US2965791A - Shock and acceleration resistant electron discharge device - Google Patents

Description

Dec. 20, 1960 R. s. BRIGGS ET AL 2,965,791

SHOCK AND ACCELERATION RESISTANT ELECTRON DISCHARGE DEVICE Filed May 17, 954 2 Sheets-Sheet 1 INVENTOR. RICHARD S. BRIGGS GEORGE E. CARTE JR.

ATTORNEY Dec. 20, 1960 R. s. BRIGGS ETAL 2,965,791

SHOCK AND ACCELERATION RESISTANT ELECTRON DISCHARGE DEVICE Filed May 17, 1954 F l G. 4

2 Sheets-Sheet 2 F I G. 5

INVENTOR. RICHARD S. BRIGGS GEORGE E. CARTER R.

BY ATTORNEY States Patent O SHOCK ANDACCELERATION RESISTANT ELECTRON DISCHARGE DEVICE Richard S. Briggs, Beverly, and George E. Carter, Jr., Danvers, Mass., assig'nors to Bomac Laboratories Inc., Beverly, Mass., a corporation of Massachusetts Filed May 17, 1954, Ser. No. 430,196

3 Claims. (Cl. 313-265) The present invention relates to electron discharge devices and more particularly to a novel thermionic tube for use under severe conditions of shock and acceleration and to a method of assembling said tube.

Thermionic tubes having conventional electrode structure mounted within an evacuated envelope cannot be employed in certain applications where the tubes and equipment are subjected to severe shocks and accelerations. Prior art tube components and structure such as mica spacers, dielectric envelopes, electrode support struts, and welded joints are subject to breakage and distortion when employed in devices operated under such abnormal conditions.

Recent military developments have shown the increasing need for thermionic tubes capable of withstanding severe shocks and accelerations up to 100,000 gravities. Further, the desired tubes must provide conventional tube characteristics.

It is an object of the present invention to provide a novel shock and acceleration resistant thermionic tube.

It is a further object to provide a novel shock and acceleration resistant thermionic tube having conventional tube characteristics.

A still further object is to provide rugged electrode support structure capable of withstanding extreme shocks and high accelerations.

Another object is to provide a method of assembling an electron discharge device of novel rugged structure.

The present invention discloses a thermionic device having metallic electrode supports disposed at the ends of an envelope of a conductive metal. The supports are assembled by utilizing glass to metal seals as well as brazing techniques and the electrode structure is positioned within the envelope by means of the rigid support structure.

The objects, features, and advantages will be more readily appreciated after consideration of the following detailed description and accompanying drawings in which:

Figure 1 is an enlarged perspective view of an illustrative embodiment of the present invention;

Figure 2 is a detailed cross-sectional view of the embodiment;

Figure 3 is a cross-sectional view along the line IIIIII in Figure 2;

Figure 4 is an exploded view in section showing the relationship of the components of the present invention, exclusive of the cathode assembly; and

Figure 5 is an enlarged view of the cathode assembly.

Referring to the drawing, Figure 1 illustrates the construction of the envelope of the embodiment of our invention. As shown, the envelope consists of cylindrical metallic members 1, 2, and 3, desirably of a conductive metal suitable for sealing to glass. Such a metal may be Kovar, which consists of nickel, iron and cobalt, and has substantially the same coeflicient of expansion of a matching glass. Center member 2 comprises the main body of the envelope and may be provided with a shoulder at each end, as at 4 and 5. In the final assembly of the 2,965,791 Patented Dec. 20, 1960 2 tube according to the method of the invention, cylindrical end members 1 and 3 are fitted on the shoulders of the center member and are sealed thereto to form a vacuum tight enclosure. The assembled envelope defines a central passageway in which the electrodes of the device are positioned.

