GB2162363A

GB2162363A - Electric storage battery

Info

Publication number: GB2162363A
Application number: GB8518020A
Authority: GB
Inventors: D E Turner
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1984-07-26
Filing date: 1985-07-17
Publication date: 1986-01-29
Also published as: GB8419064D0; GB8518020D0

Abstract

An electric storage battery wherein opposite end walls 13 of battery casing each include a plurality of parallel corrugations 15. <IMAGE>

Description

SPECIFICATION Electric storage battery This invention relates to electric storage batteries, primarily for road vehicles, and particularly, but not exclusively, to batteries of the type known as recombinant batteries.

In general recombinant batteries have their casing sealed in use and thus when operative the internal pressure exceeds ambient pressure. Moreover, it is usual not to have loose electrolyte, the electrolyte being absorbed in the separators of the battery plate packs. In order to ensure the necessary intimate contact between the plates and separators within the packs it is desirable to subject the packs to pressure and a convenient way of doing this is to fit the packs tightly within their respective battery box compartments.

It will be recognised therefore that there is a need for adequate strengt . . in the opposite end walls of the battery casing, that is to say the external end walls of the two end cell compartments of the battery casing, both to ensure that adequate pressure can be applied etween plates and separators of the battery plate packs, and to avoid outward bowing of the end walls. Such outward bowing is undesirable both because it relieves pressure on the packs, and in that it gives rise to concern on the part of the battery user. It has been proposed to produce the battery casing of a recombinant battery with relatively thick end walls, which of course is expensive in material usage.

As an alterative to produce a casing with relatively thick end walls it has been proposed to produce a casing with relatively thin end walls and to provide the thin end walls with strengthening members such as integrally formed, or separately applied, external strengthening ribs. However the use of such strengthening members, although effecting a saving in material by comparison with thick end wall constructions, is found to provide the thin end wall with only a relatively small increase in rigidity unless the ribs are inordinately high, which of course would produce an unacceptable increase in the overall length of the battery casing.

It is an object of the present invention to provide an electric storage battery wherein the aforementioned problems are minimised.

In an electric storage battery in accordance with the present invention the opposite end walls of the battery casing each include a plurality of parallel corrugations.

Preferably the corrugations extend at right angles to the base of the battery casing.

Desirably said corrugations extend at one end from a transversely extending corrugation.

Desirably said parallel corrugations extends between a pair of spaced and parallel transverse corrugations.

Conveniently said corrugations are of angular cross-section.

Preferably said corrugations are rectangular in transverse cross-section.

In the accompanying drawings, Figure 1 is a perspective view of part of a battery casing in accordance with one example of the invention.

Figure 2 is a view similar to Fig. 1 of a modification thereof, and Figure 3 is a view similar to Figs. 1 and 2, but of a casing in accordance with a second example of the invention.

Referring to Fig. 1 of the drawing, there is shown the lower part of the casing of an electric storage battery, the upper, lid of the casing being omitted. The lower part of the casing as illustrated in the drawings will hereinafter be referred as the "box".

The box is moulded in synthetic resin material, conveniently polypropylene, and includes a base wall 11, from which are upstanding integral, parallel side walls 12 and integral end walls 13 extending transverse to the side walls 12. Integral with the side walls 12 and the base 11, and equally spaced along the length of the side walls 12 are five internal partition walls 14 dividing the interior of the box into six cell compartments. The side walls 12, end walls 13 and partition walls 14 are of relatively thin cross-section.

In use of the cell compartments will receive a battery plate pack comprising positive and negative battery plates together with electrolyte impregnated separators. The packs will be a tight fit in their respective compartment and inter cell connectors will extend through the partition walls 14 electrically to interconnect the battery plate packs. A moulded polypropylene lid will be heat sealed or otherwise welded to the open upper end of the box, a weld being produced between the lid and the upper edges of the side walls, end walls, and partition walls. The battery plate packs in the two end compartments, that is to say the two compartments bounded by the end walls 13 respectively will carry external terminals which protrude through the lid to define a positive terminal at one end of the lid and a negative terminal at the other end of the lid.Within the lid there are vent passages providing communication between the six compartments of the battery, and the lid will have a vent valve which, when the internal pressure exceeds a predetermined safety level, vents to prevent rupture of the battery casing. The passage to atmosphere from the vent valve may, if desired, include a flame arrestor so that should gaes venting from the battery ignite then burning will be confined to the exterior of the battery and the flame will not burn back along the vent passage to give rise to an internal explosion within the battery. Such batteries will in general be well known and fall within the class of batteries known as recombinant batteries.

