US1936084A - Electrolytic condenser - Google Patents

Description

Nov. 21, 1933.

J. D. EDWARDS ELECTROLYTIC CONDENSER Filed Feb. 5, 1931 Mmzssss Patented Nov. 21, 1933 PATENT orrlcs EIECTBOLYTIO- connsnssa Janina D. Edwards, Oakmont, Pa., anlgnor to Aluminum Company of America, Pittsburgh,

2a., a corporation of Pennsylvania Application February 5,; 1931. Serial No. 513,649

SClaimB.

This invention pertains to electrolytic condensers and relates more particularly to an improvement in their mechanical construction, and especially that of an anode plate for such condensers.

5 The capacity of a condenser of this type, as is well known, is proportional to the effective area of the plate or electrodeimmersed in the electrolyte which carries the active film and is commonly referred to as the anode. Hence, where such condensers are used in radio sets and the like, where space is at a premium, as they very advantageously and frequently are, a problem of combining a maximum effective surface area on the anode with a minimum over-all dimension and minimum amount of plate material is presented. In the past, attempts have been made to solve this problem in various ways without entire success. In such condensers as heretofore produced, the anodes employed were either insufliciently sturdy to give satisfactory life and service, or else they have included deformations of such a nature as to obstruct the escape of the gases evolved at their surface and to entrap or collect such solids as are precipitated from the electrolyte. Due to this, the effective area, and consequently the capacity of the condenser, is reduced as the gas and solids build up. In addition, the presence of gas and solid contributes materially to the disintegration of the condenser,

so as is readily appreciated by those skilled in the art.

It is an object of this invention to provide a condenser of this type having effective provision for overcoming the above-explained difficulties and weaknesses.

Another object is to provide a condenser which is of simple, sturdy and compact construction, and susceptible of being manufactured and assembled at a comparatively low cost.

A more particular object is to provide a novel and extremely simple form of anode plate, especially adapted for use in such condensers, which is not only of sturdy construction and has a suitably large surface area in comparison with its over-all dimensions, but 'is also free from any obstruction tending to hinder the escape of any gas evolved at the anode surface or to entrap any solids precipitated from the electrolyte.

- These and numerous other objects, as well as the various novel features and advantages of the invention, will be apparent when the following detailed description is read in conjunction with the accompanying drawing wherein Fig. 1 is a longitudinal section taken vertically through a condenser constituting one embodiment of the invention; Fig. 2 a section taken on the line II-II of Fig. 1 looking toward the base of the condenser; and Fig. 3 a view, similar to Fig. 1, of another embodiment of the invention.

Referring in detail to the drawing, each embodiment of the invention comprises chiefly a cylindrically shaped housing 1, having an axially disposed anode plate 2 arranged therein in a- 7 suitable electrolyte 3, such as an aqueous solution of borax and boric acid, or the like. As shown in Fig. 1 the housing 1 is made of any suitable metal, such as aluminum, to form both a container and circuit-making electrode for theelectrolyte, and is provided at its base with a threaded projection 4 by means of which it may be readily inserted in a terminal receptacle (not shown) such as are commonly employed in radio sets and the like.

The anode 2 is made of any suitable filming metal, such as aluminum, which is especially adapted for such use, and, as illustrated particularly in Fig. 2, in the shape of a tube having a periphery approaching in contour the shape of a star. When formed in this way the anode is given both a suitably large surface area in comparison with its over-all dimensions, and an ex'- tremely rigid construction, because of the axially extending. corrugations 5 which materially add to the strength of the tube. This also permits the use of a small amount of material in the tube, as well as enhances the sturdiness and length of life of the condenser. A further advantage of extending the corrugations lengthwise of the tube is that when so disposed they in no way hinder the escape of the gas evolved at the surface of the anode or collect any such solids as may be precipitated from the electrolyte.

The particular shape of tube, which as noted hereinabove, has a periphery approaching in contour the shape of a star, is an essential feature of my invention. This form of tube gives a maximum surface area in relation to its overall dimensions. As will be seen best in Fig. 2, the corrugations or series of convolutions 5 are formed so that all portions thereof lie in planes parallel to the axis of the anode, the sides 5' of each convolution being approximately flat and extending substantially radially from the axis. The apex 5" and base portion 5'' of each corrugation arev of rounded formation for a purpose which will be noted hereinbelow. With the flat sides 5' extending in a radial direction it is possible to extend them a maximum distance towards the center while maintaining a requisite amount of clearance between the base portions 5' and without sacrificing the rounded form of the base portions 5'. With this construction the center of the anode is substantially filled" with the convoluted sides thereof and there is obtained a maximum surface area in relation to the over-all dimensions of the anode.

