DE1931332A1 - Process for the production of a sintered glass base for high vacuum tubes - Google Patents

Description

107/68 Sta

Public limited company Brown, Boveri & Cie., Baden (Switzerland)

Process for the production of a Sirrjsrglasfusses for high vacuum tubes

The invention relates to a method for producing glass feet especially for high vacuum tubes where metallic Bushings and a glass tube intended as a pump tube secured against displacement in one. Sintered form received and in it be sintered together with glass powder to form a tubular base.

With the help of such known methods can be with metallic

Plate feet provided with bushings can be made of tempered glass without any major outlay on equipment. To prevent that If the glass tube to be sintered into the base of the plate is deformed during the process, a metal wire helix is inserted into the glass tube used, which supports the inner wall of the pipe. After sintering, the wire helix can be removed very easily.

This known method is for example in the -.uch. Von W. Espe "Material science of high vacuum technology "Vol. II, VEB Deutscher Verlag

009828/0881

BATH ORIGINAL

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der Wissenschaften, Berlin I960 (see especially pages 419-420) in detail described. Disadvantages of this known method are that this wire helix can only be used once, because it is deformed when it is removed from the glass tube and that the inner wall of the pump assumes the outer shape of the helix, which leads to leads to an increase in the flow resistance during pumping. The invention is now based on the object of eliminating these disadvantages and for a sintering process for the production of glass feet

sen especially for high vacuum tubes to specify means to support the inner wall of the glass tube serving as a pump tube can be used for multiple, sinterings.

The method according to the invention is characterized in that a metal mandrel is received in a central recess of one sintering mold half, which is arranged with a free part slightly tapering towards its end inside the pump tube in such a way that it prevents deformation of the pump tube inner wall, the thermal The expansion coefficient of the material of the metal mandrel is greater than that of the glass used for the pump tube.

The invention is illustrated by the figure showing an example, explained in detail.

The figure shows a sintering mold made of graphite, prepared for sintering, with a lower and upper half 1 and 2, respectively

00 9828/0881

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Bohrungen.aufhaben, in which metallic leadthroughs 3 were added are. In a central bore of the lower sintered mold half 1, a graphite sleeve 4 is used, in which a glass tube 5 is added, which serves as a pump tube in the finished tubular foot,

while in a central hole of the upper sintering mold a metal mandrel 6 is inserted, which tapers towards its free end and which protrudes into the glass tube over the? N ge ™ extends the entire length. The metal mandrel 6 must be made of one material exist, the thermal expansion coefficient of which is greater.

ser is than that of the glass material used for the pump tube, or advantageously 1.2 to 4 times the same.

In the example described, the metal mandrel 6 consists of liikkel and is provided on its surface with a carbon layer produced by carburizing. The one from Sinter— form enclosed space between the Durch.führur.jsbolzen 3 and the ι Pump tube 5 is filled with a glass powder 7.

The sintered mold loaded in this way is now heated as usual by high frequency under a protective gas atmosphere for a certain time at a specified temperature. The glass powder 7 sinters with the pump tube 5 and the bushings 3 to form a compact, vacuum-tight body. During the sintering process , the pump tube 5, which is plastic at the sintering temperature, nestles against the metal mandrel 6 , as a result of which a smooth inner surface of the tube is achieved in the finished tube base.

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The carbon layer on the surface of the metal mandrel prevents it each sticking to the inner surface of the pump tube 5, so that after the sintering and cooling or opening of the sintering mold the metal mandrel 6 by turning it slightly from the now finished exhaust tube 5 can be removed without difficulty.

828 / 081.1. BATH ORIGINAL

Claims (1)

- 107/68 Patent claims: 1.) Process for the production of glass feet, especially for high vacuum tubes, in which metallic bushings and a glass tube intended as a pump tube secured against displacement in a sintered mold taken up and in it with glass powder to a Rb'hrenfuss be sintered together. characterized in that in a g a metal mandrel (6) is received in the central recess of one sintered mold half, with a slightly tapering towards its end free part d-erart is arranged within the pump tube (5), that it prevents the deformation of the pump channel wall, the thermal expansion coefficient of the material of the metal mandrel (6) is larger than that of the glass used for the pump tube (5). 2 »The method according to claim 1, characterized in that the thermal expansion coefficient of the material of the metal mandrel (6) is 1.2 ~ to -4 times the expansion coefficient of the glass used for the pump tube (5), _{or the like} 5ο method according to claim 2, characterized in that the K- ', alldom (β) consists of nickel =, θ 8S ^ / 0QU
BATH ORIGINAL. 6 - 107/68 4 .. Method according to claim 1 or one of the claims 2 or 2, characterized in that the metal mandrel (6) has a coating made of carbon. Public limited company BROWK, BOVERI & CIE, <ί β "" - ? J ξ »-% w> ε &: ^ y ΐ?