EP0396501B1 - Loom with easy-going warp tension device - Google Patents

Description

The invention relates to a loom with a tensioning device for tensioning warp threads of a so-called warp, consisting of a spring-loaded tensioning element for the warp threads with simultaneous deflection, one end of a spring being articulated on the tensioning element, the other end of which is mounted on the machine side, and an adjustment mechanism for the bias of the spring (23) in time with the working cycles of the loom.

Such a device is known from Japanese Patent Publication 63-67575. The warp threads are deflected by a tensioning boom that runs across the machine width and are kept tensioned, which is held in pivotable end shields. A tension spring engages on an extension of each end shield, which on the other hand engages at the end of a lever which is pivotally fixed in the machine frame and at the other end of which a push rod is articulated. One end shield is attached to this lever near the fulcrum of the lever. The push rod can be moved back and forth in the machine cycle by means of a crank mechanism, which causes the lever to pivot and the bearing plate fixed thereon to move approximately in translation be transferred. The spring end mounted on the lever end is also moved essentially translationally, the movements of the end shield and the fastening point of the spring being directed in opposite directions. Simultaneously with the formation of the warp threads, the combined movements of the lever and the end shield on the one hand shift the warp towards the shedding organs, and on the other hand the warp tension is reduced. The exemplary embodiment in the Japanese publication shows that the tensioning element, a roller, is attached to at least two bearing plates, which in turn are seated on at least two levers, each with two springs. A crank of the crank mechanism engages at each end of the lever. A practical embodiment of the example shown schematically would have numerous individual parts which cannot be moved at high frequency. Too many mass-related parts are between the drive device and the warp threads. Accordingly, one would have to expect uncontrollable vibrations in the system, in particular in an embodiment for heavy fabrics and at higher speeds, which can be up to 1000 revolutions per minute in air-jet weaving machines. The vibrations would produce large fluctuations in tension in the warp threads, which can lead to warp thread breaks and reduce the operational efficiency of the weaving machine.

Another device for tensioning warp threads is known from EP 0 136 389. The warp beam is followed by a stationary, rod-shaped deflection element for the warp threads in the warp running direction, and a deflection element that is movable under spring action is also connected downstream of the deflection element. On the warp threads between the deflecting element and the tensioning tree, a sensing element of a control device is also arranged, through which the tension or the respectively over Deflection element and spanning tree leading path of the warp threads are scanned and the warp thread lowering speed is set accordingly. The tensioning boom is passively movable under spring action, whereby a particularly large, resulting force acts on the feeler element by means of a corresponding pretensioning of its return spring, which enables precise adjustment of the warp thread lowering speed. Due to the inert mass of the tensioning tree and the feeler as well as the passive, springy tensioning of the tensioning tree, this device reacts extremely sluggishly to changes in tension of the warp threads and is therefore unsuitable, for example, to keep the warp threads under an approximately constant tension during the weaving cycle by means of the shafts more or less deflected.

It is an object of the invention to provide a smooth-running driven tensioning system for a weaving chain of a weaving machine, which is also suitable for heavy fabrics and which reacts sensitively to tension fluctuations in the warp or to changes in position in the drive of the system. This object is achieved in that the adjusting mechanism acts on the machine-side end of the spring in the form of a torsion bar which lies on the pivot axis of the tensioning element for tensioning the warp and in turn with a drive shaft of the tensioning device is connected in a rotationally fixed manner, and in that there are bearing points for the rolling bearing of the tensioning element, which are distributed rotationally symmetrically with respect to its axis of rotation, with the drive shaft being distributed over the weaving width. In addition to the tension element deflecting the warp threads, a deflection element can be arranged in the running direction of the warp threads in front of the tension element, the axis of rotation of the tension element, the pivot axis of the drive shaft and the center of the deflection element forming the corner points of an approximately equilateral triangle. The warp threads are deflected by the deflecting element and the tensioning element approximately by the same angle from an approximately vertical direction in a horizontal direction, the bisector of the angle formed by the warp threads between the deflection element and the tensioning element and the warp threads running off the tensioning element just outside the corner point at the Drive shaft of the triangle mentioned passes. The distance between the bisector and the swivel axis can be very small, for example 1/10 of the distance between the axis of the tensioning element and the swivel axis of the drive shaft.