In order to reduce the problem of developing the active film on the anode surface, as well as avoid possibility of break downs of the film surface when the condenser is in service, the apex and base of each corrugation is rounded to eliminate on the anode any surface reduced to a point. For anchoring anode 2 in the housing of the form of condenser shown in Fig. 1, a strap 6 formed in the shape of a stirrup is spot welded, or otherwise secured, to the base of the anode and to the. top of the terminal stud shaft 7 which is in turn extended through an opening 8 in the base 4. To insulate the anode from the housing and to hold it rigidly in place, an insulating bushing 9 is fitted tightly between shaft 7 and opening 8.

After the electrolyte is placed in the housing a cap or cover 11 is mounted on the top and suitably sealed in place. In this cover there may be conveniently mounted a terminal stud 12 for making electrical contact with the electrolyte, although it will be readily appreciated that the same end may be accomplished in a simpler fashion by utilizing the base 4 as the cathode terminal and employing a base socket, for placing the condenser in a circuit, of the nature commonly used for electric lamp bulbs.

In the modification shown in Fig. 3 the anode 2 is similar to the previously described anode with the exception that it is closed at its upper end and provided with a reduced end extension 13 which is passed through the top of the housing 1 and arranged to both anchor the anode in the housing and function as a terminal for the reception of a conductor 14. When so constructed, openings 15 may be formed near the upper ends of each of the axially extending corrugations to afford a means of escape for gas liberated on the inner surface of the anode, and an insulating bushing 9 is fitted between the housing and extension 13, while a' clip or stem 10 is secured to the base of the housing in place of a plug-like projection such as shown in Fig. 1. To allow gas accumulating in the container 1 to escape a small vent 20 may be provided in the upper end of the container.

In production the housings and anodes of both embodiments of the invention may, for example, be made by a process of extrusion or by any other suitable and practical method. In assembling the second embodiment of the invention shown, the upper end of the housing 1 may be originally formed similar to that of housing 1, and spun upwardly after the anode is placed in it. The spinning operation is terminated in the production of a threaded opening 16 located in the center of the housing for the reception of the extension 13 and bushing 9 as well as to aiford an opening for filling the housing with the electrolyte solution employed. To effectively anchor the anode in place, extension 13 is provided with a shoulder 17 which, when the anode is drawn into'place by a nut 18, abuts against the bottom of the bushing 9. If desired the base of this latter embodiment may be formed similar to the one shown in Fig. 1, and the anode 2 inverted and mounted therein.

As stated hereinbefore an important feature of the invention resides in the provision in the anode elementof the longitudinal or YPically disposed corrugations which give it a comparatively large surface area for a relatively small over-all dimension and also enhances the rigidity oi the structure sufiiciently to allow it to be made satisfactorily oi comparatively light weight material. Additional advantages resulting from the verticaldisposition of the corrugations are that they in no way obstruct the free movement of gases liberated at the anode surface or solids precipitated from the electrolyte, and also that they permit a free and unrestricted circulation of the electrolyte, all of which contribute materially, as will be readily appreciated by those skilled in the art, to the continued maintenance of the condensers capacity as well as enhances its length of life.

In forming the corrugations, as pointed out hereinbefore, they are sufficiently rounded to eliminate all sharp edges from the anode surface. Such edges, if permitted, as they frequently are in the older types of condensers, and especially so in those condensers where an effort has been made to reduce their over-all dimensions, add considerably to the difficulty of forming the active film on the anode surface. Furthermore, as is well known, where such edges occur high current stresses have a tendency to develop and as a result the film is frequently broken down at those points.

It is to be understood that while the invention has been herein illustrated and described in connection with a simple unit employing but a single anode structure of the nature defined, a plurality of such structures may be utilized in larger condensers without departing from the spirit of the invention.

According to the provisions of the Patent Statutes, I have explained the principle and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. An anode for an electrolytic condenser, said anode being of hollow tubular formation and having its side walls in the form of a series of convolutions all portions of which lie in planes parallel to the axis of the anode, the sides of each convolution extending substantially radially from said axis whereby the inwardly projecting portions of the convolutions extend a maximum distance toward said axis while maintaining a clearance between said inwardly projecting portions.

2. An anode for an electrolytic condenser, said anode being of hollow tubular formation and having its side walls in the form of a series of convolutions all portions of which lie in planes parallel to the axis of the anode, the sides of each convolution being substantially fiat and terminating in rounded apex and base portions. said fiat sides extending radially from the axis whereby said base portions may be arranged at a minimum distance from said axis while maintaining a clearance between adjacent base portions.

3. An electrolytic condenser comprising a hollow cylindrical container closed at its two ends, an electrolyte solution filling said container, a tubular anode closed at one end and having an anchoring and terminal forming projection on its closed end, said anode being immersed in the electrolyte solution and secured in one end of each convolution being substantially flat and terminating in rounded apex and base portions, said flat sides extending radially irom the axis whereby said base portions may be arranged at a minimum distance from said axis while maintaining a clearance between adjacent base portions.

TNIUS D. EDWARDS.

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