Improvements in the Method of Welding Metals Electrically.
Year: 1892

page_text: Date of Application, 14th June, 1892-Accepted, 16th July, 1892
Improvements in the Method of Welding Metals Electrically.
A communication by CHARLES L. COFFIN, of 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 & 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 ascer-
tained in and by the following statement :―
This invention relates to a method of welding metals electrically, hereinafter
fully described and claimed.
The drawings show apparatus which may be used to practise the invention as
applied to welding pipe or hoops, in which-
Figure 1 is an end elevation,
Figure 2 is a side elevation partly in section, and
Figure 3 is a top plan view, partly broken away, showing the invention applied
to welding pipe.
Figure 4 is a top plan view, and
Figure 5 is a side elevation showing the invention applied to welding a hoop.
C represents a suitable base on which are mounted electro-magucts or
permanent magnets A and B, their pole pieces being preferably made curved to
receive a pipe, represented by D, but insulated therefrom by a strip of insulating
material a.
QQ represent two small rollers set in the base of the machine on which the
pipe D is supported, so that it can be easily moved. R represents an upright arm
on base C, carrying two projections, one of which marked P, extends within the
pipe and carries on its end an anvil H insulated from arm P by the strip of
insulating material h. The other arm O extends over arm P above pipe D and
carries on its end an electro or permanent magnet E whose core is preferably
curved to permit it to lie near the upper surface of pipe D.
I and represent upward extensions from the poles of magnets A and B, or
from the base, through which are tapped two screws shafts F and G, whose inner
ends are provided with insulating material f g and bear against the surface of the
pipe D, the object of these two shafts being to force together the edges of the pipe
which are to be welded.
M and N represent two screw bolts tapped through the extensions I and J, but
insulated therefrom, and the inner ends of these bolts can be screwed into contact
with the pipe D. The bolt M is connected by conductor L with one pole of a
generator of electricity and the bolt N is connected by a conductor K with the
other pole of a generator.
.
In practice, it is preferred to have the conductor K include the electro-
magnets A and E before it connects with bolt M, so that the heating current will
energise said magnets. Of course this arrangement may be reversed or the
magnets may be put in shunt circuits, or may be energised from a separate source
of electricity.
When applied to welding a hoop (marked D) as shown in Figures 4 and 5, the
magnets E and B may be omitted, and also the arms P and O, in which case the
joint of the hoop is clamped between a stationary clamp R and a movable clamp S
carried on the base C, the movable clamp being operated by means of a screw
shaft T tapped into the base C and engaged with said clamp. These clamps are

page_text: insulated from base C by non-conducting material indicated at s, Figures 4 and 5.
The clamp S is connected by conductor K, which also includes the winding on
magnet A, with one pole of a generator of electricity, and the clamp R is connected
by conductor L with the other pole of a generator. The parts being assembled
as shown in Figures 1, 2 and 3, and the current being turned on, its natural path
would be to flow from bolt M to bolt N, through the pipe D in the direction shown
by the arrows in Figure 1, but this tendency is restricted and overcome by the
magnetic influence of the magnets A and B, so that the current is forced to flow
across the joint in the pipe, by which means the edges of the pipe at the joint
become heated, and when they have reached a welding heat, they are pressed
together by the action of the screw clamps F and G to form the weld, which may
At the same time,
be completed by hammering, rolling or any other known mode.
the influence of the magnet E increases the resistance of the pipe at the joint,
thereby increasing the heating effect of the current; but the principal office of the
magnet E is to prevent the welding current from traversing the finished joint,
when pipe is being welded. As the magnet E lies in such position that the finished
joint travels under said magnet as the welding operation progresses, it prevents the
current which enters the pipe at M from passing through the finished joint, and
compels the current to cross the parts to be welded. The pipe is fed' forward as
the weld progresses until it is welded through its entire length. This retarding
influence on the welding current is produced by having the lines of force in the
fields of the magnets A B and E at right angles to the line of force of the welding
current, thereby producing a molecular change in the metal at that point which
results in raising its temperature and in retarding the passage of the welding
current.
It is preferred to make the magnets A and B present their north poles to the
ring, and the magnet E present a south pole, irrespective to the direction of the
current across the joint; or magnet B may be made to present its north pole, A its
south pole and with a current passing across the joint from f to g, Figure 1, E may
present its south pole.
Various combinations may be devised, but in general my correspondent finds
that the polarity of the magnet E may be varied as the variations of polarity of
magnets A and B, for example, he may use B north, A south, with currents passing
from g to f, Figure 1, and make E present its north pole.
The operation is the same in welding a hoop as shown in Figures 4 and 5, the
magnet. A preventing the current from taking the short path through the hoop,
and forcing it to traverse the joint, and the screw shaft T serving to force the ends
of the pipes together to form the weld.
The edges to be welded may be in contact and heated simply by the current
passing through them, or they may be slightly separated to form a voltaic arc
between them, the invention serving the same purpose in either case.
Whenever, in welding two pieces of metal electrically, the weld is too long to
be made at once, as in the case of a pipe, or metal plates, the portion first welded
affords a short path for the electric current, and, if not prevented, the current
would traverse the completed weld, without heating the unjoined edges. This is
prevented by interposing the influence of a magnet to the passage of the current
through the short path, the lines of force of the magnet being at an angle to the
path of the current seeking to escape through the short cut, and blocking the
passage of the current.
.
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. The herein described method of welding a continuous piece of metal by
electricity, consisting in bringing together the edges to be welded; connecting the
material on each side of the joint with the poles of a generator of electricity,
passing an electric current through the material to be welded, intérposing magnetic

page_text: resistance to the direct passage of the current through the material without
traversing the joint, and finally pressing the edges together to form the weld.
2. The herein described method in the operation of welding metals electrically,
consisting in resisting the passage of the current through the material in any other
path than that of the proposed weld, by subjecting any shorter path to magnetio
influence.
Dated this 12th dow of Inne 1800
WM. P. THOMPSON & Co.,
Agents for the Applicant.