CONTROL MEMBER WITH A BALANCE WHEEL AND A PLANAR SPIRAL FOR A WATCH OR CLOCK MOVEMENT

摘要

A control member with a balance wheel (1) and a planar spiral (2) for a watch or clock movement, wherein the planar spiral (2) includes a rigidified portion (8) on the outer turn (7) thereof whereby deformations of the turns are substantially concentric. Said member is characterised in that the spacing (d) between an end portion of the outer turn (7) and the penultimate turn (9) of the spiral (2) is large enough for said penultimate turn to remain radially free when the spiral (2) expands with an amplitude that can substantially correspond to the maximum angle of rotation of the balance wheel in the movement.