US2948827A

US2948827A - Electric discharge device

Info

Publication number: US2948827A
Application number: US806813A
Authority: US
Inventors: Joe F Stephens
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1959-04-16
Filing date: 1959-04-16
Publication date: 1960-08-09
Anticipated expiration: 1977-08-09

Description

Aug. 9, 1960 J. F. STEPHENS ELECTRIC DISCHARGE DEVICE Filed April 16. 1959 F IGB.

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BY HIS AT rUnite States Patent M ELECTRIC DISCHARGE DEVICE Joe F. Stephens, Owensboro, Ky., assignor to General My invention relates to electric discharge devices and more particularly to improved electric discharge devices including improved integral electnode leads and tube envelope exhaust tubulations and improved tubulation seals.

In some electric discharge devices and particularly high voltage rectiers, there is incorporated a top cap-anode assembly involving a tubular anode supported solely by a tubular top cap. The top cap is sealed directly to the top of the glass dome of the tube envelope with the end extending externally of the envelope and thus is effective also for serving as an electrical contact to the anode. This type of structure is highly desirable in that it precludes the need for mica supports or other insulative supports for the anode which, when present in a tube, reduce the high voltage capabilities of the tube. This type of structure has been readily employable in tube assemblies employing an exhaust. tubulation which is integral with a stem assembly disposed at the opposite end of the envelope from the dome.

In so-called miniature high voltage rectifier types or very small tube structures space in the stem is at a premium and, heretofore, it has been necessary to locate the exhaust tubulation in the dome of the envelope. In this type of structure it has been the practice to provide a tubular anode supported in the envelope by a plurality of transverse mica supports and a lead wire extending from the top of the anode and sealed in the pinched-off tubulation. After the pinch olf of the tubulation or sealing which involves heating the tubulation adjacent the lead to a point where it collapses and subsequently pull ing off the excess portion of the tubulation it has been necessary to cement a top cap to the envelope dome for serving as an anode contact and solder the lead wire to lthe top cap to comprise the circuit between the top cap and anode. To accomplish the soldering roperation it has been generally necessary to chip excessive glass from the pinched-off tubulation from the lead wire and otherwise clean the wire to prepare it for soldering. Thevjust-L described structure and operations have been undesirable in that the mica supports reduce substantially the voltage capabilities of the tube and the various cementing, cleaning and soldering operations have ad'dedconsiderably to the time and effort of manufacture. Additionally, the various operations after pinch olf tended to affect adversely the tubulation seal.

Accordingly, the primary object of the present invention is to provide for use in the manufacture of electric discharge devices an improved assembly comprising an integral electrode lead and exhaust tubulation, which assembly is adapted for providing the sole support of an electrode in the tube envelope and enabling exhaust of the envelope through the lead.

Another object of my invention is to provide an integral improved electrode lead and tubulation assembly adapted for facilitating tip-olf sealing of the tabulation following exhaust and effecting an improved tip-off seal'.

Another object of the present invention is to provide 2,948,821 Patented Aug. 9, 196Q .ICC

improved means for enhancing the voltage capabilities of Very small high voltage rectifier tubes.

Another object of my invention is to provide an improved high voltage rectiiier device.

Another object of my invention is to provide improved means adapted for facilitating manufacture of electric discharge devices of the miniature high voltage rectifier type and substantially decreasing the effort and cost of manufacture.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of my invention I provide an electric discharge device including an insulative envelope and an electrode assembly comprising an electrode, a tubular conductive lead adapted for serving as the sole support of the electrode in the envelope. The lead or conductor is sealed to the envelope with an extending external portion for serving as a contact. The end of the lead includes a closed end wall having an aperture and sealed to the end wall and having an inner diameter greater than the diameter of the aperture is a vitreous tubulation.4 In the preferred embodiment the end of the lead is dished and the tubulation is sealed in the dished portion to provide, after exhaust and tubulation tip off, a seal of enhanced strength and which does not interfere with the attachment of an electrical contact member over the end of the lead. A tubular extension of the lead about the aperture can serve to increase the seal area between the glass and conductor thus to enhance the strength of the seal. Additionally, the lead can be formed for incorporating both the dished feature and extension. Further, the portion of the lead to which the tubulation is sealed can include a glass interface for protecting the lead from oxidation during sealing'to the tubulation and facilitating the making of the seal between the tubulation and lead.

