EP1552047B1 - Method for holding a weft yarn, and a jet weaving machine, particularly serving to carry out this method - Google Patents

Abstract

The invention relates to a method for holding a weft yarn (9) in the area of a main jet nozzle of a jet weaving machine, particularly an air jet weaving machine, particularly having multicolored pick, before a weft yarn (9) is inserted into a shed (20) formed by warp yarns (10). According to the invention, the weft yarn (9) is clamped in a direction of insertion after an injector (1) in the mixing tube of the main jet nozzle and is released shortly before insertion when a pressure pulse for inserting the weft yarn (9) is initiated by the main jet nozzle. In order to control the corresponding jet weaving machine, a clamping device (6) has a pressure sensor (7) that is connected to a compressed air source (8), a machine control (13), valves (8) and to a compressed air supply (3) of the injector (1) via signal lines (11) and (14) and via compressed air lines (15) and (17). The clamping device (6) is located between a first mixing tube section (4) and a second mixing tube section (5) to which a cutting device (18) is connected. The invention also relates to a method during which the weft yarn section is clamped, whereby holding air is only injected during the time between the capture-side arrival of a weft yarn (9) which was inserted immediately before, and the initiation of the pressure pulse for inserting the next weft yarn, which is required according to the pattern, during a released clamping.

Description

The invention relates to a method for holding a weft thread in the mixing tube of the main nozzle of a jet loom, in particular air jet loom, prior to the entry of the weft thread in a shed formed by warp threads.

In known jet looms, the weft thread to be introduced into the shed is fed by a so-called yarn store, also called a pre-pulser or a pre-pulser, to a pneumatically-acting main nozzle of a predetermined length representing a weft insertion means. The main nozzle has an injector and a mixing tube, which receives a weft thread and holds there until entry of the weft thread in the shed. The remaining part of the weft thread is located between the main nozzle and the thread storage / Vorsputer and on the thread storage / Vorspuler itself and is there held up to the entry of the weft.

In the known air jet looms, the weft thread located in the mixing tube of the main nozzle is held stretched before its entry by means of an air flow, which acts in the direction of the longitudinal central axis of the mixing tube. For this purpose, during the entire time of keeping the weft thread before its entry into the shed retaining air must be injected accordingly strong in the specified manner in the mixing tube. Compared to the time during which the weft yarn is held in the mixing tube of the main nozzle, the actual weft insertion is very short and occurs depending on the yarn quality at a pressure of between 1.0 to 6 bar, the pressure of the holding air usually between 0.1 and 1.5 bar.

In particular, depending on the pattern, several main nozzles are often required for certain tissues. The time during which the weft thread is held in the mixing tube of the main nozzle, rapport- or pattern-dependent extended in this case compared to the very short weft insertion time possibly again by a multiple.

In order to maintain a thread tension which is as constant as possible required for a high-quality fabric, in particular for elastic threads which have a more or less relatively high inherent restoring force, the pressure of the holding air in the main nozzle must be further increased in comparison to normal yarns in order to maintain the same constant as possible To achieve thread tension. However, higher pressure in the main nozzle / injector usually results in higher air consumption.

In WO 00/52 242 a device for feeding weft threads for a loom with at least one nozzle is described, which has an inflow opening for a pressure medium, which is formed so that the pressure medium undergoes a rotation about the longitudinal axis of the nozzle, whereby a in the device located weft yarn rotation or an additional rotation is granted. The thus having a swirl pressure medium keeps the weft thread between the individual shots a longer time, with too high a rotation should be avoided, since otherwise would result in a tissue with reduced quality. In this known air-jet weaving machine, therefore, the air flow having a swirl in the mixing tube of the main nozzle is exerted on the weft thread essentially during the entire time while it waits for its entry into the shed. The above-described disadvantages of holding with holding air remain intact.

