Multipass Water Filter
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`TECHNICAL FIELD
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`[0001] The present invention relatesto filters for drinking water. In particular, the present invention
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`relates to portable filter devices for filtering water using multiple passes througha filter.
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`BACKGROUND
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`[0002] Conventional waterfiltration systems for drinking water involve passing water througha filter
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`once. Improvements infiltration are therefore dependent on the design of said filter and, thus, highly
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`purified water can be complex and costly to achieve.
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`[0003] Furthermore, typical waterfiltration systems distinguish between unfiltered water reservoirs
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`and filtered water reservoirs, whereby water is taken from the unfiltered water reservoir and passed
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`through a filter so as to be deposited into the filtered water reservoir.
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`[0004] Commonhousehold waterfilter devices use the gravitational pull of water in an upper
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`reservoir to pull it through a througha filter so as to be deposited into a lower reservoir.
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`[0005] These reservoirs can be particularly configured for integration into such filter devices. Thatis,
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`the reservoirs form part of the filtration system such that the filter arrangement and/or upper reservoirs
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`can be shaped to complement the shape of the lower reservoir. This can lead to a wasted space in such
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`filter devices, as the upper reservoir is not used for storage offiltered water.
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`[0006] Moreover, although the use of gravity to move water through the filter can simplify the
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`construction of a filter device, such systems are slow and thus cannot providefiltered water on larger
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`scales.
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`[0007] Somefiltration systems employ a pumpto recirculate filtered water from the filtered water
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`reservoir back into the unfiltered water reservoir so as to further purify the water. Typically, only the
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`water in the filtered water reservoir will be made available for consumption,i.e., drinking. Thus,if the
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`total volume of water is desired for consumption, a user will be required to wait for the water in the
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`unfiltered water reservoir to be passed through the filter and into the filtered water reservoir.
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`SUMMARYOF THE INVENTION
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`[0008] The present disclosure provides an improved filter device overcoming one or more of the
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`aforementioned problemsin existing filter devices for providing drinking water.
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`[0009] According to a first aspect, there is provided a filter device for filtering drinking water,
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`comprising a housing configured for submersion in a water reservoir, comprising an intake aperture
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`arranged for intake of water from the water reservoir and a return aperture arranged for returning water
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`to the water reservoir. The housing extends along an axis. The filter device further comprises a pump,
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`housedin the housing, arranged on the axis to direct fluid from the intake aperture to the return
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`aperture, and a filter arrangement, housed in the housing, arranged along the axis from the pump in a
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`fluid path between the intake aperture and the return aperture.
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`[0010] According to this aspect, there is provided a quick and ergonomicfilter device for filtering
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`water that has a simple construction. The filter device does not require particular configuration for
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`integration into a specific reservoir, so it can be easily applied to any water reservoir, such as a
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`household water jug, saucepan, or other such water reservoirs, without modifying the filter device or
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`reservoir for mutual compatibility. The filter device can thusly create drinkable water in a simple
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`[0011] Furthermore, the configuration of the filter device as a multipass filter device allows for the
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`filters used in the filter arrangement to have a lesser degree of separation. For example,if the degree of
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`separation/filtration provided by a particularfilter is, for example, 50% of contaminants on average,
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`then it would not likely be considered for use in the aforementioned single-pass filter devices.
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`However, using the presently described multipass filter device, two passes through such a filter would
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`lead to 75% of contaminants removed, then 87.5% after three passes, 93.75% after four passes, and so
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`on. Hence, smaller and/or inexpensivefilters may be used, thus further improving the compactness of
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`the filter arrangement and simplifying its construction.
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`[0012] The housing may be formed ofa rigid material with mechanical longevity, so that a first end
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`of the housing may be used for manipulating the filter device (e.g. lifted into a reservoir, removed
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`therefrom, movedtherein, directed, etc.). The shape of the housing may take any form that extends
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`along an axis, such as a cylinder or a prism, such that the length of the housing is defined along the
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`axis. Although some examples may have constant cross-sectional profile, the cross-section of the
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`housing may instead vary along at least some of the length the housing. For example, the housing may
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`taper toward the first end so that a user may moreeasily grip the first end of the housing. Additionally
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`or alternatively, the housing may be provided with a handle for ease of manipulating the filter device.
