Page:The New International Encyclopædia 1st ed. v. 12.djvu/425

* LOCK. 375 LOCK. ever, by Linus Yale. .Jr.. the inventor of the cele- brated Yale lock. The Yale lock, with its cliar- acteristic Hat key, was invented about 18G0, and is a development of the old Egyptian pin-lock. The lock consists of a barrel, which turns in a cylinder in order to move the bolt. The barrel YALS LOCK. (1) Without key. (2) Key inserted, pins broaglit into line, and bolt beinj; tiirned. is prevented from being turned by five divided pin tumblers, which move up and down in little cylindrical rooms and pass through the lower part of the case and through the bolt, so their lower edges come in contact with the key as it is inserted. The upjjer part of each pin is forced down by a little spiral spring, which is placed above it in the pin-room. This in turn presses down the lower part of the pin. so that, wlien the key is not in the lock, the pins hold the bolt. The pins are unequally divided, and the upper -urface of the key is so shaped as to raise the pins correspondingly, as the division between each upper and lower pin is on the line between the barrel and cylinder. When the key is in- -erted the pins are gradually raised until all those in the cylinder are raised exactly to the line between the barrel and the cylinder, while the lower portions of the pins are raised to the ^Llme point, permitting the barrel to be easily turned, so as to throw the bolt. Should a false key be inserted the steps on its upper surface would not correspond to the division of the pins, but some would be raised too high, projecting from the barrel into the cylinder, and some would not be raised high enough, and thus the bolt would remain locked. Recent improvements in the form of the key render the lock still more -fcure. These consist of a peculiar form of cross-section, both of the key and its keyway, whereby these parts are interlocked throughout their length and access to the tumblers made so difficult as to render the lock practically 'un- pickable.' Perhaps the most familiar form of Yale lock is the iatch-loci:. Like all latch-locks, this one works automatically when the door is closed. It opens on the inside with a handle, and on the outside with a key. The latch is an entirely modern addition to the door-lock, which enables it to be locked or opened from the inside without a key. Classificatiox of Locks. Locks in a general way may be classified according to the use for which they are intended, as follows : ( 1 ) Front- door locks and vestibule latches, for entrances; (2) sliding-door locks; (3) night-latches: (4) store-door locks; (5) dead-locks, in which no knob is used, the key action alone being reiiuired; (6) hotel locks, which are so arranged that when locked from the inside they cannot be unlocked from the outside of the door. Mortise locks are mortised into the frame of the door, while rim locks are secured to its face, ilaster-keyed locks are so constructed that a single master-key can unlock a whole group or series, but there is also an indivi<Iual key for each lock, which will operate no other lock in the series. Dll Locks. An impoi-tant class of locks are what are called permutation and dial locks, used upon safes. One of the principal devices in them is the employment of a number of wheels, placed near together, on an a.is on which they move independently. These wheels do not inter- fere with the motion of each otiier, except when certain pins are brought in contact, the pins being movable at the will of the person adjusting the lock. In this way one having knowlcilgc of the combination may arrange the wheels so that certain slots in their peripheries will not coin- cide, and cannot be made to coincide, by any one not in possession of the arrangement. The per- son having such knowledge may, however, readily place the slots into line so that a key may be passed through them, or a handle operating the bolt mechanism released and the latter moved. An ingeniously arranged dial is placed on the outside of the safe door, through which a bolt passes attached in the lock to a wheel. This fixed wheel can be turned one way or another, and, being provided with a pin, the first of the movable wheels may be turned so that its slot will correspond to any number on the dial. The first movable wheel, being also provided with a pin upon its disk, is made to turn the second wiieel to a certain position, and so on to the last wheel, when, the slots being all brought into line, the handle operating the bolts is free to turn. There are a great many varieties of these locks, each possessing various advantages. As burglars often compel the person having the knowledge of the combination of a lock to reveal the secret, it is often the practice to provide bank-vault locks with a clockwork attachment by means of which the bolt is liberated at a certain hour, until which time nobody, not even the person possessing a knowledge of the com- bination, can open the lock. As powerful ex- plosives ■ have been inserted through the key- holes of locks, a keyless time lock has been de- vised for greater security. A case containing two very powerful springs is placed on the inside of the door and operated by a key on the out- side. One of these springs is released as the door is shut and throws the bolts into a locked position. The second spring is acted on by a clock movement, and at whatever hour the clock is set the spring is released and throws the bolts into their unlocked position. The owner, when closing his safe at night, sets the clock to run off guard at whatever hour he wishes, say nine o'clock the following morning. They may be set to run seventy-two hours. BuETS vary in shape according to the locks to which they belong. In olden times keys were ponderous affairs, which were borne on the shoul- der instead of being tucked away in the pocket. They were often several feet long. The ordinary key consists of three jiarts — the bow, or upper end; the bit, or lock end: and the connecting shank. When the cuts of the bit are on the side or edge they indicate a tumbler or lever lock; when the cuts are on the top or bottom the key l)elongs to a ward lock. ^XTien the shalik is tubu- lar it indicates a lock which can be operated from one side only, such as are used for drawers and chests, for door-lock keys have solid shanks. Cylinder locks have flat keys without a bit. or r.-ither with a shank which is a prolonged bit;