US2089541A

US2089541A - Electrode lead-in for metal vacuum vessels

Info

Publication number: US2089541A
Application number: US749984A
Authority: US
Inventors: Dallenbach Walter
Original assignee: Individual
Current assignee: Individual
Priority date: 1933-10-30
Filing date: 1934-10-25
Publication date: 1937-08-10
Anticipated expiration: 1954-08-10

Description

Aug. 10, w DALLENBACH ELECTRODE LEAD-IN FOR METAL VACUUM VESSELS Filed Oct. 25, 1934 \NVENTOR 6Pcer DHenbach ATTORNEYS Patented Aug. 19 37 ELECTRODE LEAD-IN FOR METAL VESSELS vAoUUM Walter Diillenbach, Berlin-harlottenburg, Germany Application October 25, 1934, Serial No. 749,984

In Germany October 30, 1933 7 Claims.

sleeve is sintered at high temperature, a vacuumtight connection is effected between said sleeve and said plug, on the one hand, and between said sleeve and the tank, on the other hand.

It is very difficult to obtain a reliable electrode lead-in for vacuum discharge apparatus with metal tanks, particularly if such tanks are subjected to treatment at 300 to 400 degrees for permanently separating them from the vacuum Various solutions of the problem have already been proposed and are substantially satisfactory with regard to reliability. However, the existing lead-ins require extra supporting means for the electrodes whose weight is considerable, particularly for heavy currents. The vacuum-tight sealing means themselves cannot support the electrodes, and it is obvious that the initial cost of the lead-in is much increased by the extra supporting means.

It has also been proposed to provide an insulating member of refractory material which is connected to the vacuum tank and directly supports the weight .of the corresponding electrode. However, it has not been possible heretofore to effect a connection between the insulating member and the electrode, and the wall of the tank.

which is permanently vacuum-tight and, at the same time, able to support the weight of the electrode, so that connections including an insulating member of the kind referred to, had to be abans doned notwithstanding their simplicity and cheapness.

Ihave found that the failure of the said leadins is due to the use of unsuitable materials and unsuitable connecting means.

According to my invention, areliable and highly vacuum-tight lead-in is obtained by utilizing the sintering of the insulating member for making the connection between the electrode and the member on the one hand, and the member and the wall of the tank, .on the other hand, or by obtaining the connection through the medium initial product being normally talc.

of a glass or enamel melt whose heat-expansion coefficient is substantially equal to that of the material of the insulating member. The areas of the faces by which the parts are connected, are made so large that the mechanical stresses from the weight of the electrodes are taken up without extra. supporting means for the electrodes.

Thorough investigation has demonstrated that in the manner described an electrode lead-in is obtained in which the weight of the electrodes is whose heat-expansion coeflicient is substantially equal to that of the insulating member, and the melt. However, the heat-expansion coeflicient of the metalparts may be somewhat higher than that of the insulating member and the melt, as this brings about shrinking which is favorable for the tightness and strength of the connection.

As the connection by sintering of the insulating member, or by glass or enamel melt, is made at very high temperatures, the electrode lead-in is absolutely resistant to the aforesaid heating to 300 to 400 degrees for removing the gas from the tank.

' In the accompanying drawing, three types of lead-ins embodying my invention are illustrated by way of example.

In the drawing Fig. 1 is a section of a lead-in whose insulating member is sealed against leakage by sintering of the member onto the metal parts, and

Fig. 2 is a section of a lead-in which is sealed by a melt. v

Referring now to the-drawing, and first to Fig. 1, the wall of a vacuum tank is indicated at I, and the conductor 4 of an electrode 5 is ledin through an insulating member or sleeve l. The sleeve is made of refractory material, preferably steatite, which, as is known, is a refractory prod uct' obtained by burning silicate of magnesia, the Steatite is superior to porcelain not only on account of its greater mechanical strength but also because it has a higher coeflicient of heat expansion which is equal to glass or iron.

A- plug 2 of metal is inserted at the upper end of sleeve I and an annulus 3, also of meta? is placed'about the sleeve at its lower end. The plug 2 a nd the annulus 3 are made of a metal, or alloy, whose heat-expansion coeflicient is substantially equal to that of the refractory 'mabe reduced to less than millionths per de- 5 gree by alloying with nickel, chromium, or vanadium. Two or more of the said metals may be added to iron for reducing its heat-expansion coemcient, and alloys of chromium and nickel may be used instead of iron alloys. Whatever may be the constituents of the alloy, they should be so selected as to make the heat-expansion coenlcient of the metal parts substantially equal to that of the sleeve l.

The plug 2, and the annulus 3, are embedded in the sleeve I while the sleeve is in unburnt condition, and a vacuum-tight connection is thus obtained. Upon burning, the steatite and the metal parts are permanently and vacuumtightly connected by sintering. After the unit including the sleeve I, the plug 2, and the annulus I, has been burnt in a suitable furnace, it is removed and the conductor 4 of the electrode I is inserted in a central hole of the plug. and welded. Preferably, an annular welding groove is formed in the boss of the plug at 8. A wire may be connected to the conductor 4 by a bore I in its outer end. Finally, the annulus I is inserted in a hole of the wall I, and welded to the wall.

