Molded capacitor header

A molded capacitor header with a circumferential annular flange has an inwardly adjacent elastomeric gasket retaining groove. Said header with the circumferential flange and adjacent gasket retaining groove provides a more durable and stronger seal of an electrolytic capacitor casing so that the electrolytic capacitor is less susceptible to leakage when subjected to high temperatures. Furthermore, the configuration of said electrolytic capacitor header protects the elastomeric gasket from making contact with the electrolytic vapors contained within said casing thereby discouraging the corrosion of the gasket which is initiated by the contact of the electrolytic vapors therewith.

FIELD OF THE INVENTION 
The present invention relates to electrolytic capacitors, and more 
particularly the invention is directed to an improved molded header 
construction for providing a tighter and more durable seal of the open end 
of the housing for the electrolytic capacitor. 
BACKGROUND OF THE INVENTION 
Conventionally, electrolytic capacitors comprise a case with an open top 
end and a closed bottom end, a cartridge impregnated with an electrolyte 
therein, and a molded dielectric header used in combination with an 
elastomeric or rubber gasket for sealing the open end of the case and 
encapsulating the impregnated cartridge there within. The impregnated 
cartridge, also to be referred to as the capacitor section hereinafter, is 
conventionally made up of a series of layers which include a first 
aluminum foil coated with a layer of aluminum oxide, a paper separator, a 
second layer of aluminum and a farther layer of paper. The assembled 
layers are spirally wound to form an elongated cylinder which is 
impregnated with an electrolyte solution. This capacitor section is 
contained within the case, which is normally of aluminum material. The 
upper end of the capacitor section includes first and second tabs 
connected respectively to the first and second layers of foil to provide 
anode and cathode connections. The tabs, in turn, are connected within the 
case to terminals extending through a molded capacitor header that serves 
to cover the open end of the capacitor case. 
A rubber gasket is inserted between the circumferential edges of the molded 
capacitor header and the capacitor case and afterwards, the top end of the 
open capacitor case is crimped or rolled over towards the inside of the 
case to cause the molded capacitor header to be forced tight against a 
ledge inside the capacitor case, thereby providing a sealed closure of the 
open end of the capacitor case. 
In one type of capacitor which has been available in the field for years, 
the capacitor case is made of aluminum material, the header is made of 
phenolic or similar thermosetting material, and the electrolyte is of a 
glycol type. While such capacitors have performed well over the years, the 
market requires small and large capacitors to perform in environments 
where the temperature exceeds 85.degree. C. This requirement creates the 
need and demand for capacitors of small and large size which are capable 
of operating at high temperatures and maintaining a reliable seal. 
The conventional capacitor described above is limited in its use to 
environments in which the temperature is less than 85.degree. C. The 
glycol type electrolyte used in such capacitors requires significant 
amounts of water, and with exposure of such capacitors to higher 
temperatures, the water tends to hydrate the foils with consequent injury 
to the capacitor. 
In an attempt to provide a capacitor of smaller size with operating 
capabilities which are at least the equivalent of the glycol capacitor, 
the field has turned to the use of new types of electrolytes which will 
operate reliably in environments of higher temperature. However, while 
such electrolytes are known to have inherent characteristics and 
advantages, it has been found that the header and the rubber seals of the 
conventional capacitors have a short life. After a period of use at high 
temperatures, the materials of the header and the gasket swell and become 
soggy, hence, causing leakage and sealing problems. 
Manufactures have provided headers for small and large diameter capacitors 
which withstand electrolytes that operate reliably in environments of 
higher temperatures, but capacitors employing these headers and 
electrolytes in temperatures greater than 85.degree. C., still have 
problems with the deterioration of the rubber gasket and the weakening of 
the seal it provides between the header and the case. 
DESCRIPTION OF THE PRIOR ART 
Various prior art electrolytic capacitor devices, and the like, as well as 
their apparatuses and the method of their construction in general, are 
known and are found to be exemplary of the U.S. prior art. They are: 
______________________________________ 
U.S. Pat. No. Inventor 
______________________________________ 
1,920,799 Lilienfeld 
2,018,486 Cole 
2,758,149 Brennan 
4,208,699 Philpott et al. 
