Improved Means for Insulating Electric Conductors.
Year: 1895

page_text: Date of Application, 4th Feb., 1895
Complete Specification Left, 8th Apr., 1895-Accepted, 24th May 1895
PROVISIONAL OF
Improved Means for Insulating Electric Conductors.
I, GEORGE GATton Melhuish HARDINGHAM, of 191, Fleet Street, in the
City of London, Civil Engineer and Chartered Patent Agent, do hereby declare
the nature of this invention (a communication to me from the Firm of Felten and
Guilleaume, of Mülheim-on-the-Rhine, in the German Empire, Cable Manufac-
turers,) to be as follows:-
This invention relates to the insulation of electric conductors on the air-space
system, and consists in improved means for forming the air-space about the
conductor and for preserving the same against crushing.
According to the usual practice, the air-space enclosing the conductor is circular
in cross section and readily yields to external pressure. Moreover, the conductor
is throughout its whole length in contact with the material forming the walls of the
air-space, the insulation being thereby prejudicially affected.
According to the improved method of construction, the subject of the present
invention, the tube enclosing the air-space and conductor is triangular, quad-
rangular or polygonal in cross section, and is twisted longitudinally. Owing to
the angular form of the tube, it offers considerably greater resistance to external
pressure; and, owing to the conductor only touching the sides of the spiral air-
chamber at intervals, the insulation by air exclusively is more nearly accomplished.
The conductor, taking a straight course, is shorter, and therefore less costly, than
in the case where the conductor follows the convolutions of the air-enclosing tube.
In the production of a twisted triangular, quadrangular or polygonal, tube for
air-space insulation, and in applying the same about an electric ronductor, a folder
or former of the following character is employed. The folder consists of two
parts which resemble each other in form, and are arranged the one within the
other; there being between the two a passage through which the insulating
material passes. This passage is or may be annular at the entering end and
gradually changes as it approaches the exit end to a rectangular or other form,
according to the shape of the air-enclosing tube to be produced.
Through the centre of the inner part there is an opening for the passage for
the conductor. Whilst the material for forming the air-enclosing tube traverses
the passage between the two parts of the folder or former, the instrument is
rotated, the conductor meanwhile traversing the central passage. The conductor
then issues enclosed within a twisted tube of an angular character, which tube may
then be taped and provided with an outer sheathing; or several conductors so
insulated may be assembled in a cable.
Dated this 4th day of February 1895.
G. G. M. HARDINGHAM.

page_text: Improved means for insulating Electric Conductors.
I, GEORGE GATTON MELHUISH HARDINGHAM, of 191, Fleet Street, in the
City of London, Civil Engineer and Chartered Patent Agent, do hereby declare
the nature of this invention (a communication to me from the Firm of Felten and
Guilleaume, of Mülheim-on-the-Rhine, in the German Empire, Cable Manu-
facturers,) 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 insulation of electric conductors, on the air-space'
system, and consists in improved means for forming the air-space about the
conductor and for preserving the same against crushing.
According to the usual practice, the air-space enclosing the conductor is circular
in cross-section and readily yields to external pressure. Moreover, the conductor
is, throughout its whole length, in contact with the material forming the walls of
the air-space, the insulation being thereby prejudicially affected.
In the accompanying drawings,
Fig. 1 is an elevation of an electric conductor insulated according to the improved
method; Fig. 2 being a longitudinal section.
Figs. 3 and are transverse sections of conductors respectively enclosed in
quadrangular and triangular air-space' insulating tubes.
Fig. 5 is a perspective view of a die or folding instrument adapted for use in the
production of the said tubes; Fig. 6 being a face view of the entering end thereof.
According to the improved method of construction, the subject of the present
invention, the tube a enclosing the air-space b and conductor is triangular,
quadrangular or polygonal in cross-section, and is twisted longitudinally (Figs. I
and 2). Owing to the angular form of the tube a, it offers considerably greater
resistance to external pressure than is presented by a cylindrical tube; and, owing
to the conductor c following a course parallel with the axis of the said tube, and
only touching the sides of the spiral air-chamber at intervals, the insulation by air
exclusively is more nearly accomplished. The conductor, moreover, in taking a
straight course, is shorter, and therefore less costly, than in a case where the
conductor follows the convolutions of the air-enclosing tube.
In the production of a twisted triangular, quadrangular or polygonal tube for
air-space insulation, and in applying the same about an electric conductor, a die
or folding instrument of the character illustrated in Figs. 5 and 6 is employed.
This instrument consists of two parts d, d', which resemble one another in form;
the part being arranged within the part d'. Between these two parts is a
passage e, through which the paper or other insulating material for forming the
twisted tube a passes. This passage e is or may be annular at the entering
end (Fig. 6) and gradually changes as it approaches the exit end to a triangular,
quadrangular or polygonal form, according to the shape of the air-enclosing tube
to be produced. Through the centre of the inner part, there is formed an avenue f
for the passage of the conductor c. Whilst the material for forming the air-
enclosing tube a traverses the passage e between the two parts of the folder
or former, the instrument is rotated, the conductor c meanwhile traversing the
central passage f. The conductor thus issues enclosed within a twisted tube of an
angular character; which tube may then be taped and provided with an outer
sheathing; or several conductors so insulated may be assembled in a cable.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I claim :-
1. The herein described method of insulating an electric conductor on the 'air-
space' system, same consisting in enclosing a naked conductor in a twisted quad-

page_text: rangular, triangular or polygonal tube of non-conducting material, the conductor
being entirely air-insulated, except where in contact with prominences which are
presented in the internal surface of the envelope and which result from angularity
of section and twisting.
2. An electric conductor enclosed in a twisted quadrangular, triangular or
polygonal tube of non-conducting material, said conductor being entirely air-
insulated except where in contact with prominences which are presented in the
internal surface of the envelope and which result from angularity of section and
twisting.
3. The combination, with a naked electric conductor c, of a tubular envelope b
of non-conducting material, angular in cross-section and twisted, so as to present
in its internal surface prominences with which the conductor is alone in contact,
substantially as set forth.
4. For use in the production of air-insulated electric conductors of the kind
herein referred to, a folding or forming instrument, constructed substantially as
described with reference to Figs. 5 and 6 of the accompanying drawings, and
comprising two parts arranged the one within the other, and having between
them a space or passage which gradually contracts in diameter and changes
from an annular form at the entering end to an angular at the exit end, the
inner part being moreover provided with a central opening for the passage of the
conductor.
noted the 1st day of Annil 1805
G. G. M. HARDINGHAM.