EP0294323B1 - Thread brake with electronic command and application of the thread brake - Google Patents

Description

The present invention relates to a thread brake with electromagnetically controllable braking power, to the use of such a thread brake and to an arrangement of a plurality of thread brakes. Thread brakes of this type are used, for example, as weft brakes for defenseless weaving machines such as projectile, rapier, water jet and air weaving machines and generally in those cases where a thread is not moved at a constant speed and where the thread continues to run, ie the parts overtake the weft insertion member of the thread should be avoided. There are, for example, rapier weaving machines in which the weft thread is first accelerated by the rapier rapier and then decelerated to the transfer point in the middle in order to be accelerated and decelerated a second time after transfer to the rapier rapier. Ideally, this requires a weft brake, which releases the weft completely without braking in the acceleration phases in time with these acceleration and deceleration phases, brakes more or less strongly in the deceleration phases and possibly jams, i.e. holds in a clamping manner in other phases of the weaving cycle.

From Japanese laid-open specification JP 23014/82 and Russian patent SU 1,097,727, e.g. Electromagnetically controllable disc brakes are known. The plates and actuating levers for the plates, however, have relatively large masses, which in turn results in high response times for braking power changes, or else requires complex structural measures for the magnet coils. Due to the short switching times and relatively large masses, high forces and high wear and tear occur, for example, when the movable plate strikes when opening, when the thread brake is released.

German patent DE 34.46.567 describes a weft brake, in which the thread is braked between two leaf spring-like plates and the braking power is controllably increased with additional electromagnets. The basic setting of the leaf spring brake is adjustable and predefined by the preload of the leaf springs. The thread is braked by a relatively short part, at the end of the leaf springs facing away from the holder. The electromagnets that boost the braking power are also arranged in this area, so that the braking power is always provided by this short, almost punctiform end area. With such an arrangement, the thread is loaded almost selectively, which leads to high surface pressures on the thread. If the weft thread is very uneven and there are thread defects, the momentary loading of the thread in the braking area can vary in such a way that the thread tears or, conversely, is braked insufficiently, which is annoying and undesirable in any case.

From the French patent FR-2.300.734 is an air thread brake with an electromagnetic Additional brake, known. This additional brake consists of a spring-like plate, which is not in contact with the thread when the electromagnet is de-energized and leaves a gap open so that the thread is not braked. The brake does the job of stopping and holding the thread at the end of the weft insertion. When the auxiliary brake is actuated, the resilient plate is applied. The thread is clamped between the lamella and a plate. The thread is clamped practically only on a line transverse to the thread running direction. The thread is thus subject to severe local stress. A metered braking of the thread is not possible with greater unevenness of the yarn and especially because of the attraction characteristics of the spring-like lamella and magnet.

The present invention brings significant progress here and does not have the disadvantages of known thread brakes. The invention is contained in the characterizing part of claim 1. Furthermore, the invention relates to the use of such a thread brake as a weft brake in defenseless weaving machines. The dependent claims relate to advantageous developments of the invention.

The thread brake has short response times and remains controllable even at very high thread speeds, which can be in the range of 50 m / s and higher, for example, in the case of unprotected high-performance weaving machines. Due to the transfer of the braking power to the thread over a longer thread length of, for example, a few cm, the specific surface pressure on the thread is significantly lower with the same braking power, and the thread is thus braked more gently than with known thread brakes. In particular, the high specific surface load of the thread that is disruptive in previous thread brakes is eliminated during the braking process. The lower specific stress on the braking elements also leads to an improved service life of the thread brake. In addition, the braking performance of this new thread brake is significantly less affected by the unevenness of the thread. It is also conceivable to arrange several, for example two or three, lamellar brake foils lying one above the other, the foils being able to lie freely one above the other or connected to one another. This allows the maximum braking power to be increased while the magnetic current remains the same, which can be advantageous for coarser yarns.

