HK1029380B - Pair of weft carrying and drawing grippers for weaving looms - Google Patents

Description

Paired weft yarn carrying and drawing gripper for loom

The present invention relates to a pair of weft carrying and pulling grippers for shuttleless looms, and in particular to the general construction of such grippers.

There is a constant demand in the textile market for improvements in the weft-carrying grippers of weaving looms, which ensure perfect operation of their components on most modern weaving looms, even under very severe weaving conditions. In fact, to produce high-quality valuable fabrics, weaving looms need to have an increased weaving capacity, which is particularly related to high warp tensions, the use of finer or delicate weft yarns or yarns with other special physical properties, and small shed angles; all this, coupled with extremely high loom operating speeds.

In order to obtain the above-mentioned high weaving performance, the main components of the weaving machine (such as the pair of weft carrying/pulling grippers) must be continuously improved to ensure the weft insertion performance and long working life of the grippers. Especially since the weft carrying grippers face severe operating conditions in modern weaving machines, the following requirements are most demanded in the market for weft carrying/pulling grippers: high dimensional stability under stress, i.e. high stiffness, to ensure error-free weft alternation even at high speeds; the weight is reduced to reduce the inertia load when the movement direction of the yarn clamping device is alternately changed; and high abrasion resistance, ensuring a long working life of the grippers even if they slide on the individual guides at high speed and rub against the warp yarns when the shed is closed.

The market demands to date have not been fully met because the increased hardness and abrasion resistance of the grippers with the currently used manufacturing techniques do not result in a weight reduction.

The object of the present invention is therefore to provide a pair of weft carrying and drawing grippers produced using most of the currently available materials and using different manufacturing techniques to improve the performances related to the three above-mentioned characteristics, namely shape stability, weight reduction, and abrasion resistance, to be perfectly used in the high-performance looms currently on the market, which grippers have better and longer performances and operating life than the existing grippers.

According to the invention, the above object is achieved by a pair of weft carrying and pulling grippers in a shuttleless loom, controlled to reciprocate by a band, the grippers being fixed to the ends of the band, characterized in that each gripper comprises:

a rigid structural support formed from oriented carbon fibers extruded (poltrude) from a thermoset material;

a metal body carrying the weft yarn holding device;

a wear plate for protecting the front of the bottom of the gripper; and

at least one abutment made of filled thermoplastic material;

the belt, the hard structural support, the metal body and the wear plate are combined by a threaded connecting piece and embedded into a metal seat with threads in the abutting piece or formed in the metal body or in the yarn clamping device.

Other features and advantages of a pair of weft carrying and pulling grippers according to the present invention will become more apparent from the following detailed description of some preferred embodiments thereof, given in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a carrying gripper forming part of a pair of grippers of the present invention.

Fig. 2 is an exploded perspective view of the gripper of fig. 1.

Fig. 3 is an enlarged partial cross-sectional view of one of the different structural member attachment points of the gripper indicated by circle III in fig. 1.

Figure 4 is a perspective view of a pulling gripper forming part of a pair of grippers of the present invention.

Fig. 5 is an exploded perspective view of the gripper of fig. 2. Notation 1 support 1a Upper edge 2 Metal body 2a Back extension 3 Flange 4 screw 5 wear plate 6 screw 7 abutment 7a threaded insert 7b thickening 8 screw 11 support 1a Upper edge 12 Metal body 14 screw 15 wear plate 16 screw 17 abutment 17 ' abutment 17a threaded insert 17b threaded insert 17 ' a threaded insert 17 ' b threaded insert 18 screw N strip S support base P weft clamping device

The structure of the weft carrying gripper forming part of a pair of grippers of the invention, which also occurs in weft pulling grippers to meet the required shape change, is detailed below with reference to figures 1 and 2. As shown in the exploded view of fig. 2, the transport gripper is made up of a plurality of parts, each of which is intended to improve the specific mechanical characteristics of the gripper as a whole, as will be described later. And the dimensions of the components are designed to minimize the weight, while adapting to the function to be performed, in order to achieve a reduction in the overall weight of the gripper.

