Type of wrapped textile thread and process for its production which involves thermofusion to secure wrapping to core

There is provided a new wrapped textile thread which includes a core made of threads arranged considerably parallel to each other. The core is covered by a wrapping thread which winds in a single turn, forming a regular and joined spiral around the core. This textile thread is characterized by the fact that at least one part of the peripheral surface of the core is joined together by heat sealing with the wrapping of winding thread. The textile thread is useful in textile materials which require a very good resistance against abrasion.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention deals with a new type of wrapped thread and a process 
for its manufacture. 
2. Description of the Prior Art 
It is well known how to wrap threads. Schematically, this process consists 
of spirally winding a thread, called "covering" or "wrapping thread," 
around a second thread called "core thread." Depending on whether or not 
only one or several wrapping threads are used, it is described as a simple 
or a crossed wrapping. This technique of wrapping is very widely used in 
the fabrication of fancy threads and of elastic threads with an 
elastomeric core. 
It is also known to use fragile threads, such as glass thread, threads of 
thermostable synthetic materials such as those made of aromatic polyamide, 
or threads of a refractory substance, with a cross directional sense of 
wrapping. In this case, the fragile thread forms the core, and the 
wrapping thread, advantageously made of synthetic thermoplastic material, 
is wound in a simple spiral (simple wrapping) in regular single and joined 
turns around the thread of the core which is kept in the shape of a 
straight line, whereby the wrapping thread protects the said core thread. 
Such a wrapped thread is described in the commonly assigned French Pat. 
No. 2,314,958, and it is used in the production of materials destined to 
reinforce plastic substances. 
This latter technique, notably commercialized by L. Payen & Cie, still 
shows a certain number of inconveniences. Indeed, if, as is often the 
case, the core thread has a diameter which is greater than the diameter of 
the wrapping thread, the latter has the troublesome tendency to slip over 
the mentioned core. Therefore, the core thread is at once badly protected 
against abrasion from the outside, which means the abrasion suffered by 
the core thread with respect to another element, and equally badly against 
inside abrasion, which means the abrasion which is derived fromm the 
rubbings among the elemental fibers which form the core thread. 
The present invention reduces these inconveniences. It deals with a new 
type of wrapped thread which has a very good resistance against abrasion 
from the outside as well as inside, and wherein the distinctive features 
of the core are practically unchanged by the presence of the thread of the 
outside wrapping. 
Certainly, it is already known to make use of the phenomenon of gluing to 
modify the properties of thread-like textile elements. Thus, German Pat. 
No. DE-A 2,704,836 describes stringings, especially for supporting goods 
(tennis rackets) or musical instruments, where a core is covered by a 
binding liquid substance which dries immediately. Eventually, the core is 
covered by winding loose threads around it. 
Moreover, it has been disclosed in the U.S. Pat. No. 3,644,866 to keep the 
parallel thread in position by means of a double-wrapped thread made in a 
loose manner. Before the wrapping, the core threads are bathed in a 
binding substance which ties them together. 
The U.S. Pat. Nos. 2,313,058 and 2,424,743 both describe threads formed by 
the combination, via twisting, of two threads where one of them can be 
made adhesive by heat treatment. The heat treatment joins the fibers of 
the non-thermofusible thread together and improves the properties of the 
produced articles. 
Likewise, the British Pat. No. 1,322,336 and the Luxemburg Pat. No. 66,345 
describe the use of binding substances in order to modify the properties 
of textile materials. 
Nevertheless, none of these disclosures provide wrapped threads having a 
very good resistance against abrasion from the outside as well as inside, 
and where the distinctive features of the core are practically unchanged 
by the presence of the outside wrapping thread, the latter being tied to 
the core by means of a very small quantity of heat sealing substance, 
where this substance does not modify the general distinctive features of 
the obtained thread. 
SUMMARY OF THE INVENTION 
In a general way, the invention deals with a new wrapped textile thread of 
the type which comprises a core consisting of threads which are 
appreciably parallel to one another, the mentioned core being covered by a 
wrapping thread which winds in a single turn forming a regular and joined 
spiral with at least one part of the peripheral surface of the core joined 
together by heat sealing with the wrapping thread. The textile thread is 
characterized by the fact that the binding of the core with the wrapping 
thread is obtained by fusion of a thread-like thermofusible element with a 
fusion temperature which is lower than the fusion temperature of the core 
and the wrapping. 
