IMPROVEMENTS IN THE MANUFACTURE OF SUBTERRANEAN ELECTRIC CABLES
Year: 1883

page_text: LETTERS PATENT to Herbert John Allison, of 41 Southampton Buildings,
Holborn, in the County of Middlesex, Patent Agent, for an Invention of
"IMPROVEMENTS IN THE MANUFACTURE OF SUBTERRANEAN ELECTRIC CABLES."
A communication to him from abroad by Sidney Fortescue Shelbourne,
of the City and State of New York, United States of America.
COMPLETE SPECIFICATION filed by the said Herbert John Allison at the
Office of the Commissioners of Patents on the 19th April 1883.
HERBERT JOHN ALLISON, of 41 Southampton Buildings, Holborn, in the County
of Middlesex, Patent Agent, "IMPROVEMENTS IN THE MANUFACTURE OF SUB-
TERRANEAN ELECTRIC CABLES" communicated to me from abroad by Sidney
Fortescue Shelbourne, of the City and State of New York, United States of
America.
The objections to the use of underground systems of electric cables or wires,
heretofore adopted have been obviated by my invention which chiefly consists.-
Firstly. In the employment of annular notched templates within the cable to
secure uniform distances between the wires. Secondly. In the relative disposition
of these templates in the notches of which the wires are placed so that the wires of
one series are made to cross the wires of the adjacent series and the insulating
material is continued in nearly equal bulk longitudinally. Thirdly. In the
arrangement and connection of the wires with reference to the direction of their
spirals and parallelism in the succeeding divisions of the cable. Fourthly. In the
combination of said spiral cable conduction wires with an insulated metal spiral
conductor for a distance ground connection or a return conductor. Fifthly. In the
sectional moulds by which the insulating substance is confined so as to enclose and
protect from air and moisture the wires of the cable, and Sixthly. In an insulating
composition which leaves the cable moderately flexible and permits the wires to
expand or contract without injury to the wires or the insulation.
In the drawings forming a part of this specification
Figure 1 shows a series of notched templates a, b, c, d; Figure 2, the two inner
series of templates in relation to the wires; Figure 3 the spiral directions of the

page_text: wires of the two outer series crossing each other, also the reversal of the direction
of the spirals in the adjacent sections P, R, of the cable, and on a less relative scale
a vertical section of box x with its flanges z for supporting the ends of the cable
divisions, and its cover y; Figure 4 shows box with adjacent ends of two
divisions of the cable surrounded by spiral metal strips o, o; Figure 5 the
sections P, R, of the cable and manner of connecting the wires; Figure 6, a cross
section of one member B, and parts A, C, of of the series of mould divisions in which
the cable is insulated, f being the base, g the cover and e the pouring slot;
Figure 7 a vertical longitudinal section of the same; Figure 8 a plan view showing
the position and dimensions of slots e for the admission of the insulating
composition, which flows around and encloses the wires of the cable; Figure 9 a
small metal book with an adjustable handle or support by means of which the
skeleton cable is suspended centrally in the mould divisions, and Figure 10, a cross
section of box or trough T with three compartments showing also cross section of
three complete cables.
The annular templates a, b, c, d are preferably made of hard rubber, which is
firm and elastic, but may be made of other insulating substances. The templates
are about one half an inch wide diametrically with notches about one half inch
apart. A skeleton cable formed on a series of four such templates containing
68 wires will be about four inches in diameter. The wires may be of any diameter
not greater than the width of the notches.
The sections of the trough made of any suitable material are fitted together and
levelled in a trench. Then supports are placed across the trench upon which the
wires for a cable are laid. The notches of the smallest series of templates are fitted
with wires which are temporarily held in their notches by threads wound spirally
around them. The next series of templates are passed over this core and placed in
their position to receive another series of wires and the work continued until the
notches of the last series are filled. The templates are so placed relatively to each
other in connection with the wires that no two of them are in the same diametrical
plane of the cable, the object being to prevent the longitudinal continuity of the
insulating composition being diminished except by the surface area of a single
template at any point, and thereby ensure the greatest strength and flexibility to
the cable insulation. As the notches of each successive series of templates are filled,
these templates are moved circumferentially around the wires of the series within
them thus causing the wires of that series to pass in spirals of opposite direction to
the spirals of the next inner series of wires. The same relative series of wires in
each alternate division of the cable are turned in succession from left to right and
from right to left, so that when the wires of the series in one division of the cable
are connected with the wires of the corresponding series in the succeeding division
they are in a relation to reverse the magnetic polarity of the currents in each
successive division. The skeleton cable being formed it is enclosed by the sectional
members of the insulating mould and is suspended centrally in said mould by
supporting hooks provided with adjustable handles. The handles when properly
adjusted are placed across the slots e the hooks taking hold of a wire of the cable.
The wires of the cable are then covered and sealed with insulating composition or
material.
My composition is constituted of paraffine, resin or asphalt and the product or
distillate of the residium or tar of petroleum. This composition is a good insulator
and at ordinary temperatures is both flexible and tensile. The latter qualities
which are not possessed by either paraffine, resin or asphalt are essential to the
proper insulation of underground cables, which should be moderately flexible, and
when the wires expand and contract the insulating material should come and go
with said wires. This distillate is known as "waxtailings or "roofers wax. I
designate it "petrapitta" signifying rock pitch. The material is a homologue of
paraffine and a good insulator, but not of the proper consistency to be used
separately. I use about two pounds of "petrapitta" to one of unrefined paraffine;
about three pounds to one of hard resin and about one pound to one of refined
"
"

