Vacuum relief valve for sewage holding tank

Abstract: A plastic sewage holding tank (17) in a boat (10), associated with a toilet (14), includes a vent check valve assembly (40) for providing vacuum relief. By mounting the vent check valve (40) in the top of the tank (17), when the tank is being emptied by rapid pumpout implosion or other damage to the tank is prevented. The vent check valve assembly (40) may include a valve body surface (45) operatively connected to the tank (17) and having a plurality of openings (46,47) formed in it, and a flexible material diaphragm (60) covering the openings (46,47) adjacent the inside of the tank (17), and uncovering openings (46,47) to allow air flow through the openings (46,47) substantially only when a vacuum condition exists inside the tank (17). A plastic disk (61) biases the diaphragm (60) into its opening-covering position, but a partial vacuum of at least about 2-5 inches of water allows air to flow through the openings past the diaphragm (60).

Description: It has become increasingly common to provide sewage pumpout stations for boats at docks. In such installations, a pumpout pump is provided which is connected up to a sewage holding tank (typically of plastic) in the boat, and quickly pumps all of the sewage out of the tank. Most commercial pumps for these pumpout stations have a capacity of up to about 151 liters per minute (40 gallons per minute), although capacities of as high as 170 liters per minute may be expected in the future. When such pumps are operated, it is difficult for the pump operator to know exactly when all the sewage has been pumped out of the holding tank, and the pump may stay in operation for a significant period of time, often up to about 30 seconds, after the tank has already been emptied. It has been recognized that this can exert a substantial strain on the holding tank, and can result in damage to the tank, or an implosion. Damage to the tank may result in leakage of sewage into the environment, obviously a highly undesirable event. In co-pending us-A-6,234,197 a number of different techniques are described by which damage to the tank as set forth above can be avoided by the provision of various constructions of vacuum relief means one other type of vacuum relief means is documented in document US-3228418 which is considered to be the closest prior art. According to the present invention which is claimed in independent claims 1, 4 and 12, another form of such vacuum relief means is provided which also prevents excess negative pressure inside a holding tank while being pumped out. However the vacuum relief valve assembly according to the present invention opens at about 5-7.5 cm (2-3 inches) of water, as opposed to about 33.02 cm (13 inches) of water which is typical of the structures illustrated in co-pending U.S. Patent No. 6,234,197. Also the vacuum relief valve assembly according to the present invention (as claimed in claims 1, 4 and 12) substantially prevents a "spitting" effect which is caused by impacts on the holding tank when full. Other relief valves often allow liquid to exit the valve when the tank is full and impacted with a 10-g load; the vacuum relief valve assembly according to the present invention substantially prevents this from occurring. The vacuum relief assembly according to the present invention is capable of providing sufficient air flow into the holding tank so that if the holding tank is emptied by a 170 liter per minute pump remaining in operation for 30 seconds after the plastic holding tank has been emptied, no damage to the holding tank ensues. According to one aspect of the present invention which is claimed in independent claim 12, a boat assembly is provided comprising the following components: A boat hull defining an interior boat volume. A toilet within the interior boat volume. A sewage holding tank operatively connected to the toilet, and also within the interior boat volume, the tank having an inside. An outlet conduit from the holding tank, and including a dockside pumpout fitting. An indicator of the fullness of the holding tank at at least one level of fullness thereof. A gas vent from the holding tank. And a vacuum relief valve assembly for the holding tank to prevent adverse consequences associated with a vacuum condition in the tank, the vacuum relief valve assembly comprising a valve body with a valve body surface operatively connected to the tank and having a plurality of openings formed therein, and a flexible valve disk covering the openings adjacent the inside of the tank, and uncovering openings to allow air flow therethrough substantially only when a vacuum condition exists inside the tanks, wherein said vacuum relief valve assembly further comprises a support disk mounted in contact with said flexible valve disk and providing a force on said flexible valve disk to releasably maintain said flexible valve disk in a position covering said openings. The vacuum relief valve assembly is preferably constructed and configured so that the opening when the vacuum inside the holding tank is as low as about 5-12.5 cm (2-5 inches) of water (e.g. about 5-7.5 