DE69114912T2 - Device for tensioning the warp threads in a weaving machine. - Google Patents

Description

The present invention relates to a device for tensioning the lateral edges of a warp of warp threads on a weaving machine.

It is well known that the tension of the warp threads in a row or a course of a weaving machine is different in the middle and the opposite lateral ends, which can be determined by the width of the course, i.e. the warp thread tension is lower towards the lateral ends of the course. This lower tension causes poorer separation of the warp threads when forming an open shed by forming an upper and lower course of warp threads.

If the separation of the warp threads is insufficient, especially on the side from which the weft threads are inserted, faulty weft thread insertion can occur. A device designed to increase the tension of the warp threads on the lateral edges of the warp is described, for example, in JP 52-110967, JP 58-169545 and JP 59-43150.

The devices according to JP-110967 and JP-43150 use spring forces to apply tension to the side edges of the warp. The device according to JP-169545 uses a pair of tension members arranged parallel to each other on the side of the warp to thereby hold warp threads at such an angle to a line transverse to the direction of the warp threads that the outer end of each tension element is closer to the fabric edge than that of the inner warp threads.

At each end of the devices according to JP 52-110967, FR-A-2 229 014 and JP 59-43150, substantially equal tension is applied to the side threads of the warp. If the tension is increased to improve the separation of the warp threads at the side edges, a high tension is continuously applied to the warp threads at the edges, which can lead to warp threads breaking.

In the device according to JP 58-169545, in which the warp tension is increased by increasing the opening of the shed, the time at which tension is applied depends only on a predetermined shedding curve, with the result that there is no choice for the time of application of the tension.

Even if the movement is facilitated by slackening, the warp tension is different when the shed is open and when it is closed, because each shed opens and closes at a different time compared to the others. The difference is greater on the sides of the warp where the basic tension of the warp is lower.

As a result of these differences in thread tension, the slats on the side edges of the warp vibrate and possibly jump more than slats in the more central part of the warp. Such increased vibration can cause the warp threads to become roughened or even broken at the edge and/or cause the fabric edge to become irregular.

It is therefore an object of the present invention to provide a device which allows the adjustment of the time of application of tension so that the warp threads are tensioned at the right time for weft insertion.

According to the present invention, this object is achieved with the teaching of claim 1. The dependent claims relate to particular embodiments of the invention.

The tensioning device of the device is operated in such a way that it presses on the two side ends of the warp with each weft insertion, at a selectable time that is determined by the timer device according to the invention. The warp threads on the side edges can be tensioned at the right time for the weft insertion. The timely tensioning of the warp threads on the edge, at the time of the weft insertion, leads to the smooth separation of the warp threads at the side ends, whereby the shed is immediately formed. As a result, weft errors due to incorrect shed formation are successfully prevented.

Another object of the invention is to reduce the roughening of the lateral edges of the warp threads due to vibration. According to the invention, the difference in tension in the warp threads between the open and closed shed is reduced by aligning the time of pressing on the lateral edges with the time of closing the shed. This measure considerably reduces the vibration of the slats and the roughening and thus also the warp thread breaks.

When the warp is tensioned at the moment when the shed closes, the tension of the warp in the lateral part is tightened. At the same time, the tension of the lateral part of the warp threads is limited when the shed is open and closed in the weaving cycle.

From the above it can be seen that according to the invention the time at which the tensioning device is actuated to tension the opposite lateral edge areas of the warp threads can be set as desired at the time of closing and opening of the shed.

In this way, the timing of tension application, in accordance with the timing of weft insertion, can enable the smooth separation of the weft threads at the side edges, with the shed being formed immediately. As a result, weft defects due to insufficient shed formation can be successfully prevented.

The timed application of tension to the warp threads when closing the shed ultimately reduces the difference in warp tension within a weaving cycle. This difference enables the warp threads to be smoothly separated at the side edges, forming the shed without delay. As a result, weft defects due to incorrect shedding can be successfully avoided.

The device for tensioning the warp threads allows the tensioning device to tension the warp threads on the side edges of the warp in sync with the weft insertion. This synchronized tensioning of warp threads leads to the smooth separation of the warp threads on the side edges, whereby the open shed is immediately formed. As a result, weft errors due to incorrect shed formation can be successfully prevented.

Examples of the invention are described with reference to the schematic drawings. Figs. 1 to 9 show a first embodiment and Figs. 1A to 4A show another embodiment of the invention and details thereof.

Figs. 1 and 1A are schematic side views of the device for tensioning warp threads in a weaving machine;

Figs. 2 and 2A are perspective views of the tensioning device of Fig. 1;

Figs. 3 and 3A are rear views of the clamping device;

Fig. 4(a), (b) and (c) are side sectional views showing the clamping device in different working positions;

Fig. 4A(a), (b) and (c) are side sectional views showing the clamping device in different working positions;

Fig. 5 is a diagram showing the shedding curve and the swing curve of the tension roller;

Fig. 6 is a diagram showing curves representing the distribution of warp yarn tension; and

Figs. 7 to 9 are side sectional views showing other embodiments of the present invention.

