Shock absorption device and seat including such a device

1. A shock absorption device comprising:

an absorbing shaft having a diameter; and

a plate, the plate comprising a brake cavity and a hole separated by a bridge,

wherein the hole includes a central recess in which the absorbing shaft is placed and upper and lower crack initiation zones that make the bridge locally thinner, the bridge being thinner at one of the two crack initiation zones,

wherein the dimensions of the bridge are such that it breaks at the thinner crack initiation zone when the absorbing shaft exerts a force thereon that is greater than a predetermined value, and

wherein the brake cavity includes a central cavity, a storage zone intended to receive the broken bridge, and a deformable zone extending along a reference axis and having a width that is smaller than the diameter of the absorbing shaft and is adapted to receive and be deformed by the absorbing shaft when the bridge is broken.

2. A shock absorption device according to claim 1 , wherein

the plate is made of aluminum.

3. A shock absorption device according to claim 1 , wherein

the bridge is thinner at the upper crack initiation zone than at the lower crack initiation zone.

4. A shock absorption device according to claim 1 , wherein

the reference axis is curved.

5. A shock absorption device according to claim 1 , wherein

the deformable zone is curved and has a length and a curvature such that it allows a seat back to tilt along an angle between 40° and 50°.

6. A shock absorption device according to claim 1 , wherein

the deformable zone has a width between 80% and 98% of the diameter of the absorbing shaft.

7. A shock absorption device according to claim 1 , wherein

the deformable zone has a decreasing width as it extends away from the bridge along the reference axis.

8. A shock absorption device according to claim 1 , wherein

the central recess is disk-shaped with a diameter that is substantially equal to that of the absorbing shaft.

9. A shock absorption device according to claim 1 , wherein

the central recess has a center located on the reference axis; and

the upper and lower crack initiation zones each include a center of curvature located on a periphery of the central recess,

wherein the centers of the upper and lower crack initiating zones are separated by an angle between 80° and 120° with respect to the center of the central recess.

10. A shock absorption device according to claim 1 , wherein

the upper and lower crack initiation zone are each concave toward the central recess.

11. A shock absorption device according to claim 1 , further comprising

a means for the fastening the plate to a fixed part.

12. A shock absorption device according to claim 11 , further comprising

a means for adjusting an angle of the absorption device with respect to the fixed part.

13. A shock absorption device according to claim 1 , further comprising

a fixed structure;

a pivot shaft fixed on the fixed structure; and

a back in pivoting relation with the pivot shaft.

14. A shock absorption device according to claim 13 , wherein

the plate is integral with the back; and

the absorption shaft is connected to the fixed structure.

15. A shock absorption device according to claim 14 , wherein

the back includes at least one connecting rod, one end of which is in pivoting relation with the pivot shaft; and

the plate is connected to the connecting rod.

16. A shock absorption device according to claim 15 , wherein the seat further includes

a seating part that can translate longitudinally with respect to the fixed structure; and

a mobile back in annular linear relation with respect to the back, the mobile back being further in pivoting relation about a releasable shaft with respect to the seating part;

wherein the pivoting relation between the seating part and the mobile part is provided by an open frame that is integral with the seating part in which the releasable shaft pivots, and

wherein the open frame is closed by a torsion spring that is adapted to release the releasable shaft from the open frame when the bridge breaks.

17. A shock absorption device according to claim 16 , wherein

the annular linear connection between the mobile back and the back is provided by a roller attached to the mobile back that slides in an oblong part attached to the back.

18. A shock absorption device according to claim 16 , further comprising

a jacking cylinder connected to the seating part and to the fixed structure making it possible to simultaneously adjust an angle of the mobile back about the releasable shaft and the translation of the seating part with respect to the fixed structure.