US3209195A - High voltage electron discharge diode - Google Patents

Description

Sept. 28, 1965 o. H. SCHADE, SR 3,209,195

HIGH VOLTAGE ELECTRON DISCHARGE DIODE Filed March 13, 1961 2 Sheets-Sheet l made! 3 w Mada/7a Z'Z' 07m 16 50/424 61?.

S pt 8, 1965 o. H. SCHADE, SR

HIGH VOLTAGE ELECTRON DISCHARGE DIODE 2 Sheets-Sheet 2 Filed March 13, 1961 United States Patent 3,209,195 HIGH VOLTAGE ELECTRON DISCHARGE DIODE Otto H. Schade, Sn, West Caldwell, N.J., assignor to Radio Corporation of America, a Corporation of Delaware Filed Mar. 13, '1961, Ser. No. 95,129 13 'Claims. (CL 313-246) This invention relates to electron discharge devices and more particularly to electron tubes of the high voltage rectifier type.

During the normal operation of a rectifier tube the anode thereof is alternately driven positive and negative with respect to the cathode. In certain rectifier tube applications, such as in color television receivers, the difference in potential between the rectifier anode and cathode may be as much as 30,000 volts. These potential differences produce harmful electrostatic field densities and forces within the tube, which, as well known, limit the magnitude of voltages which may be applied to the rectifier tube electrodes, thereby limiting the possible utility of the tube.

Thus, for example, if during the inverse voltage peak, that is, when the anode of the rectifier is negative with respect to the cathode, the electrostatic field density or potential gradient at the surface of the anode should reach a value of the order of 100,000 volts per centimeter, cold or field emission takes place. Electrons are pulled from the anode and are accelerated toward the cathode and metal cathode supports. Some of the electrons miss the metal supports and bombard the tube envelope, causing eventual rupture of the envelope and failure of the tube. Moreover, since cold emission of electrons from the anode surface usually occurs from small areas of the anode, the electron current being focussed onto still smaller areas of the cathode structure or envelope, the result of such cold emission is often localized heating of the tube com ponents and the formation of hot spots thereon. Such hot spots result in the evolution of gases, the gases being detrimental to the operation of the cathode.

The eifects of electrostatic forces Within the tube are that mechanical stress-es are exerted thereby on the electrodes which may also be harmful to the operation of the tube. At each negative swing of the anode potential with respect to the cathode, for example, an electrostatic force is created which tends to pull the electron emitting cathode coating from the cathode. This electrostatic force is proportional to the square of the potential gradient at the surface of the cathode, and excessive cathode surface gradients may result in a tearing or peeling off of coating from the cathode and a disruption of the electron emission therefrom.

As known, the potential gradients within an electron tube for given electrode potentials are determined by the spacings between the tube electrodes and upon the smoothness and radius of curvature of the tube components. Small electrode spacings and tube components having sharp edges or rough surfaces tend to produce high potential gradients. Prior art practice, accordingly, has been to fabricate rectifier tubes having large dimensions in order to provide large electrode spacings, to provide electrodes and other tube components having polished surfaces, and to provide gradient shields having large radii of curvature for electrostatically shielding tube components having sharp edges or rough surfaces from the other tube electrodes. Such prior art practices have resulted in rectifier electron tubes which are expensive, and which are of undesirably large size.

Accordingly, it is an object of this invention to provide an improved rectifier electron tube which is economical of manufacture and which has unusually large voltage handling capabilities with respect to its size.

3,209,195 Patented Sept. 28, 1965 A still further problem caused by high potential gradients is flash-over or break-down of the air surrounding the tube envelope. Tube flash-over is somewhat equivalent to a direct short circuiting of the tube electrodes and can result in destruction of the tube or the electronic equipment utilizing the tube. It is known that flash-over may occur even though a large insulating member is provided between the tube electrodes. That is, in some prior art tubes, the location of the tube electrodes and gradient shields with respect to the insulating member is such that the potential distribution along the insulating member separating the tube electrodes is non-linear, most of the change in potential between the electrodes occurring over only a short length of the insulating member. The result of this is that high voltage gradients are thus produced along these short lengths which often lead to localized break-down of the surrounding air and failure of the electronic equipment.

Therefore, a further object of this invention is to provide an improved rectifier tube wherein the formation of excessively large potential gradients along the insulation between the tube electrodes is avoided.

More particularly, it is an object of this invention to provide a rectifier tube of improved construction in which relative dimensions of the tube parts result in the avoidance of the formation of undesirably large potential gradients.