From DE 32 00 638 A1 it is known to keep the weft thread in the mixing tube of the main nozzle of an air jet loom by mechanical clamping. The clamping device required for this purpose is arranged in the region of the outlet end of the mixing tube in which the weft thread passes into the shed. The clamping device may for example consist of a slide which is displaceable transversely to the longitudinal direction of the mixing tube as a lifting member and clamps the weft thread located in the mixing tube between the passage opening of the slide and the inner wall of the mixing tube. Another embodiment provides a transversely displaceable punch which presses the weft thread against the inner wall of the mixing tube. Finally, a further embodiment of the known mixing device is provided, according to which a portion of the mixing tube is formed as an elastic intermediate piece. The intermediate piece is to be compressed by two diametrically opposed lifting members, when they are moved against each other. The weft is then pinched by the compressed elastic spacer.

In the first and the second embodiment of the clamping device of this air jet loom, the weft thread is displaced laterally during clamping, so it is no longer in the central longitudinal axis of the mixing tube. Also in the third embodiment, this phenomenon is to be feared because only two lifting members are provided for compressing the elastic intermediate piece, the compression is therefore not strictly centrally symmetrical. A position of the weft thread outside the longitudinal center of the mixing tube prepares difficulties in the subsequent entry of the weft thread in the shed.

In DE 32 00 638 A1 is not explained in detail how the mechanical operation of the clamping device to be formed in detail. For the slider, the stroke-adjustable punch or the lifting elements for compressing the elastic intermediate piece but in any case a mechanical drive is required, which claimed a certain installation space and also can not work vibration-free. It is already pointed to this state of the art because of the possibility of uncontrolled pivotal movements that can perform the free end of the mixing tube when you press the thread clamp. Since in particular the multicolored weft insertion of the available space for a larger number of closely juxtaposed mixing tubes is very limited, the known solution can not be readily carried out in practice. In addition, mechanical vibrations or vibrations of the mixing tubes damage the precise function of such jet looms.

WO 02/095106 A1 deals with an air-jet weaving machine in which several main nozzles are combined with the associated mixing tubes to form a compact parallel arrangement. This known air-jet loom is thus set up for generating weave patterns and processing multiple colors. The weft threads located in the main nozzle and the mixing tube are held here by clamping action until the weft thread in question is released for entry. The clamping devices are arranged between a Hilfsblasdüse and a Hauptblasdüse, so are always at the entrance of the main nozzles and thus outside of the mixing tube. In this arrangement, the position of the weft thread within the mixing tube remains indefinite, so that a central entry of the weft thread is not guaranteed in the shed after the release of the weft thread without further measures. Furthermore, the clamping device is also equipped with mechanical clamping members in the air jet loom according to WO 02/095106 A1. For this purpose, designed as a piston or plunger longitudinally displaceable clamping members are moved pneumatically. Under the influence of overpressure they clamp the associated weft thread against an inner wall of the clamping device, while the resetting of the clamping members and thus the release of the weft threads takes place in that the clamping members are connected to a vacuum source. In this known air jet loom thus the means for holding the various weft threads are already assembled very compact. However, the clamping of the weft threads at the entrance of the main nozzle and the use of relatively solid mechanical clamping members leads despite the pneumatic actuation to the disadvantages already mentioned, namely that the position of the weft yarn in the mixing tube remains indefinite and mechanical shocks can not be excluded.

Finally, a method for holding a weft thread at the entrance of a main nozzle is known, in which the weft before entering the main nozzle is pressed by cross-inflow by means of compressed air against the entry of a bypass line (Patent Abstracts of Japan 11200193A dated 27.07.99). The weft yarn is thus simultaneously exposed to a longitudinal and a cross-flow, whereby the disadvantages of holding weft yarns are not eliminated by means of holding air.

In contrast, the invention has for its object to provide a method for holding a weft yarn in the mixing tube of the main nozzle of a jet loom, in particular air jet loom, and a jet loom for performing the method with which largely independent of the nature and quality of Schussgame the amount of holding air required can be significantly reduced or even completely waived holding air, which further a compact arrangement of main nozzles and mixing tubes is possible, the waste in fabric production are reduced and a negative impact is prevented by holding on the weft yarns, and the overall quality of the fabric produced is increased.

This object is achieved by the method according to claim 1 and the jet loom, in particular for carrying out this method, according to claim 8. Embodiments of these solutions are the subject of back claims.

