DE1286605B - Process for manufacturing a switch tube with a spark gap - Google Patents

Description

The invention relates to a method for producing an interrupter with spark gap and with a metal layer applied to the ignition electrode, z. B. titanium layer in which an active gas, e.g. B. hydrogen is absorbed, the when operating the interrupter becomes free during ignition and the discharge in the spark gap initiates, the discharge vessel for degassing during the manufacture of the tube its internal components are baked out to remove the gases that are released is purged with the active gas and then that containing the active gas Discharge vessel tightly closed and cooled to a preselectable temperature as a result of which the metal layer becomes saturated with the active gas.

Interrupter tubes with spark gaps are known, the two one main spark gap forming main electrodes and removes two from them that delimit an ignition spark gap Contain ignition electrodes in the form of metal-ceramic interfaces, whereby the metal, for example titanium, loaded with an active gas, for example hydrogen is. When a voltage pulse is applied to the ignition spark gap, the generated heat releases the absorbed gas. The gas is in the ignition spark gap ionized and then injected into the main spark gap as a highly ionized plasma, whereby the flashover of the main spark gap is initiated.

During the usual manufacturing process for such interrupters are first the individual; Assembled parts. For degassing the inner The discharge vessel is then installed at elevated temperatures of z. B. 400 ° C and more baked out. Thereupon the released during the degassing Gases expelled by flushing the discharge vessel with the active gas, whereupon the discharge vessel is tightly closed and cooled. The in the discharge vessel remaining part of the active gas is absorbed by the metal layers of the ignition electrodes. Preferably, that which remains in the discharge vessel when it is closed Amount of active gas so large that a preselected pressure in the discharge vessel after cooling prevails.

The object of the invention to improve such interrupters is solved in that in the method described above, the metal already before pretreated at least once with the active gas after heating during the degassing process and becomes saturated.

The particular advantage of this measure is that it thereby the absorption capacity of a metal such as titanium, hafnium, zirconium or thorium, compared to an active gas such as hydrogen, is increased significantly. One takes suggest that this is due to the removal of surface oxides by absorption and subsequent Removal of the active gases during baking and the formation of cracks and openings in the surface are due to this pretreatment. The more often the pretreatment according to the invention, the greater the absorption capacity is performed, d. H. the more often it is alternately absorbed and desorbed.

The pre-treatment of the metal is preferably carried out by heating it carried out in the presence of the active gas and continued until saturation, the metal with the active one before it is installed in the discharge vessel Gas can be pretreated and saturated.

In a preferred embodiment, it is removed from the ignition electrode an additional amount of the metal of the metal layer is provided as a supply, the remains almost unchanged during the operation of the discharge vessel. Is through Operation of the interrupter the amount of active gas absorbed on the ignition electrode consumed, then by heating and cooling the interrupter, part of the vom additional metal supply of absorbed gas transferred to the ignition electrode and this significantly increases the service life of the interrupter.

The invention is explained in detail below with reference to the drawing described.

An interrupter with spark gap contains a according to the drawing gas-tight discharge vessel 1 made of insulating material in which two main electrodes 5 and 6 are arranged, which delimit a main spark gap 7. The main electrode 5 has a central hole, which is in a section as the main spark gap cone 9 which becomes wider towards the end is formed and an ignition electrode arrangement 10 records.

The ignition electrode arrangement 10 contains a ceramic cylinder 14 which is covered with a thin layer 15 of a gas-storing material such as titanium, hafnium, zirconium or thorium. The layer 15 is coated with an active gas, e.g. B. hydrogen loaded. After the layer 15 has been applied, a notch 16 is cut in the entire circumference of the ceramic cylinder, so that the metal is removed at this point and an insulating ceramic layer comes through. The position of the notch is chosen so that after the ignition electrode arrangement 10 has been fitted inside the electrode 5, the transition point of the cylindrical part 8 of the central bore to the conical part 9 is just above the upper edge of the notch 16. The inner end of the ignition electrode arrangement 10 is covered with a metal cap 17 which is in good electrical contact with the layer 15. A wire 18 is soldered or otherwise fastened to the metal cap 17, which wire is led to the outside through the ceramic cylinder 14 and is used to apply the ignition voltage.

The electrodes 5 and 6 are made of copper, which is almost free of gaseous Is impurities, including those that break down to form gaseous products can. The copper is subjected to a standard test and for this purpose in an evacuated one Test chamber with a capacity of a few liters and by repeated arcing strongly subject to erosion. This happens e.g. B. with a voltage source commercially available Power at a current of 100 amps or more, with the pressure in the test chamber not significantly above its initial value for some periods after arcing may increase even if the initial pressure is 10-5 mm Hg or less and neither Getter pumps are still in place. This requirement can be expressed analytically by that the contact material contains less than 10-s atomic parts of all gases combined got to.

The other metal parts inside the housing need this strict Requirement not met because it does not come into contact with an electric arc and therefore do not represent a potential source of vacuum spoilage gases. Nevertheless they should also be made of completely oxygen-free metal, because the interrupter is manufactured at higher temperatures with hydrogen and, as it should be avoided, oxygen at higher temperatures as an impurity in a substance subjected to a hydrogen atmosphere will.

To produce the interrupter according to the drawing, the individual Parts prepared and put together in any suitable way.

