GB2072930A

GB2072930A - Grid plate

Info

Publication number: GB2072930A
Application number: GB8015115A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-03-27
Filing date: 1980-05-07
Publication date: 1981-10-07
Also published as: DE3011836A1; DE3011836C2; GB2072930B; IT8021602V0

Abstract

A grid plate for an accumulator, including a section of metal strip (8) formed with cut-out slits (12) which is expanded transversely of the slits to form a mesh, and also having a connecting strip (3) extending along one edge and having a connecting tab (10) extending from it, the tab being of reduced thickness compared to the slit region. <IMAGE>

Description

SPECIFICATION Grid plate for accumulators This invention relates to a grid plate for use as a positive or negative electrode of an accumulator battery, the plate being of the kind which is formed of expanded metal with a plain edge region forming a connecting tab.

Grid plates of this type are shown in U.S. Patent Specifications 3,853,626 and 3,945,097.

For the purpose of economic production of the grid plates and to reduce the amount of scrap or waste produced in the process of forming the connecting tabs by stamping a metal strip section is used as starting material, the said section comprising two marginal strips provided with slits for forming a mesh, and a middle strip which is not formed with the said slits. The two marginal strips of the metal strip section which are provided with the said slits are initially expanded substantially transversely of the length direction of the said slits, so that a mesh is formed on each of the two sides of the middle strip and thereafter a stamping cut is made by means of which two side-by-side grid plates are formed, the connecting tabs being cut out from the middle strip not provided with slits.

The stamping cut forming the grid plates is so positioned relative to the metal strip section that the connecting tabs present on those two grid plates which are thus formed are, as it were, disposed in an intermeshed formation one behind the other in the region of the middle strip.

In spite of these precautions in the area of the middle strip of the metal strip section which serves for the formation of the connecting tabs and is not provided with cut-out slits, it has, however, been found that there is still a considerable accumulation of scrap material, because the dimension of the connecting tabs in the length direction of the separate grid plates only corresponds to a fraction of the length dimension of the said plates, so that that area of the middle strip present in the stamping pattern between two following connecting tabs has to be cut away and accumulates as waste.The dimension of the connecting tabs longitudinally of the grid plates is mainly dependent on the crosssection of the connecting tabs necessary to carry the current from the individual grid plates and accordingly is also substantially determined by the thickness of the metal strip section which is used for the manufacture of the grid plates.

Therefore, the thicker are the metal strip sections used for the manufacture of the grid plates constructed as meshed grids, the narrower the connecting tabs then have to be made on the grid plates, in order to obtain the overall crosssection most favourable for the dissipation of the electrical charge. The amount of waste produced in the middle strip of the metal strip section is accordingly found to be greater as the metal strip sections used as initial material for the manufacture of the grid plates are thicker.

However, as is apparent from German Gebrauchsmuster 79 35 703, it is particularly advantageous to produce grid plates for the formation of sets of electrode plates for accumulator batteries from metal strip sections which have a material thickness which is equal to or greater than the spacing member between the rows of cut-out slits which are provided in the metal strip section and which are adjacent one another and thus the arm width of the meshes on the expanded metal strip section corresponds to its material thickness, while the arm thickness thereof is equal to the spacer member between the cut-out slits. The grid plates are then in fact given a three-dimensional form, with which the nodal points have from the outset a thickness which is not greater than the thickness of the mesh grid in the other regions.

In connection with the manufacture of grid plates of the type as specified above, the present invention seeks to minimise the amount of waste occurring in that region of the metal strip section which serves as starting material, in which the connecting tabs of the grid plates are formed by a stamping cut. Accordingly, the invention seeks to provide grid plates of the type as hereinbefore specified with a connecting lug or tab which, while maintaining an overall cross-section most suitable for the dissipation of the charge, is such that it can be produced with the smallest possible accumulation of waste material.

Accordingly the present invention provides a grid plate for an accumulator, which plate includes a section of metal strip formed with cut-out slits and expanded substantially transversely of the length direction of the said slits to form a mesh and also includes a plain strip without slits extending at least along one edge and having a connecting lug or tab extending therefrom, the said tab being of reduced thickness compared to the slit region.