In practice, in accordance with the invention, the weight of the thread 
thus obtained will comprise, with respect to the whole produced unit, at 
the most, ten percent (10%) heat sealing substance permitting the binding 
of the core with the wrapping thread, the latter representing, at the 
most, twenty-five percent (25%) of the produced unit. 
Advantageously, in accordance with the invention, the multithreaded core 
composed of a plurality of individual threads, parallel or very slightly 
twisted, is made of fragile textile material, and is composed of, for 
example, glass threads, threads of a refractory material, such as carbon, 
boron, or silicon, or threads of an aromatic polyamide, such as the 
polymer of p-phenylene terephthalamide or similar ones like 
polyamide-imides, polyimides, etc. These substances have poor resistance 
to abrasion, outside as well as inside. 
The wrapping thread around the core is a synthetic textile material of 
continuous threads, for example, polyester, polyamide 6--6, or polyamide 
6. 
If required, the core may be composed of an aggregation of several 
multithreaded and parallel subcores with very little torsion, on the order 
of a hundred (100) turns per meter. 
The joining together of the core and the wrapping thread is achieved either 
by several separate thread-like elements spaced apart on the peripheral 
surface of said core, or by a spiral of joined or unjoined turns, 
preferably in the opposite direction to the spiral formed by the wrapping 
thread. 
As a material which permits the joining together by thermofusion of the 
core with the wrapping thread, a thread-like material is used, which 
consists of, for example, a multifilament thread made of a thermofusible 
substance compatible at the same time with the kind of threads forming the 
core as well as with the kind of threads forming the wrapping thread. This 
thread-like material has a fusion temperature lower than the fusion 
temperature, and in practice also the degredation temperature, of the core 
thread and the wrapping thread. 
A thread-like element which is particularly convenient for the 
implementation of the invention is composed of a threaded formed of a 
copolyamide 6 commercially sold under the name of GRILLON by the Grillon 
Company. The amount of this thread will be chosen in a way that the 
quantity which it represents in the formed unit does not exceed ten 
percent (10%) in weight. 
A procedure for the manufacture of thread in accordance with the invention 
consists of winding in a known and simple way in joined and regular turns, 
a thread of the multifilament wrapping, preferably a synthetic 
thermoplastic material, around a core thread which consists of threads 
arranged almost parallel to each other. Between the core and the wrapping 
thread, there is provided at least one thread-like element made from a 
thermofusible substance with a fusion temperature which is less than the 
fusion temperature of the core and of the wrapping. 
Then the unit made this way is thermally treated in order to achieve the 
fusion of the thread-like element and the joining together, by 
thermofusion, of the core with the wrapping thread. This thermal treatment 
can be achieved either continuously before winding on, or by a subsequent 
process. 
According to one way of implementing the invention, one puts in at least 
one and preferably three thread-like elements, with the thread like 
elements being spaced apart at the periphery of the core. These threads 
are lined up parallel to the mentioned core before the winding, and are 
put between the wrapping thread and the core. In this way, after the 
thermal treatment, considerable joining together of the core and the 
wrapping thread is obtained by use of the thread-like elements. Such a 
technique is particularly economic and simple because it requires one 
single operation. 
In an alternative procedure, prior to the winding of the wrapping thread, 
one makes a first winding, looose or with joined turns, by means of a 
thread-like thermofusible element. Preferably, this winding is carried out 
in the opposite direction of the final winding by the wrapping thread. 
After the thermal treatment, in this case, one obtains a joining by fusion 
of the core with the wrapping thread appreciably in the form of a spiral 
with joined or unjoined threads. 
Finally, if the core is composed of a plurality of basic multithreaded 
subcores, it is possible to proceed either as previously shown, or by 
wrapping each of the basic subcores, for example by winding with a 
thermofusible thread. After the thermal treatment, a binding by heat 
sealing is obtained by binding the subcores among themselves, on the one 
hand, and by binding those subcores with the wrapping thread, on the 
other. 