Fig. 1 is a schematic side view showing an embodiment of the device according to the present invention as used on a jet loom. Warp threads T are unwound from a warp beam 19 and guided over a support roller 1 and a stenter beam 2 and further through warp break detectors 3 and healds 4 and then beaten with the reed 5 to the fabric W which is wound on a cloth beam 6. The Reference symbol W₁ denotes the stop edge and N means a main weft insertion nozzle which oscillates together with the reed 5.

Referring to Fig. 2, the spanner 2 is supported by and between a pair of relief levers 7A and 7B which swing about the pivot pins 8a and 8b, respectively. The relief levers 7A, 7B are connected at their distal end to a pair of rods 9A, 9B which in turn are connected to a crank mechanism (not shown). The crank mechanism operates in synchronism with the drive of the loom so that the rods 9A, 9B make a reciprocating stroke for one complete revolution of the loom.

Support arms 10A, 10B are connected by connectors 12A, 12B to the proximal end of the respective levers 7A, 7B and tension rollers 11A, 11B extend inwardly over the warp T and are arranged at an angle to the plane formed by the warp threads T1 between support roller 1 and tension beam 2. The support arms 10A, 10B have elongated holes 10a through which screws 13A, 13B pass and by which they are fastened to the connectors 12A, 12B. In the above arrangement, the connectors 12A, 12B are detachably connected to the support arms 10A, 10B by the screws 13A, 13B.

As shown in sketches (a), (b) and (c) of Fig. 4, the longitudinal hole 10a extends in a direction transverse to the warp T₁, between the support roller 1 and the tension beam 2, so that the tension rollers 11a, 11b can be adjusted along the hole 10a, i.e. in a direction transverse to the warp T₁.

Sketches (a), (b) and (c) of Fig. 4 show the tension roller 11A arranged on the side of the main weft insertion nozzle N. The tension roller 11A is arranged together with the tensioning beam 2 around the pivot pin 8A. The same applies to the other tensioning roller 11B on the opposite side of the weaving machine.

Referring to Fig. 5, the curves C₁, C₂ show shedding curves of two warp thread groups alternately forming the upper and lower sheds. The curve C₃ shows the oscillation curve of the stenter beam 2 and the curve C₄ shows an oscillation curve of the tension roller 11A which is in contact with the warp T₁, and the oscillation curve C₄ represents the angle at which the tension roller 11A swings out from the upper position X. In the lower diagram of Fig. 5, the area above the abscissa X shows the area in which the tension roller 11A is in contact with the warp T₁, while the area below the abscissa X shows the area where the roller is away from the warp threads.

The sketch (a) of Fig. 4 shows the position of the tensioning beam 2 and the tensioning roller 11A when the shed is closed and the sketch (c) of the same figure shows the position of the tensioning beam 2 and the tensioning roller 11A when the warp shed is wide open. The sketch (b) of Fig. 4 shows the position where the tensioning roller is just engaging the warp or is just lifting off the warp T₁. Accordingly, the tensioning roller 11A between the states (a) and (b) of Fig. 4 corresponds to the curve C₄ in the area below the abscissa X in Fig. and the position of the tensioning roller 11A between the states (b) and (c) corresponds to the curve C₄ in the area above the abscissa X. When the chain T begins to open the shed with the warp threads, the tension rollers 11A begin to touch the warp threads at the lateral ends TL of the chain T, on the side of the main weft insertion nozzle N, or at the opposite end TR.

The basic difference of the embodiments of the invention as shown in Fig. 1A, 2A, 3A and 4A (a), (b) and (c) is that the tension rollers 11A move the chain T away from the support roller 1 and the tensioning beam 2 and not towards the support roller 1 and the tensioning beam 2 when the warp threads have to be tensioned.

Referring to the diagram of Fig. 6, the curve C5 therein shows the distribution of warp tension across the width of the warp without using the tension rollers 11A, 11B when the shed is opened. The curve C6 shows the distribution of warp tension when the tension rollers 11A, 11B are used to tension the warp. It can be seen from the diagram that the smooth separation of the warp threads into the upper and lower sheds at the lateral ends TL and TR can be improved by increasing the tension at these lateral ends of the warp. In addition to this smooth separation of the warp threads, the timing at which the tension is applied to the ends TL and TR with the tension rollers 11A, 11B is adjustable in order to form the opened shed at the correct timing of weft insertion. This is achieved by adjusting the location of the mounting of the tension rollers 11A, 11B with the elongated holes 10A in the support arms 10A, 10B, opposite the relief levers 7A, 7B, in time with the weft insertion time. With the above-described embodiment, there is no risk of warp threads breaking due to the constantly high tension, as was observed in devices according to the state of the art, since the warp is not constantly subjected to high tensile stresses at the lateral ends TL and TR.

