GB2034130A

GB2034130A - Protective means for cables and process of manufacturing the same

Info

Publication number: GB2034130A
Application number: GB7932233A
Authority: GB
Original assignee: Stamicarbon BV
Current assignee: Stamicarbon BV
Priority date: 1978-09-19
Filing date: 1979-09-18
Publication date: 1980-05-29
Also published as: DK391079A; DK152318B; GB2034130B; BE878850A; FR2437087A1; DK152318C; FR2437087B1; DE2936851A1; CH649873A5; DE2936851C2

Abstract

The invention relates to protective means 27 for cables 28 to be laid in a trench 25, consisting of two bands of material lying flat against each other, which are connected along the coinciding long side edges, and between which is provided a pulling device 11 for inserting the cables that is at least equally long as the bands of material. The invention also relates to a process of producing protective means of this type, according to which a plastic strip is folded double along its longitudinal axis whilst simultaneously the pulling device is brought in, after which the side edges are fastened to each other. <IMAGE>

Description

SPECIFICATION Protective means for cables and process of manufacturing the same.

This invention relates to protective means for cables, and to a method of manufacturing such protective means.

Cables laid in the ground are often subject to mechanical damage. Mechanical damage may also occur when laid cables are disinterred, for instance during maintenance or repair work, and when excavation is being carried out near them.

Unarmoured cables are used in communication systems e.g. cable television and are especially liable to such damage.

It has previously been proposed to prevent this damage by covering or wrapping the cables in strips of flexible plastics material, or by the use of concrete or masonry cable troughs.

When cables to be laid in the ground are wrapped with flexible strip, this is supplied wound on reels and unwound on site, and the cables laid out on the flexible strip and the side edges of the strip fastened to each other, possibly with an overlap. Fastening the side edges to each other may be effected for instance by stapling or heat welding, or by the use of means specially provided on the edges for fastening them together, for instance a snap connection. The actions of folding the strip and consolidating it to a wrapping by the use of fastening elements result in a slowing up of the speed with which cables can be laid, and another disadvantage is that the stapling or welding equipment readily becomes fouled when sited in or near trenches excavated in the ground.

The invention provides means of protection not having the abovementioned disadvantages and requiring a minimum of space in storage and transport.

According to the invention, the protective means consists of two bands of material lying flat against each other and which are connected along their side edges, and between which is provided a pulling device for-inserting the cables that is at least equally long as the bands of material.

By preference, the protective means has a continuous connection along two of the coinciding side edges. Such a means of protection may consist of a strip of plastic material folded double along its longitudinal axis. The other two coinciding side edges of the bands laid against each other are connected by means of spaced fastenings, for instance staple or heat-weld connections.

Another shape the protective means may have is that of a plastic sleeve folded flat along two folding lines running parallel to the longitudinal axis of the sleeve. Preferably, the plastic is of a type which as normal temperature is flexible and resilient, so that when cables are pulled in, the bands lying against each other come apart while offering only little counterpressure, and form a duct.

Admittedly, the German Document No. 1078201 laid open for public inspection describes a duct-shaped means of protection for electric wires, which duct contains a pulling device, but this protective means does not consist of two bands lying flat against each other. In storage and transport it takes much space, unlike the protective means for cables according to the invention, which can be stored and transported in a much more compact form.

In order that the shape of the cross section of the ultimate duct may be determined beforehand, the bands may be provided with hinge lines running parallel to the longitudinal axis of the bands and consisting of narrow zones of higher flexibility than the rest of the material of which the bands are made.

It is advantageous to have these hinge lines not coincide with the folding lines.

Preferably, the cable-pulling device extends outside the ends of the protective means.

The invention also relates to a process of producing protective means, starting from a plastic strip obtained by calendering or extrusion, which strip is provided with hinge lines. The strip is folded continuously to form two bands lying flat against each other, whilst simultaneously the pulling device is brought in, and after folding the coinciding free edges are at intervals fastened to each other, the protective means being subsequently cut off to predetermined lengths and wound up.

Before cutting, the pulling device is drawn out so far that after the protective means has been cut off to the length required and the pulling device has been cut through the latter extends some way beyond the separated parts of the protective means.

