Automatic weft yarn removal device for air-jet loom and related method
Patent Information
- Application Number
- JP2023126202
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-08-04
- Filing Date
- 2023-08-02
- Publication Date
- 2026-07-13
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to a device for air looms, in particular for air looms, for the automatic removal of erroneous weft threads and an associated method.
[0002] In particular, the automatic weft removal device of the invention is activated after an incorrect weft insertion has been signalled and the loom has stopped as a result, to remove the weft from the shed and at the same time to check that the removal has been carried out correctly and completely. If the result of this test is negative, no consent signal is sent to restart the loom, but instead a warning signal is sent to activate the operator to carry out the manual removal, thus avoiding the occurrence of defects in the manufactured fabric caused by a portion of the weft that may have become entangled in the shed. [Background technology]
[0003] In air looms, it can happen that the weft thread, which is fired by a special nozzle from one side of the loom (usually the left side as viewed from the weaver's usual working position) and crosses the shed in a dedicated channel formed in the reed, does not arrive correctly at the other side of the loom (the right side). Such incorrect insertion of the weft thread can have several causes, such as incorrect supply pressure of the weft transport system, incorrect timing of the activation of the air jets of the weft transport system, interference of the weft thread with machine elements or warp threads arranged along the reed channel, but ultimately comes down to two specific cases: a broken weft thread or a shortened weft thread. Such an outcome is verified by two optical sensors arranged along the weft thread path on the right side of the loom, namely the first optical sensor upstream of the point where the regular arrival of the weft thread free end is expected and the second optical sensor downstream of said point.
[0004] If the weft thread is correctly inserted, the first optical sensor detects its arrival within the expected time, but the second optical sensor detects nothing, since it acts on its opposite end and mechanically stops the advance of the weft thread. On the other hand, if the weft thread breaks, mechanically stopping the weft thread on the left side of the loom has no effect on the broken weft thread, which continues to run and is detected continuously by the first and second optical sensors. If the weft thread is short, i.e. if the weft thread gets tangled in the loom, the leading edge of the weft thread will not be detected on the right side of the loom by any of the two optical sensors, at least not within the set time.
[0005] In all the above mentioned cases of misinserted weft threads, an alarm is sounded as soon as the weaving machine control system detects the error, the ongoing work cycle is interrupted and an automatic procedure for removing the misinserted weft thread is started. The automatic procedure for removing the weft thread left in the weaving machine consists of the combined and coordinated action of the jets of auxiliary nozzles for transporting the weft thread and of mechanical and / or pneumatic devices for tensioning the weft thread.
[0006] Once the automatic removal procedure is successfully completed and the erroneous weft thread is removed from the loom, automatic restart of the loom is possible, therefore no defects are left in the fabric. On the other hand, if the automatic weft removal procedure is unable to complete the weft removal within a set time, automatic restart of the loom will not work and operator intervention is required to manually remove the weft thread and restart the loom.
[0007] The automatic weft thread removal devices available on the market can be divided into two families, which can be distinguished by the way in which they interact with and pull the weft thread: the first family consists exclusively of pneumatic devices, the second family also includes mechanical devices which perform the weft thread pulling action.
[0008] In the case of the fully pneumatic automatic removal procedure, shown diagrammatically in Figure 1, auxiliary nozzles arranged along the channel of the reed R simultaneously and intermittently spray to gradually move the weft thread T towards the right side of the loom, where the two optical sensors (S1; S2) mentioned above are provided together with the pneumatic device A. When the pneumatic device A is activated, it generates a pulling force F on the errant weft thread approaching it, and thanks to the pneumatic pulling action exerted by the whole of these devices, the weft thread T is gradually removed from the shed. The optical sensor S2, arranged just before the pneumatic device A, monitors the internal running of the weft thread T while it is being removed, allowing the electronic control system of the loom to check the result of the automatic removal procedure.
[0009] Indeed, if the tail end of the weft thread T disappears from the control area of the second optical sensor S2 within a set time, the removal of the weft thread is considered successful and an automatic restart of the loom is enabled. If the tail end of the weft thread T does not disappear from the control area of the second optical sensor S2 within said set time, the automatic removal procedure is considered unsuccessful and therefore the automatic restart of the loom remains inhibited until there is a manual intervention by the operator.