4,342,070 Evans 
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In all of the above-listed patents, a large portion of a rubber gasket 
contacts the inner wall of the case. Over a period of time, the 
electrolytic vapors penetrate between the capacitor header and the inner 
wall of the capacitor case and begin to deteriorate the rubber gasket, 
eventually causing the seal to fail. 
Furthermore, when closing and sealing the open end cases as in the above 
U.S. Pat. Nos. 2,018,486; 4,208,699; and 4,342,070; the excessive case 
roll-over pressure and the consequent deformation of the compressed rubber 
gasket exerts an outward force against the inner wall of the case and 
allows some of the rubber gasket to be squeezed down between the capacitor 
header and the inner wall of the case. When an electrolytic capacitor is 
exposed to excessive heat, the capacitor header, as well as the rubber 
gasket, loses some of its physical characteristics and, as the internal 
electrolyte vapor pressure increases, the capacitor header is pressed 
upward, allowing the electrolytic vapors to penetrate between the 
capacitor header and the inner wall of the case and come into contact with 
the rubber gasket. The excessive heat and electrolyte vapors accelerate 
the deterioration of the rubber gasket and decrease the life of the seal. 
The above-listed patents or known prior uses teach and disclose various 
types of electrolytic capacitors and capacitor headers of sorts and of 
various manufactures, and the like, as well as methods of their 
construction; but none of them, whether taken singly or in any 
combination, disclose the specific details of the combination of the 
present invention in such a way as to bear upon the claims herein. 
SUMMARY OF THE INVENTION 
The present invention focuses on closing and sealing an electrolytic 
capacitor. It is an object, advantage, and feature of the present 
invention to provide a novel capacitor header that better seals the open 
end of an electrolytic capacitor in use, and lends itself to applications 
with all types of current electrolytic capacitors. 
Another object of the present invention is directed further to a device 
providing for the protection of the rubber gasket sealing the capacitor 
from the electrolytic vapors contained within said capacitor. This is a 
substantial improvement over existing practices whereby the life of the 
rubber gasket is extended, and the strength of the seal increased. 
Another object of the invention is to provide a novel and improved 
construction of a capacitor header, preferably of a molded glass or 
mineral filled plastic material, including the employment of a vertically 
disposed annular peripheral flange and an adjacent concentric gasket 
retaining groove which serves to strengthen the seal of the capacitor and, 
at the same time, protect the rubber gasket from the electrolyte compound 
encapsulated within the capacitor, hence aiding to extend the life and 
improve the performance of the capacitor. 
These, together with other objects and advantages of the invention reside 
in the details of the process and the operation thereof, as is more fully 
hereinafter described and claimed. References are made to drawings forming 
a part hereof, wherein like numerals refer to like parts throughout.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawing there is shown in FIG. 1 a transverse 
sectional view of an electrolytic capacitor encasement 10 comprising a 
casing 20 with a closed bottom end 20a and an open top end 20b, made of 
aluminum or another suitable material. The casing open top end 20b retains 
a molded cylindrical header 30 made of a fiberglass reinforced or mineral 
filled plastic compound, or the like, and a rubber gasket 40, or the like. 
The casing 20 is crimped or rolled over inwardly at its upper edge 22 
thereby pressing into the rubber gasket 40 which is held in the annular 
gasket retaining groove 33 defined by the space between the annular 
peripheral flange 35 and the raised inner circular portion 37 of the 
header 30. 
The lower peripheral edge of the header 30 rests upon and engages the 
inwardly directed ledge 24 of the casing. Said ledge resists the 
downwardly directed pressure exerted by the rolled over or crimped 
peripheral edge 22 of the casing 20, thereby preventing the header 30 from 
moving downwardly inside said casing. Furthermore, the contact between the 
lower peripheral edge of the header and the inwardly directed ledge 24 of 
the casing 20 also helps to seal the entire capacitor section 
encapsulating assembly comprising the header, the rubber gasket, and the 
casing. 
