US2223985A - Thermionic valve apparatus for use on very short waves - Google Patents

Description

Dec. 3, 1940. N. E. DAVIS ETAL THERMIONIC VALVE APPARATUS FOR USE ON VERY SHORT WAVES 3 Sheets-Sheet 2 Filed June 26, 1937 MMC1 m M exam E mm: N 3?, VM .T N TE JT w A A NR M7 0 Dec. 3, 1940. N. E. DAVIS ETAL THERMIONIC VALVE APPARATUS FOR USE ON VERY SHORT WAVES 3 Sheets-Sheet 3 Filed June 26, 1957 DCV mm) QZIEQ'ZPEEv/s ERNEST GREEN BY Al FAQED IV! 000' IMl L Patented Dec. 3, 1940 UNITED STATES PATENT OFFICE THERMIONIC VALVE APPARATUS FOR USE ON VERY SHORT WAVES of Delaware Application June 26, 1937, Serial No. 150,444

In Great Britain June 26, 1936 9 Claims.

This invention, which is for improvements in or modifications of the invention claimed in our copending application Serial No. 8,470, filed Feb. 27, 1935, relates to thermionic valve or vacuum tube apparatus suitable for use on very short waves and more specifically to thermionic valve arrangements suitable for use in radio transmitters for operation upon wave lengths of the order of ten meters, or less. An important application of the invention is to television transmitters.

According to the parent invention, thermionic valve apparatus adapted to operate on very short wave lengths comprises in combination, a pair of symmetrically connected thermionic valves of the fluid-cooled type, in which the anode forms part of the envelope each mounted in and having its anode electrically connected to a metal screen or housing, said housings having their adjacent walls parallel or approximately parallel and spaced from one another, a movable conductor structure located between said adjacent walls and adapted in conjunction with said walls to constitute an anode circuit tuning condenser, a movable metal member in electrostatic association with a further wall of each of said housings, said metal members each in conjunction with the associated housing wall constituting a neutralizing condenser included in a circuit extending between the anode of one valve and the grid of the other, and a symmetrical cooling pipe arrangement extending between the anode cooling jackets and constituting a symmetrical anode circuit inductance.

The present invention provides certain constructional detail improvements in or modifications of valve apparatus in accordance with the parent invention.

In the specific embodiment described and illustrated in our parent copending application, supra, there is a slidably mounted output circuit unit which is mechanically independent of the rest of the apparatus and comprises a symmetrically arranged inductance which is adapted to be coupled magnetically to the anode circuit of the valves, the degree of coupling being adjustable by sliding the unit. This output circuit unit comprises an inductance (Ila) in Fig. l of our copending application Ser. No. 8,470, one end of which is connected to earth through a variable condenser (I I) and the other end of which is connected to an output feeder through a similar variable condenser (l lb). A feature of the present invention is concerned with the provision of an improved output circuit unit for performs ance, one of the fixed tubes being adjustably and conductively attached to an earthed carrier member (the unit as a whole being carried by this attachment) and the other fixed tube being adapted for connection to an output feeder.

The accompanying Figs. 1 to 5 show a preferred form of output circuit unit in accordance with this feature of the invention, Figs. 1, 2, 3, 4 and 5 being respectively a front elevation, a side elevation, a plan, an underside plan, and a section through the line AB of Fig. l with the coil omitted. Figs. 6 and 7 show a preferred construction of the blocking condenser that is a further feature of the invention, Fig. 6 is an elevation partly in section and Fig. 7 is a plan. Fig.

8 shows diagrammatically the position of the condenser of Figs. 6 and 7 in the circuit. Fig. 9 shows the arrangement of the cooling chambers for the valves and the neutralizing and anode circuit tuning condensers. In the construction of Figs. 1 through 5, the inductance (I la of Fig. 1

of application Ser. No. 8,470) is in the form of a two-turn rectangular pancake coil I I la composed of metal tubing through which cooling fluid may be passed if desired. The two condensers (l lb, llc of Fig. 1 of the parent specification) are constituted each by a pair of metal tubes lllb, Zllb or lllc, Zllc coaxially arranged one inside the other. The outer tubes 2| lb and 2| Ic are parallel, side by side, and are fixed to an insulated body member H l of plate-like form, the said outer tubes being fixed thereto by phosphorbronze bands 2| l 3| l which are drawn tight round the tubes to grip them. The inner tubes II It and lllc are carried by being fitted into apertures in an insulating bridge piece M l extending at right angles to the tube axes and fixed to a slidable insulating slide member 5 which extends in a direction parallel to the tube axes and can slide in the direction of its length in suitable guides on the face of the body memher Ill opposite that on which the outer tubes are held. The coil ill a is mechanically fixed to the inner tubes each end of the coil 2| la, 3l la being attached to and carried from one end of ne or other of the inner tubes lllb, lllc. Thus,

