US2533713A - Vacuum condenser - Google Patents

Description

R. H. CHAMBERLIN ETAL 2,533,713

Dec. z, 1950 VACUUM CONDENSER 2 Sheets-Sheet 1 Filed May 27, 1947 INVENTOR Richard h'. Chamber/'n BY Harold E. So/'9 ATTOENEY Patented Dec. 12, 1950 UNITED STATES PATENT OFFICE VACUUM CONDENSER Richard H. Chamberlin, San Bruno, and Harold E. Sorg, Redwood City, Calif., assignors to Eitel-McCullough, Inc., San Bruno, Calif., a corporation of California Application May 27, 1947, Serial No. '750,828

1 Claim.

Our invention relates to condensers for use in electrical crcuts, and more particularly to a condenser in which the electrodes are enclosed in an evacuated envelope.

Vacuum condensers as made in the past present a number of problems both from the standpoint of the manufacture and of electrical design. Since the capacitance is determined by spacing between the electrodes, which Spacing is necessarily quite close, there is a real problem of getting the electrodes sealed into an envelope while maintaining the proper spacing between the electrodes. consequently, precision vacuum condensers have seldom been available except at large cost. I he usual practice has been to employ electrodes in the shane of parallel plates or concentric cylinders, the latter being commonly used. These electrode structures are difficult to fabricate and assemble, and require envelopes of relatively large size for condensers in the higher capacitance ranges. Vacuum #condensers heretofore' made are also quite limited in their current ratings because of heat` problems involved, and leave much to be desired mechanically.

The broad object of our invention is to provide an improved vacuum condenser structure and fabrication method which largely overcomes the disadvantages above noted.

The invention possesses other objects and features of advantage, some of which, with the fore-.

going, will be set forth in the following description of our invention. It is tobe understood that we do" not limit ourselves to this disclosure of species of our invention as we may adopt variant embodiments thereof within the scope of the claim. i

Referring to the drawings:

Figure 1 is a longitudinal sectional View of a vacuum condenser embodying the improvements of our invention.

Figure 2 is a transverse sectional view taken in a plane indicated by line 2-2 of Fgure 1; and

Figures 3 and 4 are like views illustrating modied electrodes.

Figure' is a View similar to Figure 1 showing a condenser embodying means for establishing the final capacitance; and

Figure 6 is another similar View illustrating the method of assembly.

Figure 7 is a detail View showing analternate closure structure. v

In terms of broad inclusion, our preferred condenser structure comprises an evacuated envelope containing sets of electrodes, one electrode set having a plurality of parallel bores and the i other set having pins projecting into the bores. Theelectrode sets are preferably supported at opposite ends of the envelope and the set having the bores is preferably formed by a group of tubes arranged side-by-side. The above structure is simple to fabricate and assemble, and permits building up a large cap acitance in a compact space. An important feature of our invention is the provision of adjusting means accessible externally of the envelope for varying the spacing between electrodes to establish the final capacitance after the electrodes have been sealed in the envelope, means being also provided for sealing the adjusting means to provide a vacuum tight closure after the adjustment has been made. While this feature may be incorporatecl in vacuum condensers having other types of electrodes, our preferred electrode structure is particularly well suited because one of the electrode pins may easily be made adjustable to function as a trimmer electrode. Our method of making the condenser comprises positioning the electrode sets to approximate the final capacitance, sealing the sets sopositioned in the envelope, varying the spacing by adjusting the trimmer electrode, fixing the spacing, and then evacuating the envelope. The method also preferably includes the step of placing a dissolvable material between the electrodes to temporarily hold the electrode sets as a unit while being sealed into the envelope, which material is subsequently dissolved out prior to final adjustment and evacuation,

In greater detail, and referring first to Figures 1 and 2 of the drawing, one version of our vacuum condenser structure 'comprises a tubular or cylindr cal envelope having a side wall 2 of a vitreous insulating material such as glass or ceramic. End walls 3 of the envelope are preferably of metal selected for making suitable joints to the vitreous wall 2. For example, if the side wall is of glass, the end walls are in the nature of sealing flanges and are made of a metal having an expansio characteristic matching that of the glass so that the parts may be sealed together at seals 4.

Internally our condenser comprises a pair of cooperating sets of electrodes positioned axially of the envelope and generally indicated by the reference numerals 5 and l. Electrode set 6 simply comprises a solid body 5 of metal such as copper having parallel bores 8 disposed about the envelope azis and opening out on the inner end of body 5. These bores provide a plurality of individual hollow electrodes and are preferably arranged in concentric circles about the 'in Figure is envelope axis. An integral shank portion 9 extends through the end of the envelope to provide a terminal iii for the condenser. The outer terminal portion of the shank is preferably held in a cap li which is in turn secured to the end wall ange at braze !2.

` The other electrode l comprises a plurality of pins !3 projecting into heres These free encled pin-shaped eleotrodes are seoured at their base ends to a shank i i which extends through the other end of the envelope to provide a. second terminal i for the condenser. The shank at this end of the condenser has a cap !i secured to wall flange 3 in a manner similar to the construction at the opposite end. Pins !3 and mounting shani: !li of eiectrode set 'n' are of a suitable metal such as Copper. A metal exhaust tubulation is is preferahly brazed to terminal ID and ported into the envelope through channel ll, the tubulation being pinched ofi at tip ae after evacuaton of the envelope.

The capacitance of our condenser is deter.- minecl by the number and dimensions of bores 3 and engagecl pins ecause multiplicity of interengaged electrodes present a large total area in a compact structure, it is possible to build oondensers of large capacitance in envelopes of small physical size. Another feature of our Construction is that the relatively large mass of metal connecting the effective electrode areas with the terminals provides excellent hoat conduction so that the improved condenser, even though of small size, is capable of handling large Currents without urdue heating.

