fig. 40. The American Parautoptic lock; bolt unshot.
fig. 41. The same with the bolt shot.
In [fig. 40] the lock is represented in its unlocked state, with the cover or top-plate removed; the auxiliary tumbler and the detector-plate are also removed. In [fig. 41] it is represented as locked, with the cover and the detector-plate also removed, and the auxiliary tumbler in its place. In these two figures, the same letters of reference apply to the same parts, unless otherwise stated. B B is the bolt; T1 are the first series of movable slides or tumblers; s shews the tumbler-springs; T2 the secondary series of tumblers; and T3 the third or intermediate series—these latter coming between the first and secondary series; P P are the separating plates between the several members of the first series of tumblers; s1 are the springs for lifting the intermediate tumblers. On each of the secondary tumblers T2 is a series of notches, corresponding in mutual distance with the difference in the lengths of the movable bits of the key. It thence happens that, when the key is turned in the lock to lock it, each bit raises its proper tumbler, so that some one of these notches shall present itself in front of the tooth t in the dog or lever L L. When the bolt B is projected by the action of the key, it carries with it the secondary tumblers T2, and presses the tooth t into the notches; in so doing, it withdraws the tongues d from between the jaws j j of the intermediate tumblers T3, and allows the first and intermediate tumblers to fall to their original position. By the same movement, the secondary tumblers T2 become held in the position given to them by the key, by means of the tooth t being pressed into the several notches, as shewn in the closed state of the lock ([fig. 41]). Now let us see what results if any attempt be made to open the lock with any arrangement of key but that by which it has been locked. In such case, the tongues d will abut against the jaws j j, preventing the bolt from being withdrawn; and should an attempt be made to ascertain which tumbler binds and requires to be moved, the intermediate tumbler T3 (which receives the pressure), being behind the iron wall I I, which is fixed completely across the lock, prevents the possibility of its being reached through the key-hole; and the first tumblers T are quite detached at the time, thereby making it impossible to ascertain the position of the parts in the inner chamber behind the wall I I. K is the drill-pin, on which the key fits; and C is a revolving ring or curtain, which turns round with the key, and prevents the possibility of inspecting the interior of the lock through the key-hole. Should, however, this ring be turned to bring the opening upwards, a detector-plate D, [fig. 42], is immediately carried over the key-hole by the motion of a pin p1 upon the auxiliary tumbler T4, which is lifted by the revolution of the ring C, thereby effectually closing the key-hole. As an additional protection, the bolt is held from being unlocked by the stud or stump S bearing against the detector-plate; and, moreover, the lever l l holds the bolt, when locked, until it is released by the tail of the detector-plate pressing the pin p1; l1 is a lever which holds the bolt on the upper side, when locked, until it is lifted by the tumblers acting on the pin p1; X are separating-plates between the intermediate tumblers T3; u u1 are the studs for preserving the parallel motion of the different tumblers.
fig. 42. The detector plate of the Parautoptic lock.
[Fig. 43] represents the key in two different forms, or with the bits differently arranged. Either form will lock the lock, but the other will not then unlock it. The end of the key is represented in [fig. 44], shewing the screw which fixes the bits in their places. The bits for a six-bitted key are shewn separately in [fig. 45].
fig. 43. Key of the Parautoptic lock.