In an assembled accumulator the connecting tabs are provided in areas which are offset longitudinally in relation to one another, and the connecting tabs respectively lying in the same length region have a conducting connection with one another, so it is possible, while maintaining the overall cross-section of the connecting tabs which are best suitable for the safe dissipation of the charge, for the material thickness thereof to be such that they can be produced with a longitudinal dimension which corresponds almost to half the length of the respective grid plate.As compared with the half length of a grid plate, the connecting tab does in fact only have to be shorter by an amount sufficient to maintain a suitable spacing between the connecting tabs of the adjacent plates of the assembled set, the plates being arranged with the tabs staggered relative to each other so as to-avoid flashover between the plates.

Since the waste strip formed in this case has a comparatively small thickness, the accumulation of waste is still small, although the length of the waste strip may be somewhat greater than half the length of the grid plate.

Preferably the grid plates are made from a metal strip section including two slit regions arranged in juxtaposition, having a plain strip between them whose thickness is less than that of the two marginal slit regions adjacent longitudinal portions of the plain strip forming the tabs of each plate. In this way the accumulation of waste in that surface region or area of the metal strip section which serves for the production of the connecting tabs is almost completely avoided.

The plate may be so formed that the plain strip has one surface which is coplanar with the surface of the slit region of the plate, the other surface being recessed to provide the reduced thickness.

Alternatively the strip may have both surfaces recessed relative to the surface of the slit region.

Preferably the free end of the connecting lug or tab is provided with a bent-over portion for connection to an adjacent plate. The bent-over portion of the connecting tab preferably has a greater thickness than the section of the tab which is parallel to the plane of the plate.

Some embodiments of the invention will now be described by way of example with reference to the accompanying drawings, wherein: Figure 1 is a diagrammatic elevational view of a grid plate for accumulator batteries with a mesh grid which is formed by expansion deformation from a metal strip section with cut-out slits, Figure 2 is the elevation of a metal strip section formed with cut-out slits for the formation of a grid plate according to Figure 1, Figure 3 is a cross-section through the metal section according to Figure 2, Figure 4 is likewise a cross-section through the metal strip section according to Figure 2, but showing a somewhat modified embodiment, Figure 5 is the elevation of a metal strip section, which is suitable for the simultaneous manufacture of two grid plates in an arrangement in which they are juxtaposed in pairs, Figure 6 is a cross-section through the metal strip section according to Figure 5, Figure 7 is likewise a cross-section through the metal strip section according to Figure 5, but showing a somewhat modified embodiment, while Figure 8 is a cross-section through a set of plates composed, for example, of grid plates according to Figure 1.

Figure 1 of the drawing shows a grid plate 1 for the formation of sets of electrode plates for an accumulator which comprises a mesh 4 between a bottom, continuous marginal strip 2 and a top, continuous marginal strip 3.

Formed in one piece on the upper, mesh-free marginal strip 3 is a connecting tab 5, the purpose of which is to interconnect several grid plates 1 disposed in spaced relation to one another to form a set of negative or positive plates. One such set 6 of plates is shown, for example, in Figure 8 in vertical section, in which case four grid plates 1 are connected by way of their connecting tabs 5 to form the plate set 6.

The grid plate 1 according to Figure 1, and respectively each grid plate 1 according to Figure 8, can be produced from a metal strip section 7, which consists, for example, of lead or lead alloys and is reproduced as a constructional example in Figure 2.

This metal strip section 7 may either have the profiled cross-section which can be seen in Figure 3 or it may have the profiled cross-section which is shown in Figure 4 with a wide profiled section 8 of a greater material thickness 9 and also a narrow profiled section 10 of a smaller material thickness 11, as is clearly shown in Figures 3 and 4.