[0010] In the case of the device combining pneumatic and mechanical operation, shown diagrammatically in Fig. 2, the unwinding cycle is substantially the same, except for how the weft thread T is pulled after its tip reaches the pneumatic device A. In fact, after first being dragged by the pneumatic action of the device A, in a manner completely similar to the device described above, in this combined device the tip of the weft thread to be unwound is clamped between a pair of counter-rotating cylinders C, which approach said tip with a set contact force and, by rotating in the opposite direction, exert a mechanical pulling force added to the pneumatic pressure generated by the device A. It is clear that such an automatic unwinding device, combining pneumatic and mechanical action, guarantees a higher efficiency in the unwinding of the weft thread T, especially in situations where the weft thread is severely entangled in the shed.
[0011] However, all the above mentioned types of devices for automatically removing the erroneous weft thread have a common drawback, namely, that the integrity of the weft thread T cannot be checked during the automatic weft removal stage. Therefore, in situations where the weft thread T is severely entangled in the shed, the mechanical pulling device has a high probability of causing an unwanted breakage, which breakage becomes completely uncontrollable. In fact, even after an unwanted breakage of the weft thread T has occurred, the pulling device continues to pull the free end of the weft thread T, and when the tail end of the weft thread C, which has been removed from the loom, is detected by the sensor S2, it transmits a positive result of the automatic pulling procedure to the loom control system, which thus allows an automatic restart of the loom. However, the broken part of the weft thread C, which remains entangled in the loom, is not detected and removed, which reduces the efficiency of the automatic removal device and leads to defects in the fabric that are only detected when the fabric is finished.
[0012] Other solutions are available on the market, which can be implemented by extracting the erroneous weft thread on the left side of the machine, i.e. from its insertion side, but even with such solutions it is not possible to check the integrity of the weft thread T as it is extracted from the shed, so that pieces of broken weft thread can be left behind in the shed, which will cause defects in the final fabric when the loom is automatically restarted.
[0013] One of the latter solutions, disclosed in EP-0309013, also proposes the additional use of a mechanism for measuring the weft tension during the weft withdrawal process and interrupting the weft withdrawal operation if said tension exceeds a set threshold value. This document represents the closest prior art to the present invention and is in fact reported in the preamble of the independent claim. Summary of the Invention
[0014] Problem to be solved by the invention Considering the market demand to maintain high quality standards of fabrics produced on air looms, the technical problem addressed by the present invention is to improve the reliability of currently used automatic devices for removing erroneous weft threads and to be able to detect unwanted breakage of the weft thread that may occur during the automatic removal of the erroneous weft thread from the shed.
[0015] Breaking of the weft thread occurs during the process of drawing it out of the shed if the pulling force exerted on the weft thread by the automatic drawing device exceeds the tensile strength of the weft thread. Each type of weft thread, based on the type of material and the mechanical characteristics imparted to it by the spinning process, has in fact a well-defined tensile strength.
[0016] In order to solve the above technical problems, the first object of the present invention is to provide a device for detecting erroneous weft tension fluctuations when the weft yarn is drawn out from the shed without interfering with normal weaving operations.
[0017] A second object of the invention is to provide a method for interpreting the variations in the tension of the weft yarn, so that its possible breakage, or in any case the high probability of breakage, during withdrawal of an erroneous weft yarn from the shed can be inferred without visual detection.
