Improvements in Electric Cables, and in their Manufacture
Year: 1895

page_text: Date of Application, 30th Apr, 1895
Complete Specification Left, 30th Jan, 1896-Accepted, 7th Mar, 1896
PROVISIONAL SPECIFICATION
Improvements in Electric Cables, and in their Manufacture
We, WILLOUGHBY STATHAM SMITH of 13 Courtfield Road, South Kensington
in the County of Middlesex, Telegraphic Engineer, and WILLIAM PUDDICOMBE
GRANVILLE of 36 Oakfield Road, Stroud Green, in the same county, Electrician,
do hereby declare the nature of this invention to be as follows
Inasmuch as the specific inductive capacity of air is considerably less than that
of any known insulating material it is for many purposes of great advantage to
construct an electric cable with an air space or spaces along its interior especially
when currents of rapid variation are used since the speed of variation of the current
is effected largely by the capacity
Several methods have before been used for forming cables with such interior air
spaces all having more or less attendant disadvantages
According to this invention we construct an electric cable of gutta percha or
like insulating material with a central longitudinal air space and with two or more
wires embedded at distances apart in the gutta percha near to the inner surface of
such tubular cable
One way in which we construct such a cable is to form two semicircular crescent
shaped strips of gutta percha each having embedded within it near to its concave
or inner side one or more conducting wires Afterwards we bring together the two
semicircular crescents so that the two together form a tube and around the exterior
of this tube we form an outer tube of gutta percha or like material by an
ordinary covering machine-the crescent shaped pieces being sufficiently strong
to retain then form whilst this outer covering of gutta percha is being put around
them
In order to obtain as large an air space as practicable and yet keep the
crescent shaped strips of sufficient strength to allow of an outer tubular covering
of gutta percha being formned around them after they have been brought together
we in some cases make each strip thicker along the middle thin at its side edges
and if a single wire only is embedded in each strip it is embedded in this thicker
portion near its inner concave surface and the gutta percha where it surrounds the
we may bulge inwards somewhat into the an space so that the interior of the
tubular cable becomes somewhat of an oval form with a slight inward projection
along the centre of each of its flatter sides
If desired more than two segments may be used more especially if there are
to be more than two wires in the cable
When the cable contains say two wires only it will be less flexible in the plane
In cases where this
in which the wies lie than in a plane at 1ight angles thereto
is likely to be prejudicial we make each of the strips or segments in the form of a
helical coil in place of straight This we do by twisting the strips after they have
been brought together and before the outer covering is put on The same applies
to cables in which three or more wires are used
Dated this 29th day of April 1895
WILLOUGHBY S SMITH
W P GRANVILLE

page_text: We, WILLOUGHBY STATHAM SMITH of 13 Courtfield Road, South Kensington
in the County of Middlesex, Telegraphic Engineer and WILLIAM PUDDICOMBE
GRANVILLE, of 36 Oakfield Road, Stroud Green, in the same county, Electrician
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
Inasmuch as the specific inductive capacity of air is considerably less than that
of any known insulating material it is for many purposes of great advantage to
construct an electric cable with an air space or spaces along its interior especially
when currents of rapid variation are used since the speed of variation of the current
is effected largely by the capacity
Several methods have before been used for forming cables with such interior air
spaces all having more or less attendant disadvantages
According to this invention we construct an electric cable of gutta percha or
like insulating material with a central longitudinal air space and with two or more
wires embedded at distances apart in the gutta percha near to the inner surface of
such tubular cable
One way in which we construct such a cable is to form two semi-circular crescent
shaped strips of gutta percha each having embedded within it near to its concave
or inner side one or more conducting wires Afterwards we bung together the
two semicircular crescents so that the two together form a tube and around the
exterior of this tube we form an outer tube of gutta percha or like material by
an ordinary covering machine the crescent shaped pieces being sufficiently strong
to retain their form whilst this outer covering of gutta percha is being put around
them
In order to obtain as large an air space as practicable and yet keep the crescent
shaped strips of sufficient strength to allow of an outer tubular covering of gutta
percha being formed around them after they have been brought together we in
some cases make each strip thicker along the middle than at its side edges and if a
single wire only is embedded in each strip it is embedded in this thicker portion
near its innei concave surface and the gutta percha where it surrounds the wire
may bulge inwards somewhat into the air space so that the cross section of the
interior of the tubular cable becomes somewhat of an oval form with a slight inward|
projection along the centre of each of its flatter sides
If desired more than two segments may be used more especially if there are to
be more than two wires in the cable
When the cable contains say two wires only it will be less flexible in the plane
in which the wires lie than in a plane at right angles thereto In cases where this
is likely to be prejudicial we make each of the strips or segments in the form of a
helical coil in place of straight This we do by twisting the strips after they have
been brought together and before the outer covering is put on The same applies
to cables in which three or more wires are used
Figure 1 is a cross section on an enlarged scale of an example of a cable formed
as above described in which are two arched or crescent shaped strips each having
embedded in it a single wire
Figure 2 is a similar cross section of another example in which two conductors
are embedded in each arched or crescent shaped strip
Figure 3 is a similar cross section of another example in which there are four
segments each having one wire embedded in it

page_text: Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim 18
-
1 An electric cable of gutta percha or like insulating material formed with a
central longitudinal air space and with two or more wires embedded at distances
apart in the gutta percha near the inner circumference substantially as described
2 An electric cable composed of a tubular case enclosing a cylinder which is
built up of two or more segments and has a longitudinal central hollow air space
and also has one or more wires embedded in each segment substantially as
described
3 Twisting the segments as they are brought together and before the outer
covering is formed around them
4 The construction of electric cables substantially as hereinbefore described and
illustrated in the drawings annexed
Dated this 29th day of January 1896
WILLOUGHBY S SMITH
W P GRANVILLE