US2401637A - Electron discharge tube - Google Patents

Description

June 5- ,J. o. HARRIES 2,401,637

ELECTRON DIS CHARGE TUBE Filed Sept. 4, 1941 4 Sheets-Sheet 1 I 1 ll I \12 Fig.1. I

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Filed Sept. 4, 1941 INVENTOE June 4, 1946. J. H. b. HARRIES V240L637 ELECTRON DISCHARGE TUBE I 4 Sheets-Sheet 4 //YVENTO $1; 172.4 a

BY W

Patented June 4, 1946 UNITED. STATES PATENT OFFICE ELECTRON DISCHARGE TUBE John Henry Owen Harries, Clapham Park, London S. W. 4, England Application September 4 1941, Serial No. 409,588

' In GreatBritain September 5, 1940 9 Claims. 1

that circuits for use with a tube for both input and output purposes in general consist of an enclosed metallic structure or casing such as that of the well known shielded concentric quarter wave line. The radiation losses insuch a transmission line circuit become very considerable if the continuity of its outer conductor or shield is broken. It is not easy: to devise a construction for an electron discharge tube such as a deflection valve which enables an electron beam or stream inside the evacuated envelope of the tube to be deflected or modulated by the field of an input circuit, and which 'enablessuch' an electronbeam to give energy to an output circuit which is necessarily external to the tube, while at the same time maintaining a low loss in theinput and output circuits. This difiiculty is aggravated by the necessity of providing tuning. adjustmentmechanism for the circuits. Possibly, however; the greatest complication arises because, in addition, some means has to be. employed to remove excess-heat during operation from the assembly of the discharge tube and its circuits. This is particularly necessary in the case of tubes provided with massive copper electrodes sealed into glass envelopes. Suchv electrodes are often necessary in discharge tubes operating with ultra high frequencies in order to provide a low loss connection in the external circuit connected to the electrodes of the tube; such copper electrodes must not be allowed to rise to a point at which the joints between the copper and glass may be damaged or gas evolved from the internal parts of the tube. Water cooling of the appropriate parts is, of course, extremely effective but is most inconvenient and expensive.

The chief object of the invention is to providea methodof construction for a valve andits circuits to operate at ultra high frequencies and which are electrically efiicient and are readily and efliciently cooled during operation.

According to the present invention, an electron discharge tube is mounted on a supporting platform and a, casing forming part of a shielded circuit connected to the discharge tube, such as the output circuit, or forming. part of the input and output circuits, is; also carried by the said The temperature of- .2 platform and surrounds the tube, while means are provided for drawing a stream of air through the casing to serve as a cooling mediumior parts of the tube which during operation would otherwise become overheated. The platform may constitute a partition in the said casing which it divides electrically and mechanically into two parts which actually form parts of the input and output circuits of the discharge tube. The supporting platform may also serve for connecting an electrode in. the discharge-tube to its external circuit, and in fact, an electrode constituted by a transverse plate sealed to the envelope of the discharge tube and extending outside the envelope. In some cases, for example, in the dischargetube set. forth in patent application Serial No. 409,585, filed September 4, 1941, such an electrode has to be maintained at a different direct potential from the external circuit which may be at a. higher potential, and then the platform, while mechanically supporting the casing,

may be electrically connected to it through the dielectric of a condenser,

This arrangement enables the air stream provided for cooling purposes to be directed on to the said transverse plate electrode, and an: anode or outputelectrode may alsobe extended to the outside of the envelope and cooled by direct contact with. the air stream. Generally speaking;

the air stream may be directed into the neighbourhood of any parts which require especially effective cooling. In particular, when the easing is divided into two parts by the partition, streams of air' maybe drawn through the two parts and at one end directed towards an output electrode, and at the other end towards lead-in conductors of other electrodes. The transverse plate electrode ma be furnished with external heat radiating surfaces or fins which are cooled by the stream of air. a

As regards the tuning mechanisms, these may be mounted on those parts of the casing which form part of the external circuits and may be arranged for the adjustment of the dimensions of' the casing necessary for tuning the circuits to the required frequencies. For example, at least one end of the casing may consist of two telescoping members which maybe extended or contracted by the tuning mechanism so that for tun'-' ing purposes the effective length of the end of the casing is changed.

