Patent Application
20080185066
The invention relates to a method and an apparatus for the insertion of a weft thread into a shed of a weaving machine, in particular in accordance with the respective preambles of claims 1 and 6 and also to a weaving machine, in particular an air jet weaving machine, equipped for carrying out such a method or having such an apparatus.
In the weft insertion in an air jet weaving machine the weft thread drawn from the thread store is accelerated by acceleration nozzles mainly termed the main nozzle and the tandem nozzle, and is inserted into a shed in which it is transported further by so-called auxiliary or relay nozzles. In customary air jet weaving machines the relay nozzles are switched on and off by a pre-selected profile fixedly associated with the rotation of the machine main shaft.
In the document EP 0 554 222 A1 a method is described for the regulation of the weft insertion for an air jet weaving machine having a plurality of auxiliary nozzles and a plurality of weft thread monitors arranged in the shed in order to detect in contact-free manner the point in time at which the front end of an inserted weft thread enters at the position of one of the weft thread monitors. In the described method the point in time that is detected is compared with a preset reference arrival time and the time duration and/or the pressure of the blown in compressed air for the auxiliary nozzles or groups of auxiliary nozzles arranged before and after the weft thread monitor is changed on the basis of the comparison of the desired and actual values.
The method described in EP 0 554 222 A1 is relatively complicated because it requires supplies of compressed air with different through-flow rates for the auxiliary nozzles. The simultaneous energization of several groups of auxiliary nozzles is also disadvantageous because it is associated with a massive increase in the consumption of compressed air. In addition the arrangement of a plurality of weft thread monitors in the shed is also problematic because these can damage the warp threads and can thereby impair the quality of the cloth.
In the document WO 92/04490 a method is described for controlling a weft thread insertion system for an air jet weaving machine in which the weft thread is wound onto a drum store and the drawn off length is subsequently measured in contact-free manner during the drawing off of the weft thread by means of a so-called turn counter. An approximation for the position of the weft thread tip in the shed is determined from the turn counter signals and serves to control the air nozzles used for the weft insertion or a thread brake. In the described method the approximation determined for the position of the weft thread tip by means of the turn counter signals is additionally compared with the time of arrival determined by means of a weft thread monitor at the capture side end of the shed and the deviation is used to calculate a corrected approximation for the subsequent weft insertion.
The approximation for the position of the weft thread tip determined with the aid of the method of WO 92/04490 is comparatively imprecise since the weft thread is sometimes irregularly drawn from the drum store in that, by way of example, for a specific position of the weft thread tip in the shed, three turns are drawn off and, at the next weft insertion at the same position, three and a half turns. Moreover, the tension and elongation of the weft thread can vary in subsequent weft insertions. For the named reasons the control of the weft thread insertion while using the corrected approximation for the position of the weft thread tip is comparatively imprecise.
The object of the invention is to make available a method and an apparatus for the insertion of a weft thread into a shed of a weaving machine, in particular of an air jet weaving machine, in which measurement pickups which operate in contact-free manner are used and by means of which more precise values, in comparison to the method described in WO 92/04490, can be determined for the path that is traveled or for the speed of the weft thread without endangering the quality of the cloth by a plurality of weft thread monitors arranged in the shed. A further object of the invention is to make available a weaving machine, in particular an air jet weaving machine in order to carry out a method of this kind and having such an apparatus.
This object is satisfied in accordance with the invention by the method defined in claim 1 and by the apparatus defined in claim 6 as well as by the air jet weaving machine defined in claim 11.
