Abstract:
A filter cartridge assembly intended for replaceable installation in a demountable cartridge housing includes in one embodiment, a retaining ring that is attached to the product water tube of the filter cartridge, is inserted with the cartridge into the housing, and is locked to the housing such that, upon subsequent removal of the housing to change the cartridge, the cartridge will be forced from sealing engagement with the end cap header and caused to remain in the housing until the housing has been removed. The integral retaining ring and cartridge are then simply unlocked and removed from the housing for replacement. Brine ring embodiments that are welded to the housing or attached to the housing with a snap-in connection are also disclosed.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention pertains to replaceable cartridge type filters and, more particularly, to such a filter utilizing a semipermeable membrane cartridge with an assembly for retaining the cartridge in the housing when it is removed for replacement.  
           [0002]    Replaceable cartridge filters have been used in water treatment systems for many years. A typical filter unit of this type utilizes an elongate, generally cylindrical housing or sump which is open at one end for the receipt of a replaceable filter cartridge. The cartridge and the housing are demountably attachable to an enclosing end cap. The end cap may be a unitary cover or part of a header or manifold system for control of fluid flow into and out of the cartridge. The filter cartridge may include any of several well known kinds of filter media, and multiple housings and associated filter cartridges may be attached to a common header system for the serial removal of a wide variety of both suspended and dissolved contaminants from a liquid stream. The media used in filter cartridges varies widely, depending upon the contaminant to be removed, and such media include granular particulate materials, coarse sintered blocks, paper and plastic filters, and semi-permeable membranes.  
           [0003]    One common type of reverse osmosis (RO) filter cartridge utilizes a membrane which is spirally wrapped around a porous center tube and enclosed in an impervious cylindrical outer wrap. The opposite ends of the cartridge are open, with one of the ends receiving untreated incoming water under pressure and in which most dissolved solids are separated as the water passes through the semipermeable membrane and flows radially toward the porous center tube. The treated water (or membrane permeate) passes along the center tube to an outlet end. The untreated water containing the concentrated dissolved solids (known as the concentrate and commonly referred to as brine) passes out of the opposite end of the membrane cartridge. Such a cartridge typically includes a brine seal which is interposed between the outer cartridge wrap and the inside wall of the cartridge housing to prevent untreated water from bypassing the cartridge and mixing directly with the brine. However, in certain RO cartridge assemblies, such as an assembly in which the brine seal is located at one end of the element and the outlet for the brine flow is located at the opposite end of the element and housing, a volume of stagnant water is created between the OD of the element and the ID of the housing. This pool of stagnant water is not flushed by continuous flow through the element and therefore provides an area for the propagation of bacteria which, in turn, may lead to fouling by migration to active areas of the RO membrane surface. Depending on how a system is designed, the potential problem of pools of stagnant water, either on the untreated water side or the brine water side of the RO element, is a problem in many RO systems which utilize a brine seal.  
           [0004]    The product water outlet in the typical RO filter cartridge comprises a cylindrical neck, which is typically an extension of the center product water tube, and is received in a cylindrical sleeve which forms part of the housing end cap and contains a product water discharge port. The interface between cartridge neck and the sleeve on the cap must be tightly sealed and one typical seal arrangement comprises a pair of axially spaced O-rings which are seated in annular grooves in the cartridge neck and which engage the inside wall of the sleeve in the cap. RO filter cartridges of the foregoing general type are shown, for example, in U.S. Pat. Nos. 4,645,601, 5,002,664, 5,082,557, 5,266,195 and 5,389,260.  
           [0005]    A typical application for a reverse osmosis membrane filter cartridge of the foregoing general types is in purifying tap water for drinking. As indicated, such a filter cartridge is commonly utilized in a series arrangement with other replaceable cartridge filters which remove from the untreated water other suspended and dissolved solids which cannot be removed by membrane separation. Such water treatment units are commonly mounted beneath a sink on which the tap is located or in another confined and typically somewhat restricted space. A number of problems relating to the replacement of filter cartridges generally and RO filter cartridges particularly have arisen with the use of these systems.  
           [0006]    In multi-cartridge systems which may include three units, manufacturers like to utilize identical filter housings for simplicity in manufacturing and inventory, as well as to maintain a uniform product appearance. However, certain filter cartridges and often RO membrane cartridges, do not fit well in housings designed for other types of filter cartridges used in these multi-cartridge systems. As a result, special adapters, special covers, or special non-standard housings may have to be used. A specialized and relatively complex housing end cap is shown, for example, in the above identified U.S. Pat. No. 5,082,557. A specialized, non-standard housing is shown in U.S. Pat. No. 5,266,195.  
           [0007]    Because RO filter cartridges must handle and provide an interface for three liquid flows, namely, untreated water, treated water (membrane permeate), and brine (membrane concentrate), some means for accommodating the additional liquid flow, not present in other kinds of filter cartridges, must be utilized. In U.S. Pat. No. 5,002,664, the brine flow is accommodated by a special connection through the bottom of the RO cartridge housing. This complicates the construction of the unit, as well as the ease of filter replacement.  
