US2753478A - Corona discharge voltage regulator tube - Google Patents

Description

ET AL 2,753,478

CURRENT-MCQOAMPS Jullly 3, 1956 J. D. M COTTER, JR.

CORONA DISCHARGE VOLTAGE REGULATOR TUBE Filed March 4, 1955 A w p F a mu' W 9 +1 4 Z w 3 M j United States Patent CORONA DISCHARGE VgLTAGE REGULATOR TUB James D. McCotter, In, Philadelphia, Charles F. Schmitz, Jr., Lansdale, Ford K. Clarke, Kulpsville, and John F. McMahon, Jr., Lansdale, Pa., assignors to Philco Corporation, Philadelphia, Pa., a corporation of Pennsylvania Application March 4, 1955, Serial No. 492,206

10 Claims. (Cl. 313-484) This invention relates to voltage regulator tubes, and more particularly it relates to electric discharge tubes specially designed for high voltage regulation.

A principal object of the invention is to provide a novel construction of voltage regulator tube of the corona discharge kind as distinguished from the type of regulator tube of the glow discharge or positive column kind.

Another object is to provide a discharge tube for closely regulating very high voltages, for example those of the order of thousands of volts.

A feature of the invention relates to a corona discharge voltage regulator tube which has a substantially flat linear voltage characteristic over a wide range of current variation through the tube.

Another feature relates to a corona discharge voltage regulator tube of the concentric anode-cathode kind wherein the cathode and anode are accurately and concentrically mounted within an enclosing tubular glass bulb with a minimum of spark-over danger between the cathode and anode both internally and externally of the tube. 9 J

Another feature relates to. a novel seal-off and exhaust tubulation arrangement for high voltage electric discharge tubes. f

A further feature relates to the novel anode and metal exhaust tubulatiton and seal-otf mount for electron tubes, wherein tliei metal tubulation can also serve as the voltage supply coinductor to the anode.

A further feature relates to the novel organization, arrangement, and relative llocation and interconnection of parts whereby etficient high voltage corona discharge regulator tubes can be teconomically manufactured and assembled. g

Other features, and adrivantagesnot particularly enumerated will be apparent affter a consideration of the following detailed descriptions; and the appended claims.

In the drawing,

Fig. 1 is a plan View of .a corona discharge regulator tube according to theg'invention, with the enclosing glass bulb broken away art several points to show the interior construction morerlearly;

Figs. 2, 3, a-nfd 4 are sectional views of Fig. 1 taken respectivehaalong the lines 2-2, 33, and 4'4 thereof;

is a magnified sectional View of Fig. 1 taken yang the line 5-5 thereof;

Fig. 6 is a sectional view of the tubulation heat concentrator shown in Fig. l;

1 Fig. 7 ,is a perspective view of one of the end sparkoverprotection rings for the cathode cylinder of Fig. 1;

Fig. 8 is a characteristic curve of the tube of Fig. 1, showing the relation between the voltage at the terminals of the device as the current flow through the device varies.

In certain kinds of apparatus it is extremely important that the voltage at certain points be very accurately regulated so as to be maintained at a constant value. For example, in certain kinds of color television sets one or more of the electrodes of the color picture tube must be maintained at a steady high voltage, for example of the order of 25 kilovolts. Yet, during the operation of the apparatus, the current to and from the electrode may vary as much as several hundred per cent. Therefore, ordinary gaseous glow discharge voltage regulator tubes are entirely useless for such high voltages. It has been proposed heretofore to replace the ordinary gaseous glow regulator tube with a corona discharge tube for voltage regulation. However, such prior tubes because of the complexity of their design have been limited in their usefulness and do not lend themselves readily and economically to mass production with the desired degree of operating uniformity and accuracy. One of the difiiculties in the manufacture of such tubes is that of preserving the spark-over insulation between the two electrodes so that they do not break down either internally or externally of the tube. In one known construction of corona discharge voltage regulator tube, the cathode, which is of cylindrical metal construction, forms the major part of the enclosing envelope, and it requires sealing to a suitable glass header at each end. Such a construction requires expensive lap or feather seals between the tubular metal cathode and the glass headers. Furthermore, the cathode is completely exposed to external contact and unless the tube is inordinately long, the distance between the ends of the cathode and the sealed-in lead wire for the anode is relatively short.

The present invention, on the other hand, provides a construction for corona discharge voltage regulator tubes which overcomes the above noted and other disadvantages of the known constructions.

