US2923848A - Electron discharge device - Google Patents

Description

Feb. 2, 1960 M. E. WEISS 2,923,843

ELECTRON DISCHARGE DEVICE Filed Dec. 50, 1952 IE 2 I6 '6 IS V" 2 4; -15

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F 4 INVENTOR MORTIMER E. WEISS ATTORNEY United States Patent ELECTRON DISCHARGE DEVICE Mortimer E. Weiss, Flushing, N. assignor, by mesne assignments, to Sylvania Electric Products Inc., Wilmington, Del., a corporation of Delaware Application December 30, 1952, Serial No. 328,701

2 Claims. (Cl. 313-278) ment have been complications introduced by the space required by the vacuum tubes employed. While the size of the tube, as a whole, has been reduced by the elimination of the plastic tube bases together with the use of integral connector leads, the fragile glass portions of the tubes produced by the sealing operation have remained projecting from the top of the tube to take up an unnecessary amount of space and to endanger the integrity of the tube by increasing the chances of breakage.

Space has been occupied, too, within the vacuum tube envelope, by complicated spring suspension devices for the filament. Such devices are customarily placed, as a matter of convenience and simplicity of assembly, at the end of the vacuum tube away from the base.

An object of the invention, therefore, is reduction in over-all vacuum tube length by the elimination of spaceconsuming filament supports and tip-off structure.

Other types of vacuum tube structures than those having glass envelopes as described above have also presented problems of filament suspension. using ceramic body members for the support and spacing of vacuum tube elements have required awkward apparatus for the internal suspension of filaments; in some cases the use of cathodes rather than filaments has been mandatory. Such use of a cathode in lieu of a filament reduces the thermal efiiciency of the tube, thereby reducing thedesirability of such tube types for many applications. Further, where filaments are employed, it is essential that adequate tension be applied to the filament by the filament supporting device in order to minimize sagging and vibration of thefilament. t t

A tube embodying the solution of the problems described above, should, of course, be simple and readily adaptable to modern mass assembly techniques. It is, then, a further object of the invention to simplify the structure of filament tensioning devices without any de crease in the effectiveness of such structures.

The above objects and others which will appear from the below appended description of an embodiment of the present invention are accomplished in a vacuum tube in which a filament tensioning device for an electron tube structure is located within an exhaust tubulation extending from the base of the tube near the conducting leads projecting therefrom and which projects into space already occupied, at least in part, by existing, essential elements of the tube structure.

Alternatively, the objects of the invention are attained in a vacuum tube structure in which a resilient filament tensioning device is mounted in a tubular extension of the electrode mount of the discharge device which projects For example, tubes 2,923,848 r Patented Feb. 2, 1960 into the space between the connecting leads between the mount and the header of the discharge device.

Reference may now be had to the drawing in which:

Fig. 1 is a side view of an electron tube embodying the invention;

Fig. 2 is a view in partial cross-section of the tube of Fig. 1;

Fig. 3 is a view in partial cross-section ofan alternative embodiment of the invention as employed in a vacuum tube mount;

Fig. 4 is a view of another type of tube embodying the invention. 1 1

Referring now to Fig. 1, it will be seen that'one embodiment of the invention comprises a vacuum tube having a glass envelope 2 which encloses an electrode mount structure 3 visible in Fig. 2, leadin conductors 4 which are sealed through the envelope of the tube, and exhaust tubulation 6 sealed through the envelope of the tube and projecting therefrom in the vicinity of connecting leads 4.

Referring now to Fig. 2, it will be seen that the vacuum tube of Fig. 1 has a mount 3 containing the electrodes of a pentode having filament 8, control grid 10, screen grid 12, suppressor grid 14 and anode 16. The grids and the anode are supported between parallel mica spacers 18 and 20 by side rods 15 (all of the grid side rods are not shown) and connections thereto are made by means of connecting leads 4, 4 hermetically sealed through glass envelope 2 and extending to the mount where they are welded to the projecting extensions of the various electrodes or their supporting rods. For example, connecting lead 4', as illustrated, connects to,one of the suppressor grid side rods 14, that side rod also serving as a connection to the upper end of filament 8.

The filament structure for the tube comprises a filamentary cathode 8, which may be of a conventional type having a metallic core adapted to raise the filament temperature upon the application of a suitable voltage, and havingan emissive coating; an upper filament support bow or member 22 which is supported at either end by welded joints on suppressor grid side rods 14 and to'the central portion of which the upper end of filament 8 is welded; and a filament tensioning spring 24, anchored by a crimp 25 in tip-off tube 6, to which the lower portion of filament 8 is attached by means of tab 26.

The filament support how 22 is shown schematically to indicate that the use of a conventional support member is contemplated here, so long as that member does not contribute appreciably to the length of the finished mountstructure. The tip-off tube 6 is hermetically sealed through the glass envelope 2 of the tube and provides lateral support for filament tension spring 24. The lower portion of spring 24 is anchored against motion in the pinch-off tube 6 by crimp 25 during the assembly of the tube, and prior to closing the tip-off. The filament tensioning member 24 need not be fully contained within tubulation 6, but the structure shown is preferred, as it minimizes vibration of the attached portion of filament 8.

