Improvements in Dies for Gear Forging, and Means for Making such Dies.
Year: 1894

page_text: Date of Application, 1st Jan., 1894
Complete Specification Left, 1st Oct. 1894-Accepted, 17th Nov., 1894
PROVISIONAL SPECIFICATION.
Improvements in Dies for Gear Forging, and Means for Making
such Dies.
A communication from abroad by THE UNITED STATES PROJECTILE COMPANY,
a Corporation organized under the laws of the State of New York, United
States of America, and doing business at Brooklyn, in said State.
I, JOHN CLAYTON MEWBURN, of 55 and 56 Chancery Lane, in the County of
London, Chartered Patent Agent, do hereby declare the nature of this invention
to be as follows:-
:-
This invention relates to the making of dies from which to forge gear wheels or
pinions, etc., of steel or wrought iron or other metals of the character described in
the Specification of the Patent of E. W. Bliss, No. 5537, dated March 21, 1892.
In making such gears a heated billet of metal is placed in a female die and
subjected to hydraulic or other heavy pressure transmitted through a male die or
punch which enters the female die, the pressure being sufficient to
cause the
billet to flow and expand into and fill the teeth formed within the female die,
whereby is formed a compressed gear or pinion having its teeth ready finished
and of great strength and toughness. The gear thus formed is forced out through
the die.
The present invention provides improved means for making or preparing the
dies to be used in such forging of gear wheels and the like. Such a die requires
to be made with internal gear teeth conforming in every respect to the external
teeth to be formed on the gear or pinion, except that they are made enough larger
to allow for the shrinkage of the metal of the gear in cooling, and the die is made
of a sufficiently greater height than the length or thickness of the gear or pinion
to be made. The internal surface of the die requires to be of chilled cast iron
in order to afford such extreme hardness as will resist the cutting or tearing
tendency of the billet during the formation of the compressed gear and its
expulsion from the die.
The requisite hardness of the inner surfaces can be attained only by forming
the inner portion of the die of chilled cast iron, but as this material has not
sufficient resistance to bursting strain, it is necessarily reinforced by shrinking over
it a steel ring. The internal teeth of the die cannot be cut or finished by
machinery according to any usual methods because of the extreme hardness of
the chilled surface. Consequently it is necessary to cast them originally of the
exact form required, and with the requisite degree of smoothness.
these results, I prepare the die in the following manner :-
To accomplish
I first make a blank gear or pinion of cast iron, cutting it accurately with teeth
of the same diameter and pitch as those in the gear or pinion to be forged, except
that it is made enough larger to allow for shrinkage. This cast iron blank is also
made longer than the gear or pinion to be forged, its length being equal to or
exceeding the height of the die. Its teeth are finished with the amount of
smoothness or polish required. This cast iron blank is then used as a core, being
placed in the mould in which the inner portion of the die is cast, and the latter is
then cast around it in the ordinary way, so that the cast iron blank serves as a
chill-core to impart the requisite hardness to the inner surfaces of the die. The
core or chill is then bored out with as large a bore as can be made within the hard