The inventive solution according to claim 1 thus consists in a method for holding a weft thread in the mixing tube of the main nozzle of a jet loom, in particular air jet loom, before the entry of the weft thread in a shed formed by warp shed, wherein a flexibly formed portion of the mixing tube by applying from outside by means of a Pressure medium is compressed and holds the weft thread clamped.

According to this method, therefore, a purely hydraulic or pneumatic actuation takes place in that a pressure medium compresses the flexibly formed partial region of the mixing tube. The weft thread is held clamped; this type of clamping causes the yarn of the weft yarn is not adversely modified. It has been shown that a clamp in this regard is not critical, while holding air the game relatively quickly and adversely modified. The compression of the elastic portion of the Mixing tube by direct admission by means of a pressure medium allows a very low-inertia operation, which can accommodate the associated facilities to save space. In addition, mechanical shocks that could lead to vibrations of the mixing tubes during operation, largely avoided in this type of operation.

According to an advantageous development, in the method according to the invention the clamping takes place essentially in the region of the outlet end of the mixing tube. In this type of clamping, a largely central arrangement of the weft thread in the mixing tube is ensured even without the application of retaining air. This favorable conditions for a correct entry of the weft thread in the shed are given when the weft thread is released to the entry.

For further optimization, it is advantageously provided in the method according to the invention that the flexibly formed partial region of the mixing tube is deformed so far in the direction of its longitudinal central axis by means of the pressure medium that the weft thread is clamped in the region of the central longitudinal axis. While, for example, in the known jet loom according to DE 32 00 638 A1 two diametrically opposed lifting members are provided, which can not uniformly compress the flexible and elastic portion, but only irregularly deforming, takes place in this type of process, an exactly centralsymmetrisches, uniform compression , The weft thread is clamped and held exactly in the central axis of the mixing tube. The clamping device thus effectively forms a central closure, which aligns the weft centrally symmetrical and thus creates the optimal conditions for entry into the shed.

The already very low-inertia actuation according to the method of the invention is thereby further improved that, according to a further embodiment for accelerated cancellation of the clamping and release of the weft yarn of the flexible portion of the mixing tube is controlled from the outside under negative pressure.

Experiments have in fact revealed that the controlled release of the clamping action and the simultaneous loading of the weft yarn with entry air for re-entry of another weft thread in the shed, the elastic portion of the mixing tube not sufficiently fast enough relaxed, although due to the weft insertion into the sub-area incoming air the main nozzle helps to relax the sub-area. In unfavorable cases, this can lead to the weft thread being pulled Weft insertion still touches the inner wall of the flexible portion and leaves it traces of wear. In the long run, this would reduce the function and life of the clamping device. With the action of negative pressure when canceling the clamping these possible disadvantages are reliably avoided.

It has proven to be advantageous that the flexible portion of the mixing tube is controlled by means of compressed air at an overpressure of less than 2.0 bar for clamping and released by means of compressed air at a negative pressure of less than - 50.0 mbar.

As already mentioned, the best conditions are given for a clamping in the region of the central longitudinal axis and the outlet end of the mixing tube that the weft thread can then be inserted in the correct position in the shed. But to exclude any unwanted displacement of the weft before his entry into the shed and also to achieve its required extension, in a short transition period between the release of the clamp and the entry in the shed the weft thread can be kept temporarily by longitudinally flowing holding air. For this purpose, according to an advantageous embodiment of the method according to the invention, it is provided that a certain weft thread is held with retaining air only when it is inserted into the shed with the clamping open, when it is to be entered as the next weft thread due to the pattern.

Specifically, it can be provided that the weft yarn is held only between arrival arrival of a previously entered weft thread and triggering of the pressure pulse before the entry of the next weft with holding air.

This embodiment of the method according to the invention is of course of the utmost importance in multicolor weft insertion. For this purpose, namely a certain weft yarn to get a longer waiting time, if required by the pattern. During the entire waiting period, the weft thread is thus held solely by clamping. In this time, holding air is not required, and thus eliminates the adverse effects of holding air on the weft thread by modifying it. Only when a weft thread is previously registered immediately, and the entry of the respective held weft thread is imminent, this weft yarn is held for a short time with holding air to bring him in the optimal state for its entry and a position within the position of the mixing tube.

