EP0279756A1 - Multifilament sewing thread and method for making the same - Google Patents

Abstract

This sewing thread, whose twist coefficient is between 100 and 150, consists essentially of a core (3) of high tenacity fixed multifilaments, sheathed with a cover (4) of staple fibers, the whole being wrapped by a multifilament yarn (5). The spinning process of this sewing thread is carried out on continuous spinning, the core thread (3) and the staple of staple fibers (4) being brought to the drawing rolls (11) in the spinning plane, then that the covering yarn (5) arrives at said drawing cylinders (11) offset from the spinning plane.

Description

The present invention relates to a continuous multifilament sewing thread and its manufacturing process.

It is known that conventional sewing threads, based on fiber yarns are produced by assembling several yarns of fibers having received a twist S, this assembly being carried out in the Z direction.

To be technically efficient, a sewing thread must have a cross section as close as possible to a circular section.

It is for this reason that originally, and as can be seen in Figure 3 of the accompanying schematic drawing, the sewing threads included up to five yarns of assembled fibers. This large number has been reduced, mainly for economic reasons aimed at reducing production costs, and there are now commonly found three- or even two-end wires, as shown in Figures 1 and 2.

• 1) craquage,
• 2) étirage/mélange,
• 3) bancs à broches,
• 4) filature,
• 5) bobinage/purgeage,
• 6) puis assemblage de ces filés de fibres,
• 7) retordage,
• 8) bobinage sous tension,
• 9) fixation,
• 10) gazage,
• 11) râclage,
• 12) contrôle et épissurage.

However, this simplification of production remains very relative; the manufacture of a sewing thread currently requires a large number of steps which will be recalled below.
Preparation of single fiber yarns by

• 1) cracking,
• 2) stretching / mixing,
• 3) pin benches,
• 4) spinning,
• 5) winding / purging,
• 6) then assembly of these fiber yarns,
• 7) twisting,
• 8) live winding,
• 9) fixing,
• 10) gassing,
• 11) scraping,
• 12) control and splicing.

• a) résistance mécanique trop faible,
• b) abrasion des fibres dans le chas de l'aiguille,
• c) instabilité dimensionnelle due à l'impossibilité d'effectuer l'opération de tension et de fixation indispensable pour un 100 % filé de fibres.

Since we know that the ideal section of a sewing thread is a circular section, and that single fiber yarns have this section, we could think of avoiding all the assembly operations and using only fiber yarns simple. This did not happen proved possible, and the numerous attempts made in this direction have led to failures, the causes of which can be summarized below:

• a) mechanical strength too low,
• b) abrasion of the fibers in the eye of the needle,
• c) dimensional instability due to the impossibility of carrying out the tensioning and fixing operation essential for a 100% spun fiber.

The object of the invention is to remedy the drawbacks of the prior art by proposing a sewing thread with a multifilament core whose stitchability and resistance are equivalent to that of the sewing threads obtained by assembling fiber yarns and which can , in addition, be obtained by a very simplified manufacturing process compared to the processes used to date.

The sewing thread according to the invention is characterized in that it is essentially composed of a fixed high tenacity multifilament core, sheathed with a cover of cracked or cut fibers, the whole being covered by a multifilament thread.

Both the filament part and the cracked or cut fiber part can be made from any known textile material, whether natural fibers, artificial fibers or synthetic fibers.

• Figure 4 est une vue très schématique en perspective partielle­ment arrachée du fil à coudre selon l'invention ;
• Figure 5 est une vue schématique, en coupe transversale, d'une partie du système de filature du fil selon l'invention ;
• Figure 6 est une vue de gauche de figure 5, représentant une paire de broches.

The present invention will be better understood and its advantages will emerge clearly from the description which follows, with reference to the appended schematic drawing in which:

• Figure 4 is a very schematic perspective view partially cut away of the sewing thread according to the invention;
• Figure 5 is a schematic view, in cross section, of a part of the yarn spinning system according to the invention;
• Figure 6 is a left view of Figure 5, showing a pair of pins.

In the figures, the wire according to the invention is generally represented by 2 , and it essentially consists of a core 3 , a cover 4 and a covering 5 .

