Improvements in Conduits for Electric Conductors and Combined Conduits and Conductors and in the Manufacture of the same.
Year: 1889

page_text: COMPLETE SPECIFICATION.
Improvements in Conduits for Electric Conductors and Combined
Conduits and Conductors and in the Manufacture of the same.
We HENRY BILLINGTON TATHAM and JAMES TATHAM both of No. 226 South Fifth
Street in the City of Philadelphia State of Pennsylvania United States of America
Lead Pipe manufacturers 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 object of this Invention is to so construct a conduit for electrical conductors
that it will provide an effective insulation for the same, can be manufactured at
small cost, and will be practically indestructible under ordinary conditions of use.
This object is attained in the manner hereinafter set forth, reference being had to
the accompanying drawings, in which
Figure 1, is a transverse section of a conduit for electrical conductors male in
accordance with this invention.
Figure 2, is a longitudinal section showing a joint between successive lengths of
the conduit.
Figures 3 and 4 are transverse sections of special forms of conduit made in accord-
ance with this Invention.
Figure 5, is a longitudinal section of a branch joint between successive lengths of
conduit; and
Figure 6, is a longitudinal section illustrating the preferable method of making the
conduit.
The improved conduit consists of an outer pipe or casing a, an internal lining
tube b, and a layer d of insulating material confined or compressed between the
outer pipe or casing and the lining tube.
The outer pipe or casing a is preferably of cylindrical form and of iron or steel, an
ordinary wrought iron pipe being available for the purpose.
The interposed insulating layer d is preferably a tubular web of textile material
coated or saturated with the insulating material or compound, and the lining is in
the form of a seamless tube of metal.
An effective method of making the improved conduit according to this invention is
to draw into the outer pipe or casing first a comparatively loose fitting insulating tube,
and then a like loose fitting lining tube or the insulating tube may be first drawn over
the lining tube and the two be then introduced into the outer pipe or casing
together.
When in place in the pipe or casing the lining tube and the intermediate insulating
tube are secured in the said outer pipe or casing by radially expanding said lining
tube whereby the insulating tube is firmly compressed between the said lining tube
and the outer pipe or casing, the lining tube itself being caused to bear so firmly
against the insulating tube that any movement of one part of the conduit independently
of the other is impossible, and the conduit is thus rendered practically as homogeneous
as a single pipe.
For the purpose of expanding the lining tube within the outer pipe or casing, it is
preferable to use a hydraulic expanding device sufficient of which is represented in
Figure 6 to illustrate its operation.
This device comprises a hollow mandrilf communicating at one end with a supply
of liquid under heavy pressure, and having at the outer end a packed head f" which, in
the present instance, is inserted into the end of the lining tube of the condait, to
which it fits so snugly as to prevent the escape of liquid between the two.
The end of the conduit is then closed by means of a cap g, which forms a tight
joint with the said end of the conduit and has a stuffing box for the passage of

page_text: the hollow mandril. Liquid under pressure being admitted to the hollow mandril
escapes therefrom through openings into the space between the packed head
and the closing cap g.
The liquid, being under heavy pressure, first radially expands that portion of
the lining tube d which is between the head and the end of the conduit.
until such expansion is arrested by the compression of the insulating tube,
and as the flow of liquid is continued, the conduit, with its closing cap, is forced
along over the mandrel in the direction of the arrow, the expansion of the lining
tube progressing continuously during this movement until the packed head of the
mandril finally emerges from the opposite end of the conduit.
The lining tube and the insulating tube should in the first instance be somewhat
longer than the outer pipe or casing to compensate for the contraction in their length
which is due to their radial expansion.
Although water may be used as the expanding agent it is preferable in most cases
to use oil for this purpose, as the presence of a small quantity of oil in the conduit
is not objectionable, whereas the presence of water or the vapour of water within
the conduit is to be avoided.
A mechanical expander forced through the conduit may, in some cases, be used
instead of the fluid expansion device shewn, for expanding the lining tube or the tube
may be inserted in the outer pipe or casing and the insulating material then introduced
between the two.
In connecting successive lengths of the improved conduit together, it is preferable
to interpose between the ends of the conduit sections, a ring or washer m of insulating
material so that adjoining lengths of the conduit are effectively insulated from each
other, and as the lining of each section of conduit is insulated from the outer pipe or
casing, it follows that the conduit- provides an insulating casing or covering for the
conductor throughout its entire length.
may be
As the lining of the conduit is, moreover, perfectly smooth, the conductor
readily drawn through the same without causing excessive friction either upon the
conductor or the conduit lining, this being a matter of considerable importance where
the conductor is provided with an insulating cover, as the drawing of such conductor
through a long conduit having a rough interior surface is likely to rub the insulating
covering from the wire.
As the improved conduit is in itself an insulator, the providing of the conductor
with a special insulating covering is not absolutely necessary and in many cases the
conduit may be slotted as in Figure 3, for instance, to permit of the passage of a
contact bar making connection with a naked conductor within the conduit.
A conducting conduit can also be constructed in accordance with this Invention by
inserting and compressing within the outer pipe or casing successive insulating and
conducting tubes, for instance, in Figure 4 is shown a conduit in which a series of
insulated conducting tubes n, preferably of copper, are introduced between the outer
pipe or casing a and the lining b with intervening insulating tubes d.
In making a branch connection between successive lengths of a conduit, it is
preferable to provide this connection also with a lining and with insulating material
interposed between said lining and the outer casing, as shown for instance in
Figure 5.
Having now particularly described and ascertained the nature of our said Inven-
tion and in what manner the same is to be performed we declare that what we
claim is.
First The herein before described conduit for electrical conductors consisting of
an outer pipe or casing, a metal lining tube and an interposed layer of insulating
material immovably confined between said casing and lining, substantially as herein-
before specified.
Second-The combination, in a conduit for electrical conductors, of the conduit
sections each comprising an outer casing, a metal lining tube and a layer of insu-
lating material immovably confined between said casing and lining, with an insulating

page_text: ring or washer interposed between successive lengths of the conduit, substantially as
herein before described.
Third The herein before described compound electrical conductor, consisting of an
outer pipe or casing, a lining tube, and tubes of insulating material and tubular
conductors disposed alternately within said casing, and immovably confined between
the outer casing and the lining tube, substantially as herein before specified.
Fourth The process herein described of making a conduit for electrical conductors
the said process consisting in inserting within an outer pipe or casing a layer or
layers of insulating material and a lining tube or tubes and then expanding the said
tube or tubes so as to compress the insulating material between the same and the
outer casing substantially as hereinbefore specified.
Fifth The process herein described of making a conduit for electrical conductors,
said process consisting in inserting within an outer pipe or casing a layer or layers
of insulating material and a lining tube or tubes and then expanding the said tube
or tubes by forcing fluid under pressure into the conduit beginning at one end of the
conduit and extending progressively through the same, substantially as herein before
specified.
Dated the 17th day of December 1889.
J. H. JOHNSON & Co.,
Agents.