Cell Sealing Means

The invention relates to electrochemical cells of the alkaline type.

More particularly, the invention relates to a sealing means for an electrochemical cell to help minimize leakage of alkaline electrolytes over long periods of time. Electrolyte of sealed alkaline cells tends to slowly find its way through a seal area and appear as a white incrustation on the outside of the cell.

Existing alkaline cells have a metal top closure member encircled by a resilient sealing grommet, made for example of plastic material. The electrolyte tends to leak along a path extending between the grommet and the top closure member.

According to the present invention, in a sealed electrical cell in which a leakage path for electrolyte is present, a body of material capable of absorbing the electrolyte is placed in the leakage path.

More specifically, in the case of a sealed alkaline cell of the construction mentioned above, the absorbent material is preferably placed between the top closure member and the sealing grommet, and may e.g. be a ring or tube of absorbent material.

The incorporation of the absorbent material in the leakage path has been found to increase the time taken for electrolyte to reach the outside of the cell.

Preferably, to minimize electrolyte leakage between the grommet and the container of the cell, a high-pressure compression area is created by providing an external projection on the grommet, as disclosed in U.S. Pat. No. 3,904,438.

An alkaline cell embodying the present invention is shown in the drawings accompanying the specification, in which:

FIG. 1 is a cross section of the cell; and

FIG. 2 is a cross section of the sealing grommet of the cell.

The cell 14 has a metal container 4 with an open end, a top closure member 2 which is cup-shaped and is pressed from metal sheet or strip and in the open end of the container, and a plastic sealing grommet or sleeve 3 trapped between the outside of the top closure member and the inside of the container 4. In the lower part of the cell 14 is a depolarizing cathode 7 consolidated into the container 4 within a support sleeve 8 and covered by a barrier disc 6. In the upper region of the cell 14, inside the cup-shaped top closure member 2, are anode material 10 and an absorbent body 9 containing mobile or fluid electrolyte of the cell, in contact with the barrier disc 6. At least the inner surfaces of the cell container 4 and top closure member 2 are electrochemically compatible with the cell constituents with which they are in contact.

The sealing grommet 3 has at its lower end an internal channel 11 which accommodates the encircled edge of the top closure member 2. The top closure member 2 has an outwardly directed edge flange 12. On the outer surface of the grommet 3, in a position aligned with the outwardly directed flange 12 of the top closure member 2, is a resilient annular projection 5 whose external diameter is greater than the internal diameter of the container 4. Consequently, insertion of the top closure member 2 and grommet 3 into the container 4 causes the region of the resilient projection 5 to be highly compressed between the flange 12 and the internal surface of the container 4, as described in U.S. Pat. No. 3,904,438. The high local compression of the grommet 3 at the resilient projection 5 helps ensure that seepage of electrolyte will preferentially follow a path round the edge of the top closure member 2, and between the top closure member and the interior of the sealing grommet 3. An annular space 13 exists between the grommet 3 and the top closure member 2 and this accommodates a tube 1 of material capable of absorbing mobile or fluid electrolyte. The absorbent material is preferably a wound tube of chemically inactive bibulous paper.

The cell 14 is sealed by crimping or rolling the upper edge of the container 4 so as to compress the upper edge region of the sealing grommet 3 between the deformed edge of the container and the top closure member 2.

It is to be noted that the cell is shown much larger than actual size, the invention being directed primarily (but not exclusively) to miniature alkaline cells.

The concepts are applicable to electrical devices other than electrical cells. Such other devices include electrolytic capacitors.