TECHNICAL FIELD AND PRIOR ART

The invention relates to a backrest assembly for pile warp threads in a terry weaving machine, comprising a tension roller and a support beam, wherein the tension roller is arranged to guide the pile warp threads, wherein the support beam is mountable to a frame of the weaving machine so as to be rotatable to-and-fro about a support beam axis, and wherein the tension roller is supported in parallel to the support beam by two or more support elements, which support elements are mounted fixed in position to the support beam. As generally known to the person skilled in the art, for weaving a terry fabric, the fell line of the fabric is displaced relative to a reed for causing a variation of a distance between a constant beat-up line and the fell line. If, after a plurality of inserted weft threads and beat-ups effected at a distance from the fell line, the fell line of the fabric is displaced in such a way that the fell line is moved closer to the beat-up line of the reed, the previously inserted weft threads are carried along towards the fell line during beat-up of a next inserted weft thread. The weft threads move relative to the more tightly tensioned ground warp threads, while carrying with them the loosely tensioned pile warp threads. Thereby, the pile warp threads form loops.

For forming loops, a low pile warp tension is required. However, in terry fabrics, it is common to have a first fabric part woven as a terry fabric followed by a second fabric part woven as a normal or flat fabric. Therefore, it is generally known in terry weaving machines to use a low tension of the pile warps threads for weaving a terry fabric and high tension of the pile warps threads for weaving a flat fabric between the terry fabrics. As described for example in EP 1888826 B1 , it is known to provide a resiliently held tension roller arranged to guide the pile warp threads, which may move together with the woven fabric if the woven fabric is moved away from the beat-up line for avoiding that pile warp threads are pulled back out of the just woven terry fabric. It is one object of the present application to provide a backrest assembly with a moveably mounted tension roller, wherein it is avoided that a tension of the pile warp threads will increase substantially during a movement of the tension roller upon a displacement of the woven fabric.

It is another object of the present application to provide a backrest assembly with a tension roller mounted by support brackets on a support beam, which allows for an easy adjustment of a position of the support brackets along the support beam axis on the support beam.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, a backrest assembly for pile warp threads in a terry weaving machine, comprising a tension roller and a support beam is provided, wherein the tension roller is arranged to guide the pile warp threads, wherein the support beam is mountable to a frame of the weaving machine so as to be rotatable to-and-fro about a support beam axis, wherein the tension roller is supported in parallel to the support beam by two or more support elements, which support elements are mounted fixed in position to the support beam, and wherein the tension roller is loaded by at least one bellow spring.

The tension roller is resiliently mounted such that the tension roller is displaceable upon a movement of a woven fabric for forming loops in the pile warp threads of a terry fabric. In preferred embodiments, the backrest assembly is a passive device, wherein the tension roller is displaced due to forces applied by the pile warp threads without a drive for actively displacing the tension roller. In the context of the application, the expression tension roller describes an elongated element having as a smooth guidance surface for guiding the pile warp threads along the guidance surface of the tension roller.

A warp tension of the pile warp threads is set using at least one bellow spring. In the context of the application, the expression bellow spring is used for describing a spring comprising one bellow or several bellows filled with a compressible fluid, which bellow allows the spring to expand and contract in a linear direction. The elastic force or spring force of the bellow spring is settable by the pressure of the fluid in the bellow. In preferred embodiments, the bellow is filled with air, in particular pressurized air. The person skilled in the art will understand that instead of air another fluid can be used. The bellow spring can be designed such that the pressure and, thus, the force applied by the bellow spring does not or only insignificantly vary with the expansion and contraction of the bellow due to a movement of the tension roller.

The warp tension of the pile warp threads depends on the pressure inside the bellow spring. By setting the pressure, the warp tension can be set easily and without steps. With the movement of the tension roller, the bellow or the bellows of the bellow spring is/are expanded or contracted in a linear direction. When designing the bellow spring such that the force applied by the bellow spring does not or only insignificantly vary with the expansion and contraction of the bellow(s) due to a movement of the tension roller an at least essentially constant warp tension can be achieved in the pile warp threads guided by the tension roller even while the tension roller is moved over a large distance for a displacement of the woven fabric in use of the terry weaving machine. In other words, the backrest assembly has a low inertia and the movement of the tension roller causes only low variations or no variations in the warp tension during the terry weaving process, although the backrest assembly itself is rather rigid and the tension roller moves over a large distance.

The backrest assembly in embodiments comprises or cooperates with a pressure regulator system that is able to regulate the pressure of the fluid in the at least one bellow spring and/or to measure the pressure of the fluid in the at least one bellow spring, which pressure is proportional to the pile warp thread tension. Preferably, the used fluid is air.

In preferred embodiments, the bellow spring is a rolling-lobe spring, in particular a rolling-lobe air spring. The rolling-lobe spring comprises a bellow, which is usually attached at one end to a roll-off piston, which roll-off piston is made for example of metal or plastic. Upon a contraction, the roll-off piston moves within the bellow, and the bellow is pushed over the roll-off piston so that the bellow defines a rolling lobe which rolls over the outer surface of the roll-off piston. An internal volume of such a rolling-lobe spring only marginally changes when the rolling-lobe spring expands or contracts, i.e. when the bellow rolls over the outer surface of the roll-off piston. In alternative or in addition, the bellow spring is in fluid communication with a large fluid container, in particular a large airtank, for providing an internal volume, which only marginally changes with the expansion or contraction of the bellow spring. Several rolling-lobe springs could be combined to form one bellow spring.

