Hinge mechanism, vehicle seat comprising such a mechanism, and manufacturing method

1. A hinge mechanism comprising:

first and second hinge flanges mounted so as to rotate relative to one another about at least one axis of rotation and defining an internal volume between them,

a control device arranged in the internal volume and controlling a relative rotation of the first and second hinge flanges,

a closure ring integrally secured to the second hinge flange and retaining the first hinge flange against the second hinge flange, and

an external frame integrally secured to the second hinge flange,

wherein a weld is integrally securing the second hinge flange to both the external frame and the closure ring,

wherein the closure ring comprises a flat annular outer portion which is in axial abutment against an outer portion of the second hinge flange, the outer portion of the closure ring having a circular outer periphery with a diameter that is the same as a diameter of an outer periphery of the outer portion of the second hinge flange, said outer periphery of the closure ring and said outer periphery of the outer portion of the second hinge flange being arranged in mutual correspondence,

wherein at least the outer periphery of the outer portion of the second hinge flange is fitted into an internal opening of the external frame, and

wherein the weld covers the outer periphery of the outer portion of the second hinge flange, the outer periphery of the closure ring, and the internal opening of the external frame.

2. The hinge mechanism according to claim 1 , wherein the second hinge flange is further secured to the closure ring by crimping.

3. The hinge mechanism according to claim 2 , wherein the closure ring has a plurality of outer tabs crimped onto the outer periphery of the second hinge flange.

4. The hinge mechanism according to claim 3 , wherein the weld extends angularly across a plurality of sections where each pair of adjacent sections is separated by said outer tabs.

5. A method for manufacturing the hinge mechanism according to claim 4 , comprising the following steps:

(a) a temporary pre-assembly step, in which the closure ring is fixed temporarily to the second hinge flange, and the outer tabs of the closure ring are crimped onto the outer periphery of the second hinge flange, and

(b) an assembly step, in which the welding is carried out in a manner that permanently assembles the closure ring, second hinge flange, and external frame, wherein the welding is carried out in said plurality of sections where each pair of sections is separated by said outer tabs.

6. The hinge mechanism according to claim 1 , wherein the outer portion of the second hinge flange comprises a flat annular outer portion.

7. The hinge mechanism according to claim 1 , wherein the external frame is a lateral flange that is part of either a backrest frame or a seating portion frame.

8. The hinge mechanism according to claim 1 , wherein the external frame is a bracket adapted for attachment to a lateral flange that is part of either a backrest frame or a seating portion frame.

9. The hinge mechanism according to claim 1 , further comprising a structural part which is integrally secured by said weld to the second hinge flange, the external frame, and the closure ring.

10. The hinge mechanism according to claim 1 , wherein the first hinge flange comprises a collar extending axially along said at least one axis of rotation through the closure ring, said collar being welded to an additional external frame by an additional weld.

11. A method for manufacturing the hinge mechanism according to claim 10 , wherein the hinge mechanism has a first main face corresponding to the first hinge flange and a second main face corresponding to the second hinge flange, and wherein the method comprises the following steps:

(a) a temporary pre-assembly step, in which the closure ring is fixed temporarily to the second hinge flange,

(b) an assembly step, in which the welding is carried out in a manner that permanently assembles the closure ring, second hinge flange, and external frame, wherein the closure ring is welded to the second hinge flange and the external frame, from the first main face of the hinge mechanism, and

(c) an additional step, subsequent to step (b), in which the collar of the first hinge flange is welded to said additional external frame, from the first main face of the hinge mechanism.

12. A vehicle seat comprising first and second parts connected to each other by the hinge mechanism according to claim 1 , the first and second hinge flanges being respectively fixed to the first and second parts.

13. The seat according to claim 12 , wherein the first part of the seat is a seating portion and the second part of the seat is a backrest.

14. A method for manufacturing the hinge mechanism according to claim 1 , comprising the following steps:

(a) a temporary pre-assembly step, in which the closure ring is fixed temporarily to the second hinge flange, and

(b) an assembly step, in which the welding is carried out in a manner that permanently assembles the closure ring, second hinge flange, and external frame.