Sewage tanks and grinder pump systems

CA 02575809 2007-02-01

WO 2006/017448 PCT/US2005/027280

SEWAGE TANKS AND GRINDER PUMP SYSTEMS

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority of U.S. Provisional Application, Serial Number 60/598,231, filed August 2, 2004, the entire disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates generally to sewage tanks, and more particularly, to sewage tanks for use with pumps such as grinder pumps.

BACKGROUND OF THE INVENTION

[0003] Grinder pumps are often used in low-pressure sewage systems for pumping sewage. A grinder pump includes a grinder mechanism for cutting or grinding solids or semisolid matter in the sewage being pumped. Grinding solids and/or semisolid matter in the sewage allows the resulting particulate effluent to be transferred using a pump through small diameter pipes without clogging.

[0004] Typically, conventional sewage tanks are installed by digging a hole, placing the tank in the ground, and then pouring concrete around the bottom of the tank. The concrete provides proper ballast to prevent the tank from floating upwardly and popping out of the ground due to its buoyancy under high ground water conditions.

[0005] There is a need for further sewage tanks and pump systems employing the same.

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SUMMARY OF THE INVENTION

[0006] The present invention provides, in a first aspect, a sewage tank for use with a pump to convey sewage. The sewage tank includes a container having an upper portion and a lower portion defining a chamber for containing the pump. The upper portion has a generally constant crosssection and the lower portion has a tapered cross-section to reduce retained sewage. At least one of the upper portion and the lower portion comprise a plurality of intersecting vertical ribs and horizontal ribs defining a plurality of recessed pockets.

[0007] The present invention provides, in a second aspect, a sewage tank for use with a pump to convey sewage. The sewage tank includes a container having an upper portion and a lower portion defining a chamber for containing the pump. The upper portion has a generally constant crosssection and the lower portion has a tapered cross-section to reduce retained sewage. The lower portion of the container comprises an outwardly extending member. The taper of the lower portion of the container and the outwardly extending member are configured to allow backfilling of the sewage tank so that the backfill provides sufficient ballast under high ground water conditions.

[0008] The present invention provides, in a third aspect, a sewage tank for use with a pump to convey sewage. The sewage tank includes a container for containing the pump, and the container comprises an upper portion having an inwardly extending portion for providing an opening for a vent.

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[0009] The present invention provides, in a fourth aspect, a pump system which includes the above-described sewage tank and a pump such as a grinder pump disposable in the sewage tank.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion ofthe specification. The invention, however, may best be understood by reference to the following detailed description of various embodiments and accompanying drawings in which:

[0011] FIG. 1 is a perspective view of one embodiment of a grinder pump system including a sewage tank in accordance with the present invention;

[0012] FIG. 2 is a perspective view, partially cutaway, of the grinder pump system of FIG. 1;

[0013] FIG. 3 is a perspective view, partially cutaway, of another embodiment of a grinder pump system including a sewage tank in accordance with the present invention;

[0014] FIG. 4 is a side elevational view of the grinder pump system of FIG. 3;

[0015] FIG. 5 is a side elevational view of a plurality of grinder pump systems of FIG. 3 nested together for shipping;

[0016] FIG. 6 is a front elevational view of another embodiment of a grinder pump system including a sewage tank in accordance with the present invention;

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[0017] FIG. 7 is a front elevational view, partially cutaway, of the grinder pump system of FIG. 6;

[0018] FIG. 8 is a front elevational view, partially cut away, of the grinder pump system of FIG. 7 along with a plurality of access ways;

[0019] FIG. 9 is a perspective view of one embodiment of a top of.a sewage tank having an inwardly extending member for providing a vent in accordance with the present invention;

[0020] FIG. 10 is a front elevational view of another embodiment of a grinder pump system including a sewage tank in accordance with the present invention;

[0021] FIG. 11 is a left side elevational view of the grinder pump system of FIG. 10; and

[0022] FIG. 12 is a right side elevational view of the grinder pump system of FIG. 10.

DETAILED DESCRIPTION OF THE INVENTION

[0023] FIGS. 1 and 2 illustrate one embodiment of a low-pressure grinder pump wastewater disposal system 10 in accordance with the present invention for collecting, grinding, and pumping wastewater. System 10 generally includes a sewage tank 20 and a grinder pump 12 (FIG. 2).

