LU100829A1 - SUMMIT FLAT STRIP COMPRISING DIFFERENT NYLON REINFORCEMENT CONSTRUCTIONS 6,6 - Google Patents

Abstract

A strip of cord or woven fabric for a pneumatic tire made from alternately arranged PA66 / nylon 6.6 twisted filamentary reinforcing elements having different constructions with respect to their level of torsional structure is revealed. Such a cable strand or such a woven fabric improves high-speed durability and tread separation resistance when used in the form of a spirally wound crown ply at an angle of 0 degrees on the belt package in pneumatic tires of the radial web type.

Description

DESCRIPTION

FIELD OF THE INVENTION

The present invention relates to a new strip of cords or a new cabled fabric for a pneumatic tire made from nylon cords arranged alternately, having different constructions. A new cord band or such a new cord fabric for a pneumatic tire improves durability at high speed and resistance to separation of the tread when used in the form of a ply crown wound in a spiral at an angle equal to zero degrees on a pack of belts in pneumatic tires of the radial ply type.

FOUNDATION OF THE INVENTION

In high speed conditions, the external diameter of the tire increases under the influence of the centrifugal forces generated by the tread and the bundle of belts formed by steel cords. Such an increase in diameter or such an expansion of the pneumatic tire increases the pantographic movements of the cables at the edges of the belts, which gives rise to crack initiations, to propagation of the cracks and to separations from the terminal edges to the belts.

Furthermore, the rise in temperature at the edges of the belts under high speed conditions can trigger a deterioration in the local adhesion of the textile top ply band and gives rise to local separations between the tread and the top plies, which can ultimately result in separation of the edges of the belts in a very short period of time on the basis of non-uniform stress distributions.

The crown ply layer which wraps in a circumferential direction around the belt pack prevents excessive expansion of the tire under high speed conditions by exerting compressive forces (restraining forces) on a thick belt pack consisting of layers of steel cables of the diagonal ply type. In order to increase the restriction force, it is usual to use top ply strips having cords of the type with a high number of cords ends (high epdm value) (such as nylon, 1400x2, 110 epdm or nylon 1400x1, 140 epdm, etc.).

At present, the most widely used materials for crown plies are layers of nylon 6,6 of the multi-ply type or monolayer hybrid cords (for example hybrid aramid / nylon cords) which come wind in a spiral on a bundle of belts at angles of 0 to 5 degrees from the equatorial plane of the tire.

Nylon cords have excellent resistance to fatigue when subjected to bending and axial compression, as well as bielastic characteristics of tensile strength, which makes it possible to have an easy treatment during the making of the pneumatic tire. In addition, the generation of a thermal shrinkage force following an increase in the operating temperature under high speed conditions improves the resistance to separation at the edges of the belts, as well as durability at high speed.

It is well known that hybrid cables comprising high modulus and low modulus wires having a bielastic behavior of tensile strength are also used to act as crown plies in pneumatic tires intended for high speeds. The low modulus component of the hybrid cable allows easy lifting of the belt pack in the absence of excessive formation of tight tight cords due to its high extensibility and the high modulus component is effective under service conditions. When hybrid cables are used as the crown ply, the total thickness of the crown ply layer and the rubber content can be reduced, and the high modulus component of the hybrid cable increases the restrictive force and improve durability at high speed.

U.S. Patent 4,284,117 describes a nylon top web which is formed from individual yarns, rather than from cords. The crown ply is thinner than conventional crown plies in that it has characteristics of superior flexibility and superior heat dissipation.

In US Patent 5,115,853, a radial ply type tire is described having a crown ply structure which is disposed in the radial direction outside of the belt reinforcement structure. The top ply structure comprises nylon cords of the 420x2 type laid side by side having a cordset twist of not more than 280 rpm.

In US Patent No. ⁰ 2006/0237113, a belt reinforcement layer forming an angle of zero degrees is described, consisting of at least one first elongated element which represents a hybrid cord including at least one filament with high elastic modulus and at least one filament with low elastic modulus, twisted to one another and which are arranged alternately. The elastic modulus of said at least one second elongated element is less than the elastic modulus of said at least one first elongated element.

U.S. Patent 6,799,618 describes a textile top ply structure which overlaps in a radial direction outside the belt assembly and is reinforced with cords which are made of materials, including nylon and aramid. At the initial elongation of the cables, the wires which support the primary load are nylon wires and after appreciable elongation, the wires which support the primary load are aramid wires.

