Improvements in Insulating Electrical Conductors.
Year: 1891

page_text: Date of Application, 2nd Apr., 1891
Complete Specification Left, 1st Jan., 1892-Accepted, 13th Feb., 1892
PROVISIONAL SPECIFICATION.
Improvements in Insulating Electrical Conductors.
I, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, (a communi-
cation to me froin abroad by Edward Crawford Davidson, of 109 West 12th Street,
in the City of New York, State of New York, United States of America,
Solicitor,) do hereby declare the nature of this invention to be as follows:-
The purpose of this invention is to decrease the static capacity of insulated
electrical conductors. To this end air spaces next the conductor are provided.
These air spaces are relatively long, are parallel with the conductor, or substan-
tially so, and each air space would by preference extend the entire length of the
conductor. I am aware that heretofore air spaces next an insulated conductor have
been provided in a variety of ways, but, so far as I know, it has never before been
suggested to arrange the air spaces in the manner above mentioned. My theory is
that the influences tending to produce or create the static capacity of a conductor
tend to act in lines parallel with the conductor and that the static capacity
rises when these parallel lines are obstructed by insulating material. The invention
may be carried out in a variety of ways. For instance, I may lay cords against
and parallel with the conductor with air spaces between them and secure them in
position by a winding of suitable material, over which insulating material may he
applied in any suitable manner, as, for instance, ribbons of paper may be wound
spirally around the parallel cords; or, I may form in or upon a ribbon of paper or
other material parallel, longitudinal projections, and apply such a ribbon longi-
tudinally around the conductor with the projections on the ribbon next the
conductor; or, I may take a series of conductors composed of fat ribbons of metal
and place between them strips of insulating material leaving air spaces between the
strips of material parallel with the conductors. This pile of conductors and
insulating strips may be enveloped in a casing of any suitable character. Any
ordinary insulating compound may be used, and the conductors or cables of
conductors may be enclosed in a lead sheath.
Dated this 2nd day of Auril 1891.
CARPMAEL & Co.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Insulating Electrical Conductors.
1, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, (a communi-
cation to me from abroad by Edward Crawford Davidson, of 109 West 12th Street,
in the City of New York, State of New York, United States of America,
Solicitor,) 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:-
The purpose of this invention is to produce an insulated electrical conductor
having a minimum static capacity or a cable of insulated conductors, each having a
minimum static capacity. It is now well known that when an electrical conductor
is suspended in dry air out of contact with any substance the static capacity
of that conductor is at its minimum. Recognizing this fact, it has been proposed
to keep down the static capacity of insulated conductors by providing air-spaces
in the insulation next to the conductor. This has been accomplished in a large
variety of ways, which it is unnecessary to recite. The theory on which this

page_text: .
A
invention proceeds is that the influences, extra currents, or whatever they may be
that give rise to what is known as "static capacity" in an insulated conductor
tend to operate on straight lines parallel with the conductor, and that walls of
insulating material in their path constitute obstacles, which increase the static
capacity in proportion to their number in a given length of conductor.
theoretically perfect insulated electrical conductor according to this theory would
be one in which there was the least possible surface of contact between the
conductor and the insulating material and the greatest area of air-spaces running
parallel with the conductor. It may be further stated that true concentricity of
the insulation around the axial centre of the conductor should also, as far as
possible, be preserved. The question of static capacity is a material one in
telephonic conductors but is not of special importance in electric light and power
conductors.
This invention is not limited to the use of any specific insulating material.
As, however, conductors insulated in paper have a small static capacity as
compared with conductors insulated with many other materials, it is preferred to
use paper.
In carrying out the invention threads or cords of insulating material separated
from each other are laid parallel and in contact with the conductor to provide air-
spaces parallel with and next to the conductor, and over such threads insulating
material is applied that holds the cords in position.
The accompanying drawings show two ways of carrying out the invention.
Figure 1 is a perspective view showing the end of a conductor insulated
according to the invention.
Figure 2 is a similar view;
Figure 3 a perspective view of a paper strip, somewhat enlarged, that may be
employed in carrying out the invention.
Figure 4 is a cross section of a cable of conductors insulated according to the
invention and
Figure 5 is a perspective view of the end of a cable of peculiar construction
embodying the invention.
In Figure 1 longitudinally along the wire and at equal distances from each
other are laid two or more-six being shown-strands of fine cord or thread
preferably of such hardness that they will not flatten under the pressure of a
binding-thread that is passed around them.
A indicates the conductor; B, the cords parallel, or substantially so; and C, the
binding thread. Over the thread-binding it is preferred to place an insulation con-
sisting of a solid ribbon of paper wound spirally, any desired number of papers
being employed to give the desired thickness.
In Figures 2 and 3 is shewn a strip or ribbon of insulating material, preferably
of paper, having attached to or incorporated into its surface a series of parallel
threads or cords of a diameter properly related to the wire around which the ribbon
is placed. D indicates the ribbon and d the cords or raised parallèl projections
upon its face. Such a ribbon is folded longitudinally around a conductor A, as
indicated. In both of the forms described the insulation would be applied by
suitable machinery that would in the one case so, apply the cords B to the wire as
to maintain their parallelism with it, and consequently also the parallelism of the
air-spaces between the cords; in the other case to so apply the ribbon to the con-
ductor to so maintain the parallelism of the cords d and the intervening air-spaces
with the electrical conductor.
Wires so insulated may be laid up into cables in any desired manner and covered
with a lead sheath, as is usual and as is indicated in Figure 4, F, being the lead
sheath.
In Figure 5 the conductors A' are shown as consisting of. flat ribbons oficopper
between which parallel strips a of insulating material are laid so as to leave inter-
vening air spaces parallel with the conducting ribbons. Around this assemblage of
conductors à tube G, of insulating material is placed in such manner that the

page_text: corners of the assemblage of conductors, which is rectangular in cross section, only
make a contact with the interior wall of the tube, and consequently air spaces X
are left on each side between the conductors and the walls of the tube.
The tube G may be formed by winding around the assemblage of conductors a
heavy ribbon of paper or other suitable insulating material.
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 :-
:-
The combination, substantially as set forth, of the conductor, the insulating
cords arranged parallel, or substantially so, and in contact therewith, but separated
from each other, and exterior insulating material that holds the cords in place.
Dated this 23rd day of November 1891.
CARPMAEL & Co.,
Agents for the Applicant.