Page:The American Cyclopædia (1879) Volume X.djvu/569

 LOCK 563 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 tum- bler, 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 ap- plied 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 FIG. 5. FIG. 6. various heights in order to receive it. Chubb's lock has this form, as in fig. 6, where & 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 FIG. 7. raised to a common height by a key having corresponding elevations on its face. It was supposed that a lock of the character of Bra- mah'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 " pro- tector," 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 rivet- ed into a detached piece shown in fig. 8, which M FIG. 8. turns on a centre 7i 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 ascer- tained by the burglar. The key, fig. 9, turns on the pin &, 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 improve- ment upon the form of the Hobbs and Chubb locks, in which the combination is not change- able, 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, FIG. 10. FIG. 11. N. J., the principle of whose locks will be un- derstood by inspecting the keys, figs. 10 and 11, where the face of the key is changed by vary- ing 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 5 c d e so that their faces are even with the sur- face of the cylinder. These pins are of corre-