The transport gripper therefore comprises first of all a rigid structural support 1 to provide the gripper with shape stability and rigidity, also as a means for releasing the forces occurring during the reciprocating movement of the gripper and the forces. The support 1 is generally constructed as an angle steel, the vertical sides of which are suitably tapered along its upper edge, the warp yarns coming out of the closed shed being adjacent to the gripper at their outlet. Furthermore, the outer surface of the angle on the vertical side preferably has a shaped recess 1a for attaching the support 1 to the metal body 2 carrying the weft clamping device P. The vertical side and the horizontal base of the support member 1 are provided with a plurality of through holes for connecting with other parts of the yarn clamp, which will be described later. The base of the support 1 has a cylindrical hole, and a counter bore is formed in the side of the cylindrical hole to accommodate the head of the fixing bolt.

The structural support 1 is manufactured by extrusion of long carbon fibres, the whole of which is encased in a mould of a suitable thermosetting resin, for example an epoxy-based resin. This technique, known in the art as the "poli extrusion" extrusion technique, is carried out according to the invention by positioning the carbon fibres in the thermosetting resin mould in a specific weight percentage in both the longitudinal (parallel to the extrusion) and perpendicular directions. The fiber/resin weight ratio is preferably between 60/40 and 80/20.

The resulting part of this fabrication technique has a high degree of flatness (on the order of a few percent cm) on both the horizontal base and vertical sides, and has high temperature, moisture absorption, and viscoelastic stability (regardless of the gripper loading or unloading). Furthermore, the weight of part 1 is reduced by about 50% relative to a similar part forming part of a conventional gripper.

These features of the structural support 1 have several advantages, the following being noted in particular:

the inertia force during the reciprocating motion of the yarn clamping device is greatly reduced;

without finishing the plane surface of the part 1 in combination with other gripper parts;

no distortion is generated in the part 1 produced by the poltrudion process due to unbalanced internal tension of the machined part, because the internal tension of the extruded product is very small, and the machining only comprises the formation of the connecting holes in the forming concave part 1a and the tapered upper edge 1b of the part 1;

high stiffness, sufficient to resist longitudinal deflection and torsional stresses;

high wear resistance, mainly the upper edge 1b of the part 1 (where the warp yarns are bound at the gripper), because the carbon fibers are oriented in the longitudinal direction;

high resistance to ply cracking (i.e., cracking in the machine direction and in the anchor holes) because there is a controlled amount of carbon fiber in the cross direction.

The second embodiment of the transport gripper comprises a metal body 2, the body 2 forming the gripper head and carrying the weft gripping means P, not described in detail here, and is therefore not relevant to the present invention. The metal body 2 is preferably manufactured starting from a thin steel sheet of 1mm thickness, which is die-formed into the desired shape and deep-drawn. The metal body 2 comprises a back extension 2a, with which the recess 1a of the support 1 is connected, in order to effectively oppose the combined bending and compressive stresses exerted by the weft yarn during the insertion of the gripper into the shed of the weaving machine. For this purpose, the body 2 comprises a series of holes (3 in fig. 2), corresponding to the holes of the vertical side of the part 1, the metal body 2 being anchored permanently and firmly to the support 1 by means of screws 4.

As shown in fig. 2, the screw 4 is actually inserted inside the head part 1 and then locked in a threaded hole in the metal body 2, the locking screw 4 subjects the metal body 2 to tensile stress, while the part 1 operates only under compressive force to ensure stable bonding (even under high stress and vibration, which is the normal operation of a gripper) and to fix the screw 4 for a long period of time (if the part 1 made of plastic is screwed and the body 2 made of metal material is not screwed). Alternatively, the screw 4 may be replaced with a rivet; if so, the bond between the component 1 and the body 2 is as detailed in figure 3.

