US1890310A - Cooled electron discharge device - Google Patents

Description

Dec. 6, 1932. BENSON 1,890,310

COOLED ELECTRON DISCHARGE DEVICE Filed Aug. 1:5. 192? 2 Sheets-Sheet 1 INVENTOR Lee 11. Benson Dec. 6, 1932. H, BENSON 1,890,310

COOLED ELECTRON DISCHARGE DEVICE Filed Aug. 15. 1927 2 Sheets-Sheet 2 INVENTOR Lee H Benson ATTORNEY Patented Dec.- 6, 1932 UNITED STATES PATENT OFFICE LEE HALL BENSON, OF WILKINS BURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC 8; MANUFACTURING COMPANY, A CORPORATION OF IPENNSYL-VANIA COOLED ELECTRON DISCHARGE DEVICE Application filed August 13, 1927. Serial No. 212,788.

My invention relates'to radio tubes and particularly to tubes of large power in which the anodes comprise metallic portions of the walls of the tubes.

An object of my invention is to provide means for supporting a water jacket-upon the anode of a high power electron discharge tube.

Another object of my invention is to provide means for detachably mounting the water jacket upon the anode of an electron discharge tube of high power. I

Another object of my invention is to provide a water-tight connection for the water jacket to anodes of the character'above described, Without the necessity of welding, brazing or otherwise heating the anode to effect the attachment of the water jacket.

A further object of my invention is to provide a single means for supporting an electrostatic shield for the seal between a metallic anode and the wallportion inside an electron dischargetube, and for supporting the water jacket outside the discharge tube.

Other objects of my invention will becoine apparent upon reading the following specification taken in connection with the accompanying drawings,'whereinzf l Figure 1 is a longitudinal section of a radio tube embodying one form of my invention, and

- Fig. 2 is a longitudinal section of a radio tube embodying a different form of my invention. v

It has been common in the art of radio tubes adapted for producing considerable power outputs to make the anode in the form of a metallic shell constituting the wall at one end of the tube. The anode is then in the form of a thin-walled metallic cup which is sealed to the glass wall constituting the remainder of the container by a ring-shaped seal. It has also been customary to surround this cup-shaped anode by a jacketthrough which water circulates to eflioiently carry away the heat generated in the anode during theoperation of the tube.

Since such tubes of a largepower ordinarily have relatively high potentials im'- pressed between their electrodes, electrostatic fields" of considerable intensity are-set up in the neighborhood of" the tube walls.

The anodes are ordinarily sealed to the' glass wall atone end and termina'te in a relatively sharp edge, andthese electric fieldshave a tendency to concentrate in the seal itselfand frequently produce such high electric stresses as to cause rupture or overheating of the glass atthat point. I haveytherefore, erranged to insert directly inside the seal a metallic extension of the anode by means" of which the concentration ofthe electric field at the seals is avoided.

a .In orderto provide an anode which shall be efiiciently cooled by the surrounding water jacket, it is customary to make the metallic Wall portion 7 above described as thin as: is consistent with the ability to WV-ltllStEtIlCl the pressures of the surrounding atmosphere. A convenient wayto make such anodesis-to draw them as a thin-walled copper cup in a die-press. Such process does not adapt itself to the formation of suitable supporting collars of the size and strength necessary for attachment of the water jacket. It would, of course, be possible to braze or weld a suitable supporting collar to the outside of the anode,

but if this were done before the tube were exhausted, the interior of the anode would be-" come oxidized. Such oxide cannot be left on the anode permanently, since it occludes gases which it is almost impossible to completely remove by any known method of tube exhaust. These would gradually seep out of the oxidized layer after the tube was sealed off from the pumps and quickly cause the vacuum to deteriorate to such an extent thatthe tube would be ruined for practical pur V poses.

Furthermore, such a collar would have to be located very close to the end of the anode which is sealed to the glass container and would makethe forming of the seal thereto bythe glass blower difficult or impossible;

Such an extension of the'anode' in "close T proximity to the seal, as has been described,

above asnecessary to shield the latter from electrostatic fields, would also make great difit ficulties for theglass blower in forming the seal. It would likewise be oxidized by; the

heat of the glass blowers fires and the removal of this oxide would present considerable difficulty.- 'As previously stated, any

such oxide must be removed before the tube could be'properly exhausted.

