US2708248A - Mounts for electron tubes having filamentary cathodes - Google Patents

Description

May 10, 1955 2,708,248

N. H. GREEN MOUNTS FOR ELECTRON TUBES HAVING FILAMENTARY CATHODES Filed April 28, 1951 INVENTOR Nurval Hflre E11 United States Patent MOUNTS FOR ELECTRON TUBES HAVING FILAIWENTARY CATH'JDES Norval H. Green, Hasbrouck Heights, N. 1., nssignor to Radio Corporation of America, a corporation of Betaware Application April 28, 1%1, Serim No. 223,484

6 Claims. (Cl. 313-261) The present invention relates to mounts for electron tubes, and more particularly to a mount having elements for facilitating the assembly of a filamentary cathode therein.

, Electron tube mounts having a filamentary cathode are usually assembled with elements of the mount, such as spacer plates and other electrodes, in concentric relation around the cathode. The assembly of the cathode in the mount is usually accomplished after the other electrodes have been assembled and requires a threading hereof through apertures in the spacer plates and through a central passageway extending through the other electrodes. The insertion or threading of the filamentary cathode is a relatively slow and tedious operation be cause the filament or Wire of the cathode is flexible and therefore cannot be pushed through the apertures on the spacer plates and the passageway through the other electrodes. Where a tab is fixed to each end of the filamentary cathode to facilitate welding the ends of the filament to heavier lead-in connections, the threading operation is rendered increasingly difiicult, because the tab is likely to catchon elements of the mount, such as the grid wire of a wound type grid. Where small size tubes are involved, the apertures in the spacer plates for receiving the filament are relatively small and the space defined by the electrode adjacent the filament is relatively narrow. This further increases the difiiculty of threading the filamentary cathode into appropriate position in the mount.

Accordingly it is an object of the invention to provide an improved mount wherein the assembly of a filamentary cathode in the mount is facilitated.

- A further object is to provide a mount for a relatively small sized tube, including a filamentary cathode, wherein the cathode is supported on exposed supports for ease in mounting.

Another object is to provide an electron tube mount having a structure for rendering the assembly-of a filamentary cathode therein equally expeditious inmounts of different size including mounts for miniature and subminiature tube types.

A further object is to'provide a mount wherein a filamentary cathode is extendable laterally into desire position in the mount.

'Another object is to provide a mount of generally tubular outline and having a peripheral indentation for receiving a filamentary cathode in a relatively simple operation.

A further object is to provide a mount including two axially spaced parallel spacer plates having peripheral indentations therein for facilitating receipt and proper orientation of a filamentary cathode in the mount.

- Another object is to provide an electron tubemount having a filamentary cathode,. and other electrodes of modified form to permit mounting the cathode from a. side of the mount to facilitate assembly of the cathode in the mount.

Briefly considered, the electron tube mount of the invention includes two spaced parallel spacer plates having registering slots extending inwardly from the peripheries thereof. The bottoms of the slots are adapted to engage and position a filamentary cathode. Other electrodes, such as a grid and anode, are mounted between the spacer plates in accurate registry with the bottoms of the slots referred to. The other electrodes referred to are so constructed that no portion thereof extends across the slot. The slot therefore provides a free passageway for extension of the cathode laterally of the mount into engagement with the slot bottoms for accurate registry with the other electrodes of the mount.

The lateral assembly of the cathode in the mount avoids the dificulties above referred to that characterize the axial extension of the cathode in the mount required by prior mount constructions. The mount of the invention is particularly advantageous in connection with small sized electron tube mounts. While the present trend is towards relatively small size electron tubes using filamentary cathodes, reduction in size has been accompanied heretofore by the very serious limitations imposed by the increased difiiculty of inserting the cathode in the mount. The invention therefore removes one serious obstacle to further progress in the direction of reduced size of electron tubes.

Further objects and advantages of the invention will be made clear as the description continues.

For a better understanding of the invention a description of two embodiments thereof will be presented by way of example, taken in connection with the appended drawing in which:

Figure 1 is an elevation partly in section of an electron tube including the invention;

Figure 2 is an elevation of a grid structure employed in the tube shown in Figure 1;

Figure 3 is a persepctive view of the anode used in the tube of Figure 1;

Figure 4 is a transverse sectional View along the line 4-4 of Figure l and shows a top view of the mount of the tube depicted in Figure 1;

Figure 5 is a transverse sectional view along the line 55 of Figure l and shows the electrode arrangement of the tube; and

Figure 6 is a top view of a mount embodying a modification of the invention.

