U.S. patent application number 10/158810 was filed with the patent office on 2003-05-22 for toneable conduit and method of preparing same.
This patent application is currently assigned to CommScope Properties, LLC. Invention is credited to Bailey, Michael Ray, Bollinger, George, Gemme, Christopher, Kale, Zeb Leonard, Lumley, Scott, Morrow, Jason Norman, Ward, Robert Miller JR..
Application Number | 20030094298 10/158810 |
Document ID | / |
Family ID | 26855405 |
Filed Date | 2003-05-22 |
United States Patent
Application |
20030094298 |
Kind Code |
A1 |
Morrow, Jason Norman ; et
al. |
May 22, 2003 |
Toneable conduit and method of preparing same
Abstract
The present invention is a toneable conduit that can transmit a
signal and that can therefore be readily detected by toning
equipment. In addition, the conduit of the invention can be readily
coupled with other conduit to provide extended lengths of conduit.
The toneable conduit includes an elongate polymeric tube having a
wall with an interior surface, an exterior surface, and a
predetermined wall thickness. A channel preferably extends
longitudinally within the wall of the elongate polymeric tube and a
stabilizing rib extends longitudinally along the interior surface
of the wall of the elongate polymeric tube and is located radially
inward from the channel. A continuous wire is coincident with the
channel in the elongate polymeric tube and is preferably coated
with a coating composition that prevents the wire from adhering to
the polymer melt used to form the elongate polymeric tube. The
present invention further includes methods of making the toneable
conduit and methods of coupling a first toneable conduit with a
second toneable conduit.
Inventors: |
Morrow, Jason Norman;
(Taylorsville, NC) ; Ward, Robert Miller JR.;
(Hickory, NC) ; Kale, Zeb Leonard; (Hiddenite,
NC) ; Bailey, Michael Ray; (Statesville, NC) ;
Gemme, Christopher; (Hickory, NC) ; Bollinger,
George; (Claremont, NC) ; Lumley, Scott;
(Taylorsville, NC) |
Correspondence
Address: |
ALSTON & BIRD LLP
BANK OF AMERICA PLAZA
101 SOUTH TRYON STREET, SUITE 4000
CHARLOTTE
NC
28280-4000
US
|
Assignee: |
CommScope Properties, LLC
|
Family ID: |
26855405 |
Appl. No.: |
10/158810 |
Filed: |
May 30, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10158810 |
May 30, 2002 |
|
|
|
09989289 |
Nov 20, 2001 |
|
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Current U.S.
Class: |
174/505 |
Current CPC
Class: |
B29K 2995/0005 20130101;
B29K 2027/18 20130101; H02G 3/0481 20130101; G02B 6/4459 20130101;
G02B 6/447 20130101; B29K 2023/12 20130101; H02G 3/06 20130101;
B29C 48/022 20190201; B29C 48/15 20190201; H02G 9/06 20130101; B29C
48/06 20190201; B29K 2075/00 20130101; H02G 2200/20 20130101; B29K
2077/00 20130101; B29K 2027/06 20130101; B29C 48/09 20190201; F16L
25/01 20130101; G02B 6/4495 20130101; B29K 2069/00 20130101; B29K
2705/00 20130101; B29C 48/154 20190201; B29K 2067/00 20130101; B29K
2023/06 20130101; F16L 1/11 20130101; B29C 48/34 20190201; B29K
2023/065 20130101; H02G 9/065 20130101; H02G 1/08 20130101; Y10T
428/139 20150115; F16L 11/127 20130101; F16L 9/125 20130101 |
Class at
Publication: |
174/48 |
International
Class: |
H02G 003/04 |
Claims
That which is claimed:
1. A toneable conduit, comprising: an elongate polymeric tube
having a wall with an interior surface, an exterior surface, and a
predetermined wall thickness; and a first channel extending
longitudinally within the wall of the elongate polymeric tube; and
a continuous wire coincident with the first channel in the elongate
polymeric tube, said wire being coated with a coating composition
that prevents the wire from adhering to the polymer melt used to
form the polymeric tube; said continuous wire capable of
transmitting a toning signal to allow the conduit to be detected by
toning equipment and capable of being torn out of the polymeric
tube and remaining continuous to allow the conduit and wire to be
coupled.
2. The toneable conduit according to claim 1, further comprising a
first stabilizing rib extending longitudinally along the interior
surface of the wall of the elongate polymeric tube and located
radially inward from said channel.
3. The toneable conduit according to claim 2, further comprising at
least one additional rib extending longitudinally along the
interior surface of the elongate polymeric tube to facilitate the
installation of cable within the conduit.
4. The toneable conduit according to claim 1, wherein the coating
composition is formed of a polymeric material selected from the
group consisting of fluoropolymers, polyamides, polyesters,
polycarbonates, polypropylene, polyurethanes, polyacetals,
polyacrylics, epoxies and silicone polymers.
5. The toneable conduit according to claim 4, wherein the coating
composition is formed of a polymeric material that has a melting
temperature of at least about 500.degree. F.
6. The toneable conduit according to claim 5, wherein the coating
composition is formed of polytetrafluoroethylene.
