THREAD CLAMP

Abstract: Thread clamp, with the characteristic that it consists essentially of: a first jaw (3) with two spring arms (4, 5) which bend elastically away from and towards each other, perpendicularly to the plane in which the thread clamp opens and closes; a second jaw (6) which operates in conjunction with the first jaw; and an elastic device which serves to press the two jaws (3, 6) together.

Description: This invention concerns a thread clamp, more particularly a thread clamp of the type which consists of two opposing parts which are pressed together and between which a thread or similar can be held. In particular, the invention concerns a thread clamp for use on weaving machines, for example for a feed gripper or a receiving gripper on a thread presentation mechanism. The first requirement of a thread clamp on a weaving machine is that it must be suitable for a wide range of threads. Textiles are always composed of several types of threads which have to be gripped in turn by the same thread clamp, for example the thread clamp of a feed gripper or receiving gripper or of a thread presentation mechanism. A thread clamp should preferably be broad enough that it can handle a wide range of threads and that it does not have to be reset or readjusted when changing from one type of textile to another. Another important requirement is that the thread clamp should always operate with as much precision as possible, even when the mechanical parts become worn. An important improvement which enables these requirements to be met is described in Belgian patent No. 902.141, corresponding to US patent No. 4708174, made by the present applicant, concerning a thread camp for weaving machine grippers which is characterised by a fixed bit which operates in conjunction with an elastically deformable, wire spring, thus partly compensating for the effects of wear. Practical experience has since shown that this type of thread clamp is less suitable for certain types of thread, since thread fibres tend to come loose get wound round the wire spring, where they remain. The present invention concerns a thread clamp which does not have this disadvantage and which also gives better clamping of the thread. To this end, the thread clamp according to the invention consists essentially of: a first jaw with two spring arms which bend elastically away from and towards each other, perpendicularly to the plane in which the thread clamp opens and closes; a second jaw which operates in conjunction with the first jaw; and an elastic device which serves to press the two jaws together. In a preferred embodiment, the spring of the first jaw consists of two lamellae, while the second jaw is wedge-shaped and presses said lamellae apart. For the purpose of describing the characteristics of the invention, the following preferred embodiments are described with reference to the accompanying drawings, by way of example only and without being limitative in any way, where: _ fig. 1 shows a thread clamp according to the invention, forming part of a feed gripper; _ fig. 2 is a cross-section along the line II-II in fig. 1; _ fig. 3 is a cross-section along the line III-III in fig. 1; _ figs. 4 to 6 show variants, in the same view as in fig. 3; _ fig. 7 represents another variant of the embodiment shown in fig. 1, in the same view as in fig. 2; _ fig. 8 shows a view in the direction of the arrow F8 in fig. 1; _ figs. 9 to 11 show other variants, in the same view as in fig. 8; _ figs. 12 shows an embodiment of the thread clamp, in which the first jaw is in the form of a lever; _ figs. 13 is a cross-section along the line XIII-XIII in fig. 12; _ figs. 14 and 15 show two configurations for thread stops; _ fig. 16 shows the clamp according to the invention being used in a receiving gripper; _ fig. 17 is a cross-section along line XVII-XVII in fig. 16; _ fig. 18 is a cross-section along line XVIII-XVIII in fig. 16; _ fig. 19 shows a thread clamp according to the invention being used in a thread presentation mechanism; _ fig. 20 is a cross-section along line XX-XX in fig. 19; _ fig. 21 is a cross-section of yet another variant of the thread clamp according to the invention. As shown in figs. 1 to 3, the thread clamp 1 according to the invention _ here mounted by way of example on a feed gripper 2 _ consists essentially of: a first jaw 3 made up of two spring arms 4 and 5 which bend elastically away from or towards each other, perpendicularly to the plane in which the opening and closing movements of the clamp are carried out; a second jaw 6 which operates in conjunction with the two spring arms 4 and 5; and an elastic device 7, eg. a spring, which presses the jaws 3 and 