The side of the flexible, lamellar brake film facing away from the thread could also be provided with a very light, practically mass-free plastic layer, for example a foam, which can make handling the film easier and reduce the risk of cut injuries for the operating personnel. Several thread brakes can be combined to form a multi-shot thread brake, for example with a common control.

Fig. 1

die perspektivische Ansicht einer schematisch dargestellten, als Schussfadenbremse ausgebildeten Fadenbremse mit drei steuerbaren Magnetspulen;

Fig. 1a

schematisch die Anordnung einer Schussfadenbremse an einer schützenlosen Webmaschine;

Fig. 2

eine Seitenansicht der Fadenbremse von Fig. 1;

Fig. 3

einen Querschnitt nach III-III durch die Fadenbremse nach Fig. 2;

Fig. 4

vergrössert, ein Detail des Schnitts von Fig. 3 durch die Bremsorgane und den gebremsten Faden bei wirksamer Bremse;

Fig. 5

schematisch ein weiteres Beispiel einer Anordnung von Magnet- und Bremsorganen bei einer Fadenbremse;

Fig. 6

im Querschnitt die schematische Darstellung einer weiteren Ausführung einer Fadenbremse mit einem lamellenartigen Bremsorgan, das Distanzelemente aufweist;

Fig. 7

in einer schematischen, parallelperspektivischen Darstellung eine Ausführungsform der Fadenbremse, bei der das lamellenartige Bremsorgan in einem deckelartigen Teil gehaltert ist;

Fig. 8

einen Querschnitt nach VIII - VIII durch die Fadenbremse von Fig. 7;

Fig. 9

Einzelheiten der Halterung für das lamellenartige Bremsorgan von Fig. 7.

The invention is explained in more detail below on the basis of the exemplary embodiments illustrated in the drawings and parts thereof. Show it:

Fig. 1

the perspective view of a schematically shown, designed as a weft brake yarn brake with three controllable magnetic coils;

Fig. 1a

schematically the arrangement of a weft brake on a defenseless weaving machine;

Fig. 2

a side view of the thread brake of Fig. 1;

Fig. 3

a cross-section according to III-III through the thread brake according to Fig. 2;

Fig. 4

enlarged, a detail of the section of Figure 3 by the braking members and the braked thread with an effective brake.

Fig. 5

schematically another example of an arrangement of magnetic and braking members in a thread brake;

Fig. 6

in cross section the schematic representation of a further embodiment of a thread brake with a disk-like braking element which has spacer elements;

Fig. 7

in a schematic, parallel perspective representation of an embodiment of the thread brake, in which the disk-like braking member is held in a cover-like part;

Fig. 8

a cross-section according to VIII - VIII through the thread brake of Fig. 7;

Fig. 9

Details of the bracket for the disk-like braking element of Fig. 7th

The thread brake 1 of FIG. 1 is arranged in the schematic example shown as a weft brake between the weft thread store and a main nozzle 31 of a weaving machine 3 in the running direction of the weft thread 21. It is of no importance for the explanations below, according to which unprotected weft insertion method the weft thread 21 is inserted into the symbolically drawn shed 32.

The three controllable electromagnets 112, 113, 114 are installed in the rigid strip 11, the surface 111 of which faces the thread 21 and is provided with an abrasion-resistant surface covering which forms the actual braking surface. The electromagnets can be cast in the housing 110, which is, for example, a profile made of plastic, a non-ferromagnetic metal, ceramic, glass or another non-ferromagnetic material. In the example shown, the magnets 112, 113, 114 are pot or holding magnets with a low-iron core, which have a short switching time of, for example, five milliseconds or shorter. A lamellar, Ferromagnetic metal foil 115 forms the second braking element and is pulled by the magnets 112, 113, 114 when the current is switched on against the brake lining of the rigid magnetic strip. The ferromagnetic metal foil 115 has the function of an armature for the magnets 112, 113, 114. The weft thread experiences a braking force that can be changed and controlled with the magnetic force of the controllable electromagnets.

