US2534532A - High-voltage rectifier - Google Patents

Description

Dec. 19, 1950 o. H. SCHADE HIGH-VOLTAGE RECTIFIER 2 Sheets-She 2 Filed July 14, 1945 IN VENTOR 0/70 A! JCl/AD/F" BY )km ATTORNEY Patented Dec. 19, 1950 2,534,532 HIGH-VOLTAGE RECTIFIER Otto H. Schade, West Caldwell, N. J assignor to Radio Corporation of of Delaware America, a corporation Application July 14, 1945, Serial No. 605,131

I 19 Claims.

This invention relates to a new and useful electrical condenser of the high voltage high frequency type for use with high frequency industrial oscillators and the like.

An object of this invention is to provide an improved low cost light weight condenser of the Leyden jar type wherein the inner electrode coating exceeds the outer electrode coating in its physical length to give an increased creepage path by having an external uncoated skirt to aid in preventing corona discharge.

Another object of this invention is to provide a condenser which will be made part of the actual circuit connections by combining the condenser with high voltage rectifiers of the electron discharge type which are frequently employed in a three stage voltage multiplier or tripling circult.

Still another object of this invention is to provide an improved electrostatic condenser of the Leyden jar type which has increased electrical capacity for the same physical dimensions, and greater mechanical and electrical strength than those of the prior art.

A feature of this invention is the novel arrangement and shape of a condenser wherein the device has a re-entrant and reduced long necked portion which permits telescoping and capacitive variation with adjacent condenser units of similar shape.

Although electric condensers of the Leyden jar type are very old in the art, they are now infrequently used because of their bulk relative to the unit of electrical capacity. Also corona, discharges cause ionization and consequent heating and power loss in the air and glass dielectrics. The Leyden jars of the prior art frequently break down by an electrical puncture through the glass wall between the inner and outer electrodes at the end of each coating. This invention overcomes the objection of the prior art condenser by providing a flask shaped condenser having a reentrant portion, the outer portion of which is provided in the central dome portion. An encircling skirt decreases the tendency to form corona discharge at the termination of the outside electrode. The wall thickness is increased and curved at the portion where the skirt joins the cylindrical portion of the flask at the terntination' of the outer electrode. The outer electrode itself is rounded over at the electrode termination to further assist in the reduction of corona losses or electrical brush discharge.

The condensers of this invention have been found to be capable of standing continuous operation in high frequency rectifier service at voltages in excess of 50,000.

This invention will best be understood by referring to the accompanying drawing in which:

Fig. 1 is a longitudinal section of a condenser of this invention; also the showing of the telescoping of other similar adjacent condensers.

Fig. 2 is a cross section view taken on line 2-2 of Fig. 1.

Fig. 3 is a circuit arrangement of the series connection of the condensers of Fig. 1.

Fig. 4 is a partial longitudinal section of the top end portion showing a method of making a connection between the inner electrode and the outer electrode of an adjacent condenser.

Fig. 4A is a partial elevation of Fig. 4.

Fig. 4B is a partial longitudinal section of a condenser of this invention showing another method of making connection to the inner electrode of a condenser.

Fig. 5 is a schematic showing of a voltage multiplier circuit employing the condenser of this invention; and

Fig. 6 is a circuit diagram of a voltage multiplier.

Referring now in detail to Figs. 1 and 2 of the drawing, a flask shaped dielectric member I is shown, preferably constructed of boron silicate glass. Such a glass is particularly adapted for high frequency use such as, for example, Pyrex or Nonex glass. The flask I is provided with a re-entrant portion 2. The'reentrant portion .extends substantially beyond the center of the flask and is terminated by a dome-shaped construction, as indicated at 2. Beyond the domeshaped portion a long narrow neck 3 is formed.-