[0018] Summary of the Invention This problem is solved and these objects are achieved by a device for automatically removing erroneous weft threads from the shed of an air loom having the features defined in claim 1 and by a method for automatically removing erroneous weft threads having the features defined in claim 7. Further preferred features of the device are defined in the dependent claims. [Brief description of the drawings]
[0019] Further features and advantages of the device for automatically removing erroneous weft threads from the shed of an air loom, according to the invention, will become apparent from the following detailed description of a preferred embodiment of the device, given purely by way of non-limiting example and illustrated in the accompanying drawings, in which:
[0020] [Figure 1] FIG. 1 is a schematic plan view of a known device for the automatic removal of erroneous weft threads by pneumatic operation; [Diagram 2] FIG. 1 is a schematic plan view of a known device for automatically removing errant weft threads, combining pneumatic and mechanical operation; [Diagram 3] FIG. 2 is a schematic plan view of the automatic erroneous weft removal device of the present invention; [Figure 4] 1 shows four typical graphs (AD) showing different trend types of weft tension change with time during weft withdrawal from the shed of an air loom. [Diagram 5] Graph CD from FIG. 4 is superimposed on the corresponding graph GH where the change in the time derivative of tension is reported. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] According to the invention, in order to solve the above highlighted problem by a simple and immediately applicable solution, a known device D for drawing off an erroneous weft thread, combining pneumatic and mechanical operation, for example of the type shown diagrammatically in figure 2, is supplemented with a sensor suitable for detecting the tension of the erroneous weft thread during the drawing off of the weft thread from the shed. For the sake of simplicity, such a tension sensor will be called a tensiometer in the following. On the basis of the data provided by said tensiometer and an appropriate mode of interpretation of said data, the invention has been perfected.
[0022] For the purposes of the present invention, a tensiometer 1 mounted on a carriage movable in a direction perpendicular to the weft thread is preferably located between the optical sensor S2 closest to the right end of the loom and the pneumatic mechanical device D for pulling out erroneous weft threads. The tensiometer 1 may consist of any electronic device which measures the tension of the thread running through it and produces an electrical signal proportional to that tension.
[0023] During the procedure of automatic removal of the erroneous weft yarn, when the leading end of the weft yarn (T) reaches the drawing device D and is clamped by the cylinder C, the tensiometer 1 approaches and contacts the weft yarn T in order to measure the total pulling force F exerted by the cylinder C and the pneumatic device A in the running direction of the weft yarn T, causing the weft yarn T to deviate from its straight trajectory. A schematic diagram of the tensiometer 1 is depicted in FIG. 3, where the elements of the tensiometer 1 causing the deviation of the weft yarn T from its straight trajectory are represented by the guide rollers 2 and the sensing element of the tensiometer 1 is a roller feeler 3 interposed between said guide rollers 2, said roller feeler 3 being integrated with a load cell 4 which detects the force exerted by the weft yarn T on the roller feeler 3. When a erroneous weft yarn is detected, the tensiometer 1 advances towards the erroneous weft yarn T until it is in the working position where the guide rollers 2 and the roller feeler 3 are in contact with the weft yarn T. This action is facilitated by a V-shaped fork integral with the tensiometer 1, which intercepts the weft thread T during the approach stroke of the tensiometer 1 and guides it precisely over a guide roller 2 and a roller feeler 3.
[0024] The guide roller 2 generates a moderate wave pattern in the trajectory of the weft thread T, as shown diagrammatically in FIG. 3, and the roller feeler 3 is attached in the middle of such wave pattern, in a direction perpendicular to the running direction of the weft thread T. Thanks to this, when the tension of the weft thread T changes, the force applied to the roller feeler 3 also changes, and such change is detected by the load cell 4 and converted into an electrical signal proportional to the actual tension of the weft thread T. It is clear that the present description of how the tensiometer 1 works is given by way of example only. Thus, in practice, any type of tensiometer suitable for providing an electrical measurement of the tension of the weft thread can be used, regardless of how this measurement is obtained, and the present description does not limit the invention in any way.
[0025] The variations in the tension F of the weft thread T detected by the load cell 4 are then immediately processed by a processing device (which can be a dedicated processing device associated with the tensiometer 1 or the same central processing device of the loom) to verify whether threshold conditions set based on the weft thread characteristics and / or the actual weaving operation have been exceeded during the entire cycle of the incorrect weft thread withdrawal. If any of the threshold conditions are exceeded, it is considered that a breakage of the weft thread T has likely occurred.
