Improvements in Cartridges for Blasting and other Purposes. and
Year: 1885

page_text: Improvements in Cartridges for Blasting and other Purposes.
We, ROBERT PUNSHON of 12, Buckingham Street, Strand in the County of
Middlesex Chemical Engineer, and THE PATENT OXONITE COMPANY Limited
of 12, Buckingham Street, aforesaid, we do hereby declare the nature of our
invention for IMPROVEMENTS IN CARTRIDGES FOR BLASTING AND OTHER PUR-
POSES and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:—
Our invention refers to improvements upon an invention for which Letters
Patent were granted to Robert Punshon and Robert Robinson Vizer the 12th May
1883 No 2428 for An improved method of and apparatus for utilizing an explosive
compound for blasting or other purposes" and the object of the present Invention
is to overcome certain defects which we have found to exist in this explosive as
previously made.
We have by experiment and practice ascertained that in order to produce a good
explosive the picric acid should be much in excess of the nitric acid. The pro-
portions which we have found to answer well are from four to six parts by weight
of picric acid to one part by weight of nitric acid: (which should have a specific
gravity of 1.5) in fat, only just enough nitric acid should be used to bring the
picric acid to a plastic mass.
The nitric acid is contained in a glass vessel of preferably the following
construction: The vessel may conveniently be made in the form of a tube about
five inches long and three fourths of an inch in diameter for about two inches of
its central portion, the two ends being drawn out to fine tubes of about one
sixteenth of an inch in diameter. These ends may be conveniently sealed by
means of a blowpipe after the vessel has been filled with nitric acid.
We find that when the two acids are mixed ready for blasting, the cartridge
becomes too soft to be forced into position in the bore-hole. To overcome this
drawback we cover the outer case with a stiff varnish made of ozokerit, turpentine,
gluten and resin melted together and applied hot. This hardens the outer case
and is also sufficiently acid-proof to bear carrying and loading the bore-hole
therewith even after the two acids are mixed. An alternative composition used
by us for the same purpose consists of soda silicate and asbestos powder or powder
from any micaceous rock mixed and applied cold. Or we can use any suitable
known stiffening compound and as an alternative we can make the cartridge cases
of india rubber cloth.

page_text: The above described explosive is best exploded in the blast-hole by means of
a detonator inserted into a small pure gun cotton primer or nitro-compound upon
which the acids have no effect; or the detonator and part of the fuze may be
coated or covered with pure ozokerit or other acid proof material.
The detonator is inserted in the inverted head of the cartridge and is there held
by string or wire so that the detonator and fuse cannot be withdrawn during the
tamping or we sometimes tie the detonator on the outside of the cartridge.
"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 combination in a cartridge for blasting or other purposes of an explosive
charge consisting of picric acid made plastic by the addition of strong nitric acid
substantially as specified.
2. The combination in a cartridge for blasting or other purposes of a cartridge
case consisting of calico or other fabric stiffened by treatment with acid-proof
varnish or composition substantially as specified.
3. The combination in a cartridge for blasting or other purposes of a cartridge
case consisting of indiarubber cloth substantially as specified.
4. A glass receptacle for the nitric acid required for making any explosive
compound for blasting purposes in the form of a tube drawn out for sealing at each
end substantially as specified.
5. The combination in a cartridge for blasting or other purposes of a detonator
placed in the inverted head of the cartridge substantially as specified.
Dated this twenty fifth day of September One thousand eight hundred and