For the foregoingreasons, it is desirable that the above-mentioned support-collar. and shield extension of the anode shall not be integral parts thereof, which must have been attached previous to the time that the anode is sealed to the glass container. I have, there'- fore, devised a form of anode, which permits the attachment both of a" shieldingemon sion inside the tube andJof a support collar outside the tube, after the tube has been sealed to; the glass portionof theitube.

The method which I have devised comprises the formation of a groove in the form of a screw-thread in thelmetallic wall, of the anode andv the provision of threadedportions e on both the support collar landtheinternal shield which engage: this-threaded groove and permittheseelements to be placed in position' and removed atwlll, after the anode has been sealedto the" container. 7 V

' Aconvenient way of producin thisgroove in the anode isfthat of rolling it 111 the thin metal wall.

This process naturally-results in-theproduction of a screw -thread groove on" the exterior of the anode and it is possible to utilize. this external thread to fasten in place a Water jacket such as is common for cooling anodes in power tubes ofthis type.

Referring to Fig. 1 of the drawings, the

power tube embodying my. invention comprises av1treousconta1ner l having at its upperend a. ree'ntrant neck Q'supportinga 6,0f a well-knowntype.

press 3 is a glass neck 7 upon the exterior of press 3' at which are sealed cathode heating leads l of an ordinarytype, These leads and a support stem supporta cathode filament Surrounding the which is clamped acollar 8 which supports rodsQto forma frame work fora control electrode 10- of the conventional grid type;

r The anodefor myradio tube comprisesa V cup-like metallic cylinder 11 which is sealed to-the vitreous envelope 1 at the ring seal 12.

If the electrodes so far mentioned constitutedthe entire tube structure, very considerable electric stresses would be produced in the neighborhood ofithe seal 12 when thetube was in use. h Since these electric stresses are alternating, they produce considerable dielectriclosses in the glass L and thus'tend to over heat it. In consequence of this heating and of the electric stresses themselves, puncture of the glass at" the seal. would :be-very likely To avoid thsdiflicultiesfrom concentration ofithe electric field at theseal 12,1 provideacylindrical shield 13 which forms an extension of the anode .11 and eliminates electric stresses from' the seal 12 for reasons whichzwill be readilyapparent' from mere inspection of the drawings; Moreover, this shield reduces electric stresses in the glass 7 walls generally due to the potential difference between the anode and the grid. b

However, if the shield 13 were made integral with the anode 11, great diiliculty would be found by the glass blowers in making the ringshaped seal 12 so close to this metallic shield. Furthermore, the shield 13would be badly oxidized by the glassblowers flamesand would, in consequence, absorb'considerabl quantities. of gas which would render a suliicient evacuation of the container dlfficult jorimpossible.

I Accordingly, I have arranged the shield 13 to be detachab-lefrom the main anode 11 so that the latter may belsealed into the, glass portion ofthe envelope beforethe member 13 is put in position. In constructing the tube the, glass member 1 isfirst sealed to'the anode 11',- the upper endofmemberlb'eing left; open; 'A groove 14. in the'form .of 1a sorew-threadis provided in the' wall of anode I 11. It may readily be. formed by rolling it in the main metallic wall atithe'time the anode is made. The shieldinember13is'in the form of a thin tube and has a correspondscrew-thread rolled in it. Theseal 12 having been completed and the anodethoroughly cleaned in a manner familiar inthe art, themember 13 is screwed into position in the anode 11 from the open. upper end of the member 1., The neck 2 and press 3, on

and of the thinnessof the anode wall, this screw-thread 14 readily conforms to and makes arelatively tight fit'with thecollar 17.

However, to -make certain-that, the joint be, tween the two-11s water-tight the portion of] the anode in which the thread is rolled may be made slightly larger in diameterlthan the main wall of the anodethus'providing a shoulder againstwhich a packing- 18 of as best-es or other suitable material may be squeezed when collar 17 is secured-into place. In the modification shown in Fig. 1, the collar 17 is provided with a second collar 19 which is mounted on, and inengagement with a groove in collar 17, so that it can turn readily about the latter. The'eo'llar19may I conveniently be made in two parts to admit its ready mounting as just described. The lower face ofthe collar 17 is machined to a true surfaceadapted-to engage a suitable gashot. .flhe Water-jacket'proper-QI has an annular surface on rits upper'end adapted to surfaces to assure that their fit is a watertight one; Upon the outside of the upper end of the water jacket 21 is cut a screw thread 22 and a cap 23 with a thread adapted to engage thread 22 is arranged With a bearing on the upper surface of the collar 19. After the water jacket 21 is placed in position, the cap 23 is screwed down, drawing the water jacket tightly against the gasket aforesaid, producing'a water-tight joint at the upper end of the water acket. The freedom of collar 19 to turn on collar 17 insures that no torsional stress will be applied to the thinwalled anode 11 in screwing cap 23 onto threaded portion 22. v