page_text: metal of the casting. This leaves the teeth of the chill still embedded between
the teeth of the casting, but they are easily removed by driving them out, thereby
leaving the die perfect in shape and size, and with its teeth smooth and finished.
Its outer surface being then turned down if necessary, the cast steel ring is shrunk
upon it, thereby completing the die.
Instead of making the outer ring of solid steel or wrought iron as heretofore, I
form in it a tortuous channel for the circulation of water to cool the die. To this
end the ring is formed preferably of cast steel with a series of upright channels
or passages cored out in its outer portion, and connected together alternately at
top and bottom by cross passages or openings. The water is admitted by a pipe
and flows alternately up and down through the successive passages, finally being
conducted away by a pipe. By means of this water circulation the die is kept
cool, and its life is thereby greatly prolonged. Without the cooling effect of this
water jacket, the die would soon become heated to redness, and so weakened that
under the heavy strain it is necessary to put upon it in use, the inner portion would
crack between the teeth, dividing into segments, the slight separation of which
would throw the teeth slightly out of line and form an imperfect pinion, and the
die would soon become so injured as to be practically useless. These difficulties
are entirely overcome by the provision for cooling the die by a circulation of water
through its outer strengthening ring; and by means of the construction of the
water passages to extend vertically, with solid connecting walls between them, all
necessary strength for the steel ring is retained without making it of unduly large
diameter.
Dated this 1st day of January 1804
C
COMPLETE SPECIFICATION.
Improvements in Dies for Gear Forging, and Means for Making
such Dies.
A communication from abroad by THE UNITED STATES PROJECTILE COMPANY,
a Corporation organized under the laws of the State of New York, United
States of America, and doing business at Brooklyn, in said State.
I, JOHN CLAYTON MEWBURN, of 55 and 56 Chancery Lane, in the City
of Loudon, Fellow of the Chartered Institute of Patent Agents, 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 :-
This invention relates to the making of dies from which to forge gear wheels or
pinions, etc., of steel or wrought iron or other metals of the character described in
the Specification of the Patent of E. W. Bliss, No. 5537, dated March 21st, 1892.
In making such gears a heated billet of metal is placed in a female die and
subjected to hydraulic or other heavy pressure transmitted through a male die or
punch which enters the female die, the pressure being sufficient to cause the
billet to flow and expand into and fill the teeth formed within the female die,
whereby is formed a compressed gear or pinion having its teeth ready finished
and of great strength and toughness. The gear thus formed is forced out through
the die.
The present invention provides an improved means for making or preparing the
dies to be used in such forging of gear wheels and the like. Such a die requires
to be made with internal gear teeth conforming in every respect to the external
teeth to be formed on the gear or pinion, except that they are made enough larger
to allow for the shrinkage of the metal of the gear in cooling, and the die is made
of a sufficiently greater height than the length or thickness of the gear or pinion

page_text: to be made. The internal surface of the die requires to be of chilled cast iron in
order to afford such extreme hardness as will resist the cutting or tearing tendency
of the billet during the formation of the compressed gear and its expulsion from
the die.
The requisite hardness of the inner surfaces can be attained only by forming
the inner portion of the die of chilled cast iron, but as this material has not
sufficient resistance to bursting strain, it is necessarily reinforced by shrinking
over it a steel ring. The internal teeth of the die cannot be cut or finished by
machinery according to any usual methods because of the extreme hardness of the
chilled surface. Consequently it is necessary to cast them originally of the exact
form required, and with the requisite degree of smoothness. To accomplish these
results is the object of this invention, which will now be described with reference
to the accompanying drawings.
Fig. 1 is a perspective view of a forged gear or pinion made according to the
said Bliss Patent;
Fig. 2 is a plan view of the die ;
Fig. 3 is a transverse section thereof on the line 3-3 in Fig. 2 ;
Fig. 4 is an elevation of the cast iron blank from which the die is formed;
Fig. 5 is a horizontal section through the cast iron portion of the die on the
line 5-5 in Fig. 3, showing a stage in the formation of the die;
Fig. 6 is another similar cross-section showing a further stage in the formation
of the die;
Fig. 7 is a vertical section on the line 7-7 in Fig. 3.
The forged gear A, (Fig. 1) is made in the female die B (Figs. 2 and 3), by placing
this die on the bed of a hydraulic press, heating a billet of steel which is large
enough to drop within the die, placing it therein, placing on top of it a male die
or punch formed with teeth and conforming to and adapted to enter the female
die B, and forcing this male die into the female die by hydraulic pressure so as to
compress the heated billet and cause its metal to flow, whereby it is expanded and
fills all portions of the internal teeth of the female die, and conforms itself
accurately thereto. The pressure is then released, and by pressure subsequently
applied, the forged gear or pinion is forced out of the female die in either direction.
For a further description of the operation, reference may be made to the said Bliss
Patent.
In the manufacture of forged gears or pinions according to this method, con-
siderable difficulty has been encountered in the proper formation of the female die.
Its teeth must be perfectly smooth, as otherwise the teeth of the forged pinion
will be torn, scratched or injured in forcing it out of the die. The inner surfaces
of the die must also be extremely hard in order to resist injury during the forcing
of the hot billet to flow against them, and during the subsequent expulsion of the
pinion. The requisite hardness of the inner surfaces can be attained only by
forming the inner portion of the die of chilled cast iron, but as this material has
not sufficient resistance to bursting strain, it is necessarily reinforced by shrinking
over it a steel ring. In the drawing, a shows the inner portion of the die which
is of chilled cast iron, and b the outer portion or steel ring which is shrunk upon
it. The internal teeth of the die cannot be cut or finished by machinery according
to any usual methods because of the extreme hardness of the chilled surface.
Consequently it is necessary to cast them originally of the exact form required,
and with the requisite degree of smoothness. To accomplish these results, we
prepare the die in the following manner :-
We first make a blank gear or pinion of cast iron, cutting it accurately with
teeth of the same diameter and pitch as those in the gear or pinion to be forged,
except that it is made enough larger to allow for shrinkage. This cast iron blank is
also made longer than the gear or pinion to be forged, its length being equal to or
exceeding the height of the die. This cast iron blank is shown in Fig. 4, being
lettered c.
Its teeth are finished with the amount of smoothness or polish required.
This cast iron blank is then used as a core, being placed in the mould in which the

