US1874111A - Electrolytic condenser - Google Patents

Description

R. D. MERSHON ELECTROLYTIC CONDENSER Original Filed Dec.A 5l, 1925 Aug. 30, 1932.

' Patented Aug. 30, 1932 l UNITED STATES IPATENT OFFICE RALPH D. MERSHON, OF NEW YORK, N.

ELECTROLYTIG GONDENSER Original application tiled December 31, 1925, Seria1`No. 78,534.` Patent No. 1,773,492. Divided and this application filed January 25, 1928. Serial No. 249,314. l

This invention relates to electrolytic condensers, 4and its chief object is to provide a compact condenser of good efliciency, which can be manufactured at low cost. To this and other ends )the invention comprises the 'novel features and combinations hereinafter described.

While 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 accordinglv I have selected for illustration and .15- specific description herein an embodiment designed particularly for the purpose named. In this form it is easily possible to construct a condenser of cylindrcal shape not more than two and a fourth inches in diameter and four inches in length, having a capacity of fifty microfarads. The anode, composed of alu'- minum or thenmetal capable of forming the necessary dielectric film on its surface, may be a stripof sheetl metal fastened to and 5 wound spirally around a stiff rod of the same metal. This rod may form the anode terminal. The turns may be spaced apart in any convenient and suitable manner, t0 permit vcirculation of the electrolyte, as for examo ple by indenting the sheet metal to form numerous lugs on one side of the same. The anode, in whatever -form it is made, is immersed in a siutable electrolyte, say an aqueous solution of boraX and boric acid, vin a cylindrical vessel of sheet copper, which may serve as the cathode. One embodiment of the invention is illustrated in the accompanying drawing, in which Fig. 1 shows one end of an indented sheet metal strip before ceiling.

Fig. 2 is a section on line 2-2 of Fig. l. Fig. 3 shows one end of the strip fastened 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 a side view of the complete anode. Fig. 6 is a. section on line 6-6 of Fig. 5.

on line 7 of Fig. 5.

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

The aluminum strip 10, Fig. 1, may be of any suitable thickness, 0.006 of 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 inthe middle row are on the other side, as clearly shown in Fig. 2. The rest of the strip may be indented, in the same or in any other convenient pattern, but if the lugs are elongated, as shown at 12, forexample, 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 convection currents in the electrolyte. In any case the lugs or, generally, the spacers, are preferably as sharp as possible, and in some cases it may be advantageous to make the indentations in such manner as to actually perforate the inetal, producing sharp edges as indicated at 12a, Fig. 2, or 11a, Fig. 7, so that when the 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 llimit the axial displacement of the turns. Otherwise a slight stress exerted axially might distort the device into a pro- 60' negative terminal nounced conical form, as will be readily understood. I

The container or tank for the electrolyte and anode may be a cylindrical vessel 14, 5 Fig. 8, of suitable non-filming sheet metal. fFor economy of space the tank may be ]ust large enough to receive the anode and, preferably, leave room for an insulating lining or other means to prevent electrical Contactbe- 16 tween the anode and the tank. Otherwise it may be desirable to wrap the anode with one or more turns of filming wire (not shown) to prevent expansion of the spirally wound strip. It will be understood, however,

l that since the film formed on the anode is) non-conducting the anode may bear directly against the vessel without shorting the com denser as long as the film is in good condition. The insulatingI lining prevents electrical contact if the film should be worn olf by friction or be otherwise impaired. A lining for the purpose indicated may consisty of a bottom disk 15 of thin Celluloid orL cellophane and a strip 16 of like material bent to cylindrical form and placed loosely in the vessel, Celluloid and cellophane being unharmed by and harmless to the electrolyte.A The vessel metal anode, an electrolyte4 1n which the may be- Closed by a disk 17 of insulating material resting on a bead 18 on the inside near 3G the top. Around the closure at the edge is a thin flat ring or gasket of rubber or other suitable material, 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 4o gases resulting from electrolytic action in the electrolyte. Orthe usual disk of thin sheet rubber can be cemented over the vent hole. hen punctured with a pin the disk serves as an automatic valve, opening when the v '45 pressure of the gas rises inside the tank and closing as soon-as the pressure is relieved. The tank ispreferably deep enough, as in Fig. A8 for example', where the dotted line 20 indi-` s Cates the surface of the electrolyte, to permit sea substantial depthof electrolyte above 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. l Y

The rod 13, threaded on its upper end, extends through the lid 17 to form the positive terminal and isclamped to theelid by nuts 21 setup firmly on yielding gaskets 22.. The

may be a screw 23 on a bracket24 soldered to the can 14. f

'Ifhe electrolyte is preferably the one described in my Patent No. 1,141,402, issued June 1,-1915,' compounded -in the following C' proport1ons: saturated borax solution ('distilled water), two gallons; boric acid, three pounds; and an additional half-pound of borax. f

The necessary film can be formed on the anode in any suitable manner, as for example by the methodsv described in my prior Patents Nos. 1,012,889 of December 2 6, 1911, andl 1,388,874 of August 30, 1921. Preferably the lm is formed at such voltage as will permit the 'condenser to withstand a substantial operating voltage, say 400. I

It is to be understood that the invention 1s not limited to the specific construction herein illustrated and described but may be embodied in other forms without departure from its spirit. The anode shown forms no part of the invention, since any suitable type of anode may be used, preferably made of sheet metal so disposed as to have a large area of Contact with the` electrolyte. rlhe anode described herein is claimed in my copending application Serial No. 78,534, liledy December 31, 1925, now Patent No. 1,7 7 3,492,

issued August 19, 1930, of which the present application is a division.

Iclaim- 1". In an electrolytic condenser, a filmed anode is immersed, an unlmed metal cathode surrounding the anode and in Contact v.with the electrolyte, and a sheet of exible non-conducting material, harmless to the electrolyte and unharmed thereby, surrounding the anode between the same and the cathode. f

2. ln an electrolytic condenser, an electrode comprising a strip of filmed metal bent s pirally, an electrolyte 4in which the anode is immersed, aeCurrent-Carrying member of nonlming metal surrounding the spiral anode and in Contact with the electrolyte, and a iiexible sheet of Celluloid around the immersed spiral anode between the 'same and the non-filming metal member. A

3. In an electrolytic condenser, a cathode ice' of non-filming metal in the form of a coni taining vessel, an electrolyte therein, an anode of filming metal immersed in the electrolyte and a lining ofsheet Celluloid in the vessel b electrolyte.

4.,In an electrolytic condenser, an anode of filming metal, an electrolyte in which the anode is immersed,a cathode of non-filming sheet metal in the form of a vessel enclosing the immersed anode, and aN sheetbf flexible Celluloid around the anode between the same andthecathode. i

In testimony signature.

RALPH D. MERsHoN.

etween the same andthe immersed f whereof I` heretoI aixmy

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