For achieving these and other objects in accordance with this invention, an electron tube is provided which comprises an envelope including a cup-shaped header assembly, a tubular ceramic insulator, and a cup-shaped anode. The envelope parts referred to are secured together in stacked end-to-end relationship, the ceramic insulator separating the anode from the header assembly, and the latter two parts closing opposite ends of the envelope.

The cup-shaped header assembly comprises a conductive tubular portion having one end secured to the ceramic insulator and its other end closed by a ceramic closure member or wafer. Mounted within the header assembly and conductively secured to the tubular portion by an annular, disk-like member is an elongated tubular conductive cathode support. The cathode support extends axially of the ceramic insulator and into the anode, and has a cathode assembly including either a filamentary cathode or an indirectly heated cathode electrically connected with and supported on the end thereof within the anode. Included within the cathode support but electrically insulated therefrom is a conductor, one end of the conductor extending into the anode for supporting and making electrical contact to the cathode, the other end of the conductor being secured to a lead-in extending through the ceramic closure wafe. The lead-in and the header assembly tubular portion serve as the terminals for the cathode, the anode envelope portion serving as the anode terminal.

As will be described in detail hereinafter, advantages .of this construction are that the tube parts may be easily assembled and secured together, the electrode supports are tubular or circular having rounded and smooth surfaces for avoiding the formation of excessively high gradients, and certain portions of the electrode supports are utilized as gradient shields for certain other portions of the electrode supports.

Moreover, as will also be described hereinafter, the dimensions of the various tube parts are carefully chosen with respect to each other for reducing the formation of high potential gradients at the anode and cathode surfaces, and along the ceramic insulator.

In the drawing:

FIG. 1 is a longitudinal section, partially broken away, showing an electron tube according to this invention;

FIG. 2 is a view along line 2-2 of FIG. 1;

FIG. 3 is a partial section of a modification of the device shown in FIG. 1;

FIG. 4 is a vertical section of another modification of the device shown in FIG. 1;

FIG. 5 is a graph showing the relationship between potential gradients within an electron tube having coaxial tubular electrodes and the ratio of diameters of the tube electrodes;

FIGS. 6a, b and c illustrate the effect of tube geometry on potential distribution along the insulating member; and,

FIGS. 7 and 8 are longitudinal sections showing a brazing jig and an exhaust jig, respectively, of the types which may be employed in the fabrication of tubes made according to this invention.

As shown in FIG. 1, one embodiment of a rectifier electron tube made according to this invention comprises a .metal and ceramic envelope 10 including a cup-shaped metallic anode 12, a tubular ceramic insulator 13 and a cup-shaped header assembly 14. Header assembly 14, in turn, comprises a conductive metallic tubular portion 16 and a ceramic closure member 18. The ceramic wafer 18 is secured within a longitudinally extending flange 19 at the periphery of one end 20 of tubular portion 16, the other end 21 of tubular portion 16 being secured to ceramic insulator 13.

Axially disposed within envelope 10 is a cathode mount 24 including an elongated tubular conductor 26 mounted at one end 27 thereof to an annular flange member 29. Flange 29 has a centrally disposed tubular or cup-like portion 30 for receiving the end 27 of tubular conductor 26, and has a peripheral downwardly turned lip for engaging and securing the flange 29 with tubular portion 16 of header assembly 14. Included within tubular conductor 26 and extending axially and outwardly of each end thereof is a conductor rod 31. Conductor rod 31 is secured at its lower end 32 within the tubular portion 33 of an annular flange member 34 mounted on conductive lead-ins 36 extending through the ceramic wafer 18. The upper end 38 of conductor rod 31 is secured within tubular conductor 26 by an insulator washer 40'. Swage or flare 41 on conductor rod 31 maintains washer 40 in place, conductor rod 31 nowhere touching the inner walls of tubular conductor 26, being electrically insulated therefrom.

Tubular conductor 26 extends axially of ceramic insulator 13 into anode 12, and has mounted at the top end 43 thereof within the anode 12 a cathode filament support structure 45. As shown in FIGS. 1 and 2, filamerit support 45 comprises two U-shaped conductive rods 46 arranged to form a basket-like structure. The ends of rods 46 are formed inwardly and are secured within the top end 43 of the tubular conductor 26. Since the number of rods 46 and the diameter of the basket-like filament support 45 affect the potential gradients within the rectifier tube, as will be described hereinafter, one, two, or more rods forming support structures of varied diameters may be used depending upon the amount of filament shielding desired.

