Leak resistant battery cover

Abstract: The present invention is directed to a leak resistant battery cover for a multiple cell lead acid storage battery. The battery cover includes an intermediate cover (14) and an outer cover (16) which, when joined together provide a labyrinth of passages (26, 28, 30) therebetween which provide a path from each cell vent (22) to an atmospheric vent (38). The labyrinth is configured to provide a portion of each path above a level which the electrolyte in the respective cells attains when the battery is tipped on any one of its sides or rotated ninety degrees from an upright position. The labyrinth configuration prevents electrolyte from reaching the atmospheric vent (38) and spilling out of the battery.

Description: The invention relates to a storage battery cover, and more particularly to a storage battery cover offering added protection against leakage when a battery using the cover of the invention is tipped to any one of its sides or inverted. Conventional storage batteries include a battery housing having a housing and a cover for closing an open top end of the casing. The battery housing is a rectangular casing having multiple compartments or cells for receiving cell plates and electrolyte therein. The cover device is heat sealed to an open top end of the battery housing casing. The cover device often includes a main cover part and a sub-cover part. The main cover part has a horizontally disposed plate body with a top face formed by a rectangular confining wall. The confining wall is divided by multiple partitions and associated chambers. The main cover further includes multiple service ports for pouring electrolyte into respective cell compartments within the casing and multiple degassing vents and drain-back return holes associated with each cell. The sub-cover is integrally secured to the main cover after electrolyte has been poured into the cell compartments through the service ports. The sub-cover part is heat sealed to the main cover part along its perimeter and at top edges of the partitions and chamber walls. The chambers and partitions ultimately form enclosed chambers and associated paths from the cell vent and return hole of each cell to multiple atmospheric vents. The chambers typically include relatively large containment areas for holding electrolyte spilled into the battery cover when the battery is tipped. In operation, heat that is generated during electrolysis causes the electrolyte and water in the electrolyte to evaporate. This evaporation is referred to as "gassing". Gassing of the cell occurs at any point the battery reaches the hydrogen over-voltage, producing bubbles that break at the surface introducing a mist into the venting gas stream. In conventional batteries, the vaporized electrolyte was released to atmosphere through an atmospheric vent in the cover device. Loss of electrolyte through the atmospheric vent requires replenishing electrolyte in the battery housing periodically. In order to overcome electrolyte loss, a battery housing with a cover capable of recovering the vaporized electrolyte was developed, thereby obviating the need for replenishing the electrolyte in the battery housing. When the electrolyte in the cell compartments undergo electrolysis and evaporates due to the heat that is generated, the vaporized electrolyte flows into the path formed in the cover through the cell vents or drain-back holes. Since the interior of the cover is exposed to the atmosphere via the atmospheric vent, the interior temperature of the cover is less than that of the vaporized electrolyte entering the cover. Thus, heat transfer occurs so that the vaporized electrolyte condenses, and the resulting condensate flows back into the corresponding cell compartments via the drain-back holes. The paths are often sloped towards the drain-back holes to further facilitate the return of electrolyte to the respective cells. Since the vaporized electrolyte is recovered instead of released to atmosphere, there is no need to periodically replenish the electrolyte in the battery housing. Although these batteries prevent electrolyte loss during normal operation, the battery will leak, and in many cases pour, electrolyte from the atmospheric vents when the battery is tipped to one side, inverted or agitated. Batteries are often placed in a non-upright position during shipping, handling or accidents, such as car wrecks. A significant threat to person and property arises when electrolyte leaks from a battery. Various approaches have been taken in the past to deal with the problem of electrolyte spilling or leaking from a battery when it is tipped to any one of its sides. Many of the arrangements are acceptable in situations where the battery is tilted to its side and not subjected to vibration or other forms of movement. However, the related art has yet provided a cost effective battery cover providing total steady state leak protection when the battery is tipped to one side and substantial resistance to electrolyte leakage when subjected to vibration, agitation or inversion. U.S. Patent No. 1,605,820 to Edwards discloses a multilevel chamber configuration for each cell. The chamber includes two opposed inclined partitions for preventing electrolyte spills when the battery is tipped to one side. The chamber configuration provides no inverted leak protection. Furthermore, the large chamber configuration provides very limited protection against vibration or agitation when tipped to one side. U.S. Patent No. 3,597,280 to Hennen disclosed a multiple vent plug