cm (2-3 inches) of water) and substantially prevents the "spitting" effect. The vacuum relief valve assembly also preferably comprises the support disk which acts to releasably hold the valve disk into a position covering the openings. Preferably both the flexible valve disk and the support disk are substantially circular disks with the support disk having a diameter less than that of the flexible valve disk. A fastener assembly, such as a nut, bolt, and washer, is preferably provided to hold the disks in operative association with the valve body surface. The vacuum relief valve assembly may also comprise a splash protector which is mounted to the valve body on the opposite side from the disks as the openings. The plurality of openings comprises a plurality of openings of at least two different cross sectional areas including smaller cross sectional area openings around the periphery of the valve body. Preferably, the smaller cross sectional area openings are circular, and the difference in diameter between the valve disk and the support disk is approximately equal to the radius of the small openings. The flexible valve disk is preferably of an elastomeric material having a shore A durometer of about 50-70 (e.g. about 60) and a thickness of about 1.4-1.9 mm (.055-.075 inches). Preferably, the support disk comprises, or is equivalent to, a polypropylene disk having a thickness of between about 0.25-0.50 mm (.010-.020 inches). The flexible valve disk preferably has a diameter of between about 4.7-5.2 cm (1.85-2.05 inches), and the support disk preferably has a diameter of between about 4.2-4.95 cm (1 .65-1.95 inches). According to another aspect of the present invention which is claimed in independent claim 4, a sewage holding tank assembly is provided comprising the following components: A plastic sewage holding tank having a top and a bottom, a hollow interior, and an exterior. An outlet conduit from the holding tank and including a dockside pumpout fitting. A vent for the holding tank, adjacent the top thereof for allowing passage of gas under pressure from the tank to the exterior thereof. An inlet conduit for feeding sewage into the holding tank. And a vacuum relief valve assembly mounted to the holding tank top for allowing passage of air from exterior of the tank to the interior of the tank when a significant vacuum condition exists within the tank, the vacuum relief valve assembly comprising a valve body with a valve body surface operatively connected to the tank and having a plurality of openings formed therein, and a flexible valve disk covering the openings adjacent the inside of the tank, and uncovering openings to allow air flow therethrough substantially only when a vacuum condition exists inside the tank, wherein said vacuum relief valve assembly further comprises a support disk mounted in contact with said flexible valve disk and providing a force on said flexible valve disk to releasably maintain said flexible valve disk in a position covering said openings. The vacuum relief valve assembly is mounted to the holding tank by a peripheral upper lip on the valve body, substantially all of the valve body disposed within the tank hollow interior. Other details of the vacuum relief valve assembly are preferably as described above. According to yet another aspect of the present invention which is described in independent claim 1, a vacuum relief valve assembly per se, which acts as a vacuum relief device, is provided. The vacuum relief valve assembly comprises the following elements: A valve body comprising a tubular element having an open top (first end) and an open bottom (second end), a valve body surface disposed between the top and bottom and having a plurality of openings formed therein. A flexible valve disk having a substantially circular configuration covering the opening adjacent the second end of the valve body wherein the flexible valve disk opens with a vacuum on one side. A fastener assembly. A support disk of relatively stiff material engaging the flexible valve disk and releasably holding the flexible valve disk in a position covering the openings wherein the support disk is held by said fastener assembly. The support disk is entrapped within the valve body surface. The support disk preferably has a diameter about 85-96% that of the valve disk, and the valve body preferably is made of plastic. The other details of the vacuum relief valve assembly may be as described above. It is the primary object of the present invention to provide a simple and effective vacuum relief, valve assembly, which is particularly advantageous for use with sewage holding tanks, such as on boats. