Field of the invention

The invention relates to a filter unit as pre-filter system for the filtration of water comprising multiple filters in a single filter housing. The invention further relates to the use of such filter unit as a pre-reverse osmosis filter.

Background of the invention

Filter systems used for purification or filtration of water and in particular for the purification or filtration of water for drinking purposes generally require different filter steps to achieve an acceptable level of purity. Such filter systems comprise for example a reverse osmosis filtration step. Reverse osmosis membranes are delicate and as they are expensive it is common practice to include one or more pre-filtration steps before the reverse osmose step. By doing so, the life span of a reverse osmosis membrane can be increased considerably. Pre-filtration steps comprise for example sedimentation filtration or activated carbon filtration. Usually each pre-filtration step requires a filter unit comprising a filter medium assembled in a housing. The different filter units are then connected by tubing systems. Such filter systems not only require complex tubing connections, but also require a lot of space to install. Furthermore the installation and replacement of such filter systems is inconvenient. Because of the many connections that such tubing systems have, there are a lot of potential leakage points.

Although it is possible to position different filter media in series in a single filter housing, filter systems comprising multiple filter media in series are often not reliable. For example, such systems do not guarantee that the water flows correctly through the filter system as one or more filtration steps can be by-passed. The by-passing of one or more filtration steps can be detrimental for the reverse osmosis step. Such a system can be seen in Chinese Utility Model CN204932968U, which shows a two stage filter with a primary filter of active carbon and a secondary filter. Further systems including three filters can be seen in KR2003-0096867A, KR2012-0004816 and KR2009- 001 1436. US 20140131289 (Whirlpool Corporation) discloses a customizable multi-stage fluid treatment assembly typically includes a connector, a plurality of cartridges, and a cap. The plurality of cartridges have a treatment medium spaced within an interior volume of the individual cartridges, between the ends thereof. The ends of the plurality of cartridges are configured to receive a fluid, bring the fluid into operative contact with the treatment medium, and dispense the fluid from the opposing end of the cartridge.

Therefore there is a need to provide an improved filter unit comprising a number of filter media positioned in a single filter housing. There is a need for a filter unit which is able to provide a sealed environment to each filter and to ensure that one filtration stage is not bypassed by another. Also, such sealing is required by the design of the filtration unit to avoid separate encapsulates/housing for each filter.

There is a need to provide a filter suitable for consumer usage such that multiple filters can be changed by opening the filter unit and also avoid wastage of the filter housing material simultaneously providing an efficient mechanism for flow of water through various units without bypassing at any stage.

Summary of the invention

It is an object of the present invention to provide a filter unit suitable as a pre- filtration unit for the reverse osmosis filtration of water.

It is another object of the present invention to provide a filter unit comprising multiple filters in a single filter housing ensuring that none of the filter media is bypassed.

It is a further object of the present invention to provide a filter unit requiring a limited amount of tubings.

It is still a further object of the present invention to provide a filter unit having a compact design that can be replaced easily.

According to a first aspect of the present invention a filter unit adapted as pre- filter system for water filtration or water purification is provided. The filter unit according to the present invention comprises a water inlet and a water outlet and comprises at least a first filter and a second filter. The second filter is positioned downstream of the first filter. Possibly, the filter unit comprises more than two filters for example, a first filter, a second filter and a third filter, with the second filter positioned downstream of the first filter and the third filter positioned downstream from the second filter. The different filters of the filter unit are positioned in one single filter housing.

The first filter comprises a first tubular shaped filter material having a first central discharge channel. The second filter comprises a second tubular shaped filter material having a second central discharge channel. Each of the first tubular shaped filter material and the second tubular shaped material have a radially outward facing surface, a radially inward facing surface, a top surface and a bottom surface. The radially inward facing surface is facing the discharge channel of the tubular shaped filter material. The radially outward facing surface is facing the filter housing, more particularly the inner surface of the filter housing.

Water to be filtered enters the filter unit through the water inlet and leaves the filter unit through the water outlet. The water that entered the filter unit through the water inlet flows subsequently through the first filter and the second filter. The water flows through the first filter by entering the radially outward facing surface of the first tubular shaped filter material and by leaving the radially inward facing surface of the first tubular shaped filter material to be discharged through the first central discharge channel. Subsequently, water flows through the second filter by entering the radially outward facing surface of the second tubular shaped filter material and by leaving the radially outward facing surface of the second tubular shaped filter material to be discharged through the second discharge channel. The water leaves the filter unit subsequently through the water outlet.