In the region of its wide profiled section 8 with a greater material thickness 9, the metal strip section 7 is provided with rows 12 of cut-out slits 13 which extend parallel to one another, the said slits always having the same length 14 in the longitudinal direction of the said section. In adjacent rows 12' and 12", the said slits 13 are always arranged offset from one another longitudinally by such an amount that each slit 13 of the one row 12' overlaps the spacing region 1 5 between the ends of two slits 13 in the adjacent row 1 2", and vice versa. Each spacing region 15 between the ends of two cut-out slits 13 of the one row 12' is accordingly arranged approximately in the middle region of a cut-out slit 13 of the adjacent row 12", and vice versa.

It is apparent from Figures 2 to 4 that the slits 13, in the wide profiled section 8 having a larger material thickness 9, extend only over the middle region 16 thereof, whereas its side regions 17 and 18 do not have any such cut-out slits 13.

If the metal strip section 7 formed in the middle region 16 of its wider profiled section 8 of greater material thickness 9 having cut-out slits 13 is subjected to a stretching force in a direction substantially transversely of the length direction of the said slits 13, then the individual slits 13 are each enlarged to form diamond-shape or rhombic meshes 19, so that they form a grid 4 for the grid plate 1 in accordance with Figure 1. The side regions 17 and 18 of the wider profiled section 8 having a greater material thickness 9 in this case simultaneously form the marginal strips 2 and 2 of the grid plate 1.

Either before the expanding stress has occurred, or even after it has taken place, a stamping cut is made on the metal strip section 7 in accordance with the outline which is indicated by chain-dotted lines in Figure 2 and as a result establishes the shape of a grid plate 1 according to Figure 1. The outline for the grid plate 1 in this case overlaps from the wide metal strip section 7 of greater material thickness, into the narrow profiled section 10 of small thickness 1 1 and forms the connecting tab 5 for the grid plate 1.

Consequently, the connecting tab 5 has a wall thickness which is equal to the smaller material thickness 1 1 of the narrow profiled section 1 0; however, the region 21 is in this case of such dimensions as to maintain the overall crosssection of the connecting tab 5 which is necessary for dissipating the electrical charge. This may, for example, be seen from the fact that the length region 21 for the formation of the connecting tab 5 almost corresponds to half the length of the grid plate 1.

In carrying out the stamping cut corresponding to the contour 20 in Figure 2, waste is only produced on the metal strip section 7 over the length region of grid plate 1, which is due to stamping the narrow profiled section 10 of small material thickness 11 over the length region 22.

The amount of waste or scrap thus remains the same, independently of whether the narrower profiled section 10 of small material thickness 11 on the metal strip section 7 is arranged symmetrically in relation to the wide profiled section 8 of larger material thickness 9, as will be apparent from Figure 3, or even whether it has for this purpose a position offset to one side, as shown in Figure 4.

It is apparent from Figure 5 of the drawing that it is possible further to reduce the accumulation of waste when the grid plates 1 according to Figure 1 are produced if a metal strip section 23 according to Figures 5 to 7 is used as initial material instead of a metal strip section 7 in accordance with Figures 2 to 4.

This metal strip section 23 has a narrow, striplike control section 24 with a small material thickness 25 and, on each side thereof, a wide profiled section 26', 25" with a greater material thickness 27.

Each wide profiled section 26', 26" of larger material thickness 27 is provided in its middle region 28' or 28" with parallel rows 12 of cut-out slits 13, which are of corresponding length 14 and are disposed offset from one another longitudinally in the adjacently arranged rows 12' and 12". In this arrangement, the offset position of the slits 13 is also such that each slit 13 of the one row 12' overlaps the spacing zone 15 between the ends of two slits 13 in the adjacent row 12" and vice versa.

On both sides of the middle region 28' and 28", respectively, which contain the slits 13, lateral zones 29', 30' and 29", 30" are left which do not have any slits 13.

If the metal strip section 23, which comprises the cut-out slits 13 in the middle regions 28' and 28" of its two wider profiled sections 26' and 26", is subjected to a stretching or expanding stress substantially transversely of the length direction of the said slits 13, then the individual slits 13 are each enlarged to form diamond-shaped or rhombic meshes 19, such as those which can be seen in Figure 1. In this case, two mesh grids 4 are formed in juxtaposition in the metal strip section 23 so that the side regions 29' and 30' and the side regions 29" and 30", respectively form marginal strips 2 and 3 for a grid plate 1.

