Lock
key, bolt, door, locks, fixed, fig and security
LOCK. A mechanical device for securely fastening a door or lid, usually including a sliding bolt which may be shot by a removable key.
The Egyptian locksmith was probably the first whose products have been preserved. One of his locks was found in the ruins of Nineveh, and was apparently used to secure the door of a room in the Palace of Khorsabad. Isaiah probably referred to a similar lock when he said "and the key of the house of David will I lay upon his shoulder" (xx. 22). Fig. 1 shows an Egyptian lock dis mantled. Both the lock and the key are constructed entirely of wood.
The vertical piece of wood, the staple, is fixed to the door post and contains in the upper part movable pins, in this case six in number; the cross piece is the bolt. The pins in the staple fall into corresponding holes in the bolt and so prevent the latter moving until they are raised to the level of the top of the bolt by pins fixed on the key. Only the key made specially to fit the lock could operate it and quite a reas onable degree of security was achieved. This lock, the earliest of which the construction is known, is as will be seen later, the prototype of the modern cylinder lock.
Next in order came the fabricator of the "doore fastenings of dyverse colours made of brass and ivory," of ancient Rome, followed by the maker of the still more elaborate Serrure de Tabernacle in the mediaeval age, immortalised in early Christian missals. The Chinese locksmith also made "strange instruments having wooden slides," the architecture of which was peculiarly adapted to the Summer House of willow pattern fame. In Eng land, by the time of Queen Elizabeth, the operations of the craft were fully established "in the townes of Staffordshire, to wit, Wolverhampton, Willenhall and Wednesbury." The mediaeval period up to the late i8th century produced locks of very beautiful design as regards their exterior cases, but small attention was paid to se curity and convenience. Fig. 2 is a 17th century lock of French origin. It measures and the key is 7-i" long. Fig. 3 shows a lock 14"X 8" which belonged to Henry VIII. It is said that wherever he went the lock went with him and was screwed to his bedroom door.
Modern Improvements and Inventions.—A study of the history of locks reveals the fact that their design has followed the various periods of art until, in the loth century, utility has almost entirely displaced the beautiful specimens of earlier days. Until Robert Barron in 1778 invented his double acting tumbler lock, security depended on immovable obstructions fixed inside the lock. The single acting tumbler (fig. 4) gave practically no security as, so long as the tumbler was lifted high enough for the talon on the bolt to pass underneath, the bolt was free to move. Many cheap door locks are, however, still made with this single acting tumbler.
In England and America a ward is added for greater security, and on the Continent of Europe and in America the key-hole in the case of the lock is of a peculiar design. The most common wards are: (I) Sash (fig. 5) (2) Fine (3) Solid. A Sash ward is the most used on account of its adaptability in conjunction with levers. It is made of brass, and has circular steps which vary in height, so that many different combinations may be obtained. This ward is fixed on the inside of both the case and the cap of a door lock. Fine and Solid wards are fixed in the middle of the lock, the former made of steel and the lat ter of brass.
Barron's lock could only be opened by a key which lifted both the tumblers to an exact height, so that the talon on the bolt could pass through. A modern lever works upon this same principle, and nearly all best quality locks are now made with one or more levers.