EP0659919B1 - Weft thread brake for a loom - Google Patents

Description

The invention relates to a weft brake for a weaving machine, which can be attached between a thread store and an insertion means and which contains at least one thread guide element which is adjustable by means of a drive means and deflects a weft thread.

Thread brakes are used in particular in air jet looms to brake a weft thread towards the end of its entry. They are usually placed between a pre-unwinder and a main blow nozzle attached to a comb drawer. In a known weft brake (EP-A 0 527 510), stationary and movable thread guide elements are provided. The movable thread guide elements are arranged on a holder which can be moved by means of a controllable, electrical drive means. A drive motor, for example, serves as the drive means and is controlled by a control unit at a specific point in time during the insertion of a weft thread. The braking force that occurs is determined by the deflection angle that is achieved by the guide elements. Since a weft insertion takes only a few milliseconds in weaving machines, in particular in air-jet weaving machines, such thread braking devices must be switched on very quickly. This leads to the thread brake being entered at high speed Brakes the weft very suddenly, so that there is a brief tension peak in the weft, which can lead to a break in the thread. Such tension peaks are also disadvantageous for the thread brake itself.

A thread brake is also known (EP-A 0 356 380), in which thread deflection is effected by means of several thread guide elements for braking, this deflection being partially reversed again after the occurrence of tension peaks.

The invention has for its object to provide a weft brake of the type mentioned in such a way that short-term voltage peaks are avoided as far as possible.

This object is achieved in that between the drive means and the at least one thread guide element there is provided a transmission means which transmits the movement of the drive means and which enables a relative movement between the drive means and the thread guide element.

The weft brake according to the invention has the advantage that a rapid movement of the drive means does not immediately lead to a rapid movement of the thread guiding elements, so that the weft thread is braked without brief peaks in tension. The movement of the thread guide elements is essentially dependent on the tension of the weft thread, which moreover leads to the fact that the deflection and thus the braking is less when the tension in the weft thread is high. As a result, the increase in tension of the weft thread due to braking is limited. In addition, the thread brake according to the invention has the advantage that even if the tension of the weft thread is reduced, it is still kept taut. The controllable drive means in connection with the transfer means permitting relative movement not only allows the tension to be brought to a certain value during the insertion of the weft thread and hold. In addition, it is also possible to bring the tension of the weft thread to an increased tension after insertion, for example for cutting, which can be adapted to a specific type of weft thread.

Fig. 1

zeigt in einer schematischen Darstellung eine Luftdüsenwebmaschine, die mit einer erfindungsgemäßen Fadenbremse ausgerüstet ist,

Fig. 2

eine perspektivische Ansicht (in Explosionsdarstellung) einer ersten Ausführungsform einer erfindungsgemäßen Fadenbremse,

Fig. 3

eine Axialansicht des Ausschnittes F3 der Fig. 2,

Fig. 4 bis 6

Ansichten auf den Verlauf des Schußfadens im Bereich der Fadenbremse in verschiedenen Positionen der Fadenbremse und des Eintragsmittels für den Schußfaden,

Fig. 7

eine Ansicht des Fadenverlaufs bei einer gegenüber Fig. 6 abgewandelten Position der Fadenbremse,

Fig. 8

eine perspektivische Ansicht einer abgewandelten Ausführungsform einer Fadenbremse,

Fig. 9

einen Schnitt durch eine Fadenbremse ähnlich Fig. 2,

Fig. 10

einen Schnitt durch eine weitere Ausführungsform einer Fadenbremse,

Fig. 11

einen Schnitt entlang der Linie XI-XI der Fig. 10,

Fig. 12

einen Schnitt durch eine vereinfachte Ausführungsform einer Fadenbremse,

Fig. 13

einen Schnitt durch eine Fadenbremse mit einem linear verstellbaren Fadenführungselement und

Fig. 14

eine erfindungsgemäße Fadenbremse mit magnetischen Übertragungsmitteln zwischen Antrieb und Fadenführungselement.

Further features and advantages of the invention result from the following explanation of exemplary embodiments shown in the drawings.

