US2454741A - Ultra high frequency electronic tube - Google Patents

Description

Nov; 23, 1948. V H4 MC ARTHY 2,454,741

ULTRA HIGH FREQUENCY ELECTRONIC TUBE Filed May 24, 1944 INVENTOR.

'JGENRY JmFCARrHY YWM,

ATTORN EY Patented Nov. 23, 1948 UBE Henry J. McCarthyQDanvers; vMass; assignor to SylvaniaElectric Products Inc.,.- Salem,Mass., a corporation of Massachusetts Application May 24, 1944, Serial No". 537,145

1 Claim. 1

This invention relateswto high frequency: elec-" tronic devices and particularly-to means for facilitating the flow of energy to and from the resonating elements thereof, andhas for its general object to provide a gas tight closure for the input-and/or output apertures for such devices.

A further object of the inventionisto provide a window constructionfor'such high frequency devices which may be-manufactured and applied thereto under high volume quantity production methods with a high degree of uniformity and precision.

A'-'furth'er object of the invention is to provide, in a high frequency device,=a frangible input and/or output window having-means for preventing transmission thereto of destructive thermally produced forces.

Other objects and features-will more fullyappear from'the following description'taken in connection with the accompanying drawings and will be particularly pointed out in the claim:

The invention is especially adapted to the type of "electronic. device which functions-at ultra high frequency. Suchdevices are usually made of metal such'as copper having high conductivity to the how of electric current. In such devices their metallic resonating systems very efficiently confine alloscillations closely within the device itself and to permit a flow of current thereto or therefrom an opening or openings in their otherwise closed body must be provided. Such openings mustbe impervious to gases because the space charge chambers thereof must be evacuated as in all such'devic'es. Such windows must also be pervious to high frequency currents To'provide for the reception of such windows, apertures are cut in the walls of the resonator chamber and.

closed by glass plates fused'into metallic frames or ,bezels to form .a window structure. This win-! dow structure is hermetically sealed into the,

jected in..operation.. Thev frangibleglassplates. in the window are thus protected from -.possib1e,

fracture.

To present a better understandingiof .the invention particular embodimentsthereof will now be described inconnection withthe drawings in' which:

Figure :l is aigeneral view in perspective of a device embodying the invention;

Figure 2 is a longitudinal cross section of the device;

Figure 3 is an enlarged detail cross sectional view illustrating the elements employed in sealing an input and/or output window inthe ap-' paratus;

Figure 4 isa detail view illustrating the com pletedseal between the window and its coopei ating recess in the body of the device;

Figure 5 is a detail view of the keepalive elec-. trode; and

Figure 6 illustrates a different embodiment of the invention.

Devices of the. character herein disclosedare subjected to relatively great temperature changes. The resulting variations in thermal expansion ofthe various materials out of which they are:

made, tend to cause destructive stresses to develop which have, prior to the present invention, caused fracture of the glass plates in the windows.

The principals of the invention are applied herein to an ultra high frequency electronic resonating device used as a gas switching tube employed to. protect delicate units such as crystal detectors from destructive surges of excessive current. However, the invention may be applied equally well to any high frequency oscillator device having energy conducting openings therein.

The apparatus to which the invention is applied has a metallic generally disc-shaped body member '1 within which a space charge chamber 8 is, formed. Within the chamber a pair of cones 9 and .10 are arranged with their slightly trune cated apex endsin alignment and slightly separated to form a capacity can. The cone 9 is.

adjustable along itsaxis to vary the frequency at .which the resonator functions. The other cone is hermetically sealed into the chamber.

The cone 9 is connected to an adjustingscrew device ll capable of operation by means of a screw driver placed in the slot 12. A flexible hermetic seal is maintained between the cone 8.

and-the body member I by means of a thin diaphragm l3 sealed to a shoulder. I4 on the body I along its peripheral edge and sealed to the.

cating with thachamberfl. Projecting into the.

aperture II is a keepalive lead (6 which extends outward into a glass bulb l1 and thence through a suitable seal to the outside where it may be connected to a source of electric current. The bulb I1 is sealed to the body 1 and supplied with an exhaust tube l8 adapted to be connected to an exhaust pump to evacuate the chamber I after which it is tipped off in the usual manner.

The inner end of the lead IE is of special construction. It is provided with a sheath of glass or ceramic IS. The lead extends into the aperture IS with its sheath I 9 in contact with the wall of the aperture at its small end. The lead supported therein. In devices of the kind described much trouble has arisen from a partial bridging over across the end of theglass sheath from the lead to the cone. This bridging phenomena is due to an accumulation of metal particles deposited upon the sheath by a slight sputtering of the adjacent metallic areas.

To overcome this tendency to bridge over and partially 'shortcircuit the keepalive, an airspace is formed between'the sheath l9 and the lead, thus preventing the accumulation of particles from the lead to the cone. The construction and operation of the lead I6 is more clearly set forth in another application, filed concurrently by me and bearing the'title "Electrode construction for high frequency electronic devices, bearing Serial No..537,144 and issued as Patent No. 2,419,903.

