DE1071803B - Cable termination for electrical cables - Google Patents

Description

GERMAN

The invention relates to a cable termination for electrical cables of the type having a centrally located Have conductors and an outer jacket, both of which are electrically conductive and heat-resistant. as well as an intermediate mineral insulation filling the annular space between them. The open end of the cable is closed using ceramic insulation.

An unpleasant property of the cables of the type mentioned is that the insulating material, usually high Magnesium oxide, easily absorbs moisture, so when this happens the resistance of the insulation falls off quickly.

For example, if the cable is intended for it in sales rooms, warehouses or in public buildings to be used where the highest possible fire resistance is of the utmost importance, or for example for ignition devices for low and high voltage ignition systems in jet engines and gas turbines or other explosion engines or power plants, where the preservation of the insulating properties of the material between the conductor and the jacket is particularly important, the resistance of the insulation must not be decrease due to the influence of moisture. Accordingly, the main object of the invention is to ensure that that moisture absorption is perfectly prevented by the insulating material of the cable.

According to the invention, the cable termination is made of ceramic insulation for the types described at the beginning Cable provided on a relatively short piece, with an additional seal made of glass or a similar material with a relatively high melting point between the jacket and Conductor is introduced as moisture insulation. This glass seal is between two stoppers made of ceramic material, the inner one against the outer end face of the mineral insulation butt, arranged and as a ring with an H-shaped cross-section formed, whose web is directed perpendicular to the cable core and both of which are directed perpendicular to the web Beam in close contact with the inner surface of the outer jacket or with the surface of the conductor of the cable.

The cable connection according to the invention is i-r reaches that moisture is not in such large quantities about the ceramic. Insulation to the hygroscopic insulation of the cable at any time can penetrate in order to reduce its insulating properties.

To solve this problem, other proposals have already become known. So was z. B. tried a cable termination with a plug made of insulating material, e.g. porcelain, 211 create the against penetrating moisture in the cable termination for electrical cables

Applicant:

Lodge Plugs Limited, Rugby, Warwick (Great Britain)

Representative: 'Dipl.-Ing. C. Stoepel, patent attorney, Landau (Palatinate), Am Schützenhof

Claimed priority: Great Britain dated. June 8, 1955

Maxey Hungerford Bland,

Grandborough, Rugby, Warwick (Great Britain) has been named as the inventor

sainmenwork with one postponed on the ladder Metal pipe on the one hand and a sleeve that extends over the plug and the outer jacket of the cable on the other hand should isolate.

However, practical experience has shown that it meets the highest possible requirements the moisture insulation is not sufficient, the seal merely by fitting in make metallic parts in or on the plug made of ceramic material.

The use of ceramic and glass to seal cables ends has also been proposed has been, however, this combination in itself also does not meet the high demands to be made The intended, in any case perfectly moisture-insulating effect can only be achieved by means of certain spatial configurations and assignments of these materials can be achieved.

In the embodiment of the cable termination according to the invention, the glass or a similar material is used with a relatively high melting point only melted down when the cable end is closed. Through the The web of the H-shaped cross-section of the glass seal achieves a perfect cross-section closure. The bars ″ of the H standing vertically on the footbridge offer a relatively large distance an equally perfect seal between the insert on the one hand and the metallic conductor or the metallic protective sheath on the other hand. The glass-based materials are, of course,

909 690/436

Claims (1)

U ' of course 'about those who isolate the electric current. Glass is preferred as a seal because it has electrically insulating properties of the insulator as a whole is not impaired and when hardening is able to achieve a hermetic To form a seal that is resistant to high temperatures. d. i.e., it has one higher melting point than the temperature under which the cable is to operate. When making the cable termination the glass is pressed together between the two ceramic insulators and is preserved in the process According to the shape of the two ceramic insulators, the already described H-shaped cross-sectional shape. This achieves, in addition to the other advantages, that between the two ceramic insulators not a leakage path for the electricity between the conductor under unfavorable operating conditions and the metallic outer sheath of the cable is created. Further features of the invention and the advantages achieved by the same emerge from the following Description of an exemplary embodiment of the subject matter of the invention shown schematically in the drawing. as With 10 is the centrally arranged electrical conductor of the cable, with 11 the sheath and with 12 the hygroscopic mineral. Insulation between the two is called. At the end of the cable both extend the jacket as well as the conductor beyond the I sol ation 12. In the so-formed ring-shaped Space is a pair of ceramic stoppers 13, 14 with an annular seal 15 in the form of a mass of glass, preferably designed as a coating or other material introduced between them. Optionally, the plug 13, 14 can also be through a single ceramic stopper can be replaced and in this case the glass seal 15 between ■ introduced this stopper and the outer end of the hygroscopic insulation. The glass seal 15 consists of a ring of H-shaped cross-section, one part 15a of which in is in close contact with the inner surface of the shell 11, while the other part 15 & in the same close contact with the circumference of the conductor 10 is and the web 15 c the possibility of formation a non-conductive connection between the jacket and the conductor at the joint of the adjoining 'Excludes isolator elements, preferably between the two ceramic plugs 13, 14 in this way the glass seal forms an insulating coating or mass that penetrates must be reached before the hygroscopic insulating compound 12 can be reached from the open end of the cable can. . The jacket 11 can be made of any metal, as can the conductor 10, whereby it It is desirable that the jacket have a coefficient of thermal expansion for a truly pressure-tight seal should have which is not less than that of the end insulator 13 or the seal 15, and that. the coefficients of thermal expansion of the conductor 19, the end insulator 13 and the seal 15 are essentially should be the same. If the jacket 11 is a commercially available chromium-nickel alloy, the end insulation 13 can be used on the other side the seal is also a commercially available one that is matched to the jacket in terms of its properties ceramic insulation may be provided. In this case, glass is a perfect pressure-tight seal 15, while the conductor 10 may be made of nickel iron of suitable composition to provide a To achieve expansion coefficient, which is similar to that of the ceramic material of the insulator 13. Under conditions of use in which the penetration of moisture must be prevented, without that it would be necessary to achieve a really pressure-tight seal, both the jacket as also the conductor of the cable made of a chrome-nickel alloy consist or made of copper. In order to achieve the seal in the illustrated embodiment, the magnesium oxide insulation removed to a suitable depth at the open end of the cable, whereupon an annular one Stopper 14 of the selected ceramic material is inserted onto which a certain amount of glass follows and then a second annular plug 13 made of ceramic material. The end of the cable will then heated to the necessary temperature to melt the glass, while the outer annular Isolator 13 is pressurized. The whole is then cooled, so that when the jacket 11 a has a higher coefficient of thermal expansion than the glass and the insulating plugs 13, 14, it is in one Relatively larger extent contracts and the stopper for all occurring in practice Encloses stresses tightly enough. Claim: Cable termination for electrical cables with a centrally arranged conductor and an outer one Jacket, both electrically conductive and heat-resistant, as well as an intermediate mineral insulation using ceramic insulation to terminate the open end of the cable, thereby characterized in that this is provided on a relatively short piece and in addition a seal made of glass or a similar material with a relatively high Melting point between the jacket and conductor is introduced as moisture insulation, this Sealing between two stoppers made of ceramic material, the inner against the outer End face of the mineral insulation abuts, is arranged and as a ring with an H-shaped cross section is formed, the web is directed perpendicular to the cable core and both of which to the web vertical bars in close contact with the inner surface of the outer jacket or with the surface of the conductor of the cable. Considered publications:
French patent specification no. T 115 385,
097 249; Belgian Patent No. 530 250;
U.S. Patent No. 2,676,197. 1 sheet of drawings © 909 690/436