U.S. patent application number 09/957429 was filed with the patent office on 2002-01-17 for filter cartridge for gravity-fed water treatment devices.
This patent application is currently assigned to PUR Water Purification Products, Inc.. Invention is credited to Emmons, David J., Tanner, John D..
Application Number | 20020005377 09/957429 |
Document ID | / |
Family ID | 25290044 |
Filed Date | 2002-01-17 |
United States Patent
Application |
20020005377 |
Kind Code |
A1 |
Tanner, John D. ; et
al. |
January 17, 2002 |
Filter cartridge for gravity-fed water treatment devices
Abstract
A filter cartridge for a gravity-fed water treatment device
having a porous particulate filter disposed therein. The porous
particulate filter has an open upper end, a closed lower end, and
sidewalls therebetween. Water is treated as it flows through the
sidewalls of the filter. The cartridge also contains granular media
disposed within the porous particulate filter.
Inventors: |
Tanner, John D.; (Plymouth,
MN) ; Emmons, David J.; (Plymouth, MN) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Assignee: |
PUR Water Purification Products,
Inc.
Cincinnati
OH
|
Family ID: |
25290044 |
Appl. No.: |
09/957429 |
Filed: |
September 19, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09957429 |
Sep 19, 2001 |
|
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|
08843458 |
Apr 16, 1997 |
|
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|
6290848 |
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Current U.S.
Class: |
210/226 |
Current CPC
Class: |
C02F 2201/006 20130101;
C02F 1/283 20130101; C02F 1/003 20130101; C02F 1/42 20130101 |
Class at
Publication: |
210/226 |
International
Class: |
B01D 027/00 |
Claims
We claim:
1. A filter cartridge for a gravity-fed water treatment device,
comprising: a porous particulate filter having an open upper end, a
closed lower end, and sidewalls therebetween; and a connecting
member sealing said porous particulate filter to a portion of the
filter cartridge proximate said upper end of said filter; wherein
as water flows into said open upper end and through said sidewalls
of said porous particulate filter, air is displaced out of said
open upper end.
2. The filter cartridge of claim 1, wherein the sidewalls of the
porous particulate filter are substantially cylindrical.
3. The filter cartridge of claim 1, wherein the porous particulate
filter is microporous.
4. The filter cartridge of claim 1, wherein the porous particulate
filter comprises sheet filter media.
5. The filter cartridge of claim 1, wherein the porous particulate
filter is pleated.
6. The filter cartridge of claim 1, wherein the porous particulate
filter comprises hydrophilic material.
7. The filter cartridge of claim 1, wherein the filter cartridge
further comprises a shell having an inlet and an outlet, the shell
being disposed around the porous particulate filter, wherein water
is treated as it flows from the inlet of the shell, into the open
upper end of the porous particulate filter, through the sidewalls
of the filter, and out the outlet of the shell.
8. The filter cartridge of claim 7, wherein the shell further
comprises one or more air-outlet apertures so that, when water
enters the cartridge through the inlet of the shell, air is also
displaced out of the air-outlet apertures of the shell.
9. A filter for a gravity-fed water treatment device, comprising: a
porous particulate filter having sidewalls and an inlet; and
granular media contained within said sidewalls of said porous
particulate filter; said porous particulate filter and said
granular media being constructed and arranged such that water flows
into said inlet, through said granular media, and radially outward
through said sidewalls of said porous particulate filter as it is
treated.
10. The filter of claim 9, wherein the porous particulate filter
comprises sheet filter media.
11. The filter of claim 9, wherein the sidewalls of the porous
particulate filter are substantially cylindrical.
12. The filter of claim 9, wherein the porous particulate filter is
pleated.
13. The filter of claim 9, wherein the porous particulate filter
comprises hydrophilic material.
14. The filter of claim 9, wherein the porous particulate filter
comprises glass microfibers.
15. The filter of claim 14, wherein the porous particulate filter
further comprises a hydrophilic binder to hold the glass
microfibers together.
16. The filter of claim 9, wherein the porous particulate filter is
capable of removing protozoan cysts.
17. The filter of claim 9, wherein the porous particulate filter is
microporous.