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`[0013]
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`In some examples, the housing may be spherical, spheroidal, or ellipsoidal, e.g. extending
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`along a diameter, semi-major axis, or semi-minoraxis.
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`[0014] The intake aperture may be one or more apertures (openings, through-holes, perforations, etc.)
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`that allow for a flow of water therethrough,i.e. from an outside of the housing to an inside of the
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`housing. The intake aperture(s) may take any shape but may preferably be large enough to allow for
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`the pump to operate at full power without being limited by viscous behaviourat the intake aperture.
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`However, the intake aperture may also be advantageously small enough and/or shaped so as to
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`advantageously create a directional flow through the intake aperture. For example, a substantially
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`smooth-edged circular aperture having a suitable diameter may create a jet-like flow therethrough.
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`Thus, an intake aperture may be arranged and shapedin such a wayasto assist in directing water
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`towards the filter arrangementforfiltration.
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`[0015] The housing may further comprise one or more spacers extending from a second end, the
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`second end being opposedto the first end, wherein the one or more spacers are configured for spacing
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`the intake aperture from a surface of a water reservoir whilst allowing a passage of water into the
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`intake aperture. The spacers may take any form that provides a spacing between the housing and a
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`surface of a water reservoir. For example, if the intake aperture were disposed on a bottom surface of
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`the filter device, the placementof the filter device vertically onto a flat bottom surface of a water
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`reservoir may cause the intake aperture to be obstructed, thus limiting the water flow into thefilter
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`device. Thus, the spacers may allow for an increased water flow into the intake aperture of the
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`housing. In some examples, the spacers may be arranged so as to have a direction and/or low-drag
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`profile for water flowing towards the intake aperture. For example, the spaces may take the form of
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`fins, splines, ridges, or similar that are radially arranged aroundthe intake aperture so asto direct
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`water towardsthe intake aperture.
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`[0016] The return aperture may similarly be one or more apertures (openings, through-holes,
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`perforations, etc.) that allows for a flow of water therethrough,i.e. from an inside of the housing to an
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`outside (e.g. returning water back into a water reservoir). The return aperture(s) may take any shape
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`but may preferably be large enough not to excessively impede the flow of water. The return
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`aperture(s) may be shapedorsized so as to encourage recirculation in a water reservoir. Additionally
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`or alternatively, the return aperture(s) may be shapedor sized to maximise a surface ofthefilter
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`arrangementthat is proximate to a return aperture, thus helping to ensure that filtered water is not
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`unnecessarily retained in the filter device.
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`[0017] The housing may further comprise an access aperture for allowing accessto internal
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`components ofthe filter device (e.g. the pump and/orthe filter arrangement). The access aperture may
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`be at the first end or the second end ofthe filter device, or somewhere in between, for example taking
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`the form of a side panel or an entire side wall.
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`[0018] The access aperture is removably sealed by a sealing element which selectively allows access
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`to the access aperture. The sealing element may form an entirely waterproof seal or may have the
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`intake aperture and/or return aperture arrangedtherein. In use, a user may removethe sealing element
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`to open the access aperture and access internal componentsso that the internal components may be
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`maintained or replaced.
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`[0019] The filter device may further comprise a sub-housing housedin the housing for containing
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`liquid-sensitive components. Liquid-sensitive components mayinclude electronics, liquid-soluble
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`components and/or other components that are sensitive to liquid.
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`[0020] The sub-housing may preferably be openable for access to components stored therein. In such
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`cases, the sub-housing may be sealable closed by a waterproof seal. For example, a part of the sub-
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`housing may be comprised of the sealing element such that the sealing of the housing by the sealing
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`element also seals the sub-housing. Alternatively, the sealing element may comprise the sub-housing
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`as part of it. For example, the sub-housing may take the form of a plug, conforming to the size and
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`shape of the access aperture, such that placement of the sub-housing into the access aperture
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`removeable seals the access aperture. When removing the sub-housing from the access aperture, the
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`opening may then be on a side of the sub-housing that was spaced towardsan inside of the housing
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`such that the outer-facing portion of the sub-housing forms the sealing element for the housing and can
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`be formed without seams, thus improving the waterproofseal.