[0026] This latter information is used by the weaving control system in addition to the checks already provided in order to determine with more reliability the final result of the automatic weft removal procedure. Indeed, if the procedure has been completed successfully according to the criteria of the prior art solutions and, moreover, the inventive device has not detected any impending break in the weft thread, an automatic restart of the weaving machine can be activated. On the other hand, if the inventive device detects a weft break, the automatic restart of the weaving machine is prohibited and, even if the check according to the criteria of the known weft removal device has a positive result, a request for operator intervention is issued at the same time, so that the operator can directly visually check and, if necessary, manually remove the weft thread left in the shed and then restart the weaving machine. In this latter case, by avoiding an automatic restart of the machine, the inventive device can avoid defects in the finished fabric. As a result, the device for automatic removal of incorrect weft threads according to the invention offers an overall higher reliability than the known devices.
[0027] We now describe several possible modes for evaluating whether a weft thread breakage occurs during the weft thread withdrawal cycle by processing and analysing the data on the erroneous weft thread tension T measured by the tensiometer 1.
[0028] The first mode is based on the comparison of the value of the signal emitted by the tensiometer 1 (suitably processed to represent the overall tension F on the weft thread being drawn) with the value of the tensile strength of the weft thread itself.
[0029] Said tensile strength is known to vary with the type of fiber material used for the weft yarn, and its value is not constant over the entire length of the weft yarn, but rather depends on the mechanical characteristics introduced during the spinning process and the surrounding operating conditions. This allows the breaking tension Fb of the weft yarn T during operation and a safety tension Ft below the breaking tension Fb to be identified, forming a control band of the weft yarn tension F between which the weft yarn is statistically likely to break.
[0030] During the drawing cycle, the weft thread can repeatedly entangle and untangle, and the tension F of the weft thread T increases and decreases accordingly. All such changes of the tension F of the weft thread T are accurately detected by the tensiometer 1. Figure 4 shows four typical diagrams of different trends of the tension F of the weft thread T, which represent four different and statistically significant situations of the weft thread T, as will be better explained below.
[0031] If the measurement signal representing the tension F is always below the threshold of the safety tension Ft (curve A), the pulled-off weft thread T is considered to be intact and therefore the automatic restart of the loom is activated at the end of the automatic removal operation of the incorrect weft thread T. Conversely, if at any moment during the pulling-off cycle the tension F detected by the tensiometer 1 exceeds the safety tension Ft or even the breaking tension Fb (curve B), this situation is identified as a high probability of a weft thread T breaking and, as a result, the automatic restart of the loom is inhibited. Also, if the measured value of the tensiometer 1 gradually increases during the pulling-off cycle and then decreases sharply during the pulling-off phase (curve C), even if the breaking tension Fb is not exceeded, a high probability of a weft thread breaking is determined and the automatic restart of the loom is also inhibited in this case. In exactly the same situation, if the value of the tension F, after a high peak, gradually decreases until it recovers its initial value (curve D), this is considered to be a condition in which the weft thread has been detangled and is still intact, despite having exceeded the safety tension Ft, and an automatic restart of the loom is allowed at the completion of the drawing cycle.
[0032] An additional way of interpreting the data of the tension F of the weft thread T shown in FIG. 5 is to use a mixed approach, which adds to the above mentioned control the analysis of the derivative dF of the tension F with respect to time, the value of such derivative dF being constantly monitored during the weft thread withdrawal cycle. If the weft thread T is withdrawn from the top thread without any serious entanglement of the weft thread T, the value of the tension of the weft thread T is approximately constant and therefore the value of the derivative of such tension with respect to time is approximately zero. On the contrary, if an entanglement of the weft thread T occurs, the value of the tension F measured by the tensiometer 1 gradually increases, so that the signal of the derivative dF deviates from the zero value.
[0033] Small variations in the derivative dF in the presence of a non-zero value of the tension F signal from the tensiometer 1 at the moment following the peak of the variations (curve D) can therefore be interpreted as a state in which the weft thread has unraveled and is still intact (curve H). A negative peak in the signal of the derivative dF (curve G) is instead an indication of a possible sudden breakage of the weft thread, even if the signal from the tensiometer 1 at the moment following the sudden variation (curve C) is non-zero. Interpreting the data of the tension F of the weft thread T by this mixed approach makes it possible to define, according to preventive purposes, more stringent criteria to determine the likely breakages that will occur during the withdrawal cycle of the weft thread T, thus avoiding possible defects in the final fabric upon automatic restart of the machine.
