Abstract: The column-wheel (1) for a chronograph includes: a ratchet (2) provided with a plurality of teeth (3) the shape of which defines the direction of rotation of the column-wheel; a superstructure coaxial to the wheel and having n>=3 order rotational symmetry, the peripheral part of the superstructure forming n columns (10) parallel to the wheel axis and arranged substantially along the periphery of the ratchet (2), each column including an outer part, the cross-section of which is substantially shaped like a truncated triangle with a base substantially parallel to the circumference of the wheel and a front side (12), called the leading edge, and a back side (13), called the trailing edge, extending from the base towards the interior of the wheel. The column-wheel is characterized in that said cross-section is asymmetrical, a first angle ? between the leading edge (12) and the base (14) being smaller than a second angle ? between the base and the trailing edge (13).

Abstract: The invention relates to a driving member for a timepiece movement, that comprises two superimposed coaxial barrels (1, 11) coupled in series, each barrel including a spring provided in a cylindrical housing rotatingly mounted on a common shaft (20). The respective housings (2, 12) of the barrels are positioned opposite each other and do not include a lid, said springs (7, 17) being separated only by a separation washer (26) or a gap. Preferably, the separation washer (26) is made of a sheet of an anti-friction material and extends between the respective outer drums (4, 14) of the barrel housings. This arrangement can be used for increasing the height (H) of the springs, and thereby the amount of energy and the power reserve of the watch for an identical global volume of the driving member, or for reducing the total height of the driving member. The number of parts is also reduced and the mounting is made easier. Such a driving member is particularly intended for watches with a high power reserve.