The invention relates to a metallic reinforcing cord (10) for tyres for vehicle wheels, comprising at least two metallic wires (11) twisted together with a predetermined twisting pitch (P). The metallic reinforcing cord (10) has a part load elongation greater than 3%, preferably greater than 3.5%.

The invention relates to a process for manufacturing a metallic reinforcing cord (10) for tyres for vehicle wheels. The process comprises providing at least one elongated element (15) comprising at least one metallic wire (11) twisted together with at least one textile yarn (20) and removing said at least one textile yarn (20) from said at least one elongated element (15) to form the aforementioned metallic reinforcing cord (10). Such a metallic reinforcing cord (10) has a helical geometry, consisting only of said at least one metallic wire (11) that extends along a helical path. The invention also relates to an apparatus (1) for manufacturing the aforementioned metallic reinforcing cord (10).

The method enables the production of a final assembly (A) comprising two layers and comprises a step (100) of providing a temporary assembly (AT) comprising a temporary core (NT), a step (124) of separating the temporary assembly (AT) into a first divided assembly (AFI), a second divided assembly (AF2), a third divided assembly (AF3) and the temporary core (NT). The method comprises a step (135) of reassembling the first divided assembly (AFI), the second divided assembly (AF2) and the third divided assembly (AF3) to form the final assembly (A).

The method allows the manufacture of at least first and second assemblies (26, 28) of M1 filamentary elements and M2 filamentary elements, at least one of the first and second assemblies (26, 28) comprising several filamentary elements (14) wound together in a helix.

The method comprises a step of assembling M filamentary elements (14) together into a layer of the M filamentary elements (14) around a temporary core (16) to form a temporary assembly (22), and a step of splitting the temporary assembly (22) into at least the first and second assemblies (26, 28) of M1 filamentary elements and M2 filamentary elements.

The steel wire for the steel cord of the present invention includes a plating layer of Cu-M-Zn (M is one or two elements of Co, Ni, Cr, Mo, Al, In, or Sn) and has a concentration gradient in which the M content ratio in a region from the surface to ¼ of the plating layer is 40% or more compared with the M content ratio in the entire region of the plating layer, and the steel cord for rubber reinforcement is obtained by a manufacturing method comprising: performing sequential plating on a surface of a steel wire in the order of Cu.fwdarw.M.fwdarw.Zn; performing a primary diffusion, for concentration gradient of M, by subjecting the sequentially plated steel wire to high-frequency induction heating using 1-500 MHz; and performing a secondary diffusion, following the primary diffusion, by medium-frequency induction heating using 10-500 KHz.

A cord (50) comprises a single layer (52) of helically wound metal filamentary elements (54). The metal filamentary elements define an internal enclosure (58) of the cord of diameter Dv. Each metal filamentary element (54) has a diameter Df and a helix radius of curvature Rf. With Dv, Df and Rf being expressed in millimetres, the cord satisfies the following relationships: 9≤Rf/Df≤30 and 1.30≤Dv/Df≤2.10.

The invention relates to a metallic reinforcing cord (10) for tyres for vehicle wheels, comprising from two to ten metallic wires (11) twisted together with a twisting pitch (P) and each having a predetermined diameter. In at least some cross sections of the metallic reinforcing cord (10), at least two of said metallic wires (11) are arranged to a minimum mutual distance greater than, or equal to, 2.5 times the predetermined diameter.

A multi-strand cord (50) having a 1×N structure comprises a single layer (52) of N strands (54) wound in a helix about a main axis (A), each strand (54) having one layer (56) of metal filaments (F1) and comprising M>1 metal filaments wound in a helix about an axis (B). The cord (50) has a total elongation Δt>8.10% and the energy-at-break indicator Er of the cord (50), defined by Er=∫.sub.0.sup.Atσ(Ai)×dAi where σ(Ai) is the tensile stress in MPa measured at the elongation Ai and dAi is the elongation such that Er is strictly greater than 52 MJ/m.sup.3.

A cord (50) comprises a single layer (52) made up of N helically wound metal filamentary elements (54) having an outer diameter D, the metal filamentary elements (54) defining an internal enclosure (58) of the cord of diameter Dv. Each metal filamentary element (54) has a diameter Df and a helix radius of curvature Rf. With this cord (50), D, Dv, Df and Rf being expressed in millimeters: 0.10≤Jr≤0.25, 9≤Rf/Df≤30, and 1.60≤Dv/Df≤3.20, where Jr=N/(π*(D−Df))×(Dh×Sin(π/N)−(Df/Cos(αx π/180))) and α is the helix angle, expressed in degrees, of each metal filamentary element (54).

The method makes it possible to manufacture an assembly (A) comprising a layer (C) of metal filamentary elements (14) wound in a helix. The method comprises a step (100) of supplying a temporary assembly (22) comprising a layer (13) of M′>1 metal filamentary elements (14) and a temporary centre (16), and a step (110) of separating the temporary assembly (22) between a first split assembly (25), a second split assembly (27) and the temporary centre (16). The method comprises a step (140) of reassembling the first split assembly (25) with the second split assembly (27) so as to form the layer (C) of the assembly (A).