U.S. patent application number 09/412419 was filed with the patent office on 2001-11-08 for filter and method of filtering a fluid.
Invention is credited to HAMLIN, THOMAS J., PAUL, C. THOMAS, PULEK, JOHN L., SALE, RICHARD.
Application Number | 20010037982 09/412419 |
Document ID | / |
Family ID | 22294091 |
Filed Date | 2001-11-08 |
United States Patent
Application |
20010037982 |
Kind Code |
A1 |
PULEK, JOHN L. ; et
al. |
November 8, 2001 |
FILTER AND METHOD OF FILTERING A FLUID
Abstract
A filter including alternating layers of filter medium and
diffusion medium. The filter provides optimum distribution of fluid
over the filtering medium, a reduced pressure drop and an increased
filter life, without a reduction in filter rating. The diffusion
medium has a first plane of spaced-apart, substantially parallel
strands defining first longitudinal passages having a first height
dimension and a first width dimension, and a second plane of
spaced-apart, substantially parallel strands defining second
longitudinal passages having a second height dimension and a second
width dimension. The strands of the second plane of the diffusion
medium are oriented in a non-parallel manner with respect to the
strands of the first plane, such that the first and the second
planes define lateral openings having side dimensions. The first
and the second longitudinal passages include at least one dimension
that is smaller than any of the side dimensions of the lateral
openings. At least a portion of the layers of filter medium have
bypass apertures, wherein such portion defines at least one
pre-qualifying filter medium layer.
Inventors: |
PULEK, JOHN L.; (CHESIRE,
CT) ; HAMLIN, THOMAS J.; (VERNON, CT) ; SALE,
RICHARD; (TOLAND, CT) ; PAUL, C. THOMAS;
(MADISON, CT) |
Correspondence
Address: |
CUMMINGS AND LOCKWOOD
GRANITE SQUARE
700 STATE STREET
P O BOX 1960
NEW HAVEN
CT
06509-1960
US
|
Family ID: |
22294091 |
Appl. No.: |
09/412419 |
Filed: |
October 5, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60103233 |
Oct 5, 1998 |
|
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|
Current U.S.
Class: |
210/767 ;
210/321.74; 210/492; 210/496; 210/497.1; 210/500.38 |
Current CPC
Class: |
B01D 29/111 20130101;
B01D 2239/0618 20130101; B01D 2239/0627 20130101; B01D 39/1623
20130101; B01D 39/083 20130101; B01D 63/06 20130101; B01D 29/216
20130101; B01D 39/1692 20130101; B01D 2239/0663 20130101; B01D
2239/065 20130101; B01D 2239/0622 20130101; B01D 2239/069 20130101;
B01D 25/24 20130101; B01D 39/18 20130101; B01D 2239/0654 20130101;
B01D 2239/1291 20130101; B01D 39/086 20130101; B01D 2239/0695
20130101; B01D 69/12 20130101; B01D 2239/0668 20130101 |
Class at
Publication: |
210/767 ;
210/321.74; 210/492; 210/496; 210/497.1; 210/500.38 |
International
Class: |
B01D 063/10 |
Claims
What is claimed is:
1. A filter comprising: a) alternating layers of filter medium and
diffusion medium; b) the diffusion medium including, a first plane
of spaced-apart, substantially parallel strands defining first
longitudinal passages having a first height dimension and a first
width dimension, a second plane of spaced-apart, substantially
parallel strands defining second longitudinal passages having a
second height dimension and a second width dimension, the strands
of the second plane being oriented in a non-parallel manner with
respect to the strands of the first plane such that the first and
the second planes define lateral openings having side dimensions,
wherein the first and the second longitudinal passages include at
least one dimension that is smaller than any of the side dimensions
of the lateral openings; and c) at least one of the layers of
filter medium comprising a pre-qualifying filter medium layer
having bypass apertures.
2. The filter of claim 1 wherein the pre-qualifying layers of
filter medium extend from an outermost layer of the filter towards
an innermost layer of the filter.
3. The filter of claim 2 wherein the pre-qualifying layers of
filter medium extend from the outermost layer towards the innermost
layer to between about fifty percent and eighty-five percent of the
distance between the outermost layer and the innermost layer.
4. The filter of claim 3 wherein the pre-qualifying layers of
filter medium extend to between about sixty-six percent of the
distance between the outermost layer and the innermost layer.
5. The filter of claim 1 wherein the bypass apertures of the
pre-qualifying layer of filter medium are formed from bores
extending from the outermost layer towards the innermost layer.
6. The filter of claim 1 wherein the diffusion medium comprises
extruded bi-planar netting.
7. The filter of claim 6 wherein the diffusion medium is made from
a thermoplastic.
8. The filter of claim 7 wherein the diffusion medium is made from
polypropylene.
9. The filter of claim 7 wherein the diffusion medium is made from
nylon.
10. The filter of claim 7 wherein the diffusion medium is made from
fluoropolymer.
11. The filter of claim 7 wherein the diffusion medium is made from
polyester.
12. The filter of claim 1 wherein the filter medium comprises a
fibrous mass of non woven fibers.
13. The filter of claim 12 wherein the fibrous mass of non woven
fibers is melt blown.