The tension roller moves in a weaving plane, which is at least essentially in a horizontal plane. In one embodiment, the bellow spring is mounted so as to expand and contract in parallel to the weaving direction and coupled to the support elements for a force application. Preferably, the bellow spring is mounted so as to expand and contract in a direction substantially perpendicular to the weaving direction. According to a preferred embodiment, the at least one bellow spring is coupled to the support beam by a linkage system having at least a coupling lever attached to the support beam to rotate with the support beam. This allows for a suitable arrangement of the bellow spring at the periphery of the support beam, while keeping the support brackets, which may extend through the warp threads, small in size.

In one embodiment, a distance between the force application position of the at least one bellow spring on the coupling lever and the support beam axis is shorter than or equal to a distance between an axis of the tension roller and the support beam axis. When the distance between the force application position of the at least one bellow spring on the coupling lever and the support beam axis is shorter than or equal to the distance between the tension roller axis and the support beam axis, a leverage effect is advantageously used as any variation in the pressure applied by the at least one bellow spring will have a smaller effect on the warp tension as applied to the pile warp threads by the tension roller.

In one embodiment, the coupling lever via which the at least one bellow spring is coupled to the support beam and the support elements supporting the tension roller are arranged at an angle of approximately 75° to approximately 105°. Hence, a movement direction at a distal end of the coupling lever is almost perpendicular to a movement direction at a distal end of the support elements. Hence, when the tension roller is moved in a weaving plane, which is at least essentially in a horizontal plane, the distal end of the coupling lever is moved at least essentially in a vertical direction.

In one embodiment, the bellow spring is guided for avoiding a movement of the bellow spring in other directions than its axial direction and, thus, for avoiding a buckling or bending of the bellow of the bellow spring. In preferred embodiments, the linkage system is a four-joint-linkage comprising a rod extending in an axial direction of the at least one bellow spring or in parallel to an axial direction of the at least one bellow spring, the coupling lever being coupled to the rod at a first joint and attached to the support beam to rotate with the support beam, and an auxiliary lever arranged in parallel to the coupling lever, the auxiliary lever being coupled to the rod at a second joint and mountable to the frame of the weaving machine so as to be rotatable to-and-fro about an axis parallel to the support beam axis. The four-joint- linkage system also avoids an inclination of the rod and, thus, a movement of the bellow spring in other directions than its axial direction, wherein in addition friction forces are avoided.

In an alternative embodiment, an auxiliary tension element and a deflection beam are provided, wherein the auxiliary tension element is supported in parallel to the support beam by two or more support elements, wherein the deflection beam is mounted fixed in position to the frame of the weaving machine between the tension roller and the auxiliary tension element, and wherein the deflection beam, the tension roller and the auxiliary tension element are arranged for guiding pile warp threads. The tension roller and the auxiliary tension element in one embodiment are similar or identical in design and are arranged symmetrically at either side of the deflection beam. In one embodiment, the auxiliary tension element is supported by several or all support elements supporting the tension roller such that the number of support elements is minimized.

In one embodiment, the tension roller and/or the auxiliary tension element are supported in the support elements so as to be not rotatable about their axis. In case the tension roller and/or the auxiliary tension element are supported so as to be not rotatable about their axes, the cross-section thereof may be chosen so as to be different from a circular or annular cross-section, for example a curved cross-section, as long as a smooth guidance surface for guiding the pile warp threads along the guidance surface of the tension roller and/or of the auxiliary tension element is possible.

In one embodiment, the at least one bellow spring is mounted via a force measuring device for measuring the force acting on the bellow spring. The force measuring device is for example mounted between the bellow spring and a frame of the weaving machine. In preferred embodiments, in particular when the bellow spring is mounted to expand and contract in a vertical direction, the force measuring device is mounted below the bellow spring. In one embodiment, a warp tension is determined based on such measured forces acting on the bellow spring. In preferred embodiments, in use a warp tension is determined based on a pressure of the fluid in the bellow spring measured by a pressure sensor or any other pressure measuring device, wherein the force measuring device mounted between the bellow spring and the frame of the weaving machine is used for example for calibrating a value of the warp tension based on the value of the pressure in the bellow spring measured by the pressure sensor or any other pressure measuring device. In alternative or in addition, in case a force applied at a distal end of the coupling lever is almost perpendicular to a warp tension as applied to the tension roller by the pile warp threads in a weaving direction, in one embodiment, the support beam is mounted via a support beam force measuring device for measuring the force acting in parallel to the weaving plane on the support beam.

In alternative or in addition to the force measuring device, in one embodiment a position determination device is provided for determining a position of the tension roller. A determined position of the tension roller in one embodiment is used for controlling a rotation of a pile warp beam via which pile warp threads are supplied to the tension roller in such a way, that the tension roller moves to-and fro about this determined position within a defined range, for example a determined position, in which the support elements for the tension roller are oriented almost vertical. In one embodiment, the position of the tension roller is measured directly. In preferred embodiments, the position of the tension roller is determined indirectly by measuring an angular position of the support beam. The angular position of the support beam in one embodiment is measured using an absolute angular position sensor, for example an encoder. In other embodiments, a position detector, for example a linear distance detector, is provided on a frame of the weaving machine, which position detector cooperates with a cam profile mounted on the support beam for measuring a linear distance between the cam profile and the position detector, so that the angular position of the support beam can be determined based on the measured distance between the cam profile and the position detector. The position determination device and the at least one bellow spring can be arranged at opposite ends of the support beam. In preferred embodiments, the position determination device and the at least one bellow spring are arranged at the same end of the support beam.

