Articulation for a seat, and seat for a motor vehicle equipped with this articulation

An articulation for a seat, especially for a motor vehicle, comprising:

• two cheeks (24, 26) intended to be fixed respectively, to a seat part and to a backrest of the seat, these cheeks (24, 26) being able to rotate one with respect to the other about an axis of articulation (X) which is perpendicular to them,
• means (30) for coupling the cheeks (24, 26) together, these means being actuated by two operating members (42a, 42b) mounted so that they can rotate about the axis of articulation (X), movable 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 respectively to the first and to the second cheek (24, 26), and a second position in which this coupling member (34a, 34b) is released, and
• means (50) for elastically returning the operating members (42a, 42b) to the their first position, wherein the operating members consist of two rings (42a, 42b) centerd approximately on the axis of articulation (X) and each comprising a stud (48a, 48b) formed on their interior contour, the return means comprising a spring (50) with an angular effect hooked onto the studs (48a, 48b) in such a way as to urge the rings (42a, 42b) in opposite directions.