US2406422A

US2406422A - Electrical space discharge tube

Info

Publication number: US2406422A
Application number: US574866A
Authority: US
Inventors: Wood Ross
Original assignee: Raytheon Manufacturing Co
Current assignee: Raytheon Co
Priority date: 1945-01-27
Filing date: 1945-01-27
Publication date: 1946-08-27
Anticipated expiration: 1963-08-27

Description

Aug. 27, 1946. R. wcm- 2,406,422

ELECTRICAL SPACE DTSCHARGEl TUBE Filed Jan. 27, 1945 '2 sheets-sheet 1 /oss Waan,

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ELECTRICAL SPACE DISCHARGETUBE v Filed Jan. 2'?, 1945 la f 2 Sheds-Sheet 2 ffasWoog/j Patented Aug. 27, 1946 ELECTRICAL SPACE DISCHARGE TUBE Ross Wood, Waltham, Mass., assignor to Ray theon Manufacturing Company, Newton, Mass., a corporation of Delaware Application January 27, 1945, serial No. 524,866 c claims. (Grasa-27.5)

This invention relates to electrical space discharge tubes of small dimensions, such as those used in small portable devices, pocket radios and hearing aids, for example, which may be carried on the person. In order that the tubes may be utilized in such' devices theyn must of necessity be made extremely small.

One of the objects of the present invention is to provide a tube of the general type referred to in which certain tube elements and their arrangement are such that said elements can be assembled ina very small space, thus materially reducing the size of the tube.

Another object of the invention is to provide a tube f the type referred to which' combines small size with relatively high amplification and low operating voltage.

Another object of the present invention is to` provide a tube comprising a single filament cathode supported at two points only, a plurality of anodes cooperating with said cathode and a plurality of additional electrodes between said cathode and each anode.

A further object of the invention is to provide a double space charge tetrode in which the two tetrodes have a common cathode and are adapted to operate in cascade.

These and such other aims and objects of the invention as may hereinafter appear will be best understood from the following description, taken in connection with the accompanying drawings, of a tube incorporating one embodiment of the invention herein presented for illustrative purposes.

In the drawings:

Fig. 1 is a longitudinal section of a tube incorporating one illustrative embodiment of the in vention; v

Fig. 2 is a longitudinal cross-section on line 2--2 of Fig. 3;

Fig. 3 is a cross-section on line 3-3 of Fig. 1; and

Fig. 4 is a section on line 4-4 of Fig. 2.

'I'h'e illustrative embodiment of the invention shown in the drawings comprises an evacuated .V

envelope 2 of glass or other suitable material containing the tube assembly which comprises a single lament cathode 4, a pair of

anode plates

6 and 8 and a plurality of grids, herein three, I0, I2 and I 4, said grid Il) surrounding said cathode and said grids I2 and I4 being interposed between said grid ID and said

anode plates

6 and 8 respectively. Said filamentary cathode, anode plates and grids are suitably spaced by upper and lower insulating spacing members I6 and I8 of mica or other suitable insulating material provided with suitably spaced holes through which said lamentary cathode and the supporting means for said anode plates and said grids extend, as will hereinafter more fully appear. At their edges said spacing members are provided with resilient projections 28 (see Fig. 3) for resiliently engaging the wall of said envelope.

The two

anode plates

6 and 8 are each mounted in a frame 22 of nickel wire or other suitable material consisting of a straight top portion 24 and depending arms 26 and 28 (see Fig. l).

To assemble the anode structure, the

arms

26 and 28 ofthe anode frames are inserted through holes in said upper spacing member I6 and said frames are then pressed down until said straight portion 24 of each of said frames rests upon the upper surface of said spacing member I6, whereupon the said

anode plates

6 and 8 are welded at their edges to said

arms

26 and 28 of their frames, l with the upper edge of each anode plate against the under surface of said spacing member I6. Said anode plates may be provided with marginal grooves along their side edges to receive and the better to locate

saidside arms

26 and 28. Said arms of both anode plates are then inserted through holes in the lower spacingmember I8. A lead-in conductor 30 is welded to the anode supporting arm 26 of anode plate 6 and another lead-in conductor 32 is welded to the anode supporting arm 28 of anode plate 8 diagonally across from said anode supporting arm 26, both of said welds being close up against the underside of said spacing member I8 to hold said spacing member in place on said arms. The anode assembly is thus completed and the two anode plates are electrically connected to their lead-in wires and securely fastened in place in the insulating spacing members I6 and I8.

The grid I0 is wound upon and supported by the

grid rods

36 and 38, and surrounds the filamentary cathode 4. Grids I2 and I4 are control grids, the former being supported by

rods

40 and 42 and the latter by

rods

44 and 46.

The grid supporting rods are all in a straight line and the rods to which the ends of the grid members of one of the control grids are secured, alternate withI the rods to which the ends of the grid members of the other control grid are secured. Actually the ends of the grid members of each of the control grids are secured at one end to an endmost grid supporting rod, and at th'e other end to the next to the endmost grid supporting rod, so that the two control grids actually overlap longitudinally of their grid members. This arrangement of th'e two control grids, therefore, provides a very compact grid structure and correspondingly reduces the size of the tube.