7. The toneable conduit according to claim 1, wherein the
continuous wire has a tensile strength of at least about 150
lbs.
8. The toneable conduit according to claim 7, wherein the
continuous wire is selected from the group consisting of
copper-clad steel wire, copper-clad aluminum wire, copper wire, and
tin copper wire.
9. The toneable conduit according to claim 7, wherein the
continuous wire is copper-clad steel wire.
10. The toneable conduit according to claim 7, wherein the
continuous wire has a diameter of from about 0.32 mm to about 2.59
mm.
11. The toneable conduit according to claim 1, wherein the exterior
surface of the tube is smooth.
12. The toneable conduit according to claim 1, further comprising a
second channel extending longitudinally within the wall of the
elongate polymeric tube and a conductor selected from the group
consisting of a continuous wire and a twisted pair of continuous
wires coincident with the second channel in the elongate polymeric
tube.
13. The toneable conduit according to claim 12, further comprising:
a first stabilizing rib extending longitudinally along the interior
surface of the wall of the elongate polymeric tube and located
radially inward from said first channel; and a second stabilizing
rib extending longitudinally along the interior surface of the wall
of the elongate polymeric tube and located radially inward from the
second channel.
14. A toneable conduit, comprising: an elongate polymeric tube
formed of high density polyethylene having a wall with an interior
surface, an exterior surface, and a predetermined wall thickness; a
channel extending longitudinally within the wall of the elongate
polymeric tube; and a stabilizing rib extending longitudinally
along the interior surface of the wall of the elongate polymeric
tube and located radially inward from said channel; and a
continuous, copper-clad steel wire coincident with the channel in
the elongate polymeric tube, said copper-clad steel wire coated
with polytetrafluoroethylene to prevent the wire from adhering to
the polymer melt used to form the polymeric tube; said copper-clad
steel wire capable of transmitting a toning signal over long
distances to allow the conduit to be detected by toning equipment
and capable of being torn out of the polymeric tube and remaining
continuous to allow the conduit and wire to be coupled.
15. A method of making toneable conduit, comprising the steps of:
advancing a continuous wire; and extruding a polymer melt around
the advancing wire in the form of an elongate polymeric tube having
a wall of a predetermined thickness, an interior surface, an
exterior surface, and a stabilizing rib extending longitudinally
along the interior surface of the wall of the elongate polymeric
tube such that the wire is embedded in the wall of the elongate
polymeric tube and the stabilizing rib is located radially inward
from the wire; wherein the continuous wire is coated with a coating
composition that prevents the wire from adhering to the polymer
melt used in said extruding step.
16. The method according to claim 15, wherein said advancing step
comprises advancing a continuous wire coated with a coating
composition formed of a polymeric material selected from the group
consisting of fluoropolymers, polyamides, polyesters,
polycarbonates, polypropylene, polyurethanes, polyacetals,
polyacrylics, epoxies and silicone polymers.
17. The method according to claim 16, wherein said advancing step
comprises advancing a continuous wire coated with a coating
composition formed of a polymeric material that has a melting
temperature of at least about 500.degree. F.
18. The method according to claim 17, wherein said advancing step
comprises advancing a continuous wire coated with a coating
composition formed of polytetrafluoroethylene.
19. The method according to claim 15, wherein said extruding step
comprises forming the polymer melt into the form of an elongate
polymeric tube through the use of a die and a tip, wherein a groove
in said tip forms the stabilizing rib in the conduit.
20. The method according to claim 15, wherein said advancing step
comprises advancing the wire through a wire guide tube into the
polymer melt.
21. The method according to claim 15, wherein said extruding step
further comprises forming additional ribs extending longitudinally
along the interior surface of the elongate polymeric tube to
facilitate the installation of cable into the conduit.
22. The method according to claim 15, wherein said advancing step
comprises advancing a continuous wire having a tensile strength of
at least about 150 lbs.
23. The method according to claim 22, wherein said advancing step
comprises advancing a continuous wire selected from the group
consisting of copper-clad steel wire, copper-clad aluminum wire,
copper wire, and tin copper wire.
24. The method according to claim 22, wherein said advancing step
comprises advancing a copper-clad steel wire.
25. The method according to claim 22, wherein said advancing step
comprises advancing a continuous wire having a diameter of from
about 0.32 mm to about 2.59 mm.
26. The method according to claim 15, wherein said extruding step
comprises extruding a polymer melt in the form of an elongate
polymeric tube having a smooth exterior surface.
27. The method according to claim 15, further comprising the step
of: advancing a conductor selected from the group consisting of a
continuous wire and a twisted pair of continuous wires; wherein
said extruding step comprises extruding a polymer melt around the
advancing wire and the advancing conductor in the form of an
elongate polymeric tube having a wall of a predetermined thickness,
an interior surface, an exterior surface, and a stabilizing rib
extending longitudinally along the interior surface of the wall of
the elongate polymeric tube such that the wire and the conductor
are embedded in the wall of the elongate polymeric tube and the
stabilizing rib is located radially inward from the wire.