For a better understanding reference may be had to the accompanying drawing in which:

Figure 1 is an enlarged fragmentary partially sectionalized view illustrating one form of my invention;

Figure 2 is an enlarged fragmentary sectionalized view illustrating the lead-tubulation assembly before tip olf;

Figure 3 is an enlarged fragmentary sectional view illustrating a step in obtaining a modified form of my invention;

Figure 4 is an enlarged fragmentary sectionalized view illustrating a tubulation seal obtainable in accordance with the mentioned modiedform of my invention;

l Figure 5 is an enlarged Vfragmentary section-alized view of anotherrform of my invention; and t Figure 6 is an enlarged fragmentary sectionalized view illustrating still another form of my invention. t

Referring now'to Figure' l, there is shownfa half-wave high voltage rectifier electric discharge device"desi'gn'ate'd v1 andembodying my invention. `The device 1 includes an insulative envelope 2 and a cathode 3'. The cathode 3 and a shield member 4 are supported by a plurality of leads S extending in a sealed manner through the stem of the device.

Surrounding the cathode 3 is a tubular anode 6 which is solely supported by a tubular lead or lead-in conductor 7 which is se'aled in the end of the dome oppositethe stem by a suitable glass-to-metal seal 8. i t

The tubular conductor 7 includes a plurality. of aper tures 10 which provide communication between the in teriors of the tubular lead andenvelope. Accordingxto `my invention, and as illustrated in Figure ltheleadg? includes an end wall which is closedexcept fopen-aperture' or port 11 provided'for enabling exhaust'of the 3 envelope through the lead 7. The end wall is dished or formed to provide a reentrant portion. The reentrant portion denes a smooth round-bottomed end surface 12, the purpose of which .will be brought out in greater de.- tail hereinafter.

Disposed in the dished end wall of the conductor 7 is 4a vitreous plug 13. The plug comprises the remains of tipped-olf or sealed-off exhaust tubulation which had 'been `previously sealed to the end of the lead. Due to provision of the dished portion of the lead end wall there resul'ts a substantially increased area of sealing contact between the glass plug 13 and the lead which increases the strength of the glass-to-metal seal between these elements. The strength of the seal is further enhanced by a ,depending portion 14 of the plug which extends into the aperture 11. I have found that in a miniature device the strength of the seal between the plug and lead can be enhanced substantially when the depression is about .060 of an inch deep.

Additionally, as seen in the drawing, the plug can comprise a substantial quantity of glass without `extending Over the side wall 15 of the lead. This is highly desirable to avoid presence on the side walls of material that would tend adversely to affect attachment of an electrical connector to the lead or electrical contact between such a connector and the lead. Additionally, the smooth rounded Vsurface of the dished end wall is effective for avoiding undesirable stresses in the glass plug due to sharp corners and thus has the desirable effect of minimizing tube shrinkage or defective tubes in manufacture and increasing tube life due to the avoidance of tubulation seal leaks.

Illustrated in Figure 2 is a lead-tubulation assembly constructed in accordance with my invention and as it appears before tip olf. As seen in this figure, just the end of a glass tubulation 16 is sealed at 17 to the outer surface of the dished er reentrant portion of the end wall. As also seen, the inner diameter of the tubulation -is greater than thc diameter of the aperture 11. The relatively large diameter of the tubulation facilitates rapid exhaust of the tube envelope through the tubulation. After tip off of the tubulation 16 the glass plug 13 shown in dash lines in Figure 2 and in full in Figure l is formed which, as seen, does not extend over the side wall of the lead and, thus, cannot undesirably affect the making of the desired effective connection thereto.

Illustrated in Figures 3 and 4 is a modified form of my invention. In this form the dished surface 12 of the lead end wall is lirst provided with a glass coating or layer 18. This layer can be obtained by applying to the dished portion,.before sealing of the lead in the envelope, a quantity of glass frit in an organic binder such, for example, as isobutyl methacrylate. During sealing of the lead in the envelope dome, the binder evaporates and the glass frit provides the glass coating 18 which is held in place by a glass-to-metal seal between the coating and the dished surface 12. Subsequently the glass tubulation '16 is held in place and sealed to the glass coating 18. Thus, the tubulation is sealed to the lead through a glassto-glass seal between the tubulation and glass coating 18. Additionally, the coating 18 protects the lead end wall from undesired oxidation thereof during the sealing of the tubulation in place on the lead. After tip olf of the tubulation in the assembly shown in the process of manufacture in Figure 3, there results a glass plug and seal of the type designated 19 illustrated in Figure 4. It will be seen from Figure 4 that the plug 19 is similar to the plug 13 of Figure 1 but is held in place by a glass-to-glass seal to a glass interface 20 which, in turn, is sealed to the surface 12 by a glass-to-metal seal. In this form of my invention, also, the dished lead end increases the sealing surface contact between the plug and lead, enables strengthening of the `seal by provision of a depending portion ofthe plug extending through the aperture 11 in theflead and enables use of a substantial quantity of glass 4 in forming the plug and without flowing over the sides of the lead.