Other advantages of our condenser structure above described include the following: There are but few parts and that are` present are readily fabricated assembled; the electro-;les are easily *d for aiignmc when seaiing into the enveiope and have ample ribidity to maintain accurate alignrnent even though small interelectrode spaoiogs are involved; the rigidity above mentioned holds the capacitanoe constant under eleotrioal stresses; the condenser is ideally adapted for soale production on an economioal hasis; and the simple st *ure does not introduce problems in outgassing of parte and evacuation of 'the envelope during exhaust of the condenser.

11155634921 of making the electro-;le set 6 of a solid block of metal, :it can cellular structure made up of a group of metal tuhes iii arranged side-hy-side as shown in 3, which tubes are preferahly of copper hrazed together and to a mounting shanit. The tuhes may h oircular as in Figure 3 or flat sided Figure 4. Hexagonai` tuhes ho ted together build up a very large capacitanoe all particularly the are also h onaL Since the cellular structure has from thefahrication standpoint well providing further compactness, we prefer to use it.

Another .feature of our invention illustrated the provision of adjusting accessible externally of envelope for va'ying the spaoing hetwe n electrodes to estahlish the final capaoitance after the eiectrodes have heen sealed in the envelope. As emhodied in our pin type electrode' structure this adjusting feature utilzing the center pin ti of elec rode set i as a trimmer eleotrode. Ali of the ot electrcdes, which. are fixed at the time of them into the en'velope, will be referred to heroin as the main electrocles to distinguish them from the trimmer electrode Trimmer eleotrode i has an outer screw portion threaded into a passage 22 extending through shank i and exposed at the end of the condenser, so that the outer screw portion provides means for adjustng the electrode. A screwdriver inserted in the passage is the only tool required to make the final adjustment. After adiustment and prior to evacuation the outer endof passage 22 is sealed with a fused metallio plug 23 of solder or the like. This plug provides a vacuum tight closure and also simultaneously locks the trimmer electrode to fiX the spacing.

While we have shown the above feature in connection with our preferred pin type electrode structure, it is understood that it may be incorporated in any type of vacuum condenser where it is desired to make an adjustment for trimming the capacitance to a precise Value prior to evacuating the envelope,

Summarizing the method of making the condenser, and referring to F'igu'e 6, we first fabrieate'theeleotrode sets 6 and 'i and then engage the main electrodes and trimmer electrode to approximate the final capacitance. This positioning may be done with suitable jigs or fixtures. The electrode sets so positioned are then sealed in the envelope by fusing the vitreous side wall 2 to metal end walls sat seals 4. This sealing operation serves to fix the main electrodes in` permanent position will be readily understood. Since the final capacitance is not set during the sealing-in operation enough tolerances are allowable to permit the glass work to be done without undue restrictions. Seals 4 are made in an ordinary lass lathe.`

The next step is to trim the. capacitance by movingl electrode 2| in or out. This is preferably done withthe condenser in a capacitance measuring circuit. After adjustment a quantity of solder is poured into passage 22 to form the plug 23 (Figure 5), thereby locking the trimmer electrode and providing a vacuum tight closure for the adjusting means. The condenser is then ready for evacuation which is done in the conventional manner by connectin tubulation IE to a suitable vacuum pump.

If desired an additional step may be employed to simplify holding the electrode sets 6 and 'I as a unit during the sealing-in operation. This comprises filling several of the bores with a dissolvable material 26 such as salt or chalk to embed the engaged ;pins [3. After the envelope has been completed the material 25 is dissolved out by introducing a suitable liquid solvent through the open tubulation [6. The steps of trimming adjustment and evacuation may then be followed as previously described; Using a dissolvable material to hold the electrodes has a special advantage in making the Simpler form of structure shown in Figure 1, although the. combination of this step with a subsequent` trimming adjustment is an ideal method of making preoision condensers. Our pin type electrode structure is particularly well adapted for use of the dissolvable spacing material 25 because the only cavitics are the bores &which all face in one direction, thereby making it easy to wash out the spacing material.

A modified structure for looking the trimmer electrode and simultaneously providing a vacuum tight closure is shown in Figure 7, wherein` an extension rod 21 on electrode 2| projects through a metal tubulation 28; both of which are pinched off at tip 29. By this arrangement the extension 21; which is Originally made long enoughto project out the open end of tubulation, provides a handle for adjusting the trimmer electrode. The subsequent step of pinching through the parts serves to lock them together as well as to seal ofi' this end of the condenser. This tubulated structure on an envelope, with a rod extending through the tubulation for adjusting the position of an element within the envelope, is useful in any kind of evacuated device Where it is desirable to make a final adjustment prior to sealing the envelope.

We claim:

A vacuum condenser comprising an envelope having an end structure with a passage therein, an electrode' set supported at the opposte end of the envelope and. having parallel bores, another electrode set supported at the first mentioned end of the envelope and having pins projecting into said bores, adjusting means threaded into` said passage for varying the degree of engagement of one of said pins, and a vacuum tight closure for the outer end of the passage.

RICHARD H. CHAMBERLIN. HAROLD E. SORG.

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

UNITED STATS PATENTS Number Name Date 1,333,401 Fisk Mar. 9, 1920 1,641,687 Nolte Sept. 6, 1927 2,036,532 Knoll Apr. 7, 1936 2,154,542 Swanson Apr. 18, 1939 2,192,062 Hansell Feb. 27, 1940 2,291,445 Beyer July 28, 1942 2,324,178 Sprague July 13, 1943 2,339,663 Teare Jan. 18, 1944 2,415,412 Bushwald Feb. 11, 1947 FOREIGN PATENTS Number Country Date 416,157 Great Britain Sept. 14, 1934 523,869 Great Britain July 24, 1940

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