In order that the invention may be clearly understood and readily carried into effect, some forms of construction in accordance therewith will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a central section showing the mounting of the tube within a casing forming part of the. output circuit;

Figure 3 is a longitudinal section showing another type of tube in which the casing forms part of the input and output circuits;

Figure 4 is a longitudinal section seen at right-.

angles to Figure 3 of the end of the enclosing casing containing the tuning arrangements for the input circuit;

Figure 5 is a general diagrammatic View showing two suchtubes in their casings mounted on a deck forming the top of a cabinet; while Figure 6 is a general View showing the mountingof a tube as shown in Figure 1.

Referring to Figures 1 and 2, the anode end of a tube is shown of the construction set forth in patent application Serial No. 409,585, filed September 4, 1941, or in Figures 1 to 11 of the draw ings accompanying the specification of patentapplication Serial No. 409,589, filed September 4, 1941. The upper part of the envelope E is shown with the output target or anode T fused into a re-ntrant seal, while the sub-anode SA is sealed to the two parts of the glass envelope E. The tube is mounted by bedding the sub-anode SA on to a seating of a brass ring'3ll with a thin silver ring 3| interposed to make good contact. The sub-anode SA is pressed on to the seating by three equally s aced screws 32 screwed radially into the ring 30, and formed with conical pointswhich press the sub-anode SA on to the seating,

as shown in detail inFi ure 2. A voltage of 1500 volts for the sub-anode is applied to a ring 38a which is in metallic contact with the ring 30 so that the rings 30. 30a constitute a metal platform support for the discharge tube. The terminal of the target T consists of a rod I2 which is actually'tubular as shown. and is perforated near its lower end for cooling purposes. For this purpose. air is forced into the upnerend of the rod I2 and passes out through the perforations at the bottom into contact with the tar et T and into the inside of a telescoping casing 33, 3! which form's'part of the output circuit. .It passes out of this casing through vent holes 40a in the upper wall 45 of the casing. The rod I2 is screwed into the target T so that both it and the dischar etube, which is a deflection valve. are fixed relatively to the'brass ring 30. The part 33 of the casing which is of sheet metal and open at the top. is soldered 'to another brass ring 34 secured by screws 35 to a third brass ring 36. A s eet metal cap 31, which also has its lower end split at 38, telesco es into the part 33 and has a tubular sleeve 39 soldered into the end wall 49. The sleeve 39 is capable of sliding on the rod l2 so that the latter, the sleeve 39, the end wallMJ, the cap 31. the sheet metal casing 33, and the brass rings 34 and 3B, are all subjected to the voltage of the target T, which in this example is 2500 volts. Therefore, these parts have to be insulated from thread engaged by "a threaded sleeve 5i fixed by' connected. This assembly, as a whole, will be recognised as a concentric line type of tuned circuit. To reduce losses while enabling sufficient mechanical strength to be maintained, the parts 33, 31, 40, and the rings 30, 30a, 34 and 36, should be made of brass andbe silver-plated. Good contact surfaces must be maintained.

'It is arranged that the metal cap 31 can slide for tuning purposes relatively to the sheet metal casing 33 and the brass rings which are fixed to the sub-anode SA, and to enable this to be done, a sleeve 45 is secured by grub screws 48 to the sleeve .39 and is provided with a right-handed screw-thread 41 on its outer surface This screw thread engages an internal right-handed thread in a nut 48 fixed within an ebon'it'e adjusting disc 49. On the other sideof this disc the'le'ls a nut 50'which has an internal left-handed screw grub screws 52 to the upper part of the rod l2.