As the coinciding side edges of the bands lying against each other have already been fastened to each other during production, under conditions that can be so selected as to be favourable for this operation, this time-consuming operation need not be carried out when the cables are being laid, and it is not necessary to use equipment liable to fouling. The protective means is flat after production, and can in this shape be stored and transported after having been wound up. It will be clear that if the same protective means were already duct-shaped upon production, it would be much more difficult to wind up and would take up much more space.

At the spot where the cables are to be laid the protective means is unwound. Thereafter the cables are fastened to one end of the pulling device and pulled into the protective means by exerting a pulling force at the other end. In this operation, the cables exert outwardly-directed lateral force on the bands of the protective means, which, because they consist of a flexible material, move apart, and comes to form a duct. As hinge liries are provided, the shape of the cross section of this duct can be largeiy determined beforehand.

As no hinge line coincides with a folding line, the resilience of the material, which, already when the protective means is in the unwound condition and before the cables have been pulled into it, exerts a lateral and outwardly-directed force on the bands of material, can be used to advantage.

This reduces the force needed for pulling the cables into the protective means, because the component of the pulling force required to move apart the side walls is in part supplied by the resilience of the material.

The invention will be elucidated with reference to the embodiments shown in the drawing.

Fig. 1 is a diagram showing a side view of equipment for producing a protective means according to the invention; Fig. 2 is a top view of this equipment; Figs. 3 - 5 show the cross section of the strip in the places A, Band Cin Fig. 2; Figs. 6-7 show, respectively, the sections of a different design of the original strip and the resulting protective means; Figs. 8-9 represent the cross section of the protective means for cables according to the designs shown in Fig. 5 and Fig. 7, after the cables have been pulled in; Fig. 10 shows yet another design of the protective means; Fig. 11 is a diagram showing how cables are inserted and connected up when use is made of the protective means according to the invention.

A thermoplastic material, such as polyethylene, polypropylene, polyvinylchloride etc., or a mixture or copolymers of these plastics, is extruded to a strip 2 by means of an extruder 1. By means of a number of special-section rollers 3 the strip is provided with hinge lines 4 in the shape of grooves running parallel to the longitudinal axis of the strip 2. Number and locations of these hinge lines may be selected in dependence on the desired cross section, as will be explained hereinafter. The strip is then-cooled in a cooling tank 5 and passed over rollers 6 and 7. Between the rollers 6 and 7 a certain length of strip can be buffered, so that, with the extruder in continuous operation, the strip can be given an intermittent after-treatment.Next, the strip passes through a folder device, 8, 9, where - in this particular case -the strip is folded double along the central hinge line 4'. Here, folding line and hinge line coincide. It may be advantageous, however, to have the hinge line so located that a hinge line is not at the same time the folding line. During folding, a pulling device for a cable, for instance a nylon cord, is inserted, from roller 10, between the bands 1 2 and 13 to be laid against each other.

The rollers 9 and 14 next transport the bands lying flat against each other to a fastening device 1 5, where the free long side edges of the bands lying against each other are connected by means of fastenings 1 6. The fastenings 1 6 are staples or clamps provided at intervals along the length of the protective means. Fastening may also be done in other ways, for instance, by welding, bonding by means of an adhesive, or punching. The transport to the fastening device is effected stepwise. After each step, corresponding to the required distance between the fastening places, the fastening device starts operating. After the fastening has been effected, the strip, folded flat, is wound onto a reel 17. A counter 18 measures the length to be wound on the reel.When the length has reached a preset value the drive of the strip and winding roller 17 is switched off. The pulling device 11 is manually drawn out between two fastenings, as indicated at 11' in Fig. 2. Now a cutter 19 is put into operation, which cuts the strip through. At the same time, the pulling device 11 is cut through.

The reel with the length of strip on it is now removed, after which the drive is started again.

The protective means wound on the reel is secured against unwinding for instance by means of a retaining band.

As Figs. 6 and 7 show, the case here described concerns a strip 2 with hinge lines 4.

The strip is folded double to a flat shape along its longitudinal axis indicated by 20, which forms the folding line, and the free edges are fastened to each other (Fig. 7). Along the axis 20 the material of the protective means is under tension, exerting a force which tends to move apart the bands 1 2 and 1 3 lying against each other.

