EP0475892B1 - Yarn brake for looms - Google Patents

Description

The invention relates to a thread brake according to the preamble of claim 1 and projectile and rapier weaving machines with such thread brakes.

In projectile weaving machines there are thread tensioners between the supply bobbins and the shed, each consisting of a thread brake and a retraction or tensioning lever. A thread brake, which has proven itself very well in practice, has on the one hand a resilient metal band, which is held under tension by a spring, and on the other hand a brake body, the braking part of which is, for example, spoon-shaped. The thread can be clamped between the band and the brake body, the brake body being pressed against the brake band. Since the brake band is flexible, partial braking can also be carried out, in which the thread can still be pulled between the two braking components of the thread brake against frictional forces. The brake body is moved mechanically via a linkage that is controlled by means of a camshaft. Such a thread brake is e.g. known from document US-A-4 431 036.

Electromagnetically controlled thread brakes are also known, in which one or more brake bodies are moved by electromagnets or in which the brake gap between a ferromagnetic plate and a fixed counter surface is influenced by means of electromagnets (EP-A-0 294 323 = T.735). Such thread brakes have the advantage that their braking power can be controlled by means of a logic circuit and that the braking power can be easily adjusted, for example with regard to changing yarn properties, in particular when changing articles.

The demands on the control of the thread brake are greatest during the projectile launch phase. Until the thread is transferred to the projectile, the brake gap of the thread brake must be closed and released after firing when the weft thread is pulled. In high-speed weaving machines, the thread brake must be released within a few milliseconds. This is not possible with today's cam controls; they would have to be lightweight, but would be very expensive. Reliable functionality of the thread brake is also difficult to achieve with electromagnetic control.

There is also a problem with fast-running rapier weaving machines, in which the weft thread is inserted into the center of the shed by a bringer rapier and taken over by a rapier rapier, which can be solved with fast-controllable thread brakes. After acceleration of the weft thread by the rapier gripper, during which the thread brake must be released, there is a delay towards the transfer point in the center, at which the weft thread can run onto or overtake the rapier gripper due to its inertia. In order to keep the weft thread taut during the deceleration phase, the thread brake must be activated. However, immediately after the handover to the picker, the weft has to be used again be released. This requires a fast-reacting thread brake during thread transfer.

It is an object of the invention to provide a thread brake for high-speed projectile or rapier weaving machines, the mechanical brake components of which are formed by conventional and well-proven means, namely the brake band and brake body, the brake bodies of which, on the other hand, are controllably moved by means which meet the requirements mentioned for high-speed Weaving machines are enough. This object is achieved by the features of the characterizing part of claim 1.

A stepping motor is advantageously used as the servomotor for moving the brake body of the thread brake according to the invention, which has a drive shaft which, together with a permanent magnet attached to it, is rotated by a stationary ring of small electromagnets. The electromagnets are arranged uniformly at angular intervals of, for example, 7.5 degrees and can be excited sequentially at time intervals of, for example, 2.5 milliseconds. With such a stepper motor, the brake can be opened in around 10 milliseconds.

Further embodiments of the invention are set out in claims 2-11.

Fig.1

ein erstes Ausführungsbeispiel der erfindungsgemässen Fadenbremse,

Fig.2a

den zeitlichen Verlauf der Bremskörperstellung über einen Webzyklus (Hubkurve) für eine Projektilwebmaschine,

Fig.2b

eine Hubkurve für eine Greiferwebmaschine,

Fig.3a

ein zweites Ausführungsbeispiel der erfindungsgemässen Fadenbremse in Seitenansicht auf mindestens zwei parallel angeordnete Fadenbremsen, wobei bei der einen einzelne Teile als Schnitte dargestellt sind,

Fig.3b

eine Draufsicht auf Fadenbremsen gemäss Fig.3a,

Fig.4a

eine schematische Darstellung der beim Schusseintrag wichtigen Komponenten einer Projektilwebmaschine im Moment der Fadenübergabe an das Projektil und

Fig.4b

die entsprechende Darstellung wie in Fig.4a kurz nach dem Projektilabschuss.

The invention is explained in more detail below with reference to the drawings. Show it:

Fig. 1

a first embodiment of the thread brake according to the invention,

Fig.2a

the time course of the brake body position over a weaving cycle (stroke curve) for a projectile loom,

Fig.2b

a stroke curve for a rapier weaving machine,

Fig.3a

2 shows a second exemplary embodiment of the thread brake according to the invention in a side view of at least two thread brakes arranged in parallel, with one of the individual parts being shown as sections,

Fig.3b

a plan view of thread brakes according to Fig.3a,

Fig.4a

is a schematic representation of the components of a projectile weaving machine that are important for weft insertion at the moment the thread is transferred to the projectile and

Fig. 4b

the corresponding representation as in Fig.4a shortly after projectile launch.

