Title of Invention

LEAK RETARDANT AUTOMOTIVE BATTERY

Abstract

a housing (1) for a plurality of cells (c1 to c6) housed therein and having a battery cover (2) fitted and heat-sealed to said housing to overlie the cells; a pair of terminals (T1, T2) mounted on the battery cover and connected to the cells; wherein: said battery cover is divided into two compartments (2, 2') by means of a central blockage (X) such that each compartment overlies a set of cells; said battery cover being connected by means of side vent lines (3, 3') so that cells in each set are in communication with each other; and said side vent lines are connected respectively at one end to said central blockage (X) and a vent cap assembly (Y) is provided at the other end of each side vent line for allowing the escape of vented gases.

Full Text

This invention relates to a leak retardant automotive battery. Background of the Invention For automotive applications, batteries with free electrolyte are still maintaining their pre-eminent position in the industry primarily due to lower cost as well as ease of manufacture. Furthermore, the flooded battery designs are known to have certain technical advantages in comparison to the acicUstarved designs; but the major limitation of the flooded designs lie in the inherent possibility of acid leakage during handling, transportation and charging, resulting from internal pressure build-up. As a result, a small percentage of automotive batteries are being converted to leak proof, VRLA (Valve Regulated Lead Acid) type batteries' assembled with AGM (Absorptive Glass Mat) separators in spite of a higher cost. Thus it is evident that there is a strong need to develop low cost, leak retardant/resistaht batteries containing free electrolyte, particularly suitable for the use in automobiles. Hitherto, there have been many attempts to develop leak resistant batteries with free electrolyte using specially designed battery covers. Of the several patents filed in this connection, a few of them are being cited below for reference in view of their relative importance: -2- Patent No. Published on US 5,843,593 December 1, 1998 US 5,683,830 November 4, 1997 US 5,424,146 June 13, 1995 US 5,380,604 January 10, 1995 EP 0639862 Bl September 18, 1996 In most of the patents cited leak retardant characteristics are achieved by using a relatively complex battery cover design which usually comprises an upper lid and a lower lid, i.e. there is a part of the battery cover which is fixed to the main cover either by heat sealing or ultrasonically. In the event that the battery tilts sideways or in the inverted position, some electrolyte flows out of the container into the space provided between the upper and lower lids of the battery cover which is returnable when the battery is restored to its upright position. The design based on a two-piece battery cover is relatively expensive and more complex at the manufacturing stage. Clearly, there is a need for a simple, one piece leak retardant cover design without adversely affecting the cost competitiveness. Accordingly, the present invention provides a leak retardant automotive battery comprising: a housing for a plurality of celis housed therein, each said cell having a filling plug; a battery cover fitted and heat-sealed to said housing to overlie the cells; and -3- a pair of terminals mounted on the battery cover and connected to the cells; characterised in that said battery cover is divided into two compartments by means of a central blockage, each, compartment overlying a set of cells; vent holes in the battery cover overlying each said set of ceils are connected by means of a side vent line so that cells in each set are in communication with each other; said side vent lines are connected respectively at one end to said central blockage so as to isolate the two compartments; and a vent cap assembly is provided at the other end of each side vent line for allowing the escape of vented gases. The central blockage preferably comprises of an additional separating wall to isolate the two side vent lines, a sealing ring being provided for sealing said central blockage in said battery cover. The vent cap assembly may additionally comprise the vent cap fitted to said 'other end of the side vent line, with a gas filter fitted into the vent cap for allowing the vented gas to escape. In one embodiment of the present invention, the vent cap has a vent hole in communication with said other end of said vent line, a first upwardly extending vertical hole extending from said vent hole to the outer periphery of the vent cap, a helical path on the outer periphery connected at its one end to said first vertical