Means to guide the motion of weft grippers inside the shed of shuttleless looms

Abstract: Means to guide the motion of a pair of weft grippers inside the shed of shuttleless looms - of the type comprising two control straps (2) movable on a substantially horizontal plane thanks to the action of two gearwheels with reciprocating motion, and a plurality of elements (1) to guide the straps, aligned on the sley facing the reed and positioned perpendicularly thereto - provide for the straps to have a substantially rectangular section and to have on each side a shaped recess, and for the guide elements to comprise tooth projections (3) shaped like said recesses so as to engage into the same, thereby supplying a guide for the straps.

Description: The present invention concerns means to guide the to-and-fro motion of a pair of weft grippers inside the shed of looms with continuous weft feed, of the type comprising two control straps movable on a substantially horizontal plane thanks to the action of two gearwheels with reciprocating motion, and a plurality of elements to guide the straps, aligned on the sley facing the reed and positioned perpendicularly thereto. It is known that modern shuttleless looms, of the type specified heretofore, still have to solve the problem of efficiently guiding the weft grippers - so as to guarantee that the reciprocal movements of said grippers, as well as their motion in respect of the sley and of the reed, are correct - and, at the same time, of limiting as far as possible the wear of the grippers, of the straps and of the other members involved in their motion, and the stresses on the warp yarns through which weft picking is carried out. This problem has been faced for many time by a great number of planners who have given different solutions. It is suitable to cite in particular the GB-A-257363 solution, which foresees a couple of guide elements, in engagement with the vertical sides of the straps. However these guide elements are continous, so that an uninterrupted contact thereof with the straps is impossible at high speed movements of the straps. In any case the guide elements of GB-A-257363 are not and cannot be positioned (to guide the strap) into the shed. The problem has also been faced by the Applicant who has supplied in successive times, some interesting solutions thereof, among which the solutions of the EP-B1-137376, EP-B1-204274 and in particular EP-B1-275479 deserve to be remembered. The present invention intends to overcome the remaining drawbacks of these solutions and to supply an improved and more satisfactory solution apt to solve, above all, the problems concerning the stresses on the warp yarns, the bulks inside the shed, and the efficient and reliable guiding of the grippers, without acting negatively on the other parameters involved in the essential function of weft picking inside the shed of gripper looms. For this purpose, the present invention supplies means to guide the motion of a pair of weft grippers inside the shed of shuttleless looms - of the type comprising two control straps movable on a substantially horizontal plane thanks to the action of two gearwheels with reciprocating motion, and a plurality of strap guide elements, said elements being aligned in the shed on the sley facing the reed and positioned perpendicularly thereto - characterized in that the straps have a substantially rectangular section and are provided with a shaped recess on each vertical side, and in that the guide elements are opposed and offset at a distance one from the other and comprise inwardly facing tooth projections, shaped like said recesses so as to engage into the same the strap side. Said recesses and said projections are preferably wedge-shaped, the apexes of the wedges being more or less on the centre of the straps. Said straps are also preferably wider and thicker in the area and close to the area where the grippers are fixed thereto, whereby the recesses are made deeper in said areas so as to allow a more reliable and efficient engagement of the tooth projections of the guide elements into said recesses. The invention is now described in further detail, with reference to a preferred embodiment thereof, illustrated on the accompanying drawings, in which: Fig. 1 is a plan view of the system to guide the motion of weft grippers according to the invention; Figs. 2 and 3 are two side elevations showing two pairs of guide elements for a gripper strap (shown in section) according to the invention, the strap being engaged by said elements in correspondence of its area carrying the gripper (fig. 2) and, respectively, in correspondence of its area far from the gripper (fig. 3); and Figs. 4 and 5 show how the strap and its guide elements behave in respect of the warp yarns of the loom, and show the wide space available for the motion of the grippers inside the warp shed. With reference to the drawings, it can be seen in fig. 1 how the motion of the grippers G inside the warp shed of a loom - of which the reed C and the fabric T being formed are shown - is guided by a plurality of opposed and offset guide elements 1 engaging the gripper strap 2 