Field of the invention

The invention relates to a method for converting a coaxial cable to a glass-fibre cable, the coaxial cable comprising:

- an electrically conducting core extending centrally and longitudinally;

- a coaxial, cylindrical, electrically conducting shield extending longitudinally; and

- a dielectric extending between the core and the shield.

The invention also relates to a device for converting such a coaxial cable to a glass-fibre cable.

In the context of the invention 'glass-fibre cable' is always understood to mean a cable comprising at least one optically conductive glass fibre. This will generally be a plurality of glass fibres, wherein a 'glass-fibre cable* can also comprise one or more electrical conductors. The dielectric can comprise a number of radially extending spacers, or be formed for instance by a foamed material such as foamed polyethylene, all of this as is usual.

Background of the invention

Many networks for telecommunication still consist wholly or partially of underground coaxial cables. For various technical and economic reasons there is a great need to replace these coaxial cables with glass-fibre cables. The transition from 'copper to glass', or 'fiberization' of a network, does however entail high cost and takes a great deal of time, particularly because of the labour-intensive and time-consuming excavation work that is required and because of the time necessary to obtain the required permits for excavation in public spaces, in pavements, cycle paths and the like. The present invention now provides a solution with which much work and time are saved and costs are drastically reduced.

Summary of the invention

The invention provides a method as according to claim 1 and a device as according to claim IS. A coaxial cable can thus be converted relatively easily to a glass-fibre cable with a minimum of work and excavation within a relatively short time and at greatly reduced costs. The at least partially softened dielectric is preferably deformed and/or melted material of the at least partially melted dielectric is spread by means of advancing longitudinally inside the cable and inside the shield a first member provided for the purpose and configured and suitable therefor, which first member is more preferably advanced, pushed and/or pulled inside the cable and inside the shield by means of an elongate second member provided for the purpose and configured and suitable therefor. The dielectric can be heated here by means of the first member and/or the core and/or the shield, preferably resistively by means of realizing an electric current through the first member and/or the core and/or the shield. The core can be displaced radially here to a non-central position inside the cable and inside the shield. The frictional resistance between the second member and what surrounds it can thus be reduced. The core can also be wholly removed from the coaxial cable. At least one glass fibre is men introduced into the passage. At least one electrical conductor can here also be introduced into the passage. Via the at least one electrical conductor, optionally together with the shield, an amplifier present in the network of which the coaxial cable forms part can for instance be powered. The at least one glass fibre can be introduced into the passage in a usual manner such as blowing, but optionally also by pulling, wherein possible use can be made of the core during the removal thereof or of the second member during withdrawal thereof from the passage. Brief description of the drawings

The invention is further elucidated hereinbelow on the basis of a number of exemplary embodiments. In the drawings, more or less schematically:

- figure 1 shows a cross-section of a coaxial cable;

- figure 2 shows a cut-way side view thereof;

- figure 3 shows a cross-section of a coaxial cable during the conversion to a glass-fibre cable according to a first embodiment of a method according to the invention; and

- figure 4 shows a cross-section of the coaxial cable thus converted to a glass-fibre cable; - figure 5 shows a cross-section of a coaxial cable during the conversion to a glass-fibre cable according to a second embodiment of a method according to the invention; and

- figure 6 shows a cross-section of the coaxial cable thus converted to a glass-fibre cable;

- figure 7 shows a cross-section of a coaxial cable during the conversion to a glass-fibre cable according to a third embodiment of a method according to the invention; and - figure 8 shows a device according to the invention.

Exemplary embodiments Figures 1 and 2 show a coaxial cable (1) comprising a core (3), a shield (4) and a dielectric (5) which in the shown example comprises a number of radially extending spacers (6). Figure 3 shows the conversion of coaxial cable (1) to a glass-fibre cable (2) according to a first embodiment of a method according to the invention. During the conversion the spacers (6) are heated such that spacers (6) at least partially soften and/or at least partially melt The at least partially softened spacers (6) are deformed and/or the melted material of the at least partially melted spacers (6) is spread such that a passage (8) is created which is sufficiently large and suitable for introducing therein at least one glass fibre (7), in the shown example an entity of multiple glass fibres (7), two electrical conductors (14) and a jacket (23). Core (3) is here removed from coaxial cable (1).

