GB2064058A - Wiring guide - Google Patents

Abstract

A wiring guide for telephone or electric lines in which the lines can easily be inserted through the pipe through length of more than 100 meters. The wiring guide is formed as a fiber-reinforced plastics bar having a flexural rigidity of at least 2 x 10<6> kg mm<2> and a weight per unit length of no more than 160 g/m. Long reinforcing fibers are arranged at an angle of up to +/-45 DEG with respect to the longitudinal direction. For the reinforcing fibers, carbon fibers can be used alone or carbon fibers along with other organic fibers. The plastics bar may be made electrically conductive so that its position can be detected by an electric field generated by passing a current through the bar, and it may be hollow. Reinforcing materials and resins are listed.

Description

SPECIFICATION Wiring guide The present invention relates to a wiring guide which is used to lay electrical wires in pipes or conduits buried under the ground. The invention is intended to provide a wiring guide of which the flexural or bending rigidity and the weight per unit length are set in suitable ranges so that it can readily guide an electrical wire or the like through a very long pipe buried under the ground which was heretofore considered impossible. It is also intended to provide a wiring guide which can be wound on a reel smaller than two meters in diameter so that it can be readily handled and carried.

In most cases, telephone lines and electric wires are still primarily laid over poles in urban areas. However, it is desirable to lay such wiring under the ground from an aesthetic point of view.

In fact, many areas now require by law that new wiring be laid under the ground. Accordingly, recently telephone lines and electric wires are often laid by using pipes buried under the ground.

If the length of a pipe buried under the ground is relatively short, for instance several tens of meters, electrical wires or telephone lines can be readily inserted through the pipe. That is, feeding the wires through the pipe can be achieved using a steel wire with a pushing rod as a guide.

It has been desired in some instances to increase the length of such a pipe to correspond to wiring intervals of one hundred meters or, in some cases, even more than two hundred meters. In wiring over such a long distance, the use of a steel wire as a wiring guide suffers from the following difficulties. As the rigidity of the steel wire is not sufficiently great, the steel wire may buckle or it may snaf in the pipe as a result of which it is not possible to feed the wire through the pipe through the desired length. Furthermore, as the wiring guide itself is relatively heavy, it is inconvenient to handle.

In order to overcome these difficulties, the invention provides a wiring guide constructed as a fiber-reinforced plastics bar having a flexural rigidity of at least 2 x 106 kg mm2 and a weight per unit length of no more than 160 g/m. More preferably, the weight per unit length is in a range of 100 to 130 g/m. The fiber-reinforced plastics bar of the invention preferably includes long reinforcing fibres arranged at an angle of +450, more preferably 1300, with respect to the longitudinal direction of the fiber-reinforced plastics bar. The plastics bar may include carbon fibers for reinforcing fibers thereof alone or be a hybrid-fiber-reinforced plastics bar composed of carbon fibers and other reinforcing fibers.In one embodiment, the plastics bar including the carbon fibers as reinforcing elements thereof is made electrically conductive so that a current can be passed through the plastics bar thereby producing an electric field which may be detected from the surface of the earth so as to determine the longitudinal position of the plastics bar within a pipe buried under the ground. An electrically insulating carbon layer may be provided over the fiber-reinforced plastics bar.

In the accompanying drawings:- Figs. 1 to 4 are sectional views showing various examples of wiring guide constructed according to the invention.

In view of the foregoing, the inventors have conducted intensive research in order to provide a wiring guide which can use in wiring over long distances. As a result, it has been found that the distance in a buried pipe through which a wiring guide can be extended depends on two parameters, namely, the flexural rigidity and weight of the guide, According to this finding, the inventors have determined particularly desirable values for these two parameters. The use of a barshaped wiring guide which fulfills the two parameters thus determined makes it possible to readily achieve wiring over three hundered meters which was heretofore considered impossible.

Furthermore, as a wiring guide of the invention is light in weight, it can be readily handled, and wiring operations for a long pipe buried under the ground can be achieved with a relatively small number of workers.

A wiring guide according to the invention is provided as a bar, or more specifically a fiberreinforced plastics bar, which has a flexural rigidity of at least 2 x 106 kg mm2 and a weight per unit length of 1 60 g/m or less.

If a bar whose flexural rigidity is less than 2 x 106 kg mm2 is inserted as a wiring guide into a buried pipe, when it is inserted about 200 m, it tends to buckle. If such a wire is further inserted into the pipe, then it may actually break.

