Apparatus for presenting weft threads The invention relates to an apparatus for presenting weft threads to an insertion device of a weaving machine, wherein at least one presenting element, such as a needle, is mounted displaceable in longitudinal direction between a rest position and a feed position by means of a crank mechanism.

An apparatus which selects and presents weft threads to an insertion device of a weaving machine is shown for example in EP 0 598 264 B1 . This apparatus comprises at least one needle for presenting a weft thread to the insertion device and driving means with an individual crank and an individual drive motor for selectively moving the needle between a rest position and a feed position, wherein the needle is directly connected to the crank and wherein guiding means are provided at each needle for guiding the needle in the movement between the rest and feed positions and for compensating transverse movements of the crank.

JP 10-212641 A and CN 2628554 Y each show an apparatus which selects and presents weft threads to an insertion device of a weaving machine using a crank, wherein a connecting rod is provided between a needle presenting the weft thread and the crank, and the needle is mounted displaceable in longitudinal direction.

It is an object of the invention to provide an apparatus of the type described above, wherein a large stroke of the presenting elements is pos- sible at high speeds.

This object is solved by an apparatus for presenting weft threads to an insertion device of a weaving machine, comprising at least one present- ing element mounted displaceable in the longitudinal direction between a rest position and a feed position and a crank mechanism with a crank and a connecting rod for driving the at least one presenting element, wherein the at least one presenting element is connected to the connect- ing rod, and wherein the connecting rod is supported by a guiding element for compensating transverse forces exerted on the connecting rod by the crank.

By providing the guiding element for supporting the connecting rod, per- pendicular forces, that occur when the connecting rod is driven by the crank, are compensated by the guiding element and not transferred to the presenting element. Thereby, frictional forces in bearing points of the presenting element are avoided and the presenting element may be moved with high speeds over a large distance in its longitudinal direc- tion.

In one embodiment, the presenting element is connected to the connecting rod by a pivot, wherein the pivot is formed at the height of the guiding element. In particular, a sleeve or an axle of the pivot is formed integral- ly with the guiding element. Due to this, the number of elements to be moved and thereby the inertia of the crank mechanism is minimized.

According to another embodiment, the presenting element comprises a thread receiving end, wherein the connecting rod is attached to the op- posite end of the presenting element. The thread receiving element is designed as a thread eye or thread clamp for receiving the weft thread to be presented.

In a preferred embodiment, a frame is provided, wherein the presenting element and the connecting rod are mounted to the frame. The frame may comprise a plurality of frame parts. In preferred embodiments, only one frame part is provided, allowing for a simple design with a high stiffness. According to one embodiment, the frame is provided with a guide groove extending in the longitudinal direction of the presenting element, wherein the guiding element is slidingly disposed in said guide groove.

In preferred embodiments, the at least one presenting element is mounted displaceable to the frame by at least one bearing point, preferably by two bearing points. Preferably, the at least one bearing point comprises a bearing bush for receiving the respective presenting ele- ment and a support on which the bearing bush is attached to the frame. The support on which the bearing bush is attached to the frame preferably comprises an elastic rubber socket. Due to the mounting of the presenting elements with "elastic" supports, the presenting elements are allowed to move within defined limits with the weft thread. In addition or as an alternative, the bearing bush comprises a pin received rotatably by the support for allowing the presenting elements to move with the weft thread.

According to another embodiment, the frame is provided with a recess for accommodating the crank in order to allow a movement of the crank. Thereby, walls of the recess may be used as end stops for the movement of the crank.

In another embodiment, each presenting element together with the re- spective frame and the respective crank mechanism forms one module. The apparatus can comprises a plurality of presenting elements depending on the number of weft yarns required for a certain fabric. Providing a module simplifies a matching of the number of presenting elements to the requirements of a certain fabric. Moreover, the module may be ex- changed as a unit in case of defect.