The film 115 is fastened to the axis 116, which are fastened in bores of the two webs 117. In the example shown, the film 115 is slightly pretensioned, but due to the very small bending moment of the film, this does practically nothing to contribute to the braking performance. This only ensures that the film 115 bears against the thread and counteracts a possible fluttering of the film 115. It is essential that the film 115, which has a very low mass and is therefore almost weightless, rests over most of its length on the rigid braking surface 111 of the strip 11, or on the thread 21, at most with its own weight. The braking power is practically exclusively provided by the electromagnets 112, 113, 114 when the film 115 is more or less attracted by them. When braking, the metal foil 115 is deformed transversely to the thread running direction and wraps around the thread in a larger angular range, as is shown and described with reference to FIG. 4. With the thread brake released, however, i.e. When the electromagnets 112, 113, 114 are switched off, the practically weightless metal foil 115 is in contact with the thread 21 only along a line, so that the thread 21 is practically not braked.

The control electronics 4 for the thread brake 1 and the main nozzle 31 change those on the weft thread 21 Braking force exerted, for example, as a function of the position of the tip of the weft thread 21 in the shed 32 and the angle of rotation of the weaving machine (FIGS. 1, 1a). With weaving machines, the sequences of many functions are defined based on the angle of rotation of the main drive shaft. The control electronics 4 continuously uses the sensor 41, for example, to determine this angle of rotation. The sensor 42 determines the point in time at which the tip of the weft thread 21 passes through at a specific position in the shed 32 and can, for example, also emit a thread running signal of the weft thread to the control electronics. The three sensors 43 monitor the weft thread in the final phase of the weft insertion, it being possible for the thread directly or the weft insertion member to deliver the signals for the control electronics. From these signals from the sensors 41, 42 and 43, the control electronics 4 are able to determine the braking power currently required and to change the power of the brake magnets 112, 113, 114 via the inputs 44 and to adapt them to the respective requirements. It is possible to control each of the magnets 112, 113, 114 separately or to connect them in series and to control them in the same direction. It would also be possible to group magnets in groups, the magnets of which are connected in series, for control purposes. In our example, the two magnets, for example 112 and 114, could be connected in series and the third magnet 113 could be connected in parallel. In the example shown, the control electronics also takes over the control of the valve 45 of the main nozzle 31. The control 4 for the thread brake 1 can be an independent unit or a part, for example, of a central control electronics and can be fully integrated therein.

The three can be seen in the partially sectioned, schematic side view of the thread brake 1 from FIG. 2 Pot magnets 112, 113, 114, which are combined in the housing 110 to form a strip 11. The surface 111 of the strip 11 facing the thread 21 forms the actual thread brake with the lamellar, ferromagnetic metal foil 115. This metal foil forms the anchor of the pot magnets 112, 113, 114. The ferromagnetic metal foil can, for example, be a steel lamella of a few hundredths of a millimeter thickness. Films made of non-crystalline metal, known as glass metals, which combine the properties of high wear resistance and good magnetic properties, have also proven particularly useful. A layer of non-ferromagnetic glass metal with high wear resistance would also be suitable as a surface covering on the surface 111 facing the thread 21, ie the braking surface of the strip 11.

A thread brake with a single elongated, strip-shaped magnet would also be conceivable, which magnetically influences the metal foil over a substantial part of its length.

In Fig. 3, which shows a schematic section according to III-III of Fig. 2, the practically weightless metal foil 115 lies on the thread 21 and the thread experiences practically no braking effect. As soon as the brake magnets 112, 113, 114 are switched on, the lamellar foil 115 deforms as shown in FIG. 4 in such a way that the wrap angle of the metal foil around the thread 21 increases and / or the thread 21 is flattened such that the contact surface between thread 21 and the surface 111 of the strip 11 facing the thread 21 and the metal foil are enlarged. The thread 21 is braked very gently by the large braking surface. Because the braking power over a Greater length, for example five or more centimeters is provided on the thread, and that the metal foil adapts to a certain extent to the thread cross-section, the time variation of the braking power, which is caused, for example, by irregularities in the thread diameter, is less than, for example, in the case of disc brakes or leaf spring brakes, in which the total braking power is provided on a shorter thread length and, in addition, the braking members have a larger mass and thus a greater inertia.

