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BACKGROUND OF THE INVENTION
The present invention relates to purification of drinking water, and
particularly to a device for purifying drinking water immediately prior to
consumption by an individual.
With the increase of population of the world, together with increasing
development of new chemical compounds and disposal of industrial waste
over many years, increasing amounts of contamination are found in even the
cleanest sources of available surface water and in well water. Adequate
purification is not provided for publicly available drinking water in many
areas of the world, and travelers not accustomed to the particular water
supply in an area being visited often are made ill by contamination
present in the water, although local residents are not noticeably
affected. Additionally, dissolved gases and minerals present in the water
may cause unpleasant taste or odor in the water, even though the water is
safe for drinking. Furthermore, medical science is learning that many
compounds often found in drinking water supplies may, over long periods of
time, be carcinogenic.
As a response, water filtration devices have become available for
incorporation in individual household water supply systems to purify
drinking water. However, when water from other sources must be consumed,
as in restaurants or when a person is traveling and filtered water supply
sources are not readily available, it has previously not been convenient
to obtain adequately purified drinking water, nor to purify the water
which is available.
Gartner U.S. Pat. No. 4,298,475 discloses a portable water purifier
including a filter including mechanical filtration elements, bactericidal
agents, and an adsorbent material contained within the tubular filter
housing so that a user may supply suction from the mouth to draw water
through the tube to filter out foreign material and purify the water prior
to use. Gartner makes no provision, however, for retention of water within
the filter medium for any particular length of time as may be necessary
for adsorption of contaminating materials from a quantity of water, with
the resultant likelihood of inefficient purification of water by the
device disclosed in that prior patent.
Gartner U.S. Pat. No. 4,420,590 discloses certain resins useful as filter
media for treatment of drinking water.
Athletes, in particular, often require relatively large quantities of water
for consumption during athletic exercise, as, for instance, during long
foot races, bicycle races, soccer games, and hiking. Recently, plastic
squeeze bottles with drinking tubes extending through removable caps have
become popular, particularly for use by athletes, who carry the bottles
full of water o other electrolyte-replacement liquids for consumption
during the course of athletic events. Such bottles are convenient, for
example, for bicyclers, who can carry them clipped to the frame of the
bicycle, or for track and swimming competitors, who have their preferred
liquids available in such bottles to be drunk between heats. However, such
bottles contain a limited amount of water brought from an available source
of water of satisfactory purity, and once consumed, such water must be
replaced by whatever water is available, which may not always be
acceptably pure.
What is needed, therefore, is a way to purify locally available water to
provide drinking water which is acceptably pure and free from
objectionable odors and tastes, as well as being acceptably free of
microbial organisms which might cause illness. Preferably such a water
purification device should be easily portable, and should be convenient
for use in places such as restaurants, so that travelers will not
jeopardize their health by being embarrassed to use such a device in a
restaurant.
SUMMARY OF THE INVENTION
The present invention provides an unobtrusive portable personal water
filter device which resembles an oversized drinking straw in its
appearance and which is able to filter and purify drinking water
adequately to protect the user from illness caused by foreign material
suspended or dissolved in an unfamiliar supply of water. A tubular filter
housing contains mechanical filtration elements at each end, and an
activated charcoal filter in an intermediate location adsorbs many
chemical contaminants which might cause objectionable odor or taste or be
injurious if consumed. The mechanical filter layers at each end of the
filter have pores small enough to retain water within the interior of the
filter, and thus the filter assures adequate contact time between the
water being filtered and the activated charcoal filter medium. The filter
can be cleared of water upon completion of use, by blowing air in a
reverse direction through the filter unit.
For use by hikers and athletes, a bottle for carrying a personal supply of
drinking water is equipped with a similar filter unit, so that water
consumed from a supply carried in the bottle is filtered as it is removed
from the bottle through a flexible drinking tube.
A mouthpiece used with the portable personal filter unit and the flexible
drinking tube connected to the filter unit contained within the portable
water bottle both restrict the flow of water through the filter unit to a
rate which provides ample time of contact between the water and the
activated charcoal filter medium, in order to provide for efficient
adsorption of materials from the water being purified.
It is therefore a principal object of the present invention to provide a
device for purifying a personal supply of drinking water immediately prior
to consumption.
It is a further object of the present invention to provide a device which
enables a user safely to drink available water, such as that found in
streams along a hiking route.
It is an important feature of the present invention that it provides a
filter unit which is as small as is practical, consistent with effective
filtration, reasonable cost, pressure drop no greater than can be produced
easily by oral suction, and a reasonably good rate of flow for drinking.
