[Object] A hollow stranded wire line, for manipulation, having an excellent torque transmittability is provided. [Solution] A hollow stranded wire line 2 for manipulation is a hollow stranded wire line 2 that is advantageously used as a stranded wire line for manipulation in a medical instrument, and a side wire 4 or a side strand which is an outermost layer has a forming rate that is greater than 100% and not greater than 110%. The side wire 4 or the side strand having been formed has a spiral shape in which a flatness that is an aspect ratio obtained by a major axis being divided by a minor axis is preferably not less than 1.01 and preferably not greater than 1.10.

A cord of a band of a tire has a single-stranded structure in which steel filaments are stranded, and the number of the filaments is not less than three and not greater than six. In a cross-section of the cord, when represents a diameter of a smallest circle that surrounds cross-sections of the filaments, and represents a diameter of each filament, a gap is formed between the filaments such that the diameter is not less than three times the diameter and not greater than six times the diameter in the case of the number of the filaments being three or four. An initial elongation of the cord is not less than 0.1% and not greater than 1.5%.

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) 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/(?*(D?Df))?(Dh?Sin(?/N)?(Df/Cos(???/180))) and ? is the helix angle, expressed in degrees, of each metal filamentary element (54).

A torque coil (two-layer coil structure) of the disclosed embodiments includes an inner coil formed by spirally winding metal wire, and an outer coil arranged to be in close contact with the outer periphery of the inner coil and formed by spirally winding metal wire. A winding direction of the inner coil and a winding direction of the outer coil are opposite from each other, and when the torque coil is twisted in the circumferential direction in which the diameter of the inner coil is increased, a change amount of the diameter of the outer coil is larger than a change amount of the diameter of the inner coil. The two-layer coil structure has high twisting rigidity, thus suppressing the occurrence of kinks due to rotational resistance.

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.

[Object] A hollow stranded wire line, for manipulation, having an excellent torque transmittability is provided.

[Solution] A hollow stranded wire line 2 for manipulation is a hollow stranded wire line 2 that is advantageously used as a stranded wire line for manipulation in a medical instrument, and a side wire 4 or a side strand which is an outermost layer has a forming rate that is greater than 100% and not greater than 110%. The side wire 4 or the side strand having been formed has a spiral shape in which a flatness that is an aspect ratio obtained by a major axis being divided by a minor axis is preferably not less than 1.01 and preferably not greater than 1.10.

A multi-strand cord (50) having a 1N 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 At>8.10% and the energy-at-break indicator Er of the cord (50), defined by Er=.sub.0.sup.At(Ai)dAi where (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.

The invention provides a steel cord with a construction of n1, 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=LH.sup.2/4, and Vs>20 mm.sup.3. The invention steel cord is beneficial for the stress distribution.