Endless belt with improved load carrying cord

1. In an endless belt comprising a belt body of cast urethane and a load carrier cord embedded in said body; said cord comprising a plurality of yarns having a first twist corresponding to a first twist multiplier and a first twist direction, and said cord having a second twist corresponding to a second twist multiplier in a direction opposite said first twist direction; the improvement characterized in that the ratio of said first twist multiplier to said second twist multiplier is greater than about 1.5.

2. The belt of claim 1 wherein said yarns comprise a plurality of fibers, wherein at least half of said fibers comprise an organic fiber selected from the group consisting of aramid, para-aramid, meta-aramid, polyethylene naphthalate, poly(p-phenylene-2,6-benzobisoxazole), liquid crystal polyester-polyarylate, and combinations thereof.

3. The belt of claim 2 selected from a multi-v-ribbed belt, a v-belt, a toothed synchronous belt, and a flat belt.

4. The belt of claim 3 wherein said first twist multiplier is in the range of from about 2 to about 9.

5. The belt of claim 3 wherein said first twist multiplier is in the range of from about 4 to about 6.

6. The belt of claim 3 wherein said second twist multiplier is in the range of from about 0.5 to about 6.

7. The belt of claim 3 wherein said second twist multiplier is greater than about 1.8 and less than about 3.5.

8. A belt drive comprising the belt of claim 3 trained about, at least, one driver pulley and one driven pulley.

9. In an endless multi-v-ribbed belt comprising an elastomeric belt body and a load carrier cord embedded in said body; said cord comprising a plurality of yarns having a first twist corresponding to a first twist multiplier and a first twist direction, and having a second twist corresponding to a second twist multiplier in a direction opposite said first twist direction; the improvement characterized in that the ratio of said first twist multiplier to said second twist multiplier is greater than about 1.5.

10. The belt of claim 9 wherein said yarns comprise a plurality of fibers, wherein at least half of said fibers comprise an organic fiber selected from the group consisting of aramid, para-aramid, meta-aramid, polyethylene naphthalate, poly(p-phenylene-2,6-benzobisoxazole), liquid crystal polyester-polyarylate, and combinations thereof.

11. The belt of claim 10 wherein said cord has adhesive treatment for bonding said fibers together and said cord to said body.

12. The belt of claim 11 wherein said elastomeric belt body comprises an elastomer selected from the group EPDM, HNBR, EPM, EOM, EBM, EBDM, EODM, NBR, PU, CR, NR, SBR, BR, EAM, EVM, silicone, and blends thereof.

13. The belt of claim 12 wherein said first twist multiplier is in the range of from about 2 to about 9.

14. The belt of claim 12 wherein said first twist multiplier is in the range of from about 4 to about 6.

15. The belt of claim 12 wherein said second twist multiplier is in the range of from about 0.5 to about 6.

16. The belt of claim 12 wherein said second twist multiplier is greater than about 1.8 and less than about 3.5.

17. A belt drive comprising the belt of claim 12 trained about, at least, one driver pulley and one driven pulley.

18. A power transmission belt comprising a belt body portion, a sheave contact portion and a load carrying cord embedded in said belt body portion; said load carrying cord comprising a plurality of twisted yarns, and having a first yarn twist corresponding to a first twist multiplier and a second cord twist corresponding to a second twist multiplier; and characterized in that the ratio of said first twist multiplier to said second twist multiplier is in the range of from about 1.5:1 to about 4:1.

19. The power transmission belt of claim 18 wherein said belt is a multi-v-ribbed belt wherein said sheave contact portion comprises a plurality of ribs comprising raised apexes alternating with a plurality of trough areas defining there between oppositely facing sides.

20. The belt of claim 18 wherein said belt body portion comprises an elastomer composition and an adhesive rubber member, and said cord is in contact with at least a portion of said adhesive rubber member.

21. The belt of claim 18 wherein said plurality of twisted yarns are of a material selected from aramid, para-aramid, meta-aramid, polyethylene naphthalate, poly(p-phenylene-2,6-benzobisoxazole), liquid crystal polyester, and combinations thereof.

22. The belt of claim 18 wherein said second twist multiplier is greater than about 1.8 and less than about 3.5.

23. A belt drive comprising the belt of claim 18 trained about at least one driver pulley and one driven pulley.

24. A method for making an endless power transmission belt having improved flex fatigue resistance and comprising a belt body portion and a load carrier cord comprising base yarns of high-modulus organic fibers, said cord embedded in said belt body, comprising the steps:

twisting one or more said base yarns together in a first twist direction with a first twist multiplier to form strands;

twisting one or more said strands together in a second twist direction opposite said first direction with a second twist multiplier to form said cord; and

selecting said first twist multiplier to be at least about 1.5 times said second twist multiplier.

25. The method of claim 24 further comprising the step: selecting for the high-modulus organic fibers at least one material from the group: aramid, para-aramid, meta-aramid, polyethylene naphthalate, poly(p-phenylene-2,6-benzobisoxazole), and liquid crystal polyester.

26. The method of claim 25 further comprising the step: selecting for the belt body an elastomer composition comprising an elastomer selected from EPDM, HNBR, EPM, EOM, EBM, EBDM, EODM, NBR, millable PU, cast PU, CR, NR, SBR, BR, EAM, EVM, silicone, and blends thereof.