The body member 1 is provided with apertures 2| extending into the chamber 8 through which a flow of high frequencycurrent may pass in or out. The apertures 2| desirably are situated adjacent thecapacity gap between the cones and preferably are cylindrical in form. i

The apertures must be closed. to the passag of gas since the chamber is evacuated. The window must also permit. free passage of electromagnetic current therethrough. To accomplish this endthe apertures are closed by means of glass windows 22. -Desirably the windows are. secured in-counterbored recesses 23 concentric.

with the apertures 2|. r

The glass portion of the windowssare sealed in gas- -tight union within metallic frames or bezels 24 inany suitable. manner. The bezels in turn are sealed in the recesses. 23 by 'means of solder 25applied along their, peripheral edge 26 only, and to the peripheralwall 21 of the recess 23. The selection of materials to insure proper functioning of thedevice in other respects results in the use of materials for the body 1 and the bezels 24 which have difierent coefiicients of thermal expansion.- If the sides of the bezels were soldered to the bottom walls 28 of the recesses therefore, a bimetallic action would take,

place between the two metals which would cause distortion of the bezelsand probable fracture of the glass. By soldering the edges only of; the bezels, this source of'trouble is largely overcome. To further reduce the breakage of the glass Windows the bezels are provided with resilient means acting to absorb stresses developed by the unequal expansion of the materials. This may desirably be done'by forming an annular fold 29 in the bezels between the glass and their peripheral edges. Radial stresses developed by thermal expansion are thus absorbed by the resiliency of the fold. The glass is thusprotected' and the device will continue to'fuhctiondespite the'wide range of temperatures to which it issubjected.

A modified form of the window is'illustrated in Figure 6 wherein the bezel an is of special form."

Its general shape is that of a flat frustrum of a cone and desirably is provided with a central interned flange 3| within which the glass plate 32 is sealed. The peripheral edge of the bezel is soldered to the wall 21 of the recess 23. In this form of the invention stresses created by thermal expansion are absorbed by the flexibility of the cone which is deflected upward upon the application of excessive stress thereto thus protecting the glass from intensive radial pressure. The bezel in this form of the invention is so placed in the recess that its side faces slope away from the bottom Wall 28 of the recess 23. Consequently, solder applied to the peripheral edge of the bezel to seal the wind-ow in place will be confined to its peripheral portions only.

Referring to the window construction first described, it is desirable that the bezels employed in their construction be coated in any suitable manner to repel the flow of solder to all areas except their peripheral edges. It may be found that in the process of manufacturing when the glass plates are-fused into their bezels that sufficient'oxide or other coating is deposited on the surface thereof to repel the solder in the manner desired. In such case before the windows are sealed in their recesses the peripheral edgesof the bezels must be cleaned to receive the solder.

To further secure an absolutely tight and uniform union of the'window with the recess the bezel should be slightly less in diameter than the recess thus insuring free flow of solder at the joint. The bezels desirably are also chamfered along their edges as at 33 and a ring of copper 34 or other suitable metal may be placed between the bevel face 33 and the wall 21 of the recess prior to the soldering operation. In this manner additional strength and uniformity is imparted to the seal since the solder will flow along the increased surface areas afforded by the ring and the chamfer.

In the interest of rapid and accurate production of the device and the maintenance of uniformly .high quality of workmanship, it is desirable that just the correct amount of solder be applied to and evenly distributed throughout the joint. To accomplish this end a ring of solder 35 of the desired size is placed in the joint before the application of heat thereto.

As above suggested the tube described herein may be employed in various capacities. One such adaptation is that of a gas switching tube. In such case the keepalive I6 is energized by a local source of current such as a battery thereby maintaining a feeble flow of electrons at the gap 36 to insure instantaneous operation of the device. An incoming flow of energy is fed to the chamber 8 from a source such as an incoming signal through one ofthe apertures 2| and flows out through the other aperture. The current is fed to and from the device by means of wave guides 31. The tube functions in a manner well known to those skilled in the art to pass a current of allowable intensity but to automatically block an excessive volume of current.

rigidmetallic" body member. a space charge chamber therein whose walls present a resonator system said body having a plurality of apertures communicating from said chamber to the outside, glass windows for said openings, sheet metal bezels in which said Windows are hermetically sealed, said bezels having a bevelled peripheral edge, a coating repellant to solder covering all REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,050,576 Kronquest Aug. 11, 1936 2,075,477 Smith Mar. 30, 1937 2,106,770 Southworth Jan. 1, 1938 2,129,713 Southworth Sept. 13, 1938 2,187,126 Kern et a1. Jan. 16, 1940 2,296,307 Power Sept. 22, 1942 2,351,744 Chevigny June 20, 1944 2,364,732 Ludi Dec, 12, 1944

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