EP1659201B1 - Method for braking the weft yarn in a fluid jet loom - Google Patents

Description

The invention relates to a method for braking a weft thread of a jet loom, as well as a jet loom for carrying out the method according to the preamble of the independent claim of the respective category.

As is known, so-called ABS brakes are used in jet looms, in particular in air jet looms, for the controlled braking of the weft thread. ABS stands for automatic weft braking device in the context of this application. The aim is to avoid overstressing the weft yarn, which is particularly caused by the abrupt braking of the weft yarn, e.g. caused by the stopper pin of the thread store. The ABS brake is e.g. realized in the form of a movable bracket with two or three deflection points. The braking force is influenced by a weft deflection caused by the brake bar. The bracket is usually rotatably mounted and is connected to a drive, e.g. with a solenoid coil, or with an electric motor in operative connection, which is signal-connected to the control and / or regulation of the drive with a suitable control.

In the WO 02/10493 a jet loom and a method for braking a weft thread is already disclosed, in which a braking element is brought into contact with a weft thread, so that the weft thread can be deflected by the braking element according to a position function, and the weft thread can be braked according to a braking profile.

In the ABS brakes known from the prior art, the bow deflection is linear with time, for example up to a maximum predetermined Deflection of the stirrup, which in turn is linearly returned to its original position.

In the context of the present application, the term "linear" (with time) refers to the distance traveled and is intended to characterize that the speed of the object to be viewed, e.g. a braking element or a weft thread, at least partially constant and the path - time - course at least partially linearly increasing or decreasing. The end of such a section is usually characterized by an abrupt change in speed, so by a "kink" in the way - time - course. Correspondingly, "nonlinear" characterizes that the acceleration of the object to be observed is not equal to zero and the path - time - course of the same is therefore nonlinear. Abrupt changes in speed, ie kinks in the path - time - course, can of course occur in principle in nonlinear motion sequences.

The disadvantage of such a ramped position specification is that the bow deflection is always changed linearly with time, regardless of a braking phase. This has the consequence that a larger weft load can be caused just at the beginning of the braking phase, when e.g. the weft speed is still very high. Even at the reversal point, that is, when the direction of the ironing movement is reversed, the weft yarn is loaded abruptly. Due to this uneven weft load it comes in practice in jet looms repeatedly weft thread breaks.

The object of the invention is therefore to propose an improved method for braking a weft yarn, so that occurring loads on the weft yarn are minimized.

The problem solving this object in terms of process and apparatus of the invention are characterized by the features of the independent claim of the respective category. The dependent ones Claims relate to particularly advantageous embodiments of the invention.
According to the invention, a method for braking a weft thread of a jet loom is proposed, in which method a braking element is brought into contact with the weft thread, wherein the braking element is moved by means of a drive for a predetermined path - time - course, so that the weft thread through the brake element is deflected according to a position function and decelerated according to a braking profile, wherein the position function is adapted to the braking profile of the weft. According to the invention, in an initial braking phase, the weft yarn is deflected by the braking element according to the position function with continuously increasing speed from a rest position to a first position and returned in an end-braking phase from a second position with continuously decreasing speed in the rest position.
The braking profile is the speed - time course of the weft. In order to achieve optimum braking results, the position function of the weft yarn, ie the time course of the deflection of the weft yarn during braking must be adapted to the predetermined braking profile. The time course of the deflection of the weft thread by the braking element during deceleration is therefore non-linear at least in certain braking phases in contrast to the methods known from the prior art. Rather, the deflection speed of the weft yarn is continuously adapted to the brake profile to achieve an optimal braking performance and thus to achieve an optimal weft insertion.
Since the frictional force on the weft at the point of action of the braking element, ie at the point where the braking element rubs on the weft yarn, usually depends nonlinearly on the speed of the weft thread, it has been shown that the deflection of the weft thread according to the position function advantageously designed non-linear can be. The brake elements known from the prior art are firstly moved out of the rest position at a constant speed and, secondly, the bearing surface of the braking element for the weft thread is designed in such a way that Also, the weft is deflected linear or almost linear. Thus, the weft, which has a very high speed at the beginning of the braking phase, exposed to an unnecessarily high load. "Resting position" is understood to mean the position in which the weft thread is not deflected, that is to say the position in which the braking element is not in contact with the weft thread. In contrast to the methods known from the prior art can be extended by the inventive method, the weft at the beginning of a braking phase, for example, at low speed from the rest position, the speed of deflection of the weft yarn is then increased continuously. Under braking phases is understood in the context of this application, an operating condition in which the braking element is in contact with the weft. The high frictional and thus braking forces on the same caused by the high speed of the weft yarn at the beginning of the braking phase can be adapted to the current weft yarn speed with decreasing speed of the weft yarn by suitable control and / or configuration of the braking element.