SUMMARY OF THE INVENTION

The present invention relates to a new strip of cords or a new cabled fabric for a pneumatic tire comprising alternately arranged nylon 6,6 cords having different constructions, more precisely, first cords having constructions of the two-ply type or of the type with three plies and second cables wired in the form of twisted wires of the type with only one ply. A new strip of woven fabric of this type combines the high energy absorbing properties in the event of impact of cables of the two-ply type or of the three-ply type and the upper initial module of twisted nylon 6 yarns, 6 of the single ply type.

A new cord band or such a new cord fabric for a pneumatic tire improves durability at high speed, resistance to separation of the tread and impact resistance when used under the tire. form of a crown ply wound in a spiral at an angle of zero degrees on the belt pack in pneumatic tires of the radial ply type.

As is well known, nylon 6,6 has an excellent resistance to fatigue and a bielastic behavior of tensile strength, which makes possible the lifting process in the absence of a formation of tightly tight cords and this which provides a sufficient restrictive force under high speed conditions. However, because of the low initial modulus of nylon 6,6 cords, it is necessary to use bands or fabrics having a high epdm value (number of ends of cords high per decimeter) in order to obtain the restriction force. sufficient with regard to the belt package (as can be seen in Figure 1).

On the other hand, the distance from cord to cord (rivet) in strips or in fabrics of this type is too narrow, which makes it difficult for the rubber to penetrate between the cables, without premature vulcanization. In addition, cracks in the rubber can easily occur between cables having a narrow rivet under dynamic conditions on the basis of high shear stresses.

According to the invention, the nylon 6,6 cables having different constructions in strips of crown plies have different modules (or different LASE values) and different thermal shrinkage values. During uplift (during expansion) during the vulcanization process, twisted nylon 6,6 threads of the single ply type (high modulus, cords with little stretch) are subjected to a load far greater than that of two-ply or three-ply high-twisted cords (low modulus, highly extensible cords). In addition to the higher tensile strength of the cable, the twisted nylon 6.6 single-ply, low-twist yarns subjected to higher loads generate a higher thermal shrinkage force (a greater contraction force) than the vulcanization temperature. On the basis of a higher cable load and a higher thermal shrinkage force, the nylon 6,6 strands of the single ply type penetrate better than twisted cords of the two ply type or three plies through the compound acting as a scrub layer.

On the basis of the difference in penetration (H) of the twisted wires of the single ply type and of the twisted cords of the two ply or three ply type in the compound serving as a gumming layer, the top band layer of the type with a single ply transforms into a top strip partly of the bilayer type (wavy) (as can be seen in Figure 2).

DEFINITIONS

Wired: reinforcing element obtained by reciprocal twisting of 10 wires of the type with two or more layers.

Denier; the weight in grams of a wire having a length of 9000 m.

Dtex; the weight in grams of a wire having a length of 10,000 m.

LASE; the load at a specified elongation.

LASE 7%; the load at 7% elongation in the load / elongation curve.

Linear density: the weight per unit of length expressed in g / dtex or in g / d (denier).

Restrictive force: the force exerted by the crown ply on the pack of belts while driving to prevent expansion of the tire.

Total linear density: the sum of the nominal linear densities of the ply wires of the cable.

Wired two-ply type; wired which is prepared by reciprocal twisting of two-ply type wires.

Three-ply type cable: cable that is prepared by reciprocal twisting of three-ply type wires.

Twist: the number of turns per meter (rpm or rpm).

Torsional coefficient: rpm x dtex ^1/2 .

Warp: the group of threads or cords in all the woven fabrics, which extend in a longitudinal direction and parallel to the selvedge and which come to intertwine with the filling material.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a cross-sectional view of a conventional nylon crown ply (from the prior art) over a packet of belts formed by steel cords of the diagonal ply type, after the vulcanization process.

a represents a pack of belts constituted by steel cables of the diagonal ply type;

b represents a conventional crown ply on a pack of belts;

c represents a tread.

FIG. 2 is a cross-sectional view of a nylon top ply according to the invention on a pack of belts formed by steel cords of the diagonal ply type, after the vulcanization process.

a represents a pack of belts constituted by steel cables of the diagonal ply type;

b represents a crown ply on a pack of belts according to the invention;

c represents a tread.

FIG. 3 is a cross-sectional view of arrangements of nylon top ply cords and of wires according to the invention on a pack of belts constituted by steel cords of the diagonal ply type, (1) before the vulcanization process; (2) after the vulcanization process.

