Multi-strand cord in which the basic strands are dual layer cords, rubberized in situ
View Patent ↗J strands form a core. K outer strands are wound around it in a helix with pitch P K , each having a cord with an L wire inner layer of diameter d 1 , and an M wire outer layer of diameter d 2 , wound around the inner layer in a helix with pitch p 2 ; with (in mm): 0.10<d 1 <0.50; 0.10<d 2 <0.50; 6<p 2 <30; its inner layer is sheathed with filling rubber; over any length P K of the outer strand, filling rubber is in each of the capillaries delimited by L wires of the inner layer and M wires of the outer layer, and also, when L is equal to 3 or 4, in the central channel delimited by L wires of the inner layer. Filling rubber in said outer strand is 5 to 40 mg per g of strand.
1. A multistrand metal cord having two layers of J+K construction, which can notably be used for reinforcing tires for industrial vehicles, consisting of a core comprising J strands forming an inner layer, J varying from 1 to 4, around which core are wound, in a helix, with a helix pitch P K of between 20 and 70 mm. K outer strands forming an outer layer around said inner layer, each outer strand:
comprising a cord having two layers of L+M construction, rubberized in situ, comprising an inner layer comprised of L wires of diameter d 1 , L varying from 1 to 4, and an outer layer of M wires, M being equal to or greater than 5, of diameter d 2 , which are wound together in a helix with a pitch p 2 around the inner layer; and
having the following characteristics (d 1 , d 2 and p 2 being expressed in mm):
0.10<d 1 <0.50;
0.10<d 2 <0.50;
6<p 2 <30;
wherein the inner layer of the outer strand is sheathed with a rubber composition called a “filling rubber”;
over any length of the outer strand equal to P K , the filling rubber is present in each of the capillaries delimited by the L wires of the inner layer and the M wires of the outer layer, and also, when L is equal to 3 or 4, in the central channel delimited by the L wires of the inner layer; and
the amount of filling rubber in said outer strand is between 5 and 40 mg per g of strand.
2. The multistrand cord according to claim 1 , wherein, in each outer strand, the following characteristics are satisfied:
0.15< d 1 <0.35;
0.15< d 2 <0.35.
3. The multistrand cord according to claim 1 , wherein, in each outer strand, p 2 is in the range from 12 to 25 mm.
4. The multistrand cord according to claim 1 , wherein, P K is in the range from 25 to 60 mm.
5. The multistrand cord according to claim 1 , wherein, P K satisfies the relationship:
1.5≦ P K /p 2 ≦3.0.
6. The multistrand cord according to claim 1 , wherein, in each outer strand, L is equal to 1.
7. The multistrand cord according to claim 6 , wherein, each outer strand, L is equal to 1 and M is equal to 5, 6 or 7.
8. The multistrand cord according to claim 1 , wherein, in each outer strand, L is different from 1 and the L wires of diameter d 1 are helically wound with a pitch p 1 satisfying the relationship:
20< p 1 /d 1 <100.
9. The multistrand cord according to claim 1 , wherein, in each outer strand, L is different from 1 and the L wires of diameter d 1 are helically wound with a pitch p 1 satisfying the relationships:
0.5≦ p 1 /p 2 ≦1.
10. The multistrand cord according to claim 9 , wherein, in each outer strand, p 1 lies in the range from 6 to 30 mm.
11. The multistrand cord according to claim 8 , wherein, in each outer strand, p 1 is equal to p 2 .
12. The multistrand cord according to claim 8 , wherein, in each outer strand, L is equal to 2 and M is equal to 7, 8 or 9.
13. The multistrand cord according to claim 8 , wherein, in each outer strand, L is equal to 3 and M is equal to 8, 9 or 10.
14. The multistrand cord according to claim 8 , wherein, in each outer strand, L is equal to 4 and M is equal to 8, 9, 10 or 11.
15. The multistrand cord according to claim 1 , wherein, in each outer strand, the following relationship applies:
0.7≦ d 1 /d 2 ≦1.3.
16. The multistrand cord according to claim 1 , wherein, in each outer strand, the wires of the outer layer are helically wound with the same pitch and in the same twist direction as the wires of the inner layer.
17. The multistrand cord according to claim 1 , wherein, in each outer strand, the wires of the outer layer are helically wound either with a different pitch, or in a different twist direction, or with both a different pitch and a different twist direction, compared to the wires of the inner layer.
18. The multistrand cord according to claim 1 , wherein, in each outer strand, the outer layer is a saturated layer.
19. The multistrand cord according to claim 1 , wherein J is equal to 1 and K is equal to 5, 6, 7 or 8.
20. The multistrand cord according to claim 1 , wherein J is equal to 3 and K is equal to 8, 9, 10, 11 or 12.
21. The multistrand cord according to claim 1 , wherein, in each outer strand, the rubber of the filling rubber is a diene rubber.
22. The multistrand cord according to claim 21 , wherein, in each outer strand, the diene elastomer of the filling rubber is chosen from the group formed by polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers and the blends of these elastomers.
23. The multistrand cord according to claim 22 , wherein, in each outer strand, the diene elastomer is natural rubber.
24. The multistrand cord according to claim 1 , wherein, in each outer strand, the amount of rubber filling compound is between 5 and 35 mg per g of strand.
25. The multistrand cord according to claim 1 , wherein, in an air permeability test, each outer strand has an average air flow rate of less than 2 cm 3 /min.
26. The multistrand cord according to claim 1 , wherein each of the J strands of the core, J varying from 1 to 4, is itself formed by a two-layer cord of L+M construction that satisfies the characteristics of the K outer strands.
27. The multistrand cord according to claim 26 , wherein each of the J strands of the core, J varying from 1 to 4, has an identical construction to that of the outer strands.
28. The multistrand cord according to claim 26 , wherein each of the J strands of the core, J varying from 1 to 4, has a different construction from that of the K outer strands.
29. The multistrand cord according to claim 26 , comprising in total 6 strands, a central strand forming the core or inner layer and 5 outer strands forming the outer layer, said cord having the 1×(1+6)+5×(3+9) construction.
30. The multistrand cord according to claim 26 , comprising in total 7 strands, a central strand forming the core or inner layer and 6 outer strands forming the outer layer, said cord having the (1+6)×(1+6) or (1+6)×(3+9) construction.
31. The multistrand cord according to claim 1 , wherein, comprising in total 8 strands, a central strand forming the core or inner layer and 7 outer strands forming the outer layer, said cord having the 1×(3+9)+7×(1+6) construction.
32. The multistrand cord according to claim 1 , wherein the core of the cord, which core is formed by the J strands, J varying from 1 to 4, is itself sheathed with the rubber filling compound.
33. A tire comprising a cord according to claim 1 .
34. The multistrand cord according to claim 1 , wherein P K is in the range from 30 to 50 mm.
35. The multistrand according to claim 1 , wherein P 1 lies in the range from 6 to 25 mm.
36. The multistrand cord according to claim 25 , wherein said average air flow rate is less than or at most equal to 0.2 cm 3 /min.