28. A method of coupling a first toneable conduit with a second
toneable conduit, comprising the steps of: providing a first
toneable conduit comprising an elongate polymeric tube having a
wall with an interior surface, an exterior surface, and a
predetermined wall thickness; and a channel extending
longitudinally within the wall of the elongate polymeric tube; and
a continuous wire coincident with the channel in the elongate
polymeric tube and coated with a coating composition that prevents
the wire from adhering to the polymer melt used to form the
polymeric tube; providing a second toneable conduit comprising an
elongate polymeric tube having a wall with an interior surface, an
exterior surface, and a predetermined wall thickness; and a channel
extending longitudinally within the wall of the elongate polymeric
tube; and a continuous wire coincident with the channel in the
elongate polymeric tube and coated with a coating composition that
prevents the wire from adhering to the polymer melt used to form
the polymeric tube; tearing the wire of the first toneable conduit
through the exterior surface of the first toneable conduit; tearing
the wire of the second toneable conduit through the exterior
surface of the second toneable conduit; mechanically connecting the
first conduit and second conduit; and electrically connecting the
wire from the first toneable conduit and the wire from the first
toneable conduit.
29. The method according to claim 28, said providing steps
comprising providing a first toneable conduit and a second toneable
conduit each further comprising a stabilizing rib extending
longitudinally along the interior surface of the wall of the
elongate polymeric tube and located radially inward from said
channel.
30. The method according to claim 28, said providing steps comprise
providing a first toneable conduit and a second toneable conduit
wherein the wire in the first toneable conduit and in the second
toneable conduit is coated with a coating composition that
comprises polytetrafluoroethylene.
31. The method according to claim 28, said providing steps
comprising providing a first toneable conduit and a second toneable
conduit wherein the wire in the first toneable conduit and in the
second toneable conduit has a tensile strength of at least about
150 lbs.
32. The method according to claim 31, said providing steps
comprising providing a first toneable conduit and a second toneable
conduit wherein the wire in the first toneable conduit and in the
second toneable conduit is a copper-clad steel wire.
33. The method according to claim 28, wherein: said first providing
step comprises providing a first toneable conduit comprising an
elongate polymeric tube having a wall with an interior surface, an
exterior surface, and a predetermined wall thickness; a first
channel and a second channel extending longitudinally within the
wall of the elongate polymeric tube; and a stabilizing rib
extending longitudinally along the interior surface of the wall of
the elongate polymeric tube and located radially inward from the
first channel; a continuous wire coincident with the first channel
in the elongate polymeric tube and coated with a coating
composition that prevents the wire from adhering to the polymer
melt used to form the polymeric tube; and a conductor selected from
the group consisting of a continuous wire and a twisted pair of
continuous wires coincident with the second channel in the elongate
polymeric tube; said second providing step comprises providing a
second toneable conduit comprising an elongate polymeric tube
having a wall with an interior surface, an exterior surface, and a
predetermined wall thickness; a first channel and a second channel
extending longitudinally within the wall of the elongate polymeric
tube; and a stabilizing rib extending longitudinally along the
interior surface of the wall of the elongate polymeric tube and
located radially inward from the first channel; a continuous wire
coincident with the first channel in the elongate polymeric tube
and coated with a coating composition that prevents the wire from
adhering to the polymer melt used to form the polymeric tube; and a
conductor selected from the group consisting of a continuous wire
and a twisted pair of continuous wires coincident with the second
channel in the elongate polymeric tube; said first tearing step
comprises tearing the wire and the conductor of the first toneable
conduit through the exterior surface of the first toneable conduit;
said second tearing step comprises tearing the wire and the conduit
of the second toneable conduit through the exterior surface of the
second toneable conduit; and said electrically connecting step
comprises electrically connecting the wire from the first toneable
conduit with the wire from the second toneable conduit and
electrically connecting the conductor from the first toneable
conduit with the conductor from the second toneable conduit.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of copending U.S.
patent application Ser. No. 09/989,289, filed Nov. 20, 2001.
FIELD OF THE INVENTION
[0002] The present invention relates to toneable conduit and more
particularly to toneable conduit that can be detected by
conventional toning equipment and that includes a wire that is
capable of being torn out of the conduit to allow the conduit and
wire to be coupled.
BACKGROUND OF THE INVENTION
[0003] Conduit is often buried to provide an underground path for
cables such as coaxial cables and fiber optic cables. In
particular, conduit is typically formed of a plastic material that
protects the coaxial cables and fiber optic cables from the
moisture and other hazards of the underground environment. The
cable is typically installed in the conduit by pulling the cable
through the conduit although the cable can be provided in the
conduit when it is installed underground.
[0004] One issue with conduit is that it can be difficult to locate
underground when it is either empty or it contains a non-metallic
cable, such as a fiber optic cable. As a result, conduit has often
been outfitted with a metallic or magnetic strip or wire that
allows the conduit to be detected by metal detecting equipment on
the ground surface. Although these types of detection devices are
useful, they cannot always locate conduit that is buried deep
underground (e.g. greater than 5 feet). As an alternative to these
types of detection devices, toning equipment is commonly used that
operates by transmitting a signal along a metallic wire or strip
associated with the conduit and detecting the signal from the
ground surface.
