| 摘要 |
<p>A protective device for key-operated door locks comprises a housing 2 mountable to the door 4 over the keyhole 8 of a lock 6 mounted within the door. A guard plate 26 is movable to a blocking position to block access to the keyhole 8, or to an unblocking position to permit access to the keyhole 8 by way of a rotary knob 24 rotatable to a plurality of positions and having markings 38 thereon indicating its position. A transmission mechanism including a plurality of notched code discs 30, 32 is provided between the rotary knob 24 and the guard plate 26 for moving the guard plate 26 from its blocking position to its unblocking position when the code discs 30, 32 have been positioned to predetermined coded positions such that further rotation of the knob 24 moves the guard plate 26 from its blocking position to its unblocking position.</p> |
