US2130073A - Electrolytic condenser - Google Patents

Description

Sept. 13, 1938.

C. DE LANGE ET AL ELECTROLYT IC CONDENSER Filed Feb. 17, 1937 g, jlvvalvro as vie Z nge Q Patented Sept. 13, 1938 UNITED STATES PATENT OFFICE.

Johannes Claassen, assignors to N. V.

Eindhoven, Netherlands, Philips Gloeilampenfabrieken, Eindlioven, Netherlands Application February 19,1937, Serial No. 126,702 In Germany February 22, 1936 7 Claims.

Our invention relates to electrolytic condensers. and more particularly to wet electrolytic condensers for-operation on voltages of the order of 350 volts and more.

It is general practice to construct electrolytic condensers with a metal electrolyte container serving as the cathode, and to provide within this container an anode having a large surface area to obtain a maximum capacity with condensers of a given size. For this purpose, the anode may be a corrugated strip, a strip bent into a starshape, or may be formed of a spirally-wound sheet of aluminum apertured at various points to permit free circulation of the electrolyte.

Such condensers, however-particularly when they are for operation on voltages in excess of 350 volts-have several disadvantages due to the unequal and large distances between the cathode container and various points on the anode. As will be explained in more detail hereinafter, this results in large and varying partial series resistances which very unfavorably effects the total series resistance of the condenser, and makes the total capacity of the condenser highly dependent upon the frequency of the operating voltage.

The main object of our invention is to overcome the above difficulties, and to provide an electrolytic condenser in which the partial series resistances of each point of the anode with respect to the cathode are equal and as small as possible.

Another object of our invention is to produce a compact multiple condenser unit.

In accordance with the invention, we form the anode as a cup-shaped member, and so arrange same with respect to a cathode container having a cup-shaped portion projecting into the hollow of the anode, that the distance between the cathode and anode is small and substantially the same throughout the entire surface thereof.

The construction of condensers according to the invention is simple, provides a low and constant series-resistance, and the cup-shaped electrodes can be formed in asimple manner by impact extrusion methods.-

In one embodimentof our invention, We house a second condenser within the hollow of the cathode portion projecting into the cup-shaped anode, to produce a multiple condenser unit which is simple and compact and is of particular advantage for use in power supply filters for radio sets.

We are aware that dry electrolytic condensers are constructed with strip electrodes substantially equally spaced apart by an absorbent spacer carrying a pasty electrolyte. With such condensers however, a. puncture in the dielectric film can be automatically restored only with difliculty or not at all, with the result that a short circuit between the electrodes will not be removed. Furthermore, it has been proposed to use an irregularly shaped anode and a similarly shaped cathode arranged to provide equal spacing therebe-,

tween. Such constructions, however, have either been so fragile that there is danger of short circuitingof the electrodes or of damage to the dielectric film, or have been provided with so many supporting members as to make the construction very complicated and entirely unsuited for mass production.

In order that our invention may be clearly understood and readily carried into effect, we shall describe same more fully with reference to the accompanying drawing in which-- Figure 1 is a sectional view of a condenser according to the prior art,

Fig. 2 is a sectionized view of a condenser according to the invention,

Fig, 3 is a sectionized view of a portion of the condenser of Fig. 2 with a second condenser mounted therein, and

Fig. 4 is a schematic diagram illustrating an application of the condenser of Fig. 3.

Figure 1 is a cross-section of a prior-art condenser having a star-shaped anode 33 and a cylindrical cathode-container 34. In such a condenser, the distances between the anode and cathode vary, and as a result the partial capacities which make up the total capacity of the con denser have difierent series resistances which, in the construction shown, may have appreciably high values. If the condenser is for operation at a high voltage, for example 500 volts, the specific resistance of the electrolyte will be compartively high, as this specific resistance increases about proportionally with the sparking voltage which controls the maximum voltage of the electrolyte. For instance, electrolytes for operation on 500 volts, would have a specific resistance of about 10,000 ohms per cubic centimeter at 20 0., whereas an electrolyte for operation on 550 volts would have a specific resistance of from 15,000 to 20,000 ohms per cubic centimeter at the same temperature.

Assuming, in Fig, 1, that the condenser has a" total capacity of 18 mid. and that a partial capacity of. 6 mfd. is supplied from an anode surface of 100 square centimeters lying 2 centimeters from the cathode. If the electrolyte has 'a specific resistance of 15,000 ohms per "ibic centimeter, the series resistance corresponding to the 6 mfd. will be:

2 15,000 XI0 300 ohms This involves an enormous resistance loss as the impedance of 6 mid. at a frequency of 100 cycles per second will be 260 ohms. Furthermore, the total capacity of the condenser will vary greatly with the frequency, and as this difiiculty is more acute with electrolytes for higher voltages, it is very important that the distances between the anode and cathode of condensers operating at voltages of the order of 400 volts, be small and equal. Amore detailed discussion of the above difllculties has been given in our copending U. S. patent application Ser. No. 107,290 filed Oct. 23, 1936 In accordance with our present invention, the above difliculties are overcome by forming the condenser in a manner as illustrated in Fig. 2, in which the reference numeral 1 indicates a cup-shaped anode whose surface area is preferably increased by etching in the manner described in the copending U. S. patent application Ser. No. 724,565 to Emmens et al., filed May 8, 1934.