The filter unit is furthermore provided with at least a first gasket and a second gasket. The first gasket and the second gasket prevent water from flowing from the water inlet to the second filter without passing the first filter. This means that the first gasket and the second gasket ensures that all water that enters the filter unit through the water inlet flows to the first tubular shaped filter material of the first filter before flowing to the second tubular shaped filter material and/or before leaving the filter unit through the water outlet.

The first gasket is preferably positioned between the first and the second filter, i.e. between the top surface of the first tubular shaped filter material of the first filter and the bottom surface of the second tubular shaped filter material of the second filter. The second gasket is preferably positioned at the bottom surface of the first tubular shaped filter material of the first filter.

The first gasket comprises a tubular shaped body and at least one main extension. Possibly, the first gasket furthermore comprises at least one additional extension. The tubular shaped body is preferably extending upwards, i.e. extending towards second tubular filter material of the second filter while the at least one main extension and/or the at least one additional extension is/are extending downwards, i.e. extending towards the first tubular shaped filter material of the first filter.

The tubular shaped body of the first gasket is preferably extending at least partially around the second tubular shaped filter material of the second filter. More preferably the tubular shaped body of the first gasket is extending around the second tubular shaped filter material of the second filter over the full length of the second tubular shaped filter material.

Preferably, the at least one main extension is at least partially penetrating in the first central discharge channel of the first tubular shaped filter material of the first filter at the top surface of the first tubular shaped filter material. The at least one main extension comprises a central discharge channel allowing water to flow from the first central discharge channel of the first filter to the second filter.

Preferably, the at least one main extension comprises a tubular or conical shaped body possibly provided with lateral openings.

The at least one main extension of the first gasket seals the first central discharge channel at the top surface of the first tubular shaped filter material of the first filter so that no water can by-pass the filtration step through the first tubular shaped material of the first filter.

Possibly, the first gasket comprises one or more additional extensions. The one or more additional extensions of the first gasket are preferably extending downwards, i.e. extending towards the first tubular shaped filter material of the first filter and possibly penetrating the first tubular shaped filter material of the first filter at the top surface of the first tubular shaped filter material of the first filter. The one or more additional extensions of the first gasket seal the top surface of the first tubular shaped filter material of the first filter to avoid water by-passing the filtration step through the first tubular shaped filter material of the first filter. The one or more additional extensions of the first gasket prevents water entering the first tubular shaped filter material of the first filter through the top surface of the first tubular shaped filter material of the first filter instead of through the radially outward surface of the first tubular filter material of the first filter and/or water flowing to the second filter without having passed through the first tubular shaped filter material of the first filter.

The second gasket comprises at least one main extension. Possibly, the second gasket furthermore comprises at least one additional extension. The at least one main extension and the at least one additional extension of the second gasket is preferably extending upwards, i.e. extending towards the first tubular shaped material of the first filter.

The at least one main extension of the second gasket is preferably at least partially penetrating in the first central discharge channel of the first tubular shaped filter material of the first filter at the bottom surface of the first tubular shaped filter material.

The second gasket can be part of the filter housing. The second gasket can for example be integrated in the filter housing, more particularly integrated in the inside of the filter housing at the bottom side of the filter housing.

The one or more additional extensions of the second gasket are preferably extending upwards, i.e. extending towards the bottom surface of the first filter material of the first filter and possibly penetrating the first tubular shaped filter material of the first filter at the bottom surface of the first tubular shaped filter material of the first filter.

The one or more additional extensions of the second gasket seal the bottom surface of the first tubular shaped filter material of the first filter to prevent water bypassing the filtration step through the first tubular shaped filter material of the first filter. The one or more additional extensions of the second gasket prevent water entering the first tubular shaped filter material of the first filter through the bottom surface of the first tubular shaped filter material of the first filter instead of through the radially outward surface of the first tubular filter material of the first filter and/or water flowing to the second filter without having passed through the first tubular shaped filter material of the first filter.

In preferred embodiments the filter unit according to the present invention furthermore comprises a third filter in addition to the first filter and the second filter of a filter unit as described above. The third filter is preferably positioned downstream the second filter. The third filter comprises for example a planar filter, for example, a planar microfilter.

