Device for the fine adjustment of a balance wheel/hairspring

A fine adjusting device for a sprung balance, formed of a balance provided with poising screws, pivoted between a plate and a balance cock supporting an index, and a balance spring, by means of poising screws and tightening devices provided at the balance cock and the index, wherein the balance cock is provided with a first lug comprising a first device tightening the end of the balance spring, said device being formed by a clamp comprising a fixed arm in the shape of a stirrup extending said lug perpendicularly and in which there is hinged an L-shaped rocking element that can be manoeuvred by a flanged screw, wherein the index is provided with an extension comprising a second device tightening the outer curve of the balance spring, said device being identical to the first and able to be manoeuvred by a flanged screw, and wherein the balance cock is provided with a second lug comprising a third tightening device formed by a screw screwed into said lug through an oblong aperture of an annular extension of the index to lock said index in a determined position, the three screws enabling a fine adjustment to be carried out.