assembly for merely reducing spillage when a battery is partially tipped or completely inverted. The plug assembly incorporates a multi-chamber configuration designed to contain a substantial portion of electrolyte prior to spilling the electrolyte to atmosphere. The Hennen patent does not disclose a chamberless cover design or provide substantial leak protection over extended periods of time. U.S. Patent No. 4,348,466 to Elehew et al. discloses a large rectangular chamber configuration having an inlet in communication with a respective cell. Each chamber has an outlet off to one side of and below the inlet. A passage associated with the chamber outlet is provided for containing and holding electrolyte. The passage has an outlet in communication with an atmospheric vent. The arrangement is such that the chambers and associated passages are of sufficient volume to retain the amount of electrolyte displaced into them when equilibrium is achieved between levels of electrolyte in the cells and respective chambers and passages. The Elehew et al . patent requires that a portion of the passage be above the chamber inlet regardless to which side the battery is tipped. When the chambers and the passages fill with electrolyte, an airlock is developed which prevents additional flow of electrolyte from the cell into the chamber and passage configuration. The Elehew et al . patent provides no leak protection when the battery is inverted and provides only steady state protection when the battery is tipped to one side. As seen from viewing the chamber and passage configuration of the Elehew et al . patent, when a battery using the Elehew et al . cover is tipped on various sides and vibrated or agitated, it is very likely that electrolyte will spill out of the chamber and run into the passage to the venting area. The large chambers and passage configuration in Elehew et al . allows substantial amounts of electrolyte to spill into the battery cover; thus, increasing the likelihood of electrolyte being spilled into the venting area and ultimately leaking outside the battery system. The Elehew et al . patent is directed towards preventing leak protection at a steady-state equilibrium when the battery is tipped to one side. Having substantial amounts of electrolyte in the cover and limited flow restriction substantially increases the likelihood that electrolyte will spill if the battery is vibrated or agitated after arriving at an equilibrium in a non-upright position. Similar configurations are shown in US Patent No 5 380 604 to Hampe et al . and US Patent No 5 424 146 to Lin. Both patents disclosed leak resistant battery covers having chambers associated with each cell. The chambers have guides for controlling the flow of acid. However, each cover is designed to allow a significant amount of electrolyte to flow into the respective cover and provides no protection against electrolyte leakage when the battery is inverted and very limited protection when vibrated or agitated. German Patent No 4 216 563 discloses a dual section cover having a chamber associated with each cell. Each chamber is sized so that when the battery is tipped or inverted, no more acid from a respective cell enters the gas collection chamber than the chamber can contain. Although the German patent attempts to address inverted leak protection, allowing such substantial amounts of electrolyte to flow out of the cells and into the cover substantially increases the risk of electrolyte leaking outside of the battery system. Aside from the above arrangements, far more complex arrangements are known which are used on aircraft batteries and the like which not only deal with the problem of electrolyte flowing from the cell when tipped to any one of its sides, but also maintain the battery in operation when completely inverted. These designs are not cost effective for the majority of battery applications. EP-A-0 503 264 to Bosch discloses a leak resistant battery cover generally of the type recited in the precharacterising clause of claim 1, which includes a housing having a plurality of cells containing electrolyte and a plurality of partition walls separating said cells, said cover comprising: a floor and a ceiling forming an interior area therebetween, said floor sealably engaging the housing and partition walls; a plurality of cell vents in and extending through said floor, each cell vent being adapted to communicate gases within a corresponding one of the cells of the battery to said interior area of said cover; an atmospheric vent on said cover adapted to communicate gases from said interior area of said cover to atmosphere; a labyrinth system between said floor and ceiling in said interior area of said cover formed of a plurality of passages, said passages forming a plurality of substantially convoluted paths to communicate each said cell vent to said atmospheric vent, wherein each said cell vent communicates substantially immediately with one said passage of said labyrinth system; and a plurality of cell drains in and extending through said floor, which communicate with said passages and communicate liquid electrolyte in said passages to respective cells; said passages of said labyrinth system being so arranged that each of said paths has a branch which, in use of the cover, is above the liquid electrolyte level for the corresponding cell when the battery is rotated as much as ninety degrees from an upright position. Whilst the configuration disclosed in the EP-A may create an airlock in some of the positions in which the battery is placed, a