TECHNICAL FIELD AND PRIOR ART

The invention relates to a thread clamp with a moveable lever for a gripper of a gripper weaving machine, to a moveable lever for a thread clamp, to a gripper and to a gripper weaving machine.

As generally known, gripper weaving machines typically comprise two grippers for a transport of weft threads through a weaving shed, referred to for example as drawing gripper and taker gripper, wherein the drawing grippers are designed to guide a weft thread through the first half of a weaving shed, and the taker grippers are designed to guide a weft thread through the second half of the weaving shed after having picked up the weft thread from the drawing gripper.

For clamping a weft thread during transport, grippers having thread clamps are known, wherein the thread clamps have a moveable lever pivotally mounted to a gripper body, which moveable lever is forced towards a counter-element, which counter-element is mounted to the gripper body or is part of the gripper body.

EP 0207 533 A1 discloses a thread clamp with a moveable lever in the form of a needle having a circular cross-section and a counter-element in the form of a bit, which is provided with a groove, preferably with a V-shaped groove, at its upper surface arranged opposite to the needle.

SUMMARY OF THE INVENTION

It is the object of the invention to provide a moveable lever for a thread clamp for a gripper of a gripper weaving machine, a thread clamp with a moveable lever, a gripper and a gripper weaving machine allowing for a secure clamping of different weft threads without causing damage to the weft thread.

According to a first aspect of the invention, a moveable lever for a thread clamp for a gripper of a gripper weaving machine is provided, which moveable lever has a first contact surface for cooperating with a second contact surface of a counter-element arranged opposite to the first contact surface, wherein the first contact surface is provided with an inwardly arched portion, which inwardly arched portion is curved about an axis parallel to a longitudinal direction of the moveable lever and which inwardly arched portion extends longitudinally along said axis, wherein the width of the inwardly arched portion is at least twice its height.

In the context of the application, the expression “an arched portion extends longitudinally along an axis” is used to describe that the arched portion has a longitudinal extension in the direction of said axis, wherein said axis is also referred to as longitudinal direction of the arched portion. Further, in the context of the application, an arched portion having a width that is at least twice its height is also referred to as flat arched portion.

The moveable lever having a flat inwardly arched portion allows for a reliable clamping, wherein a weft thread can be clamped between the moveable lever and a counter-element with a clamping force having an at least essentially uniform force distribution along the width of a clamping zone of the thread clamp and with only a small deflection, so that a risk of damaging or breaking the weft thread is reduced.

A cross-section of the moveable lever is chosen by the person skilled in the art so that the lever has a sufficient stiffness and low weight. A cross-section of the moveable lever in embodiments of the invention is in the form of a rectangle, in particular a rounded rectangle.

In one embodiment, the curvature of the inwardly arched portion is in the form of an oval or elliptic arc, in particular is in the form of an oval or elliptic arc, which in one embodiment is further symmetrical with respect to a middle plane of the inwardly arched portion. In the context of the invention, a plane extending in the longitudinal direction of the inwardly arched portion and intersecting the inwardly arched portion through its apex is referred to as a middle plane of the arched portion. In particular embodiments of the moveable lever, the curvature of the inwardly arched portion is in the form of a circular arc. This allows amongst others for a simple and cost-efficient manufacture.

In one embodiment, the curvature of the arched portion extends between opposing edge regions of the first contact surface. In other embodiments, the first contact surface is provided at its edge regions with two planar surface portions, wherein the inwardly arched portion is arranged between the two planar surface portions. Providing planar surfaces at the edge regions allows for a simple manufacturing while avoiding sharp edges. In addition, a moveable lever having an arched portion and a planar surface portion can be combined with different counter-elements having a complementary arched portion at the second contact surface or having a planar second contact surface.

