Improvements in Cables Containing Electric Conductors.
Year: 1889

page_text: Date of Application, 22nd Nov., 1889-Accepted, 28th Dec., 1889
COMPLETE SPECIFICATION.
Improvements in Cables Containing Electric Conductors.
I, SYDNEY PITT of Sutton, in the County of Surrey, Gentleman, (a communi-
cation to me from abroad by Anthony Dey of New Brunswick, New Jersey,
United States of America, Gentleman) do hereby declare the nature of this inven-
tion and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement:-
The invention relates to that class of armoured cables in which the conductor or
individual conductors are insulated by paper. A cable of such insulated conductors
containing any desired number of wires, say one hundred-is preferably wrapped
with a cording or taping to bind the conductors together and give a smooth, cylin-
drical surface, and then is preferably passed through a bath of rosin, or other
insulated compound, which renders the exterior of the bundle of conductors
impervious to air and moisture. A lead sheath is then formed around the conductors
to complete the cable.
The particular kind of paper insulation which I employ is indicated in the
drawings; that is, I wrap each conductor with a number of ribbons of paper spirally,
the winding of one ribbon covering the joint of the winding beneath.
The paper which I employ is made of pure manilla fibre, as free as possible from
gums, silex and chemicals.
Figure 1 shows a section of a conductor in process of being covered with paper
ribbons.
Figure 2 indicates a couple of such paper cover conductors twisted together.
Fifty of such double twisted strands as shown in Figure 2 may be twisted together
in the formation of a complete cable, such as shown in Figure 3.
In manufacturing this cable, I proceed as follows: The individual wires are
wrapped spirally with the paper insulation, as indicated in Figure 1, by any suitable
machinery. Pairs of conductors so covered are twisted together, and then any desired
number of such twisted pairs are twisted into a cable. This cable, or bunch of wires,
is then served with the wrapping of cord, braid or tape.
The cable is then kiln dried for the purpose of driving off all moisture, and is
finally passed through a bath of rosin and covered with lead as above mentioned.
The paper insulation is of the character described in the British Patent of Edwin
Dodd McCracken No. 11,894 dated 2nd September 1884. Experience has demonstrated
that an insulation of pure paper fibre applied in the manner shown affords a most
perfect insulation; and a cable with the conductors so insulated has an extremely
low static capacity. Actual tests of such cable, as compared with the best cables in
the market, show that they have from 25 to 30 per cent. lower static capacity, and
this fact is believed to be due, primarily, to the character of the paper and the
manner of its application to the conductors, and, secondly, to the complete protection
of the conductors by a sheath impervious alike to air and moisture, such for instance
as lead.
As is now the practice, I should of course in laying the cable carefully seal the
ends at the man-holes and junction boxes, to prevent air and moisture penetrating
inside the sheath along its length.
In each figure, A indicates a paper wrapped conductor, B indicates the wrapping
around the bundle of conductors, and the lead sheath.
Having now particularly described and ascertained the nature of my said Inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. An electric cable comprising a conductor or multiple conductors, each covered

page_text: with a spiral wrapping of paper ribbon, and the whole being enclosed in an impervious
sheath, such for instance, as lead.
2. An electric cable comprising multiple conductors, each wrapped spirally with
insulating ribbons of manilla paper, the conductors being twisted in pairs, and all
the twisted pairs then twisted together, and an impervious sheath, such for instance
as lead, closely enveloping all of the conductors.
Dated this 22nd day of November 1889.