Timepiece with a mechanical oscillator

1. A sprung balance type mechanical timekeeper including:

a spiral spring ( 10 ),

a balance ( 20 ),

an escapement mechanism ( 30 ) connected to the spiral spring ( 10 ) and arranged to sustain an oscillation of the balance ( 20 ), wherein the escapement mechanism ( 30 ) is connected to the spiral spring ( 10 ) by a chassis ( 40 ) pivoted about an axis (A) of the balance ( 20 ), an outer end ( 12 ) of the spiral spring ( 10 ) being attached to this chassis ( 40 ) at a location on one side of the axis (A), and

an escape wheel ( 32 ),

wherein the escapement mechanism ( 30 ) includes a detent-type escape lever ( 36 , 37 , 38 , 39 ) that is located on another side of the axis (A) of the balance ( 20 ) and acts on the chassis ( 40 ) so as to make the chassis ( 40 ) rotate and thus make the outer end ( 12 ) of the spiral spring ( 10 ) rotate,

wherein the balance ( 20 ) is mounted on, and coaxial with, a fixed ring gear ( 22 ), and the chassis ( 40 ) carries, at said another side of the axis (A), a planet wheel ( 42 ) which is engaged with said ring gear ( 22 ) and which is driven in a stepped manner by the escapement mechanism ( 30 ),

wherein the escape wheel ( 32 ) is coaxial with and secured to the planet wheel ( 42 ), and the detent-type escape lever ( 36 , 37 , 38 , 39 ) pivots between a rest position engaged with the escape wheel ( 32 ) and a position cleared off the escape wheel ( 32 ), and

wherein the outer end ( 12 ) of the spiral spring ( 10 ) is attached to the chassis ( 40 ) by a stud ( 14 ) which extends vertically between a plane of the chassis ( 40 ) and a plane of the spiral spring ( 10 ), the plane of the spiral spring ( 10 ) being disposed between the plane of the chassis ( 40 ) and the balance ( 20 ),

wherein a sum of inertia of the escape wheel ( 32 ) and inertia of the chassis ( 40 ) is selected so that a direct impulse of a tooth ( 52 ) of the escape wheel ( 32 ) on an additional pin ( 48 ) occurs when a passage speed of the balance ( 20 ) is low, that is to say when an oscillation amplitude of the balance ( 20 ) is low.

2. The timekeeper according to claim 1 , wherein the chassis ( 40 ) includes several branches extending on either side of a disk ( 44 ) coaxial with the balance ( 20 ) and forming with the chassis ( 40 ) a rotary plate whose axis of rotation is coincident with an axis of oscillation of the balance ( 20 ).

3. The timekeeper according to claim 2 , wherein the planet pinion ( 42 ) and the chassis ( 40 ) are arranged so as to be driven in rotation by a chassis pinion ( 45 ), said planet pinion ( 42 ) being retained in rotation by blockage of the escape wheel ( 32 ) by the escapement mechanism ( 30 ), rotation of the escape wheel ( 32 ) being performed once for each oscillation cycle of the balance ( 20 ), when the balance ( 20 ) releases the escape lever ( 36 , 37 , 38 , 39 ), so that the rotary plate performs a rotation, whose amplitude depends on a ratio of number of teeth of different wheels of the timekeeper, the rotation of the rotary plate causing a displacement of the stud ( 14 ) to ensure or contribute in sustainment of the oscillation amplitude of the balance ( 20 ).

4. The timekeeper according to claim 3 , wherein an arm of the escape lever ( 36 , 37 38 39 ), pushed by the escape wheel ( 32 ), is extended so that the escape lever ( 36 , 37 , 38 , 39 ) also acts on an impulse pin ( 24 ), the energy transmitted to the balance ( 20 ) to sustain the oscillation amplitude then being distributed between a displacement of the stud ( 14 ) and impulse of an extended arm of the escape lever ( 36 , 37 , 38 , 39 ).

5. The timekeeper according to claim 3 , wherein the chassis pinion ( 45 ) is arranged so as to perform a rotation ensuring counting of oscillations cycles performed by the balance ( 20 ).

6. The timekeeper according to claim 1 , wherein the escape lever ( 36 , 37 , 38 , 39 ) includes a short inner arm ( 36 ) provided with an engagement tooth ( 37 ) which is engaged with the escape wheel ( 32 ), and a long outer arm ( 38 ) located in a path of an impulse element ( 24 ) secured in oscillation with the balance ( 20 ), wherein the impulse element ( 24 ) is brought, during the oscillation of the balance ( 20 ), to displace the escape lever ( 36 , 37 , 38 , 39 ) from the rest position towards the position cleared off the escape wheel ( 32 ).

7. The timekeeper according to claim 1 , wherein the escape lever ( 36 , 37 , 38 , 39 ) is pivotally mounted at an outer end of an arm ( 39 ) which extends, coplanar with the chassis ( 40 ), outwardly from an axis of the planet wheel ( 42 ) and of the escape wheel ( 32 ).

8. The timekeeper according to claim 1 , wherein impulses by displacement of a point of attachment of the stud ( 14 ) to the chassis ( 40 ) take place regardless of the oscillation amplitude the balance ( 20 ).

9. The timekeeper according to claim 1 , wherein the escape wheel ( 32 ) has teeth ( 52 ) and a clearance plane ( 50 ) on its teeth ( 52 ) interacting with a short arm ( 36 ) of the detent mechanism ( 30 ), said clearance plane ( 50 ) preventing a too rapid return of the escape lever ( 36 , 37 , 38 , 39 ) after a release thereof.

10. The timekeeper according to claim 1 , wherein the escape wheel ( 32 ) is provided with a clearance plane ( 50 ) such that the escape lever ( 36 , 37 , 38 , 39 ) remains held in a passing position when the balance ( 20 ) is cleared, the clearance of the balance ( 20 ) being guaranteed by an interaction between a tooth of the escape wheel ( 52 ) and the additional pin ( 48 ).

11. The timekeeper according to claim 10 , wherein during passage of the balance ( 20 ) in a direction of clearance of the escape lever ( 36 , 37 , 38 , 39 ), the balance ( 20 ) makes the escape lever ( 36 , 37 , 38 , 39 ) pivot through the pin ( 48 ), a beak of the tooth of the escape wheel ( 52 ) leaving a rest plane of the escape lever ( 36 , 37 , 38 , 39 ) to lie on an inclined plane ( 54 ) of the escape lever ( 36 , 37 , 38 , 39 ) and make the latter pivot so as to let the balance ( 20 ) pass.

12. A timepiece, selected from a wristwatch, a table pendulum or a wall pendulum, including the timekeeper according to claim 1 .