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a schematic view of a boat assembly according to the present invention incorporating a vacuum relief valve assembly for a sewage holding tank, as according to the invention; FIGURES 2 and 3 are top and bottom plan views, respectively, of an exemplary configuration of a vacuum relief valve assembly according to the present invention; FIGURE 4 is a longitudinal view, mostly in cross section but partly in elevation, of the vacuum relief valve assembly of FIGURES 2 and 3 mounted in the holding tank, and with the flexible valve disk and support disk removed for clarity of illustration; FIGURES 5 and 6 are full size top and side views, respectively, of an exemplary flexible valve disk according to the present invention; FIGURES 7 and 8 are full size top and side views, respectively, an exemplary support disk of a vacuum relief valve assembly according to the invention; and FIGURE 9 is a top plan view of an exemplary splash protector disk according to the present invention. DETAILED DESCRIPTION OF THEDRAWING A boat assembly according to the present invention of claim 12 is shown generally by reference numeral 10 in FIGURE 1. It includes a boat hull 11 which defines an interior boat volume (perhaps with other structure such as a deck 12 and a super structure above the deck). A toilet 14 is mounted within the interior boat volume (e.g. on deck 12), and is connected by a hose 15 or the like to an inlet 16 to a plastic holding tank 17. The holding tank 17 has a top 18, closed side walls 19, and a bottom 20, and is also mounted within the interior boat volume (typically below the deck 12). The holding tank 17 has an outlet 21 which is connected to an outlet conduit 22. The outlet conduit 22 includes at least one branch 23 which is connected to a dockside pumpout fitting 24 (e.g. associated with deck 12). The outlet conduit 22 can also have a second branch 25 which is connected to a small pump 26 also mounted within the interior boat volume, which in turn is connected by a hose 27, typically having a vented loop 28, to a seacock 29. The vented loop 28 is vented as indicated by vent line 30 and vent opening 31 in hull 11. As typically associated with a tank 17, a gas vent line 33 is preferably provided, which may have a filter 34 therein, and a vent opening 35 in the hull 11. Also an indicator 37 of the fullness of the tank 17 at at least one fullness level thereof, is provided. The indicator 37 may, for example, be a Tankwatcho® level indicator sold by Sealand Technology, Inc. of Big Prairie, Ohio. The indicator 37 typically at least indicates a three-quarters fullness level of the tank 17, and preferably also an approximately full level. What has heretofore been described is conventional. What is provided according to the present invention of claim 1 in order to prevent an implosion of the tank 17, or other damage thereof, due to rapid pumpout through the outlet conduit 22 and dockside pumpout fitting 24, is the vacuum relief valve assembly 40. The vacuum relief valve assembly 40 includes a substantially tubular valve body 41, preferably of a relatively rigid and tough plastic, such as injection molded in one piece from ABS. Body 41 includes a first (top) end 42 and a second (bottom) end 43, both of which are substantially open. The body 41 has a peripheral lip 44 adjacent the top end 42 thereof which facilitates mounting of the vacuum relief valve assembly 40 in the opening 39 (see FIGURE 4) of the top 18 of the holding tank 17. Any other mounting components can be utilized that are desired, such as an interference fit between the outside circumference of the valve body 41 and the opening 39, or extraneous fasteners, adhesive, or the like. Preferably the peripheral lip or ring 44 mounts the vacuum relief valve assembly 40 so that substantially all of the body 41 us within the interior volume of the tank 17, as seen in FIGURE 4. The vacuum relief valve assembly 40 further comprises a valve body surface 45 (see FIGURES 2 and 4) between the ends 42, 43 of the body 41 and typically integral therewith, and having a plurality of openings 46, 47 therein. Preferably at least two different sized sets of openings 46, 47 (as seen most clearly in FIGURE 2) are provided, larger openings 46 which extend substantially all the way from the center of the surface 45 toward the periphery, and the smaller openings 47 disposed between the larger openings 46 adjacent the periphery. The openings 47 are of a smaller diameter than the openings 46, and preferably both the openings 46, 47 are circular, although other shapes of openings (including slits, rings, polygons, arcs, or the like) may be utilized. In the exemplary embodiment of the invention illustrated in the drawings, for example, the openings 47 may have a diameter of about 6.4 mm (a quarter of an inch) while the openings 46 have a diameter of about 1.58 cm (.625 inches). The valve body 41 also preferably includes a central tube 49 which extends upwardly from the surface 45 to substantially even with the top 42 of the body 41, as seen most clearly in FIGURE 4. The tube 49 has a central bore 50 which is associated with a fastener system 51 (see FIGURE 4). The fastener assembly 51 is for holding other valve components (as will be hereinafter described) to the body 41. In the preferred embodiment illustrated in the drawings the fastener assembly 51 comprises a bolt having a head 52 and a screw threaded shank 53, an internal threaded nut 54 for cooperation with the shank 53, and a metal washer 55. The bolt 52, 53 and nut 54 also are preferably made of metal although they (and the