According to a preferred embodiment, a drive motor is assigned to the crank mechanism, such that the crank is driven by its own drive motor. The drive motor is preferably integrated in the module. In one embodiment, the motor is arranged to drive the crank to and fro over a defined angular range. The motor may also be arranged to rotate in one direction, wherein the presenting element is moved in longitudinal direction only, as the direction of rotation does not influence the linear movement direction of the presenting element.

In a preferred embodiment, the connecting rod is attached to the crank on the outer side of the crank. With this arrangement, a height of the module perpendicular to the plane of the crank can be minimized.

In preferred embodiments, the presenting element is a needle with a thread eye. In another embodiment, the presenting elements are arranged with yarn clamps such as are known in the art.

Preferred embodiments are defined in the dependent claims and the drawings.

In the following, an embodiment of the invention will be described in de- tail based on several schematic drawings in which

Figs. 1 - 3

are perspective schematic views of an apparatus for selecting and presenting weft threads with a presenting element according to the invention, wherein the presenting element is shown in three different positions.

Figs. 4 - 6

are schematic front views corresponding to that of Figs. 1 to 3.

Fig. 7 shows a cross section at the height of the guiding element and a bearing point.

Figs. 1 to 3 show a single module 1 of an apparatus for presenting weft threads, more particularly an apparatus for presenting weft threads to a gripper of a gripper weaving machine. In preferred embodiments, the apparatus comprises a plurality of identical modules 1 . In such an apparatus for selecting and presenting weft threads the modules, for example, can be disposed as the modules in EP 0 598 264 A1 .

Each module 1 comprises a presenting element 2, wherein in Figs. 1 and 4 the presenting element 2 is in a rest position, in Figs. 3 and 6 the presenting element 2 is in a feed position, and in Figs. 2 and 5 the presenting element 2 is in an intermediate position. In the embodiment shown the presenting element 2 is designed as a needle, one end 41 of which includes a thread eye 20 for guiding a weft thread (not shown).

The different modules 1 of an apparatus in one embodiment are arranged in one plane. When arranged in one plane, the presenting ele- ments in one embodiment are directed to one common point, as known from EP 0 362 089 A1 . In other embodiments, the presenting elements are arranged in a so called fan arrangement, as known from EP 0 638 677 A1 . In a preferred embodiment the presenting elements are arranged in a plane and the modules can be arranged in two rows as known from EP 0 598 264 A1 .

Each module 1 further comprises a crank mechanism 3 with a crank 30 and a connecting rod 31 , a drive motor 4 with a shaft 40 and a frame 5 on which the presenting element 2, the crank 30, the connecting rod 31 and the drive motor 4 are mounted. The drive motor 4 is connected via the crank mechanism 3 to the presenting element 2. The connecting rod 31 is pivotably attached to the crank 30 by a pivot 32. The connecting rod 31 is attached to the crank 30 on the outer side of the crank 30, i.e. on the side facing away from drive motor 4. The presenting element 2 is attached to the connecting rod 31 at the end 42 opposite the thread eye 20 by a pivot 60. Further, the presenting element 2 is mounted to the frame 5 by two bearing points 7 for a longitudinal movement of the presenting element 2. As shown in Fig. 7, the bearing points 7 each comprise a bearing bush 70, wherein the present- ing element 2 passes through the bearing bush 70, and a support 71 by which the bearing bush 70 is attached to the frame 5, for example by means of an elastic or a non-elastic pin 72. In the embodiment shown, the pin 72 is arranged rotatable in the frame 5 at a fixed position by using a bush 73.

The supports 71 provided for of the presenting elements 2 are designed as elastic rubber sockets, as a result of which the presenting elements 2 are elastically supported in the transverse direction. Hence, the presenting elements 2 are allowed to move within limits defined by the elasticity of the support 71 . This movement allows that the presenting element 2 can move somewhat under the influence of forces exerted by a weft thread at the height of the thread eye 20 and/or forces that arise by supporting the presenting element 2 in three points. The crank 30 is fixed to the shaft 40 of the drive motor 4. The drive motor 4 is arranged to a back side of the frame 5 by suitable fixing means such as screws. For allowing a movement of the crank 30, in the embodiment shown the frame 5 is provided with a recess 50. The recess 50 is formed by a base and two steps 52 projecting from the base. According to an embodiment the motor can move to and fro over an angular range of approximately 180°. In use, the range may be chosen smaller for example an angular range between approximately 90° and approximately 170° may be sufficient for an intended application. In the embodiment shown, the maximum angle of rotation of the crank 30 is bounded by the walls of the recess 50. The shape and/or size of the recess 50 may be chosen suitably. In the embodiment shown, the shape is chosen in such a way that for the rest and feed positions, shown in Figs. 1 , 4 and Figs. 3, 6, respectively, the crank 30, the connecting rod 31 and the presenting element 2 are aligned.