Now if the ebonite disc 49 is rotated so as to'cau'se" the nut 58 to ride up on the screw-thread of the sleeve 5|, owing to the fact that the sleeves 5! and 45 have threads of opposite hand, the sleeve] 45 will be drawn upwards into the nut 48 at doublethe rate if the pitches of the two screw-threads are the same. Thus, the sleeve 39, a d the sheet metal cap 31 are drawn up relatively to the metal casing 33. Similarly, if the disc 49 is rotated in the opposite direction, the cap 31 is forced down into the casing 33, and in this way tuning of'the concentric. conductors l2 and 33, 37is efiected. The loop [5 is a pick-up loop connectedto conductor 53 for connection to a di-pole transmitting aerial. The loop 54 is a tuning loop connected directly to a small lamp 55 which, by its;

brilliance, indicates the tuning point.

In Figures 3 to 5, the mounting of tubes is shovm. the envelope of each of which has a central copper section between two end sections of glass, as shown in Figures 12 to 21 of the draw ings accompanying patent application Serial No] 409,589 referred to above. The output circuit arrangements making use of a concentric'conductor system shown in Figure 3, includesa sheet metal casing 33 with a cap 31 and endwall 43, to the latter of which is secured the'slee've 39 which is caused to slide over the tubular conductor l2 which is screwed into the target'elec trode T. It will be noticed that in this case the target electrode is not sealed into a re-entrant' the brass ring 33a which, as already mentioned,

is at the sub-anode voltage of 1500 volts. For this purpose, a sheet of mica 4| about0.01 inch in thickness is interposed between-the brass rings 36a and 36. but these'rings are mechanically seseal and is more accessible to the cooling .air which enters through apertures H0 and leaves through the outlet pipeslll. j 1

The tube is secured in this case to a deck- 83, and for this purpose, while the sub-anode SA is'bedded on to a plate 30 which again forms a metal platform support separated from the parts metallically 'connectedto the target electrode T by a sheet of mica 4| forming the "clielectric of a condenser as described above'with reference to Figuresl and 2, the central copper part E of the envelope of the discharge tube has a system of cooling fin forced on to it. This .face of the ring 84 have a slight taper. The

surfaces are cleaned and the ring 84 pushed on to the'tube 'E' to make good thermal con-i tact with it, At the lower outer edge of the fins 85, there is an outwardly-extending ring :or.

flange 86 which is secured by screws B'I'to the"- deck 83.

The tuned input circuit also consists of a shielded two-wire adjustable transmission line. Its shielded casing provides a means of applying air cooling and acts as a support for the lead-in wires. Thus, the ring 84 is extended downwards at 88 beyond the fins 85, and this downward ex- I tension receives the cylindrical shield 89 of the input circuit which consists of metal tubing fixed in position by screws 90. The lead-in conductors d d tothe parts D D of the deflection cylinder are connected by short lengths of braided flexible conductor W to a pair of'Lecher wires 92. For tuning purposes a piston orplunger 93 is provided which can slide in the casing 88 and forms the adjustable bridge-piece between the Lecher wires 92. In order to facilitate assembly, the casing 83 has a flanged joint at 94. The piston 93 is adjusted by a handle 95 on the lower end of a screw-threaded rod 95 which, as seen in Figure 5, is taken out through insulating bushings 91 mounted in the lower wall 98 of the casing or cabinet 99' which encloses the pair of tubes shown in that figure. The rod 96 screws in a nut Hi6 forming part of the bottom wall of the casing 89; and the rod 96 extends through the wall of the piston 93 in which it can turn but is prevented from sliding relatively to the piston by a pair of nuts Ill-I pinned to it. The input supply is brought to it by a pair of shielded conductors I82 which feed into a loop Ill-'3 carried inthe wall of the piston 93, by an insulated thimble I04. All high frequency tuning conductors may be of brass and should be silverplated to reduce losses.