A: represents a nylon 6.6 cable of the two-ply type having a high coefficient of twist, a low modulus and a higher extensibility;

B: represents a nylon 6,6 twisted wire of the single ply type having a low coefficient of twist, a high modulus and a lower extensibility;

H: represents the difference in penetration of A and B in a rubber matrix.

Figure 4 shows the changes in the distance between a cable and another cable (rivet area, spacing) after the vulcanization process; (1) before the vulcanization process; (2) after the vulcanization process:

; wired to wired distance between A and B before the expansion and vulcanization process;

: distance from wired to wired between A and B after the expansion and vulcanization process;

: distance from wired to wired between A and A after the expansion and vulcanization process;

: distance from wired to wired between B and B after the expansion and vulcanization process;

Figures 5 and 6 are similar to Figures 3 and 4, but with twisted nylon 6,6 yarns of the single ply type, having a lower dtex value; (1) before the vulcanization process; (2) after the vulcanization process.

FIG. 7 represents 1 + 2 + 1 arrangements of wires and cords of crown plies; (1) before the vulcanization process; (2) after the vulcanization process;

(1) arrangement of cables A + B + B + A + B + B + A + ... before the expansion and vulcanization process;

(2) arrangement of cables A + B + B + A + B + B + A + ... after the expansion and vulcanization process.

FIG. 8 represents 2 + 1 + 2 arrangements of wires and cords of crown plies; (1) before the vulcanization process; (2) after the vulcanization process:

(1) arrangement of cables A + A + B + A + A + B + A + A + ... before the expansion and vulcanization process;

(2) arrangement of cables A + A + B + A + A + B + A + A + ... after the expansion and vulcanization process.

DETAILED DESCRIPTION OF THE INVENTION

According to the invention, strips of crown plies or fabrics of crown plies wound in a spiral on bundles of pneumatic bandage belts of the radial ply type in circumferential direction, having nylon 6,6 cords and wires twisted in nylon 6,6 of the single ply type, as a chain:

- improve the durability at high speed on the basis of the medium to high modulus of the strip and on the basis of the greater distances from cabled to cabled and from wire to wire (by reducing the shear stresses) because of the shifts of the wires in the vertical direction ( formation of two layers or zigzag configuration, as can be seen in Figures 3, 4, 5 and 6);

- improve the impact resistance manifested by the pack of belts on the basis of a higher absorption of energy by nylon cords of the high torsion type and highly extensible (cords of a higher level are more sensitive to shocks and lower level cables are more sensitive to expansion of the tire); and also improve the resistance to separation between the tread and the crown plies thanks to the corrugated surface structure of the crown ply. The zigzag configuration of the surface also improves the mechanical connection between the compound serving as the crown ply and the compound serving as the tread.

Nylon 6.6 cables have two-ply or three-ply cable constructions. The wires arranged alternately represent twisted son of the single ply type.

The angle formed by the strips of crown plies wound in a spiral with respect to the circumferential midline (or with respect to the equatorial plane of the tire) rises from 0 to 5 °.

In order to be able to obtain the advantages which have been mentioned above, the torsion coefficient of the nylon cords 6.6 which is determined in accordance with the formula (1a) shown below amounts to at least 10,000 and a maximum of 15,000.

Torsion coefficient = cable twist (rpm) x (total linear cable density expressed in dtex) ¹⁷² (1a)

In accordance with the similar formula indicated below (1b), the twist coefficient of the twisted wire of the single ply type amounts to a minimum of 5000 and a maximum of 8000.

Torsion coefficient = twist in the ply of the wire (rpm) x (linear density of the wire expressed in dtex) ¹⁷² (1b).

In accordance with the invention, the coefficient of twist of the nylon 6.6 twisted wire of the single ply type is less by at least 5000 units than the twist coefficient of the cord in the same strip of crown ply (by example 1400x2, 250/250 rpm and 1400x1, 180 rpm).

When the difference in the coefficient of torsion is less than 5000 units, the corrugated area of the crown ply cannot be obtained on the belt pack of the tire.

In accordance with the invention, the total linear density of the cable amounts to a minimum of 700 dtex and a maximum of 5000 dtex and the total linear density of twisted wire of the single ply type amounts to a minimum of 350 dtex and maximum at 3000 dtex. These linear density limits prevent excessive cutting of rubber and excessive thickness of the rubber. Excessive cuts in the rubber can give rise to contact on the one hand between the cords of crown plies and the wires and on the other hand the steel cords of the belt layers, as well as to ruptures induced by the abrasion. Too high a thickness of rubber in the crown area gives rise to a strong accumulation of heat and to higher rolling resistance.

