DE3241500A1 - Cable containing at least one conducting element in a protective covering - Google Patents

Abstract

In a cable containing at least one conducting element in a protective covering, in particular optical cable, the protective covering contains cavities into which a substance has been introduced which is capable of swelling in the event of ingress of moisture and which contains salts of alginic acid. To solve the problem of achieving a rapid plug formation to obtain longitudinal water tightness and also of preventing a gradual continued creep of the moisture, it is proposed that the substance which is capable of swelling is composed of a mixture of water-soluble salts of alginic acid with cation-forming organic or inorganic salts.

Description

Cable with at least one arranged in a sheath

conductive element The invention relates to a cable im Such cables are generally known.

The swellable substance is introduced so that in the event of water penetration at any point on the cable a further penetration de. Water lengthways of the cable is prevented. The water causes an increase in volume of the swellable Substance which as a result completely fills the cavity inside the envelope and such a plug forms a sealing plug in the longitudinal direction.

Achieving longitudinal watertightness by means of swellable substances is particularly suitable for optical cables with optical waveguides loosely guided within the sheath advantageous because the relatively small amount of the swellable substance does not restrict the freedom of movement of the optical waveguides too much.

A rapid clogging effect on ingress of water was with use known swelling substances, however, only possible if a relatively large volume fraction the cavity was filled with swellable substance. But then there was a certain one Peeintrachtigung the optical properties of the fiber optic cable cannot be avoided. Gradual "creeping on" of the moisture in the ling direction was also possible of the cable cannot be prevented.

The invention is based on the object of a swellable substance to find, which increases the volume to a great extent and quickly when exposed to water and also prevents the moisture from gradually creeping on.

The solution is achieved by the features characterized in claim 1. Advantageous developments of the invention are identified in the sub-claims.

Algin> ,: iure is a polysaccharide containing carboxyl groups.

It is insoluble in water, but swells considerably in water.

The potassium, sodium, ammonium and magnesium salts of alginic acid are water-soluble, preserve the salts with calcium, aluminum and most others Bases are insoluble in water.

All derivatives of alginic acid, salts or esters, which are called alginates are designated, but swell strongly under the action of water.

Alginic acid and alginato are particularly useful for optical cables Advantage that they swell quickly in gel form with a considerable increase in volume, so that if water gets into the part of a cable, a blocking Plug forms. Since the entsitehencle plug is relatively soft, will be the optical properties of the optical fibers despite strong swelling of the introduced Substance hardly noticeably influenced, so that the operability of the cable is preserved remain.

Another advantage of the alginate and the alginates is their non-toxicity. Cables filled with these substances can be used during manufacture and by the user be handled without any danger.

Of the swellable substance according to the invention, only 1-20 % of the void volume of the envelope is filled. These small amounts can not to hinder the free movement of the optical fibers within the envelope. The more swellable substance is introduced, the faster it can penetrate to be blocked by water. Even minimum quantities of 1% still allow, however after a shortened time, the blocking effect. For shares of more than 20 96 exists the risk of an impermissible obstruction of the free movement of the fiber optic cables.

Particularly beneficial results, namely rapid plug formation without hindering the mobility of the optical waveguides, were filled with fillers from 6 - 10 96 achieved.

A disadvantage of conventional swelling powder is that the formed Dissolve plugs especially with pressurized water, so that the water gradually in Longitudinal direction of the cable penetrates further. This disadvantage is alleviated by the invention largely avoided, dissolution of the plug is completely prevented if this is insoluble in water according to the invention. The insolubility can except through Use of alginic acid or the water-insoluble derivatives also through mixing in itself water-soluble components can be achieved that a enter into a chemical reaction through which in water-insoluble plug arises. According to the invention, such mixtures consist of water-soluble salts the organic or inorganic salts which form alginic acid and cations. the powdered starting materials are mixed and then introduced into the cable sheath. The chemical reaction only takes place when there is access to water and very quickly. Particularly beneficial results have been obtained with a mixture of sodium alginate and calcium citrate achieved. These mixtures can also be stored in a humid atmosphere, since only the Adding water in liquid form causes a chemical reaction.

In certain skins, e.g. when touching the one proposed according to the invention Substances with dirty water, there is a risk that these substances gradually become organic decompose, especially when exposed to bacteria. To take this risk with you To exclude safety, it can be advantageous to add a preservative; are, for example phenol derivatives. One must choose such preservatives, which do not attack the cable structure elements.

The volume proportions of the mixture components by no means need im optimal stoichiometric ratio to be measured. The proportion of water-soluble Alginate is advantageously 55-90%, the proportion of the cation-forming salts is 10 - 45 96.

In the case of zi small amounts of cation-forming salts, in particular The length of the white water in the cable is too large, as there is a solid plug forms too slowly. Too large a proportion results in clogging, which is because of the too high Content of soluble constituents does not prevent the water from gradually penetrating; can prevent. A proportion of cation-forming has proven to be advantageous Salts, especially calcium citrate, of 25 - 35%.

7 claims 4 pages description

Claims (1)

P a t e n t a n s p r ii c h e 1. Cable with at least one, in a conductive element arranged in a sheath, in particular an optical cable, wherein There are cavities within the egg shell, into which one in the event of moisture ingress swellable substance is introduced, characterized in that the swelling Substance alginic acid and / or its salts or esters contains 2 cables according to claim 1, characterized in that the swellable substance consists of a mixture of water-lc'-lichen Salts of alginic acid with organic or inorganic salts which form cations consists. 3. Cable according to claim 2, characterized in that the cations The forming salt is a calcium salt, especially calcium citrate. 4. Cable according to claim 2 or 3, characterized in that the water-soluble Alginic acid salt is a sodium alginate. 5. Cable according to one of claims 2 to 4, characterized in that that the proportion of the water-soluble alginate 55-90%, preferably 65-75, and that of the cation-forming salt 10-4596, preferably about 25-35% by weight of the swellable substance. 6. Cable according to one of claims 1 to 5, characterized in that that the ileal spaces at least 1 96, at most 20 96, preferably 6-10% of the swellable Contain substance. 7. Cable according to one of claims 1 to 6, characterized in that that a preservative is added, for example a phenol derivative.