The device can have a sensor for detecting a signal which represents a measure of the relationship between warp thread consumption in the weaving machine and the subsequent delivery of warp threads from the warp beam, which signal is transmitted to a control device for the device. In an advantageous embodiment of the device, a drive motor for the warp beam for unwinding the warp threads is connected to the control device. The sensor can be designed, for example, as a force sensor for registering the pretensioning force in the device. The drive shaft of the tensioning device is in at least two bearings within the machine frame of the weaving machine carried. Several bearing points for the tensioning element are attached to the drive shaft, which in turn carry rollers in which the tensioning element is mounted.

Due to the high sensitivity due to the low mass and the low-friction mounting of the tensioning element, the device can work at an operating point at which the tensioning element is in a position in which the resulting force from the warp threads passes just short of the pivot axis of the tensioning element. The torque in the drive shaft for the tensioning device thus remains very small, which is why a weak spring is sufficient to preload the drive shaft. Thus, the forces and loads within the clamping device remain very small, which is why the parts of the clamping device can be easily dimensioned and are therefore suitable for high working frequencies.

Fig. 1

zeigt einen schematischen Grundriss einer Webmaschine mit der Erfindung zusammenhängende Funktionselementen einer Webmaschine,

Fig. 2

ist eine Detailansicht einer Spannvorrichtung in Längsrichtung der Webmaschine,

Fig. 3

ist eine Detailansicht der Spannelemente mit dem Kettfadenverlauf in einer Ansicht gemäss Pfeil A in Fig. 2,

Fig. 4

zeigt Details der Vorrichtung ähnlich wie in Fig. 2,

Fig. 5

zeigt zwei Arbeitsstellungen der Spannvorrichtung in schematischer Darstellung mit den Kräfteverhältnissen aufgrund der Spannung der Kettfäden.

The invention is explained in more detail below with reference to drawings 1-5.

Fig. 1

shows a schematic plan view of a weaving machine functional elements of a weaving machine related to the invention,

Fig. 2

is a detailed view of a tensioning device in the longitudinal direction of the loom,

Fig. 3

is a detailed view of the tensioning elements with the warp thread in a view according to arrow A in Fig. 2,

Fig. 4

shows details of the device similar to that in Fig. 2,

Fig. 5

shows two working positions of the tensioning device in a schematic representation with the force relationships due to the tension of the warp threads.

1, the weaving machine 1 contains a main drive motor 13, which can be coupled to a main shaft 13 '. A shaft drive unit 15 'can be coupled to the main shaft 13' by means of a clutch 13 ''. A pair of bevel gears 15 ″ ensures the transmission of the drive energy to the shafts 15, which are connected to the shaft drive unit 15 ′. On a drive shaft 33, which can be coupled to the main drive shaft 13 ', there is an eccentric 33' which drives a push rod 34 of an adjusting mechanism 3 for the tensioning device 2. The push rod 34 is interrupted by a force sensor 35, which registers the forces in the push rod. The warp threads 11 ', which are processed in the weaving machine, are wound on a warp beam 12 as a warp chain 11. They are unwound from the warp beam 12 by means of a drive motor 12 ', the warp beam 12 being connected to the drive motor 12' via a pair of gearwheels 12 ''. The warp threads 11 'run through the shafts 15 and are alternately raised and lowered by them. The tensioning device 2 with a deflection element 25 and a tensioning element 22 serves to keep the warp threads 11 'tensioned when these are more or less deflected by means of the shafts. The clamping element 22 of the clamping device 2 has a plurality of bearing points 24 for a rolling mounting of the clamping element 22, these bearing points being firmly connected to a drive shaft 22. Concentric with the pivot axis 21 'of the tensioning element and at the same time the axis of rotation of the drive shaft 21, a spring 23 extends in the form of a torsion bar to the adjusting mechanism 3, which acts on a hub at the end of the spring 23. A control line 35a runs from the force sensor 35 to the control unit 14, which performs the control functions of, for example, the main drive motor 13 via the control line 13a or the drive motor 12 'for the warp beam 12 via a control line 12a. The force measured by the force sensor 35 increases and exceeds a border guard, the control unit 14 causes a higher speed of the drive motor 12 '.

