CONSTRUCTION OF LOCKS AND KEYS.
plates around the lock were broken away, as if they had been merely cardboard. We have thought it right to bring these circumstances under the notice of our readers, for the subject is of such extreme importance, that it cannot be too often considered. In all cases, where practicable, we should recommend the use of an iron bolt and gratings, in addition to the iron door ; the bolt to proceed through the floor of the sleeping-room of the party having charge of the bank, and being immediately over the strong-room, and to be fastened down by him every night."óBankers' Magazine, April 1845.
The lock patented by John Chubb in 1846 is especially intended for the fastenings of bankers1 and merchants' strong rooms, and other analogous uses. It is called " The Quadruple Lock," (Fig. 7,) and consists of a combination of
Fig. 7. QUADRUPLE LOCK.
four separate and distinct locks in one, all being acted upon at the game time by a single key with four bits. It will be seen, in Fig. 7, that the main bolts are attached to an eccentric wheel, throwing them each way; and to these bolts ten, or twenty bolt-heads may be fitted. The Quadruple Lock has six tumblers in each set, making altogether twenty-four tumblers, all of which must be acted upon simultaneously, by the motion of the proper key, before the eccentric wheel can be turned; it is thus utterly impossible, from the extensive combinations, for any attempt by a false instrument to succeed in unlocking it.
As a further security, there is a check-lock, with a small key, which throws a hard steel plate over the large key-hole. Thus, in a banking establishment, a confidential clerk may carry the quadruple key, and the principal having the smaller key can at all times prevent the fire-proof safe, or strong room from being opened, unless in his own presence.