Spinning is carried out on conventional conventional spun yarn for core yarn of the type commonly known as "core-spun"; this continuous was however modified, according to the invention, by adding a device 8 for supplying the covering wire 5 , as seen in FIGS. 5 and 6.

The diagram of the spinning process will now be explained with reference to Figures 5 and 6.

After having undergone the operations of cracking, drawing / mixing and passage on a bench with spindles (not shown in the drawing), the wick of fibers 4 , coming from the reel 7 , passes between the food rolls 9 , then between the rolls intermediate 10 , before arriving at the stretching cylinders 11 . The core wire 3 , supplied by the reel 6 , is also brought to these drawing cylinders 11 , and this in the spinning plane, as is the wick of fibers 4 . The wire 2 thus obtained is subjected to the conventional winding, purification and splicing operations, not shown in the drawing.

Finally, and according to the invention, a covering wire 5 , supplied by the reel 8 , also arrives at the drawing cylinders 11 , but offset from the spinning plane, as can be seen in FIG. 6.

A wire is thus obtained as schematically represented in FIG. 4.

It is quite obvious, and this is part of the invention, that the angle of inclination of the fibers is of fundamental importance. It is this angle, β, which conditions the degree of closure of the wire 2 and, consequently, the binding of the fibers 4 of the cover by the covering filament 5 .

This angle β is a linear function of the twist of the wire.
If T is the twist in turns per meter,
Nm the metric number and
α the coefficient of torsion,
T = α √Nm
and β = f (α, Nm), is therefore a function of two independent variables.

For each metric number, the value of Nm obviously becomes constant and we actually have:
β = f (α), which is a linear function.

The numerous tests carried out by the Applicant have made it possible to determine that α must be between 100 and 150.

This high level of the coefficient of torsion does not cause any significant decline in the physical characteristics of the wire. Multifilaments indeed maintain a higher residual resistance than fiber yarns.

The mechanical resistance of the wire 2 is communicated to it largely by the core wire 3 . The covering fibers 4 substantially boost this resistance and the covering thread 5 has the main function of blocking the staple covering fibers 4 , in order to cancel their corrosion when passing through the eye of the sewing needle.

Example

According to the process described above, a sewing thread is made from the following elements:
core filaments 3 : 24.6% 74dtex Trevira T712 fixed
covering 5 : 16.6% 50 dtex Trevira T712 fixed
covering filaments 4 : 58.8% Trevira fibers glossy T 132, 1.3 dtex
α = 130 Nm = 33.3 (equivalent to 100/3)
twist T = 130 √33.1 = 750 S direction

The following table compares the properties of the thread thus obtained with a conventional sewing thread:

We can see a remarkable equality of the different parameters.

In addition, machine sewing tests also give comparable results.

• 1) craquage
• 2) étirage/mélange
• 3) bancs à broches
• 4) filature
• 5) bobinage/épuration/épissurage.

We therefore obtain a thread that is comparable in every way to the best sewing threads, but with a process that is much more economical to implement, since, instead of the twelve successive operations required in the conventional system and listed above, its manufacture does not require than the following five operations:

• 1) cracking
• 2) stretching / mixing
• 3) pin benches
• 4) spinning
• 5) winding / purification / splicing.

Claims (4)

1- Sewing thread with multifilament core, characterized in that it is essentially composed of a core (3) of high tenacity multifilaments fixed, sheathed with a cover (4) of staple fibers, the whole being covered by a multifilament yarn (5). 2- sewing thread according to claim 1, characterized in that its twist coefficient is between 100 and 150. 3- A method of manufacturing the sewing thread according to claim 1 and claim 2, characterized in that it comprises the following operations:
cracking of a ribbon of wire, drawing and mixing of the fibers obtained, passage on spindle benches, spinning, winding, purification and splicing. 4- A method of spinning sewing thread according to claim 3, characterized in that it is carried out on continuous spinning, the core thread (3) and the staple of staple fibers (4) being brought to the cylinders of drawing (11) in the spinning plane, while the covering yarn (5) arrives at said drawing cylinders (11) offset from the spinning plane.

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