In FIG. 2, the drive shaft 33 with the eccentric 33 ′ and then the push rod 34 with the built-in force sensor 35 can be seen in an enlarged illustration in a side elevation of the weaving machine according to FIG. 1. The push rod is essentially pushed back and forth in the direction of the double arrow 34 '. An adjusting device 37 for adjusting the length of the push rod 34 can be seen below the double arrow 34 '. This also achieves the basic setting of the clamping device. The push rod 34 engages a hinge point on the lever 36, which is non-rotatably connected to the end of the torsion bar 23. FIG. 2 also shows a cross member 16 ', the deflection element 25 and the tensioning element 22, furthermore a support 16' 'for the deflection element 25 and tensioning element 22, which is screwed onto the cross member 16'. The warp threads 11 'come from below in FIG. 2 from the warp beam, not shown, are deflected by the deflecting element 25 and the tensioning element 22. The tensioning element 22, which can be pivoted with the torsion bar 23, ensures a length compensation in the warp threads when these are pulled into different positions by the shafts 15.

FIG. 3 is a view of the arrangement according to FIG. 2 in the direction of arrow A. On the frame 16, the cross member 16 'is screwed, which holds several carriers 16''distributed over the width of the weaving machine. The drive shaft 21 which is rotatable about the pivot axis 21 'is mounted in the carriers 16''. The bearings 24 are screwed to the drive shaft 21. The torsion bar 23 is non-rotatably connected to the drive shaft 21 at one end by means of the driver 23 ″, on the other hand it is non-rotatably seated within the Hub 23 ', which is supported by the cross member 16' in rolling bearings. The lever 36 is screwed onto the hub 23 '.

In FIG. 4, parts of the tensioning device 2 are again shown enlarged compared to FIG. 2. A stationary deflection element 25 deflects the warp threads 11 'from an approximately vertical position in the direction of the tensioning element 22, which is supported by a plurality of rollers distributed over the weaving width and held by bearing points 24. Due to the multiple mounting of the tensioning element 22 on the rollers 24 ', the tensioning element can be made relatively thin. The rollers 24 'ensure easy rotation of the tensioning element about its own axis. In addition, the unit tensioning element 22, bearing points 24, drive shaft 21 can perform rapid pivoting movements, since the mass moment of inertia of this unit is relatively small compared to the device mentioned at the outset according to the Japanese publication. If the warp threads 11 'are displaced in the longitudinal direction due to the movements of the heald frames 15 and thereby cause compensating movements of the tensioning device 2, the unit tensioning element', bearing point 24 ', drive shaft 21 can very quickly follow the longitudinal displacement of the warp threads, this being due to the kinematic conditions Clamping element 22 rotates on its own axis on rollers 24 '. The rollers 24 'can have a tread made of plastic, for example Vulkollan, which has the advantage that deposits from the possibly dusty air of the weaving room are pushed away from the contact surfaces by the elastic deformation of the rollers 24' in contact with the tensioning element 22. The function of the tensioning device is discussed below with reference to FIG. 5.

