Open steel cord structure

A steel cord comprising:

• a plurality of first strength elements;
• at least one second strength element, the first and second strength elements each being twisted with a twist pitch into the cord, each of the first and second strength elements having a projection in a plane perpendicular to a longitudinal central axis of the steel cord and taking the form of a two-dimensional curve throughout at least one twist ditch length thereof, as viewed into the longitudinal axis direction,
• wherein the curve of at least the second strength element is convex throughout the at least one twist pitch length, with a radius of curvature thereof varying between a maximum and a minimum so that micro-gaps are formed between the second strength element and the first strength elements adjacent thereto, the micro-gaps being substantially smaller than the twist pitch and enabling rubber penetration.

A steel cord comprising:

• a plurality of filaments, wherein more than half of the filaments are steel, each of the filaments being twisted with a twist pitch to form the cord, each of the filaments having a generally spiral twist, which forms a plurality of projections formed perpendicularly along a longitudinal central axis of the steel cord, the projections of each filament forming a curve throughout at least one twist pitch length thereof, as viewed into the longitudinal axis direction,
• wherein the curve of at least one of the filaments is convex throughout the at least one twist pitch length thereof, with a radius of the curvature thereof varying between a maximum and a minimum taken perpendicularly from the longitudinal axis of the cord so that micro-gaps are formed between the convexly curved filament and other filaments adjacent thereto, the micro-gaps being adapted to allow rubber penetration.