COVER FOR A STORAGE BATTERY

Abstract: A cover for a storage battery adapted to contain an electrolyte in at least two cells provided side by side, and a method of making such a cover and a battery comprising such a cover, said cover comprising channels (3) in order to convey gas being developed in the cells (5) to the exterior of the battery through a common outlet. Said channels are formed in the top of the cover, and are defined by walls (6) which protrude perpendicularly to the top of the cover, and in partition walls (9) in the cover, adapted to form partitions between the cells (5) in co-operation with partition walls in a battery box, are apertures which make adjacent cells communicate with each other through said channels (3), and at least one cell communicates with the surroundings. The channels (3), which can be shaped like labyrinths, are cast as open channels in the top of the cover, whereupon a channel bottom is formed or fastened subsequently to the casting, preferably by melting together the edges (7) and the cast walls (6) of the channels (3), said melting being preferably performed simultaneously with the melting together of the cover and a battery box.

Description: Cover for a Storage Battery. The present invention relates to a cover having a venting device for a storage battery, and a battery comprising such a cover. Moreover, the invention relates to a method of making such a cover having a suitable venting device and such a battery. It is known to equip batteries, for instance a lead battery, with devices for venting of gas being developed in the cells. Usually the gas venting apertures are combined with plugs situated in the holes for filling of acid. The simplest types of such plugs have a small opening in the top of the plug, in order that the developed gas may escape easily. In order to prevent splashing of acid through the gas venting opening a tongue or a simple channel system is provided in the lower part of the plug. With such a construction the developed gases are for instance vented into the space where the battery is situated. Moreover .are known (DAS 1240965, DAS 1277396 and DAS 2358517) devices which collect the gas from each cell and convey it away through a hose. Other known solutions for providing communication from cell to cell consist in that the cover is cast in two parts, each having a groove, so that mutually facing grooves in the two parts define channels. Also this solution is expensive with respect to production. Common to all said devices is, however, whether the batteries have boxes of hard rubber or of polypropylene, that the production costs are substantially higher than for corresponding batteries without such devices. The requirement of tight plugs and a common gas outlet from all the cells is primarily an economical problem, and as mentioned the known solutions resul.t in relatively high production costs. The object of the present invention is to provide a cover for a storage battery which can be made in an economi¬ cally favourable manner, and which simultaneously permits that the possibility of placing the acid filling holes freely is maintained. Another object of the invention is to provide a suitable and simple method of making such a cover and of making a battery having such a cover. According to the invention the above objects are achieved with a cover, a storage battery and a method, respect¬ ively, as defined in the succeeding claims. The present invention provides a multi-cell storage battery having a gas venting device which with respect to the forming tool and: the assembly work does not depart very much from a conventional embodiment without such a device, with respect to costs. Moreover, it is safer with respect to self-discharge and brings about several advantages relatively to existing devices. When for instance tight plugs, communicating channels between the cells and a common gas outlet are employed, freedom of choice with respect to the location of the acid filling holes in the cover is achieved. This can be taken advantage of in order to achieve a better emptying of the cells. This is desirable for storing of charged, unfilled batteries. Said holes can be located along a longitudinal edge of the cover, so that when the battery is tilted towards said edge mainly all the electrolyte is able to flow out when the plugs are unscrewed. The cover according to the invention comprises channels which provide communication from cell to cell, and said channels are partly defined by walls in the cover which protrude perpendicularly to the top of the cover. This makes it possible to cast said walls integrally with the cover. The only amendment with respect to production is that the casting mould for the cover must be modified. The channels can be completed by fastening a bottom to the edges of said walls, by gluing or welding. According to a favourable embodiment, however, the bottom of the channel system is formed by heating of the edges in order to cause that material from adjacent edges is melted together. This can advantageously be performed in con¬ nection with joining together of the cover and a battery box in a known manner by fusion welding. Such welding can be carried out by heating, by use of a so-called heat mirror, the edges of the partition walls in the cover and partition walls in the box which are adapted to co¬ operate to form tight walls between the cells and tight outer walls. Said heating of the edges of the channel walls can be performed simultaneously with the heating of said walls and partition walls in the box and the cover, for instance by use of the same heat mirror as for these. Thereby is avoided a separate heating in order to achieve melting together of the channel