Fig. 1

shows a schematic representation of an air jet weaving machine which is equipped with a thread brake according to the invention,

Fig. 2

2 shows a perspective view (in an exploded view) of a first embodiment of a thread brake according to the invention,

Fig. 3

3 shows an axial view of section F3 of FIG. 2,

4 to 6

Views of the course of the weft thread in the area of the thread brake in different positions of the thread brake and the insertion means for the weft thread,

Fig. 7

6 shows a view of the thread course in a position of the thread brake which is modified compared to FIG. 6,

Fig. 8

2 shows a perspective view of a modified embodiment of a thread brake,

Fig. 9

3 shows a section through a thread brake similar to FIG. 2,

Fig. 10

3 shows a section through a further embodiment of a thread brake,

Fig. 11

10 shows a section along the line XI-XI of FIG. 10,

Fig. 12

2 shows a section through a simplified embodiment of a thread brake,

Fig. 13

a section through a thread brake with a linearly adjustable thread guide element and

Fig. 14

a thread brake according to the invention with magnetic transmission means between the drive and thread guide element.

The air jet weaving machine (1) shown in FIG. 1 contains a thread brake (2) which is arranged between a thread store (3) for the weft thread (30) and an entry means (4) for this weft thread. The thread store (3) consists of a prewinder which has a winding arm (5) which is driven by a drive motor (6) and which winds the weft thread (30) in windings (17) on a winding drum (7). The pre-winding device contains a magnetically actuatable pin (9) which can be advanced to the winding drum (7), in order to prevent or release the winding (17) from the winding drum. The winding drum (7) is also assigned a winding detector (10) which detects the number of windings (17) drawn from the winding drum (7). A stationary thread eyelet (8) is arranged after the thread store (3) for guiding the weft thread (30).

A main blowing nozzle (4), which is arranged on a comb (11) of the air jet weaving machine (1) and therefore carries out the movement of the comb (11), serves as the entry means. On the comb drawer (11) there is a profiled reed (12) and auxiliary blowing nozzles (13) which help to insert a weft into a shed.

A bobbin (14) for a bobbin (15) with a weft thread is arranged in front of the thread store (3) and runs through a thread eyelet (16) to the winding arm (5). Fig. 1 further shows a control unit (18), the function of which, insofar as it is important for the present invention, will be explained below.

The thread brake (2) is arranged after the thread eyelet (8) in the illustrated embodiment. It is fastened, for example, to a frame (48) of the thread store (3). After the thread brake (2), this frame (48) also has a second thread eyelet (19). In the exemplary embodiment shown, the thread brake (2) has two pin-shaped thread guide elements (20, 21) by means of which the weft thread (30) can be deflected between the stationary thread eyelets (8, 19). Scissors (31) for the weft thread (30) are arranged on the weaving machine frame between the main blowing nozzle (4) and the reed (12).

In addition, it should be mentioned that the thread eyelets (8, 19) can also be part of the thread brake (2). It should also be mentioned that, for example, an auxiliary main blowing nozzle can be arranged on the frame (48) after the thread eyelet (19).

A first embodiment of a thread brake (2) according to the invention is shown in FIGS. 2 and 3. For the sake of clarity, the components are shown in an exploded view far apart in FIG. 2. The thread brake (2) has two pin-like thread guide elements (20, 21) which are arranged diametrically opposite one another on a disc-shaped, rotatably mounted holder (22). The position of the thread guide elements (20, 21) is specified by means of a drive which can be controlled by the control unit (18). The drive consists of a drive motor (23), on the drive shaft (25) of which the holder (22) is mounted by means of a roller bearing (26). Between the drive shaft (25) and the holder (22) of the thread guide elements (20, 21) is a transmission means which transmits the movement of the drive shaft in the form of a spiral wound Spring (24) provided. The outer end (27) of the coil spring, which is angled, is inserted into a bore (29) in the holder (22). The inner end (28) of the spiral spring (24), as shown in FIG. 3, is held in a bore (32) in the drive shaft (25).

