U.S. Pat. No. 7,108,328 describes an armrest comprising an arm support rotatably mounted for pivoting about an axis and that can be locked in various positions by a latch movable between a locked position and a released position. A lockable ratchet mechanism is provided for this purpose, so that the arm support can be moved upward in the locked position, but a downward movement is blocked. The latch moves out of the locked position into the released position only when the arm support has been pivoted upward beyond a certain upper position, whereupon the arm support can be pivoted downwardly. As soon as the arm support is pivoted beyond a certain lower position, the latch moves back into the locked position.
The latch has two annular parts with interengaging toothed faces, namely a first part connected to the armrest in terms of movement and a second part nonrotatable about the axis. The second part is mounted on the axis so as to be displaceable axially and, in the locked position is engaged with the teeth of the first part and in the released position is out of mesh with the teeth of the first part. A spring force applies a load to the second part so as to mesh its teeth with those of the first part.
The pivot axis, the first part and the second part are formed of metal to be able to absorb high retaining forces despite having a low space requirement, so that the latch does not significantly impair the design of the armrest.