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`[0021] The pump may be an electric pump or a mechanically powered pump. For example, the pump
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`may comprise an electric motor and an impeller driven by the electric motor.
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`[0022]
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`In some examples, the electric motor may be arranged spaced along the axis of the housing
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`from the impeller. The electric motor may be powered by a battery housed inside or outside the
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`housing, or by a mains connection. In some examples, the filter may further comprise a power cable
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`for communicating power from outside the housing to internal electronic componentsofthe filter
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`device.
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`[0023] Alternatively, the pump may comprise an impeller (or propeller) mechanically engaging a
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`gearing assembly that is driven through actuation of the filter device, e.g. against a surface of a water
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`reservoir. That is, in some examples, the second endofthe filter device may comprise a driving screw
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`and actuation ofthe filter device may cause the driving screw to rotate and, via the gearing assembly,
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`drive the impeller of the pump. A biasing means such as a spring may be providedto return the driving
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`screw to its original extended position. Such a mechanical arrangement may advantageously reduce
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`the electricity required to operate the filter device.
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`[0024] The pump may be shaped similarly as the housing, thus optimising the utilisation of space
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`within the housing and allowing for a more compact device. For example, one or both of the motor
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`and the impeller may be shapedso as to have a similar cross-section to the housing; e.g., if the housing
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`were cylindrical, the motor and/or the impeller may be shaped so as to also be substantially
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`cylindrical. Furthermore, the pump may be arranged concentrically with the shape of the housing.
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`[0025] Similarly, the filter arrangement may be shaped similarly as the housing, e.g. a cylindrical
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`filter arrangement arranged concentrically with a cylindrical housing. The pump and/or the housing
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`may alternatively be shaped as a prism, extending along an axis.
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`[0026] The pump may comprise an intake and an outlet, wherein the pump is configured to take water
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`in at its inlet and eject water from its outlet. The inlet may be arranged proximate to the intake aperture
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`such that water is drawn directly into the inlet of the pump from the intake aperture. Alternatively, the
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`pumpinlet may be arranged remote from the intake aperture, for example at an opposite end thereto.
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`In this latter arrangement, it is still possible for the pump to generate a flow such that fluid is directed
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`from the intake aperture to the return aperture.
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`[0027] The intake and/or outlet of the pump may be configured such that the pump directs fluid along
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`the axis. The return aperture may then advantageously be arranged perpendicular to the axis such that,
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`for example, water exiting the return aperture can encourage greater circulation in the water reservoir.
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`[0028] The filter arrangement may enclose a space thatis in fluid communication with the outlet of
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`the pump,so that the pump directs water into said enclosed space. Water within the enclosed space
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`maythen befiltered through the filter arrangement before it can exit through the return aperture. In
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`this way, it may be better ensured that more water passes throughthe filter arrangementasit is
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`circulated through the multipassfilter device.
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`[0029] Thefilter arrangement may comprise onefilter or a plurality of different filters, for example,
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`each having different filtration characteristics. Examples offilters include paperfilters, adsorption
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`filters such as activated carbonfilters, ion exchangers (for improving the hardness qualities of water),
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`amongst others. In some examples, the filter arrangement comprises a UV light source arranged to
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`direct UV light towards water in the fluid path. The use of such a UV light has the further advantage
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`that bacteria and other organic contaminants in the water may be destroyed. In other words, anyfilter
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`for providing drinkable water may be usedin the filter arrangement.
