A metallic cord for the reinforcement of elastomers

Abstract: The present invention relates to a metallic cord (1) for the reinforcement of elastomers. The cord has seven strands (30,32,34,36,38,40,42) of two filaments (2,4; 6,8; 10,12; 14,16; 18,20; 22,24; 26,28) wherein one strand (30) is surrounded by six strands and the six strands are twisted in the same direction and have the same lay length.

Description: Background of the Invention While the invention is subject to a wide range of applications, it particularly relates to metal cord, such as that used to reinforce elastomers. More particularly, the present invention is directed to a metallic cord construction used to reinforce rubber articles, including pneumatic tires. It is known to manufacture metal cords from a plurality of filaments having the same diameter twisted together in the same direction and having the same lay length. The cord is said to have a compact cross-section which is generally the same over the length of the cord. The filaments in the cross-section are arranged in concentric layers in which the filaments are tangential to all the filaments surrounding an individual filament. The single operation produces a cord having a single, compact strand. The single strand, compact cord has the advantages of a reduced cord diameter. These advantages include: (1) a calendared ply having a reduced thickness and, therefore, requiring less calendar rubber; (2) a potential increase in the ends per inch for a given width of ply; and (3) an increased ply strength resulting from an increase in the ends per inch. The uniform cross-section is thought to more uniformly distribute the load carried by the cord to each individual filaments. The result is a higher breaking load. Further, the cord is thought to have improved fatigue resistance and greater flexibility. In a conventional pneumatic radial tire using metal cords, as described above for reinforcement, the fatigue properties of the carcass ply and belt layer are degraded, mainly by material fatigue due to repeated strain and fretting wear in the contact portion between adjacent filaments. Both of these problems are said to be alleviated by penetration of rubber into the inside of the cord. The rubber layer interposed between the steel filaments is believed to prevent rubbing between adjacent filaments, the so-called "fretting wear." Research disclosure, no.340, 1 August 1992, pages 624-633, XP000324123 "High tensile strength steel cord construction for tyres" discloses a multitude of cord constructions for reinforcing pneumatic tires, hoses or belts and more specifically layered cord constructions such as 2x0.35 + 5x0.35 and 2x0.22 + 7x0.22 + 0.15, the lay direction being respectively SS or SZ and SSZ. EP-A- 781 883, published on 2 July 1997 and therefore relevant only for assessing novelty under Article 54(3) EPC, and which is considered closest prior art, discloses a steel cord for reinforcing rubber products, and more specifically a steel cord of 7 strands of two filaments that are paired substantially parallel to each other. The invention has as object to provide a cord with improved rubber penetration into the inside of the cord. The improved rubber penetration will also provide the cord with higher corrosion resistance should the cord be exposed to moisture. Summary of the Invention The present invention relates to a metallic cord for the reinforcement of elastomers and to an article including such cord, as defined in the appended claims. Brief Description of the Drawings Figure 1 is a cross-sectional view of a steel cord having a construction of the present invention; Figure 2 is a cross-sectional view of a steel cord having a construction of the present invention; Figure 3 is a cross-sectional view of a steel cord having a construction of the present invention; and Figure 4 is a cross-sectional view of a steel cord having a construction of the present invention. Detailed Description of the Preferred Embodiment The present invention will be explained in more detail referring to the accompanying drawings. In Figures 1-4, there is illustrated a metallic cord 1 for reinforcing elastomers comprising seven strands, 30,32,34,36,38,40,42. Cords may be known by different nomenclatures. For example, the cord of the present invention may be called 1x2+6x2, 2+6x2 or 7x2. Each strand consists of two filaments, 2 and 4, 6 and 8, 10 and 12, 14 and 16, 18 and 20, 22 and 24, and 26 and 28. One strand 30 is surrounded by the remaining six strands, 32,34,36,38,40,42. The term "lay length" as used in connection with a strand is the distance along the length of the strand in which the filament makes a complete 360° revolution around the outside of the strand. The lay length of the strand or each filament relative to each other in the same strand may range from 2 to 18 mm. Preferably, the lay length ranges from 4 to 12 mm. The lay length of the one strand 30 may have the same length as the other six strands 32,34,36,38,40,42 or the lay lengths may be different. In all cases, the lay length of the surrounding six strands 32,34,36,38,40,42 are the same. All six of the surrounding strands 32,34,36,38,40,42 are twisted in the same direction, relative to each other. The center strand 30 may be twisted in the same direction as the other six strands 32,34,36,38,40,42 or may be in the opposite direction as the surrounding six strands in the cord. The diameter of a filament 2 may vary, depending on the intended use of the cord 1. The diameter of the filament 2 may range from .10 to .50 mm. Preferably, the diameter of the filament 2 ranges from .15 to .35 mm. The tensile strength of each filament should be at least 3040 MPa -(1200 × D) where D is the diameter of the filament. Preferably, the tensile strength of each filament ranges from 3040 MPa -(1200 × D) to 4400 MPa - (2000 × D). After each of the seven strands 30,32,34,36,40,42 have been prepared, the strands 30,32,39,36,40,42 are twisted to form the cord 1 of the present invention. The one strand 30 is in the center with the remaining six strands 32,34,36,38,40,42 being twisted around the center strand 30. As used in connection with the cord, the term lay length means the distance along the length of the cord for one of the surrounding six strands 32,34,36,38,40,42 to make a complete 360° revolution around the outside of the cord 1. The lay length of the cord 1 ranges from 3 to 25 mm. Preferably, the lay length of the cord 1 ranges from 5 to 20 mm. The helix angle of the cord will generally range from 80° to 86°. Preferably, the helix angle ranges from 82° to 84°. The cord 1 of the present invention may optionally have a spiral wrap (not shown). The spiral wrap may have a diameter from .1 to .3 mm. Preferably, the diameter is .15 mm. The lay direction of the spiral wrap is generally in the opposite direction and the cord lay direction with the lay length ranging from 3 to 7 mm. Preferably, the lay length of the spiral wrap is 5 mm. The intended use of the cord of the present invention is in a rubber-reinforced article. Such articles will incorporate the cord of the present invention and impregnated with rubber as known to those skilled in the art. Representative of articles may use the cord of the present invention include belts, tires and hoses. In the most preferred application, the cord of the present invention is used in a belt ply of a pneumatic tire or the carcass ply of a pneumatic tire.