According to a variant, a drive motor 4 may be provided that rotates in one direction, as the direction of rotation does not influence the linear movement direction of the presenting element 2. In this case no recess

50 will be provided.

Due to the movement of the crank 30, forces are acting on the connecting rod 31 in a direction transverse to the longitudinal direction of the presenting element 2. For compensating these transverse forces of the crank 30, the connecting rod 31 is supported by a guiding element 6. The guiding element 6 is able to compensate the transverse forces, so that the presenting element 2 is only subjected to forces in its longitudinal direction, also referred to as length direction.

In the embodiment shown, the frame 5 is provided with a guide groove

51 extending in the longitudinal direction of the presenting element 2, in which guide groove 51 the guiding element 6 is slidingly arranged. The material and/or the size of the guiding element 6 and the guide groove 51 are chosen for ensuring only a limited friction upon the sliding movement and to avoid wear. The guide groove 51 is for example fully open, this means extends through the frame 5, in order to prevent that weaving dust accumulates at the height of the guide groove 51 . The guiding element 6, the guide groove 51 and the bearing points 7 are aligned with the presenting element 2, i.e. are arranged in a plane passing through the axis of the presenting element 2. Due to the elasticity of the supports 71 comparatively large tolerances are allowed. Further, due to the additional guiding element 6, one of the bearing points 7 may be omitted, for example the bearing point 7 near the guiding element 6.

Upon rotation of the crank 30, the presenting elements 2 move along their longitudinal direction, wherein the stroke of the presenting elements 2 depends on the length of the crank 30. The crank 30 may be chosen comparatively large allowing for a large stroke, wherein forces in transverse direction are compensated by the guiding element 6. As shown in Fig. 7, in the shown embodiment the guiding element 6 comprises a cylinder shaped bottom part 62, that is arranged rotatable and slidingly displaceable in the guide groove 51 , and a connecting part 63 that is one-piece with the bottom part 62. The connecting part 63 is one-piece with or connected to the connecting rod 31 . A pivot 60 is formed between the presenting element 2 and the guiding element 6, which pivot 60 allows a mutual rotation of the connecting rod 31 and the presenting element 2. In the embodiment shown, the pivot 60 comprises an axle 65 attached to the presenting element 2 and a sleeve 64 received by the connecting part 63. De sleeve can also be replaced by a bearing.

According to a variant not shown the bottom part 62 can consist of a guide block to which a pivot 60 is arranged, which pivot 60 allows a mutual rotation of the connecting rod 31 and the presenting element 2.

The masses of the parts to be moved by the drive motor 4, namely of the crank 30, the connecting rod 31 , the presenting element 2 and the guiding element 6 are comparatively small. For this purpose, the crank 30 is for example also provided with a clearance 33. As a result of the small masses, only relatively low inertias need to be overcome to move the presenting element 2. Consequently, higher operational speeds and/or the use of relatively low-power drive motors 4 are possible. As shown in the Figs, the base surface of the frame 5 is tapering from the area of the drive motor 4 toward the end 41 . This shape is advantageous for an arrangement of the module 1 in an apparatus, but not mandatory.

Having thus described preferred embodiments of the invention and variants and modifications thereof in sufficient detail enable the person skilled in the art to make and to use the invention based on the above description and accompanying drawings, it is nevertheless intended that the invention is not be limited by the description or illustrations, but rather that it be defined solely by the appended claims.