In alternative embodiments, the first contact surface is provided with at least two notches extending longitudinally along at least a part of the moveable lever. In one embodiment, the notches are provided in the region of the inwardly arched portion extending from a surface thereof. In other embodiments, the notches are provided at least partly adjacent to the inwardly arched portion. The notches allow for a combination of the moveable lever with a counter element having protruding ribs, wherein the position, number, shape and size of the notches is chosen complementary to the position, number, shape and size of the protruding ribs. In one embodiment, the first contact surface is provided with an even number of notches, which notches are arranged symmetrically with respect to the middle plane of the inwardly arched portion. As explained above, in the context of the invention, a plane extending in the longitudinal direction of the inwardly arched portion and intersecting the inwardly arched portion through its apex is referred to as the middle plane of the inwardly arched portion.

In still another embodiment of the moveable lever, the first contact surface is provided at its edge regions with two planar surface portions, wherein the inwardly arched portion is arranged between the two planar surface portions, and wherein the first contact surface is further provided with two notches extending longitudinally along at least a part of the moveable lever, which notches are arranged at both sides and symmetrically with respect to the middle plane of the inwardly arched portion, and wherein each one of the two notches is arranged between the inwardly arched portion and one of the planar surface portions. This moveable lever can be combined with several different counter-elements for a reliable clamping of weft threads.

In embodiments of the moveable lever, an inner edge of each of the two notches is inwardly offset to an outer edge of said notch. In other words, the inner edge and the outer edge extend the curvature of the arched portion. In one embodiment, the offset is chosen such that the arched portion, the inner edge and the outer edge are arranged on a common circular arc.

According to a second aspect, a thread clamp for a gripper of a gripper weaving machine is provided, which comprises a moveable lever with a first contact surface having a flat inwardly arched portion and a counter-element provided with a second contact surface arranged opposite to the first contact surface.

In one embodiment, the second contact surface of the counter-element is planar. In other embodiments, the second contact surface is provided with an outwardly arched portion, which outwardly arched portion is complementary in shape to the inwardly arched portion of the moveable lever. Such a thread clamp is advantageous for allowing a good clamping with an at least essentially uniform force distribution while avoiding a strong deformation of the weft thread, which could lead to damage of the weft thread or thread breakage.

In one embodiment, the counter-element is part of a gripper body. In other embodiments, the counter-element is a lamella. The lamella can be mounted to the gripper body. In one embodiment, the lamella can be mounted to the gripper body so as to be replaceable for example upon wear or tear.

According to a third aspect, a gripper for a gripper weaving machine comprising a gripper body and a thread clamp is provided.

In one embodiment, the moveable lever is at least partly resiliently deformable and forced due to its internal restoration force against the counter-element. In other embodiments, the moveable lever is pivotally mounted to the gripper body, wherein the moveable lever is forced towards the counter-element using at least one elastic element. This allows for a stiff moveable lever and high clamping forces. In particular, in one embodiment, the moveable lever is a two- sided lever, wherein one end is provided with the first contact surface, whereas the opposite end is co-operating with the elastic element for forcing the first end towards the counter element.

In one embodiment, the counter-element is part of the gripper body. In other embodiments, the counter-element is a lamella which is mounted to the gripper body, wherein in particular at least one elastic support element is provided on the gripper body, and at least a portion of the lamella opposite the second contact surface is supported on the gripper body via the at least one elastic support element. The elastic support element influences a clamping force applied to the weft thread. In one embodiment, the at least one elastic support element and/or the lamella are replaceable, wherein several different interchangeable lamellas and/or several different interchangeable elastic support elements are provided allowing for a customization of the gripper for different weft threads and/or different weaving conditions, for example different weaving speeds.

According to a fourth aspect, a gripper weaving machine is provided comprising a gripper with a thread clamp according to one of the embodiments as described above. The gripper with the weft thread clamp according to the invention is in particular used as a drawing gripper, also named bringer gripper, which is guiding a weft thread through a first half of a weaving shed. BRIEF DESCRIPTION OF THE DRAWINGS

In the following, embodiments of the invention will be described in detail with reference to the drawings. Throughout the drawings, the same or similar elements will be denoted by the same reference numerals.

Fig. 1 shows in an exploded view a gripper.

Fig. 2 shows in a side view selected parts of the gripper of Fig. 1.

Fig. 3 shows a first embodiment of a thread clamp with a moveable lever and a counter element in cross-section along a line ll-ll in Fig. 2. Fig. 4 shows a second embodiment of a thread clamp with a moveable lever and the counter-element of Fig. 3 in cross-section along a line ll-ll in Fig. 2.