It is another feature of the present invention that it provides a filter
unit which is equipped with a mouthpiece limiting the rate of flow of
water through the filter unit to provide for ample time of contact between
the water being purified and the adsorbent filter medium contained within
the filter unit.
The foregoing and other objectives, features, and advantages of the
invention will be more readily understood upon consideration of the
following detailed description of the invention, taken in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially cut-away view of a personal portable drinking water
filter according to the present invention in use in filtering water from a
drinking glass.
FIG. 2 is a fragmentary view of the portable personal water filter shown in
FIG. 1, taken in the direction indicated by the line 2--2.
FIG. 3 is an end view of the mouthpiece of the portable personal water
filter shown in FIGS. 1 and 2.
FIG. 4 is a pictorial view showing the portable personal water filter shown
in FIGS. 1-3 in an associated carrying case.
FIG. 5 is a sectional view of a personal drinking water container including
a filter according to the present invention.
FIG. 6 is a view of a detail of the personal drinking water container and
filter combination shown in FIG. 5.
FIG. 7 is a view similar to FIG. 3, showing another embodiment of the
mouthpiece of the filter shown in FIGS. 1 and 2.
DETAILED DESCRIPTION OF THE INVENTION
Referring first to FIGS. 1-3, a portable personal water filter 10 is shown
as if being used to drink water from a water glass 12. The personal water
filter 10 includes a filter unit 13 including a housing 14 which is
generally tubular and elongate, having a lower or inlet end 16, with a
retainer fitting 17 and an upper or outlet end 18 with a similar retainer
fitting 19. A mouthpiece 20 is attached to the outlet end 18 and defines a
conduit 22 through which water can pass in the direction indicated by the
arrows 24 in response to a person sucking on the upper end 26 of the
mouthpiece 20 as if the personal water filter 10 were a drinking straw.
Preferably, the filter housing 14 is of polystyrene, PVC, or ABS plastic
and has an overall length 28 of about 6 inches and an outside diameter 30
of about 0.55 inches, with a wall thickness 32 of about 0.035 inches,
leaving an inside diameter 34 of about 0.480 inches.
The conduit 22, in a preferred embodiment of the invention, has an internal
diameter 36 of about 0.125 inch over at least a portion of its length.
This size limits the rate of flow of water through the personal portable
water filter 10, so that water passes through the filter medium slowly
enough to provide ample time for contaminants to be adsorbed by the filter
medium. The interior of the mouthpiece 20 is tapered between the conduit
22 and the outlet end 18 to define a cavity 38 above the outlet end 18 of
the filter housing. The middle portion of the mouthpiece 20 is conically
tapered, and the upper end 26 has a pair of parallel upper and lower faces
40 so that in end view, as shown in FIG. 3, the upper end 26 has a lozenge
shape, to make it comfortable to receive the upper end 26 of the
mouthpiece 20 between a person's lips sealingly, and also to provide for
the possibility of holding the upper end portion 26 of the mouthpiece 20
between a person's front teeth. This shape is beneficial when using the
filter 10 in cold weather, since when one's face is cold it becomes
difficult or impossible to seal the lips tightly around a small circular
mouthpiece such as an ordinary drinking straw, yet the upper end portion
26 can be held sealingly by a user's lips, even when cold, because of the
wider, lozenge shape. A lenticular shape of the upper end 26 (see FIG. 7)
might be easier to use, but would be more difficult to produce.
The lower end of the mouthpiece 20 defines an interior annular ledge 42
which abuts against the upper or inlet end 18 of the filter housing 14,
with the inside diameter of the portion of the mouthpiece below the ledge
42 being large enough to fit with a snug push fit over the outlet end 18
portion of the filter housing 14.
Preferably, the filter housing 14 and the mouthpiece 20 are manufactured of
appropriate plastics materials with sufficient elasticity so that the
mouthpiece 20 grips the outlet end 18 of the filter housing 14 to connect
the mouthpiece 20 to the filter housing 14 without the need for an
adhesive.
Within the filter housing 14, a multi-layer filtering medium includes at
least three functional layers, of which a lower, or inlet end layer 44,
preferably having a thickness 46 of about 0.125 inch, serves a dual
purpose of filtering particulate matter from water drawn through the
filter and of retaining the material of the middle layer 48 within the
filter housing 14. The upper, or outlet end layer 50 may be of similar
material, of a preferred thickness 52 also of 0.125 inch, leaving the
middle layer 48 with a thickness 54, extending longitudinally of the
filter housing 14, of at least about 5.5 inches. This size has been
determined, on the basis of calculations and empirical testing, to be the
minimum size required to accomplish satisfactorily effective filtration
practically, that is, to provide clean, substantially tasteless drinking
water.
