IMPROVEMENTS IN THE MANUFACTURE OF METALLIC CARTRIDGE CASES, AND IN TOOLS AND MACHINERY TO BE USED IN THE SAID MANUFACTURE
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by Henry Skerrett at the Office of the
Commissioners of Patents on the 19th November 1880.
HENRY SKERRETT, of 6, Whitby Road, Sparkbrook, near Birmingham, in County
of Warwick, Mechanical Engineer. "IMPROVEMENTS IN THE MANUFACTURE OF
METALLIC CARTRIDGE CASES, AND IN TOOLS AND MACHINERY TO BE USED IN
THE SAID MANUFACTURE."
In the ordinary method of manufacturing solid headed cartridge cases discs are
cut out from sheet metal of the proper thickness and formed into cups. These cups
are annealed and passed through different sized dies several times until the proper
diameter and length of cartridge case or shell is obtained. In the whole process of
cupping and drawing through, the cup, shell, or case under operation always
preserves the same diameter throughout its length, that is to say, each cupping or
drawing through die produces a length of shell or case, the sides or walls of which
are of the same diameter throughout its length; this, the ordinary process of
drawing through, reduces the thickness of the metal both at the head and at the
sides or walls of the cartridge case next the head, which is desirable.
The object of the first part of my Invention is to produce solid headed cartridge
cases, having a considerable thickness of metal both at the head or base part and
for a short distance up the walls next to the head or base part or shell so as to
strengthen the head and sides or walls of the case nearest the said head, and
thereby render them less liable to burst.
This I accomplish in the following manner:-I take a thick disc cut from sheet
metal and raise from out of its centre or middle part a sunken cavity or well, the
outside diameter of which (when the walls of the case at the base end require to
have a considerable thickness of metal) said cavity or well is exactly equal to the
diameter of the sides or walls of a finished cartridge case or shell to be produced.
The
The cavity or well may be produced at a press, or by a stamp, or by rolls.
before described blank with the cavity or depression in its middle is next passed
through a cupping die, and a cup produced having two diameters. That part of
the cup next to the base or closed end is of less diameter than the 'part at the
mouth or open end of the said cup. It is from the part of larger diameter that
the thin walls of the finished cartridge case are produced by the usual drawing
through dies.

page_text: .
By this method of manufacture in conjunction with the tools constituting part of
my Invention, a cartridge case is produced in which the contracted or throttled
base end of the shell passes through the several dies without touching the acting
surfaces of the said dies, so that by the diminution of diameter at the base end of
the cup or shell, the successive drawings through of the part of larger diameter of
the said cup or shell are effected without the base and contracted end being
operated upon by the walls of the dies, the elongation of the case or shell being
produced as aforesaid from the mouth end, or that part of the case or shell of
larger diameter lying above the throttled part.
Further, a cartridge case is produced in which the metal at the base end of the
case is not deteriorated in ductility or tenacity by the repeated action of the tools
used in the formation of the said cartridge case or shell. The last drawing through
reduces the shell or case to a uniform diameter: Where a less thickness of metal
at the base end of the walls of the cartridge case is required, the throttle or
contracted end is made larger in diameter than that before described, or is made
larger in diameter than the finished cartridge case to be produced. In using this
kind of base end, the latter drawings through also operate upon the base end as
well as upon the mouth end of the shell or case under operation.
The throttling and cupping of the blank may be effected at one operation. The
cap chamber anvil and flange are produced in the case made as described in the
ordinary way.
Or the cap chamber and anvil may be produced in the blank before the said
blank is converted into a cup with a contracted or throttled base part, that is to
say, the said dise having in its middle or centre a cap chamber and anvil is passed
with its cap chamber and anvil undermost partially through a throttling cupping
die, or a die, the parallel sides of which have two diameters. There is thus
produced a cup with a contracted or throttled closed end with a cap chamber,
anvil, and an annular rise or mound in the head to form the flange of the finished
case, or the said disc may be formed with cap chamber and anvil together with the
annular flange rise or mound.
Further, the cup with a contracted base or head, cap chamber, anvil, and flange
mound may be produced from a blank before its passage through the drawing-
through dies. When that part of the case or shell of larger diameter has been
drawn to the required length the flange is "knocked up" from the annular mound
in the usual way to complete the cartridge case.
The throttling or contracting of the base end of a case or shell as before described
may also be produced either after cupping the blank, or at one of the early stages of
drawing through.
Instead of a blank or disc as described a short length of tubing may be operated
upon at one end by gathering in or closing tools. The said gathering in or closing
tools contract the walls at one end of the said tube until it assumes a closed head
with a throttled or contracted base, as before explained with respect to the first
described part of my Invention.
Or the short length of tubing may be closed at one end and expanded or
enlarged at the other or open end, thereby producing a long cup closed at bottom
and having two diameters.
The cases or shells described may be formed from two or three thin discs of the
same or of different metals, the said thin disc may be of the same size or of different
sizes, which said discs are placed flat upon each other and raised into cups to be
afterwards drawn.
Or cases or shells may be produced from metal that will draw or roll when at a
red heat (in a soft state), that is to say, an alloy of copper and zinc, known
in commerce as Muntz's metal, viz., 60 per cent. of copper to 40 per cent. of
zinc or thereabouts.
When the cases are made of this metal they may be drawn at one operation in
the ordinary way of drawing through metals, excepting that the mandril or
plunger on which the case is drawn is preferably made in two parts.
The inner

page_text: mandril strips the cartridge case from the outer one before the contraction of the
said case upon the said outer mandril, or where the whole case is produced at one
operation, as last described, I prefer to use a bulbed mandril and drawing-through
die, combined with rolls.
Or cartridge cases made from lengths of thin tubing, one end of the said lengths
of tubing being thickened by upsetting or by back drawing, or by other means.
This thickened end is closed by spinning or by closing tools so as to produce a
thick ended closed tube, or the end of the tube may be closed first and afterwards
thickened.
My Invention consists further in rolling strips of metal having raised or thick
metal bosses at determinate or equal distances apart along the middle of the said
strip, and cutting from the said strips discs to be afterwards formed into cartridge
cases. Each disc has a central boss of thick metal, while the edge of the said disc
are of thin metal. The thick metal centre or boss may be plain or have a contour
or formation resembling the head, cap chamber, anvil, and flange mound of a
solid headed metallic cartridge before the flange has been formed. The tapering of
the thin edges of the disc commences where less metal is necessary to form the base
end of the cartridge case. These discs with thin edges and thick centres are
formed into solid headed cartridge shells or cases by drawing-through dies with
fewer processes and with less labour than by the ordinary method of drawing
down a thick short cup.
"
I produce by rollers constructed as hereinafter described, the before described
strip which I call the "disc strip in the following manner :-I take a strip of
metal of a width considerably less than the disc strip to be rolled, and of a
thickness about equal to the thickness of the bosses to be formed on the said disc
strip. This thick strip of metal is then passed through two rolls, one of which has
cut away parts at equal distances on the periphery of the said roll, the second roll
is plain. The said cut away parts for the counterparts of the bosses to be left on
the disc strip, so that the strip is left unoperated upon by the rolls at the cut away
parts, but the metal lying radially around the said cut away parts is thinned or
flattened by the action of the plain surfaces of the rolls.
When the thickened part is to take the conformation of the head, cap chamber,
and anvil of a case before the flange has been produced, I form depressions in the
periphery of one roll and studs or raised parts upon the other roll.