Liquid purification or separation – Flow – fluid pressure or material level – responsive – Filter cleaning
Reexamination Certificate
1999-08-11
2001-07-31
Drodge, Joseph W. (Department: 1723)
Liquid purification or separation
Flow, fluid pressure or material level, responsive
Filter cleaning
C210S335000, C210S408000, C210S409000, C210S414000, C210S497010
Reexamination Certificate
active
06267879
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a high efficiency continuous liquid filtering apparatus with automatic electromechanical self-cleaning system.
More specifically the present invention relates to an apparatus useful for removing particles from liquids, having a pre-filtering unit equipped with a coarse filter for removing rough particles from the liquid, and a fine filtering unit with a multi-layer sintered filtering element for removing (according to the specific filtering application) particles of between 2 and 500 Microns, and further having an electromechanical self-cleaning unit automatically activated and stopped during the filtration process according to a predetermined sediment blockage level measured at the sintered filtering element.
BACKGROUND OF THE INVENTION
One inevitable problem of many existing filtering systems is the accumulation of sediments on the filtering element during filtration, blocking its porous surface and lowering the filtration rate until totally preventing it. Thus, plain filtration systems have to be treated occasionally by cleaning the used blocked filtering element or by replacing it with a clean one, which means interrupting and stopping the filtration process from time to time.
The present invention focuses on (but not limit itself to) the fields of filtration of liquids, irrigation water, recycling of sewage and industrial waste water, recycling of cooling towers water, filtration and purification of drinking water etc.
The aim of the present invention is to provide a high efficiency continuous liquid filtering apparatus having self-cleaning mechanism allowing the continuous filtering operation, i.e. without interrupting the supply of filtered liquid.
Self-cleaning filter devices are known in the art, but they are not efficient enough—in the filtration rate and in the self-cleaning quality. The filter elements used by the said known in the art devices are comprised of PVC support screens combined with one layer of screen mesh. The filter element void rate in such combination of screens is only about 60% of the filter surface, meaning bulky and inefficient filter element. Another problem in said filter elements is that during the filtration a significant amount of particles are trapped between the PVC support and the mesh, which reduces the cleaning efficiency and further reduces the void rate.
The apparatus of the present invention overcomes the abovementioned disadvantages, and increases the efficiency of the filtration process and the self cleaning of the continuous filtering apparatus, by using a unique combination of a cylindrical multi-layer sintered body of metallic screens as a filtering element, and an electro mechanical self-cleaning system.
Said cleaning system is based on a back and forth helical motion of a dirt collector having dirt suction members equipped with spraying nozzles. The spraying nozzles use the filtered liquid after being pressurized by a booster pump for vibrating and rinsing the sediments accumulated on the sintered filtering element, while the pressure-difference between the pressure of the liquid within the apparatus and the pressure of the free atmosphere outside of the apparatus is utilized as a suction force for the operation of the dirt suction members.
SUMMARY OF THE INVENTION
The present invention relates to a continuous liquid filtering apparatus, comprising;
a preliminary filtering chamber having a liquid inlet and a coarse filtering screen; a final filtering chamber having a cylindrical multi-layer sintered filtering element in liquid communication with said preliminary filtering chamber across said coarse filtering screen; a filtered liquid chamber in liquid communication with said final filtering chamber across said sintered filtering element and having a liquid outlet; an electromechanical cleaning system adapted to remove sediments from the sintered filtering element; and controlling means for activating the said cleaning system during the filtration process, for limited periods (according to one operation mode) or continuously (according to another operation mode).
In the context of the present invention the term “multi-layer sintered filtering element” relates to any type of metallic body constructed from a plurality of metal screens of different densities or patterns, or of a plurality of metal wires, sintered together for being one integral metallic body useful for the filtration of particles from a substance flowing across its multi layers.
According to one preferred embodiment of the present invention the cleaning system is consisting of (a) a collector unit comprised of a pipe having an open end for dirt draining positioned along the line of symmetry of the cylindrical filter and further having a plurality of dirt suction members spaced from each other along the pipe length each equipped with a spraying nozzle, both suction member and nozzle extend to the inner circumference of the cylindrical filter; (b) a bidirectional electrical motor connected through a helical driving mechanism to the said collector unit for simultaneously revolving it and moving it slowly along the cylindrical filter back and forth; (c) a switching arrangement adapted to invert the motor rotation direction at the limits of said back and forth movement; (d) a booster-pump having a liquid inlet fed with filtered liquid from the fine filtering chamber and a liquid outlet feeding the spraying nozzles with a filtered liquid having a relatively high pressure; (e) at least one draining valve buffering between the pipe open end and the free atmosphere;
According to one preferred embodiment of the apparatus according to the present invention, the preliminary filtering chamber and the filtered liquid chamber are two compartments within one tube shape envelope, separated from each other by an inner rim parting between the coarse screen and the outer circumference of the cylindrical filter.
According to the preferred embodiment the coarse screen has a cylindrical shape, and the cylindrical coarse screen and the cylindrical filter element have similar diameters, and are positioned adjacently, forming one elongated final filtering chamber being the interior of the two adjacent cylinders. However according to the present invention the coarse screen is not limited to a cylindrical shape, to specific dimensions, or to a specific configuration relatively to the sintered filtering element, and may be shaped and positioned in any configuration useful for supplying liquid cleansed of rough particles to the sintered filtering element.
According to the preferred embodiment, the apparatus is further comprising a draining chamber encompassing the pipe open end and having a draining outlet to which connected the at least one draining valve.
Preferably the cylindrical filter element of the apparatus of the present invention is of metallic screens, providing a maximal void rate (nearly 60% more than conventional filters), thus increasing the apparatus efficiency. In addition, the sintered body better cooperates with back-washing (i.e. washing the dirt by a reverse liquid stream) than conventional filtering elements, since the screen layers constructing it are arranged progressively (the sintered body construction is comprising only screens, i.e. differently than conventional filters in that no additional support is required), thus preventing the capture of dirt particles between the screens.
According to one preferred embodiment, the controlling means for activating the cleaning system for limited periods are comprising at least one differential pressure detector (in the context of the present invention called also DP “sensor” or “gauge”) for activating the cleaning system whenever the detected value of the liquid differential pressure between the final filtering chamber and the filtered liquid chamber indicates that the sintered filtering element requires a cleaning treatment.
According to various embodiments, the controlling means for activating the cleaning system for limited periods comprises a timer for activating th
Cecil Terry K.
Drodge Joseph W.
Lowe Hauptman & Gilman & Berner LLP
Odis Irrigation Equipment Ltd.
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