Mounted within filament support 45 is a cathode filament 48. One end of filament 48 is secured to and suspended from the inside top end 49 of filament support 45 and the other end thereof is secured to the top end 38 of conductor rod 31. The complete electrical circuit for the cathode filament 48 comprises lead-ins 36, which serve as one terminal for filament 48, annular flange 34, conductor rod 31, the cathode filament 48, the filament support 45, tubular conductor 26, flange 29, and header assembly tubular portion 16. Tubular portion 16 serves as the other terminal for filament 48.

As shown in FIG. 3, an alternative construction of the tube shown in FIG. 1 employs an indirectly heated cathode 52 comprising a cathode support sleeve 53 mounted on the end 43 of tubular conductor 26, and a cathode cup 54 mounted on sleeve 53. Cathode cup 54 has an electron emissive material 55 coated thereon. Included within sleeve 53 is a heating element 56 in the form of a helical coil, one end of the coil being secured within cathode sleeve 53 and the other end thereof being secured to conductor rod 31, as by welding. Aluminum oxide insulating material 57 is provided on the heating coil 56 and the end of conductor rod 31 for insulating the turns of the heating element 56 from each other and from the cathode sleeve 53 and for insulating conductor rod 31 from the inner walls of cathode support 26. Since aluminum oxide has a certain degree of structural strength, a sufficient quantity of it is used for insulatingly supporting conductor rod 31 within cathode support 26, thereby eliminating the need for insulating washer 40 used in the embodiment of FIG. 1. Also, the tube portion shown in FIG. 3 is part of a tube having a lower end similar to that of the tube shown in FIG. 1. For the tube of FIG. 3, however, lead-ins 36 serve as one terminal for the heating element 56, while header assembly tubular portion 16 serves as the terminal for both cathode 52 and the other end of heating element 56, the latter being electrically secured to cathode 52, as described.

Having thus described an embodiment of this invention, certain advantages and features thereof will now be discussed.

In FIG. 5 is shown a graph illustrating the relationship between the magnitude of potential gradients within a coaXial tubular electrode electron tube and the ratios of electrode diameters. The ordinate of the graph indicates potential gradients in kilovolts per centimeter, and the abscissa indicates the ratio of cathode to anode diameters for a tubular electrode structure. Curve 2 indicates the potential gradient at the surface of the anode, and curve 1 the gradient at the surface of the cathode. For the purpose of illustration, the diameter of the anode is two centimeters, and the potential differential between anode and cathode is one thousand volts. For the computation of the cathode to anode diameter ratios, the diameter of the largest element of the cathode assembly within the anode electrode at cathode potential is taken as the cathode diameter. This is because the largest diameter element determines the maximum anode surface gradient, and to a large degree, as will be discussed hereinafter, the maximum cathode surface gradient. In this embodiment the value of cathode assembly diameter is the outer diameter of filament support 45 for the tube construction shown in FIG. 1 or the diameter of cathode cup 54 for the construction of FIG. 3. For tubular electrode structures having other values of anode diameters and potential differentials, the shape of the curves shown in FIG. 5 is unaffected, the actual values of potential gradients being calculable by use of suitable multiplying factors.

It is apparent from these graphs that low electrode diameter ratios produce small gradients at the anode surface (curve 2), while small diameter ratios produce large gradients at the cathode surface (curve 1). The applicant has discovered, however, that the effects of large potential gradients at the anode surface are more likely to cause disruption of tube performance than are large gradients at the cathode surface. Moreover, because the rate of reduction in potential gradients at the cathode surface with increasing diameter ratios is very rapid at low diameter ratios while the rate of cathode surface gradient improvement with increasing diameter ratios is much smaller at higher ratios, the applicant, has determined that practical upper and lower limits for the diameter ratios are in the order of 0.2 and 0.09, respec: tively. At the lower limit, the anode surface gradinet is small while the cathode surface gradient is not excessively high. At the upper limit, the anode surface gradient has not yet become too high, whereas further in-' creases in diameter ratios have little effect towards improving the cathode surface gradients.

In the drawings of FIG. 6a, b and c, the effect of the ratio of tubular conductor 26 diameter to ceramic insulator 1 3 diameter upon the linearity of the potential distribution along ceramic insulator '13 is shown. The numbered dash lines 60 of these drawings are equipotential lines, the electrostatic field being normallized such that the anode potential is at a potential of 1.0 volts and the cathode assembly, tubular conductor 26 and flange 29 are at zero volts potential. The spacing of the equipotential lines 60 indicate the magnitude of the potential gradients at and near the lines, the closer the spacings between lines 60, the greater the potential gradients.

