US2889482A - Electron tube - Google Patents

Description

June 2, 1959 D. A. SOKOLOV 2,889,482

ELECTRON TUBE Filed Feb. 18. 1953 INVENTOR I 1 David A.SokoloV ATTORNEY ELECTRON TUBE David A. Sokolov, Lynn, Mass, assignor to Columbia Broadcasting System, Inc., a corporation of New York, doing business as Hytron Radio & Electronic Co., Danvers, Mass, a division of Columbia Broadcasting System, Inc.

Application February 18, 1953, Serial No. 337,530

2 Claims. (Cl. 313-278) This invention relates in general to electron tubes and in particular to rectifying types.

In those rectifier applications where power transformers are used, low voltage power rectifiers usually employ filimentary cathodes rather than indirectly heated sleeve cathodes. Numerous reasons exist for the practice, one of which is the cost factor, filamentary cathodes being cheaper to construct than the heaters and sleeves of indirectly heated cathodes. Also, since the rectifier output is to be filtered before use, no hum problem is encountered. Finally, no heater-cathode leakage or breakdown need be considered and greater efficiency is achieved.

Quite often, the low voltage power rectifiers in question are of the full Wave type. However, since the two sections are identical, the description hereinbelow will be of a single section. Each such section usually includes a flattened oval anode with a hairpin filament ribbon within the oval. The filament is arranged to be as widespread as possible at the open end which is normally at the bottom for convenient attachment to stem leads. At the top the closed end is looped over a mica support which is a part of the mica disk which supports and spaces States Patent all of the tube elements from each other and from the bulb. The anode is usually constructed of nickel or nickel alloy which is carbonized to aid in heat dissipation. The base metal is a relatively poor conductor of heat and those areas on the oval which are closest to the filament actually reach red heat from the electron bombardment when the tube is run at peak ratings. The emission current density in the areas of peak emission current flow between the filament and the closest portions of the anode becomes so great that the voltage required on the anode for proper operation also becomes undesirably high.

- Another problem associated with the conventional design in filamentary type rectifiers is sagging and general structural weakness of the filament which is a relatively flexible ribbon. This problem is accentuated by expansion due to the high temperature at which the filament is run. It is sometimes desirable to mount the rectifier in positions other than vertical where sagging can cause portions of the filament to approach the anode creating further maldistribution of heating or, in the worst case, shorting of the filament to the anode and tube failure.

Therefore, it is an object of the present invention to provide a rectifier having permanent geometric relationships between elements.

It is a further object to provide a rectifier having a non-sagging filament.

It is a still further object to provide a vacuum tube filament and anode which are matched for more efiicient use of anode surfaces.

It is still another object to provide a vacuum tube anode having symmetry about a filament.

It is another object to provide a rectifier having low voltage drop across its elements.

. 12 as well as to give In general, the present invention consists in a double section rectifier tube each section of which includes a filamentary cathode and an anode which are matched in structure for efiiciency of material utilization. The anode has a contour which places a maximum surface area equidistant from the filament. The filament itself is supported in such a manner that the conditions of optimum geometry are maintained at all times despite expansion or sagging of the filament. This permits mounting of the tube in any position, lowers the tube drop and generally improves tube operation. For a better understanding of the invention, together with other and further objects, features, and advantages, reference should be made to the following description which is to be read in connection with the accompanying drawings in which:

Fig. 1 is an elevation view, partly cut away, of a double diode rectifier embodying principles of the present invention;

Fig. 1A is a cross-sectional view of the rectifying tube shown in Fig. 1 taken along the plane of line 1A1A. Fig. '2 is an enlarged top view, partly cut away, of the mica support and associated components utilized in the diode rectifier of Fig. 1; and

Fig. 3 is a view of a section of Fig. 2 along line 3-3.

Referring now particularly to Fig. l, and Fig. 1A, there is disclosed a glass envelope 12 which is attached in conventional fashion to a base 13. Within the envelope are similar anodes 14 and 15. Anode 14 which is visible in considerable detail in this view is formed of two similar carbonized nickel stampings, each stamping having a pair of semi-cylindrical channels out along its length. These channels at one end of the stamping approach the longitudinal axis of the stamping and diverge symmetrically from the axis along its length. Each side of the stamping is turned through along its length, and two of the stampings are welded together to form each anode. The anodes 14 and 15 thus have a substantially T-shaped cross-section, the diverging c'hannels matching, however, to form two diverging cylinders through the length of each anode.

As is conventional in vacuum tube practice, a top mica 16 is used to retain the anode and other tube elements in spaced relationship from each other and from bulbstructural rigidity to the whole device. Top mica 16 is provided with additional openings for purposes explained below. Mounted on top mica 16 are getter support rods 17 and 18. Rods 17 and 18 are actually formed from a single wire loop welded to a plate 19 disposed beneath top mica 16. The ends of the loop then are bent to pass upwardly through openings in top mica 16.