The loads that act on the weft in the operating state, you can often roughly divided into two groups: on the one hand braking loads and on the other dynamic loads. In the context of the invention, brake loads are to be understood as those which change their sense of direction at most when the direction of movement of the brake element also changes. Dynamic loads are those which can constantly change their direction or sense of direction during the braking process and which, for example, result from the properties of the entire vibration system. For example, it may be stochastic, or more or less periodic oscillations. Under vibration system is understood in the following, the mechanical system with jet loom and brake element.
Among the brake loads that usually occur during braking on the weft include, inter alia, such frictional forces caused by the Friction of the braking element occur on the example uneven weft thread surface and forces emanating from the deflection, which happens to be the weft. Among other things, the braking element itself belongs to the deflection points. All these external forces lead to tensions in the weft thread, which in turn cause reaction forces which counteract the forces acting from outside. With decreasing speed of the weft these forces can be smaller and smaller and disappear substantially at standstill of the weft.

The dynamic loads, or forces, resulting from the vibrations that occur in particular during the braking process on the weft. They lead to dynamic stresses in the weft.
The tensions which occur due to this collective load in the weft yarn can lead to the destruction of the weft thread in the worst case if certain limit values are exceeded.

In order to achieve a reduction of the loads, suitable measures are taken according to the invention for brake loads and dynamic loads:
By slowly increasing the speed of the deflection of the weft yarn at the beginning of the braking phase, it is achieved that, in particular, the braking loads acting on the weft yarn at the beginning do not become too great. As a result, of course, the dynamic forces, respectively loads are reduced.
By choosing the path changes in the path - time - course of the braking element so that it is smooth, that is essentially without kinks, one improves significantly the vibration characteristics of the vibration system. Thus, by such a movement of the braking element load peaks can be avoided, which is to be understood by load peaks that they are more or less briefly occurring mechanical stresses with a large amount of the weft, by general vibration effects, how, for example, resonance arises and has as cause, for example, impact, jerk, shock, friction or vibration.

At this point it should be expressly pointed out that the path - time - course can be realized in different ways. In the drive unit, e.g. the path - time - course of the braking element are specified directly, which usually, the correct path - time - course must be determined by transformation from the predetermined position function of the weft deflection. In this transformation, in particular, the geometric features of the braking element can be crucial. However, the position function as such is ultimately essential for the loads on the weft thread, since it makes a direct reference to the forces in the weft.

The asymmetry of the path - time - course is particularly advantageous in that the braking element is slowly extended from the rest position at the beginning and is retracted quickly to the rest position at the end. In the course of a time optimization of the braking process, the path-time course is particularly advantageously designed so that a predominant proportion of the speed reduction of the weft yarn occurs while the weft yarn is moved from the rest position to the maximum position. Once this has been achieved, the weft thread can be quickly returned to the rest position, whereby, taking into account the dynamic loads, it should again be noted that the retraction movement is advantageously continuous and jerk-free.

The yarn loads can be further reduced by making the surface of the braking member which is brought into frictional contact with the weft yarn so that the force is not transmitted in a dot-like manner but spread over a surface. As a result, the frictional heat that occurs is distributed better over the weft thread.