In one embodiment, the position determination device is used for determining whether the tension roller is within a defined range. In other embodiments, in alternative or in addition a safety detector device is provided for detecting whether a position of the tension roller is within a defined range, which safety detector device comprising a sensor and a detection object, wherein one of the sensor and the detection object is arranged to move with the support beam and the other one is mounted fixed in position on the frame of the weaving machine. The sensor or the detection object, which is arranged to move with the support beam, in one embodiment is attached to the support beam itself. In other embodiments, it is attached to a further element, which is coupled to the support beam so as to move with the support beam. For example, it could be attached to the cam profile of the position determination device, to one of the support elements, to any of the elements of the linkage system, for example the coupling lever, or to an additional element, which is coupled to the support beam so as to move with the support beam. The safety detector device and the at least one bellow spring can be arranged at opposite ends of the support beam. In preferred embodiments, the safety detector device and the at least one bellow spring are arranged at the same end of the support beam.

In preferred embodiments, the pressure of the at least one bellow spring is variable between a low pressure and a high pressure to allow weaving with different warp tensions, for example for different weaves. As described above, in use of terry weaving machines, it is well known to produce a terry towel, which has a first part having terry loops and which has a second part, for example an end border, which second part is a normal or flat fabric without terry loops. It is common practice to weave such a second part with a rather high tension for the pile warp threads. Hence, in one embodiment, the pile warp threads are guided along the tension roller so as to have a higher tension when a normal fabric has to be woven, than when a terry fabric has to be woven, wherein the warp tension is regulated by varying the pressure of the at least one bellow spring. ln order to allow for a simple adjustment of the tension of the pile warp thread, in one embodiment at least a first bellow spring and a second bellow spring are provided, wherein preferably the pressure in the first bellow spring is settable differently to the pressure in the second bellow spring. With such an embodiment, for example the first bellow spring is set to a low pressure, so that the resulting pile warp tension is suitable for weaving the terry fabric, wherein the tension applied in preferred embodiments is at least essentially constant for allowing the formation of loops of rather constant height. The second bellow spring is set to a high pressure for weaving a flat fabric, for example an end border. In one embodiment, the second bellow spring is mechanically decoupled from the support beam for weaving the terry fabric. In other embodiments, the second bellow spring is in addition set to a low pressure or even an at least almost zero pressure when weaving the terry fabric.

In other words, providing at least two bellow springs offers the advantage that the pressure of the first bellow spring can be set to the desired low pressure and the first bellow spring can be regulated to maintain the desired low pressure as constant as possible, for example to a constant value. This low pressure is present in the first bellow at least during terry weaving, and preferably also when weaving a flat fabric. On the other hand, the pressure at the second bellow spring is variable and set to a high pressure for weaving a flat fabric and set to a low or zero pressure when weaving a terry fabric. For this purpose, in one embodiment, a suitable pressure regulator system, in particular a valve system, is provided for supplying a fluid of high pressure via the regulator system to the second bellow spring when weaving a normal fabric, and to allow the fluid to escape, for example via an escape valve, for weaving a terry fabric. In one embodiment, the regulator system comprises a shut-off valve, which is arranged between a fluid inlet to the second bellow spring and a large fluid container. For weaving a normal fabric, the shut-off valve is closed in order to hinder the fluid present in the second bellow spring from escaping the bellow and from flowing towards the large fluid container, so that the second bellow spring acts as a spring with a more rigid or stronger characteristic. When providing a second bellow spring with a relatively small volume, this allows for a rapid increase of the pressure of the fluid in the second bellow spring. ln an alternative embodiment, instead of a second bellow spring a mechanical spring assembly is provided, which is coupled to the supply beam for weaving a flat fabric and decoupled from the supply beam for weaving the terry fabric.

In an embodiment, the first bellow spring and the second bellow spring are arranged at opposite ends of the tension roller.

According to a second aspect, a backrest assembly for pile warp threads in a terry weaving machine, comprising a tension roller and a support beam is provided, wherein the tension roller is arranged to guide the pile warp threads, wherein the support beam is mountable to a frame of the weaving machine so as to be rotatable to-and-fro about a support beam axis, wherein the tension roller is supported in parallel to the support beam by two or more support elements, which two or more support elements are mounted fixed in position to the support beam, in particular fixed in a settable position to the support beam, wherein the support beam is provided at its shell surface with a positioning element extending in parallel to the support beam axis, and wherein the support elements are displaceable along the support beam axis and aligned to each other by means of the positioning element.

To allow for a sufficient load bearing capacity, it is generally known to provide a number of support elements, which are distributedly arranged along the support beam. Preferably, in order to not harm the warp threads that extend within a woven terry fabric, the support elements are arranged between two towels to be woven next to one another. Due to this, only warp threads might be damaged that extend between two terry towels to be woven, and damaged warp threads will not be present in the towel itself. It is therefore generally known to adjust the number and/or position of the support elements along the support beam axis depending on a width of a towel to be woven and/or a number of towels to be woven simultaneously.

