Water filter abstract
The invention provides a water filter, particularly suited for
household use, with valving which enables either a bypass mode or
a filtering mode. During the filtering mode the water flows through
a number of filtering layers one of which is a microporous membrane
and during the bypass mode the water flows parallel to and against
the membrane so as to cleanse the membrane of material accumulated
thereon during the filtering mode.
Water filter claims
What is claimed is:
1. A water filtering device comprising a plurality of filtering
layers one of which is a submicron pore size porous membrane having
an entrance surface for receiving water to be filtered by said membrane
by flow therethrough after the water has flowed through other of
the filtering layers, means for causing water to flow through all
of said filtering layers for filtration thereby, and means for causing
water to bypass filtration thereof by said membrane and to cause
it to flow in a path parallel to and in contact with said surface
of said membrane thereby to cleanse said surface.
2. A water filtering device comprising a casing containing a plurality
of filtering layers one of which layers is a submicron pore size
porous membrane having an entrance surface for receiving water to
be flowed through said membrane for filtration thereby after the
water has flowed through other of the filtering layers, and a channel
through said casing extending parallel to said surface, said surface
forming a wall of said channel.
3. A water filtering device as set forth in claim 2 and including
means in said channel for causing turbulence in water flowing therethrough.
4. A water filtering device as set forth in claim 2 and including
means for draining water from within the casing when not in use.
Water filter description
The subject matter of the present invention is a water filter particularly
suited for household use as by connection to a water faucet.
The prior art shows water filters wherein the water is caused to
flow through a plurality of filtering layers, one of which layers
is a porous membrane of submicron pore size. The submicron pore
size membrane is an important element in such filters in that it
not only blocks the passage of submicron deleterious solids such
as asbestos, grit and the like, but it also blocks the passage of
bacteria. The prior art also shows that such filters can be provided
with valving whereby the water can be caused to bypass the filter
whenever potable water is not required. This extends the life of
the filter for providing potable water when it is needed for drinking
and cooking. U.S. Pat. No. 4025438 shows such a filter.
But even with the bypass feature and the other features described
in the aforesaid patent for extending the life of the filter, it
does, nevertheless, have only a limited period of usefulness. And
the limitation is due to the membrane, the useful life of which
is tolled by one or the other, or both, of two conditions occurring.
One of the conditions which can arise is that the surface of the
membrane becomes clogged with submicron or larger particles of any
sort. Of course, where the water being filtered contains considerable
solid material of sufficiently small particle size to escape filtration
by earlier filter layers, this condition can arise after a relatively
short period of filter use.
The other condition which can arise is by way of bacteria filtered
from the water, and the growth or multiplication of the bacteria.
It is a strange fact that even though a submicron pore size filter
can block the flow of bacteria therethrough, nevertheless the bacteria
can multiply and grow through the pores of the filter. That is,
after some bacteria are captured on the upper or water entrance
surface of the submicron pore size filter layer, they can, given
the time to do so, culture and multiply progressively through the
pores until they appear on the water exit surface of the filter
layer, then to appear in water passed through the filter. The occurrence
of this condition can be prevented or inhibited by the use of a
bactericide in the filter; however, this has disadvantage in that
no matter the conventionally used bactericides are substantially
insoluble in cold water, they do have some solubility in warm water
thereby giving rise to the possibility of being ingested if warm
drinking or cooking water is drawn from the filter.
DISCLOSURE OF THE INVENTION
The filtering device of the present invention incorporates a plurality
of filtering layers one of which is of submicron pore size, thereby
to block the passage of submicron particles and bacteria, but with
this submicron pore size layer being spaced from the other layers
to provide a channel for the flow of water parallel to and against
the water entrance surface of the submicron pore size layer. The
filter is provided with appropriate valving to cause the water either
to flow through the filter for filtration thereby, or to bypass
such filtration but with this bypass water flowing through the aforesaid
channel to cleanse the submicron pore size layer. Hence, the continued
accumulation of particles or bacteria on the submicron pore size
layer is inhibited thereby significantly extending the useful life
of the filter.
BRIEF DESCRIPTION OF DRAWING
In the drawing there is shown a side view in section of a filter
embodying the invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring now to the drawing, the filter shown comprises a casing
2 of rectangular cross section, a water inlet 4 and two water outlets
6 and 7. The casing contains a plurality of filtering layers, layer
8 being activated charcoal particles, layer 10 being of a fibrous
material and having a pore size of from about 1 to 10 microns, and
layer 12 being a submicron pore size porous layer, preferably a
membrane, having a pore size of from 0.02 to 0.5 microns. This submicron
pore size layer is supported by a perforated wall, such as grid
14 suitably secured to the casing, and the filter layer 10 is supported
by a porous rigid backing 16 the porosity of the backing being
much greater than that of the filter layer 10. As in the filter
shown in the aforesaid patent, so also in this embodiment of the
present invention, the charcoal is primarily to remove deleterious
dissolved materials in the water and the filter layer 10 is to remove
relatively large size solids and to block passage of the charcoal
particles to the surface of the membrane 12.
The submicron pore size filter layer 12 and the backing 16 for
the filter layer 10 are parallel to, and spaced from, each other
thereby providing a flow channel 18 one wall of which flow channel
is formed by the water entrance surface 19 of the submicron pore
size filter layer. A perforated rigid sheet 20 of sinuous cross
section is suitably secured in the channel 18 and functions as a
means for creating turbulence in the water flowing through the channel.
The water inlet 4 has a valve 22 which is manually operable to
selectively cause the water to flow into the charcoal layer 8 or
to flow into the channel 18. A suction breaker 21 is interconnected
between the valve 22 and the channel 18. The outlet 7 of the channel
18 also has a manually operable valve 24 to selectively either allow
or block the flow of water from the channel.
In operation, when it is desired to draw unfiltered water, the
valve 22 is positioned to cause the water from the inlet 4 which
ca be a faucet, to flow through the suction breaker 21 and into
and through channel 18; the valve 24 being set in its open position
to enable the water to flow out of the channel. When it is desired
to filter the water, the valve 22 is positioned to cause the water
from the inlet 4 to flow into the charcoal layer; the valve 24 being
then moved to its closed position, preferably after any unfiltered
water in the channel has been allowed to flow out of the channel.
The water entering the charcoal layer flows therethrough and then
through the filter layer 10 the porous backing 16 across the channel,
through the perforated sheet 20 and through submicron pore size
filter layer 12 whereupon it enters and flows longitudinally down
through channel 26 and then exits through the outlet 6. In the course
of filtering the water, the water-entrance surface of the submicron
pore size filter layer 12 which is the surface forming the wall
of the channel 18 accumulates bacteria and other solid material
thereon. However, when periodically the valves are positioned to
provide the filter bypass mode, the water flowing longitudinally
through the channel 18 flows against the surface 30 and thereby
cleanses the surface of the bacteria or other solid material. The
turbulence of the water flowing through the channel, caused by the
turbulence-inducing sheet 20 assists this cleansing action. The
suction breaker 21 permits drainage through the valve 24 when the
filter is not in use.
It will be understood that while the invention has been described
specifically with respect to a particular embodiment thereof, various
changes and modifications may be made all within the full and intended
scope of the claims which follow.