Anode l is provided with a boss 2 and a cylindrical projection having a. hollow end, and is secured to a member 3 of insulating material, for example molded bakelite, by spinning over the end of projection 5 at 6. A gasket 4, far instance of rubber, is disposed between boss 2 and member 3, where as an anode lug I is secured under the spun edge at 6. For securing the condenser to a panel member 3 is externally threaded at 8.

The anode I may be simply and inexpensively formed by impact extrusion, such as described in copending U. S. patent application Ser. No. 97,200 to Kipperman et al., filed August 21, 1936.

The cathode-container A comprises a cupshaped member ID and a cylindrically-shaped member 9 secured together at the top by having their edges rolled over, whereas the bottom of member 9 is spun over the edge of member 3 with the interposition of gasket 4 to form a liquidtight seal. Secured to the bottom of member 9 is acathode lug 35.

The space formed between members 9 and I0, and anode I is filled with a suitable liquid electrolyte 26, for example a mixture of 240 grams of boric acid (HJBOI), 1, grams of glycerin 1,000 c. c. of ammonia (NHAOH), and 30 cubic centimeters of water.

To allow for the escape of gases produced during the operation of the condenser, member ID is provided with a groove 81 having one or more apertures II and embraced by a rubber band l2 which is pricked with, a pin at portions corresponding to apertures ll. pressure of the gas above the surface of the electrolyte exceeds atmospheric pressure, the band I2 expands at apertures H and the gas escapes thru the small expanded holes therein.

The member Ill forms a cylindrical space 14 which is closed by acover l5 spun over the edge of cathode-container A. As shown member I! is of metal, however in some cases it is prefer-' able to make it of insulating material.

A condenser of the construction shown in Fig. 1 is very compact, for example with an anode having a diameter of 30 mms. and a height of 80 mms. and having an etched surface as above mentioned, a capacity of from 8 to 16 mfd. at an operating voltage 550 volts is obtained. FurthermL-e, due to the small spacing between the anode Thus when the and cathode, for instance 2 mms., the series resistance is very low, for instance about 20 ohms, and the angle of loss is considerably less than 0.1. In addition, the leakage current is small, for example only 0.1 amp. per mfd., and due to the equal spacing between the electrodes, the dependency of th capacity upon the frequency of the operating voltage is also very low.

The space I4 in the condenser of Fig. 2 is particularly suited for housing a second condenser, and such a construction is shown in Fig. 3 in which parts similar to those in Fig. 2 are indicated by the same reference numerals.

As shown in Fig. 3 there is disposed within space H, a second condenser E, which is preferably of the type described in the copending U. S. patent application Ser. No. 54,881 filed Dec. 17, 1935, now Patent #2,099,599. Condenser B comprises a star-shaped anode 2|, an electrolyte 38, and a cup-shaped cathode-container I9. The top of container l9 forms a protuberance 2! provided with apertures 3| and embraced by a rubber band 29 to form a vent for the gases developed during the operation of the condenser. Secured to the top of container ill by having its end rolled into a groove, is a cup-shaped cover I! carrying two bushings l8 and housing a porous liquid-absorbing material 30, for instance saw dust, which serves to absorb any electrolyte which might be carried out through apertures 3| by the escaping gases. Condenser B is supported from a metal plate 45, secured to cathode-container A by a flanged ring l3, by two screws 20 cooperating with bushings l8.

Anode 2| is provided with a soldering lug 22 to which is connected a lead 23 passing through an aperture 24 in plate 45 whereas cathodecontainer I9 is provided with a. lug 26 to which is connected a lead-21 passing through plate 45. By making the plate 45 of metal, the cathodes oi the two condensers are connected together and lead 21 serves as the common lead thereto, or the lug 25 of Fig. 2 may be used as the common cathode connection. In such cases leads 23 and 21 are insulated from plate 45 by insulating bushings 24.

On the other hand by making the plate 45 of insulating material the two condensers are insulated from each other whereby leads 23 and 21 serve only as the connection to the anode and cathode respectively of condenser E, whereas the connections to the outer condensers are made in the manner indicated in Fig. 2. In such a construction the insulating bushings 24 can be eliminated.

With the first construction, 1. e., with metal plate 45, the condenser unit is of especial advantage in filter circuits such as illustrated in Fig. 4,in which latter C indicates the condenser unit of Fig. 3. D indicates the condenser'of Fig. 2, and B indicates the inner condenser of Fig. 3. In the iilter circuit shown, 40 and 4i indicate the terminals of a pulsating D. C. supply whereas reference numerals 42 and 43 indicate the output terminals for supplying the smoothed current to a radio or amplifying system, (not shown); the inductance being provided by the field coil 32 of aloud speaker.