[0005] One conventional conduit construction that can be detected
by conventional metal detection devices and even the toning devices
discussed above includes an exterior rib that houses the metallic
ribbon or wire. For example, Japanese published application JP
5-106765 describes an embodiment that includes an exterior rib
including a conductive wire. Although these types of constructions
have found use, it is difficult to couple this conduit with another
conduit because the exterior rib prevents the connector from
fitting flush onto the conduit. As a result, moisture can enter the
conduit at the connection and can cause damage to the cable
installed therein. In addition, the exterior rib can cause problems
during installation in that the exterior rib and associated wire
can be ripped off of the conduit if the conduit is being installed
by directional boring or plowing methods.
[0006] Another conduit construction that is designed to be detected
by metal detection devices includes a metallic ribbon or wire that
is provided at intermittent lengths. For example, U.S. Pat. No.
6,092,558 describes such an embodiment wherein discrete lengths of
a magnetic strip are spaced apart longitudinally along the conduit.
U.S. Pat. No. 5,045,368 also describes a similar construction
having markers at intervals along the length of the conduit.
Although this type of conduit can be detected by the metal
detection devices discussed above, it cannot be detected by
conventional toning equipment because a signal cannot be
transmitted along the conduit.
[0007] Alternatively, some conduit constructions use continuous
lengths of strip or ribbon formed of metal or a magnetic material
to allow the conduit to be detected by metal detecting equipment.
For example, U.S. Pat. Nos. 5,051,034 and RE 34,701 describe this
type of construction and use a ribbon of magnetic material to allow
the conduit to be detected at three to five feet underground. U.S.
Pat. Nos. 5,006,086, 5,017,873 and 5,114,517 use a magnetic ribbon
that is spirally wound around the exterior surface of the conduit.
Although the strip or ribbon in these constructions can be detected
by conventional metal detecting equipment, it does not have a
suitable construction for transmitting a toning signal for extended
distances and at the depths desired in the art.
[0008] As demonstrated above, there is a need in the art to provide
a conduit that can be detected by toning equipment for extended
distances and at the depths desired in the art. In addition, there
is a need in the art to provide conduit that can be coupled to
provide extended lengths of underground conduit that can be
detected by toning equipment.
SUMMARY OF THE INVENTION
[0009] The present invention provides a conduit that can transmit a
signal over great distances and that can therefore be readily
detected by toning equipment. In addition, the conduit of the
invention can be readily coupled to provide extended lengths of
conduit. In particular, the present invention uses a continuous
wire to provide the toning signal that is capable of being torn out
through the conduit to allow the conduit to be coupled over
extended lengths by forming an electrical connection between the
wire of adjacent segments of conduit. In addition, the connectors
used for the conduit can be connected flush against the exterior
surface of the conduit to prevent the leakage of moisture into the
conduit and thus prevent damage to the cable within the conduit.
The conduit of the invention also has excellent crush strength as
is desired in the art. The conductive wire also includes a coating
that allows the conductive wire to be protected in the underground
environment and that facilitates the continuous production of the
conduit of the invention.
[0010] The above advantages are achieved through the use of a
toneable conduit that includes an elongate polymeric tube having a
wall with an interior surface, an exterior surface, and a
predetermined wall thickness. A channel extends longitudinally
within the wall of the elongate polymeric tube and a stabilizing
rib preferably extends longitudinally along the interior surface of
the wall of the elongate polymeric tube and is located radially
inward from the channel. A continuous wire is coincident with the
channel in the elongate polymeric tube and is preferably coated
with a coating composition that prevents the wire from adhering to
the polymer melt used to form the elongate polymeric tube.
Preferably, the wire has a tensile strength of at least about 150
lbs. and is preferably a copper-clad steel wire, copper-clad
aluminum wire, copper wire or tin copper wire. More preferably, the
wire is copper-clad steel wire. The wire also preferably has a
diameter from about 0.32 mm to about 2.59 mm. More preferably, the
wire has a diameter of 1.02 mm. In accordance with the invention,
the wire is capable of transmitting a toning signal to allow the
conduit to be detected by toning equipment and is capable of being
torn out of the polymeric tube to allow the conduit to be coupled.
The wire is preferably coated with a coating composition that is
formed of a high melting temperature polymeric material, preferably
having a melting temperature of at least about 500.degree. F.
Preferably, the high melting temperature polymeric material is
selected from the group consisting of fluoropolymers, polyamides,
polyesters, polycarbonates, polypropylene, polyurethanes,
polyacetals, polyacrylics, epoxies and silicone polymers and is
more preferably polytetrafluoroethylene. Preferably, the conduit is
formed of polyethylene or polyvinyl chloride and more preferably
high-density polyethylene (HDPE). The conduit also preferably has a
smooth exterior surface and can further include at least one
additional rib (in addition to the stabilizing rib) extending
longitudinally along the interior surface of the elongate polymeric
tube to facilitate the installation of cable within the
conduit.
[0011] According to an alternative embodiment of the invention, the
toneable conduit can further include a second channel that extends
longitudinally within the wall of the elongate polymeric tube. A
conductor can be provided coincident with the second channel such
as a continuous wire like the one discussed above or a twisted pair
of continuous wires to provide a return path for signals that can
be used to monitor the status of the cable. A second stabilizing
rib can also extend longitudinally along the interior surface of
the wall of the elongate polymeric tube and can be located radially
inward from the second channel.