The retainer fittings 17 and 19 are connected to the tubular body of the
housing 14 either by an adhesive or by being welded thermally or
ultrasonically to the tubular body of the housing 14, and extend radially
inward a small distance, great enough to retain the respective layer 44 or
50 within the filter housing 14.
The material of the middle layer 48 is preferably a granulated silver
impregnated activated charcoal. Preferably, charcoal made of coconut shell
is prepared and ground to pass a 12.times.30 mesh. The charcoal is
impregnated according to EPA-approved industry standard methods to contain
0.026% silver, by weight, and is placed within the filter housing 14 to
provide free space equal to about 5% of the volume defined between the
filter medium materials of the inlet end or lower layer 44 and the outlet
end or upper layer 50, to allow for expansion of the charcoal granules
upon being wetted by the water being filtered without choking the filter.
The above-described volume accommodates at least about 0.2 ounce, and
preferably 0.2105 ounces, or slightly more, of such granular activated
charcoal. This amount of such charcoal provides exposed surface area
adequate for satisfactory adsorption of removable impurities at the flow
rate through the filter developed by the vacuum generated by a normal
person sucking on a drinking straw, that is, a vacuum of about 5 inches of
mercury. The diameter 34 provides a great enough cross-sectional area of
the end layers 44 and 50 that the pressure drop across those layers does
not reduce the flow of water through the filter 13 too greatly for
reasonable ease of use of the filter 10. This amount of the activated
charcoal filter medium has been shown to be sufficient to adsorb a very
high percentage of most materials likely to be encountered which would
cause objectionable taste or odor in the water, as well as many other
potentially harmful contaminants.
The length or thickness 54 of the middle layer 48 of granular activated
charcoal is sufficient to assure ample contact time for adsorption of
impurities from water being filtered during its flow through the
multi-layer filter unit 13. Use of a significantly smaller thickness 54 of
the middle layer 48 can result in less than the desired duration of
contact with the granular activated charcoal. On the other hand, a smaller
diameter 34, with a similar volume of granular activated charcoal,
requires a greater pressure drop across the filter unit 13 to be provided
by the user, and it would thus be more difficult to achieve a satisfactory
flow rate through the filter. Additionally, the silver content acts in a
well-known bacteriostatic manner against organisms which might be present
in the water being filtered.
The porosity of the inlet end or lower layer 44 end and the outlet end or
upper layer 50 of the filter is such that it permits passage of water
therethrough under the forces provided normally by a person sucking on the
mouthpiece, normally a pressure drop across the filter of about 5 inches
of mercury or less, yet withstands the force of gravity acting on water
which has been drawn through the three layers 44, 48, and 50 of filter
material into the cavity 38, so that water will not flow backwards out of
the portable personal filter 10. For example, the lower layer 44 and upper
layer 50 may both be of porous material made of 100-micron-diameter
polypropylene particles sintered to pass particles having a 5-10 micron
particle size while blocking larger particles, referred to commonly as
8-micron filter material, each layer 44, 50 being thick enough to be
self-supporting. As a result, filtered water remains within the cavity 38,
where it is available to be drawn through the conduit 22 into a person's
mouth immediately when desired, and a quantity of water remains within the
middle layer 48, in contact with the activated charcoal filter medium,
permitting continued adsorption of foreign material from the water during
the time between when sips are actually being taken from the mouthpiece 20
by the user.
The positions of the inlet end and outlet end layers 44 and 50 of
mechanical filter material are established by the retainer fittings 17 and
19, respectively, and by annular ledges 47 and 53 respectively defined in
the tube wall of the body 14 and projecting radially inward about 0.010
inch.
When use of the personal portable filter device 10 has been completed at a
particular time, any water remaining within the filter medium and the
cavity 38 can be removed from the filter 10 by blowing back through the
mouthpiece 22, forcing air into the filter housing 14 and through the
layers of filter medium to drain the layers of filter material, so that
water will not drip out of the personal water filter 10.
As shown in FIG. 4, the portable personal water filter 10 may conveniently
be carried in a generally tubular carrying container 56 having a closed
bottom end 58 and a removable cap 60 located at its upper end. The
container 56 encloses the portable personal filter 10 sealingly to protect
it from contamination, so it can be carried ready for use, as when
traveling in areas where the drinking water quality is doubtful. The
container 56 may be of any suitable material, such as a molded transparent
plastic, for example.
