Патент USA US2500632код для вставки
' March 14, 1950 Mu RmdEO“Min;mumD’ NME6 Ehm.“ 6 E w wk0 2 4r.T 5, ¢m.m wEé 8%,RIM W0.A V! V, PM 2,500,532 141m" ' umrso " ffPATENT " 0mm j ‘ "239.3821 ~ I > M... E. if:T33. ‘122:... to run > Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York 1 Application Decemberv 28, 1946, Serial No. 718,945 4 Claims. (Cl. 175-315) ' 2 of the type having means for relieving high gas - Fig. 4 is an enlarged sectional view of a frag ment of the modification shown in Fig. 3, a por tion of the plugging material being shown in pressures created within the capacitors because section. This invention relates to electrolytic devices and more particularly to electrolytic capacitors conditions. There are a number of conditions giving rise to high internal gas pressures arising among _ Referring now to the drawing, the electrolytic capacitor there shown comprises a container l . qt a heating thereof due to abnormal operating . which may be- of metal. such as aluminum, an electrolytic capacitor or capacitor element 2, having wires 1 connected to terminals 4 which which may be mentioned: over-voltages such as might occur under open-circuiting'conditions oi 10 may be embedded in a cover 5 of insulating material, for example, a phenolic condensation the load in rectifying circuits, application of po product, having a boss or stud B integrally formed tentials with reverse polarity or polarized capac~ therewith. The purpose of the boss is to provide itors, and improper electrolyte and poor oxide film better sensitivity to the heat emitted by the formation permitting large direct current leakage capacitor element. The cover plate 5 is held in currents at elevated temperatures. place by crimping the edge 25, a suitable gasket Usually the capacitor element of an electro lyte capacitor is sealed in a container of metal, 26 being interposed between the cover plate 5 such as aluminum. and a shoulder 21 on the container i. Anv aper It the condenser is over ture Ill extends through the cover plate 5 and the heated due to abnormal operating conditions, the vaporized moisture of the electrolyte oi the 20 center of the boss 6. This aperture I0 is tapered where it passes through the main portion of the capacitor can result in a very violent explosion cover plate. unless the container is properly vented. A shoulder H and a threaded portion l2 are Although a satisfactory form of vent from a provided in the boss portion of the aperture for safety standpoint might be one which functions as a result of pressure alone, it is dimcult to pro 251 the plugging materials. Plugging materials for vents, such as waxes vide such a vent. and asphalts, usually used, have a very high co One object of this-invention therefore is to e?icient of expansion which frequently causes increase the reliability of electrolytic capacitors. them to loosen in the vent and destroy the seal, Another object of the invention is to decrease the dangers due to explosion of electrolytic .30 especially at low temperatures. To overcome this difficulty a plugging material capacitors. for the inner end of the aperture Hi, i. e., in the Another object of the invention is to improve boss, is provided consisting of an eutectic metal the sealing and venting of electrolytic capacitors. alloy element in the form of a disc 15 (Fig. 2) In accordance with one feature of this inven which is ?rst disposed in the aperture of the boss tion, a combination thermal and pressure vent is and a hot melt plastic material It having ethyl provided for an electrolytic capacitor to enable alcohol as a base combined with iron oxide to im the escape of gases when it becomes overheated. In accordance with another feature of the invention the sealing means for the pressure relief means for an electrolytic'device has a co prove its heat conductivity is then deposited in said aperture. 40 ' The plastic material preferably has a thermal coe?lcient of expansion vsimilar to that of the eflicient of expansion substantially the same as insulating material of the cover l0 so that a gas that portion of the device wherein it is situated. tight seal in the cover over the required range 01' These and other features oft-he invention will temperature may be maintained. At tempera be understood more clearly and fully from the following detailed description when read in con 45 turcs sufficiently high to generate explosive gas pressures the plastic material softens or lique nestion with the accompanying drawing in which: ?es and is ejected to relieve the pressure. The Fig.1 is an elevational view. partly in section of liquefying temperature