significant amount of electrolyte will be lost before the airlock can be established, because of the configuration of the convoluted paths followed by the passages interconnecting the atmospheric vent with the individual combined cell vents and drains. Accordingly, there remains a need to provide an anti-spill battery cover for liquid electrolyte batteries which is relatively inexpensive to manufacture, prevents spillage of electrolyte when tipped toward or onto any one of its sides, provides additional resistance to spillage when vibrated or agitated while tipped toward or onto any one of its sides, and prevents spillage of electrolyte when the battery is substantially or completely inverted. Furthermore, there is a need for a chamberless battery cover of limited volume capable of forming an airlock in a short period of time after being tipped or inverted in order to minimize the amount of electrolyte entering the cover and significantly reducing the potential of electrolyte reaching an atmospheric vent. A need exists for a chamberless, leak resistant battery cover using only one atmospheric vent in order to further reduce the likelihood of electrolyte spills. A need remains for a battery cover having the above features in order to prevent harm to person and property caused by contact with electrolyte or from the potential of fire and explosion if exhaust gases are ignited. According to the present invention, there is provided a leak resistant battery cover as defined in the characterising clause of claim 1, wherein: each cell vent is a slotted cell vent extending from said ceiling through a corresponding cell drain in said floor, each cell vent having an opening therein to communicate gases from within a corresponding one of the cells of the battery to said interior area of said cover; the labyrinth system includes walls substantially encircling and immediately adjacent each respective cell vent, and forming an initial passageway around each vent opening in which electrolyte escaping from said cell vent at times when the battery is in a non-upright position can collect, each of said initial passageways substantially encircling a corresponding vent opening and communicating with at least one first common passage, said at least one first common passage communicating with a final common passage such that said final common passage is in communication with each of said plurality of cells; and said single atmospheric vent is in communication with said final common passage. The leak resistant battery cover embodying the invention provides a labyrinth of passages providing a path from each cell vent to the atmospheric vent. The labyrinth is configured to provide a portion of each path above a level in which the electrolyte in the respective cells attains when the battery is tipped on any one of its sides or rotated ninety (90) degrees from an upright position. The labyrinth configuration prevents electrolyte from reaching the atmospheric vent and spilling out of the battery. The passages of the labyrinth may include partitions extending horizontally from a passage wall towards the center of the passage. These horizontally extending partitions are generally perpendicular to the passage wall or angled in a manner obstructing the flow of electrolyte toward the atmospheric vent. Preferably, the horizontally extending partitions alternate from opposing sides of the passage. The labyrinth configuration provides improved leak protection over the above discussed prior art when the battery is tipped to one side. Additionally, the substantially convoluted passages provide inverted leak resistance. The convoluted passages in conjunction with the partitions operate to form an airlock between the cell vent and the atmospheric vent. By providing such a convoluted path for air to travel, an airlock is formed in the passages. When air is prevented from entering the battery, additional electrolyte is prevented from leaving each cell, entering the labyrinth and ultimately leaking through the atmospheric vent. The passages of the labyrinth may also include partitions extending vertically from a passage floor or ceiling. The vertically extending partitions provide enhanced leak protection when the battery is inverted. Preferably, the vertically extending partitions alternate from the floor and ceiling and the partitions extending from the ceiling are substantially longer than the partitions extending from the floor in order to provide a greater electrolyte barrier when inverted. The vertically extending partitions aid in forming an airlock and preventing air from entering the cells. The labyrinth is adapted to provide for two or more of the passages communicating with each cell vent to converge into a common passage in the labyrinth prior to the atmospheric vent, wherein the path from each cell vent to the atmospheric vent is common for respective cells. Furthermore, all of the passages communicating with each cell vent may converge into a final common passage in the labyrinth prior to the atmospheric vent. The labyrinth may have passages sloped towards the cell drains to allow liquid electrolyte in the passages to flow into respective cells. Additionally, the cell vent and the cell drain may be an integrated vent and drain-back unit. The passages of the labyrinth are substantially convoluted and substantially or entirely encircle each respective cell vent. Preferably, each path to atmosphere for each cell has a branch running substantially near a portion of the periphery of the cover. The labyrinth may be such that each path