According to the method of the invention, therefore, the weft thread is held with a defined clamping force, so that it does not slip out of the main nozzle and still retains the optimum position for later entry as possible. With the method according to the invention, it is possible to interweave yarns which hitherto could not or could not be readily woven with jet looms, in particular air jet looms, even for a high-quality fabric. These include, for example, caterpillar twine and twisted elastic yarn, which can now be processed relatively easily with the method according to the invention, especially in air jet looms.

The method can be used particularly advantageously if weft threads of different colors are introduced in order to be able to weave specific patterns. A significant advantage of the method according to the invention is that according to the pattern repeat in the case of several, usually for the main nozzle associated with each color, the clamping of the weft thread is pattern-dependent. In this case, the weft thread is kept clamped during its entire "waiting time" on the entry until just before his entry.

The short-term holding by means of holding air represents only an additional optimization, because in a centrally symmetric clamping anyway good conditions for a correct entry of the weft thread are given. However, it has been found that the maintenance of a constant yarn tension is an important criterion for a high-quality fabric and can be achieved particularly well by holding by means of holding air. The weft thread receives the necessary thread tension and an optimal position in the mixing tube. Because of the only short exposure time of the holding air in the case of the method according to the invention, wherein retaining air is only required if the entry of the weft thread imminent, avoids the adverse modification of the weft thread by the holding air.

The object underlying the invention is further achieved with a jet loom, in particular for carrying out the method according to one of claims 1 to 7, with at least one main nozzle, comprising an injector with a compressed air connection and a mixing tube adjoining the injector,
with a clamping device arranged in the mixing tube, which is formed by a flexibly formed portion of the mixing tube and for clamping a weft thread located in the mixing tube to the inner wall of the mixing tube, and with a device for acting on the flexibly formed portions of the mixing tube by the pressure medium in the manner that the subregions when pressurized by the pressure medium under a certain pressure P, the weft thread clamping be compressed and return to its original position when pressure relief.

As has already been stated in connection with the method, such a design of the jet loom allows a low-inertia, compact and largely vibration-free function. It is therefore particularly suitable for the creation of weave patterns with different colors, in which numerous main nozzles must be assembled with the associated mixing tubes in a compact arrangement. The operation and control by a hydraulic or pneumatic pressure medium, preferably compressed air, also leads to a low-vibration operation, so that the individual mixing tubes with respect to the shed their optimal exact position can largely meet even in continuous operation.

It is advantageous if the clamping device is a central closure in the form of a pneumatic or hydraulic muscle. Here, an embodiment is preferred in which the pneumatic or hydraulic muscle clamps the weft thread substantially in the region of the central longitudinal axis of the mixing tube.

The hydraulic or pneumatic muscle is due to the fact that a portion of the mixing tube is made of a flexible and highly elastic material. The pressure medium, especially compressed air, acts uniformly from the outside and centrally symmetric on the muscle, so that with maximum security a clamping in the region of the central longitudinal axis of the mixing tube comes about.

The pneumatic or hydraulic muscle is arranged between a first and a second mixing pipe section and connects the two mixing pipe sections sealingly, wherein the pressure medium acts on the muscle in a surrounding chamber.

An optimal positionally correct holding of the weft thread is achieved in that, according to a development, the clamping device is arranged on the nozzle opening of the mixing tube.

The control of the pneumatic or hydraulic muscle can be carried out in such a way that the pressure pulse triggered in the injector of the main nozzle for insertion of the weft thread releases the clamping effect of the clamping device.

This training is advantageous because the clamping must be canceled anyway before the entry of the weft thread in the shed.

Advantageously, it can further be provided that for fast pressure relief of the pneumatic or hydraulic muscle, the chamber can be connected to a vacuum source.

The release of the clamping action is thus not simply by the fact that the action of an overpressure from the outside is terminated on the muscle, but at the same time compressed air is blown through the interior of the muscle, and also the chamber surrounding the muscle can be exposed to the action of negative pressure.

