EP1377701B1 - Clamping device for seam weaving machines - Google Patents

Abstract

The gripping collet ( 10 ) for grasping a thread during the preparation of a woven seam is arranged at the end of a draw-through gripper and has a first and a second clamping element, the first and the second clamping element ( 20, 24 ) being able to be clamped against each other for grasping the thread using a pneumatic cylinder. The first clamping element has two cylinder surfaces ( 20 ) at a distance from each other and the second clamping element has one cylinder surface ( 24 ). The arrangement of the cylinder surfaces ( 20, 24 ) is such that the axes of the cylinder surfaces lie parallel to each other and essentially at right-angles to the axis of the pneumatic cylinder and, in the extended state of the pneumatic cylinder, the cylinder surface ( 24 ) of the second clamping element lies between the two cylinder surfaces ( 20 ) of the first clamping element.

Description

The invention relates to a collet for detecting a thread. The collet is arranged at the tip of a movable gripping arm of a pull-through gripper, which serves for introducing the thread, a so-called auxiliary weft thread, into the seam weaving compartment in a seam weaving machine.

In papermaking, a dewatering screen or forming fabric is used to dewater the paper web which initially consists primarily of water fractions. The Entwässerungssiebe consist of Kunststoffmonofilamenten and are woven on wide weaving machines, then made endless with a provisional seam us heat-set on fixing machines, so that the cranks of the warp and weft threads are permanently imprinted. Thereafter, the dewatering screens are again cut apart and stitched in a final process step by means of a woven seam to form an endless cloth. The woven seam is an extremely sensitive as well as time-consuming step in the production process of a dewatering screen. To improve this time-consuming work process, weaving machines or seaming machines have been developed.

To produce a woven seam, warp threads are exposed over a length of, for example, 15 cm to the fabric ends to be joined together by removing the weft threads in this area. From the resultant warp thread fringes and the weft threads removed from the fabric end, the so-called woven seam is then formed, in which the original fabric weave is exactly restored. For this purpose, an auxiliary weaving shed or seam shed is stretched out of the removed weft threads, in which the removed weft threads act as auxiliary warp threads. In this seam weave become alternately From the two fabric ends the warp thread fringes entered as auxiliary weft threads. From the plurality of warp thread fringes protruding from each end of the fabric, a separator ( DE-U-87 13 074 . EP-A-0 301 174 and DE-U-90 02 278 ) a Kettfadenfranse removed and held. A transfer gripper transports this warp thread fringe to a pull-through gripper, which then inserts it as an auxiliary weft thread into the seam weaving shed, in such a way that the auxiliary weft thread initially lies tightly in the seam weaving shed.

The pull-through gripper is of the type mentioned above and is for example from the DE-U-81 22 449 , of the EP-A-0 043 441 and the EP-A-0 236 601 known. The presence of the warp thread fringe is no longer checked by the pull-through gripper.

In this process, the auxiliary weft thread must be held by the collet, which is integrated in the pull-through gripper, with different voltages. From DE-U-92 15 498 (= EP-A-0 597 494 ) known collet consists of a collet body and a pressure piece, which is moved by a pneumatic cylinder. Between a flat clamping surface on the collet body and a flat surface on the pressure piece which are parallel to each other, the auxiliary weft yarn is tensioned with a corresponding pressure generated by the pneumatic cylinder. When retracting the auxiliary weft thread through the Nahtwebfach the pneumatic cylinder is usually subjected to a higher pressure than the subsequent rolling by means of the sley. This rolling is in DE-U-92 11 353 (= EP-A-0 586 959 ).

New, more complex fabric designs require on the one hand a particularly high clamping force when pulling in and on the other hand a more sensitive, ie lower, clamping force during rolling in. This can not always be achieved by the collets with flat, parallel clamping surfaces collet body and on the pressure piece.

The invention has for its object to provide a collet, which can be controlled so that on the one hand securely holds the thread, so that a high tensile force can be exerted on the thread, and that on the other hand, a very low clamping force can be reproduced reproducible ,

According to the invention this object is achieved in that the first clamping element has two spaced cylindrical surfaces and that the second clamping element has a cylindrical surface, wherein the arrangement of the cylindrical surfaces is such that the axes of the cylindrical surfaces are parallel to each other and substantially perpendicular to the axis of the pneumatic cylinder and in the extended state of the pneumatic cylinder, the cylindrical surface of the second clamping element lies between the two cylindrical surfaces of the first clamping element.

1. 1. Durch die Verformung des Kettfadens, wobei die Achse des Fadens und die Achse der Zylinderflächen senkrecht zueinander stehen, so daß zwischen dem Faden und den Zylinderflächen eine Punktauflage entsteht. Unter Berücksichtigung der Verformbarkeit des aus Kunststoffmaterial, z.B. Polyester oder Polyamid, bestehenden Fadens entstehen sehr kleine Berührungsflächen mit entsprechend hohem Berührungsdruck beim Festspannen des Fadens zwischen den Spannelementen.
2. 2. Durch den Reibwert und die daraus resultierende Reibkraft.
3. 3. Durch die Umschlingungsreibung.

