Improvements in the Manufacture of Tubular Conduits for Electric Conductors.
Year: 1891

page_text: Date of Application, 2nd Nov., 1891-Accepted, 5th Dec., 1891
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Tubular Conduits for Electric
Conductors.
I, GEORGE FREDERICK REDFERN, of the firm of G. F. Redfern & Co., the
General Patent Office, No. 4, South Street, Finsbury, in the County of Middlesex.
Patent Agents, do hereby declare the nature of this invention (a cominunication
to me by Sigmund Bergmann, of 14 Fennstrasse, Berlin, in the Empire of
Germany, Manufacturer,) 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 to the manufacture of tubular conduits for underground
electric wires or cables, which conduits while being of a relatively small diameter
shall be capable of effectually resisting chemical as well as mechanical influences
arising from the nature of the soil.
In the accompanying drawings,
Figures 1, 2 and 3 are respectively an elevation; a longitudinal section and a
cross section of a portion of a tubular conduit for electric conductors made
according to this invention.
Figures 4, 5 and 6 are respectively an elevation, a cross section and a longitudinal
section illustrating a modification.
In carrying out this invention the conduit is made of a tube A of paper which
is repeatedly immersed in a liquid insulating waterproof substance such as petroleum
residue or pitch so as to form a kind of crust of the consistence of vulcanite or
ebonite adhering closely to the exterior of the tube.
The paper tube A with its insulating covering B is then enveloped in a metallic
covering C which serves to give the tube A B intended to receive the electric
conductor, a greater resisting power against external influences.
By combining a paper tube treated in the hereinbefore described manner with a
tight fitting metal cover an underground conduit for the reception of electric wires,
cables etc. is produced which will not only have great resisting power and withstand
the action of acids or the like, but will be relatively light and of small diameter.
It should be observed that the insulating covering need not necessarily be
produced before the outer metal cover, (which may consist of a strip of sheet iron
as shewn in Figure 1 or of a tube as shewn in Figure 4) is put on, but that the
insulating covering can be produced by dipping the paper tube, with its metal
covering applied thereto, repeatedly in the liquid insulating substance so that the
paper tube becomes thoroughly saturated and the insulating substance completely
fills its pores and any spaces that may be between the paper tube and its metal
covering. This method of applying the insulating substance however, requires a
greater number of immersions.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what 1
claim is :-
1. The manufacture of tubular conduits for underground electric wires, cables
and the like, by saturating and coating a paper tube with a liquid insulating
substance and surrounding it with a tightly fitting metal cover either before or
after such treatment, substantially as hereinbefore described.

page_text: 2. Tubular conduits for electric conductors made in the manner referred to in
the preceding claiming clause.
Dated the 2nd day of November 1891.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.