formed by the passages forms one path to atmosphere for each cell. Various portions of each path may be common to another path. Additionally, the passages of the labyrinth may be adapted to provide a path from each cell vent to the atmospheric vent which crosses the lateral axis twice. The battery cover may have a transverse axis perpendicular to the lateral axis, with passages adapted to provide a path from each cell vent to the atmospheric vent having a portion substantially along the transverse axis. Furthermore, the battery may have each cell vent, each cell drain and the atmospheric vent on one side of the lateral axis. Generally, the battery cover is adapted for a six cell lead acid battery wherein the battery cover includes six cell vents, six cell drains and one atmospheric vent. Preferably, the battery cover is constructed of a lower cover portion and an upper cover portion. The lower and upper cover portions sealably engage one another to form the labyrinth system. The cover may include a second atmospheric vent wherein approximately half of the cell vents communicate with each atmospheric vent. The passages of the labyrinth may be provided with a plurality of horizontally extending partitions extending into the passages to provide resistance to any flow of liquid towards the atmospheric vent when the battery is toppled. The horizontally extending partitions extend from interior sides of the passages of the labyrinth and are often slanted against a direction of flow of electrolyte toward the atmospheric vent to provide further resistance against the flow of liquid electrolyte towards the atmospheric vent when the battery is toppled. Preferably, the horizontally extending partitions alternate from opposing interior sides of the passages of the labyrinth. The passages of the labyrinth may be provided with a plurality of vertically extending partitions extending into the passages to provide resistance to the flow of liquid towards the atmospheric vent. The vertically extending partitions aid in restricting electrolyte flow in the passages and in providing an airlock between the cells and the atmospheric vent when the battery is inverted. The vertically extending partitions may extend from either an upper or lower portion of the passages. Preferably, the upper and lower vertically extending partitions alternate along the passage. The vertically extending partitions extending from the upper portion of the passage extend below a level in which the vertically extending partitions extending from the lower portion extend. The vertically extending partitions provide an obstructed path along the passage. The common passage of the labyrinth may be provided with a plurality of substantially vertically extending partitions adapted to provide resistance to the flow of liquid towards the atmospheric vent. The vertically extending partitions extend from an upper and lower portion of the common passage and alternate along the common passage. The vertically extending partitions extending from the upper portion of the common passage extend below a level in which the vertically extending partitions extending from the lower portion extend. The partitions provide an obstructed path to the atmospheric vent. The vertically extending partitions extending from the upper and lower portions of the common passage are preferably substantially adjacent along the common passage. The common passage of the labyrinth may be provided with an entrance including a vertically extending partition adapted to provide resistance to the flow of liquid towards the atmospheric vent. The vertically extending partition at the entrance further aids in providing an airlock between the cells and the atmospheric vent when the battery is inverted. Reference will now be made to the accompanying drawings, in which: FIGURE 1 is a perspective view of a battery having a leak resistant battery cover. FIGURE 2 is a top view of the labyrinth of passages in an intermediate cover of a leak resistant battery cover constructed according to a first embodiment of the present invention. FIGURE 3 is a bottom view of the labyrinth of passages in an outer cover of the leak resistant battery cover mating with the intermediate cover shown in Figure 2. FIGURE 4 is a top view of a second embodiment of an intermediate cover constructed according to the present invention. FIGURE 5 is a bottom view of the labyrinth of passages in the outer cover of the leak resistant battery cover constructed according to the present invention. FIGURE 6 is a partial cross-sectional view of a joined intermediate and outer cover along live 6-6 illustrating the upper and lower vertically extending partitions and the atmospheric vent constructed according to the present invention. FIGURE 7 is a partial cross- sectional view of the intermediate cover, taken along line 7-7 shown in Figure 2, for illustrating the sloping passages of the labyrinth constructed according to the present invention. FIGURE 8 is a partial top perspective depicting electrolyte gas flow according to the present invention. FIGURE 9 is a partial cross-sectional view of a battery cover constructed according to the present invention illustrating electrolyte level in the labyrinth of passages when the battery is tipped onto one side in the direction of the arrow. FIGURE 10 is a partial cross-sectional view of a battery cover constructed according to the present invention illustrating electrolyte level in the labyrinth of passages when the battery is tipped onto one side in the direction of the arrow. FIGURE 11 is a