The water jacket 21 is provided with suitable inlet and outlet connections for the cooling water. The construction of these is so well known nation. 7

Referring to the modification shown in Fig. 2, this differs from that shown in Fig. 1 in the detail of the method of attaching the water jacket proper to the collar.- As shown in the drawings, the water acket 25 may be of drawn metal having an annular surface on its upper end 26 adapted to cooperate with a similar annular surface on the support collar 27. A suitable gasket may be provided to render this joint water-tight, the pressure being provided by a ring of nuts 30 and bolts 31 around the cooperating edges. The ease with which the junction between the support collar 27 and the threaded groove of the anode 11 can be made water-tight is such that the water jacket may be removed from the tube by merely unscrewing the latter from the inside of thecollar 27. The structure shown in Fig. 2 has the advantage that practically the entire length of the anode is subjected to water-cooling.v

It is, therefore, apparent that I have deviseda convenient methodfor mounting the water jacket on the metallic anode of a high power radio tube and one which permits the easy exhaust of the tube and does not interfere with the glass blowers work of sealing the anode to the glass container. The same means is further used to support the electrostatic shield inside thetube, which prevents injury of the glass in the neighborhood of the seal from electrostatic stresses incident to the operation of the tube. To support a shield for the seal of a power tube by this method is not my invention, but is claimed in copending application of Mouromtsefl and Deak, Serial No. 188,420, assigned to the Westinghouse Electric & Manufacturing Company.

While I have described my invention in a connection with the particular embodiment here illustrated, it will be evident to those as not to require detailed explaskilled in the art that many departures from the proposed structure and process of [construction which I have described may be'made without departing from the principles of my invention. I, accordingly, desire that the terms of the claims shall be given their broadest reasonable. significance excepting so far as limitations are expressly madeor are imposed by the prior art. V I claim as my invention: a

1. An electrical dischargedevice comprising a vacuum-tight container, a cathode with in said container, a portion of said container constituting the anode of said device and having threads consisting of undulations in said portion, a collar having an annular face on one side thereof, and adapted to engage said threaded portion,ja split ring rotatably supported onv said collar, a water-jacket having an annular face adapted for water-tight engagement with said first'annular face, and

a screw cap adapted to engage said split ring and said water jacket, to press said two annular facestogether. l

2. An electrical discharge device comprisinga vacuum-tight container, a portion of the wall of said contalner being simultaneously threaded on both sides constituting the anode of said device, an electrode in said container, a metallic member insidesaid container in engagement with said threaded portion and a collar external to said contain-er adapted to engage said threadedportion. V

3. An electrical discharge device comprising a vacuum-tight container, a portion of the wall of said container being simultane- IOU ously threaded on both sides constituting the anode of said device, an electrode in said 0011- tamer, a metallic member inside said contamer inengagement with said threaded por- 'tion, a collar adapted to externally engage I said threadedportionand a waterjacket supported by said collar.

4. An electrical discharge device comprising a vacuum-tightcontainer having a metal- 11c wall portion, a portion on said wall 'bemg simultaneously threaded on hothsides, constituting the anode of said device, an electrode 1n said container, a metallic member inside said container in engagement with said wall of said container constituting the anode of said device andhavingportions bent to form threads, said bent portions forming threads both inside and outside said contain'er, an electrode in said container, at metallic member inside said-container in screwthreaded engagement With said bent por tions, and a collar external to said container and in screw-threaded engagement with said bent portions; 7 1 I 6. An electrical discharge device comprising a vacuum-tight container, part of the Wall of said container constituting the anode of said device having portions bent to form threads, saidcbent portions formingthreads both inside-and outside said container, an electrode in said container, a metallic member inside said container in screw-threaded engagement withisaid bent portions, said threads outside'said container being adapted to make threaded engagement With a collar supporting a Water jacket for cooling said anode, i V V 2" Intestimony whereof, I have hereunto subscribed myname this 3rd day of August 1927; 1 1 7 LEE IIALL BEN SON.

' Hal;

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