Cooling is partially eiTected by a relatively slow current of air indicated by the arrows I85, which flows in radially between the fins 85 and through the annular hole I86 in the deck 83, as seen in Figure 3. In addition to this, the lower seals for the lead-in wires of the valve and the target seal are cooled by higher speed air currents. It has already beenmentioned that for the latter air is drawn in as indicated by the arrows Hil in the outlet" circuit casing 33 and is taken away through two outlet pipes I'Ii which may be of glass and pass through the end wall 40 of the cap 31. For the lower seals the air'passes in through inclined glass tubes Iill which are optional but which, when provided, prevent this air from coming into contact with the fins 85 and thus becoming heated. The high speed air current follows the arrows I93 into contact with the lower seals and is; taken away laterally through the casing 89 by way of an outlet pipe I89.

The arrangement is capable of modification by" altering the tubes and aperture so as to direct the air to desired parts of the assembly. The outlet pipes may be of any material not having high electrical losses. A by-pass condenser is shown as formed of a copper band I I2 encircling the input casing 89' and separated. from it by a sleeve of mica H3; The lead-in conductors may be by-passed to the case with respect to ultra high frequency currents, by the method illustrated, by way of example, in the drawings by the conductor. 8 which is brought out through a bushing H4 in the side of the casing 89 and is connected by a wire. I IE to the copper band II2 of the condenser. A piece of mica (not shown) may be'used to keep dust out of the condenser 36, 38 and the entering air may be cleaned or filtered in any convenient Way.

In the complete arrangement shown in Figure 5, two tubes enclosed in casings, as shown in Figures 3 and 4, are mounted on a deck 83 which 6 forms the top of a cabinet 95. The lower outlet pipes I09 from the tubular casings 89 and the upper outlet pipes II I are both brought into an outlet manifold H 6 from which the heated. air

I is" withdrawn by a fan. at H 1" driven. by at small Figure 1. Again, it is mounted on a deck 83 'forming' the top of the cabinet 99', but in this case the tube is inverted with respect to Figure 1' so that the end containing the cathode is uppermost and the end containing the output target is directed downwardly. The telescoping casing 33, 3?: with the outlet conductorsit! and tuningmec'hanisrn 55 are shown as in. Figure 1, and indeed the arrangementonly differs from that figure in details; for example, the tubular rod I2 and the sleeve 39 are lengthened so that the tuning: handle d9 can be located outside the cabinet: 99.- The sleeve 39 in fact passes. through the bottom of the cabinet by way of an insulating bushing 39a; The discharge tube itself is fitted with fins 85 similar to those shown in Figure 3, but they are in contact with the condenser plate 38- in which the sub-anode SA is clamped. The cooling 1 of the target end of the tube is efiected inthiscase by allowing air to enter the casing 33; 31 through inlet pipes I21I as shown by arrows I-22. These pipes I2 I are brought through the deck Ei3-an d communicate with the inside of the casing 83 The upper end of the discharge tube with the leadin wires for the otherelectrodes is, as shownat the top of Figure 6, located in the surrounding air. The tubular rod I2 is connected at its lower end toa tube I35 outside thecabinet 99 and connectedto the fan II 5 driven by the electric motor M8 by aninternal pipe I23. Thus, the tan I-ti' draws in air as shown. by the arrows I2 2, which flows into the casing 33, 3-1 in contact with the target through the tubular conductor rod I2 by way of the tube H6 and pipe I23, and out through the fan III. In order to cool the outside of the casing 33, 3-1, air is drawn in through the deck 83 around the tube itself", as shown by the arrows I24. This relatively slow stream of air is drawn out from the cabinet 99 by the fan I I9 driven bythe electric motor I28.

I claim:

1. Anelectron discharge tube instailation comprising a metal platform support, an. electron discharge tube having a plurality of electrodes including an. electrode extending outside the envelope of said tube where same is in contact with support, a layer of (ii-electric material in contact with said platform support, a metal plate spaced from said platform by said (ii-electric material, a metallic casing, enclosingat least part of. said discharge tube and secured to said metal plate and electrically connected to a further electrode of said tube, and formed with. inlet and;

outlet apertures for cooling fluid and means con prising an electron discharge tube having-an electrode extending outside the envelope of said tube, a metal partition in contact with and supporting said electrode outside the envelope of said tube, a layer of di-electric material covering a surface of said partition,.a metal plate spaced from said partition by said di-electric material, a metallic casing enclosing said tube and divided by said partition electrically and mechanically into two parts connected respectively to input and output electrodes of said tube and secured respectively to said partition and said metal plate, each being provided with inlet-and outlet apertures for cooling fluid and means connected to said outlet apertures for passing a stream of cooling fluid through the parts of said casing to serve as a cooling medium for said discharge tube. V

