Patent Publication Number: US-6709603-B2

Title: Split-flow water filtration apparatus and method

Description:
This application is a continuation-in-part of, and claims priority from, prior application Ser. No. 09/387,272 filed Aug. 31, 1999, issuing Aug. 21, 2001 as U.S. Pat. No. 6,277,292, which is a division of prior application Ser. No. 08/678,484 filed Jul. 9, 1996, issued on Aug. 31, 1999 as U.S. Pat. No. 5,944,989. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to water filter or treatment systems, and, more specifically, to systems including intermediate storage for filtered or treated water. 
     2. Related Art 
     Conventional filter systems permit water to flow in a single pass through filter or treatment media to a storage tank, water tap, or other usage device. When additional filtering of stored water is desired to move contamination or biocides immediately before use, conventional systems typically require multiple filter canisters and complicated valving and piping. 
     Reid (U.S. Pat. No. 5,248,417) discloses a double-flow-through system using a single filter housing. In this system, water flows through a single bed of filter media and then through a combination outlet-inlet port to a storage tank. When a tap or faucet is opened, the stored water flows back through the combination port into the filter housing to flow again through the filter media bed and then out to the tap. Thus, the Reid &#39;417 system provides two passes through a single bed of filter media, with intermediate storage between the two passes. 
     The Reid &#39;417 apparatus includes a pair of check valves to control flow to and from the combination port, and, thus, to and from storage. When the water tap is closed, unfiltered water enters the upper portion of the filter housing through the inlet port and is prevented by a cup-type check valve from flowing directly to the combination outlet-inlet port. The water passes a first time through the media and flows up through a filter tube to the combination port. A slit-type check valve disposed at the top of the filter tube prevents water from flowing from the combination port back into the filter tube. Once the water tap is opened, the cup-style check valve allows water to flow from storage through the combination port, through the cup check valve into the top portion of the filter housing, through the media a second time, and then to the tap. 
     Reid (U.S. Pat. No. 5,232,590) discloses a water filtration apparatus with an internal by-pass for conducting water from a water source to a storage tank without passing through the filter media. When the tap or faucet is opened, water then flows back from the storage tank into the filter housing, through the filter media, out the outlet port, and out of the faucet. 
     Grayson, et al. (U.S. Pat. No. 5,082,557) discloses a filter control head for directing water to various locations. The control head can direct water to a first filter canister, to a drain, and to a storage tank. When a downstream usage device demands water, purified water may then flow from the storage tank, back to the control head, and then to a separate, second filter canister and a downstream usage device. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an economical system with at least two stages of filtration or treatment and with intermediate storage. The invention features a “split-flow” scheme in which inter-stage liquid is split off to intermediate storage and then subsequently returned to a later stage of processing, preferably in the same filter housing, combined with liquid flowing through the first stage of processing. Another object of the invention is to provide an apparatus wherein the first and second filtration/treatment zones are both contained in a single filter housing. Another object of the invention is to provide a system having two or more filtration zones that each may be operated at different flowrates. 
     The present invention comprises a filter housing comprising first and second filtering zones in series, and removal means and return means for conducting liquid to and from storage in between the zones. Separate, intermediate outlet and inlet ports may extend through the housing wall, or, preferably, a single, intermediate combined outlet-inlet port may accommodate flow in both the outward (to storage) and the inward (from storage) directions. 
     In a preferred embodiment, the intermediate outlet and inlet ports is combined into a single port, which is in fluid communication with an elongated filter tube extending through the first zone. The bottom of the filter tube is located near the bottom of the first zone and near the top of the second zone. Therefore, the filter tube collects water after passage through the first zone and allows it to flow out of the intermediate port to storage. Upon opening of a tap, which is in fluid communication with the outlet of the second zone, the stored water flows back into the intermediate port and into the filter tube, out of the bottom of the filter tube, through the second zone, and through an outlet port to the water tap. 
     Each of the multiple zones of the present invention may include one or more beds or layers comprising filter media, treatment media, or void space. In a preferred embodiment, the first zone comprises both anti-bacterial treatment with an iodinated resin and extended contact between bacteria and the iodide/iodine species in a void chamber. In this preferred embodiment, the intermediate storage provides additional contact time between biocide and bacteria, and the second zone filters the water and removes the biocide from the water immediately before use. The structural configurations of the zones may be designed for either axial flow, radial flow, or both types of flow distribution. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional side view of one embodiment of the invention having axial-flow first and second filtration zones. 
     FIG. 2A is a schematic cross-sectional side view of the embodiment of FIG. 1, showing liquid flow when the tap is closed and the storage tank is filling. 
