Abstract: The engagement between the first and second members is accomplished by the wedging of roller members so that the first and second members can be held rotationally fast to each other in a continuous manner or at any desired angular position. A pair of roller members are received in a chamber defined between the first and second members, and are normally urged into wedging engagement in the circumferential ends of the chamber under the spring force of a spring member, but may be disengaged so as to allow free relative rotation between the first and second members by displacing the roller members toward each other against the spring force of the spring member by using actuation members. Thus, the relative rotation in either direction can be prevented, and the releasing of the first and second members can be accomplished simply by slightly moving the roller members.

Abstract: An emergency locking scat hinge device includes an inner and outer members defining a plurality of chambers therebetween, each having a relatively wide central part and end parts which get progressively narrower circumferentially away from the central part, a rolling member received in each of the chambers, a resiliently supported retaining member which retains each of the rolling members in the side central part of the corresponding chamber, and an acceleration sensitive locking device which actuates the retaining member so as to cause the rolling members to wedge between the inner and outer members. Because this seat hinge device permits free rotation under normal condition but prevents the relative rotation in a high acceleration situation, it can effectively increase the mechanical strength and rigidity of a seat back against tilting particularly when it is used on one side of a vehicle seat while a normal recliner hinge device is used on the other side of the vehicle seat.

Abstract: A reclining device comprises a housing fixed to a seat cushion of a seat, a shaft connected to a seat back, and a locking member. A helical thread groove is formed in the outer peripheral surface of the shaft. The locking member has thread ridges that can engage the shaft. The locking member is movable between a lock position in which the thread ridges engage the thread groove of the shaft and an unlock position in which the thread ridges are disengaged from the thread groove of the shaft. The locking member is held in the lock position by means of a cam member that is urged toward a first position by means of a spring. The locking member can be moved to the unlock position when the cam member is moved to a second position.