Accordingly, the wiring guide of the invention must have a flexural rigidity of at least 2 x 106kg mm2.

Furthermore, it is desirable that the weight per unit length of the bar used as the wiring guide be less than 1 60 g/m, more preferably 100 to 130 g/m. If a heavier bar is used as the wiring guide, that is, a bar whose weight per unit length is more than 160 g/m is used as the wiring guide, during the course of pushing the wiring guide into the buried pipe the bar will bend and then buckle under its own weight. That is, it becomes difficult or impossible to insert it into the buried pipe and, in any event, it is impossible to insert it beyond a distance of 200 m.

The fiber-reinforced plastics bar forming the wiring guide according to the invention may be produced by using reinforcing long fibers and/or by braiding reinforcing long fibers. Examples of suitable reinforcing fibers are carbon fibers, silicon carbide fibers, boron fibers, aromatic polyamide fibers and glass fibers. However, it is more preferable that carbon fibers be used alone or carbon fibers and other organic fibers such as nylon fibers, polyester fibers, polyproplylene fibers or aromatic polyamide fibers be used in combination as such fibers can readily satisfy the above-described two parameters required of a wiring guide according to the invention.

It is preferable that the reinforcing fibers be arranged in an angled manner within +450, preferably 1300 with respect to the longitudinal direction of the fiber-reinforced plastics bar. The provision of a layer of reinforcing fibers thus orientated makes it possible to readily manufacture fiber-reinforced bars whose characteristics conform to the object of the invention.

A variety of thermoplastic resins or thermosetting resins may be employed as matrix resins used in forming the fiber-reinforced plastics material. Examples of these resins are polyethylene, polypropylene, plasticized polyvinyl chloride, polyamides, unsaturated polyesters, vinylester resin, phenol resin, polyimdes, and epoxy resin.

A method of manufacturing a wiring guide according to the invention is as follows. Molten or liquid-phase resin is impregnated into parallel-laid strands of reinforcing fibers. The parallel strands thus treated are formed into a bar, for instance by drawing. If necessary, the resin of the bar is subjected to a cross-linking hardening or solidification process.

In accordance with the invention, the bar may be formed in a number of different configurations.

That is, the above-described hollow bar, a pipeshaped bar, or a bar having a rectangular section may be employed. However, the reinforcing fibers buried in the bar must include at least one layer arranged in the longitudinal direction of the bar. It is difficult to fabricate an effective wiring guide which satisfies the objects of the invention from a bar which does not include the above-described layer.

The fiber-reinforced plastics bar may employ as its core a rod made of polyamide, polyurethane, polypropylene, polyvinyl chloride or polycarbonate, or a reinforced plastics pipe made of hollow fibers.

A wiring guide according to the invention may be provided as a bar which is essentially made of carbon-fiber-reinforced plastics material and which is high in rigidity and light in weight. Therefore, the wiring guide of the invention can be extended a greater distance in a buried pipe than any previously-known wiring guide. It is excellent not only as to its surface friction and wear resisting characteristics, but also in its strength and creep characteristics. Accordingly, it can be wound on a reel having a diameter of less than two meters, which is convenient for handling and for transporting, making it possible to conveniently store the guide for a long period of time.

An example of a wiring guide of the invention is a fiber-reinforced plastics bar which is fabricated using carbon fibers for reinforcing fibers. In this case, the wiring guide is electrically conductive.

Therefore, if an electric current is applied to the wiring guide while it is being inserted into a buried pipe, the electric field generated by the wiring guide can be measured on the ground.

Accordingly, the depth and direction of the buried pipe can be detected. This is an advantageous effect of the invention.

The invention will be described in more detail with reference to actual examples: EXAMPLE 1 A fiber-reinforced plastics material was prepared by impregnating epoxy resin in parallellaid carbon fibers. The material thus prepared was subjected to a drawing operation to provide a solid bar 2 (see Fig. 1) which, was 10 mm in diameter and had a fiber content percentage of 50% by volume. As a result, a wiring guide having a flexural rigidity of 5.40 x 1 06 kg mm2 and a weight per unit length of 122.5 g/m was obtained.

With the wiring guide, electrical wiring operations were carried out in a pipe having a length of 300 m which was buried 2 m under the ground. In this operation, the wiring guide never buckled and never snagged in the pipe, and accordingly the wiring operation could be achieved readily. The bending strength of the wiring guide was sufficiently high, 1 50 kg/mm2, and therefore it could be wound on a reel 1 m in diameter. Thus, the wiring guide could be readily handled and transported.

