DE1029063B - Method for lining tubular, especially difficult to bend waveguides with a thin, dielectric layer - Google Patents

Description

The invention relates to a method for lining tubular waveguides with a thin, dielectric layer. Such waveguides are used to carry electrical alternating currents highest frequencies over considerable distances such as B. in radio frequency connections within a city.

There are already methods of lining such waveguides with a dielectric layer became known, but these are relatively flexible pipes that one z. B. can still wind up on larger cable drums. In such flexible pipelines it is known the wetting of the inner wall of the pipe, i.e. the lining, to be achieved by the pipe conductor from a cable drum is wound onto a second cable drum to form a slack and the liquid dielectric is in the sag, filling the pipe cross-section through the Pushes the pipeline through. This known method cannot be carried out with non-flexible pipes. It also has deficiencies in preventing undesirable oxidation of the wetting layer as well as with regard to the relatively large amount of time required for the hardening of the wetting layer.

For lining tubular waveguides, especially those that are difficult to bend, with a thin, dielectric layer is specified according to the invention, a method in which the preferably vertically arranged waveguide over its entire length with a loosened and possibly preheated dielectric is filled and then emptied again, depending on the type of the Dielectric containing solution, the wall of the conductor is heated or not heated, both at the filling and emptying the solution is moved by means of an inert gas, and that after emptying the dielectric layer produced by wetting the inner wall of the waveguide by blown through it inert gas brought to a temperature favorable to drying and / or polymerization will.

With reference to the drawing, which shows an embodiment of the system, by means of which the method can be carried out, the invention will be explained in more detail.

It is known in such a system, which serves to wet a metal surface, the metal surface first to be chemically cleaned so that the dielectric layer to be applied, the z. B. made of polyethylene can exist, adheres well. Such chemical cleaning can e.g. B. by successively application of high-temperature steam

procedure

for lining tubular,

especially difficult to bend

Waveguides with a thin,

dielectric layer

Applicant:
International

Standard Electric Corporation,
New York, NY (V. St. A.)

Representative: Dipl.-Ing. H. Ciaessen, patent attorney,
Stuttgart-Zuffenhausen, Hellmuth-Hirth-Str. 42

Claimed priority:
Great Britain 9 February 1956

John A. Leno, Walter E. Simpson

and Paxton D. Wilbraham, London,

have been named as inventors

temperature, acid and distilled water for washing out.

The drawing shows at 1 a container that is filled with the dissolved dielectric such. B. a solution of Polyethylene is filled in xylene with the exclusion of air and which has a heater at 2 that controls the temperature the solution keeps at about 90 to 100 ° C. The already chemically cleaned pipe 3, which leads to the the actual waveguide lined with a thin dielectric layer is to be formed, is arranged approximately vertically above the container 1 and with it through the supply pipe 4 via the Valve 5 connected. From the upper end of the pipe 3, a pipe 6 continues, in which an indicator at 7 for the level of the liquid is built in. While the supply pipe 4 almost to the bottom of the container 1 is enough, the pipe 6 is connected to the automatic valve 8 and the valve 9 Space of the container 1, which is located above the surface of the solution reservoir.

The inert gas necessary for the process, such as. B. nitrogen flows into the system via the pipes 10 and 11 a. Between the automatic valve 8 and the liquid level indicator 7

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a branch pipe 12 with the vent valve 13 is arranged. At 14, the container 1 still has an auxiliary pipe with valve 15. The same pipe contains the supply pipe 4 at 16 with the valve 17. The tube 3 is heated over its entire length by means of heating elements arranged at 18.