Fig. 5 shows a thread brake according to the invention, in which in the bar 11 'in addition to four magnet coils B1, B2, B3 and B4, which are the brake magnets, the three air coils L1, L2 and L3 are also present. On the lamellar metal foil 115 ', the air coils opposite, on the side facing away from the thread 21, permanent magnets P1, P2, P3 attached. When the brake magnets B1, B2, B3, B4 are switched off, it is possible to lift the metal foil completely, ie to release the thread brake, with correctly polarized air coils, ie if the same poles of permanent magnets and air coils are opposite each other. By reversing the polarity of the air coils, they could also provide braking performance. The permanent magnets P1, P2, P3 increase the rigidity of the metal foil 115 'in their area, the flexibility of the foil between the permanent magnets and thus the thread-saving braking properties, but are largely retained. In addition, there are flexible permanent magnetic materials that only slightly increase the rigidity of the metal foil. The additional weight of the metal foil due to the permanent magnets can, if necessary, be compensated with the air coils.

In the embodiment shown greatly enlarged in Fig. 6, the metal foil 115 '' in the thread running direction, on both sides at the edge of spacers 118, which between the metal foil 115 '' and the braking surface 111 '' of the bar 11 '' a gap for the Release the unbraked thread. When the brake magnets are switched on, which, for example, are located between the spacer elements when viewed in the direction of travel of the thread, the yarn is braked in the manner described. If spacer elements 118 are also present in the area of the brake magnets, the metal foil is deformed and the metal foil is adapted to the thread 21, transversely to the thread running direction, for example in the manner shown in dashed lines in FIG. 6.

In the thread brake 7 of FIGS. 7, 8 and 9, the metal foil 715 is fastened to the cover-like carrier 71 with the L-shaped fastening brackets 72, 73. The carrier 71 with the metal foil 715 in turn is attached to the bar 711, with the braking surface 711 'with the two pivot tabs 74 and 75 and screws. The distance between the metal foil 715 and the braking surface 711 'can be adjusted with the adjusting screw 7111 by changing the angular position of the swivel tabs 74 and 75. In the example shown, the swivel tabs 74 are held in the selected position by the spring 76, one end of which is fastened to the swivel tab 74 and the other to the bar 711.

As in the schematic sectional drawing of Fig. 8, the distance between the metal foil 715 and the braking surface 711 'can be chosen approximately in the order of magnitude of the diameter of the thread 721. The recess 70 in the carrier 71 permits the passage of thick spots in the thread 221 without the thread tension being increased too much, by dodging the metal foil 715 in the caressed position 715 'in the recess 70. When braking, the metal foil 715 can nestle under the action of the magnetic forces similar to the thread 721 as shown in FIG. 6.

Fig. 9 shows L-shaped mounting bracket 73, with the two holding pins 77, 77 'which engage in holes 7150 and 7150' of the metal foil 715. At its other end, the metal foil 715 can be fastened in the holder 72 in the same way. With this type of installation, the metal foil 715 need not be clamped between the fastening bracket 73 and the carrier 71. The holes in which the holding mandrels can engage are oversized, so that the metal foil lies loosely and freely movable only with part of its own weight and only temporarily on the thread.

It would also be possible to fix the metal foil, viewed in the direction of the thread, only at the beginning. In this case, the metal foil could also be clamped between the carrier and the holder.

Claims (23)

1. A yarn brake (19) whose braking force is controllable electromagnetically, with one rigid (11, 111) and one lamella-like flexible and at least partly ferromagnetic brake element (115) which are disposed in the direction of movement of the yarn (21) to be braked, the same extending between the brake elements and controllable magnet members (112-114) being provided for variing the forces operative between the brake elements (111, 115) characterised in that the lamella-like brake element (115) is substantially flat and strip-like and that the brake elements (111, 115) in braking, act over a substantial portion of their length corresponding to more than their width on the yarn (21) in the direction of movement thereof and the strip-like brake element (115), when in its non-braking condition, rests on the yarn over much of its length at the most by its own weight.