Fig. 5 shows a third embodiment of a thread clamp with a moveable lever and the counter-element of Fig. 3 in cross-section along a line ll-ll in Fig. 2.

Fig. 6 shows a fourth embodiment of a thread clamp with a moveable lever and a counter-element in cross-section along a line ll-ll in Fig. 2.

Fig. 7 shows a fifth embodiment of a thread clamp with the moveable lever of Fig. 6 and a counter-element in cross-section along a line ll-ll in Fig. 2.

Fig. 8 shows a sixth embodiment of a thread clamp with the moveable lever of Fig. 6 and a counter-element in cross-section along a line ll-ll in Fig. 2. Fig. 9 shows a seventh embodiment of a thread clamp with the moveable lever of Fig. 6 and a counter-element in cross-section along a line ll-ll in Fig. 2.

DETAILED DESCRIPTION OF THE DRAWINGS

Fig. 1 shows in an exploded view a gripper 1, in particular a drawing gripper of a gripper weaving machine (not shown) and Fig. 2 shows in a side view selected parts of the gripper 1 of Fig. 1. The gripper 1 has a gripper body 7, a thread clamp 2, a cover plate 20 and a guide element 21 arranged between the gripper body 7 and the cover plate 20. It will be understood by the person skilled in the art that the guide element 21 is only optional and in other embodiments, the guide element 21 is omitted. In an alternative embodiment the gripper body 7 and the cover plate 20 can be made in one piece.

The gripper body 7 shown is in the form of a profile, which can be attached in a known manner to a rapier or a gripper band (not shown) for moving the gripper 1 through a weaving shed.

The thread clamp 2 comprises a moveable lever 3 with a first contact surface 4 and a counter element 5 provided with a second contact surface 6 arranged opposite to the first contact surface 4.

The moveable lever 3 is mounted to the gripper body 7 so as to be pivotally about a pivot axis 10. In the embodiment shown, the moveable lever 3 is a two-sided lever, having two arms 8, 9 arranged at opposite sides of a pivot axis 10 of the moveable lever 3. A first arm 8 of the moveable lever 3 is provided with the first contact surface 4 and is forced towards the counter element 5 by an elastic element 11, which in the embodiment shown is in the form of a spring, acting on the second arm 9 of the moveable lever 3.

In the embodiment shown, the counter-element 5 is a lamella mounted to the gripper body 7. More particular, in the embodiment shown, the counter-element 5 is mounted in the region of the second contact surface 6 to the gripper body 7 and is supported via three elastic support elements 12, which elastic support elements 12 support the counter-element 5 and force at least a part of the counter-element 5 provided with the second contact surface 6 towards the moveable lever 3. The number of elastic support elements 12 is only by way of example and in other embodiments more or less than three elastic support elements 12 are provided, for example one or two elastic support elements 12 are provided. In the embodiment shown, the three elastic support elements 12 and the counter-element 5 are replaceable, wherein in one embodiment, the elements are replaced if required due to wear and tear. In other embodiments, several different interchangeable counter-elements 5 and/or several different interchangeable elastic support elements 12 are provided allowing for a customization of the gripper 1 for different weft threads and/or different weaving conditions.