14. The filter of claim 12 wherein the filter medium is made from a
thermoplastic.
15. The filter of claim 14 wherein the filter medium is made from
polypropylene.
16. The filter of claim 14 wherein the filter medium is made from
nylon.
17. The filter of claim 14 wherein the filter medium is made from
fluoropolymer.
18. The filter of claim 14 wherein the filter medium is made from
polyester.
19. The filter of claim 12, wherein at least a portion of the
filter medium is calendered.
20. The filter of claim 12 wherein the filter medium has a
substantially constant pore size.
21. The filter of claim 12 wherein the filter medium has a
substantially constant fiber dimension.
22. The filter of claim 1 wherein the filter medium comprises a
porous membrane.
23. The filter of claim 22 wherein the porous membrane filter
medium is nylon.
24. The filter of claim 1 wherein the filter medium comprises wet
laid paper.
25. The filter of claim 1 wherein: the diffusion medium is
comprised of one sheet; the filter medium is comprised of at least
one sheet; and the sheet of diffusion medium and the at least one
sheet of filter medium are coiled.
26. The filter of claim 25 wherein the at least one sheet of filter
medium is perforated near the outermost layer of the filter to
comprise the pre-qualifying medium layer, with the perforations
comprising the by-pass apertures.
27. The filter of claim 25 wherein the at least one sheet of filter
medium comprises a non-perforated qualifying layer nearest the
innermost layer of the filter.
28. The filter of claim 25 wherein the at least one sheet of the
filter medium includes two non-perforated sheets that are layered
prior to being coiled with the sheet of diffusion medium
29. The filter of claim 28 wherein the layered non-perforated
sheets have different average pore sizes.
30. The filter of claim 25 wherein the at least one sheet of filter
medium includes multiple sheets of filter medium having varied
numbers of perforations, with the perforated sheets forming the
pre-qualifying layers of filter medium and the perforations
comprising the by-pass apertures.
31. The filter of claim 1 further comprising an elongated, porous
core around which the filter medium and the diffusion medium are
wound.
32. The filter of claim 31 wherein the diffusion medium comprises a
single sheet secured at one end to the core, with the core being
wrapped at least once with the diffusion medium.
33. The filter of claim 1, wherein a plurality of pre-qualifying
layers are defined and further wherein the bypass apertures vary in
number as between at least two of said plurality of pre-qualifying
layers.
34. The filter of claim 1, wherein the ratio between the lesser of
the side dimensions of the lateral openings and the greatest of the
height dimensions of the first and second longitudinal passages is
greater than 1.5:1.
35. The filter of claim 34, wherein said ratio is about 4:1.
36. A method of filtering a volume of fluid comprising: forcing a
portion of the volume of liquid laterally through at least one
pre-qualifying layer of filter medium, and a remainder of the fluid
volume laterally through by-pass apertures in the at least one
pre-qualifying layer; re-mixing and passing the volume of fluid
through a diffusion layer having lateral openings and longitudinal
passages, wherein the longitudinal passages include at least one
dimension smaller than any dimension of the lateral openings; and
forcing all of the volume of fluid laterally through at least one
qualifying layer of filter medium.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to U.S. provisional
patent application Ser. No. 60/103,233, filed Oct. 5, 1998, the
disclosure of which is incorporated herein by reference.
BACKGROUND OF THE DISCLOSURE
[0002] 1. Technical Field
[0003] The present disclosure relates, in general, to a filter, a
method of making a filter and a method of filtering a fluid.
[0004] More particularly, the present disclosure relates to a
filter having alternating layers of non-filtering diffusion medium
and filter medium. Some of the layers of the filter medium are
provided with bypass apertures, while the remaining layers do not
include bypass apertures so that they act as qualifying layers for
the filter. Filters according to the present disclosure have been
found to provide improved fluid distribution over the filter
medium, reduced pressure drop and increased filter life, without a
reduction in filter rating.
[0005] 2. Discussion of Background Disclosures
[0006] In general, a filter assembly is used for removing
contaminants from fluids, i.e., liquids or gases. Such filter
assemblies, for example, are used in chemical and hydrocarbon
applications such as polyethylene manufacturing, food and beverage
applications, electronic applications such as circuit board
construction, coating applications such as high quality spray
painting, and industrial applications such as paper manufacturing.
Many filter assemblies include a tubular filter cartridge contained
in a filter housing. The filter housing includes a sump, wherein
the filter cartridge sits, and a head sealing the filter cartridge
within the sump such that the housing acts as a fluid-tight
pressure vessel. The filter head includes an inlet between the sump
and the filter cartridge, and an outlet aligned with the tubular
filter cartridge. Contaminated fluid is pumped into the filter
housing through the inlet, and radially inwardly through the filter
cartridge to produce filtered fluid, which then exits the filter
housing through the outlet.
[0007] Normally, such a filter cartridge includes an elongated,
tubular, perforated core wrapped with layers of depth filter
medium. A typical depth filter medium is a non-woven, porous,
melt-blown sheet or sheets of polypropylene micro fibers. The depth
filter medium can have a uniform pore structure or a graded or
tapered pore structure, whereby the pore size of the depth filter
medium decreases in the direction of fluid flow, i.e. from an outer
to an inner diameter of the filter. The depth filter medium can
also be provided with fibers of varying diameter.