The necessary connections can be made via solenoid valves, and as a vacuum source can serve a vacuum pump.

An advantageous development further consists in that the inventive jet loom is provided with a control device which causes a coordinated interaction in the supply of compressed air from a compressed air source to the injector and provided with a pressure sensor clamping device, wherein the compressed air serves as a pressure medium for the clamping device ,

Such networking of the operation of the main nozzle and the clamping device leads to a compact and economically operating control.

In this case, it is furthermore advantageously provided that the clamping device can be held in its open position immediately before the entry of the weft thread and holding air can be introduced into the mixing tube only when the clamping device is open via the injector.

In this embodiment, the weft thread is held in the longest span of its "waiting time" by clamping by means of the pneumatic or hydraulic muscle. Only shortly before its entry is held by means of retaining air, whereby the position and the condition of the weft thread are optimally prepared for the entry in the shed. Compared to the prior art, this significantly reduces the risk that the game will be adversely modified by the holding.

After the entry of the weft thread into the shed, the weft thread is separated in the direction of insertion by means of a cutting device. This happens at a time in the pressure pulse triggered by the injector of the main nozzle has dropped again so far that the pressure in the chamber surrounding the muscle outweighs and re-clamps the weft thread at the nip. Alone on the choice of the pressure difference between the pressure pulse of the injector and pressure in the surrounding chamber of the muscle, the control of the opening and closing of the clamping device takes place in dependence on the property of the muscle forming elastic piece of hose.

Such a pressure-balanced system in terms of the maximum pressure of the output from the injector of the main nozzle pressure and the pressure of the pressure medium, which compresses the muscle for holding the weft yarn is for particularly fast changing cycles, that in this case weaving cycles, for air jet looms particularly high speed suitable.

Finally, the inventive jet loom can still be modified with such a design of the control device in an advantageous manner that the clamping device is close enough to close the end of the entry of the weft yarn that the weft yarn is braked during this phase of his entry, so that he braked by the Clamp slips through. This can be achieved by targeted control of the pressure difference / the pressure differences between the pressure pulse or the shape of the pressure pulse and the pressure or the pressure curve in the chamber surrounding the clamping device. The clamping device then acts as a brake during a time range shortly before the end of the weft insertion.

Depending on the dimensioning of said pressure difference, this braking device can achieve a gentle removal of kinetic energy from the weft thread which has been accelerated to a high speed during the application. In this way, the directed at the end of the weft yarn usually to stop stop the Vorspulers movement of the weft yarn (spring back) is largely avoided. With such a respect to the braking effect, serving as a thread brake clamping device can be counteracted this jumping back (loosening) of the weft thread to stop element, without - as it is common in the art - a higher Stafettendüsendruck, the use of a stretching nozzle and / or increased waste lengths are the result. The clamping action during the gradual deceleration is controlled by the pressure difference so that the weft thread slips smoothly through the clamping device, without being himself modified. It has been found that the adjustments between the pressure or pressure curve in the chamber and the pressure pulse or the shape of the pressure pulse are so fine can be realized that the braking action is optimally adjustable depending on the type and quality of the weft. This effect is achieved without a deterioration of the tissue quality. Rather, the opposite is the case, because the quality of the fabric was significantly improved compared to an unrestrained entry of the weft.

It is also possible that a pre-pulse is triggered by the injector, which is detected by the pressure sensor and serves as a trigger of opening the clamp. The amplitude of the pre-pulse is chosen so that it is greater by a defined amount than the pressure in the chamber surrounding the muscle, the duration of the pre-pulse at least equal to the duration of the entry of the protective thread.