[0024] System 10 is readily installable in the ground by connecting the system to a wastewater feed pipe 14 (FIG. 2), a wastewater discharge pipe (FIG. 2), and an electrical power supply (not shown). The system may also be connected to or include a vent (not shown). The exemplary

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WO 2006/017448 PCT/US2005/027280 wastewater disposal system provides a convenient, self-contained unit. In addition, the exemplary system is readily accessible and serviceable by a technician or a repair person.

[0025] Sewage tank 20 includes a container 21 having a lower portion 22 and an upper portion 24 which together define a sealable chamber 30 (FIG. 2) therein for receiving wastewater, for example, from a building. In one aspect, the upper portion has a generally constant cross-section and the lower portion has a tapered cross-section to reduce retained sewage. The upper portion and/or the lower portion may include a plurality of vertical ribs 25 and horizontal ribs 27 defining a plurality of recessed pockets 29. The plurality of vertical ribs, the plurality of horizontal ribs, and the plurality of recessed pockets are configured to provide an opening for installation of at least one of an inlet, an outlet, and a vent. The ribs and pockets may provide an inlet, an outlet, or a vent at continuous selectable vertical elevations along the upper portion of the container. As best shown in FIG. 2, the bottom of the sewage tank may include a concave bottom 23.

[0026] Another aspect of the present invention is the elimination of conventional concrete ballast thereby eliminating the need and labor associated with pouring concrete around the bottom of the sewage tank in the ground to prevent it from floating upward due to its buoyancy under high ground water conditions.

[0027] As shown in FIGS. 1 and 2, sewage tank 20 may include a twopiece ring or flange 40 that may be connectable to the bottom of the tank. Flange 40 increases the footprint of the sewage tank (e.g., extends laterally outward from the sidewall) so that the soil above the flange acts as a ballast preventing the sewage tank from floating upwardly and popping out of the ground during high ground water conditions. The flanges may include bolt-5CA 02575809 2007-02-01

WO 2006/017448 PCT/US2005/027280 on flanges, snap-on flanges, or other suitably connectable flanges. The flange may be provided with an inwardly-extending tongue 42 that is received in a groove 26 extending around the bottom of the sewage tank. In addition, the sewage tank without the flange may allow conventional installation with concrete. For example, the concrete can grab on or secure to the groove on the bottom of the sewage tank.

[0028] The size of the flange may be determined based on the displaced volume of the soil and/or the volume of the sewage tank in order to provide suitable ballast under high ground water conditions. In one embodiment, a sewage tank about 95 inches high (with access way extension) and about 29 inches wide may include a flange having an outer circular edge with a diameter of about 40 inches.

[0029] The bottom portion of the sewage tank may be tapered so that when the pump shuts off the sewage remaining in the bottom of the sewage tank is reduced compared to a tank having a constant cross-section from top to bottom. Desirably, the taper is not too great thereby making it difficult to backfill and compact the backfill during installation.

[0030] FIGS. 3 and 4 illustrate another embodiment of a sewage tank 100 in accordance with the present invention (generally similar to sewage tank 20) which includes an integrally formed stepped ballast ring 110 that extends around the bottom of the sewage tank and which is sized to eliminate the need for installing a concrete ballast. In addition, the stepped configuration allows a plurality of sewage tanks to be nested together for shipment as best shown in FIG. 5. For example, on one side of the sewage tank, a portion of the flange is disposed at a different vertical height than an opposite portion of the flange. The lower and higher portions of the flange allow a plurality of

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WO 2006/017448 PCT/US2005/027280 sewage tanks to be compactly arranged as shown in FIG. 5 to optimize shipping.

[0031] Another feature is that the top may incorporate two flats 112 on the side of the tank so that a forklift truck can readily grab the tank and so that the need to bolt the tank to a traditional pallet is eliminated. The forklift truck may engage the top of the tank by either of two directions and reduce the effort required in loading and unloading the tank.

[0032] In addition, upwardly-extending protrusions or stops 120 (FIG. 3) may be molded into the inner bottom surface for receiving and retaining the stand for supporting the grinder pump in the center of the tank. For example, four protrusions may be provided.