Referring to the drawing, the tube according to the invention comprises a cylindrical glass bulb 10, of hard or lead glass tubing, for example of approximately 1 /2 inches outside diameter and with a Wall thickness of approximately 0.1 inch. The opposite ends of the tubing 10 are closed by rounded or hemispherical domes ll, 12. Dome 11 may be formed as an integral part of the tubing 10, whereas the dome 12 may be preformed as a separate member to act as a header for the anode and exhaust tubulation mount to be described. The dome portion 12, after assembly of the mount parts thereon, is fused to the end of tubing 10, as indicated by the numeral 13.

Vacuum-tight sealed through the lateral wall of tubing 10 is any well known form of contact button 14 for making electrical connection with the cylindrical metal cathode 15. Located concentrically within the cathode 15 is an elongated cylindrical metal rod 16 which, like the cathode 15, is preferably of stainless steel. In order to maintain the anode 16 in its accurate concentric position with respect to the cathode 15, it is supported at one end by means of a disc 17 of mica or similar insulation. Preferably, the disc 17 is of polygonal shape so that its polygonal corners are a somewhat tight fit against the inner face of tubing 1t Mica 1? has a central opening through which the anode rod 16 tightly asses and the end 18 of the anode rod is rounded to reduce the chances of sparkover to the edge of the cathode .55. Rod 16 at its opposite end is supported in its concentric position by being fitted within the open end of a metal exhaust tubulation 19. However, the internal diameter of tubulation 19 is. substantially larger than the outside diameter of rod 16, andthe tubulation 19 near its end is pressed inwardly at opposite sides as shown in the enlarged sectional view of Fig. 5, to contact the rod 16 at a plurality of points at which it is welded to the rod. This construction leaves a plurality of ports by means of which the device can be evacuated through the tubulation 19 and by means of which the desired gas at the proper pressure can. be forced into the device.

The tabulation 19 is made of a. suitable alloy which;

is capable of being sealed in a vacuum-tight manner through the wall of the dome 12. For example, the tubulation 19 may be made of any well known and relatively cheap alloy which has substantially the same coeflicient of expansion and contraction as that of the glass forming the dome 12. It will be understood, of course, that the metal tubulation 19 is accurately and centrally sealed through the dome 12 as a preformed unit therewith.

The tubulation 19 adjacent its inner end is formed with a constricted portion 20, and located between the end 21 of rod 16 and the constricted portion is a glass pellet 22 which can be heated by high frequency induction to its melting point so that upon cooling it flows into contact with and seals the constricted portion 29 in a vacuum-tight manner. We have found that in order to improve the sealing operation, while at the same time concentrating the induced heat at the constricted region 20, a metal heat concentrator or bafiie should be attached to the tubulation 19 adjacent the constricted portion 21). This heat concentrator (see Fig. 6) may take the form of an annular cup-shaped metal member 24 formed with a plurality of integral prongs 25 so that the member can be fitted over the tubulation 19 and the prongs can be forced into the external constricted portion 20 to hold the said heat concentrator in place.

From the foregoing it will be seen that the mount elements 12, 19, 16, 22, and 24 can be assembled as a unit prior to fusing this unit to the end of the tubing 10. Prior to assembling this unit in place the cathode 15 is inserted into the tubing 10. As shown more clearly in Fig. 3, the cathode 15 is formed of two identical semi-circular stainless steel members 26, 27. Each of these members is formed at diametrically opposite points with radially extending flanges 28, 29, 30, 31, which abut against each other and are welded together throughout their length. We have found that this manner of constructing the cylindrical cathode 15 lends itself to economical manufacture with a high degree of cylindrical precision, and the abutting flanges can be so shaped that to all intents and purposes the interior surface of the cathode 15 is a perfect cylinder, free from edges or cylindrical irregularities which would otherwise tend to produce spark-over.

Fitted over each end of the cathode cylinder are respective rounded spark-over protecting end rings 32, 33. As shown more clearly in the perspective vieW of Fig. 7, the ring 33 for example consists of a metal ring having its outer edge turned back upon itself to form a rounded lip 34. The spacing between this turned-back lip 34 and the ring proper provides an annular recess to receive the end of the cathode 15, it being understood that the ring portion 35 is a tight fit within the end of the cathode 15. Welded or otherwise rigidly fastened to the lip 34 are three equally spaced fiat metal spring members 36, 37, 33, which are adapted to engage flexibly the inner wall of the tubing 14 so as to maintain the cathode 15 concentric with respect to the anode 16.

