US1849848A

US1849848A - Electric discharge apparatus

Info

Publication number: US1849848A
Application number: US374132A
Authority: US
Inventors: George F Murphy
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1929-06-27
Filing date: 1929-06-27
Publication date: 1932-03-15
Anticipated expiration: 1949-03-15

Description

March 15, 932. a. F MURPHY ELECTRIC DISCHARGE APPARATUS Filed June 27, 1

Will-Ill nventor 26 T. murph l l/LM His Attorne Patented Mar. 15, 1932 UNITED STATES PATENT OFFICE GEORGE E. MURPHY, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK ELECTRIC DISCHARGE APPARATUS Application filed June 27,

The present invention relates to electric discharge apparatus and more particularly to power tubes which employ electrodes of considerable size.

While in the manufacture of all kinds of radio tubes it is desirable to space the elec- 4 trodes accurately at predetermined distances apart in order to obtain the proper operating characteristics, this requlrement 1s absolutely imperative in power tube construction. In tubes of larger size, i. e. transmitting amplifiers, oscillators, modulators or the llke, the electrodes, particularly the grid and anode are often very closely spaced and in view of the considerable extent of the surfaces which may parallel one another at this close spacing, also in view of the considerable electrostatic mutual attraction between the surfaces at high operating potentials, it is necessaryto maintain the position of the electrodes rigidly with respect to one another in the assembly, and to provide an exceptional degree of ruggedness of electrode construction as well as an effective support at the place where the assembly is attached to the envelope. The last mentioned requirement, i. e. the rigid support between the electrodes and the envelope, heretofore has been satisfactorily met by the employment of two oppositely directed reentrant stems between which the electrodes are positioned by collars embracing the stems, secured thereto by clamps. However, it has been found that notwithstanding the rigidity offered by the stem and collar arrangement referred to, the operating characteristics of each tube made in quantity production are not always strictly alike according to predetermined required values and there have also been cases of tube failure during operation. These results have been attributed to the fact that there may have been a distortion or twist of the electrode assembly when the elements were aligned and fitted between the stems, which irregularities of construction were accentuated at the elevated temperatures to which the tubes are subjected during operation or else the electrode structure was such as to lend itself to warping under heated conditions, or both. I have found that when the electrodes and their 1929. Serial No. 374,132.

supports are fabricated in the manner described hereinafter, not only will the operating characteristics of the various tubes of 7 similar type be substantially alike but also tube failure may be reduced in a large degree.

Accordingly, one of the objects of my inventlon is to improve the electrode structure of power tube apparatus whereby the tube gives longer operating life than devices heretofore constructed, the improved construction to be characterized by being reproducible on a quantity production basis and to endow the devices made in the imp oved manner with similar predetermined opgrating characteristics per tube. This object is attained in brief by providing an improved form of anode, also an improved arrangement for supporting the anode and grid within the electrode assembly. Other objects and features will be apparent as the specification is perused in connection with the accompanying drawings in which Fig. l is an elevational view of a tube and electrodes improved in accordance with my invention while Fig. 2 is an elevational view in perspective of the electrode assembly secured in place between the reentrant stems of an envelope (not shown in this figure).

In the drawings, numeral 1 designates an evacuated envelope terminating at opposite ends in reentrant stems 2, 3. The electrode assembly is supported between these stems by means of collars 4, 5 and clamp rings 6. There is secured a fiat member 7 preferably of lava or steatite fired in hydrogen to the collar 4. The latter is closed at its lower end, as shown, by a metal plug 30 which is spot welded or otherwise secured to the collar. The plug is counter-bored to reduce the amount of contained metal and is provided with a pair of tapped holes which receive two screws 31 for securing the member 7 to the collar. I11 accordance with my invention the collar 5 is provided with a metal flange member 8 which has oppositely extending portions 9, 10 containing two pairs of holes through which are threaded two pairs of parallelly extending uprights or stay rods 11, 11 which may be riveted to the flange member at the under side. The other ends of the rods are I loosely threaded through suitabl spaced openings in the member 7. A gri 12 00111- posed of wire mesh is wound about the rods 11 and secured-thereto in any suitable manner, e. g. by spot welding or bound with wire. There is an M-shaped filament (not shown) within the grid having its upper apices secured to

anchor wires

13, 13 which are mounted under tension by means of a pair of

compression springs

14, 14. These springs are fitted at each end with caps 15, the anchor wires being rigidly connected to the upper caps. The caps are seated on a lava member 16 which is rigidly secured to the grid stay wires 11, and above this member is another lava piece 17 separated from the member 16 by spacing collars 18, serving to limit the upward movement of the compression springs. The lower ends of the filament as shown terminate in tic wires 19 and lead-in conductors 2O fused in the stem. According to another feature of my invention the anode takes the form of a hollow perimetrically complete body 21 preferably of molybdenum and fabricated in four sections, the two

outer sections

21, 21 having square ends and provided with normally extending

flanges

22, 22. The

inner sections

23, 23 are straight for the major portion and also terminate in flanges which are bent to conform to those of the outer sections to which they are secured by riveting. Extending horizontally across the entire width of the anode there are several rigidly secured channel bars 2-l to strengthen the anode; the

