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

A hinge mechanism for fitting to a vehicle seat comprising a seat proper and a seat-back that is pivotable relative to the seat proper, the mechanism comprising:

• first and second cheek-plates, one for securing to the seat proper and the other to the seat-back, said cheek-plates being pivotally mounted relative to each other about an axis of rotation, the second cheek-plate being permanently secured with a set of teeth extending over at least an arc of a circle centered on the axis of rotation and being radially inwardly directed;
• at least one locking slug provided with a set of teeth suitable for co-operating with the teeth of the second cheek-plate, said locking slug being guided in radial sliding by a guide secured to the first cheek-plate, to slide between an engaged position in which the teeth of the locking slug co-operate with the teeth of the second cheek-plate to lock the mechanism, and a retracted position in which the teeth of the locking slug do not co-operate with the teeth of the second cheek-plate, said locking slug also including a first peg which projects axially towards the second cheek-plate;
• a locking cam for controlling the sliding of the locking slug, said locking cam being urged by resilient means towards a rest position in which said locking cam places the locking slug in its engaged position;
• a first control member for moving the locking cam from its rest position towards an actuation position in which said locking cam enables the locking slug to slide towards its retracted position;
• means for displacing the locking slug from its engaged position to its retracted position when the locking cam passes from its rest position to its actuation position;
• and
• a circular guide mechanically linked to the second cheek-plate and co-operating with the first peg so as to hold the locking slug positively in its retracted position when said locking slug is in a predetermined range of angular positions relative to said circular guide, said circular guide having at least one gap in which the first peg can engage when the locking slug is not in said predetermined range of angular positions, then allowing the locking slug to slide radially outwards to its engaged position;
• wherein:
• the circular guide is formed by a rim belonging to memory equipment which is pivotally mounted relative to the first and second cheek-plates to pivot about the axis of rotation;
• the gap of the circular guide forms a radial guide in which the first peg can slide radially, substantially without play in the circumferential direction;
• the memory equipment further includes a memory plate and a memory slug, said slug being mounted to slide radially on the memory plate between an engaged position in which said memory slug co-operates with said second cheek-plate to prevent the memory plate from moving relative to said second cheek-plate, and a retracted position in which said memory slug does not co-operate with the second cheek-plate and allows the memory plate to turn freely relative to said second cheek-plate;
• a control plate is pivotally mounted about the axis of rotation to pivot between a rest position which is fixed relative to the first cheek-plate and an active position, said control plate being resiliently urged towards its rest position and being capable of being moved into its active position by a second control member, and said control plate being shaped to enable the locking slug to move radially inwards to a disengagement position in which the first peg can disengage from its radial guide to slide against the circular guide when the control plate is placed in its active position, the control plate being connected to the locking cam with a certain amount of angular clearance, so that said control plate remains in its rest position while the locking cam is moved from its rest position to its active position by the first control member, and so that said control plate entrains the locking cam to its active position when said control plate is moved from its rest position to its active position by the second control member, means being provided to entrain the locking slug from its engaged position to its disengagement position when the control plate is displaced from its rest position to its active position, after a certain amount of angular lost motion in which displacement of the control plate does not entrain displacement of the locking slug;
• the control plate is secured to a memory cam which co-operates with the memory slug to place said memory slug in its retracted position when said control plate is in its rest position, and to enable said memory slug to move into its engaged position during the angular lost motion of the control plate;
• and
• the memory slug is urged resiliently towards its engaged position.