A skirt 4 is formed. at substantially the central portion thereof and connects the outer wall portion of the flask I with the neck portion 3. At the junction of skirt 4 and the outer cylindrical portion l, the wall thickness of the dielectric member is substantially increased in thickness at point 5 and provided with a radius 6 which is suiflcient to prevent corona discharge at the operating voltage of the condenser. The outer cylindrical portion of flask I (starting at radius 6) and the re-entrant portion including dome 2 is coated with a metallic electrode 1 which is preferably formed on the glass by applying a thin coating of silver paste, and then heating the glass to a temperature suflicient to melt the silver and unite it with the glass, which temperature is in the order of 400 to'500 degrees centigrade. The inner portion of flask I is entirely coated with a etallic electrode 8 which is also formed with then the surplus removed, after which it is heated in a maner mentioned above in connection with electrode I. Electrode 8 terminates Just short of the extreme end of the condenser at a point 0. The wall thickness l' is approximately 2 millimeters thick, and when constructed of special glass for high frequency rectifier use (the condenser being used as a filter condenser) will stand approximately 50,000 volts D. C. at a ripple frequency of about 100 kilocycles and carry current in the order of 200 miiliamperes. It is noted that the increased portion of the wall thickness at point I is curved in three different directions, the first being formed by radius 0, the second by the curved inner wall and the point III, which curvature follows substantially the curve of dome 2. The third or outer curvature is formed at point II. This increased wall thickness is located at a point wherethe electrostatic stress of the surrounding air is normally most intense, and by this construction the stress is considerably decreased so that all tendency of the formation of corona discharge at this point is substantially eliminated. The provision of the skirt 4 electrically subdivides the creepage path betwe the outer electrode 1 and inner electrode 0. urthermore, the shape and arrangement of the upper portion of the flask, starting from point 8 and terminating at the radius of curvature 8 on the inner portion of skirt 4, is such that in event an excess voltage is applied, the condenser will be discharged by an electric are which will form at this point. The ratio of length of this creepage path and the wall thickness of the glass is such that the arc will discharge before the voltage is built up suificiently to puncture through the glass wall. In one form of condenser which was constructed in accordance with this invention, the total length of the flask was about inches long, 2 inches in diameter at the outer portion of the fiask, 1% inch at the re-entrant portion, and 1% inch at the neck portion, the outer diameter of the skirt being 3 inches in diameter and the wall thickness approximately .784 or about 2 millimeters thick. The curvature of radius 6 was equal to about V; of an inch. Such a, condenser has a capacity of 500. micromicrofarads and will .stand 50,000 volts. The cost of a condenser of this type is about one quarter of an equivalent prior art type of the same capacity and voltage rating.

As shown in Fig. 3, the condensers of Fig. 1 are teiescoped and connected in series, the connection from the inner electrode 8 being formed by placing a flexible metallic member I! over the inside metallic coated wall of the re-entrant dome portion 2. This connection I! may be formed of spring metallic material or flexible "Belden or stranded copper braid which, as shown by Fig. 1, extends beyond the end of neck portion 3 and terminates in a flexible band I! and is soldered thereto. The other end is located at and extends beyond the metallic base of dome portion 2. The outer electrode 1 is connected by a split band clamp ll which clamp may also form a supporting base to be secured to an insulator IS, the clamp It being secured to'insulator Ii by means of a bolt It. In order to provide intimate contact between clamp 4 and electrode I, a soft lead gasket i1 is provided. Likewise, if desired, a soft gasket I! may be interposed between electrode 'l of the adjacent condenser and member II. The two ends of the band clamp II are clamped together by means of bolt is and nut 20.

Fig. 4 shows a modified telescoping method {baud a semi-fluid silver paste which is poured in and "whereby a telescoping placing a resilientsstopper 21' of rubber in the neck of the condenser J2. The

braid I! is carried beyond the' of and clamped by a split end cap N which is constructed of spring metal, such as phosphorous and p is provided with bent fingers'llA, the arrangement being such that the bent fingers make a good sliding contact with the outside electrode 1 of an adjacent condenser. A screw 12 and nut it retains the end cap in position.

When a connection other than the series arrangement shown by Figs. 3 and (is desired, an alternative arrangement shown by Fig. 4B is provided. This method is used as a terminus of the end condenser, or when parallel or non-telescoping arrangements of the device as desired. The construction of the terminal electrode of Fig. 43 includes a resilient rubber stopper member IIA having a central aperture therein through which passes a terminal screw A which is provided with a clamp nut A. In order to prevent formation of corona at this point and also the entry of dust or moisture, a spherical shaped metallic member flB is provided. The connection is made by means of a metallic tubing 20. To insure positive connection between the inner electrode I and terminal screw 22A, a soft lead gasket 26 is provided between the glass and rubber stopper. Alsoa metal washer TI is placed beneath the terminal nut 23 to distribute the pressure on stopper II when it is compressed by screw 22A.

