in area B of the gripper belt are then used to:

[0090] e. evaluating the deviation from the above initial reference value determined in step c above in region A of the gripper strip, said deviation, if any, being attributed to wear;

[0091] f. evaluating the trend of the wear condition by comparing the historical sequence of the corresponding portion of the saved optical profile previously acquired in the region B;

[0092] g. Compare the degree of wear in terms of depth, size and trend with appropriate thresholds to send an alarm message to the user, or reduce the loom speed, prohibit the loom from restarting or stop the loom immediately.

[0093] From the above description it is clear how the invention fully achieves the proposed objectives. Firstly, in fact, the predictive validity of monitoring the wear of the gripper strip by optical detection has been experimentally confirmed, proposing an optical detection of reflected radiation, which exploits the different frequencies of the light radiation emitted on various areas of the gripper strip characterized by different degrees of wear, thereby eliminating detection interferences arising from the different surface colors of the gripper strip, which were originally generated during manufacture and were later considered to be the result of the weaving process.

[0094] A special position of the optical detector 1 is subsequently identified which is particularly effective for avoiding any additional bulk on the weaving machine and for perfectly protecting the optical sensor from ambient light and dust.

[0095] Finally, with the aid of a dedicated software module, the monitoring device of the invention is perfectly integrated in the central control unit LCU of the loom in order to utilize the resources of this unit for saving and processing the collected data, in addition allowing alarm messages to be displayed only to the operator or to directly influence the operation of the loom.

[0096] It should be understood, however, that the present invention should not be interpreted as being limited to the specific arrangements described above, which merely constitute exemplary embodiments of the present invention, and that several variations are possible and within the capabilities of a person skilled in the art without thereby departing from the scope of protection of the present invention, which is limited only by the following claims.

Claims

1. A gripper loom comprising a weft insertion system, wherein: In a shed formed by the warp yarns, a weft-sending gripper and a weft-joining gripper are driven by means of an alternating motion by means of a pair of gears (W) with the aid of corresponding flexible gripper belts (T), said corresponding flexible gripper belts (T) carrying said weft-sending gripper and said joining gripper, respectively, at one end, said gripper belt (T) being meshed with said gears (W) through a series of holes formed longitudinally in the body of said gripper belt (T) and being kept attached to a sector of said gears (W) by means of a guide slide (S), the operation of said system being controlled by a central control unit (LCU) of a loom, said loom further comprising: An optical monitoring device for monitoring the wear condition of at least one of the gripper strips (T), the optical monitoring device comprising at least one light source (2) having a predetermined wavelength and emitting light radiation towards the surface of the gripper belt (T) when the gripper belt (T) moves, at least one sensor (3) which detects the intensity of the light radiation reflected by the gripper belt (T) during the movement of the gripper belt (T) and emits a corresponding sequence of electrical signals, It is characterized in that it also includes an acquisition and buffer memory device, which acquires the electrical signal sequence and transmits the electrical signal sequence converted into a digital signal to the central control unit (LCU) of the loom, a memory unit, wherein said digital signal is saved as a historical sequence of optical profiles of said gripper strip (T) at said wavelength at subsequent times, and A comparison unit that compares the latest optical profile processed with a historical sequence of saved optical profiles and provides an assessment of the progressive wear condition of the gripper strip (T).

2. A gripper loom according to claim 1, wherein the optical monitoring device comprises two optical detectors (1), each optical detector (1) being placed on a corresponding gripper belt (T), and an electronic infrastructure (10) for processing the electrical signals from the optical detectors (1).

3. A gripper loom according to claim 2, wherein the optical detectors (1) are arranged adjacent to the guide slide (S) and each comprises at least one LED light source (2) and an analog sensor (3), wherein the at least one LED light source (2) and the analog sensor (3) are oriented relative to each other so that most of the light emitted by the light source (2) and reflected by the surface of the gripper belt (T) is converged onto the analog sensor (3).

4. A gripper loom according to claim 3, wherein the LED light source (2) and the analog sensor (3) are arranged inside the optical detector (1), behind a window formed on the lower surface of the optical detector (1), facing the channel (4) in which the gripper belt (T) slides, and enclosed by a glass sheet or any other suitable material sheet that is transparent to the wavelength of the emitted and reflected light radiation.

5. A gripper loom according to any one of claims 2-4, wherein the LED light source (2) is at least one IR type LED light source (2r) emitting infrared light radiation, and an RGB type LED light source (2v) emitting visible light radiation in the three primary colors of the RGB color model, each of the optical profiles containing a complete and coordinated sequence of intensity values ​​of the reflected radiation of each of the emitted radiations.