In FIG. 6a the ratio of tubular conductor 26 outer diameter to the ceramic insulator 13 inner diameter is 0.5, in FIG. 6b, 0.2; and in FIG. 60, 0; tubular conductor 26 being assumed to have an infinitestimal diameter in the latter figure for the purpose of illustration. As shown, the smaller the diameter ratio, the more uniform are the spacings between the equipotential lines 60. For a fixed length of ceramic insulator 13, the smallest value of the maximum potential gradient along ceramic insulator 1-3 occures when the spacings between equipotential lines 60 are preferably equal, that is, when the diameter -of tubular conductor 26 is infinitesimal.

For providing adequate strength to tu'bular conductor 26 for supporting itself and the cathode mounted therein, tubular conductor 26 must have a diameter greater than some minimum value. Since the tubular conductor is at cathode potential and extends into anode 12, the upper diameter limits imposed upon the cathode assembly within the anode, as described, also apply to tubular conductor 26. The maximum diameter of the tubular conductor, or at least that portion of it within anode 12, therefore, should be no greater than the diameter of the cathode 52 or filament support 45. Since the diameter of ceramic insulator '13 may be less than the diameter of anode 12, as shown in FIG. 3, however, the applicant has determined that the largest diameter of tubular conductor 26 within ceramic insulator 16 for preventing excessively high gradients along the ceramic insulator should be less than 0.2 of the inner diameter of the ceramic insulator. Likewise, the minimum diameter of the portion of tubular conductor 26 within ano'de 12 should be no less than 0.09 of the inner diameter of the anode. Within ceramic insulator 16, the tubular conductor diameter should be as small as possible consistent with the mechanical strength requirements of the tubular conductor and conductor rod 31 therein.

A feature of the invention is that the electrodes and electrode supports of the rectifier tube either have rounded and smooth surfaces or else are electrostatically shielded for preventing formation of high potential gradients.

The tubular anode 12, tubular ceramic insulator '13, and the tubular portion 16 of the header assembly 14 are all provided with smooth surfaces having large radii of curvature. Within header assembly 14 (FIG. 1) annular flange 29 represents a large, smooth surface towards the anode end of the tube and serves as a gradient shield for the end 27 of tubular conductor 26, the end 32 of conductor rod 31, and lead-ins '36 extending through closure wafer 18. For preventing the formation of a large potential gradient at the joint 15 between anode 12 and ceramic insulator 13, the inner edge 61 of the insulator is beveled as shown in FIG. 1. An alternate arrangement, as shown in FIG. 3, is to provide a gradient shield 62 secured to anode =12, shield 62 extending downwardly past the anode-insulator joint 15 to electrostatically shield the joint from the cathode. A still further alternative, as shown in FIG. 4, comprises a ceramic ring 68 which is provided between the ends of the ceramic insulator 1'3 and the anode 12. The ring 68 is brazed to these parts by a suitable brazing material by suitable known techniques. Upon heating and flow of brazing material to provide the brazed joints, the molten brazing material flows over and coats the entire ring 68 with a smooth metallized surface. This surface along with the curved inside surface 69 of the ring 68 avoids excessive gradients at the anode-ceramic insulator joint.

The cathode assembly is also designed to present the smoothest possible surface towards the anode for avoiding excessively large gradients. Extrusion or drawing methods are employed to fabricate cathode sleeve 53 and cup 54 (FIG. 3), whereby these elements as provided are seamless and completely smooth surfaced. The heating element 56 and the upper end 38 of conductor rod 31 are wholly contained within sleeve 53, thereby being completely shielded from the anode 12. In the construction illustrated in FIGS. 1 and 2, the basket-like filament support 45 serves as a gradient shield for the cathode filament 48. The support acts as a low mu grid surrounding the cathode filament 48, the larger the number of U-shaped rods 46, the greater the shielding effect of the support 45 on the filament 48. The ends of the rods 46 are formed inwardly to terminate within tubular conductor 26, as mentioned, and the upper end of the cathode filament 48 is carefully welded to the underside of the connecting portion 64 (FIG. 2) of the 'U-shaped rods 46 so as not to extend outside the confines of the support structure 45. By these means, any sharp edges at the ends of the filament wire or U-shaped rods 46 are carefully shielded and prevented from being the cause of localized excessively high gradients.