[0008] Even with a tapered pore structure and/or varying fiber
diameters, however, it has been found that many depth filters
actually act as "low area" surface filters, since only one or two
of the multiple layers of filter medium within the depth are
heavily loaded and plugged with contaminants after use, while the
remaining layers are relatively clean (it should be noted that
these are general observations, as the performance of a particular
filter can depend on the particle size and distribution of
contaminants in a fluid to be filtered). When a depth filter
cartridge mimics a surface filter and collects contaminants in
primarily one layer, the results are an inefficient distribution of
fluid over the filter medium, a higher pressure drop for fluid
passing through the filter and a lower flow rate capability for the
filter. Such filters also tend to have a shorter useful life, and
thus must be replaced more often.
[0009] A variety of depth filter cartridge configurations have been
proposed and/or utilized over the years in efforts to provide
improved performance. For example, U.S. Pat. No. 4,863,602 to
Johnson shows a filter element that includes a plurality of layers
of flexible, fluid permeable filtering material, at least one layer
of which includes an opening through which fluid may pass, a layer
of flexible, fluid-permeable, substantially nonfiltering transport
material, and a layer of flexible prefiltering material positioned
upstream of the plurality of layers of filtering material to
"filter out from the fluid substantially all particles that could
otherwise become lodged in the transport material but not to filter
out significantly smaller particles."
[0010] U.S. Pat. Nos. 5,174,895 and 5,015,379 to Drori disclose
filter elements featuring at least one coiled filter strip defining
first and second butt ends. The Drori filter elements fail to
optimally enhance fluid flow while providing extended filter
service life. Additional filter designs of background interest are
disclosed in U.S. Pat. No. 4,877,526 to Johnson; U.S. Pat. No.
4,882,056 to Degen et al.; U.S. Pat. No. 5,468,382 to Cook et al.;
and U.S. Pat. No. 5,591,335 to Barboza et al.
[0011] Despite the various configurations known in the art,
however, there remains a need for a filter cartridge providing
improved distribution of fluid over the filter medium therein, a
lower pressure drop and long useful life, without reducing the
filter rating and that is economical to manufacture and
utilize.
SUMMARY OF THE DISCLOSURE
[0012] A filter for filtering contaminated fluid is disclosed
herein. A preferred filter includes alternating layers of a filter
medium and a diffusion medium, with at least a portion of the
layers of the filter medium having bypass apertures and acting as
pre-qualifying filter medium layer(s).
[0013] The diffusion medium includes a first plane of spaced-apart,
substantially parallel strands defining first longitudinal
passages. The longitudinal passages have a height dimension and a
width dimension. The diffusion medium further includes a second
plane of spaced-apart, substantially parallel strands defining
second longitudinal passages. The second longitudinal passages also
define a height dimension and a width dimension. The diffusion
medium's second plane of strands are oriented in a non-parallel
manner with respect to the strands of the first plane such that the
first and the second planes define lateral openings. Those lateral
openings define side dimensions. The first and the second
longitudinal passages are sized such that at least one dimension is
smaller than any of the side dimensions of the lateral
openings.
[0014] Filters of the type disclosed herein demonstrate superior
fluid distribution over the filter medium contained therein, and an
optimum use of the filter medium. Filters according to the present
disclosure, therefore, have an increased life and a lower pressure
drop without a reduction in filter rating, and provide more cost
effective filtering.
[0015] The filters of the present disclosure may be used in methods
to filter contaminated fluids in a wide range of commercial
applications. Such filters and filtration methods are described in
greater detail hereinbelow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] To provide those of ordinary skill in the art to which the
present disclosure pertains with an understanding as to how to
construct a filter as disclosed and claimed herein, filters
according to the present disclosure are described in detail below
with reference to the attached drawings wherein:
[0017] FIG. 1 shows an isometric side/end view of a filter
cartridge of the type disclosed herein;
[0018] FIG. 2 shows an enlarged sectional view of the filter
cartridge taken along line 2-2 of FIG. 1;
[0019] FIG. 3 shows an enlarged isometric view of a portion of a
non-filtering diffusion layer and a non-qualifying filter layer of
the filter cartridge of FIG. 1;
[0020] FIG. 4 shows a sectional view of the diffusion layer and the
non-qualifying filter layer of the filter cartridge of FIG. 1 taken
along line 4-4 of FIG. 3;
[0021] FIG. 5 shows a sectional view of the diffusion layer and the
non-qualifying filter layer of the filter cartridge of FIG. 1 taken
along line 5-5 of FIG. 3;
[0022] FIG. 6 shows a sectional view, similar to FIG. 4, of a
diffusion layer and an alternative filter layer for use with the
filter cartridge of FIG. 1;
[0023] FIG. 7 shows a top plan view of a continuous sheet of
non-filtering diffusion medium and sheets of filter medium being
wound onto a core to form a filter cartridge of the type shown in
FIG. 1;
[0024] FIG. 8 shows an isometric, exploded view of a continuous
sheet of non-filtering diffusion medium and sheets of filter medium
prior to being wound onto a core to form an alternative filter
cartridge according to the present disclosure;
[0025] FIG. 9 shows a sectional view, similar to FIG. 2, of a
further filter cartridge according to the present disclosure;
and
[0026] FIG. 10 shows an isometric view of a continuous sheet of
non-filtering diffusion medium, a sheet of filter medium, and
spaced-apart strips of filter medium being wound onto a core to
form an alternative filter cartridge according to the present
disclosure
DETAILED DESCRIPTION
[0027] Referring to FIGS. 1 through 5, a filter cartridge 10
according to the present disclosure includes an elongated, porous,
rigid core 12 having a multiplicity of openings 36, and an
elongated, hollow filter 14 coaxially mounted on the core 12.