In the event of a change in the position of the warp threads 11 ″ during the so-called shedding in the weaving machine into one The intermediate element 11 ″ a migrates, for example, from the extended position into the dashed position. The resulting force W or W 'generated by the warp threads 11' or 11a lies on the bisector of the line formed by the warp thread course 11 ', 11''or11'a or 11''a. The resulting forces W and W ', which result from the vectorial addition of the warp thread forces K and K', run past the pivot axis 21 'of the drive shaft 21 as line-volatile vectors at intervals H2 and H1. If the amounts of the forces W or W 'are measured in any unit from the associated lines of the warp threads to their apices, the following values result: $$\text{W = 80; W '= 69}$$

$$\text{M2 = H2 x W = 6 x 80 = 480}$$

Multiplied by the distances H1 and H2, the torques have the following values as a result of the forces: $$\text{M1 = H1 x W '= 15 x 69 = 1035}$$

$$\text{M2 = H2 x W = 6 x 80 = 480}$$

The values are dimensionless and should indicate the tendency when the clamping element 22 changes position. When it changes its position from the extended position to the dashed position corresponding to the positions of the warp threads 11 ″ or 11 ″ a, the torque increases approximately twice as a result of the warp thread tensions with respect to the pivot axis 21 ′. The pivoting angle of the tensioning element 22 is shown in FIG. 5 with α, the value of which is 9 °. The dimensions of the spring or of the torsion bar 23, that is to say the length and diameter of the spring, are to be selected such that the torque increase during the additional rotation by the angle α in the torsion bar also increases from the value 480 to the value 1035. The bias of the Spring 23 is to be selected such that the torque also reaches the value 480 due to the pretensioning of spring 23 in the extended position of tensioning element 22. Under these conditions, a constant warp thread tension would be guaranteed when changing the position of the warp threads from position 11 '' to position 11''a. Without the adjusting device 3, the effective pivoting angle of the tensioning element 22 would exceed the angle α = 9 °, so that it would not be possible to change the torque in all positions of the tensioning element 22 due to the changed position of the warp thread forces with the corresponding change in the rotation of the spring 23 compensate. This is where the action of the adjustment mechanism 3 begins, in which the machine-side end of the spring 23 in the hub 23 'is pivoted back and forth in a harmonic oscillation as a result of the rotation of the eccentric 33' on the drive shaft 33. This harmonic oscillation takes place synchronously with the up and down movement of the shafts, which likewise bring about an approximately harmonic oscillation of the tensioning element 22 about the axis 21 'due to the displacement of the warp threads 11'. If the pivot angle α of the tensioning element 22 is approximately equal to the angle of rotation of the machine-side end of the spring 23 due to the movement of the adjusting mechanism 3, the torsion of the spring 23 also remains approximately constant, so that the torque in the tensioning device 2 due to the torsion of the spring 22 does not varies widely. If the pivoting angle of the lever 36 generated by the adjusting mechanism 3, the pretensioning of the torsion bar or the spring 23 and the geometric conditions in the tensioning device 2, that is to say the relative position of the tensioning element 22, the pivot axis 21 'and the deflection element 25 to one another, are selected in a clever manner, so can with a practically constant tension in the warp threads 11 ', 11''or11'a,11''a even with a larger swivel angle α of the tensioning device can be calculated, which is necessary with a larger longitudinal displacement and change in position of the warp threads 11 '' or 11''a due to larger strokes of the shafts 15.

Due to the rotatability of the relatively thin tensioning element 22 on a plurality of rollers 24 'in the bearing points 24, it is possible to select the geometry of the entire tensioning device in such a way that the resulting force W of the warp threads in the extended position of the tensioning element 22 is only a short distance away the pivot axis 21 'passes. The torque generated thereby is therefore comparatively small, so that the torsion bar 23, the lever 36 and the entire adjustment mechanism 3 can be dimensioned weak. If the tensioning element 22 were not or only difficult to rotate about its own axis, the warp threads 11 'would generate frictional forces due to their relative movement on the surface of the tensioning element 22 when the tensioning element changes position and thus also a frictional torque which, in relation to the torque due to Force would be relatively large. The additional frictional moment would disturb the balance between the moment due to the warp thread tension and the torque generated by the prestressing of the torsion bar 23 in the opposite direction, which would also have adverse effects on the tension in the warp threads.

