Liquid purification or separation – With repair or assembling means
Reexamination Certificate
1999-06-22
2002-01-08
Walker, W. L. (Department: 1723)
Liquid purification or separation
With repair or assembling means
C210S238000, C210S323200, C210S333010, C210S415000, C210S416100, C210S435000, C210S497010, C210S470000, C210S450000
Reexamination Certificate
active
06337013
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to improved fluid filter systems, and more particularly to apparatus for releasably sealing filter elements in a filter system and in particular, self-cleaning filter systems.
BACKGROUND OF THE INVENTION
It has been recognized that the use of a plurality of filter elements connected together to accommodate a high flow of fluid is preferable to using a single large filter. Previously, such devices used compressible gaskets, O-rings, or the like in conjunction with male-female fittings or tangs to effect a liquid seal between the tubular filter elements; see, for example, U.S. Pat. No. 5,141,637 to Reed et al. These sealing methods may be suitable for small, low flow filter units which can be coupled and uncoupled by hand. In a large filter unit (for example, one in which the tubular filter elements are too large to be grasped and rotated easily), such a sealing arrangement is unsatisfactory as it is very difficult to break the seal between filter elements when a filter element requires replacement or when the unit is undergoing routine maintenance. Even in the case of a filter unit having only one filter element, the use of compressible gaskets to provide a seal about the filter element within the unit make removal of the filter element quite difficult if the filter element weighs more than one hundred pounds, is vertically oriented, or both.
Prior art filter systems are difficult to service and repair because it is typically not possible to observe the interior of the device without extensive disassembly of it. For large filter units, disassembly and reassembly require relatively long shutdown periods, the efforts of two or more workers and the assistance of additional machinery to lift and move various components. Because prior devices often do not have ways to readily align components during assembly, expensive tubular filter elements can be damaged in the course of maintenance or repair of such devices.
For example, U.S. Pat. No. 4,863,598 to Drori teaches a device for holding a stack of filter disks using externally located rod members which are secured at either end to annuli which secure the disks. However, stacked filter disks may induce a pressure drop of approximately 25 psi (1750 kg/cm
2
) or more from one side of the filter element to the other, and therefor are not suitable for many applications, such as the high volume filters required by power generating plants. Furthermore, this manner of filter assembly allows material to become trapped between the disks. Consequently, the only effective way to clean these disks is to release the filter elements, separate them, clean them and subsequently reassemble them.
Known methods of self-cleaning a filter element often involve scraping or brushing the filter element. U.S. Pat. No. 5,569,383 to Vander Ark, Jr. et al, PCT patent application number WO95/00230, U.S. Pat. No. 4,156,647 to Nieuwenhuis and U.S. Pat. No. 5,614,093 to Mueggenburg et al. all teach filters which use a rotor with cleaning blades or brushes to scrape clean the pre-filtration side of the filter element. The use of scrapers or brushes for cleaning can damage the filter element either directly or by forcing material through the filter elements.
Other methods of self-cleaning a filter element involve backwashing, i.e. reversing the pressure differential between the pre- and post-filtration sides of the filter element to expel particular matter trapped in the filter element. Typically, such backwashing requires closing the main inlet and outlet valves and opening backwashing valves to reverse the pressure differential (see, for example, U.S. Pat. No. 5,312,544 to Kinney).
U.S. Pat. Nos. 4,045,345 and 5,228,993 to Drori and U.S. Pat. No. 5,108,592 to Wilkins et al. teach filters which use a series of valves and other mechanical devices to automate a backwashing procedure for cleaning the filter element. Cleaning is accomplished by reversing the flow of water through the filter element (i.e. exposing the post-filtration side of the filter element to a high pressure) to expel particulate matter caught in the filter element. In U.S. Pat. No. 4,045,345 Drori teaches the reverse flow is induced by pressure at the outlet of the filter, and particulate matter is expelled through a slotted purging chamber which rotates, along with the filter housing, around the filter element. U.S. Pat. No. 5,228,993 to Drori and U.S. Pat. No. 5,108,592 to Wilkins et al. teach cleaning using a reverse flow through the filter achieved by pressure from a supply pipe. In all of these teachings, particulate matter is expelled from the filter element by spraying the post-filtration side of the filter element through rotating nozzles. The use of spray force for cleaning can damage the filter element either directly or by forcing material through the filter elements. Furthermore, all of these methods of self-cleaning require the cessation and reversal of normal filter flow.
SUMMARY OF THE INVENTION
The present invention addresses these and other problems associated with prior devices by providing a liquid filtration device, comprising a housing having an inlet, an outlet and an inner surface, the housing comprising:
(i) a removable filter element having an inner face, an outer face and first and second flanged ends, each flanged end having a sealing surface and a rod aperture, and the rod apertures of the first and second ends align in a lengthwise direction;
(ii) a housing flange on the housing inner surface, the housing flange being sealable with the first flanged end sealing surface of the filter element;
(iii) a sealing face on the housing inner surface, the sealing face being sealable with the second flanged end sealing surface of the filter element;
(iv) a rod extending in a lengthwise direction through the rod apertures, the rod having a first rod end for releasably securing the filter element and a second rod end secured to the housing; and
(v) a fastening device for securing the first rod end, wherein, upon securing the fastening device, sufficient force is applied to the sealing surfaces to define a liquid flowpath through the inlet, through the inner face of the filter element to the outer face of the filter element and out the outlet.
In another preferred embodiment, the filter has a plurality of filter elements connected in series, and each filter element has a first sealing surface sealable with a second sealing surface of an adjacent filter element. The sealing surface may be chamfered. In a further preferred embodiment, the filter element is cylindrical.
The invention also teaches a door on the housing and the filter elements are removable and replaceable through the door. The door may be hinged. In a further preferred embodiment, the filter has removable extensions for extending the length of the rods to the door.
In a preferred embodiment, the filter has a plurality of rod apertures at the first and second flanged ends and a plurality of rods extending therethrough.
Preferably, the flowpath through the filter surface is perpendicular to the inner face. Preferably, the filter element comprises a structural screen and a mesh screen, the structural screen consisting of a rigid or semi-rigid plate having multiple apertures, and the mesh is fixed to the structural screen by a sintering process. Preferably, the mesh screen is the inner face and the structural screen is the outer face. Preferably, the mesh screen has a mesh size of 30 to 40 microns.
In a preferred embodiment the invention also has a pre-screen positioned in the flowpath between the inlet and the filter element, and a pre-screen drain positioned in the flowpath between the pre-screen and the inlet.
In another preferred embodiment, the filter has a housing having an inlet, an outlet and an inner surface, the housing comprising:
(i) a removable filter element having an inner face, an outer face and first and second flanged ends, each flanged end having a sealing surface, the first flanged end having a guide receptacle and the second flanged end having a guide projecti
Koopmans Robert
McCauley Kevin Graydon
Bacon & Thomas PLLC
Ontario Power Generation Inc.
Sorkin David
Walker W. L.
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