It has been found that when using an elemental metal for the layer 15 although limited amounts of active gas are absorbed, but that the absorbency is significantly increased if one is before the final Bakeout and loading uses a layer instead of an elemental metal that already consists of gas-laden metal. That's partly due to the elimination of Surface oxides from the elemental metal during the previous absorption and removal of active gas during bakeout, but sometimes it also stirs from the formation of small cracks or openings in the metal during the cyclical Repetition of this pretreatment, which is also carried out during the absorption process Can absorb and absorb gas. In other words, through a certain amount of titanium is set to a certain amount of absorbable hydrogen Maximum increases, the more often the alternating absorption and removal of active Gas is repeated or the more often the resulting titanium hydride in the presence of hydrogen is alternately heated and cooled.

Accordingly, the layer 15 before the final evacuation and loading at least once, but preferably several times, treated with hydrogen ("Before" -loaded).

During its manufacture, the interrupter is first fully assembled, in an atmosphere of active gas, e.g. B. hydrogen, arranged in a soldering furnace and heated to an elevated temperature of about 850 ° C. Be at this temperature Apply the required soldering points with the help of a suitable soldering agent. During the heating process, but before the soldering points are made, the loaded Material releases some hydrogen, which together with the hydrogen in the soldering furnace each other atmosphere or all adsorbed by the heat from the internal parts the interrupter replaced dissolved gases. Because the hydrogen pressure inside the interrupter is the same as that inside the soldering furnace and the temperature is also known also a known amount of hydrogen trapped in the interrupter. If the Soldering is finished and the gas is sealed in the tube, the tube becomes slowly cooled, the hydrogen trapped in the housing from the material the layer 15 is absorbed. Because the amount of hydrogen needed to properly reduce of the pressure must be absorbed is known, the necessary amount of the Material of the layer 15 are predetermined. In particular, there is so much of that Material provided that the hydrogen pressure at room temperature is less than 10-5, is preferably about 10-7 torr.

Due to the use of one already loaded before the evacuation Layer, e.g. B. titanium hydroxide, it is possible to use very large switching tubes with relatively produce small amounts of titanium or other active metal. Large layers of titanium namely, are expensive, thick on the other hand inexpedient, since they have a bad effect on the operating properties the interrupter can affect. The higher absorption rate that the invention is achieved, also allows the capture of larger ones, for a long life of the Tubing sufficient amounts of hydrogen without reducing the partial pressure of hydrogen becomes too big inside the tube.

According to a further feature of the invention, a cylindrical component 25 is provided within the interrupter, which is protected from the main spark gap by a ring 26. On this cylindrical member 25 , some metal hydride is deposited, e.g. B. in the form of powder 27, which is enclosed in a network 28. This network can, for. B. consist of molybdenum. Despite the use of a “pre-loaded” layer, it may be inexpedient to provide as much active metal in layer 15 as is necessary for suitable absorption of all of the gas present in housing 1. The additional material 27 also absorbs hydrogen. With suitable dimensions of the discharge vessel and of the metal, the pressure can be reduced to the order of magnitude of 10-7 Torr.

The presence of the active metal 27 is also advantageous if the arc between the main electrodes is to be ignited or extinguished very often or almost continuously. During the frequent switching, the hydrogen of the layer 15 can be so consumed that it is no longer sufficient for the correct ignition of the main discharge.

If this is the case, the interrupter is simply up to an elevated temperature, e.g. B. over 600 ° C when using titanium and hydrogen, heated, the gas absorbed in the powder 27 flows out into the discharge vessel. When it cools down, the metal of layer 15 absorbs part of this gas and is refilled in this way. The cylindrical shape of the component 25 shown in the drawing is only intended to serve as an example. In principle, it is sufficient to provide an additional amount of gas-absorbing metal at some relatively cool point within the interrupter.

The ignition voltage is placed between the electrode 5 and the wire 1.8 . The main voltage lies between a carrier plate for the electrode 5 and a carrier plate for the anode 6. Due to the high vacuum inside the vessel 1, very high voltages can be applied to the electrodes 5 and 6 without the main spark gap breaking down. When an ignition pulse is applied via the wire 18, a spark discharge is ignited via the notch 16, which heats the metal layer 15 so that hydrogen flows out into the vicinity of the arc. Magnetic forces drive the resulting hydrogen plasma into the main spark gap and thus initiate the main discharge.

The pretreatment of the layer 15 can also take place before this layer is applied to the ceramic cylinder 14. In such a case, the titanium hydride is evaporated onto the ceramic cylinder under vacuum and heated in a hydrogen atmosphere to compensate for the losses during the evaporation. On the other hand, the elementary titanium can also first be applied to the ceramic cylinder, after which the entire arrangement is then subjected to the described pretreatment.

Claims (4)

Claims: 1. A method for producing a switching tube with Spark gap and with a metal layer applied to the ignition electrode, e.g. B. titanium layer in which an active gas, e.g. B. hydrogen is absorbed, the when operating the interrupter becomes free during ignition and the discharge in the spark gap initiates, the discharge vessel for degassing during the manufacture of the tube its internal components are baked out to remove the gases that are released is purged with the active gas and then that containing the active gas Discharge vessel tightly closed and cooled to a preselectable temperature is, whereby the metal layer is saturated with the active gas, d u r c h characterized in that the metal is at least prior to the bake-out during the degassing process is pretreated and saturated once with the active gas. 2. The method according to claim 1, characterized in that the pretreatment of the metal by heating it made in the presence of the active gas and continued until saturation. 3. The method according to claim 1, characterized in that the metal of the metal layer pretreated with the active gas before installation in the discharge vessel and becomes saturated. 4. The method according to any one of claims 1 to 3, characterized in that that removes an additional amount of the metal of the metal layer from the ignition electrode is provided as a supply, which almost during the operation of the discharge vessel remains unchanged.