The unit i, I, I is built up as a self-contained part because, as described, it is burned in a furnace while the welding operations at 2 and I can be performed anywhere, and because its metal parts 2 and I are comparatively small and cheap in proportion, asagalnst a tank made of chromium-nickel or other alloy, whose cost would be prohibitive. Referring now to Fig. 2, the arrangement of parts is the same as described with reference 40 to Fig. 1 but here the plug 2 is'connected to the sleeve l by a melt I of glass or enamel, and the annulus is connected to the sleeve by a melt I. The operation is performed without difficulty, as the melting point of the glass or ensmel is normally below the point at which the steatite of the sleeve becomes plastic. The heat-expansion coemoient of the melt should besuhstantially equal to that of the metal or alloy of the plug I and annulus I, and of the any rmed by the movement of aline. around another line to which the first line is 1 parallel, and therefore includes elements ofany 0 cross section.

I claim:

1. A short, shallow seal for a lead-in construction for vacuum discharge apparatus. comprising a metal member adapted to form a part 06 of the wall of a vacuum vessel, a metal electrode lead-in adapted to support an electrode, an insulating member fitting in said metal member for mporting directly said lead-in, said insulating member comprising a sleeve of steatite, said 70 lead-in passing through. said sleeve, ametal plug secured'to said lead-in and secured'to said sleeve, the areas of contact between said sleeve and said metal member and plug having sub-. stantlally cylindroidal form, said metal memllberandplusbein'gformedofmaterialhaving substantially the same coefliclent of expansion as steatite, and sealing Joints at said areas of contact forming a vacuum tight seal between said sleeve and said metal member and plug, the axial lengths of said sealing joints being relatively short compared to the diameters thereof.

2. In a device as claimed in claim 1, said metal member and plug being composed of an alloy selected from the group consisting of nickeliron, chromium-iron, vanadium-iron, and chromium-nickel alloys.

3. A short,shallow seal for a lead-in construction for vacuum discharge apparatus, comprising a metal member adapted to form a part of the wall of a vacuum vessel, is metal electrode leadin adapted to support an electrode, an insulating member fitting in said metal member for supporting directly said lead-in, said insulating member comprising a sleeve of steatite, said lead-in passing through said sleeve, a metal plug secured to said lead-in and secured to said sleeve,

the areas of contact between said sleeve and said metal member and plug having substantially cylindroidal form, said metal member and plug being iormed of material having substantially the same coefficient of expansion as steatite, and

contact forming a vacuum tight seal between said sleeve and said metal member and plug,

sulating member fitting in said metal member for supporting directly said lead-in, said insulating member being formed of steatite, said leadin passing through said insulating member, a-

metal plug secured to said lead-in and secured to said insulating member, the areas of contact between said insulating member and said metal member and plug having substantially cylindroidal form, whereby mechanical strains arising at the point of connection between the insulating member and the metal parts are taken up without provision of any othersupport for the electrode, said metal member and plug being formed of material having substantially the same coemcient of expansion as steatite, and sealing Joints oi a fused material at said areas of contact forming a vacuum tight seal between said insulating member and said metal member and plug, the axial lengths of said sealing Joints being relatively short compared to the diameters thereof.

5. A short, shallow seal for a lead-in construction for vacuum discharge apparatus, comprising a metal member adapted to form a part of the wall of a vacuum vessel, a metal electrode lead-in adapted torsupport an electrode, an insulating member fitting in said metal member for supporting directly said lead-in, said insulating member being formed of steatite, said lead-in passing through said insulating member, a metal plug secured to said lead-in and secured to said insulatmember andplug being formed of material having member, the areas of contact between said ining substantially the same coemcient of expansion assteatite, and sealing joints oi a fused material selected from the group consisting oi glass and enamel and having substantially the same coeiiicient of expansion as steatite at said areas of contact forming a vacuum tight seal between said insulating member and said'metal member and plug, th'e'axial lengths of said sealing joints being relatively short compared to the diameters thereof.

6. A short, shallow seal for a lead-in construetion for vacuum discharge apparatus, comprising a metalmember adapted to form apart of the wall of a vacuum vessel, a metal electrode leadin adapted to support an electrode, an insulating member fitting in said metal member for supporting directly said lead-in, said insulating member being formed of steatite,- said lead-in passing through said insulatingmember, a metal plug' secured to said lead-in and secured to said insulating member, the areas oi contact between having substantially the same coefllcient of expansion as steatite, and sealing joints termed by fusion of said steatite with said metalmemvacuum tight seal between said insulating member and said metal member and plug, the axial lengths of saidsealing joints being relatively short compared to the diameters thereof.

7. In a device as claimed in claim 6, said metal member and plug being composed of an alloy selected from the group consisting of nickel-iron, chromium-iron, vanadium-iron, and chromiumnickel alloys;

WAL'I'ER niimnmaacn,

10 ber and plug at said areas of contact forming a