LOCK CYLINDER WITH AN IMPROVED SECURITY

The present invention proposes a lock cylinder (10) for use with a flat key (40) having an abutment section (41) on a key shaft (42), comprising: a cylinder body (30) having a central longitudinal axis (X); a rotor (20) having a keyway (11) for receiving the key (40), rotatable within the cylinder body (30); a set of housings aligned in a vertical axis (Y) relative to the central longitudinal axis (X); and each housing containing a pin spring (33), a body pin (31), and a rotor pin (32) partly project into the keyway (11); the pins being urged by the spring towards the keyway (11) and ensuring, in the absence of the flat key (40), blocking of the rotor (20) with respect to the cylinder body (30). The lock cylinder (10) further comprises: a spring-biased movable counter-abutment (14) guided in a hollowed portion (16) formed on the rotor (20) wherein the counter-abutment (14) is movable between a release position and a lock position in the hollowed portion (16). Advantageously, the movable counter-abutment (14) is arranged and configured such that, on an introduction of the flat key (40) into the keyway (11), the abutment section (41) pushes the movable counter-abutment (14) to the released position to correspond to one of the body pins (31) for allowing the rotation of the rotor (20).