Improvements in Keys for Door and other Locks.
Year: 1888

page_text: Date of Application, 16th Oct., 1888
Complete Specification Left, 16th July, 1889-Accepted, 17th Aug., 1889
PROVISIONAL SPECIFICATION.
Improvements in Keys for Door and other Locks.
I, THEODOR KROMER, of Freiburg, in the Empire of Germany, Manufacturer, dó
hereby declare the nature of this invention to be as follows:-
My invention relates to keys for door and other locks, and is chiefly designed to
prevent or render very difficult the obtaining of correct impressions in wax or other
material of the two sides of the bit of a key, and the production thereby of imitations
or duplicates of the said key.
For this purpose, in applying my invention to stepped keys, such as are used for
"Chubb" and other locks, I make the two sides of the bit of the key unsymmetrical
by grooving or hollowing out one or more of the steps on one side so that the hollow
groove extends beyond the centre.
In stepped keys as heretofore made, the sides of the rounded ends of the steps are
symmetrical, therefore it is comparatively easy to take impressions of, and cast or
otherwise form, duplicates of such keys.
In carrying my invention into practice, I make the rounded end, either of a single
step or of all the steps, unsymmetrical by grooving or hollowing out one side of the
rounded or operative part of the step by means of a cutter so that the hollow or groove
extends beyond the centre; the remaining part being rounded off. The key has, there-
fore, no longer any plane of symmetry that enables an accurate mould or impression
to be taken therefrom, that is to say, although a correct impression of one side of the
key-bit can be obtained, the impression taken from the other side will be imper-
fect, as the part of the hollow or groove beyond the centre will not have its counter-
part in the said impression. The several steps of the key are in some instances,
grooved or hollowed out in different manners, or some of them are hollowed out more
than others.
My said invention is also applicable to keys for locks in which a cylinder is fitted to
turn in another cylinder, and pins or slides are arranged in the said cylinders in such
a manner that they will permit the turning of the inner cylinder when, but not until,
they are moved into certain positions by the key.
My invention can, moreover, be applied to keys with one or more bits.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Keys for Door and other Locks.
I, THEODOR KROMER, of Freiburg, (Baden), in the Empire of Germany, Manu-
facturer, do hereby declare the nature of this invention and in what manner the
same is to be performed to be particularly described and ascertained in and by the
following statement:-
My invention relates to keys for door and other locks, and is chiefly designed to
prevent or render very difficult the obtaining of correct impressions in wax or other
material of the two sides of the bit of a key, and the production thereby of imitations
or duplicates of the said key.
In stepped keys (for "Chubb" and other locks) as heretofore made, the sides of the
rounded ends of the steps are symmetrical, therefore it is comparatively easy to take
impressions of, and cast or otherwise form duplicates of such keys.
But according to my invention, I make the two sides of the bit of the key
unsymmetrical by grooving or hollowing out one or more of the steps on one

page_text: side, so that the hollow or groove ‘extends beyond the centre, as hereinafter more
particularly described. .
In the accompanying drawing,
Figure 1ista rear elevation showing a cylindrical lock open, with an ordinary
double bitted key in position therein, a portion of the casing of the said lock being
removed.
Figure 2 is a similar view to figure 1 showing a similar lock: fitted with my
improved key with two bits.
Figures 3 and 4 are rear elevations showing my improvements applied to keys with
one bit.
Like letters indicate corresponding parts throughout the drawing.
A is the lock, B is one of the bolts or slides thereof, C is the stem of the key,
D, D, are the bits thereof.
The
The rounded end either of a single step or of all the steps of the bit or bits of
the key are formed unsymmetrical, by grooving or hollowing out one side of the
rounded or operative part of the step by means of a cutter so as to form a hollow or
groove D extending beyond the centre, the remaining part being rounded off.
key has, therefore, no longer any plane of symmetry (as indicated by the dotted line in
figure 1). that enables an accurate mould or impression to be taken therefrom, that is
to say, although a correct impression of one side of the key-bit D can be obtained, the
impression taken from the other side will be imperfect, as the part of the hollow or
groove D beyond the centre will not have its counterpart in the said impression.
The several steps of the key are in some instances, grooved or hollowed out in different
manners, or some of them are hollowed out more than others.
Figures 3 and 4 show different manners of hollowing or grooving out the steps of
the bits of keys in accordance with my said invention.
Although I have hereinbefore described and illustrated my said invention as applied
to keys for locks in which one cylinder is fitted to turn in another cylinder and bolts
or slides are arranged in the said cylinders, in such a manner that they will permit the
turning of the inner cylinder, when but not until, they are moved into certain positions
by the key; it is obvious that my improvements are also applicable to other locks, and
to keys with any number of bits.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
A stepped key having grooves or cavities formed in one or more of the step-ends
and extending beyond the centre of the bit, for the purpose above specified.
Dated this 16th day of July 1889.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.