Fig. 3 shows a first embodiment of a thread clamp 2 with a moveable lever 3 and a counter element 5 in cross-section along a line ll-ll in Fig. 2. As shown in Fig. 3, the first contact surface 4 of the moveable lever 3 is provided with an inwardly arched portion 13 that extends longitudinally along the moveable lever 3, i.e. perpendicular to the drawing plane. More particular, the inwardly arched portion 13 extends longitudinally along an axis A, which axis A is parallel to a longitudinal direction of the moveable lever 3. The inwardly arched portion 13 has a smooth surface and has a width W that is at least twice its height H. The width W of the inwardly arched portion 13 is defined as its extension perpendicular to the longitudinal direction between its opposite ends, i.e. a horizontal extension in the drawing plane. The height H is defined as its extension between an apex 30 and edges 31 of the inwardly arched portion 13, i.e. a vertical extension in the shown drawing plane. A plane extending in the longitudinal direction of the inwardly arched portion 13 and intersecting the inwardly arched portion 13 through its apex 30 is referred to as the middle plane M of the inwardly arched portion 13. In the embodiment shown, the inwardly arched portion 13 is symmetric with respect to the middle plane M, and the middle plane M is a central plane of the cross-section of the moveable lever 3. More particular, in the embodiment shown, the curvature of the inwardly arched portion 13 is in the form of a circular arc. This allows for a simple and cost-efficient manufacture. In an alternative embodiment (not shown) the inwardly arched portion 13 is not perfectly symmetric, but somewhat asymmetric with respect to the middle plane M. In another alternative embodiment (not shown), the middle plane M is not aligned symmetric with a central plane of the cross-section of the moveable lever, but somewhat offset from the central plane of the cross-section of the moveable lever.

The inwardly arched portion 13 is arched about the axis A, which axis A is also referred to as center axis A of the inwardly arched portion 13 in the form of a circular arc. The center axis A lies in the middle plane M. In the embodiment shown, the moveable lever 3 has apart from the inwardly arched portion 13, a rounded rectangular cross-section, which is also preferably symmetric to the middle plane M.

In case the inwardly arched portion 13 is in the form of a circular arc, the width-to-height-ratio W/H depends on the central angle a and the radius R. In the embodiment shown, a central angle is between about 40° and about 70°, and in particular about 55°.

The second contact surface 6 at the counter-element 5 is provided in the embodiment shown in Fig. 3 with an outwardly arched portion 14, which outwardly arched portion 14 is complementary in shape to the inwardly arched portion 13 of the moveable lever 3. In the embodiment shown, the curvature of the inwardly arched portion 13 and the curvature of the outwardly arched portion 14 are both in the form of a circular arc having a common center axis A, wherein a radius of curvature of the inwardly arched portion 13 is at least almost the same as the radius of curvature of the outwardly arched portion 14 allowing the inwardly arched portion 13 and the outwardly arched portion 14 to abut each other in the absence of a weft thread. In an embodiment, the radius of curvature of the inwardly arched portion 13 is slightly larger than the radius of curvature of the outwardly arched portion 14, so that a small gap having a constant thickness is formed between the two arched portions 13 and 14 for clamping a weft thread.

Fig. 4 shows a second embodiment of a thread clamp 2 with a moveable lever 3 and a counter element 5 in cross-section along the line ll-ll in Fig. 2. The counter-element 5 shown in Fig. 4 is the same as that shown in Fig. 3. The moveable lever 3 shown in Fig. 4 differs from the moveable lever 3 of Fig. 3 in that the first contact surface 4 in addition to the inwardly arched portion 13 is further provided at its edge regions with two planar surface portions 15, wherein the inwardly arched portion 13 is arranged between the two planar surface portions 15. As shown in Fig. 4, in case the counter-element 5 is not provided with corresponding planar surface portions, when closing the thread clamp 2 the moveable lever 3 only contacts the counter-element 5 with the inwardly arched portion 13. It will be understood by the person skilled in the art that the moveable lever 3 shown in Fig. 3 in an alternative embodiment can be combined with a counter-element having only a planar second contact surface, wherein when closing the thread clamp 2 the moveable lever 3 only contacts such a counter-element with the planar surface portions 15.

Fig. 5 shows a third embodiment of a thread clamp 2 with a moveable lever 3 and a counter element 5 in cross-section along the line ll-ll in Fig. 2. The counter-element 5 shown in Fig. 4 is the same as that shown in Fig. 3 and the moveable lever 3 shown in Fig. 5 is similar to that shown in Fig. 3, wherein the first contact surface 4 is provided with an inwardly arched portion 13 and the second contact surface 6 is provided with an outwardly arched portion 14. The curvature of both arched portions is in the form of a circular arc, which circular arcs are concentric to each other. However, in contrast to the embodiment of Fig. 3, in the embodiment of Fig. 5, a width W13 of the inwardly arched portion 13 of the moveable lever 3 is smaller than a width W14 of the outwardly arched portion 14 of the counter-element 5.