In the collet according to the invention, a very high clamping force is achieved with a relatively small cylinder. This is achieved by means of three physical effects

1. 1. Due to the deformation of the warp thread, wherein the axis of the thread and the axis of the cylindrical surfaces are perpendicular to each other, so that a point support is formed between the thread and the cylindrical surfaces. Taking into account the deformability of the existing plastic material, such as polyester or polyamide, existing thread very small contact surfaces with a correspondingly high contact pressure when tightening the thread between the clamping elements.
2. 2. Due to the coefficient of friction and the resulting frictional force.
3. 3. By the wrap friction.

1. 1. Dem Reibwert und der daraus resultierenden Reibkraft.
2. 2. Der reduzierten Umschlingungsreibung.

The extremely low and reproducible warp tension during the rolling is achieved by a force balance by the gas pressure in the cylinder is reduced so far that the pressure exerted by the gas pressure on the piston force is approximately equal to the restoring force of the cylinder spring. It is thereby achieved a floating state of the piston of the pneumatic cylinder, in which no significant deformation of the thread occurs and the frictional force is reduced. In this state, the actual frictional force thus results:

1. 1. The coefficient of friction and the resulting frictional force.
2. 2. The reduced wrap friction.

An advantage of the collet according to the invention is that it is largely insensitive to contamination. The clamping force is only slightly influenced by adhering dirt.

Fig. 1

die Spannzange in einer räumlichen Darstellung;

Fig. 2

die Spannzange von oben in geschlossener Stellung;

Fig. 3

die Spannzange in der Stellung bei reduziertem Gasdruck im Pneumatikzylinder (Kraftwaage);

Fig. 4

die Spannzange in einer räumlichen Darstellung in teilweiser geschlossener Stellung, jedoch ohne Faden und

Fig. 5

die Spannzange im Schnitt.

An embodiment of the invention will be explained below with reference to the drawing. Show it:

Fig. 1

the collet in a spatial representation;

Fig. 2

the collet from above in closed position;

Fig. 3

the collet in the position with reduced gas pressure in the pneumatic cylinder (force scale);

Fig. 4

the collet in a spatial representation in partial closed position, but without thread and

Fig. 5

the collet on average.

The collet 10 is a total of cylindrical and is composed of a clamping body 12 and a pneumatic cylinder 14, which are connected by means of an adapter ring 16.

The clamping body 12 has a transverse cut, which forms a mouth 18. At the front end of the mouth, two cylinder body 20 are inserted or arranged, whose distance is about 70% of its diameter and whose axes are perpendicular to the axis of the collet 10, wherein both cylinder body 20 have the same distance from this axis. The cylinder body 20 represent a first clamping element.

At the front end of a piston rod 21 of the pneumatic cylinder 14, a pressure piece 22 is provided, in the end face of another cylinder body 24 is inserted or arranged. The axis of the further cylinder body 24 is also at right angles to the axis of the collet 10, wherein this cylinder body 24 is located exactly on the axis of the collet 10. The pressure member 22 is guided against rotation in the clamping body 12, so that the parallel alignment of the axes of the cylinder body 20, 24 is always guaranteed. The piston 25 is reset by a return spring 26 in the open position shown in FIGS. 1 and 5. The further cylinder body 24 constitutes a second tensioning element.

By means of the pneumatic cylinder 14, the pressure member 22 can be extended with the other cylinder body 24, so that a thread F inserted into the mouth 18 as shown in Fig. 2, between the cylinder bodies 20, 24 is deformed and thereby tightened, i. is held by clamping and deformation.

On the pressure piece 22, a pin 28 pointing in the axial direction is further fastened above the further cylinder body 24 (not shown in FIGS. 2 and 3) which, when extending into a suitable bore 30, is inserted at the tip of the clamping body 12 (FIG ). By this pin 28 prevents a captured in the collet 10 thread F could solve in the radial direction from the collet 10. The diameter of the pin 28 is slightly smaller than that Distance of the cylinder body 20 so that the pin 28 can drive between the two cylinder bodies 20 through.

The cylinder bodies 20, 24 are made of a hard, abrasion resistant material, e.g. Carbide or ceramic. They are attached in matching cavities on the clamping body 12 and on the pressure piece 22. The cylinder bodies 20, 24 can also be integrated in the shape of the clamping body 12 and the pressing piece 22. The clamping body 12 and the pressure piece 22 are then made entirely of the hard, abrasion-resistant material.

Essential to the invention is not that the first and second clamping elements are formed as complete cylinder body, but that the mutually facing surfaces of the first and second clamping elements are curved about parallel axes.