hole and at its other end to a second -4- vertical hole extending downwards and also extending to the center of the vent cap so as to be in communication with the gas filter. The gas filter is preferably a water-repeilant microporous gas filter. The microporous filter preferably has a grain size of about 70 microns. The gas filter is push fitted into the vent cap and then covered with a filter cover having a hole for the escape of vented gas. Each filling plug having an "0" ring seal may be fitted into each cell. The present invention is based on making a battery leak retardant by creating an air-lock, in addition to using the specially designed vent tube tightly enclosing a microporous gas filter to resist free flow of acid when the battery is rotated or tilted in either direction. A multi-cell (12 volt) configuration with side venting arrangement is divided into 2 isolated chambers by blocking the common, side vent line through the battery cover at a location corresponding to the middle partition of the battery container. This leaves each of the 3-cell battery chamber with a single vent opening fitted with a special type of vent tube enclosing.a micro porous gas filter. In addition to providing an effective air-lock to prevent the free flow of electrolyte when the battery is tilted in either direction, there is an additional advantage in the present invention of minimizing the transfer of _5_ electrolyte from the upper to the iower cells when tilted on the shorter side along the vent line. This is due to the fact that the central blockage on the vent line in the middle of the battery cover having an additional separating wall prevents the transfer of electrolyte from the upper three cells to the lower three cells. As a result, after the tilt for a stipulated period, when the battery is reverted to its original upright condition, a negligible cell to cell variation in the electrolyte levels is observed, as compared to the normal, side vented designs having a common vent line, through the cover. In the present invention, the vent cap containing the micro porous filter is so designed that the electrolyte is required to traverse vertically up and move along the helical path on the periphery and then allowed to descend to its central position before coming in contact with the micro porous gas filter. This arrangement provides a significant resistance to the flow of electrolyte when the battery is tilted in different directions. Another notable feature of the present invention is that the vent cap assembly can be easily push fitted and locked-in into the side vent line without the need for any separate heat sealing or ultrasonic sealing. This simplifies the manufacturing operation, thereby resulting in iower cost. Furthermore, in the vent cap used in the battery of the present invention, a fine grain (approx. 70 micron) micro porous gas filter can be used, which is made of plastic alloy -6- and then chemically treated to exhibit water-repellant characteristics. This provides a substantial resistance to the leakage of electrolyte through the vent hole. The invention will now be described with reference to accompanying drawings which show a preferred embodiment of the invention. In the accompapyiCng drawings, Figs. 1 and 1A show front elevation and plan view of the automotive battery according to the present invention; Figs. 2 and 2A show rear view and side view of the battery of Fig. l; Fig. 3 shows sectional view along line B-B in Fig. 1A; Fig. 4 shows sectional view along line A-A in Fig, 1A; Figs. 4A and 4B show enlarged views of circled portions X and V marked in Fig. 4; Fig. 5 shows perspective view of vent cap assembly used in the battery of the present invention; Fig. 5A shows plan view of the vent cap assembly of Fig. 5 ,- Fig. SB shows sectional view of the vent cap assembly line along line C-C in Fig. 5A; and Fig. 6 shows graphical representation of test analysis of the battery according to the present invention. Figs. 1, 1A, 2 and 2A show plan view and elevational views of the leak retardant automotive battery according to the present invention. The battery has a housing 1 in which six ceils Ci to C6 are mounted. A battery cover 2 is fitted on and heat-sealed to the housing so that the undersurface of -7- the battery cover is flush with the cells. Battery terminals Tl and T2 are connected to the cells. The battery cover 2 is divided into two compartments 21 and 2" as can be seen from Fig. 4, so that compartment 2' covers cells Cl to C3 and compartment 2" covers cells C4 to C6. In compartment 21, side vent line 3 interconnects the spaces above the cells Ci to C3. Similarly, side vent line 31 in compartment 2" interconnects