ber 8 which embraces an elongated cylindrical H metal carrier 9 from which the whole unit is carried and which is earthed. The carrier member is hollow and its axis is parallel to the tube axes. adjustment of the position ofthe unit relative to the carrier is preferably arranged coaxially bvithin the said carrier. Means (l l I I) are provided for locking the adjustments provided. .In

use, the unit (with its output feeder) is carefully pre-tuned and then it is adjusted on the carrier for optimum coupling as regards the coil. The tubular condenser design described is of great advantage in minimizing stray capacity effects and giving good high frequency current distribution, low inductive reactance in the condensers themselves, and high frequency capacity values approximately to static values.

In the specific embodiment described and illustrated in the parent specification application Ser. No. 8,470 there are two valves feeding into a tuned circuit comprising an inductance (Ba/and b-see Fig. 1 of application Ser. No. 8,470) which is coupled to the inductance (lid) in the output. circuit unit and which connects the anodes (I, 2) of the valves together, anode feed being supplied to the anodes via the electrical center of the coil 9!; and b. In the case of a powerful transmitter, e. g., a kw. transmitter-theoscillatory anode circuit current may be very highe. g., about 90 amperesand in order that a true balance of power generation may be obtained as between the two valves, it is very desirable to provide means whereby the anode feed currents may be separately measured. Accordingly, in accordance with a further feature of this invention, the inductance 9a and b is divided centrally into two' similar inductances which are connected together by a preferably tubular blocking condenser so that feed currentsmay be applied to the two valves separately via the two opposite terminals of the blocking condenser; The blocking condenser is preferably of the tubular type in order to obtain the good high frequency current distribution and large effective surfacefor high frequency currents offered by this type of con denser.

A preferred construction embodying this feature of thepresent invention is illustrated in the accompanying Figs. 6 and 7 in which Fig. 6 is an elevation, partly in section and Fig. 7 is' a plan. Referring to these'figures, each of. the two half inductances which together constitute the in ductance 9a and b is constituted by 'a lengthof closely spaced, parallel, conductive fluid cooling pipes (not shown) which leadat one end to'rubberhose water supply connections (not shown) and at the other to the water cooling chamber for one of the valves (not shown). The tubular blocking condenser which is to connect the two half inductances together comprises two simi-' lar cylindrical metal tubes MTI, MTZ having their axes in the same straight line,'said tubes beingarranged end-to-end but spaced a little apart; a centrally positioned layer .LMyof' mica or other insulation which encirclesboth tubes but does not extend to the outermost ends;: and'a' A handle or shaft IOH for facilitatin split phosphor-bronze band or clamp MBC which embraces the insulation and is tightened up about it (e. g., by means of clamp bolts and nuts at MBCI) so as to hold the tubes and insulation firmly. This condenser is thus in effect two capacities in series, i. e., the capacity between one tube and the band MBC and that between said band and the other tube. The outer end of each tube is fixed to or unitarily formed with an arouate part-cylindrical metal member MM! or MMZ, embracing about a quarter of a circle, the axes of the part cylinders being parallel to one another and at right angles to the axes of the tubes. Attached to one end of each part cylindrical member is a metal strap or band MMCl or MMC2, whose other end is attached to a screwed stem MMSI or MMSZ, which passes through a bolt hole in said member and is adapted to receive a knurled'nut, as shown. In use, the pipes (not shown) constituting the half inductances are' placed 'againstythe part-cylindrical members MMLMMZ at'the outer ends of the tubes, the straps MMCI, MMC2 attached to those members are passed round the said pipes, the screwed.

stems MMSI, MMS2 are inserted in their appropriate bolt holes-and the knurled nuts are then screwed tight so that thesaicl straps clamp the pipes firmly against the appropriate part-cylindrical members so as to provide firm mechanical and electrical connection for the blocking condenser. The overall length of the condenseris, of course, made approximately equal to the distance between the half inductances. It will be appreciated that this overall length can be adjusted by slacking the clamp MBC which holds the tubes and moving said tubes nearer together or further apart. Obviously, howeveig-the said tubes must not be allowed to touch one another. The clamp can be drawn very tight to prevent the occurrence of air pockets between the condenser electrodes which might adversely afiect high frequency current distribution. The accompanying Fig. 8 shows diagrammatically the position of the condenser of Figs. 6 and 7 in the circuit, the said condenser-being marked BC in Fig. 8. In the said Fig.8, WSare rubber hose water columns, the instruments DCA and DCV are direct current D. C. voltage measuring instruments, respectively, the terminals FT; HT+ and HT-; GB-land GB; and FV are, respectively, filament supply terminals, high tension supply terminals; grid bias supply terminals; and filament voltmeter terminals, and the other references correspond with those used in Fig. 1 of the parent case.