Some idea of the advantages provided by this invention may be realized by a comparison of a tube made according to this invention with a commercially available and extensively used rectifier tube having a coaxial tubular electrode structure. Tube type 3A3 is a glass octal tube type having an envelope diameter of 1.125 inches, an anode inner diameter of .563 inch, a cathode diameter of .025 inch, and a cathode support structure comprising a single U-shaped rod, the planar distance between the outside surfaces of the legs of the U (that is, the outer diameter of the support) being 0.250 inch.

For a value of inverse voltage of 50 kilovolts, analysis of the 3A3 structure reveals that the maximum potential gradient at the surface of the anode is about eighty-six thousand volts per centimeter, and about two-hundred and twenty-five thousand volts per centimeter at the surface of the filament. For a tube made according to this invention having an envelope diameter of only about .790 inch, an anode inner diameter of about .780 inch, and a filament support 45 outer diameter of about 0.080 inch, the maximum anode potential gradient is only twenty-two thousand volts per centimeter, while the cathode potential gradient is about two-hundred and twenty thousand volts per centimeter. The reason for the large differences in anode potential gradients between the two tubes is apparent upon examination of the graphs of FIG. 5. The cathode-anode diameter ratios for the 3A3 and the tube of this invention are 0.44 and 0.1, respectively, and from curve 2 of FIG. 5 it is to be expected that the anode surface gradient for the 3A3 would be much greater than the anode surface gradient for the tube of this invention.

The fact that the cathode potential gradients are about the same is explained as follows: Because of the relatively small shielding effect of the single rod filament support upon the filament of the 3A3, the potential distribution about the surface of the 3A3 filament is nonuniform. That is, because of the low mu of the filament support and its relatively close spacing to the anode, the shielding effect of the support on the filament varies materially from a point on the filament surface in the plane of the sides of the U-shaped support to a point on the filament surface in a plane perpendicular to the first plane. In the first plane, the value of cathode to anode ratio is 0.44, as mentioned, which results in a low cathode surface potential gradient. In the plane perpendicular to the first plane, however, the shielding effect of the support on the filament is so slight that the diameter ratio cannot properly be considered as 0.44.. In this plane, the diameter ratio is nearer a value of 0.05 which is the value computed on the basis of the diameter of the cathode filament itself with respect to the anode. From curve 1 of FIG. 5, it is apparent that the cathode surface gradient for such a low diameter ratio is very high. Thus, although parts of the filament of the 3A3 have relatively low surface gradients, other parts thereof have relatively large gradients, the larger gradients, as known, being the limiting factors determining the utility of the tube. A further advantage of this invention is the ease with which the tube may be assembled. As shown in FIG. 7, a jig 70 for fabricating the electron tube shown in FIG. 1 includes a number of jigging surfaces or elements 71 therein adapted for receiving certain ones of the tube components in properly spaced relationship. In the assembly and fabrication of the electron tube, the jig 70 is oriented with its open end up and the conductor rod 31, tubular conductor 26, and ceramic insulator 13 are loaded into contact with the jigging elements 71 as shown. The tubular portion 16 is then loaded on top of ceramic insulator 13, and flanges 29 and 34 are deposited in the order named onto the ends of tubular conductor 26 and conductor rod 31, respectively. The ends of tubular portions 30 and 33 of flanges 29 and 34, respectively, have inwardly turned lip portions 66 for providing positioning and balancing means for the flanges 29 and 34 on the ends of conductor 26 and rod 31. Closure Wafer 18 is then fitted to tubular portion 16 within flange 19 thereon, and lead-ins 36 are dropped through bores extending through wafer 18 to engage with and rest upon flange 34. Prior to such assembly, the ceramic wafer 18 has been provided with a metallic coating on its outer periphery which engages flange 19, and the walls of the bores likewise. The lead-ins 36, flanges 29 and 34, and tubular portion 16 have also been suitably coated with a brazing material.

The loaded jig 70 is then inserted into a furnace and heated in a reducing atmosphere at a temperature sufiicient to melt the brazing metal coatings. Upon cooling, the parts referred to are uniformly and completely brazed together to form a unitary mount structure.

Following the brazing operation, the mount structure is removed from the jig 70, and an insulating washer 40 is inserted into tubular conductor 26 and fitted onto'the conductor rod 31 therein. Also, the filament support structure 45 and the cathode filament 48 are welded .to the ends 43 and 38 of tubular conductor 26 and conductor rod 31, respectively, one end of the filament 48 having been previously welded to the support structure 45.