2. A yarn brake according to claim 1, characterised in that a number of electromagnets (112-114) are disposed in the rigid brake element (11) in the direction of yarn movement and the magnetic circuit of such electromagnets is closed by parts of the flexible lamella-like brake element (115).

3. A yarn brake according to claim 1 or 2, characterised in that the controllable magnet members (112, 113, 114) are pot magnets having a low-iron core.

4. A yarn brake according to any of claims 1 to 3, characterised in that the lamella-brake element (115) is a metal strip having a thickness from a few hundredths to 50 preferably from 5 to 30, hundredths of a millimetre.

5. A yarn brake according to any of claims 1 to 4, characterised in that the lamella-like brake element (115) is made of rapidly solidified products (RSP).

6. A yarn brake according to any of claims 1 to 5, characterised in that at least two controllable magnet members (112 to 114) are connected in series.

7. A yarn brake according to any of claims 1 to 5, characterised in that at least two controllable magnet members (112 to 114) are connected in parallel.

8. A yarn brake according to any of claims 1 to 5, characterised in that the controllable magnet members (112 to 114) are connected in series in groups and the groups are connected in parallel on one another.

9. A yarn brake according to any of claims 1 to 8, characterised in that the controllable magnet members (112 to 114) are electromagnets having a switching time of less than 6 ms.

10. A yarn brake according to any of claims 1 to 9, characterised in that permanent magnets (P1, P2, P3) operative between the brake element (11′, 115′) are present in addition to the controllable magnet members (B1, B2, B3, B4, L1, L2, L3).

11. A yarn brake according to any of claims 1 to 10, characterised in that at least one of the brake elements (111, 115) has an abrasion-resistant coating on the side near the yarn.

12. A yarn brake according to any of claims 1 to 11, characterised in that the brake members (11, 111, 115) act on the yarn (21) over a length of more than 50 mm.

13. A yarn brake according to any of claims 1 to 12, characterised in that the lamella-like brake member (115) of the yarn brake is secured, as considered in the direction of yarn movement, at one end at the start with securing means (116, 117).

14. A yarn brake according to any of claims 1 to 13, characterised in that that side of the lamella-like brake element (115˝) which is near the yarn (21) and/or the rigid brake member (11˝, 111˝) have on the side near the yarn and outside the movement zone thereof spacing elements (118).

15. A yarn brake according to any of claims 1 to 14, characterised in that controllable magnet members (112 to 114) are combined in the direction of yarn movement in a magnet strip (111) comprising a number of electromagnets.

16. A yarn brake according to any of claims 1 to 15, characterised in that the lamella-like brake member (15) has on the side remote from the yarn a coating of low-weight plastics or plastics foam.

17. A yarn brake according to any of the claims 1 to 16, characterised that the lamella-like brake element (715) is fixed with fixing elements (72, 73, 77, 77′) on a support (71) on the side remote from the yarn.

18. A yarn brake according to claim 17, characterised in that the fixing elements (72, 73, 77, 77′) are placed in the direction of yarn movement at the beginning the support (71).

19. A yarn brake according to claim 18, characterised in that the fixing elements (73, 77, 77') are placed in the direction of yarn movement at the end the support (71).

20. A yarn brake according to any of the claims 17 to 19, characterised in that the support (71) has a recess (70) on the side facing the lamella-like brake element (715).

21. A yarn brake according to any of the claims 17 to 20, characterised by spacer means (74, 75) that define the distance between the support (71) with the lamella-like brake element (715) and the rigid brake element (711, 711′).

22. A yarn brake according to any of the claims 17 to 21, characterized by means (74, 75, 7111) for setting the distance between support (71) with the lamella-like brake element (715) and the rigid brake element (711′).

23. Use of one or more yarn brakes (1) according to any of claims 1 to 22 as weft yarn brakes for a shuttleless loom (3).

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