US2922090A - Electrolytic condenser - Google Patents

Description

Jan. 19, 1960 s. GoToR cARRAU 2,922,090

ELECTROLYTIC CONDENSER Filed Jan. 27, 1955 2 Sheets-Sheet 1 FIG 2 Sani/'agol Gafor L15/wok BY Hmm, Wl @i fm A fromeys Jan. 19, 1960 s. GoToR CARRAU 2,922,090

'Y ELECTROLYTIC CONDENSER Filed Jan. 27, 1955 2 Sheets-Sheet 2 thereof and apparently functions as a dielectric.

ELECTROLYTIC CONDENSER Santiago Gotor Carrau, Barcelona, Spain Application January 27, 1955, Serial No. 484,540

Claims priority, application Spain June 3, 1954 4 Claims. (Cl. 317-230) The electrolytic condensers known hitherto, particuylarly those of the type called dry condensers, consist of yserving for giving the suitable polarity to the electrolyte that impregnates the finished condenser bobbin.

The winding of these condensers `always has been performed so that the unformed aluminum or cathode envelopes the positive aluminum, the two laminations being left trimmed at about the same position at the end of the bobbin, with the cathode at the outer side and covering the bobbin. The absorbent material, usually a paper strip does not end at the tip of the aluminum laminations and generally extends further around the bobbin.

It may be appreciated that in the last turn of the condenser bobbin there is always an external turn which is not covered by the associated electrode.

It is a well known fact that the useful life of all of the condensers of this type is restricted by the gradual formationof corrosion on the outer face of the last turn of cathode. In fact, it has been ascertained that a condenser having a very noticeable leakage current and no other damage, may be placed in an operating condition which is about the same as the initial condition, when it is deprived of the-last turn where the corrosion is present.

These corrosions are formed by oxidation of the aluminum with production of aluminum oxide compounds such as alumina (A1203). rIhese oxidations which are already formed on the aluminum lamination due to the natural oxidation under exposure to the atmospheric air, increase to the pureness of the aluminum itself and also of the materials forming the electrolyte, as well as the pH of the said aluminum.

Now, it has been found that by subjecting the external section of the last turn of the cathodic lamination to the action of an electric tield (that is, subjecting to an electric field the portion of aluminum which does not have opposed thereto a corresponding portion of the opposite electrode), a deoxidizing effect takes place on the aluminum and prevents, or at least diminishes, the above corrosion effects, thus eliminating one of the causes responsible for the aging of the electrolytic condensers. This always takes place in the condensers involved, sooner or later and independently of the condenser effective working time. It is obvious that the improvements of the invention constitute a great advantage over the known United States Patent ice art since, on the one hand the useful life of the condenser is lengthened and, on the other hand the condenser that is put in operation after a period of storage regains its initial specitications easily, particularly that of the leakage current, which fact does not take place with any of the condensers now available in the market.

Several constructions may be utilized to constitute the electrostatic field on the outer face of the last turn of the condenser bobbin, by arranging things so that the cathode always has a positive anode respective thereto on both its faces. The simplest manner of attaining this is by cutting the last turn of the cathodic lamination. In this manner the eld lines produced are normal to both the laminations throughout the length of the latter. However, since the iield intensities which usually are involved in this kind of condensers are usually rather high, due to the fact that the working voltages are somewhat high, it is not at all necessary that the two electrodes forming the field be opposed to one another, and the same may be placed close to one another in a more or less direct fashion, so that an electrostatic eld is always formed and associated with the cathode outer face. This alternative embodiment may be carried into practice by forming the cathode outer turn with openings or by trimming Yportions thereof which leave the anode exposed therethrough and across the absorbent paper. A field will likewise be created between these anode portions and the external cathode surface and will meet with `the above requirements.

In the case of trimming the last cathode turn, the anode remains as a covering and at the outer side of the latter another field is created with respect to the metal casing of the condenser which generally is connected to the cathode.

The above features may be also obtained by furnishing the condenser with a shield electrically connected with the condenseranode and so arranged that it surrounds the condenser bobbin thus forming an external spire. y

In order to facilitate the discussion, a sheet of drawings is attached to the present specification and shows diagrammatcally two developed cross sections of con-- denser bobbins according to the invention as compared with a similar View of a conventional condenser bobbin, which are cited solely by way of examples by no means restrictive of the scope of the invention.

In the drawings:

Figure 1 shows a diagrammatical cross section of a conventional condenser bobbin showing how the last outer turn of the laminations corresponds to a cathode;

Figure Z shows a condenser according to the invention wherein the cathode is thoroughly covered by the anode; l

Figure 3 shows a condenser according to the invention with the cathode surrounded by an additional anode;

Figure 4 is a plan View of the end of the ensemble of the condenser strip according to the invention; y

Figures 5 to 7, inclusive, show embodiments of the invention based on the principle of Figure 3, and

Figure 8 is an operative layout of a winder utilizable for the manufacture of condensers according to the invention.