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`[0030] The filter device may further comprise a backflow prevention valve configured to prevent a
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`backflow of water out from the intake aperture. The backflow prevention valve may, for example, be
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`fitted as part of the housing or the pump, and may enforce a unidirectional flow of water through the
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`filter device. Thus, it is possible to prevent water from flowing in an opposite direction to that
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`intended, e.g. from the return aperture to the intake aperture, or an ‘incorrect’ progression through the
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`filter arrangement, hence preventing sediment or other impurities from being returned into the water
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`reservoir.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`[0031] One or more embodiments will be described, by way of example only, and with reference to
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`the following figures, in which:
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`[0032] Figure 1 schematically showsa filter device according to an embodiment;
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`[0033] Figure 2 showsa cross-section ofa filter device in a water reservoir, according to an
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`embodiment;
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`[0034] Figure 3 showsa side view ofa filter device, according to an embodiment;
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`[0035] Figure 4 showsa perspective view ofa filter device according to an embodiment,tilted to
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`show an end surface;
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`[0036] Figure 5 showsa cross-section through a filter device according to an embodiment; and
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`[0037] Figure 6 showsa perspective view of a portion ofa filter device, according to an embodiment,
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`with the housing made transparent to show internal components ofthe filter device.
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`[0038] Whilst the invention is susceptible to various modifications and alternative forms, specific
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`embodiments are shown by way of example in the drawings as herein described in detail. It should be
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`understood, however, that the detailed description herein and the drawings attached hereto are not
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`intended to limit the invention to the particular form disclosed. Rather, the intention is to coverall
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`modifications, equivalents, and alternatives falling within the scope of the appended claims.
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`[0039] For example, although ‘water’ has been referred to throughout the application,it will be
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`appreciated that any suitable drinking liquid in needoffiltration could be substituted without departing
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`from the scope of the appended claims.
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`[0040] Any reference to prior art documents or comparative examples in this specification is not to be
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`considered as an admission that such prior art is widely known or forms part of the common general
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`knowledgein the field.
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`[0041] As usedin this specification, the words “comprise”, “comprising”, and similar words are not
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`to be interpreted in the exclusive or exhaustive sense. In other words, they are intended to mean
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`“including, but not limited to”.
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`DETAILED DESCRIPTION
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`[0042] The present invention is described in the following by way of a numberofillustrative
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`examples. It will be appreciated that these examples are provided for illustration and explanation only
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`and are not intended to be limiting on the scope of the present invention. Instead, the scope of the
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`present invention is to be defined by the appended claims. Furthermore, although the examples may be
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`presented in the form of individual embodiments, it will be recognised that the invention also covers
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`combinations of the embodiments described herein.
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`[0043] Figure | schematically showsa filter device 100, according to an embodiment.
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`[0044]
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`In the illustrated embodiment, the filter device 100 has a housing 102 configured for
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`submersion in a water reservoir. The water reservoir may hold water that in some way is
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`contaminated,i.e., in need offiltration before drinking. The housing 102 may be any waterresistant or
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`waterproof material having suitable rigidity so as to hold its shape when submerged in a water
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`reservoir. For example, the housing 102 may be madeofplastic, non-corroding metal such asstainless
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`steel, silicon rubber, or the like.
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`[0045] The housing 102 has an intake aperture 104 and a return aperture 106. In the illustrated
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`embodiment, these are arranged at opposing ends of the housing 102, although they may be arranged
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`in any suitable position that allows for a placementof a filter arrangement 112 in a fluid path there
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`between.
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`[0046] Housedin the housing, there is a pump 110 anda filter arrangement 112. The pump 110 may
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`be an electric or mechanically powered pumpandis arrangedto direct fluid from the intake aperture
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`104 to the return aperture 106. Although the pump 110 is illustrated as being in the fluid path between
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`the intake aperture 104 and the return aperture 106 (the fluid path being shownas dotted arrows), it
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`may also be arranged in any suitable position in or away from the fluid path where the pump has
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`sufficient fluid communication with the intake aperture 104 and/or return aperture 106 to promote the
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`flow of fluid therethrough.
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`[0047] Thefilter arrangement 112 may be formed of one or morefilters and/or, for example, a UV
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`light. The filter arrangement 112 is arranged in the fluid path between the intake aperture 104 and the
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`returm aperture 106 so as to remove contaminants (particulates, bacteria, sediment, etc.) from the water
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`passing therethrough for creating drinkable water.