It will be recognised that both by virtue of the need to exert pressure on the battery plate packs in a direction parallel to the length of the battery, and to withstand the increased internal pressure, by comparison with ambient atmospheric pressure without bowing, the end walls 13 need to be rigid. Thus the end walls 13 are moulded in a corrugated configuration, the wall thickness being substantially constant, and the corrugations 15 being parallel to one another and at right angles to the base 11. In the box illustrated in Fig. 1, the corrugations 15 are integral, at their lower ends, with a transverse corrugation 16, the transverse corrugation 16 thus "anchoring" the corrugations 15 at their lower end.It will be recognised that transverse anchorage of the upper ends of the corrugations 15 is provided by the lid of the battery casing to which the corrugated upper edge of each of the end walls 13 is welded. Thus the upper and lower ends of the corrugations 15 are fixed in use and the corrugated configuration provides excellent rigidity in the end wall 13 without the relatively huge material wastage which would occur if the end walls 13 were of sufficient thickness to have equal rigidity, or were provided with sufficiently thick and/or high ribs to achieve the same rigidity.

The lower transverse corrugation 16 can constitute a "hold-down" rib if desired to facilitate anchorage of the battery. Thus a clamping arrangement may incorporate fingers which, in use, extend between the vertical corrugations 15 to. engage the transverse, and generally horizontal corrugation 16.

Fig. 2 illustrates a modification of the box shown in Fig. 1 wherein the upper ends of the corrugations 15 are integral with a second transverse corrugation 17. The Fig. 2 arrangement is in some respects advantageous over the Fig. 1 arrangement in that the exposed edges, to which the lid must be welded, are straight, whereas using the box of Fig. 1, the edges of the end walls are sinuous, and therefore may prove more problematic to weld.

In the second example, illustrated in Fig. 3, the end walls 13 are again formed with vertically extending corrugations 15 and transverse corrugations 16, 17, but in this instance the vertical corrugations 15 which extend integrally downwardly from the upper transverse corrugation 17, terminate short of the lower transverse corrugation 16. Thus in the second example of the invention the corrugations 15 define a buttress configuration and the lower ends of the vertical corrugations 15 are "anchored" by being closely adjacent the transverse corrugation 16.

In each of the constructions disclosed above the lower transverse corrugation 16 may, in order to simplify the core construction of the mould tool for moulding the box, be solid rather than hollow. This is not however essential, and to save weight and material it may prove desirable to utilize a slightly more complex mould core and the produce the lower transverse corrugation 16 as true hollow formations. The configuration shown in Fig. 3 leaves the upper external surface of the transverse corrugation 16 free for unhindered engagement by a "hold-down" clamp.

In each of the constructions it will be recognised that the corrugations 15 and the corrugations 16, 17 are of angular form rather than being curved, and preferably the corrugations are rectangular in transverse crosssection. The corrugations illustrated are not rectangular since they are provided with a "draw-angle" to facilitate removal of the mould parts. However, by using a mould with vertical draw parts, that is to say parts which are removed longitudinally of the corrugations it would be possible to produce corrugations of rectangular transverse cross-section.

The embodiment described above relate particularly to lead-acid batteries but it is to be understood that similar techniques can be employed with alkaline batteries.

Claims

1. An electric storage battery wherein opposite end walls of the battery casing each include a plurality of parallel corrugations.

2. A battery as claimed in claim 1 wherein said corrugations extend at right angles to the base of the battery casing.

3. A battery as claimed in claim 1 or claim 2 wherein said corrugations extend at one end from a transversely extending corrugation.

4. A battery as claimed in anyone of claims 1 to 3 wherein said parallel corrugations extend between a pair of spaced and parallel transverse corrugations.

5. A battery as claimed in anyone of claims 1 to 4 wherein said corrugations are of angular cross-section.

6. A battery as claimed in anyone of claims 1 to 4 wherein said corrugations are rectangular in transverse cross-section.

7. An electric storage battery substantially as hereinbefore described with reference to Fig. 1 and to accompanying drawings.

8. An electric storage battery substantially as hereinbefore described with reference to Fig. 2 and to accompanying drawings.

9. An electric storage battery substantially as hereinbefore described with reference to Fig. 3 and to accompanying drawings.