     FIG. 2B is a schematic cross-sectional side view of the embodiment of FIG. 2A, showing liquid flow when the tap is open and the storage tank contains liquid. 
     FIG. 2C is a schematic cross-sectional side view of the embodiment of FIG. 2A, showing liquid flow when the tap is open and the storage tank is empty. 
     FIG. 3A is a schematic cross-sectional side view of an alternative embodiment of the invention having radial-flow first and second filtration zones, showing liquid flow when the tap is closed and the storage tank is filling. 
     FIG. 3B is a schematic cross-sectional side view of the embodiment of FIG. 3A, showing liquid flow when the tap is open and the storage tank contains liquid. 
     FIG. 3C is schematic cross-sectional side view of an alternative radial-flow embodiment of the invention, wherein a liquid-permeable elongated return tube is included in the first zone to create a media axial passage. FIG. 3C shows liquid flow when the tap is open and the storage tank contains liquid. 
     FIG. 4 is a schematic cross-sectional side view of an alternative embodiment of the invention, having a combined outlet-inlet intermediate port located part of the way down the filter housing sidewall, and showing liquid flow when the tap is open and the storage tank contains liquid. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the Figures, there are shown several, but not the only, embodiments of the invented split-flow water filtration apparatus, which is herein called a “filter” but which may include adaptations for filtration, treatment, and other forms of component removal and addition from/to liquid. In FIG. 1, there is shown the preferred embodiment, including a central return tube that both collects water after the first stage of filtration and distributes water to the second stage of filtration. 
     Filter  10  comprises a filter housing  12  with inlet port  14 , intermediate port  16 , and outlet port  18 . The housing  12  is a generally cylindrical shape with an interior cavity  20  for holding filter or treatment media. The inlet port  14  and intermediate port  16  extend through a first wall, preferably the top wall  15  of the housing  12 , and the outlet port  18  extends through a second wall, preferably the bottom wall  19  of the housing  12 . The inlet port  14  is in fluid communication with a water source  21  and the outlet port  18  is in fluid communication with a water usage device, such as a tap  22 . 
     The intermediate port  16  is connected to and in fluid communication with storage tank  24 . Associated with storage tank  24  is a pressurizing means, for pressuring or pumping liquid back to the filter  10  when the tap  22  is opened. The pressurizing means may be apparatus to pressurize the tank, pressurize a bladder, or to pump liquid. 
     The central return tube  26 , which in FIG. 1 has a non-perforated side wall, extends down through the first zone  28  of the filter  10  and is in fluid communication with the intermediate port  16 . The top end  30  of the return tube  26  may be sealed in the filter head by one or more o-rings  34 . The bottom end  36  of the return tube  26  extends to the bottom  38  of the first zone  28  and to near the top  40  of the second zone  42 . The tube bottom end  36  is held in the center of the cavity  20  by a retaining means, which is preferably a radially-disposed support disk  44  having a tube retainer  46  at the center of the disk  44  for connection to the tube bottom end  36 . 
     The first zone  28  comprises a first bed  48  of resin followed by a dwell chamber  50 , which is a void space not containing any filter or treatment media. The second zone  42  is a filter bed  52 , containing a filter media such as activated carbon. Resin bed  48 , dwell chamber  50 , and filter bed  52  are separated/supported by support disks  54  and felt  56 . The resin bed  48  is held in compaction by a spring disk  58 , and the filter bed  52  is supported by felt  56  on top of the bottom interior surface of the housing  12 . Disks  54 , felt  56 , and spring disk  58  support and/or separate the media beds while letting fluid pass from one bed or zone to the next, as is well-known in the art of filters. 
     The preferred embodiment of FIG. 1 is designed for anti-bacterial treatment with an iodinated resin, followed by residence time in the dwell chamber  50  for extended contact between bacteria and the iodide/iodine species in the water for a high percentage of bacteria destruction. The dwell chamber  50 , which is preferably empty except for the water being treated, maximizes residence time for a given volume of filter housing, as is disclosed in Hughes (U.S. Pat. No. 5,407,573). The storage tank  24  provides additional contact time, and the second zone  42  filters and removes biocide from the water immediately before use. 
     In use, when the tap  22  is closed, water or other fluid from the source enters the filter  10  through inlet port  14  and flows axially down through the first bed  48  and into the dwell chamber  50 . From the dwell chamber  50 , the water flows up through the central return tube  26  to the intermediate port  16  and to the storage tank  24 . This first stage filtration flow scheme, shown schematically in FIG. 2A, continues until the storage tank  24  is full or until the tap  22  is opened to demand water for use. When the storage tank  24  is full and the tap is closed, water flow stops unless the system is fitted with an optional drain for maintaining a small flow through one or more of the filter zones. 