The way in which the invention can be carried out and the advantages which 
derive from it are better shown by the preferred embodiments, given as a 
guide but not restrictive, and which are illustrated by the appended 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In a general way, according to the invention, the textile threads consist 
of a plurality of threads which are arranged substantially parallel to 
each other to form a core, and this core is covered by a wrapping thread, 
wound in a single turn to form a regular and joined spiral. In accordance 
with the invention, at least one part of the peripheral surface of the 
core is joined together by heat fusion with the wrapping thread. 
In the example shown in FIG. 1, the wrapping thread 2 is joined together 
with core 1 by heat fusion by means of several thread-like elements 3 
spaced apart on this core 1. 
Such a thread can be produced by an installation such as that shown 
schematically in FIG. 4. In this manner of manufacture, core 1 is composed 
of five basic threads 11, joined with themselves without notable torsion, 
which means practically parallel. These threads come from a core 10, 
whereupon the bobbins of basic thread 11, are placed; then they pass 
through tighteners 12, for example, of a bar or rack type, and they are 
joined together by a convergence guide 13 in such a way as to form an 
aggregation, without appreciable torsion, of a plurality of threads 
composing core 1. 
From spindle 14, kept continuously rotating, for example by a strap not 
shown, carrying a bobbin 15 of wrapping thread 2, said wrapping thread 2 
is wound up in regular and joined turns around the formed core 1. This 
operation of winding is carried out in a conventional manner and will not 
be described in detail. The assemblage is made at the level of a guide 16, 
and then the wrapped thread is wound on a receiving bobbin in a classical 
manner by means of a guide 17 which goes back and forth on a receiving 
bobbin 18. 
In accordance with the invention, one brings forward in parallel fashion, 
the thread-like elements 3 carried by the bobbins under the hollow spindle 
14 before wrapping of the core thread 1 by the wrapping thread 2, and the 
thread-like elements 3 are spooled to the periphery of the formed core 1. 
These thread-like elements consist of a thread with a fusion temperature 
less than the fusion temperature of the wrapping thread 2 and the threads 
of core 1. These threads 3 are, therefore, surrounded and held by the 
wrapping thread 2. Before the winding on, or at a later stage, according 
to the invention, the formed thread is submitted to a heat treatment at a 
temperature which provokes the fusion of the thread-like elements 3 
followed by the heat sealing of the core with the wrapping thread 2. 
In the example shown in FIG. 2, the thermofusible thread-like element 6 is 
not arranged as separate thread-like elements spaced apart on the core but 
rather covers the core, for example, by the wrapping around of the core in 
joined or unjoined turns. This operation is carried out with the same 
material as that previously described. After this has been done, the final 
wrapping is carried out with the wrapping thread 5 in an equally 
conventional material. In this case, the two windings are carried out 
preferably in the opposite direction. After the thread has been made, it 
is likewise heat treated in a way to provoke the fusion of the thread-like 
element 6, thereby bringing about the binding of core 4 with the wrapping 
thread 5. 
In the method of carrying out the invention which is shown by FIG. 3, core 
7 is equally composed of the aggregation without appreciable torsion of 
five (5) basic subcores. Prior to their aggregation and to their wrapping 
by thread 8, these ends were wrapped individually by a thread-like element 
9. The unit thus formed is likewise submitted to a heat treatment which 
provokes the fusion of the thread-like elements 9 and the heat sealing, on 
the one hand, of the basic subcores among themselves, and the sealing of 
these subcores with the wrapping thread 8, on the other. 
EXAMPLE 1 
With textile material for conventional wrapping such as that shown in FIG. 
4, a thread is produced which is in accord with the invention, and which 
is pictured in FIG. 1. 
This thread is composed of a core 1 of six (6) basic threads made of poly 
(p-phenylene terephthalamide), commercially sold by the E.I. DuPont de 
Nemours & Company under the trademark KEVLAR, with the individual fineness 
of 1,670 decitex, each basic thread composed of 1000 strands, not allowing 
any torsion, and a wrapping thread 2 composed of a polyester thread, 440 
decitex, 100 strands, zero (0) torsion turn per meter. Prior to the 
wrapping, three (3) threads are formed, the three threads being composed 
of a copolyamide 6--6 of 220 decitex, 20 strands, commercially sold under 
the name GRILLON by the Grillon Company. 
