US1773492A - Electrolytic condenser - Google Patents

Description

AB T9T l 930. R. D. MERSHON ELECTROLYTIC CONDENSER Original Filed Dec. 31, 1925 1e 23 Ii; 21 {T 14 (Java/atom. R ga/7.0. fife/she. 16- $5 flame/1 Patented 1 9, 1930 mm: D. nmnsnorr, or new roux, n. Y.

nnncraomrrrc coimnusnn Application filed December 31, 1925, Serial 110.

This invention relates to electrolytic condensers, and its chief object is to provide a condenser of good efli capacity in proportion manufactured at low cost. To this and other ends the invention comprises the novel features and combinations hereinafter described.

ile the invention can be employed in various situations the advantages above mentioned make it especially useful in radio apparatus, as for example as a smoothing condenser in devices for eliminating the ripple in rectified alternating current, and accordingly I have selected for illustration and specific description herein an embodiment designed particularly for the purpose named. In this form it is easily possible to construct a condenser of cylindrical shape not more than two and a fourth inches in diameter and four inches in length, having a capacity of fifty microfarads. In the preferred form of the invention the anode, composed of aluminum or other metal capable of forming the necessary dielectric film on its surface, is a strip of sheet metal fastened to and wound spirally around a stiff rod of the same metal.

This rod may form the anode terminal. The

turns maybe spaced apart in any convenient and suitable manner, to permit circulation of the electrolyte, as for example by indenting the sheet metal to form numerous lugs on one side of the same. "As thus constructed the anode is immersed in a suitable electrolyte, say an aqueous solution of borax and boric acid, in a cylindical vessel of suitable nonfilming metal, which may serve as the cathode.

The embodiment outlined above is illustrated in the accompanying drawing, in which Fig. 1 shows one end of the indented sheet metal strip before coiling.

Fig. 2 is a section on line 2,2 of Fig. 1.

Fig. 3 shows one end of the strip fastened 5 to the rod around which it is to be coiled.

Fig. 4 is a section on line 4-4 of Fig. 3.

Fig. 5 is aside view of the complete anode.

Fig. 6 is asection on line 66 of Fig. 5.

Fig. 7 is a detail section, on a larger scale,

on line 7 of Fig. 5.

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Fig. 8 shows the complete condenser, partly in section.

The aluminum striplO, Fi 1, may be of.

any suitable thickness, .006 0 .an inch being satisfactory for a condenser of the size and capacity mentioned above. Along one edge, or both if desired, are three rows of indentations parallel to the edge, forming three rows of small lugs or bosses 11. Those in the upper and outer row are on, or protrude from, one side of the strip and those in the middle row are on the other side, Fig. 2. The rest of the strip may be indented, in the same or in any other con venient pattern, but if the lugs are elongated, as shown at 12, for example, I prefer to make them in diagonal lines, as being less apt to cause the spiral turns of the strip, in coiling it around the center stem or rod, to take polygonal cross section. I also prefer separated lugs rather than continuous ribs, as permitting freer flow of convention currents in the electrolyte. In any case the lugs or, generally, the spacers, are preferably .as s arp as possible, and in some cases it may be advantageous to make the indentations in such manner as to actually perforate the metalla producing sharp edges as indicated at 12,

strip is coiled the point of contact between the apex of the lug and the adjoining turn or convolution will have a very minute area,

as I have found that the smaller the area of contact the less opportunity there is for corrosion at such points.

The aluminum rod 13 is split for a portion of its length to receive the end of the strip 10,'which is welded to the rod along its end edge. The strip is then coiled around the rod in spiral form, the lugs or spacers holding the turns apart to permit access of the electrolyte to all parts of the spiral anode thus formed and to allow free circulation of the electrolyte. The three parallel rows of lugs or spacers at the upper edge interlock,

as it were, in the manner indicated in Fig. 7 and thus'serve to limit the axial displacement of the turns. Otherwise a slight stress exerted axially might distort the device into as clearly shown in 1g. 2, or 11, Fig. 7, so that when the v-rrrnjsn-res PATENT a pronounced conical form, as will be readily understood.

