GB2034511A - Vented battery - Google Patents

Abstract

In a battery comprising a plurality of cells (1) housed in a sealed casing (8), venting means (6) are provided for conducting any gas released by the cells (1) away from the casing (8). The venting means is in the form of a gas conduit which extends through, and is sealed in a gas tight manner to, an end of the casing. The cells may be either of the "button-type" or cylindrical cells. The casing may be of a heat-shrinkable material and a path to the venting means for gas released by each cell in the casing may be formed by the shrinking of the casing around a connecting wire which extends along the inner surface of the casing.

Description

SPECIFICATION Battery This invention relates to a battery containing a plurality of cells, in which gases released by the cells in use of the battery may be safely conducted away from the cells. The invention also includes within its scope a method of making such a battery.

It has been found that in such a battery containing a plurality of cells, the cells may in adverse conditions release gases under high pressure. if the cells are in a sealed container, as is usually the case, a rapid build up of pressure may result and rupture the container, thus causing a danger to both health and safety and also a danger of damage to nearby equipment.

The object of the present invention is to provide a battery in which gases released by the cells may be safely conducted away from the cells so that the above-mentioned dangers may be substantially reduced or eliminated.

According to the invention, in a first aspect thereof, in a battery comprising a plurality of cells housed in a sealed casing, venting means are provided for conducting any gas released by said cells away from said casing, said venting means extending through, and being sealed in a gas tight manner to, an end of said casing.

The said venting means is preferably in the form of a gas conduit. Said cells are preferably of the "button-type" and are preferably stacked within said casing. The end of said casing preferably corresponds to the positive terminal of the battery and, where said cells are of the said "button-type", said venting means preferably extends into the battery at least as far as the negative face of the cell of the stack which is nearest to said end.

A path to said venting means for gas released by each cell in said casing may be formed by spacing means between said cells and said casing, and said spacing means may comprise a connecting wire extending from an end of said casing, opposite to said first-mentioned end, along the inner surface of said casing and through said first-mentioned end of said casing, to which it is sealed in a gas tight manner. A further said connecting wire preferably extends through, and is sealed in a gas tight manner to, said end of said casing.

The said casing is preferably of a heat-shrinkable material such as polyvinyl chloride such that it may be shrunk around the first-mentioned connecting wire to form said path.

The cells of said stack may be of rechargeable nickel-cadmium "button-type", that is of the type commonly used e.g. in hearing aids. Alternatively the cells may be primary or rechargeable cylindrical (i.e. elongate) cells, in which case they may be grouped side-by-side and/or end-to-end within the casing.

According to the invention, in a second aspect thereof, in a method of manufacturing a battery comprising a plurality of cells, said cells are posi tioned in a casing, venting means are arranged to extend through an end of said casing and said casing is sealed in a gas tight manner around said cells and said venting means so that any gas released by said cells may be conducted, by said venting means, away from said casing.

When the said casing is of a heat-shrinkable material as aforesaid, the method further comprises heating said casing so as to shrink it to give a close fit around the cells, and also forming a path to said venting means for gas released by each cell in said casing, by means of spacing means provided between said cells and said casing, said spacing means preferably being provided by passing a connecting wire from an end of said casing, opposite to said first-mentioned end, along the inner surface of said casing and through said first-mentioned end of said casing to which it is sealed in a gas tight manner.

The casing is preferably sealed by means of an adhesive applied to its ends.

Batteries embodying the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a fragmentary view, partly in section, of a first embodiment of the invention; Figure 2 is a plan view of the battery when viewed from the left-hand side of Figure 1; Figure 3 is a greatly enlarged sectional view of the details contained in the circle denoted A in Figure 2; and Figure 4 is a fragmentary view of a second embodiment of the invention.

Referring to Figures 1 to 3, the battery comprises a plurality of stacked rechargeable nickel-cadmium "button-type" cells 1, housed in a sealed casing 8.

Venting means in the form of a gas conduit defined by a tube 6 are provided for conducting any gas released by the cells 1 away from the casing 8. The tube 6 extends through, and is sealed in a gas tight manner to, the end 8a of the casing 8 which is adjacent the positive terminal of the stack of cells.

The tube 6 could, however, be provided at the other end of the casing.

Adjacent pairs of cells 1 of the stack are welded together in a known manner by means of weld cups 2 and spot welds. A solder tag 3 is welded to each end of the stack of cells so as to define the positive and negative terminals of the stack. To the positive and negative terminals are attached a connecting wire 4 and 5 respectively. These are conventional PVC covered electrical wires which may be coloured red and black respectively to denote polarity.

The negative wire 5 extends from the negative terminal of the stack of cells along the inner surface of the casing 8 and through the end 8a of the casing, to which it is sealed in a gas tight manner.

The tube 6 extends along the inside of the casing, as far as the negative face of the cell 1 which is nearest the end 8a, but need only extend far enough into the casing 8 so that it will not easily be pulled out.