In the method of the invention for the insertion of a weft thread into the shed of a weaving machine having a thread store and a transport device the weft thread is inserted by means of the latter into the shed. In the case of an air jet weaving machine the transport device includes at least one acceleration nozzle and a plurality of auxiliary nozzles, with the weft thread drawn off from the thread store being accelerated by means of the at least one auxiliary nozzle, being supplied to the shed and being transported further in the shed by means of the auxiliary nozzles. Furthermore, measured values dependent on the speed of the weft thread and/or on the path traveled by the weft thread are measured in contact-free manner by means of one or more measurement pickups. In the method at least one of the measurement pickups, which is termed a special measurement pickup in the following, is additionally designed for multiple or continuous measurement within the weft insertion (meaning within one weft insertion step prior to the next) and is arranged at a thread centering device provided at the outlet of the thread store or after the same, or at or after a thread brake provided separate from the thread store, or at or after a first acceleration nozzle following the thread store. During the weft insertion measurement values are measured in contact-free manner a plurality of times or continuously by means of the at least one special measurement pickup from which values for the speed of the weft thread and/or for the path traveled by the weft thread and/or for a parameter linked to the speed of the weft thread and/or the path traveled by the weft thread are determined during the weft insertion. For the continuous measurement during the weft insertion a measurement pickup can for example be used which delivers an analogue output signal. Furthermore, values determined during the weft insertion are used for the regulation and/or control of the weft insertion, advantageously of the current weft insertion, for example in that a thread brake is controlled and/or in that the time of switching on and off of the acceleration nozzles and/or auxiliary nozzles is controlled in an air jet weaving machine and/or, for example, with deviations of a measured speed profile from a desired profile, a pressure is varied with which the nozzles are fed.
In an advantageous variant measurement values dependent on the speed of the weft thread and/or on a path traveled by the weft thread are measured in contact-free manner at least 50 times or at least 200 times or at least 500 times within one weft insertion or a part of the same by means of the at least one special measurement pickup. In a further advantageous variant measurement values dependent on the speed of the weft thread and/or the path traveled by the weft thread are measured in contact-free manner during the weft insertion or during a part of the same by means of the least one special measurement pickup continuously, or at least every 0.5 ms, or at least every 0.2 ms, or at least every 0.05 ms.
The at least one special measurement pickup can for example operate in accordance with a laser interference method, laser Doppler method or in accordance with a spatial filter method or, together with a second measurement pickup, in accordance with a correlation method.
In an advantageous embodiment the at least one special measurement pickup is arranged between the thread centering device and the thread brake, or between the thread brake and the first acceleration nozzle, or between the first acceleration nozzle and the end of the shed, or between the first acceleration nozzle and a second acceleration nozzle, or between the last acceleration nozzle in the weft insertion direction and the shed, or at the entry to the shed, for example at a slay or a reed.
The apparatus in accordance with the invention for inserting a weft thread into a shed of a weaving machine includes a thread store, a transport device to insert the weft thread into the shed and one or more measurement pickups. In the case of an air jet weaving machine, the transport device includes at least one acceleration nozzle in order to accelerate the weft thread drawn from the thread store and to supply it to the shed and a plurality of auxiliary nozzles in order to transport the weft thread further in the shed. In the apparatus at least one of the measurement pickups, which-will be termed a special measurement pickup in the following, is formed for the multiple or continuous measurement within the weft insertion and is arranged after a thread centering device provided at the outlet of the thread store or after the latter, or at or after a thread brake provided separate from the thread store, or at or after a first acceleration nozzle following the thread store in order to measure measurement values multiply or continuously during the weft insertion that are dependent on the speed of the weft thread and/or the path traveled by the weft thread in contact-free manner. For the continuous measurement during the weft insertion a measurement pickup can for example be provided which delivers an analogue output signal. The apparatus additionally includes an evaluation part in order to determine, from the measurement values measured during the weft insertion by means of the at least one special measurement pickup, values for the speed of the weft thread and/or the path traveled by the weft thread and/or for a parameter linked to the weft thread and/or the path traveled by the weft thread and a control part in order to regulate and/or to control the weft insertion, in particular the current weft insertion by means of the values determined during the weft insertion, for example in that a thread brake is controlled and/or the point in time for the switching on and the switching off of the acceleration nozzles and/or of the auxiliary nozzles is controlled in an air jet weaving machine and/or for example with deviations of a measured speed profile from a desired profile a pressure with which the nozzles are fed is varied. If required the evaluation part can be integrated into the control part.