the spaces above the ceils C4 to C6. The cells are provided with filling plugs 4 which extend into and are flush with the top surface of the cover 2. From Fig. 3, it can be seen that filling plug 4 passes through the cover 2 into the ceil C6 and is push-fitted on to the cover 2 by means of an "0" ring 5 so that no electrolyte contained in the cell spills out. At the middle of the battery, a central blockage is provided in the battery cover. This is marked as X in Fig. 4 and shown in detail in Fig. 4A. The blockage comprises of a body 6 sealed in the battery cover 2. The body 6 has a hole 6' for entry of one end of side vent line .3 and another hole 6" for entry of one end of side vent line 31. The two holes 6! and 6" are isolated from each other by a partition 7 in the body 6. The body 6 is fitted on the battery cover 2 with the help of an "0" ring 5. Thus, the vent lines 3 and 31 are isolated from each other. At the other end of each side vent line, a vent cap assembly is push-fitted. This is marked as Y in Fig. 4 and shown in detail in Fig. 4B. In said other end of each side -8- vent line, there is a cylindrical hole into which the vent cap assembly is fitted on a side of the battery cover. Figs. 5, 5A and SB show the vent cap assembly in greater detail. The vent cap assembly comprises a vent cap 8 fitted to the other end of the side vent line 3/3'. The vent cap 8 has a vent hole 9 and is fitted into the other end of the side vent iine 3/3 ' so that vent hole 9 is in communication with the side vent line 3/3'. An upwardly extending vertical hole 10 in the vent cap 8 connects the vent hoie 9 to the outer periphery of the vent cap. On the outer periphery of the vent cap, a helical path Ii is provided, extending from the vertical hole 9 to a second vertical hole 12 which extends downwards to the centre of the vent cap at the end of the vent cap, remote from the vent hole 9. At this end of the cap, a water-repellant microporous gas filter 13 is fitted with the help of a filter cover 14 having a hole 15. When any gas is vented by any cell of the battery, due to the central blockage, it cannot escape from one compartment 2' to the other compartment 2" and it is forced to escape through the other end of the side vent line into the vent hole 9. The gas then passes through first vertical hole 10 and traverses along the helical path 12 and enters through second vertical hole 12. The gas is subsequently filtered by filter 13 and vented to the atmosphere through hole 15 in the filter cover 14. By this arrangement the direct contact of the electrolyte with the filter is prevented. -9- Due to the novel construction described above, an airlock is present due to the combination of the central blockage and vent cap assembly. The battery of the present invention is highly resistant to acid leaks when turned through 90° on the front face or inverted, i.e., rotated through 18O°C. No acid leakage was noticed in the above tilted positions during the period of testing upto 12 hours. The conventional side vented batteries are prone to acid leaks, when rotated through 90° along the shorter side -in the direction of the vent line. It is in this direction that the efficacy of the central blockage of the vent line is revealed. Whereas without the central blocking, the air can pass freely through the vent line, resulting in continuous leakage of acid from the side vent when tilted through 90° in the direction of the vent with the central blockage of the vent line according to the present invention, an air-lock is effectively formed which greatly reduces the leakage of electrolyte when the battery is tilted through 90* along the vent line. In addition to providing air lock preventing free flow of electrolyte when the battery is tilted, the central blockage also minimises cell-to-cell variation of electrolyte when tilted, by preventing transfer of electrolyte from one set of cells to the other set of cells. -10- The vent cap assembly provides significant resistance to flow of electrolyte when the battery is tilted in different directions. Further vent cap assembly can be easily push-fitted into the side vent line and thus separate heat-sealing and ultrasonic sealing can be avoided. Fig. 6 shows a comparative analysis of the tilt tests at 90° along the vent line: - Electrolyte spillage with new vent cap design vis-a-vis conventional side vented battery; and - Effect of central blockage of the vent line, creating an air-lock and thereby substantially retarding the acid leakage to a negligible level. Prom the graph, it can be seen that the spillage of electrolyte when vent cap assexribly is used is less than the spillage when no special vent