The operation of the collet is explained below. The thread F, which is a warp thread fringe or so-called auxiliary weft thread, is inserted in the usual manner by a transfer gripper into the mouth 18 of the collet 10. The pneumatic cylinder 14 is then pressurized, so that the further cylinder body 24 is moved to the cylinder bodies 20 and the inserted thread F is clamped between the cylinder bodies 20, 24, wherein the thread is cranked or deformed as shown in Fig. 2. The cylinder body 20, 24 press with their cylindrical surfaces in the thread F and give the thread a resulting frictional force and wrap friction force. The collet forms the front end of a conventional and therefore not shown pull-through gripper. After the detection of the thread F, the head of the pull-through gripper is moved through the seam weaving compartment, so that the thread comes to rest as an auxiliary weft thread in the seam weaving compartment. The auxiliary weft thread is the fringe of a warp thread, so that it has the permanently applied by the above-mentioned heat setting waveform.

Since the shed is formed from auxiliary warp threads, that is, from threads that have been removed from the fabric to be made endless, the auxiliary warp threads likewise have a wave form permanently applied by the heat setting. For the stability and reliability of the woven seam, it is essential that the corrugations of the auxiliary weft threads and the auxiliary warp threads conform to each other according to the weave pattern. This results in a positive connection of a very high strength of the woven seam guaranteed. Thus, the troughs and mountains of the auxiliary weft threads and the auxiliary warp threads can fit into each other according to the Geweberapport, a very high tension must be applied to the auxiliary weft threads after passing through the shed. This high tensile stress is generated by the pull-through gripper, to which the auxiliary weft thread F must be clamped as firmly as possible in the collet 10.

After drawing the auxiliary weft thread F in the shed and the construction of a high tensile stress in the auxiliary weft thread F of the auxiliary weft thread is rolled by means of the sley. In order to ensure the positive engagement of the wave troughs and mountains of the auxiliary weft thread between the auxiliary warp threads, the auxiliary weft yarn is not struck simultaneously over the entire width of the shed, but starting from the fabric end to which it hangs as Kettfranse, successively across the width of the shed. This process is called "rolling in". For the positive interlocking of the waveform of the auxiliary weft threads and the auxiliary warp threads of the auxiliary weft thread must be able to shorten its length during the rolling. Before the rolling, the pressure in the pneumatic cylinder 14 is therefore reduced so far that it approximately compensates for the force of the return spring 26 (force balance). The pressure piece 22 with the further cylinder body 24 is thereby moved back slightly by the thread F, which elastically relaxes after the reduction of the gas pressure in the pneumatic cylinder 14 in the direction of its diameter, as can be seen in FIG. By the force balance between the gas pressure in Pneumatic cylinder and the force of the return spring 26 floats the pressure piece 22, ie it exerts neither in one direction nor in the other direction of a force and is pressureless to the thread F on. The auxiliary weft thread F is therefore held only by the belt friction in the collet 10, while it is rolled from the sley along the selvedge.

It has been found that the tensile stress which occurs in the auxiliary weft thread is highly reproducible, which improves the quality and uniformity of the woven weave produced.

The necessary time control of the pressure in the pneumatic cylinder 14 takes place in a known manner by means of signals which are derived from the control of the seam loom.

LIST OF REFERENCE NUMBERS

10

collet

12

tensioning body

14

pneumatic cylinder

16

adapter ring

18

mouth

20

Cylinder body (first clamping element)

21

piston rod

22

Pressure piece

24

further cylinder body (second clamping element)

25

piston

26

Return spring

28

pen

30

drilling

Claims (5)

1. Gripping collet (10) for grasping a thread (F) during the preparation of a woven seam, the gripping collet being arranged at the end of a draw-through gripper and having a gripping collet body (12), a pneumatic cylinder (14) with an extendable and retractable piston (25) and a first and a second clamping element, the first and the second clamping element (20, 24) being able to be clamped against each other to grasp the thread (F) by means of the pneumatic cylinder, characterized in that

   - the first clamping element has two cylinder surfaces (20) at a distance from each other and

   - the second clamping element has a cylinder surface (24),

   - the arrangement of the cylinder surfaces (20, 24) being such that the axes of the cylinder surfaces lie parallel to each other and essentially at right-angles to the axis of the pneumatic cylinder (14) and, in the extended state of the pneumatic cylinder (14), the cylinder surface (24) of the second clamping element lies between the two cylinder surfaces (20) of the first clamping element.
2. Gripping collet according to claim 1, the first clamping element (20) being the stationary one and the second clamping element (24) being the movable one.
3. Gripping collet according to claim 1 or 2, the pneumatic cylinder (14) working against the force of a spring (26), so that the gripping collet is opened in normal state.
4. Gripping collet according to claim 3, the gripping collet having a control device by means of which firstly the two clamping elements (20, 24) can be moved against each other by the supply of compressed gas to close the gripping collet and grasp the thread (F), secondly by interrupting the supply of compressed gas the two clamping elements (20, 24) can be moved away from each other by spring force to open the gripping collet and release the thread and thirdly, the pressure of the compressed gas can be set so that the spring force is essentially compensated for and the two clamping elements (20, 24) press with an at most low force against a thread (F) arranged between them.
5. Gripping collet according to one of claims 1 to 4, with a pin (28) pointing in the direction of movement of the piston (25), which, together with the two clamping elements (20, 24) and the gripping collet body (12), surrounds a grasped thread (F) on all sides.

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