18. The filter of claim 9, wherein the granular media is carbon, an
ion exchange resin, or a combination thereof.
19. The filter of claim 18, wherein the carbon in the granular
media comprises granular activated carbon.
20. The filter of claim 9, wherein the granular media is
hydrophilic.
21. A filter cartridge for a gravity-fed water treatment device,
comprising: a porous particulate filter having glass fibers and a
hydrophilic binder to bind the fibers together, the filter being
capable of removing greater than 99.95% of 3-4 micron cyst
particles from water; and a connecting member sealing said porous
particulate filter to a portion of the filter cartridge.
22. The filter cartridge of claim 21, wherein the glass fibers
comprise glass microfibers.
23. The filter cartridge of claim 21, wherein the porous
particulate filter has sidewalls.
24. The filter cartridge of claim 21, wherein the porous
particulate filter is substantially cylindrical.
25. The filter cartridge of claim 21, wherein the porous
particulate filter comprises sheet filter media.
26. The filter cartridge of claim 21, wherein the porous
particulate filter is pleated.
Description
FIELD OF THE INVENTION
[0001] This invention relates to filter cartridges for use in
gravity-fed water treatment systems. In particular, this invention
relates to a filter cartridge having novel filter media.
BACKGROUND OF THE INVENTION
[0002] Domestic water treatment devices are known in the art. Among
these devices are self-contained systems which process water in
batches. Examples of batch devices are pitchers/carafes and larger
reservoirs where treated water is poured, for example, from a
spigot. These self-contained systems typically have upper and lower
chambers separated by a filter cartridge. They rely on gravity to
force water from the upper chamber, through the cartridge, and into
the lower chamber, thereby producing treated water.
[0003] The presence of unwanted and potentially harmful
contaminants in water, especially drinking water, is of concern to
many people. This concern creates a desire for water treatment
devices in the home and elsewhere. Many water treatment devices and
methods have been developed to remove or neutralize chemical and
particulate contaminants. Some of these devices and methods
incorporate chemically active materials to treat the water. For
example, activated carbon is capable of removing the bad taste and
odor from water as well as chlorine and other reactive chemicals.
Ion exchange resins are useful for removing metal and other ions
from water. However, no single material or chemical has been found
that will remove all contaminants.
[0004] In addition to chemical and particulate contaminants, water
often contains biological contaminants. These contaminants often
can not be entirely removed by activated carbon, ion exchange
resins, or other chemically active water purifiers. The biological
contaminants may be susceptible to harsher chemical treatment, but
such chemicals are, typically, themselves contaminants or can not
be easily incorporated in gravity-fed treatment devices, especially
those for household use. In addition to being resistant to removal
by standard chemical means, many of these biological contaminants,
such as protozoan cysts like cryptosporidium, are only a few
microns in size.
[0005] Because of their small size and the relative unavailability
of suitable chemical removal methods for these biological
contaminants, a gravity-fed water treatment device which can remove
protozoan cysts and still retain satisfactory flow rate has been
very difficult to develop. Present devices which filter cysts out
of water require pressurization, either from the tap or by manual
pumping, to achieve a satisfactory flow rate. However, such devices
are relatively complex and expensive, and in the case of manual
pressurization systems, harder to operate. Thus, there is a need
for a gravity-fed water treatment device that is capable of
removing biological contaminants, including cysts like
cryptosporidium, while providing an acceptable flow rate.
SUMMARY OF THE INVENTION
[0006] According to the present invention, a filter cartridge for a
gravity-fed water treatment is provided. In one aspect of the
invention, the filter cartridge includes a porous particulate
filter that has an open upper end, a closed lower end, and
sidewalls between the two ends. The porous particulate filter is
sealed to a portion of the filter cartridge by a connecting member.
Water is treated as the water flows into the open upper end and
through the sidewalls of the porous particulate filter. Air within
the filter, that is displaced by incoming water, flows out of the
open upper end of the filter.
[0007] In another aspect of invention, the filter cartridge
includes a porous particulate filter with sidewalls and an inlet.
Granular media is contained within the sidewalls of the filter.