[0012] The present invention further includes a method of making
toneable conduit, comprising the steps of advancing a continuous
wire and extruding a polymer melt around the advancing wire in the
form of an elongate polymeric tube having a wall of a predetermined
thickness, an interior surface, an exterior surface, and a
stabilizing rib extending longitudinally along the interior surface
of the wall of the elongate polymeric tube such that the wire is
embedded in the wall of the elongate polymeric tube and the
stabilizing rib is located radially inward from the wire. In
accordance with the invention, the advancing step comprises
advancing a wire coated with a coating composition that prevents
the wire from adhering to the polymer melt used in said extruding
step. Preferably, the polymer melt extruded into the form of an
elongate polymeric tube through the use of a die and a tip, wherein
a groove in said tip forms the stabilizing rib on the interior
surface of the conduit. A wire is preferably advanced through a
wire guide tube into the polymer melt. A conductor such as an
additional continuous wire or a twisted pair of continuous wires
can also be advanced into the polymer melt and the polymer melt
extruded around the advancing wire and the advancing conductor. The
method of the invention can also include forming additional ribs
extending longitudinally along the interior surface of the elongate
polymeric tube in the extruding step to facilitate the installation
of cable into the conduit. The wire that is advanced into the
polymer melt preferably has a tensile strength of at least about
150 lbs. In particular, the wire is preferably a copper-clad steel
wire, copper-clad aluminum wire, copper wire or tin copper wire and
is more preferably copper-clad steel wire, and preferably has a
diameter of from about 0.32 mm to about 2.59 mm. The wire is also
preferably coated with a coating composition formed of a polymeric
material selected from the group consisting of fluoropolymers,
polyamides, polyesters, polycarbonates, polypropylene,
polyurethanes, polyacetals, polyacrylics, epoxies and silicone
polymers. Preferably, the polymeric material has a melting
temperature of at least about 500.degree. F., and is more
preferably polytetrafluoroethylene. The polymer melt is preferably
extruded in the form of an elongate polymeric tube having a smooth
exterior surface.
[0013] The present invention also includes a method of coupling a
first toneable conduit with a second toneable conduit, comprising
the steps of providing a first toneable conduit as discussed above
and providing a second toneable conduit as discussed above, tearing
the wire of the first toneable conduit through the exterior surface
of the first toneable conduit, tearing the wire of the second
toneable conduit through the exterior surface of the second
toneable conduit, mechanically connecting the first and second
toneable conduits, and electrically connecting the wire from the
first toneable conduit and the wire from the second toneable
conduit. In addition, the first and second toneable conduits can
include a second channel and a conductor such as a second
continuous wire or a twisted pair of continuous wires coincident
with the second channel and the conductors in the first and second
toneable conduits can also be torn through the exterior surface of
the toneable conduits and electrically connected with one
another.
[0014] These and other features and advantages of the present
invention will become more readily apparent to those skilled in the
art upon consideration of the following detailed description and
accompanying drawings, which describe both the preferred and
alternative embodiments of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a cross-sectional view of a toneable conduit
according to the present invention.
[0016] FIG. 2 is a side view of the toneable conduit illustrated in
FIG. 1 according to the present invention.
[0017] FIG. 3 is a cross-sectional view of a toneable conduit
according to an alternative embodiment of the present invention
further including an additional continuous, high tensile strength
wire.
[0018] FIG. 4 is a cross-sectional view of a toneable conduit
according to an alternative embodiment of the present invention
further including a twisted pair of wires.
[0019] FIG. 5 schematically illustrates a method of making toneable
conduit corresponding to a preferred embodiment of the
invention.
[0020] FIG. 6 is a cross-sectional view along line 4-4 of FIG. 3
illustrating the interior of the crosshead used to form the conduit
according to the preferred embodiment of the invention.
[0021] FIG. 7 is a side view of the toneable conduit according to
the present invention wherein the wire has been torn through the
exterior surface of the conduit.
[0022] FIG. 8 is a side view of two adjacent coupled sections of
conduit in accordance with the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] In the drawings and the following detailed description,
preferred embodiments are described in detail to enable practice of
the invention. Although the invention is described with reference
to these specific preferred embodiments, it will be understood that
the invention is not limited to these preferred embodiments. But to
the contrary, the invention includes numerous alternatives,
modifications and equivalents as will become apparent from
consideration of the following detailed description and
accompanying drawings. In the drawings, like numbers refer to like
elements throughout.
[0024] FIGS. 1 and 2 illustrate a toneable conduit according to the
present invention. As shown in these figures, the conduit is formed
of an elongate polymeric tube 10 that includes a wall 12 having a
predetermined thickness 14 and further includes an interior surface
16 and an exterior surface 18. The exterior surface 18 is
preferably smooth so that the conduit can be effectively coupled as
discussed in more detail below. The conduit can be formed of any
suitable polymeric (i.e. plastic) material and suitable polymeric
materials for conduit are known in the art such as polyethylene or
polyvinyl chloride. Preferably, the elongate polymeric tube 10 is
formed of high density polyethylene (HDPE). The polymeric material
can also be blended with certain additives, e.g., for UV
protection. The wall 12 of the elongate polymeric tube 10 typically
has a predetermined thickness 14 of from about 0.05 inches to about
0.75 inches. Moreover, the elongate polymer tube 10 typically has a
nominal inside diameter of from about 0.5 inches to about 6.5
inches.