In case the filter unit comprises a third filter, the filter unit further preferably comprises a third gasket to prevent water from flowing from the second filter to the water outlet without passing the third filter. The third gasket is preferably positioned between the second filter and the third filter. The third gasket preferably comprises a tubular shaped body and at least one main extension having a central discharge channel. Possibly, the third gasket further comprises at least one additional extension. The central discharge channel of the main extension of the third gasket is preferably provided with lateral openings. The tubular shaped body is preferably extending upwards, i.e. extending towards the third filter. Preferably the tubular shaped body of the third gasket is adapted to hold the third filter. The at least one main extension and/or the at least one additional extension is/are preferably extending downwards, i.e. extending towards the second tubular shaped filter material of the second filter. Third gasket can include a further extension, for example, extending upwards between the third gasket and the cap. Additional gaskets can be included between the tubular shaped body and the third filter (for example, at the bottom of the filter to help avoid water bypass) and/or between the cap and the housing.

Preferably, the at least one main extension of the third gasket is at least partially penetrating in the second central discharge channel of the second tubular shaped filter material of the second filter at the top surface of the second tubular shaped filter material. More preferably, the at least one main extension of the third gasket is penetrating in the second central discharge channel of the second tubular shaped filter material of the second filter over the full length of the second tubular shaped filter material. The at least one main extension of the third gasket comprises a central discharge channel allowing water to flow from the second central discharge channel of the second filter to the third filter. The central discharge channel of the at least one main extension of the third gasket is preferably provided with lateral openings.

Preferably, the at least one main extension comprises a tubular or conical shaped body. More preferably, the at least one main extension comprises a tubular or conical shaped body provided with lateral openings. The second filter can include an end cap at a base of the second filter. This can allow the second filter to be screwed into the third gasket (for example, a stem of the third gasket), sealing by compressing the third gasket into a filter housing cap. The end cap of the second filter can ensure that the second filter is sealed against the housing cap and that the end of second filter is enclosed to ensure that water passes radially inwards through the second filter. The screwing into a stem can ensure there is no leakage between the stem and the cap.

Water that is leaving the radially inward facing surface of the second tubular shaped filter material of the second filter will enter the lateral openings of the at least one main extension of the third gasket and will be discharged through the central discharge channel of the at least one main extension to flow to the third filter. The third gasket prevents water by-passing the filtration step through the second tubular shaped material of the second filter.

Possibly, the third gasket comprises one or more additional extensions. The one or more additional extensions of the third gasket are preferably extending downwards, i.e. extending towards the top surface of the second tubular shaped filter material of the second filter and possibly penetrating the second tubular shaped filter material of the second filter at the top surface of the second tubular shaped filter material of the second filter. The one or more additional extensions of the second gasket seal the top surface of the second tubular shaped filter material of the second filter to avoid water by-passing the filtration step through the second tubular shaped filter material of the second filter. The one or more additional extensions of the third gasket prevent water entering the second tubular shaped filter material of the second filter through the top surface of the second tubular shaped filter material of the second filter instead of through the radially outward surface of the second tubular filter material of the second filter and/or water flowing to the third filter without having passed through the second tubular shaped filter material of the second filter.

The filter housing preferably comprises a polymer material, for example polypropylene. The polymer material can be one varied for expected conditions, for example, to withstand varying input water pressures throughout the life of the filter.

The filter housing comprises a container and a cap. The container and the cap are preferably threaded so that the cap can be screwed on the container. This can help with ease of cleaning (for example, in case of clogs), or for regular servicing and/or maintenance.

The first gasket, the second gasket and the third gasket preferably comprise a polymer material, for example polypropylene. Other gasket or gasket extensions can be made of other materials, for example silicon.

The filter unit may further comprise one or more sealing rings, for example one or more O-rings.

According to a second aspect of the present invention the filter unit as described above can be used as a pre-reverse osmosis filter.

Brief description of the drawings

The invention will now be described into more detail with reference to the accompanying drawings whereby

- Figure 1 is an illustration of the cross-section of a filter unit according to the present invention;

Figure 2 is an illustration of a first gasket of a filter unit according to the present invention;

Figure 3 is an illustration of a third gasket of a filter unit according to the present invention.