washer 55) may be made of hard plastic in some circumstances. The vacuum relief valve assembly 40 further comprises a flexible valve disk 60 (seen most clearly in FIGURES 3, 5, and 6) which covers the openings 46, 47 at the bottom-most face of the surface 45 as seen in FIGURE 4. That bottom-most face, 59 in FIGURE 4, preferably is slightly radiused (e.g. forming a spherical segment based upon an arc/sphere having a radius of about 11.4-15.2 cm (4.5-6 inches), e.g. about 13.66 cm (5.38 inches)). The flexible valve disk 60 preferably comprises a substantially circular disk of an elastomeric material, such as elastomeric plastic, synthetic rubber, or natural rubber. In the preferred embodiment the material of flexible valve disk 60 is nitrile rubber. The flexible valve disk 60 preferably has a Shore A durometer of between about 50-70 (e.g. about 60). In the preferred embodiment illustrated in FIGURE 5 flexible valve disk 60 has a diameter of about 4.7-5.2 cm (1.85-2.05 inches) (e.g. about 5 cm (1.94 inches)), with a central opening 62 therein having a diameter of about 6.3 mm (a quarter of an inch), for receipt of the shank 53 of the fastener assembly 51. In the preferred embodiment the flexible valve disk 60 has a thickness of between about 1.4-1.9 mm (.055-.075 inches) (e.g. about 1.6 mm (.063 inches)). To support the flexible valve disk 60 so that it does not sag or flap under normal circumstances, a support disk 61 is provided, as seen in FIGURES 3, 7 and 8. The support disk 61 preferably has a circular configuration and is in the form of a disk, as seen in FIGURES 3, and 7. Disk 61 is preferably flexible, but made of a relatively rigid material, such as a relatively rigid plastic such as polypropylene. The disk 61 has a diameter that is between about 85-96% of the diameter of the valve disk 60. For example, in the preferred embodiment illustrated in the drawings the disk 61 has a diameter ofbetween about 4.2-4.95 cm (1.65-1.95 inches), e.g. about 4.6 cm (1.81 inches), or about 93-94% that of the flexible valve disk 60. The support disk 61, when tightened into contact with the shank 53 passing through the opening 63 (FIGURE 7) and tightened by the nut 54, holds the flexible valve disk 60 against the surface 59, covering the openings 46, 47. However, the support disk 61 has sufficient flexibility so that when a vacuum condition of about 5-12.5 cm (2-5 inches) of water (or greater) e.g. about 5-7.5 cm (2-3 inches) of water (or greater) exists in the tank 17 both the support disk 61 and the flexible valve disk 60 will be deformed by air rushing through at least some of the openings 46, 47 to equalize the pressure in the tank 17. In the preferred embodiment illustrated, the support disk 61 (as seen in FIGURE 8) has a thickness of about 0.25-0.50 mm (.01-.02 inches) (e.g. about 0.38 mm (.015 inches)). The valve body 41 may also include a ring-shaped channel 66 (see FIGURE 4) which can hold the splash protector disk 67 (see FIGURE 9) to protect the components 53-55, 61, and 60 from sewage splashing thereon, and facilitating corrosion thereof, or interfering with the performance thereof. For example, the splash protector 67 which is mounted in the ring shaped channel 66 on the opposite side of the flexible valve disk 60 from the support surface 45, may be a disk of any material which allows the substantially free passage of air therethrough, but will substantially prevent liquid from splashing up onto the components 53-55, 61, 60. For example, the protector disk 67 may be a stiff cloth disk, woven or non-woven, made of a non-corrosive material, such as nylon, fiberglass, or the like, and if desired partially impregnated with resin (while not interfering with its ability to pass air therethrough in an effective manner) to enhance is rigidity. The splash protector disk 67 may be replaced as necessary, and the valve assembly 40 may be removed from the opening 39 for this purpose. In operation, during pumpout of the sewage holding tank 17 (or in other aberrant conditions where a partial vacuum may exist within the tank 17), the vacuum relief valve assembly 40 allows air to flow from the exterior of the tank through at least some of the openings 46, 47, past the disks 60, 61, into the tank 17. The ability of the vacuum relief valve assembly 40 to allow the passage of air typically must be sufficient so that it is capable of providing sufficient air flowing into the tank 17 so that if the tank 17 is emptied by a 170 liter per minute pump remaining in operation for 30 seconds after the plastic tank 17 has been emptied, no damage to the tank 17 ensues. The particular vacuum relief valve assembly 40 according to the present invention also opens quickly (e.g. when there is a partial vacuum only between about 5-12.5 cm (2-5 inches) of water, and the configuration of the vacuum relief valve assembly 40 prevents a "spitting effect". While the preferred use of the vacuum relief valve assembly 40 is in a holding tank (as in claim 4) particularly on a boat, it may be used in other circumstances where a check valve is necessary but operates at a relatively low pressure differential, but can allow a relatively high volume flow of fluid therethrough. It will thus be seen that according to the present invention a highly advantageous boat assembly (as in claim 12) sewage holding tank (as in claim 4) and valve assembly (as in claim 1) therefor, have been provided. The valve assembly according to the invention is reliable, relatively inexpensive, and the only movable components thereof are easy to replace or clean. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

