| 摘要 |
PURPOSE:To prevent illegal unlocking and protect a key from being damaged by mounting a high hardness material-made disk-shaped guard plate to an end face of a rotor by way of a ball check mechanism and by idling the guard plate in case when the key is illegally unlocked. CONSTITUTION:There is formed a housing unit 7 which mounts a guard plate 9 having a key hole 10 to an end face of a key cylinder 1 which is used for a steering block device, for example. This guard plate is made of a high hardness material and formed in the shape of a disk while it is provided with a recessed part 12 into which a ball 15 of a ball check mechanism 11 is fitted. Usually, it is so arranged that a key hole 8 of a rotor 4 may be equivalent to a key hole of the guard plate 9. When any attempt is made to unlock illegally with a tool or the like, only the guard plate is set so that it may idle against a spring force of the ball check mechanism 11. This construction makes it possible to prevent any attempt to unlock illegally and protect the key cylinder from being damaged by illegal unlocking. |