A weft insertion and the function of the thread brake (2) controlled by the control unit (18) will now be explained with reference to FIGS. 4 to 6. At the beginning of the weft insertion, the comb drawer (11) with the main blowing nozzle (4) is in the position shown in FIG. 4, in which the weft thread (30) runs straight through the thread eyelets (8, 19) and the main blowing nozzle (4). This is an advantageous position for starting a weft insertion in an air jet loom, because in this case the friction of the weft thread (30) on the thread eyelets (8, 19) and on the main blowing nozzle (4) is minimal. In this position, the pin (9) is withdrawn from the winding drum (7) in such a way that windings (17) are pulled off the winding drum (7) and the weft thread can thus be introduced into a shed by means of the main blowing nozzle (4). In this position, the thread guide elements (20, 21) are free of the weft thread (30). The position of the drive shaft (25) is shown by means of a thick line (40) which lies in the connecting line of the two thread guide elements (20, 21). Then the comb drawer (11) with the main blowing nozzle (4) is moved back in the direction of the arrow (P1) until the main blowing nozzle (4) is in the rear position (4A). Then the comb drawer (11) moves forward with the main blowing nozzle (4) according to the arrow (P2), as shown in FIG. 5.

The winding detector (10) detects each winding (17) drawn from the winding drum (7) and sends a corresponding signal to the control unit (18). If the length of a weft thread (30) to be entered corresponds to, for example, five windings, the control unit (18) can function the thread brake after detecting the third drawn winding (2) start. 5, the control unit triggers via the drive motor (23) and a rotation of the drive shaft (25) in the direction of the arrow (R1), so that it assumes the position shown by the line (40) in FIG. 5 . The drive shaft (25) is rotated by an angle specified by the control unit (18). The thread guide elements (20, 21) at least initially do not perform the same rotation angle movement, but rather remain due to the forces exerted on them by the weft thread (30). There is a balance between the torque that the spring (24) exerts on the holder and the torque that the weft thread (30) exerts on the holder (22) via the thread guide elements (20, 21).

The comb drawer (11) then moves forward together with the main blowing nozzle (4) in the direction of the arrow (P3) until the stop position (4B) is reached. Then the comb drawer (11) with the main blowing nozzle (4) moves back into the position shown in FIG. 6. In this position, the weft is usually cut with the scissors (31). Since the distance between the thread eyelet (19) and the main blowing nozzle (4) decreases when the main blowing nozzle (4) moves back from the stop position to the position shown in FIG. 6, the tension in the weft thread (30) becomes less or is even completely canceled. This can make it difficult to cut the weft thread (30). In the thread brake (2) according to the invention, however, this risk is reduced or eliminated, since the thread guide elements (20, 21) are moved further by means of the spring (24) and follow the drive shaft, so that the weft thread (30) is kept under tension.

In order to bring the tension of the weft thread (30) to a higher value during cutting, it is provided according to the exemplary embodiment according to FIG. 7 that the control unit (18) causes the drive shaft (25) to continue in the direction of the arrow before cutting (R2) rotated until the drive shaft (25) is in the position shown in Fig. 7 (see line (40)).

If the comb drawer (11) with the main blowing nozzle (4) moves back from the position shown in FIG. 6 after cutting the weft thread (30) to the position shown in FIG. 4, the main blowing nozzle (4) remains with compressed air ( with a lower pressure and / or a lower air flow). Since the distance between the guide eyelet (19) and the main blowing nozzle (4) shortens, the weft thread (30) protrudes from the main blowing nozzle (4) with a greater length in the position according to FIG. 4 than in the position according to FIG. 6. When weaving with several weft feeds and thus with several main blowing nozzles (4), this additional length of weft thread (30) can be a hindrance for the insertion of a weft thread from another main blowing nozzle. To prevent this, the drive shaft (25) can be rotated further by means of the control device (18) (arrow (R2) of FIG. 7) in order to pull the weft thread (30) back into the main blowing nozzle (4).

It is of course also possible to change the course of the braking force of the thread brake (2) during a weft insertion. For example, the drive motor (23) can rotate the drive shaft (25) with a certain course from a certain point in time of the entry, for example when the main blowing nozzle is in the position shown in FIG. 5, so that the weft thread (30) increases with increasing strength is braked. The angular position of the drive shaft (25) can also be controlled as a function of the point in time at which the winding detector (10) detects windings (17). If, for example, the third winding is detected earlier than at the expected time, the thread brake (2) can be switched on earlier and also with a larger angular rotation of the drive shaft (25).