6. A gripper loom according to claim 5, wherein each of the optical detectors (1) comprises two analog sensors (3) arranged corresponding to the outer area (U) in the gripper belt (T), and each analog sensor (3) is coupled to two corresponding light sources (2r, 2v) comprising an IR type LED and an RGB type LED.

7. Gripper loom according to claim 1, wherein said sensor (3) is an analog sensor and said gripper belt (T) moves at the standard operating speed of the loom.

8. Gripper loom according to claim 1, wherein said sensor (3) is a digital sensor and said gripper belt (T) moves at a slow motion weaving speed of said loom.

9. The gripper loom according to claim 1, wherein said storage unit and said comparison unit are contained in said central control unit (LCU) of the loom.

10. The gripper loom according to claim 2, wherein said electronic infrastructure comprises a front end (FE), a back end (BE) and a central control unit (LCU) of the loom.

11. Gripper loom according to claim 10, wherein the front end (FE) comprises the following functions: a. irradiating the holder with (T) by means of a light source (2); b. obtaining radiation reflected by the gripper with (T) as an analog signal by means of a sensor (3); c. converting the analog signal corresponding to the reflected radiation into a digital signal; d. Send the digital signal to the back end (BE).

12. The gripper loom according to claim 10, wherein the back end (BE) comprises the following functions: a. Adjust the illumination of the light source (2); b. Manage analog / digital converters; c. Receive digital signals from the front end (FE) at high speed; d. Acquiring and buffering the digital signal; e. Transmit digital signals to the central control unit (LCU) of the loom at low speed.

13. The gripper loom according to claim 10, wherein said central control unit (LCU) of the loom comprises the following functions: a. Acquired angle synchronization; b. Plan acquisition; c. Creation and storage of optical profiles of the gripper strip (T) and their historical sequence; d. comparing the most recently acquired gripper belt (T) profile against said historical sequence of saved gripper belt (T) profiles, and evaluating the progressive wear condition of the gripper belt (T); e. Management of user messages and loom control.

14. The gripper loom according to claim 13, further comprising a message display device (V), wherein a message related to the evaluation of the wear condition of the gripper belt (T) is displayed.

15. Gripper loom according to claim 10, wherein the reflected radiation is detected in two areas of the gripper belt (T) with different levels of wear, and wherein: The data obtained in the area (A) where the wear level of the gripper strip (T) is low is used to: a. Modulating the intensity of the constant current supplied to the IR type LED light source (2r) and the RGB type LED light source (2v) to obtain an optimal signal level; b. defining the level of the "base signal" of the reflected radiation in the absence of wear, said base signal being characteristic of the particular gripper strip (T) being inspected and constituting the initial reference value for that gripper strip (T); c. before starting each data acquisition group, modulating the intensity of the constant current supplied to the IR type LED light source (2r) and the RGB type LED light source (2v) until the same initial reference value as in step b above is obtained for the reflected radiation in the area (A); d. If the initial reference value of the reflected radiation as in step c above cannot be reached, an error message is sent to the display device (V) indicating the need for: i. Cleaning the protective sheet of the light source (2) and the sensor (3); and / or ii. Checking the correct operation of the optical detector (1); The data obtained in the area (B) where the wear level of the gripper strip (T) is high is used to: e. evaluating the deviation from the above initial reference value determined in step c above on the area (A) of the gripper belt (T) where the wear level is low; f. evaluating the trend of the wear condition by comparing the historical sequence of corresponding parts of the saved optical profiles acquired previously in said area (B) where the wear level of the gripper belt (T) is high; g. Compare the degree of wear in terms of depth, size and trend with appropriate thresholds to send an alarm message to the user, or reduce the loom speed to prohibit the loom from restarting or stop the loom immediately.

16. An automatic control method for controlling a gripper weaving machine according to claim 10, wherein the speed of the weaving machine is reduced to a predetermined value when the evaluation of the wear condition of at least one gripper belt (T) of the weaving machine exceeds a first predetermined threshold value.

17. Automatic control method of a weaving machine according to claim 16, wherein the weaving machine is prevented from restarting after a first stop when the evaluation of the wear condition of at least one gripper belt (T) of the weaving machine exceeds a second predetermined threshold value.

18. Automatic control method of a weaving machine according to claim 16, wherein the operation of the weaving machine is stopped when the evaluation of the wear condition of at least one gripper belt (T) of the weaving machine exceeds a third predetermined threshold value.

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