Detailed description of the invention

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto by only by the claims. The drawings are only schematic and are not limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustration purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention. Figure 1 is an illustration of a cross-section of a filter unit 100 according to the present invention. The filter unit 100 has a water inlet 102 and a water outlet 104 (through cap 105). The filter unit comprises at least a first filter 106, a second filter 108 and a third filter 1 10. The first filter 106 and the second filter 108 comprise a tubular filter. The third filter 1 10 comprises a planar filter. The first filter 106, the second filter 108 and the third filter 1 10 are positioned in a single filter housing 101 . The second filter 108 is positioned downstream the first filter 106 and the third filter 1 10 is positioned downstream the second filter 108. The first filter 106 and the second filter 108 are preferably oriented on top of each other with their main axis parallel oriented parallel or substantially parallel with the main axis 1 1 1 of the filter housing 101 . The plane of the planar filter 1 10 is preferably oriented perpendicular or substantially perpendicular to the main axis 1 1 1 of the filter housing 101 . The water inlet 102 is preferably positioned in the lower part of the filter housing 101. The water outlet 104 is preferably positioned in the upper part of the filter housing 101 , for example at the top of the filter housing 101 .

The first filter 106 comprises a first tubular shaped filter material 1 12 and a first discharge channel 1 14.

The first filter 106 may for example comprise a sediment filter or a carbon filter. In preferred embodiments the first filter 106 comprises a sediment filter. The sediment filter is preferably designed to filter out fine and coarse particles such as dirt, silt, sand and other sediment. By filtering such fine and coarse particles the life time of the reverse osmosis membrane is increased.

The first tubular shaped filter material 1 12 of the first filter 106 comprises, for example, polymer fibers, for example extruded polymer fibers. In a preferred embodiment the first tubular shaped filter material 1 12 of the first filter 106 comprises polypropylene fibers.

Preferably the first tubular shaped filter material 1 12 of the first filter 106 captures particles having a certain equivalent diameter, for example, larger than 5 μηη. Equivalent diameter or equivalent spherical diameter of an irregularly shaped body is used to mean the diameter of a sphere of equivalent volume.

To avoid fouling or clogging of the first filter 106, the first tubular shaped filter material 1 12 of the first filter 106 is preferably washable or flushable.

The second filter 108 comprises a second tubular shaped filter material 1 16 and a second central discharge channel 1 18. The second filter 108 also includes an end cap 109.

The second filter 108 may for example comprise a sediment filter or a carbon filter. In preferred embodiments the second filter 108 comprises a carbon filter, more particularly an activated carbon filter. An activated carbon filter removes chlorine and/or organic compounds. Furthermore such filter may remove taste and odor contaminants.

The activated carbon filter comprises, for example, an extruded carbon medium of activated carbon particles having an equivalent diameter ranging between 75 to 400 μηι.

The third filter 1 10 comprises for example a planar filter, for example, a planar microfilter having a pore size ranging between 0.1 and 10 μηη, for example ranging between 1 and 5 μηη.

The third filter 1 10 comprises for example a mesh, a woven structure or a non- woven structure. In a preferred embodiment, the third filter 1 10 comprises a nylon mesh.

Water enters the filter unit 100 through the water inlet 102, flows through the first filter 106 by entering the radially outward facing surface of the first tubular shaped filter material 1 12 of the first filter 106 and by leaving the radially inward facing surface of the first tubular shaped filter material 1 12 of the first filter 106 to be discharged through the first central discharge channel 1 14 of the first filter 106. There should be sufficient space around first filter 106 to ensure lower restriction for water to flow (e.g., lower pressure drops across the filters).

Subsequently, the water flows through the second filter 108 by entering the radially outward facing surface of the second tubular shaped filter material 1 16 of the second filter 108 and by leaving the radially inward facing surface of the second tubular shaped filter material 1 16 of the second filter 108 to be discharged through the second central discharge channel 1 18 of the second filter 108. Subsequently the water flows through the third filter and leaves the filter unit 100 through the water outlet 104. Outlet from first filter 106, through first central discharge channel 1 14, gasket 102 central discharge channel 128 and below end cap 109 are all dimensioned larger than inlet 102 to ensure smooth flow from inlet 102 through filter unit 100. Water outlet 104 should also have sufficient area to ensure a smooth flow of water out (i.e., a low pressure drop).

