Patent Application
20070221819
The present invention pertains to a system for fabricating septic tanks.
Septic tanks typically must be built to conform to regulations promulgated by one or more respective governmental entities such as state governments, city governments and other such municipalities, etc. These governmental regulations seek to ensure that septic tanks used in commercial or residential construction are structurally sound and are accessible for maintenance. For example, many jurisdictions have standards setting the amount of fluid pressure that commercial and residential septic tanks must be capable of withstanding. Conformance with these standards is usually tested by filling a finished septic tank with an amount of water sufficient to provide the pressure that the septic tank must be built to withstand.
Existing concrete septic tanks are typically formed by pouring concrete into an outer mold, and around an interior plug positioned within the mold. In order to facilitate the bulk fabrication of septic tanks, it is desired that both the outer mold and the inner plug be reusable to permit multiple concrete castings, thus reducing the cost of fabricating septic tanks. For example, U.S. Pat. No. 3,990,673 to Jones et al. and U.S. Pat. No. 3,687,597 to Lavergne Jr. each disclose respective reusable systems in which the inner plug and the outer mold may be detached from the hardened concrete septic tank. Though detachment of the outer mold from the hardened concrete is easily accomplished, detachment of the inner plug is often complicated. First, to facilitate removal of the plug from the interior of the hardened concrete casting, only five sides of the septic tank are poured using the aforementioned mold and plug assembly, with the remaining side poured separately, as will be later described. Once the concrete surrounding the plug has hardened, the plug must be detached from the five faces of the concrete tank and removed through the open side. Detachment of the plug from the concrete casting in which it is encased may involve either overcoming a substantial amount of friction generated over the large surface area where the plug and the concrete press against each other, or alternatively, some systems, such as the aforementioned patent to Jones et al., employ a complicated structure by which the inner mold is collapsed inward, and away from the concrete walls to avoid the resisting friction on the plug.
Once the plug has been removed, a cover (or top) of the septic tank is secured to the remainder of the tank enclosure. The cover is typically formed by pouring concrete into another mold that provides for an opening through the cover so that the interior of the finished septic tank may be accessed for maintenance.
Unfortunately, pouring a septic tank using the previously described prior art reusable mold and plug systems produces a finished septic tank that often fails to meet the required standards for fluid pressure containment. Specifically, when the tanks are tested by filling them with water to a required pressure, leakage occurs at the junction between the cover and the poured five-sided enclosure. Essentially, the economic incentive to reuse a plug, which dictates that the poured enclosure have an open side for removing the plug, weakens the septic tank structurally at the connection between that poured enclosure and the separately-poured cover.
What is desired, then, is a system for pouring septic tanks that includes a reusable plug and that produces a poured septic tank having improved structural strength over septic tanks fabricated using existing systems.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.
Referring to
Preferably, the plug and truss assembly 10 includes a plug 16, one or more trusses 18, and one or more retaining members 20 that in the disclosed plug and truss assembly 10 are shown as hoops having a circular cross section. Alternatively, the retaining members 20 may be of any other desired shape, such as square, etc. Preferably, each hoop 20 is positioned between a respective truss 18 and the plug 16, and the truss 18 preferably includes arms 22 that may rest on the outer mold 12. Each truss 18 may include a positioning mechanism 24 that operates to adjust the height of the plug 16 with respect to the bottom surface 26 of the outer mold 12, which may be a wall 14, the bottom surface of a hole in the ground, etc. Thus, the positioning mechanism 24 is used to lift the plug with respect to the outer mold so that concrete 28, when poured in the gap 30 between the plug 16 and the outer mold 12 as shown in
Referring specifically to
Furthermore, the plug 16 may be of a type that can be reused. Referring to
The respective hoops 20 preferably have a diameter (or other dimension if a non-circular retaining member 20 is used) of a size so that the periphery of the hoop 20 extends beyond that of the aperture panel 38. As can be seen in
One preferred embodiment of the disclosed exemplary septic tank system utilizes an assembled plug having exterior dimensions of 110 inches length, 69 inches width, and 56 inches height. In this embodiment, each corner panel 32 has two perpendicular sides 44, each having height of 28 inches and a 10 inch length lc and connected together by a beveled corner 46, so as to form a panel having a substantially U-shaped cross section. Each side panel 34 is substantially L-shaped in cross section, with two perpendicular sides 48 connected by a beveled section 50, so that the side panel 34 has a width ws of 20.5 inches and a height and length hs each of 28 inches. The L-shaped cross section of the side panels and the U-shaped cross section of the corner panels each give the respective panels around the top periphery of the plug 16 an overhanging center of gravity in the assembled plug 16. Thus, when a person is disassembling the plug 16, each of those upper side and corner panels will conveniently tilt downwards and inwards once separated from their neighboring panels, facilitating separation and removal of the individual panels from the hardened septic tank around the outer periphery of the plug 16. Similarly, end panels 35 also have an L-shaped cross section, but compared to the side panels 34, have a shorter top-section length of 10 inches, matching that of a corner panel 32. Each of the top panels 36 are 20.5 inches square, as are the aperture panels 38 which each define an opening 42. The aperture panels 38 may include tabs 52 that each help retain the hoop 20 in position around the opening 42. Similarly, the hoop 20 may include tabs 54 upon which spacers 55 on a respective truss 18 may rest. Each of the panels 30 may be formed of any suitable material, such as steel, but are preferably made of a lightweight material such as aluminum or a fiber-reinforced composite material.
One novel feature of the disclosed exemplary septic tank system is that the plug 16 may be assembled to enclose an arbitrary volume by utilizing more or less panels than that shown in
The outer mold 12 may comprise five walls 14 attached together to form an open-ended enclosure. Once the concrete 28 or other hardenable material poured inside the mold 12 and around the plug 16 has set, each of the walls 14 may be detached from its neighboring walls 14 and removed form the outer periphery of the septic tank. The outer mold 12 may comprise any appropriate material, such as iron, steel, aluminum, fiber-reinforced composite, etc.
Referring to
Another novel feature of the disclosed exemplary septic tank system is that a septic tank could simply be poured in the ground. In this embodiment, a hole is dug that then serves as the outer mold to the plug and truss assembly 10. The plug 16 is assembled, either in the hole itself or lowered into the hole after being assembled. The truss assemblies 18 are then used to raise the plug 16 relative to the hole and concrete 28 is poured into the hole and around the plug 16. Once the concrete 28 sets, a person can then climb inside the septic tank and disassemble the plug 16, removing each panel 30 from the septic tank through the opening 42.
It will be understood to those familiar in the art that the foregoing description of a septic tank fabrication system is exemplary only, and the members and methods described therein can be easily modified in scale and configuration. For example, the panels 32 and 34, described as having generally U-shaped and L-shaped cross sections, respectively, can be modified to be larger and/or have cross sections of other shapes. Moreover, though the preceding description of an exemplary method for fabricating a septic omitted discussion of forming required inlet and outlet valves for a formed septic tank, such details are well known to those skilled in casting septic tanks.
The terms and expressions that have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only the claims that follow.
The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.
