Water filter abstract
An orally operable water filter includes an outer covering formed
of a flexible, water impervious material and which defines an elongate
enclosure. A flexible microporous filter membrane, having a pore
size of not more than one micron, is disposed within the elongate
enclosure and divides the enclosure into respective fluid inlet
and fluid outlet compartments, such that the outlet may be placed
in the mouth of the user and the fluid inlet may be contacted with
a source of water to be filtered by drawing the water through the
filter using oral suction. Furthermore, the filter includes a flexible
separator, disposed at least in the outlet compartment, for preventing
the blocking of fluid over the surface of the filter membrane.
Water filter claims
I claim:
1. An orally operable water filter, comprising an outer covering
formed of a flexible, water impervious material, and defining an
elongate enclosure,
a flexible microporous filter membrane, having a pore size of not
more than one micron, disposed within the elongate enclosure, and
dividing the enclosure into respective fluid inlet and fluid outlet
compartments,
means defining a fluid inlet for the inlet compartment formed in
the elongate enclosure and disposed proximate a first end of the
enclosure,
means defining a fluid outlet for the outlet compartment formed
in the elongate enclosure and disposed proximate a second end of
the enclosure, such that the outlet may be placed in the mouth of
a user and the fluid inlet contacted with a source of water, to
be filtered, and fluid drawn through the filter by oral suction,
wherein the filter includes flexible separator means, disposed
at least in the outlet compartment, for preventing the blocking
of fluid flow over the surface of the filter membrane.
2. A filter as claimed in claim 1 including separator means in
the inlet compartment for preventing the blocking of fluid flow
to the surface of the filter membrane.
3. A filter as claimed in claim 1 wherein the separator means
comprises a water permeable gauze or mesh disposed in the outlet
compartment.
4. A filter as claimed in claim 1 wherein the filter membrane
extends along substantially the whole of the length of the elongate
enclosure.
5. A filter as claimed in claim 1 wherein the outlet compartment
is an inner compartment bounded only by the filter membrane, and
wherein the inlet compartment is an outer compartment bounded on
its outside by the water impervious material, and on its inside
by the filter membrane.
6. A method of obtaining a supply of drinking water comprising:
(1) providing an orally operable water filter, comprising,
an outer covering formed of a flexible water impervious material,
and defining an elongate enclosure,
a flexible microporous filter membrane, having a pore size of not
more than one micron, disposed within the elongate enclosure, and
dividing the enclosure into respective fluid inlet and fluid outlet
compartments,
means defining a fluid inlet formed in the elongate enclosure and
disposed proximate a first end of the enclosure,
means defining a fluid outlet for the outlet compartment formed
in the elongate enclosure and disposed proximate a second end of
the enclosure, such that the outlet may be placed in the mouth of
a user and the fluid inlet contacted with a source of water, to
be filtered, and fluid drawn through the filter by oral suction,
and
flexible separator means, disposed at least in the outlet compartment,
for preventing the blocking of fluid flow over the surface of the
filter membrane;
(2) immersing the said fluid inlet in water which it is desired
to filter,
(3) inserting the said fluid outlet in the mouth of the user, and
(4) applying oral suction to draw filtered water through the filter
and into the mouth of the user.
Water filter description
This invention relates to water filters, and in particular to water
filters which are operable by mouth. In particular, the invention
relates to orally operable water filters which can be constructed
simply and cheaply, such that after use, they may discarded and
replaced.
Various proposals have previously been made for personal water
filters, adapted to be operated by mouth, and of a suitable size
as to be readily transportable by the user. For example, U.S. Pat.
Nos. 1333011 1000332 3389803 and U.K. Patent Specification
No. 2080278 all disclose examples of such filters.
Existing such devices essentially comprise a rigid outer container,
containing a filtering medium. Such existing devices suffer from
a number of disadvantages. Their major disadvantage is that their
rigid structure imposes severe and practical limitations upon their
usefulness to potential users. Typically, such users might be businessmen
or the like, travelling in parts of the world in which the purity
of water cannot be guaranteed. An important requirement for such
users is that orally operable filters should be readily transportable,
for example in a pocket, without the risk of damage. Existing filters
do not readily lend themselves to construction in a flexible form,
because of the nature of the filtering materials used, and the method
of construction of the devices.