of one of the plastic anelectrolytic capacitor including a vent con materials employed in carrying out vthis invention structed in accordance with this inventionwa was about 165° C. This material will extrude at portion of the container being broken away; 100° C. due to cold ?ow through the aperture Fig. 2 is an enlarged sectional view of the vent under a gas pressure of live to ten pounds per embodied in the device shown. in Fig. 1, a por square inch. tion of the vent being broken away, In‘ order to prevent cold ?ow and premature Fig. 3 is va fragmentary sectional view showing a modi?cation of the vent oi Fix. 1; and venting at the elevated temperatures and internal 3 8,500,888 gas pressures to which capacitors are subjected in normal service, the disc or pellet oi eutectic alloy is anchored adjacent to the plastic material as an outer blocking or strengthening member. The disc I 5 shown in Fig. 2 is an alloy of his muth, tin and lead having a very sharp melting point at about 97° C. A suitable proportion of 4 cessive 1pressure created within said container by overheating said electrolyte, said means in cluding an eutectic alloy member in combina tion with a backing member of thermoplastic material adapted to remain solid and sealed in the container at normal temperatures and to iuse at abnormal operating temperatures. these materials is 50 per cent bismuth, 18.8 per 2. In an electrolytic device including a metallic cent tin and 31.2 per cent lead. A disc having container enclosing an electrolytic member a diameter of .080 inch and a thickness of .030 ll) sealed therein, means for relieving excessive pres inch has been employed successfully. The thick sure within said container including a disc of ness of the disc is dependent primarily on the an eutectic alloy in combination with a plastic strength required to resist the heat of the plastic material having ethyl cellulose as a base com material during injection. . bined with iron oxide. The hot plastic material may be inJected into 3. An electrolytic device comprising a metallic the aperture in the boss under suitable pressure. container, a cover of insulating material for said The pressure must be suillcient to insure that container having an aperture therein, and a plug the plastic material is forced into the spaces around the metal disc and into the anchoring threads. The diameter of the disc I5 is made slightly smaller than the diameter of the aper ture in which it rests to facilitate assembly and to insure sufficient air leakage around the disc to prevent the trapping of air and the forma~ tion of bubbles in the plastic material. The ‘ portion of the aperture occupied by the plastic material is threaded to increase the effective length of the seal and to retain the plastic ma terial in position. Figs. 3 and 4 show a modi?cation of the ar in said aperture comprising an alloy of bismuth, tin and lead and a plastic material having a coe?icient of expansion substantially equal to that of the insulating material of the cover. 4. An electrolytic device comprising a con tainer having an electrolytic element therein, said container having an aperture in a wall thereof, one portion of the boundary of said aperture being threaded, another portion of said aperture being provided with a shoulder, a disc of an eutectic alloy in said aperture resting against said shoulder, and a thermoplastic ma terial adjacent said disc and positioned in the rangements shown in Figs. 1 and 2, the modi?ca threaded portion of said aperture. tion consisting of utilizing a phenolic insert 20 RALPH E. DRAKE. instead of molding a boss integrally with the cover member 5. The insert 20 may be cemented REFERENCES CITED ?rmly into the cover by the use of any suitable 35 The following references are of record in the cementing material, for example, a cold setting file of this patent: formaldehyde resin. Although speci?c embodiments of the inven UNITED STATES PATENTS tion are shown and described, it is to be under Number Name Date stood, of course, that various modi?cations may 4 U 2,012,359 Sprague _________ __ Aug. 27, 1935 be made therein without departing from the 2,058,773 Cole ____________ __ Oct. 27, 1936 scope and spirit of the invention as de?ned in 2,282,459 Deeley __________ __ May 12, 1942 the appended claims. OTHER REFERENCES What is claimed is: 1. In an electrolytic device including a metallic 45 Handbook of Chemistry and Physics, 26th edi container adapted to enclose an electrolyte her tion, by Hodgman and Holmes, published by metlcally sealed therein, means for relieving ex Chemical Rubber Publishing Co., page 1200.