Another way to avoid disturbing loads is that it is ensured by means of a scheme that a maximum force from the brake element acting on the weft yarn is not exceeded. In this case, ideally, no travel time curve for the braking element must be specified, e.g. in the form of a mathematical function by means of an MC control, but the braking element can e.g. can only be controlled with one control. The deflection of the braking element then takes place e.g. depending on the reaction force of the thread which is transferred to the braking element. The regulation can then take place via the current of the drive of the braking element and / or via the measurement of the reaction force of the weft thread. Of course, the entire process of the deflection of the brake element is also here preferably shock and jerk-free.

In an embodiment which is particularly relevant in practice, in an initial braking phase the weft thread is deflected by the braking element according to a position function with continuously increasing speed from a rest position to a first position and in a final braking phase from a second position with continuously decreasing speed brought back the rest position.

In another embodiment, the weft thread is moved by the brake element according to a position function in an intermediate braking phase from the first position to a maximum position and moved back from the maximum position to the second position. The transitions at the beginning and end of the intermediate braking phase should preferably take place in such a way that the rise or fall of the speed at the transitions is not changed abruptly.

In a further preferred embodiment, the position of the weft yarn in the intermediate braking phase is maintained substantially constant over a predetermined period of time. In essence, here means that the Position change of the weft thread over a predetermined period within a predetermined tolerance remains. The range within which a change in position is tolerable depends essentially on the thread condition and the thread speed.

In a particularly important embodiment, the positional function of the weft yarn becomes asymmetrical, e.g. in the form of a tangent hyperbolic function, in particular a composite tangent hyperbolic function. With suitable geometry of the braking element, then e.g. also the path - time - course of the braking element will be a tangent hyperbolic function, i. In this case, the path - time - course of the braking element and the position function of the weft - deflection to each other in proportional or approximately proportional dependence.

The tangent hyperbolic function can be used particularly advantageously in order to implement the features of the position function according to the invention in a simple manner. That with it, the features of the invention can emulate particularly advantageous.

In a specific embodiment, a drive unit for controlling the drive of the brake element is provided. Control units are here all suitable control devices, e.g. MC controllers from industrial control technology.

Of course, the position function can also be realized by suitable design of the shape of the braking element, as will be described below.

The movement of the braking element can be realized by a motor, in particular an electric motor, or a magnet, in particular electromagnet or a mechanical drive. Electric motors are in the frame This application, for example, all DC, AC, three - phase, linear and stepper motors. The mechanical drive can for example be realized such that the braking element is driven via the main drive shaft of the loom. This relatively uncomplicated type of drive can be found quite frequently in the art under the term master-slave connection. For example, eccentric devices, the path - time - course of the brake element and thus the position function can be adapted to the respective needs in almost any way on unevenly translating gear, so for example via cam gear, in the closer sense.
Alternatively, a simple path - time - course for the drive movement of the brake element can be provided and for the geometry of the brake element can be chosen such that the desired position function for the weft - deflection is achieved.
Furthermore, the invention comprises a jet loom, in particular air jet loom comprising a braking element, for braking a weft thread, wherein the braking element is configured and arranged such that it can be brought into contact with the weft thread and by means of a drive according to a predetermined path - time - course is movable , In this case, the weft yarn is deflectable by the braking element according to a position function and the weft yarn can be braked in accordance with a braking profile. The jet loom is designed such that the positional function is adaptable to the braking profile of the weft thread. According to the present invention, a drive unit for controlling and / or regulating the drive is provided, with which the drive is controlled so that in an initial braking phase, the weft with continuously increasing speed from a rest position can be deflected to a first position and in a End braking phase from a second predetermined position with continuously decreasing speed can be returned to the rest position.
It is understood that the list of embodiments described above, the jet loom according to the invention and the embodiments described is not exhaustive and the Aufzählungsvarianten can be advantageously combined in any suitable form.