With the positioning element, a position along the axis of the displaceably arranged support elements can be easily adjusted while the positioning element provides for a perfect aligning of the support elements to each other. This allows to arrange all support elements in a same angular position with respect to the support beam. Such a support beam having a positioning element is advantageous for different types of backrest assemblies. In such a backrest assembly preferably the tension roller is loaded by at least one bellow spring. In other embodiments, in such a backrest assembly having a positioning element, the tension roller is loaded by a mechanical spring assembly or only loaded by means of an active device for displacing the tension roller.

In preferred embodiments, the positioning element comprises at least one rail segment, wherein the support elements are each provided with a guide groove, which guide groove is shaped complementary in shape to the rail segment and adapted to receive the rail segment to slidingly connect the associated support element to the support beam. A rail segment is advantageous for preventing dust accumulation.

In one embodiment, a positioning element made from a single rail segment, also to be named as rail, extending over the full length of the support beam is provided. In other embodiments, the positioning element comprises at least two rail segments which are arranged aligned to one another and, for example, adjacent or at a small distance to one another.

In one embodiment, the support elements are mounted to the rail segment. In preferred embodiments, the rail segment provides for an alignment, wherein the support elements are mounted to the support beam in each case by means of a brace assembly surrounding the support beam, the brace assembly comprising at least a first brace and a second brace, which first brace and second brace together surround the support beam. This allows for a secure mounting with a sufficient load bearing capacity.

According to a third aspect, a terry weaving machine comprising such a backrest assembly is provided.

According to a forth aspect, a use of a bellow spring in a backrest assembly for pile warp threads in a terry weaving machine is provided, which backrest assembly comprises a tension roller arranged to guide the pile warp threads, wherein the tension roller is loaded by the bellow spring. Using a bellow spring in a backrest assembly for pile warp threads in a terry weaving machine is advantageous as it allows for a movement of the tension roller over a large distance for a movement with the woven fabric. Preferably the backrest assembly and/or the bellow spring is/are designed such that upon the movement of the tension roller a pile warp tension at least essentially remains constant.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, an embodiment of the invention will be described in detail with reference to the drawings. Throughout the drawings, the same elements will be denoted by the same reference numerals. In the schematic drawings

Fig. 1 shows a terry weaving machine with a backrest assembly for pile warp threads.

Fig. 2 is a perspective view of a backrest assembly for pile warp threads. Fig. 3 is a perspective view of the backrest assembly of Fig. 2 without a frame of the weaving machine.

Fig. 4 shows a detail of the backrest assembly of Fig. 2.

Fig. 5 shows in a side view detail of the backrest assembly of Fig. 2 without the frame of the weaving machine. Fig. 6 shows a position measuring device of the backrest assembly of Fig. 1.

Fig. 7 shows in detail a part of a tensioning roller mounted to a support beam by a support bracket.

Fig. 8 shows a detail of the backrest assembly according to a second embodiment similar to Figs. 2 to 7 seen from another side. Fig. 9 shows a terry weaving machine with a backrest assembly for pile warp threads according to a third embodiment similar to Fig. 3.

Fig. 10 shows an air supply system for a terry weaving machine with a backrest assembly of Fig. 9. Fig. 11 shows a detail of a terry weaving machine with a backrest assembly according to a third embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Fig. 1 schematically shows a terry weaving machine 1 with a backrest assembly 3 for pile warp threads 13, which backrest assembly 3 comprises amongst others a tension roller 16 and a support beam 33. The terry weaving machine shown in Fig. 1 is similar to the terry weaving machine known from EP 1888826 B1. A terry weaving machine can be a rapier weaving machine, an air-jet weaving machine or any other similar type of weaving machine.

The terry weaving machine 1 shown in Fig. 1 comprises a warp beam 10 with ground warp threads 11 and a warp beam 12 with pile warp threads 13. The ground warp threads 11 are deflected over a backrest 14 into the weaving plane. The pile warp threads 13 run over a deflector 15 to a tensioning roller 16 and via the tensioning roller 16 into the weaving plane. Both the ground warp threads 11 and the pile warp threads 13 travel to shedding devices indicated by arrows 17.

Upstream of the backrest 14 for the ground warp threads 11 a stationary deflection roll 44 is provided, such that the ground warp threads 1 1 always are guided towards the backrest 14 with the same angle, irrespective of an amount of ground warp threads 11 wound to the warp beam 10 as indicated by broken lines 11 A, 1 1 B. For the same purpose, a stationary deflection roll 45 is arranged upstream of the deflector 15, such that the pile warp threads 13 always run in the same direction to the deflector 15, wherein the path of the pile warp threads 13 is indicated by broken lines 13A, 13B.

