Improvements in Welding Metals by Electricity.
Year: 1890

page_text: Date of Application (in United Kingdom), 22nd May, 1890
Complete Specification Left, 22nd May, 1890-Accepted, 2nd Aug., 1890
COMPLETE SPECIFICATION.
Improvements in Welding Metals by Electricity.
I, CHARLES LEWIS COFFIN of Detroit, County of Wayne, State of Michigan,
United States of America, Chemist 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 :-
My invention relates to the method of welding metals by electricity, in which the
articles to be welded are connected with the poles of a source of electricity; and it
consists in creating an electrical resistance at the joint greater than that of the two
articles to be welded, whereby the heating effect of the current is increased.
The drawing is a perspective of mechanism which may be used to practise my
invention.
A represents a base on which is carried a clamp N N, insulated therefrom by
suitable insulating material D.
B represents a standard rising from base A, carrying at its upper end a head E,
insulated therefrom by suitable insulating material C.
Frepresents a dovetail groove in head E.
HH represent the two parts of a clamp, one of which is fitted with a dovetail
projection to engage with and travel in groove F.
I represents a screw-shaft swivelled in a bracket J on head E and engaging with a
nut tapped in a projection K on one part of clamp H H.
The two parts of clamps N N and H H are drawn together by screw bolts, as
indicated in the drawing.
G and M represent the articles to be welded-for example, two bars of iron.
L represents a substance which is a conductor of electricity, but whose electrical
resistance is greater than that of G and M, and for convenience L is held by an
insulating handle.
P and O represent electrical conductors by which the clamps H H and N N are
respectively connected with the opposite poles of a generator of electricity.
The operation of my invention is as follows:-
The articles G and M being firmly secured in the clamps H and N, the clamp H
is fed down by the screw-shaft I until the ends of G and M come in contact. The
electric current is now passed through conductors P O, clamps HN, and bars G M.
If the electrical resistance of G M at their point of contact is sufficient to materially
impede the passage of the available current, the ends of G and M will be heated; but
if the electrical resistance of G and M at their point of contact is sufficiently low to
perinit the ready passage of the available current, no heating effect, or only slight
heating effect, will be produced, and G and M cannot be welded by this method.
this point, my invention comes into play. The material L, which may be platinum
or any conductor of electricity having a greater electrical resistance than G and M at
their point of contact, is laid upon the end of M, and the end of G is brought into
contact with the upper surface of L. The current being turned on, L becomes
At

page_text: beated and heats the ends of G and M. As the ends G and M become hot, their
electrical resistance increases, and thus increases the heating effect of the current,
until finally a welding heat is attained, and the weld is completed by pressing G
against M by means of a screw shaft I. L may be withdrawn (by slightly raising G)
at any time after the ends G and M become hot enough to offer sufficient resistance
to the passage of the current, or if it is a substance of litttle value, which will volatilize
or become alloyed with the metal being treated at or below a welding heat, it may
be permitted to volatilize or become alloyed, and G and M then brought into contact.
This process admits welding large masses by a current of insufficient power or volume
to heat the materials in the ordinary mode, and the interposed material L may also
be used as
a reducer of the local heating effect of the current by carrying the
extreme heat itself and gradually bringing the materials to be welded to the desired
heat.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The herein-described method of welding metals electrically, consisting in inter-
posing between the surfaces to be welded a conductor of greater electrical resistance
than the materials being operated upon, and passing the electric heating current
through the said materials and the conductor, substantially as described.
2. The herein-described method of welding metals electrically, consisting in
bringing the surfaces to be welded in contact with a conductor of greater resistance,
passing heating currents through the articles to be welded and the interposed conductor,
removing said interposed conductor and completing the weld by pressure.
Dated this 20th day of Mar 1900
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.