Note: Descriptions are shown in the official language in which they were submitted.
2038~87
OVERHEAD ELECTRIC & OPTICAL CONDUCTOR MANUFACTURE
This invention relates to composite flexible
overhead electric and optical conductors suitable for
incorporation in an overhead electric and optical
transmission system in which at least one such composite
conductor is suspended freely in long lengths between
towers or other upstanding supports mutually spaced
along the route of the system.
In the Complete Specification of our British
Patent No: 1598438 there is described and claimed a
composite flexible overhead electric and optical
conductor which is now widely used in overhead electric
and optical transmission systems both in the United
Kingdom and elsewhere and which comprises at least one
layer of helically wound bare elongate elements of metal
or metal alloy, at least one elongate compartment within
and extending throughout the length of the conductor
and, loosely housed in the elongate compartment or at
least one of the elongate compartments, at least one
separate optlcal fibre and/or at least one optlcal
bundle.
In one preferred embodlment of the composite
flexlble overhead electric and optical conductor in
accordance wlth our aforesaid patent, the or each
elongate compartment ls disposed withln a substantially
circumferentlally rlgid central core around which the
bare elongate elements of metal or metal alloy of the or
each layer are helically wound.
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2.
It is an object of the present invention to
provide an improved method of manufacturing a composite
flexible overhead electric and optical conductor in
accordance with our aforesaid patent, which method of
manufacture is simple and substantially less expensive
than methods of manufacture hitherto proposed and used.
According to the invention, the improved method
comprises causing a flexible central core to travel in
the direction of its length; helically winding around
the advancing core at least one layer of bare elongate
elements of metal or metal alloy to form a flexible
electric conductor having within and extending
throughout the length of the conductor at least one bore
or other passage; winding the flexible electric
conductox around the hub of a cable drum in such a way
that each end of the wound conductor is exposed and
accessible; and accommodating at least one length of
flexible optical guide comprising at least one optical
fibre throughout the length of the bore or other passage
or of at least one of the bores or other passages wlthin
the wound conductor by introducing a leading end of the
length of optical guide into the end of said bore or
pas~age at one exposed end of the wound conductor and by
propelllng the optical guide along said bore or passage
of the wound conductor by fluid drag of a gaseous medium
which will have no deleterious effect on the optical
guide or on the conductor and which is passed through
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3.
said bore or passage in the deslred direction of advance
at such a pressure that the length of optical guide is
carried along said bore or passage until the length of
optical guide is loosely housed in and throughout the
length of said bore or passage of the wound conductor.
Preferably, the length of optical guide loosely
housed in the bore or other passage of the wound
conductor wlll substantially exceed the length of the
bore or passage so that there is an excess length of
optical guide within the bore or passage.
At least one said bore or other passage may be
within the flexible central core - in which case the
flexible central core will be substantially
clrcumf~erentlally rigid - or said bore or other passage ;
may be within a bare metal elongate element, or between
ad~acent bare metal elongate elements, of the layer or
at least one of the layers of hellcally wound bare metal
elongate elements. ~ ~
Where the or each bore or other passage i8 wlthin
a bare metal elongate element, or between ad~acent bare
metol elongate elements, of the layer or at least one of
the layers of hellcally wound bare metal elongate
elements, the flexlble central core may be a single bare
wlre or other elongate element of metal or metal alloy
or a plurallty Or such bare wlres or other elongate
elements assembled together.~
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4.
The leading end of the length of optical guide may
be introduced into the end of said bore or passage at
either exposed end of the wound conductor but,
preferably, it is introduced into the end of said bore
or passage at the exposed leading end of the wound
conductor, that is to say the end of the wound conductor
nearer the hub of the cable drum, and, for this purpose,
preferably the leading end of the wound conductor
protrudes through a hole in a flange of the cable drum.
10By virtue of the fact that both ends of the wound
conductor are exposed and accessible, after a flexible ;
optical guide has been accommodated in the or a bore or
other passage in the wound conductor, the flexible
optical guide can be readily tested.
15The or each flexible optlcal guide may be
propelled along the bore or other passage of the wound
conductor by fluid drag of the gaseous medium using the
method and apDaratus as described ln our Britlsh Patent
Specification No: 2179471B but lt ls to be clearly
; ~ 20 understood that any suitable method hltherto proposed
and used of propelling a flexlble optical guide along a
~ bore or other passage by fluid drag of a gaseous medium
;~ can be employed.