Of course, it is also possible to control the thread brake (2) at other times in the course of a weft insertion in order to achieve a specific thread deflection and thus a desired braking. This point in time can be either at the beginning or in the middle of a shot entry.

In addition, it should be noted that the control unit also controls the prewinder. For example, it can be provided that the drive motor (6) of the pre-winding device is controlled by the control unit (18) at an average speed such that the winding arm (5) makes an average rotation when the winding detector (10) pulls out a winding (17). detected. When the fourth drawn-out winding (17) is detected, the pin (9) is then brought back to the winding drum (7), for example, in order to prevent more weft thread (30) from being pulled off the winding drum (7) than is required.

The embodiment according to FIG. 8 corresponds in principle to the embodiment according to FIG. 2. However, a disk-shaped holder (33) is arranged in a rotationally fixed manner on the drive shaft (25) and is provided with an opening (34) into which the inner end (28 ) of the spiral wound spring (24) is inserted.

The embodiment according to FIG. 9 essentially corresponds to the embodiment according to FIG. 2. In addition, a second, cup-shaped holder (35) is rotatably mounted on the drive shaft. This holder is provided with a collar (36) which receives the holder (22) so that the area of the spring (24) is shielded from dust. The outer end (27) of the spring (24) is connected to the frame (22) and the inner end (28) to the drive shaft (25) according to FIG. 2.

10 and 11, the thread guide elements (20, 21) are rotatable on the drive shaft (25) of the drive motor (23) mounted holder (22) extended towards the drive motor (23) and connected to the drive shaft (25) by means of a leaf spring (37). The leaf spring (37) is fixed in a groove (32) to the drive shaft (25) and engages in grooves (38) of the stanchion elements (20, 21). The leaf spring (37) can thus move in the grooves (38) so that a relative movement between the thread guide elements (20, 21) and the drive shaft (25) is possible.

In the embodiment according to FIG. 12 it is provided that the thread guide elements (20, 21) are connected directly to the drive shaft (25) by means of elastic means, in particular a leaf spring (39). A holder (22) can thus be omitted. Due to an elastic deformation of the leaf spring (39), the thread guide elements (20, 21) can perform a relative movement in the form of a twist to the drive shaft (25).

In the embodiment according to FIG. 13, a linearly movable thread guide element (41) is provided, which is immersed between two thread eyelets (8, 19) and thus deflects the weft thread (30). An electromagnet (42) serves as the drive means, to which a drive element (43) designed as a plunger anchor is assigned, which can be moved in the direction of arrow (B) by switching on the electromagnet (42), ie in the direction of a thread deflection. A return spring (44), which resets the drive element (43) against the direction of the arrow (B), engages on a support (45) which is fixedly connected to the drive element (43). Elastic transmission means (46) are provided between the drive element (43) and the thread guide element (41), which allow a relative movement between the thread guide element (41) and the drive element (43) against the direction of the arrow (B). The elastic means can be, for example, a spring (46), which is arranged in a recess of the drive element (43), in which a kind of piston rod (47) of the thread guide element (41) is performed. In modified embodiments, rubber-elastic bodies or an air cushion or the like are used as elastic means instead of the spring (46). intended.

In the exemplary embodiment according to FIG. 14, magnetic transmission means (49) are provided between the drive shaft (25) of the drive motor (23) and the thread guide elements (20, 21). These magnetic transmission means (49) consist of two permanent magnet sets, which face each other with opposite poles. A set of permanent magnets (50, 51) is arranged on a holder (33) which is non-rotatably connected to the drive shaft (25). The second set of permanent magnets (52, 53) is attached to the disk-shaped holder (22) which carries the guide elements (21, 22) and which is mounted on the drive shaft (25) by means of a roller bearing (26). For example, the permanent magnets (50, 53) are assigned with their north pole to the south poles of the permanent magnets (51, 52). In a departure from the illustration made for the sake of clarity, the holders (22, 23) lie opposite each other at a short distance, so that the permanent magnets (50, 52) and the permanent magnets (51, 53) attract each other. Without external stress, the permanent magnets (50, 52) and (51, 53) ensure that they are exactly opposite each other. However, the magnetic transmission means (49) allow the holder (22) with the thread guide elements (20, 21) to rotate relative to the drive shaft (25) due to external forces. The magnetic transmission means perform the same function as described in connection with the elastic transmission means (24, 37, 39, 46) using the exemplary embodiments according to FIGS. 1 to 13. The magnetic transmission means (49) themselves do not contain any moving parts that have inertial forces, so that fast reaction times are possible. The permanent magnets (50, 51 and 52, 53) are mutually magnetically isolated. Of course it is without further possible to provide more than two permanent magnet sets (50, 52; 51, 53).