3. An electron discharge tube installation comprising a metal support, an electron discharge tube having an electrode extending outside the tube and secured to said support, an enclosing metallic casing secured to said support but spaced therefrom by dielectric material, and connected electrically to a, further electrode of said tube to form a part of a circuit thereof, an outer containing housing having an upper wall or deck formed with an air inlet aperture and bearing said casing and electron discharge tube with at least part of said casing enclosed in said housing, means connected to said metallic casing for passing a stream of air through said easing into contact'with a part of said electron discharge tube and means connected with the interior of said housing for passing a stream of air into said housing for cooling the external surface of said metallic casing.

4. An electron discharge tube installation comprising an electron discharge tube having an electrode extending outside of the tube, a metal partition to which said electrode is secured, a metallic casing enclosing said discharge tube and divided by said partition into two parts connected respectively to input and output electrodes of said tube, one of said parts being secured to said partition and the other being spaced therefrom by dielectric material, an outer containing housing having an upper wall or deck formed with an air inlet aperture and bearing said casing and electron discharge tube with one part of said metallic casing enclosed in said housing, means r connected to said casing for passing streams of air through the parts of said metallic casing to cool said discharge tube and means connected with the interior of said housing for passing a stream of air into said housing for cooling the external surface of the part of said metallic casing within said housing;

5. An electron discharge tube installation comprising a metal support, an electron discharge tube having a plurality of electrodes including an electrode extending outside the tube and secured to said support and provided with heatradiating fins externally of said tube, a metallic casing enclosing at least part of said tube and electrically connected to a further electrode thereof, said casing being secured to said support but electrically insulated therefrom, means for passing coolin fluid through said casing into.

contact with a part of said tube which is heated in operation, a housing enclosing said fins at least in part, and means for passing cooling fluid through said housing to abstract heat from said fins.

6. An electron discharge tube installation comprising a metal support, an electron discharge tube having a plurality of electrodes including an electrode extending outside the tube and securedto said support and provided with heat-radiating fins externally of the tube, a metallic casing enclosing said tube and comprising two parts electrically connected respectively to input and output electrodes of said tube, one of said parts being secured to said support and the other being electrically insulated therefrom, means for pass-- ing cooling fluid through said parts into contact with portions of said tube which areheated in operation, a housing enclosing said fins at least in part, and means for passing cooling fluid through said housing to abstract heat from said 7. An electron-discharge tube installation comprising a metal support, an electron discharge tube having a plurality of electrodes including an electrode extending outside the tube and secured to'said support, a metallic casing enclosing- 8. An electron discharge tube installation comprising a metal support, an electron discharge tube having a plurality of electrodes including-an electrode extending outside the tube and secured to said support, a metallic casing enclosing said tube and comprising two parts electrically connected respectively to input and output electrodes of said tube, one of said parts being secured to said support and the other part comprising telescoping sections one of which is electrically insulatedfrom said support and the'other of which is con nected to a tube electrode to form part of a shielded circuit of said tube, adjusting means for effecting relative sliding of said telescoping parts to adjust the resonant frequency of said shielded circuit, and, means for passing cooling fluid through said casing parts into contact with portions of said tube which are heated in operation.

9. An electron discharge tube installation comprising a metal support, an electron discharge tube having a plurality of electrodes including an electrode extending outside the tube and secured to said support, a metallic casing enclosing said conductors and slidably mounted in ,said' second casin part, adjusting mechanism for effecting sliding movement of said member to adjust the resonant frequency of said input circuit,.

and means for passing cooling fluid through said casing parts into contact with portions of said" tube which are heated in operation.

JOHN HENRY OWEN 'HARRIES.

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