     When the tap  22  is opened, as shown in FIG. 2B, water flows in the reverse direction from the storage tank  24 , enters the tube top opening  25 , flows axially down through the tube  26  and out the tube bottom opening  64 , through the second zone  42 , and out the outlet port  18 . In most designs, when the tap is open, some water also flows from the inlet port  14 , down through both the first zone  28  and second zone  42 , and out the outlet port  18 . When the tap  22  is open but the storage tank  24  is empty, as shown in FIG. 2C, water continues to flow from the inlet port  14  through both zones  28 ,  42  and out the outlet port  18 . 
     The split-flow filter  10  system allows the flowrates through the first zone  28  and second zone  42  to be different. The flowrates through the first and second zones are determined by the pressures of the water source and storage tank, the various pressure drops through the system, etc., as is known in filter design and fluid mechanism. Thus, when the tap  22  is open and the water flowing to the tap is a combination of water from storage  24  and water that has come from the inlet port  14  directly through the two zones, the relative proportions of these two water types is also a function of tank pressure, source pressure, pressure drop, etc. In the preferred system, the flow of water from storage  24  through the second zone  42  to the tap  22  is relatively fast compared to the flow of water either through the first zone  28  to storage  24  or through the first zone  28 , second zone  42 , and tap  22 . 
     In FIGS.  1  and  2 A-C, the first zone  28  is portrayed as having a central return tube  26  with a non-liquid-permeable side wall. This non-permeable return tube is one example of a support structure defining an axial passage through the first zone  28 . 
     Alternative embodiments may have other means for creating an internal axial passage through the first zone media. For example, a solid media may have an internal media cavity defined by the media inside diameter and running axially through the media. Such an embodiment is depicted in the radial-flow filter  100  of FIGS. 3A and 3B. In such a solid media embodiment, a separate support structure at the media&#39;s inside diameter is normally unnecessary. Alternatively, another structure for creating an axial passage through media is a perforated, slotted, or otherwise liquid permeable central return tube (such as shown in the filter  110  of FIG. 3C) that holds the media in place but allows radial-flow of liquid through the media and through the wall of the return tube. Such a return tube may be used for granular media in the first and/or second. 
     In the radial-flow filter embodiment  100  of FIG. 3A, unfiltered water enters the inlet port  14 , flows radially through the first zone  28 ′, flows out from the inside diameter  62  of the media into the media cavity  26 ′, and flows up to the intermediate port  16  and to storage  24 . When the tap  22  is opened, as in FIG. 3B, the stored water flows back into the intermediate port  16 , down through the media cavity  26 ′, out the bottom  64 ′ of the cavity  26 ′, and to the second zone  42 ′. In the second zone  42 ′, the water flows radially into the second zone media cavity  60  formed by the inside diameter of the radial flow media, to the outlet port  18 , and to the tap  22 . 
     Included in the filter embodiment  100  portrayed in FIG. 3A and B is a sealing means resting on top of the media, for sealing the media to the tube  69  that extends through the intermediate port  16 . The sealing member  70  has a plate covering the top end surface of the media and one or more o-rings for creating a seal between the member  70  and the tube  69 . Alternatively a sealing member may be designed to seal the media to the head of the filter at the intermediate port  16 . Such an alternative embodiment includes a plate for covering the media, and a cylindrical extension upending to contact and seal with the intermediate port by the use of o-rings encircling the upper end of the cylindrical extension. 
     A sealing means is preferably located on the top end surface of the second zone media. The sealing means may be an end plate  72  that prevents water from entering media cavity  60  from the top. Both end plate  72  and the first zone sealing member  70  may be attached to media by, for example, hot gluing. 
     Therefore, in both axial-flow and radial flow embodiments, the first and second zones are in series-flow liquid communication, wherein the effluent of the first zone flows directly, or by way of storage, to the inlet of the second zone. The first zone inlet may be either the top end  63  of a axial-flow bed or the outer annular surface  65  of a radial-flow bed. The first zone outlet may be either the bottom end  38  of an axial-flow bed or the inner annular surface  66  of a radial-flow bed. The inlet and outlet of an axial-flow second zone are at the top end  40  and bottom end  67  of the zone, respectively. The inlet and outlet of a radial-flow second zone are the outer annular and inner annular surfaces, respectively. Therefore, by saying the central return tube bottom opening  64  or the bottom  64 ′ of the media cavity is “near the second zone inlet”, it is meant that the bottom opening  64  or cavity bottom  64 ′ may either be near the top end of an axial-flow bed (so that the first zone effluent flows axially down into the second zone) or near the top end of a radial-flow bed (so that the first zone effluent flows down to the annular feed  68  space and then radially into the second zone). Thus, the return tube bottom  64  or cavity bottom  64 ′ is in fluid communication with the second zone inlet, whether the second zone is axial or radial. 
