Mechanical horological movement comprising a magnetically-pivoted balance

A mechanism comprising a rotary element and a magnetic device for guiding said rotary element in rotation, said magnetic device being arranged so as to exert a radial magnetic biasing force on the rotary element when a central axis of said rotary element undergoes a radial movement relative to an axis of rotation which is predefined for the rotary element in the mechanism;

• wherein the magnetic device comprises a pair of annular magnets the first annular magnet of which is carried by the rotary element, so that its centre remains coincident with said central axis, and the second annular magnet is carried by a structure of the mechanism so that its centre remains coincident with said axis of rotation;
• and wherein the second annular magnet is parallel and at least partially axially superimposed with the first annular magnet when the central axis of the rotary element is coincident with the axis of rotation, the first and second annular magnets being arranged in magnetic attraction so as to impart on one another a first axial magnetic force and, substantially as soon as the central axis of the rotary element deviates radially from the axis of rotation, a first radial magnetic force,
• wherein the magnetic device further comprises at least one first end magnet which is axially arranged opposite a first end of a shaft of the rotary element, said shaft being formed at least partially by a soft ferromagnetic material or a magnetic material so that the first end magnet exerts a second axial magnetic force, which should be magnetically-attractive and with the same direction as the first axial magnetic force and, when the central axis of the rotary element is radially remote from the axis of rotation, also a second radial magnetic force on said shaft,
• wherein the first annular magnet has, on the side of the second annular magnet, a first plurality of annular magnetised areas having alternate polarities and the second annular magnet has, on the side of the first annular magnet, a second plurality of annular magnetised areas having alternate polarities, at least two annular magnetised areas of the first plurality being, when the central axis of the rotary element is coincident with the axis of rotation, substantially entirely axially superimposed with two respective annular magnetised areas of the second plurality and in magnetic attraction with these two respective annular areas, and
• wherein the first annular magnet comprises N annular magnetised areas, N being greater than 1, and the second annular magnet comprises N+1 annular magnetised areas, the N annular magnetised areas of the first annular magnet being, when the central axis of the rotary element is coincident with the axis of rotation, respectively axially superimposed with N annular magnetised areas, including an internal area, of the second annular magnet, the second plurality of annular magnetised areas comprising an external area which extends radially beyond the first annular magnet.

A mechanism comprising a rotary element and a magnetic device for guiding said rotary element in rotation, said magnetic device being arranged so as to exert a radial magnetic biasing force on the rotary element when a central axis of said rotary element undergoes a radial movement relative to an axis of rotation which is predefined for the rotary element in the mechanism;

• wherein the magnetic device comprises a pair of annular magnets the first annular magnet of which is carried by the rotary element, so that its centre remains coincident with said central axis, and the second annular magnet is carried by a structure of the mechanism so that its centre remains coincident with said axis of rotation;
• and wherein the second annular magnet is parallel and at least partially axially superimposed with the first annular magnet when the central axis of the rotary element is coincident with the axis of rotation, the first and second annular magnets being arranged in magnetic attraction so as to impart on one another a first axial magnetic force and, substantially as soon as the central axis of the rotary element deviates radially from the axis of rotation, a first radial magnetic force,
• wherein the magnetic device further comprises at least one first end magnet which is axially arranged opposite a first end of a shaft of the rotary element, said shaft being formed at least partially by a soft ferromagnetic material or a magnetic material so that the first end magnet exerts a second axial magnetic force, which should be magnetically-attractive and with the same direction as the first axial magnetic force and, when the central axis of the rotary element is radially remote from the axis of rotation, also a second radial magnetic force on said shaft,
• wherein the first annular magnet has, on the side of the second annular magnet, a first plurality of annular magnetised areas having alternate polarities and the second annular magnet has, on the side of the first annular magnet, a second plurality of annular magnetised areas having alternate polarities, at least two annular magnetised areas of the first plurality being, when the central axis of the rotary element is coincident with the axis of rotation, substantially entirely axially superimposed with two respective annular magnetised areas of the second plurality and in magnetic attraction with these two respective annular areas, and
• wherein the first annular magnet comprises N annular magnetised areas, N being greater than 1, and the second annular magnet comprises N+2 annular magnetised areas, the N annular magnetised areas of the first annular magnet being, when the central axis of the rotary element is coincident with the axis of rotation, respectively axially superimposed with N inner annular magnetised areas of the second annular magnet which are located between an external area and an internal area of the second plurality of annular magnetised areas, these internal and external areas extending radially respectively from both sides of the first annular magnet.