walls-. For the latter embodiment or method the heat mirror must have surfaces which heat the edges of the channel walls simultaneously with said other edges of the walls and partition walls. This will be taken into account when making the heat mirror and has small influence, if any, on the heat mirror costs. The channels may in their simplest design be channels which protrude some distance into two adjacent cells. In the finished battery the channels are situated above the electrolyte level, and they, therefore, establish communication for gas between the cells. However, in order to increase the safety against bypass of electro¬ lyte the channels may be formed as labyrinths. These may in the principle be made in the same manner as straight channels, in that the channel walls are shaped in such a manner that they define open channels, which are subse¬ quently closed, either by fastening a bottom to the edges of the channel walls or by melting together of the edges of the channel walls, in the manner described above. Regardless of whether the channels are relatively short channels or labyrinths the channel walls which are per¬ pendicular to the top of the cover are made by casting them integrally with the cover. The most near at hand is to cast said channels on the inner side of the cover. It is, however, also possible to cast the channels on the outer side of the cover, in such a manner that the cover top is recessed in the channel area, so that the recessed portion of the cover top forms the bottom of the channels , while the upper wall must be provided separately, i.e. after the casting of the cover. Also in this case the top may be made as a plate which is fastened to the upper edges of the channel walls and forms the upper top portion of the cover. Alternatively may be used the same method as when the channel walls protrude downwardly from the cover, that is to say melting together of the upper edges of the channel walls. In this case this melting together must be performed separately, and may be performed prior to or after the joining together of the cover and the battery box. When designing battery covers for practical and economi¬ cal use the choice of solution with respect to channels is a compromise between what leads to a simple forming tool and a low cycle period at the cover manufacturer, simple assembly and versatility with respect to applica¬ tions for the battery manufacturer and the ability to fulfil as many requirements as possible for the consumer. The invention will hereinafter be explained more detailed by means of embodiments shown in the accompanying drawings, Fig. 1 shows one half of a cover according to the invention, in a condition prior to closing of the cast channels. Fig. 2 shows a section along the line A-A i fig. 1, and moreover are shown the upper portions of walls in a battery box to which the cover is to be fastened. Fig. 3 shows in perspective a portion of the cover in the area where channels have been cast. Fig. 4 shows a section perpendicularly through the channel walls and the cover top shown in fig. 3. Fig. 5 shows in perspective the same portion as shown in fig. 3 after the channels have been closed at their bottoms. Fig. 6 shows a section perpendicularly through the walls and the bottom of the channels and the cover top. Fig. 7 shows how the cover has been raised relatively to a battery box, in order to introduce a heat mirror for melting the edges .of the vertical walls which are to be joined, possibly also for making a channel bottom. Fig. 8 shows, seen towards the underside, a battery cell provided with a labyrinth channel which provides communication between the cell and an adjacent cell to the left of the cell shown. Fig. 9 shows in an enlarged scale a device which may be used in one of the end cells, between channels in the cell and an outlet aperture. Fig. 10 shows a section along the line B-B in fig. 9. Fig. 11 shows, in the same manner as fig. 1, a cover seen towards the underside, in another embodiment, and Fig. 12 shows a section along the line A-A in fig. 11. Figs. 1 and 11 show a cover defined by outer walls 10, and having partition walls 9 which together with corresponding walls in a battery box are adapted to form partitions between the cells. Thus, the partition walls 9 define cell units 5, together with the outer walls 10 and the top of the cover. The cover has holes 1 for filling of acid and replenishment of water. Channels 3 are formed from cell to cell, defined by walls 6 being cast integrally with the remainder of the cover. The inlets and the outlets, respectively, of the channels 3 are located mainly in the middle of each cell, except from in the end cell furthest to the right in fig. 1. The channels 3 constitute labyrinths 12. Figs. 2 and 12 also show an outer wall 10 and partition walls 9 between the cells, and the upper portions of partition walls 9 in a box to which the cover is to be fastened are also shown. It appears that the partition walls of the cover and the box, respectively, are in mutual engagement with their lower and upper edges 24, respectively, and the same applies to the outer walls 10. Moreover, the cover may be provided with bevelled lugs 25 for mutual guiding of the walls when the cover is lowered towards the box. The channels 3, which are' defined by the walls 6 cast integrally with the' cover top 8, are open in the downward direction, and the walls 6 terminate in free edges 7. In order to make closed channels 6 the edges 7 can be melted, so that material from adjacent walls flows together. This may, as mentioned, be carried out simultaneously with the melting and flowing together of the partition walls 9 of the cover and the box along their edges. Thus, figs. 1, 2, 11 