Note: Descriptions are shown in the official language in which they were submitted.
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A~ IMPROVED FLEXIBLE EL~iCTRICALLY INSULATED
ELECTRIC CONDU~.TOR
This invention relates to flexible electrically
insulated electric conductors o~ the kind compri~ing a
plurality of wire stranded, bunched or otherwise
assembled together and surrounded by at least one layer
of electrically insulating material. Flexible
electrically insulated electric conductors of this kind
include flexible electrically insulated cords for
connection to domestic electrical appliances such as,
for example, electric irons, lamps and electrically
operated devices used in a kitchen, and flexible single
core and multi-core power cables incorporating one or
more than one flexible electrically insulated electric
conductor for connection to electrically operated tools
and equipment used in industry, e.g. equipment
incorporating a reeling and de-reeling facility, and by
a handyman.
We have found that, over a period of time,
freguent flexing of a flexible electrically insulated
electric conductor can cause a wire of the conductor to
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break and an end part of such a broken wire sometimes
penetrates outwardly into and through the overlying -
layers or layers of electrically insulatlng material. A
flexible electrically insulated electric conductor which
is connected to an electrical appliance and which has a ;~
live wire or live wires protruding through its -`~
electrically insulating layer or layers is extremely
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dangerous, especially if handled with damp hands - as
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may be the case where the el~ctrical appliance to which
the flexible electrically insulated electric conductor
is connected is in a kitchen.
It is an object of the present invention to
provide an improved flexible electrically insulated
electric conductor of the kind described in which the
aforesaid risk is eliminated or at leas* substantially
reduced.
According to the invention, the improved flexible
electrically insulated electric conductor comprises a
plurality of wires stranded, bunched or otherwise
assembled together, a flexible barrier of plastics
material surrounding and immediately adjacent the
conductor throughout its length and, overlying the
flexible barrier, at least one layer of electrically
insulating material, the plastics material of the
flexible barrier being substantially tougher than the
material or materials of the overlying layer or layers
and being of such radial thickness as to inhibit
penetration by a broken wire of the conductor.
` ` The flexible barrier may be in the form of an
extruded layer of said plastics material or it may be in
the form of one or more than one layer of helically
applied tape of said plastics material. In the latter
case, where~the flexible barrier comprises two or more
layers of helically applied tape of said pla~tics
material, preferably adjacent layers of helically
applied tape!s will be of opposite hand to one another.
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Preferably, the flexible barriex has a radial
thickness lying in the range 0.0ld to 0.10d, where d is
the overall diameter of the bare conductor.
The plastics material of the flexible barrier
preferably is a relatively tough polymeric material;
suitable relatively tough polymeric materials include
urethanes, polyurethanes, thermoplastic polyurethane
elastomers, polyesters and polyamides.
; Where the layer immediately overlying the flexible
~: ~ 10 barrier is of electrically insulating plastics material,
~: the plastics material of the flexible barrier may itself
have electrically insulating properties or it may be
rendered semi-conductive by the incorporation of carbon
black or other electrically conductive filler so that
the flexible barrier also constitutes a semi-conductive
~; conductor screen or shieldO ::~
Where the layer immediately overlying the flexible ~-
barrier is of a semi-conductive plastics material and
; ~ ; constitutes a conductor screen or shield, the plastics
20 ~ material of the flexible barrier will incorporate carbon
; black or other electrically conductive filler rendering
the plastics material of the flexible barrier semi- -`.~
conductive. ..
Since the plastics material of the flexible
karrier may constitute a part of the electrical
insulation of the conductor or a part of the semi~
conductive conductor screen or shield, the overall :~
diameter of the improved flexible electrically insulated ;;~ ;
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electric conductor need be no greater than that of a
comparable flexible electrically insulated electric
conductor in which no flexible barrier i~ incorporated.
The invention also includes a multi-core flexible
power cable in which at least one of the cores is an
improved flexible electrically insulated electric
conductor a~ hereinbefore described.
The invention is further illustrated by a
description, by way of example, of two preferred
flexible electrically insulated electric conductors with
reference to the accompanying drawing, in which:-
Figure 1 is a transverse cross-sectional view,
drawn on an enlarged scale, of a preferred flexible
electrically insulated cord for connection to a domestic
~ eLectrical appliance, and
Figure 2 is a transverse cross-sectional view,
drawn on an enlarged scale, of a core of a preferred
f1exible multi-core power cable for connection to
industrial equipment incorporating a reeling and de-
reeling facility for the cable.
Referring to Figure l, the preferred flexible
electrically insulated cord comprises a conductor 1
; consisting of a multiplicity of wires bunched together,
a flexible barrier 2 of extruded electrically insulating
poLyurethane surrounding and immediately adjacent the
conductor throughout its length and, overlying the
flexible barrier, a layer 3 of extruded electrically
insulating ethylene propylene diene rubber (EPDM). The
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bare conductor 1 has an overall diameter of 10.5 mm and
the flexible barrier 2 has a radial thickness of
approximately 0.3 mm and is su~Eficiently tough to
inhibit penetration of the flexible barrier by a broken
wire of the conductor. The ~lexible electrically
insulated cord has an overall diameter of 14.8 mm.
Referring to Figure 2, the preferred flexible
multi-core power cable comprises three sllbstantially
identical flexible cores laid up together and surrounded
by an overall cable sheath, one of which cores is
illustrated in the Figure. The core comprises a
conductor 11 consisting of a plurality of wires stranded
together, a flexible barrier 12 of extruded semi-
conductive polyurethane surrounding and immediately
adjacent the conductor throughout its length, a layer 13
of extruded semi-conductive polyolefin overlying the
flexible barrier which, in combination with the layer ;~
13, constitutes a conductor screen or shield, a layer 14
of extruded electrically insulating ethylene propylene
diene rubber (EPDM) overlying the layer 13 and a layer
15 of extruded semi-conductive polyolefin overlying the ~-
layer 14 and constituting a dielectric screen or shield.
The bare conductor 11 has a diameter of 10.5 mm and the
flexible barrier 12 has a thickness of 0.3 mm and is
sufficiently tough to inhibit penetration of the
flexible barrier by a broken wire of the conductor. The
core ha~ an overall di~meter of ls . a r~. ~
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As has been previously indicated, since the
electrically insulating flexible barrier 2 of the
preferred flexible electrically insulated cord
constitutes a part of the electrical insulation of the
conductor 1 of the preferred flexible electrically
insulated cord and the semi-corlductive flexible barrier
12 constitutes a part of the conductor screen or shield
of the conductor 11 of the core of the preferred
flexible multi-core power cable, the overall diameters
~ 10 of the preferred flexible electrically insulated cord
::~ ; and of the preferred flexible multi-core power cable
need be no greater than that of comparable cords and
cables in which no flexible barrier is provided.
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