US2213209A - Electrolytic condenser - Google Patents

Description

Sept. 3, 1949 c. DE LANGE ET A1. 2,233,209

ELECTROLYTIC CONDENSER Filed April 26, 1959 Patented Sept. 3, 1940 UNITED STATES PATENT OFFICE ELECTROLYTIC' CONDENSER Application April 26, 1939, Serial No. 270,267 In Germany May 30, 1938 1 Claim.

This invention relates to an electrolytic condenser having a cathode body located within a tubular anode, and more particularly to an electrolytic condenser comprising two condenser 5 units.

The term anode as used herein is to be understood to mean an electrode which is provided with an oxide iilm serving as a dielectric, and the term cathode is to be understood to mean l that part or parts which constitute a. current supply conductor for the electrolyte.

It has been suggested, for example in the U. S. Patent 2,130,073 to de Langeet al., to give the anode of an electrolytic condenser a tubular l shape and to house therein a second tubular member which is closed at the lower end and acts as a cathode. Although such a construction makes it possible to produce a condenser having the lowest possible series-resistance, there is a )o large amount of unused space inside the tubular cathode. In this patent it has also been proposed to utilize at least a major portion of this space by housing a second complete condenser unit therein, and thereby form a condenser comis prising two units each having their own electrodes.

The main object of our invention is to produce a simpler and less expensive condenser assembly of the above general type.

l0 A further object is to produce a condenser assembly which may be used in cases where two condenser units are required, for example, for smoothing the direct current supplied to the eld coil of an electro-dynamic speaker.

35 A further object is to reduce the size of and the amount of material used in such condenser assemblies.

A still further object is to produce a multiple condenser of the above type in which the con- 0 denser units have a common cathode and electrolyte.

Further objects and advantages of the invention will appear as the description progresses.

In accordance with the invention we locate 45 within the inner tubular cathode a second nlmforming electrode which forms with said cathode a second condenser unit having a separate anode vsupply connection. In this manner the space ,f within the irst condenser unit is efficiently 50 utilized, and theinner surface of the tubular cathode is also used. The film-forming electrode, or internal anode, is arranged with its surface close to the inner surface of the tubular cathode with the result that this second conla denser unit has a low series resistance, and the series resistance can be further decreased by giving the nlm-forming electrode a shape corresponding to that of the cathode.

In one embodiment of the invention the internal anode is shaped as a hollow cylinder to 5 reduce the weight as much as possible, and is provided with slots to form short paths for the iiow of current through the electrolyte from the cathode to the inner surface of the internal anode.

The condenser according to the invention can be so constructed that the supply connection for the internal anode may be at either end of the condenser, and this connection -as well as the connection for the first anodemay be at the same end.

In order that the invention may be clearly understood and readily carried into effect, We shall describe the same in more detail with reference to the accompanying drawing in which: 2@

Fig. l is a sectionized viewof a condenser according to the invention, and

Fig. 2 is a sectionized View of a condenser according to another embodiment of the invention.

The condenser illustrated in Figure 1 com- 25 prises a cylindrical cathode-container I of aluminium whose upper end forms a dome 2 provided with several vent holes 3 and having a tubular extension 4. The bottom edge of container I is spun over the edge of a member 5 30 of insulating material, such as Bakelite, with the interposition of a gasket 6, for instance of rubber. Member 5 has a threaded tubularportion 7 for securing the condenser to a support and its upper surface is corrugated.

Within the container I is a cup-shaped anode 8, for instance of aluminum, having a rodshaped extension 9 passing through a bore in member 5. The end of the extension 9 is riveted over at I I with the interposition of a terminal IU, whereby a liquid-tight seal is made between the bottom of anode 8 and the corrugated upper surface of member 5 by means of the gasket 6.

Secured to the top of container I by several rivets 48 is a cup-shaped cathode I2 which extends within the anode 8 with its outer surface parallel to the inner surface of the anode. Instead of being riveted, the cathode I2 may be spot Welded to the container I, and if the cathode I2 is 50 made by extrusion, small projections may be formed on its upper surface and used as rivets.

Within cathode I2 is a second or internal anode I3 of cup-shape which has a rod-shaped extension I4 passing through the tubular pro- 35 jection 4. A tubular'gasket I5, for

instance of rubber, is placed over extension I8, and the projection 4 is grooved, for instance by rolling, at IEA to effect a liquid-tight seal and a supporting connection. If?. desired the extension 4 may be provided with a plurality of groovings I 5A. The anode I3 is provided with a plurality of slots I6, for instance saw-cuts, to reduce the paths of the current owing from the inner surface of cathode I2 to the inner surface of anode I3.

