Note: Descriptions are shown in the official language in which they were submitted.
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COUPLING APPARATUS AND ME TROD
The present invention relates to coupling apparatus for
fitting to a conductor or cable. In particular, it
refers to high frequency coupling apparatus suitable for
telecommunications signals propagated, at least in part,
along conventional power distribution cables.
The transfer of communication signals along electricity
distribution and/or transmission networks is a promising
development in the telecommunications industry. The
communication signals may be transferred even whilst the
power cables/conductors are energized.
Various technical aspects of systems whereby
telecommunications signals can be conveyed along an
electricity distribution and/or transmission network are
disclosed in published patent applications of the present
applicant. These applications include the following:
W094/09572, W095/29572, W095/29537, W096/07245,
W098/19398, the disclosures of which are incorporated
herein by reference.
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It is desirable that the coupling of telecommunication
signals onto power distribution and/or transmission
networks be achieved in a safe, efficient and cost-
effective way.
The present invention aims to provide a method and
apparatus for effectively coupling communication signals
onto and off an existing, possibly energized, mains
electricity distribution and/or transmission network.
Accordingly, in a first aspect, the present invention
provides a coupling apparatus suitable for coupling with
an electricity cable, where the cable includes an
electrically insulated conducting member, where the
coupling apparatus includes cable insulation penetration
means for penetrating the electricity cable to provide an
electrical connection to the conducting member, the
penetration means being electrically connected to a
coupling member suitable for connection to a
telecommunications signal source or receiver.
In this way, a coupling member suitable for connection to
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a telecommunications signal source or receiver may be
electrically connected to the conducting core of a power
cable or other type of conductor.
Thus the coupling device could be retro-fitted to an
existing power distribution and/or transmission network.
To minimize disruption to consumers' power supplies and
to avoid time-consuming installation, preferably the
coupling device should be adapted to be fitted to, for
example, an insulated power cable without disconnecting
that power cable from the power source, i.e. while the
cable is "energized" or live.
The coupling member is electrically isolated at low
frequencies (e.g. 50/60 Hz or possibly up to 100 or 200
Hz) from the insulation penetration means using a low
frequency protection means such as a high pass filter,
for example a suitable capacitor. Furthermore, the
coupling member may be electrically protected from the
cable insulation protection means by, for example a fuse
and/or transformer, e.g. a balun transformer.
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The insulation penetration means is adapted to pierce a
sleeve of electrical insulation material around the power
cable or conductor and hence come into and establish
electrical contact with the electrical current carrying
part of the conductor. In this way, the coupling device
is suitable for attachment to a power cable or conductor
at many different places along the cable or conductor
length.
In some instances, it might not be desirable for the
electronic components to be attached to the cable at all
times. Accordingly, in a second aspect, the present
invention provides a coupling device including a clamp
and a clamp head. The clamp includes the insulation
penetration means and means for fitting the insulation
penetration means to the cable. The clamp head includes
a coupling member suitable for connection to a
telecommunications signal source or receiver. The
coupling member is preferably protected by low frequency
protection means such as a high pass filter, for example
a suitable capacitor. Furthermore, the coupling member
may be electrically protected from the cable insulation
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penetration means by, for example, a fuse and/or balun
transformer.
In a preferred embodiment of the present invention, one
5 end of the primary winding and/or one end of the
secondary winding of the transformer is/are electrically
bonded to an earth potential. Furthermore, in another
preferred embodiment, one end of both the primary and
secondary windings of the transformer are electrically
bonded to the same earth potential.
In another preferred embodiment of the present invention,
the cable insulation means includes a spike.
Additionally or alternatively, this spike may be rigid.
Additionally or alternatively, the spike may be
electrically conducting. Additionally or alternatively,
there may be a plurality of spikes, preferably spaced 0.5
- l.5cm apart, most preferably around lcm apart.
Preferably, the present invention includes clamping means
for urging the penetration means into the cable the
clamping means may include a screw operated compression
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member.
Preferably, the present invention includes a housing
which, in use, fits around the cable.
In another preferred embodiment of the present invention,
the coupling apparatus includes a two part housing, the
first part containing the coupling member and the second
part containing the penetration means wherein the two
parts are releasably joined together. Preferably, the
clamping means is included in the second part of the
housing.
