| 摘要 |
<p>The invention involves a mechanism for simultaneously retracting two separate latch bolts which have previously been extended by their individual separate mechanisms. The individual mechanisms comprise a substantially conventional knob actuated latch bolt, and what is commonly called a locking dead bolt. There is a lever arm attached to the knob spindle and a bell crank arm on a thumb turn shaft of the dead bolt. A flexible strip anchored at one end to the free end of the lever arm projects slidably through a swivelling sleeve on the free end of the bell crank. By providing a stop at the extremity of the strip by rotation of the knob spindle and its lever arm the bell crank is induced to rotate and withdraw the dead bolt to unlocked position, at the same time that the latch bolt is withdrawn to open the door. Conversely, when the dead bolt only is withdrawn, by rotation of the thumb turn shaft merely to unlock the door, the strip will slide through the swivelling sleeve. The lever arm of the knob spindle remains undisturbed and the latch bolt, therefore, remains in extended position, holding the door closed until withdrawn by knob action.</p> |