Figur 1

zeigt die prinzipielle Ansicht einer Hauptdüse mit Injektor und Mischrohr mit in das Mischrohr integrierter Klemmeinrichtung zum Klemmen eines Schussfadens mit einer Steuereinrichtung, welche das Klemmen des Schussfadens und das Auslösen eines Druckimpulses durch den Injektor aufeinander abstimmt;

Figur 2

beinhaltet das Ausführungsbeispiel einer Klemmeinrichtung in Form eines pneumatischen / hydraulischen Muskels in geöffneter Position, d. h. in einer Position, in welcher der Schussfaden durch den Muskel nicht geklemmt ist;

Figur 3

stellt einen in das Mischrohr integrierten pneumatischen hydraulischen Muskel in der Position dar, in welcher der Schussfaden nach seinem Eintrag abgeschnitten und durch die Klemmeinrichtung gehalten ist;

Figur 4

enthält Einzelheiten einer erfindungsgemäßen Düsenwebmaschine mit abgewandelter Steuerung des pneumatischen/hydraulischen Muskels, der in seiner Klemmstellung dargestellt ist;

Figur 5

ist einer der Figur 4 entsprechende Darstellung bei Freigabe der Klemmung.

Further advantages, features and possible applications of the invention are explained in detail below on the basis of an embodiment on the basis of the attached drawings. In the drawings, the following is shown:

FIG. 1

shows the principal view of a main nozzle with injector and mixing tube with integrated into the mixing tube clamping device for clamping a weft with a control device which tunes the clamping of the weft thread and the triggering of a pressure pulse through the injector to each other;

FIG. 2

includes the embodiment of a clamping device in the form of a pneumatic / hydraulic muscle in the open position, ie in a position in which the weft thread is not clamped by the muscle;

FIG. 3

represents a pneumatic hydraulic muscle integrated in the mixing tube in the position in which the weft thread is cut off after its entry and held by the clamping device;

FIG. 4

contains details of a jet loom according to the invention with modified control of the pneumatic / hydraulic muscle, which is shown in its clamping position;

FIG. 5

is a representation corresponding to Figure 4 upon release of the clamp.

Figure 1 shows the basic structure of a main nozzle with injector 1 and mixing tube 2 and the mixing tube integrated clamping device 6 and the connection of the clamping device 6 with a control device 13, via which a connection between the control of the injector 1 and the control of the clamping device 6 can be realized. In the main nozzle with the injector 1 and the mixing tube 2, a weft thread 9 is arranged, which extends substantially along the longitudinal central axis of the mixing tube 2. In the mixing tube 2, the clamping device 6 is integrated between a first mixing tube section 4 and a second mixing tube section 5, which is shown enlarged in Figures 2 and 3. At the outlet of the weft thread 9 from the second mixing tube section 5, a cutting device 18 is shown in principle. The cutting device 18 is located between the second mixing tube section 5 and the shed 20 shown in plan view, in which the weft thread is to be entered. The shed 20 is formed by a plurality of warp threads 10.

Connected to the clamping device 6 is a pressure sensor 7, which is connected via a signal line 11 to the control device 13. Via further signal lines 14 valves 8 are controlled by the control device 13, which in turn are connected to a compressed air source 19 and allow a corresponding air supply via a compressed air line 15 to the clamping device 6 and via a further compressed air line 17 to a compressed air connection 3, which in turn to the injector 1 of the main nozzle is connected and via which the compressed air supply to the injector 1 for the supply of holding air and for the entry of the weft thread 9 takes place. Via the signal lines 14 and 11, the time dependence between the closing and opening of the clamping device 6 and the triggering of a pressure pulse for the entry of the weft thread 9 and the beginning and end of the blowing of holding air is controlled.

FIG. 2 shows an enlarged sectional view of the clamping device 6 according to FIG. 1 in the opened state. Under open state, the state is understood, in which the clamping device 6, the weft thread 9 is not jammed, d. H. the weft 9 either to the entry or during the entry releases. However, if the weft thread is not yet to be registered due to the pattern, no holding air is blown in, but according to the invention, the weft thread is clamped (see FIG. 3).

