US2940021A - Electrolytic capacitors - Google Patents

Description

Jne 7, 1960 R. v. HIPPERsoN 2,940,021

ELECTROLYTIC CAPACITORS Filed April 26. 1957 United States Patent i Ofiice ELECTROLYTIC CAPACITORS Filed Apr. 2'6, 1957, Ser. No. 655,442 4 Claims. (Cl. 317-230) England, assignor Ilford, England, a

This invention relates to electrolytic capacitors more particularly to miniature capacitors in aluminium cans of less than 0.5" diameter.

In capacitors of these small dimensions it is common practice to effect the seal and end closure by inserting a bung of suitable resilient material into the open end of the can. The anode riser or lead out wire is passed through the centre of the bung and the lip of the case is spun or pressed into the side Wall of the bung.

This type of assembly is not considered entirely satisfactory since cold flow and ageing of the bung material cause it to take on a permanent set which in turn renders the seal ineffective.

A much lmore satisfactory seal is obtained with the conventional rubber faced resin bonded disc but its application is generally limited, wherever small diameter cans are involved, owing to the possibility of short crcuit occurring between the solder tag and the spun rim of the case.

An object of this invention is to provide an improved capacitor which obviates the above mentioned defects.

Another object is to provide an improved construction of electrolytic capacitor of the type having a metal can closed by a disc over the edges of which the edge of the can is rolled, wherein the anode connection of the capacitor element is connected to an external terminal conductor by means of a rivet extending through the disc, means being provided which without requiring the use of a moulded cover, provide effective protection against accidental contact of the anode connector with the rolled-over portion of the can.

According to this invention the capacitor is of the kind specified and is characterised by the addition of an insulating member which surrounds the terminal connection on the outermost surface of the sealing disc to separate the external lead and riveting assembly from the peripheral edge of the can.

Preferably the insulating member is in the form of a cup and is made from such suitable material as a thermo plastic having suficiently high electrical resistance or alternatively the cap may be produced from natural or synthetic rubber.

Advantages of the invention are:

(a) The thickness of the base of the cup raises the tag and rivet head above the face of the sealing disc, thus increasing the distance between tag and case.

(b) The wall of the cup effects a complete separation between tag and case and enables the tag strip to be bent at right angles to the case without fear of short circuit.

(c) A double seal is produced round the `shank of L1 attached to one surface of 2,940,021 'Patented June 7, 1960 the rivet by the inward pressure of the compressed materials i.e. the rubber face of the sealing disc and the base of the exible insulating cup.

A The invention will now be described with reference to the accompanying drawing which shows a sectional elevation of one embodiment.

Referring to the drawing- A miniature capacitor unit `1 of such dimension is provided which will fit into aluminium can 2 of say 0.25 of an inch diameter. The cathode lead 3 of capacitor 1 is secured together with an aluminium washer 4 inside the base of the can 2, and a terminal lead 5 is fixed to the outer surface thereof by means of an aluminium rivet 6. Adisc 8 of phenol-formaldehyde plastic provided with a rubber coating 7, has an aluminium washer 9,anode riser 10 and a plastic insulating shroud the disc, and a pliable cupshapedinsulating member 12 with a lead-out wire 13 located therein are secured to the outer surface of thedisc 7, 8, by means of an aluminium rivet 14.

The disc assembly is next inserted into the can 2 in such a manner that the insulating cup-shaped member 12 is uppermost, after which the end of the can 2 is spun over and embedded into the rubber face 7 ofdisc 8, thereby sealing off the contents of the can. The insulating shroud 11 prevents theanode riser 10 short circuiting to the inside of the can 2.

The upstanding flange of the cup-shaped member 12 separates the external positive lead 13 from the can so that, in the event of the lead being bent through 90' or more the possibility of its short circuting to the can 2 is reduced to a I claim:

1. An electrolytic capacitor comprising a metal can sealed at one end by a disc of insulating material, the free edge of the can being spun over the edge of the disc, a capacitor element having an anode riser formed v with a loop-shaped portion, and arranged inside the can in spaced relation thereto, a cup-shaped member of insulating material, separate from the disc and having an external diameter smaller than the inside diameter of the spun-over edge of the can, placed in contact with the outer side of the disc, with the open side of the cup facing outwardly, a terminal conductor having an end loop bent at right angles to the adjacent part of the conductor, said loop being accommodated in the cup-shaped member, said loop-shaped portion of the anode riser being placed on the inner side of the disc in alignment with said end loop, and a rivet extending through said aligned loop-shaped portion and end loop and through the disc and cup-shaped member so as to secure said anode riser, disc, cup-shaped member, and end loop together in close mechanical contact and electrically connect said anode riser to said conductor.

2. An electrolytic capacitor as claimed in claim l, wherein said disc consists of thermoset plastic lined on its outer side with elastomer material.

3. An electrolytic capacitor as claimed n claim l, including a shroud of plastic insulating material interposed between thc loop-shaped portion of the anode riser and the disc and 'extending inside the can for part of the length thereof to encircle the adjacent part of the capacitor element.

4. In a miniature electrolytic capacitor having a capacitor element in a metal can closed by a disc of in- `sljlating material secured inhe can by the metal edge of the can being rolled over .the `edge of .the disc, the combination of an external conductor having a bentovei lug, a cup-shaped member of insulating material in which said lug is accommodated, an anode conductor extending from the capacitor element and having a lug placed at the inner side of the disc, said cup-shaped member being placed at the outer side of the disc with its bottom separating the lug of the external conductor from the disc, and a rivet` of conductive material extending through said lugs .and through the discv and .the .bottom of .the `cup-shaped member and holding the :same

References Cited in the tile of this patent UNITED STATES PATENTS Claassen Dec. 12, 1939 Linder Dec. l0, 1940 Brennan T Jan. 5, 1954 FOREIGN vPATENTS Great Britain Jan. 13, 1938

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