Double-layer multi-strand cable having improved bending endurance

Patent metadata

Field	Value
Publication number	US-12467199-B2
Application number	US-202118012327-A
Country	US
Kind code	B2
Filing date	Jun 18, 2021
Priority date	Jun 24, 2020
Publication date	Nov 11, 2025
Grant date	Nov 11, 2025

Abstract

A multi-strand cord ( 50 ) comprises an internal layer (CI) of the cord made up of K=1 three-layer (C1, C2, C3) internal strand (TI), with the internal layer (C1) being made up of Q internal metallic threads (F1), the intermediate layer (C2) being made up of M intermediate metallic threads (F2) and the external layer (C3) being made up of N external metallic threads (F3), and an external layer (CE) of the cord made up of L>1 three-layer (C1′, C2′, C3′) external strands (TE) wound around the internal layer (CI) of the cord, with the internal layer (C1′) being made up of Q′ internal metallic threads (F1′), the intermediate layer (C2′) being made up of M′ intermediate metallic threads (F2′) and the external layer (C3′) being made up of N′ external metallic threads (F3′). The cord ( 50 ) has an endurance criterion SL≤40 000 MPa·mm with
S ⁢ L = max ⁡ ( Δ ⁢ σ bending ⁢ _ ⁢ CI Cp ; Δ ⁢ σ bending ⁢ _ ⁢ CE C r × Cp ) ;
and a size criterion Ec≥0.46 with Ec=Sc/Se.

First claim

The invention claimed is:

1 . A two-layer multi-strand cord comprising:
an internal layer of the cord made up of K=1 three-layer internal strand comprising:
an internal layer made up of Q=1, 2, 3 or 4 internal metallic threads of diameter d1;
an intermediate layer made up of M intermediate metallic threads of diameter d2 wound around the internal layer; and
an external layer made up of N external metallic threads of diameter d3 wound around the intermediate layer; and
an external layer of the cord made up of L>1 three-layer external strands wound around the internal layer of the cord comprising:
an internal layer made up of Q′=1, 2, 3 or 4 internal metallic threads of diameter d1′;
an intermediate layer made up of M′ intermediate metallic threads of diameter d2′ wound around the internal layer; and
an external layer made up of N′ external metallic threads of diameter d3′ wound around the intermediate layer,
wherein the cord has a bending endurance criterion SL≤40 000 MPa·mm with

SL
=

max
⁡
(

Δ
⁢

σ

bending
⁢
_
⁢
CI

Cp

;

Δ
⁢

σ

bending
⁢
_
⁢
CE

C
r

×
Cp

)

,

and a size criterion Ec≥0.46 with Ec=Sc/Se, where:
Δσ bending CI =Msteel×Max(d1; d1′; d2; d2′)/2 in MPa·mm is a maximum bending stress per unit curvature seen by the internal threads of the internal and external strands or intermediate threads of the internal and external strands, Δσ bending_CE =Msteel×Max(d3; d3′)/2 in MPa·mm is a maximum bending stress per unit curvature seen by the external metallic threads of the internal and external strands, M steel — 210 000 MPa is the modulus of the steel, d1, d1′, d2, d2′, d3 and d3′ are expressed in mm,

Cp
=

CpIT
+
CpTE

2

,

Cp is a penetration coefficient for the cord with Cp IT an inter-strand penetration coefficient and Cp TE a penetration coefficient for the external strands with:
Cp IT =0.4 when the inter-strand distance E of the external strands of the external layer E<30 μm; or
Cp IT =1.0 when E>70 μm; or
CP IT =0.015×E−0.05 when 30 μm≤E≤70 μm; and

CpTE
=

CpC
⁢

3
′

+

min
⁡
(

CpC
⁢

2
′

;

CpC
⁢

3
′

)

2

,

where CpC2′ is a penetration coefficient for the intermediate layer of the external strand and CpC3′ is a penetration coefficient for the external layer of the external strand such that:
Cp C2′=0.4 when the inter-thread distance I2′ of the intermediate metallic threads of the intermediate layer I2′<10 μm; or
Cp C2′=1.0 when I2′>40 μm; or
Cp C2′=0.02×I2′+0.2 when 10 μm≤I2′≤40 μm; and
Cp C3′=0.4 when the inter-thread distance I3′ of the external metallic threads of the external layer I3′<10 μm; or
Cp C3′=1.0 when I3′>40 μm; or
Cp C3′=0.02×I3′+0.2 when 10 μm≤I3′≤40 μm;
Cr is a dimensionless performance coefficient of the cord with

C
r

=

1
-

(

sin
⁡
(

∝
f

)

d
⁢
3
×
d
⁢

3
′

×

(

∑

i
=
1

Q
′

+

M
′

+

N
′

⁢

F
mi

Assignees

• Michelin & Cie

Inventors

• Chevalley Marianna
• Barbat Romain
• Gianetti Alexandre
• Laurent Stephane

Classifications

• D07B2501/2046

  Tyre cords · CPC title

• D07B2401/208

  Enabling filler penetration · CPC title

• D07B2401/206

  Improving radial flexibility · CPC title

• D07B2205/3025

  Steel · CPC title

• D07B2201/2061

  resulting in a twisted structure · CPC title