It will be noted that in assembling the structure of Figure 4, as well as the other forms of my invention using the reentrant or dished lead end, the dished surface or depression serves to center the tubulation during sealing thereof to the lead and, thus, serves to facilitate manufacture, especially when automatic sealing equipment is used.

Illustrated in Figure 5 is a modified form of my structure which is also adapted for increasing the sealing contact between the remainder of the tipped-olf glass tubulation and the lead end. In this form, instead of utilizing a depression or dished end, i provide a tubular extension 2l on a tubular lead 22. The extension 21 is of smaller diameter than the lead 22 and delines an exhaust port or aperture 23 in the otherwise closed end wall 24 of the lead. As seen, the extension 21 extends longitudinally beyond the transverse end wall 24 of the lead. Over the tubular extension 21 I tit a glass tubulation 25, the end of which I seal by means of a glass-to-metal seal 26 to the transverse end wall 24 of the lead. The inner diameter of the Vtubulation is greater than that of the sleeve and facilitates rapid exhaust of the envelope.

After tip olf of the tubulation 25 a glass plug generally of the configuration illustrated in dash lines and designated 27 is formed. The extension 25 serves to increase the sealing area between the plug 27 and lead end vfor increasing the strength of tip ofi seal. The strength of the seal is further enhanced by a depending portion 28 of the plug 27' which extends partially through the tubular extension 21. Additionally, the extension 21 aids in l0- cating and holding in place the tubulation 25 during sealing to the lead.

Illustrated in Figure 6 is another form of my invention which. incorporates the desirable features of both the dished end wall and the extending tubular portion. In this form a tubular conductive lead 3) includes a tubular extension 31 of smaller diameter than the lead 30 and defines an exhaust port or aperture 32 in the otherwise closed end wall 33 of the lead. The extension 31 projects beyond the transverse end wall 33 of the lead, and formed in the end wall 33 about the extension is an annular depression 34. A glass tubulation 35 is iitted over the extension 31 and is seated in and sealed at 36 to the bottom of the depression 34. After tip olf of the tubulation a plug of the general construction illustrated in dash lines in Figure 6 and designated 37 is formed of the remaining potion of the glass tubulation. As seen in Figure 6, the plug 37 fills the depression 34 and extends over the tubular extension 31 with a depending portion 38 extending partially in the extension. Thus, in this embodiment I have obtained a tubulation seal which has a glass-to-rnetal sealing area which has been increased substantially by the provision of the depression 34 and the extension 31. The increased area and the depending portion 38 of the plug 37 increase substantially the strength of the tubulation seal or tip otf. Also, the depression 34 tends to avoid the outward ow ofl glass toward the sides of the lead.

Thus, it will be seen that I have provided an integral lead-tubulation assembly which is adapted for providing for exhaust of an envelope through the lead and affording the sole support for an electrode in an envelope. Additionally, by providing a longitudinally extending surface at the end of the lead and which can be reentrant in the lead end or projecting externally from the lead end, I have provided means for increasing the sealing area between a tip-olf sealing plug and the lead. Further, I have provided means for confining the plug material to the end surface of the lead to avoid its undesired presence on the side wall of the lead and for enabling the use of an increased amount of plug material to increase sealing strength.

.While I have shown and described specic embodiments of my invention I do not desire my invention to be limited to the particular forms shown and described, and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. For use in manufacturing an electric discharge device an assembly comprising an electrode, a tubular conductor for mounting said electrode in an envelope with a portion of said tubular conductor extending through said envelope for making an electrical connection to said electrode, the outer end of said conductor being closed except `for a single relatively small aperture therein, a vitreous tubulation sealed to the outer surface of said end of said conductor, and said end of said conductor including a surface extending longitudinally of said conductor and providing a greater sealing area for glass from said tubulation after tip off thereof than would be provided by a plane transverse end surface of said conductor.

2. For use in the manufacture of an electric discharge device an assembly comprising an electrode, a tubular conductor for mounting said electrode in an envelope with a portion of said conductor extending from said envelope for making an electrical connection to said electrode, the outer end of said conductor being closed except for a single relatively small aperture therein, said end including a reentrant portion, and a vitreous tubulation positioned in and sealed to the outer surface of said reentrant portion.