The perspective view of the thread brake in Fig.1 shows the following components: the brake band 1; the brake body 2, which is pivotable about the axis 2a; a lever-like piece of sheet metal 3, over which the brake band 1 is tensioned by means of a spring 4; a horizontal, mandrel-like rod 5, at the tip of which the piece of sheet metal 3 is tiltably attached and which is connected at the other end 5a to other components of the weaving machine, not shown, for example a weft monitor and a supporting frame; Eyelet body 6a and 6b for guiding the weft 10; a vertical support beam 7, on which various components of the thread brake are attached.

The following components can also be seen in FIG. 1: a support plate 8 for the stepper motor 20, which can be fastened in height on the support beam 7 by means of a screw 9; the drive shaft 21 and the connecting cable 22 of the stepping motor 20; a lever 23 fastened on the drive shaft 21 and a tab 24, via which a rotary movement of the stepping motor 20 can be converted into a lifting movement of the brake body 2; finally, a small permanent magnet 29 placed on the lever 23, which allows an inductive sensor 31 to determine a reference position of the stepping motor 20.

The stepper motor 20 is connected via the connection cable 22 to a control circuit and a logic circuit, not shown. The sensor 31 transmits its signals to this logic circuit. A control program can be stored in the memory of the logic circuit for each thread brake, which generates a stroke curve that is optimally adapted to the yarn properties of the weft thread, for example.

The stroke curve in FIG. 2a shows the course over time of the position which the braking surface of the brake body 2 occupies. (Instead of the time t, the phase of the machine cycle (machine degree) is usually used as a variable, which can be determined by a crank angle encoder on the main shaft.) The period length T of the weaving cycle (corresponding to 360 machine degrees) is of the order of magnitude of 200 milliseconds. The stroke H is positive if the brake gap is open, i.e. the brake is released. Since the brake band 1 is flexible, the stroke H can also be negative. With a weakly negative stroke, the Thread are still pulled between brake band 1 and brake body 2.

At the beginning of the weaving cycle and at the end, the thread brake is in the "partial braking" state: curve pieces 50 and 50 '. During the interval 70, during which the projectile flight takes place, the thread brake is in the released state, with the exception of a short initial phase: curve piece 51. The thread brake opening corresponding to curve piece 60 takes place within approximately 10 to 15 milliseconds. The braking of the thread - curve piece 61 - is carried out less abruptly than the release in order to protect the weft thread; it is transferred to a state of "full braking": curve section 52. After a brief full braking, curve section 62 again sets the partial braking. Further details of the stroke curve of the thread brake in projectile weaving machines are discussed below in connection with FIGS. 4a and 4b.

For example, it is also possible to operate the thread brake in such a way that partial braking is dispensed with. The state of the thread brake then only changes between full braking and thread release.

The stroke curve shown in FIG. 2b for rapier weaving machines, as is made possible by the thread brake according to the invention, differs significantly from that in FIG. 2a by the intermediate braking (curve piece 55). As has already been explained in the introduction, when inserting the weft (interval 70) before the thread transfer from Bringeran Holergreifer is advantageously braked briefly and then the thread brake is released again (curve piece 51 ').

In the second embodiment shown in Fig.3a, the lifting movement of the brake body 2 'is generated directly via a threaded spindle 21'. The brake body 2 'is guided in a link-like sleeve 201, wherein rotation is prevented, for example, by a groove in the brake body 2' and a comb in the sleeve 201. The thread brake shown in the foreground is in the state of full or partial braking; the thread brake in the background is released.

The brake band 1 and the eyelet bodies 6a and 6b can be of the same design as in the first exemplary embodiment (FIG. 1). As indicated in FIGS. 3a and 3a, the brake band 1 is anchored in the eyelet bodies 6a and 6b by means of suppositories 101, which are welded onto the band, for example. The eyelet body 6a is fastened, for example, with a screw 102 to the sheet metal piece 3 that transmits the spring tension.

In the exemplary embodiments, the stepper motor 20 has the shape of a flat box (diameter around 60 mm, height around 30 mm). Thanks to this shape, a compact arrangement can be set up for several thread brakes operating in parallel as shown in FIG. A compact arrangement is also possible for the thread brakes according to FIG. 3a if they are arranged offset, as shown in FIG. 3a.