FIG. 6, a sectional view of the invention, shows the improved molded header 
comprising: an annular vertically disposed peripheral flange 35 with an 
inward and downwardly sloping upper surface 34 that forms a sharpened edge 
36 where the upper surface meets the outer circumferential vertically 
oriented surface of the flange; a concentric gasket retaining groove 33; 
an inner central raised circular portion 37 with terminals 50, made of 
aluminum or the like, extending therethrough; and an axially aligned 
cylindrical protrusion 38 with a rounded, or similarly shaped, lower end 
that functions to anchor the capacitor section within the encasement 
assembly 10. 
Now referring to FIGS. 2 and 4, there is shown, respectively, a sectional 
view and an auxiliary sectional view of the improved header with the 
rubber gasket 40 retained therein. In the preferred embodiment, the top 
horizontal surface 41 of the gasket falls level with the top sharp edge 36 
of the annular peripheral flange 35; however, the height of the gasket 40 
(relative to the annular flange) may vary within any suitable range. 
When the upper edge of the aluminum casing 20 is crimped or rolled over, as 
is shown in detail in the auxiliary sectional view of the FIG. 3, the 
rubber gasket only contacts the header 30 and the small crimped or rolled 
over portion 22 of the aluminum casing 20. The annular peripheral flange 
35 of the new capacitor header prevents the rubber gasket 40 from 
contacting the inner wall of the case 20. 
With both the new capacitor and conventional capacitors, the downward 
pressure exerted by the rolling over or crimping of the upper edge of the 
open end case forces the capacitor header down the inwardly directed ledge 
of the case. The action of the header moving down the inwardly directed 
ledge 24 forces outward the side wall of the case and increase the 
tolerance between: (1) the portion of the inside wall of the case located 
between the inwardly directed ledge 24 and the rolled over or crimped 
upper edge 22 and (2) the circumferential outside wall of the header. With 
the conventional header, once the electrolytic vapors escape past the 
point of contact between the header and the inwardly directed ledge 24, 
the vapors come into immediate contact with the gasket and begin to 
deteriorate said rubber gasket. However, the new header engages the case 
at the underside of the arc of the rolled over or crimped portion of the 
case and at the inwardly directed ledge of the case, thus creating two 
seals that must be penetrated by the electrolytic vapors before they come 
in contact with the rubber gasket--the third and final seal. The new 
header construction reduces the potential for electrolytic vapor leak 
paths and adds resistance to the electrolytic vapor penetration between 
the capacitor header and the inner wall of the case. 
When a capacitor is exposed to excessive heat, the molded capacitor header, 
made of plastic or the like, begins to lose some of its physical 
properties. As temperature increases, the electrolytic vapor pressure 
increases, the plasticity of the molded header increases, and the 
increasing compressive force exerted on the underside of the header by 
vapor pressure begins to move the header upward. With the new capacitor 
header, as the header is compressed upwards, the sharp edge 36 of the 
annular flange 35 is pressed inward along the convex inner arcuate surface 
of the rolled over or crimped portion 22 of the case. The angle of the 
downward and inwardly sloping upper surface 34 of the annular flange 35, 
and the compressive forces exerted by the gasket 40 compel the annular 
peripheral flange 35 against the inner wall of the case 20. Consequently, 
said annular peripheral flange remains between the compressed gasket and 
the inner wall of the case while the lower peripheral edge moves up off of 
the inwardly directed ledge 24 of the case 20. 
As the temperature abates, the vapor pressure decreases and the compressive 
forces of the rubber gasket compel the header back down against the 
internal shoulder of the casing. Likewise, as the header returns down to 
its original location, the compressive forces of the rubber gasket push 
the annular flange back into its original shape and position. 
At the end of the temperature cycle, the header has resumed its original 
shape and rigidity, and the rubber gasket is still protected from the 
electrolytic vapors which injure it and, therefore, shorten the life of 
the effective operation of the capacitor. 
The foregoing is considered as illustrative of the principle of the 
invention. Further, since numerous modifications and changes will readily 
occur to those skilled in the art, it is not desired to limit the 
invention to the exact construction and operation shown and described, and 
accordingly, all suitable modifications, and equivalents which may be 
resorted to, fall within the scope of the invention.