partial cross-sectional view of a battery cover constructed according to the present invention illustrating electrolyte level in the labyrinth of passages when the battery is tipped onto one side in the direction of the arrow. FIGURE 12 is a partial cross-sectional view of a battery cover constructed according to the present invention illustrating electrolyte level in the labyrinth of passages when the battery is tipped onto one side in the direction of the arrow. FIGURE 13 is a top view of a third embodiment of an intermediate cover constructed according to the present invention. In the following description, like reference characters designate like or corresponding parts throughout the several views. Also in the following description, it is to be understood that such terms as "forward", "rearward", "left", "right", "upwardly", "downwardly", and the like are words of convenience and are not to be construed as limiting terms. Referring now to the drawings in general, and Figure 1 in particular, it will be understood that the illustrations are for the purpose of describing a preferred embodiment of the invention and are not intended to limit the invention thereto. As best seen in Figure 1, a battery, generally designated 10, is shown constructed according to the present invention. The battery 10 includes three major subassemblies: a battery housing 12, an intermediate cover 14, and an outer cover 16. The intermediate cover 14 is normally heat sealed or glued to housing 12 and the outer cover 16 is normally heat sealed to the intermediate cover 14. The battery housing 12 typically includes a plurality of partitioned cells 18A-F which are substantially isolated from each other when the covers 14, 16 are sealed onto the housing 12. Since the embodiments of the invention are directed towards providing a leak resistant battery cover, it is understood that various types of venting devices may be incorporated in the leak resistant arrangement and thus particular venting arrangements are not described in detail. The intermediate cover 14 and outer cover 16 are designed to form an enclosed labyrinth of passages 20 when the covers 14, 16 are joined. Turning now to Figure 2, a top view of the intermediate cover 14 is shown. A cell vent 22 and cell drain 24 (shown in Figure 3) are provided for each battery cell 18. Preferably, the drain 24 is an aperture in the intermediate cover 14 and the vent 22 is formed by a slotted tube 23A-F extending downward from the outer cover 16 into and partially through the aperture forming the drain. This drain/vent technique is conventional in the art. The cell vent 22 allows for the escape of electrolyte from each cell 18 of the battery 10. In normal operation, the electrolyte gas will condense back into liquid form and drain back into the cell 18 through the cell drain 24. Thus, in a typical 12-volt automotive or vehicle battery 10, there are six cells 18A-F, cell vents 22A-F, and cell drains 24A-F. When electrolyte gas escapes through cell vent 22, it communicates into an initial passage 26 of the labyrinth 20 through a passage entrance 28. Each cell 18 is associated with one initial passage 26A-F and one passage entrance 28A-F. The initial passage 26 ultimately leads to atmosphere. Multiple initial passages 26A-F converge into a first common passage 30 at a first convergent point 32. Although there may be many convergent points, the first embodiment initially brings two passages 26B-C, 26D-E together at the first convergent point 32A', 32B'. The paths from the outermost initial passages 26A, 26F join at points 32A" and 32B", respectively. Thus, the first common passages 30A', 30B' form a portion of the path to atmosphere for three cells 18A-C, 18D-F, respectively. The two first common passages 30A', 30B' ultimately combine to form a final common passage 34 at a final convergence point 36. The path to atmosphere for each cell 18 is provided by the final common passage 34. The final common passage 34 leads to atmosphere via an atmospheric vent 38 placed near the end of the final common passage 34. In the preferred embodiment, the atmospheric vent 38 is a porous disk located on the outer cover 16. The labyrinth of passages 20 is designed to form a very convoluted path to atmosphere. The initial passages 26A-F substantially encircle their respective cell vents 22A-F, service ports 40A-F, and typically includes a portion substantially near and along the perimeter portion of the battery prior to reaching the first convergent point 32. The perimeter portion of the electrolyte path may also be provided in the first common passage 30 after the first convergent point 32. It is important for the labyrinth of passages 20 to form very convoluted paths prior to reaching the atmospheric vent 38. Figure 4 shows a second embodiment of the battery cover constructed according to the present invention. As with the embodiment in Figure 2, electrolyte gases escape through cell vents 122, communicate into an initial passage 126 of the labyrinth 120 through a passage entrance 128 and converges into a first common passage 130A, 130B at a first convergent point 132A, 132B. The three initial passages 126A-C, 126D-F for each side of the battery converge into the common passages 130A, 130B, at convergence points 132A, 132B, respectively. The common passage 130A ultimately combines with a similar common passage 130B from the other half of the battery to form a final common passage 134 at a final convergent point 136. Figure 13 shows yet a further cover embodiment. Similar to the earlier embodiments, the