In an advantageous variant the at least one special measurement pickup is suitable for measuring in contact-free manner measuring values which are dependent on the speed of the weft thread and/or the path traveled by the weft thread within one weft insertion or a part of the same at least 50 times, or at least 200 times, or at least 500 times. Measured values of the named kind can advantageously be measured in contact-free manner and continuously during the weft insertion or a part of the same by means of the at least one special measurement pickup. In a further advantageous variant the at least one special measurement pickup is suitable for measuring in contact-free manner the measurement values dependent on the speed of the weft thread and/or on the path traveled by the weft thread during the weft insertion or during a part of the same at least every 0.5 ms, or at least every 0.2 ms, or at least every 0.05 ms.
The at least one special measurement pickup is advantageously a pickup which operates in accordance with a laser interference method, a laser Doppler method or in accordance with a spatial filter method or a measurement pickup which operates together with a second measurement pickup in accordance with a correlation method.
In an advantageous embodiment the at least one special measurement pickup is arranged between the thread centering device and the thread brake, or between the thread brake and the first acceleration nozzle, or between the first acceleration nozzle and the end of the shed, or between the first acceleration nozzle and a second acceleration nozzle, or between the last acceleration nozzle in the weft insertion direction and the shed, or at the entry to the shed.
Furthermore, the invention includes a weaving machine, in particular an air jet weaving machine equipped for carrying out a method in accordance with one of the above-described embodiments and variants and/or with an apparatus in accordance with one of the above-described embodiments or variants.
The method and the apparatus in accordance with the present invention and also a weaving machine in accordance with the invention, in particular an air jet weaving machine, have the advantage that, thanks to the arrangement of a special measurement pickup after a thread centering device following the thread store, or at or after a thread brake or a first acceleration nozzle, more precise values for the speed of the weft thread and/or the path traveled by the weft thread and/or for a parameter linked thereto are available during the weft insertion than those which could previously be determined by means of a turn counter at the thread store, since the irregularities during the drawing of the weft thread from the thread store are no longer of interest, and a distance between the weft thread tip and the measurement location is reduced compared to a measurement at the thread store, whereby the influence of the thread tension and the thread elongation on the measurement is reduced. Moreover, the weft thread is largely extended after the thread brake or the first acceleration nozzle during the insertion which is likewise good for the measurement accuracy.
Compared with the customary method, in which the point in time at which the front end of the inserted weft thread arrives at the position of a weft thread monitor is determined by means of weft thread monitors arranged in the shed, the method and the apparatus in accordance with the present invention and also the weaving machine of the present invention, in particular the air jet weaving machine, have the advantage that no danger exists that the warp threads are damaged during the shed change. Moreover it is possible, thanks to the special measurement pickup which measures multiply or continuously during the weft insertion, to determine, at shorter intervals or continuously, values for the speed of the weft thread and/or the path traveled by the weft thread than is possible with a restricted number of weft thread monitors in the shed. Thus it is also possible to detect breakdown in the weft insertion more rapidly, such as for example a weft thread break
As a result of the values for the speed of the weft thread and/or for the path traveled by the weft thread and/or for a parameter linked to the speed of the weft thread and/or to the path traveled by the weft thread which are available continuously or at shorter intervals and which are determined during the weft insertion by means of the method, of the apparatus and of the weaving machine, in particular the air jet weaving machine in accordance with the present invention, it is possible to match the weft insertion more precisely to desired parameters such as for example a preset speed profile, the total flight time or the point in time of the use of the brake which are specified with regard to a problem-free weft insertion for the individual weft yarns and/or to react more quickly to breakdowns. For the weft insertion a closed regulating circuit can for example be provided in order to control individual desired parameters during the weft insertion. The values determined continuously or at shorter intervals enable the regulation and/or control of the current weft insertion, with the time constants for the regulation and/or the delay being able to be kept comparatively small.
The above description of embodiments merely serves as an example. Further advantageous embodiments can be seen from the dependent claims and the drawing. Moreover, individual features from the described and illustrated embodiments and variants can be combined with one another to form new embodiments within the context of the present invention.