[0025] The toneable conduit preferably includes a stabilizing rib
20 that extends longitudinally along the interior surface 16 of the
elongate polymeric tube 10. As shown in FIGS. 1 and 2, the
stabilizing rib 20 is integral with the elongate polymeric tube 10
and formed of the same material as the elongate polymeric tube. The
stabilizing rib 20 maintains the wall thickness 14 of the conduit
when the wire is torn out of the conduit as discussed in more
detail below such that it can withstand the forces typically
associated with installation, use and transport of the conduit.
Typically, the stabilizing rib 20 extends from the interior surface
16 of the elongate polymeric tube 10 such that the distance 22 from
the wire to the interior edge 23 of the stabilizing rib is at least
equal to the wall thickness 14. The stabilizing rib 20 is also
located radially inward from the wire used in the invention. The
stabilizing rib 20 illustrated in FIGS. 1 and 2 has a generally
semicylindrical shape (i.e. an arcuate cross-section) but can have
a rectangular or trapezoidal shape, for example, so long as it
provides the desired amount of strength and stability to the
conduit wall 12. In addition to the stabilizing rib 20, the conduit
can include additional ribs (not shown) extending longitudinally
along the interior surface 16 of the elongate polymeric tube 10 and
integral with the elongate polymeric tube to facilitate the
installation of cable in the conduit by decreasing the surface area
in contact between the interior surface of the elongate polymeric
tube and the cable.
[0026] As shown in FIGS. 1 and 2, the toneable conduit includes a
wire 24 that extends longitudinally along the length of the
elongate polymeric tube 10 and is coincident with a channel the
extends longitudinally within the wall 12 of the elongate polymeric
tube 10. The wire 24 runs continuously along the length of the
elongate polymeric tube 10 and is embedded within the wall 12 of
the elongate polymeric tube. In particular, the wire 24 is
typically provided completely within the wall 12 of the elongate
polymeric tube 10. Preferably, the wire 24 extends parallel to a
central longitudinal axis A of the elongate polymeric tube 10.
[0027] The wire 24 possesses sufficient tensile strength and
elongation to allow the wire to be torn out through the exterior
surface 18 of the elongate polymeric tube 10 (e.g., by using a pair
of pliers). The wire 24 used in the invention preferably has a
tensile strength of at least about 150 lbs. as measured according
to ASTM method B869. In addition, the wire 24 preferably has an
elongation of at least about 1% as measured according to ASTM
methods B3 and B869. The wire 24 is preferably a copper-clad steel
wire, copper-clad aluminum wire, copper wire or tin copper
(tin-clad copper) wire. More preferably, the wire 24 is a
copper-clad steel wire. The wire 24 preferably has a diameter of
from 0.32 mm (28 gauge) to 2.59 mm (10 gauge), and more preferably
is a copper-clad steel wire having a diameter of 1.02 mm (18
gauge).
[0028] As mentioned above, the wire 24 runs continuously along the
length of the elongate polymeric tube 10 and thus it can transmit a
toning signal along the length of the conduit to allow the
underground conduit to be detected from the surface by toning
equipment. Moreover, because of the "skin effect" associated with
signal transmission as understood by those skilled in the art, the
signal is transmitted along the outer surface 26 of wire 24 and
thus takes advantage of the conductivity of the copper portion
present in the preferred wires used with the invention. As a
result, the wire 24 of the conduit can transmit signals over long
distances as desired in the art (e.g. at least 5 miles). It has
been discovered that a larger diameter wire 24 (e.g. 18 gauge)
transmits a toning signal over longer distances than a smaller
diameter wire. Moreover, a larger diameter wire 24 is stronger than
a smaller diameter wire and thus can more effectively be torn out
of the conduit when it is coupled with other conduit.
[0029] The wire 24 is coated with a layer 30 of a coating
composition. The coating composition layer 30 typically has a
thickness of from about 1 to about 15 mils, and is more preferably
about 8 mils. The coating composition layer 30 is formed of a
material that prevents the wire 24 from adhering to the polymer
melt used to form the elongate polymeric tube 10. Accordingly, the
coating composition layer 30 is typically formed of a polymeric
material that has a melting temperature above the temperature of
the polymeric melt so that is does not melt during the formation of
the elongate polymeric tube 10. Preferably, the coating composition
layer 30 is formed of fluoropolymers (e.g. polytetrafluoroethylene
(PTFE), fluorinated ethylene-propylene (FEP),
ethylenetrifluoroethylene (ETFE), and
ethylenechlorotrifluoroethylene (ECTFE), polyvinyl fluoride (PVF)
and polyvinylidene fluoride (PVDF)); polyamides (e.g. nylon);
polyesters (e.g. polyethylene terephthalate (PET)); polycarbonates;
polypropylene; polyurethanes; polyacetals; polyacrylics; epoxies;
silicone polymers; and mixtures thereof. The high melting
temperature polymeric materials used in the coating preferably has
a melting temperature of at least about 500.degree. F. More
preferably, the coating composition layer 30 is formed of a
fluoropolymer and is more preferably polytetrafluoroethylene
(TEFLON.RTM.). Advantageously, because the wire 24 is coated with
polytetrafluoroethylene, it also protects the wire 24 from the
underground environment when it is torn out of the conduit and
electrically connected to the wire from an adjacent conduit as
discussed in more detail below. In particular, the coating
composition layer 30 preferably provides corrosion resistance to
the wire 24.
