Note: Descriptions are shown in the official language in which they were submitted.
CA 02307796 2006-O1-27
CA PATENT
File No. 45081.1
AERIAL CONDUCTOR SUSPENSION CLAMP
FIELD OF THE INVENTION
The present invention relates to a suspension clamp for aerial electric
conductors.
BACKGROUND OF THE INVENTION
Conductor galloping is a phenomenon observed in aerial transmission lines when
high
winds are blowing across the conductors. The conductors oscillate at a low
frequency, typically
0.5 to 1 Hz, and may reach peak to peak amplitudes of 10 feet or more.
Conductor galloping can
damage transmission towers and take down power transmission lines.
Conventional suspension clamps and spacer dampers clamp onto the conductor and
suspend it from tower crossarms in such a manner that both longitudinal
movement and rotation
of the conductor is restricted.
It is believed that conductor galloping may be reduced or eliminated if the
suspension
clamp would allow rotational movement while still preventing longitudinal
movement of the
conductor. Therefore, there is a need in the art for a suspension clamp which
permits rotation of
the conductor within the clamp while restricting longitudinal movement.
In Canadian Patent No. 1,161,913 (U.S. Patent No. 4,381,422) a spacer-damper
is
disclosed which includes a vice enclosing a roller bearing or sleeve bearing
within which the
conductor wire rests. In this apparatus, the conductor wire is not firmly
fixed within the spacer-
damper and a strong longitudinal force may cause the conductor wire to slip
within the device. It
is necessary to introduce a durable grease into the cavity containing the
roller bearing and to
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provide a gasket seal to protect against the penetration of dust, water or the
like. If any portion of
the roller bearing or sleeve enclosing the wire is made of a ferromagnetic
material such as steel,
two additional disadvantages result. First, current in the conducting wire
will produce
considerable heat in the roller bearing races which may cause its premature
failure. Second, the
ingress of water may cause corrosion of the aluminum conductor wire as a
result of its contact
with the steel bearing race.
A similar spacer-damper is disclosed in U.K. Patent No. 1,320,893. In this
patent, the
conductor wire is clamped within a roller bearing by a resilient rubber
member. This spacer also
permits rotation of the conductor wire while resisting longitudinal movement.
Again, a strong
longitudinal force will likely displace the conductor wire within the spacer
because of the
tenuous hold the spacer has on the conductor wire through the resilient rubber
member. Also, the
bearings may overheat and fail as a result of current being conducted through
the conductor wire
and the ingress of dust particles.
It is also a concern with this prior art using roller bearings that the
bearing races must be
constructed in split halves in order to be placed around the wire, which adds
complexity and
expense to the device.
Therefore, there is a need in the art for a suspension clamp which mitigates
the problems
in the prior art.
SUMMARY OF THE INVENTION
The present invention is directed to a suspension clamp for aerial power
transmission conductors. In one aspect of the invention, the invention
comprises a clamp for
suspending an aerial conductor, said clamp comprising:
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(a) a clamshell housing which, when closed, defines an elongate central
cavity, the
clamshell housing further defining an end opening on each side of the central
cavity
wherein said end openings have a smaller diameter than the central cavity and
wherein the conductor may pass through both openings and the central cavity;
(b) two split sleeves each of which fit within the central cavity and each of
which has an
inside diameter slightly greater than or closely matching the outside diameter
of the
conductor wherein said split sleeves abut the ends of the central cavity when
installed
on the conductor; and
(c) a restraining sleeve which, when affixed to the conductor, fits within the
central
cavity, between the split sleeves and which has an outside diameter greater
than the
inside diameter of the split sleeve assemblies and less than the inside
diameter of the
central cavity;
(d) wherein the conductor may be placed within the central cavity such that
the
restraining sleeve is disposed between and restrained by the two split sleeve
assemblies and the conductor passes through the said split sleeves and the end
openings.
The split sleeve assemblies preferably comprise a low-friction material such
as
polytetrafluoroethylene. The restraining sleeve may be a compression repair
sleeve which is
attached to the conductor by implosion or by hydraulic press.
In another aspect of the invention, the invention further comprises a deadend
clamp
comprising:
(a) a deadend housing defining a central bore and having an internal shoulder
defining an opening; and
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(b) a terminal connector having an enlarged end which fits within the deadend
housing and rests against the shoulder and an elongate end which passes
through
the opening;
(c) wherein the enlarged end of the terminal connector bears against and is
retained
by the shoulder but may still rotate within the housing and wherein the
elongate
end of the terminal connector may be attached to a terminal end of the aerial
conductor.
The deadend clamp may preferably further comprise a thrust bearing disposed
between the
enlarged end of the terminal connector. Preferably, the deadend housing
defines a cylindrical
central bore and the enlarged end of the terminal connector is a substantially
flat disk.
In another aspect of the present invention, the invention comprises a kit for
suspending an aerial
conductor, the kit comprising:
(a) a clamp comprising:
(i) a clamshell housing which, when closed, defines an elongate central
cavity, the
clamshell housing further defining an end opening on each side of the central
cavity wherein said end openings have a smaller diameter than the central
cavity
and wherein the conductor may pass through both openings and the central
cavity;
(ii) two split sleeves each of which fit within the central cavity and each of
which has
an inside diameter slightly greater than or closely matching the outside
diameter
of the conductor wherein said split sleeves abut the ends of the central
cavity
when installed on the conductor; and
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(iii) a restraining sleeve which, when affixed to the conductor, fits within
the central
cavity, between the split sleeves and which has an outside diameter greater
than
the inside diameter of the split sleeve assemblies and less than the inside
diameter
of the central cavity;
(iv)wherein the conductor may be placed within the central cavity such that
the
restraining sleeve is disposed between and restrained by the two split sleeve
assemblies and the conductor passes through the said split sleeves and the end
openings; and
(b) a deadend clamp comprising:
(i) a deadend housing defining a central bore and having an internal shoulder
defining an opening; and
(ii) a terminal connector having an enlarged end which fits within the deadend
housing and rests against the shoulder and an elongate end which passes
through
the opening;
(iii) wherein the enlarged end of the terminal connector bears against and is
retained
by the shoulder but may still rotate within the housing and wherein the
elongate
end of the terminal connector may be attached to a terminal end of the aerial
conductor.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of an exemplary embodiment with
reference to the accompanying simplified, diagrammatic, not-to-scale drawings.