In the following the invention will be described in more detail with reference to embodiments and to the drawing. There are shown:
In the apparatus in accordance with the present invention at least one of the measurement pickups, which is termed a special measurement pickup 6 in the following, is designed for the multiple or continuous measurement within the weft insertion and is provided after a thread centering device 23 provided at the outlet of the thread store 21 or after the same or at or after a thread brake 9 provided separately from the thread store 21 or, as shown in
In the embodiment the acceleration nozzles include a main nozzle 3 and a tandem nozzle 4 which are respectively supplied with compressed air via a control valve 13, 14, for example a solenoid valve. A single main nozzle can also be provided at the position of the main and tandem nozzles 3, 4 or a plurality of the main nozzles, frequently termed pre-nozzles and main nozzles, can be arranged in series in order to accelerate the weft thread. Naturally a plurality of main nozzles 3 lying alongside one another or above one another can be provided in order to alternately insert different weft threads 2 which can differ in color, fineness, texture and material. The auxiliary nozzles 5.1 a-c to 5.n a-c can be supplied individually with compressed air or combined into groups of two to five or more nozzles, with the nozzles of a group respectively being jointly supplied with compressed air via a control valve 15.1 to 15.n, for example a solenoid valve. The control valves 15.1 to 15.n are expediently connected to a compressed air reservoir and/or compressed air distributor 12 which is supplied via a pressure line 11 with compressed air. A plurality of compressed air reservoirs and/or distributors 12 can also be provided which can have different pressure levels.
The apparatus can if required include a thread brake 9 which is controlled by the control 10. The weft thread 2 can be braked by means of the thread brake 9, for example at the end of the weft insertion, when the weft thread tip approaches the capture side end of the shed. Furthermore, the apparatus can if required include a thread centering device 23 which, as shown in
In an advantageous variant the at least one special measurement pickup 6 is suitable for measuring in contact-free manner measurement values dependent on the speed of the weft thread and/or on the path traveled by the weft thread at least 50 times, or at least 200 times, or at least 500 times within a weft insertion. Measurement values of the named kind can advantageously be measured in contact-free manner in a continuous sequence during the weft insertion or a part of the same by means of the at least one special measurement pickup. In a further advantageous variant the at least one special measurement pickup 6 is suitable for measuring in contact-free manner measured values dependent on the speed of the weft thread and/or on the path traveled by the weft thread during the weft insertion or part of the same continuously, or at least every 0.5 ms, or at least every 0.2 ms, or at least every 0.05 ms.
The at least one special measurement pickup is advantageously a measurement pickup operating in accordance with a laser interference method, laser Doppler method or in accordance with a spatial filter method or a measurement pickup operating with a second measurement pickup in accordance with a correlation method. For the spatial filter methods both optical processes are known, for example the method described in DE 43 07 530 A1 which uses a line grid and also electrostatic methods which evaluate the influence of charges on a running thread. A method of this kind in which a thread is moved past an electrostatic pickup having a periodic spatial sensitivity is for example described,in EP 1 0333 579 A2. In the correlation method optical and electrostatic methods are likewise known in which, in each case, the signals of two pickups arranged spaced apart along a thread are evaluated and the speed of the thread is determined from a spacing of the pickups and the time shift between the two signals. An electrostatic method of this kind is for example described in GB 1 249 610. A suitable electrostatic pickup for correlation methods is for example described in DE 44 08 312 A1.