In the embodiment according to the invention, the device can thus be operated under geometric conditions if the resulting force W only slightly misses the pivot axis 23. If the distance between the pivot axis 21 'and the deflection point of the warp threads 11' on the tensioning element 22 is L, then a ratio L / H2 in the range between 10 and 15 can be defined, in which the tensioning device 2 according to the invention is still used can be worked without interference. In the known tensioning devices according to the prior art, this ratio L / H2 must be significantly smaller so that the tensioning device works sufficiently far from the self-locking, at which H2 = O. It is therefore essential for the present invention that the prestressing of the tensioning element 22 is effected with a low-mass spring 23 and that the tensioning element 22 itself is mounted on several rollers and consequently also has only weak dimensions. This is the only way to ensure that the tensioning device can react sensitively to displacements of the warp threads 11 '' or 11''a, the tension fluctuations in the warp threads induced by the inherent dynamics of the tensioning device also remaining negligible. In this way it is possible to carry out the weaving operation under certain textile technical conditions at a significantly lower tension level of the warp threads compared to tensioning devices according to the prior art, whereby the tension fluctuations, i.e. the difference between the largest and the lowest tension values, also remain relatively small. A lower stress in the warp is to be expected, which also results in fewer disruptions in weaving operations, for example due to warp thread breaks.

Claims (8)

1. A weaving machine having: a device (2) for tensioning warp yarns (11') of a warp and comprising a resiliently borne element (22) for tensioning and deflecting the warp yarns, a spring (23) having one end articulated to the tensioning element (22) and its other end (23') mounted on the machine; and an adjusting mechanism (3) for selectively influencing the biasing of the spring (23) at the cadence of and within the weaving machine cycles, characterised in that the adjusting mechanism (3) acts on the machine-mounted end (23') of the spring (23) in the form of a torsion rod which is disposed on the pivot axis (21') of the warp-tensioning element (22) and which is connected for co-rotation to a drive shaft (21) of the tensioning device, and in that bearing places (24) for a rolling mounting (24') of the tensioning element (22), which is symmetrical in rotation around its rotational axis (22'), are distributed over the weaving width and co-rotate with the drive shaft (21).
2. A weaving machine according to claim 1, characterised in that the adjusting mechanism (3) is embodied by a lever (36) which acts on the spring (23), by a thrust rod (34) articulated to the latter lever (36) and by an eccentric (33') which is disposed at the other end of the thrust rod (34) on a drive shaft (33) for the adjusting mechanism (3).
3. A weaving machine according to claims 1 and 2, characterised in that a force sensor (35) is disposed in the adjusting mechanism (3) in extension of the thrust rod (34).
4. A weaving machine according to claims 1 - 3, characterised in that the force sensor (35) is connected by way of a control line (35a) to a controller (14) operatively connected by way of a control line (12a) to a driving motor (12') for a warp beam (12) on which the warp (11) has been wound.
5. A weaving machine according to claim 1, characterised in that the bearing places (24) are rigidly mounted on the drive shaft (21) and carry rollers (24') on which the tensioning element (22) is borne in freely rotatable manner.
6. A weaving machine according to claim 1, characterised in that in addition to the element (22) for tensioning and deflecting the warp yarns (11') a deflecting element (25) is disposed before the tensioning element (22) as considered in the direction of warp yarn movement and in that the rotational axis (22') of the tensioning element (22), the pivot axis (21') of the drive shaft (21) and the centre (25') of the deflecting element (25) form the vertices of a substantially equilateral triangle.
7. A weaving machine according to claim 6, characterised in that the warp yarns (11') are deflected by the deflecting element (25) and the tensioning element (22) by substantially the same angle from a substantially vertical direction into a horizontal direction, the bisector (W) of the angle which is formed, on the one hand, by the warp yarns present between the deflecting element (25) and the tensioning element (22) and, on the other hand, by the warp yarns (11') leaving the tensioning element (22), moving past and just outside the drive shaft vertex (21) of the triangle, the distance H2 between the bisector and the pivot axis (21') being only approximately 10% of the distance (L) between the tensioning element axis (22') and the pivot axis (21').
8. A weaving machine according to claim 5, characterised in that the running surfaces of the rollers (24') are made of plastics, for example, Vulkollan.

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