Referring now to Fig. 3 it will be seen that an alternative embodiment of the invention is a unitary mount structure having a cylindrical metal eyelet 27, anchored, by means of ridge 28 (around the eyelet) and turnedover lip 30, in aperture 31 of mica spacer 32 of a mount of the type illustrated in Fig. 2. Included in the view of Fig. 3 are a partial cross-sectional view of an anode 34, concentric grids 36, 37 and 39, and a filament 38 extending upward away from a tab 40 which is used, as above, to anchor the bottom end of filament 38 to a resilient helical tensioning member 42 within the extended sleeve of eyelet 27. The tensioning member, or spring, 42 is retained in place by a crimp 44, or pressedin portion, in the neck of eyelet 27, the crimp extending inwardly of the eyelet and firmly engaging a number of' body 46 is internally slotted (as shown and claimed in copending patent to Weiss 2,731,579 granted January 17, 195.6) to provide support for the generally parallel electrodes of the discharge device, and is closed at either end by ceramic top cap 48 and bottom cap 50, the latter two portions of the tube being hermetically sealed to the body 46 by glass frit seals 51. Metal straps 52 are sealed into the frit seals 51 to facilitate electrical-connections to the various electrodes. A filament 54 is centrally supported within body 46 by means of bottom filament lead 55 which passes through a suitable aperture in bottom plate 50 and is sealed and supported therein by means of frit seal 51. The upper end of filament 54 is supported by means of a tensioning device 60 sealed through top cover member 48. The filament tensioning assembly 60 includes an exhaust tube 58 which holds helical spring 61 at one end by means of a circumferential crimped portion 62, the free portion of the spring serving to support and maintain filament 54 under tension by means of welded connections to filament anchor slug 64. The exhaust tube 58 is anchored in closure member 48 by means of a hermetic frit seal 66.

In operation, the filament tensioning device illustrated in detail in Figs. 2, 3 and 4, and described above, provide a new filament support which is easy to fabricate and which firmly supports the filament. The size of the filament spring may be conveniently changed to adapt the structure to varying conditions, as, for example, where the length of the filament and its mass per unit length are varied. The structure is capable of a maximum of tensioning effort, and, at the same time, provides a high degree of lateral support to the ends of the filament.

As may be noted from the drawings, particularly in Figs. 1 to 3, the filament structure readily lends itself to the fabrication of compact tubes, since it may be located in spaces already occupied by other portions of the tube structure. In Fig. 2, where the filament support spring is located in the tip-01f, and brought out between the connecting leads at the base of the tube, the filament supporting structure occupies space which would other- Wise be left unoccupied, for, even if the leads 4 are bent as they leave the tube, there must be a reasonable radius of curvature in that bend, in order to avoid damage to the glass to metal seals or to the leads' themselves. Similarly, in Fig. 3, the filament support structure occupies space directly beneath the lower mica of the mount, space which must be provided in the vacuum tube to permit entry of welding tools, etc., for the purpose of joining the side rods and electrodes to the various connecting leads.

Many ways of utilizing the above described invention and its various embodiments will suggest themselves to those skilled in the art. For example, this filament supporting structure may be readily modified to accommodate it for use with U shaped filaments by the simple addition of a supporting hook at the inner end of the spring. Similarly, it need not be confined to use with filaments, but may be used with equal success With other vacuum tube electrodes. Accordingly, it is desired that the scope of the below-appended claims should not be limited to the above described embodiments, but rather, that the claims should be given the broadest interpretation consistent with the spirit of the invention.

WhatI claim is:

1. An electron discharge device having a number of electrodes adapted to be disposed in a hermetically sealed envelope, means for maintaining a number of said electrodes in predetermined spaced relationship and means for maintaining a further electrode in predetermined spaced relationship with said first named number of electrodes, said second named means including a metallic tubular member supported in fixed relationship to said first named means, and a resilient tensioning member disposed in said tubular member and laterally supported thereby along its length, said tensioning member having an end portion anchored by a crimped area of said tubular member, said further electrode being supported by another portion of said tensioning member.

2. In a mount for use in an electron discharge device, a number of electrodes disposed in pre-determined, spaced relationship between a pair of parallel, generally oppositely disposed insulating members, one of said members having an aperture, a tensioning device for an electron-emissive filament in said mount having a tubular sleeve supported in said aperture and surrounding a substantially concentrically disposed, helical tensioning member anchored at one end to said sleeve and supported substantially along its length by said sleeve, the other end of said tensioning member being attached to said filament.

References Cited in the file of this patent UNITED STATES PATENTS 250,192 Bohm Nov. 29, 1881 2,480,608 Rangabe Aug. 30, 1949 2,506,895 Sassaman May 5, 1950 2,522,902 Shamos May 19, 1950 2,731,579 Weiss Jan. 17, 1956

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