IE79449B1

IE79449B1 - Empty conduit with detachable cable assembly and method of making same

Info

Publication number: IE79449B1
Application number: IE922590A
Authority: IE
Inventors: James A Cole
Original assignee: Integral Corp
Priority date: 1991-08-16
Filing date: 1992-08-14
Publication date: 1998-05-06
Also published as: SE9202352L; NL193878B; FR2684247A1; AU664376B2; NL9201468A; CH688214A5; NO923203D0; DE4227464A1; ITRM920607A1; ITRM920607A0; ES2040661B1; IE922590A1; IT1263227B; NO923203L; NL193878C; AU2106392A; GB2258711A; SE9202352D0; FI923659A0; ES2040661A2

Abstract

An empty conduit (12) with a communication cable (10) of one type detachably connected to the outer wall (14) of the conduit can be installed in a conventional manner but also enables the future installation of one or more further communication cables (20), particularly of a different type, within the conduit. The detachable connection may be effected by, for example, a frangible surrounding jacket (24), a frangible web (26, Fig 3 not shown) or a pair of resilient extensions (28, Fig 4 not shown). The cable (10) may be electrical and the cable (20) may be an optical fibre. The conduit (12) may be pre-lubricated, of PVC or polythene and provided with a pull member (18, Figs 2-4, not shown). Cable (10) may be attached during or after extrusion of the conduit (12).

Description

t EMPTY CONDUIT WITH DETACHABLE CABLE ASSEMBLY ' AND METHOD OF MAKING SAME Field of the Invention This invention relates generally to communication cable systems, more particularly to cable conduit and cable assemblies, and even more particularly to cable conduit and cable assemblies with means for expanding cable capability.

Background of the Invention The continuing dynamic growth in the communications 10 industry has resulted in the ever increasing demand for additional and different types of communication cables. For example, the initial installation of telephone cables in a particular locality is soon overloaded, with additional cable installations required to meet the expanding communications requirements in that locality. Furthermore, while the vast majority of present day telecommunication, video and data transmissions are over twisted pair telephone and coaxial cables, optical fiber cables are clearly becoming the future transmission media for the communications industry. As a consequence, it becomes imperative that existing non-optical fiber cable assembly installations incorporate assemblies which provide not only for additional future cable installations, but also the capability of installing optical fiber transmission cables in the future without the need of unearthing or replacing the initial installations.

Description of the Prior Art There are existing prior art systems which have attempted to provide this expanded cable capability. For example, U.S. Patent No. 3,862,349 discloses an underground telephone cable assembly installation in which the telephone cable is disposed inside a flexible outer housing having an outside diameter sufficiently larger than the contained telephone cable so as to provide fop future placement of at least one additional cable, a pull wire also being installed along side of the existing cable for this future placement. U.S. Patent No. 3,383,456 discloses a flexible conduit with the electrical conductors being provided within or adjacent the conduit wall so that additional conductors when needed may be drawn through the conduit at a later time without having to remove the conduit.

While these prior art systems in a broad sense enable expanded cable capability, they are not completely satisfactory and have a number of disadvantages associated therewith. For example, in addition to the fact that the existing cable or conductors are located inside the conduit and would thus interfere with the future placement of additional cables therein, as well as increasing the pulling resistance of the future cable installation, the overall construction and design of the prior art systems are deficient in many material respects.

Objects of the Invention It is therefore the principal object of this invention to provide a new and improved conduit/communication cable assembly which provides for expanded cable capability for the future.

Summary of Invention According to the invention there is provided a conduit assembly comprising a conduit containing a pull member for drawing in a length of subsequently installed cable through the conduit and attachment means for detachably fastening an external cable along an external portion of the conduit. In the conduit assembly, a communication cable is detachably connectable to the outer surface of a flexible, elongated empty cable conduit, with pull means provided for the future installation of one or more communication cables within the empty conduit, for example after the conduit assembly with attached cable has been installed underground. In accordance with one particular feature of the invention, the detachably connected cable is of one type, for example a twisted pair telephone cable, while the subsequently installed cable is of a different type, for example an optical fiber cable.

Advantageously, the invention may thus provide an Improved conduit assembly which enables subsequent additions or upgrades to an existing cable installation at a minimum of installation cost and a minimum of inconvenience to the customer.

Specific and additional features of the Invention, as well as additional objects and advantages thereof, will become readily understood by those skilled in the art from the following detailed description, taken in conjunction with the accompanying drawings.

Brief Description of the Drawings Figure 1 is a partial perspective view of a section of the conduit and original communication cable combination in accordance with the teachings of the present invention, illustrating in phantom an optical fiber cable which will be pulled through the conduit in the future; Figure 2 is a cross sectional view of the conduit and original communication cable illustrating one method of attachment of the original communication cable to the conduit; Figure 3 is a cross sectional view of the conduit and original communication cable illustrating a second method of attachment of the original communication cable to the conduit; Figure 4 is a cross sectional view of the conduit and original communication cable illustrating a third method of attachment of the original communication cable to the conduit; ς Figure 5 Is a diagrammatical view of the conduit and ί cable combination, illustrating the ends of the cable having been detached or stripped from the conduit surface.

The drawings are not necessarily to scale, and certain 0 portions may have been exaggerated to emphasize certain details of the invention.