The linear density of twisted wires of the single ply type is at most 50% lower than the total linear density of the cable.

According to the invention, the sequence of cables and wires which are parallel to one another in a strip of crown ply, represents an alternating form as indicated below: A + B + A + B + A + B +. .. etc., in which A represents a nylon 6,6 cable of the two-ply type or of the three-ply type and B represents a twisted nylon 6,6 wire of the single-ply type (as can be seen in Figures 3, 4, 5 and 6). Such a strip of crown ply makes it possible to obtain a uniform corrugated surface after the vulcanization process, which comes to bind strongly to the compound acting as a tread by improving the resistance to separation of the tread under conditions of great speed.

According to the invention, the sequence of cables and wires, which are parallel to each other in a strip of crown ply, represents an alternating shape as indicated below: A + B + B + A + B + B + A + B + B + ... etc., in which A represents a nylon 6.6 cable of the two-ply type or of the three-ply type and B represents a nylon 6.6 twisted wire of the one single layer (as can be seen in Figure 7).

According to the invention, the sequence of cables and wires, which are parallel to each other in a strip of crown ply, represents an alternating form as indicated below: A + A + B + A + A + B + A + A + B + ... etc., in which A represents a nylon 6,6 cable of the two-ply type or of the three-ply type and B represents a nylon 6,6 twisted son of the single-ply type tablecloth (as we can see in figure 8).

In accordance with the invention, the number of cable ends in the strip amounts to a minimum of 70 epdm (ends per decimeter). In the case of numbers of ends of cables whose value is less than 70 epdm, the efficiency of the surface ripple is not sufficient to obtain a mechanical connection to the tread.

According to the invention, the width of the strips of crown plies is between 8 and 25 mm, preferably between 10 and 15 mm.

Claims (10)

1. Strip of crown ply produced from nylon 6,6 cords and nylon 6,6 twisted threads of the single ply type, woven in 2. The top ply strip according to claim 1, wherein said nylon 6,6 cords are cords of the two ply type. 3. The top ply strip according to claim 1, wherein Said nylon 6,6 cables are cables of the three-ply type. 4. crown ply strip according to claim 1, in which the coefficient of twist of said nylon 6.6 twisted yarn of the single ply type, which is determined according to the formula shown below: twist coefficient = twist in the ply of the wire (rpm) x (linear density of the wire expressed in dtex) ¹⁷² ; amounts to a minimum of 5000 and a maximum of 8000. 5. The top ply strip of claim 1, wherein the linear density of said nylon cords 5 alternation, which is wound in a circumferential direction around a pack of belts of a pneumatic tire of the radial ply type, characterized in that the coefficient of torsion of said nylon cords 6,6, which is determined in accordance with the formula shown below; twist coefficient = cable twist (rpm) x (total linear cable density expressed in dtex) ^1/2 amounts to a minimum of 10,000 and a maximum of 15,000; the coefficient of twist of said single ply nylon 6.6 twisted yarn is less than at least 5000 units less than the twist coefficient of said nylon 6.6 cord in the same top ply band 6.6 amounts to a minimum of 700 dtex and a maximum of 5000 dtex. 6. The top ply strip of claim 1, wherein the linear density of said nylon 6.6 twisted yarn of the single ply type is a minimum of 350 dtex and a maximum of 3000 dtex. 7. strip of crown ply according to claim 1, in which the The linear density of said single ply nylon 6.6 twisted yarn is not less than 50% of the total linear density of said nylon 6.6 cord. 8. The top ply strip of claim 1, wherein The arrangement of said nylon 6.6 cords (A) and said nylon 6.6 twisted yarns of the single ply type (B) in said strip is as indicated below A + B + A + B + A + B, etc. 9. The top ply strip of claim 1, wherein The arrangement of said nylon 6,6 cables (A) and of said nylon 6,6 twisted wires of the single ply type (B) in said strip is as indicated below A + B + B + A + B + B + A + B + B + A, etc. 10. The top ply strip of claim 1, wherein The arrangement of said nylon 6,6 cords (A) and of said twisted nylon 6,6 wires of the single ply type (B) in said strip is as indicated below A + A + B + A + A + B + A + A + B, etc. 11. strip of crown ply according to claim 1, in which the number of ends of cables in said strip amounts to a minimum of 70 epdm (ends per decimeter). 12. top ply strip according to claim 1, in which the width of said top ply strip amounts to a minimum of 8 mm and a maximum of 25 mm. 13. The top ply strip according to claim 1, wherein the width of said top ply strip is a minimum of 10 mm and a maximum of 15 mm.