Weft threads (not shown) are inserted into the sheds formed by the ground warp threads 11 and the pile warp threads 13, commonly referred to as warp threads. A reed 19, which is mounted to and swiveled with a sley 18, brings the inserted weft threads to a beat-up line. At the beat-up line, the weft threads are tied up by means of the warp threads 1 1 , 13 when the shed is changed. A woven fabric 20 formed in this way is drawn off by means of a draw-off roller 21 and then wound onto a fabric beam 22. In the embodiment shown in Fig. 1 , a breast beam 23 and two deflectors 24, 25 are arranged upstream of the draw-off roller 21 , which draw-off roller 21 is driven in the draw-off direction. The woven fabric 20 deflected downwards by the breast beam 23 out of the weaving plane is deflected by the deflector 25 in such a way that the same fabric side (bottom side of the fabric) which lies on the breast beam 23 also lies on the circumferential surface of the draw-off roller 21. In an alternative not shown, the deflector 25 is omitted an the woven fabric 20 lies with its top side on the circumferential surface of the draw-off roller 21 , and is further guided via another guide to the fabric beam 22, similar as shown in the embodiment shown in Fig. 12 of EP 1899515 B1 incorporated herewith by reference.

The backrest 14 of the ground warp threads 11 and the breast beam 23 may be moved to and fro as indicated respectively by double-headed arrows A and B. In this embodiment, the backrest 14 for the ground warp threads 1 1 is swivelable by means of levers 26 holding its two ends. The levers 26 are coupled to a stationary shaft 40 arranged coaxial to the axis 48 of the backrest 14 for the ground warp threads 11. The lever 26 which bears the backrest 14, comprises an arm 46, which is held by a spring element 47 which is supported on the frame of the weaving machine. In the embodiment shown in Fig. 1 the spring element 47 is arranged at the right side of the backrest 14. In an alternative the spring element 47 can be arranged on the left side of the backrest 14. The breast beam 23 is mounted on both sides via levers 27, which are swivelable about an axis coaxial with the axis of the deflector 24.

The levers 26, 27 are acted upon by transmission bars 28, 29, whose respective other ends are coupled to a swivel arm 30. On either side of the fabric width, such swivel arms 30 are arranged non-rotatably on a shaft which may be swiveled to and fro by means of a drive motor 31 , for example a stepping motor or a geared motor. By means of this drive system 32 comprising the levers 26, 27, the transmission bars 28, 29, the swivel arms 30 and the drive motor 31 , the backrest 14 for the ground warp threads 1 1 and the breast beam 23 may be moved to and fro in the same direction. During this to-and-fro motion, the woven fabric 20 is displaced relative to the reed 19, which may be swiveled between a rear position and a front position. In the process, the distance from the fell of the woven fabric 20 to the beat-up line of the reed 19 is varied.

In the embodiment shown, the backrest assembly 3 for the pile warp threads 13, the design of which will be explained in greater detail below, is not driven by the drive system 32. However, the tensioning roller 16 is resiliently mounted, such that it is moveable in a direction, which at least substantially coincides with the weaving plane. Hereby, the tensioning roller 16 can follow the movement of the woven fabric 20. The tension roller 16 is part of the backrest assembly 3, which further comprises a support beam 33, wherein the tension roller 16 is supported in parallel to the support beam 33 by two or more support elements 51.

If, for example, provision is made for the woven fabric 20 to be moved away from the reed 19, to the left in Fig. 1 , after beat-up of a weft thread to the fell of the fabric, the next weft threads are not beaten up to the fell, but rather remain at a distance therefrom. If, for example, the woven fabric 20 with its fell is then moved back closer to the reed 19 after two to four or more insertions, by moving the backrest 14 and the breast beam 23 accordingly (to the right in Fig. 1 ), the reed 19 moves the last inserted weft threads up to the fell on the next beat-up. In the process, these weft threads slide along the ground warp threads 1 1 , which are relatively tightly tensioned. The pile warp threads 13 are less tightly tensioned, such that the weft threads carry the pile warp threads 13 with them during the beat-up movement. In this way, the respective parts of the pile warp threads 13 are formed into loops. If the backrest 14 and the breast beam 23 are then swiveled again by means of the drive motor 31 in such a way that the fell of the woven fabric 20 moves away from the reed 19 (to the left in Fig. 1 ), the pile warp threads 13 are tightened. The pile warp threads 13 then draw the tensioning roller 16 in the direction towards the reed 19, wherein the resilient mounting of the tensioning roller 16 allows a movement of the tensioning roller 16 in such way that the previously formed loops are not pulled back out of the woven fabric 20 as the woven fabric 20 is displaced. In preferred embodiments, the deflector 15 assists in this resilient function, wherein the deflector 15 being to this end of elastic construction. The deflector 15 preferably is a cylindrically curved spring steel sheet whose edges are attached to a bar, similar as shown in the embodiment shown in Fig. 3 of EP 1888825 B1 incorporated herewith by reference. In another embodiment (not shown), the deflector 15 is mounted rotatably and/or provided with a rotary drive.

Figs. 2 to 7 show an embodiment of a backrest assembly 3 for pile warp threads 13 (see Fig. 1 ). The backrest assembly 3 shown in Figs. 2 to 7 comprises the support beam 33, wherein the support beam 33 is mounted to a frame 50 (see Fig. 2) of the weaving machine 1 (see Fig. 1 ) so as to be rotatably to-and-fro about a support beam axis 34 (see Fig. 3) as indicated by a double-headed arrow R in Fig. 2.