For completing the tube assembly, an exhaust jig 80 (FIG. 8) is employed. Jig 80 comprises a cup portion 82 adapted for receiving the anode 12 therein, and a tubular jig insert 84 adapted for receiving the ceramic insulator 13. Cup portion 82 and insert 84 are dimensioned to receive their receptive tube parts in relatively snug fit.

In the final assembly of the tube, the anode 12 is first dropped into cup portion 82. A ring of preformed brazing material 86 is then placed on the end of the anode 12. Thereafter, a flange portion 87 of insert 84 is engaged with a flange portion 88 of the cup portion 84, and the mount structure then inserted into insert 84. Ceramic insulator 13 is automatically aligned with the end of anode 12 as shown whereby exact centering of the anode 12 with respect to the mount structure and hence the cathode assembly is achieved. Exact centering and concentricity of the anode and cathode structures is very important for avoiding non-uniform electrostatic forces about the surface of the cathode assembly. Such non-uniform stress, as known, tend to cause distortion 8 of the fragile filament 48 and eventual destruction of the electron tube.

The loaded exhaust jig is then subjected to a final heating in vacuum. This final processing step serves to evacuate the tube, activate the cathode filament 48, and solder the anode 12 to the ceramic insulator 13. The temperature employed in this final step is substantially below the previous brazing temperature. Accordingly, the previously made brazes are not affected. Although not described, the tube constructions shown in FIGS. 3 and 4 may be fabricated in substantially the same manner.

What is claimed is:

1. An electron discharge device comprising an envelope including a header assembly, a tubular member, and an anode, said tubular member having a predetermined inner diameter, an elongated conduct-or extending through said tubular member and into said anode, a portion of the length of said conductor and substantially the entire length of said tubular member defining an unoccupied space therebetween, and a cathode assembly mounted on the end of said conductor within said anode, the maximum radial dimension of said portion of said conductor being less than 0.2 of said predetermined diameter.

2. An electron discharge device comprising an envelope including in stacked end to end relationship, a cup-shaped header assembly, a tubular member, and a cup-shaped anode, said tubular member being intermediate and separating said header assembly and said anode, and said tubular member having a predetermined diameter inner, an elongated conductor supported at one end thereof within said header assembly, said conductor extending axially of said envelope from said header assembly through said tubular member and into said anode, a portion of the length of said conductor and substantially the entire length of said tubular member defining an unoccupied space therebetween, and a cathode assembly mounted on the end of said conductor Within said anode, the maximum radial dimension of said portion of said conductor being less than 0.2 of said predetermined diameter.

3. An electron discharge device comprising an envelope including a tubular member, and an anode, said anode having a tubular portion of a first predetermined diameter, and said tubular member having a second predetermined diameter, an elongated conductor extending through said tubular member and into said anode, and a cathode assembly mounted on the end of said conductor within said anode, the radial dimensions of said cathode assembly being less than 0.2 and more than 0.09 of said first diameter, and the maximum radial dimension of said conductor being less than 0.2 of said second diameter.

4. An electron discharge device comprising an envelope including a header assembly, a tubular member, and an anode, said anode having a tubular portion of a first predetermined diameter, and said tubular member having a second predetermined diameter, an elongated conductor supported at one end thereof within said header assembly, sa d conductor extending from said header assembly into said anode, and a cathode assembly mounted on the end of said conductor within said anode, the radial dimensions of said cathode assembly being less than 0.2 and more than 0.09 of said first diameter, and the maximum radial dimension of said conductor being less than 0.2 of said sec- 0nd diameter.

5. An electron discharge device comprising an envelope including in stacked end to end relationship, a cupshaped header assembly, a tubular member, and a cupshaped anode, said tubular member being intermediate and separating said header assembly and said anode, said anode having a tubular portion of a first predetermined diameter, and said tubular member having a second predetermined diameter, an elongated conductor supported at one end thereof within said header assembly, said conductor extending axially of said envelope from said header assembly through said tubular member and into said an- 9 ode, and a cathode assembly mounted on the end of said conductor within said anode, the radial dimensions of said cathode assembly being within 0.09 and 0.2 of said first diameter and the maximum radial dimension of said conductor being less than 0.2 of said second diameter.