on the sides. As shown in figs 2 and 3, the guide elements 1 are characterized - according to the invention - by tooth projections 3, which engage the strap 2 into recesses of complementary shape, formed on the sides thereof, the strap being made of suitable thickness. The shape of the tooth projections 3 and of the corresponding recesses in the strap sides will preferably be a wedge shape, with triangular section, as clearly illustrated. As can be seen at once from figs. 1 to 3, the strap 2 is preferably thicker and wider in correspondence of its end area where the gripper P is fixed thereto, and close to said area (figs. 1 and 2), which is smoothly radiused to all the remaining part of the strap having a constant section and being thinner and narrower (figs. 1 and 3). Of course, in order to be able to guide such a strap 2 with said guide elements, the recesses formed in the strap sides in correspondence of its thicker and wider area should be far larger and deeper than in the remaining major part of the strap, so as to be able to properly house a far larger portion of the wedge-shaped tooth projections 3 of the elements 1 than that housed by the narrower and thinner area of the strap. In use, the strap 2 is very well guided by the guide elements 1, thanks to the precise and efficient engagement of the wedge-shaped tooth projections 3 of said elements into the corresponding recesses of the strap sides, throughout the length of the strap. In particular, said engagement is increased and improved in correspondence of the strap areas where the weft gripper is fixed, and in the area just adjacent thereto, because of the increased width and thickness of the strap, and the consequent greater extension of the cooperating and guiding surfaces between the teeth 3 of the elements 1 and the widened side recesses of the strap 2. This improved guiding action is accompanied by an exceptional behaviour of the means according to the invention for what concerns the stresses on the warp yarns. In fact, as can well be seen from fig. 4, when a warp yarn f, lifted or lowered by a link M of the healds, engages the strap 2 slidable on the guide elements 1 - thanks to the substantially rectangular section of the strap 2 and to the particular cooperation between the guide elements 1 and the strap 2, obtained by engagement of the tooth projecttions 3 of said elements into the side recesses of the strap - the yarn f can by no means insert itself between the strap and the wedgeshaped teeth, since in both cases the edge of the strap keeps the yarn well apart from the end contact areas of the two mutually sliding parts, into which it could get caught (it in fact often gets caught and torn or damaged in the conventional solutions). On the other hand, as can be been equally well from fig. 5, when the guide elements 1 move down towards the lower warp web, due to the motion of the loom sley to which they are fixed, the typical phenomenon of the warp yarns getting caught into the guide teeth - which frequently leads to the breakage and still more frequently to the damage of said yarns in conventional looms - does not take place. In fact, the yarn, engaged by the strongly inclined lower portion of the wedge-shaped tooth 3 of the guide elements 1 according to the invention, easily and harmlessly slips upward to the side of said tooth, instead of remaining caught and violently stressed downward, as it happens with the conventional guide members, which are made - as known - in the form of hook projections, the lower side of which is not inclined but substantially horizontal. The means to guide the motion of weft grippers in looms, according to the invention, thus realize - very efficiently - the double object of obtaining a reliable and precise guiding action and of preventing any troublesome stresses on the yarns of the two warp webs.

Claims: Means to guide the motion of a pair of weft grippers inside the shed of shuttleless looms - of the type comprising two control straps (2) movable on a substantially horizontal plane thanks to the action of two gearwheels with reciprocating motion, and a plurality of strap guide elements (1), said elements being aligned in the shed on the sley facing the reed and positioned perpendicularly thereto - characterized in that the straps (2) have a substantially rectangular section and are provided with a shaped recess on each vertical side, and in that the guide elements are opposed and offset at a distance one from the other and comprise inwardly facing tooth projections (3), shaped like said recesses, so as to engage into the same the strap sides. Means to guide the motion of weft grippers, as in claim 1), wherein said recesses and said projections (3) are wedge-shaped, the apexes of the wedges being more or less on the centre of the straps (2). Means to guide the motion of weft grippers, as in claims 1) and 2), wherein the straps (2) are wider and thicker in the area, and close to the area, where the grippers are fixed thereto.

Inventors: PEZZOLI LUIGI, PEZZOLI, LUIGI
Applicants: VAMATEX NUOVA SPA, NUOVA VAMATEX S.P.A.
Application year: 1989
Main classification: D03D47
IPC codes: D03D47