Fig. 1

ein Ausführungsbeispiel einer an sich bekannten Düsenwebmaschine mit einem erfindungsgemäßen Bremselement

Fig. 2a

ein aus dem Stand der Technik bekannter Weg - Zeit - Verlauf des Bremselements

Fig. 2b

eine aus Fig. 2a resultierende Positions-Funktion der Auslenkung des Schußfadens

Fig. 3a

ein Bremsprofil des Schußfadens mit dazugehörigem Weg - Zeit-Verlauf des Bremselements

Fig. 3b

ein Ausführungsbeispiel einer erfindungsgemäßen Positionsfunktion

Fig. 4

ein Ausführungsbeispiel eines Bremselements in Bügelform

Fig. 5

ein Ausführungsbeispiel eines Bremselements in Gabelform

Fig. 6

ein Ausführungsbeispiel eines Bügelbremselements mit flächiger Reib - Angriffsfläche

Fig. 7a

ein Bremselement gemäß Fig. 4 erweiterten geometrischen Merkmalen

Fig. 7b

ein weiteres Bremselement gemäß Fig. 7a erweiterten geometrischen Merkmalen

In the following the invention will be explained in more detail with reference to the drawing. In a schematic, not to scale representation:

Fig. 1

an embodiment of a per se known jet loom with a brake element according to the invention

Fig. 2a

a known from the prior art way - time - course of the braking element

Fig. 2b

one out Fig. 2a resulting position function of the deflection of the weft

Fig. 3a

a braking profile of the weft with associated path - time course of the braking element

Fig. 3b

an embodiment of a position function according to the invention

Fig. 4

an embodiment of a brake element in ironing shape

Fig. 5

an embodiment of a brake element in fork shape

Fig. 6

an embodiment of an ironing brake element with flat friction - attack surface

Fig. 7a

a braking element according to Fig. 4 extended geometric features

Fig. 7b

another brake element according to Fig. 7a extended geometric features

The method according to the invention, which is designated by the reference numeral 1 below, is used for braking a weft thread in jet looms, in particular in air jet looms.

Fig. 1 In detail, such a per se known air jet loom 10, which comprises a brake element 2 according to the invention and a control unit according to the invention 4. This essentially comprises a yarn package 6, of which a weft yarn 3 is wound on a drum memory 5 in a suitable length, a brake element 2, a Auxiliary nozzle 7 and a main nozzle 8, wherein in the operating state of the weft yarn 3, coming from the drum memory 6, performed by the brake elements 2, accelerated in the two nozzles 7 and 8 and then transported along a reed 9 through the shed. Furthermore, the drive 21 of the brake element 2 are shown. The details of the weft insertion of the jet loom 10 are known per se and therefore need not be explained in detail. On the representation of the shed and other, known per se components of the jet loom was omitted for reasons of clarity.

Fig. 2a FIG. 1 shows a path-time curve 22 'designed according to a method 1' according to the prior art, after which the braking element is moved. The time on the abscissa is linear and the path on the ordinate is linear. Characteristic of such a way - time - course 22 'are the kinks in the movement. The movement of the braking element is linear with time, ie its speed is constant in sections. For example, the brake element is brought from a rest position 111 'to a maximum predetermined deflection 121' and then back to the rest position 111 '. The disadvantage of such a ramped position specification is that, as already explained; the bow deflection always varies linearly with time, regardless of the braking phase. This has the consequence that a larger weft load is caused just at the beginning of the braking phase, if, for example, the weft speed is still very high. Even at the reversal point, so when the direction of the ironing movement is reversed, the weft yarn is relieved abruptly. Due to this uneven weft load, it can in practice in jet looms repeatedly to weft thread breaks come.

Fig. 2b shows the from the in Fig. 2a shown path - time - course 22 'resulting position function 23' of the weft - deflection. On the abscissa the time is linearly plotted and on the ordinate the position of the weft thread. The path - time - course 22 ', ie the path time course of the deflection of the brake element and the position function 23', so the weft deflection are proportional to each other here. For brake elements whose function results from the rotation of an element about an axis, this proportionality can be assumed if the weft thread does not slide off substantially, for example, towards the axis of rotation.