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`[0048]
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`It may be preferable to prioritise fluid flow through the filter arrangement 112 over superior
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`filtration characteristics of the filter arrangement 112, so as to allow for improvedcirculation of water
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`through the water reservoir and increase the rate at which multiple passes through thefilter
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`arrangement may be achieved.
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`[0049] The housing 102 is extended along an axis 108, shown as a dotted line. Thus,the filter device
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`100 has an ergonomic configuration such that a user may easily place the filter device 100 into a water
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`reservoir, remove it therefrom, and/or direct it therein. For example, a user may wish to movethefilter
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`device 100 aroundin the water reservoir so asto target particular areas where sediment maybevisible,
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`or simply to expedite the circulation of most/all of the water through the filter device 100. By allowing
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`this, the filter device 100 can more swiftly filter the water and ensure that it is in a drinkable condition.
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`[0050] The pump 110 and the 112 are arranged along the axis 108. Thus, the extended shape of the
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`housing 102 (delimiting the overall shape of the filter device 100) may remain compact and
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`ergonomic.
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`[0051] Asillustrated in figure 1, there may be one or morefluid paths from the intake aperture 104 to
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`the return aperture 106 that do not pass throughthe filter arrangement 112. This may be preferable so
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`as to encourage greater circulation through the water reservoir (i.e. without slowing/impeding fluid
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`flow by forcing it through the filter arrangement 112), which may allow fora faster filtration of all of
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`the water in the water reservoir using multiple passes.
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`[0052] The pump 110 andthe filter arrangement 112 as shownin figure | are arranged centrally in
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`the housing 102. However, their placement may instead be more towards one side than another,if
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`particular fluid flows are desired or if any other mechanical constraints exist when arranging the
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`internal components inside the housing 102.
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`[0053] Figure 2 showsa cross-section ofa filter device 100 in a water reservoir 120, according to an
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`embodiment. Components having reference numerals that are also used in figure 1 may be the same or
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`similar components as those with corresponding reference numerals in figure 1.
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`[0054] The filter device 100 shownin figure 2 has an intake aperture arranged at the bottom of the
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`filter device (as illustrated), as with figure 1, however the return aperture in the filter device 100
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`shownin figure 2 is arranged at a side of the filter device 100, i.e. perpendicular to the axis 108.
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`[0055] The pump 110 is formed of two sub-components: an electric motor 110a and an impeller 110b
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`arranged proximate to the intake aperture 104. The electric motor 110a may be battery powered or
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`mains powered. If the electric motor 110a is mains powered, for example, the filter device 100 may
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`further comprise power connection cables extending through the housing 102 (e.g. through the access
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`aperture or some other opening) for connecting the electric motor 110a to a mains power supply.
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`[0056] When operated, the impeller 110b draws water through the intake aperture 104 and into the
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`housing 102. The portion of the housing 102 that houses the pump 110 is connected to the portion that
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`housesthe filter arrangement 112 in such a way that the outlet of the impeller 110b is in fluid
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`communication with the filter arrangement 112.
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`[0057]
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`In particular, the filter arrangement 112 can be seen in figure 2 as enclosing a space 126 and
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`the outlet of the impeller 110b is in fluid communication with this space 126. Thus, water cannot
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`escape the space 126 through the return aperture 106 without passing throughthefilter arrangement
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`112. In theillustrated embodiment, the space 126 is formed as a central core of thefilter arrangement
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`112 however, other arrangementsare possible.
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`[0058] The filter device 100 has a first end (indicated generally as 114) and a second end (indicated
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`generally as 118) being opposed along the axis 108.
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`[0059] The first end 114 may be configured for manipulation by a user. That is, in the illustrated
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`example, the filter device 100 is shownas being in a water reservoir 120, for example a jug of water
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`(water not shown). It can be seen that the first end 114 is appropriately proportioned for a hand of a
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`user to ergonomically grasp such that the filter device 100 may be moved within the water reservoir
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`120 or removed therefrom. In some examples, the first end 114 may further comprise a handle for
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`further ease of manipulation by a user. As stated, the water reservoir 120 may for example be a jug of
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`water in need of purification prior to being drinkable. By allowing the filter device 100 to be placed in
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`the water it may be filtered and made drinkable. And by allowing the user to manipulate the filter
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`device 100 this process can be accelerated.