In accordance with a first aspect of the invention, there is provided
an orally operable water filter, comprising:
an outer covering formed of a water impervious material, and defining
an elongate enclosure,
a flexible microporous filter membrane, having a pore size of not
more than one micron, disposed within the elongate enclosure, and
dividing the enclosure into respectively fluid inlet and fluid outlet
compartments,
a fluid inlet for the inlet compartment disposed proximate a first
end of the enclosure,
a fluid outlet for the outlet compartment disposed proximate a
second end of the enclosure, such that the oulet may be placed in
the mouth of a user, and fluid drawn through the filter by oral
suction,
wherein the filter includes flexible separator means disposed at
least in the outlet compartment, for separating the filter membrane
from an adjacent surface.
A filter in accordance with the present invention may be constructed
easily and cheaply, by laying up a flexible microporous polymer
sheet, having a pore size of not more than one micron, preferably
not more than 0.5 micron, with at least one sheet of a water impervious
covering material,
welding the sheets together so as to form a flexible elongate enclosure,
having inlet and outlet compartments,
providing an inlet for the inlet compartment proximate a first
end of the enclosure,
providing an outlet for the outlet compartment proximate a second
end of the enclosure,
and providing flexible separator means at least in the outlet compartment
for separating the filter membrane from an adjacent surface.
The use of a microporous membrane, and a flexible outer covering,
means that an orally operable water filter can be produced which
is not only cheap and convenient to manufacture, but also readily
transportable without risk of damage. However, because of the flexibility
both of the membrane, and the outer covering material, the possibility
exists for the membrane to collapse on to an adjacent surface, for
example a surface of an adjacent filter membrane, or of the outer
covering material, thus blocking the flow of water through the filter
membrane. For this reason, separator means are provided at least
in the outlet compartment, and preferably also in the inlet compartment,
to ensure free fluid flow over the filter membrane surface. The
separator means may comprise any suitable means for preventing the
filter membrane from clinging to the adjacent surface, and blocking
fluid flow, for example a sheet of a gauze or mesh placed adjacent
the filter membrane. In an alternative embodiment, the separator
means may comprise a plurality of raised portions, for example ribs,
formed on the surface adjacent the filter membrane, for example
on the water impervious outer cover.
In order to increase the filtering surface available, the filter
membrane preferably extends along substantially the whole of the
length of the elongate enclosure, and it preferably defines an inner
compartment, an outer compartment bounded by the water impervious
material being formed around the inner compartment.
In a particularly preferred embodiment of the method of producing
a filter in accordance with the invention, welding is carried out
so as to form a pair of elongate welds between a filter membrane
and the covering material, and a plurality of transverse welds are
then formed, between the elongate welds, to define the elongate
enclosures. In a further preferred embodiment, a multi-layer structure
is produced comprising the filter material and the impervious material,
of which the impervious covering material forms an outer layer,
and in which a plurality of fluid inlets are disposed between the
elongate welds, generally along a line parallel with them. The two
elongate welds are then caused to overlie each other, before the
transverse welds are formed. Thus, the outer covering is folded
such that the inlets are disposed proximate the folded edge, and
the transverse welds are formed such as to weld together at least
two layers of filter membrane, and at least two layers of outer
covering, along each transverse weld line, thereby defining an inner
compartment bounded by the filter membrane, and an outer compartment
bounded on the outside by the water impervious material, and on
its inside by the filter membrane.
Separator materials, for example in the form of gauze or mesh,
may be laid up with the filter membrane material and outer covering
material.
Any suitable water-impermeable material may be utilised for the
covering material, preferably one which can readily be welded utilising
conventional thermal or ultrasonic welding techniques. Preferred
examples are polyproylene, polyethylene, nylon, polyurethane, or
woven or knitted fabrics treated with suitable waterproofing compounds.
The microporous filter material with a pore size not exceeding
one micron, and preferably of 0.4 microns or less. Various materials
are suitable, for example cellulose acetate, or fluorine-containing
polymers. These two materials however suffer from the disadvantages
that they are, respectively, relatively readily frangible, and difficult
to weld. Accordingly, in a particularly preferred embodiment, the
microporous filter sheet is a polyamide material. Polyamides have
the additional advantage that they are hydrophilic, and therefore
the initial pressure differential required before filtering takes
place is reduced, as compared with other, more hydrophobic materials.
This is particularly important for an orally operable filter, in
which suction must be applied by mouth.
A preferred embodiment of the invention will now be illustrated
with reference to the accompanying drawings, in which:
FIG. 1 is a plan view of a mandrel suitable for producing a water
filter in accordance with the invention,
FIG. 2 is an end view of the mandrel of FIG. 1
FIG. 3 is a perspective view illustrating a preferred method of
construction, and
FIG. 4 is a section on line 4--4 of FIG. 3.
