Rudimentary Treatise on the Construction of Locks

by A. C. Hobbs; George Dodd

fig. 53.

In the invention of the Improved Lock and Key now to be described, and which has been termed the adytic lock,[13] the writer’s object has been to meet this requirement. In [fig. 53] is shown an elevation of this lock, such as is made for an iron safe; two of the front cover plates being removed to show the construction.

[13] From the Greek αδυτος, inaccessible.

The head B of the main bolt is of such a thickness as to be flush with the face of the levers L and guard A; and the strap or tail D of the bolt is thin, and passes behind the levers and guard, and also behind the plate H H. The part of the tail D which would lie under the levers L and cylinder C is removed, as seen in [fig. 54], and replaced by a separate flat plate or stump-bolt, carrying the stump S. This stump-bolt has a projection K upon it, let into a recess in the tail D of the main bolt, but with ¹⁄₁₀th inch vertical play in the recess. A spring in the tail of the main bolt presses the stump-bolt downwards, keeping the stump S in the notches of the levers L, as shown in [fig. 53]. The stump-bolt can thus descend ¹⁄₁₀th inch at first without moving the main bolt, and this amount of vertical movement is sufficient to carry the stump in and out of the notches in the levers; but the stump-bolt cannot descend further without taking the main bolt with it.

fig. 54.

fig. 55.

Immediately in front of the bolts comes the fixed plate H H, in which is cut the cam groove shown by the dotted line J J; and also the vertical slot E for the pin P to work through, together with another vertical slot in which the stump S fits and works. This plate carries the centre pin U on which the levers L turn. The levers are six in number, though any other number may be used; and they occupy collectively ³⁄₈ths inch thickness. In front of the plate H is fixed the guard A, which is made of iron or steel, and has the brass cylinder C ground into it. The guard is made a shade thicker than the levers L, in order to prevent the back plate H and the corresponding front plate from being so tightened on the levers as to impede their freedom of movement. The cylinder C is the same thickness as the levers, excepting the centre boss F, which projects from the back of the cylinder and works in a bearing in the back plate H, and also projects in front through the thickness of the two front cover plates. The small keyhole in the centre of the boss goes only a short distance into the cylinder C, being merely for the purpose of enabling the stem of the key M, [fig. 55], to turn the cylinder; the bit of the key is a separate piece, N, [fig. 57], which is inserted through a separate keyhole into the radial slot of the revolving cylinder C, as shown at N in [fig. 53].

This radial slot is cut in the side of the cylinder C that is furthest from the levers when the cylinder is in the position shown in [fig. 53]; and in the slot fits the slide block R, which is a steel block having a pin projecting on each side. The back pin enters the guide groove J J in the back plate H, as shown by the dotted line, and the front pin enters the corresponding guide groove in the front cover plate, which is shown removed. The back pin of the slide block projects through the back plate H, as shown in [fig. 56], and works in the cam groove O in the tail of the stump-bolt S, [fig. 54], which is so shaped that as the slide block travels round the guide groove J J, shown by the dotted lines, it moves the stump-bolt vertically as may be required according to the position of the bolts and levers.