Septic tank fabrication system

A system for fabricating a septic tank using an outer mold and an inner removable plug, between which hardenable fluid material is poured. Preferably, the plug and mold are positioned with respect to one another in a manner that permits a septic tank to be fabricated in a single pour.

BACKGROUND OF THE INVENTION

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.

DETAILED DESCRIPTION

Referring toFIGS. 1-3, an exemplary septic tank fabrication system may include a plug and truss assembly10and an outer mold12(shown inFIG. 3) surrounding the plug and truss assembly10. The outer mold12in one embodiment may be fashioned of multiple walls14forming a five-sided enclosure that may be positioned around the plug and truss assembly10. In another embodiment, as further described later in this specification, the outer mold12may simply be the walls of a hole in the ground. It should also be understood that, although the plug and truss assembly10and the outer mold12are each of a substantially rectangular or cubical construction, and thus forming a box-like septic tank, alternate embodiments of the disclosed septic tank fabrication system may utilize molds and plug assemblies of other desired shapes, e.g. cylindrical, spherical, etc.

Preferably, the plug and truss assembly10includes a plug16, one or more trusses18, and one or more retaining members20that in the disclosed plug and truss assembly10are shown as hoops having a circular cross section. Alternatively, the retaining members20may be of any other desired shape, such as square, etc. Preferably, each hoop20is positioned between a respective truss18and the plug16, and the truss18preferably includes arms22that may rest on the outer mold12. Each truss18may include a positioning mechanism24that operates to adjust the height of the plug16with respect to the bottom surface26of the outer mold12, which may be a wall14, the bottom surface of a hole in the ground, etc. Thus, the positioning mechanism24is used to lift the plug with respect to the outer mold so that concrete28, when poured in the gap between the plug16and the outer mold12as shown inFIG. 3, forms a septic tank in a single pour.

Referring specifically toFIGS. 5 through 7, fluid concrete or other hardenable material may be poured into the aforementioned exemplary septic tank fabrication system such that the fluid concrete28or other hardenable material flows beneath the plug16, begins to rise along the sides of the plug16, and finally begins to flow over the top of the plug16. At that time, the poured fluid concrete28will have two cross sections, as seen inFIGS. 6 and 7, respectively, each mutually perpendicular to each other, and each self bounded. The fluid concrete will then flow around the hoops20and may then be allowed to harden. Once hardened, the fluid material, such as concrete, will form an integral septic tank enclosure that will not be weakened by a joint between an open-ended enclosure and a separately-formed cover. Thus, a septic tank fabricated using the disclosed system will be more durable and better able to withstand both testing and operational fluid pressures.

Furthermore, the plug16may be of a type that can be reused. Referring toFIGS. 2 and 4, the plug and truss assembly10may comprise individual panels30that are each of a size that fits within the opening42of the septic tank formed by a respective hoop20. The disclosed plug16includes panels30of several shapes. For example, the plug16may comprise corner panels32, side panels34, corner panels35, top panels36, as well as aperture panels38over which a respective hoop20may rest as concrete is poured. Each of the panels30may be selectively, detachably secured to one or more other panels30to form the plug16. The panels30may be secured to each other using any suitable means, such as bolts40.

The respective hoops20preferably have a diameter (or other dimension if a non-circular retaining member20is used) of a size so that the periphery of the hoop20extends beyond that of the aperture panel38. As can be seen inFIG. 4, this ensures that the aperture panel38, when disassembled from the other panels30, may fit through one of the concrete openings42of the septic tank28that is formed by a respective hoop20. Similarly, each of the panels30may preferably be small enough to fit through an opening42of the septic tank28. It should be understood that, although the disclosed plug16comprises individual panels, each selectively, detachably securable to one another, and each sized to fit through an opening42of the septic tank, other such systems may include some panels30that are of a size that do not fit through an opening42. In that instance, though some panels may remain in the interior of the septic tank, the panels30that are removed can be reused and therefore increase the economic efficiency by which multiple septic tanks may be fabricated.

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 panel32has two perpendicular sides44, each having height of 28 inches and a 10 inch length lcand connected together by a beveled corner46, so as to form a panel having a substantially U-shaped cross section. Each side panel34is substantially L-shaped in cross section, with two perpendicular sides48connected by a beveled section50, so that the side panel34has a width wsof 20.5 inches and a height and length hseach 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 plug16an overhanging center of gravity in the assembled plug16. Thus, when a person is disassembling the plug16, 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 plug16. Similarly, end panels35also have an L-shaped cross section, but compared to the side panels34, have a shorter top-section length of 10 inches, matching that of a corner panel32. Each of the top panels36are 20.5 inches square, as are the aperture panels38which each define an opening42. The aperture panels38may include tabs52that each help retain the hoop20in position around the opening42. Similarly, the hoop20may include tabs54upon which spacers55on a respective truss18may rest. Each of the panels30may 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 plug16may be assembled to enclose an arbitrary volume by utilizing more or less panels than that shown inFIG. 1, whose size is described in the preceding paragraph. As can easily be seen fromFIG. 2, for example, if a septic tank of a larger volume is desired, more side panels34may simply be inserted into the plug16to increase the length and/or the width of the plug16. Similarly, the addition of top panels36between respective top and bottom side panels34around the lateral periphery of the plug16would increase the height of the plug16, if desired. Thus, the disclosed exemplary septic tank system is not only economically efficient in that it may be reused, it also is efficient in that it obviates the need to have plugs or plug molds of different sizes in inventory.

The outer mold12may comprise five walls14attached together to form an open-ended enclosure. Once the concrete28or other hardenable material poured inside the mold12and around the plug16has set, each of the walls14may be detached from its neighboring walls14and removed form the outer periphery of the septic tank. The outer mold12may comprise any appropriate material, such as iron, steel, aluminum, fiber-reinforced composite, etc.

Referring toFIGS. 2 and 3, the truss assembly18may include two lateral support arms22at each end of the truss assembly18. The truss assembly18may also include a positioning mechanism24comprising a threaded bolt64rotatably mounted in a mating sleeve66and having a planar flanged end68secured to its lower end. As can be seen inFIG. 3, each respective truss18may be mounted onto the plug16so that each lateral arm22of a respective truss18rests on a side of the outer mold12. The flanged end68is inserted through the opening42so as to engage the upper interior surface of the plug16around the periphery of the opening42. In this configuration, rotation of the threaded bolt64will raise the plug16relative to the bottom of the mold12between a first, upper position where the hoop20presses against the truss18and a lower position where the plug16rests on the lower wall14of the mold12. In this manner, the vertical position of the plug16may be adjusted relative to the mold12so as to permit fluid material such as concrete28to flow both beneath and above the plug16, and form a septic tank in a single pour. Adjustment of the height of the plug16may also be used to determine the thicknesses of the top and bottom portions of the septic tank, as well. An alternate configuration could rotatably secure the bolt64of the truss18to a fixed support above the plug and truss assembly10and an outer mold12.

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 assembly10. The plug16is assembled, either in the hole itself or lowered into the hole after being assembled. The truss assemblies18are then used to raise the plug16relative to the hole and concrete28is poured into the hole and around the plug16. Once the concrete28sets, a person can then climb inside the septic tank and disassemble the plug16, removing each panel30from the septic tank through the opening42.

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 panels32and34, 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.