Figs. 5 and 6 illustrate the improved voltage tripling circuit wherein the capacitors of this invention are arranged to form a compact circuit structure with other associated apparatus such as, for example, a high voltage Tesla coll II which includes a primary winding I connected to an alternating current input source IIA which may be that of an oscillator having a frequency of 100 kiiocycles. A high voltage secondary winding 82 is located above the primary winding 8i and is supported by an air core tubular insulating member 30A. The output voltage derived at the terminals of the secondary winding 32 is preferably in the order of 30 kilovolts, and as shown in Fig. 5, one side is connected to the cathode of a rectifier tube 33. The rectifier tube 31 is preferably that of the RCA tube 8016 type. The cathode of rectifier tube 33 is connected to the terminal 248 of condenser iA which is the type shown in Figs. 1 to 4 inclusive. is connected to ground. The rectifier voltage between plate "A and ground SIB is approximately 30 kilovolts.

Because the voltage is too high at a point ad- Jacent the rectifier tube It and condenser IA to insure sufiicient insulation to the filaments of the rectifier, the ordinary filament heating transformer which is generally employed in lower voltage rectifier circuits cannot be employed. Therefore, in order to heat the cathode or filament at this point, a. small resonant circuit. sufficient to heat the rectifier filaments to approximately 200 -miliiamperes, is provided. This circuit includes The other side of secondary I! tialiy well above the ground potential indicated at SIB. The transformer 40 i generally tuned to the fundamental frequency. However, if desired, it may be tuned to a harmonic frequency if the harmonic content is sufficient to permit constant energy to be derived to properly heat the filament of the rectifier tube. The current passing through the transformer ll is the current passing through the tube capacitance between anode and filament. As shown in Fig. 6, the filament is connected from one side of coil 40 to th tap A. A second rectifier tube I4 is supported by an insulating tube "A, extending out from the re-entrant portion of condenser IA, and is electrically connected to the outside electrode I by the supporting band I 4 of one of the ca thus keeping the entire radio frequency substanpacitors of this invention. The filament or cath ode of rectifier I4 is heated by coil 40 and condenser 4| in the same manner as mentioned above in connection with the heating of themetifier 83. A third rectifier tube 35 also has its anode connected to electrode I of condenser IA. At this point, the voltage from rectifier l4 and ground 33B is now increased to 90 kilovolts; and there is connected in series between the anode of rectifier tube it and ground the two condensers IB and IQ of this invention. A connection is made from band ll of condenser IB to the cathode of rectifier 35 and the anode of rectifier 33. The filament of rectifier 85 is heated by an autotransformer 40 in thesame manner mentioned above in connection with rectifier 33, although the tap A may be for a different value of voltage and current. Also, if desired, a different type of rectifier may be employed than the previously mentioned rectifiers for the reason that the voltage is substantially increased at this point. It will be noted that by the use of condensers of this invention, the structural arrangement of the high voltage circuit is substantially reduced in physical dimensions over that of the type wherein ordinary condensers are employed. Also the shape and structural features of the condensers IA, IB and IC of this invention permit complete freedom of design, allowing the condensers to be interchanged from a series telescoping arrangement to that of a parallel arrangement with a minimum amount of supporting structure.

The mode of operation of the high frequency high voltage source shown by Figs. 5 and 6 is as follows: A radio frequency voltage of approximately 100 kilocycles and 30 kilovolts is obtained from the alternating current generated source impressed on the Tesla coil II. The output alternating current voltage from the secondary 82 is rectified by the first rectifier 33, which charges condenser IC to a peak voltage E of 30 kilovolts. The alternating current generator in series with the condenser IC charged by rectifier it acts in eflect as the energizing source for the second rectifier 35, and thus condenser IA is charged to a double voltage 2E of 60 kilovolts Rectifier I4 is energized (going from the plate toward the cathode) by the voltages on condenser IA, the alternating current generator, and the condenser IC in series. As the polarity of condenser IC is opposing, the total energizing voltage on rectifier I4 is composed of two parts, one part being equal in magnitude to 2E (due to the voltage on condenser IA plus the voltage of the alternating current generator), and the other part in an opposing sense, a minus voltage E (on condenser IC) efiectivel producing a voltage E on condenser IB. With respect to ground,'-fiowever, the

a cathode of rectifier 84 is at triple potential, or has a voltage SE of kilovolts. The filament heating auto-transformer ll receives its current through the alternating current generator I. It will be seen that the high radio frequency voltage E from the secondary :2 drives a current through the plate-cathode or interelectrode capacitance of the diodes over the respective filter condensers. The radio frequency current flowing through the rectifier interelectrode capacitance is stepped down by the auto-transformer winding 40 which together with the small variable condenser H is brought into resonance to obtain the proper value for heating the filament of the rectifiers.