End members 1 and 3 have sealed at their outer ends, cylindrical grid supports 6 and 7 of a similar conductive metal having a smaller diameter than said end members. A concentric glass bead 8 and 9 of a suitable dielectric material such as Corning 7052 or 707 glass maintains the positioning of the grid supports coaxially with the end members 1 and 3. The point. of seal of the glass head is approximately, but not limited to an intermediate point with the inwardly extending end rigidly supporting the grid 10. Slots may be provided at the inner end of the grid supports to allow for a snug engagement of the grid. In the embodiment of the invention, we have provided four slots, three of which are visible in Figure 2 at 11, 12 and 13. If desired, the grid may be brazed to the inner wall of the supports 6 and 7.

Grid 10 consists of a frame having parallel metallic side rods 15 and 16 with a plurality of turns of a suitable wire helically wound and fixed thereon. The ends of the side rods have a substantial Y bend as at 17. The overall shape of the grid is generally rectangular as shown in Figure 3.

Cathode support members 18 and 19 of a still smaller diameter are next supported coaxially by grid supports 6 and 7. A glass bead 20 and 21 positions the cathode supports in a similar manner to that previously described. Filamentary cathode 22 is firmly suspended within the central passageway by means of a spring bearing pin 38 and tubular member 23. One end of the filament may be swaged to the tubular member 23 as at 24. The other end is spring tensioned by means of a reverse coil spring 25 attached to a mandrel section 26 on pin 38. The ends of spring 25 may be: ai'fixed to the mandrel section by welding or brazing. After assembly of the filamentary cathode in the tube, the ends of the cathode members 18 and 19 may be sealed, as by soldering, as at points 27 and 28 to provide a vacuum tight enclosure.

As shown in Figure 5, the filamentary cathode 22 is coated with a suitable emissive material 31 by the commonly employed methods such as spraying or cataphoretically coating said wire. In the illustrative embodiment we have found the coating of barium and strontium carbonates with a bonding agent produces the desired result with a tungsten wire filament.

The concentricity and radial spacing of the electrodes will be appreciated in Figure 3. Outer envelope section 2 serves as the anode or plate electrode. Spaced within the central passageway defined by the envelope and centered around a common axis are the cathode 22 and grid 10 electrode. The latter two electrodes are rigidly supported to resist shock and acceleration by the tubular metallic members which also provide good electrical conductivity. Since the selected metal Kovar possesses the desired characteristics for sealing to glass, this metal has been employed for all the supporting members, however, any other suitable metal having similar characteristics for scaling to a matching glass may be employed, if desired.

The advantages of the telescoping arrangement of all the metallic supporting members will be appreciated in the ease of assembling and processing the tube of our invention.

Figure 4 shows the arrangement of the component parts in the method of assembling the tube. Two end sub-assemblies are glass beaded to maintain the parts in their desired relationship. Since both tube assemblies possess similar element spacings, a jig may be provided for this operation. The assembly of parts 3, 9, 7, 21, and 19 are next supported in a suitable holding fixture in an upright position. Grid'ltl is then fitted in the supporting member 7 and is rigidly held by the slotted section.

Next, the center body member 2 is positioned on the assembly with a solder ring 32 resting against shoulder and the lip of this shoulder in-a snug relationship with the inner wall of the end member 3. Another solder ring 33 is fitted over shoulder 4 of said center body member followed by the sub-assembly 1, 8, 6, 20, and 18. Grid engages the inner wall of the slotted support member 6. The dimensions of the assembled components are selected to provide proper alignment of the electrodes. Hence, the shoulders 4 and 5 have dimensions which allow excellent electrical continuity between members 1, 2, and 3, as well as a close fitted relationship at the ends of the grid 10 against support members 6 7'- Lastly, an exhaust tube 29, which is provided with a shoulder 35 and a solder ring 36 is inserted in a passageway 37 in the center body 2.

After assembly, the tube is fired or baked in an inert non-oxidizing atmosphere, such as hydrogen, to a temperature necessary to braze the joined members. Such heat treatment serves to both clean the components as well as to braze the assembly. It will be evident that the danger of contamination of the cathode is avoided by providing this novel structure and assembly. The brazed assembly is now ready 'for insertion of the cathode assembly.