The filter unit 100 is provided with a first gasket 120, a second gasket 124 and a third gasket 140. The first gasket 120 is preferably positioned between the first filter 106 and the second filter 108. The second gasket 124 is preferably positioned at the bottom of the filter housing 101 , i.e. at the bottom surface of the first filter 106. The third gasket 140 is preferably positioned between the second filter 108 and the third filter 1 10.

The second filter 108 is screwed into a stem of the third gasket 140, sealing by compressing the third gasket 140 in the cap 1 13, more specifically, compressing gasket 149 to ensure there is no leakage between the stem and cap 1 13. The end cap 109 of the second filter ensures that the second filter 108 sealed against the cap and that the end of second filter 108 is enclosed to ensure that water passes radially inwards through the second filter 108. All gaskets should be sufficiently compressed to ensure there are no leaks. There is also space provided below end cap 109 to ensure there is little restriction and no loss of pressure.

Figure 2 shows the first gasket 120 in more detail. Figure 3 shows the third gasket 140 in more detail.

The first gasket 120 comprises a tubular shaped body 124, at least one main extension 126 and possibly at least one additional extension 127. The tubular shaped body 124 is preferably extending upwards, i.e. extending towards the second tubular filter material 1 16 of the second filter 108 while the at least one main extension 126 and/or the at least one additional extension 127 is/are extending downwards, i.e.

extending towards the first tubular shaped filter material 1 12 of the first filter 106. This at least one additional extension 127 should have sufficient intrusion into first filter 106 to ensure liquid from inlet 102 does not bypass filter 106 on the top to enter first central discharge channel 1 14.

The tubular shaped body 124 of the first gasket 120 is extending at least partially around the second tubular shaped filter material 1 16 of the second filter 108. More preferably, the tubular shaped body 124 of the first gasket 120 extends around the second tubular shaped filter material 1 12 of the second filter 108 over the full length of the second tubular shaped filter material 1 12.

Preferably, the at least one main extension 126 of the first gasket 120 is at least partially penetrating in the first central discharge channel 1 14 of the first tubular shaped filter material 1 12 of the first filter 106 at the top surface of the first tubular shaped filter material 1 12. This can help to keep the first filter 106 centrally aligned in the housing on the top side. The at least one main extension 124 of the first gasket 120 comprises a central discharge channel 128 allowing water to flow from the first central discharge channel 1 14 of the first filter 106 to the second filter 108. First gasket 120 is preferably such a height to ensure there is sufficient sealing between housing 101 and first gasket 102.

Preferably, the at least one main extension 126 of the first gasket 120 comprises a tubular or conical shaped body possibly provided with lateral openings (not shown).

The at least one main extension 126 of the first gasket 120 seals the first central discharge channel 1 14 of the first tubular shaped filter material 1 12 of the first filter 106 at the top surface of the first tubular shaped filter material 1 12 of the first filter 106 so that no water can by-pass the filtration step through the first tubular shaped material 1 12 of the first filter 106.

The one or more additional extensions 127 of the first gasket 120 are preferably extending downwards, i.e. extending towards the top surface of the first tubular shaped filter material 1 12 of the first filter 106 and possibly penetrating the first tubular shaped filter material 1 12 of the first filter 106 at the top surface of the first tubular shaped filter material 1 12 of the first filter 106. The one or more additional extensions 127 of the first gasket 120 seal the top surface of the first tubular shaped filter material 1 12 of the first filter 106 to avoid water by-passing the filtration step through the first tubular shaped filter material 1 12 of the first filter 106. The one or more additional extensions 127 of the first gasket 120 prevent water entering the first tubular shaped filter material 1 12 of the first filter 106 through the top surface of the first tubular shaped filter material 1 12 of the first filter 106 instead of through the radially outward surface of the first tubular filter material 1 12 of the first filter 106 and/or water flowing to the second filter 108 without having passed through the first tubular shaped filter material 1 12 of the first filter 106.

The second gasket 122 comprises at least one main extension 130. The at least one main extension 130 of the second gasket 122 is preferably extending upwards, i.e. extending towards the bottom surface of the first tubular shaped material 1 12 of the first filter 106. The at least one main extension 130 of the second gasket 122 is preferably at least partially penetrating in the first central discharge channel 1 14 of the first tubular shaped filter material 1 12 of the first filter 106 at the bottom surface of the first tubular shaped filter material 1 12. The second gasket 122 can be part of the filter housing 101. The second gasket 122 can for example be integrated in the filter housing 101 , more particularly integrated in the inside of the filter housing 101 at the bottom side of the filter housing 101 .

