[0001] The present invention concerns a weft yarn drawing gripper for shuttleless looms.
As known, the "grippers" are members of shuttleless looms by means of which the weft
yarns are picked up at one side of the loom and carried through the warp shed to the
opposite side of the loom. The carrying gripper picks up the weft yarn from a weft
feeding device at one end of the shed and carries it up to the middle of the shed,
while the drawing gripper receives the weft yarn from the carrying gripper, at the
middle of the shed, and draws it to the opposite end of the shed.
[0002] There are known to be many types of grippers performing this function, all of which
have undergone successive improvements differing one from the other as far as even
slight constructive details and yet all aiming to improve, on one hand, the working
life of the gripper, and on the other hand, yarn gripping and releasing. In fact,
the transfer of weft yarn from the carrying gripper to the drawing gripper is one
of the most delicate steps in the operation of the looms of this kind: at this stage
either the impairing (or complete breakage) of the yarn or the unsuccessfull transfer
of the weft yarn, which is not picked up from the carrying gripper by the drawing
gripper, may take place.
[0003] In an attempt to overcome the above mentioned drawbacks, grippers have been proposed
in the art, whose clamping member consists of, rather than a stiff member, a flexible
elastic member.
[0004] EP-137 377 discloses, e.g., grippers for shuttleless looms wherein the clamping member
consists of a flexible metallic lamina fixed at one end thereof to the gripper and
freely oscillating at the other end. The same clamping member is also illustrated
in EP-164 628.
[0005] EP-207 533 discloses grippers for shuttleless looms wherein the clamping member consists
of a wire spring fixed at both ends to the gripper, devices being also provided for
controlling the tension thereof.
[0006] In the various solutions proposed in the prior art for the grippers with clamping
member consisting of a flexible elastic member - such as those above specifically
described - said member alone exerts the gripping action on the yarn, cooperating
with an opposed rigid wall of the gripper.
[0007] In order to ensure a sufficiently strong gripping action, said flexible element must
therefore be "stiff" enough so as to exert a stress, due to its deformation, sufficient
for safely retaining the weft yarn. Moreover, it should not undergo an excessive deformation
during the closing of the gripper, so as to avoid bearing on the rigid body of the
gripper from which it projects, because it would of course loose, in that event, any
kind of flexibility, to produce again the same operation mode of the previously known
rigid grippers.
[0008] The above shown grippers have overcome the mentioned drawbacks for several kinds
of yarns. However, they give not yet satisfactory results in the case of parallel-filament
or flat-section synthetic yarns, having a poor delamination resistance along the axis
of the yarn, such as those often used in the manufacturing of mattress fabrics, propylene
bottoms for moquettes, as well as for hante couture articles.
[0009] With this kind of yarns, the action of the flexible elastic gripping elements of
the known type is in fact still too "stiff" for safely retaining the whole yarn section.
Thus, it still occurs with a certain frequency that the gripper carries to the opposite
side of the fabric being woven only a few filaments of parallel-filament yarns, or
a longitudinal portion of the flat-section yarn, which breaks along its axis.
[0010] The object of the present invention is hence to provide a drawing gripper which eliminates
the last aforesaid drawbacks, so as to ensure a perfect retaining of the weft yarn
over the whole clamping surface, even in the case of a synthetic yarn of the aforementioned
kind. This object is achieved by means of a drawing gripper for shuttleless looms
- of the type comprising, on one hand, a fixed gripping hook, having a first metallic
clamping surface and, on the other hand, a wedge fixedly connected to a movable slider
and having a second metallic clamping surface, this latter being apt to cooperate
with said first surface in order to clamp and retain the weft yarn - characterized
in that, one of said clamping surfaces consists of a flexible metallic lamina whose
clamping zone bears onto an elastic pad.
[0011] Further characteristics and advantages of the drawing gripper according to the present
invention will anyhow be more evident from the following detailed description of a
preferred embodiment thereof, given by way of example and illustrated on the accompanying
drawings, in which:
fig. 1 is a side view of the gripper according to the invention;
fig. 2 is a top view of the same; and
figs. 3 and 4 show, in enlarged-scale views similar to fig. 1, the gripping end of
the gripper, in yarn retaining and releasing position, respectively.