upright flange members

22, 22

are provided with openings to receive these bars in the manner shown. The anode thus has a strictly rectangular cross section because it is found that the square end construction not only offers advantage over the prior art semicircular ended type by way of greater ease of manufacture but also lends considerable strength to the structure. In being arranged normal to the sides of the anode the metal of the ends offers a greater compressional resistance to deformation or warp of the anode as a whole than in the case of the semicircular end. Moreover, by providing a member of rectangular cross section, it is possible to extend the laterally positioned bars to the extreme width of the member thereby providing additional ruggedness to the sides of this electrode. The use of channels as strengthening members is decidedly advantageous in providing the greatest amount of strength for the minimum amount of material involved, also in offering the greatest amount of surface for radiating heat, thus causing the entire surface of the anode to run at a very even temperature. The anode is supported at the upper end as illustrated by four stay rods 25 secured to the anode at the flanges 22; the rods fit tightly in small openings boredthrough the plug 30 of collar 4 and are anchored thereto preferably by spot welding. The other end of the anode likewise is supported by stay rods 26 attached to the flanges 22 and extending parallelly downward or rectilinear with respect to the anode to a plaje member 27, preferably of lava which fixes the lateral spacing of these rods. This plate member is provided with projections 28 in which suitably spaced holes are drilled to receive the grid uprights 11 and also the rods 26, the lava member being fixed to the uprights 11. The rods 26 pass through the holes with a sliding fit in order to accommodate the longitudinal expansion of the anode. It will be noted that the eifective width of the member 27 is such as to allow the rods 26 to extend directly downward from the flanges 22 without necessitating a bend inwardly as is present in the prior constructions on account of the narrowness of this lava piece in the prior art tubes. Hence, the improved shape of the lava member 27 provides the maximum amount of support to the anode from a torsional standpoint w-hile accommodating the longitudinal expansion of the latter and of the anode stay rods during operation. Moreover, it is apparent that by increasing the width of the member 27 over the prior constructlons, the leakage distance between the grid stay wires 11 and the anode rods 26 is increased accordingly. It will also be apparent that the flange member 8 to which the grid stay wires are riveted rigidly fixes these wires in place and together with

lava mem bers

7 and 27 positively precludes displacement of the grid with respect to the anode structure by twist or other distortional stress. It has been found that an anode unit constructed in the manner set forth hereinbefore and temporarily assembled before the collars were placed over the stems 4c, 5 constitutes a rigid body as a whole and positively precludes torsional strain or other displacement of the various electrodes with respect to one another. Hence, a construction of this sort is particularly desirable in the cases Where electrodes are of large area and the spacing therebetween is close and critical. This unusual degree of ruggedness and rigidity of the electrode assembly is enhanced by the fact that the electrode unit is securely attached to the reentrant stems 2,3 which form part of the envelope.

If desired, and as shown in Fig. 2, a capsule 29 containing getter material for the well understood purpose may be attached to the projection 9; the capsule feature, however, does not constitutea part of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is,-

1. In an electric discharge device, an evacuated envelope terminating in oppositely directed stems, an electrode assembly arranged between the stems, said assembly including a grid and an anode, means for rigidly positioning the grid in place, said means comprising a flange member secured to one of the stems, stay rods aflixed at one end to said memher for supporting the grid and at the other end to a plate member secured to the other of said stems, means for rigidly supporting the anode from the stem to which said plate member is attached, the opposite end of the anode being provided with rods, a second plate member positioned between said flange memberand the grid, said second plate member being secured to the stay rods and adapted to receive the anode rods whereby the electrode assembly constitutes a rigid unit and distortion by twist is precluded. Y 2. In an electric discharge device, an evacuated envelope terminating in oppositely directed stems, an electrode assembly arranged between the stems, said assembly including an anode'of rectangular cross section and a grid, said anode constituting closely spaced surfaces of relatively large area, means for rigidly positioning the grid in place, said means comprising a flange member secured to one of the stems, stay rods aflixed at one end to said member for supporting the grid and at the other end to a plate member secured to the other of said stems, means for rigidl supporting the anode from the stem to whic said plate member is attached, the opposite end of the anode being provided with rods, a second plate member positioned between said flange member and the grid, said second plate member being secured to the grid stay rods and adapted to receive the anode rods whereby the electrode assembly constitutes a rigid unit and the spacing between the electrodes is strictly maintaine under operating conditions.

3. In an electric discharge device, an evacu- 40 ated envelope terminating in oppositely directed stems, an electrode assem 1y arranged between the stems, said assembly including a grid and an anode, means for rigidly positioning the grid in place, said means comprising a flange mem er secured to one of the stems, stay rods ailixed at one end to said mem her for supporting the grid and at the other end to a plate member securedto theother of said stems, means for rigidly supporting the anode from the stem to which said late member is attached, the opposite end 0 the anode being *rovided with rods, a second plate member positioned between said flange member and the grid, said second plate memher being secured to the grid stay rods and adapted to receive the anode rods whereby the electrode assembly constitutes a rigid unit and distortion by twist is recliided. In witness whereof, have hereunto set my hand this 26th day of June, 1929.

GEORGE F. MURPHY.