Description of the Preferred Embodiment In the description which follows, like parts are indicated throughout the specification (and drawings) with the same respective reference numerals.

Referring initially to FIGURE 1 of the drawings, a cable conduit 12 having an outer wall 14 and an inner wall 16 is depicted. The cable conduit 12 is of the type conventionally known in the industry and is generally formed by the extrusion of polymeric material, such as a polyethylene or polyvinyl chloride, to form an elongated, flexible duct to serve as a protective underground housing for a communication transmission cable. One such form of conduit is currently being sold by Integral Corporation of Dallas, Texas, the assignee of this invention, under the CABLECON trademark.

In accordance with conventional approaches, the cable conduit is buried underground with the particular transmission cable normally either already having been pre-inserted within the conduit or inserted within the conduit after the conduit is buried.

In accordance with the present invention, however, and with reference again to FIGURE 1, the transmission cable 10 is - 5 attached to and in parallel with the outer wall 14 of conduit 12. This assembly is then installed underground, and cable 10 provides the initial communication link at the time of installation. The cable 10 will therefore be hereinafter referred to as the "original cable, and under present day applications would normally be either a twisted pair or coaxial type cable. The conduit 12, being completely empty, thus serves as a raceway for the future insertion of a cable 20. Cable 20 will therefore be hereinafter referred to as the subsequently installed cable, and in this example would be an optical fiber cable.

To facilitate the future installation of the subsequently installed cable, a string or pull member 18 (FIGURES 2-4) is also preinstalled in the conduit 12, paralleling the length of the conduit, for use in pulling or drawing in the cable through the empty conduit. In addition, it is desirable that the inner wall 16 of the conduit be prelubricated or formed of prelubricated material to facilitate this cable pull-through.

In accordance with a principal feature of the present invention, the original cable 10 is detachably connected to the conduit wall 14 so that the cable, when necessary, may be separated or stripped from the conduit 12 at its splicing ends 10a, as illustrated in FIGURE 5. Accordingly, three different methods or embodiments for effecting this detachable connection are respectively depicted in FIGURES 2, 3 and 4, and are now described.

Referring to FIGURE 2, the conductor cable 10 is removably attached, and held in parallel proximity, to the conduit 12 by a frangible polymer jacket 24 formed along the length of the cable-conduit assembly (as illustrated in FIGURE 1). This jacket, preferably of a thickness not greater than 0.76 mm may be coextruded at the same time as the extrusion of conduit 12, with the original cable 10 being positioned between the outer wall 14 and jacket 24 during the co-extrusion process. - 6 Alternatively, and with reference to FIGURE 3, a thin frangible web 26 may be formed intermediate, and along the length of, the cable 10 and conduit surface 14, the web 26 retaining the original cable 10 to conduit 12 until it is broken to free the c ends 10a from the conduit outer wall.

In the embodiment illustrated in FIGURE 4, a pair of I resilient grasping extensions 28 with retention fingers 28a may be integrally formed as part of, and at the time of the extrusion of, the conduit 12, these extensions retaining the cable 10 in parallel and proximate to the conduit wall 14. In this example, the original cable 10 will be removably connected with the conduit after the completion of the extrusion process.

The detachable connection of original cable 10 with conduit 12 enables the release of the cable, as shown in FIGURE 5, in order to alter the direction of the flow of the cable and conduit at the splicing ends, for example. In the example shown in FIGURES 1-3, the detachment will be effected by selectively fracturing the jacket 24 or web 26; in the example shown in FIGURE 4, the cable 10 is selectively pulled free from the resilient grasp of grasping assembly 28.

While preferred embodiments of the present invention have been shown and described herein, further modifications and improvements may be made by those skilled in the art without departing from the spirit and scope of the invention, as solely defined by the appended claims.

V

Claims

1. A conduit assembly comprising a conduit (16) containing a pull member (18) for drawing in a length of subsequently Installed cable (20) through the conduit (16) and attachment means (24,26,28,28a) for detachably fastening an external cable (10) along an external portion (14) of the conduit.

2. A conduit assembly according to claim 1, in which the attachment means comprises a frangible jacket (24).

3. A conduit assembly according to claim 1, in which the attachment means comprises a frangible web (26).

4. A conduit assembly according to claim 1, in which the attachment means comprises a resilient grasping extension assembly (28,28a).

5. A conduit assembly according to any preceding claim, in which the external cable and the internal cable are different types of communication cable.

6. A conduit assembly according to any preceding claim, in which the internal cable is an optical fibre cable.

7. A method of making a conduit assembly according to any preceding claim, characterised in that the conduit assembly is manufactured by extrusion, the attachment means being coextruded therewith and the external cable being positioned within or attached to the attachment means during the coextrusion process.

8. A method of making a conduit assembly according to claim 4, characterised in that the conduit assembly is extruded, the external cable being fastenable to the resilient grasping extension assembly after manufacture of the conduit assembly.

9. A cable conduit assembly comprising a conduit (16) containing a pull member (18) for drawing in a length of 8. subsequently installed cable (20) through the conduit (16), an external cable (10), and attachment means (24,26,28,28a) for detachably fastening the external cable (10) along an external portion (14) of the conduit.