refill valves in single point battery watering systems that utilize a porous internal flame arrestor in the path of the water prevent the internal propagation of flames between battery cells through the tubing network . the use of such flame arrestors in the refill valves of spw systems is advantageous because it prevents internal flame propagation without requiring frequent hydration . the use of such flame arrestors also eliminates the potential for valve malfunction arising from contaminants found in water traps . the internal flame arrestor of the present invention has the same flame arresting properties as the prior art external flame arrestors and flame arrestors in battery vent plugs . however , it was believed that this type of flame arrestor would be too restrictive to water flow to be used in the water flow path , and that the small pores would become clogged with waterborne debris . on the contrary , the internal flame arrestors of the present invention do not interfere substantially with water flow . turning now to fig1 , a refill valve 10 suitable for use in the present invention is shown . refill valve 10 contains an internal fluid flow path from the input port of the valve to the output port of the valve . fluids enter the refill valve at the proximal end through water inlet connector 11 and exit into battery cells at the distal end . the distal end comprises cell gas vent ports 13 for receiving gases that are displaced when the valve is inserted into the cells . these gases enter the refill valve through the ports and exit through cell gas outlet ports 12 . the individual components of refill valve 10 , including a porous internal flame arrestor 14 that is positioned within the fluid flow path , is shown in fig2 . it is also shown in fig2 that the refill valve of the present invention may further comprise an external flame arrestor 16 for preventing external flame propagation . turning now to fig3 , a cross - sectional view of a typical refill valve 10 is shown . it is shown that internal flame arrestor 14 is preferably located between water inlet connector 11 and inlet port 20 . it is also shown that external flame arrestor 16 is preferably located in valve cap 18 and held in place by cover 15 and baffle 17 . such a location ensures that displaced gases that enter cell gas vent ports 13 are exposed to the external flame arrestor before they exit the valve through cell gas outlet ports 12 . flame arrestor 14 is preferably a porous disc with a plurality of pores . preferably , the pores are 90 - 120 microns in diameter , and more preferably about 120 microns in diameter . the thickness of flame arrestor 14 is preferably less than 1 inch , and more preferably about ⅛ inch in thickness . it is desirable that the pores comprise about 30 - 40 % of the volume of internal flame arrestor 14 . internal flame arrestors with pore sizes , porous volumes and thicknesses outside the preferred ranges may also be used in the present invention , as long as they do not substantially block water flow . likewise , flames arrestors with shapes other than discs ( e . g ., cubes , balls or cylinders ) may be suitable for use in the present invention . in one embodiment , internal flame arrestor 14 may be composed of one or more ceramic materials , such as aluminum oxide ceramics . in another embodiment , internal flame arrestor 14 may be comprised of a thermoplastic polymer , such as polyvinyl chloride , nylon , fluorocarbon , polyethylene , polyurethane , polystyrene , polypropylene , cellulosic resin , and acrylic resin . an example of an internal flame arrestor that is suitable for use in the present invention is x - 5666 , a porous polypropylene flame arrestor by porex technologies corporation . the flame arrestor is a disc with a diameter of ⅜ inch , a thickness of ⅛ inch , a pore size of about 120 microns , and a porous volume of about 30 - 40 %. the battery flame retardant venting systems test sae j1495 was used to demonstrate that x - 5666 in the refill valves of a single point battery watering system inhibited flame propagation between cells in lead - acid batteries . other tests have indicated that the internal flame arrestor did not show any signs of degradation or erosion after an equivalent five year of service life at high pressure flow . tests have also demonstrated that the x - 5666 flame arrestor showed no signs of flow restriction . the water supplied in the tests was tap water , with an inline strainer having an 80 mesh screen , which is typical of industrial water supplies used with single point watering systems . the flow restriction due to this flame arrestor was found to be equivalent to a 1 / 16 diameter orifice , which is about the size of the refill valve inlet port 20 shown in fig3 . in addition , the cumulative cross - sectional area of the pores on the internal flame arrestor was estimated to be about 10 times higher than the cross - sectional area of the inlet port 20 . a more detailed cross - sectional view of refill valve 10 is shown in fig4 . it is shown that fluids enter refill valves through inlet connector 11 . the fluids then flow through internal flame arrestor 14 and inlet port 20 into reservoir 21 , which serves as an internal water trap . once filled , the fluids in reservoir 21 flows into chamber 22 . the refill valve shown in fig4 is in a closed position as occurs when the cells in the battery are filled with fluid . a displacer 26 is directly connected to stem 27 of a valve support assembly . when fluid level is low , the displacer rests in its reset position , which opens both upper valve 28 and lower valve 29 . in this orientation , water is free to flow from chamber 22 to upper and lower valve ports 23 and 30 . the water then flows into the battery cells through opening 24 . upper valve port 23 also provides another opening 25 that allows water flow to the cells . when the electrolyte level rises sufficiently to lift the displacer 26 , the upper and lower valves are pressed against their respective seats , 31 and 32 , by the pressure of the supply line , blocking further flow into the cell . such an assembly is described in more detail in u . s . pat . no . 6 , 227 , 229 and incorporated into this application by reference . though only a single internal flame arrestor is shown in fig2 - 4 , a plurality of flame arrestors may also be used in another embodiment of the present invention , as long as the flame arrestors do not interfere substantially with water flow . the refill valves of the present invention may also be used with different spw systems . in one embodiment , the spw system may comprise a plurality of refill valves 10 with water inlet connectors 11 , a single water source , and a tubing network that supplies water to the refill valves through the inlet connectors . examples of such spw systems and variations thereof are described in detail in u . s . pat . nos . 5 , 832 , 946 , 5 , 284 , 176 , 5 , 482 , 794 , and 5 , 453 , 334 . the disclosures of these patents are hereby incorporated by reference . single point battery watering systems with rigid manifold arrangements may also be used with the refill valves of the present invention . such spw systems comprise several rigid manifolds , where each manifold houses a plurality of refill valves . each manifold also contains a longitudinal water feed tube that places the housed refill valves in fluid communication with one another . in addition , a tubing network places the manifolds in fluid communication with each other and with a water supply tube . spw systems with such rigid manifold arrangements are disclosed in u . s . pat . no . 6 , 782 , 913 , u . s . pat . no . 6 , 644 , 338 , and u . s . pat . app . no . 2004 / 0161661 . these disclosures are also incorporated into this application by reference . the battery used with the spw systems of the present invention may be any wet cell battery , preferably a wet cell lead - acid battery , and more preferably a deep cycle lead - acid battery used in fast - charge installations . though the refill valves of the present invention are preferably used with spw systems to refill water in battery cells , they may also be used to supply cells with other fluids , such as electrolytes . it will be evident that there are numerous embodiments of the present invention which , while not expressly described above , are clearly within the scope and spirit of the invention . the above description is therefore intended to be exemplary only and the scope of the invention is to be determined solely by the appended claims .
the present invention is directed to a refill valve for use in single point battery watering systems for refilling wet cell batteries . the refill valve comprises a porous internal flame arrestor that is in the path of the liquid . such a design is advantageous because it prevents the internal propagation of flames between battery cells through the battery watering system under dry conditions .