6 together. The spring arms 4 and 5 consist essentially of two lamellae mounted a short distance apart. The first jaw 3 may be in the shape of a fork, as shown in fig. 2. The spring arms 4 and 5 may diverge towards the open end 8. At the base 9 the first jaw 3 is provided with an adjustment device 10 consisting of a slit 11 and a screw 12, by means of which the first jaw 3 at the open end 9 can be moved away from or towards the second jaw 6. The second jaw 6, as shown in figs. 1 to 3, consists of the end of a lever 13, which at its other end is activated by an elastic device 7. Further, the second jaw 6 consists essentially of a wedge-shaped element, in particular as shown in fig. 1. The first and second jaws 3 and 6 and their cooperating edges 14 and 15 are shaped so that they come into contact only at a certain point when there is no thread between them, ie. so that the second jaw 6 does not make contact with the first jaw 3 over its whole length. This is achieved by the divergence of the spring arms 4 and 5, also by the curved shape of the two jaws, in particular as seen in fig. 1. The thread clamp 1 may also have stops 16 and 17 alongside one or both of the jaws 3 and 6 in order to prevent a thread held in the clamp 1, eg. a weft thread 18, entering too far between the spring arms. Alternatively, the stops 16 and 17 may be positioned so that they place a limit on the amount by which the spring arms 4 and 5 can open, as indicated by the broken line in fig. 2. The operation of the device shown in figs. 1 to 3 is essentially as follows: when a thread 18 is not present, the cooperating edges 14 and 15 of the first and second jaws 3 and 6 cooperate, so that the wedge-shaped second jaw 6 penetrates by a certain amount between the spring arms 4 and 5 and presses them elastically away from each other. When the feed gripper is presented to a taut weft thread 18, the thread 18 enters between the first and second jaws 3 and 6 and is clamped between them, as shown in figs. 2 and 3. It can clearly be seen that due to the spring action of the arms 4 and 5 the first and second jaws 3 and 6 always fit perfectly together, so that the thread 18 is always firmly clamped. It should be noted that the point C at which the first and second jaws 3 and 6 make contact with each other when a thread 18 is not present should preferably be behind the thread stop 16 or the thread stops 16 and 17, ie. between the relevant stop 16 and/or 17 and the base 9 of the first jaw 3. This gives the advantage that any thread fibres which come loose from the thread do not remain stuck in the clamp when the thread is removed from the clamp. Figs. 4 to 6 show some variants with differences in the shape of the cooperating edges 14 and 15 of the first and second jaws 3 and 6. Fig. 7 shows a variant in which the sides of the second jaw 6 diverge towards the top of the second jaw 6. It is also possible for the shape of the cooperating edge 15 of the second jaw 6 to vary along the length of the jaw. For example, angle or the radius of the cooperating edge 15 may increase towards the top of the jaw 6. In the embodiment shown in fig. 1 the spring arms 4 and 5 each have a free end 8. As shown in particular in fig. 8, there may a device 19 at the ends of the spring arms 3 and 4 in order to limit their movement. Figs. 9 to 11 shows variants of such an arrangement. In figs. 1 and 8, the device 19 for limiting the movement of the spring arms 4 and 5 consists essentially of a recess of slot 20 or suchlike, into which the ends 8 of the spring arms 4 and 5 reach. When the jaws 3 and 6 come together the ends 8 of the spring arms 4 and 5 can only move apart to a maximum of the full length L of the slot 20. In Fig. 9 the abovementioned device 19 consists of two recesses 21 and 22 or suchlike, into which the ends 8 of the spring arms 4 and 5 reach. By such an arrangement, the spring arms 4 and 5 can be pretensioned so that a certain amount of resistance first has to be overcome before they can be opened further. There may also be an adjusting device 23 between the spring arms 4 and 5 in order to set the amount by which the spring arms are forced apart, thus enabling the degree of pretension to be adjusted. As shown in fig. 11, the amount of pretension on the spring arms 4 and 5 can be such that the spring arms are held in their maximum open position. Figs. 12 and 13 show a variant of the thread clamp 1 according to the invention, again used in a feed gripper 2. In this case it is the first jaw 3 which forms part of the lever 13 instead of the second jaw 6. The spring arms 4 and 5 here consist of lamellae which extend freely from the end of the lever 13. The second jaw 6, or at least