Lock, a fastening for doors, boxes, etc, designed not to be opened except by an instrument called a key especially adapted to the lock, or by manipulating some secret arrangement of bolts and pins. The Egyptians used locks of a simple construction about 4,000 years ago, and more perfectly constructed locks have been used by the Chinese for centuries. The Chinese lock is furnished with parts which are called tumblers, and resemble the modern tumbler lock. The locks in use in England about 100 years ago are still found in that country and in the United States to a limited extent on common doors and boxes. They are called spring locks, and their general construction is represented in fig. 1. The bolt b passes through a rectangular hole in each end of the lock, and is held either out or in by two notches c e, which are pressed against the edge of the hole by the spring a. The face of the key is seen to lie in a semicircular notch in the lower edge of the bolt, which is by that means moved backward and forward. A number of circular partitions, called wards, whose edges are seen surrounding the shaft of the key, prevent any key which has not corresponding open spaces from being used.

The ordinary key may have the form shown in fig. 2, but it is evident that it will answer the purpose of opening the lock as well if the parts are cut away, as in fig. 3; this is called a skeleton key, and is in common use among thieves in picking locks. The common tumbler lock, which has only been in use in Europe and this country during the last 100 years, is represented in its simplest form in fig. 4. The bolt b b is moved out and in by the key in the same manner as in the spring lock, but it is held from moving by processes or projections in a tumbler, a, which are thrown by a spring into notches in the upper edge of the bolt. This tumbler has to be raised by the key before the bolt can be moved. Barron's lock, patented in 1778, is so contrived that the processes in the bolt have to be raised to a particular height in order that the bolt may be moved, because if raised higher they are thrown into opposite notches. The plan is represented in tig. 5. This lock was considered secure for several years, when the ingenuity of burglars discovered a method of picking it. Mr. Barron subsequently added another tumbler, which had to be raised to correspond to another set of notches in the bolt, and thereby greatly increased the security of the lock.

It is not certain that Barron applied more than two tumblers, but the principle of the many-tumblered lock is his. The form has been changed by putting a single pin called a stump in the bolt, which passes into slots in the tumblers, and these have to be raised to various heights in order to receive it. Chubb's lock has this form, as in fig. 6, where 1) is the bolt, t the tumblers (six in this cut), turning on the common pin a, d six springs to press down the six tumblers, and n the slots into which the stump s is drawn when the tumblers are raised to the proper height. The principle of Bramah's lock is similar, except that instead of tumblers turning upon a common pin, there are a number of independent slides having notches at different heights, but which are raised to a common height by a key having corresponding elevations on its face. It was supposed that a lock of the character of Bramah's could not be picked; and during the world's fair at London in 1851 a challenge from the Messrs. Bramah, offering a reward of 200 guineas to any one who could pick a lock of theirs on exhibition, was accepted by Mr. Hobbs, an American. He succeeded after a trial of 51 hours, embraced in a period of 30 days.

Hobbs invented a lock called a " protector," which is represented in fig. 7. This is much like Chubb's lock, except that the stump s, instead of being riveted to the bolt, is riveted into a detached piece shown in fig. 8, which turns on a centre h when the stump s is pressed by the bolt. This action brings the attached arm against the case of the lock, by which means the tumblers are relieved from pressure by the stump, so that their positions cannot be ascertained by the burglar. The key, fig. 9, turns on the pin k, and the tumblers rest on the piece r. This lock, after defying the ingenuity of English locksmiths, was at last opened by Mr. Linus Yale, jr., of Philadelphia, who has since invented the celebrated Yale lock, which is now used all over the world. An improvement upon the form of the Hobbs and Chubb locks, in which the combination is not changeable, is the addition of a device by which the position of the slots and pins and the face of the key may be changed at pleasure. This was effected by Dr. Andrews of Perth Amboy, N. J., the principle of whose locks will be understood by inspecting the keys, figs. 10 and 11, where the face of the key is changed by varying the positions of the separate pieces held in it.

The lock is too complicated to admit of a description within the limits of this article. It was long extensively used by banks and large stores, and its success caused numerous competitors to appear, prominent among whom was Mr. Newell, the inventor of Day and New-ell's "parautoptic lock." The general plan of the Yale lock above mentioned is represented in section in the Yale night latch, figs. 12 and 13. An end view is shown in fig. 12, where a cylinder c, having a number of holes drilled along its whole length, as shown in fig. 13, may be turned when the key, K, raises the pins a b c d e so that their faces are even with the surface of the cylinder. These pins are of corresponding different lengths in each lock, no two locks being alike. The flat key has bevelled-edged notches in one of its edges, corresponding to the lengths of the pins. The parts of the lock shown here are called the "escutcheon," which not only comprises the cylinder, hut the part above it, containing holes corresponding to those in the cylinder, and holding the same number of pins, 1, 2, 3, 4, 5, which, by means of spiral springs, are partly forced down into the holes in the cylinder when the key is withdrawn, thus fastening the lock.

It will be seen that the faces of the two sets of pins must be in a line before the cylinder can be turned. Attached to the end of the cylinder, and not shown in the cut, there is a cam by means of which the bolt of the lock is moved. The unlocking of the cylinder is performed by simply thrusting the key into it, and of the bolt by turning the cylinder with the key. - A variety of locks which are usually placed upon fire- and burglar-proof safes, called permutation and combination dial locks, are now in extensive use, and a number of different patents embrace a variety of devices, which are however modifications of one general principle. This general principle will be understood if we suppose the tumblers in a Chubb or Hobbs lock, instead of turning on a hinge at one end, to be converted into wheels, and made to turn upon an axis, and, instead of having the slots brought to coincide by a key, adjusted by turning the wheels alternately one way and the other upon the axis on which they move independently.

