IMPROVEMENTS IN METALLIC CIRCUITS FOR ELECTRICAL TRANSMISSION
Year: 1881

page_text: LETTERS PATENT to Edgar Edmonds, of the Firm of Robertson, Brooman,
and Company, of 166, Fleet Street, in the City of London, Patent Agents,
for an Invention of "IMPROVEMENTS IN METALLIC CIRCUITS FOR ELECTRICAL
TRANSMISSION." A communication from abroad by George M. Mowbray, of
North Adams, Massachusetts, U.S.A.
COMPLETE SPECIFICATION filed by the said Edgar Edmonds at the Offico
of the Commissioners of Patents on the 2nd June 1881.
EDGAR EDMONDS, of the Firm of Robertson, Brooman, and Company, of
166, Fleet Street, in the City of London, Patent Agents. "IMPROVEMENTS IN
METALLIC CIRCUITS FOR ELECTRICAL TRANSMISSION. A communication from
abroad by George M. Mowbray, of North Adams, Massachusetts, U.S.A.
This Invention consists of two conductors combined and arranged in close
proximity to each other, onc uninsulated, say, of iron, with or without ground
connections, the other insulated, the pair forming a complete metallic circuit for
electrical purposes.
The construction, as hereinafter described, is durable, not
liable to get out of order, convenient for laying underground or under water, as
easily set upon poles as the ordinary telegraph or telephone wires, can be readily
repaired, and is of moderate cost, and the arrangement of the wires satisfies the dual
nature of an electric current, so that where a number of circuits consisting of a
number of these composite wires are bunched together in contact, each individual
circuit transmits without injurious interference with the others. In order better
to comprehend the Invention, reference may be had to the Drawings accompanying
this Specification, showing 9 figures enlarged for sake of distinctness to four times
their actual size, and in which Figure 1 is a longitudinal section of the outor
protective conductor.
Figure 2 is a cross section of the same showing its groove B to receive the
insulated copper wire; Figure 3, a longitudinal section of inner insulated wire;
Figure 4, cross section of Figure 3.
Figure 5, a longitudinal section of the outer protective conductor with the inner
insulated wire or core in position.
Figure 6, a cross section of Figure 5; Figure 7, a longitudinal section of a

page_text: four grooved rod or wire, and Figure 8 a cross section of same with 4 B¹, B¹, B¹, B¹,
insulated cores in position, and before tho jaws of the grooves are approximated.
Figure 9 shows diagramatically an entire metallic circuit with ground con-
nections. These ground connections may be dispensed with in some cases, not
being absolutely essential to the Invention. Their use is defined hereafter.
A represents a well annealed soft iron telegraph wire of suitable diameter, say,
from No. 3 to No. 7 American wire gauze, in which is first run a groove B in the
direction of its length, as shown in Figure 1, and of about 3/, its diameter in depth,
as shown in Figuro 2; C represents copper wire of, say, from No. 14 to No. 24,
American wire gauze insulated in any suitable manner, as shown by the letter D
in Figures 3 and 4; the common methods of spirally winding with yarn of cotton,
hemp, or jute, and then slushing a hot cement of gas tar tempered by evaporation
and addition of asphaltum being suitable.
This insulated copper wire whilst the insulating cement is hot and plastic is
inserted in the groove B of the soft iron wire, as shown in Figure 5. Finally, these
two conductors, viz., the outer protective grooved wire A carrying in its groove B.
The inner insulated coro C, D, are passed between suitable rollers or drawn through
a suitable die so as to nearly but not quite close up the jaws of the groove, as
shown in Figure 6. With a larger outer wire or rod A¹ a series of grooves B' may
be drawn or pressed, say, three, four, five, or six, and into each of these an insulated
copper core may be inserted, as shown in Figure 8, in cross section, where four
grooves are shown, each carrying an insulated conducting core in that stage of the
manufacture previous to the final process of closing the lips of the several grooves
nearly but not quite together. Multiple cores thus imbedded might serve for a
short river or lake cable, but for underground communication, telephonic or
telegraphic, I prefer bunching a series of single grooved wires hereinbefore
described, because less cumbersome to handle and easier to repair in case of
injury.
I do not confine myself to iron alone for the outer conductor, nor to copper alone
for the inside core, nor to any particular material for the insulation, but prefer
the above metals as conductors on account of their tenncity, durability, and relative
conducting power, and I furthermore prefer a fibrous insulation rather than a
plastic gum alone, because a fibrous material will be less apt to permit contact
between the two conductors than simple gums without interposed fibro. The jaws
or edges of the grooves should not be brought together so as to touch, neither
should they overlap, because as I have found that injurious or undesirable effects
are less pronounced and are more readily and rapidly dissipated with a slotted
envelope than with an envelope made seamless, or so as to entirely surround the
inner conductor.
In Figure 9 this wire used as a complete metallic circuit is shewn as combined
with ground connections; T, T, represent arbitrarily any form of electrical apparatus
such as relays, telephones, and the like.
The line L is formed of the compound wire, the core a and envelope b being
separated at the terminals to make proper connections with T, T. Connected to
the envelope b ground wires 1, 2, at the terminals or in the centre of the line, or
either or all, may be used, so that the potential of the earth and the line shall be
maintained constant, while at the same time all the advantages of both complete
metallic and earth circuits are secured.
The requisite size of the two conductors must be determined by the electrician,
and depends on the distance or length of circuit. The conductivity of the metals
selected for the present purpose, whether telegraphic, telephonic, or thermo-electric,
and the strength of the current necessary to overcome the resistance.
Having thus described the nature of the said Invention, and in what manner
the same is to be performed, I declare that what I claim as new and desire to
secure by Letters Patent is,-
First. A compound electrical wire cousisting of an insulated conductor nearly
surrounded by an enveloping conductor, substantially as set forth.

page_text: Secondly. A compound wire for forming a complete metallic circuit composed of
a. metallic protective covering serving as one member of the circuit, and nearly
surrounding an inner insulated metallic core which serves as the other member of
the circuit, substantially as set forth.
Thirdly. The combination with a complete metallic circuit for electrical uses
formed of a compound wire having an insulated core and exterior metallic covering
nearly surrounding the core of one or more ground connections, substantially as
set forth.
In witness whereof, I, the said Edgar Edmonds, have hereunto set my hand
and seal, this First day of June, One thousand eight hundred and eighty
one.
EDGAR EDMONDS. (L.S.)