Claims: A metallic cord for the reinforcement of elastomers having a first strand (30) of two filaments (2, 4) surrounded by six strands (32, 34, 36, 38, 40, 42) of two filaments (6,8; 10,12; 14,16; 18,20; 22,24; 26,28) wherein the two filaments in each of said six strands are twisted in the same direction and have the same lay length in the cord, the cord having optionally a spiral wrap. The cord of claim 1 characterized in that the first strand (30) has a different lay length than the surrounding six strands (32,34,36,38,40,42) . The cord of claim 1 characterized in that the first strand (30) has the same lay length as the surrounding six strands (32,34,36,38,40,42) . The cord of any preceding claim characterized in that the lay length of each of the six strands (32,34,36,38,40,42) range from 2 to 18 mm. The cord of any preceding claim characterized in that the lay length of the first strand (30) ranges from 2 to 18 mm. The cord of any preceding claim characterized in that the first strand (30) is twisted in the same direction as the surrounding six strands (32,34,36,38,40,42) . The cord of any of claims 1-5 characterized in that the first strand (30) is twisted in an opposite direction as the surrounding six strands (32,34,36,38,40,42) in the cord. The cord of any preceding claim characterized in that the diameter of each filament (2,4; 6,8; 10,12; 14,16; 18,20; 22,24; 26,28) ranges from .1 to .5 mm. The cord of any preceding claim characterized in that the tensile strength of each filament is at least 3040 MPa -(1200×D) where D is the diameter of the filament. The cord of any preceding claim characterized in that the tensile strength of each filament ranges from 3040 MPa -(1200 × D) to 4400 MPa - (2000 × D) . The cord of any preceding claim characterized in that said cord (1) is impregnated with rubber. The cord of any preceding claim characterized by having a spiral wrap. The cord of claim 12 characterized in that the diameter of the spiral wrap is from .1 to .3 mm. The cord of claim 13 characterized in that the lay direction of the spiral wrap is in the opposite direction to the cord lay direction. An article characterized by at least the cord of claim 1. The article of claim 15 characterized in that said article is selected from the group consisting of belts, tires and hoses. The article of claims 15 or 16 characterized in that said article is a pneumatic tire. The article of claim 17 characterized in that said cord is used in a belt ply of said pneumatic tire. The article of claim 17 characterized in that said cord is used in the carcass ply of said pneumatic tire.

Inventors: MACKLIN ADAM RICHARD, SINOPOLI ITALO MARZIALE, MACKLIN, ADAM RICHARD, SINOPOLI, ITALO MARZIALE
Applicants: GOODYEAR TIRE & RUBBER, THE GOODYEAR TIRE & RUBBER COMPANY
Application year: 1997
Main classification: B60C9
IPC codes: B60C9, D07B1