Jeff Burrows, age 13, of Tacoma, Wash., for his question:
WHEN WAS THE FIRST LOCK MADE
A lock is a mechanical device used for fastening doors and lids, etc., consisting essentially of a bolt guarded by a mechanism released by a key or a combination. The earliest lock in existence is a wooden Egyptian model with a key, found in the ruins of Nineveh, in ancient Assyria. In construction it is the prototype of the modern cylinder lock
Locks and keys are also mentioned in the Old Testament, and the Greeks and Romans used locks of simple design. Medieval artisans designed locks of exquisite detail, the perforations and carvings often having no relation to the work on the lock.
With the exception of the development of ward locks, however, little was done to improve the efficiency and convenience of locks until the late 18th century.
The simplest form of lock is a ward lock, which is essentially a bolt containing a notch known as a talon. The bolt is moved backward or forward by engaging a key in the talon. A back spring attached to the bolt holds it in place once it is released by the key.
In the 19th century ward locks were improved and tumbler or lever locks, pin tumbler or cylinder locks, and keyless locks were invented and improved.
The tumbler or lever lock, similar to the ward lock, contains one or more pieces of metal of different heights, known as tumblers, levers or latches, which intercept the bolt and prevent it from being moved until the tumblers are raised or released by the action of the key.
The so called pin tumbler cylinder lock, or Yale lock, introduced about 1860 by an America inventor named Linus Yale, was the first device to employ a small, flat key in place of a large, cumbersome one. The Yale lock consisted essentially of a cylindrical plug placed in an outer barrel. The plug is rotated by a key and in turn moves the bolt of the lock by means of a cam. In order to rotate the plug the inserted key must raise five pins of different sizes into corresponding holes in the plug.
In the Yale lock, five similar pins are contained in the upper part of each of the holes. If the pins are not raised to the circumference of the plug, the plug cannot be turned.
The most common type of cylinder lock used in the home is the so called night latch, operated by a key from the outside and a knob from the inside.
Another type of lock that is increasing in use is the magnetic lock, which is essentially the same as the cylinder lock, except the pins need a suitably magnetized key to bring them into alignment to allow the plug to be turned.
Of the various types of locks that are not operated by keys, the dial or combination lock is the most common. .A set of tumblers, or wheels, is actuated by a spindle that can be rotated by a graduated dial on the outer end of the lock. Spinning the dial according to the proper combination arranges the tumblers so that the bolting mechanism is released.
Combination locks of intricate design are produced for safes and bank vaults. They can have more than 100 million changes of combination. The combination locks are sometimes safeguarded by a time lock, which allows the vault to be opened at certain specific times.