Referring now in more detail to the drawing, an electron tube in which the invention is included is shown in Figures 1 to 5. This electron tube includes an envelope 10, to one end of which is afiixed a base 11 having contact prongs 12 suitably connected to electrodes of an electrode cage within the envelope.

The electrode cage includes two spaced insulating spacer plates 13, 14 which may be of mica, for example. Between the spacer plates referred to are mounted electrodes comprising agrid 15, an anode having sections 16, 16a and two filamentary cathodes 17, 18. The anodev sections may be connected to each other electrically.

The grid 15, as shown in Figures 2 and 5, includes two plates 19, 20 having slots 21, 22 and side wings 23, 24;

The two plates 19, 20 are fixed as by welds 25, to a sup-' port plate 26, having cars 27, 28, shown in Figure 4, for fixing the grid at each end thereof to the spacer plates 13, 14. The plates 19, 29 are so oriented on the supportplate 26, that adjacent slots 21, 22 on the two plates are in registry as shown in Figure 5. The side wings 23, 24' are provided for facilitating the assembly of the filamentary cathode in the amount, aswill appear more fully v in the following. j 1

The anode comprises two similar sections 16, 16a, one of which is shown in Figure 3. Each section includes spaced plates 31, 31a, having edges 29, 30. The spaced plates are tied together by integral strips 32, 32a. Each anode section: is provided with ears 33 at its upper and lower ends for engaging the spacer plates 13, 14, the

'upper ears being shown in engagement with the upper are in registry with the slots 21, 22 in: the grid plates Each of the spacer plates 13, 14 is provided with peripheral indentations or slots 34, 35 shown in Figures 4 and S. The slots in each of the plates have bottom edges 36, 37 disposed in predetermined accurate registry with the space between the registering slots 21 and the registering slots 22. Thus when filamentary cathodes are extended laterally through the slots 34, 35 in the spacer plates 13, 14 and into engagement with the bottom edges 36, 37, each of the cathodes will be in accurate registry with two registering slots in the grid plates 19, 20 and with one of the edges 29, 30 on each of the two anode sections 16, 17. The filamentary cathodes may be supported at their upper ends by tension hooks 38, 3? fixed to standards 40, 41 extending through the'mount and fixed to the spacerplates 13, 14.

It will be noted from the foregoing that the mount described is particularly advantageous as regards extension of the filamentary cathodes therein. The mount permits the filaments to be assembled in the mount by extending'them laterally into the slots 34, 35 in the two spacer plates of the mount. During the extending operation no forceis applied to a filament axially thereof so that there is no danger of buckling of the filament. In

'fact, the filament may be supported at both ends thereof during a mounting operation to provide further assurance against deformation. Furthermore, the path for the filament during an inserting operation provided by the slots in the spacer plates is free from interference by other electrodes or mount parts, so that there is complete freedom from contact between the filament and such parts during a filament inserting operation. To particularly assure freedom from cathode contact with the grid plates 19, 20, the grid plate wings 23, 24 are bent outwardly to provide a separation at their free edges that exceeds that of opposite walls of the slots 34, 35.

But utilizing the edges 29, 30 of the anode sections as the active'surfaces of the anode, very close spacings are permitted between the anode and grid. Moreover, this spacing is maintained uniform during operation of the tube due to the freedom from buckling of the active surfaces of the anod'e'in the direction of the grid. Where a flat and relatively large surface of the anode faces the grid, any buckling thereof that might occur in response to'temperature conditions within a device in which it is the invention to a side insertion of a filament, such as is accomplished by rendering the edges 29, 30 of the anode the active surfaces thereof, the further advantages of such anode structure, as referred to above, are realized.

Moreover, the grid in the embodiment shown is of filamentary cathode 54 in an electrode assembly. To

this end, two spaced insulating spacer plates, one of which is shown at 42, are provided with indentations or slots 43 extending from a central portion of the plates to their peripheries. Adjacent the peripheries of the plates, the slots are flared as shown at 44 to facilitate a side extension of the filament. thereinto.

