Liquid purification or separation – With repair or assembling means
Reexamination Certificate
1998-05-21
2001-08-07
Popovics, Robert (Department: 1723)
Liquid purification or separation
With repair or assembling means
C210S314000, C210S439000, C210S488000, C210S497100
Reexamination Certificate
active
06270668
ABSTRACT:
I. FIELD OF INVENTION
The field of the present invention relates to fluid filtering systems and techniques in general and to fluid filter collector systems in particular.
II. BACKGROUND OF THE INVENTION
There is a maxim that four quarts of clean oil mixed with one quart of dirty oil makes five quarts of dirty oil. In the area of fluid filtering apparatus and related filtering applications, this is especially true. Modern vehicles and industrial machinery rely on a number of recirculating fluids for effective operation. Effective filtration of these fluids can extend the life of the apparatus and maintain the operation at high levels of performance. Furthermore, to the extent fluids can be maintained free of contamination, the life of the fluid itself is extended, saving cost due to fluid replacement and machinery downtime.
One particularly effective type of fluid filter causes fluids to flow interstitially between layers of fibrous tissue which have been wound about an inner core. Such fluid filters may be packaged either as disposable canisters, replaceable cartridges, or as containers for containing generally one or more filter elements. In-flow and out-flow connections provide the container's inlet and outlet ports. By flowing interstitially between the layers of filtering tissues, dirt and smudge is removed from the fluid by the tissue layers. The fluid exits the filter element and then is directed by a fluid collector through passageways to a flow path which is fluidicly connected to the outlet port.
Because of the efficiency and quality of wound fibrous tissue filtering systems, the popularity of such systems has increased. However, this popularity has not been without a need to improve the various sealing areas of the filtering tissue systems. For instance, because the filtering fluid typically flows interstitially and not transversely through the wound media, a problem known as “channeling” can occur. Channeling typically has the effect of short circuiting the filtering process. It may occur, for instance, due to localized high pressures that open the space between wound layers of fibers such that a larger portion of unfiltered fluid may pass. Furthermore, in using these and other types of filters, other leakages can occur. For instance, leakages can occur around the ends of the filtering elements such that unfiltered fluid from an unfiltered flow path leaks into a filtered flow path and contaminates what fluid was actually filtered. Thus, it is critical to seal the unfiltered fluid from the filtered fluid.
Another example relates to the use of multiple filter element in a filtering system. To increase the flow through a filtering system, it is often desirable to provide a plurality of stacked tissue elements to minimize flow resistance. However, the junctions between the multiple elements is prone to leakage of unfiltered fluid into filtered fluid. To reduce this problem, a fluid collector is typically used.
A typical fluid collector serves to seal the end of the filter element from leakage of unfiltered fluid to filtered fluid. In multiple tissue element systems, it may also separate the fibrous tissue rolls from one another and provide passage for filtered fluid to leave the filter element. Fluid collectors, generally known in the art, may be formed which may have a plurality of alternating radial slots and ridges with the ridges serving to space the fibrous tissue roll elements from the collector and the slot serving to direct the filtered fluid into a central flow tube. A separate fluid collector may be used or the function of a fluid collector may be built into a container. Typical materials include various hard plastics known to those in the art such as Delrin 500, nylon, or other suitable materials.
A further complication of using wound fibrous layers is from the differential pressure generated from the unfiltered flow path to the filtered flow path. Typically, the unfiltered flow path will have a higher pressure than the pressure of the filtered flow path due to the pressure drop through the fluid filter. This differential pressure may create extra stress on the fibrous layers and overall compress the layers away from the higher pressure, typically, toward the inner core and the filtered fluid path. These substantial compressive forces are described in U.S. Pat. No. 4,792,397 to Rasmussen in column 1, lines 35-49 as follows:
Substantial compressive forces are exerted hydraulically on the tissue layers. These forces tend to compress and deform the filter elements, particularly at the end of each filter element where the filter fluid exits into a collector. As disclosed in U.S. Pat. No. 4,017,400 to Schade, these collectors often have an annular portion which extends into the adjacent filter element ends to form a seal which separates the filtered fluid from the unfiltered fluid. Nevertheless, deformation of the filter element at its exit end may cause flow channels to form which then allow fluid to flow around the annular seal and thus entirely bypass the filter element. As a result, a significant amount of unfiltered fluid can pass around the deformed filter element without removal of contaminants.
Obviously, in using these wound fibrous tissue filter elements, such leakage can occur from using one or a plurality of such filter elements in any given system. As is noted in U.S. Pat. No. 4,773,990 to Hood in column 1, lines 24-42:
A significant problem associated with the use of axial flow filters has been leakage of contaminated fluid around the wound tissue filter element. Ordinarily, filter elements are positioned on a flow tube and contaminated fluid is directed to one axial end surface of the element where the fluid enters the tissue layers in an axial direction, flows through the layers, and out the opposite axial end surface of the element into an annular channel then into the flow tube. The pressure differentials between the axial ends of the element, and between the outer cylindrical surface of the elements and the annular channel are typically very high, encouraging leakage around the elements, permitting unfiltered fluid to contaminate the filtered fluid. Numerous attempts have been made to fashion a seal which will prevent a flow bypass of this type.
In recognizing some of the problems, various inventors have suggested solutions. One such solution is seen in U.S. Pat. No. 271,850 to Stutzman. In that patent, reduction of leakage bypassing is discussed in terms of axial compression in column 5, lines 18-23:
Bypassing is precluded in the apparatus of this invention by squeezing the filter cartridge from top and bottom between circular stub edges to indent the cartridge faces so tightly that no fluid can flow regularly to the axial bore or the outflow pipe without proceeding axially through one-half of the dual cartridge.
However, other inventions realize that there is a practical limit to how tight the actual ends can be squeezed to reduce leakage and perhaps rely instead on other methods of sealing.
U.S. Pat. No. 4,017,400 to Schade appears to attempt to find a solution in sealing the outer periphery of the filter element against the container wall and providing an “interlocking annular seal” in column 1, line 64-column 2, line 2.
An interlocking annular seal provided in the manner of this invention is enhanced in efficiency by application of radial pressure and will resist failure under extreme pressure better than seals formed by axial compression of a filter element or by an annular sealing ring which causes the filter element to be squeezed and deformed radially.
Noteworthy, this was a single ring which apparently attempted to restrain the filter element from pulling away from the inner container wall surface. Unfortunately, Schade and others apparently realized subsequent to this patent that this was not a final solution.
While the Schade '400 reference may have recognized an issue of radial compression, it apparently did not offer a satisfactory solution. In U.S. Pat. No. 4,366,057 to Bridges et. al., the Schade '400 reference is
Gryder Edd D.
Morgan Dennis R.
Harvard Corporation
Popovics Robert
Santangelo Law Offices P.C.
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