[0030] Although not illustrated in FIGS. 1 and 2, the conduit of
the invention can include one or more cables such as coaxial
cables, fiber optic cables, twisted pair cables, electrical cables,
support or messenger cables, and the like. The advantages of the
invention are particularly evident when toning equipment is used to
locate empty conduit (not including any cable) or conduit
containing non-metallic cable such as fiber optic cable as metallic
cable can be detected underground without the need to use the
conduit of the invention. Nevertheless, the conduit of the
invention can be used to house metallic cable such as coaxial
cable.
[0031] FIGS. 3 and 4 illustrate toneable conduits according to
alternative embodiments of the invention. As shown in FIGS. 3 and
4, the toneable conduit can further include a conductor such as a
second continuous wire 32 (FIG. 3) or a twisted pair of continuous
wires 34 (FIG. 4) that extends longitudinally along the length of
the elongate polymeric tube 10. The conductor is coincident with a
channel that extends longitudinally within the wall 12 of the
elongate polymeric tube 10 and that is typically different than the
channel that is coincident with the wire 24. The conductor runs
continuously along the length of the elongate polymeric tube 10 and
is embedded within the wall 12 of the elongate polymeric tube. In
particular, the conductor is typically provided completely within
the wall 12 of the elongate polymeric tube 10. Preferably, the
conductor extends parallel to a central longitudinal axis A of the
elongate polymeric tube 10. As shown in FIGS. 3 and 4, the toneable
conduit can also include a stabilizing rib 33 that is located
radially inward from the conductor used in the invention in the
same manner as the stabilizing rib 20.
[0032] Like the wire 24, the wire 32 illustrated in FIG. 3
possesses sufficient tensile strength and elongation to allow the
wire to be torn out through the exterior surface 18 of the elongate
polymeric tube 10. The wire 32 preferably has a tensile strength of
at least about 150 lbs. as measured according to ASTM method B869.
In addition, the wire 32 preferably has an elongation of at least
about 1% as measured according to ASTM methods B3 and B869. The
wire 32 is preferably a copper-clad steel wire, copper-clad
aluminum wire, copper wire or tin copper (tin-clad copper) wire.
More preferably, the wire 32 is a copper-clad steel wire. The wire
32 preferably has a diameter of from 0.32 mm (28 gauge) to 2.59 mm
(10 gauge), and more preferably is a copper-clad steel wire having
a diameter of 1.02 mm (18 gauge). The wire 32 is also preferably
coated with a layer of a coating composition 35 like the coating
composition described above with respect to the wire 24.
[0033] Each of the wires 36 and 37 in the twisted pair of
continuous wires 34 illustrated in FIG. 4 preferably has sufficient
tensile strength and elongation to allow the twisted pair of wires
to be torn out through the exterior surface 18 of the elongate
polymeric tube 10. For example, the continuous wires 36 and 37 used
in the twisted pair of continuous wires 34 can be formed of the
wire described above with respect to the wire 24. In addition, the
wires 36 and 37 are also preferably coated with a layer of a
coating composition 38 and 39 like the coating composition
described above with respect to the wire 24.
[0034] As mentioned above, the wire 32 and the twisted pair of
wires 34 run continuously along the length of the elongate
polymeric tube 10. Thus, the wire 32 and the twisted pair of wires
34 can provide a return path for signals that can be used to
monitor the status of the cable. For example, the wire 32 and the
twisted pair of wires 34 can be used with time-domain reflectometer
(TDR) devices to determine if there are damage points along the
length of the conduit. As is well understood to those skilled in
the art, TDR devices are meters with an oscilloscope-type display
that send out a pulse along a line of cable and that measures any
inconsistencies in the cable. The pulse is reflected back to
accurately determine where a break or other problem is in the
cable. The TDR devices greatly reduce the time that would otherwise
be needed to physically locate problems in the cable.
[0035] FIG. 5 illustrates the preferred method embodiment for
producing the toneable conduit of the invention. As shown in FIG.
5, the wire 24 is taken from a supply reel 40 and is fed through a
wire guide 42. The wire 24 then passes through a lubrication
apparatus 44 that lubricates the wire for further downstream
processing. The lubricated wire 24 then advances into a crosshead
46, which communicates with an extruder apparatus 48 via a flow
channel (not shown). Although not illustrated in FIG. 5, a second
wire 32 or a twisted pair of wires 34 can also be taken from a
supply reel (not shown), fed through a wire guide, lubricated and
advanced into the crosshead 46 in the manner described herein with
respect to the wire 24 to produce the toneable conduits illustrated
in FIGS. 3 and 4.
