Improvements in Conduit Tubes, more especially suitable for Electrical Conductors.
Year: 1896

page_text: Date of Application, 1st Aug., 1896-Accepted, 5th Sept., 1896
[Communicated from abroad by EDWIN TRUMAN GREENFIELD, of No. 44
Broad Street, New York City, in the County of New York, and State of
New York, United States of America, Electrician.]
Improvements in Conduit Tubes, more especially suitable for
Electrical Conductors.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, 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 to improvements in armoured conduit tubes, such as those
that are used for the purpose of protecting electrical conductors, and its object is
to provide conduit tubes with insulation on the inner side of the tube made either
wholly or in part of material which will fuse or liquefy under abnormally high
temperatures, and with an interior lining of metal or other relatively non-fusible.or
non-combustible material.
In the use of armoured conduit tubes in buildings and analogous places where
electrical conductors are protected by such conduit tubes, it often becomes necessary
to locate the same in close proximity to steam pipes or to flues, hot air shafts and
Under these circumstances
other places where abnormally high temperatures occur.
it has been found that where such armoured conduit tubes are provided either
wholly or in part with an insulating lining which liquefies when subjected to
abnormally high temperatures, the insulation breaks down and is in effect destroyed;
the liquefied material also frequently attaches itself to the enclosed conductor or
conductors, thereby rendering it impossible to withdraw it or them when necessary.
It is also found that where crossings occur between the conductors or where there
is abnormal current leakage, sufficient heat may be generated to break down or
destroy the insulation and also to unite the conductors to the walls of the tube by
the agency. of the liquefied. medium.
The present invention effectually overcomes this trouble by firmly maintaining
the insulating lining against the inner walls of the armoured tube or pipe.
The said invention will be fully understood by referring to the accompanying
drawing which is a longitudinal sectional view of portions of two armoured
conduit tubes joined end to end by a screw-threaded collar and provided with
an interior lining of insulating material, preferably paper tubing treated with
asphalt or bitumen in any well known manner, and my improved metallic lining
located within said insulating lining.
The armoured conduit tubes which are screw-threaded at their adjoining ends
and united by a collar or nut C are composed of iron armour P P, and insulating
linings II, preferably of paper treated with liquid asphalt, paraffin, or any well
known insulating medium; or the said linings may be of pure asphalt or paraffin,
or any medium either in whole or in part which will liquefy under abnormally high
temperatures.
My improvement consists in lining the interior insulating lining I with a metallic
or other comparatively non-fusible or non-combustible lining P¹, preferably of
thin sheet iron, although it may be of brass, copper, tin, or any material which will
not liquefy and which is not combustible under such temperatures as are found in

page_text: the places indicated above, or under such temperatures as result from an arc
between any two enclosed conductors. When this interior lining is of iron or any
other metal which is of comparatively high inductive capacity, I separate the ends
of the linings at the joints by definite spaces, as shown in the drawing, so as to
overcome the inductive effect upon the enclosed conductors throughout a system
in which such conduit tubes are used.
I am aware that it is not new to line the interior of an armoured conduit with
sheet lead for the purpose of firmly holding the insulation against the inner walls
of the conduit, such an arrangement having before been utilized in connection with
a felt lining in an iron armoured conduit, but as far as I am aware it is new to
utilize a non-fusible or non-combustible interior lining for armoured conduit- tubes
where the insulation, held between the armour of the couduit tube and the interior
lining, is either wholly or in part of a material which will fuse or liquefy under
abnormally high temperatures.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me 'by
my foreign correspondent, I declare that what I claim is :-
1. An armoured conduit tube having an insulating lining composed either wholly
or partly of a material which liquefies at an abnormally high temperature, in com-
bination with a non-combustible non-liquefiable interior lining, substantially as
described, and for the purpose specified.
2. A longitudinal series of armoured conduit tubes each provided with a lining,
which is either wholly or in part liquefiable at abnormally high temperatures, in,
combination with internal tubular linings for said armoured tubes of iron or other
inductive metal, said linings being slightly separated at their ends by definite spaces,
substantially.às and for the purpose specified.
3. An armoured conduit tube having iron or other metal armour and insulating
lining composed of paper or equivalent fibrous material treated with an insulating
material in combination with an internal tubular lining of metal or equivalent
non-combustible non-liquefiable material, substantially as and for the purpose
described.
Dated this 1st day.of August 1896.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, W.C., Agents for the Applicant.