Also passing through openings in top mica 16 are filaments for each of the anodes. Filaments 20 and 21 are welded at their lower ends to stem leads of the tube and pass upwardly centrally of the diverging cylinders of anodes 14 and 15,-through openings in top mica 16 and are returned to the stem through other openings in top mica 16 and through the other cylinders of their respective anodes. A spring mica 22 and double coiled springs 23 and 24 are also provided as may be better seen and explained by reference to other figures of the drawing.

Referring now to Figs. 2 and 3 of the drawing, spring mica 22 is provided with openings to accommodate filaments 20 and 21, and getter support rods 17 and 18. Between the openings for filament 20, a bridge of mica is formed to support filament 20. Similar support is afforded filament 21. Openings are also provided in top mica 16 for filaments 20 and 21, getter support rods 17 taken through a portion and 18, and anode tabs 25 and 26. The openings in both top mica 16 and spring mica 22 for getter support rods 17 and 18 are only slightly larger than the rods themselves. Double coiled springs 23 and 24 are compressed between top mica 16 and spring mica 22, the internal diameter of the smaller coil of each of springs 23 and 24 being of a size to fit getter support rods 17 and 18 fairly closely, the springs being free to move, however. The external diameter of the smaller coils is smaller than the internal diameter of the larger coils which permits the smaller coils to nest within the larger when the mount is assembled on the stem of the tube. In other words, when the tube is assembled the ends of filaments 20 and 21 are threaded through spring mica 22 and top mica 16 and are passed through the proper cylinders of anodes 14 and 15. At the stem, the filaments are pulled taut bending spring mica 22 slightly as shown in Fig. 3 and compressing springs 23 and 24. Thus, any expansion of filaments 20 and 21 is compensated for by springs 23 and 24 which will expand to force spring mica 22 away from top mica 16 and stretch filaments 20 and 21 taut to maintain them centrally disposed within their respective anode cylinders. The location of the return loops of filaments 20 and 21 on spring mica 22 is such that a balanced springing action is had. The filaments are maintained centrally of the anode cylinders despite orientation of the tube.

The diverging design of the cylinders of anodes 14 and 15 permits a more natural positioning of hairpinshaped filaments 2t and 21 and, more important, brings more of the anode surfaces into play in dissipating heat. As was mentioned, previously, the carbonized nickel alloy of which the anodes are made is a relatively poor heat conductor, and carrying the cylinders outwardly to the edges of the anodes aids in distributing the heat over more anode surface for easiler dissipation.

The walls of the anode cylinders being equidistant from the filaments about their entire 360 provides so much more anode area being bombarded by electron emission that the anode runs much cooler than the conventional flattened oval. anode. Also, the provision of greater useful anode area decreases the emission current density, the current paths no longer being confined to segments as in the flattened oval but flowing in complete circular planes about the filaments to the anode cylinders. The resulting decrease in current density gives less tube voltage drop and a voltage output which is higher than that derived from the prior art design in similar circuit applications.

This invention should be limited only by the spirit and scope of the appended claims.

What is claimed is:

l. A rectifier tube comprising, a hairpin-shaped filament attached at its open end to leads of said tube, an anode having cylindrical Walls, said cylindrical walls being symmetrically disposed about the straight legs of said hairpin-shaped filament, a mica disk having a pair of openings receiving said filament, and spring means resiliently urging the portion of said mica disk between said openings against the closed end of said filament to maintain said filament under tension and centrally disposed in said cylindrical walls.

2. A rectifier tube comprising, an evacuated envelope having leads extending through the lower end thereof, a pair of anodes of rectangular configuration each being disposed with its longitudinal axis parallel to that of said envelope, said anodes being supported by said leads at said lower end, a first mica disk supporting said anodes at the upper end of said envelope, a metal plate attached to the under side of said first mica disk, a pair of upwardly extending getter support rods passing through said first mica disk and Welded to said metal plate, a second mica disk disposed parallel to and above said first mica disk, said getter support rods also passing through said second mica disk, a coiled spring wrapped on each of said getter support rods between said first and said second mica disks, eachof said anodes having two cylindrical walls running longitudinally thereof, the axes of said cylindrical Walls lying on either side of the longitudinal axis of their respective anodes and diverging symmetrically therefrom toward the lower end of said anodes, a hairpin-shaped fine ribbon filament threaded centrally through said cylindrical chambers of each of said anodes and welded at its ends to two of said leads at said lower end, said filaments passing through spaced openings in said first and saidsecond mica disks, the closed loop of said hairpin-shaped filament passing over the upper surface of said second mica disk, the ends of said filament being welded to said leads, the length of said filaments being suificient to compress said springs, whereby said second mica disk maintains tension in said filaments and retains them centrally in said cylindrical walls.

References Cited in the file of this patent UNITED STATES PATENTS 1,522,286 Clausen Jan. 6, 1925 1,558,111 Metcalf Oct. 20, 1925 1,597,893 Huppert Aug. 31, 1926 1,605,735 Hough Nov. 2, 1926 1,657,221 Metcalf et al. Ian. 24, 1928 1,689,971 Robinson Oct. 30, 1928 1,720,442 Robinson July 9, 1929 1,905,872 Houck Apr. 25, 1933 1,999,300 Lyle Apr. 30, 1935 2,075,611 Hoffman Mar. 30, 1937

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