6. An electron discharge device comprising an envelope including in stacked end to end relation, a cup-shaped header assembly, a tubular ceramic member and a cupshaped anode, said ceramic member being intermediate and separating said header assembly and said anode, said anode having a tubular portion of a first predetermined diameter, said tubular ceramic member having a second predetermined diameter, and said header assembly comprising a conductive tubular portion closed at an end remote from said ceramic member by a ceramic closure member, an elongated tubular conductor supported at one end thereof within said header assembly and secured to said tubular portion, said tubular conductor extending axially of said envelope from said header assembly through said tubular ceramic member and into said anode, and a cathode assembly mounted on the end of said tubular conductor within said anode, the radial dimensions of said cathode assembly being within 0.09 and 0.2 of said first diameter and the maximum radial dimension of said tubular conductor being less than 0.2 of said second diameter.

7. An electron discharge device comprising in stacked end to end relation, a cup-shaped header asembly, a tubular ceramic member, and a cup-shaped anode, said ceramic member being intermediate and separating said header assembly and said anode, said stacked elements providing a closed envelope, the inner peripheral lip of the end of said ceramic member in engagement with said anode being beveled, said anode having a tubular portion of a first predetermined diameter, said ceramic member having a second predetermined diameter, and said header assembly comprising a conductive tubular portion closed at an end remote from said ceramic member by a ceramic closure member, an elongated tubular conductor supported at one end thereof Within said header assembly and secured to said tubular portion, said tubular conductor extending axially of said envelope from said header assembly through said ceramic member and into said anode, a conductor rod extending through and outwardly of said tubular conductor, said rod being supported at one end thereof by a lead-in extending through said ceramic closure member, and an electron emitting element supported at one end thereof on the end of said tubular conductor within said anode and having its other end supported by said conductor rod, radial dimensions of said electron emitting element being Within 0.09 and 0.2 of said first dimension, and the maximum radial dimension of said tubular conductor being less than 0.2 of said second dimension, said tubular portion and said lead-in serving as thermals for said electron emitting element.

8. A high voltage rectifier electron tube comprising a shallow cup-shaped header assembly, said header assembly including a conductive, open-ended tubular member having a flange at the periphery of one end thereof, a ceramic closure member sealed within said tubular member at said flange, an elongated ceramic tubular envelope portion of a first predetermined diameter having one end sealed to the other end of said tubular member, an elongated cup-shaped anode sealed to the opposite end of said ceramic tubular portion and providing with said ceramic tubular portion and said header assembly an envelope, said anode having a tubular portion of a second predetermined diameter, an elongated conducting tubular member secured at one end thereof to the tubular portion of said header assembly and extending axially of said ceramic tubular portion and into said anode, said conducting tubular member having an outer diameter less than 0.2 of said first predetermined diameter, a U-shaped supporting element mounted on the other end of said conducting tubular element within said anode, the radial di- 10 mensions of said U-shaped supporting element being within 0.09 and 0.2 of said second predetermined diameter, a conductor rod extending upwardly through and out wardly of each end of said conducting tubular member, said rod being secured at its lower end to a lead-in extending through said ceramic closure member, and a cathode filament secured at one end thereof to a portion of said -shaped supporting element and having its other end connected to said rod, said lead-in and said tubular portion of said header assembly serving as the terminals for said cathode filament.

9. A high voltage rectifier electron tube having an envelope comprising a tubular conductive member, an elongated tubular insulating member sealed at one end to one end of the tubular conductive member, an inverted cup-shaped anode electrode sealed to the other end of said elongated tubular insulating member, an insulating closure member'sealed to the end of said conductive tubular member at its opposite end from said elongated tubular insulating member, a first transverse flange secured at its periphery to the interior of said tubular conductive member, an elongated tubular conducting member secured at one end to said flange centrally thereof and supported thereby, a conductor extending through said elongated tubular conducting member, a second flange positioned between the first transverse flange and said insulating closure member, said conductor secured to and supported by said second flange, a lead extending through and sealed in said closure member, one end of said lead being secured to said second flange, and a cathode assembly supported at the end of said elongated tubular conducting member Within said anode, said conductor and said elongated tubular conducting member providing electrical connection with said cathode assembly.

10. A high voltage rectifier electron tube comprising a shallow cup-shaped header member, said header member including a conductive, open-ended tubular member having a flange at the periphery of one end thereof, a ceramic closure member sealed within said tubular member at said flange, an elongated ceramic tubular envelope portion having one end sealed to the other end of said tubular member, an elongated cup-shaped anode sealed to the opposite end of said ceramic tubular portion and providing with said ceramic tubular portion and said header an envelope, an elongated conducting tubular member secured at one end thereof to the tubular portion of said header and extending axially of said ceramic tubular portion and into said anode, a U-shaped supporting element mounted on the other end of said conducting tubular .element Within said anode, a conductor rod extending upwardly through and outwardly of each end of said conducting tubular member, said rod being secured at its lower end to a lead-in extending through said ceramic closure member, and a cathode filament supported at one end thereof to a portion of said U-shaped supporting element and having its other end secured to said rod, said lead-in and said tubular portion of said header serving as the terminals for said cathode filament.

