Kissen für einen Sitz mit verstellbarer Sitzfläche und Anwendung bei einem Fahrzeugsitz

The cushion comprises a fixed part and a moving part (21) which is mounted to tilt about an axis ( DELTA ) and exhibits at least one curved external surface (2122) which is convex with respect to this axis ( DELTA ), a recess (22) formed in the fixed part and intended to receive, at least partially, this moving part which is equipped with a curved internal surface (2211) which is concave with respect to this axis ( DELTA ) and complements this external surface (2122) and which is situated facing it, a support (23) joining these fixed and moving parts with at least one articulation which defines this axis ( DELTA ) in order to allow this moving part to retract at least partially into this recess, and immobilisation means associated with these surfaces (2122, 2211) of the fixed and moving parts (21) and intended to hold this moving part in the position in which it has been placed relative to this fixed part. Application to the seat part of a seat.