The backrest assembly 3 further comprises the tension roller 16, which tension roller 16 is supported in parallel to the support beam 33 by six support elements 51. In an embodiment, the tension roller 16 is supported in the support elements 51 so as to be rotatable about its axis 35. Preferably, the tension roller 16 is supported in the support elements 51 so as to be not rotatable about its axis 35. The support elements 51 are mounted fixed in a settable position along the support beam axis 34 to the support beam 33. It will be understood by the person skilled in the art that the number and relative position of support elements 51 is only by way of example and can be adjusted for example depending on the number of terry fabrics woven in parallel.

The tension roller 16 is further loaded by a bellow spring 52, in particular a rolling- lobe bellow spring. In the embodiment shown, the bellow spring 52 is coupled to the support beam 33 by a linkage system 53, for indirectly applying a load to the tension roller 16 via the support beam 33.

As best shown in the detail of Fig. 4, in the embodiment shown, the linkage system

53 is a four-joint-linkage with a rod 54 extending in parallel to an axial direction 42 of the bellow spring 52 and a coupling lever 55 attached to the support beam 33 to rotate with the support beam 33, wherein the coupling lever 55 is coupled to the rod

54 at a first joint 56. The linkage system 53 further has an auxiliary lever 57 arranged in parallel to the coupling lever 55, wherein the auxiliary lever 57 is coupled to the rod 54 at a second joint 58 and mountable to the frame of the weaving machine so as to be rotatable to-and-fro about an axis 59 parallel to the support beam axis 34 (see Fig. 3). In the embodiment shown, the bellow spring 52 and the rod 54 are vertically arranged, i.e. the bellow spring 52 extends or contracts in the vertical direction. The four-joint-linkage system provides a linear movement of the rod 54 along its length direction, i.e. in the embodiment shown in the vertical direction as indicated by a double-headed arrow C in Fig. 4, and avoids inclinations of the rod 54. Hence, forces on the bellow spring 52 in other directions than its length direction, i.e. the vertical direction in the embodiment shown, are avoided. In the embodiment shown, the rod 54 is arranged in parallel to the axial direction 42 of the bellow spring 52. This arrangement is advantageous for mounting the bellow spring 52 to the frame 50. In other embodiments, the rod 54 is arranged collinear to the axial direction 42 of the bellow spring 52.

The length of the coupling lever 55 and the position of the first joint 56 are chosen such that a distance between the force application position of the bellow spring 52 on the coupling lever 55 and the support beam axis 34 (see Fig. 3) is shorter than a distance between the axis 35 of the tension roller 16 and the support beam axis 34. Therefore, an effective lever-arm for a force applied by the bellow spring 52 is shorter than an effective lever-arm for a resulting force at the tension roller 16. This leverage effect is advantageous as only a low warp tension is required for the pile warp threads.

In the embodiment shown, the coupling lever 55 and the support elements 51 are arranged at an angle of approximately 100°. Hence, a movement direction of the rod 54 coupled to the coupling lever 55 is almost perpendicular to a movement direction of the tension roller 16 supported by the support elements 51.

As best shown in the details of Fig. 4 and 5, in the embodiment shown, the backrest assembly 3 further comprises a force measuring device 60 for measuring the force acting on the bellow spring 52. In the embodiment shown, the force measuring device 60 is arranged below the bellow spring 52, between a support 49 for the bellow spring 52 and a mounting bracket 61 , which mounting bracket 61 is fixed to the frame 50 of the weaving machine. The force measuring device 60 measures the force acting on the bellow spring 52.

The force measured by the force measuring device 60 in one embodiment is used for regulating the warp tension. Preferably, a pressure of the fluid in the bellow spring 52 is also measured for example by means of a pressure sensor (not shown), wherein the warp tension is regulated based on a measured pressure of the fluid in the bellow spring 52. The force measured by the force measuring device 60 is then used for calibrating the value of the warp tension based on the value of the pressure of the fluid in the bellow spring 52 measured by a pressure sensor. As best shown in the detail of Fig. 5 and 6, in the embodiment shown, the backrest assembly 3 further comprises a position determination device 62 for determining a position of the tension roller 16. In the embodiment shown, the position of the tension roller 16 is determined indirectly by measuring an angular position of the support beam 33. The position determination device 62 of the embodiment shown comprises a position detector 63 for example a linear distance detector, which is arranged fixed in position on the frame 50 of the weaving machine 1 . A cam profile 64 is mounted on the support beam 33 to rotate with the support beam 33. The position detector 63 cooperates with the cam profile 64 for measuring a linear distance D between the cam profile 64 and the position detector 63. As the cam profile 64 rotates with the support beam 33, the angular position of the support beam 33 can be determined based on the measured distance D between the cam profile 64 and the position detector 63.

In the embodiment shown, the position determination device 62 and the bellow spring 52 are arranged at the same end of the support beam 33. In other embodiments, the position determination device 62 and the bellow spring 52 are arranged at opposite ends of the support beam 33.

The support elements 51 are mounted fixed in a settable axial position to the support beam 33, and in a defined angular position with respect to the support beam 33. As best seen in Fig. 7, in the embodiment shown the support beam 33 is provided at its shell surface with a positioning element 65 in the form of a rail segment 66 extending in parallel to the support beam axis 34, wherein the support elements 51 are each provided with a guide groove 67, which guide groove 67 is complementary in shape to the rail segment 66 and adapted to receive the rail segment 66 to slidingly connect the associated support element 51 in a determined angular position to the support beam 33. As shown in Fig. 2, in the embodiment shown, the positioning element 65 comprises several rail segments 66, which are arranged aligned and adjacent to one another.