Annular end caps 38 are bonded to the ends of the filter to prevent
contaminated fluid from by-passing the filter 14.
[0028] The filter 14 includes at least one sheet of filter medium
16, with at least a portion of the filter medium 16 including
bypass apertures 18, and a sheet of non-filtering diffusion medium
20. The sheets of the filter medium 16 and the diffusion medium 20
are wrapped, or coiled, to form alternating layers of filter medium
and diffusion medium extending from an innermost layer 22 to an
outermost layer 24 of the filter 14. In a preferred embodiment, the
diffusion medium 20 is bonded to itself at the outermost layer 24
to prevent the filter 14 from unwinding or unwrapping during
shipping, handling and use. As such, the diffusion medium 14
defines the outermost layer 24 of the filter 14.
[0029] 1. The Diffusion Medium
[0030] The diffusion medium 20 includes a first plane of
spaced-apart parallel strands 26 forming longitudinal passages 28,
and a second plane of spaced-apart parallel strands 30 forming
longitudinal passages 32, as illustrated by arrows fl, f2 in FIG.
3. The strands 30 of the second plane are oriented such that they
are not parallel with the strands 26 of the first plane, such that
the first and the second planes form lateral openings 34. In a
preferred embodiment, strands 26 are substantially perpendicular to
strands 30. The longitudinal passages 28, 32 are preferably smaller
in at least one dimension as compared to the smallest dimension of
the lateral openings 34. In particular, a height h of the
longitudinal passages 28, 32, as best shown in FIG. 4, is
preferably smaller than the length or width of the lateral openings
34.
[0031] The longitudinal passages 28, 32 of the diffusion medium 20
distribute the fluid to be filtered through flow channels f1, f2,
such that the diffusion medium 20 allows for, and assists in, the
longitudinal, or circumferential and/or axial, flow of the
contaminated fluid within the filter 14 between the innermost layer
of the filter medium 16 and the core 12, and/or between adjacent
layers of the filter medium. Such longitudinal flow assists in
minimizing the pressure drop across the filter cartridge 10 and in
dispersing the filtration function. The diffusion medium 20 is
preferably positioned between the core 12 and the innermost layer
of the filter medium 16 to facilitate the passage of fluid through
the openings 36 in the core 12. In a preferred embodiment, the core
12 is surrounded by a plurality of diffusion medium 20 layers to
provide a collection area for the flow prior to exiting through
openings in the core 12. Positioning of the diffusion medium 20
between adjacent layers of the filter medium 16 similarly maximizes
the use of the filter medium surface area within each layer for
contaminant loading, thereby reducing pressure drop and optimizing
filter medium usage to extend filter life.
[0032] In preferred embodiments, the dimensions of the lateral
openings 34 and the longitudinal passages 28, 32 of the diffusion
medium 20 are purposely selected to be substantially larger than
any contaminant to be filtered from the contaminated fluid. As a
result, the diffusion medium 20 does not act as a filter. Since the
diffusion medium 20 does not act, and is not used, as a filter to
trap contaminants, the diffusion medium does not substantially
contribute to the pressure drop across the filter 14, and in fact
minimizes the pressure drop by providing unobstructed flow channels
f1, f2 for contaminated fluid. In addition, the diffusion medium 20
provides structural rigidity and protects the filter medium 16 from
damage. The filter 14 is advantageously provided with an extra
outer layer of the diffusion medium 20 to add support and
protection to the filter 14.
[0033] The diffusion medium 20 is made from a suitable material
that is temperature and fluid compatible with the filtering
application to be carried out. Preferably, the diffusion medium 20
is made of a suitable thermoplastic. For example, for lower
temperature filtering applications (i.e., below 180.degree. F.),
the thermoplastic can comprise polypropylene, while for higher
temperature applications (i.e., above 180.degree. F.) or chemical
compatibility with different fluids, the thermoplastic can comprise
nylon, polyester, or melt-processible fluoropolymer.
[0034] The diffusion medium 20 preferably comprises thirty
thousandths of an inch (30 mils) thickness, bi-planar strand
orientation (17 mil strand size), twelve strands per inch,
polypropylene extruded netting. Such netting is available, for
example, under the trademark Plastinet.RTM., manufactured by
Applied Extrusion Technologies, Inc. of Middleton, Del., or
Naltex.RTM., manufactured by Nalle Plastic, Inc. of Austin, Tex.
