A hollow stranded wire (2) has a first layers (4) and second layers (6). The second layer is located outside the first layer. The first layer is formed by twisting eight first element wires (8) which are flat wires. The second layer is formed by twisting eight second element wires (10) which are flat wires. A ratio (Ww/Tw) of a width Ww to a thickness Tw of each flat wire is from 2 to 11. A twisting direction of the second element wires is opposite that of the first element wires. A twisting angle of each first element wire is not greater than 85°. A twisting angle of each second element wire is not greater than 85°. A ratio (D/T) of an average diameter D to a thickness T of the hollow stranded wire is not less than 5 and not greater than 20.

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).

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.

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).

The invention provides a steel cord with a construction of n×1, n is the number of the steel filaments of the steel cord, the steel cord has an elongation at 2.5N-50N of less than 1.2% and a twist pitch of greater than 16 mm, each of the steel filaments has a form of helical wave with a wave length L expressed in mm and a wave height H expressed in mm when being unravelled from said steel cord, L is greater than 16 mm, each of the steel filaments has a space volume Vs satisfying that, Vs=L×H.sup.2×π/4, and Vs>20 mm.sup.3. The invention steel cord is beneficial for the stress distribution.

The subject of the invention is a cord (50) comprising 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.

A hollow stranded wire (2) has a first layers (4) and second layers (6). The second layer is located outside the first layer. The first layer is formed by twisting eight first element wires (8) which are flat wires. The second layer is formed by twisting eight second element wires (10) which are flat wires. A ratio (Ww/Tw) of a width Ww to a thickness Tw of each flat wire is from 2 to 11. A twisting direction of the second element wires is opposite that of the first element wires. A twisting angle of each first element wire is not greater than 85. A twisting angle of each second element wire is not greater than 85. A ratio (D/T) of an average diameter D to a thickness T of the hollow stranded wire is not less than 5 and not greater than 20.

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.