EXAMPLE 2 As shown in Fig. 2, a core 1 having a diameter of 5 mm made of nylon was employed. A surface layer 2 was formed on the core 1 by drawing a carbon-fiber-reinforced plastics material which was prepared by impregnating epoxy resin into carbon fibers with a round bar 10 mm in diameter produced. As a result, a wiring guide having a flexural rigidity of 5.10 x 106 kg mm2 and a weight per unit length of 115.5 g/m was obtained.

In a manner similar to Example 1, electrical wiring operations were conducted with the wiring guide.

The electrical wiring operations could be achieved considerably smoothly. The wiring guide could be handled with ease.

EXAMPLE 3 As shown in Fig. 3, a glass-cloth-reinforced plastics pipe having an outside diameter of 6 mm was employed as a core 3. A surface layer 2 was formed on the core 3 by drawing a carbon-fiberreinforced plastics material composed of carbon fibers and epoxy resin from which a round bar 10 mm in diameter was fabricated. Thus, a wiring guide having a flexural rigidity of 5.00 x 106 kg mm2 and a weight per unit length of 109.8 g/m was produced. Similar to Example 1, electrical wiring operations were conducted with the wiring guide. The electrical wiring operations could be achieved smoothly, without encountering any difficulties.

EXAMPLE 4 As shown in Fig. 4, three pipes 4, 8 mm in outside diameter and 6 mm in inside diameter, were prepared by drawing a carbon-fiber reinforced plastics material composed of carbon fibers and epoxy resin. A rubber cover layer 5 was formed around the three pipes providing a wiring guide having a flexural rigidity of 5.00 x 106 kg mm2 and a weight per unit length of 105.5 g/m. Similar to Example 1, electrical wiring operations were carried out with the wiring guide. The wiring operations could be accomplished smoothly. It has been confirmed the wiring guide with a rubber cover layer is scarcely damaged by friction and it is-not in any case broken by action of friction. By applying electric current to the wiring guide inserted into a pipe buried under the ground, the electric field induced by the wiring guide was measured to detect the position of the wiring guide. As a result, it was ensured that the wiring guide was inserted into the buried pipe at the expected depth and over the expected distance.

Claims (11)

1. A wiring guide comprising a fiber-reinforced plastics bar having a flexural rigidity of at least 2 x 106 kg mm2 and a weight per unit length of no more than 160 g/m.

2. A wiring guide as claimed in claim 1, in which said fiber-reinforced plastics bar comprises long reinforcing fibers which are arranged at an angle of i45c with respect to the longitudinal direction of said fiber-reinforced plastics bar.

3. A wiring guide as claimed in claim 1 or 2, in which said fiber-reinforced plastics bar has carbon fibers as reinforcing fibers thereof.

4. A wiring guide as claimed in claim 2, in which said fiber-reinforced plastics bar is a hybridfiber-reinforced plastics bar having carbon fibers and other reinforcing fibers as reinforcing fibers thereof.

5. A wiring guide as claimed in claim 2, in which said fiber-reinforced plastics bar (contains reinforcing) carbon fibers as reinforcing fibers and is electrically conductive.

6. A wiring guide as claimed in claim 5, further comprising an electrically insulating cover layer upon said fiber-reinforced plastics bar.

7. A wiring guide as claimed in any preceding claim, wherein said weight per unit length is in a range of 100 to 130 g/m.

8. A wiring guide as claimed in claim 2, wherein said reinforcing fibers are arranged at an angle of +300 with respect to the longitudinal direction of said fiber-reinforced plastics bar.

9. A wiring guide as claimed in claim 4, wherein said other reinforcing fibers comprise fibers selected from nylon fibers, polyester fibers, polypropylene fibers and aromatic polyamide fibers.

10. A wiring guide as claimed in claim 2, wherein said reinforcing comprise fibers selected from carbon fibers, silicon carbide fibers, boron fibers, aromatic polyamide fibers and glass fibers.

11. A wiring guide as claimed in claim 2, wherein said fiber-reinforced plastics bar comprises a resin impregnated with said reinforcing fibers, said resin being selected from polythylene, polypropylene, plasticized polyvinyl chloride, polyamides, unsaturated polyesters, vinylester resin, phenol resin, polyimides, and epoxy resin.

1 2. A wiring guide substantially as hereinbefore described in any one of example 1 to 4.