Abstract: A hinge joint for use in the seats of motor vehicles to permit changes of inclination of the back rest has a first leaf secured to the body supporting portion of the seat, a second leaf secured to the back rest and a composite shaft having an eccentric cylindrical portion turnably mounted in the first leaf and two coaxial conical portions flanking the eccentric portion and turnably mounting the second leaf. At least one conical portion has a cylindrical core of a metallic material and elastic sleeve surrounding the core and having a conical external surface. A diaphragm spring reacts against the shaft and urges the second leaf axially of the shaft against the first leaf, and a spur gear of the first leaf mates with an internal gear of the second leaf.

Abstract: A pair of hinge fittings is mounted at opposite lateral sides of the seat. Each fitting includes a first strap that is fixedly connected with the seat member and a second strap that is fixedly connected with the back member. A pivot connects the straps of each for relative pivotal movement. One strap of each fitting carries an arcuate gear segment and the other strap carries an engaging member which is permanently biased into engagement with the respective gear segment by a biasing spring. A control arrangement is provided which permits the engaging member to be moved out of contact with the respective gear segments. This control arrangement includes on each fitting a pivotal first arm that can be moved into and out of engagement with the respective engaging member and, when it is in such engagement, prevents the engaging member from moving out of engagement with the gear segment.