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`[0060] The second end 118 may be configured to be spaced from a surface of the water reservoir 120
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`(e.g. the bottom surface 120a, as in figure 2). In the illustrated example, this spacing is achieved by
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`one or more spacers 116 which space the intake aperture 104 from the bottom surface 120a of the
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`water reservoir 120, thus allowing a flow of water to the intake aperture 104. The spacers 116 are
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`advantageousin that the filter device 100 does not need to be fastened to, for example, a wall of the
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`water reservoir 120 but can be placed anywhere within the water reservoir 120 andstill allow fora
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`flow of water to the intake aperture 104.
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`[0061] The filter device 100 further comprises a sub-housing 122 housed in the housing 102. In the
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`illustrated example, the sub-housing 122 is arrangedatthe first end 114 of the filter device 100 and is
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`sealed by a sealing element 124.
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`[0062] The sub-housing 122 may be completely or substantially waterproof so as to be configured for
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`containing liquid-sensitive components (not shown). Liquid-sensitive components maybeelectronics,
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`soluble components, or other components that are not well suited for submersion in water (or other
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`liquids). In the illustrated example, the sub-housing 122 is removeably sealed by a sealing element
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`124, taking the form of a lid (cap, topper, etc.). The sealing element 124 may be attached with a
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`threaded attachment, a push-in attachments, a bayonet attachment, or some other meansthat allows for
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`the creation of a substantially waterproofseal.
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`[0063] As shownin figure 2, the sealing element 124 also seals the housing 102 at the first end 114.
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`If the sealing element 124 were removed, the housing 102 would haveits access aperture (blocked in
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`this view) openedfor access to the internal components, such as the sub-housing 122 (including the
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`liquid-sensitive components contained therein), the filter arrangement 112, and/or the pump 110.
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`[0064]
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`In some alternative arrangements, the sub-housing 122 may have an openable sealing onits
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`other end (i.e. towards the second end 118) and the sub-housing 122 may take the form ofa plug,
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`conforming to the size and shape of the access aperture of the housing 102 such that, when the sub-
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`housing 122 is pushed into the access aperture at the first end 114, the sub-housing 122 seals the
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`housing 102 in a substantially waterproof manner.
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`[0065]
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`It will be appreciated that, if the first end 114 ofthe filter device 100 is not intended to be
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`fully submersed in water, the sub-housing 122 and/or the sealing element 124 may not necessarily be
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`required to be entirely waterproof.
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`[0066] Figure 3 showsa side view ofa filter device 100, according to an embodiment. The internal
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`components such as the pump 110 andthe filter arrangement 112 are not visible in this view.
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`[0067] Theillustrated housing 102 is cylindrical in shape, having a circular sealing element 124
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`arranged to seal the housing 102 at the first end 114, and a plurality of spacers 116 arranged atthe
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`second end 118 for spacing the filter device 100 from a surface of a water reservoir (as discussed
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`above).
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`[0068] As shownin figure 3, the return apertures 106 of the housing 102, according to the illustrated
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`example, extend across a length of the housing 102 and are arranged perpendicular to the axis 108 of
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`housing 102. The return apertures 106 are evenly arranged around a circumference of the cylindrical
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`housing 102 so as to provide a large area for returning water into the water reservoir. The return
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`apertures 106 may have a grid or mesh thereacross so as to prevent an entry of debris, contaminants,
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`etc. from the water reservoir.
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`[0069] The housing 102, spacers 116, and sealing element may be formed from a same material (e.g.
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`plastic, stainless steel, silicon rubber, or the like) or different materials.
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`[0070] Figure 4 showsa perspective view ofa filter device 100 according to an embodiment,tilted to
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`show an end surface of the second end 118. Elements having like reference numerals as in figure 3
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`may be the same or similar to those discussed in figure 3.
