Page:The American Cyclopædia (1879) Volume X.djvu/570

564 LOOK spending different lengths in each, lock, no two locks being alike. The flat key has bevelled- edged notches in one of its edges, correspond- ing to the lengths of the pins. The parts of FIG. 12. FIG. 13. the lock shown here are called the " escutch- eon," which not only comprises the cylinder, hut the part above it, containing holes corre- sponding 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1, 2, 3, 4, 5, which, by means of spiral springs, are partly forced down into the holes in the cylinder when the key is withdrawn, thus fastening the lock.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 cylin- der, 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 per- formed by simply thrusting the key into it, and of the bolt by turning the cylinder with the key. A variety of locks which are usual- ly placed upon fire- and burglar-proof safes, called permutation and combination dial locks, are now in extensive use, and a number of dif- ferent patents embrace a variety of devices, which are however modifications of one gen- eral 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 an- other ; then one wheel will move its neigh- bor, and carry it around . to any de- sired distance. Again turning it in the op- posite 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 in- deed any desired number of wheels (the num- FIG. 14. FIG. 15. ber rarely exceeding four), may be adjusted with all their slots coinciding. The action is represented in fig. 14, where a, 5, 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 axes of the wheels , 5, 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 num- ber upon the dial by adjusting the pin, and that by means of this dial the slot may be 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 num- ber 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 oppo- site 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 5, and this in the third revolu- tion 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. Rever- sing the motion of the dial, the wheel ft 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 FIG. 16. 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