Impact-proof timepiece escapement

1. A timepiece escapement having an escapement wheel ( 1 ) and an anchor ( 2 ), the anchor ( 2 ) comprising an entry pallet ( 6 ) and an exit pallet ( 7 ) cooperating with teeth ( 8 ) on the escapement wheel ( 1 ), each of the entry and exit pallets ( 6 , 7 ) having a back side ( 9 ), an impulse beak ( 10 ), an impulse face ( 11 ) and a lock face ( 12 ), the anchor ( 2 ) and/or the escapement wheel ( 1 ) comprising means ( 17 , 18 ) for limiting the oscillations of the anchor ( 2 ) during normal operation of the escapement to a range of displacement defined by an entry lock position where the entry pallet ( 6 ) blocks the escapement wheel ( 1 ) and by an exit lock position where the exit pallet ( 7 ) blocks the escapement wheel ( 1 ), wherein the escapement wheel ( 1 ) comprises, at a periphery, protrusions ( 20 , 21 , 22 ) arranged so that:

upon an impact having the effect of causing the anchor ( 2 ) to leave the said range of displacement in a first direction (F 3 ), the impulse face ( 11 ) and the back side ( 9 ) of the entry pallet ( 6 ) can come into abutment on two ( 20 , 21 ) of the protrusions ( 20 , 21 , 22 ) respectively and thus stop the anchor ( 2 ), without contact between the impulse beak ( 10 ) of the entry pallet ( 6 ) and the escapement wheel ( 1 ),

and/or so that

upon an impact having the effect of causing the anchor ( 2 ) to leave the said range of displacement in a second direction (F 4 ), the impulse face ( 11 ) and the back side ( 9 ) of the exit pallet ( 7 ) can come into abutment on two ( 22 , 20 ) of the protrusions ( 20 , 21 , 22 ) respectively and thus stop the anchor ( 2 ), without contact between the impulse beak ( 10 ) of the exit pallet ( 7 ) and the escapement wheel ( 1 ).

2. The escapement as claimed in claim 1 , wherein said protrusions ( 20 , 21 , 22 ) comprise first protrusions ( 20 ) located between the teeth ( 8 ) of the escapement wheel ( 1 ) and each being able to serve as an abutment for the impulse face ( 11 ) of the entry pallet ( 6 ) in the event of an impact having the effect of causing the anchor ( 2 ) to leave the said range of displacement in the first direction (F 3 ), and to serve as an abutment for the back side ( 9 ) of the exit pallet ( 7 ) in the event of an impact having the effect of causing the anchor ( 2 ) to leave the said range of displacement in the second direction (F 4 ).

3. The escapement as claimed in claim 2 , wherein said protrusions ( 20 , 21 , 22 ) comprise second protrusions ( 21 ) located on the rear flanks of the teeth ( 8 ) of the escapement wheel ( 1 ) or between the said teeth ( 8 ) and each being able to serve as an abutment for the back side ( 9 ) of the entry pallet ( 6 ) in the event of an impact having the effect of causing the anchor ( 2 ) to leave the said range of displacement in the first direction (F 3 ).

4. The escapement as claimed in claim 1 , wherein said protrusions ( 20 , 21 , 22 ) comprise second protrusions ( 21 ) located on the rear flanks of the teeth ( 8 ) of the escapement wheel ( 1 ) or between the said teeth ( 8 ) and each being able to serve as an abutment for the back side ( 9 ) of the entry pallet ( 6 ) in the event of an impact having the effect of causing the anchor ( 2 ) to leave the said range of displacement in the first direction (F 3 ).

5. The escapement as claimed in claim 1 wherein said protrusions ( 20 , 21 , 22 ) comprise third protrusions ( 22 ) located on the front flanks of the teeth ( 8 ) of the escapement wheel ( 1 ) or between the said teeth ( 8 ) and each being able to serve as an abutment for the impulse face ( 11 ) of the exit pallet ( 7 ) in the event of an impact having the effect of causing the anchor ( 2 ) to leave the said range of displacement in the second direction (F 4 ).