and 12 show the cover in its condition after the casting. In fig. 2 the section is taken through a filling hole in cell No. 2 from the right. The device in the cell furthest to the right in figs. 1 and 2 will be explained more detailed. Said device, which comprises a hopper 17 and a vertical tube.18, is situated between the outlet c the channel 3 and the gas venting aperture 11. The channel 3, which in this cell has its inlet close to- the partition wall 9, ends in an opening 19 in the hopper 17 (fig. 1). The hopper 17 is closed at the top, and may contain a disc 20. Said disc may constitute a check valve, and it may constitute a flame preventer, in order to prevent that a possible fire outside of the battery propagates into the battery. Gas in the channel 3 coming from cell No. 2 from the right is admitted into the cell 5 furthest to the right, and gas from the cells furthest to the right may flow through the channel 3 and into the hopper 17. The gas may flow up through the disc 20 and out through the aperture 11. If gas condensates in the hopper the acid may flow down into the cell through the tube 18 which protrudes down into the electrolyte in the cell. The stability requirement with respect to the tool of the cover manufacturer leads to the conclusion that the width of the channels 3 prior to the melting together should be relatively large. In order to achieve an adequate fusion welding when making the bottom of the channels the channel width should be so small that the mass is not pulled out by the heat mirror 14 (fig. 7). Moreover, the channel walls 6 should be so thick that there is sufficient of mass to seal the channels by means of a typical melt down of 1 to 3 mm. Too thin channel walls 6 may lead to mechanical unstability which results in that the walls tend to tilt during the melting together of the channel edges, and the danger of leakage from the channels is severe. In order to reduce the cycle period when producing the covers it is advantageous that the walls are as thin as possible, thereby reducing the amount of heat and the cooling period. A channel width 3 of approximately 0,5- to 3 mm and a wall thickness of 1 to 5 mm are found to be practical values. With a common gas outlet there must be at least one channel between each neighbour cell and a channel leading to the surroundings. In for instance a 6-cell battery having two possible venting areas there will be 5 + 2 = 7 channels (five neighbour cells and two outlets). When seven equal labyrinths are distributed over six cells, each labyrinth will cover 6/7 of the cell width. This is inconvenient to cover manufacturers, who cannot divide the forming tool in a simple manner. By making the labyrinths different, as shown in fig. 1, it is possible to achieve simpler equipment of manufacture without too large functional losses. The labyrinths also contribute to a certain tilting safety, and as shown in fig. 1, channel portions may be perpendicular to each other in order to avoid a siphon effect when the battery is tilted and laid on its longitudinal sides or the end surfaces . Figs. 3 and 4 show, in perspective and in a vertical section, respectively, a portion of the cover top 8 and the cast channel walls 6 which define the channels 3. Fig. 5 and 6 show, in the same manner as figs. 3 and 4, the cover top 8, cast walls 6 and a bottom 13 for the channels 3, fastened or made by melting together. Fig. 7 illustrates how a heat mirror 14 is used to join the cover and the box. The cover 15, comprising a top 8, outer walls 10, a hole 11 and inner, not shown partition walls having lower edges 24, is presupposed to have inner, open channels as shown in figs. 1, 2, 3 and 4, and are held in a distance above the box 16, which comprises outer walls 10 and inner partition walls having upper edges. In the box all the elements which the box is to contain have been mounted. From the shown position the heat mirror 14 is introduced between the cover 15 and the box 16, and is lowered into engagement with the box, while the cover is lowered into engagement with the upper side of the heat mirror 14. Thereby the edges of the outer walls 10 and of the partition walls in the cover and the box are heated, and moreover the lower edges 7 of the walls 6 (not shown in fig. 7) which define the channels 3 are heated. Thereupon the cover 15 is raised, the heat mirror 14 is retracted to the shown position, and the cover 15 is lowered towards the box 16, so that the outer walls 10 and the not shown partition walls in the cover and the box, respectively, are situated edge to edge and are pressed somewhat together, so that the edges melt together. Because of the melting of the edges 7 of the walls 6 material from neighbour walls flows together and forms a bottom, such as the bottom 13 shown in figs. 5 and 6. Fig. 8 shows, seen towards the underside of a cover, a cell portion 5 defined by outer walls 10 and partition walls 9. A channel 3, shaped as a labyrinth 12 of a simpler type than that shown i figs. 1 and 2, connects the cell portion 5 with the neighbour cell to the left in the figure. The labyrinth channel 12 starts in the partition wall 9 to the right, and terminates on the left side of the same partition wall, inside of the cell portion 5. In the partition wall 9 to the right is an aperture into a corresponding labyrinth channel to the right of the shown cell portion 5. Moreover is shown a hole 1 for filling of acid and replenishment of water. Fig. 9 shows another embodiment of the device shown in the cell portion furthest to the right in fig. 2, adapted to achieve return of acid to the cell to which this cell portion belongs. Fig. 10 shows a section along the line B-B in fig. 9. To the left in the figures is shown a