Security device, in particular an anti-theft device for the steering wheel of a motor vehicle

A security device, in particular an anti-theft device for the steering wheel of a motor vehicle, the device being of the type suitable for constraining the steering column to rotate with the steering wheel, or for allowing the steering wheel to rotate relative to said column, wherein the device comprises:

• a base secured to the steering column, said base comprising a base plate extending perpendicularly to the axis of said steering column, and a central locking head;
• a box secured to rotate with the steering wheel and mounted on the base so as to be capable of rotating about the axis of the steering column, said box including a guide passage in which a coupling slider in the form of a plate is received, said coupling slider having a central opening through which the central locking head of said base passes, and being furthermore received to slide along a sliding direction substantially perpendicular to the axis of the steering column between a coupled position where said coupling slider is directly coupled with the central head of said base and an uncoupled position where said coupling slider is uncoupled from said central head, said coupling slider having an extension which penetrates transversely into a secondary housing of the box and also being subjected to the action of resilient means urging it towards its coupled position;
• a lock assembly disposed in the secondary housing, said lock assembly including a cycle cylinder mounted stationary in the box to determine a cycle of insertion for a key, and a moving shaft associated with said cycle cylinder and axially linked to a lock plug, said moving shaft being movable about an axis substantially transverse to the sliding direction of the coupling slider, and co-operating with the extension of the coupling slider to lock said coupling slider in its uncoupled position or to release said slider to take up its coupled position, said co-operation being possible only with a correct insertion of the key in compliance with the cycle determined by said cylinder;
• and
• a pushbutton activatable from outside the box enabling the coupling slider to be returned to its uncoupled position against the associated resilient means.