Another feature of this invention is concerned with the arrangement of .the cooling chambers for the valves and the neutralizing and anode circuit tuning condensers 8r, Y5Y, (see Fig. 1) of the parent specification. According to a further feature of: this invention, the anode cooling chamber proper of each valve is in communication with a flat metal cooling liquid box, the two boxes beingJparaIIel and spaced apart and the valves being positioned outwardly thereof, the anode circuit tuning condenser including a movable box-like conductor structure which is longitudinally slidable between the parallel walls of the spacedboxes and each of the neutralizing condensers including an electrode adjacent one of said walls.

A preferred embodiment of this featuresis'shown in diagrammatic perspective in mounted vertically outside the other box CB2. Short fluid fiow metal pipes FMP support the valves from their respective boxes and put the opposite ends of the respective valve anode jackets into communication with the opposite ends of the appropriate cooling box. Between the two cooling boxes is a slidably mounted box-like eonductor structure BXC which with said boxes constitutes the anode circuit tuning condenser, this structure generally resembling the corresponding structure (5) of the parent specification and performing the same electrical functions. The functions of the walls YY (so far as this condenser is concerned) of the arrangement illustrated in the parent specification are thus performed by the fiat cooling box walls between which the movable conductor structure is positioned. These said walls are also utilized to perform the functions of the walls IQ! of the arrangement illustrated in the parent specification, for the neutralizing condensers are constituted each by one of the said walls (of a cooling box) in conjunction with an electrode adjustably positioned adjacent thereto, there being two such electrodes-one adjacent a wall of each cooling box-in the space between the two boxes. Only one such electrodewhich is marked FIX-appears in Fig. 9. The anode inductance pipes communicate with the flat cooling boxes, as shown.

In one embodiment described in the parent specification and suitable for use where a wide bandpass is required, a substantial resistance is imparted to the inductance 9a and 9b by spraying the copper tubes constituting the said inductance with soft malleable annealed iron or material of similar properties. As a result of this, the high frequency currents, which will pass by reason of skin efiect mostly along the outsides of the conductors 9a, 9b will suffer considerable loss due to the high permeability of the iron surface while at the same time the advantages of copper piping for carrying the water are still obtained. In broad principal, this method of obtaining loss to secure a desired inductance/resistance ratio consists in utilizing the water passing down the tubes 9a, 9b to dissipate the required proportion of energy; that is to say, the high frequency loss is induced by reason of the external soft iron coating but the heat generated by that loss is quickly and eiiiciently dissipated by reason of heat conduction through the copper pipe to the water. Although this method of introducing loss may be employed in carrying out the present invention, it is at present preferred to introduce the loss in the grid circuit. In accordance with another feature (not illustrated) of this invention, therefore, a fluid cooled input inductance, corresponding to the inductance 20a of Fig. 1 of specification application Ser. No. 8,470 and adjustably coupled by a trombone slide arrangement with an inductance corresponding to the inductance l8 (of the same figure), is shunted by a resistance consisting of a series of cylindrical resistance units which are physically parallel to one another but electrically in series and are disposed along a circle the axis of each cylindrical unit lying on an imaginary cylinder and being parallel to the axis thereof. The resistance units are air cooled, air being passed up through the resistance units which are formed hollow. The said resistance units are mounted over insulating nozzles in a circular air admission conduit memher so that air passes from said nozzles up through the resistance units, the other ends of said units communicating with a common drawoff pipe in which a motor driven fan is situated the fan serving to draw air along the exteriors and interiors of the units.

What is claimed is:

1. improved radio transmitter arrangement comprising an input circuit and an output circuit, said output circuit having a high potential and a ground terminal, means for coupling said output circuit with a pair of symmetrically arranged electron discharge tubes, said means comprising two concentric tube condensers each having a movable tube and a tube which is normally fixed when said transmitter is in operation, said movable tubes being arranged to move together for capacity adjustment, and each being electrically connected to one end of an inductance, one of said normally fixed tubes being adjustably and conductively connected to said ground terminal, the other normally fixed tube being connected to the high potential terminal of said output circuit.

2. An improved radio transmitter arrangement comprising an input circuit and an output circuit, said output circuit having a high potential and a ground terminal, means for coupling said output circuit with a pair of symmetrically arranged electron discharge tubes, said means comprising a slidably mounted condenser unit arranged independently of the apparatus in the input circuit, said condenser unit having a symmetrically arranged inductance secured thereto which is magnetically coupled to the anode circuit of said symmetrically arranged tubes, the degree of coupling between said anode and said output circuit being determined by sliding said condenser unit.