The zero position of the stroke curve (H = 0) can be easily changed in the first embodiment (FIG. 1) by moving the support plate 8 along the support beam 7. Correspondingly, the zero position can also be shifted vertically in the second exemplary embodiment (FIG. 2a) change the stepper motor with respect to a support structure, not shown.

Based on FIGS. 4a and 4b, additional explanations and additions to the projectile weaving machine now follow. The following schematically illustrated components can be seen: the thread supply 11 with the weft thread 10; the thread brake according to the invention with the brake body 2 and the stepper motor 20, which is connected to the control and logic circuit 30; the tension lever 40 and the thread transmitter 41; the striker 42 and the projectile 43; the fabric 12 and the shed 13; the catch brake 80 for the projectile 43; a weft monitor 32 at the exit of the thread brake and a projectile catch monitor 33 on the catch side, both sensors 32 and 33 being connected to the logic circuit 30.

In the situation represented by FIG. 4 a, the thread transmitter 41 transfers the weft thread 10 to the projectile 43 and the thread brake begins with the lifting movement of its brake body 2. At the moment the projectile is fired, which is given by the time A in FIG. 2 a, the tensioning lever swivels 40 from its retracted position into the extended position, which is indicated in Fig.4b. After this swiveling movement, during which the thread length buffered in the thread tensioner is released, the thread brake must be released; because now, with full force, the weft thread 10 is drawn off from the supply spool 11 or from a thread store, not shown, by the accelerated projectile 41. The weft thread 10 suffers the so-called draw stroke; this takes place at time S in the diagram in FIG. 2a. The control of the thread brake must be programmed so that the Curve section 60 intersects the abscissa between points A and S.

The projectile 43 is brought to a standstill in the catch brake 80 at time B. At the same time, the thread brake also stops the movement of the weft thread 10. The state of full braking (curve piece 52) ensures that, when the tensioning lever 40 is subsequently retracted, only weft thread 10 comes from the shed 13 and not also from the supply spool 11 (or from one thread store, not shown) is tightened.

It is known to use a sensor 33 on the catch side to monitor the arrival time of the projectile 43 in order to regulate the thread tension and thus the flight duration by influencing the initial conditions when the weft is fired. Thanks to the logic circuit 30, such a regulation can easily be implemented with the thread brake according to the invention.

In the described exemplary embodiments of the thread brake, the variety of possibilities for how the brake band 1 and the brake body 2 can be implemented has not been discussed in detail. However, the following should also be mentioned: instead of the spoon shape, the brake body 2 can also be designed, for example, in the form of a double finger or in the form of a metal belt loop.

Claims (11)

1. A yarn brake for looms, comprising a brake band (1) and a controllably movable brake member (2), the yarn (10) being passed between the brake band and the brake member, characterised in that the brake member is adapted to be actuated by a servomotor (20) connected to a triggering and logic circuit (30), a rotary movement of the servomotor shaft (21) being converted into a reciprocating movement of the brake member (2).
2. A yarn brake according to claim 1, characterised in that the servomotor (20) is a stepping motor.
3. A yarn brake according to claim 1 or 2, characterised in that the logic circuit is connected to a sensor (31) which can record a reference position of the servomotor shaft (21).
4. A yarn brake according to any one of claims 1 to 3, characterised in that the servomotor (20) is pivotally connected to the brake member (2) via a lever (23) and a link (24), the brake member being pivotable about an axis (2a).
5. A yarn brake according to claims 3 and 4, characterised in that a permanent magnet (29) is disposed on the lever (23) and in that the sensor (31) is an inductive sensor, by means of which the position of the permanent magnet (29) can be locked in the reference position.
6. A yarn brake according to any one of claims 1 to 3, characterised in that the servomotor (20) moves the brake member (2') linearly via a screw spindle (21').
7. A projectile loom having at least one yarn brake according to any one of claims 1 to 6.
8. A projectile loom according to claim 7, comprising a catch stop motion (33) on the catcher side, said stop motion being connected to the logic circuit (30) of the yarn brake.
9. A gripper loom having at least one yarn brake according to any one of claims 1 to 6.
10. A method of operating a projectile loom according to claim 7, characterised in that the yarn brake is released after the projectile pick (time A) and before the stretch stroke (time S).
11. A method according to claim 10, characterised in that the opening of the yarn brake takes less than 15 milliseconds.

Images