Referring first to FIGS. 3 and 4 orally operable water filters
are produced comprising an outer layer 1 of a polypropylene sheet,
and a layer 2 of a polyamide microporous filter material (nypor
45 produced by Domnick Hunter Filters Limited, having a pore size
of 0.45 microns). Sheets 1 and 2 define between them an inlet compartment
3 for water, and sheet 1 is provided with inlet holes 4 to enable
foul water to enter compartment 3. Separators 5 and 6 of a 20 denier
monofilament nylon mesh are provided within compartment 3 and a
further separator 7 is provided within an inner compartment defined
by filter sheet 2. Separator 7 is likewise formed of a 20 denier
monofilament nylon mesh. Sheets 1 2 5 6 and 7 are welded together
along longitudinal weld lines "a" and "b".
Transverse welds 10 shown on FIG. 3 seal together all ten layers
of material, so as to define elongate enclosures 12 each having
an inner compartment 13 having a outlet 15 which can be sucked
by mouth, and an outer compartment 3. A further separator 17 is
then inserted into each compartment 13 through outlet 15. Thus,
separators 17 and 7 serve to prevent the collapse of microporous
membrane 2 onto the opposite microporous membrane surface, when
suction is applied to outlet 15. Separators 5 6 and 7 also carry
out some coarse filtration.
The filter illustrated in FIGS. 3 and 4 may be conveniently manufactured
utilising a mandrel as illustrated in FIGS. 1 and 2.
FIG. 2 illustrates a mandrel plate suitable for use in producing
the filters in accordance with FIGS. 3 and 4. The mandrel plate
of FIGS. 1 and 2 includes a central part 19 and two wings 20 and
21 secured in central part 19. Means are provided on the central
part 19 for securing sheet plastics materials. In the embodiment
illustrated, such securing means includes four magnetic strips 23
24 25 and 26 secured to the central part 19 and corresponding
elongate magnetic strips (not shown) which may be fixed magnetically
to strips 23 24 25 and 26 after the sheet material has been interposed.
Immediately adjacent each magnetic strip 23 24 25 and 26 is a
mould welding surface 29 30 31 and 32 to act as a support for
an ultrasonic welding tool. The length L of the mandrel plate corresponds
to the width in which the various sheet materials making up the
filters are supplied by the manufacturers.
In use, the five layers shown in FIG. 4 which constitute a single
side of the resulting filter, i.e. the outer covering layer 1 two
separating layers 5 and 6 the microporous filter layer 2 and additional
separating layer 7 are laid up with their edges parallel, and their
edges are laid along magnetic strip 24. These sheets are then wrapped
around wing 21 over magnetic strips 26 and 25 on the rear of the
plate, and over magnetic strip 23. The sheets are trimmed to size
such that their edges protrude a little way and over magnetic strip
23.
Magnetic clamping strips are then applied to each of magnetic strips
23 24 25 and 26 to secure the five layers in position.
An ultrasonic welding tool is then run along the outermost sheet,
over the mould surfaces 29 30 31 and 32 so as to weld all five
layers securely together along a longitudinal weld line. The sheets
are then cut between strips 23 and 24 so as to produce two substantially
identical elongate multi-layer pocket like structures, each of which
has a cross-section substantially as illustrated in FIG. 4 except
that the separator 17 is not yet present. The part 35 of FIG. 3
illustrates the appearance of the laid up sheets at this stage.
Each assembly of laid up sheets is then removed from the mandrel,
and a series of tranverse welds 10 are formed, to produce a plurality
of enclosures 12. An outlet for each enclosure 12 is provided by
its mouth part 15 and inlets are provided by a plurality of holes
4 formed along lines generally parallel to the weld lines "a"
and "b".
Finally a coarse but resilient flexible mesh tube 37 is placed
inside each enclosure, to provide additional support to prevent
collapse of the two surfaces of filter membrane 2.
In an alternative embodiment, a plurality of layers of microporous
filter membrane may be provided, preferably having differing pore
sizes.
Because all of the components of the filter device in accordance
with the invention are flexible, the device can readily be carried
without risk of damage either to the device, or the carrier. Furthermore,
a plurality of filter devices in accordance with the invention may
conveniently be packed into a suitable package or carrying pouch.
In a preferred embodiment, each filter device may be sealed within
an individual sterile compartment, such that filters may be extracted
when need, and discarded after use.
The particular construction method in accordance with the invention
enables the filters to be produced at minimum cost such that it
becomes economic to discard them after use.
Although the microporous filter of the kind described above has
been found to remove most noxious substances encountered in foul
water, for example bacteria and some viruses, additional filtering
materials may also be incorporated, for example activated carbon
ion exchange resins and the like. |