The strands 26 of the first plane may be transversely oriented with
respect to the strands 30 of the second plane such that the two
planes form generally square or diamond-shaped lateral openings 34
having side dimension of about 0.066 inches. Thus, a preferred
diffusion medium 20 exhibits a ratio between lateral opening 34
side dimensions to lateral passage 28, 32 height (hereinafter
"Side-to-Height Ratio") of approximately 66:17 or 3.9:1. In
addition, the sheet of the diffusion medium 20 is oriented so that
the square lateral openings 34 form diamonds between ends 40, 42 of
the cartridge 10 to advantageously distribute flow over the tubular
filter.
[0035] Alternative netting dimensions may be utilized according to
the present disclosure. In preferred embodiments, however, to
ensure that the diffusion medium 20 does not function as a filter,
the Side-to-Height Ratio should be greater than about 1.5:1 and
preferably greater than 3:1. As noted hereinabove, a preferred
diffusion medium 20 according to the present disclosure exhibits a
Side-to-Height Ratio of about 4:1.
[0036] 2. The Filter Medium
[0037] According to preferred embodiments of the present
disclosure, the filter medium 16 is preferably of the depth filter
type, wherein contaminants are trapped within the medium, as
opposed to on an outer surface of the medium. A preferred depth
filter medium 16 is comprised of one or more sheets of non woven
thermoplastic micro fibers. The non woven thermoplastic micro
fibers may be melt blown, spunbond, carded, or hydroentangled, for
example. For lower temperature filtering applications (i.e., below
180.degree. F.), the thermoplastic can comprise polypropylene, for
example, while for higher temperature applications (i.e., above
180.degree. F.) or chemical compatibility with other fluids, the
thermoplastic can comprise nylon, polyester or melt-processible
fluoropolymer, for example.
[0038] Furthermore, filter medium suitable for use in accordance
with the present disclosure includes porous membrane, such as a
cast nylon porous membrane available as Zetapore.RTM. from CUNO,
Incorporated of Meriden, Conn. Other filter medium suitable for use
in accordance with the present disclosure includes wet laid paper
made with such raw materials as glass or cellulose. An example of a
suitable wet laid filter medium is TSM.RTM., available from CUNO,
Incorporated of Meriden, Conn. Woven material can also be
incorporated as the filter medium in accordance with the present
disclosure.
[0039] The filter medium 16 is preferably provided in discrete
sheet form, as opposed to being melt blown directly onto the
diffusion medium, for example, such that the sheets can be
inspected prior to being incorporated into the filter 14. The use
of discrete sheets of depth filter medium 16 has been found to
simplify quality control inspection of the filter medium and make
the physical properties of each filter cartridge 10 more
consistent. The ability to control the consistency of the physical
properties of the depth filter medium 16 provides a unique ability
to achieve sharp, well-defined, and optimized control over the
removal efficiency and dirt capacity of the resulting filter
cartridge 10. It should be understood, however, that a filter in
accordance with the present disclosure could be provided with a
single continuous sheet of filter medium.
[0040] According to preferred embodiments of the present
disclosure, the porosity of the filter medium 16 may be constant
between the inner and the outermost layers 22, 24 of the filter 14.
Alternatively, a filter medium 16 can be provided having a porosity
that varies between the outermost layer 24 and the innermost layer
22 of the filter, e.g., a filter having a tapered or graded pore
structure. If, as preferred, the filter medium 16 comprises
meltblown, non woven polypropylene micro fibers, the pore size
and/or fiber diameter geometries can be constant or varied between
the outermost layer 24 and the innermost layer 22 of the filter. A
depth filter medium 16 having a relatively uniform pore size and
fiber geometry is shown in FIGS. 4 and 5, while a filter medium 17
having a decreasing pore size is shown in FIG. 6. The sheets of
depth filter medium can also be processed, e.g., calendared or
compressed, to change its porosity in instances where it is desired
to utilize filter medium porosity to achieve desired filtration
results.
[0041] 3. The Bypass Apertures
[0042] According to preferred embodiments of the present
disclosure, a portion of the depth filter medium 16 includes a
multiplicity of spaced-apart bypass apertures 18. Preferably, the
bypass apertures 18 extend from the outermost layer 24 of the depth
filter medium 16 for a distance equal to between fifty and
eighty-five percent (50%-85%) of the overall radial distance from
the outermost layer 24 to the innermost layer 22 of the filter 14.
Most preferably, the bypass apertures 18 are extend to about
sixty-six percent (66%), i.e. two-thirds, of the radial distance
from the outermost layer 24 to the innermost layer 22 of the filter
14.
[0043] According to the preferred embodiments, the filter medium
layers 16 closest to the core 12 do not include bypass apertures
such that all of the fluid must pass through the inner layers. In
this way, the innermost layers of the filter medium 16 act as
qualifying layers for the filter 14, thereby permitting the filter
14 to be rated based upon the particle retention of the qualifying
layers. In like manner, the outer layers of filter medium 16 having
the bypass apertures 18 act as pre-qualifying layers.