channel 3, which ends in a hopper 17 having a tube 18 protruding down from the bottom. The channel 3 ends in the hopper in an opening 19. Higher in the hopper 17 is a disc 20 which functions as a check valve, as explained in connection with figs. 1 and 2, and the outlet 22 from the hopper is above the disc 20, below the cover top 8. The disc 20 may rest against a shoulder 21 in the hopper 17. The hoppers shown in figs. 1, 2, 9 and 10 are only necessary in the common gas outlet for all the cells of a battery when return of acid is desired. When the location of the battery during use is uncertain, as for instance in the engine compartment of an automobile, it is, however, appropriate to make the battery symmetrical about its vertical transverse middle plane (i.e. the furthest to the left in figs. 1 and 2), so that the gas venting aperture is accessible notwithstanding the direction in which the battery is placed. Thus, when an end cell is to communicate with the gas venting aperture there may be provided an outlet opening and a device for return of acid associated with each of the end cells, and the outlet opening which is not used is closed, for instance by the insertion of a plug or a stopper. The discharge does not necessarily have to be from one of the end cells. . It is possible to provide discharge from one of the intermediate cells, in that the channels between the cells are connected to the intermediate cell in question. Moreover, the outlet aperture or apertures may be situated in the cover top or in one of the side walls or both the side walls. The invention is not limited to labyrinth channels, in that the channels may have a simple design, for instance relatively short and straight channels. Irrespectively of the design of the channels they can be made by casting, integrally with the cover, in such a manner that channels without bottom are formed primarily. As explained, the bottom may be made in several ways, but it is considered to be particularly advantageous to make the bottom by melting together the edges of the channel walls, which may possibly be performed simultaneously with the melting together of the edges of the remaining walls in the cover and the box, respectively.

Claims: CLAIMS.- 1. Cover for an electric storage battery adapted to contain an electrolyte in at least two cells provided side by side, said cover comprising channels (3) in order to convey gas being developed in the cells to the exterior of the battery through a common outlet, said channels being formed in the top of the cover and are defined by walls (6) which protrude perpendicularly to the top and by a bottom (13), and in partition walls (9) in said cover which together with partition walls in a battery box are adapted to form partitions between the cells are apertures which make adjacent cells communicate with each other through the channels (3), and at least one cell communicates with the surroundings, c h a r a c t e r i z e d i n that said bottom (13) is made by melting together of the edges (7) of the walls (6) protruding perpendicularly to the top, in such a manner that said edges are sealingly melted together. 2. Cover as defined in claim 1, c h a r a c t e r i z e d i n that the ratio between •the thickness of the walls (6) defining the channels (3) and the width of the channels is within the range 0,4 to 5 3. Cover as defined in claim 1 or 2, c h a r a c t e r i z e d i n that f.he channels (3) form labyrinths (12) in order to achieve a long flow ' path for the gases from cell to cell. 4. Cover as defined in.claim 1 to 3, c h a r a c t e r i z e d i n that a hopper (17) in which the channel ends is provided between the channel (3) in a cell and an outlet opening (11), and that said outlet opening is situated higher than the end of the channel, and a check valve or a gas permeable disc (20) is provided in said hopper, between the end of the channel and the outlet opening (11). 5. Cover as defined in claim 4, c h a r a c t e r i z e d i n that a hopper is provided between each end cell and an associated outlet opening, in order to be used at choice. 6. Cover as defined in claim 4 or 5, c h a r a c t e r i z e d i n that the hopper (17) has a tube (18) protruding downwardly from the bottom, adapted to protrude down into the electrolyte. 7. A method of making a cover for an eletric storage battery, said battery being adapted to contain an electrolyte in at least two cells which are provided side by side, said cover comprising channels in order to convey gas being developed in the cells to the exterior of the battery through a common outlet, said channels being cast as open channels in the cover top, in such a manner that they are defined by walls protruding from said top, whereupon a bottom which closes the channels and which bridges partition walls in the cover is formed, c h a r a c t e r i z e d i n that said bottom is formed by melting of the free edges of the walls protruding from the top, in such a manner that the edges melt together. 8. A method as defined in claim 7, c h a r a c t e r i z e d i n that the melting is performed in connection with the melting together of the cover and a battery box. 9. A method as defined in claim 8, c h a r a c t e r i z e d i n that the melting in order to form the bottom is performed by means of the same melting tool as used for melting the edges of partition walls in the cover and partition walls in the box, respectively, which are adapted to co-operate in order to separate the cells from each other and outer walls adapted to seal the battery externally.

Inventors: SVERDRUP GUNNAR, SVERDRUP, GUNNAR
Applicants: SOENNAK BATTERIER, SOENNAK BATTERIER A.S.
Application year: 1985
Main classification: H01M2
IPC codes: H01M2