page_text: •
inner portion a of the die is cast, and the latter is then cast around it in the
ordinary way, so that the cast iron blank c serves as a chill-core, to impart
the requisite hardness to the inner surfaces of the die. Fig. 5 is a section of the
casting thus produced around this core or chill c. The core or chill is then bored
out in the manner shown in Fig. 6, with as large a bore as can be made within the
hard metal of the casting. This leaves the teeth of the chill still embedded
between the teeth of the casting, but they are easily removed by driving them
out, thereby leaving the die perfect in shape and size, and with its teeth smooth
and finished. Its outer surface being then turned down if necessary, the
cast steel ring b is shrunk upon it, thereby completing the die, as shown in
Figs. 2 and 3.
Instead of making the outer ring b of solid steel or wrought iron as heretofore,
we now form it in a tortuous channel for the circulation of water to cool the die.
To this end the ring is formed preferably of cast steel with a series of upright
channels or passages dd cored out in its outer portion, and connected together
alternately at top and bottom by cross passages or openings ee, as shown best in
Fig. 7. The water is admitted by a pipe f (Fig. 2) and flows alternately up and
down through the successive passages d, finally being conducted away by a pipe g
(Fig. 2). By means of this water circulation the die is kept cool, and its life is
thereby greatly prolonged. Without the cooling effect of this water jacket, the
die would soon become heated to redness, and so weakened that under the heavy
strain it is necessary to put upon it in use, the inner portion a would crack between
the teeth, dividing into segments, the slight separation of which would throw the
teeth slightly out of line and form an imperfect pinion, and the die would soon
become so injured as to be practically useless. These difficulties are entirely
overcome by the provision we have made for cooling the die by a circulation of
water through its outer strengthening ring, and by means of the construction of
the water passages to extend vertically, with solid connecting walls between
them, whereby all necessary strength for the steel ring is retained without making
it of unduly large diameter.
Having now particularly described and ascertained the nature of the said inven-
tion, as communicated to me, and in what manner the same is to be performed, I
declare that what I claim is
1. The improved method of making a die in which to forge gear wheels,
consisting in cutting a cast iron blank with gear teeth of the diameter and pitch
required for the gears to be forged except enough larger to allow for shrinkage,
and of a length equal to the die to be made, then casting the die around said
blank as a chill-core, and then boring out said blank and driving out its teeth,
leaving the die of the exact shape, size and finish required, substantially as
herein before set forth.
2. The improved method of making a die in which to forge gear wheels,
consisting in cutting a cast iron blank with gear teeth of the diameter and pitch
required for the gears to be forged except enough larger to allow for shrinkage,
and of a length equal to the die to be made, then casting the die around said blank
as a chill-core, and then boring out said blank and driving out its teeth, and finally
shrinking a steel ring around the exterior of said cast die, substantially as herein-
before set forth.
3. The improved method of making a die in which to forge gear wheels,
consisting in casting the inner portion of the die around a cut blank as a chill-
core, then boring out and removing said blank, casting on a steel ring with
connected water passages cored out around its upper portion, and finally shrinking
said ring around the exterior of said cast die, substantially as hereinbefore set
forth.
4. The improved die for forging gear wheels, etc., consisting of an inner
toothed portion of chilled cast iron, and an outer strengthening ring shrunk upon
it, with sinuous water passages formed around the die in the outer portion of said

page_text: ring and extending between opposite ends of the die, for enabling the cooling of
the die by the circulation of water through said passages, substantially as
herein before set forth.
J. C. MEWBURN.