Fig. 3a schematically shows a braking profile 31 for the weft 3. The abscissa is the time removed linearly and on the ordinate on the one hand, the position function 23 of the weft yarn 3, and on the other hand, the speed of the weft 3. The position function 23 is shown by a dashed line. The illustrated sales are only to be understood as an example and may be different in practice. As can be clearly seen, the position function 23 is adapted to the braking profile 31 of the weft thread 3. That is, the course of the position function 23 of the weft yarn 3 is not, as in the prior art, regardless of the course of the braking profile 31 of the weft yarn third

Fig. 3b FIG. 2 shows a position function 23 of the weft deflection designed according to the method 1 according to the invention and a corresponding velocity-time curve 24. The abscissa shows the time in linear fashion and the ordinate linearly the velocity and the path. The position function 23 is represented by a solid line trace and the speed-time curve 24 by a dashed line trace. The characteristic positions in which the weft yarn 3 is moved are indicated by their reference characters on the ordinate.

In an initial braking phase 11, the weft yarn 3 is deflected from a rest position 111 into a first position 112 at a continuously increasing speed. Subsequently, the weft thread 3 is moved in an intermediate braking phase 13 from the first position 112 to a maximum position 113 and moved back from the maximum position 113 to the second position 121. Finally, in the end braking phase 12, the weft yarn 3 is returned to the rest position 111 from the second position 121 at a continuously decreasing speed. It is crucial that all path changes in the position function 23 in contrast to the known from the prior art position function 23 'in Fig. 2b especially in the initial braking phase 11 and in the final braking phase 12 are continuous and smooth and not, as before at Fig. 2 described, piecewise linear and / or with kinks. The position function 23 shown here is a tangent hyperbolic.

Figure 4 shows a known from the prior art brake element 2, which is designed as a bracket element and can be controlled with a drive unit 4, not shown here according to the method 1 according to the invention. The weft thread 3 is deflected twice at the two outer deflection points 16 once and on the movable bracket 15. At these deflection points is often the largest weft stress. Of course, the bracket can also be designed as a simple rod with only one, or more than two deflection points. The axis of rotation 17 of the bracket 15 may be stored on one or both sides .. The performance of the brake element 2 results essentially from it; that friction work and deformation work on the weft thread 3 is performed at the deflection points. The kinetic energy of the weft yarn 3 is converted by the attacking friction and bending loads into heat and the weft yarn 3 loses its energy. The drive 21 of the brake element 2 can be effected by a magnet, in particular an electromagnet, a motor, in particular an electric motor, or a mechanical drive.

Fig. 5 shows another brake element 2, which is also signal-connected with a drive unit 4 not shown here according to the invention and can be controlled by the method 1 according to the invention. It is designed here as a fork element and the axis of rotation 171 of the fork 151 is in the normal direction with respect to the weft 3. The shapes of the fork 151 can of course be varied. Again, the axis of rotation 171 can be stored on one or both sides. The drive 21 of the Gabeielements can be done in an analogous manner by similar drives as in the Fig. 4 discussed embodiments.

Fig. 6 shows a further embodiment of a braking element 2 for performing the method 1 according to the invention, the braking characteristics of in 4 and FIG. 5 shown brake elements 2 to improve even further. Characterized in that a shape is selected for the braking element 152, which ensures a wide bearing surface of the weft yarn 3, one reduces point loads occurring at a high amount and produces instead over a wide range of the weft yarn surface loads with a relatively small amount. As a result, lower maximum loads occur, whereby the tearing of the weft yarn 3 is virtually eliminated. Of course, all deflection of the brake element 2, such as the deflection points 162 can be adapted in shape so that punctually occurring loads are reduced by a large amount. The drive 21 of the brake element 2 can be done by the same, or similar drives, as in Fig. 4 ,

The following two figures show, in a highly simplified, schematic illustration, brake elements 2 which realize an embossed, non-linear position function 23 when the deflection of the brake element 2, e.g. in a linear or non-linear manner.