As shown in fig. 1 and 2, the upper edge 1b of the support element 1 and the top of the rear extension 2a of the metal body 2 have the same shape, without projections or sharp bends, providing a uniformly inclined and radiused support surface between the gripper head and the strip N for the warp yarns coming out of the shed of the loom to rest on the gripper surface. In order to allow a high number of weft threads to be inserted per unit time, it is now customary to engage the shed closure during the return stroke of the gripper, so that the warp threads can bear against the gripper surface and generate a compressive load and a corresponding friction. The gripper construction described above allows the warp to be loaded perfectly and gradually according to the shed closure, so that there are no peaks (which are immediately impacted by the high speed movement of the gripper).

According to a preferred embodiment, as shown in fig. 3, the surface of the gripper on which the warp threads slide (not formed by the upper edge 1b of the support 1 and the back extension 2a of the metal body 2 adjacent to the top) is formed by a flange 3 of the back extension 2a, which is bent by 90 ° during the deep drawing process of the metal body 2, so as to cover the entire upper edge 1b of the support 1. The advantage of this solution is to improve the rigidity and mechanical resistance of the rear extension 2a of the metal body 2; however, in order to ensure the working life of the carrying gripper with respect to the drawing gripper, it is preferred in this embodiment to surface-harden the flange 3 so that its wear resistance corresponds to the extrusion (polising extrusion) material forming the corresponding part of the drawing gripper.

The third component constituting the gripper is a wear plate 5, which is fixed by means of screws 6 in suitable threaded seats in the support base S of the clamping device P housed in the metal body 2. The support base S is preferably molded from plastic, in which case the threaded base includes a metal insert that is internally threaded and embedded into the base S during the molding process. The wear plate 5 forms the final length of the gripper strip N in a known manner; in fact it is replaced more frequently than the other parts, subject to more wear, equalizing the working life of the gripper parts and the strip. The wear plate is preferably made of a cotton fabric impregnated with a phenolic resin or a polystyrene fabric impregnated with an epoxy-based resin, which may be artificially aged to enhance its wear resistance, for example by oven drying after immersion in an oil bath.

After the different gripper parts have been joined together as described above by means of the screws 4 and 6, they are finally fixed to the gripper strip N by means of an abutment 7 (the fourth and last gripper part). The abutment 7 has a plurality of threaded inserts 7a (for example made of copper or other metallic material) embedded in moulds made of thermosetting plastic (for example polyamide resin) and filled with brittle glass or carbon fibre. The fiber/resin weight ratio is preferably between 20/80 and 40/60. The abutment 7 is preferably injection-molded by placing metal inserts 7a provided with threads in a mold at suitable intervals and in a mold cavity provided for this purpose.

The purpose of the abutment 7 is to distribute the fixing load concentrated on the threaded insert 7a evenly over the bearing surface of the support 1 and at the same time to make the assembly time shorter by providing a threaded insert whose shape is easy to handle and at a preset mounting position and distance. To achieve these objects, while ensuring that the abutment 7 is at its lightest, the abutment 7 has a thickened portion 7b corresponding to the insert 7a and a thinner portion between the two inserts. It is more important that the abutment 7 has a perfectly flat bearing surface to uniformly engage the horizontal base of the support 1 being supported.

The fixing of the strip N to the gripper body is in fact carried out by means of screws 8 (4 in figure 2) passing through corresponding through holes in the strip (eventually to the end of the wear plate 5) and in the horizontal base of the support 1, finally locked to the threaded metal insert 7a of the abutment 7. Thus, in this type of coupling, as previously described for the coupling between the metal body 2 and the support 1 and between the wear plate 5 and the metal body 2, the tensile stresses of the fixing means are released to the metal material component and the compressive stresses are released to the plastic component.

In addition to providing a fixing system which is easy, quick and safe to use, the above-mentioned abutment 7 has the additional advantage of being low-cost, and if the fixing means are damaged (for example, the thread is stripped), the component can be replaced immediately, without the need to replace the more important and more expensive component of the gripper.

