A method for manufacturing a straight steel monofilament for the reinforcement of belt ply of a pneumatic tyre, where the arc-height of the straight steel monofilament is less than 30 mm. The steel monofilament is plastically deformed by a twisting along the axis of the steel monofilament on a double-twist apparatus. The plastic twist deformation eliminates the surface stress difference on the steel monofilament and provides a strainght steel monofilament for belt ply reinforcement. This provides a simple solution with existing apparatus to manufacture straight steel monofilament suitable for tire reinforcement with high speed for mass production.

An apparatus for producing an assembly of filamentary elements that are wound together in a helix includes a twisting device, a preforming device, and an assembling device. The twisting device is structured to twist at least first and second filamentary elements individually, such that each filamentary element is twisted separately from another filamentary element, to produce at least first and second twisted filamentary elements. The preforming device, which is arranged downstream of the twisting device, is structured to preform each of the twisted filamentary elements individually into separate preformed helixes, to produce at least first and second preformed helixes. The assembling device, which is arranged downstream of the preforming device, is structured to assemble the preformed helixes into an assembly.

A steel cord and a manufacturing process are disclosed. The steel cord includes a steel core wire located in the center and having a diameter of d; and M sheath-layer steel wires arranged around the steel core wire in the center, tangent to the steel core wire, and having a diameter of d1, at least two gaps L existing between the M sheath-layer steel wires, where M is 4; d, d1, and L satisfy the following relationship: 0.420<(d/d1)<0.800, d1 is between 0.20 mm and 0.44 mm, and L0.0008 mm. The steel cord of the present invention may allow rubber to be fully penetrated into the gaps, thereby reducing air content in the steel cord, avoiding point contact friction between the layers of steel wires due to insufficient rubber penetration, and further solving the problem of failure of the bearing capacity of the steel cord due to abrasion.

A method for manufacturing a straight steel monofilament for the reinforcement of belt ply of a pneumatic tyre, where the arc-height of the straight steel monofilament is less than 30 mm. The steel monofilament is plastically deformed by a twisting along the axis of the steel monofilament on a double-twist apparatus. The plastic twist deformation eliminates the surface stress difference on the steel monofilament and provides a straight steel monofilament for belt ply reinforcement. This provides a simple solution with existing apparatus to manufacture straight steel monofilament suitable for tire reinforcement with high speed for mass production.

In a tire the strength of steel cord and the resilience of rubber are a successful combination. However, in some specific areas of a tire, more elongation is expected from the steel cord, while still a sufficient degree of stiffness is expected. A steel cord is presented that has these properties. The steel cord comprises two or more steel elements that are twisted together. The steel elements comprise one or more steel filaments. In total the steel cord comprises N filaments, each with a cross sectional area A. When the steel elements are individualised out of the steel cord they show a helix pitch length of L.sub.o, while a single pitch has a centre line length of S. The inventive steel cord shows a P value of at least 50 newton, wherein P=NE (A/S).sup.2. Further methods are presented to produce this steel cord.

An apparatus for producing an assembly of filamentary elements that are wound together in a helix includes a twisting device, a preforming device, and an assembling device. The twisting device is structured to twist at least first and second filamentary elements individually, such that each filamentary element is twisted separately from another filamentary element, to produce at least first and second twisted filamentary elements. The preforming device, which is arranged downstream of the twisting device, is structured to preform each of the twisted filamentary elements individually into separate preformed helixes, to produce at least first and second preformed helixes. The assembling device, which is arranged downstream of the preforming device, is structured to assemble the preformed helixes into an assembly.

A metal cord has an M+N construction with two concentric layers. An internal first layer or core includes M wire(s) of diameter d.sub.1, M having a value from 1 to 4. An external second layer includes N wires of diameter d.sub.2 and is positioned around the core, the N wires being wound in a helix. Between the wires of the two layers are gaps, some or all of which include a filling rubber based on an unsaturated thermoplastic elastomer. The filling rubber may be, for example, based on an SBS or an SIS block copolymer. When used in a molten state, the thermoplastic elastomer presents no problem due to unwanted stickiness if the filling rubber overspills outside the cord after manufacture. The unsaturated and therefore (co)vulcanizable nature of the thermoplastic elastomer makes it compatible with diene rubber matrices used as calendering rubber in metal fabrics intended for reinforcing tires.

A method of manufacturing a metal cord with two concentric layers of wires is provided. The cord includes an internal layer of M wires, M having a value from 1 to 4, and an external layer of N wires. The cord is rubberized from within in situ. That is, during manufacture of the cord, the cord is rubberized from inside. According to the method, the internal layer is sheathed with rubber or a rubber compound by passing the internal layer through an extrusion head, and the N wires of the external layer are assembled around the sheathed internal layer to form a two-layer cord rubberized from the inside. The rubber is an unsaturated thermoplastic elastomer that is extruded in a molten state, and preferably is a thermoplastic styrene (TPS) type of thermoplastic elastomer, such as an SBS or an SIS block copolymer, for example.

A steel cord and a manufacturing process are disclosed. The steel cord includes a steel core wire located in the center and having a diameter of d; and M sheath-layer steel wires arranged around the steel core wire in the center, tangent to the steel core wire, and having a diameter of d1, at least two gaps L existing between the M sheath-layer steel wires, where M is 4; d, d1, and L satisfy the following relationship: 0.420<(d/d1)<0.800, d1 is between 0.20 mm and 0.44 mm, and L0.0008 mm. The steel cord of the present invention may allow rubber to be fully penetrated into the gaps, thereby reducing air content in the steel cord, avoiding point contact friction between the layers of steel wires due to insufficient rubber penetration, and further solving the problem of failure of the bearing capacity of the steel cord due to abrasion.