The lining of the pipe 3 is now carried out in such a way that with closed valves 15 and 17 and When the valves 5 and 9 are open, the inert gas, that is to say preferably nitrogen, is injected through the pipe 11 and presses on the surface of the solution in the container 1, causing it to pass through the tube 4 in the tube 3 is pushed up until the liquid level indicator 7 is recognized that the tube 3 with Solution is filled. The solution, which has already been heated to 90 to 100 ° C in the container 1, has due to the filling of the tube 3, the inner wall of which is completely wetted and is kept at a temperature of 120 ° C by the tube 3 The pipe wall held is heated until the temperatures in the pipe wall and the solution have adjusted to each other. Here, the valves 5 and 9 are kept closed. If the If heat has been equalized, the valve 5 is opened so that the solution runs out of the tube can, while with the valve 13 closed, the automatically operating valve 8 to the nitrogen gas The upper part of the tube 3 gives access so that the gas follows the solution flowing downwards. The speed at which the solution flows off depends on the viscosity of the Solution and the degree of opening of the valve 5, but also on the pressure of the nitrogen gas, which through the automatic valve 8 can be kept at a certain height.

Since the thickness of the lining of the pipe 3 or. in other words, the thickness of the dielectric Layer on the inner wall of the tubular waveguide has a significant influence on the transmission of high frequency waves, care must be taken to keep the speed at which the solution drops from the pipe 3, is not only always the same, but also during the drop in the solution in the Tube 3 can be regulated. The automatic valve 8 serves this special task.

When the solution has run out of the tube 3, the valve 5 is closed and the valve 17 is opened. The nitrogen gas then flowing through the pipe 3 from above drives the evaporated residues of the Solvent, so for polyethylene z. B. xylene, through the tube 16 from. The nitrogen gas is used at this point within the pipe 3 also to the pipe, the heater 18 of which has already been switched off, to cool and also protects the thin dielectric now adhering to the inner wall of the pipe Layer of oxidation. As far as that from the entry of the solution into the pipe 3 is still present in this pipe If the temperature is sufficient, the polymerization of the thin dielectric layer can thereby be accelerated will. If necessary, the heater 18 can also be used to accelerate the Polymerization appropriate temperature can be maintained in the tube 3 until the dielectric Layer is hardened.

The method according to the invention can also be carried out if the inner wall is covered with a metal such as B. cadmium by plating, vapor deposition or the like. B. is occupied with a thickness of 0.1 μ or when an oxide film has been formed on the metallic inner wall.

The solution to be used with advantage for the process contains 15 parts by weight of polyethylene a molecular weight of about 20,000. Polystyrene can also be used in solution of toluene, with however, other solution and processing temperatures are required.

The process allows the production of such dielectric linings even of greater thickness, such as B. 12 or 25 μ, if the viscosity of the solution is adjusted accordingly or the method repeated more often if the viscosity is relatively low.

Claims (7)

Claims 1. Method for lining tubular, particularly difficult to bend waveguides with a thin, dielectric layer, characterized in that the preferably perpendicular arranged waveguide over its entire length with a loosened and possibly preheated Dielectric is filled and then emptied again, depending on the type of the Dielectric-containing solution, the wall of the conductor is heated or not heated that Both during filling and emptying the solution is moved by means of an inert gas and that after emptying the dielectric generated by wetting the inner wall of the waveguide Layer by blowing through inert gas on one of the drying and / or polymerization favorable Temperature is brought. 2. The method according to claim 1, characterized in that to achieve a uniform Thickness of the dielectric layer is the speed at which the pipe, which is wetted on the inner wall, is emptied via the inert gas flowing in is controlled pneumatically by an automatic reducing valve. 3. The method according to claim 1 and 2, characterized in that the thickness of the individual dielectric Layer is influenced by adjusting the viscosity of the solution. 4. The method according to claim 1 to 3, characterized in that thick dielectric layers can be generated by repeating the process. 5. The method according to claim 1 to 4, characterized in that nitrogen is used as the inert gas will. 6. The method according to claim 1 to 5, characterized in that that the dielectric layer consists of polyethylene, which is applied dissolved in xylene will. 7. The method according to claim 1 to 5, characterized in that the dielectric layer consists of Polystyrene, which is applied dissolved in toluene. 1 sheet of drawings © 809 508/244 4.58