CA2094059A1 - Non-metallic conduit which is locatable when buried underground and a method of manufacture of same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A method of making a non-metallic conduit which is locatable when buried underground. The method includes the step of incorporating a longitudinally extending wire into a sidewall of a non-metallic conduit.

Description

The present invention relates to a non-metallic conduit `which i~ locatable when buried underground and a method of manufacturing the same.

~`.1 BACKGROUND OF THE INVENTION
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.~Thexe are two type~ of non-metallic conduit in widespread use; polymer pipe and fibreoptic cable. Polymer pipe has a useful life of appro~imately 300 years, as compared to metallic ''pipe which has a useful life of approximately 50 years. One would expect that, with thi~ dramatic dif~erence in useful :~life, polymer pipe would have totally replaced metallic pipe ~;~15 in all utility networks. Polymer pipe has one inherent c~drawback, however, which has impeded its universal acceptance.
Polymer pipe, once buried underground, ca~not be readily ;~relocated. The accurate relocation of utility networks i~ of critical importance, especially in populated areas. Utility companies and civic gover~ments mu~t be able to locate utility lines for purposes of maintenance and in order to avoid severing the utility lines whene~er construction i~ being undertaken in the vicinity.
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The technology currently used wh~n laying polymer pipe to address this critical problem i~ to lay a "tracer wire"
~eparately in the same trench as the pol~mer pipe. In theory the tracer wire provideæ a metalli~ trace material which enables the polymer pipe to be located. In practise, the tracer wire is o~ten broken by burrowing animals, farm machinery, construction crews and other causes~ There are vast sections of utility networks laid with polymer pipe that are dif~icult, if not impossible, to accurately locate.

SVMMARY OF T~E INVENTION

What is required is a method o~ making a non-metallic i conduit which i~ locatable when buried undergroundO

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According to one aæpect of the invention there i8 provided a method of making a non-metallic conduit which is locatable `~when buried underground. The met,hod i~ comprised of the step of incorporating a longitudinally extending wire into a sidewall of a non-metallic condu:it.

Accordiny to another aspect of the present invention there is provided a non-metallic conduit which includes a tubular sidewall and a longitudinally extlending wire incorporated into the ~idewall.

A non-metallic conduit aonstructed in accordance with the teaching of the present invention i8 readily locatable underground and remains 30 for it~ useful life. The tracer wire can only be damaged by a blow of ~uch magnitude that the sidewall o~ the conduit is dam~ged. The embedding of a wire in the conduit makes it a conductor which can be of ignificance in expanding the u e of the conduit for use in intelligent networks having remote sensor~ coupled by means of ~-the wire with microprocessors.
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Although beneficial re~ult~ may be obtained through the use of the method, as described, in order to be suitable for high pressure applications care must be taken not to weaken the ~idewall of the conduit which would adversely effect the mechanical properties of the conduit. Even more beneficial resultæ may, therefore~ be obtained by having the longitudinally extending wire confined within a longitudinal appendage to the conduit thereby maintaining minimum wall thickness of the conduit 50 not a~ to interfere with mechanical properties of the conduit.

Once it wa~ conceived to addreæ~ the problem of breakage of the tracer wire by incorporating a wire into the sidewall of the polymer pipe or other non-metallic conduit the problem remained to determine what was the best method for .

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accomplishing this objective. One method explored was adhesion. In this proces~ an adhesive is used to ~ecure the tracer wire to the pipe by an overlay or pressure bonding process. Another method explored wa~ welding. In this process the tracer wire is welded to the pipe by plastic fusion.
Another method explored was profi]e extrusion. In this process a tracer wire receiving channel is extruded on the exterior of the pipe and the tracer wire is subsequently inserted into the channel. These methods did not prove to be cost effective as they required additional labour intenæive proce~sing and the use of expensive equipment and materials.

The most cost effective manner o~ incorporating a ~ longitudinally extending wire into a sidewall of a polymer ',f'il, 15 conduit was determined to be introduction through the extrusion die used to extrude the conduit. This method includes the following described steps. Firstly, form a duct through a barrel of a polymer extruderO Secondly, feed wire through the duct into a extrusion die attached to the barrel, ~uch that the ~ 20 wire extends longitudinally along the path to be followed ii~ through the die by extruded polymer when orming the conduit.
Thirdly, extrude the polymer such that polymer flows through the die pulling the wire along with it~ whereby conduit exiting the barrel of the polymer extruder has a longitudinally extending wire incorporated in it's sidewall.

When following this method the extrusion die can be modified to in~lude a wire receiving pas~age appended to and in liquid communication with a sidewall portion of the extrusion die such that the longitudinally extending wire is confined within a longitudinal appendage to the conduit ~idewall thereby maintaining a minimum wall thickness of the conduit.

By following the teaching~ of the described method a tracer wire can be incorporated in any form of non-metallic conduit which iB extruded at minimal expense. With fibreoptic ?A'~

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cable a polymer sheathing constructed, as deæcrib2d, can be ~abricated.