For fixing the support elements 51 in a chosen position to the support beam 33, each support element 51 is further provided with a brace assembly 68 surrounding the support beam 33. In the embodiment shown, the brace assembly 68 comprises a first brace 69, which is fixed to the support element 51 by means of two screws 70. The brace assembly 68 further comprises a second brace 71 , which is screwed to the first brace 69 with screws 72 (see Fig. 6) for clamping the support beam 33 between the two braces 69 and 71. The positioning element 65 in one embodiment is provided with marks indicating predefined positions for the support elements 51.

It will be understood by the person skilled in the art that other devices for fixing the support elements 51 can be combined with the backrest assembly 3 having a tension roller 16 loaded by a bellow spring 52, as well as the brace assembly 68 can be advantageously used in a backrest assembly 3, wherein the tension roller 16 is not loaded by a bellow spring 52.

In one embodiment, the position determination device 62 described above is further used for determining whether the tension roller 16 is within a defined range, wherein leaving the defined range causes an emergency stop of the weaving machine 1.

Fig. 8 shows a detail of the backrest assembly 3 according to a second embodiment. The backrest assembly 3 of Fig. 8 is similar to that of Figs. 2 to 7, wherein the same reference numbers are used for the same or similar elements. In the embodiment shown in Fig. 8, in addition to the position determination device 62 a safety detector device 36 is provided for detecting whether a position of the tension roller 16 is within a defined range. The safety detector device 36 comprises a sensor 73 and a detection object 74, for example a portion of the auxiliary lever 57, wherein the sensor 73 is mounted fixed in position by means of a fixation plate 37 on a frame of the weaving machine. It will be understood that the detection object 74 could be a portion of any part of the linkage system 53. In the embodiment shown, the safety detector device 36 and the bellow spring 52 are arranged at the same end of the support beam 33. In other embodiments, the safety detector device 36 and the bellow spring 52 are arranged at opposite ends of the support beam 33.

In the embodiments shown above, one bellow spring 52 provided. It will be understood by the person skilled in the art, that instead of one bellow spring 52, two or more bellow springs could be provided which are arranged at the same or opposite ends of the support beam 33. In alternative or in addition, each bellow spring or individual ones of a plurality of bellow springs in one embodiment comprise more than one bellow, wherein the bellows are coupled via a common linkage system to the support beam 33. As generally known, in terry fabrics, it is common to have a first fabric part woven as a terry fabric followed by a second fabric part woven as a normal or flat fabric, for example at an end border. For weaving the flat fabric, a higher warp tension of the pile warp threads is required. Therefore, in one embodiment, the pressure in the bellow spring 52 is variable between a low pressure for weaving a terry weave and a high pressure for weaving a flat weave.

Figs. 9 and 10 show a backrest assembly 3 according to a third embodiment and a fluid supply system 75 for such a backrest assembly 3, respectively. The backrest assembly 3 of Fig. 9 is similar to that of Figs. 2 to 7, wherein the same reference numbers are used for the same or similar elements. In the embodiment shown in Fig. 9 and 10, two bellow springs 52, 152 are provided, which are arranged at opposite ends of the support beam 33. The bellow springs 52, 152 are each coupled to the support beam 33 via a linkage system 53, 153. Both linkage systems 53, 153 are designed as a four-joint-linkage with a rod 54, 154 extending in parallel to an axial direction of the bellow spring 52, 152 and a coupling lever 55, 155 attached to the support beam 33 to rotate with the support beam 33, wherein the coupling lever 55, 155 is coupled to the rod 54, 154 at a first joint 56, 156. Each linkage systems 53, 153 further comprises an auxiliary lever 57, 157 arranged in parallel to the coupling lever 55, 155, wherein the auxiliary lever 57, 157 is coupled to the rod 54, 154 at a second joint 58, 158 and mountable to the frame of the weaving machine so as to be rotatably to-and-fro about an axis 59, 159 parallel to the support beam axis 34 (see Fig. 3).

In one embodiment, the pressures within the two bellow springs 52, 152 at all times are set so as to be almost identical, in other words at least within limits identical.

In preferred embodiments, the pressure in the first bellow spring 52 is set differently to the pressure in the second bellow spring 152. For example the first bellow spring 52 is set to a low pressure, so that the resulting pile warp tension is suitable for weaving the terry fabric, the pressure in the first bellow spring 52 is kept constant for all weaving operations. The pressure in the second bellow spring 152 is variable. In one embodiment, the pressure in the second bellow spring 152 is set to a high pressure for weaving a flat fabric, for example an end border, and set to a low pressure or even an at least almost zero pressure when weaving the terry fabric. ln the embodiment shown in Fig. 9, each bellow spring 52, 152 is mounted via a force measuring device 60, 160 to the frame 50 of the weaving machine. Further, a position determination device 62 is arranged at the side of the support beam 33 at which the first bellow spring 52 is provided. It will be understood that the position determination device 62 could also be arranged at the opposite side of the support beam 33 at which the second bellow spring 152 is provided. In still another embodiment, no position determination device 62 is provided.