This invention is not to be construed as limited to the modifications described.

What is claimed is:

1. An electric condenser comprising a hollow member and a metallic electrode coating on a portion of the outside wall of said dielectric member.

2. A high electrostatic condenser comprising a hollow cylindrical dielectric member having anentrant portion and a neck portion of reduced diameter located above said re-entrant portion, the reduced diameter of said neck po tion being such as to permit telescoping of a si ilar condenser at the re-entrant portion of said similar condenser, a metallic electrode coating on substantially the entire inside wall of said dielectric member and a metallic electrode coating on a portion of the outside wall of said dielectric member.

3. A high voltage electric condenser comprising a glass cylindrical flask having a re-entrant portion extending substantially midway in said fiask, a neck portion having a width such as to permit telescoping of a similar condenser at the re-entrant portion of said similar condenser, a metallic electrode coating on substantially the entire inside wall of said flask, a metallic electrode coating on the outside wall of the re-entrant portion of the outside wall and terminating substantially midway on said flask and a thickened glass portion located at the termination of said outside electrode. 7 4. A high voltage electric condenser comprising two cylindrical walls of dielectric material. said cylindrical walls being connected together at the lower portion thereof, the innermost cylindrical wall being terminated by a dome portion. the outermost cylindrical wall having a skirt portion forming a corona shield for said condenser, a metallic electrode coating on the entire inside wall .of both of said cylindrical walls and a metallic electrode coating on the outside wall adjacent said skirt of the outermost cylinder, and the outside wall of said innermost cylinder, including said dome portion.

5. An electric condenser arrangement for a high frequency voltage multiplier circuit comprising a plurality of rectifiers of the electron discharge device type and a plurality of condenser elements having a cylindrical dielectric member with a re-entrant portion, a metallic electrode on the inside walls, a metallic electrode coating on a portion of the outside walls of said dielectric member and at least two of said conwithin the re-entrant portion of an adjacent condenser.

'densers connected in series by a connection made 6. An electric condenser arrangement for a" high frequency voltage multiplier circuit comprising a plurality oi rectifiers of the electron discharge device type and a plurality of -condenser elements havinra cylindrical dielectric "member with a 're-entrant portion and a long neck portion, a metallic electrode coating on the inside walls of said cylindrical dielectric member. a metallic electrode coating on a portion of the outside walls of said cylindrical dielectric member, and means to provide a connection irom element having a cylindrical dielectric member with oppositely disposed neck and re-entrant portions. said re-entrant portion extending to a point intermediate the ends of said condenser element. the width of said neck portion being such as to pennit the teleswping of a similar condenser element at the re-entrant portion of said similar condenser element, a metallic electrode on the inside wall of said dielectric member, a metallic electrode coating on the outside wall of said reentrant portion and on a portion of the outside wall of said condenser, a skirt portion located at the termination of the coating on the outside wall of said condenser to form a corona shield to prevent brushing between the inside and outside electrodes.

8. An electric condenser arrangement for high irequency and high voltage use comprising a plurality of condenser elements having cylindrical re-entrant portions, a metallic electrode on the inside wall of said cylindrical dielectric elements. a metallic electric coatingvon a portion oi the outside wall of said dielectric elements, supporting means for said condenser elements, the arrangement being such that adjacent condenser elements telescope within the re-entrant portion so as to provide variation in capacity between adjacent condenser elements.

condensers being arranged to support some of said rectifiers and means to heat the filaments of said rectifier by a transformer tuned to the resonant frequency of the input source of said rectifier circuit.

11. A high voltage rectifier circuit including a high voltage oscillation circuit. a plurality of rectifiers connected to said oscillation circuit, a plurality of condensers of the type having a cylindrical fiask with a re-entrant portion with inner and outer electrodes, a transformer surrounding and supported by the'base of said rectifiers to heat the filaments thereof by being tuned to the resonant frequency of said oscillation circuit, and a a plurality of condensers of said first mentioned a e s:

a I form a voltage divider between the output of said rectifier circuit and ground.