In an advantageous embodiment the at least one special measurement pickup 6 is, as shown in
The air jet weaving machine 1 can, as shown in
In the embodiment shown in
If required the apparatus shown in the embodiment of
The variants described in the context of the embodiment of
An example of the method of the invention for the insertion of the weft thread into a shed of an air jet weaving machine will be described in the following with reference to
In the said method at least one of the measurement pickups, which is termed a special measurement pickup 6, 6.1-6.5 in the following, is additionally designed for multiple or continuous measurement within the weft insertion and is arranged after a thread centering device 23 provided at the outlet of the thread store 21 or after the same, or at or after a thread brake provided separately from the thread store 21, or at or after a first acceleration nozzle 3 following the thread store. During the weft insertion measured values are measured multiply or continuously in contact-free manner by means of the at least one special measurement pickup 6, 6.1-6.5 from which values for the speed of the weft thread 2 and/or the path traveled by the weft thread 2 and/or for a parameter linked to the speed of the weft thread and/or of the path traveled by the weft thread are determined during the weft insertion. Furthermore, the values determined during the weft insertion are advantageously used during the current weft insertion for the regulation and/or controlling of the weft insertion, for example in that a thread brake is controlled and/or the time of switching on and switching off of the acceleration nozzles and/or auxiliary nozzles in an air jet weaving machine is controlled and/or a pressure with which the nozzles are fed is varied, for example on deviations of a measured speed profile from a desired profile.
In an advantageous variant of the method measured values dependent on the speed of the weft thread 2 and/or on the path traveled by the weft thread 2 are measured in contact-free manner within a weft insertion or a part of the same by means of the at least one special measurement pickup 6, 6.1-6.5 at least 50 times, or at least 200 times, or at least 500 times. In a further advantageous variant measurement values dependent on the speed of the weft thread and/or on the path traveled by the weft thread are measured in contact-free manner during the weft insertion or a part thereof by means of the at least one special measurement pickup 6, 6.1-6.5 at least every 0.5 ms, or at least every 0.2 ms, or at least every 0.05 ms.
The at least one special measurement pickup 6, 6.1-6.5 can for example operate in accordance with a laser interference method, laser Doppler method or in accordance with a spatial filter method or together with a suitable measurement pickup in accordance with a correlation method. Suitable special measurement pickups have been explained in more detail above in the context of the description of the embodiments of the apparatus of the invention.
In an advantageous embodiment the at least one special measurement pickup 6, 6.1-6.5 is arranged between the thread centering device 23 and the thread brake 9, or between the thread brake 9 and the first acceleration nozzle 3, or between the first acceleration nozzle 3 and the end of the shed, or between the first acceleration nozzle 3 and a second acceleration nozzle 4, or between the last acceleration nozzle 4 in the weft insertion direction and the shed, or at the entry to the shed, or on a slay or on a reed 8 of the air jet weaving machine 1.
For the regulation of the weft insertion a closed regulating circuit can for example be provided in order to regulate individual desired parameters such as for example a preset speed profile, the total flight time or the use of the brake during the weft insertion. The values determined continuously or at shorter intervals for the speed of the weft thread and/or the path traveled by the weft thread and/or for a parameter linked with the latter enable the regulation and/or control of the current weft insertion, with the control deviations and/or time delays in the regulating circuit being able to be kept comparatively small.
Furthermore the invention includes a weaving machine, in particular an air jet weaving machine equipped to carry out a method in accordance with the above description and/or with an apparatus in accordance with one of the above-described variants.
The above described method and the above-described apparatus are suitable for all kinds of weaving machines, such as for example air jet weaving machines, rapier weaving machines and projectile weaving machines. In rapier weaving machines the lead of the weft thread during the braking of the bringer rapier prior to the thread take-over by the taker rapier can for example be detected by means of the above-described method and by means of the above-described apparatus and a thread brake provided in the apparatus can be controlled in order to reduce or remove the lead of the weft thread.
The method and the apparatus for the insertion of a weft thread into a shed and also the weaving machine, in particular the air jet weaving machine in accordance with the above description, make it possible to determine during the weft insertion continuously or at shorter intervals values for the speed of the weft thread and/or the path traveled by the weft thread and/or for a parameter linked to the latter. Thanks to the values determined in this way it is possible to control and regulate the current weft insertion with increased accuracy in comparison to the prior art. Thus, for example, break-downs in the weft insertion can be detected more rapidly by means of the described method and by means of the described apparatus in a weaving machine, such as for example in an air jet weaving machine, a rapier weaving machine or a projectile weaving machine and it is possible to react more quickly to break-downs than was previously the case.
| Number | Date | Country | Kind |
|---|---|---|---|
| 07101692.7 | Feb 2007 | EP | regional |
