Abstract: This articulation comprises two coaxial annulus gears with internal sets of teeth (20, 22) of different pitch, one stationary and the other mobile, meshing with at least one planet (S1 to S4) bearing two external sets of teeth (24, 26) capable of mating with the internal sets of teeth (20, 22). The external set of teeth (26) that mates with the mobile internal set of teeth (22) extends over a shorter sector than the other external set of teeth (24), which means that the planet (S1 to S4) can move over a travel in which its two external sets of teeth (24, 26) are in mesh with the two internal sets of teeth (20, 22), between two end-of-travel positions beyond which the stationary internal set of teeth (20) is kept in mesh with the mating external set of teeth (24) while the other external set of teeth (26) is disengaged from the mobile internal set of teeth (22).

Abstract: The hinge comprises a flange (26) for connection to a seat cushion or squab, a support-flange (38) and at least one lever (34d) for coupling the flanges (26, 38) together having a first end (36A) mounted to pivot on the support-flange (38) so that the coupling lever (34d) can pivot between a position in which a second end (36B) of the lever (34d) is attached to the connecting flange (26) by virtue of cooperation of complementary shapes and a position in which the second end (36B) is released. The hinge further comprises means (100-104) for immobilising the second end (36B) of the coupling lever in the attached position, preferably comprising a weakened area (104) of the support-flange (38) that can deform when the flanges (26, 38) are subjected to an accidental torque to enable movement of the lever (34d) to the point of cooperation of ramps (100, 102) immobilising the lever (34d) in the attached position.

Abstract: An articulation has two cheeks 24, 26, intended to be fixed to a seat part and a backrest of the seat. The cheeks can rotate with respect to each other about an axis X. The articulation also includes structure 30 for coupling the cheeks together, which are actuated by two rings 42a, 42b centered substantially on the axis. The rings can be moved in two opposite directions for respectively adjusting the inclination of and for folding down the backrest, between a first position in which at least one coupling member 34a, 34b is secured to the first and to the second cheek respectively, and a second position in which the coupling member is released. The rings each comprise a stud 48a, 48b formed on their interior contour, and a spring 50 hooked onto the studs to elastically return the rings in opposite directions, into their first position.

Abstract: The articulation comprises two cheeks (24, 26), one of which, which is stationary, is intended to be fixed to the seat part, and the other of which, which can move, is intended to be fixed to the backrest. The cheeks (24, 26) can rotate one with respect to the other. The articulation also includes a coupling mechanism (30) for coupling the cheeks (24, 26) together, controlled by a member (32) which can be actuated in the direction for adjusting the inclination of the backrest and in the opposite direction for temporarily folding this backrest down. The coupling mechanism (30) comprise at least one lever (34a, 34b) having two ends (36A, 36B), each of which can be secured to a cheek (24, 26) by the interaction of complementary shapes (SA, SB, TA).