11. A high voltage rectifier electron tube comprising a shallow cup-shaped header member, said header member including a conductive, open-ended tubular member having a flange at the periphery of one end thereof, a ceramic closure member sealed Within said tubular member at said flange, an elongated ceramic tubular envelope portion having one end sealed to the other end of said tubular member, an elongated cup-shaped anode sealed to the opposite end of said ceramic tubular portion and providing with said ceramic tubular portion and said header an envelope, an elongated conducting tubular member secured at one end thereof to the tubular portion of said header and extending axially of said ceramic tubular portion and into said anode, a supporting element mounted at the other end of said conducting tubular element within said anode, said supporting element comprising a plurality of U-shape rods arranged to form a basketlike structure, a conductor rod extending upwardly through and outwardly of each end of said conducting tubular member, said rod being secured at its lower end to a lead-in extending through said ceramic closure member, and a cathode filament supported at one end thereof to a portion of said supporting element remote from said tubular conducting member and having its other end secured to said rod, said lead-in and said tubular portion of said header serving as the terminals for said cathode filament.

12. A high voltage rectifier electron tube comprising a shallow cup-shaped header member, said header member including a conductive, open-ended tubular member hav ing a flange at the periphery of one end thereof, said flange extending parallel to and in the same direction as said tubular member, a ceramic closure member sealed within said tubular member at said flange, an elongated ceramic tubular envelope portion of a first predetermined diameter having one end sealed to the other end of said tubular member, an elongated cup-shaped anode sealed to the opposite end of said ceramic tubular portion and providing with said ceramic tubular portion and said header an envelope, said anode having a tubular portion of a second predetermined diameters, an elongated conducting tubular member secured at one end thereof to the tubular portion of said header and extending axially of said ceramic tubular portion and into said anode, said conducting tubular member having an outer diameter less the 0.2 of said first predetermined diameter, an indirectly heated cathode mounted at the other end of said conducting tubular element within said anode, the largest radial dimension of said cathode being within 0.09 and 0.2 of said second predetermined diameter, a conductor rod extending upwardly through and, outwardly of each end of said conducting tubular member, said rod being secured Cir at its lower end to a lead-in extending through said ceramic closure member, and said rod being insulatingly supported adjacent its upper end within said conducting tubular member, and a heating element included within said cathode, one end of said heating element being secured to said cathode, and the other end thereof being secured to said rod, said tubular portion of said header serving as terminals for said cathode and said heating element, and said lead-in serving as the other terminal for said heating element.

13. An electron discharge device comprising an envelope including a header assembly, a tubular member having a predetermined inner diameter, and an anode, an elongated conductor extending through said tubular member, a portion of the length of said conductor and substantially the entire length of said tubular member defining and unoccupied space therebetween, and a cathode assembly mounted on the end of said conductor within said anode, the maximum radial dimension of said portion of said conductor being less than 0.2 of said predetermined diameter.

References Cited by the Examiner UNITED STATES PATENTS 2,719,185 9/55 Sorg et al 3l3250 X 2,812,466 11/57 Murdock 313-3 17 FOREIGN PATENTS 815,655 5/56 Great Britain.

DAVID J. GALVIN, Primary Examiner.

RALPH G. NILSON, ARTHUR GAUSS, JAMES D.

KALLAM, Examiners.

Claims (1)

1. AN ELECTRON DISCHARGE DEVICE COMPRISING AN ENVELOPE INCLUDING A HEADER ASSEMBLY, ATUBULAR MEMBER, AND AN ANODE, SAID TUBULAR MEMBER HAVING A PREDETERMINED INNER DIAMETER, ADN ELONGATED CONDUCTOR EXTENDING THROUGH SAID TUBULAR MEMBER AND INTO SAID ANODE, A PORTION OF THE LENGTH OF SAID CONDUCTOR AND SUBSTANTIALLY THE ENTIRE LENGTH OF SAID TUBULAR MEMBER DEFINING AN UNOCCUPIED SPACE THEREBETWEEN, AND A CATHODE ASSEMBLY MOUNTED ON

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