[0001] The present invention concerns a device to carry out the slotted leno heald weave
on selvedges of fabrics as they are formed on shuttleless looms.
[0002] As known, in weaving, the warp yarns positioned at the right and left ends of the
fabric, besides moving up and down to form the fabric, also interlace horizontally,
twisting around the weft to obtain a weave thereof. For this purpose, to carry out
the so-called "slotted leno heald" weave, the half-link system - shown in fig. 1 of
the accompanying drawings - is commonly used. With this system, two links A and B
move in synchronism with the respective heald frames inside the lap. Between said
links there is positioned a half-link C, connected to an elastic element - for the
purpose of interlacing two yarns D and E - and pulled down alternatively by either
one of the links A and B, starting from the overlapping position of said yarns D
and E which have a common apex F. This system, which is extremely practical, allows
to obtain a perfect weave, but it has the serious drawback of using up two heald frames
to work in the lap, so that, if the loom works with other ground weaves, there are
less heald frames available to work said ground weaves. Furthermore, since two heald
frames - provided to merely carry out the slotted leno heald weave - are interposed
between the ground frames and the reed, the distance between the utilizable frames
and the area of weft insertion is disadvantageously increased, thereby facilitating
the forming of flaws which can cause yarn breakages and faults in the fabric.
[0003] To prevent these drawbacks, various types of devices M have been realized - as shown
in fig. 2 of the accompanying drawings - to work the slotted leno heald weave. Such
devices are interposed - movable through the loom width - between the first heald
frame and the reed, and they can for example be controlled by a cord system, the cord
1 being moved by a cam 2 in opposition to a return spring 3, or by an articulated
leverage (not shown in the drawings).
[0004] The device according to the present invention now advantageously replaces said known
devices M and adopts for the first time the half-link system, so far exclusively applied
on heald frames, allowing to obtain all the known advantages typical of this system
- i.e. simplicity, functionality, easy threading, and strong weaves with the use
of only two threads (thereby creating no thickenings in the fabric) - without however
suffering from its drawbacks when applied, as in conventional technique, to heald
frames.
[0005] More precisely, the movable device according to the invention, apt to carry out the
slotted leno heald weave on selvedges of fabrics as they are formed - of the type
independent from the heald frames, with a separate control therefrom which alternatively
causes the lifting and lowering of selvedge shafts - is characterized in that, at
least one group of two links with a half-link of reduced dimensions is associated
to said selvedge shafts, and in that, said selvedge shafts control said links and
half-link to carry out the slotted leno heald weave.
[0006] The invention is now described in further detail, with reference to a preferred embodiment
thereof, shown on the accompanying drawings, in which:
Figs. 1 and 2 show, respectively, the half-link system and the conventional M devices
system to obtain the slotted leno heald weave according to known technique, as already
seen above;
Fig. 3 is a front view of a device according to the present invention; and
Fig. 4 is a lateral view of the same device.
[0007] The device according to the invention (figs. 3 and 4) is applied similarly to the
conventional devices M of fig. 2 (which refers to the weaving of a double roll of
fabric with four selvedges) and is likewise controlled by a cord 1, the motion of
which is caused by a cam 2 in opposition to a return spring 3 (fig. 2) positioned
at opposite ends of the loom. Said cord 1 - by means of secondary cords 4 and 5 (fig.
3) connect ed thereto and rotating on pulleys 6 and 7 - pulls in alternatively opposite
directions two racks 8 and 9 (fig. 4) cooperating by way of an interposed sprocket
10. According to the invention, on the racks 8 and 9 there are mounted small plates
11, 12, 13 and 14 - forming two pairs of selvedge shafts - which, following the movements
of said racks, are alternatively lifted and lowered in accordance with the motion
of the loom. Onto the selvedge shafts (or small plates) 11 to 14 there can be mounted
links 15 for the weave - in a manner known per se - of the split selvedge and/or two
links 16 combined in known manner (according to the diagram of fig. 1) with a half-link,
to carry out a slotted leno heald weave. The links 15 are provided merely in the external
devices M of of fig. 2 (associated to the links 16) and are instead missing in the
central device M (which thus only includes the links 16). The links 16, and the half-link
associated thereto, are suitably of reduced size - as compared to the conventional
links used in heald frames to carry out slotted leno heald weaves - so as to be fit
for the device of the present invention. A spring 17 acts as return element for the
half-link.
[0008] In use, the device according to the invention is controlled - like the devices M
of fig. 2 - by the cord 1 which, moving horizontalwise alternatively in the two directions,
according to the motion law of the loom, under the control of the cam 2 in opposition
to the return spring 3, operates said devices M. In practice, the racks 8 and 9 of
the device are alternatively moved up and down and cause the alternative lifting and
lowering of the selvedge shafts 11 to 14 and, therewith, similar movements of the
links 15 (where present), so as to form the split selvedge, and of the links 16, so
as to carry out (in cooperation with the half-link associated thereto) the slotted
leno heald weave.
[0009] Since the devices according to the invention can be interposed - and easily adjusted
along the width of the loom - in the gap between the loom reed and the first heald
frame - which is also the first utilizable frame for the ground weave of the fabric
- the invention provides all the advantages of the half-link system, without suffering
from its main draw back of increasing the distance between the reed and the first
utilizable frame.
[0010] Suitable modifications can be introduced in the described and illustrated device,
without thereby departing from the scope of the present invention; in particular,
the links 15 to form the split selvedge can be replaced by links 16 for the slotted
leno heald weave, so as to carry out the slotted leno heald weave on the split selvedge.
This allows to use less arp yarns in the split selvedge and to reduce the length of
the weft tails, allowing to save on split selvedge wastes.
[0011] It should be noted, furthermore, that this last configuration of the fabric can advantageously
be obtained in that the device allows to have an out-of-phase advance or delay motion
in respect of the motion of the ground frames. This phase difference is normally carried
out in the movement of the split selvedge, which has to retain the weft released by
the drawing gripper independently from the closing of the shed. Said function would
not be obtainable with a slotted leno heald weave device mounted on the heald frames,
since these move exclusively in synchronism with the ground weave. Thus, the device
of the present invention will allow to carry out, far more than in the past, the slotted
leno heald weave on split selvedges, often given up now-a-days for the remarkable
complications (especially for what concerns adjusting the width of the fabric being
formed) created by the conventional devices adopted for this purpose.