The container or tank for the electrol te and anod'e may be a cylindrical vessel 14, B ig. 8, of suitable sheet metal. For economy of space the t 11k may be ust large enough to receive the anode and leave room for an insulating lining or other means to prevent electrical contact between the anode and the tank. Otherwise it'rnay be desirable to wrap the anode with one or more turns of filming Wire (not shown) to prevent expansion of the spirally wound strip. A lining for the purpose indicated may consist of a bottom disk 15 of thin celluloid or cellophane and a strip 16 of like material bent to'cylindrical form and placed loosely in the vessel. The vessel may be closed by a disk 17 of insulating material resting on a bead 18 on the inside near the top. Around the closure at the edge is a thin fiat ring or gasket of rubber or other suitable ma-' terial, and the edge of the vessel is crimped or turned in and down upon this gasket, forming a seal. A vent hole 19 is provided in the cover 17. This can be plugged with Wax to prevent spilling of the electrolyte in shipment and handling. When the condenser is put into service the wax can be perforated with a pin to permit escape of any gases resulting from electrolytic action in the electrolyte. Or the usual disk of thin sheet rubber can be cemented over the vent hole. When punctured with a pin the disk serves as an automatic valve, opening when the pressure of the gas rises inside the tank and closing as soon as the pressure is relieved. The tank is preferably deep enough, as in Fig. 8 for ex ample, where the dotted line 20 indicates the surface of the electrolyte, to ermit a substantial depth of electrolyte a ove the anode. The reserve thus provided takes care of the slow loss by electrolytic decomposition and in most cases makes it unnecessary to provide the vessel with a filling aperture and a removable closure therefor.

The rod 13, threaded on its upper end, extends through the lid 17 to'form the positive terminal and is clamped to the lid by nuts 21 set up firmly on yielding gaskets 22. The negative terminal may be a screw 23 on a bracket 24 soldered to the can 14.

The electrolyte is preferably the one described in my Patent No. 1,141,402, issued June 1, 1915, compounded in the following proportions: saturated borax solution (distilled water), two gallons; boric acid, three pounds; and an aditional half-pound of borax.

The necessary film can be formed on the anode in any suitable manner, as for example by the methods described in my prior Patents Nos. 1,012,889 of December 26, 1911, and 1,388,874 of August 30, 1921. Preferably the film is formed at such voltage as will peroperating voltage, say

mit the condenser to Withstand a substantial It is to be understood that the invention is not limited to the specific construction herein illustrated and described but can be embodied in other forms Without departure from its spirit. Features not claimed herein are claimed in my copending application Serial No. 249,314.

I claim- 1. An electrolytic condenser comprising a metallic vessel adapted to serve as the negative electrode, an electrolyte in thevcssel and in contact therewith, and a positive electrode comprising a central stem or rod and a strip of filming sheet metal found spirally around the stem' with its turns spaced apart and provided with parallel rows of inter-engaging lugs serving to prevent endwise displacement of the turns of the spiral relative to each other.

2. An electrolytic condenser as described in the preceding claim, in which the vessel forming the negative electrode is provided with an insulating lining and the spirally wound anode is free to expand against the lining.

3. In an electrolytic condenser, an electrode comprising a spirally coiled strip of filming metal provided with a plurality of spaced diagonal rows of spacing lugs to separate the convolutions of the spiral.

4. In an electrolytic condenser, an electrode comprising a spirally coiled strip of filming metal provided with parallel rows of lugs on opposite sides of the strip to provide an interlock for limiting endwise displacement of the convolutions of the spiral.

5. In an electrolytic condenser, an electrode comprising a split rod of filming metal and a strip of filming sheet metal having one end inserted in the split in the rod and Welded thereto, said strip being coiled spirally around the rod and having inclined rows of lugs pressed out of the sheet to form spacing lugs and having a plurality of rows of similar lugs on opposite sides of the strip and parallel to an edge thereof to provide an interlock for limiting axial displacement of the convolutions of the spira v In testimony whereof I hereto aflix my signature.

RALPH 1). MERSHON.

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