third embodiment allows electrolyte gas to escape through a cell vent 222 into an initial passage 226 through a passage entrance 228. In the third embodiment, the initial passages 226A, 226B and 226C converge into a first common passage at substantially the same point 232A, 232B. The first common passage 230A, representing the flow path for one-half of the battery, converges with the first common passage 230B, representing the other half, into a final common passage 234 at final convergent point 236. The third embodiment differs from the earlier embodiments in that the final common passage 234 ultimately splits into diverging passages 237A, 237B. Each diverging passage 237 communicates with atmospheric vents 238A, 238B, respectively. This arrangement is preferred in dual atmospheric vent embodiments. The horizontal and vertical partitions are selectively optional in any of the embodiments. Returning now to Figure 4, located along the various passages 126, 130 and 134 are a plurality of perpendicular horizontally extending partitions 142 and angled horizontally extending partitions 144. The partitions 142, 144 provide a substantially obstructed path for electrolyte gas or liquid along the passages 126, 130 and 134. The angled horizontally extending partitions 144 are preferably angled against the direction of electrolyte flow towards the atmospheric vent 138. The horizontally extending partitions 142, 144 extend from the side of the passages 126, 130, 134 towards the center thereof. Preferably, these partitions 142, 144 are arranged to alternate along the passages 126, 130, 134 to provide more effective path obstruction without blocking the path entirely. Furthermore, the horizontally extending partitions 142, 144 are positioned in a manner ensuring that electrolyte condensate will not lodge between the partitions 142, 144 or anywhere along the electrolyte path to effectively block the electrolyte path while in normal operation. Referring to Figures 4 and 5, the electrolyte path may also include a plurality of upper vertically extending partitions 150 (shown only in Figure 5) and lower vertically extending partitions 146 (shown only in Figure 4) extending from an upper and lower portion of a passage, respectively. The upper vertically extending partitions 150 extend downwardly from the upper portion of the passage 134 while the lower vertically extending partitions 146 extend upwardly from the passage 134. Preferably, the vertically extending partitions 146, 150 are located along the final common passage 134 prior to reaching the atmospheric vent 138. Also, a lower vertically extending entrance partition 152 may be placed at the final convergence point 136. The vertically extending partitions 146, 150, 152 extend across the width of the entire passage 134. The vertically extending entrance partitions 152 (shown only in Figure 4) and the lower vertically extending partitions 146 extend from the intermediate cover 114. The upper vertically extending partitions 150 extend from the outer cover 116 and between the lower vertically extending partitions 146 on the intermediate cover 114. Figure 6 depicts a cross-sectional view along the final common passage 134 formed by joining the intermediate cover 114 with the outer cover 116. When the upper and lower vertically extending partitions 146, 150 are alternatingly positioned. a series of "up-and-overs" are formed along the electrolyte path. As depicted, the lower vertically extending partitions 146 and upper vertically extending partitions 150 extend past the ends of the respective partitions 146, 150. Preferably, the upper vertically extending partitions 150 extending from the outer cover 116 are substantially longer than the lower vertically extending partitions 146 extending from the intermediate cover 114. Having the vertically extending partitions 146, 150 configured in this manner provides greater electrolyte leakage protection while inverted. Inverted leak protection is discussed in further detail below. The final common passage 134 extends along a transverse axis 154 bisecting the length of the battery. As best seen in Figures 4 and 5, the upper portion of the intermediate cover 114 is configured to substantially mirror the lower portion of the outer cover 116 to form the labyrinth of passages 120 and the plurality of various partitions placed throughout. Once the covers 114, 116 are sealed, the passages 126, 130, 134 seal and form enclosed paths. The passages 126, 130, 134 which make up the path from the passage entrance 128 to the atmospheric vent 138 are configured to continuously slope from the atmospheric vent 138 to the respective drain hole 124A-F of each cell 18A-F. This sloping configuration returns the electrolyte condensate back to the cells 18A-F after the electrolyte gas has condensed back into a liquid during normal operation. The angled horizontally extending partitions 144 are oriented in a manner preventing entrapment of electrolyte condensate during its return to a cell 18A-F. Figure 7 is a cross-sectional view of the initial passage 126A and depicts the continuously sloped elevation of the initial passage 126A as it substantially circles and re-circles the cell vent 122 and service port 140. As best seen in Figure 8, in normal operation of the battery, electrolyte gas will rise from the cells 18A-F and enter the initial passage 126A-F through the passage entrance 128A-F. The arrows show the path the electrolyte gas would take from each respective passage entrance 128A-F of each cell 18A-F to the atmospheric vent 138. The arrows