Claims: A vacuum relief valve assembly (40) comprising: a valve body (41) comprising a tubular element having an open top first end (42) and an open bottom second end (43), a valve body surface (45) disposed between said top (42) and bottom (43) and having a plurality of openings (46, 47) formed therein; a flexible valve disk (60) having a substantially circular configuration covering said openings (46, 47) adjacent said second end (43) of said valve body (41), wherein the flexible valve disk (60) opens with a vacuum on one side; and a fastener assembly (51), characterized by : a support disk (61) of relatively stiff material engaging said flexible valve disk (60) and releasably holding said flexible valve disk (60) in a position covering said openings (46, 47); wherein the support disk (61) is held by said fastener assembly (51). A valve assembly as recited in claim 1 wherein said support disk (61) having a diameter about 85-96% that of said flexible valve disk (60), and said valve body (41) is made of plastic. A valve assembly as recited in claim 1, wherein said flexible valve disk (60) is of an elastomeric material having a shore A durometer of about 50-70 and a thickness of about . 1.4-1.9 mm (.055-.075 inches) and wherein said support disk (61) comprises or is equivalent to, a polypropylene disk having a thickness of between about 2.5 - 5 mm (.010-.020 inches) and wherein said flexible valve disk (60) has a diameter of between about 4.7-5.2 cm (1.85-2.05 inches) and said support disk (61) has a diameter of between about 4.2-4.95 cm (1.65-1.95 inches) and wherein said plurality of openings (46, 47) comprise a plurality of openings of at least two different cross section areas including smaller cross sectional area openings (47) around the periphery of said valve body (41), said smaller cross sectional area openings (47) being circular; and wherein the difference in diameter between said flexible valve disk (60) and said support disk (61) is approximately equal to the radius of said smaller cross sectional area openings (47). A sewage holding tank assembly comprising: a plastic sewage holding tank (17) having a top (18) and a bottom (20), a hollow interior, and an exterior; an outlet conduit (22) from said holding tank (17) and including a dockside pumpout fitting (24); a vent for said holding tank (17), adjacent said top (18) thereof for allowing passage of gas under pressure from said holding tank (17) to the exterior thereof; an inlet conduit (15) for feeding sewage into said holding tank (17); and a vaccum relief valve assembly (40) mounted to said holding tank top (18) for allowing passage of air from exterior of said holding tank (17) to the interior of said holding tank (17) when a significant vacuum condition exits within said holding tank (17), said valve assembly (40) comprising a valve body (41) with a valve body surface (45) operatively connected to said tank and having a plurality of openings (46, 47) formed therein, and a flexible valve disk (60) covering said openings adjacent said inside of said tank, and uncovering openings to allow air flow therethrough substantially only when a vacuum condition exists inside said tank, wherein wherein said vacuum relief valve assembly (40) further comprises a support disk (61) mounted in contact with said flexible valve disk (60) and providing a force on said flexible valve disk (60) to releasably maintain said flexible valve disk (60) in a position covering said openings (46, 47). A sewage holding tank assembly as recited in claim 4 wherein said vacuum relief valve assembly (40) is constructed and configured so that said flexible valve disk (60) uncovers openings (46, 47) to allow air flow therethrough when the vacuum within said holding tank is as low as about 5-12.5 cm (2-5 inches) of water, and substantially prevents spitting. A sewage holding tank assembly according to claim 4 wherein said flexible valve disk (60) is a substantially circular disk, and wherein said support disk (61) is also a substantially circular disk having a diameter less than the diameter of said flexible valve disk (60). A sewage holding tank assembly as recited in claim 4 whrein said flexible valve disk (60) and said support disk (61) are releasably held to said valve body (41) with a fastener assembly (sol). A sewage holding tank assembly as recited in claim 4 wherein said plurality of openings (46, 47) comprise a plurality of openings of at least two different cross sectional areas including smaller cross sectional area openings (47) around the periphery of said valve body (41), said smaller cross sectional area openings (47) being circular; and wherein the difference in