The casing 8 is a PVC heat-shrinkable tube which is placed over the stack of cells. Typical dimensions of the casing of this embodiment are 56.5 mm long and 0.2 mm thick. A disc 7 is positioned within the casing 8 adjacent the negative terminal of the stack. When heat is applied to the casing 8 it shrinks to give a tight fit over all the elements within it. Thus the disc 7 seals the negative end of the casing and, as shown in Figure 2, "bumps" 10 and 10' are formed around the periphery of the battery by the casing material shrinking around the wire 5 and the tube 6 respectively. The "bump" 10 formed by the wire 5 is shown more clearly in Figure 3.

In order to seal the battery, a sealant 9 is applied at each end of the casing 8. The sealant 9 may be a room temperature vulcanising silicone rubber - for example "Silastromer 731" (registered trade mark), manufactured by Dow Corning.

As shown most clearly in Figure 3, by virtue of the "bump" 10 caused by the wire 5, gas released from any cell within the stack has a path from its point of release to the tube 6, via cavities 11 produced by the casing 8 being unable to shrink closely around the wire 5. The gas may then be conducted by the tube 6 away from the casing to an area in which it is safe to release such gas.

Referring now to the embodiment shown in Figure 4, the battery comprises a plurality (three as shown) of cylindrical cells 1', housed side-by-side in a straight line in a sealed casing 8', which is of a similar material and construction to the casing 8 previously described. A tube 6', extending through the casing 8', comprises venting means for conducting gases released by the cells 1' away from the casing 8'.

The cells 1', which are held together by selfadhesive foam pads (not shown) placed between their abutting sides, are connected in series by means of connecting tags 12. A solder tag 3' is provided at each terminal of the series to define positive and negative terminals of the battery.

Connecting wires are attached to the solder tags 3' and are routed within the casing 8' to exit therefrom adjacent the tube 6'. The tube 6' and the connecting wires are sealed in a gas tight manner to the point at which they leave the casing 8'.

As in the previous embodiment, sealant is used to seal the casing 8'.

Claims (18)

1. A battery comprising a plurality of cells housed in a sealed casing, wherein venting means are provided for conducting any gas released by said cells away from said casing, said venting means extending through, and being sealed in a gas tight mannerto, an end of said casing.

2. A battery according to Claim 1, wherein said venting means is in the form of a gas conduit.

3. A battery according to Claim 1 or Claim 2, wherein said cells are of the "button-type" and are stacked within said casing.

4. A battery according to Claim 3, wherein the end of said casing corresponds to the positive terminal of the battery and said venting means extends into the battery at least as far as the negative face of the cell of the stack which is nearest to said end.

5. A battery according to any one of the preced ing claims, wherein a path to said venting means for gas released by each cell in said casing is formed by spacing means between said cells and said casing.

6. A battery according to Claim 5, wherein said spacing means comprises a connecting wire extending from an end of said casing, opposite to said first-mentioned end, along the inner surface of said casing and through said first-mentioned end of said casing, to which it is sealed in a gas tight manner.

7. A battery according to Claim 6, wherein a further said connecting wire extends through, and is sealed in a gas tight manner to, said end of said casing.

8. A battery according to any one of the preceding claims, wherein said casing is of a heatshrinkable material.

9. A battery according to any one of the preceding claims, wherein said cells are rechargeable nickel-cadmium cells.

10. A battery according to any one of Claims 1 to 8, wherein said cells are primary or rechargeable cylindrical cells and they are arranged side-by-side and/or end-to-end within said casing.

11. A battery constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated in Figures 1 to 3 or Figure 4 of the accompanying diagrammatic drawings.

12. A method of manufacturing a battery comprising a plurality of cells, wherein said cells are positioned in a casing, venting means are arranged to extend through an end of said casing and said casing is sealed in a gas tight manner around said cells and said venting means so that any gas released by said cells may be conducted, by said venting means, away from said casing.

13. A method according to Claim 12, wherein said casing is of a heat-shrinkable material and said method further comprises heating said casing so as to shrink it to give a close fit around the cells.

14. A method according to Claim 12 or Claim 13, wherein said method further comprises forming a path to said venting means for gas released by each cell in said casing, by means of spacing means provided between said cells and said casing.

15. A method according to Claim 14, wherein said spacing means is provided by passing a connecting wire from an end of said casing, opposite to said first-mentioned end, along the inner surface of said casing and through said first-mentioned end of said casing to which it is sealed in a gas tight manner.

16. A method according to any one of Claims 12 to 15, further comprising sealing said casing.

17. A method of manufacturing a battery substantially as hereinbefore described with reference to Figures 1 to 3 or Figure 4 of the accompanying diagrammatic drawings.

18. A battery which has been manufactured by a method according to any one of Claims 12 to 17.