The vessel I is filled to a level above the anode I3 by a suitable electrolyte Il for instance a mixture of 240 grams of boric acid (HsBOa), 1,000 grams of ethylene glycol, 30 c.c. of ammonia (NHiOH) and 1,000 c.c. of water.

To prevent corrosion of the non-formed parts in contact with the electrolyte, both surfaces of cathode I2 and the inner surface of the container I may be chromium plated.

'To increase the surface area and hence the capacity, the surfaces of anodes 8 and I3 are preferably etched by any of the methods kno-w in the art.

A band I8 of flexible material, such as rubber, surrounds the dome 2 and normally closes the vent holes 3. During operation of the condenser the gases produced within the container I escape through holes 3 in known manner. To asorb any electrolyte which may be carried out through holes 3 by the escaping gases, a mass of absorbent material I9, such as saw-dust or cottonwool, is located within a cover 20 secured, for instance Welded, to container I, and provided with an aperture 2|.

A condenser of the construction shown is very compact and has extremely desirable electric properties.

When the two electrodes 8 and I3 are etched,

.they can supply an extremely large capacity.

For example, if the external anode 8 has a diameter of 24.5 mm. and a height 80 mm., it will have a capacity of 16 microfarads at a working voltage of 450 volts, and if the internal anode I3 has a diameter of 17.5 mm. and a height of 80 mm. it will supply a capacity of 16 microfarads at a working voltage of 300 to 320 volts. Since the spacing between the active surfaces is very small, as appears from the diameters given above, the series resistance has a very low value and the alternating current load may be increased to a high value. If the condenser illustrated is used in a smoothing system and the external condenser unit is connected directly after the rectifier, i. e. the condenser unit which is calculated for the highest lworking voltage and has the electrode 8 as an anode, a superimposed alternating current voltage of at least 45 volts is admissible.

In the condenser illustrated in Figure 1 the connection for the external anode 8 leaves through the lower end of the assembly and the connection for the internal anode I3 leaves through the upper end. However, the invention can also be carried into eifect witha construction in which the connections to both anodes leave at the same end, and such a construction is illustrated in Figure 2.

The condenser illustrated in Figure 2 comprises a cup-shaped cathode-container 23, for instance of aluminum, whose closed end is formed as a dome 2li provided with a plurality of vent holes 25. The bottom end of container 23 is spun over the edge of a tubular member 26 of insulating material, such als Bakelitef .with the interposition of a gasket 2l, for instance of rubber, to form a liquid-tight joint.

Within container 23 is a cup-shaped external anode 28 of a film-forming metal, such as aluminum, which has a tubular extension .29 passing through the bore of member 26. The end of extension 29 riveted over upon a shoulder of member 25 with the interposition of a terminal 38.

A cathode 3| in the form of a cylinder of aluminum has a flared upper end which is secured, for instance welded, to the container I.

A second or internal anode 32 in the form of a cylinder of aluminum provided with several saw-cuts 33, has a rod-shaped portion 34, ex-

tending throughthe bore of the extension 29 of anode 28. A bushing 44, for instance of rubber, is disposed between portion 3f! and extension 29 and serves to provide a liquid-tight seal and also to insulate anode 32 from anode 28.

The bottom end of portion 34 is riveted over upon a bushing 35, for instance of Bakelite, which bears upon the end of anode 28 at 36. A terminal 3l for anode 32 is secured at this riveted. joint.

As described in connection with Figure l, a rubber band I6 normally closes the vent holes 25, and a ring 38 of liquid-absorbent material, such as cotton Wool, located within a cover 39 secured to container 23, for instance by welding, serves to absorb any escaping electrolyte. Cover 39 is provided with a vent hole 40.

In order that possible displacement of the electrodes will not result in a short circuit, We prefer to provide anodes 28 and 32 and cathode 3| with bands 4| of insulating material, such as rubber.

We wish it to be understood that'we do not wish to be limited to the exact details of construction shown and described, because obvious modiiications will readily occur to one skilled in the art.

What we claim is:

An electrolytic condenser comprising a cupshaped cathode-container, a cup-shaped cathode supported from said container and forming an annular space therewith, a cup-shaped anode having an active tubular portion extending into said space and forming a condenser unit with said cathode, means insulatingly supporting said anode from the open end of said container, a second cup-shaped anode having a tubular portion extending in closely-spaced relationship with the inner surface of said cathode to form a second condenser unit therewith, means in-y CORNELIS DE LANGE. JOHAN DIRK DE VRIES.

Images