Patent ID: 8920021

Claim:
A column-wheel for a three stroke chronograph mechanism, comprising: a ratchet provided with 3*n teeth, where n is equal to or greater than 4; a central hub; and a superstructure coaxial to the column-wheel and exhibiting n-fold rotational symmetry, the superstructure comprising n radial arms and n columns parallel to an axis of rotation of the column-wheel, the columns being regularly distributed along the circumference of the column-wheel and separated from each other by n empty spaces forming as many openings between the columns, each column including an external face and an internal face connected to each other by a leading edge and by a trailing edge, the external face having a rounded shape concentrically to the axis of rotation of the column-wheel, and the internal face being connected to the hub by a radial arm, wherein a width of the columns measured between the leading edge and the trailing edge is larger than a width of the openings between the columns, and wherein a width of the arms at a narrowest point thereof is less than half the width of the columns, wherein a height of the hub and the arms is comprised between 20 and 60% of a height of the columns, wherein in a transverse section, the internal face of the columns has a convex shape in a part of the columns that exceeds the height of the arms, a radius of curvature of the internal face being larger in an area of the trailing edge than in an area of the leading edge, wherein an angle formed by the internal face of one column with the external face in the area of the leading edge is comprised between 55° and 65° , and wherein an angle formed by the internal face of one column with the external face in the area of the trailing edge is comprised between 25° and 35° .