[0044] It should be noted, however, that if the filter cartridge 10
is to be used within a filter assembly wherein contaminated fluid
is forced to flow radially outwardly therethrough, i.e., the
orientation of the fluid flow through the filter cartridge 10 is to
be reversed relative to the embodiments described heretofore, then
the bypass apertures 18 may be advantageously provided to extend
from the innermost layer of the depth filter medium 16 to a radial
distance of about fifty to about eighty-five percent (50%-85%) of
the overall radial distance between the innermost layer 22 and the
outermost layer 24 of the filter 14. When so oriented, the inner
layers of the filter medium 16 will act as pre-qualifying layers,
while the outer layers act as the qualifying layers.
[0045] It should also be noted that a filter according to the
present disclosure is not limited to the coiled designs shown in
the attached figures. The unique elements of the present
disclosure, i.e., alternating layers of filter and diffusion
mediums as disclosed and claimed herein, can be utilized in other
filter structures, such as a pleated filter cartridge or a filter
bag.
[0046] The bypass apertures 18 may be uniformly spaced-apart in
predetermined patterns, and provided as generally circular
openings. The geometry and relative sizes of the apertures 18,
however, may be advantageously varied, e.g., circular holes and
elongated slots of varying sizes are contemplated, and combinations
thereof. The apertures 18 may also be provided as slits, cuts or
perforations in the filter medium 16, and such slits, cuts or
perforations may be designed such that they do not fully open until
a predetermined pressure differential is created across the filter
cartridge 10. In addition, the multiplicity of bypass apertures may
be provided in a number of different patterns, e.g., linearly
aligned, diagonally aligned, or random, and the pattern(s) may vary
from layer to layer of the filter medium 16.
[0047] During operation with a filter cartridge 10 in which the
fluid flow is radially inward, contaminated liquid or gas passes
laterally (i.e., radially) inwardly through the lateral openings 34
in the outermost layer(s) of the diffusion medium 20. The
contaminated liquid or gas then contacts an outermost layer of the
filter medium 16. Contaminated liquid or gas that does not
immediately pass through the outermost layer of the filter medium
16 or the bypass apertures 18 in the filter medium may be directed
longitudinally, or substantially parallel with respect to the
outermost layer of the filter medium 16, through the longitudinal
passages 28, 32 of the diffusion medium 20, depending on the
relative resistance to flow.
[0048] For each of the non-qualifying layers of filter medium 16,
the bypass apertures 18 allow a portion of the fluid to pass
therethrough instead of passing through the filter medium of that
particular layer. After passing through one of the non-qualifying
layers of filter medium, the fluid passing through the bypass
apertures 18 and the fluid passing through the filter medium 16 are
re-mixed and diffused in the diffusion medium 20 before being
filtered by the next layer of filter medium 16. The bypass
apertures 18, accordingly, help utilize all available filter medium
16 and help to reduce the pressure drop through the filter 14.
Preferably, the bypass apertures 18 provide uniform contamination
loading of the non-qualifying layers of filter medium 16.
[0049] 4. Performance
[0050] The combination of the filter medium 16, the diffusion
medium 20 and the bypass apertures 18 in the manner described
hereinabove has been found to have the synergistic effect of
simultaneously increasing filtration capacity and minimizing
pressure drop across the filter cartridge 10, without reducing the
filter rating. This synergistic effect is demonstrated by the
following test results:
[0051] A filter cartridge ("Test Cartridge 1") utilizing
non-filtering diffusion medium along with filter medium, but
without bypass apertures, exhibits a filter life about two times
greater than a "control" filter cartridge having neither
non-filtering diffusion medium nor bypass apertures.
[0052] A filter cartridge ("Test Cartridge 2") utilizing bypass
apertures along with filter medium, but without diffusion medium as
described herein, does not exhibit a greater filter life than the
control filter cartridge.
[0053] A filter cartridge 10 ("Test Cartridge 3") according to the
present disclosure utilizing non-filtering diffusion medium 20
having a Side-to-Height Ratio of about 4:1 and relatively uniform
bypass apertures 18 extending about two-thirds of the radial
distance from the outermost layer to the innermost layer, exhibited
three to four times the filter life of the control filter
cartridge.
[0054] A filter cartridge 10 ("Test Cartridge 4") according to the
present disclosure utilizing both the non-filtering diffusion
medium 20 and bypass apertures 18 as described for Test Cartridge
3, and wherein the number of bypass apertures 18 increases towards
the outer diameter of the filter 14, exhibits from four to five
times the filter life of a control filter cartridge.
[0055] Test Cartridge 4 exhibits from two and a half to three times
the filter life of a filter cartridge utilizing both non-filtering
diffusion medium and bypass apertures, wherein the number of bypass
apertures increases towards the outer diameter of the filter, and
wherein the diffusion medium comprises a polyolefin spunbond web
available as POWERLOFT.RTM. media from Kimberly-Clark Corporation
of Roswell, Ga.
[0056] The advantageous performance described above for Test
Cartridges 3 and 4 is confirmed by visual inspection. Upon
dissection of the Test Cartridge 3 after testing, the filter medium
16 displayed contaminant loading to a radial depth from the
outermost layer 24 of about fifty percent (50%) of the filter 14.
In comparison, only the outermost layer of filter medium displayed
contaminant loading in Test Cartridge 1. Thus, the combination of
the diffusion medium 20 and the bypass apertures 18 as described
for Test Cartridges 3 and 4 provides a synergetic effect that was
not to be expected based upon the performances of Test Cartridges 1
and 2 possessing either non-filtering diffusion medium or bypass
apertures, respectively, but not both.
