Hinge mechanism for a vehicle seat, and a seat fitted with such a mechanism

A hinge mechanism for a vehicle seat to adjust the inclination of a seat back relative to a seat proper about a pivot axis, the mechanism comprising:

• first and second rigid strength members mounted to pivot relative to each other about the pivot axis, one of these strength members being for connection to the seat back and the other one for connection to the seat proper;
• a set of teeth secured to the first strength member and forming at least one circular arc centered on the pivot axis;
• at least two toothed slugs mounted on the second strength member and movable at least radially relative to the pivot axis between a locking position in which each slug co-operates with the set of teeth to prevent the first and second strength members moving relative to each other, and a retracted position in which each slug does not interfere with the set of teeth;
• a control device mounted to pivot about the pivot axis and adapted to provide positive control over the displacement of each slug from its locked position to its retracted position, and vice versa;
• and
• an at least partially-circular stepped ramp secured to the first strength member, said ramp having an unlocking angular sector for co-operating with a control slug and for holding the control slug in its retracted position, and a locking angular sector in which the ramp does not interfere with the control slug;
• wherein the angular sum of the locking and unlocking angular sectors, for the control slug able to co-operate with the ramp, extends over more than 120° about the pivot axis.