Multi-strand steel cord having a core and peripheral strands surrounding the core

A steel cord having a diameter D and comprising a core strand and up to five peripheral strands surrounding the core strand, the core strand having a diameter D1 and the peripheral strands having a diameter D2, a ratio of the core strand diameter to the peripheral strand diameter D1/D2 being greater than 0.70, each strand comprising a center of one or more center filaments and two or more layers of filaments surrounding the center, all the filaments of each layer having substantially the same diameter, the filament diameter in each layer being smaller than a total diameter of the center of the same strand, the filament diameter in a radially outer layer being smaller than the filament diameter in a radially inner layer of the same strand, a twist angle of a radially outer layer being smaller than a twist angle of a radially inner layer of the same strand, the twist angle of each layer being determined by the diameters and a lay length of the filaments, a first free space ranging from 0.0015.times.D to 0.0075.times.D being provided in at least the core strand between each pair of filaments of the radially most inner layer.

A steel cord having a diameter D and comprising a core strand and up to seven peripheral strands surrounding the core strand, the core strand having a diameter D1 and the peripheral strands having a diameter D2, a ratio of the core strand diameter to the peripheral strand diameter D1/D2 being greater than 1.39, each strand comprising a center of one or more center filaments and two or more layers of filaments surrounding the center, all the filaments of each layer having substantially the same diameter, a twist angle of a radially outer layer being smaller than a twist angle of a radially inner layer of the same strand, the twist angle of each layer being determined by the diameters and a lay length of the filaments, a first free space ranging from 0.0015.times.D to 0.0075.times.D being provided in at least the core strand between each pair of filaments of the radially most inner layer.

A steel cord having a diameter D and comprising a core strand and up to eight peripheral strands surrounding the core strand, the core strand having a diameter D1 and the peripheral strands having a diameter D2, a ratio of the core strand diameter to the peripheral strand diameter D1/D2 being greater than 1.73, each strand comprising a center of one or more center filaments and two or more layers of filaments surrounding the center, all the filaments of each layer having substantially the same diameter, a twist angle of a radially outer layer being smaller than a twist angle of a radially inner layer of the same strand, the twist angle of each layer being determined by the diameters and a lay length of the filaments, a first free space ranging from 0.0015.times.D to 0.0075.times.D being provided in at least the core strand between each pair of filaments of the radially most inner layer.

A steel cord having a diameter D and comprising a core strand and up to nine peripheral strands surrounding the core strand, the core strand having a diameter D1 and the peripheral strands having a diameter D2, the a ratio of the core strand diameter to the peripheral strand diameter D1/D2 being greater than 2.07, each strand comprising a center of one or more center filaments and two or more layers of filaments surrounding the center, all the filaments of each layer having substantially the same diameter, a twist angle of a radially outer layer being smaller than a twist angle of a radially inner layer of the same strand, the twist angle of each layer being determined by the diameters and a lay length of the filaments, a first free space ranging from 0.0015.times.D to 0.0075.times.D being provided in at least the core strand between each pair of filaments of the radially most inner layer.