US2174437A - Electrolytic device - Google Patents

Description

Filed Sept. 21, 1936 IN VENT OR. JOSEPH L. COLLINS ATTORNEYS Patented Sept. 26, 1939 UNITED. STATES ELECTROLYTIC DEVICE Joseph L. Collins, North Adams, Mass, assignor to Sprague Specialties Company, North Adams, Mass., a corporation of Massachusetts Application September 21, 1936, Serial No. 101,841

' 3 Claims.

The present invention relates to electrolytic devices, and will be described in connection with electrolytic condensers, for which it is of particular usefulness.

I shall describe my invention in connection with so-called wet'electrolytic condensers, although it is also applicable to so-called dry electrolytic condensers.

As the electrolyte of electrolytic condensers, l particularly in the case of wet electrolytic condensers, is much affected by contaminations, such condensers are usually of the sealed-container type.

0n the other hand, as during operation of the i5 condensers gases are liberated at the electrodes, provision has to be made for the escape thereof.

Various venting means have been therefore suggested for such sealed condensers, many of which however have the drawback of permitting electrolyte to be carried away with the escaping gases, thus causing a loss of electrolyte of the condensers. The venting means described in the U. S. Patent No. 2,005,055 to Robert C. Sprague and John F. McCann overcome this difliculty and 5 have been widely used with good success.

In the construction described in the above patent, the container of the condenser is provided with a semi-permeable vent, which permits escape of the gases, but prevents escape of the electrolyte.

This is accomplished, for example, by providing an open-ended container with a metal cap as closure member, said cap being crimpedly secured to the container with the interposition of a senilpermeable gasket.

Such a semi-permeable gasket may be, for example, a fabric washer impregnated with wax or with other water-repellent material the washer being sufllciently porous to permit the escape of the gases but sufficiently impervious to the electrolyte to prevent its escape through the gasket with the liberated gases.

In the usual type of condensers and under usual operating conditions, the rate at which gas is liberated in the condenser is not in excess of the rate at which these gases can pass through the above-described venting means.

However, there are types of electrolytic condensers, applications and operating conditions, 'where the amount of gas liberated in the condenser and the rate at which such liberation takes place is too large for the above type of.

erableincrease in the dimensions of the condenser, both of which are obviously objectionable.

For example, in the type of condensers described in the copending application Ser. No. 743,469, filed September 10, 1934, of Preston Robinson and Joseph L. Collins, now U. S. Patent #2,122,393 issued June 28, 1938, which condensers are now widely used as so-called regulating condensers, there are operating conditions in the normal use of such condensers under which a very large amount ofgas is liberated in a very short time. Such regulating condensers, have their filming electrodes usually formed to medium voltages of about 250 to 350 volts, at which voltages the condensers show a small leakage current, for example in the case of a 16 microfarad condenser, a current of the order 05 1.5 milliamps. At such a low leakage current the liberation of gases is small.

When such regulating ,condensers are submitted to high voltages, for example to 500 volts, they exhibit a sharp increase in leakage current Without, however, showing any sparking or a substantial heating up of the filmed surface.

Such condensers are widely used in the filter circuits of radio receiving sets, where they take up substantially the full plate voltage, for example 500 volts, at the instant the set is put into operation; however as the receiving tubes gradually heat up, the voltage across the condensers gradually drops to a final value of 250 to 300 volts.

During such heating up of the receiving tubes, the very large leakage currents passing through the condensers, which for a 16 microfarad condenser may be initially as high as 50 milliamps and more, cause a. correspondingly large amount of gas to be liberated, which during the first seeonds after the set is placed in service may be 30 to 40 times as large as the gas liberated per seconc l after the voltage across the condenser hasdropped to the normal operating voltage, 1. e., 250 to 300 volts.

The purpose of my invention is'to provide venting means to safely handle even such suddenly liberated very large amounts of gases.

While I prefer to combine the novel venting means of my. invention with the venting means of the above referred to patentgthey can be also successfully used without the same and also in combination with other types of known venting means.

According to my invention I provide a member. preferably in the form of a cap or diaphragm, which is provided with one or wer fissures,

minute holes or similar type of openings having areas of the order of a few thousandths to a .few ten-thousandths of an inch eifective opening, and

which in operation act as follows:

liberated increases, pressure builds up in the.

container and this pressure causes such movement of the diaphragm as to expose the above fissure or fissures, and permit them to pass all of the gas liberated. As soon as the pressure on the diaphragm is reduced, the diaphragm returns into its original position and passage through the fissuresis again substantially blocked, the diaphragm remaining in this condition as long as the rate of gas liberation is small.

In the preferred embodiment of my invention I provide the fissures on a cap member which is of somewhat'similar shape as the crowned cap described in the Patent No. 1,969,630 to Robert C. Sprague and Joseph L. Collins, althoughit is less. domed and instead of increasing the strength of the container bottom, the doming is provided to help to bias the diaphragm in its normal position.'