A complete spring tensioned and coated filament cathode assembly is mounted -in the tube in an upright position with tubular member 23 being introduced through support member 18. Downward travel of the cathode assembly will be terminated when the swaged portion 24 engages an internally chamfered portion of member 19 as at 34. Tubular member 23 is then secured to the cathode support member 19 by soldering.

With one end of the cathode securely positioned, tension may be placed on the pin 38. We have provided the pin 38 with a longer overall dimension to facilitate the tensioning operation. As soon as the desired tension has been attained, pin 38 may be cut and similarly soldered to support member 18.

The tube is next evacuated and gettered by known techniques and exhaust tube 29 tipped and sealed as at 30.

External electrical connections for the components may be made in a simple and efficient manner. The grid electrode supports 6 and 7 furnish means for attaching lead wires to energize the grid and similar connecting wires may be attached to tubular members 18 and 19 to energize the cathode electrode. Since the outer envelope section 2 forms the anode electrode, a lead wire may be similarly attached to this section.

Other forms of electrical connections, such as a elamping device having electrically conductive tabs may also be employed.

The embodiment of our invention may be further strengthened by securing the suitable lead wires and then immersing the tube in a rubber or plastic coating compound to cover all exterior surfaces.

Tubes of the character described have performed satisfactorily as an oscillator with warm-up times of under three-tenths of a second. With suitable circuitry the tube may also be adapted to function as an amplifier, rectifier or detector tube.

Due to the compactness of the structure the device disclosed also lends itself quite readily to modern high speed production methods.

While we have described an illustrative embodiment of the invention, various modifications of the structure or method may occur to those skilled in the art. It is, therefore, our intention to cover in the appended claims such modifications or variations as fall within the spirit and scope of the invention.

What is claimed is:

1. A shock and acceleration resistant thermionic tube comprising a cylindrical anode electrode, a first pair of tubular electrode supports sealed at the ends thereof by means of a dielectric material, a grid electrode extending axially between said supports, a second pair of tubular electrode supports sealed at the ends of said first pair of supports by means of a dielectric material, a cathode electrode extending axially between said supports, said first and second pair of electrode supports being in telescoping arrangement and said electrodes being disposed eoncentrically around a common axis with the ends or each of said electrodes in contiguous'relationship'with said electrode supports. I

2. .An electron discharge device comprising a cylindrical'envelope of a condu ctive metal, said envelope 'defining a central passageway therein, a plurality of metallic tubular electrode support members disposed at each end of said passageway, said metallic tubular support members being disposed in axial alignment and supported radially one from the other in telescoping arrangement by means of a dielectric seal therebetween, said dielectric seals being disposed at the ends of each of said tubular support members, said tubular support members having in contiguous relationship therebetween a grid electrode and filamentary cathode electrode assembly, said grid electrode. and cathode electrode assemblies being disposed concentrically within said central passageway around a common axis with each electrode being supported at opposed ends by said tubular support members. v

3. electron discharge device comprising a cylindrical envelope having a center metallic body section and a metallic tubular section disposed at each "end thereof, said envelope defining a central passageway, a first pair of metallic tubular-electrode supports of smaller diameter axially and oppositely disposed at each end of said central passageway, said supports being joined by means of a. dielectric material to the ends of said'tubular sections, a grid electrode-extending axially between the inner ends of said first pair of tubular supports, a second pair of metaliictubular electrode supports of still smaller diameter joined by means of a dielectric material to 'the ends of said first parrot tubular supports, said second pair of tubular supports defining wall structure permitting access to the central'passageway, a filamentary cathode assembly extending axially through said central pass'ageway with the supporting members of said cathode assembly engaging the inner walls of said second pair of tubular electrode supports.

References Cited in the file of this patent UNITED STATESPATENTS 1,709,029 Little Apr. 16, 1929 2,128,231 Dalleilb aeh Aug. 30, 1938 2,478,969 Ishler Aug. 16, 1949 2,509,906 Clark et al. May 30, 1950 2,521,315 Victoreen Sept. .5, 1950

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