For regulating the variable pressure of the second bellow spring 152 as well as for regulating the pressure of the first bellow spring 52 in order to achieve a desired warp tension, in the embodiment shown the fluid supply system 75 as shown in Fig. 10 is provided. In the embodiment shown, a pressure in the two bellow springs 52, 152 is regulated in the same way but by independent elements to allow for an independent pressure setting.

The fluid supply system 75 is connected to a fluid supply 76, in particular an air supply. Between the fluid supply 76 and the bellow spring 52, 152 in each case is provided a controlled pressure regulator system 77, 177 allowing a controllable fluid feed to the bellow spring 52, 152 or a controllable fluid escape from the bellow spring 52, 152. Downstream of the pressure regulator system 77, 177, a fluid container 78, 178 such as an airtank is provided, which is in fluid communication with the associated bellow spring 52, 152 via a controlled shut-off valve 79, 179. The pressure downstream of the pressure regulator system 77, 177 is measured using a pressure sensor 80, 180, also to be named as a pressure gauge.

The pressure in the first bellow spring 52 can be set with the shut-off valve 79 open, i.e. with the bellow spring 52 in fluid communication with the fluid container 78. The pressure is set by the pressure regulator system 77 to a low value suitable for weaving a terry fabric.

As described above, in one embodiment, the pressure in the second bellow spring 152 is set to a high pressure for weaving a flat fabric, for example an end border, and set to a low pressure or even an at least almost zero pressure when weaving the terry fabric. For setting the pressure in the second bellow spring 152 to a low value, the pressure can be set with the shut-off valve 179 open, i.e. with the second bellow spring 152 in fluid communication with the fluid container 178 as described for the first bellow spring 52. In alternative, the pressure regulator system 177 is controlled so that fluid can escape from the bellow spring 152, so that no force is applied by the second bellow spring 152 to the tension roller 16 (see Fig. 9). For this purpose, the shut-off valve 179 is preferably closed, so that the fluid present in the second bellow spring 152 can escape rather fast out of the bellow spring 152, while the pressure present in the fluid container 178 remains. In order to set the pressure to a high value, in one embodiment the pressure regulator system 177 is controlled so that fluid flows from the fluid supply 76 to the bellow spring 152, for example when the shut-off valve 179 is closed so that the supplied fluid is hindered from flowing towards the large fluid container 178. In result, the pressure in the bellow spring 152 can increase rather fast. Further, when the shut-off valve 179 is closed, the second bellow spring 152 acts as a spring with a more rigid or stronger characteristic. In particular, when providing a second bellow spring 152 with a relatively small volume, this allows for a rapid increase of the pressure of the fluid in the second bellow spring 152.

Fig. 11 shows a detail of a terry weaving machine 1 with a backrest assembly 3 according to a third embodiment. The terry weaving machine 1 and the backrest assembly 3 shown in Fig. 11 are similar to the terry weaving machine 1 and the backrest assembly 3 shown in Fig. 1 . Therefore, identical reference signs are used for the same or similar elements and a detailed description of such elements is omitted.

The backrest assembly 3 for pile warp threads 13 comprises a support beam 33 and a tension roller 16, which tension roller 16 is supported in parallel to the support beam 33 by support elements 51 so as to rotate with the support beam 33. The tension roller 16 shown in Fig. 11 has an essentially semicircular shape and is mounted in a non-rotatable manner to the support elements 51. Upstream of the tension roller 16, the pile warp threads 13 are guided along the support beam 33, wherein the support beam 33 deflects the pile warp threads 13 so as to be guided towards the elements arranged downstream thereof at an angle, which does not depend on the remaining amount of pile warp threads 13 on the pile warp beam 12.

In addition, in the embodiment shown in Fig. 1 1 , for tensioning the pile warp threads 13 a deflection beam 39 and an auxiliary tension element 38 are provided. The deflection beam 39 is mounted fixed in position to the frame 50 of the weaving machine 1. The tension roller 16 and the auxiliary tension element 38 are arranged at either side of the deflection beam 39. The auxiliary tension element 38 is supported in parallel to the support beam 33 by the support elements 51 so as to rotate with the support beam 33. The person skilled in the art will understand that in an alternative arrangement, a deflection beam mounted fixed in position may be arranged downstream of the tension roller 16.

In the embodiment shown, the tension roller 16 and the auxiliary tension element 38 are arranged at common support elements 51 such that the number of support elements 51 is minimized. In other embodiments, the tension roller 16 and the auxiliary tension element 38 are at least partially arranged on different support elements 51. In the embodiment shown, the tension roller 16 and the auxiliary tension element 38 are similar or identical in design. In other embodiments, the tension roller 16 and the auxiliary tension element 38 differ in design.

A bellow spring 52 is coupled to the support beam 33 via a coupling lever 55 for loading the tension roller 16 and the auxiliary tension element 38.

In the embodiments shown, the backrest assembly is a passive device without a drive for actively displacing the tension roller. In another embodiment, a drive device is assigned to the backrest assembly for the pile warp threads comprising the tension roller for an active displacement of the tension roller, which drive device can be similar as the drive device shown in the embodiment shown in Fig. 3 of EP 1888825 B1 incorporated herewith by reference. In still another embodiment, a drive device is assigned to the bellow spring for an active displacement of the bellow spring, thereby causing a displacement of the tension roller.