6. The escapement as claimed in claim 1 , wherein said protrusions ( 20 , 21 , 22 ) are rounded.

7. The escapement as claimed in claim 1 , wherein said means for limiting the oscillations of the anchor ( 2 ) comprise a corner defined by the lock face ( 12 ) of the entry pallet and/or of the exit pallet ( 6 , 7 ) and with which a lock beak ( 19 ) of the teeth ( 8 ) of the escapement wheel ( 1 ) can cooperate.

8. The escapement as claimed in claim 7 , wherein the corner is defined by a return plane ( 18 ) and by a lock plane ( 17 ) which are formed on the lock face ( 12 ) of the entry pallet and/or of the exit pallet ( 6 , 7 ), and wherein said protrusions ( 20 , 21 , 22 ) are arranged so that:

after an impact having the effect of causing the anchor ( 2 ) to leave the said range of displacement in the first direction (F 3 ) as far as the said stopping of the anchor ( 2 ), one ( 20 ) of the said two protrusions ( 20 , 21 ) can push the anchor ( 2 ) towards its entry lock position until cooperation between the lock beak ( 19 ) of a tooth ( 8 ) of the escapement wheel ( 1 ) and the return plane ( 18 ) of the entry pallet ( 6 ) finishes returning the anchor ( 2 ) to its entry lock position under the action of the rotation of the escapement wheel ( 1 );

and/or so that:

after an impact having the effect of causing the anchor ( 2 ) to leave the said range of displacement in the second direction (F 4 ) as far as the said stopping of the anchor ( 2 ), one ( 22 ) of the said two protrusions ( 22 , 20 ) can push the anchor ( 2 ) towards its exit lock position until cooperation between the lock beak ( 19 ) of a tooth ( 8 ) of the escapement wheel ( 1 ) and the return plane ( 18 ) of the exit pallet ( 7 ) finishes returning the anchor ( 2 ) to its exit lock position under the action of the rotation of the escapement wheel ( 1 ).

9. The escapement as claimed in claim 1 , wherein the escapement wheel ( 1 ) is produced as a single piece.

10. The escapement as claimed in claim 1 , wherein the anchor ( 2 ) is produced as a single piece.

11. The escapement as claimed in claim 1 , wherein at least one of the anchor ( 2 ) and the escapement wheel ( 1 ) is produced from a fragile material.

12. The escapement as claimed in claim 11 , wherein said fragile material is glass, diamond, silicon, silicon carbide, crystallised aluminium oxide or another material based on one of these materials.

13. The escapement as claimed in claim 1 , wherein the anchor comprises a fork having a fork notch ( 28 ) and horns ( 26 ), and wherein the inner face ( 25 ) of each horn ( 26 ) is rounded so as to soften the transition between this inner face ( 25 ) and the corresponding inner face ( 27 ) of the fork notch ( 28 ).

14. The escapement as claimed in claim 1 , further comprising a member ( 30 ) for transmission between the anchor and a balance staff, wherein this member ( 30 ) comprises a part ( 29 ) acting as an impulse pin ( 15 ), wherein said part ( 29 ) comprises convex active surfaces ( 33 ) and an inactive surface ( 34 ) connecting the active surfaces ( 33 ) to each other, and wherein the inactive surface ( 34 ) is convex with a radius of curvature which is greater than that of the active surfaces ( 33 ), so as to soften the transition ( 35 ) between the inactive surface ( 34 ) and each of the active surfaces ( 34 ).

15. The escapement as claimed in claim 14 , wherein said member ( 30 ) is a single-piece member comprising an opening ( 31 ) for its mounting on the balance staff and a protrusion ( 29 ) extending radially and constituting the said part ( 29 ) acting as an impulse pin ( 15 ).

16. The escapement as claimed in claim 1 , wherein the escapement is a Swiss lever escapement.

17. A timepiece comprising an escapement as claimed in claim 1 .