Antitheft device for motor vehicles

An antitheft device for locking the steering shaft, which can be operated by means of a cylinder lock and is provided with a latch which is brought into its locking position by a spring when the ignition key is extracted from the rotating cylinder of the lock, for preventing the rotation of the shaft of the steering wheel of a motor vehicle, a rod associated with said latch, said rod being slidingly mounted in an axial hole of a stationary cylinder, a stop element co-operating with said rod and being axially movable with said rod during the unlocking movement of the latch and radially movable with respect to said rod at the end of the unlocking movement of the latch, a first control member carried by the lock and projecting in said axial hole of the stationary cylinder, a second control member carried by said rod, the relative position of said stop element with respect to one of the two control members depending on the presence of the key in the lock and said stop element preventing the accidental movement of the latch into its locking position when the key is inserted in the rotating cylinder of the lock, characterized in that:

• the stop element consists of a ball (46) inserted between the rod (42) of the latch (36,60) and the rotating cylinder (24,68) of the lock,
• the cylindrical surface of the rotating cylinder (24,68) is provided with a first substantially hemispherical cavity or recess (54) extending into the key slot (26) and a second substantially hemispherical cavity or recess (56) angularly displaced and axially positioned towards the upper end portion of the rotating cylinder (24,68) with respect to the first cavity (54), said cavities (54,56) being able to be engaged by said ball (46), respectively, when the key (28,66) is removed and at the end of the unlocking movement of the latch (36,60),
• the first control member carried by the lock is a part (48) of the stationary cylinder (20) adjacent to the lower end portion of the rotating cylinder (24,68),
• the axial hole (40) of the stationary cylinder (20) is provided with a reaction surface (50a,76a) facing the ball (46) on the opposite side of the first control member (48) carried by the lock,
• the second control member carried by the rod (42) consists of a projection (44,74) directed towards the rotating cylinder (24,68) and having two respectively upper and lower inclined surfaces (44a,44b;
• 74a,74b) converging towards the free end of said projection (44,74), the upper inclined surface (44a,74a) bearing against the ball (46) during the unlocking movement of the latch (36,60) and the lower inclined surface (44b,74b) bearing against the ball (46) at the end of said unlocking movement, said ball (46) moves from the upper inclined surface (44a,74a) to the lower inclined surface (44b,74b) over the free end of said projection (44,74) when the ball (46) seats in the second cavity (56) of the rotating cylinder (24,68) and under the action of said reaction surface (50a,76a).