IMPROVEMENTS IN SAFETY BLASTING CARTRIDGES AND DETONATORS
Year: 1885

page_text: We THE PATENT OXONITE COMPANY Limited of 12 Buckingham Street, Strand,
in the County of Middlesex and ROBERT PUNSHON of 12 Buckingham Street
aforesaid, Chemical Engineer do hereby declare the nature of our invention for
IMPROVEMENTS IN SAFETY BLASTING CARTRIDGES AND DETONATORS, and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :—
Our invention is designed to obviate several important defects that have been
found to exist in Safety blasting Cartridges as ordinarily constructed and used.
By Safety Blasting Cartridges we mean Cartridges in which the explosive com-
pound consists of two parts each of which is in itself practically a non-explosive, the
two parts being kept separate until required to be mingled for the purpose of
explosion. For example a case filled with picric acid in the midst of which a tube
containing nitric acid is imbedded forms a safety blasting cartridge which does not
become efficiently explosive until the tube is broken and the two acids commingle.
The use for explosive purposes of the said two acids and indeed of most com-
binations produced by the admixture of combustible and oxidising substances kept
separate until required for explosion has long been known and was fully described
in the specification filed by Hermann Springel in connection with his application
for Letters patent N° 9211871 and N° 26421871. The said Hermann Springel did not
however specify any particular method of keeping the said substances separate and
of causing them to combine when required for use. One such method was described
by Robert Punshon and Robert Robinson Vizir in the specification filed by them
in connection with Letters Patent N° 2428188 and consisted in "taking a vessel of
glass or other acid proof and friable substance containing nitric acid and hermeti-
cally sealed by means of glass or other acid proof material and introducing the said
vessel into a case or receptacle in which the said vessel is surrounded or covered
with picric acid "-the combination of the two acids being brought about by breaking
the inner vessel. In another specification filed by Robert Punshon and Adam Kay
Anderson in connection with an application for Letters Patent N° 16419 the
glass vessel containing the nitric acid is described as being preferably "in the
form of a tube say a quarter of an inch in diameter and about four inches in
length with a bulb at or about the middle of the tube" and the outer case of the

page_text: cartridge is described as being covered on the outside with a stiff varnish or hard
composition; while the explosion is described as being brought about by means of
a detonator inserted in the inverted head of the Cartridge.
In practice it is found that the above described methods of constructing and
using safety blasting cartridges are defective. In the first place the filling and
sealing of the glass tubes holding the nitric acid is a difficult and troublesome
operation and the sealed ends are very brittle and liable to fracture. Secondly the
imbedding of the tubes in the loose picric acid is a troublesome operation to carry
out at the mine or other place where the Cartridge is to be used; and if the
Cartridges are made up at the outset with the tubes in place, the advantage of
being able to transport the explosive in separate portions is done away with.
Thirdly the breaking of the tube in the cartridge is also troublesome and leads to
a very imperfect incorporation of the two acids unless the Cartridge be well
kneaded Fourthly, the stiffening of the outer case by a composition applied to
the outside thereof is objectionable by reason of its occupying space in the bore-
hole with matter which is not only inert but may, produce flame and smoke.
Fifthly the method of firing by means of a detonator tied in the inverted head of
the Cartridge is apt to diminish the initial velocity of the explosion, and the device
of inserting the detonator into the combined acids, even though the detonator may
be protected by a coating of ozokerite is a very possible source of danger.
We have entered into these particulars in order to more clearly indicate the
nature of our invention which relates principally to the practical details of the
construction and use of safety cartridges and detonators.
We construct our Safety Cartridges in two portions which we denominate respec-
tively, the shell and the core. The Shell is composed of an outer case or wrapper
of paper waterproof cloth or other suitable material. In this we insert a thin tube,
closed at one end, of plaster of Paris mixed with a saturated aquous solution of
picric acid.
The length of this tube corresponds with the ultimate length of the
Cartridge when its contents are mixed together and ready for explosion.
In the centre of the Shell we place a perforated paper tube having an internal
diameter equal to the core. In this paper tube we place a wooden rod and then
we pack the annular space between the paper tube and the plaster tube or outer
casing with picric acid, after which we close the outer case in such a manner that
the end of the wooden rod projects sufficiently to enable the rod to be conveniently
withdrawn.
The core is composed of a glass tube closed at one end and having a glass cap at
the other. Such glass cap being lined with a thin coating of paraffine wax. We
fill the tube with nitric acid and close it by means of the cap, the total length of
the core being that of the wooden rod above referred to.
We construct our safety Detonator in the form of a hollow stem leading to an
Explosion chamber of larger diameter, composed, together with the stem, of thin
copper or other suitable material. We fill the explosion chamber with fine grained
Gunpowder and secure it by a plug of compressed gunpowder or other suitable
material thrust down the stem and we sometimes wrap a layer of guncotton round
the outside of the chamber; or we thrust the chamber into a cap containing gun-
cotton, Dynamite, Cotton powder or some other detonating compound which will
not explode by ordinary percussion. A Detonator thus constructed may be exploded
by means of an ordinary fuse thrust into the stem.
The method of using our Safety Cartridge and detonator is as follows: The Shell,
the Core, and the Detonator are kept separate until actually required for use.
The central rod is then withdrawn from the shell and the core is inserted in the
place of the same with the cap downwards. The glass tube is then gently with-
drawn from the cap, and the shell, so that the nitric acid' escapes at the bottom of
the plaster tube and the picric acid in the upper portion of the shell is pressed
down into the plaster tube where it becomes thoroughly incorporated with the
nitric acid and the outer casing may be folded down tightly into the upper portion

page_text: of the plaster tube. The detonator is then placed in position at the top of the
cartridge and suitably secured, a fuse having previously been fixed in the stem.
The cartridge is then ready for firing.
In some cases we dispense with the plaster of Paris tube and make the outer
casing of the cartridge of acid proof material We also do not restrict ourselves to
the use of picric and nitric acids as our invention is applicable to any known
explosive combinations consisting of two substances which are capable of inter-
mingling when liberated in the presence of each other. Our detonators also may
be used apart from the cartridge and vice versa.
Having now particularly described and ascertained the nature of our said
Invention, and in what manner the same is to be performed, we declare that what
we claim is
1. The construction and use of Safety Blasting Cartridges substantially as
specified.
2. The construction and use of Safety Detonators substantially as specified.