The adjustment of the mounting position of the tension rollers 11A, 11B can be carried out simply by moving the connectors 12A, 12B, in the holes 10a of the support arms 10A, 10B, with the screws 13A, 13B loosened. This adjustment shifts the curve C₄ in Fig. 5 in the direction up or down, with respect to the abscissa X.

According to this embodiment, where the tension rollers 11A, 11B are moved back and forth by the relief levers 7A, 7B, no additional drive is necessary and thus no additional costs are necessary.

It should be noted that the present invention is not limited to the embodiments described above but can be used in various other ways, as illustrated, for example, with the embodiments of Figs. 7 to 9.

In Fig. 7, an air cylinder 14 is provided with a movable rod, at the distal end of which a tensioning device 14a is mounted. The tensioning device 14a is moved by the air cylinder 14 to press the lateral ends of the warp T₁ between the support roller 1 and the stenter beam 2. The operation of the air cylinder 14 is controlled by an electromagnetically actuated valve (not shown) which is actuated by being turned on or off depending on the timing of weft insertion. Thus, the timing at which the lateral ends of the warp threads of the warp T₁ are to be tensioned can be set as desired, thus tensioning the warp threads at the proper timing of weft insertion.

In the embodiment shown in Fig. 8, and which is used on a weaving machine having no support roller, there is an air cylinder 14 which carries a tensioning device 14a which is movable to press between the tensioning beam 2 and the warp beat-up beam 15 on a lateral end of the warp T.

In the embodiments of Figs. 7 and 8 shown above, the air cylinder 14 can be replaced by another suitable device, such as an electric solenoid.

With reference to Fig. 9, which shows a further embodiment of the invention, there is a lever 16 which is attached in a pendulum manner to a rotatable shaft 20 and has at one of its ends a tensioning element 16a which acts on a lateral end of the warp. The lever 16 is connected at its other end via a rod 18 to a crank disc 17, which in turn is coupled to a drive of the weaving machine. The end of the rod 18 facing away from the connection to the lever 16 is adjustably connected to an elongated hole 17a in the crank disc 17. Adjusting the position of the rod 18 to the crank disc 17 allows tension to be applied to the lateral ends of the warp T with the tensioning element 16a in a timely manner.

As is apparent from the foregoing, according to the invention, the timing at which the tensioning element is actuated to create tension in the opposite lateral ends of the warp can be timed in accordance with the timing of weft insertion. By timing the tension in warp threads, the smooth division of weft threads at the lateral ends can be enabled, thus enabling the smooth, immediate opening of the shed. As a result, weft defects due to insufficient formation of the shed can be successfully prevented.

Tension rollers, 11A, 11B; device with elongated holes 10a, for timely adjustment of the tension, connectors 12A, 12B and screws 13A, 13B; warp T; side ends TL, TR of the warp.

The device 9A, 7A, 10a, 10b, 11A for tensioning the warp threads T allows the warp threads of the opposite lateral ends of the warp to be tensioned by actuating the tensioning device 11A, 11B and can, if necessary and desired, be adjusted in accordance with the time of weft insertion and/or the time of closing the shed. The timed tensioning of the warp threads at the time of weft insertion leads to the smooth separation of the warp threads at the side ends, whereby the open shed is formed without delay. As a result, weft errors due to incorrect and incomplete shed formation are successfully avoided. Reducing differences in the thread tension in the weaving cycle, with an open shed and a closed shed, reduces the vibration of the slats and, as a result, also the roughening of the warp threads T and even the number of warp thread breaks.

Claims (7)

1. Device for tensioning warp threads in a weaving machine, comprising a mechanism (9A, 7A, 8A) for tensioning the warp threads, which has a tensioning device (11A) for applying tension to opposite lateral ends (TL, TR) of a warp (T) by pressing on the lateral ends, characterized in that it has a device for adjusting the time of pressing with the tensioning device (11A) on the lateral ends (TL, TR) of the warp (T) during a desired period of time in order to compensate for the differences in the tension of the warp threads across the width of the warp (T) in each weaving cycle. 2. Device for tensioning warp threads according to claim 1, in which the desired time of tensioning in a weaving cycle is correlated with the weft insertion time and falls within it. 3. Device for tensioning warp threads according to claim 1, in which the desired time of tensioning in a weaving cycle is correlated with and falls within the time of the closed warp thread shed (T). 4. A warp tensioning device according to any one of claims 1 to 3, comprising a tensioning device (11A, 11B) extending inwardly of the warp and arranged at an angle to the plane defined by the warp (T₁) such that the increase in tension is highest in the outermost part of the lateral end part of the warp (T₁). 5. Device for tensioning warp threads according to one of claims 1 to 4, which has a device for actuating which is driven depending on the angle of rotation of the main shaft of the weaving machine. 6. Device for tensioning warp threads according to one of claims 1 to 5, which has a pneumatic or hydraulic drive (14) for actuating the device (14a) for tensioning. 7. Device for tensioning warp threads according to one of claims 1 to 5, which has a lever (16) which is rotatably mounted on a pivotable shaft (20), the device for tensioning (16a) being mounted on one side of the lever (16).