Fig. 6 shows a fourth embodiment of a thread clamp 2 with a moveable lever 3 and a counter element 5 in cross-section along the line ll-ll in Fig. 2, which fourth embodiment is similar to the embodiment shown in Fig. 4, wherein the first contact surface 4 is provided with an inwardly arched portion 13 and two planar surface portions 15 provided at the edge regions of the inwardly arched portion 13. In contrast to the embodiment shown in Fig. 4, the first contact surface 4 is further provided with two notches 16 extending longitudinally along the moveable lever 3. The notches 16 are arranged symmetrically with respect to the middle plane M of the inwardly arched portion 13 and each one of the notches 16 is arranged between the inwardly arched portion 13 and one of the planar surface portions 15.

In the embodiment shown, the inner edges 17 of the notches 16 are inwardly offset to the outer edges 18 of the notches 16, in other words the inner edges 17 of the notches 16 arranged closer to the middle plane M are inwardly offset to the outer edges 18 of the notches 16 arranged farther away from the middle plane M. More particular, in the embodiment shown, the inner edges 17 and the outer edges 18 are arranged on a virtual circular arc extending the curvature of the inwardly arched portion 13. This allows that the outer edges 18 also make contact with the outwardly arched portion 14, when the inwardly arched portion 13 makes contact with the outwardly arched portion 14, in other words when the thread clamp 2 is in a closed state.

As will be shown in the following, the moveable lever 3 of the embodiment of Fig. 6 can be combined with several different counter-elements 5 for clamping weft threads.

Fig. 7 shows a fifth embodiment of a thread clamp 2 with a moveable lever 3 and a counter element 5 in cross-section along the line ll-ll in Fig. 2. The moveable lever 3 shown in Fig. 7 is the same as that shown in Fig. 6. In contrast to the embodiment shown in Fig. 6, a second contact surface 6 of a counter-element 5 shown in Fig. 7 is planar and not provided with an outwardly arched portion, wherein when closing the thread clamp 2 the moveable lever 3 only contacts such a counter-element 5 with the planar surface portions 15.

Fig. 8 shows a sixth embodiment of a thread clamp 2 with a moveable lever 3 and a counter element 5 in cross-section along the line ll-ll in Fig. 2. The moveable lever 3 shown in Fig. 8 is the same as that shown in Fig. 6. In contrast to the embodiment shown in Fig. 6, a second contact surface of a counter-element 5 shown in Fig. 7 is planar and not provided with an outwardly arched portion, wherein when closing the thread clamp 2 the moveable lever 3 only contacts such a counter-element 5 with the planar surface portions 15. In addition, the counter element 5 shown in Fig. 8 is provided with a longitudinal groove 36 arranged opposite the inwardly arched portion 13 of the moveable lever 3.

Fig. 9 shows a seventh embodiment of a thread clamp 2 with a moveable lever 3 and a counter element 5 in cross-section along the line ll-ll in Fig. 2. The moveable lever 3 shown in Fig. 9 is the same as that shown in Fig. 6. In contrast to the embodiment shown in Fig. 6, a second contact surface 6 of a counter-element 5 shown in Fig. 7 is planar and not provided with an outwardly arched portion, wherein when closing the thread clamp 2 the moveable lever 3 only contacts such a counter-element 5 with the planar surface portions 15. In addition, the counter element 5 shown in Fig. 9 is provided with two longitudinally extending ribs 37 arranged at a second contact surface opposite to the notches 16 of the first contact surface. When closing the thread clamp 2, the ribs 37 are received in the notches 16. It will be understood by the person skilled in the art that the moveable lever 3 shown in Figs. 6 to 9 can be combined with several different counter-elements 5. In embodiments of the invention, several different interchangeable counter-elements 5 in the form of lamellas are provided allowing for a customization of the thread clamp 2 for different weft threads and/or different weaving conditions. Furthermore, it will be apparent to those skilled in the art that the various features described in relation to the various embodiments could be combined, in alternative embodiments, in any combination to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description.