[0012] The drawing gripper consists, in a known way, of an elongated body 1 (not wholly
shown in the drawings), which terminates with a sharpened end, shaped as a gripping
hook 2, having a first metallic clamping surface. A slider 4 is mounted on the body
1, sliding along the longitudinal axis of the gripper and bearing on its end 4a a
wedge provided with a second clamping surface. This latter being apt to cooperate
with the first one clamping surface in order to clamp the weft yarn (not shown), to
allow its drawing.
[0013] According to the invention, the wedge forming said second clamping surface consists
of a metallic lamina 5 and a pad 6 onto which said lamina bears. The lamina 5 - one
end 5a thereof is fixed, to the slider 4, e.g. through a screw 7 or the like - has
a undulated configuration, comprising however a flat part 8, which is apt to contact
the clamping surface 3, fitting therewith. To this purpose, the lamina 5 is provided
with high elasticity and flexibility, to the extent that it is not able to clamp the
weft yarn by itself, i.e. without the bearing action provided by the elastic pad 6.
[0014] The pad 6 is made of a gum-like material, such as "Vulcollan" or the like, and has
a configuration comprising, as above mantioned, a flat part apt to support the flat
part 8 of the lamina 5. The material forming the pad 6 is sufficiently yielding to
follow the movement of the lamina 5, without however allowing an excessive shape variation
thereof. In the bearing zone, the lamina 5 may be provided with a window or slit 9,
apt to further increase the flexibility of the lamina.
[0015] The other end 5b of the lamina 5, opposed to the fixed end 5a, is bent at right angle
and is guided, freely sliding, within a guide hole provided at the end 4a of the slider
4. In such a way, said end 5b, together with the flat part 8, are elastically yielding
in a direction perpendicular to the clamping surfaces 3 and 8.
[0016] Morevore, the undulated shape of the lamina 5 is such as to form, in correspondence
of the tip 2a of the hook 2, a lead-in zone 10 apt to allow an easy insertion of the
weft yarn between the clamping surfaces.
[0017] The wedge of the slider 4 according to the present invention, comprising the pad
6 and the lamina 5 has therefore a large clamping surface - flexible and yielding
longitudinally as well as perpendicularly to the axis of the gripper - apt to ensure
a perfect retaining action of the yarn against the clamping surface 3 of the hook.
The gripper of the present invention is then apt to ensure, on one hand, an easier
and surer gripping of the weft yarn through the lead-in zone 10 and, on the other
hand, a perfect retaining action of said weft yarn between the clamping surfaces 3
and 8. These successfull results are reached even when the above mentioned parallel-filament
yarn or flat-section synthetic yarn having a poor delamination resistance are used,
so as to fully achieve the object of the invention.
[0018] The invention has been disclosed with reference to a preferred embodiment thereof,
but it should be understood that it is not in any way limited thereto. The scope of
the invention comprises therefore possible variations and improvements, all within
reach of a technician skilled in the art and all thus falling within the scope of
the invention, as it is defined by the accompanying claims.
1. Drawing gripper for shuttleless looms - of the type comprising, on one hand, a fixed
gripper hook (2) having a first metallic clamping surface (3) and, on the other hand,
a wedge fixedly connected to a movable slider and having a second metallic clamping
surface (8), this latter being apt to cooperate with said first surface in order to
clamp and retain the weft yarn - characterized in that, one of said clamping surfaces
consists of a flexible metallic lamina (5) whose clamping zone (8) bears onto an elastic
pad (6).
2. Drawing gripper as in claim 1), wherein said metallic lamina (5) is mounted springing
in a direction substantially perpendicular to the clamping surfaces (3, 8).
3. Drawing gripper as in claim 1) or 2), wherein said metallic iamina (5) has lightening
window or slit (9) in correspondence of its clamping zone (8).
4. Drawing gripper as in claim 1), wherein said elastic pad (6) is a rubber pad.
5. Drawing gripper as in anyone of the previous claims, wherein said metallic lamina
(5) forms said second clamping surface (8).
6. Drawing gripper as in claim 5), wherein said metallic lamina (5) has a general undulated
configuration comprising at least one flat part (8), which forms said second clamping
surface (8), radiused to at least one curved part which delimits, with said fixed
hook (2), a lead-in zone (10) for yarn gripping.
7. Drawing gripper as in claim 6), wherein said metallic lamina (5) is fixed by one end
(5a) to the slider (4) carrying the clamping wedge.
8. Drawing gripper as in claim 7), wherein the other end (5b) of said melllic lamina
(5) freely oscillates and is guided into a hole (4a) at the end of the slider carrying
the clamping wedge.