Water is treated as it flows through the inlet of the filter,
through the granular media, and radially outward through the
sidewalls of the filter.
[0008] In a further aspect of the invention, the filter cartridge
includes a porous particulate filter which includes glass fibers
and a hydrophilic binder. The porous particulate filter is sealed
to a portion of the filter cartridge by a connecting member. Water
that is treated by the filter cartridge has greater than 99.95% of
3-5 micron cysts particles removed.
[0009] These and other advantages and features of novelty which
characterize the invention are pointed out with particularity in
the claims annexed hereto. However, for a better understanding of
the invention and its advantages, reference should be made to the
drawings which form a further part hereof, and to the accompanying
descriptive matter in which there is illustrated and described a
preferred embodiment of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] A preferred embodiment of the present invention will be
described with reference to the accompanying drawings, wherein like
reference numerals identify corresponding parts:
[0011] FIG. 1 is an exploded perspective view of an embodiment of a
filter cartridge according to the present invention; and
[0012] FIG. 2 is a partial cross-sectional view of the filter
cartridge shown in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0013] The filter cartridge 20 described herein can be used in a
variety of gravity-fed water treatment devices. Referring to FIGS.
1 and 2, this preferred embodiment of the filter cartridge 20
contains a porous particulate filter 24 with granular media 26
disposed within particulate filter 24. Filter cartridge 20 also has
a shell 22 which surrounds porous particulate filter 24 to provide
mechanical support for the particulate filter. Shell 22 has a
collar 36 which seals porous particulate filter 24 to cartridge 20
so that water flowing through the cartridge must pass through
porous particulate filter 24 and is, thereby, treated.
[0014] Porous particulate filter 24 mechanically filters particles
and biological contaminants, such as protozoan cysts, out of the
water. To effectively filter biological contaminants, porous
particulate filter 24 should have pores smaller than the size of
the contaminants that are to be filtered. Biological cysts, such as
cryptosporidium, are only a few microns in size. An effective
cryptosporidium filter must have pores that are less than about 5
microns, and preferably less than about 2 microns, in diameter.
Thus, porous particulate filter 24 is, preferably, microporous,
which means that the particulate filter has pores which are
approximately 1-3 microns or smaller in size.
[0015] Preferably porous particulate filter 24 removes greater than
99.95% of 3-4 micron cysts particles from water treated with the
filter cartridge. The level of cyst filtration is determined using
the protocols of NSF 53 .sctn.6.5 and 6.12, incorporated herein by
reference.
[0016] Porous particulate filter 24 is preferably formed in a shape
having sidewalls 25 and an open upper end. Sidewalls 25 of porous
particulate filter 24 are substantially cylindrical. However, other
shapes of the sidewalls are also included within the scope of the
invention. Moreover, sidewalls 25 of particulate filter 24 may be
flat or pleated, as shown in FIG. 1. Pleated sidewalls provide
greater filter surface area than do flat sidewalls for an otherwise
identical filter configuration. However, the pleats should not be
closely spaced or the flow rate through the pleats will be
decreased.
[0017] The upper end of particulate filter 24 is at least partially
open so that water can flow into particulate filter 24 and air
within particulate filter 24 can escape as it is displaced by the
water. The bottom end of porous particulate filter may be closed
(not shown) or open (see FIGS. 1 and 2). If the bottom end is open
then porous particulate filter 24 should be attached to an object,
such as a bottom cap 29 of shell 22, which will prevent the flow of
water out of the open bottom end of particulate filter 24.
[0018] Porous particulate filter 24 can be formed from a wide
variety of materials. Preferably, sidewalls 25 of porous
particulate filter 24 are made from a hydrophilic, microporous
filter media. Optionally, if the bottom end of porous particulate
filter 24 is closed, then the bottom can also be made from the
hydrophilic, microporous filter media. One example of a suitable
hydrophilic, microporous filter media is a carbon block which has
been hollowed out to create sidewalls and a open upper end.
[0019] The preferred hydrophilic, microporous filter media for the
construction of porous particulate filter 24 is fibrous sheet
filter media. The fibers of this sheet filter media can be either
natural, such as fiber made of cellulose or cellulose derivatives,
or synthetic, such as fibers made from polymers or glass.
