Improvements in Insulating Electrical Conductors.
Year: 1891

page_text: Date of Application, 2nd Apr., 1891
Complete Specification Left, 1st Jan., 1892-Accepted, 6th 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 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 to be as follows:-
This invention relates to insulated conductors in which paper applied in the form
of a ribbon constitutes the insulating material. The object of the invention is to
provide an insulation with air spaces next the wire which serve to reduce the static
capacity of the insulated conductor, and also to increase the tensile strength of the
paper ribbons wound around the conductor whereby liability of breakage and
consequent stoppage of machinery are reduced. To this end I wind spirally around
the conductor twisted paper. The paper may be loosely twisted into a somewhat
rove like form, and if applied damp will, when dry, contract and more firmly grasp
the conductor. The application of paper insulation when damp spirally around a
conductor is broadly a feature of my invention. I may employ paper cord or more
loosely twisted paper, or paper in other forms. Where loosely twisted paper is
applied the twisting may be done at the time of the application of the paper to the
wire or previously. As many strands as are desired are laid around the wire which
is preferably then covered with a winding of a flat smooth ribbon of paper. Any
suitable insulating compound may be employed. If paper cord is used I may wind
it in close or open spirals upon the conductor, or may braid it thereon. Where the
conductor is very small and to braid the paper cord directly upon it would be
difficult, I may first wind paper cord around the conductor and then braid on top of
this winding. The braiding may be wrapped with the solid ribbon and any
suitable insulating compound employed.
Dated this 2nd day of April 1891.
CARPMAEL & Co.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Insulating Electrical Conductors.
I, 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 :-
This invention relates primarily to that class of insulated conductors, in which
paper applied in the form of a ribbon constitutes the insulating material. The
object of this part of the invention is to improve such insulated conductors-more
especially those used for telephonic purposes, by applying the insulating paper in
such a manner as to leave a number of air spaces throughout the insulation. To so
apply the paper to the wire as to permit of an increased speed of working, thereby
reducing cost; and to so manipulate or treat the paper before its application to
the conductor that its tensile strength will be increased and liability of breakage
and consequent stoppage of machinery reduced.
These ends are accomplished by twisting the ribbons of paper and then spirally
winding or braiding them around the conductor. By preference the paper ribbons

page_text: are dampened so that they have more or less elasticity and may be readily twisted
into the preferred loose rove-like condition. This may be accomplished by any
suitable machinery and the means of performing the operation described form no
part of my invention.
The next part of the invention consists in first dampening paper insulation to be
applied to a conductor then winding it on or otherwise applying it to the conductor
in any desired manner, and then drying the insulation, whereby it is caused to
contract and take a firm hold upon the conductor.
In the accompanying drawings:
Figure 1 is a view of a section of electrical conductor insulated according to my
invention;
Figure 2 a cross section of a cable of such insulated conductors;
Figure 3 a perspective sectional view shewing the end of an insulated electric
light or power conductor;
Figure 4 is a view shewing the paper insulation applied in the form of a cord;
Figure 5 a similar view, the application of the cord being slightly modified; and
Figure 6 a perspective view of the end of a conductor provided with such paper
cord insulation.
Referring first to Figures 1, 2 and 3:
A indicates the electrical conductor and B a series of paper ribbons, four being
shewn, applied thereto. As stated, these ribbons are preferably dampened and are
loosely twisted as indicated in the drawing before being wound or it might be
braided around the conductor. The twisting is preferably not carried to such
an extent as to form a hard paper cord, but is on the contrary, only carried
sufficiently far to form a loose twisted body. The conductor thus insulated would
by preference and as is commonly practiced, be passed through a die to more or
less compact the paper upon the wire, and give it a uniform cross section. The
twisting of the paper materially increases the tensile strength of the ribbon, and
liability of breakage is therefore reduced. In the subsequent drying of the
insulation the paper will contract more or less, but this is in some respects an
advantage as it causes the paper to take a firm hold of the central conductor.
The paper being applied more or less loosely for the purpose of providing air
spaces, and being pressed into position by the die, the different ribbons or twists
are more or less interlocked and when dry tend to remain in position around the
conductor, and do not readily become disengaged therefrom when the wire is cut,
so as to leave a free end. As is well understood, the object sought in providing
the air spaces is to reduce the inductive capacity of the insulated conductor, this
being specially desirable in cables of telephone conductors.
Sometimes the paper cords are braided together into a flat braid and this is
wound spirally upon the conductor.
To complete the insulation thus far described it is preferred to wind a flat,
untwisted ribbon of paper around it in overlapping spirals as indicated by C. The
conductor may then if desired be passed through a bath of insulating, scaling and
waterproofing compound, indicated by D. Where the wires are laid up in cables
the individual wires may be first so treated, or the bundle or cable of wires may be
passed through the insulating compound.
A telephone cable having very low static capacity may be made of a bundle of
wires individually insulated with a braiding of paper cord, and (without insulating
compound filling the interstices) included in an impervious sheath of lead or other
material.
Where the insulation is applied to an electric light or power conductor a lead
sheath E may be placed around it. Such a conductor is indicated in Figure 3.
The more or less loosely twisted paper insulation is indicated at D. The exterior
flat ribbon covering is shown at C, the insulating compound at D, and the lead
sheath at E. A lead sheath would also by preference be placed around the cable
of conductors, as indicated in Figure 2.
In Figure 4 the paper insulation is shown applied in the form of a paper cord,

page_text: that is to say the twisting is carried to such an extent as to form a comparatively
hard body or cord. The cord b may be wound around the conductor in a closed or
solid spiral as in this figure, or in an open spiral as seen in Figure 5, and over that
winding a series of paper cords 6' may be braided as at 2. The spiral winding is
applied first in cases where the conductor is too small, to properly receive the
braiding, and also in cases where it is desired to provide air spaces. In Figure 6
the wire A being larger the paper is braided directly thereon.
This paper insulation, however applied is first dampened and the covered wire is
subsequently dried, and in drying the paper by its contraction draws down tight
upon the wire. Further the paper being damp, in passing through the dies it is
readily compacted to the desired extent and reduced to uniform cross section.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, 1 declare that what I
claim is:
1. The combination, substantially as set forth, of an electrical conductor and
loosely twisted ribbons of paper wound or braided around the same.
2. The combination, substantially as set forth, of an electrical conductor, and
loosely twisted ribbons of paper wound or braided directly upon the conductor and
an exterior wrapping that binds said insulation in place.
3. The combination, substantially as set forth, of an electrical conductor, loosely
twisted ribbons of paper wound or braided directly upon the conductor, a flat
ribbon of paper wound over the twisted paper, an insulating, sealing and water-
proofing compound applied outside of the flat ribbon and a lead sheath.
4. The combination, substantially as set forth, of an electric conductor and
insulation consisting of twisted paper wound spirally or braided directly upon and
in contact with the conductor.
5. The combination, substantially as set forth, of an electric conductor, insulation
consisting of twisted paper wound spirally directly or braided upon and in contact
with the conductor and insulating material applied outside of the twisted paper to
hold it in position.
6. The herein described method of applying paper insulation spirally around
electrical conductors which consists in first dampening the paper, then winding or
braiding it on the conductor and then drying the paper, whereby it is caused to
contract and firmly embrace the conductor.
Dated this 23rd day of November 1891
CARPMAEL & Co.,
Agents for the Applicant.