IMPROVEMENTS IN THE MANUFACTURE OF METALLIC CARTRIDGE CASES
Year: 1879

page_text: LETTERS PATENT to John Harley Burt, of No. 37, Gracechurch Street, in the
City of London, for the Invention of "IMPROVEMENTS IN THE MANUFACTURE
OF METALLIC CARTRIDGE CASES."
Sealed the 4th July 1879, and dated the 28th April 1879.
PROVISIONAL SPECIFICATION left by the said John Harley Burt at the
Office of the Commissioners of Patents on the 28th April 1879.
JOHN HARLEY BURT, of No. 37, Gracechurch Street, in the City of London.
"IMPROVEMENTS IN THE MANUFACTURE OF METALLIC CARTRIDGE CASES."
My Invention relates to the manufacture of metallic cartridge cases of such
material and in such manner as to effect very considerable economy in the time,
labour, and cost of their production. For this purpose instead of employing the
comparatively costly metal copper or its alloys which are ordinarily used I employ
the cheaper metal zinc, either pure or in alloy, with a small proportion of other white
metal, and instead of having recourse to the expensive and dilatory processes now
in use for producing the blanks and punching and drawing them into form, I adopt
the following method of manufacture:-I melt the zinc and pour the melted metal
into a cup shaped mould, and while the metal is in the act of setting in the mould
I subject it to the pressure of a round nosed punch of smaller diameter than the
mould so as to squeeze a portion of the metal up into the annular space between
the punch and the interior surface of the mould." The metal is then extruded from
the mould in the shape of a short tube with one end closed in rounded form. This
tube constitutes the blank which by several successive drawings in the ordinary
way, but without the need for annealing, is converted into the cartridge case, the
head being formed and the mouth being closed in by the usual processes according
to the pattern desired. In these processes it is of advantage to keep the tools warm
by steam or other convenient means of heating so as to give greater ductility to the
metal. By treating zine, or zinc slightly alloyed, in the manner described I am
enabled by the one operation of casting and squeezing before the metal has set to
produce closed tubes or blanks in the form which when copper and its alloys are
used requires for its production a number of successive operations, that is to say, the
Prin

page_text: copper or brass has to be melted, cast into ingots, and rolled into sheet or bar; from
the sheet or bar pieces of disc form have to be punched, and these discs have to be
hollowed by pressure into the form of cups which have to be deepened and narrowed
by successive punching and drawing operations, with intermediate annealings, until
they are brought to the shape of the blank such as I produce by the one operation.
Moreover, in reducing the zinc blanks to their finished shape by further punching
and drawing I find fewer operations necessary than are required for blanks of
copper or its alloys, and I entirely dispense with the several annealing processes
which are applied for giving the latter material the required ductility. I am thus
enabled by the use of a cheap material and by the suppression of a number of the
stages of operation required for the treatment of the more expensive material to
effect a large economy in the time, labour, and cost of producing metallic cartridge
cases,

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Harley Burt in the Great Seal Patent Office on the 27th
October 1879.
JOHN HARLEY BURT, of No. 37, Gracechurch Street, in the City of London.
"IMPROVEMENTS IN THE MANUFACTURE OF METALLIC CARTRIDGE CASES."
My Invention relates to the manufacture of metallic cartridge cases of such
material and in such manner as to effect very considerable economy in the time,
labour, and cost of their production. For this purpose instead of employing the
comparatively costly metal copper or its alloys, which are ordinarily used, I employ
the cheaper metal zinc, either pure or in alloy, with a small proportion of other
white metal, and instead of having recourse to the expensive and dilatory processes
now in use for producing the blanks and punching and drawing them into form, I
adopt the following method of manufacture:-I melt the zinc and pour the melted
metal into a cup shaped mould, and while the metal is in the act of setting in
the mould I subject to the pressure of a round nosed punch of smaller diameter
than the mould so as to squeeze a portion of the metal up into the annular
space between the punch and the interior surface of the mould. The metal is then
extruded from the mould in the shape of a short tube with one end closed in rounded
form. This tube constitutes the blank which by several successive drawings in the
ordinary way, but without the need for annealing, is converted into the cartridge
case, the head being formed and the mouth being closed in by the usual processes
according to the pattern desired. In these processes it is of advantage to keep the
tools warm by steam or other convenient means of heating so as to give greater
ductility to the metal.
By treating zinc, or zinc slightly alloyed, in the manner described I am enabled
by the one operation of casting and squeezing before the metal has set to produce
closed tubes or blanks in the form which when copper and its alloys are used
requires for its production a number of successive operations, that is to say, the
copper or brass has to be melted, cast into ingots, and rolled into sheet or bar; from
the sheet or bar pieces of disc form have to be punched, and these discs have to be
hollowed by pressure into the form of cups which have to be deepened and narrowed
by successive punching and drawing operations, with intermediate annealings, until
they are brought to the shape of the blank such as I produce by the one operation.
Moreover, in reducing the zinc blanks to their finished shape by farther punching
and drawing I find fewer operations necessary than are required for blanks of
copper or its alloys, and I entirely dispense with the several annealing processes
which are applied for giving the latter material the required ductility. I am thus
enabled by the use of a cheap material, and by the suppression of a number of the
stages of operation required for the treatment of the more expensive material, to
effect a large economy in the time, labour, and cost of producing metallic cartridge
cases.
In order to protect cartridge cases thus produced from the corrosive action of
their charges it is of advantage to line their interior with paint, varnish, or other
suitable coating.
Having thus described the nature of the said Invention, and in what manner the
same is to be performed, I claim,-
The manufacture of cartridge cases of zinc pure or slightly alloyed effected by

page_text: casting the metal in a cup mould, pressing a rounded punch into the metal while it
is setting, and reducing the blank so produced to the desired form by several
drawing operations as herein described.
In witness whereof, I, the said John Harley Burt, have hereunto set my hand
and seal, this Twenty seventh day of October, in the year of our Lord One
thousand eight hundred and seventy nine
JOHN HARLEY BURT. (L.S.)