US1821351A - Vacuum tube and method of making same - Google Patents

Description

Sept. 1, 1931. B. LOEWE 1,821,351

VACUUM TUBE AND METHOD OF MAKING SAME Filed March 2, 1927 lba INVENTO'R BERNHARD LOEWE BY 1a;

ATTORNEY 45 leads.

Patented Sept. 1, 1931 .UNlTED STATES PATENT OFFICE BERNHABD LOEWE, OF BERLIN-FRIEDENAU, GERMMY, ASSTGNOR TO RADIO CORPO- RATION OF AMERICA, A CORPORATION OF DELAWARE VACUUM TUBE AND METHOD OF MAKING SAME Application filed March 2, 1927, Serial No.

or pipe. After the process of exhaustion has been terminated, the pumping tube is withdrawn or sealed off, and this results in the well known tip. The avoidance of such tips is of technical importance and practical value,

for these tips are often the cause of damage to the bulbs or tubes.

Processes have previously been disclosed to the end of making, for instance, glowlamps and radio tubes without tips. In these processes, the tip that is sealed off is located at another place, ordinarily in' the base, in which case the tip is covered by the base and' thus protected from damage.

of manufacturing tipless vacuum vessels from glass, quartz, or the like in such a way that no sealing tip is produced.

Therefore, it is an object of this invention 5 to provide a substantially tipless tube.

which Figure 1 shows a resistance enclosed within a vacuum tube made according to my invention, i

Figure 2 shows the tube during manufacture, and

Figure 3 shows a tube during manufacture wherein a slightly modified method of making same is utilized: P

The method will be explained by the aid of 49 the problem of makinga vacuum vessel of the kind illustrated, for instance, in Figure 1.

Referring to the drawings, 1 is the glass bulb, 2 and 3 are supply leads of any desired sort, and 4t and 5 are the seals containing said It is immaterial in this connection what parts are located inside the vacuous ves, sel, and whether the electrodes 2 and3 are located at different ends ofthe tube or bulb, or whether they are brought in at one end, or

50 whether a plurality of electrodes are sealed Now, the, 20 method hereinafter to be described allows 171,937, and in Germany March 15, 1926.

in. Merely for the sake of affording a better understanding, the assumption will be made that electrodes 2 and 3 are fused or welded into a glass rod 6 which, for instance, may bear a resistance coat or film so that the assembly forms what is known as a vacuum resistor of the kind used, for example, in wireless telcgraphy work. However, instead of the resistance body, also fine wires for makingvacuum-type lightning arresters may be stretched out between the electrodes, or else a filament for making rod-shaped glowlamps. As shown in the drawings, the vac-- uum vessel in Figure 1 "has no sealed-oil point at all, and the same can be exhausted on a pump without having a sealing tip produced. 1 a

The method and process will be further explained by reference to Figures 2 and 3. First the glass rod-6 which carries the two electrodes 2 and 3 is inserted inside the bulb, the latter having a constricted portion 5 (Figure 2), at the place where the second seal is going to be. The glass has another constricted portion 7, and is fitted to a vacuum pump at point 8. After the vacuum has been produced, sealing off is produced at point 7. After the body has been withdrawn,

it is allowed to run together at 5 by fusion so that'it comes to lie closely around the wire 3. As soon as the seal has been made the glass is cut through or is squeezedofi", and this can be accomplished in a safe manner since the constriction at point 5 is already tightly sealed around the electrode 3. The

cutting edges which result are thereupon molten down by a flame so that a blunt end 5 is produced.

- The method can be modified as illustrated in Figure 3. In this case the glass bulb-previously welded onto the electrode 2 at one end is provided only with one additional constriction, namely, at 5'. The glass bulb is again connected with the pump at 8;

vacuum space is obtained, the upper glass part 9 remains still in connection with the lower glass part 10. After the seal at point has been established by welding, air is admitted into the lower part 10 so that the whole body can be taken off from the pump at 8. Again as in Figure 1, blowing ofi' or cutting off of the lower glass piece takes D place at the closure, and the edges are molten down. The final result, as in Figure 2, is a tipless vacuum body of the shape shown in Figure 1.

Mechanical severing can be effected either by cutting with the glass knife or by blasting or fusing ofl. What is essential is that before this is done, at a point turned towards the vacuous space, a hermetical seal of the supply electrode or electrodes by allowing the glass to collapse is produced. If desired and necessary for mechanical reasons, subsequent welding and Wrapping with a glass bead may be effected.

Having thus described my invention, I claim:

The method of manufacturing vacuum tubes, which comprises forming a tube with three constrictions, sealing at least one of the electrodes to one constriction by closing the said constriction about the electrode, exhausting the tube'through the second and third constrictions, sealing the tube between the second and third constrictions, and cutting ofi the tube between the second and third constrictions.

BERNHARD LoEWE.

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