           [0008]    Another problem unique to filter cartridges having a neck on one end for the treated water outlet, which includes an O-ring seat arrangement engaging the cylindrical ID of a sleeve in the end cap, is that the resulting tight seal causes the filter cartridge to hang up in the end cap when the housing is unscrewed from the end cap for removal and replacement of the filter cartridge. The filter housing must be slid downwardly along the entire length of the file cartridge before the cartridge can be independently removed from its sealed attachment to the end cap or header. When operating in a confined space, such as under a kitchen sink, this lack of head space may present a serious obstacle to ease of replacement. This problem is addressed and solved in U.S. Pat. No. 4,645,601 by providing an integral cartridge and housing which are removed together. Such an arrangement, though convenient, is extremely uneconomical because the housing must be replaced each time the filter cartridge is replaced.  
           [0009]    One solution to the problem is shown in U.S. Pat. No. 5,891,334 where a cartridge retaining ring is used to hold the filter cartridge in place within the housing and to retain it in place when the housing is unscrewed or otherwise removed from the end cap or header for cartridge replacement. After insertion of the filter element into the housing, the cartridge retaining ring is placed over the upper end of the filter element and engages with a brine ring attached to the housing. The retaining ring bears against the upper end of the element as the housing is removed and forces the neck of the element to disengage from the end cap.  
           [0010]    Although the use of the foregoing retaining ring arrangement has worked well, it still presents a number of drawbacks. First of all, the retaining ring, as a separate piece, requires separate additional assembly and disassembly steps and is subject to being misplaced and lost. Because the retaining ring is operatively attached to the housing, but not to the filter element, removal of the housing causes the retaining ring to bear on the end of the element which may cause damage to a fragile reverse osmosis membrane. Finally, in filter units where the brine ring must be welded to the interior wall of the housing, the need to provide a sonic weld relatively deep inside the housing has created problems of weld equipment accessibility and weld quality.  
         SUMMARY OF THE INVENTION  
         [0011]    In accordance with one embodiment of the present invention, a filter cartridge retaining ring is secured directly to the neck of the product water tube that supports the membrane of an RO filter cartridge. The combined ring and cartridge are inserted together into an open-ended filter housing, and the housing is threadably attached to an enclosing end cap. Interengaging coupling parts on the retaining ring and the housing cooperate when the filter element is inserted into the housing to lock the cartridge therein. The end cap includes an integral center sleeve that surrounds the neck of the cartridge, when the housing is attached to the end cap, and provides therewith a liquid-tight seal. When the housing is subsequently removed from the end cap, as to change the filter cartridge, the filter cartridge neck is pulled from the end cap center sleeve because of the rigid interconnection between the cartridge and the housing provided by the retaining ring. This allows the housing and cartridge to be removed together.  
           [0012]    In the preferred embodiment, a brine ring is attached to the inner wall of the housing adjacent the open end, and the coupling parts include interengaging connectors on the retaining ring and the brine ring. Preferably, the brine ring comprises a cylindrical tubular sleeve and the connectors comprise a pair of diametrically opposite slots in the upper end of the tubular sleeve and a pair of lugs on the retaining ring adapted to be received in the slots.  
           [0013]    The reverse osmosis filter cartridge used in the filter assembly of this invention includes a cylindrical body that is covered with an impervious outer layer. A liquid-tight outer wrap seals the interface between the retaining ring and the outer layer of the cartridge body to provide an inner brine seal component. A first annular seal carried on an outer surface of the retaining ring engages an inner surface of the brine ring, upon insertion of the filter cartridge into the housing, to provide an intermediate brine seal component. A second annular seal is carried on an outer surface of the brine ring and engages an inner surface of the end cap, upon attachment of the housing to the end cap, to provide an outer brine seal component. In a preferred operational orientation, an untreated water inlet is located in the neck end of the RO cartridge, and the flow passage defined by the neck comprises a treated water outlet. The other end of the cartridge includes a brine water outlet. The three brine seal components form a composite brine seal that provides liquid separation between the brine water outlet and the untreated water inlet.  
           [0014]    In an alternate embodiment of the brine ring, the ring may be made for a snap-in attachment to the cartridge housing, rather than welded or bonded to the inner wall of the housing. This modified brine ring is, however, intended to be left in place when the filter cartridge and retaining ring are removed for cartridge replacement. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a vertical section through a filter assembly showing the integral retaining ring and cartridge assembly of one embodiment of the present invention in its operative installed position.  
         [0016]    [0016]FIG. 2 is a vertical section through the filter assembly of FIG. 1 showing the separation of the interconnected housing and filter cartridge from the end cap.  
         [0017]    [0017]FIG. 3 is a vertical section similar to FIGS. 1 and 2 showing separation of the integral retaining ring and filter cartridge from the housing after unlocking the interengaging connectors.  