[0057] The testing procedure included a single pass test at a flow
rate of three gallons per minute of water containing between about
0.39 to about 1.0 grams per gallon of contaminant. Two standard
contaminants were used: 0-30 micron contaminant (ISO COARSE, A.T.D.
12103-1, A4, available from Powder Technologies, Inc. of
Burnsville, Minn.) and 0-10 micron contaminant (A.T.D. nominal 0-10
microns, also available from Powder Technologies, Inc). All of the
filter cartridges tested had an outer diameter of about 2.5 inches
and were about 10 inches long. The life of a filter for purposes of
the tests is defined as the amount of contaminant challenged for
the pressure drop across the filter to increase by 20 psid due to
contaminant loading in the tested filter.
[0058] 5. Examples
[0059] Additional exemplary filters made in accordance with the
present disclosure are described hereinbelow. However, these
exemplary filters are merely illustrative of filters that may be
made according to the present teachings, and are not intended to be
limiting thereof.
[0060] Example I:
[0061] Referring to FIG. 7, an exemplary filter 48 according to the
present disclosure is shown. The filter 48 includes a single
continuous sheet of diffusion medium 20 comprising thirty
thousandths of an inch (30 mils), bi-planar strand orientation (17
mil strand size), twelve strands per inch, polypropylene extruded
netting. The Side-to-Height Ratio of such diffusion medium is
approximately 4:1. The filter material, which comprises melt-blown,
non woven polypropylene micro fibers, is provided in a plurality of
discrete sheets 16a, 16b, 16c. The plurality of sheets of filter
medium 16a, 16b, 16c exhibit substantially equal and consistent
pore size and fiber geometries. As shown, the ends of the sheets
16a, 16b, 16c are overlapped. The overlapping ends of the sheets
16a, 16b, 16c, however, are not sealed or bonded since the tightly
wound sheet of the diffusion material 20 provides an adequate seal
between the overlapping ends of filter medium.
[0062] Inner (with respect to the core 12) sheets 16a of the depth
filter material do not have bypass apertures, while outer sheets
16b, 16c of the filter material have bypass apertures 18 (it should
be noted that only the ends of the non-perforated qualifying layers
16a need to be overlapped). The outermost sheets 16c of filter
material are preferably provided with more numerous bypass
apertures 18 than the intermediate sheets 16b.
[0063] The bypass apertures 18 in sheets 16b, 16c are formed by
perforating the sheets 16b, 16c prior to winding or coiling the
sheets of diffusion medium 20 and filter medium 16a, 16b, 16c. In
particular, sheets 16b are provided with circular perforations
having diameters of about {fraction (5/32)} inches, which are
arranged in straight rows at intervals of about 1.2 inches, and
wherein the rows are aligned and spaced at intervals of about 1.2
inch. Sheets 16c are provided with circular perforations having
diameters of about {fraction (5/32)} inches, which are arranged in
straight rows at intervals of about 1.2 inches, and wherein the
rows are staggered and spaced at intervals of about 0.6 inches. In
sum, sheets 16c contain almost twice as many perforations 18 as do
sheets 16b. In general, it has been found that for a 2 to 2.5 inch
outer diameter filter, rated between about 2 and about 70 microns,
the apertures 18 should consume about 2.5 percent of the area of
each of sheets 16c, and should consume about 1.25 percent of the
area of each of sheets 16b.
[0064] A first end of the sheet of the diffusion medium 20 is
secured to the core 12, using heat bonding for example, and the
sheet is wound about the core to create a first or innermost layer
of the diffusion medium. The sheet of diffusion medium 20 and the
sheets of filter medium 16a, 16b, 16c are then coiled together
about the innermost layer. The sheet of the diffusion medium 20 is
longer than the sheets of the filter medium 16a, 16b, 16c such that
the sheet of diffusion medium will form an outermost layer around
the filter medium. The outermost layer of the diffusion medium 20
is then secured to the adjacent layer of diffusion medium, using
heat bonding for example, such that the filter is tightly and
securely wound. Surprisingly, it has been found that winding the
layers tightly does not affect either the removal efficiency or the
dirt capacity of the filter 48.
[0065] Example II:
[0066] Referring to FIG. 8, a second example of a filter 50
according to the present disclosure is shown. The filter 50
includes a single continuous sheet of diffusion medium 20
comprising thirty thousandths of an inch (30 mils), bi-planar
strand orientation (17 mil strand size), twelve strands per inch,
polypropylene extruded netting. The Side-to-Height Ratio of the
diffusion medium 20 is approximately 4:1. The filter material,
which comprises melt-blown, non woven polypropylene micro fibers,
is provided in a plurality of discrete sheets 16a, 16b, 16c,
16d.
[0067] The sheets of filter medium 16a, 16b, 16c exhibit
substantially equal and consistent pore size and fiber geometry.