The weft drawing gripper configuration forming a pair of grippers of the present invention is shown in fig. 4 and 5, which is the same as the weft carrying gripper configuration described above, and therefore like components are designated with like reference numerals, but preceded by 1.

With reference to fig. 5, it can be seen that the metal body 12 of the traction gripper (carrying gripper) has a shorter longitudinal extension than the corresponding metal body 2 of the transport gripper. As is known, this depends on the main body being subjected to simple tensile forces of the weft yarns. The metal body 12 is of shorter extension and the support member 11 is longer than the support member 1 corresponding to the carrying gripper, the wear plate 15 in this case being fixed to the support member 11 by means of an additional abutment member 17'. In addition, the traction gripper has no other structural changes compared with the transport gripper.

The present invention has been described in terms of the preferred embodiment, but it will be apparent to those skilled in the art that the scope of protection encompasses any possible variations, which should be within the scope of the invention as defined by the appended claims.

Claims (15)

1. A pair of weft carrying and pulling grippers for a loom, controlled by a band to reciprocate, the grippers being fixed to ends of the band, characterized in that: each gripper comprises:

a rigid structural support (1; 11) formed of carbon fibres extruded with thermosetting plastic polstrusion;

a metal body (2; 12) carrying the weft yarn gripping device (P);

a wear plate (5; 15) for protecting the front of the bottom of the gripper; and

at least one abutment (7; 17, 17') made of filled thermoplastic material; wherein the strip (N), the rigid structural support (1; 11), the metal body (2; 12) and the wear plate (5; 15) are joined by means of a threaded connection (4, 6, 8; 14, 16, 18) to a threaded metal seat embedded in the abutment (7; 17, 17') or formed in the metal body (2; 12) or in the weft clamping device (P).

2. Paired weft carrying and pulling gripper according to claim 1, characterized in that the rigid structural part (1; 11) is in the shape of an angle steel.

3. Paired weft carrying and pulling gripper according to claim 1, characterized in that the rigid structure (1; 11) comprises a main warp in longitudinal direction formed by long carbon fibers and a secondary warp in transverse direction formed by long carbon fibers.

4. The paired weft carrying and pulling gripper according to claim 1, wherein the thermosetting plastic comprises an epoxy resin.

5. Paired weft carrying and pulling gripper according to claim 4, characterized in that the weight ratio of carbon fibers and epoxy resin is between 60/40 and 80/20.

6. Paired weft carrying and pulling gripper according to claim 1, characterized in that the metal body (2; 12) is made of sheet metal die-formed and deep drawn.

7. Paired weft carrying and pulling gripper according to claim 6, characterized in that the sheet steel forming the metal body (2; 12) is about 1mm thick.

8. Paired weft carrying and pulling gripper according to claim 6, characterized in that the steel sheet forms a stiffening flange (3) covering the entire upper edge (1b) of the structural support (1).

9. Paired weft carrying and pulling gripper according to claim 8, characterized in that the steel sheet is surface hardened at least at the flanges (3).

10. Paired weft carrying and pulling gripper according to claim 1, characterized in that the abutment (7; 17, 17 ') comprises a threaded metal insert (7 a; 17a, 17' a) embedded in the component during the molding process.

11. Paired weft carrying and pulling gripper according to claim 10, characterized in that the threaded metal inserts (7 a; 17a, 17' a) are made of copper.

12. Paired weft carrying and pulling gripper according to claim 10 or 11, characterized in that the thermoplastic material is a polyamide resin.

13. Paired weft carrying and pulling gripper according to claim 12, characterized in that the weight ratio between glass or carbon fibers and polyamide resin is between 20/80 and 40/60.

14. Method for producing paired weft yarn delivering and pulling grippers according to one of claims 1 to 13, characterised in that the rigid structural part (1; 11) is manufactured by means of the polstrusion process, after which holes are drilled and finally tapered by means of machining.

15. Method for producing paired weft yarn carrying and pulling grippers according to one of claims 1 to 13, characterized in that the abutment (7; 17, 17') is injection molded starting from a thermoplastic material filled with brittle glass or carbon fibers.