Improvements in Electric Conductors for the Distribution of Electric Currents and in Conduits therefor.
Year: 1891

page_text: Date of Application, 13th Oct., 1891-Accepted, 14th Nov., 1891
COMPLETE SPECIFICATION.
Improvements in Electric Conductors for the Distribution of Electric
Currents and in Conduits therefor.
1, RICHARD THRELFALL, of Sydney, in the Colony of New South Wales,.
Professor of Physics in the University of Sydney, 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 :-
My invention consists partly in a new or improved conductor for the distribution
of electric currents particularly adapted for use underground and which is so
constructed that the section of the said conductor may be increased as required
with cheapness and facility and so that the number of insulating supports which are
ordinarily required for a conductor placed underground may be lessened. My
invention further comprises the construction of a cover for an underground conduit
for such or any conductor so as to render the conduit completely water-tight and
to admit of its being readily opened as required for making connections or other
purposes.
The only mode in which the section of a bare underground conductor has hitherto
been increased without opening the whole of the conduit containing the same has
been by laying additional strips of copper which have to be drawn through. In
order to prevent injury to the insulators it has been found necessary for this
purpose to have a junction box at each insulator (these junction boxes being
ordinarily about twelve feet apart) and to open the conduit at each of the junction
boxes for the purpose of guiding the strip past the insulator. By the use of a
conductor of the form I have invented the insulators are protected from injury
during the process of drawing in additional copper and the points at which it is
necessary to open the conduit are much further apart, while at the same time the
superior rigidity of the conductors reduces the number of insulators required.
The details of my invention are shewn on the accompanying drawing in which
Fig. I. is a transverse section of a suitable conduit showing a concrete channel
with insulators and mains in position on the three wire system.
Fig. II. is the elevation and plan of cover as constructed by me showing method
of jointing the same.
Fig. III. is a side elevation of the insulators with conductors in position.
Fig. 1V. is a transverse section of the insulators.
Fig. V. is a plan of the insulators.
Fig. VI. is a plan of the cast iron base or soleplate.
To construct a suitable conduit for the purposes of my invention, the necessary
excavation having been made a channel of concrete is formed in the usual manner
and of the width and depth necessary. The thickness of the concrete may be varied
with the conditions of the ground but under ordinary conditions will be from two to
five inches. The inside surface J of the channel will be coated with cement- and
should the ground be wet it may be rendered still more water-tight by one or two
coats of boiled oil or other water-proofing substance.
During the construction of this concrete light channel irons A. A are to be
embedded on each side of the top so as to form two continuous grooves for receiving
the sides of the cover and these grooves are filled with marine glue asphalt or other
substance of a like nature.
I construct the covers B of sheet steel, iron, Muntz metal or other suitable
material with the sides turned down so as to dip into grooves P of the channel
iron A. The grooves P being previously filled with marine glue or asphalt or
other substance as before stated the sides of the cover B are heated and pressed
down into the material in the grooves thus making a perfectly water-tight joint.

page_text: The cover may be removed at any time by softening the material through the
application of heat.
In order to make the junction of the sections of the covers water-tight the
ends R R are formed into corrugations which lap over each other the joints being
filled with marine glue, asphalt or other elastic material after the ends of the
covers have been heated.
An approved mode of construction for the supporting insulators will be to place
iron soleplates or bases at convenient intervals in the channel and to secure the
same to the floor by bolts and washers embedded in the concrete while soft.
A form of soleplate is shown at G secured by bolts K K and washers L L this
soleplate being provided with lugs M M for the purpose of holding the insulator.
The insulators F constructed of glass porcelain or earthenware would combine
strength with cheapness but any other convenient form or suitable material would
suffice for the purpose of my invention. The insulators F have troughs O for
holding non-conducting liquid and are provided with parts QQQ shaped to the
form of the conductors which they are intended to carry. The conductors are
shown at C. D. E. N N are the projections which fit into the lugs M M of the
soleplate G and cause the insulators to be held firmly in position.
The improved conductor invented by me is constructed as follows:-I obtain a
ribbon of copper of as great a length as possible and of the required sectional area.
This ribbon is drawn through dies or rolled until it assumes one of the forms shown
at ST UV in which the section is such as to enable the material to sustain its own
weight without much sagging between the insulators.
The conductor thus formed will be mechanically stiff and will permit of the
insulators being proportionally far apart and it will allow more copper to be drawn
in without injury to the insulators, and without opening the conduit otherwise than
by removing the cover at the junction boxes required.
For the purpose of drawing in the junction boxes can be set much further apart
than in the case of bare conductors of ordinary construction. This distance may
probably amount to as much as 200 feet.
The conductors can be jointed by telescoping the ends of the sections into each
other for a short distance and completing the joints with solder or by brasing, care
being taken to leave no edges or corners which might interfere with the drawing in
of additional copper.
The form of my improved conductor gives great facility for connecting branch
lines which can be done by the ordinary means of clamping with properly shaped
clamps and soldering, the circular section being specially good in this respect.
Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed I declare that what I
claim is-
1. The improved cover for an underground conduit for electrical conductors and
the construction of a conduit with grooves for receiving the same substantially as
herein described and for the purposes set forth.
2. The improved form of electrical conductors for the distribution of electrical
currents as herein described and for the purposes set forth.
3. The method of constructing an electrical conductor for underground mains so
as to admit of the section thereof being easily increased by forming such conductor
of a shape to admit of copper of any suitable form being drawn through with the
increased facility herein before mentioned for the purposes set forth.
Dated this Nineteenth day of August 1891.
"
RICHARD THRELFALL.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, Agents for the Applicant.