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`[0071] The intake aperture 104 and the spacers 116 are more clearly shown in the view of figure 4. In
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`the illustrated example, there are four spacers 116 taking the form of fins protruding from the circular
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`lower surface of the cylindrical housing 102 and extending along a radial direction.
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`[0072] The spacers 116 preferably have a substantially even or flat construction on their lowerside,
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`so as to allow for the filter device 100 to be stable when placed on a bottom surface of a water
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`reservoir. To this end, the spacers 116 may preferably extend in a radial direction enough to
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`collectively provide a stable surface. The present design is advantageoussinceit allowsthe filter
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`device 100 to be placed in a water reservoir forfiltering and purifying water to create drinkable water.
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`In other words, the filter device 100 does not need to be fastened in any way and can thusly be used
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`easily in any type of water reservoirfor filtering the water and ensuring that it is drinkable.
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`[0073] Furthermore, the spacers 116 preferably have a low-drag profile viewed from the intake
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`aperture 104 and may be arranged for directing water towards the intake aperture 104. Thus, water
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`being drawn in by the pump 110 (e.g. by an impeller such as the impeller 110a shownin figure 2) does
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`not excessively drag against the spacers 116, which may causethe filter device 100 to moveor tip
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`over in the water reservoir.
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`[0074] Although only four spacers 116 are shown,it will be appreciated that there may be more or
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`fewer spacers 116, and these may have a different shape or configuration, although the aforementioned
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`considerations of stability and fluid drag profile maystill apply.
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`[0075] The intake aperture 104 is shown as being a circular aperture concentrically arranged at a
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`centre of the circular lower face of the cylindrical housing 102. The spacers 116 are arranged at a
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`radius beyond the intake aperture 104, although in some examples these mayradially overlap (e.g. the
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`spacers 116 may form a cross shape across the intake aperture 104). It will also be appreciated that the
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`intake aperture 104 may take any shapethat is suitable for allowing sufficient fluid flow therethrough.
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`[0076] The intake aperture 104 may have a backflow prevention valve (not shown) arranged
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`proximate thereto, for example immediately at its entry. The backflow prevention valve may ensure
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`that water flowing in through the intake aperture 104 cannot flow back out, for example if the pump
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`110 is turned off, or if there is a malfunction. Thus, it is possible to prevent contaminants that have
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`been filtered out from the water from being returned to the water reservoir. The intake aperture 104
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`may further comprise a mesh, screen, or grid arranged thereacross for preventing solids of a particular
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`size from entering the filter device 100 and potentially damaging the internal components.
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`[0077] Figure 5 showsa cross-section throughafilter device 100 according to an embodiment.
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`[0078] As with the filter devices 100 shownin figures 3 and4, the illustrated example has a circular
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`cross-section. However, the housing 102 (and/or pump 110,filter arrangement 112, or other internal
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`components) may instead have a different cross-section, such as a triangular or rectangular cross-
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`section.
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`[0079] The cylindrical housing 102 has a plurality of return apertures 106 extending through the
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`thickness of the housing 102 and arranged evenly around its circumferences. In some examples, the
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`return apertures 106 may be unevenly distributed about a perimeter of the housing 102, for example
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`directionally distributed so as to encourage circulation in a water reservoir in a particular direction.
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`[0080] As shownin figure 5, the filter arrangement 112 has a circular cross section and is arranged
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`concentrically with the housing 102. The filter arrangement 112 is shown having a homogeneous
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`construction, although the filter arrangement 112 may instead havea plurality of layers therein, such
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`as a sequenceofdifferent filters having different filter characteristics. For example, an innermostlayer
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`may be a coarse spongefilter, whilst an outermost layer may be a fine activated carbonfilter. The
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`filter arrangement 112 is configured to enclose a space 126, which is shown as a concentric circle at a
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`radial centre of the cross-section. Water may be directed, by the pump 110, into this space 126,
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`

`

`11
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`wherefrom it flows through the filter arrangement 112 and out through the return apertures 106, as
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`indicated by the dotted arrows.
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`[0081]
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`In theillustrated example, there is a further spa