Two-layer multi-strand cords having very low, low and medium moduli
A two-layer multi-strand cord ( 60 ) comprises an internal layer (CI) of the cord made up of J>1 internal strands (TI) and an external layer (CE) of the cord made up of L>1 external strands (TE). The cord satisfies the relationship 95≤MC≤175, where MC=(J×MI+L×ME)/(J+L); MI=200×cos 4 (α)×[Q×(D 1 /2) 2 ×cos 4 (β)+P×(D 2 /2) 2 ×cos 4 (δ)+N×(D 3 /2) 2 ×cos 4 (γ)]/[Q×(D 1 /2) 2 +P×(D 2 /2) 2 +N×(D 3 /2) 2 ]; and ME=200×cos 4 (α′)×[Q′×(D 1 ′/2) 2 ×cos 4 (β′)+N′×(D 2 ′/2) 2 ×cos 4 (γ′)]/[Q′×(D 1 ′/2) 2 +N′×(D 2 ′/2) 2 ], where D 1 , D 1 ′, D 2 , D 2 ′, and D 3 are in mm, α and α′ are the helix angle of each internal and external strand (TI), β and β′ are the helix angle of each internal thread (F 1 , F 1 ′), δ is the helix angle of each intermediate thread (F 2 ) and γ and γ′ are the helix angle of each external thread (F 3 , F 2 ′).
1. A two-layer multi-strand cord comprising:
an internal layer of the cord made up of J>1 internal strands wound in a helix, each internal strand having three layers and comprising an internal layer made up of Q≥1 internal threads of diameter D 1 , an intermediate layer made up of P>1 intermediate threads of diameter D 2 wound around the internal layer, and an external layer made up of N>1 external threads of diameter D 3 wound around the intermediate layer; and
an external layer of the cord made up of L>1 external strands wound around the internal layer of the cord, each external strand having two layers and comprising an internal layer made up of Q′≥1 internal threads of diameter D 1 ′, and an external layer made up of N′>1 external threads of diameter D 2 ′ wound around the intermediate layer,
wherein the cord satisfies the following relationship:
95≤ MC≤ 175
where MC =( J×MI+L×ME )/( J+L ),
where MI= 200×cos 4 (α)×[ Q ×( D 1/2) 2 ×cos 4 (β)+ P ×( D 2/2) 2 ×cos 4 (δ)+ N ×( D 3/2) 2 ×cos 4 (γ)]/[ Q ×( D 1/2) 2 +P ×( D 2/2) 2 +N ×( D 3/2) 2 ],
where D 1 , D 2 and D 3 are expressed in mm, α is the helix angle of each internal strand in the internal layer of the cord, β is the helix angle of each internal thread in the internal layer within each internal strand, δ is the helix angle of each intermediate thread in the intermediate layer within each internal strand, and γ is the helix angle of each external thread in the external layer within each internal strand,
where ME= 200×cos 4 (α′)×[ Q ′×( D 1′/2) 2 ×cos 4 (β′)+ N ′×( D 2′/2) 2 ×cos 4 (γ′)]/[ Q ′×( D 1′/2) 2 +N ′×( D 2′/2) 2 ], and
where D 1 ′ and D 2 ′ are expressed in mm, α′ is the helix angle of each external strand in the external layer of the cord, (β′ is the helix angle of each internal thread in the internal layer within each external strand, and γ′ is the helix angle of each external thread in the external layer within each external strand.
2. The two-layer multi-strand cord according to claim 1 , wherein 95≤MC≤170.
3. The two-layer multi-strand cord according to claim 1 , wherein 77≤MI≤196.
4. The two-layer multi-strand cord according to claim 1 , wherein 81≤ME≤182.
5. The two-layer multi-strand cord according to claim 1 , wherein 0.70≤ME/MI≤1.30.
6. The two-layer multi-strand cord according to claim 1 , wherein the helix angle α of each internal strand in the internal layer of the cord ranges from 4° to 36°.
7. The two-layer multi-strand cord according to claim 1 , wherein the helix angle α′ of each external strand in the external layer of the cord ranges from 10° to 32°.
8. The two-layer multi-strand cord according to claim 1 , wherein 26°≤3α+β+δ+γ≤162°.
9. The two-layer multi-strand cord according to claim 1 , wherein 28°≤2α′+β′+γ′≤96°.
10. The two-layer multi-strand cord according to claim 1 , wherein 64°≤3α+β+δ+γ+2α′+β′+γ′≤224°.
11. The two-layer multi-strand cord according to claim 1 , wherein J=2, 3 or 4.
12. The two-layer multi-strand cord according to claim 1 , wherein L=7, 8, 9 or 10.
13. The two-layer multi-strand cord according to claim 1 , wherein the external layer of the cord is desaturated.
14. The two-layer multi-strand cord according to claim 1 , wherein the cord has a modulus EC such that 50 GPa≤EC≤160 GPa.
15. A tire comprising the two-layer multi-strand cord according to claim 1 .