An
assembly comprising a first part (12) and a second part (14) movable relative to each other in translation along a connecting axis (D) between a locked configuration and an unlocked configuration. The first part comprises one of a rail and one of a groove, and the second part comprises the other, the rail being configured to slide axially in the groove. The
assembly includes a ring (16) rotatably mounted on the first part about the connecting axis, the ring having at least one pin (46). The second part defines a locking ramp (88), a first housing (90), and an unlocking ramp (92). The
assembly (10) includes a return mechanism for exerting a
restoring force on the ring to a
rest position.The locking ramp and the first housing are configured so that a manual movement (D1) causes a first slip (G1) of the pin on the locking ramp, and an automatic movement (D2) of the ring angularly in one direction between the
rest position and a first intermediate position, then an automatic movement of the ring angularly in the opposite direction from the first intermediate position to a locking position under the action of the return
system, the pin being received in the first housing, the first housing defining a first axial stop (94) adapted to block the pin axially.The unlocking ramp (92) is configured so that a manual movement of the rotating ring in said direction from the locking position removes the pin from the first housing and causes a second slide of the pin on the unlocking ramp, the unlocking ramp reacting axially on the pin to move the first part and the second part away from each other from the locked configuration.