Method of Welding Metals Electrically.
Year: 1890

page_text: Complete Specification Left, 22nd May, 1890-Accepted, 2nd Aug., 1890
COMPLETE SPECIFICATION.
Method of Welding Metals Electrically.
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 consists in an improved method of welding metals electrically,
hereinafter fully described and claimed.
The drawings represent various forms of apparatus by which my invention may be
practised :-
Figures 1 and 2 are side and end elevations showing two articles ready to be
welded.
Figures 3 and 4 are side elevations with mechanism for regulating the force of the
magnets, and
Figure 5 a side elevation showing a switch for reversal of the currents.
The principle of my invention consists in forming a weld between two pieces of
metal whose edges have been brought to a welding heat in any of the known modes-
namely, by passing heating-currents through them while in contact, or by springing a
voltaic are between the edges, or by springing an arc between the edges to be welded
and an extraneous conductor (all of these being known methods fully described in
prior patents to other parties and myself) by pressing together the articles to be
welded by the force of one or more magnets, which may be either in the direct
circuit of the welding-current or in a shunt-circuit from the welding-circuit, or
separately energised.
A description of Figure 1 will fully explain my invention, and it will then be
only necessary to point out the mechanical modifications illustrated in the other
figures.
Relating now solely to Figures 1 and 2 :-
A and A' represent two electro-magnets mounted on bases E E¹, one or both of
said magnets being movably mounted upon its base as, for instance, by dovetail pro-
jections F, formed on the magnet and engaging with similar grooves in the base.
These magnets are shown separated for convenience. In practice they will be
approached until D D' are in contact or near enough together to close the circuit and
form a voltaic arc between them. B B represent cores of said electro-magnets,
which mutually attract each other when the magnets are energised by both being
embraced in the same circuit. C C¹ represent a U-shaped extension of the cores B B¹
of said electro-magnets, by which both poles of said cores are made to co-operate in
drawing said electro-magnets toward each other. 00' represent plates of metal on
the upper side of said magnets, insulated by the strips of insulating material P P₁,
upon which are clamped (by any suitable clamping mechanism) the pieces of metal D'D'
which are to be welded together, or they are retained in position by the upturned ends
of plates O O', which bear against the rear ends of the metal pieces D D', as clearly

page_text: shown in Figure 1. G G represent binding-screws. H and I represent an electric
conductor, being connected with one pole of a generator of electricity-for
example, the positive pole-and I being connected with the other pole. The con-
ductor H is connected with one end of the bobbin of electro-magnet A, the other end
of said bobbin being connected with the metal plate or metal piece D, and the
bobbin of electro-magnet A¹ is similarly connected with the plate O' or article D'
and with the other pole of the generator through conductor I. The path of the
current then entering through conductor H is through the bobbin of magnet A,
binding-post G, and plate O to the piece of metal D,.and thence through the metal
piece ₁, plate O¹, binding-screw G, and the bobbin of electro-magnet A¹ and con-
ductor I to the other pole of the generator. If the edges of D D' are in contact, the
passage of the current heats them, and at the same time the magnets A A¹ are
energised, their poles B B¹ attract each other and D D¹ are pressed together (by
mutual attraction of said magnets) to form the weld. If the articles D D₁ are to be
heated without actual contact-that is, by springing a voltaic arc between them-the
approach of the magnets A A¹ is resisted by any mechanical means until the edges
of D D are brought to a welding heat, and then the magnets are permitted to force
the heated edges together to form the weld, or the distance to which said magnets
may approach each other, and consequently, the amount of pressure between the
heated edges of D D', may be regulated by any adjustable stop.
If it is desired to regulate the force of the magnet and the compression of D D',"
the bobbin of magnet Å may be divided into a number of separate coils, (illustrated
in Figure 3 as A2, A3, A4 and A') the terminals of which are connected with contact-
plates K', governed by a switch K, by means of which the operator may throw in or
cut out one or more of said coils, and thus increase or decrease the power of the
magnet.
In Figure 4, the bobbins of electro-magnets A and A¹ are not in the main
welding-circuit, but are in a shunt-circuit H¹ I', in which is interposed a series of
resistance-coils M, connected by a plug M' with a plate N in the shunt-circuit, by
which the resistance of the shunt-circuit can be increased or decreased at will. In
this form, the resistance to the welding-current at the point of contact between D
and D₁ increases as the edges become heated, so that a greater proportion of the
current is shunted into the circuit H¹ I', thereby increasing the effective force of the
magnets A A¹ and the compression between D D' at the time when such force becomes
necessary for welding.
The clamp shown in Figures 3, 4 and 5 consists of a bottom plate R', fastened to
plate O, a cap R, and bolts S for fastening the cap to the plate R', the articles D
or D¹ being thus clamped between the cap R and the plate R.
In Figure 5, the switch X is for reversing the current in one of the electro-
magnets when it is desired to cause them to recede from each other to bring a stress.
upon the joint.
The conductors H and I being connected with the poles of a generator and the
articles D D¹ being in contact at the joint, the current enters the main H at a binding-
post T on the switch X, takes the direction T U V W, through the coils of the
magnet A, and into the material, its direction being indicated by the full line arrows.,
When it is desired to reverse the direction of the current through H, the switch T is
drawn to the left and the current then passes as shown by the dotted arrows. This changes
the polarity of the coils of magnet A', and the magnets A and A' tend to repel each
other, either separating the articles at the joint, or, if an incipient weld has been
formed, it creates a strain at the joint, which increases the heating effect 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, I declare that what I
claim is :-

page_text: bringing the edges to be welded to a welding heat by the action of an electric
current and pressing them together by the attractive force of a magnet.
2. The hereindescribed method of welding metals electrically, consisting in
bringing the edges to be welded to a welding heat by the action of an electric
current, pressing them together by the attractive force of a magnet, and putting the
weld under strain while subject to the action of the welding current.
.
01
1000
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.