3. An improved radio transmitter arrangement comprising an input circuit and an output circuit, said output circuit having a high potential and a ground terminal, means for coupling said output circuit with a pair of symmetrically arranged electron discharge tubes, said means comprising two concentric tube condensers, each having a fixed and a movable tube, said movable tubes being arranged to move together for capacity adjustment, an inductance coil, one of said fixed tubes being mechanically and electrically connected to one end of said inductance coil, one of said fixed tubes being adjustably and conductively connected to said ground terminal, the other fixed tube being connected to the high potential terminal of said output circuit.

4. An improved radio transmitter arrangement comprising an input circuit and an output circuit, said output circuit having a high potential and a ground terminal, means for coupling said output circuit with a pair of symmetrically arranged electron discharge tubes, said means comprising two concentric tube condensers each having a fixed and a movable tube, an insulating bridge member secured to said fixed tube, said movable tubes being arranged to slide through said bridge member for capacity adjustment, and each being electrically connected to one end of an inductance, one of said fixed tubes being adjustably and conductively connected to said ground terminal, the other fixed tube being connected to the high potential terminal of said output circuit.

5. In an improved radio transmitter arrange ment comprising input and output circuits, said output circuit having a high potential and a ground terminal, means for coupling said output circuit with a pair of symmetrically arranged electron discharge tubes, said means comprising an inductance and two concentric tube condensers each having a fixed and a movable tube, each end of said inductance connected to said movable tube condensers, a second inductance coupled to said first mentioned inductanceand symmetrically divided into two portions, the outer ends of said inductance portions connected to the anode circuit of said electron discharge tubes, each of the two portions of said second inductance coupled together by a metallic member insulated from said portions and bya plurality of tubes forming a blocking condenser so that feed currents may be supplied to the two symmetrically arranged discharge tubes separately by means of two opposite terminals on said blocking condenser.

6. An improved radio transmitter arrangement comprising an input circuit and an output circuit, said output circuit having a high potential and a ground terminal, means for coupling said output circuit with a pair of symmetrically arranged electron discharge tubes, said means comprising an inductance and two concentric tube condensers each having a fixed and a movable tube, said inductance having each of its ends connected to said movable tubes, one of said fixed tubes being adjustably and inductively connected to said ground terminal, the other fixed tube being connected to the high potential terminal of said output circuit, a second inductance coil symmetrically divided at its center and connected together by a condenser comprising two fixed and'two'movable tubes each having their axis in the same straight line and arranged end-to-end but spaced apart from each other, a centrally positioned layer of insulation encircling both the said tubes, and a split bandclamp embracing said layer of insulation and having means for tightening up so as to hold the tubes and insulation firmly in position, said movable tubesbein'g connected to the divided center ends of said second inductance coil.

'7. An improved radio transmitter arrangement comprising an input circuit and an output circuit, said output circuit having a' high potential and a ground'terminal, means for coupling said output circuit with a pair of symmetrically arranged electron discharge tubes, said means comprising two concentric tube condensers each having a fixedand a movable tube, said movable tubes being arranged to move together for capacity adjustment, a pipe-like inductance coil secured to at least one of said concentric tubes, one of said fixed tubes being adjustably and conductively connected to said ground terminal, the other fixed tube being connected to the high potential terminal of said output circuit.

8. An improved radio transmitter arrangement comprising an input circuit and an output circuit, said output circuit having a .high potential and a ground terminal, means for coupling said output circut with a pair of symmetrically arranged electron discharge tubes, an anode cooling chamber forsaid electron discharge tubes, a fiat metal cooling liquid box in fluid communication with each of the anodes of said tubes, the 7 two boxes being arranged parallel to and spaced apart from each other, said electron discharge devices being positioned outwardly thereof, two

variable tuning condensers including a movable box-like conductor structure which is longitudinally slidable between the parallel walls of said cooling liquid boxes, a neutralizing condenser having at least one of its electrodes adjacent one of said Walls of said cooling liquid boxes.

9. An improved radio transmitter arrangement comprising an input circuit and an output circuit, said output circuit having a high potential and a ground terminal, means for coupling said output circuit with a pair of symmetrically arranged electron discharge tubes, said means comprising two concentric tube condensers each having a fixed and a movable tube, said movable tubes being arranged to move together for capacity adjustment, and each being electrically connected to one end of an inductance, a resistance in shunt with said'inductance which serves to introduce losses to provide a desired width of bandpass, one of said fixed tubes being adjustably and conductively connected to said'ground terminal, the other fixed tube being connected to the high potential terminal of said output

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