Sheet 16a does not have bypass apertures, while outer sheets 16b,
16c have bypass apertures 18. The outermost sheet 16c of filter
material is preferably provided with more numerous bypass apertures
18 than the intermediate sheets 16b. Most preferably, the sheets
16b, 16c are perforated in a manner substantially similar to the
corresponding sheets of FIG. 7.
[0068] Sheets 16d comprise melt-blown, non woven polypropylene
micro fibers that are calendared, i.e., compressed between two
rollers. Prior to being calendared, sheets 16d have an
substantially identical fiber geometries to the fiber geometries of
sheets 16a, 16b, 16c. In the calendering process, to the extent the
dimensions of the fibers are affected, the fibers assume a greater
dimension in the plane of the sheet 16d. As a result, after being
calendared, the sheets 16d have a reduced pore diameter as compared
to sheets 16a, 16b, 16c.
[0069] As shown, prior to the filter 50 being coiled, sheet 16a is
placed under sheet 16d adjacent sheet 16b. After being coiled, the
filter 50 includes: 1) inner layers of filter medium (innermost
sheet 16d) having a reduced pore size, 2) intermediate layers of
filter medium (laid over sheets 16a and 16d) that have a pore size
that alternates between a relatively smaller and larger size, and
3) outer layers of filter medium (sheets 16b and 16c) that have a
relatively larger pore size.
[0070] Example III:
[0071] Referring to FIG. 9, another filter cartridge 70 according
to the present disclosure is shown. The filter cartridge 70 is
similar to the filter cartridge 10 of FIG. 7, and elements that are
the same have the same reference numerals. The filter cartridge 70
includes a filter 72 having alternating layers of filter medium 74
and diffusion medium 76.
[0072] The filter medium 74 has bypass apertures formed from bores
78 extending from an outermost layer 80 towards an innermost layer
82 of the filter. The continuous bores 78 each extend to a uniform
depth within the filter 72. Preferably, the bores 78 extend
continuously to between about fifty and eighty-five percent
(50%-85%) of the radial distance from the outermost layer 80 to the
innermost layer 82 of the filter 72. More preferably, each of the
bypass bores 78 extends continuously to about sixty-six percent
(66%) of such radial distance. It should be noted that the filter
medium of the filter cartridge 70 can be provided with bypass
apertures formed by bores continuously extending from an outermost
layer 80 towards an innermost layer 82 of the filter, but to
non-uniform depths within the filter 72.
[0073] A method for manufacturing the cartridge 70 generally
includes winding or coiling the sheet of the diffusion medium 76
and the sheet(s) of the filter medium 74 into alternating layers
extending between the innermost and the outermost layers 82, 80,
and piercing the layers from the outermost layer towards the
innermost layer to produce the multiplicity of bypass bores 78 in
the filter. The bypass bores may be created by piercing the
outermost layer 80 of the filter 70 with one or more elongated,
narrow, sharp instruments, such as steel pins. A multiplicity of
parallel steel pins, for example, are mounted on a flat base, and
the filter cartridge 70 is simply pushed onto the spikes and
pierced to create the bypass bores.
[0074] Example IV:
[0075] Referring to FIG. 10, a further filter cartridge 110
according to the present disclosure is shown (filter cartridge 110
is not shown with end caps; as will be readily apparent to persons
of skill in the art). The filter cartridge 110 is similar to the
filter cartridge 70 of FIG. 7, and elements that are the same have
the same reference numerals. The filter cartridge 110 includes a
filter having a single continuous sheet of diffusion medium 20 and
at least one sheet of filter medium 16a wound around a core 12. The
filter 110 also includes strips of filter medium 114 wound within
the sheet of diffusion medium 20 between the sheet of filter medium
14 and the outer diameter of the filter. The strips 114 are spaced
apart to create gaps that comprise bypass apertures 116.
[0076] As shown, the strips of filter medium 114 are arranged
longitudinally with respect to the core 12, but the strips can be
oriented in other directions, such as diagonally with respect to
the core. The strips 114 are equally spaced apart from one another
such that the resulting bypass gaps 116 are of substantially equal
size. Alternatively, the strips can be spaced such that the
resulting bypass gaps become larger towards the outer diameter of
the respective filters, for example. It has been found that a
filter cartridge 110 of the type disclosed in FIG. 10 provides
about the same improved performance as provided by the filter
cartridge 10 disclosed in FIG. 7.
[0077] The presently disclosed filter cartridges can be used in a
variety of end uses, including, but not limited to, chemical and
hydrocarbon applications such as polyethylene manufacturing, food
and beverage applications, electronic applications such as circuit
board construction, coating applications such as high quality spray
painting, and industrial applications such as paper manufacturing.
It should be noted that while the examples of filters disclosed
herein are elongated tubes with cylindrical cross-sections, filters
in accordance with the present disclosure can be provided in other
suitable configurations, such as elongated tubes with a square,
elliptical, or oval cross-sections.
[0078] The filters and methods according to the present disclosure
have been described in detail in the foregoing specification, with
specific examples provided. Filters and methods in accordance with
the present disclosure, however, are not to be construed as limited
to the particular examples shown, as these examples are regarded as
illustrious rather than restrictive. Moreover, variations and
changes may be made to the exemplary filters by those skilled in
the art without departing from the spirit of the present disclosure
as set forth by the following claims.
* * * * *