Tow wound filter cartridge

Details Tow wound filter cartridge Tow wound filter cartridge

2000-01-20

2001-12-11

Reifsnyder, David A. (Department: 1723)

Liquid purification or separation

Magnetic

With additional separator

C210S457000, C210S484000, C210S494100, C210S494200, C210S497010, C210S497100

Reexamination Certificate

active

06328887

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a tow wound filter cartridge comprising a permeable core and one or more tows wound in a helicoidally or diamond-like shaped way or serpentine-like way around the core.
BACKGROUND OF THE INVENTION
Tow wound filter cartridges are known as such in the art.
As a matter of example, U.S. Pat. No. 5,679,251 discloses a tow wound filter cartridge, which comprises polyester yarns. The filter is used as a secondary oil filter in diesel engines.
Next to their filter rating, these types of filter cartridges, however, suffer from some major disadvantages.
One of the main disadvantages is that such a filter cartridge is not fit to be cleaned or back-flushed several times. These filter cartridges are used and simply discarded after their use.
Another disadvantage is that such a filter cartridge is not fit to operate in severe circumstances such as under high pressures or under high temperatures. Indeed textile filter cartridges are not stable. Textile filter cartridges swell as they become wet and the outside wraps or layers slides down the outside surfaces.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a filter cartridge with an improved filter rating compared to the tow wound filters as known in the art.
It is another object of the present invention to provide a filter cartridge, which can be cleaned several times.
It is also an object of the present invention to provide a non-disposable filter cartridge.
It is yet another object of the present invention to provide a filter cartridge with an improved integrity and stability of the filter medium.
According to the invention, there is provided a tow wound filter cartridge comprising a permeable core and one or more tows wound in a helicoidally or diamond-like shaped way or serpentine-like way around the core in order to obtain an absolute filter rating of below 75 micrometer. The tows may comprise metal fibers and, in a preferred embodiment of the invention, the tows consist of only metal fibers. It is even so that tow wound filters as subject of the invention can be provided, retaining more than 95%, e.g. more than 99% of all particles larger than 20 &mgr;m, even of all particle larger than 10 &mgr;m or 5 &mgr;m. Tow wound filters as subject of the invention may retain more than 95% of all particles larger than 1 &mgr;m or 0.75 &mgr;m.
One tow or bundle may comprise between 100 and 15000 fibers, for example 10000 or 12000 fibers. The filter may comprise more than one tow where each tow has a different number of fibers or where each tow has a different type of fibers, e.g. with fibers of a different diameter. Tows in a cartridge as subject of the invention have a zero twist degree, which means that the individual fibers in a tow run about parallel and untwisted one adjacent to the other. The result of this zero twist degree is that during the winding operation the tow is applied to the core in the form of a flat tape rather than an oval shaped yam. This results in lower void volume in the filter, which in turn leaves less space for small particles to pass through. So the zero twist degree allows obtaining lower filter ratings in comparison with wound tow cartridge filters with tows having a twist.
The tows of the filter cartridge may form a plurality of layers around the core of the cartridge. Each of the layers may consist only of fibers of an equal fiber diameter and the diameter of the fibers may vary depending upon the layer in which the tow is positioned.
In this way asymmetric filter structures may be formed by winding different fiber diameters in layers onto the core in an ascending or descending fiber diameter order.
Within the context of the present invention, the terms “metal fibers” refer to fibers which can be manufactured by abrading the upper edge of a rolled metal foil, as described in U.S. Pat. No. 4,930,199, or by using the bundled drawing technique, as described, e.g., in the patent U.S. Pat. No. 3,379,000, or by means of a melt extraction technique. The metal fibers have an equivalent diameter ranging between 1 &mgr;m and 100 &mgr;m, preferably ranging between 1.5 &mgr;m and 45 &mgr;m, for example between 2 &mgr;m and 30 &mgr;m. The terms “equivalent diameter of a fiber” are defined as the diameter of an imaginary round fiber having the same cross-section as that of the real fiber concerned.
In a preferred embodiment of the present invention, a filter cartridge comprise or even consists of metal fibers, most preferably stainless steel fibers, e.g. of alloy AISI 302,AISI 304, AISI316 or AISI316L.
The metal fibers may have a composition, which is resistant to high temperatures and to thermal shocks. For this purpose, they may comprise minimum amounts of Al (aluminum) and Cr (chrome). Examples of such a composition are Fe
a
Cr
b
Al
c
Y
d
. alloys such as disclosed in EP 0 157 432.
In a particular embodiment of the present invention, the magnetic properties of the metal fibers in the tows of the filter cartridge are used. Bundled-drawn stainless steel fibers are ferromagnetic, i.e. when applied in an external magnetic field, they have a relative magnetic permeability &mgr;
r
which is a number of times greater than one. Ferromagnetic materials e.g. comprise components chosen among Fe, Co, Co, Cu, Ni, . . . Usually the higher the Fe, Co, Cu or Ni contents, the more pronounced the ferromagnetic properties. A tow wound filter cartridge with ferromagnetic fibers has the advantage of being more effective in removing magnetic and para-magnetic particles from, for example, lubricating oils. Indeed it is important that engine oil filters for internal combustion engines can remove the small iron particles which are produced by the wear cycles. By placing tow wound cartridges of this type in a magnetic field, the iron particles can be filtered out of the engine oil more effectively. This is an additional advantage of some of the inventive tow wound filter cartridges in comparison with textile filters or paper filters.
In still another embodiment of the present invention the tow wound filter cartridge comprising metal fibers has been sintered, e.g. hydrogen-sintered in order to avoid fiber transfer. So the integrity of the filter medium has been increased by the sintering operation. Such a sintered version is more adapted to be used in more demanding applications such as highly loaded liquids or gases, high turbulencies and filter cartridges operating under high vibrations. The sintering operation, however, removes the ferromagnetic properties of the fibers, i.e. the relative magnetic permeability &mgr;
r
becomes one after the sintering operation.
Tow wound filters as subject of the invention, comprising mainly metal fibers are more stable, since they don't swell significantly under use, and are more resistant to higher temperatures, pressure and aggressive circumstances. It is even so that, after being cleaned several times by applying a black-flush, tow wound filters comprising mainly metal fibers maintain their filter performance to a large extend, so providing a non-disposable filter madium.


REFERENCES:
patent: 3065856 (1962-11-01), Goldman
patent: 3379000 (1968-04-01), Webber et al.
patent: 3828934 (1974-08-01), Green et al.
patent: 3977070 (1976-08-01), Schildbach
patent: 4048075 (1977-09-01), Colvin et al.
patent: 4269707 (1981-05-01), Butterworth et al.
patent: 4930199 (1990-06-01), Yanagisawa
patent: 5679251 (1997-10-01), Swanson et al.
patent: 36 02 153 (1987-07-01), None
patent: 0 493 049 (1992-07-01), None
patent: 0 810 020 (1997-03-01), None
patent: 00/45937 (2000-08-01), None
International Search Report dated May 3, 2000 that is from a counterpart International Application No. PCT/EP00/00345, filed Jan. 13, 2000, and published as International Publication No. WO 00/45937, published Aug. 10, 2000.
Patent Abstracts of Japan; vol. 005, No. 071 (C-054), May 13, 1981 & JP 21618 (1 page).
English language Abstract/Data Sheet of EP 0 810 020, printed out Jun. 21, 2001, 2 pp.

Affiliated with

Also associated with

Rating

Tow wound filter cartridge does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Tow wound filter cartridge, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tow wound filter cartridge will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2566584