Figs. 8 and 9 clearly show that the cross section of the protective means, after the cables have been pulled into it, is determined substantially by location and number of the hinge lines.

Fig. 10 shows a modified design of the protective means after the cables have been pulled into it. In this case it is formed by a plastic sleeve 21 made by extrusion. The extruder die is so shaped that the extruded sleeve possesses hinge lines in the form of longitudinal grooves 22 that can serve as folding lines. The pulling device is introduced into the sleeve during extrusion, through a central supply channel. After cooling, the sleeve is folded flat and locally provided with openings 23, e.g. by punching out material along the folding line. Before the sleeve, in its fiat condition, is wound onto the reel 17, the pulling device is drawn out over a certain distance, so that it projects outside the end.

For connecting up dwelling houses (see fig. 11), for instance to a telephone or cable-television system, a trench 25 is dug along the houses 24, into which trench open entry channels 26 for the equipment to be connected up. The protective means 27 is unwound alongside the trench, and the required length of cable 28 are measured off At 29 the cables are tied together at their common end, and this end is attached to the pulling device where this projects beyond that end of the protective means 27 which is farthest removed from the terminal box 30. The loose ends of the cables have been marked, e.g. by means of ribbons attached to them. The protective means is shaped into a duct by exertion of some pressure from the sides, after which the cables are pulled into the duct. At the connection for each house, the end of the cable marked with a coloured ribbon-visible through the slot between the locally joined side edges of the strip or through the openings 23 in the sleeve - is pulled out of the duct, and then connected to the length of cable leading into the house either before or after the duct has been laid in the trench. After this, the trench can be filled up.

Claims

1. Protective means for cables, characterized in that the protective means consists of two bands of material lying flat against each other and which are connected along their side edges, and between which is provided a pulling line for drawing a cable between the said bands, of length at least the length of the bands.

2. Protective means according to Claim 1, wherein the said bands lying against each other are formed by folding a strip of plastics material along its length.

3. Protective means according to Claim 1 or Claim 2, wherein the said bands are connected along at least one of their side edges by spaced fastenings.

4. Protective means according to Claim 1, wherein the said bands lying against each other are formed by folding flat a plastics sleeve along two folding lines running parallel to each other along its length.

5. Protective means according to any of Claims 1 to 4, wherein the said bands are made of a resilient plastics material which is flexible at normal temperature.

6. Protective means according to any of Claims 1 to 5, wherein the said bands are provided with hinge lines running parallel to each other along the length of the bands, the said hinge lines being - lines of reduced thickness of the material of the bands providing greater flexibility of the material than provided by the rest of the material of the bands.

7. Protective means according to Claims 2 to 6, wherein the line of folding and the said hinge lines do not coincide.

New claims or amendments to claims filed on date of issue of search report Superseded claims 2 New or amended claims:

2. Protective means according to Claim 1, wherein the said bands lying against each other are formed by folding a strip of plastics material along its longitudinal axis.

8. Protective means according to any of Claims 1 to 7, wherein said pulling line projects outside the ends of the protective means.

9. Protective means for cables as claimed in Claim 1, substantially as hereinbefore described, with particular reference to Figures 5 to 10 of the accompanying drawings.

10. A method of manufacturing a protective means according to Claim 1, wherein a strip of plastics material provided with hinge lines is continuously folded to form bands lying flat against each other whilst simultaneously a pulling line is inserted between the bands during folding and after folding the free side edges are fastened together at intervals, and the protective means thus formed is subsequently cut off at a predetermined length, and wound up.

11. A method according to Claim 10, wherein prior to the predetermined length of formed protective means being cut off the pulling line is drawn out at the location where the formed protective means is to be cut off so that after the protective means has been cut off and the drawn out pulling line has likewise been cut through, the latter projects beyond the separated parts of the protective means.

12. A method according to Claim 10 or Claim 11, substantially as hereinbefore described and illustrated in Figures 1 to 10 of the accompanying drawings.

1 3. Protective means obtained by a method as claimed in any of Claims 10 to 12.