the wedge-shaped part of it, is solidly attached to the feed gripper 2. The operation is similar to that of the other variants described above. The use of the thread stops 16 and 17 has already been described with reference to the variant shown in figs. 1 to 3. Figs. 14 and 15 show yet another two variants of the thread stops, with the particular characteristic that the stops 16 and 17 are shifted with respect to the long axis of the thread clamp 1. This gives better clamping of the thread 18 in the direction in which the thread is stressed by the clamp. In fig. 15, the stop 16 is formed by the body of the feed gripper 2. Figs. 16 to 18 show how a thread clamp 1 according to the invention is used in a receiving gripper 24. The construction is essentially similar to that of the embodiments already described. Figs. 19 and 20 show yet another thread presentation arm 25 using a thread clamp 1 according to the invention. Such a thread presentation arm 25 can for instance form part of the thread presentation mechanism described in Dutch patent application No. 8600857 by the present applicant. As shown in fig. 21, the second jaw 6 may also consist of a a groove 26, eg. a V shape, whose sides 27 and 28 cooperate with the edges 14 and 15 of the spring arms 4 and 5 of the first jaw 3. This embodiment of the thread clamp 1 can of course be used in a feed gripper 2, receiving gripper 24 or thread presentation arm 25 as described above. The present invention is in no way limited to the variants described by way of example and shown in the accompanying drawings; on the contrary, such a thread clamp may be made in various forms and dimensions while still remaining within the scope of the invention.

Claims: 1. Thread clamp, with the characteristic that it consists essentially of: a first jaw (3) with two spring arms (4, 5) which bend elastically away from and towards each other, perpendicularly to the plane in which the thread clamp opens and closes; a second jaw (6) which operates in conjunction with the first jaw; and an elastic device which serves to press the two jaws (3, 6) together. 2. Thread clamp as in claim 1, with the characteristic that the second jaw (6) consists essentially of a wedge-shaped element. 3. Thread clamp as in claim 1, with the characteristic that the second jaw (6) consists essentially of a groove (26) whose sides (27, 28) slope towards each other. 4. Thread clamp as in any of the above claims, with the characteristic that at least one of the cooperating edges (14, 15) of the jaws (3, 6) is curved. 5. Thread clamp as in any of the above claims, with the characteristic that the spring arms (4, 5) consists of lamellae which are attached solidly to each other at at least one end (9). 6. Thread clamp as in claim 5, with the characteristic that at the fixed end (9) of the spring arms (4, 5) there is an adjustment device (10) which makes it possible to move the first jaw (3) away from or towards the second jaw (6). 7. Thread clamp as in any of the above claims, with the characteristic that the spring arms (4, 5) of the first jaw (3) also diverge from each other away from the fixed end (9) when the thread clamp (1) is open. 8. Thread clamp is in any of the above claims, with the characteristic that one of the jaws (3 or 6) forms part of a lever (13) operated on by an elastic device (7), while the position of the other jaw is fixed. 9. Thread clamp as in claim 7, with the characteristic that the diverging spring arms (4, 5) have free ends (8). 10. Thread clamp as in claim 9, with the characteristic that the free ends (8) of the spring arms (4, 5) of the first jaw (3) are provided with a device (19) to limit their movement, consisting essentially of one or more recesses or slots (20, 23) into which the free ends (8) reach. 11. Thread clamp as in any of the above claims, with the characteristic that beside the jaws (3, 6) there is at least one stop (16, 17) for the thread (18). 12. Thread clamp as in claim 11, with the characteristic that on opposite sides of the jaws (3, 6) there are two stops (16, 17) for the thread (18), and that these stops (16, 17) are shifted along the long axis of the thread clamp. 13. Thread clamp as in any of the above claims, with the characteristic that it forms part of a feed gripper (2). 14. Thread clamp as in any of the claims 1 to 13, with the characteristic that it forms part of a receiving gripper (24). 15. Thread clamp as in any of the claims 1 to 13, with the characteristic that it forms part of a thread presentation mechanism (25).

Inventors: COOPMAN, LUCIEN, MOENECLAEY, DENIS, VICTOOR, JOHNNY
Applicants: PICANOL N.V.
Application year: 1988
Main classification: D03D47
IPC codes: D03D47