SU871670A1 - Cathode unit and method of manufacturing the same - Google Patents

Abstract

1. A cathode assembly containing a preheater interposed with a core and a screen, whose surfaces facing the preheater are covered with a metal sponge with an insulating layer applied to it, in order to increase the durability of the cathode assembly between the side surface of the core and the preheater there is an insulating element made in the form of a metal tape with a metal sponge applied on it and an insulating layer and fixed on the core. 2, The method of manufacturing a cathode assembly according to claim 1, comprising the step of sequentially applying to the insulated surfaces a core, a screen and a metal tape of a metal sponge and an insulating layer, semi-thinned by a plasma method, characterized in that the insulating layer (L pressure layer is pressed at a specific pressure of 1, 5-5 t / cm.

Description

The invention relates to electronic engineering, in particular, to the design and method of manufacturing cathode assemblies of vacuum devices.

The known design of the end cathode assembly of indirect heating, in which a tungsten spiral heater is placed between the cathode core and a plate (screen), having the same shape as the cathode core. The core of the cathode and the plate are made of nickel alloy and fastened together by spot welding. To insulate the filament, the sides of the core of the cathode and the plate facing the heater are covered with insulating material.

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In the manufacture of such cathode | An insulating layer is deposited by a plasma method on the inner surfaces of the cathode core and the screen.

However, the disadvantages of this design and manufacturing method are the uneven distribution of temperature over the working surface of the cathode, since the dimensions of the preheater are made significantly smaller than the emitting surface of the cathode, in order to prevent the preheater from closing with the inner side surface of the cathode, and insufficient adhesion of the insulating layer to the surface .Sh core and screen.

Uneven heating of the cathode working surface and spalling of the insulating layer under mechanical loads reduce the durability of especially large cathode assemblies.

Also known cathode assembly containing a heater located between the core and the screen, the surfaces of which, facing the heater, are covered with a metal sponge coated with an insulating layer. The metal sponge provides a stronger bond between the insulating layer and the core of the cathode and the screen.

In the manufacture of the cathode assembly by this method, metal powder is applied first to the inner surfaces of the core-electrode and the screen, then it is sintered and an insulating layer is applied to the resulting sponge using the plasma method.

To prevent possible contact of the preheater with the core when the insulating layer is peeled off, the preheater is additionally isolated.

Such a cathode assembly and method. Its manufacture has the following disadvantages:

1) an increase in the size of the side surface of the node and time, readiness;

2) increasing the heat load on the heater,

3) in the presence of a sponge, the roughness of the insulating coating increases and the risk of spallation of the insulating layer increases under thermomechanical loads.

All of these shortcomings lead to a reduction in the durability of the cathode assembly.

The aim of the invention is to increase the durability of the cathode assembly.

For this purpose, in the cathode assembly containing a heater located between the core and the screen, the surfaces of which, facing the heater, are covered with a metal sponge with an insulating layer deposited on it, 50 th

between the side surface of the core and the preheater there is an insulating element, made in the form of a metal tape with a metal sponge applied on it and an insulating layer and fixed on the core. The tape is usually made of screen material and is shaped into the inner surface of a cathode core.

In order to increase the durability of the cathode assembly during its manufacture, including the steps of sequential deposition on the insulating surfaces of the core, screen and metal tape of a metal sponge and an insulating layer obtained by the plasma method, the insulating layer is pressed at a pressure of 1.5-5 T / cm. Pressing additionally increases the adhesion of an insulating material to a metal sponge, drastically reduces the roughness of the coating and reduces its friction with the preheater, which increases the reliability of the heat chain. Applying a specific pressure of crimping less than 1.5 T / cm is not enough, as the insulating layer and the metal sponge are incompletely shrunk. At a pressure of 1, T / cm, the shrinkage and above the surface roughness stabilize, the application of a pressure of more than 5 T / cm is impractical because of the possibility of deformation of the substrate material.

The drawing shows the end of the cathode node. The outer end of core 1 is covered with a metal sponge 2 and an emission coating 3 is applied to it. The inner end of core 1 and the outer end of screen C is also covered with a metal sponge 5 and an insulating layer 6 is applied to it. Between the insulating layers of core 1 and screen k there is an uninsulated one. the heater 7, the conclusions of the heat of which is conventionally not shown. To protect the preheater from closing with the inner cylindrical surface of the core 1, a metal tape 8 is attached to it. The metal tape on the placement side of the preheater is covered with an insulating layer, which 5 is also applied to a metal sponge.

The manufacture of the cathode assembly with an oxide sponge emitter was carried out as follows: Kern 1 of the cathode, made, for example, from a nickel outer end with nickel powder, and along the inner end face molybdenum. powder. The screen and the tape 8 made of nickel of the NPOE brand cover the side facing the heater 7 with molybdenum powder. Then the powders are burned to the substrates in the hydrogen furnace. An NB-3V emission grade is applied to the resulting nickel sponge, a coating of a triple carbonate of alkaline earth metals is coated, and an insulating aluminum oxide coating is applied to the molybdenum sponge. The emission and insulating coatings are applied by the plasma method. The molyblenum sponge is an insulated floor (a 100% coating is chosen to match the thermal expansion coefficients of alumina with a nickel substrate. The applied emission and insulating coatings are pressed at a pressure of 1.52 t / cm, while the roughness of the pressed surfaces does not exceed 2 microns. Then the cathode surface is installed first, an I tape was welded to the inner surface of core 1 of the cathode. Then an uninsulated heater 7 and a screen were inserted into core 1. The screen was welded to the core 1 of the cathode with a point contact Cooking. The use of the cathode assembly and the method of its manufacture provides, in comparison with the existing assemblies and methods, the following advantages: 1) uniform heating of the cathode and reduction of the heating time; 2) increase resistance to thermomechanical loads 3) increase durability.

Claims (2)

1. A cathode assembly comprising a heater located between the core and the screen, the surfaces of which facing the heater are covered with a metal sponge with an insulating layer applied to it, characterized in that, in order to increase the durability of the cathode assembly, between the side surface of the core and the heater an insulating element is located, made in the form of a metal tape with a metal sponge and an insulating layer deposited on it and fixed to the core. 2. A method of manufacturing a cathode assembly according to claim 1, including the steps of sequentially applying a core, screen and metal tape to a metal sponge and an insulating layer obtained by the plasma method on the insulated surface, characterized in that the insulating layer is pressed at a specific pressure of 1.5 ~ 5 t / cm ^{* 2} .