Preferably, the cable insulation penetration means and
the coupling member are electrically connected via a
conducting spring.
Embodiments of the present invention will now be
described with reference to the accompanying drawings in
which:-
Figure 1 is a schematic diagram of a coupling device
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according to a first embodiment in which the main
internal components are illustrated.
Figure 2 is an exploded schematic diagram of a coupling
device according to the first embodiment, showing the
device in its two main component pieces.
Figure 3 is an exploded schematic diagram of a coupling
device according to the first embodiment, corresponding
to a section viewed in a plane which is perpendicular to
the axis of the cable at the line marked "X-X" in Figure
2.
Figure 4 is a schematic diagram of a coupling device
according to a second embodiment in which the main
internal components are illustrated.
Figure 5 is an exploded schematic diagram of a coupling
device according to the second embodiment, showing the
device in its three main component pieces.
Figure 6a is a side view of a coupling device according
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to a further embodiment of the present invention;
Figure 6b is an end view of the device of Figure 6a;
Figure 7a is a side view of a further embodiment of a
coupling device according to the present invention; and
Figure 7b is an end view of the device of Figure 7a.
Figures 1, 2 and 3 show a coupling device according to
the first embodiment of the present invention. The unit
consists of two parts 21 and 22, constructed in part
using a strong, non-conducting material, which are
clamped tightly together using, for example, two screws
7. The device is preferably clamped across an insulated
power cable 2. The outline of the unit is preferably
shaped to fit an insulated cable 2 between the two parts
of the coupling device 21 and 22. For example, the
outline of the coupling device is concave, as shown in
Figure 3. The insulation penetration means preferably
includes a rigid conducting spike 3. This spike
protrudes a pre-set distance into the concave outline of
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the unit. The insulation 8 is pierced and electrical
contact is made between the rigid conducting spike 3 and
the metallic power conductor 1 as the clamping screws 7
are tightened.
The rigid conducting spike 3 is electrically connected to
a circuit 4, schematically shown in Figure 1. This
circuit preferentially includes one or more protection
devices such as a fuse and a balun _transformer. The
circuit further includes a low frequency protection
device such as a high pass filter for the high frequency
communication signals, for example a suitable capacitor.
The circuit is provided with a coupling member such as a
communications signal input/output port, typically a
coaxial, unbalanced, high frequency, standard BNC
connector 5 well known in the art. Preferably, a safety
earth is attached via 6 in Figure 1. Additionally or
alternatively an isolation capacitor may be included on
the "braid" side of the coaxial connector 5 in order to
isolate it from the mains electricity supply in the event
of a fault.
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In this first embodiment, the circuit 4 is entirely
contained within the insulating casing of the device.
Therefore, during installation of the coupling device, no
'live' conducting elements are exposed, either on the
5 cable or on the device itself.
Figures 4 and 5 illustrate a coupling device according to
a second embodiment of the present invention. The device
is constructed in part using a strong, non-conducting
10 material and is made up of three main parts 51, 52 and
53. Main parts 51 and 52 are shaped, for example in a
concave sense, so that an insulated cable 31 may fit
between them in a similar sense to the first embodiment,
shown in Figure 3. Parts 51 and 52 may be clamped
tightly together using a single screw 40. A rigid
conducting spike 34, similar to a spike 3 in the first
embodiment, protrudes a pre-set distance into the concave
outline of part 52. The insulation 42 is pierced and
electrical contact is made between the rigid conducting
spike 34 and the metallis power conductor 32 as the
clamping screw 40 is tightened.
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The rigid conducting spike may be electrically connected
to a fuse carrier and link 36 via a conducting spring 35
when the clamp 33, made up using main parts 51 and 52, is
attached to a clamp head 37 (or 53) via screws 41. The
clamp head contains a circuit 36, preferentially
including protection devices such as a fuse and a balun
transformer. The circuit further includes a low
frequency protection device such as a high pass filter
for high frequency communication signals and is similar
to the circuit 4 described in outline in the first
embodiment of the invention. The circuit 36 is provided
with a coupling member such as a communications signal
input/output port, typically a coaxial, unbalanced, high
frequency, standard BNC connector 38 well known in the
art. Preferably, a safety earth is attached via 39.
