GB2043328A - Multi-tubular battery plates - Google Patents

Abstract

A multi-tubular battery plate comprises a plurality of tubes containing active material and a conductive spine extending along its length. Each tube is closed at one end by a bung 10, and the bungs are connected together to form a bottom bar. Each bung affords a space within it accommodating the end of a spine and having a seal, such as a flange 22 forming a frustum at its upper end, which surrounds the spine and through which the spine may slide. Thus any increase in length of the spines can be accommodated by the bottom bar and does not stress the components or seals of the battery in which the plate is used. <IMAGE>

Description

SPECIFICATION Multi-tubular battery plates The present invention relates to multi-tubular plates for use in electric cells or batteries for example for vehicle traction, and relates in particular to the so called bottom bars for use with such plates.

Conventional traction cells use multi-tubular plates comprising a plurality of adjacent tubes of a nonwoven material which are usually connected together, though they may be separate. The tubes are filled with active electrode material, and a plurality of lead spines interconnected by a common lead yoke are pushed into the tubes from what will be their top end, one in the centre of each tube and extending along its full length. The bottom ends of the tubes are then closed by a bottom bar, comprising a plurality of circular section interconnected bungs or stoppers of plastic material each of which closes the bottom of a respective tube. Each bung or stopper has a "blind" hole in its surface which receives the end of a respective spine thus retaining it centrally within its respective tube.

In use the plates rest on "mud ribs" carried by the floor of the cell container, and the positive and negative plates are interconnected by respective positive and negative group bars. The group bars are in turn connected to, or integral with, a terminal connectorwhich passes through the lid of the cell.

During service the crystal structure of the lead spines in the positive plates gradually alters, and this results in an increase in length of these spines. Due to the fact that the spines are in contact with the ends of the holes in the bottom bar this increase in length stresses the group bars, the terminal connectors, and the cell lid, but in conventional cells which use pitch seals the stress can be accommodated without severely harming the cell.

It has however been found that if the cell container is made of plastics material, such as polypropylene, having a lid of similar material welded to it, the stress that occurs may lead to failure of either the terminal seal or the seal between the lid and the container.

The spines for plates of differing sizes, or even for plates of the same size, may be of different diameter.

In the past it has been necessary to have a different sized bottom bar for each different diameter of the spines.

According to the present invention a multi-tubular battery plate comprises a plurality of tubes containing active material, each tube also containing a conductive spine extending along its length and being closed at one end by a respective bung, the bungs being connected together to form a bottom bar and each affording a space within it accommodating the end of a spine and having a seal which surrounds the spine and through which the spine may slide. Each bung may of generally tubular form, the seal comprising a resilient flange integral with and projecting inwardly from the wall of the bung.

Preferably the flange depends downwardly and inwardly into the space within the bungs to form a frustum. The invention also embraces a bottom bar for use with such a battery plate.

Thus in the construction in accordance with the invention the increase in length of the spines can be accommodated by the bottom bar, the spines simply sliding down into the bungs without impairing the seal with the resilient flange.

In addition the preferred embodiment of the invention permits a bottom bar to accommodate spines of slightly different diameters by virtue of the provision of the flange which is capable of yielding by different amounts according to the size of the spine which is slid into it.

Further features and details of the invention will be apparent from the following description of one specific embodiment which is given by way of example with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a bottom bar in accordance with the invention; Figure 2 is a plan view of the bottom bar of Figure 1; Figure 3 is a sectional elevation on the line 3-3 in Figure 2 on an increased scale; and Figure 4 is a sectional elevation on the line 4-4 in Figure 2, also on an increased scale.

As seen in Figure 1 the bottom bar is a single moulding of plastics material, such as polypropylene, comprising a number of bungs 10 connected in a line.

As best seen in Fig ures 3 and 4, each bung is of a generally tubular form having a hole 12 in its upper end. Each bung includes a lower portion 14 of part annular form integral at two diametrically opposite points with a respective connecting member 16 of inverted channel form connecting the bung to a similar bung on each side. Integral with the lower portion 14 is an upper tubular portion 17 of reduced wall thickness which converges to an upper edge 20.

