Liquid purification or separation – Structural installation – Grated inlet surface drain
Reexamination Certificate
2000-04-26
2001-04-17
Upton, Christopher (Department: 1724)
Liquid purification or separation
Structural installation
Grated inlet surface drain
C210S166000, C210S265000, C210S282000, C210S299000, C404S004000
Reexamination Certificate
active
06217757
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to filters for filtering debris, hydrocarbons, and other contaminants from water flowing into storm drains.
2. Prior Art
Storm drains are provided in streets, parking lots, gas stations, and highways for draining water runoff. Some storm drains are provided with internal filters for preventing debris, hydrocarbons, and other contaminants from entering waterways.
My prior U.S. Pat. No. 5,958,226 discloses a storm drain filter sized to be positioned inside a storm drain. It includes a top debris tray detachably positioned within a bottom media tray. Each tray includes a peripheral trough surrounding a central overflow opening. The top tray is shorter in height than the bottom tray, so that a filter media receiving chamber is defined between the top tray and the bottom tray. Filter medium is positioned in the filter medium receiving chamber. In a first embodiment, the bottom surfaces of the top and bottom trays are perforated. In a second embodiment, the bottom of the top tray and the inner wall of the bottom tray are perforated. In either embodiment, water flowing into the filter is distributed around the top trough, passed through the perforated surface of the top tray, the filter medium, the perforated surface of the bottom tray, and into the storm drain. Hydrocarbons and other contaminants are filtered by the filter medium. Large particles and debris are collected in the trough of the top tray. The filter may be cleaned by lifting out the top tray, shaking out the debris, and replacing it in the bottom tray. However, the perforated surface of the top tray is relatively small, so that it may quickly clog when a large amount of debris flows into the filter. The top tray can be removed by pulling on a handle attached thereto, but the bottom tray cannot be lifted with the handle.
U.S. Pat. No. 5,720,574 to Barella discloses a filter for being positioned inside a storm drain. It includes a peripheral trough surrounding a central overflow opening. A set of cartridges containing filter medium are positioned in the trough. Water flowing into the drain is distributed around the trough, and passes through the cartridges before exiting through a screen on the bottom of the trough. When water flow is high, excess water overflows through the central opening without passing through the cartridges. However, gravel, leaves, and other debris accumulate on top of the cartridges and block water flow, so that a worker must reach in and dig them out by hand, which is slow and time consuming. The horizontal screen has a relatively small surface area which may quickly clog when the inflow of debris is high. There is no handle for lifting the filter from the drain. U.S. Pat. No. 5,632,889 to Tharp discloses a similar filter.
U.S. Pat. No. 5,480,254 to Autry et al. discloses a storm drain filter that comprises a box with porous vertical walls and an opening on the bottom. It is wider than a storm drain for being positioned on top of and across it; it cannot be installed inside the storm drain. Storm water is filtered by the porous vertical walls as it flows through the filter and into the drain. The filter element of crushed stone is housed in a single chamber, but is too coarse to filter out anything but the largest pieces of debris. The filter element cannot be removed for cleaning or replacement.
OBJECTS OF THE INVENTION
Accordingly, objects of the present invention are:
to filter out debris, hydrocarbons, and other contaminants from water runoff flowing into a storm drain;
to continue unimpeded filtering even after collecting a large amount of debris;
to prolong filtering time;
to be impossible to clog;
to be easily lowered into or lifted from a storm drain as a single unit;
to have a filter cartridge which is easily replaced;
to provide different filter media for more effectively filtering different types of pollutants;
to be usable at building construction sites for filtering large particles without becoming clogged; and
to be usable after building construction for filtering small particles and pollutants.
Further objects of the present invention will become apparent from a consideration of the drawings and ensuing description.
BRIEF SUMMARY OF THE INVENTION
The present storm drain filter comprises a tubular housing with a solid vertical surrounding wall and sized for being recessed inside a storm drain. The housing is supported in the drain by a flange around its top edge. A tubular cartridge is detachably attached to a solid annular bottom plate of the housing. The cartridge comprises a solid annular top cover coaxial with a solid annular bottom closure; vertical tubular inner, intermediate, and outer screens concentrically connected between the top cover and bottom closure; and filter media enclosed between the screens. A central overflow opening inside the inner screen is aligned with a hole on the bottom plate of the housing. An annular debris trough is defined between the cartridge and the housing. Debris flowing into the filter is collected in the trough. As the level of debris rises and obstructs the lower part of the outer screen, the unobstructed upper part of the outer screen continues to filter the water. The vertical outer screen is tall enough to provide a large area which will take a long time to obstruct. When the screens or media are completely clogged, water will continue to flow by passing through the central overflow opening. A handle on the cartridge is used to lift or lower the entire filter in the drain. The top cover on the cartridge is removable for changing the media.
REFERENCES:
patent: 528888 (1894-11-01), McGill
patent: 783556 (1905-02-01), Van Buskirk
patent: 1862134 (1932-06-01), Boosey
patent: 2283365 (1942-05-01), Heinkel
patent: 3289847 (1966-12-01), Rothemund
patent: 3487940 (1970-01-01), Morris
patent: 4107929 (1978-08-01), Ebeling et al.
patent: 5284580 (1994-02-01), Shyh
patent: 5480254 (1996-01-01), Autry et al.
patent: 5632889 (1997-05-01), Tharp
patent: 5720574 (1998-02-01), Barella
patent: 5744048 (1998-04-01), Stetler
patent: 5925242 (1999-07-01), McGhee
patent: 5958226 (1999-09-01), Fleischmann
patent: 6083402 (2000-07-01), Butler
patent: 3001833 (1981-07-01), None
Lo Jack
Upton Christopher
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