Preferably the cap is provided with a substantially fiat rim having fissures, whereby when pressure is built up in the condenser the fiat rim 'is temporarily raised, which causes the fissures to be exposed. The resiliency of the -cap causes it to assume its normal position when the pressure has been relieved, thus blocking the fissures.

The fissures can be applied to such a diaphragm member in various forms, for example by drilling in the fiat rims of the above cap a hole or preferably a plurality of uniformly distributed' minute holes, for example of the size of about 5; of an inch (although somewhat smaller or larger holes can be equally well used). When the cap is crimped to the container. these I holes deform to form lineal fissures. The thick ness of the material and the shape of the r ip are so selected as to insure the desired resiliency and biasing of the cap. t In the drawing forming part of this specificaion:

Figure 1 is a vertical sectional view of a condenser in accordance with the invention;

Fig. 2 is an enlarged perspective view of the cap member before it is secured to the container;

Fig. 3 is an enlarged section of the cap-end of the container showing the diaphragm raisedunder pressure.

Referring to Fig. 1, the condenser comprises a cylindrical metallic container II, which preferably constitutes the cathode of the condenser, and is provided at oneend with a reduced neck or tubular extension II. A seal provided in such tubular extension consists of a plug l2 of rubber or other resilient material filling and extending slightly beyond both the inner and outer end of the tubular extension.

The plug I2 is provided with a central bore through which protrudes a support I! of an anode I. said support being secured 'in place by suitably crimping the neck I I around the plug I2 and the end of support It. The container is almost completely filled with a suitable liquid electrolyte of the usual type, for instance with an aqueous solution of ammonium-borate.

The other end of the container is open and ends in a horizontal fiange 84 and is adapted to receive a cap or diaphragm (as shown in Fig. 2) preferably of metal, the cap comprising a central depressed portion 2| which fits inside of the container at 22, and the middle portion of which is slightly domed. The cap is furthermore provided with a flange having an inner horizon tal portion 2| and an outer beveled portion 32.

The portion 3! of the flange is provided with minute perforations, for example with four holes All of inch diameter which are-equally spaced along the periphery of the cap.

The cap shown in Fig. 2 is secured to the container by interposing between the cap and the flange 34 of the container, a washer or gasket 39 of wax-impregnated cloth. The rim 32 of the cap with the interposed washer 39 is spun over the flange 34 of the container, as shown in Fig. 1.

The holes are thereby deformed into lineal fissures 40a.

The anode it supported by the support l5 comprises an aluminum foil of relatively small'thickness folded back and forth upon itself in the manner of accordion pleating, which is riveted or otherwise secured to the support l5.

Suitable means. (not shown) may be provided to properly space the anode l6 from the container Ill so as .to prevent short-circuits between the same.

In operation the gas liberated at the electrodes normally escapes mainly through the pores of the vent gasket peripherally, as shown by the arrows in Fig. 3, although some gas also passes via a portion of the gasket through the fissures 40a. 3

When for some reason or other, for example in the case of the above referred to regulating condensers, a sudden increase in gas liberation takes place, pressure builds up in the condenser which causes the flange portion 3| of the cap to be raised, and which thereby permits a rapid escape For example, if a condenser because of unusually high ambient temperatures or sustained abnormally high voltages, assumes for a considerable length of time a higher temperature than is the temperature for which it has been designed, such increased condenser temperature will result, because of increased current, in an increased liberation of gases. The venting means of my invention will in such case fully safeguard the continued escape of such gases without any inJury to the condenser; whereas other types of venting means unless they also permit the escape of the electrolyte would be unable to handle such.

condensers using, for example, the vent gaskets? of the above referred to patent, were destroyed after relatively short time periods, whereas condensers having venting means in accordance with the invention remained intact indefinitely.

While I have described my invention in connection with a specific construction and in-a specific application, I do not wish to be limited thereto, but desire the appended claims to be construed as broadly as permissible in view of the prior art.

What I claim is:

1. Venting means for electrolytic devices comprising a resilient cap member provided with a fissured flange portion, a gasket cooperating with said flange portionto normally close the fissures, said flange portion being partly lifted from said gasket by pressure of accumulated gases to permit the gas to escape through said fissures, said cap member being biased by its own resiliency to assume its normal position when said gas pressure is relieved.

2. An electrolytic condenser comprising a container, a diaphragm member having a flssured portion and a gasket normally closing the fissures, said member and gasket being crimpedly secured to said container, said flssured diaphragm portion being adapted to be raised from said gasket under the pressure of gases liberated within the condenser to permit escape of said gases through said fissures, said diaphragm member having a resiliency suflicient to return the flssured portion to its normal position.

3. In an electrolytic condenser, in combination, a metallic containeropen at one end, a metal diaphragm forming a closure member therefor,

said diaphragm having a substantially fiat fls- 1 sured flange portion and a domed central portion, a semi-pervious gasket interposed between the container end and the flat diaphragm portion normally closing said fissures, said fissured portion being raised when gas pressure is built up within the container to relieve the gas pressure, and being returned by the resiliency of the diaphragm when pressure has been relieved.

JOSEPH L. COLLINS.

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