cap assembly is used. When the central blockage is used, the amount of spillage gets greatly reduced. Furthermore, central blockage of the vent line, greatly reduces the cell to cell variation of the electrolyte level after a prolonged tilt at 90° along the shorter side, in the direction of the vent line. Whereas there are significant variations in the cell to cell electrolyte levels after 2 hours of tilt at 90° on the shorter side with the conventional side vented design, in the new leak retardant battery under the present invention, only a negligible variation of electrolyte level is seen in a stabilized condition after the tilt test for 2 hours. -11- Although the invention has been described with reference to a preferred embodiment, the invention includes all modifications and improvements coming within the scope of the invention as claimed. -12- WE CLAIM: 1. A Leak retardant automotive battery comprising: a housing for a plurality of cells housed therein, each said cell having a filling plug; a battery cover fitted and heat-sealed to said housing to overlie the cells; and a pair of terminals mounted on the battery cover and connected to the cells; characterised in that said battery cover is divided into two compartments by means of a central blockage, each compartment overlying a set of cells; vent holes in the battery cover overlying each set of cells are connected by means of a side vent line so that cell's in each set are in communication with each other; said side vent lines are connected respectively at one end to said central blockage so as to isolate the two compartments; and a vent cap assembly is provided at the other end of each side vent line for allowing the escape of vented gases. 2. Battery as claimed in claim 1, wherein said central blockage comprises of an additional separating wall to isolate the two side vent lines, a sealing ring being provided around the filling plug for sealing said central blockage in said battery cover. -13- 3. Battery as claimed in claim 1 or 2, wherein said vent cap assembly comprises a vent cap fitted to said other end of said side vent line, with a gas filter fitted into the vent cap for allowing the vented gas to escape. 4. Battery as claimed in claim 3, wherein said vent cap has a vent hole in communication with said other end of said side vent line, a first upwardly extending vertical hole extending from said vent hole to the outer periphery of the vent cap, a helical path on the outer periphery connected at its one end to said first vertical hole and at its other end to a second vertical hole extending downward and also extending to the center of the vent cap so as to be in communication with the gas filter. 5. Battery as claimed in claim 3 or 4, wherein said gas filter is a water-repellant microporous gas filter. 6. Battery as claimed in claim 5, wherein said microporous filter has a grain si2e of about 70 microns 7. Battery as claimed in any of claims 3 to 6, wherein said gas filter push fitted into the vent cap is covered by means of a filter cover having a hole for the escape of vented gas. -14- 8. Battery as claimed in any of claims 1 to 7, wherein each filling plug having an "0" ring, is fitted into each cell. 9. A leak retardant automotive battery substantially, as herein described, particularly with reference to the accompanying drawings. a housing (1) for a plurality of cells (c1 to c6) housed therein and having a battery cover (2) fitted and heat-sealed to said housing to overlie the cells; a pair of terminals (T1, T2) mounted on the battery cover and connected to the cells; wherein: said battery cover is divided into two compartments (2, 2') by means of a central blockage (X) such that each compartment overlies a set of cells; said battery cover being connected by means of side vent lines (3, 3') so that cells in each set are in communication with each other; and said side vent lines are connected respectively at one end to said central blockage (X) and a vent cap assembly (Y) is provided at the other end of each side vent line for allowing the escape of vented gases.

Documents:

00209-cal-2001 abstract.pdf

00209-cal-2001 assignment.pdf

00209-cal-2001 claims.pdf

00209-cal-2001 correspondence.pdf

00209-cal-2001 description(complete).pdf

00209-cal-2001 drawings.pdf

00209-cal-2001 form-1.pdf

00209-cal-2001 form-18.pdf

00209-cal-2001 form-2.pdf

00209-cal-2001 form-3.pdf

00209-cal-2001 letters patent.pdf

00209-cal-2001 p.a.pdf

209-CAL-2001-CORRESPONDENCE 1.2.pdf

209-CAL-2001-CORRESPONDENCE-1.1.pdf

209-CAL-2001-CORRESPONDENCE.pdf

209-cal-2001-office-letter(form-15).pdf

209-CAL-2001-OTHERS 1.2.pdf

209-CAL-2001-OTHERS-1.1.pdf

209-CAL-2001-OTHERS.pdf