At its upper end the lamentary cathode 4 is welded to one end of a conducting spring member 48 which is welded at its other end to a rodl extending through said spacing rmembers I6 and I8. The lower end of said filamentary cathode is welded to a tab 50 which is welded to a crossbar 52 carried by two studs 54 riveted to the lspacing. .member I and to whichr cross-.bar52 is welded in turn'alead-in conductor 56, The lamentary cathode 4 passes through a triangular slot 58 in said spacing member I8 and throughY `a similar slot (not shown) in the spacing member i5 and'is maintained in an apex of each Vof Vsaid slots by the resilient tension exerted upon said lamentary cathode by the aforesaid spring mem--v `ber 48.

In addition to the above-mentioned lead-in

1conductors

30 and 32 for the "two anode plates, and the lead-in conductor 56 for the lamentary cathode, additional lead-in

conductors

62, 64, 66 and 68 are provided for the lamentary cathgrid I2 supporting rod 4e.

All of the above lead-in conductors are sealed `through a suitable press formed externally lupon the base 0f the envelope 2.

A getter 'I2 may be conveniently welded to the upper end of the supporting rod 46 of the half The arrangement of the electrodes and other elements of the tube embodying the present invention is extremely compact with the result that `the tube 4may be very small, and the electrode assemblyzcomprising a single cathodecooperatjing with two anodes and three grids constitutes in fact a double space charge tetrode in which the two tetrodes are sufliciently isolated for operating in cascade. rihe present invention there- `fore provides 'a tube which produces a degree of amplification substantially equal to that `ob `tainable from two Separate complete tetrodes, while dispensing with the additional structure and consequent greater bulk which the addition of the second cathode would involve.

While in the illustrative embodiment ofthe invention herein described two control grids and twoanode plates are used, it will be apparent to those vskilledV in the art that 'a tube comprising a greater number of control grids and vanodes lwould fall within the scope of vthe present invention, and this would be true also oi the combination of a single filament cathode with a plurality of cooperating anodes and a pluralityof additional electrodes between-the common cathode and each anode, the number of additional electrodes between the common cathode and one of said anodes not necessarily` being the same as the number of-additional electrodes between said common cathode and another of said anodes. Thus a tube having a'certain number of electrodes could be combined with'another tube having a lesser ora greater number of electrodes, the two tubes having a single filament cathode in common, and still be within the scope of the present invention. f Y Y The drain in small batteries that must be used in portable devices, to be carried on the person, such as those to which this invention mainly relates, is a serious matter. V'Ihe present invention aims to reduce this loss of energy as much as possible. It has' been demonstrated that an appreciable part of the energy-delivered tothe cathode is lost due to the escape of heat from the Epoints o f ,Contact of thecathode with the supporting structure.

In accordance with the present invention, therefore, a single iilament cath- Y ode is used which having only two ends or points of contact with the supporting structure reduces to a minimum theloss of energy from the abovementionedcause 1 I am aware'that the present invention can be embodied in other specific forms without departing from the spirit or essential attributes thereof, yand I'therefore desire to present description to I be considered in all respects as illustrative and the other end to an intermediate rod.

not restrictive, reference being had to the appended claims rather than to the aforesaid deoperating anode at each side o'f said cathode, a

space charge grid surrounding saidrcathode, and two substantially parallel control grids, one between each of said anodes and said space charge grid, said control grids overlapping each other lengthwise of their grid members.

k3. In an electrical space discharge tube, the Acombination of la cathode, a cooperating anode ateach side of sa'id'cathode, a space charge grid surrounding's'a'id cathode, a vcontrol grid between said space charge grid and each-anode, said control grids being substantially parallel', and rods disposed inva straight line 'for supporting- -said grids, the grid members of each f said-control grids beingsecured at one 'end to an Ae'ndmost rod of said line of grid supporting rodsandjat e. 'In an electrical space discharge "tube, the combination of afsingle filament cathode, Vla cooperating anode at each side of said cathode, a

`space charge grid surrounding sa'idcathode, a

` control grid between said spaceV charge grid and each anode, and rods disposed in astraiglit line for supporting said grids, the giidmembers of eachofrs'aid control grids being secured atone l endlto an endmost rodof said line of gridY :sup-

ginal portions of the otherf porting rods and at the other end to therod Vnext to the en'dmost rod.

5. In an electrical space discharge tube, a

cathode, two anodes, one on each side 'of said cathode, a space charge grid surrounding said cathodaand two control grids, one between each of said anodes and said space charge grid, said control grids being parallel and offset with-'reyspect to each other.

of said anodes and said space charge grid-said Y vcontrol grids .having offset central portions and Vcurved marginal portions, Vwith the curved marginal portions of one overlapping the curve-d `inar-