The second gasket 122 may comprise one or more additional extensions 132.

The one or more additional extensions 132 of the second gasket 122 are preferably extending upwards, i.e. extending towards the bottom surface of the first filter material 1 12 of the first filter 106 and possibly penetrating the first tubular shaped filter material 1 12 of the first filter 106 at the bottom surface of the first tubular shaped filter material 1 12 of the first filter 106. This penetration should be sufficient to ensure that liquid from inlet 102 does not bypass filter 106 on the lower end, and must travel through first filter 106 to enter first central discharge channel 1 14.

The one or more additional extensions 132 of the second gasket 122 seal the bottom surface of the first tubular shaped filter material 1 12 of the first filter 106 to prevent water by-passing the filtration step through the first tubular shaped filter material 1 12 of the first filter 106 at the bottom. The one or more additional extensions of the second gasket 122 prevent water entering the first tubular shaped filter material 1 12 of the first filter 106 through the bottom surface of the first tubular shaped filter material 1 12 of the first filter 106 instead of through the radially outward surface of the first tubular filter material 1 12 of the first filter 106 and/or water flowing to the second filter 108 without having passed through the first tubular shaped filter material 1 12 of the first filter 106. A central extension, as shown in second gasket 122 also helps to centrally align the first filter 106 at a bottom end.

The third gasket 140 preferably comprises a tubular shaped body 142 and at least one main extension 144 having a central discharge channel 148. The central discharge channel 148 of the main extension 144 of the third gasket 140 is preferably provided with lateral openings 150. These openings 150, as well as second central discharge channel 1 18, can be dimensioned to allow small granules to flow through (for example, carbon granules of about 250 microns). Thus, if there is loose carbon, for example, knocked loose during assembly, the carbon flows through, not blocking flow, and is collected by the third filter 1 10. The tubular shaped body 142 is preferably extending upwards, i.e. extending towards the third filter 1 10. Preferably the tubular shaped body 142 of the third gasket 140 is adapted to hold the third filter 1 10. The at least one main extension 144 is preferably extending downwards, i.e. extending towards the upper surface of the second tubular shaped filter material 1 16 of the second filter 108. The third gasket 140 can be provided with at least one additional extension 145, extending upwards between third gasket 140 and cap 105. Additional extensions can extend downwards, i.e. towards the upper surface of the second tubular shaped filter material 1 16 of the second filter 108. A further gasket 147 can be located at the bottom of the third filter 1 10 to avoid bypass of the third filter 1 10. An additional gasket 149 can also be included to ensure sealing and proper direction of the water.

Preferably, the at least one main extension 144 of the third gasket 140 is at least partially penetrating in the second central discharge channel 1 18 of the second tubular shaped filter material 1 16 of the second filter 108 at the top surface of the second tubular shaped filter material 1 16. More preferably, the at least one main extension 144 of the third gasket 140 is penetrating in the second central discharge channel 1 18 of the second tubular shaped filter material 1 16 of the second filter 108 over the full length of the second tubular shaped filter material 1 16. The at least one main extension 144 of the third gasket 140 comprises a central discharge channel 148 allowing water to flow from the second central discharge channel 1 18 of the second filter 108 to the third filter 1 10.

Preferably, the at least one main extension 144 of the third gasket 140 comprises a tubular or conical shaped extension body. More preferably, the at least one main extension 144 comprises a tubular or conical shaped body provided with lateral openings 150.

Water that is leaving the radially inward facing surface of the second tubular shaped filter material 1 16 of the second filter 108 will enter the lateral openings 150 of the at least one main extension 144 of the third gasket 108 and will be discharged through the central discharge channel 148 of the at least one main extension 144 to flow to the third filter 1 10. The third gasket 140 prevents water by-passing the filtration step through the second tubular shaped material 1 16 of the second filter 108.

The filter unit 100 may further comprise a number of O-rings 152.

While different features and embodiments have been described as preferable, this is for certain embodiments and situations and is not to be construed as limiting. Furthermore, while the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all

embodiments falling within the scope of the appended claims.