3. For use in the manufacture of an electric discharge device, an assembly comprising an electrode, a tubular conductor for mounting said electrode in an envelope wit-h a portion of said tubular conductor extending from said envelope for making an electrical connection to said electrode, the outer end of said conductor being closed except for a single relatively small aperture therein, a glass coating sealed to the outer surface of said outer end of said conductor about said aperture, and a glass tubulation sealed to said glass coating.

4. For use in the manufacture of an electric discharge device, an assembly comprising an electrode, a tubular conductor for mounting said electrode in an envelope with a portion of said tubular conductor extending from said envelope for making an electr-ical connection to said electrode, the outer end of said conductor being closed except for a single relatively small port defined by a tubular extension of smaller diameter than said lead, and a vitreous tubulation fitted over said extension and sealed to the outer surface of said end.

5. For use in the manufacture of an electric discharge device, an assembly comprising an electrode, a tubular conductor for mounting said electrode in an envelope with a portion of said tubular conductor extending from said envelope for making an electrical connection to said electr-ode, the outer end of said conductor being closed except for a single relatively small port defined by a tubular extension of said conductor, an annular depression in said end about said extension, and a vitreous tubulation fitted over said extension and sealed to the outer surface of said end in said depression.

6. An electric discharge device comprising an insulative envelope, electrodes within said envelope, a tubular leadin conductor sealed through said envelope and supporting one of said electrodes, whereby said tubular conductor has a portion extending externally of said envelope, said portion including a transverse outer end wall having a relatively small aperture therein for enabling exhaustion of said envelope through said conductor, and a vitreous plug sealed and confined to only said end wall of said conductor for sealing said aperture.

7. An electric discharge device comprising an insulative envelope, electrodes yWithin said envelope, a tubular lead-in conductor sealed through said envelope and providing the sole support for one of said leads, whereby vsaid tubular conductor has a portion extend-ing externally of said envelope, said portion including a reentrant end wall defining a depression, an exhaust aperture in said end wall, and a vitreous plug sealed to said end wall and including a portion extending into said aperture for sealing said aperture, and the major portion of said plug being confined to said depression.

8. An electric discharge device comprising an insulative envelope, electrodes within said envelope, a tubular lead-in conductor sealed through said envelope and supporting one of said leads, whereby said tubular conductor has a portion extending externally of said en- Velope, said portion including an inwardly dished end wall having a smooth rounded bottom and having an exhaust aperture therein, and a vitreous plug sealed to substantially -all of the outer surface of said end wall and extending into said aperture for sealing said aperture and with the major portion of said plug being confined to the dished portion of said end wall, and the smooth rounded bottom of said end Wall being effective to avoid undesired stresses in said plug.y

9. An electric discharge device comprising an insulative envelope, electrodes within said envelope, a tubular lead-in conductor sealed through said envelope and supporting one of said leads, whereby said tubular conductor has a portion extending externally of said envelope, said portion including an aperture in the end wall for enabling exhaustion of said envelope, a glass coating bonded by a glass-to-metal seal to said end surface, and a glass plug bonded by a glass-to-glass seal to said glass coating for sealing said aperture.

10. An electric discharge device comprising an insulative envelope, electrodes within said envelope, a tubular lead-in conductor sealed through said envelope and supporting one of said leads, whereby said tubular conductor has a portion extending externally of said envelope, said portion including an end Wall having a tubular extension of smaller diameter than said portion and defining an exhaust port in said end wall, and a vitreous plug sealed to the outer surfaces of said end wall and said extension and including a portion extending partially in said extension and sealed to the inner surface thereof, the material of said plug being confined to said end wall.

11. An electric discharge device comprising an insulative envelope, electrodes within said envelope, a tubular lead-in conductor sealed through said envelope and supporting one of said leads, whereby said tubular conductor has a portion extending externally of said envelope, said portion including an end Wall having -a tubular extension of smaller diameter than said portion and defining an exhaust port in said end wall, an annular depression in said end lwall about said extension, and a vitreous plug sealed to the outer surface of said end Wall and said extension and extending including a portion over and partially in said extension and sealed to the inner surface oi said extension, the material of said plug being laterally confined to the margin of said depression.

References Cited in the file of this patent UNITED STATES PATENTS 2,419,578 Litton Apr. 29, 1947 2,472,865 Stutsman June 14, 1949 2,888,590 Taylor May 26, 1959