highlight the highly convoluted path to atmosphere associated with each cell 18A-F. Note that the electrolyte will condense well before reaching the atmospheric vent 138. The path to atmosphere for the cells 18A-F not depicted is a mirror image of the path for the cells 18A-F depicted in Figure 8. As best seen in Figures 9-12, the labyrinth of passages 120 is configured to provide a path from each cell vent 122A-F and drain hole 124A-F to the atmospheric vent 138. Each path is configured to have a portion above the electrolyte level 162 when the battery is tipped to any one of its sides 164, 166, 168 and 170 or up to ninety (90) degrees from an upright position. Referring to Figure 9 in particular, a partial cross-sectional view of the labyrinth of passages 120 is shown when the battery is tipped onto side 164. The effective electrolyte level in the cells 18A-F is shown at line 162. When the battery 10 is tipped to one of its sides, electrolyte 160 will spill into the initial passage 126A-F and any other passages, such as the first common passage 130A, 130B, until an airlock is formed by the electrolyte 160 blocking airflow from the atmospheric vent to the cell 18 and/or when the electrolyte 160 spilling into the labyrinth of passages 120 reaches a level equal to the electrolyte level 162 in the cells 18A-F. When the battery 10 is tipped onto side 164, the electrolyte 160 remains in the initial passage 126A-F because the electrolyte level in the cells 18A-F is below portions of the path formed by the initial passage 126A-F. Figure 10 depicts the battery 10 tipped onto side 66. As can be seen, the initial passage 126A-F provides a path above the electrolyte level 162 in each cell 18A-F. Thus, the amount of electrolyte 160 spilling into the labyrinth of passages 120 is stopped once a level equal to the level of electrolyte in the cells 18A-F is reached. Figure 11 depicts the battery 10 tipped onto side 168. As can be seen, the electrolyte level in each cell 18A-F is higher than the level at which most of the labyrinth of passages 120 is located. However, a path above the electrolyte level 162 is provided for each cell. Thus, the electrolyte 160 will never reach a level higher than the electrolyte level 162 in the cells 18A-F. In many instances, an airlock will be formed prior to the electrolyte 160 reaching the level shown in Figure 11 because of the very convoluted paths formed by the passages 126, 130, 134. These paths provide a substantial hurdle for the electrolyte 160 to overcome in order to reach the atmospheric vent 138. Substantial leak protection is accomplished even during agitation. Given the lack of containment chambers and the use of convoluted, narrow paths, applicants' invention provides significant leak protection over existing battery covers. Figure 12 depicts the battery 10 tipped onto side 170. Again, the amount of electrolyte 160 spilled into the cover system is substantially limited to the initial passage 126A-F. A path above the cell electrolyte level 162 traps the electrolyte 160. In order for the electrolyte 160 to reach the atmospheric vent, the battery 10 would have to undergo substantial rotation and agitation. The amount of protection provided by the applicants' invention far exceeds those of the prior art in an economical fashion. Not only is the side tipping protection greatly enhanced over the prior art by the applicants' invention, the battery cover also provides substantial leak resistance in an inverted position as well. When the battery covers 114, 116 include the upper and lower vertically extending partitions 146, 150, the covers 114, 116 are virtually leak proof. The alternating vertically extending partitions 146, 150 help develop an airlock between the cell 18A-F and atmospheric vent 138. The effect is further enhanced if the upper vertically extending partitions 150 on the outer cover 116 are increased in length. Typically, the lower vertically extending partitions 150 will extend into the path by more than 50% of the path height. Preferably, the vertically extending partitions 150 extend into the path by more than 75% of the path height. The amount of extension for both the lower and upper vertically extending partitions 146, 150 and the spacing between these partitions 146, 150 are such that liquid electrolyte will not form an airlock when the battery is operating in an upright position. The covers 114 and 116 provide substantial leak resistance in an inverted position without using the lower and upper vertically extending partitions 146, 150. When inverted, the intricate, convoluted paths formed by the labyrinth of passages 120 in conjunction with the numerous alternating perpendicular and angled horizontally extending partitions 142, 144 will provide a substantial airlock in the paths between the cells 18A-F and the atmospheric vent 138. As seen in Figures 4 and 5, ambient air entering the labyrinth of passages 120 will have substantial difficulty in reaching the cells 18A-F through the various convoluted paths associated therewith. Electrolyte will not enter the labyrinth of passages 120 from the cells 18A-F without air being transferred into the cells 18A-F. Thus, providing an extremely difficult path for air to travel through the electrolyte to the cells 18A-F will substantially reduce electrolyte flow from cells 18A-F. Certain modifications and improvements will occur to those skilled in the art upon a reading of the foregoing description. It should be understood that all such modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the following claims.