12. A high voltage rectifier circuit including a high voltage oscillation circuit, a plurality oi rectifiers connected to said osicllation circuit, a plurality oi condensers of the type having a cylindricalfiaskwithare-entrantportionwithinner andouter electrodes, a transformer surrounding and supported by the base oi said rectifiers and a variable condenser supported by the base of said rectifier tubes to heat the filaments thereof by being tuned to resonant frequency of said oscillation circuit and a plurality of condensers connected together in series to form a voltase divider between the output of said rectifier circuit 13. a high voltage rectifier circuit including in alternating current input source, a rectifier of the type having a filament and an insulating base, means including an inductive element which is secured to and surrounds said insulating base which is connected to said filament to heati filament of said rectifier, said inductive element being tuned substantially to the resonant frequency oi the input source of said 'rectifiercircuit.

14. A high voltage high frequency rectifier circuit including a rectifier of the type having a filament,,a condenser of the type having a reentrant portion; said rectifier being insulatingly supported by. electricall connected to and located adiacent said condenser at the re-entrant portion thereof; inductive means to heat the filament of said rectifier; and means capacitively and cooperatively associated with said inductive means to tune said combination substansource of said high voltage high frequency.

15. A high voltage high frequency rectifier circuit comprising an alternating current input source, a tube having a base. said tube being energiaed by said alternating current, a transformer mounted on said base and having a winding positioned in the neighborhood oi said base, and a condenser connected in shunt with said winding for tuning said transiormer.

16. In a high voltage high frequency rectifier circuit, a plurality of rectifiers, a plurality of condensers. at least one of said condensers being of the hollow cylindrical type having a neck portionandare-entrantportion,afirstoneoisaid rectifiers insulatingly supporting one end of said one condenser at said neck portion, a second rectifier insulatingly supporting the other end of said one condenser at an end opposite said neck portion, and a third rectifier insulatingly supported at one end by said one condenser at the re-entrant portion, the other endof said third rectifier being insulatingly supported by at least another condenser.

17. A high voltage rectifier circuit operable to rectify currents having high frequency components including a rectifier of the type having an anode and a filament with inter-electrode capacity therebetween, means tuned to resonate at the high frequency components including an autotransiormer having an inductive winding and shunt capacitance, said winding including a tapped portion to heat the filament of said rectifier, said transformer winding and shunt capacitance being tuned substantially to the resonant frequency of the input source of said rectifier circuit, means connecting the transformer winding in series with the rectifier anode-filacondenser type connected together in series to II ment inter-electrode capacity whereby, the high and means connecting said filament; to the tapped portion of the inductive winding.

18. A high voltage rectifier circuit for rectifying high frequency components including a rectiher of the type having an anode and a filament with inter-electrode capacity therebetwee'n, a parallel resonant circuit including an inductance and capacitance tuned to the frequency of the applied high frequency components, means connecting the parallel resonant circuit in series with the high frequency components that are applied to the rectifier whereby the high frequency components transmitted by the inter-electrode capacity of the rectifier are effective to energize the tuned circuit. and means connecting the filament of the rectifier across at least a portion of the inductance element of the tuned circuit to thereby energize the filament.

19. A high voltage circuit operable to rectify currents having high frequency components including a high frequency source of energy, a rectifier of the type having an anode and a filamentary thermionic electron emitter, a parallel resonant circuit including an inductance and a capacitance tuned to substantially the frequency of the high frequency components, means to apply energy from the high frequency source across the rectifier in series with the tuned circuit whereby the tuned circuit may be energized due to energy passed by the inter-electrode capacity of the rectifier, and means to connect the filamentary electrode emitter across at least a portion of the in- 10 ductance element of the tuned circuit to supply energy to the filament of the rectifier in order that the applied high frequency energy may be rectified.

O'IIO H. SCHADE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I'ENTS Number Name 6 Date 454,622 Tesla June 23, 1891 1,863,477 Gebhard June 14, 1932 1,870,960 Nyman et ai Aug. 9, 1932 2,028,907 Higgins Jan. 28, 1936 2,045,034 Kuntke June 23, 1936 2,163,218 Schlesinger June 20, 1939 2,302,900 Vance Nov. 24, 1942 2,369,772 Bouwers Feb. 20, 1945 2,373,165 Cawein Apr. 10, 1945 2,374,499 Quayle et a1 Apr. 24, 1945 2,459,988 Boadle Jan. 25, 1949 FOREIGN PATENTS Number Country Date 6,575 Great Britain Mar. 16, 1914 511,126 Germany Oct. 30, 1930 576,869 Germany May 18, 1933 660,890 Germany June 4, 1938 OTHER REFERENCES Schade Pub. No. ST-235, April 1943, R. C. A.

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