Releasable lock for a motor vehicle locking system

A disengageable cylinder, for a motor vehicle lock mechanism, comprising:

• a fixed stator;
• a tubular intermediate sleeve which is mounted in rotation about its axis in the stator and which is fixed axially with respect to the stator;
• a rotor which is mounted in rotation in the sleeve, which is fixed axially in the sleeve and which comprises tumblers which can move radially under the action of a key intended to be inserted axially into the rotor, the rotor and the intermediate sleeve being blocked against rotation with respect to one another by the tumblers when the key is not appropriate;
• a driver providing a coupling between the rotor and a cam actuator, when the key is appropriate;
• and
• an indexer which can move axially between a rest position and a disengagement position, under the effect of a rotation of the sleeve with respect to the stator subsequent to the rotor being rotated by means of an inappropriate key, so as to move the driver axially toward a disengaged position,
• wherein the cylinder comprises a means for returning the cam actuator from a transient position located between the engaged and the disengaged positions to a rest position, which the cam actuator previously occupied, during the disengagement of the cylinder, and
• wherein the driver is uncoupled from the cam actuator, in said disengaged position, and the indexer is coupled in rotation with the cam actuator, in said disengaged position, thereby blocking the cam actuator from rotation in said disengaged position;
• wherein the indexer and the driver are cylindrical parts surrounding the rotor and can move while fitted one inside the other, in that the driver is connected in translation on the rotor, and in that the indexer is rotationally immovable and connected in translation in the stator.