Fig. 7a schematically shows a bracket 153 in the non-deflected state, which bracket 153 with sections of constant speed around a Rotation axis 173 can be moved and its construction geometry is designed such that the weft thread 3 is deflected according to a position function 23 according to the invention. The weft 3 can move over the bracket 153, whereby a position function 23 according to the invention with smooth transitions arises, as in Fig. 3b shown.

Fig. 7b schematically shows another bracket 154 according to Fig. 7a , By way of example illustrated here, complicated geometry of the bracket 154, a more complicated position function 23 for the weft yarn 3 can be specified.

With the method according to the invention, it is thus possible to realize an improved control of an ABS brake, so that occurring loads on the weft thread are reduced. In the way - time - course, the braking element is deflected in an initial braking phase from a rest position to a first position with continuously increasing speed and returned in a final braking phase from a second position with continuously decreasing speed in the rest position. By the method according to the invention, the braking element can e.g. be extended from the rest position at low speed at the beginning of the braking phase, the speed is then increased continuously. The high frictional and thus braking force on the same caused by the high speed of the weft yarn at the beginning of the braking phase can be adapted to the actual weft speed with a decreasing speed of the weft thread by a suitable control of the braking element.

Claims (10)

1. A method for braking a weft thread (3) of a jet weaving machine, in which a braking element (2) is brought into contact with the weft thread (3), the braking element (2) is moved by means of a drive (21) in accordance with a distance/time plot to be preset so that the weft thread (3) is deflected by the braking element (2) in accordance with a position function (23) and the weft thread (3) is braked in accordance with a braking profile (31), wherein the position function (23) is matched to the braking profile (31) of the weft thread (3), characterized in that, in an initial braking phase (11), the weft thread (3) is deflected by the braking element (2) in accordance with the position function (23) at continuously increasing speed from a rest position (111) up to and into a first position (112) and, in a final braking phase, (12) is brought back from a second position (121) into the rest position (111) at continuously diminishing speed.
2. A method in accordance with claim 1, wherein the weft thread (3) is moved in an intermediate braking phase (13) out of the first position (112) into a maximum position (113) and is moved back out of the maximum position (113) into the second position (121).
3. A method in accordance with any one of the preceding claims, wherein the position of the weft thread (3) remains substantially constant in the intermediate braking phase (13) over a predetermined period of time.
4. A method in accordance with any one of the preceding claims, wherein the distance/time plot of the braking element is linearly preset at least section-wise.
5. A method in accordance with any one of the preceding claims, wherein the position function (23) of the weft thread (3) is an asymmetrical position function.
6. A method in accordance with any one of the preceding claims, wherein the position function (23) of the weft thread (3) is preset in at least one of the braking phases by a real or complex trigonometric position function.
7. A method in accordance with any one of the preceding claims, wherein the position function (23) is a hyperbolic tangent function.
8. A method in accordance with any one of the preceding claims, wherein the braking element (2) is moved by a motor, in particular by an electric motor, or by a magnet, in particular by an electromagnet, or by a mechanical drive.
9. A jet weaving machine, in particular an air jet weaving machine (10), including a braking element (2) for braking a weft thread (3), wherein the braking element (2) is designed and arranged such that it can be brought into contact with the weft thread (3) and can be moved by means of a drive (21) in accordance with a predeterminable distance/time plot, wherein the weft thread (3) is deflectable by the braking element (2) in accordance with a position function (23) and wherein it is possible to brake the weft thread (3) in accordance with a braking profile (31), and wherein the position function (23) can be matched to the braking profile (31) of the weft thread (3), characterized in that a control unit (4) is provided for the controlling and/or regulating of the drive (21), with which the drive (21) can be controlled such that, in an initial braking phase (11) , the weft thread (3) can be deflected at continuously increasing speed from a rest position (111) into a first position (112) and can be brought, in a final braking phase (12,) from a second predeterminable position (121) back into the rest position (111) at continuously diminishing speed.
10. A jet weaving machine in accordance with claim 9 11, wherein a magnet, in particular an electromagnet, a motor, in particular an electric motor, or a mechanical drive is provided as the drive (21) of the braking element (2), and wherein the braking element (2) is provided as a hoop element or as a rotable fork element.

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