[0036] The polymeric materials and any additives such as colorants
that are used to form the elongate polymeric tube 10 (and
stabilizing rib 20) are fed to the extruder apparatus 48, e.g.,
through a hopper (not shown). In the preferred embodiment of the
invention, the polymeric materials include HDPE as discussed above.
The extruder apparatus 48 operates at an elevated temperature above
the melting temperature of the polymeric materials used to form the
elongate polymeric tube 10 to provide a polymer melt. For example,
in the preferred embodiment of the invention wherein the conduit is
formed of HDPE, the extruder apparatus 48 is operated at a
temperature of from about 300.degree. F. to about 500.degree.
F.
[0037] FIG. 6 illustrates the formation of the conduit of the
invention in more detail. A wire guide tube 50 delivers the wire 24
to an annular gap 52 between a tip 54 and a die 56 of the crosshead
46 while the extruder apparatus 48 delivers the polymer melt to the
annular gap through a flow channel (not shown). The tip 54 and the
die 56 form the annular gap 52 and shape the polymer melt into a
tubular configuration to form the elongate polymeric tube 10. In
particular, the tip 54 provides the shape of the interior surface
16 of the elongate polymeric tube 10 while the die 56 provides the
shape of the exterior surface 18 of the elongate polymeric tube. A
groove 60 provided in the tip 54 forms the stabilizing rib 20 in
the conduit. Although not shown, additional grooves can be provided
in the tip 54 to provide additional ribs along the interior surface
16 of the elongate polymeric tube 10 to facilitate the installation
of cable in the conduit. The polymer melt forms around the wire 24
and the wire becomes embedded in the wall 12 of the elongate
polymeric tube 10. The coating composition layer 30 on the wire 24
and the lubricant applied to the wire advantageously prevent the
wire 24 from sticking to the polymer melt and facilitate the
formation of the conduit of the invention.
[0038] Referring again to FIG. 5, the conduit leaves the crosshead
46 and advances to a cooling trough 62 that utilizes water to cool
the conduit to allow it to harden. The conduit is then advanced to
a take-up reel 64. The conduit can be stored or shipped on the
take-up reel 64 and can readily be installed by unwinding the
conduit from the take-up reel.
[0039] As mentioned above, the conduit of the invention can be
readily coupled with other conduit. In particular, as shown in FIG.
7, the wire 24 can be torn out through the exterior surface 18 of
the elongate polymeric tube 10 by applying a force on the wire
perpendicular to the axis A in a direction 62. As discussed above,
the preferred wire 24 used in accordance with the invention has
sufficient tensile strength and elongation to tear through the HDPE
conduit. Once the wire 24 is torn out through the conduit, the
conduit can be coupled with an adjacent conduit.
[0040] As shown in FIG. 8, a first conduit 70 is coupled with a
second conduit 72. A conduit connector 74 is fitted onto the first
conduit 70 and the second conduit 72 to provide a connection
between adjacent segments of conduit. A wire 76 torn out of the
first conduit 70 and a wire 78 torn out of the second conduit 72
are electrically connected or coupled together through the use of a
suitable device such as the electrical connector 80. If the first
conduit 70 and the second conduit 72 include a wire 32 or a twisted
pair of wires 34 as illustrated in FIGS. 3 and 4, the wire or
twisted pair of wires can also be torn through the conduits and
electrically connected in the manner described with respect to the
wires 76 and 78. In accordance with the invention, because the
conduit of the invention has a smooth exterior surface, the conduit
connector 74 fits flush to the exterior surfaces of the first
conduit 70 and second conduit 72. As is understood in the art, the
first conduit 70, second conduit 72, conduit connector 74, wire 76,
wire 78 and electrical connector 80 can optionally be wrapped by a
shrink wrap film that is heated to allow it to shrink around the
conduit to prevent the ingress of moisture into the conduit along
the conduit connector 74.
[0041] The conduit of the invention can advantageously be detected
with conventional toning equipment used in the art. In particular,
when the conduit of the invention is buried underground, even if it
is empty or contains a non-metallic cable, it can be detected by
toning equipment by transmitting a signal along the wire 24 and
detecting the signal from the ground surface. As a result, the
conduit of the invention can be detected at levels at deep as 10
feet underground or even at greater depths through the use of
toning equipment. Moreover, the conduit of the invention can also
be detected by metal detecting equipment at the lower underground
depths (e.g. 3-5 feet) where those types of devices are useful. In
addition to being detectable by toning equipment, i.e., toneable,
because the conduit of the invention can be readily coupled as
discussed above, the conduit of the invention can be detected
underground over extended lengths, e.g., 5 to 10 miles, as desired
in the art. Furthermore, the conduit can include a wire 32 or a
twisted pair of wires 34 and can be used to provide a return path
for signals to determine if damage points exist along the
cable.
[0042] It is understood that upon reading the above description of
the present invention and reviewing the accompanying drawings, one
skilled in the art could make changes and variations therefrom.
These changes and variations are included in the spirit and scope
of the following appended claims.
* * * * *