The spark-over protection ring 33 is of similar construction to ring 32, except that one of the spring fingers, for example the finger 39, is longer than the remaining two fingers, enabling finger 39 to engage the inwardly projecting base portion 40 of the contact button 14, thus providing a positive metallic connection between the said button and the cathode 15. It will be understood, of course, that after the glass pellet 22 has been melted to seal 01f the device after evacuation and filling with the desired gas pressure, the externally projecting end of the tubulation 19 serves as the lead-in connection to the anode 16. It is believed that the manner of assembling of the various elements above described will be clear from the foregoing description.

It has been found that with a tube such as that described, it is possible to maintain a substantially flat voltage characteristic at the terminals of the tube for a very great change in current through the tube. For example, as shown in Fig. 8, the tube maintains a substantial constant value of 25 kilovolts even though the current through the tube should vary between 50 and 500 microamperes. In such a tube, the gas filling was substantially pure hydrogen at a pressure of approximately 40 pounds per square inch. With such a tube the rod 16 extended approximately 1 /2 inches beyond the left-hand end of the cylindrical cathode 15, that cathode having an internal diameter of 1.5 inches and an axial length of approximately 4.8 inches. The anode rod 16 has a diameter of approximately 0.125 inch.

Various changes and modifications may be made in the disclosed embodiment without departing from the spirit and scope of the invention. For example, while reference has been made to the anode 16 as being in the form of a solid rod, it will be understood that it may be in the form of a cylindrical stainless steel tube, both ends of which are open to facilitate exhaustion of the envelope. In that event the tubular anode 16 may be a telescopic fit with respect to the metal tubulation 19. Furthermode, in certain cases the anode 16 may be an integral continuation of the exhaust tubulation, thus performing a triple function, namely as anode, exhaust tubulation and lead-in.

What is claimed is:

1. A high voltage regulator tube of the corona discharge kind, comprising, an enclosing envelope of insulating material containing a gas, a cylindrical cathode open at both ends, a cylindrical anode passing interiorly through and extending beyond the ends of said cathode, means sealed through the wall of said envelope for making electrical contact with said cathode, a rigid metal lead-in sealed through one end of said envelope in alignment with said anode and rigidly fastened to one end of said anode, and insulating means through which the opposite end of the anode passes to maintain the anode concentric with the cathode.

2. A high voltage regulator tube, according to claim 1, in which the internal diameter of said cathode and the external diameter of said anode are correlated with the gas pressure within said envelope to stabilize the voltage applied to said cathode and anode. by corona discharge therebetween.

3. A high voltage regulator tube of the corona discharge kind, comprising a vitreous enclosing envelope containing an ionizable gas at high pressure, a contact member sealed through the envelope wall for making electrical contact with said cathode, a cylindrical anode concentric within said cathode, at metal exhaust tubulation sealed through one end of {the envelope concentric with said anode and fastened thereto, and fusible means within said tubulation for vacutjim-tight sealing of said envelope. 1

4. A high voltage regulator tulpe according to claim 3, in which said metal tubulation hi1 which said anode and exhaust tubulation are telescopicailly joined while providing a plurality of exhaust ports th :rebetwcen.

5. A high voltage regulator tube according to claim 3, in which said anode is in the form hgf a cylindrical metal tube with open ends.

6. An electron discharge tube, compili'sing an enclosing envelope closed at one end by an insulatingxheader, a plurality of spaced electrodes within said envelop a metal exhaust tubulation vacuum-tight sealed throng lx said header and having one end extending into said envelopex said one end being fastened to one of said electrodes, said tubulation having a constricted region, and a fusible material located within said tubulation adacent said constricted region to form a vacuum-tight seal for said tubulation at said constricted region.

7. An electron discharge tube according to claim 6, in which said constricted region and said fusible element are located entirely within said envelope and in spaced relation to the sealing-in region between said tubulation and said header.

8. An electron discharge tube according to claim 7, in which said tubulation carries adjacent said constricted region a heat concentrator for concentrating to said constricted region the heat required for fusing said fusible material.

9. An electron discharge tube according to claim 7, in which the heat concentrator is in the form of an annular metal flange fastened to the exterior to said tubulation adjacent said constricted region.

10. A high voltage regulator tube of the corona discharge kind, comprising an enclosing envelope having an insulating header at one end, an insulation bridge closely fitted within the end of said envelope opposite to said 10 header, metal rod means having one end. passing through said bridge and the opposite end sealed through said header, said opposite end being tubular to form an exhaust tubulation, a cylindrical metal cathode surrounding said rod means, means to support said cathode at opposite ends against the wall of said envelope and concentric with said rod means, and a fusible element within said tubulation portion of said rod means to seal said tube vacuum-tight.

No references cited.

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