To avoid contact with other electrodes of the mount during the operation of extending the filament therein, the grids, which. may be. three in number, 45, 46, 4.7,. are supported to one side of the plane of grid side rods 48 and bent away from the plane of the side rods to clear the bottom 49 of the slot 43. The anode may include two spaced plates 50, 51 connected together by a strap 52 disposed out of registry with the slot 43. The anode plates are fixed to the spacer plates by means of ears 53 bent against the plates.

The bottom 49 of the slot 43 may be disposed beyond the plane of the side rods 48, as shown in Figure 6, to dispose the filament relatively close to the'number one grid 47. Instead of disposing the slot 43 as shown, the grids may be flattened to a greater degree than shown to secure the desired spacing between the filamentary cathode 54 and the grids. The cathode 54 is supported resiliently by a filament anchor wire 55 which is in turn fixed to a standard 56 suitably supported in the mount.

It will be apparent from the foregoing that I. have provided an improved mount having a filamentary cathode and that is characterized by increased facility in the assembly of the cathode therein. The mount is particularly suited for relatively small sized electron tubes and for tubes of indifferent size having criticalcharacteristic requirements.

What is claimed is: I

1. An electron tube mount comprising an insulating spacer plate, having slots at opposite edge portions thereof communicating with the periphery of said plate,

a grid structure comprising two electrodessupported'onsaid plate and havingactive portions adjacent the side edges and closed ends only. of said' slots, and filamentary cathodes extending through said slots axially of said tube and adjacent said active portions, whereby said cathodes are adapted to be positioned in predetermined orientation with respect to said grid in a relatively easy side extension thereof into said slots.

2. An electron tube mount comprising an insulating spacer plate having a slot extending inwardly from the periphery thereof, an anode supported on said plate and having opposite edges in registry across said slot, 9. grid supported on said plate and havingactive portions in registry with said edges, said grid having a flared open side adjacent the periphery of said plate, and a fiIa-' mentary cathode supported in said slot in registry with said opposite edges and said active portions, whereby a I in assembly is provided.

3. An electron tube mount comprising an anode,-said anode comprising a U-shaped' structure including two spaced parallel plates in'face registry connected by a mount having increased ruggedness and increased facility transverse portion at adjacent longitudinal edges thereof,

the edges of said plates opposite said adjacent edges defining the sole active anode portion of said structure, said structure being mounted with said active anode portions extending longitudinally of the mount, a gridcomprising a plate having slots in registry with said active anode portions and filamentary cathodes in registry with said active anode portions and said slots, whereby a ruggedized mount is provided.

4. A mount for an-electron tube comprising a grid including three plates in sandwiched relation, having two of .said plates exposed, said two exposed plates being wider than the intermediate one of said plates, said two plates including spaced portions extending beyond oppo-. site 'sides of said intermediate plate, said portions on each of said sides defining an 'open sided rectilinear said channels, said opposite sides of said intermediate plate being spaced farther from the peripheryof' said plate than the bottoms of said indentation therein, an anode. having edge portions only disposed in. opposite relation across said opposite slots and extending along said channel, and cathode filaments bearing against said bottoms of the indentations and extending along said channel in lateral registry with said opposite slots and edge portions, whereby a ruggedized and easily assembled mount is provided.

5. A mount for an electron tube comprising an elongated fiat grid structure having two wings extending from opposite sides thereof, said grid structure having longitudinal slots therein, said Wings defining troughs having bottoms extending along said opposite sides or" the grid structure, insulating spacer plates supporting said grid structure, said plates having peripheral indentations partly registering with said troughs, said indentations having bottom bearing portions closer to the periphery of said plates than the bottoms of said troughs, and cathode filaments engaged by said bearing portions spacing said filaments from said grid wings, said bottom bearing portions disposing said filaments in lateral registry with said longitudinal slots.

6. An electron tube mount comprising two spaced 20 insulating plates, said plates having indentations at opposite edges thereof, an anode supported between said plates and comprising two U-shaped portions having edges only in registry across said indentations and defining slots, said indentations having bottoms lying in the spaces between opposite ones of said edges, two filamentary cathodes supported in said slots, and spring means mounted on one of said plates and in a plane extending between said indentations thereof for urging said cathodes against said bottoms, whereby a mount structure is provided adapted to provide a relatively easy assembly of said cathode therein.

References Cited in the file of this patent UNITED STATES PATENTS 2,115,934 Smith May 3, 1938 2,250,409 Krahl July 22, 1941 2,433,410 Walker et al Dec. 30, 1947

Images