A New or Improved System of Wiring Electrical Installations.
Year: 1899

page_text: Date of Application, 30th Mar., 1899-Accepted, 8th July, 1899
COMPLETE SPECIFICATION.
A New or Improved System of Wiring Electrical Installations.
I, FREDERICK BATHURST, of No. 4, Limes Villas, West Hill Road, in the County of
Surrey, Electrical Engineer, 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 relates to a new or improved system for wiring electrical installations
and has for its object the use of a single bare wire or bare-stranded conductor carried
through an armoured conduit, or metallic tube, with a lining or sheath made of any
insulating material of an elastic nature as an internal covering. The bare wire or
cable in this case forms the positive (+) lead, and the metallic tube or armouring
the negative (-) or return lead. This system is of the type in which the return (-)
lead is not insulated but left in a condition so as to be normally at "earth potential."
It is not in my especial case necessary to furnish a drawing, since the description
of an ordinary metal tube, with an insulating lining of any elastic and suitable
material or substance is at once apparent to those conversant with electricity and
electrical installations, and the introduction of a bare wire or stranded conductor is
also obvious.
وو
In carrying my invention into effect I employ a. metal pipe or armoured conduit
as aforesaid, with any resilient or elastic insulating lining or sheath which may be
erected in buildings or the like, as an installation in the same manner appertaining to
ordinary gas or water pipes, with the necessary elbow, tee and socket joints screwed
to fit together; and where an open joint is requisite for breaking the system between
junction boxes or the like I employ a "running joint," i.e., the male screw thread
"back nut
carried back sufficiently to clear the sleeve, with a
or lock nut" to
close and hermetically seal the joint when completed. The chief point in fitting
lengths and joints together is in preserving the perfect continuity of the metallic
outside connection also the perfect abutment of the interior insulating lining at each
joint. This is effected naturally by the cutting of the pipes, and the elastic or
resilient nature of the substance forining said lining which protrudes in the process
of cutting or screwing the pipe, sufficiently to secure abutment when two sections are
joined. The insulation test is carried out by means of a "fishing wire" which is a
wire or spiral tape having a weighted end which being pushed through the bore is
blocked by any break or obstacle in the continuity thereof, and the position of the
same may be exactly located. Said " fishing wire" always operated with a rotary
and forward motion, also serves to guide the bare conductor through the system of
insulated pipes. When said installation is established the ordinary tests may be made
to determine the relative resistances of the inner conductor and the earthed outer
conduit or metal pipe, and the hermeticity thereof may be tested as a whole, or in
sections by an ordinary hand worked air pump having a suitable gauge or indicator to
show any degree of leakage. All outlets for ceiling roses, wall plugs, switches, fuses,
and the like are connected up in the same manner to boxes having an interior lining
of insulating substance or material upon which the base of the fitting or appliance is
fixed, the insulating lining of the pipe or conduit being caused to abut thereupon
and fit within holes formed in said boxes. The terminals (+) and (-) are respec-

page_text: tively connected within the boxes or any equivalent base, the insulation between the
two potential points being guarded in the usual manner, by the interposition of an
insulating bridge or the like.
―or other-
I have found by experiment that a bare wire within an insulated tube such as
hereinbefore described may be electrically heated to the point of fusion by the passage
of an excessive current without injuriously disturbing the insulation, which proves a
distinct advantage over a wire upon which the insulation is closely wound-
wise closely surrounds it. A further advantage is in the accessibility of any part of a
circuit or installation since the whole arrangement is analogous to, and is identical in
manipulation with ordinary gas or water service, except in the care that must be
exercised in maintaining the continuity of the interior insulating lining throughout.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
First. In an electrical circuit the use of a metallic pipe having a lining of any
insulating substance carrying interiorly a bare metallic conductor of single or multiple
strands freely lying in it forming one lead, the metallic pipe forming the other lead,
substantially as herein described.
Second. In an electrical circuit, the use of a metallic pipe having an insulating
lining and carrying a bare conductor interiorly, in combination with a method of
fitting together lengths or parts of the outer pipe by screwing, afterwards drawing in
the conductor within the insulated bore, substantially as herein described.
Third. In an electrical circuit in which the two components are an interiorly
insulated metal tube and a bare metal conductor carried freely therein, the method of
and means for preserving the continuity of the insulation by the introduction of metal
boxes with insulating linings at each outlet, substantially as described.
Dated this with day of
_L1000
FREDK. WALKER,
73, St. Stephen's Road, Upton Park, London, E.,
Agent for the Applicant.