Where the advanclng flexible central core is
substantiallY circumferentially rigid and has at least
one bore or other passage within and extendlng
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5.
throughout its length, preferably the central core
comprises a seamless tube of aluminium or of other metal
or metal alloy having a single central bore - in which :
case the seamless tube may be made by the Conform
process - but, where lt ls deslred that the central core
includes two or more passages extendlng wlthin and
throughout the length of the core, the:central core
preferably is of composite form and comprises a central
elongate member of metal or metal alloy having in its
10 outer surface a plurality of circumferentlally spaced -~
grooves extending helically around the member and,
surrounding the helically grooved central member, a
separately formed circumferentially continuous wall of
metal or metal alloy, which wall may conslst of a
longitudinally extending, transversely folded strip of
metal or metal alloy.
The bare metal elongate elements of the or each
~: layer may each be of circular or non-circular transverse
cross-section. Where two or more layeræ of bare metal
elongate elements are hellcally wound around the
advanclng central core, preferably the elongate elements
of ad~acent layers are helically wound in opposlte
~- dlrections. ~:
. The or each flexible optical guide may be a
separate optical fibre or it may be an optical fibre
element comprlsing two or more optical fibres assembled
;~ together such as, for example, a flexible plastlcs tube
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having two or more optical fibres loosely housed in the
bore of the tube or, for example, an optical fibre
ribbon comprising a plurality of optical fibres
extending side by side with their axes lying in a
substantially common plane. One optical fibre ribbon
structure which is especially suitable for use in the
improved method of the present invention is described
and claimed in the specification of;our British Patent
No: 2141558B.
The invention also includes a composite flexible
overhead electric and optical conductor when
manufactured by the improved method herelnbefore
described.
The invention is further illustrated by a
lS description, by way of example, of the preferred method
~ of manufacturing a composite flexib}e overhead electric
;- and optlcal conductor with reference to the accompanying ~ `
drawings, in which:-
Figure 1 1s a transverse cross-sectional vlew of
the composite overhead flexlble electric and optical
conductor to be manufactured by said preferred method:
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-~ Figure 2 is a diagrammatic sectional side view of
preferred apparatus used for introducing a flexible
optical guide into the central bore of the wound
electrlc conductor, and.
~- Figure 3 ls a diagrammatic pictorial view of the
ap~aratus employed in effecting the final step ln said
preferred method.
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Referring to Figure 1, the composite flexible
overhead electrlc and optical conductor 1 to be
manufactured by the preferred method of the invention
comprises a central seamless circumferentially rigid
aluminium tube 3 in the bore 4 of which throughout the
length of the conductor is looæely housed a flexible
optlcal guide 2, the length of the optical guide
exceeding the length of the tube. The seamless
aluminium tube 3 ls surrounded by three layers 6 of
helically wound bare aluminium wires 7 each of circular
cross-section, the helical lay of the wires of each
layer being of opposlte hand to that of the helical lay
of the wires of the or each ad~acent layer.
The flexlble optical guide 2 may be of any one of a
number of forms includinq a separate optical fibre and
an optlcal fibre element comprising two or more optical
f1bres, e.g. an optical fibre ribbon.
In the preferred method of manufacturlng the
composite flexlble overhead electrlc and optlcal
conductor 1 shown ln Flgure 1, the steps ln the
manuracture of the electrlc conductor that are effected
prlor to introductlon of the flexible optlcal guide 2
are conventlonal and well known in the art. The central
seamless clrcumferentially rlgid aluminium tube 3 -
whlch may be formed by the Conform extrusion process orby any other suitable extrusion process - is caused to
travel ln the dlrection of its length towards and
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through stranding apparatus (not shown) at which three
layers 6 of aluminium wires 7 are helically wound around
the advancing tube, the wires of each of the outer two
layers being helically wound in~the opposite direction
to that of the hellcally wound wlres of the underlying
layer. Downstream of the stranding apparatus, the
leading end 11 of the flexible electric conductor 10 so
formed i8 threaded through a hole 16 ln a flange lS of a
cable drum 14 (Pigure 3) so that it is exposed and
accesslble and the flexible conductor is then wound
: around the hub of the drum leaving the tralllng end 12
of the wound conductor exposed and accesslble.