Either before, or even after, the application of the expanding stress, a stamped cut can be made on the metal strip section 23, the contours 31' and 31" of the said cut being indicated by chaindotted lines in Figure 5. It is therefore apparent that the two outlines 31' and 31" of the stamped cut in the region of the strip-like, middle section 24 of small material thickness 25, do, as it were, engage in toothed formation one within the other, and always length regions 32' and 32" of the two contours 31' and 31" are disposed adjacent each other in the profiled section 24.

In this case, only a short length region 33 remains between the two length regions 32' and 32", and it is only this region 33 which forms waste when the stamping cut is made when two grid plates 1 arranged juxtaposed in pairs are made from the metal strip section 23.

Consequently, using the construction of the metal strip section 23 in accordance with Figures 5 to 7, it is also possible to substantially reduce the accumulation of scrap or waste as compared with the formation of a metal strip section 7 in accordance with Figures 2 to 4.

When the narrow profiled sections 10 or 24 of small material thickness 11 and 25, respectively, on the metal strip sections 7 and 23, respectively, have the width shown in the drawings, it is advantageous for the capable of being bent over in the manner which can be seen from Figure 8. It then becomes possible in a simple manner for the bent-over portions of the connecting tabs to be arranged to abut with their free ends against the apex of the likewise bent-over connecting tabs 5 of adjoining grid plates 1 and form a connection at this position between the connecting tabs 5 of adjacent grid plates 1 , for example, by soldering or welding.

In this way the additional connecting bars which hitherto were usually employed and which were positioned over the connecting tabs of all juxtaposed grid plates 1, and connected to the said plates, can be dispensed with.

In this connection, it has in many cases proved to be advantageous if the bent-over portion of the connecting tab 5 has a greater material thickness than that connecting tab section which remains parallel to the plane of the plates, because thereby sufficient material is then made available for forming a safe connection between the ccnnecting tabs 5 of adjacent grid plates 1. That region or area of the connecting tabs 5 which has the greater material thickness could, for example, be formed on metal strip sections 23 according to Figures 5 to 7 by the fact that the contours 31' and 31" of the stamping cuts always extend, even if only slightly, into the lateral regions 29' and 29" of the metal strip sections 26' and 26" having a larger material thickness 27.

On the other hand, with a metal strip section 7 according to Figures 2 to 4, it would be necessary, for this purpose, to provide a bead-like thickened portion on the outer longitudinal margin of the narrow profiled section 10 having a small material thickness 11.

Claims

1. A grid plate for an accumulator, which plate includes a section of metal strip formed with cutout slits and expanded substantially transversely of the length direction of the said slits to form a mesh and also includes a plain strip without slits extending at least along one edge and having a connecting lug or tab extending therefrom, the said tab being of reduced thickness compared to the slit region.

2. A grid plate according to claim 1 in which the tab is formed by stamping.

3. A grid plate according to claim 1 or claim 2, which is formed as one of a pair, from a metal strip section including two slit regions arranged in juxtaposition, having a plain strip between them whose thickness is less than that of the two marginal slit regions adjacent longitudinal portions of the plain strip forming the tabs of each plate.

4. A grid plate according to any preceding claim in which the plain strip has one surface which is coplanar with the surface of the slit region of the plate, the other surface being recessed to provide the reduced thickness.

5. A grid plate according to any of claims 1 to 3 in which the plain strip has both surfaces recessed relative to the surfaces of the slit region.

6. A grid plate according to any preceding claim in which the free end of the connecting lug or tab is provided with a bent-over portion for connection to an adjacent plate.

7. A grid plate according to claim 6 in which the bent-over portion of the connecting tab has a greater thickness than the section of the connecting tab which is parallel to the plane of the plate.

8. A grid plate according to any preceding claim in which the bent-over portion of the connecting tab is formed from a region or area of the metal strip section, which corresponds to that of the slit region.

9. An accumulator having grid plates in accordance with any preceding claim.

10. A grid plate substantially as herein described with reference to the accompanying drawings.