Improvements in Detonators for Railway Signalling Purposes.
Year: 1893

page_text: Date of Application, 1st Sept., 1893-Accepted, 14th Oct., 1893
COMPLETE SPECIFICATION.
[Communicated from abroad by HENRY FROST CLARK, a citizen of the United
States of America, residing at Easton, in the State of Pennsylvania, Engineer.]
Improvements in Detonators for Railway Signalling Purposes.
I, JOHN PATRICK O'DONNELL, of 70 & 71 Palace Chambers, Bridge Street,
Westminster, in the County of Middlesex, Civil Engineer, 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 consists in improvements in the construction of detonators designed
more especially for use in fog signalling apparatus, but may be used in substitution
for the ordinary detonators and exploded by the wheels of the engine or vehicle
passing over them, as at present.
In some particular variety of fog signalling apparatus a magazine is generally
provided filled with detonators which are carried or pushed, as required, and are
exploded under a hammer operated by the flange of the wheel.
My object is to make the detonator of such material and construction so that
after the explosion there will be very little residue of the detonator left to clog or
otherwise hamper the further proper working of the machine and will also allow
the machine to work to a greater degree of accuracy.
My detonator is formed of an inner case of tin, in which is placed an annular
shaped piece of glass provided with a suitable number of supports for the purpose
of affixing detonating caps, this inner case is then filled with fulminite and the
whole is enclosed in a suitable thin casing of metal and made watertight.
In the drawing annexed
Figure 1 is an elevation of my detonator, and Figure 2 a section, Figure 3 a plan
on top and Figure 4 a plan with the cover removed showing the glass anvil within
the inner casing.
Figure 5 is an elevation of the inner casing free of the rest of the detonator, and
Figures 6 and 7 an elevation and plan respectively of the glass anvil.
The following letters refer to the various parts throughout the drawing
:-
a is the outer casing, 6 the lid or cover which is crimped and laps over the edge
of the casing a and is made watertight by filling the space at c with white lead or
other suitable material. d is the inner case of tin, in which is placed the glass
anvil e, with supports f, g, h, cast on for the caps i, j, the rest of the case being filled
in with fulminite k.
The action is as follows:-
The hammer striking on the detonator explodes the fulminite by means of the
caps and j, fixed on the supports f, and reduces the glass anvil to atoms, and the
inner and outer casings being of such thin material very little resistance is offered
to the hanimer, and the whole is crushed into an exceedingly small space.
In the event of the failure of the caps to explode, the breaking of the glass will
be sufficient to ignite the fulminite.
proper
The inner casing d is made sufficiently strong to keep the detonator in
shape resisting ordinary rough usage without exploding, but necessitating, to cause
explosion, a sharp and decisive blow.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1. In detonators for audible railway signalling purposes, a glass anvil with
upright projections to receive caps, substantially as and for the purposes set forth
and as illustrated in the drawing annexed.

page_text: 2. In detonators for audible railway signalling purposes, an inner case such as d
to receive the glass anvil and for giving rigidity to the detonator necessitating a
harder blow for the purpose of explosion, substantially as described and as illustrated
in the drawing annexed.
3. In detonators for audible railway signalling purposes, the construction of the
outer case ab, the cover b being crimped so as to be made water tight by the
insertion of white lead, or other suitable water tight joint, substantially as and for
the purposes set forth and as illustrated in the drawing anuexed.
4. In detonators for audible railway signalling purposes, the combination of the
anvil e, fulminite k, inner casing d and outer casing a-b, substantially as described
for the purposes set forth and as illustrated in the drawing annexed.
Dated this First day of September 1893.
JOHN P. O'DONNELL,
70 & 71, Palace Chambers, Bridge Street, Westminster, London, S.W.,
Agent for the said Applicant.