Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,...
Patent
1982-02-26
1985-11-19
Taylor, Dennis L.
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
294265, 156 48, 174 37, 405303, H02G 112
Patent
active
045538778
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for converting cables existing in the ground, in buildings, on free line sections between masts etc., into closed guiding tracks for reception of new conductors.
The provision of cables for transmission of telecommunication services is connected with high costs and the need of detailed planning as well as a high amount of labour force by the operation, as considerations have to be made with respect to existing pipelines, cables etc., buildings and traffic conditions.
By the change to transmission of telecommunication services through optical fibres, it will be common to put down in the earth a new system with cables based on this technique. A great deal of older cable types, such as telecommunication cables and coaxial cables, however, thereby will become redundant of use.
So far no method is known for the withdrawal of the internal conductors and insulation materials in such cables. By such a method already existing cables could be used as the cable mantle would serve as a guiding track for the new conductors which could be optical fibres or other conductors. Great savings as to time and also economy will be achieved.
Actual cables in this connection are coaxial cables and telecommuniction cables. Even if the coaxial cables formerly used and put down in the earth have different constructions, different electrical parameters and different reinforcement, the pipes and insulation material of the cables are substantially the same. The very first cables, however, had distance washers made of ebonite, whereas the neweer cables have distance washers made of polyethylene. As an example can be disclosed that a large coaxial cable with an internal diameter of 9.5 mm and a center conductor with a diameter of 2.6 mm, has distance washers with a thickness of 2 mm every 33rd mm. The telecommunication cable or twin set cable has a plurality of pairs with copper conductors usually insulated with paper, possibly with cotton.
For the removal of the conductor or conductors of those cables, the conductor or conductors as well as the insulation material may be transformed to free particles by a suitable method, the particles thereafter being removed by suitable means, or the insulation material of the cable may be dissolved or broken down and thereafter being removed by suitable means, whereafter the conductor/conductors may be withdrawn out of the cable pipe.
The method according to the invention therefore comprises removing the internal insulation material of the cable over a suitable length and withdrawing the conductor/conductors out of one end of the cable.
Removal of the insulating material may be performed by supply of a chemical solvent, e.g. xylene, copper ethylene diamin or an oxidizing agent, e.g. pressurized oxygen, from one end, thereby dissolving or breaking down the material.
In connection with a coaxial cable the chemical solvent may be introduced into the internal part of the cable pipe through a thin hose, the dissolved material thereby being transported back along the hose and out of the pipe. The center conductor hereby may be withdrawn as there will be a sufficiently large clearance between the center conductor and the coaxial cable pipe.
By another embodiment of the method according to the invention, heat is used to melt the insulation material in coaxial cables, the insulation material thereby being transformed to a coating substantially continuosly provided on the internal wall of the cable pipe. The heat for melting the insulation material may be supplied by means of a suitable heat element guided on the center conductor of the coaxial cable, the element being supplied with electrical energy by the center conductor, the outer conductor of the cable and/or a pushing hose provided around the core, which hose forces the element through the length of the cable pipe. Heat may also be supplied by applying electrical potential to the center conductor and/or the outer conductor, the insulation material thereby being melted by the heat developed from the electrical resistance.
REFERENCES:
patent: 2731738 (1956-01-01), Kossa
patent: 3132415 (1964-05-01), Johnson et al.
patent: 3290194 (1966-12-01), Gillemot
patent: 3661358 (1972-05-01), Dill
patent: 4018058 (1977-04-01), Eichenseher et al.
patent: 4197628 (1980-04-01), Conti et al.
patent: 4281444 (1981-08-01), Smith
patent: 4372988 (1983-02-01), Bahder
Optical Fiber Cable Installing Technique in Underground Plant, Japan Telecommunication Review, Jul. 1981, pp. 261-270.
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