US2528217A

US2528217A - Process of hermetic sealing of an evacuated enclosure, applying in particular to theluminescent discharge tubes

Info

Publication number: US2528217A
Application number: US778210A
Authority: US
Inventors: Dussaussoy Pierre
Original assignee: CSF Compagnie Generale de Telegraphie sans Fil SA
Current assignee: Thales SA
Priority date: 1946-11-26
Filing date: 1947-10-06
Publication date: 1950-10-31
Anticipated expiration: 1967-10-31
Also published as: FR936619A

Description

Oct. 31, 1950 P. DUSSAUSSOY 2,528,217

PROCESS OF HERMETIC SEALING OF AN EVACUATED ENCLOSURE, APPLYING IN PARTICULAR TO THE LUMINESCENT DISCHARGE TUBES Filed Oct. 6, 194'! PIERRE DUSSAUSSOY E T R- fiwh Q 0 1i] ATTORNEY Patented Oct. 31,1950

PROCESS or IlERMETIC SEALING OF AN "EVACUATED ENCLOSURE, APPLYING IN CHARGE TUBES QPARTICULARTO THELUMINESGENT s-1 I Pierre "Dussaussoy, Paris; France, assigno'r to Compagnie Generale De Telegraphic Sans Fil,

I a corporation of France Application October 6, 1947;.seria1No. 778,210. In France November 26, 1946 f? My invention relates-to a process of execution of an hermetic sealing between an evacuated en- .closuraor bulb and the extremity of an exhaust .tube which constitutes a stem for the. said bulb.

In the sealing processes of the edge to edge seal 3 Claims. (0.250419 type heretofore utilized for the discharge tubes,

a rough provisory seal is first utilized between the tube and the stem, through heating by a flame, and there remains to be realized the tightness of the seal thus obtained, which i shaped by a further heating operation carried out in a flame at a relatively hightemperature, of the order of 900-950", accompanied by ablowing of air inside the tube for avoiding deformation of the latter.

This second operation of heating results in developing mechanical stresses which compromise the tightness of the tubes, especially if their leading-in wires extend through the glass enclosure:

in the immediate neighborhood ofthe stem, such stresses being, moreover, hardly tolerable in the tubes which contain fragile components.

My invention does away with these drawbacks: It consists in proceeding, after the execution of a rough assembly seal, instead of shaping the a bulb as I have mentionedabove, in placing, at

the'spot reserved to the seal, a fusible glass (or enamel) having practically the same dilatation coefficient as the assembled pieces, and in making it flow through a moderate heating (for instance at a temperature of the order of 550 C.).

It appears therefrom that the process of my invention is simpler than the prior processes (since it needs no special shaping and no blowing of air). On the other hand, by the fact that my process uses a heating of less intensity and shorter duration, it does not risk to injure the internal components of the tube, nor to alter the shape of the-glass parts, and moreover it does not result in a defective tightness due to mechanical stresses-the duty of mechanically supporting the components of the device being incumbent upon the glass and not upon the enamel.

My invention will be more clearly understood by reference to the accompanying drawings which set forth my invention in an illustrative sense and not in a limitative sense as applied to a process of making an electronic discharge tube wherein the lead-in wires extend through the tube envelope in the position where the seal is made and in which:

Figure 1 represents a cross-sectional longitudinal view of a tube envelope, in which the lead-in wires traverse the envelope through the stembulb seal;

Fig. 2 is a top view corresponding to Fig.1; and

' Fig. 3 is a top View of an electronic tube en velope, in which t-he-"lead-in wires are sealed through the flange of the tubularstem:

The bulb-or tube l shown in Fig. l' hasan'annular cross section 'to whichmust be sealed the flanged extremity of the exhaust tube 2, in proximity to the leading-in wires 3, embedded in a bead of glass 4 and previously sealed to the flange. In th manufacture of the tube l acommon rotary movement is communicated to the tube or envelope and the exhaust tube 2. Then the tube is heated tangentially, at the level of its seal, by means of an extremely thin flame to a softening temperature variable from 700 C. to 800 C. according to the kind of glass to be shaped.

Then, by means of a graphite tool the edges of the tube are turned down on the flange. If the inward diameterv of the bulb exceeds by an in-- 'finitesimal amount the diameter of the stem flange, no bending is necessary, but in every case is made, on the spot, of a certain amount of finely pulverised glass having a low melting point as shown in ion the figure. V

Then the assembly is again rotated and heated;

so that the enamel melts and flows, thus closing the holes eventually existing, and completing a' seal which ofiers a smooth surface quite exempt of asperities.

' What I claim is:

1. The method of air-tight sealing of the finished tubular stem of a space current tube and a bulb, the stem having the form of a flanged tube whose flange is traversed by the electrode leads and supports, the bulb being made of the same glass as the stem and having an annular crosssection whose inside diameter is at least equal to the flange diameter, which comprises placing the stem flange in the bulb so that the rim of the bulb slightly overlies the, edge of the flange, heating the exterior face of the bulb rim to the softening temperature, bringing this rim in close contact with the stem flange in all points of its edge, depositing on the stem edge a layer of pulverized glass having practically the same dilatation coefficient as theparts to be sealed and a melting point much lower than the above-mentioned softening temperature and heating and melting this glass layer to form an air-tight seam between the flange and the rim of the bulb after cooling.

2. A space current tube having an air-tight glass envelope comprising, a glass stem having the form of a flanged tube, a bulb having an annular cross-section formed from the same kind of glass as the glass stem and placed over the flanged tube so that the rim of the bulb slightly overlies the exterior face of the flange on the tube, and a glass seam interposed between the, exterior face of the flange and the interior overlying face of the glass bulb.

3. A space current tube having an air-tight glass envelope comprising a glass stem terminating in a circular flange extending in a plane normal to the axis of the stem, a glass bulb enclosing the peripheral edge of said circular flange and having an inturned flattened portion coextensive with the surface of said circular flange and encircling the exterior of said glass stem, glass beads extending transversely through both said flattened portion of said glass bulb and.through,,

the peripheral edge of said circular flange, leadin wires extending through said glass beads and a layer of pulverized glass interposed between one side of said circular flange and the flattened portion of said glass bulb and coextensive therewith, said pulverized glass forming a seam extending in an annular path contiguous with the flattened portion of the glass bulb and the circular flange of said glas stem for sealing said bulb, beads and flange in an air-tight envelope.

PIERRE DUSSAUSSOY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,911,410 Xalverde May 30, 1933 2,188,061 Scharfnagel Jan. 23, 1940 2,248,644 Reger et al. July 8, 1941 2,264,183 Nash Nov. 25, 1941 2,273,437 Dunn Feb. 12, 1942 2,296,579 Seelen Sept. 22, 1942 FOREIGN PATENTS Number Country Date 495,417 Great Britain Nov. 14, 1938 OTHER REFERENCES Housekeeper-The Art of Sealing Base Metals Through Glass in Journal of the American Institute of Electrical Engineers, vol. XLII-9, 1923.