Depending from the upper edge 20 is a resilient integral flange 22 forming a frustum extending a short distance downwardly and inwardly into the space defined by the tubular portion 18 and inclined at about 25 to the vertical.

In use, the bottom bar is fitted to a multi-tubular battery plate so that each bung closes the bottom of a respective tube and each spine slides into its respective bung. The bottom bar is pressed home until the material of the tube 24 contacts the external annular shoulder 26 between the lower and upper portions 14 and 18 of the bung, as shown in dotted lines in Figure 4. The spine within the tube has a diameter slightly greater than that of the hole defined by the lower edge of the frustum 22, and the spine thus presses the frustum radially outwardly so that the frustum is sealed to the surface of the spine.

In a typical embodiment the total height of each bung is 10 mm, and the spines may extend 5 mm down into them. As the spines of the positive plates extend in service, they will merely slide further down into the bungs. It will be appreciated that in the specific example 5 mm of expansion can be accommodated within the bungs. Thus the expansion of the spines is accommodated at the lower ends of the plates and the battery seals are not placed under stress.

It will be appreciated that a further advantage of this construction is that it can accommodate spines of slightly differing diameters merely by deforming the resilient flange 22 to a greater or lesser extent.

Sometimes the spines in such battery plates have a series of "flights" or webs arranged down their length and offset by 1800. These flights are intended to engage the inner surface of the tubes to maintain the spines centrally within the tubes. If such a flight is positioned immediately above the flange of its respective bung, expansion of the spine into the bung will be prevented. Nevertheless the construction will provide the advantage that the bottom bar can accommodate spines of different diameters.

It has been found in practice that if all the bungs are open bottomed, a small amount of active material can accumulate at those points where the plates rest on the mud ribs on the cell floor, and that this can ultimately lead to short-circuiting of adjacent plates of opposite polarity. Thus in accordance with a preferred feature of the invention, at least those bungs that will, in use, be situated over a mud rib have closed bottoms. Thus in a specific embodiment, a bottom bar has five open-bottomed bungs, then two closed-bottom bungs alternately.

Various modifications and alterations may be made to the construction described, but it will be appreciated that it is important that the bungs make a seal with the spines. If there is not an adequate seal, active material will fall out of the plate and will either lead to "sludging" and eventual shortcircuiting of the plates if the bungs on the bottom bar are open at the bottom, or will lead to the cavity within the bungs becoming filled with active material thus preventing movement of the spines if the bungs are closed at the bottom.

Claims (9)

1. A multi-tubular battery plate comprising a plurality of tubes containing active material each tube also containing a conductive spine extending along its length and being closed at one end by a respective bung, the bungs being connected together to form a bottom bar and each affording a space within it accommodating the end of a spine and having a seal which surrounds the spine and through which the spine may slide.

2. A battery plate as claimed in Claim 1 in which each bung is of generally tubular form, and the seal comprises a resilient flange integral with and projecting inwardly from the wall of the bung.

3. A battery plate as claimed in Claim 2 in which the resilient flange depends downwardly and in wardly into the space within the bungs to form a frustum.

4. A battery plate as claimed in Claim 1 or Claim 2 in which at least some of the bungs are open bottomed.

5. A battery plate as claimed in Claim 4 in which those bungs which will, in use, be positioned above a mud rib on the floor of an electric cell have closed bottoms.

6. A battery as claimed in any one of the preceding Claims in which all the bungs are integral and formed of plastics material as a single moulding.

7. A battery as claimed in any one of the preceding Claims in which each bung affords an external peripheral rib in engagement with the end of a tube.

8. A multi-tubular battery plate incorporating a bottom bar substantially as herein described with reference to the accompanying drawings.

9. A bottom bar for a battery plate as claimed in any one of the preceding Claims comprising a plurality of bungs connected together each bung affording a space within itto accommodate the end of a spine and having a seal adapted to surround the spine and permit the spine to slide through it.