~ These and other features of t]he invention will kecome more ;~; apparent from the following deæcription in which reference is made to the appended drawingæ, wherein:
FIGU~E la is a transverse section view of a polymer conduit constructed in aacordance with the teachings of the present invention.
FIGURE lb is a transver~e æection view of a polymer conduit constructed in accordance with the teachings of the present invention.
FIGURE ~ i a ~ide elevation view in longitudinal section of a polymer extruder adapted for uæe in accordance with the teachings of the preæent method.
FI~URE 3 is a detailed side elevation view in longitudinal æection of ~he polymer extruder illustrated in FIGUR~ 2.
~ FI~URE 4 is a end elevation view of the polymer extruder ¦ illuætrated in FIGURE 3.
' l 25 DETAILED DESCRIPTION OF TEIE PREFERRED EMBODIME~T

The preferred embodiment, a non-metallic conduit gen~rally ~ identified by reference num~ral 10, will now ~e deæcribed with ¦ reference to FI¢URE8 la through 4. The illuætrated non-metallic conduit iæ made of polymer material and will hereinafter be referred to a~ such.

Referring to FIG~ la, polymer conduit 15 haæ a tubular sidewall 12 with a longitudinally extending wire 14 incorporated into sidewall 12. Referring to FIGURE lb, a version of polymer conduit 10 intended for high pressure applications i8 illustrated. In order not to weaken sidewall 209~ 05~

12, longitudinally extending wire 14 is confined within a ~, longitudinal appendage 15 to polymer conduit 10. This maintains minimum wall thickness of sidewall 12 so the incorporation of longitudinally extending wire 14 will not interfere with mechanical properties of polymer conduit 10. The preferred method of incorporating longitudinally extending wire 14 into sidewall 12 of polymer plastic conduit 10 is illustrated in FIG~RE~ 2 and 3. Firstly, form a duct 22 thr~ugh a barrel 18 of a polymer extruder 20. Secondly, wire 14 through duct 22 extending into a extrusion die 24 attached to barrel 18. Wire 14 extends longitudinally along a path to be followed through die 24 by the extruded polymer 26 when forming polymer conduit 10. ~hirdly, extrude polymer 26 through barrel 18 such that polymer 26 flows through die 24 pulling wire 14 along with it. Polymer conduit 10 exiting extruder 20 has wire 14 embedded in it. It should be noted that molten polymer 26 must capture wire 14 for this method to work success~ully. It may, therefore, be necessary to temporarily stop the extrusion process to permit polymer 26 to ~olidify sufficiently to "capture" wire 140 Thereafter, as polymer 26 ig moved by the action of extrusion screw 27, wire 14 will be pulled alongO

In order to produce polymer conduit 10 with a longitudinal appendage 15, as illustrated in FI~U~E l~r extrusion die 24 should be modifiedO The modified form of extrusion die 24 i~
illustrated in FIGURE 4. A wire receiving pasæage 30 i8 appended to and in liquid communication with a ~idewall portion 32 of extrusion die 24~ When extrusion die 24 is modifiedl a~
described, polymer 26 pu118 longitudinally extending wire 14 along during the extrusion process, however, wire 14 i confined within longitudinal appendage 15~ This enables polymer conduit 10 to have wire 14 embedded within ~idewall 12 while maintaining a minimum wall thickness.
If electrical conductivity i~ of importance in view of the ~nd use, it may be desirable to have wire 14 extend past the :,, ~, :'~
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i ends of polymer conduit 10. The exposed portion of wire 14 can be protected by an insulating waterproof encapsulation. No ~, special driving gear is necessary for moving wire 14, as the extruded polymer material 26 is driven through barrel 18 and 5 consequently through die 24 by the extrusion ~crew 27.
~' It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention aæ defined 10 by the Claims.

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Claims (5)

1. A method of making a non-metallic conduit which is locatable when buried underground, comprising the step of:
incorporating a longitudinally extending wire into a sidewall of a non-metallic conduit.

2. The method of making a non-metallic conduit which is locatable when buried underground as defined in Claim 1, the longitudinally extending wire being confined within a longitudinal appendage thereby maintaining minimum wall thickness for pressure applications.

3. A method of making a non-metallic conduit which is locatable when buried underground, comprising the steps of:
a. firstly, forming a duct through a barrel of a polymer extruder;
b. secondly, feeding wire through the duct and extending into an extrusion die attached to the barrel such that the wire extends longitudinally along the path to be followed through the die by extruded polymer when forming the conduit;
c. thirdly, extruding the polymer such that polymer flows through the die pulling the wire along with it whereby conduit exiting the barrel of the polymer extruder has a longitudinally extending wire incorporated in a sidewall.

4. The method of making a non-metallic conduit which is locatable when buried underground as defined in Claim 3, a wire receiving passage being appended to and in liquid communication with the extrusion die such that the longitudinally extending wire is confined within a longitudinal appendage to the conduit thereby maintaining a minimum wall thickness of the conduit.

5. A non-metallic conduit, characterized by:
a. a tubular sidewall; and b. a longitudinally extending wire incorporated into the sidewall.