The wheels are placed near together, with washers between, and do not interfere with the motion of each other except when certain pins, which may at pleasure be moved to various positions, collide with one another; then one wheel will move its neighbor, and carry it around to any desired distance. Again turning it in the opposite direction, but through a smaller arc, another wheel may be turned until the slot in it is made to coincide with the first. A third and a fourth, and indeed any desired number of wheels (the number rarely exceeding four), may be adjusted with all their slots coinciding. The action is represented in fig. 14, where a, b, c, d are four wheels placed within the lock. Each wheel has a pin (shown only on d) which may be placed at pleasure upon any radius. A dial (fig. 15), turning by means of a knob upon an index plate, is placed upon the outside of the safe. A shaft passes through the door and through the axis of a wheel to which it is fixed, and also through the axis of the wheels a, b, c, d, which however are free to turn.

If now the fixed wheel has a pin upon its inner side which can be brought against the pin on the wheel a, it is evident that the slot may be made to correspond with any number upon the dial by adjusting the pin, and that by means of this dial the slot may bo placed in any determined position. If now the dial is turned around four times, the wheel d must be moved before or at the end of the revolutions by means of the pins in the wheels successively colliding. Suppose the wheel d to have its pin so placed that when the number 20 stands opposite the index on the index plate its slot will be in the position given in the cut. Now, on turning the dial in the opposite direction, the wheels will be unlocked, but in the course of one revolution the fixed wheel will again lock with the wheel a, and this again in the course of the second revolution will lock with the wheel b, and this in the third revolution with the wheel c. If this latter wheel has its pin so adjusted as to be opposite the number 40 when its slot is brought to coincide with that of the wheel d, this will be indicated when the number 40 is opposite the index. Reversing the motion of the dial, the wheel b may have its slot brought to coincide with that of c and d during the second revolution.

Again reversing the motion of the dial, the wheel a will have its slot brought to coincide with that of all the others. When the slots in all the wheels coincide the stump of the bolt may be thrown into the common slot, or a dog may fall into it, leaving the bolt free to move, or any other arrangement can be made which may be thought advantageous. There are a number of excellent patents of combination locks in this country, some possessing advantages of one kind and some of another. In the simple form just described, represented in fig. 16, where the stump of the bolts passes directly into the slot, there is danger of a burglar detecting its position by feeling while pressing it against the periphery of the wheel, and thus discovering the combination. This is prevented by various devices. One of those used upon Hall's lock is shown in fig. 17. It consists in notching the fixed wheel, which is somewhat larger than the others, so that the stump shall be pressed against it or into its slots instead of against the other wheels. The latter also are not circular, but polygonal, so that on turning them inequalities are felt which cannot be distinguished from slots.

The device employed in the "Dexter lock," used on the Herring safe, is shown in figs. 18, 19, and 20. A false wheel, a, fig, 18, smaller than the others, has a slot which receives an extra bar, c, fig. 20, shorter and placed beneath the common bar for the other wheels; and also a shoulder, s, which prevents the "fence," a, fig. 20, from descending when the slot is not uppermost. Over this small wheel is a cam, b, fig. 19, which contains in each corner an octagonal roller, upon which the piece d, fig. 20, rests when the fence is raised. This piece d is constantly pressed by spiral springs, by which means all possibility of ascertaining when the bar h is brought opposite a slot in a wheel, or opposite any depression, is prevented. The locking in this arrangement is performed by raising the "fence" until the notch e, fig. 20, is brought to embrace the pin g attached to the bolt f. When the fence is depressed the bolt may be moved backward or forward. In Sargent and Greenleafs lock the bolt is composed of a roller, b, fig. 21, in which there is a slot, c, into which the sliding bolt, a part of which is represented at m, may be passed when the slot is brought opposite. This can be done when the bar a passes into the slots in the wheels, by turning the dial knob.

The parts are simplified in this drawing for convenience of illustration. Marvin's lock has a device shown in fig. 22. When the bar b falls into the common slot, turning the knob draws the piece a out of the chamber, when the bolt may be slid into it. In the lock itself the piece a is behind and partially hidden by the wheels, but the one shown in the cut is made smaller than natural for convenience of illustration. Sargent and Greenleaf have lately patented a clock-work attachment to one of their locks, by means of which the bolt is liberated from a catch at a set hour, before which time nobody, not even the person possessing a knowledge of the combination, can enter the safe through the agency of the lock.

Lock 1000201

Fig. 1.

Lock 1000202

Fig. 2.

Lock 1000203

Fig. 3.

Lock 1000204

Fig. 4.

Lock 1000205

Fig. 5.

Lock 1000206

Fig. 6.

Lock 1000207

Fig. 7.

Lock 1000208

Fig. 8.

Lock 1000209

Fig. 9.

Lock 1000210

Fig. 10.

Lock 1000211

Fig. 11.

Lock 1000212

Fig. 12.

Lock 1000213

Fig. 13.

Lock 1000214

Fig. 14.

Lock 1000215

Fig. 15.

Lock 1000216

Fig. 16.

Lock 1000217

Fig. 17.

Lock 1000218

Fig. 19.

Lock 1000219

Fig. 18.

Lock 1000220

Fig. 20.