The winding of the wrapping thread 2 is done in such a way that the spiral 
turns formed around the core are regular and joined ones. This wrapping is 
made by 2000 turns per meter in an S direction. 
The formed thread in which the GRILLON threads are firmly held between the 
core and the wrapping thread, is wound, and the formed bobbins are heat 
treated with steam at a temperature of one hundred five degrees Centigrade 
(105.degree. C.) for thirty (30) minutes. This operation of heat treatment 
achieves the fusion of the three threads made of GRILLON and provokes the 
binding of core 1 with the thread of outside wrapping 2. This outside 
wrapping 2 is kept completely against core 1 and protects the threads 
which compose it against outside abrasion, and to a certain degree, 
equally against interior abrasion of the threads among themselves. 
EXAMPLE 2 
Example 1 is repeated with the variation that instead of incorporating 
three parallel GRILLON threads with the formed core thread 4 the core is 
covered beforehand by wrapping (as shown in FIG. 2) with a GRILLON thread 
6 of 220 decitex, 20 strands, wound with 300 turns per meter around the 
core. This is done in the opposite direction of the external wrapping, 
i.e., in the Z direction in the present case. 
After this thread has been made, an external wrapping 5 is produced in the 
same way as in Example 1, and with the same polyester thread. 
As done before, the obtained thread is heat treated with steam at one 
hundred five degrees Centigrade (105.degree. C.) for thirty (30) minutes, 
and the fusion of the GRILLON thread 6 would around core 4 is equally 
provoked. In this case, the binding of core 4 with the outside wrapping 5 
is appreciably done in a spiral with practically joined turns. 
The obtained thread also shows a very good resistance against outside 
abrasion, as well as an excellent protection against internal abrasion. 
EXAMPLE 3 
A thread a shown in FIG. 3 is produced. 
This thread is composed of a core 7 formed by six (6) basicc subcores of a 
poly-(p-phenylene terephthalamide) commercially sold by the E.I. DuPont de 
Nemours & Company under the brand name KEVLAR with an individual fineness 
of 1,670 decitex, 1000 strands, without torsion. 
Prior to the winding with the wrapping thread 8, each of these basic 
subcores is covered by a GRILLON 9 thread with the fineness 220 decitex, 
20 strands, the winding being carried out by 2,150 turns per meter in the 
Z direction. 
As in Example 1, five (5) of these basic wrapped threads are joined by 
using a wrapping thread 8, wound with joined turns, made of polyester of 
400 decitex, 100 strands, the wrapping being carried out with 2,100 turns 
per meter in the S direction. 
The threads thus produced are submitted to a heat treatment with steam of a 
duration of thirty (30) minutes at a temperature of one hundred and five 
degrees Centigrade (105.degree. C.). This treatment achieves the melting 
of the GRILLON wrapping 9 and provokes the binding, on the one hand, of 
the basic subcores 7, among themselves, and on the other hand, the binding 
with the wrapping thread 8. 
Such a thread provides, in comparison to the previously produced threads, a 
more improved protection of the outside surface, as well as improved 
protection against internal abrasion. 
The threads which are obtained in accordance with the invention are 
essentially characterized by a substantial, if not total, decrease of the 
sliding of the wrapping thread about the core thread, and this is the 
case, if ever the latter has a considerably larger diameter than said 
wrapping thread. Furthermore, these threads retain all the properties of 
the core, given the small proportion of the wrapping thread and the 
material which permits the heat fusion. These threads can be successfully 
used in all applications called upon where the core thread is a fragile 
material. As examples, industrial fabrics, cables, straps, screens, etc., 
can be mentioned. 
In another respect, given the fact that the material permits the binding of 
the core with the wrapping thread, the carrying ouf of the process of the 
present invention is particularly easy to achieve because of the presence 
of a thread-like binding element. Special material, such as a device for 
the binding material, is not necessary since this thread-like element can 
be directly built into the material which serves to produce the thread 
itself.