The weft thread 9 extends through the first mixing tube section 4, through the clamping device 6 and through the second mixing tube section 5 along the central longitudinal axis of the mixing tube. The clamping device 6 connects, so to speak, a mixing tube divided into two by the mixing tube sections 4 and 5 in airtight manner with one another. Different In other words, the clamping device is designed such that in the region of the clamping, the wall of the mixing tube 2 is designed to be flexible as a flexible piece of tubing, that the wall upon application by means of a pressure medium, represented by the arrow in the direction of the inlet into the clamping device 6, with the pressure P is compressed or returned to its original position when pressure relief. Inside the mixing tube, the pressure P _m prevails. The flexible wall of the clamping device is designed as a pneumatic or hydraulic muscle 16. This pneumatic or hydraulic muscle 16 is surrounded by the chamber 12, in which via the compressed air line 15 (Fig. 1), the pressure medium with the pressure P is introduced into the clamping device 6. The pressure medium deforms at a correspondingly increased pressure (P> P _m ) the flexible wall of the pneumatic or hydraulic muscle in the direction of the central longitudinal axis of the mixing tube and thus on the weft thread 9 to the chamber 12 of the pressure sensor 7 is connected, which via the signal line 11 is connected to the control device 13 (see FIG. 1). By means of the pressure sensor 7 is effected by a corresponding control circuit via the valve 8, the controlled supply of the pressure medium from the pressure source 19 or the interruption of the supply of pressure medium to the respective state of the clamping device 6, ie terminals of the weft thread 9 or releasing the same, time-dependent from the triggering of a pressure pulse from the injector 1 of the main nozzle for introducing the weft thread 9 into the shed 20. About the compressed air line 17, the compressed air supply to the injector. 1

Fig. 3 shows the state of the clamping device 6, wherein the pressure of the pressure medium P in the chamber 12 is greater than the internal pressure P _m in the mixing tube, so that the flexible wall of the pneumatic or hydraulic muscle 16 in the direction of the central longitudinal axis of the mixing tube 2 is deformed so far that the weft thread 9 is securely clamped centrally, so that its thread tension in the region of the first mixing pipe section 4 is maintained in the desired manner. The separated by means of cutting device 18, not shown in FIG. 3, located in the second mixing tube section 5 section of the weft thread is then on the inner wall of the second mixing tube section 5 to stress. Since the clamping device 6 with the muscle 16 is relatively close to the interface, that is at the front in the insertion direction of the weft thread and since the clamping device retaining air is largely avoided, so a thread modification in the immediate terminal area does not occur substantially, therefore, the quality of Tissue high and waste low. Only the part of the weft thread which is essentially located in the first mixing tube section 4 and has a substantially constant thread tension is woven into the finished fabric, so that otherwise varying tissue tension causing varying thread tensions are avoided.

The gas-tight connection between the first mixing pipe section 4 and the second mixing pipe section 5 is achieved by an annular collar 21 in the form of a union nut in conjunction with an O-ring seal 22 which is screwed onto the housing of the clamping device 6 in the axial direction, so that the screwing of the annular collar 21, the seal 22 pressed and thus their sealing effect is achieved.

FIGS. 4 and 5 show the modified control of a jet loom designed according to the invention. In this case, those parts which remain unchanged from the embodiment described above, with the same reference numerals as previously designated.

To actuate the pneumatic / hydraulic muscle 16 is a solenoid-way valve 23 which is controlled by the control device 13 and via pressure lines 24, 26, the chamber 12 of the clamping device 6 connects to a pressure source 25. Thereby, the pneumatic / hydraulic muscle 16, so the flexible and highly elastic trained portion of the mixing tube, symmetrically and uniformly compressed in the direction of the longitudinal center axis of the mixing tube 2 and clamps the weft thread 9 firmly

To cancel the clamping action, the solenoid valve 23 is reversed and thereby connects the chamber 12, the pressure line 26 and the connection guide 27 with a vacuum source 28. This results in a rapid pressure relief of the pneumatic / hydraulic muscle 16. The acceleration of the release process leads In addition, the weft thread 9, which immediately sets in motion, can no longer grind along the flexible and highly elastic wall of the muscle 16. Damage to the muscle 16 is thereby avoided even with prolonged service life.