Claims: A leak resistant battery cover for a lead acid battery of the type including a housing (12) having a plurality of cells (18) containing electrolyte and a plurality of partition walls separating said cells, said cover comprising: a floor (14) and a ceiling (16) forming an interior area therebetween, said floor sealably engaging the housing (12) and partition walls; a plurality of cell vents in and extending through said floor, each cell vent being adapted to communicate gases within a corresponding one of the cells of the battery to said interior area of said cover; an atmospheric vent (38) on said cover adapted to communicate gases from said interior area of said cover to atmosphere; a labyrinth system (20) between said floor and ceiling in said interior area of said cover formed of a plurality of passages, said passages forming a plurality of substantially convoluted paths to communicate each said cell vent to said atmospheric vent, wherein each said cell vent communicates substantially immediately with one said passage of said labyrinth system; and a plurality of cell drains in and extending through said floor, which communicate with said passages and communicate liquid electrolyte in said passages to respective cells; said passages of said labyrinth system being so arranged that each of said paths has a branch which, in use of the cover, is above the liquid electrolyte level for the corresponding cell when the battery is rotated as much as ninety degrees from an upright position; characterised in that: each cell vent is a slotted cell vent (22) extending from said ceiling (16) through a corresponding cell drain (24) in said floor (14), each cell vent having an opening therein to communicate gases from within a corresponding one of the cells of the battery to said interior area of said cover; the labyrinth system includes walls substantially encircling and immediately adjacent each respective cell vent (22), and forming an initial passageway (26) around each vent opening in which electrolyte escaping from said cell vent at times when the battery is in a non-upright position can collect, each of said initial passageways substantially encircling a corresponding vent opening and communicating with at least one first common passage (30), said at least one first common passage, communicating with a final common passage (34) such that said final common passage is in communication with each of said plurality of cells (18); and said single atmospheric vent (38) is in communication with said final common passage (34). The cover according to claim 1, wherein at least one of said common passages (30,34) includes a plurality of generally horizontally extending partitions (142) extending into said passage to provide, in use, resistance to any flow of liquid electrolyte towards said atmospheric vent. The cover according to claim 1 or 2, wherein at least one of said common passages (30,34) includes a plurality of angled generally horizontally extending partitions (144) extending into said passage to provide, in use, resistance to any flow of liquid electrolyte towards said atmospheric vent. The cover according to claim 1, 2 or 3, wherein at least one of said common passages (30,34) includes a plurality of upper generally vertically extending partitions (150) and lower generally vertically extending partitions (146) extending from respective upper and lower portions of said passage, said partitions forming an upwardly and downwardly directed convoluted path. The cover according to any preceding claim, wherein said initial passageways (26) and common passages (30,34) slope downwardly from said atmospheric vent (138) to said cell drains (124).

Inventors: FRITTS ROBERT W, REVAK DAVID M, FRITTS, ROBERT W., REVAK, DAVID M.
Applicants: DOUGLAS BATTERY MFG COMPANY, DOUGLAS BATTERY MANUFACTURING COMPANY
Application year: 1998
Main classification: H01M2
IPC codes: H01M2