The heating and deforming of spacers (6) takes place by advancing, in the shown example pushing, a first member (9) longitudinally inside cable (1) and inside shield (4), mis by means of an elongate second member (11). First member (9) here comprises a first central cavity (15) in which core (3) can move longitudinally. First member (9) here also comprises an electrical conductor (16) for electro-resistive heating of first member (9) so that spacers (6) can also be heated by means of first member (9). Second member (11) comprises for this purpose electrical conductors (18) for conducting electric current to first member (9). Second member (11) is tubular here and comprises a second central cavity (17) in which core (3) can again move longitudinally. Figure 4 shows a section of the coaxial cable (1) thus converted to a glass-fibre cable (2). Figure 5 shows the conversion of a coaxial cable (1) to a glass-fibre cable (2) according to a second embodiment of a method according to the invention. Core (3) is now not removed here but displaced radially to a non-central position inside cable (1) and inside shield (4). This takes place by means of third means (22) which are situated between first member (9) and second member (12) and comprise for this purpose a third cavity (24) in which core (3) can again move longitudinally. Third cavity (24) is curved such mat core (3) is guided to the outermost part of passage (8) as shown in figure 5. The fiictional resistance between second member (9) and the wall of passage (8) and me displaced core (3) is thus reduced.

Second member (12) can now be solid or, as in the shown example, comprise a passage (25) for passage of for instance a liquid or gas for heating, cooling or lubrication, or as in the shown example, for throughfeed of electrical conductors (18) for conducting electric current via electrical conductors (26) provided for this purpose in third means (22) to first member (9), in this case the electrical conductor (16) for electro-resistive heating of first member (9). Figure 6 shows a section of the coaxial cable (1) thus converted to a glass- fibre cable (2). An amplifier present in the network of which coaxial cable (1) forms part can now for instance be powered via the core (3), which is left in place, together with shield (4).

Figure 7 shows the conversion of a coaxial cable (1) to a glass-fibre cable (2) according to a third embodiment of a method according to the invention. A second member (13), here in the form of a pull cable, now serves to pull a first member (10) longitudinally inside the cable and inside the shield. Core (3) is removed beforehand, for instance by means of the first embodiment of a method according to the invention described above and shown in figure 3.

In other embodiments of a method according to the invention the dielectric is (also) heated by means of the core and/or the shield, for instance by means of realizing an electric current through the core and/or the shield. The at least partial softening and/or melting of the dielectric can thus be accelerated. The core can in principle also be removed after heating of the dielectric solely by means of the core. The temperature can also be measured at a location appropriate therefor inside the coaxial cable by means of a temperature sensor, and the measured value can be used to control the temperature at a location appropriate therefor in the coaxial cable. The process of softening and/or melting of the dielectric can thus be better regulated and controlled. The second member is preferably provided with a cover layer for the purpose of reducing the frictional resistance between the second member and what surrounds it, the wall of the passage and/or the core. The maximum length of the coaxial cable to be converted can thus be increased.

Figure 8 shows a device according to the invention comprising storage means (19), here in the form of a reel, for at least partially storing the second member. The device here also comprises drive means (20) for driving the second member as well as control means for controlling drive means (20). The force exerted on second member (11,12), and thereby the force exerted on first member (9), as well as the speed at which the first member moves through coaxial cable (1), can thus be better regulated and controlled. The device also comprises guide means (21) for guiding second member (11,12) between drive means (20) and coaxial cable (1). Such a guiding is particularly important in the case second member (11,12) moves the first member (9) by means of pushing.

It will be apparent mat the invention is not limited to the given exemplary embodiments but mat diverse variants and combinations obvious to a skilled person are possible within the scope of the invention.