The second embodiment of the present invention allows the
clamp head 53 to be easily removed from the cable clamp
51 and 52 whilst, if desired, leaving the cable clamp 51
and 52 still attached to the cable. The cable clamp may
then be covered using a fascia plate. This removes the
need to place an insulating sleeve over the puncture hole
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in the cable insulation if it is required to remove the
coupling device from the cable at some later date.
The embodiment of the invention shown in Figures 6a and
6b consists principally of a first part 60 of the
coupling unit and a saddle 61. As will be seen, the
saddle 61 sits on top of the coupling unit part 60. The
saddle may, for example, be made of steel and may be
around 20 x 30 x 3mm in size including a taped hole for
receipt of a screw 62, with for example a 5mm thread.
In use, the unit 60 is placed against an insulated cable
63 to a conductor of which contact is required to be
made . Initially, the saddle lies against or adj acent the
top of the part 60 as shown in Figure 6a. The contacts
(not shown) project against the cable 63.
One or more cable ties 64 (in this embodiment, two ties
are used) secure the unit 60 against the cable 63. In
this embodiment each of the cable ties 64 is located on
a respective side of the screw 62 and also serve to hold
the saddle against the unit 60. As will be seen more
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clearly in Figure 6b, the eye 65 of each cable tie abuts
against a sa_uare edge 66 of the saddle 61. By contrast,
the edge 67 of the saddle 61 over which the elongate
portion of the cable tie 64 lies is rounded so as to
relieve the stress on the cable tie. Also optionally
provided are locating notches in the saddle 61 (not
shown) which serve to locate the elongate portion of the
cable ties 64. In some embodiments, the rounded edges
mentioned previously may only be provided in the locating
notches.
Once the cable ties have been tightened as much as
possible by hand in the conventional manner, the machine
screw 62 may then be operated (in this case turned
clockwise) so that its end moves against the top of the
unit 60 and forces the saddle 61 away from the unit 60.
This action serves to drive the electrical connection
spikes through the installation cable 63. As will be
apparent to the skilled person, means other than the
screw 62 may be provided to perform this same function.
Figures 7a and 7b show a further embodiment of the
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present invention which is similar to the embodiment of
Figures 6a and 6b with the exception that the saddle is
omitted. The cable tie locating notches may instead be
formed directly in an upper edge 70 of the unit 71.
Means are provided inside the unit 71 (not shown) for
moving the tips of the electrical connection spikes in a
direction away from the unit 71 so that, in use, the
spikes extend further towards the cable 72. These means
are operable by, in this example, rotation of a rnd head
73 which is located on the top surface of the unit 71.
Naturally other means for operating the spike driving
means will be apparent to the skilled person and may be
used instead.
In use, the unit 71 is placed adjacent the cable 72 and
the cable ties 74 are tightened by hand as previously.
The rod 73 (which may be made of nylon of, for example a
millimetre diameter) is then operated (e. g. turned
clockwise) to drive the contact spikes) out of the base
of the coupler into the cable thereby tensioning the
cable ties and piercing the cable insulation to make
contact with the conductor.
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In either of the embodiments of Figure 6 or Figure 7, or
indeed in any of the embodiments described previously,
the base 68, 78 of the unit 60, 71 may be shaped
differently to that shown in the drawings. In a
5 preferred embodiment, the base 68, 78 may be shaped so as
to conform more closely to the surface shape of the cable
which, in this example, is roughly circular. This
enables the unit 60, 71 to be more easily located against
the cable.
Each of the embodiments of the present invention
described above may be self supporting in that they are
supported only by the cable to which they are clamped.
A further embodiment of the invention includes having one
or more lugs attached to the clamp devices. In this way,
the clamps themselves may be attached to a suitable
surface.
Furthermore, the embodiments described above are also
suitable for coupling communications signals to/from
cables with more than one conducting core. In this way,
a range of, for example differential, phase to phase,
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phase to neutral/earth, phase to earth, neutral to earth
or polyphase modes of high frequency signal coupling may
be provided.
S As will be appreciated, the above embodiments are given
by way of example only and modifications will be apparent
to those skilled in the art.
