[0001] The present invention concerns a support and guide element to form guide tracks for
gripper straps in a gripper loom.
[0002] Strap guide tracks of this type are known, in the sector, as "floating" tracks, as
opposed to the conventional tracks wherein the strap bears with its bottom surface
onto a suitable sliding surface formed on the sley, rubbing onto the lower warp yarns.
In the floating tracks the strap is instead supported, along its path, by a plurality
of support and guide elements positioned at intervals along the track and fixed to
the sley, so that the strap moves in an intermediate position of the loom shed, without
thereby interfering either with the lower warp yarns or with the upper warp yarns.
A strap guide track of this type is known, for example, from EP-A-275.479.
[0003] More recently, the Applicant has proposed - in the EP-A-709.505, the contents of
which are incorporated herein by way of reference - a new type of floating track,
wherein the support and guide elements of the strap, instead of clamping the gripper
strap on both sides - as in prior art - are shaped as simple brackets and are of two
different types, namely an upturned bracket (Gi) and a downturned bracket (Gs), alternately
positioned along the track, as illustrated in fig. 1 of the drawings. This new type
of track has provided a high number of advantages in respect of the previous tracks,
thanks to the "open" configuration of the bracket type support and guide elements
which, on one hand, leads to a considerably reduced number of warp yarn breakages
determined by the yarn getting caught into the support and guide elements and, on
the other hand, allows to make the surfaces of the support and guide elements, onto
which slides the strap, with characteristics of perfect flatness and smoothness, thereby
considerably reducing the phenomena of vibration and wear of the strap. Furthermore,
the lack of a guiding support on the lateral surface of the strap prevents any possible
roughening of its edges and, consequently, any possible negative effects due to pulling
of the warp yarns sideways during motion of the strap.
[0004] In spite of all the aforecited advantages, the EP-A-709.505 has still not fully solved
the problems determined by the presence in the shed of deeply angled warp yarns, such
as can be found either at the ends of the shed - where the fabric gets laterally deformed
due to the tensioning action of the templates - or even inside the shed, due to some
irregularity which may have occurred during weft yarn insertion. In fact, in the presence
of deeply angled warp yarns, it may happen that, during opening of the shed, such
warp yarns fail to be evenly parted from the tip of the support and guide elements
whereby, instead of being tidily arranged along the sides thereof, they position themselves
across the bracket surface of said support and guide elements, that is, onto the sliding
surface of the strap. In this case, the sliding of the strap onto the support and
guide elements may thus determine the breakage of the warp yarn, especially when this
latter is positioned upstream of the tip of said elements in respect of the strap
moving forward direction; in fact, in this case, the tip of the support and guide
element imparts a pulling action on the warp yarn, preventing it from freely moving
under the action of the advancing strap.
[0005] The object of the present invention is to thus supply a support and guide element
to form guide tracks for gripper straps in looms which, while providing all the advantages
of the aforedescribed support and guide elements of prior art, also allows to eliminate
or anyhow considerably reduce the drawback of the frequent warp yarn breakages in
the presence of deeply angled warp yarns.
[0006] According to the present invention, said object is reached by means of a support
and guide element t'o form guide tracks for gripper straps in a gripper loom, of the
type comprising at least a horizontal sliding surface for the strap, projecting like
a bracket from the body of the support and guide element, characterized in that said
horizontal sliding surface for the strap comprises a central depression.
[0007] The invention will now be described in further detail, with reference to the accompanying
drawings, in which:
[0008] Fig. 1 is an axonometric view, with an enlarged detail, showing a part of a loom
weaving zone incorporating a known-type floating guide for the gripper straps;
[0009] Fig. 2 is an axonometric view of a lower support and guide element, shaped as an
upturned bracket, according to a first embodiment of the present invention;
[0010] Fig. 3 is a side elevation of the support and guide element shown in fig. 2; Fig.
4 is a plan view of the support and guide element of fig. 2;
[0011] Fig. 5 shows three views - an axonometric view, a side elevation and a plan view,
respectively - similar to those of figs. 2, 3 and 4, of a different embodiment of
the lower support and guide element according to the present invention; and Fig. 6
shows three views, similar to those of fig. 5, of an upper support and guide element
according to the embodiment of the invention illustrated in fig. 5.
[0012] The assembly view of fig. 1 represents a part of the loom weaving zone incorporating
a known-type floating guide, so as to clearly illustrate the arrangement of the single
components and, in particular, of the support and guide elements according to the
present invention.
[0013] Fig. 1 shows the following loom components: the sley A comprising a rail R to which
can be fixed the support and guide elements G; the reed P; the warp yarns O and the
shed F formed by such yarns; a gripper S and the respective strap N; and, finally,
the fabric T being woven. As said above, the support and guide elements G are of two
types and, precisely, the lower support and guide elements Gi shaped as upturned brackets
and the upper support and guide elements Gs shaped as downturned brackets, alternately
positioned along the rail R.