diameter between said flexible valve disk (60) and said support disk (61) is approximately equal to the radius of said smaller cross sectional area openings (47). A sewage holding tank assembly as recited in claim 4 further comprising a splash protector disk (67) mounted to said valve body (41) on the opposite side of said flexible valve disk (60) and supportdisk (61) from said openings (46, 47). A sewage holding tank assembly as recited in claim 4 wherein said flexible valve disk (60) is of an elastomeric material having a shore A durometer of about 50-70 and a thickness of about 1.4-1.9 mm (.055-.075 inches) and wherein said support disk (61) comprises or is equivalent to, a polypropylene disk having a thickness of between about 2.5 - 5 mm (.010-.020 inches) and wherein said flexible valve disk (60) has a diameter of between about 4.7-5.2 cm (1.85-2.05 inches) and said support disk (61) has a diameter of between about 4.2-4.95 cm (1.65-1.95 inches). A sewage holding tank assembly as recited in claim 4 wherein said valve assembly (40) is mounted to said holding tank (17) by a peripheral upper lip (44) on said valve body (41) substantially all of said valve body disposed within said tank hollow interior. A boat assembly, comprising: a boat hull (11) defining an interior boat volume; a toilet (14) within the interior boat volume; a sewage holding tank (17) operatively connected to said toilet (14), and also within said interior boat volume, said tank having an inside; an outlet conduit (22) from said holding tank (17), and including a dockside pumpout fitting (24); an indicator (37) of the fullness of said holding tank (17) at at least one level of fullness thereof; a gas vent from said holding tank (17); and a vacuum relief valve assembly (40) for said holding tank (17) to prevent adverse consequences associated with a vacuum condition in said tank, said valve assembly (40) comprising a valve body (41) with a valve body surface (45) operatively connected to said holding tank (17) and having a plurality of openings (46, 47) formed therein, and a flexible valve disk (60) covering said openings adjacent said inside of said tank, and uncovering openings (46, 47) to allow air flow therethrough substantially only when a vacuum condition exists inside said holding tank (17), wherein said valve assembly (40) further comprises a support disk (61) mounted in contact with said flexible valve disk (60) and providing a force on said valve disk (60) to releasably maintain said valve disk (60) in a position covering said openings (46,47). A boat assembly as recited in claim 12 wherein said vacuum relief valve assembly (40) is constructed and configured so that said flexible valve disk (60) uncovers openings (46, 47) to allow air flow therethrough when the vacuum within said holding tank (17) is as low as about 5-12.5 cm (2-5 inches) of water and substantially prevents spitting. A boat assembly as recited in claim 12 wherein said flexible valve disk (60) is a substantially circular disk, and wherein said support disk (61) is also a substantially circular disk having a diameter less than the diameter of said flexible valve disk (60) A boat assembly as recited in claim 12 wherein said flexible valve disk (60) and said support disk (61) are releasably held to said valve body (41) with a fastener assembly (51). A boat assembly as recited in claim 12 further comprising a splash protector disk (67) mounted to said valve body (41) on the opposite side of said flexible valve disk (60) and support disk (61) from said openings (46, 47). A boat assembly as recited in claim 12 wherein a plurality of openings (46, 47) comprise a plurality of openings of at least two different cross sectional areas including smaller cross sectional area openings (47) around the periphery of said valve body (41). A boat assembly as recited in claim 12 wherein said plurality of openings (46, 47) comprise a plurality of openings of at least two different cross sectional areas including smaller cross sectional area openings (47) around the periphery of said valve body (41), said smaller cross sectional area openings (47) being circular; and wherein the difference in diameter between said flexible valve disk (60) and said support disk (61) is approximately equal to the radius of said smaller cross sectional area openings (47). A boat assembly as recited in claim 12 wherein said flexible valve disk (60) is of an elastomeric material having a shore A durometer of about 50-70 and a thickness of about 1.4-1.9 mm (.055-.075 inches) and wherein said support disk (61) comprises or is equivalent to, a polypropylene disk having a thickness of between about 2.5 - 5 mm (.0 10-.020 inches) and wherein said flexible valve disk (60) has a diameter of between about 4.7-5.2 cm (1.85-2.05 inches) and said support disk (61) has a diameter of between about 4.2-4.95 cm (1.65-1.95 inches).

Inventors: FRIEDMAN WILLIAM J, MCKIERNAN EDWARD, SIGLER JAMES A, FRIEDMAN, WILLIAM J., MCKIERNAN, EDWARD, SIGLER, JAMES A.
Applicants: SEALAND TECHNOLOGY INC, SEALAND TECHNOLOGY, INC.
Application year: 1999
Main classification: F16K17
IPC codes: F16K24, B63B29