In the drawings:
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Figure 1 is a longitudinal cross-section through a suspension clamp of the
present
invention showing the installation of the clamp onto a conductor.
Figure 2 is a transverse cross-section of the clamp of Figure 1.
Figure 3 is a cross-sectional view of a deadend clamp for use with the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
The apparatus (10) according to the Figures comprises a body shell housing
(12), a pair of
split collars (14) and a restraining sleeve (16) which is bonded to the
conductor (18).
In one embodiment, the housing (12) is cylindrical and hollow, having closed
ends (20)
which define conductor openings (22). The housing (12) opens clamshell style
as it is comprised
of two pieces hinged (24) at one side as shown in Figure 2. Once assembled,
the housing (12) is
bolted shut through flanges (12a, 12b). It is preferable that the housing be
made from aluminum.
The collars (14) are split collars which preferably fits loosely around the
conductor (18),
permitting the conductor (18) to rotate within the housing (12) along its
longitudinal axis. If the
collars (14) fits tightly around the conductor (18), the collars (14)
themselves must freely rotate
within the housing (12). The collars are preferably made from or coated with a
low-friction
material such as polytetrafluoroethylene.
The restraining sleeve (16) is tightly bonded to the conductor (18) and has a
length which
is slightly less than the distance between the two collars (14), as is shown
in Figure 1. As is
readily apparent, the restraining sleeve (16) will then abut both collars (14)
and therefore is
restrained from moving longitudinally within the housing (12). As a result,
the conductor (18)
cannot move longitudinally within the housing (12). The restraining sleeve
(16) may rotate
within the housing (12) provided that its outside diameter is less than the
inside diameter of the
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housing (12) and that there is not excessive friction between the restraining
sleeves and one or
both of the collars (14). As referred to above, such friction may be minimized
by making the
collars (14) from a low-friction material or coating the collars with a low-
friction material.
The restraining sleeve (16) may be a compression repair sleeve as is well
known in the
art. Such compression repair sleeves may be press-fit onto the conductor (18)
using a hydraulic
press or by implosion joining. Any structure which clamps onto the conductor
(18) and has
sufficient structural strength to restrict longitudinal movement between the
collars (14) may be
suitable as a restraining sleeve (16) for the present invention. It is
preferable for the outside
diameter of the sleeve (16) to be less than the inside diameter of the housing
(12) to allow for
free rotation within the housing (16). It is preferable for the restraining
sleeve to be made from
aluminum.
The embodiment depicted in the figures and described above may be assembled by
first
bonding the restraining sleeve (16) onto the conductor (18). The
conductor/restraining sleeve
combination may then be placed within the opened housing (12) and fitted into
one-half of each
of the split collars (14). The remaining half of each of the split collars
(14) may then be placed
onto the conductor (18) and the housing (12) closed around the assembly and
bolted shut.
The terminal end (30) of the conductor (18) must also be permitted to rotate.
In one
embodiment of the invention, the terminal end (30) of the conductor is
connected to the deadend
device (32) illustrated in Figure 3. The conductor (18) may have an internally
concentric steel
reinforcing rod (34) which extends beyond the end of the conductor (18)
although not all
conductors have this reinforcement (34). The steel reinforcement (34) is
inserted into the rod end
(36) of a terminal connector (38) which then abuts the end (30) of the
conductor (18). A sleeve
(40) is placed over the joint and is bonded to both the conductor (18) and the
rod end (36) to join
the two together. The sleeve (40) may be an aluminum compression sleeve
similar to that used
in the suspension clamp of the present invention. Its function is to
permanently join the
conductor (18) to the terminal connector (38). It is not necessary to have a
reinforcing rod (34),
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in which case the terminal end (30) of the conductor (18) is still bonded to
the rod end (36) of the
terminal connector by the sleeve (40).
The disk end (42) of the terminal connector (38) is contained within a housing
(44) is
hollow and cylindrical. One end of the housing (44) defines a shoulder (46)
and an opening (48).
The rod (36) of the terminal connector (38) passes through the opening (48)
while the shoulder
(46) retains the disk end (42) within the housing (44). A thrust bearing (SO)
is provided between
the disk end (42) and the shoulder (46) so that the terminal connector (38)
may rotate within the
housing (44) as the conductor (18) rotates. The open end of the housing (44)
may be threaded to
a cap (52) which is attached to the tower (not shown) as is shown in Figure 3.
A conducting terminal pad (60) may be attached to the sleeve (40) and/or to
the rod end
(36) of the terminal connector which connects to a slack jumper loop (62) to
conduct power to
the next conductor (18) as is shown schematically in Figure 3.
As is apparent from the Figures, the conductor (18) may freely rotate because
the terminal
connector (38) may freely rotate in the deadend housing (44). The thrust
bearing (50) permits
such rotation even while the conductor (18) is under longitudinal tension.
As will be apparent to those skilled in the art, various modifications,
adaptations and
variations of the foregoing specific disclosure can be made without departing
from the scope of
the invention claimed herein.
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