[0014] Figs. 2 to 4 show a lower support and guide element Gi, formed according to a first
embodiment of the invention. As opposed to the known-type support and guide elements,
which comprise a continuous bracket horizontal surface to support the strap, the bracket
horizontal surface of the support and guide elements according to the present invention
comprises a central depression 1, so that the bracket surface, onto which slides the
strap N, is reduced to two separate surfaces 2 and 3 between which is interposed said
depression 1.
[0015] In this first embodiment of the invention, the depression 1 has a characteristic
saddle shape, which is radiused to said horizontal strap sliding surfaces 2 and 3
only sideways in respect of a plane of symmetry of the support and guide element G,
whose trace is indicated in fig. 4 by the dashed line a. In fact, in correspondence
of a wide central zone of the depression 1, the two sliding surfaces 2 and 3 extend
into said depression with arched buttresses 2a and 3a having substantially vertical
walls, radiused only at their base to the saddle-shaped surface of the depression
1, as shown in fig, 3.
[0016] This particular configuration of the depression 1 allows, on one hand, to obtain
an overall area of the sliding surface of the strap N (sum of the areas of the surfaces
2 and 3) which is sufficiently wide as not to impart any excessive stresses to said
strap and, on the other hand, to highly facilitate the shifting of any possible angled
warp yarns O into one of the two positions illustrated in figs. 2 and 4, namely inside
the depression 1 and away from the surfaces 2 and 3.
[0017] Fig. 5 illustrates a second embodiment of the invention, of simpler construction,
wherein the depression 1 has a V-shaped configuration and its radiusing edges to the
surfaces 2 and 3 consist of segments perpendicular to the plane of symmetry of the
support and guide element G (indicated in fig. 4 by the dashed line
a) and do not have the arched buttresses with vertical walls described with reference
to the first embodiment of said support and guide element G.
[0018] When, on opening of the shed F, an angled warp yarn O bears onto the bracket surface
of the support and guide element G, the bearing contact almost exclusively takes place
(considering any possible angles involved) onto the surface 2, namely the surface
further from the tip 4 which parts said yarns 0. As the opening of the shed F continues
or, at the latest, when the gripper approaches, the special configuration of the aforedescribed
support and guide element G causes the warp yarns still bearing onto the surface 2
to be easily and promptly shifted into the depression 1 - as illustrated in figs.
2 and 4 for two warp yarns O having different inclinations - where they are no longer
subjected to the rubbing action of the strap.
[0019] The first embodiment of the support and guide elements according to the present invention
is particularly meant for yarns which are more likely to get entangled as, for example,
in the case of natural yarns. In fact, the presence of the buttress 2a on the surface
2 facilitates the fast shifting of the warp yarn O, while the presence of the buttress
3a on the surface 3 prevents the warp yarns O - in the event they should be pulled
by the gripper - from bearing onto said surface 3.
[0020] It is evident that the warp yarns O behave as described heretofore both in correspondence
of the lower support and guide elements Gi - shown in figs. 2 to 5 - and in correspondence
of the upper support and guide elements Gs. The configurations of the horizontal bracket
surface of the upper support and guide elements Gs, and thus of the depression 1 provided
therein, are in fact perfectly symmetrical to those described for the two embodiments
of the lower bracket elements Gi and, for the sake of simplicity, are illustrated
in fig. 6 merely with reference to the second embodiment of the invention.
[0021] The present invention has been described with reference to the two specific embodiments
illustrated heretofore, but it is evident that its protection scope is not limited
to such embodiments, but should instead comprise any possible variants - for instance
in the shape of the depression 1 - within reach of a technician skilled in the art,
falling within the definitions contained in the following claims.
1. Support and guide element to form guide tracks for gripper straps in a gripper loom,
of the type comprising at least a horizontal sliding surface for the strap (N), projecting
like a bracket from the body of the support and guide element (G), characterized in
that said sliding surface for the strap (N) comprises a central depression (1).
2. Support and guide element as in claim 1), wherein said depression (1) forms two separate
sliding surfaces (2, 3) for the strap (N) onto said horizontal bracket of the support
and guide element (G).
3. Support and guide element as in claim 2), wherein said depression (1) is saddle-shaped.
4. Support and guide element as in claim 3), wherein said saddle-shaped depression (1)
is radiused to said strap sliding surfaces (2, 3) only sideways in respect of a plane
of symmetry of the support and guide element (G), while, in correspondence of a wide
central zone of the depression (1), the two sliding surfaces (2, 3) extend into said
depression (1) with arched buttresses (2a, 3a) having substantially vertical walls.
5. Support and guide element as in claim 2), wherein said depression (1) is V-shaped.
6. Support and guide element as in claim 5), wherein said V-shaped depression (1) is
radiused to said strap sliding surfaces (2, 3) along segments perpendicular to a plane
of symmetry of the support and guide element (G).