page_text: Trinidad asphalt. The "petrapitta" is first heated until a proper consistency is
attained for the desired combination, and then the other materials are added and
when melted is thoroughly mixed. The composition is then ready for use or it
may be run into moulds and stored.
The ends of the insulating moulds must be stopped by cotton-wool or other
material when the composition is poured through the slots. The interior surface of
these moulds may be rubbed with glycerine or lined with paper to prevent the
composition sticking to the moulds. Any number of members of the mould may
be employed and several hundred feet of the cable may be insulated at one
operation. When the insulating material is hardened the members of the mould
may be removed. Then the metal strips o are wound around the insulation in a
spiral direction opposite to the spirals of the outer series of wires. The cable is
then spirally wound with bandages saturated in a heated composition of about
equal parts of "petrapitta," Trinidad asphalt and coal tar resin in two thicknesses,
the spirals crossing. A preparation of coal tar pitch and asphalt, the first pre-
dominating, is then applied and the supports being removed, the cable falls into
the trough and the divisions are united ready for use.
I claim as new in the manufacture of these subterranean electric cables :—
First. A series of annular notched templates so formed that ench smaller series
will pass within the templates of the next larger series for the purpose and sub-
stantially as set forth.
Second. A cable the wires of which are arranged in circumferential series upon
annular notched templates, so that each larger series of wires passes over and is
separated from the wires laid in the notches of the next smaller series of templates
substantially as set forth.
Third. A cable formed of wires insulated in a body, said wires being supported
on a series of notched templates, each template arranged in a different-cross section
of the cable for the purpose and substantially as set forth.
Fourth. The combination of wires, annular notched templates and a flexible
insulating composition in body of cable substantially as set forth.
Fifth. The combination of series of wires supported on annular templates, and so
arranged relatively that the wires in each series pass in spirals of opposite direction
and cross the like spirals of the wires of the next adjacent series substantially as
set forth.
Sixth. The arrangement of the divisions of said cable relatively so that the wires
of the same corresponding series in one pass from left to right and those of the
adjacent division from right to left for the purpose and substantially as set forth.
Seventh. The combination of a spiral metallic strip with the outer series of
wires of the cable, said wires and strip running spirally in opposite directions,
the strip being insulated from the ground by the exterior wrapping of the cable
for the purpose and substantially as set forth.
Eighth. The mould composed of sectional members provided with pouring slots
for the purpose and constructed substantially as set forth.
Ninth. The said insulating composition composed of the substances and
constituted substantially as set forth.
In witness whereof, I, the said Herbert John Allison have hereunto set my
hand and seal this nineteenth day of April in the year of our Lord One
Thousand Eight Hundred and Eighty-three.
HERBERT J. ALLISON (L8.)