Referring now also to FIGS. 5 and 6, a further embodiment of the invention
is exemplified in a drinking water container such as a molded plastic
bottle 70. The bottle 70 is of a convenient size and shape for being
carried by a user while containing a suitable quantity of water to be
drunk over a period of time by, for example, runners, bicyclists, or other
athletes performing at levels of exertion which require regular
replacement of body fluids lost through perspiration and respiration. For
example, a generally cylindrical, molded, resiliently flexible plastic
drinking water bottle having a capacity of one liter is commonly used by
athletes, and is appropriate for the present invention. The bottle 70 has
a mouth 72 which is large enough to permit the bottle to be filled easily
with water and ice cubes, as desired. The mouth 72 is selectively closed
by a cover 74 which is removable, as by the use of mating threads in the
cover and about the neck of the bottle 70. The cover 74 defines a hole 76
through which a flexible drinking tube 78 extends into the bottle 70. The
hole 76 fits the flexible tube 78 snugly enough to prevent the flexible
tube 78 from sliding too freely, but permitting the flexible tube 78 to be
adjusted in its position with respect to the cover 74, and allowing only
gradual passage of air into the interior of the bottle 70 around the tube
78.
Inside the bottle 70 is a filter housing 71 which is substantially
identical with the filter housing 14 of the portable personal water filter
10, and which contains a filter unit 13 whose components are designated
herein by the same reference numerals used in describing the filter 10.
The filter housing 71 is interconnected operatively with the lower end 81
of the flexible tube 78 by a reducing coupling 82, which fits over the
upper or outlet end 18 of the filter housing 14 in a fashion similar to
that in which the mouthpiece 20 fits atop the outlet end 18. Over a short
distance 84, such as about 1/2 inch, the coupling 82 is tapered in
diameter, from an inside diameter great enough to receive the outlet end
18 to a smaller inside diameter 86 substantially equal to the outside
diameter of the flexible tube 78, that is, about 0.375 inch in one
embodiment of the device. Preferably, a radial ledge 88 is provided in the
smaller end of the reducing coupling 82 to limit the extent to which the
flexible tube 78 is inserted into the reducing coupling 82, and,
similarly, a radial ledge 90 is defined in the lower, larger diameter, end
of the reducing coupling 82 to locate the coupling 82 properly with
respect to the upper or outlet end 18 of the filter housing 14. The
reducing coupling 82 may be molded, for example, of a polyurethane plastic
material.
Preferably, the sizes of the mating portions of the reducing coupling 82,
the flexible tube 78, and the upper o outlet end 18 of the filter housing
14 are interrelated to provide a push fit tight enough to maintain
airtight interconnection of the parts ordinarily, yet allow them to be
separated as desired, particularly for replacement of the filter unit 71
after it has been used long enough to reduce the efficiency of the filter
media.
A removable cap 92 is preferably provided on the outer end of the flexible
tube 78 as protection against contamination.
Preferably the bottle 70 is manufactured of a resiliently flexible molded
plastic material which is unbreakable, and, to some extent, squeezable. By
squeezing the bottle 70, it is possible to suck water through the tube 78
from within the bottle 70 at a rate greater than that which can be
replaced easily by air passing into the bottle 70 around the tube 78
extending through the hole 76. Preferably, the tube 78 fits tightly enough
in the hole 76 so that water can be forced through the filter unit 71 and
the drinking tube 78 by manually squeezing the bottle 70 with a moderate
force, without losing significant quantities of water through the hole 76.
At the same time, the interior diameter of the conduit for filtered water
defined by the flexible tube 78 is small enough, for example, about 0.235
inch or less, to limit the flow of water through the filter unit 71 to
some extent, so that ample contact time is provided for purification of
water by the charcoal filter medium of the middle layer 48 contained
therein. Particularly in this embodiment of the invention, moreover, the
normal pattern of use by an athlete, of occasionally sipping some water
from the flexible tube 78, or squeezing the bottle 70 to squirt a small
amount of water into his or her mouth, results in water remaining in
contact with the charcoal filter medium for a long enough time for
effective purification of the water consumed.
The terms and expressions which have been employed in the foregoing
specification are used therein as terms of description and not of
limitation, and there is no intention in the use of such terms and
expressions of excluding equivalents of the features shown and described
or portions thereof, it being recognized that the scope of the invention
is defined and limited only by the claims which follow.
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