[0034] The introduction of a tensiometer 1 for measuring the tension F of the weft thread T during the withdrawal of the incorrect weft thread from the shed, and the processing and interpretation of the signals generated by said tensiometer 1, makes it possible to significantly improve the quality of the manufactured fabric, avoiding defects caused by incomplete removal of the weft thread T by the automatic removal device in which this operation is performed.
[0035] However, the present invention should not be considered as being limited to the particular arrangements illustrated above, which are merely exemplary embodiments thereof, but rather it is understood that different modifications are possible within the reach of a person skilled in the art without departing from the scope of protection of the present invention, which is defined solely by the following claims.
Claims
1. A device for automatically removing an incorrect weft yarn from the shuttle of an air loom, comprising: a pneumatic or pneumatically operated weft yarn (T) extraction device (D); a tensiometer (1) positioned upstream of the extraction device (D) and detecting changes in the tension (F) applied to the weft yarn (T) by the extraction device (D) during the process of removing the weft yarn (T) from the shuttle; and a processing unit that processes the changes in the tension (F) of the weft yarn (T) and disables the automatic restart of the loom if the change in tension (F) meets a set threshold condition, wherein the tensiometer (1) includes a guide element (2) that deviates the weft yarn (T) from its straight trajectory, and sensing elements (3, 4) interposed between the guide element (2) and detecting changes in the tension (F) of the weft yarn (T), The device for automatically removing an incorrect weft from the shuttle of an air loom is characterized in that the tensiometer (1) is mounted on a carriage that is movable in a direction perpendicular to the weft insertion direction, and when incorrect weft insertion is detected, the guide element (2) and the sensing elements (3, 4) are moved closer to the incorrect weft (T) until they come into contact with the incorrect weft (T).
2. A device for automatically removing a wrong weft from the shuttle of an air loom according to claim 1, further comprising at least one V-shaped fork integrated with the tensiometer (1) for blocking the weft (T) and guiding it onto the guide element (2) and the sensing elements (3, 4) while the tensiometer (1) is brought close to the weft (T).
3. The sensing element (3, 4) comprises a roller feeler (3) arranged perpendicular to the direction of travel of the weft yarn (T), and a load cell (4) integrated with the roller feeler (3), for automatically removing an incorrect weft yarn from the shuttle of an air loom according to claim 2.
4. The device for automatically removing an incorrect weft thread from the shuttle of an air loom according to any one of claims 1 to 3, wherein the threshold condition is met when the instantaneous value of the tension (F) of the weft thread (T) is greater than the safe tension (Ft) of the weft thread (T).
5. The threshold conditions are as follows: i. The instantaneous value of the tension (F) of the weft (T) is greater than the safe tension (Ft) of the weft (T), and ii. The derivative (dF) of the tension (F) of the weft (T) with respect to time has a negative peak. A device for automatically removing an incorrect weft thread from the shuttle of an air loom according to any one of claims 1 to 3, when the following occur simultaneously.
6. The apparatus for automatically removing an incorrect weft thread from the shuttle of an air loom according to any one of claims 1 to 3, wherein the tensiometer (1) includes an electronic device suitable for measuring the tension (F) of a weft thread (T) running inside it and generating an electrical signal proportional to the tension (F) of the weft thread (T).
7. A method for automatically removing a erroneous weft (T) from the shuttle of an air loom, comprising a pneumatic or pneumatically operated erroneous weft (T) puller (D), a. A step of detecting a change in the tension (F) applied to the weft yarn (T) by the pulling device (D) during the pulling of the weft yarn (T) from the shuttle, using the means of a tensiometer (1) positioned upstream of the pulling device (D); b. A step in the processing unit to compare the change in tension (F) with a set threshold condition; c. A step of disabling the automatic restart of the loom when the threshold condition is met; and simultaneously, d. A process of issuing a warning signal to the operator in order to manually remove the incorrect weft thread. Includes, The threshold conditions are as follows: i. The instantaneous tension (F) of the weft (T) is greater than the safe tension (Ft) of the weft (T), and, ii. The derivative (dF) of the tension (F) of the weft (T) with respect to time has a negative peak. A method characterized by occurring when the following two things happen simultaneously.