Referring to Figures 2 and 3, the preferred
apparatus used for introduclng a flexible optical guide
into the central bore of the wound electric conductor 10
. comprises a substantially fluid-tight housing 21 of
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elongate shape having, at one end of the housing, an end -
wall 22 and, at the other end of the housing, an end
wall 23 of hemi-spherical shape. Mounted in the housing
~ 20 21 is a pay-off stand 24 on whlch ls freely plvotally
-~ mounted a reel 25 on which ls wound a flexlble optlcal
guide 18.
In the end wall 22 of the housing 21 is an inlet
port 27 throu~h which pressurised air from a source (not
; 25 shown) can be introducod into the housing, the rate of
. lntroductlon o~ the air belng controllable by a~valve
~8. A v1nual lndlcatlon of the pres~uee of the a1r
2~387~37
within the housing 21 is given by a pressure meter 29.
Connected to an outlet 31 in the end wall 22 of the
housing 21 is a pipe 32 of transparent plastics material
for connection to the central bore of the wound electric
conductor 10 at its leading end 11.
Posltioned within the housing 21 between the reel
25 and the outlet 31 is a pair of rubber-coated pinch
wheels 34, one of which is rotatably driven through a
gear box (not shown) by a 12 v.d.c. motor 35, the leads
from the motor passing through a fluid-tight seal in an
aperture 36 in the end wall 22 via an electro mechan,cal
relay (not shown), controlled by a programmable
controller, to a power supply (not shown).
The housing 21 may have at least one window in its
wall and may incorporate an internal lighting system to
enable the behaviour of the flexible optical guide 18
and the reel 25 to be continuously monitored, thereby
giving an indication of any obstruction in the central
bore of the wound electric conductor 10.
In employing the apparatus shown ln Figure 2 to
lntroduce the flexlble optical gulde 18 ~rom the reel 25
into the bore of the flexible electric conductor 10
wound on the hub of the cable drum 14, the flexible
optical guide ls passed from the reel through a guide
tube (not shown) between and in contact with the pair of
wheels 34, through another guide tube (not shown) and
through the pipe 32. A flexible lightweight body,(not
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shown) similar in shape to a parachute or umbrella and
having a transverse cross-sectional area substantially
greater than that of the optical guide 18 may be
attached to the leading end of the flexible guide and be
S lntroduced into the central bore of the wound conductor
10 at its leading end 11. The pipe 32 is then connected
to the central bore of the flexible conductor 10 at its
leading end 11 to effect a fluid-tight seal.
Air under pressure is then introduced into the
housing 21 through the inlet port 27 so that the housing
is substantially filled with air at a predetermined
pressure, the hemi-spherical end wall 23 of the housing
belng so shaped as to deflect the air smoothly so that
it flows towards and out of the outlet 31 through the
lS pipe 32 and into the central bore of the wound conductor ~-
10. As the pressure of the air withln the housing 21
approaches the required level, the pair of wheels 34 is
rotatably driven by the motor 35 at continuously varying
~: speeds between upper and lower iimits to prodùce a
~;: 20 pulsing effect serving to provide an intermlttent
release of flexible optlcal guide 18 from the reel 25.
The rate at whlch the flexlble optical guide 18 is
unwound intermittently from the reel 25 by the palr of
wheels 34 and the pressure and rate at which air is
continuously lntroduced into the fluid-tlght housing 21
are such that regular pulsed progression of the flexible
optical gulde along the pipe 32 and lnto the central
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bore of the wound conductor 10 is produced by
combination of the continuous varied drive and fluid
drag of the air; where a flexible lightweight body is
attached to the leading end of the flexible optical
guide, the in~ected air will bear against the flexible
body which assists in effecting advance of the flexible
optical guide along the central bore.~ The process is
continued until the desired length of flexible optical
guide 18 is loosely housed in and throughout the length
of the central bore of the wound conductor 10.
The improved method of the invention has the very
important advantage that the cost of manufacture of the
composite flexible overhead electric and optical
conductor is substantially reduced because the or each
lS flexible optical guide is not accommodated in the
electrlc conductor during manufacture of the conductor.
Thus, conventional and long proved successful methods of
manufacturing~the electric conductor can be used.
Furthermore, a flexible optlcal gulde of any desired
form can subsequently be accommodated ln a bore or other
passage ln a wound electrlc conductor at any tlme as and
when a partlcular composite flexlble overhead electric
and optical conductor is required by a customer. Thus,
a manufacturer need only keep in store standard forms of
; 25 the flexible overhead electric conductor havlng
throughout its length at least one bore or other
passage.
