Vehicle seat hinges

A seat hinge for a vehicle seat, comprising:

• a first cheek plate for fixing to a framework of a seat back;
• a second cheek plate for fixing to a framework of a seat proper and co-operating with the first cheek plate to define a housing;
• a ring having a first set of inside teeth and secured to the first cheek plate inside the housing and having a ring axis coinciding with the hinge axis;
• a first control member accessible to a user of the seat;
• and
• a first mechanism inside the housing, controllable by said first control member, and co-operating with the first set of teeth of the ring to transform rotation of said first control member into angular displacements of the first cheek plate and of the seat back and into commands enabling and disabling such angular displacements, the toothed ring being rotatively mounted relative to the first cheek plate, said hinge further including a second mechanism inside the housing, cooperating with the toothed ring and the first cheek plate in reversible manner, said second mechanism including:
• at least one locking member displaceable between a locked position wherein said locking member couples the toothed ring and the first cheek plate with respect to their angular displacements about the hinge axis of rotation, and an unlocked position wherein said locking member enables angular displacements of the first cheek plate relative to the toothed ring about the ring axis,
• elastic means for urging the locking member towards said locked position,
• a second control member easily accessible from behind the seat back for displacing said locking member into said unlocked position,
• two abutments angularly fixed relative to the toothed ring and to the first cheek plate respectively, and defining, by mutual angular engagement, a predetermined angular position of the first cheek plate relative to the toothed ring, said abutments enabling only angular displacement of the first cheek plate in a first angular direction starting from said predetermined relative angular position and preventing angular displacement of said first cheek plate in a second, opposite angular direction starting from said pre-determined relative angular position, and
• means cooperating with said locking member when the first cheek plate is not in said predetermined relative angular position, for maintaining said locking member in said unlocked position.