| 摘要 |
<p>A security type dead bolt for a door is arranged so that a key must be used on the inside, as well as on the outside, to extend the dead bolt to locked position, in that way to prevent an unauthorized person opening the door from the inside after surreptitious entry. To make certain that when the occupant is at home and with the latch bolt extended by the inside key to locked position, there can be no lost key situation blocking exit by the occupant in case of an emergency such as a fire, the dead bolt mechanism is arranged to trap the key in the lock whenever the dead bolt is extended to locked position, but to release the key when withdrawn. A yieldable mechanism permits unlocking the latch bolt from the outside even when a key is left in the lock on the inside.</p> |
