Multi-stage fluid filter, and methods of making and using same

Details Multi-stage fluid filter, and methods of making and using same Multi-stage fluid filter, and methods of making and using same

2000-05-08

2002-04-30

Hoey, Betsey Morrison (Department: 1724)

Liquid purification or separation

Processes

Chemical treatment

C210S209000, C210S252000, C210S314000, C210S505000, C210S508000

Reexamination Certificate

active

06379564

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to fluid filters, and to specific applications thereof More particularly, the present invention relates to multi-stage fluid filters containing a mechanically active filter element for straining impurities out of fluid as it passes therethrough, and a chemically active filter element made of fibers impregnated with one or more chemical reagents, to chemically interact with a fluid passing therethrough. The chemical reagents in the chemically active filter element may work to reduce contaminants by precipitating those contaminants out of solution in the fluid, may release a beneficial reagent into such fluid, may react with and immobilize deleterious components, or may perform all of these functions in a single filter apparatus.
2. Description of the Relevant Art
Many different types of fluid filters are known. Most such filters use a mechanical or ‘screening’ type of filtration, with a replaceable cartridge having a porous filter element therein.
In the oil filtration art, it is well known that normal operation of an internal combustion engine, particularly a diesel engine, results in the formation of contaminants. These contaminants include, among others, soot, which is formed from incomplete combustion of the fossil fuel, and acids that result from combustion. Both of these contaminants are typically introduced into the lubricating oil during engine operation, and tend to alter oil viscosity and to generate various engine deposits, leading to increased engine wear.
The conventional solution to these problems has been to place various additives into lubricating oils. In order to combat soot-related problems, most conventional lubricating oils include dispersants that resist agglomeration of soot therein. These work well for a short period, but may become depleted. Additionally, due to the solubility and chemical stability limits of these dispersants in the oil, the service lives of the lubricating oil and the oil filter are less than optimal.
For combating combustion acid related problems, many conventional systems include neutralizing additives known as over-based detergents. These are source of TBN (total base number), which is a measure of the quantity of the over-based detergent in the oil. The depletion of the TBN is an important limiting factor for many internal combustion engines, and in particular for heavy-duty applications with diesel engines.
In order to improve engine protection and to combat other problems, conventional lubricating oils often include one or more further additives, which may be corrosion inhibitors, antioxidants, friction modifiers, pour point depressants, detergents, viscosity index improvers, antiwear agents, and/or extreme pressure additives. The inclusion of these further additives may be beneficial; however, with conventional methods, the amount and concentration of these additives are limited by the ability of lubricating oils to suspend these additives, as well as by the chemical stability of these additives in the oil.
Other solutions have been proposed in addition to the conventional method of mixing additives with lubricating oil. For example, in order to combat the build up of sludge in oil, U.S. Pat. No. 5,478,463, issued in 1995 to Brownawell et al, and entitled Method of Reducing Sludge and Varnish Precursors in Lubricating Oil; and U.S. Pat. No. 5,042,617, issued in 1991 to Brownawell, and entitled Method of Reducing the Presence of Sludge in Lubricating Oils, each disclose an oil filter and method for reducing the amount of sludge in lubricating oil as it circulates throughout an engine. These Brownawell patents provide for the inclusion of particles in an oil filter that are oil insoluble and oil wettable, and which complex with sludge such that at least some of the sludge that these particles come into contact with is immobilized on the particles. The Brownawell '617 patent discloses the inclusion of oil insoluble and oil wettable particles in an oil filter that are retained on a pelletized substrate, whereas the Brownawell '463 patent discloses the inclusion of such particles that are not retained on a substrate, but are nonetheless retained in the oil filter.
Another Brownawell patent, which relates to the reduction of combustion acids in lubricating oil, is U.S. Pat. No. 5,069,799 issued in 1991 and entitled Method For Rejuvenating Lubricating Oils. This Brownawell patent discloses an oil filter and method for reducing the Amount of combustion acids in lubricating oil. In particular, it discloses a method of rejuvenating Lubricating oil, which includes reduction of combustion acids, by serially passing the oil through first a chemically active filter media, then a physically active filter media, and finally an inactive filter media. In this '799 patent, the chemically active filter media includes a strong base, to displace weak bases that have combined with combustion acids. The combustion acid and the strong base then combine to form a salt, which is then physically trapped by subsequent mechanical filter media.
U.S. Pat. No. 5,225,081 to Brownawell discloses method of removing polynuclear aromatics from used lubricating oil. The method of the Brownawell '081 reference involves passing oil through a staged oil filter system, which may include a chemically active filter media. The chemically active filter media is made of a composite material including particles of an active component and a and a thermoplastic binder, which are a product of a heated extrusion process. Basic materials are given as one example of materials suitable for use as materials usable as chemically active filter media. Activated carbon is also emphasized as a preferred component of the filter media.
Some designs for multiple stage oil filters are known such as those disclosed in U.S. Pat. No. 4,557,829 and 4,886,599. U.S. Pat. No. 4,886,599 to Bachmann et al. discloses a filter cartridge with sequential concentric cylindrical filter elements, for both chemical and mechanical filtration of oil contained in an oil-sealed vacuum pump.
Other designs for oil filters that contain extra additives and dispense those additives into oil, over time, are disclosed in U.S. Pat. No. 4,075,098 and 5,552,040.
Many patents have been issued for fuel filters, including 5,017,285, 5,076,920, and 5,766,449.
Although they are useful for their intended purposes, conventional fluid filters have several shortcomings. A need still exists in the art for an improved fluid filter that increases the useful life of a filtered fluid by removing contaminants therefrom, in a way that is superior to the previously known methods. A need also exists for an improved fluid filter including a mechanism that provides for better in-line delivery of additives than the known filter designs.
SUMMARY OF THE INVENTION
The present invention has been developed to overcome the foregoing limitations and disadvantages of conventional staged fluid filters, and other proposed methods for increasing the useful life of lubricating oil and protecting the engine. The present invention, generally, provides a fluid filter that increases the usefull life of the filtered fluid by removing contaminants therefrom, by modifying the filtered fluid, and/or by optionally providing in-line delivery of additives to the filtered fluid.
According to a first embodiment of the invention there is provided a fluid filter that includes a casing which defines a hollow space therein, a mechanically active filter element within that space, and a chemically active filter element also retained within the hollow space. The mechanically active filter element may be a conventional paper filter element. An intermediate member may, optionally, be provided to separate the mechanically active filter element from the chemically active filter element within the chamber.
In a second embodiment of the invention, a filter assembly in accordance with the invention may include a first casing having a mechanically active filter member therein, an

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