The condenser bobbin 10 is formed of a cathode 11 and an anode 12 and respective strips made of dielectric and absorbent material such as paper, shown at 13, 14 in whichstrips the electrolyte is located. Generally speaking the correlation of these electrodes and electrolyte is common in condensers of the type set forth, and also the nature of the electrolyte formulation. The cathode 11 is merely an aluminum lamination for transferring the operative polarity to the electrolyte. Anode 12 is an aluminum lamination chemically or mechancally'treated for providing a rough surface and further oxidized. l

According to the constructions hitherto common, both electrodes 11 and 12, with their insulations 13 and 14 Areference to FigureZ, the anode 12 is not terminated just at the end of the cathode, but it is lengthened and made to extend a little more than a complete turn around the bobbin, that is from-the point 15 adjacent to the cathode until it covers the end of the same, so that the cathode is completely'covered by the anode, or alternatively the last cathode turn is cutoff.

The same covering elect may be attained by arranging a supplemental anode 16 around the usual condenser bobbin, such as shown in the` Figure 3, whichianodemverely consistslin a formed aluminum lamination or a piece of condenser anode, which is electrically connected'with-'the anodey 12 by means of a connection partially shown in the drawing and marked with the numeral 17. In these two embodiments, wherein the external face of` an anode'is atAthe outside of the bobbin, the vouter portion of the anode has as its cathode the proper condenser metallic casing.

These two` embodiments are based on what Vmight be called direct association of the outer surfacefarea of duction, where-the condenser working'- voltages arerhigh enough, Aan indirect association may be obtained "bylplaoing Vthe cathode terminal 4outer surface ofFigure 2 7a`t a short distance from'the anode outer surface. -Thisffmay be vcarried through by trimming the cathode endas described in connection with the Figures 4 to 7,'i`nc'lusiv'e.

lIn Figurei4 the cathode end has a trimmed'central portion with parallel edges so that an elongated rectangular recess 18 is formed, which extends from thecathode terminal edge.

In Figure'S the recess 19 is restricted or comprises half the width of the lamination forming'the cathode, soithat the end `of lthe latter has a recessed instep at one side thereof.

In Figure 6Y the relative positions of the recess andthe cathode sectionsv of Figure 4 have been reversed, so that nowY the cathode has two recesses 20 similary to that marked 19 in Figure 5, between which an intermediate cathode section is located. i

In Figure 7 the recesses described have been changed to rectangular shaped openings 21 distributed lalcjfng the cathode end. Y

AWithin the general scope described, it is alsopossible to develop the cathode screening by reversing :the rela tive positions of the two electrodes during the condenser winding operation. This arrangement is likewise new since the fact of mounting the csathode at the outsideof thecondenser bobbin is derived Kfrom the specialmanner according to which the actualwinding machinesffw'ork.

In-v Figure `8 there is schematically illustrated theparrangementiof a 'winding' machine utilizable forjthefmanufacture of condensers according tothe inventionJfQZ is the condenser bobbinformed by the described elements and denoted with the same reference numerals.

that since theoperator is 'placed in front of the machine,

these anodes shouldwbe .insertedin'th'e inner part of the bobbin in order that the same are always within the operators sight. y

Were the relative -positions of the two electrodes reversed, theinner endsvof the assembled strip are: liable to be exposed to the corrosion effects which are' to be avoidedby` the present invention, and it is obvious that thesame construction described for-the outerlyends of the` electrodes may be likewise applied tothe inner ends of the same in'all the cases where the practicemayfbe vshown to be desirable.

It may be easily understood Athat any fshape given to the recesses or openings described, as well as eventual ,changes in the number anddistribution-thereof V vvilllbe likewise covered by the principlesofthe presentminve'ntion. lIt may, thus, be constrctedinany ,shapefand size, withy the most suitable materials since all this ,remains'vwithin ythe scope of the Yfollowing'clair'ns. Iclaim:

l. An electrolytic condenser comprising a dielectric coveredcathode strip and afdielectric covered anodestrip extending spirally outwardly from a common center With theI .dielectric covered cathodefstrip anddielectriclcoveied `anode strip forming ,alternate layers along'a radiusv of the condenser, the endof said cathode stripbeingfon lthe outside of the condenser and having at least fone'aperture therein exposing a portion of said anodest'rip for causing a charge of the same nature asl the ychargeforifthe anode on both sides of said cathode stripv 2. An electrolytic condenser as claimed in claim 1 in which the end of said cathode stri'pfhas apertures in both edges of the end thereof tofform recesses in'the sides of the end of said cathode stri'pfL i 3.An electrolytic condenser `asV claimedfinclaim l in whichisaid cathode strip has an' open s igdedaperture therein to form a recess in the end of said eathodestrip.

4. A'An electrolytic condenser as vclvtirnetllhinfclairn l inlwhich said cathode striphas at least'oneclosed sided aperture therein exposing a portion'of the afndestrip.

` References Cited in the file ofV thiswpatent `UNITED STATES PATENTS Great Britain VSept.30,;,1953

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