The thread brake (2) according to the invention makes it possible to limit the tensions in the weft thread (30) and therefore to reduce the number of weft thread breaks. A voltage peak at the start of a weft insertion is limited by the alignment of the thread brake (2) and the thread eyelets (8, 9) to the main blowing nozzle. Tension peaks during sudden start-up of the thread brake (2) are limited by the elements (24, 37, 39, 46, 49) that allow a relative movement between the drive means and the thread guide elements. The tension peak at the end of a weft insertion, namely when the weft thread (30) is blocked by the pin (9) returning to the winding drum (7), is reduced in that the thread brake (2) has already partially braked the weft thread (30) beforehand.

It is of course possible to set the desired tension in the weft threads (30) by exchanging the transmission means (24, 37, 39, 46, 49) for others which generate a different tension. For example, springs can be replaced by springs with different spring constants. In the case of a spirally wound spring (24), it is possible to connect a few windings to one another, so that the spring constant is thereby changed. Permanent magnets can also be exchanged for permanent magnets with other magnetic forces. It is also possible to vary the number of permanent magnet sets.

Of course, it is also possible to provide more than two thread guide elements (20, 21). For example, four thread guide elements can be provided, which are each arranged in pairs symmetrically to the drive shaft (25) and at different distances from this drive shaft (25). In addition, it is also possible to switch between such To provide sets of thread guide elements additional, stationary thread eyelets.

Claims (7)

1. Weft brake (2) for a weaving machine, which can be applied between a thread-store means (3) and a feed means (4) and which includes at least one thread guide element (20, 21; 41), which guides a weft (3) round and is movable through use of a drive means (23, 25; 42, 43), characterised in that, between the drive means (23, 25; 42, 43) and the at least one thread guiding element (20, 21: 41), there is at least one transmission means (24, 37, 39, 46, 49) which transmits movement of the drive means (23, 25; 42, 43) a said transmission means enabling relative movement between a said drive means and said thread guiding element.
2. Weft brake in accordance with claim 1, characterised in that a rotating drive (23) with a drive shaft (25) is provided as the drive means which is connected to the at least one movably, coaxially disposed thread-guiding element (20, 21), by a transmission means (24, 37, 39, 49).
3. Weft brake in accordance with claim 1 or 2, characterised in that one holding means (22) is provided, for at least one thread-guiding element (20, 21), which is rotatably supported on a drive shaft (25) and is connected to this latter by means of a transmission means (24, 37, 49) which enables relative movement in a peripheral direction between a said drive shaft and a said holding means.
4. Weft brake in accordance with any one of claims 1 to 3, characterised in that a spring-elastic transmission means (24, 37, 39, 46) is provided between a drive means (23, 25: 42, 43) and at least one thread-guiding element (20, 21; 41).
5. Weft brake in accordance with claim 4, characterized in that a spirally wound spring (24) is provided between a drive shaft (25) and at least one thread-guiding element (20, 21).
6. Weft brake in accordance with any one of claims 1 to 3, characterized in that magnetic transmission means (49) are disposed between a drive means (23, 25) and at least one thread-guiding element (20, 21).
7. Weft brake in accordance with claim 6, characterized in that a holding means (33) which is fixed, in terms of rotation, to a drive shaft (25), and a holding means (22) which carries at least one thread-guiding element (20, 21) and can rotate on a said drive shaft (25), are provided, said holding means being provided with opposing permanent magnets (50, 51, 52, 53).

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