Condenser D, which has the higher capacity and operating voltage has its anode connected to one side of the coil 22 as indicated by 1', whereas condenser B, which has a lower capacity and lower maximum voltage, has its anode connected behind coil 32 as indicated'by 22'. The cathodes of the condensers B and D, which are connected together by a metal plate 45 (see Fig. 3), are connected to the negative terminals 4| and 43.

Such a multiple condenser unit comprising a high voltage condenser of large capacity and a second condenser of lower capacity and voltage, can be used to advantage in other circuit arrangements.

Although we have described our invention with reference to specific examples and applications, we do not wish to be limited thereto but desire the appended claims to be construed as broadly as permissible in view of the prior art.

What we claim is:

1. An electrolytic condenser comprising a cupshaped anode having a cavity, a container acting as a cathode and having a cupshaped portion extending into said cavity, a liquid electrolyte within said container, substantially the entire surface of said anode being equidistantly spaced from said cathode-container, and venting means including an aperture in said cup-shaped cathode portion above the level of said electrolyte, and a rubber band within said container and normally closing said aperture, said band being provided with a pin-prick at the aperture.

2. A multiple condenser unit comprising an electrolytic condenser having a cup-shaped anode, a container acting as a cathode and having a cupshaped portion projecting into the cavity of said anode, and a liquid electrolyte within said container, substantially the entire surface of said anode being equidistantly spaced from said cathodecontainer, and a second electrolytic condenser disposed within the cavity of the cup-shaped cathode portion of said first condenser, said second condenser comprising a container having a double-walled end, an electrolyte within said container, an anode within said container and having an electrical connection extending through the end of the container opposite a double-walled end, venting means within the space formed at the double-walled end, and means for supporting the condenser from the container of the first condenser comprising a member positioned within the space formed at the double-walled end.

3. An eletcrolytic condenser comprising a cylindrical-shaped container acting as a cathode, a cup-shaped anode insulatingly supported at its bottom from the bottom of said container, a lead for said anode extending through the bottom of said container, said container comprising a cupshaped portion extending within the hollow of said anode and occupying substantially the entire space thereof, substantially the entire surface of said anode being equidistantly spaced from said extending portion, and a liquid electrolyte within the space formed between the container and cupshaped portion and completely, covering said anode.

4. An electrolytic condenser comprising a substantially cylindrical container acting as a cathode, a cup-shaped anode insulatingly supported at its bottom from the lower end of said container, a cover for said container comprising a cup-shaped portion extending within the hollow of said anode and occupying substantially the entire space thereof, a liquid electrolyte within the space formed between the container and cupshaped portion and completely covering said anode, said cup-shaped portion being provided with an aperture at a point above the level of the electrolyte, and a rubber band embracing said cupshaped part and provided with a pin-prick at said aperture to allow for the escape of high-pressure gases developed within the condenser.

5. A multiple condenser comprising an elec-' trolytic condenser having a cylindrical-shaped container acting as a cathode, a cup-shaped anode insulatingly. supported at its bottom from the bottom of said container, a lead for said anode extending through the bottom of said container, said container comprising a cup-shaped portion extending within the hollow of said anode, and a liquid electrolyte within the space formed between said container and cup-shaped portion and completely covering said anode, and a second electrolytic condenser disposed entirely within the hollow of said cup-shaped portion.

6. A multiple condenser comprising an electrolytic condenser having a cylindrical container acting as a cathode, a cover for said container comprising an inwardly-extending cup-shaped portion, a cup-shaped anode insulatingly supported at its bottom from the bottom of said container and extending between said container and the cup-shaped portion, a lead for said anode extending through the bottom of said container, a liquid electrolyte Within the space formed between said container andcup-shaped part and completely covering said anode, and a second electrolytic condenser disposed entirely within the hollow of said cup-shaped portion of the first condenser, said second condenser comprising a container having a double-walled end, an electrolyte within said container, an anode within said container and having an electrical connection extending through the end of the container opposite the double-walled end, and means for supporting said second condenser from the container of the first condenser comprising a member positioned within the space formed at the double-walled end.

'7. A multiple condenser for smoothing pulsating direct current comprising a high-voltage electrolytic condenser having a cylindrical container acting as a cathode, a cup-shaped anode insulatingly supported at its bottom from the bottom of said container, a lead for said anode extending through the bottom of said container, said container comprising a cup-shaped portion extending within the hollow of said cup-shaped anode and occupying substantially the entire space thereof, substantially the entire surface of said anode being equidistantly spaced from said cupshaped portion, and a liquid electrolyte within the space formed between said container and cupshaped portion and completely covering said an- .ode, and a lower-voltage eletcrolytic condenser disposed entirely within the hollow of said cupshaped portion and comprising an anode, an electrolyte, and a cathode-container electrically and mechanically connected to the container of the high-voltage condenser.

CORNELIS ns LANGE. ANTHONY FREDERIK PETER JOHAN'NES CLAASSEN.

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