Preferably, the fibers are synthetic fibers, and more preferably,
the fibers are glass microfibers. Often natural fibers, such as
cellulose fibers, are thicker than synthetic fibers resulting in
fewer pores and a correspondingly slower flow rate.
[0020] The flow rate of water through a given porous particulate
filter is of critical importance in determining the acceptability
of porous particulate filter 24 for a gravity-fed water treatment
device. Flow rate is typically determined by the size of the pores,
the pressure applied to the water to push it through the pores, and
the composition of the filter. In gravity-fed devices, such as
carafes or household water storage containers, the pressure exerted
on water to push it through filter cartridge 20 is due only to a
gravitational force on the water itself. For household gravity-fed
water treatment devices, such as carafes, the pressure exerted on
the water is typically less than about 0.5 lb/in.sup.2.
Consequently, the gravity-induced flow rate through a typical
microporous particulate filter is very slow and not practical for a
gravity-fed water treatment device.
[0021] To overcome this limitation, the preferred porous
particulate filters 24 of the invention contain hydrophilic
material. Hydrophilic materials, as defined for purposes of the
present invention, are those materials, which when dry, are quickly
wetted (i.e., they absorb droplets of water quickly). The
hydrophilicity of these materials is due to an attractive force
between the hydrophilic material and water which is greater than
the surface tension of the water at the water/filter interface
(i.e. the attractive force between the individual water molecules
at the interface).
[0022] The hydrophilicity of porous particulate filter 24 may be a
result of the hydrophilic nature of the fibers or other material of
the porous particulate filter. Alternatively, the hydrophilicity of
the filter may be due to an additive to the material of the filter.
Such an additive may be capable of creating a hydrophilic
particulate filter even if the filter contains non-hydrophilic or
hydrophobic fibers.
[0023] A hydrophilic additive to the filter may also serve other
functions within the filter material. One example of such an
additive is a hydrophilic binder which is added to the media, not
only to impart hydrophilicity to the binder, but also to bind the
microfibers of the media together to form a sheet. Hydrophilic
sheet filter media having these properties is available from
Alhstrom, Mt. Holly Springs, Pa. (Grade 2194-235). Suitable
hydrophilic binder for use in binding glass microfibers is
available from Goodrich (Part No. 26450).
[0024] Sheet filter media was obtained from the above-named source.
The sheet filter media had an average pore size of about 1.2 .mu.m
and a thickness of about 0.024 in. The porous particulate filter
was about 3 in. tall and had a 1.75 in. outer diameter. The porous
particulate filter was pleated to give 40 pleats uniformly spaced
around the filter with a pleat depth of about 0.25 in., giving the
filter an inner diameter of 1.25 in.
[0025] To protect porous particulate filter 24 from damage, a shell
22 may be disposed around filter 24. Shell 22 has three connectable
pieces, a top cap 28, a bottom cap 29, and a body 30, as shown in
FIGS. 1 and 2. This configuration allows for easy placement of
particulate filter 24 in filter cartridge 20. Other shell
configurations may be used and are included within the scope of the
invention.
[0026] Shell 22 also has one or more inlet apertures 32 and one or
more outlet apertures 34 through which water enters and exits
filter cartridge 20, respectively. Inlet apertures 32 are
positioned in an upper portion of shell 22 in either top cap 28
(see FIGS. 1 and 2) or an upper portion of body 30 (not shown).
[0027] Outlet apertures 34 are typically located in the bottom cap
29, but could also be on the side of body 30. Inlet apertures 32
and outlet apertures 34 are positioned within shell 22 so that
water flowing into inlet apertures 32 goes through granular media
26 and porous particulate filter 24 prior to exiting out outlet
apertures 34.
[0028] Porous particulate filter 24 is adhesively connected to
bottom cap 29 to provide a seal to prevent water from flowing
around the bottom of filter 24. Bottom cap 29 also contains one or
more ridged columns 31 which, when bottom cap 29 is slid into body
30, will contact a lip of an indentation 35 in the interior portion
of body 30 to firmly hold cap 29 in place. There are spaces between
ridged columns 31 of cap 29 to allow water to flow out of filter
cartridge 20 through outlet apertures 34 in bottom cap 29.