     Optionally, the present invention may include an adjustment means for shortening the length of the central return tube  26 ,  26 ″, in order to adjust the location of the first and second zones in the filter cavity and change the portions of cavity used as first and second zones. In an axial-flow filter, for example, shortening or lengthening the return tube  26  changes the location of the first zone outlet and second zone inlet, and allows the filter cavity to be loaded with different volumes of first and second zone media. 
     FIG. 4 illustrates another alternate filter embodiment 200, in which the combined outlet-inlet intermediate port  16 ′ is located in a third wall of the housing  12 ′, that is, the sidewall of the preferably cylindrical housing  12 ′. In this embodiment, water flows through the first zones  28 ″ and to storage through the intermediate port  16 ′, which is located near the bottom of the first zone  28 ″. When the tap  22  demands water, the stored water returns to the filter through the intermediate port  16 ′, and flows through the second zone  42 ″ to the tap  22 . As in the other embodiments, the pressure balance at the various locations through the system would control the flows through the first zone  28 ″, intermediate port  16 ′, and second zone  42 ″ of this filter and would control the ratio of storage water/first-zone-water flowing to the second zone and out to the tap. 
     The invention preferably has only two zones with adaptation for flow out and in between the two zones, preferably via a single combined outlet-inlet port. Alternatively, the invention may include more than two stages, with removal and return of the liquid intermediate between all or some of the stages. Each removal and return of liquid between stages preferably is done via a combined (single) intermediate port located in each inter-zone area, rather than via separate outlet port and inlet port structures in each of the inter-zone areas. Thus, preferably, the stages of filtration/treatment are accomplished in zones with combined outlet-inlet intermediate ports that are all contained in a single filter housing, and, preferably, only a single pipe extends out from each combined outlet-inlet intermediate port. The preferred embodiments, with their minimized vessel, piping and valving requirements, are therefore economical and efficient in structure, use, and installation. 
     The preferred embodiments comprise careful control of liquid flow through the various zones of the filtration system, depending on what process step is being conducted. Particularly, FIGS. 2B,  3 B,  3 C, and  4  illustrate process steps in which the tap is open, and stored water from the storage tank is returning to the filter, preferably after a storage time of several minutes or hours. These Figures represent the stored water flowing to the outlet of the first zone of treatment via a conduit and port that delivers the stored water “directly” to the first zone outlet, that is, not delivery to the first zone outlet via the first zone media or second zone media. In other words, the stored water does not flow through the first zone media or the second zone media on its way to the second zone inlet for flowing through the biocide-removal media in the second zone. Thus, returning the stored liquid from said storage tank to the filter is done by delivering/forcing the stored liquid to the fluid outlet of the first zone; preferably done without allowing the liquid to flow through the first zone media or the second zone media. Then, the stored liquid is forced from its delivered location at the fluid outlet of the first zone to the second zone fluid inlet and through the second zone. 
     The plurality of zones in the filter housing may all be axial-flow, as illustrated in FIG. 1, may all be radial flow, as illustrated in FIGS. 3A, B and C, or some may be axial-flow and some may be radial. Conventional aspects of filter design, such as retainer disks, felt, o-rings, port connections, housing shape, etc., may be varied according to known filter art and still be within the scope of this invention. 
     The configuration of the filtering/treatment zones may be changed to accommodate various types of filter or treatment media. For example, desirable first zone media may include biocide resins, ion exchange resins for softening, demineralizing, desilicizing, or disinfecting, and resins for removal of tannin/organic, nitrate, and alkalinity, etc. Desirable second zone media may include felt wrap, pleated material, folded material, carbon, block activated carbon, granular carbon, etc. Many combinations and arrangements of media may be used, including a plurality of beds within a single zone. 
     In this Description and the Claims, the words “filtering”, “filtration”, “treatment”, or “filtration media” are not intended to limit the invention to media which performs a particular filtration function, but, rather, include media that removes material from a liquid, adds material to a liquid, otherwise treats or transforms a liquid, or is inert to the liquid under different circumstances. The zones may also be empty or have spaces that are empty of media, as in the dwell chamber in FIG.  1 . Also in the description and Claims, the terms “up” or “down” are not intended to limit the invention to particular orientations relative to the ground or gravity, but are used to clarify directions of liquid flow relative to the apparatus. 
     Although this invention has been described above with reference to particular means, materials, dimensions, embodiments, and methods of installation, it is to be understood that the invention is not limited to these disclosed particulars, but extends instead to all equivalents within the scope of the following claims.