Improvements in Forges or Furnaces for Heating or Working Metals Electrically.
Year: 1894

page_text: Date of Application, 9th Jan., 1894-Accepted, 1st Dec., 1834
COMPLETE SPECIFICATION.
Improvements in Forges or Furnaces for Heating or Working Metals
Electrically.
A communication by CHARLES LEWIS COFFIN, of 980, Jefferson Avenue,
Detroit, in the County of Wayne, and State of Michigan, United States of
America, Chemist.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of The Agency for
Foreign Patent Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street,
Manchester, both in the County of Lancaster, and 323, High Holborn, in the
County of Middlesex, Civil Engineer, 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 consists in an improved forge or furnace for heating or working
metals electrically, hereinafter fully described and claimed.
Figure 1 is a side elevation with the upper portion in vertical central section;
Figure 2 is a longitudinal sectional view through the refractory bed J';
Figure 3 is a detail vertical central sectional view of the upper part like that
of Figure 1, but with the articles to be worked in position; and
Figure 4 is a detail sectional view through the upper part of Figure 1.
T represents a table having a top and legs. J represents a bed of refractory
non-conducting material in which may be a coil of pipe B, whose inner end comes
up through the centre of the bed J¹ thro' the stop of refractory material P, as
shown in Figure 1, while its lower end leads downwards through the table for the
purpose of being connected to any suitable source of supply of air, gas or vapour.
I represents insulating material, and the bed of refractory material J' is flanked on
each side by blocks of insulating material. C and CC represent carbons, each of
which is held in a tube D, upon which is a shoulder K, and each tube D is
encircled by a spring S, which presses against shoulder K, and against a fixed
stop k, supported on the table, but insulated therefrom, by means of which springs
the carbons C and CC are constantly pressed towards each other, but are prevented
from coming into contact by a stop P of refractory non-conducting material, which
is carried on the bed of refractory material J₁ between the points of said carbons.
The carbon C C is hollow and through the bore passes a smaller carbon or
pencil C. E represents a collar clamped on carbon pencil C₁, and provided with a
pin which engages with a slot in a lever F pivoted to the table. The lower end of
this lever is connected to the core L of a sucking coil m, and also to a spring H,
the other end of which spring is fastened to a lug on the table, whereby said
lever F is swung (when the magnet is not energized) in such manner as to project
the carbon pencil C₁ through the hollow carbon C C in contact with the carbon C.
J represents a block of refractory material through the centre of which is an
opening shown in Figures 1 and 4 which lies upon the bed of refractory material in
such manner as to enclose the carbons, and yet permit them to move between
block J and bed J. The opening in block J is over the upturned end of coil B,
and over the space between the carbons C and CC. V represents a jacket of
refractory material, having a chamber formed therein to serve as a furnace, and
having openings OO formed therein at opposite sides communicating with the
chamber, for the introduction of the article or articles to be heated. G represents
a generator of electricity, one pole of which is connected by conductor a through
the coil of magnet m with carbon CC, while the other pole is connected by
conductor with the carbon C, and in this conductor y, it is preferred to interpose
a resistance switch R of any known type. M represents an electro magnet carried

page_text: on suitable supports from legs of the table, as shown in Figure 1, whose
terminals 2 and 3 may be either connected with, the circuit of generator G by a
high resistance shunt, or may be connected with the poles of an independent
generator of electricity. The core of magnet M lies directly beneath the space
between the carbons C and C C, so that the influence of said magnet when
energized deflects the arc formed between said carbons. W and W represent two
metal bars inserted in the openings OO to be heated.
The operation of the invention is as follows:-
When the generator G is at rest, the parts lie in the position shown in Figure 1.
Upon starting the generator, a current traverses conductor .r, part of which is the
coil of magnet m, and then to carbon C C, carbon pencil C, carbon C and back
through conductor y to the other pole of the generator. This energises magnet m,
drawing in the core L against the resistance of spring H, and drawing carbon
pencil away from carbon C, thus establishing a voltaic are between the carbon C
and C C. This arc causes an intense heat, and may be reinforced by forcing air,
gas or vapour through the coil B into and through the arc, said air, gas or vapour
becoming heated as it traverses said coil, and also by energizing the magnet M,
which then deflects said arc by a magnetic blast. Air, gas or vapour through
coil B may be used alone, or the magnet M may be used alone or both may be used
together, or neither may be used. One or more articles W may be inserted
through the openings O in jacket V into proximity to the arc until heated, when it
or they can be withdrawn and welded or worked in any desired manner.
carbons C and C C consume, they are fed forward by the springs S, thus keeping
said carbons at a constant distance from each other, as they always lie in contact
with the stop P. For purposes of illustration, said carbons C and C C are shown
as not in contact with stop P, this being merely for the purpose of avoiding
confusion of lines.
As the
The heat generated in this forge or furnace is so intense that great difficulty has
been found in obtaining refractory material, as the best make of fire brick, it is
found, very soon melts and disintegrates. My correspondent, after many
experiments, has discovered a material which will stand the heat to a satisfactory
degree, and this material is oxide of calcium, made from well burned dolomite, or
limestone, or marble. He prefers to use lime which is but slightly silicious and
after being well burned to mould or press it into the desired shape. It is found
that this material when raised to such incandescence does not readily fuse, gives
out no vapours or fumes injurious to either the work or the operator, and has little
tendency to flux or amalgamate with or form a coat upon the material being
worked. Should the intense heat develop cracks in the refractory material, these
can be stopped by powdered oxide of calcium, which after a few applications fills
the cracks and adds to the life of the refractory jacket.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed as communicated to me by
my foreign correspondent, I declare that what I claim is :-
1. In an electric forge, the combination of a support, a refractory bed containing
a coil of pipe, the end of which opens through said bed, means for forcing air, gas
or vapour, through said coil, and mechanism for maintaining a voltaic arc on said
bed over the end of said pipe, substantially as shown and described.
2. In an electric forge, the combination of a support, a bed of refractory material,
a coil of pipe located in said bed, and one end of which opens through said bed; a
voltaic arc on said bed, a jacket of refractory material enclosing the arc, a magnet
for deflecting the are, and a resistance switch in the arc maintaining mechanism,
substantially as shown and described.
Dated this 8th day of January 1894.
WM. P. THOMPSON & Co.,
Agents for the Applicant.