[0029] Shell 22 also has a collar 36 acting as a connecting member,
which provides a seal between porous particulate filter 24 and
filter cartridge 20 so that water flowing through inlet apertures
32 must pass through porous particulate filter 24 before exiting
through outlet apertures 34. Collar 36 has an annular cup formed by
a cylinder 37 and a base 39. Porous particulate filter 24 is
adhesively attached within the annular cup formed by cylinder 37
and base 39 to provide a water-tight connection to collar 36. Other
methods of sealing porous particulate filter 24 to cartridge 20 are
also included within the scope of the invention.
[0030] Shell 22 is typically constructed of a plastic or polymeric
material. Shell 22 is preferably made from a molded plastic.
[0031] The flow rate of water through porous particulate filter 24
is often diminished by the presence of air adjacent to porous
particulate filter 24. Air trapped near particulate filter 24 forms
an interface with the water in particulate filter 24. There will be
a surface tension associated with this interface. Unless there is
enough pressure to break this surface tension, the water will not
flow. Thus, it is desirable that there be a path for the escape of
air as it is displaced by water flowing into filter cartridge 20.
One advantage of the filter configuration depicted in FIGS. 1 and 2
is that air in the interior of the shape formed by porous
particulate filter 24 can flow out the open upper end of porous
particulate filter 24 and exit filter cartridge 20 through inlet
apertures 32.
[0032] When shell 22 is provided around porous particulate filter
24, air may also be trapped in gap 38 between shell 22 and
particulate filter 24. The presence of trapped air may reduce the
flow rate through filter 24 as the water level within gap 38
rises.
[0033] Air outlet apertures 40 are provided in shell 22 so that the
air can escape from gap 38, especially when outlet apertures 34 are
below the water level of the water treatment device. Air outlet
apertures 40 are often provided near the upper end of gap 38 which
is proximate the sealed connection between shell 22 and porous
particulate filter 24. This configuration will allow most or all of
the air to escape the cartridge as air will naturally rise to the
highest possible level due to the buoyancy of air in water. In
addition to providing an escape path for air, air outlet apertures
38 may also function as water outlet apertures.
[0034] Granular media 26 is typically disposed within shell 22 to
provide additional water purification. As shown in FIG. 2, granular
media 26 is preferably disposed within porous particulate filter
24. This configuration is advantageous because particulate filter
24 will prevent granular media 26 from coming out of filter
cartridge 20. In addition, granular media can be disposed within a
separate granular media containment region 41 of shell 22 (see FIG.
2).
[0035] Granular media 26 comprises chemicals or materials that are
suitable for treating water. Granular media 26 typically includes
chemicals or other materials that are capable of removing,
reducing, or deactivating one or more of the following elements:
bad odor, bad taste, organic contaminants, chemical contaminants,
and metal or other unwanted ions, such as chlorine. Suitable
granular media 26 includes carbon, zeolites, an ion exchange resin,
or a combination thereof. A preferred form of carbon for use as
granular media is granular activated carbon. A preferred granular
media for use in the filter cartridges of the invention is a
mixture of a weak-acid cation exchange resin and granular activated
carbon.
[0036] In one embodiment of the invention, at least a portion of
granular media 26 is hydrophilic. Hydrophilic granular media
includes granular activated carbon. A hydrophilic granular media
disposed within porous particulate filter 24 may facilitate the
flow of water through porous particulate filter 24. Hydrophilic
granular media in contact with porous particulate filter 24 may
provide a less resistive flow path for water into and through the
(preferably hydrophilic) sidewalls 25 of porous particulate filter
24.
[0037] It should be understood that the present invention is not
limited to the preferred embodiment described above, which is
illustrative only. Changes may be made in detail, especially
matters of shape, size, arrangement of parts, or materials of
components within the principles of the invention to the full
extent indicated by the broad general meanings of the terms in
which the appended claims are expressed.
* * * * *