[0033] FIGS. 6-8 illustrate another embodiment for a sewage tank 200 in accordance with the present invention (generally similar to sewage tank 20) that includes the sewage tank having a relatively large diameter flange formed integral with the tank. The flange is desirably sized large enough to provide suitable ballast to keep the sewage tank from floating without the need for concrete. It is also noted that concrete may be employed for increasing the retention of the sewage tank in the ground.

[0034] The various tanks may incorporate a series of four vertical ribs. The vertical areas are designed so that an opening may be cut along the vertical area for receiving a feed wastewater pipe. A grommet may be placed in the opening for receiving and sealing around the inlet pipe. Similarly, an opening may be cut along a vertical area through which a discharge pipe may pass. In addition, an opening may be cut along the vertical area through which a vent may pass. The feed wastewater pipe,

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WO 2006/017448 PCT/US2005/027280 discharge pipe, and vent may also pass through the horizontal ribs or pockets between the ribs.

[0035] The top may also be set up to receive an access way extension (e.g., as shown in FIG. 8) so that the height ofthe sewage tank could be increased in various increments. In addition, the sewage tank may include a releasably sealable cap having a vent opening (e.g., FIG. 7).

[0036] During fabrication of the tank, a top may be integrally formed with the side wall and bottom. The top can then be cut out, e.g., trimmed to provide an opening to the tank, during installation. Desirably, the top or cover may be either isolated or contain a vent tab allowing either internally venting through a cover system or laterally through the sidewall. FIG. 9 illustrates a top having inwardly extending portion 50 forming a kidneyshaped cutout in the top. The inwardly extending portion may include a vent opening 52.

[0037] FIGS. 10-12 illustrate another embodiment for a sewage tank 300 in accordance with the present invention which is generally similar to sewage tank 20. A plurality of pads 310, 320, and 330 are provided for use in providing an opening for providing an inlet for a feed wastewater pipe or discharge pipe. The pads, ribs, and pockets allow providing an opening for installation of at least one of a feed wastewater pipe and a discharge pipe at continuous selectable elevations along the upper portion of the sewage tank.

[0038] The grinder pump for use in the various systems may include a grinder mechanism for pulverizing solids or semisolid matter in the wastewater, a pump assembly attached to the grinder mechanism for pumping ground wastewater through the grinder pump, and a motor. For example, a grinder mechanism may include a stationary outer ring and a

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WO 2006/017448 PCT/US2005/027280 rotating cutting blade, and a pump assembly may include a progressing cavity pump having a pump housing, a pump stator, and a pump rotor. It will be appreciated by those skill in the art that other suitable grinder pumps, grinding mechanisms and pump assemblies may be employed.

[0039] A motor housing casting houses the electric motor for powering both the grindermechanism and the pump assembly. As noted above, the housing is preferably attached to a support that sits on the bottom of the sewage tank.

[0040] As noted above, the grinder pump is connected to wastewater discharge pipe. In operation, wastewater is drawn into grinder mechanism for cutting or grinding of the solids or semisolid matter in the wastewater.

The resulting processed particulate effluent passes through pump assembly and then through the wastewater discharge pipe. The processed wastewater may travel to a remote location, e.g., to a pressure sewage main and ultimately to a sewage treatment plant.

[0041] The grinder pump may include one or more sensing tubes to sense pressure variations for measuring the level of wastewater collected in tank. A processor and/or a mechanical-electrical relay are desirably operable, upon the wastewater reaching a predetermined wastewater level, to energize the motor within the motor housing casting.

[0042] The various sewage tanks may be rotational molded and formed from high density polyethylene. A mold may be set up so that a sewage tank may be formed for use with a detachable flange or with a relatively small integral flange for use with concrete or a relatively larger flange so that concrete is not required.

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[0043] For the embodiments of the sewage tank where the flange is not needed or where concrete is required, installation may include digging a hole, placing the sewage tank in the ground, and then pouring concrete down in the bottom of the hole.

[0044] While various embodiments of the present invention have been illustrated and described, it will be appreciated by those skilled in the art that many further changes and modifications may be made thereunto without departing from the spirit and scope of the invention.