Claims (19)

1. Method for holding a weft thread (9) in the mixing tube (2) of the main jet nozzle of a jet loom, particularly an air-jet loom, before insertion of the weft thread (9) into a shed (20) formed by warp threads, characterised in that a flexibly constructed subregion of the mixing tube (2) is compressed by external action of a pressure medium and clamps the weft thread (9).
2. Method according to claim 1, in which clamping is effected substantially in the region of the exit end of the mixing tube (2).
3. Method according to claim 1 or 2, in which the flexibly constructed subregion of the mixing tube (2) is deformed so far towards its longitudinal centre line by the pressure medium that the weft thread (9) is clamped in the region of the longitudinal centre line.
4. Method according to any one of claims 1 to 3, the flexible subregion of the mixing tube (2) is set under a low pressure, under external control, for accelerated termination of clamping and release of the weft thread (9).
5. Method according to claim 4, in which the flexible subregion of the mixing tube (2) is controlled by means of compressed air at an overpressure of less than 2.0 bar to effect clamping, and is released by means of compressed air at a low pressure of less than -50.0 mbar.
6. Method according to any one of the preceding claims, particularly with multicoloured weft insertion, in which, before insertion into the shed (20), a specific weft thread (9) is held by means of holding air, with clamping released, only when it is to be inserted as the next weft thread (9), as required by the pattern.
7. Method according to claim 6, in which the weft thread (9) is held with holding air only between arrival on the capture side of an immediately previously inserted weft thread (9) and initiation of the pressure pulse for insertion of the next weft thread (9).
8. Jet loom, especially for implementing the method according to any one of claims 1 to 7, having at least one main nozzle, comprising an injector (1) with a compressed air connection (3) and a mixing tube (2) adjoining the injector (1), having a clamping device (6) arranged in the mixing tube (2), characterised in that the clamping device (6) is formed by a flexibly constructed subregion of the mixing tube (2) and serves for clamping a weft thread (9) located in the mixing tube (2) against the inner wall of the mixing tube, and having an arrangement for pressurizing the flexibly constructed subregion of the mixing tube (2) by means of the pressure medium such that, on being pressurized with pressure medium at a specific pressure P, the subregion is compressed so that it clamps the weft thread (9), and when the pressure is eased it returns to its original position again.
9. A jet loom according to claim 8, in which the clamping device (6) is a central closure in the form of a pneumatic or hydraulic muscle (16)
10. A jet loom according to claim 9, in which the pneumatic or hydraulic muscle (16) clamps the weft thread substantially in the region of the longitudinal centre line of the mixing tube (2).
11. A jet loom according to claim 8 or 9, in which the pneumatic or hydraulic muscle (16) is arranged between a first mixing tube portion (4) and a second mixing tube portion (5) and joins the two mixing tube portions (4, 5) in a sealed manner, the pressure medium acting on the muscle (16) in a chamber (12) surrounding the same.
12. A jet loom according to any one of claims 8 to 11, in which the clamping device (6) is arranged at the delivery opening of the mixing tube (2).
13. A jet loom according to any one of claims 8 to 12, constructed such that the pressure pulse released in the injector (1) of the main nozzle for insertion of the weft thread (9) releases the clamping action of the clamping device (6).
14. A jet loom according to any one of claims 11 to 13, in which the chamber (12) is connectible to a low-pressure source (28) for rapid pressure relief of the pneumatic or hydraulic muscle.
15. A jet loom according to claim 14, in which the connection is effected by way of a magnetic directional control valve (23).
16. A jet loom according to claim 14 or 15, having a vacuum pump serving as the low-pressure source (28).
17. A jet loom according to any one of claims 8 to 16, having a control arrangement (13) for co-ordinated interaction between the supply of compressed air from a compressed air source (19) to the injector (1) and the clamping device (6) provided with a pressure sensor (7), the compressed air acting as a pressure medium for the clamping device (6).
18. A jet loom according to claim 17 having a control arrangement (13) constructed such that the clamping device (6) is arranged to be held in its opened position immediately before the insertion of the weft thread (9) and holding air is arranged to be introduced into the mixing tube (2) via the injector (1) only when the clamping device is open.
19. A jet loom according to claim 17 or 18 having a control arrangement (13) constructed such that, shortly before the end of insertion of the weft thread (9), the clamping device (6) can be closed far enough for the weft thread (9) to be decelerated during this phase of its insertion so that it slips, decelerated, through the clamping device (6).

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