         [0018]    [0018]FIG. 4 is an exploded perspective view of the filter cartridge with integral retaining ring prior to insertion into and locking within the housing.  
         [0019]    [0019]FIG. 5 is an exploded perspective view of an RO filter cartridge of the preferred embodiment of the present invention.  
         [0020]    [0020]FIG. 6 is a horizontal section taken on line  6 - 6  of FIG. 3.  
         [0021]    [0021]FIG. 7 is a partial sectional view taken on line  7 - 7  of FIG. 3.  
         [0022]    [0022]FIG. 8 is an exploded isometric view of another embodiment of the invention in the form of a brine ring attachable with a snap-in connection to the interior of a housing.  
         [0023]    [0023]FIG. 9 is a top plan view of the FIG. 8 housing with the brine ring in place.  
         [0024]    [0024]FIG. 10 is a sectional detail taken on line  10 - 10  of FIG. 9.  
         [0025]    [0025]FIG. 11 is a side elevation view of a modified snap-in brine ring similar to the type shown in FIG. 8.  
         [0026]    [0026]FIG. 12 is an enlarged vertical section through the upper portion of a filter housing showing the snap-in mounting of the brine ring shown in FIG. 11. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]    Referring to FIG. 1, a replaceable filter cartridge  10  is contained inside a tubular housing  11  which is removably attached to an upper end cap  12 . The filter cartridge  10  utilizes a semi-permeable reverse osmosis membrane to remove dissolved solids from untreated water by reverse osmosis. The construction of the filter cartridge  10  is generally conventional and is of a type presently available from several manufacturers. The cartridge includes an interior spirally wound membrane  13  which may include an intermediate separator layer, shown schematically in FIGS. 1 and 5. The membrane  13  is wound around a central hollow product water tube  14 , which extends the length of the cartridge  10 , and is provided in its outer surface with a pattern of through holes  15 . The membrane is closed by an impervious outer cover  16  which may be plastic or any other suitable material. The lower end of the cartridge has a short central extension  18 , and the opposite upper end has a small diameter cylindrical neck  20  both of which preferably comprise integral extensions of the interior product water tube  14 . The neck  20  is provided with a pair of axially spaced annular grooves  21  in which are received sealing O-rings  22 . The opposite axial ends of the cartridge  10 , adjacent, respectively, the cylindrical neck  20  and the lower extension  18 , are open to expose the membrane  13  to an incoming flow of untreated water and an outgoing flow of brine. The brine flow comprises the high volume concentrate of water and dissolved solids which does not pass through the semi-permeable membrane. Although membrane filter cartridges of the type used in this invention may accommodate untreated water and brine water flows through either end, the cartridge in the present embodiment is oriented with the untreated water inlet  23  on the upper end and the brine water outlet  24  on the lower end.  
         [0028]    The filter housing  11  is of conventional molded plastic construction, which includes an elongated cylindrical side wall  25  and a closed bottom end  26 . The open, upper end of the housing has an enlarged diameter end portion  27  with a threaded ID adapted to engage a correspondingly threaded OD on a cylindrical boss  28 , which depends downwardly from the underside of the end cap  12 . In this embodiment, the end cap comprises the lower portion of a multi-unit manifold header  29  which, as indicated previously, may accommodate several different types of filter units, each of which is contained in a housing similar to housing  11 , threadably attached to a similar cylindrical boss  28 . The remainder of the header (not shown) includes a pattern of passageways and valves to accommodate the flow of water through the system. Details of such a multi-unit system are shown in co-pending and commonly owned application Ser. No. 09/633,995 entitled “Flow Control Module for RO Water Treatment System” filed Aug. 8, 2000, and which is incorporated by reference herein.  
         [0029]    In accordance with the present invention and referring particularly to FIGS. 4 and 5, the filter cartridge  10  and the filter assembly in which it is used are modified to provide a retaining ring  30  that is fixed to the filter cartridge and a composite brine seal that eliminates the skirted brine seal attached to the outside of the filter cartridge. The retaining ring  30  cooperates with a brine ring  31  in the housing  11  such that insertion of the combined cartridge and retaining ring into the housing allows the combination to be locked in place.  
         [0030]    After the basic reverse osmosis filter element, comprising a semipermeable membrane  13  wound on a central product tube  14  and enclosed by an outer cover  16 , is prepared, the retaining ring  30  is placed over the exposed neck  20  of the product water tube  14 , slid downwardly along the neck, and locked in place. The retaining ring  30  includes an upper large diameter ring portion  32  joined integrally to a smaller diameter lower ring portion  33  by an intermediate frustoconical surface  34 . The interior of the retaining ring is provided with a central web  35  provided with a center opening  36  sized to receive the product tube neck  20 . The lower edge of the center opening  36  is provided with an annular rib  37  that snaps into an annular groove  38  in the neck  20  of the product water tube located just above the filter membrane  13 . The center opening  36  in the retaining ring center web  35  is provided with a number of spaced notches  40  that interrupt the annular rib  37 , thereby allowing the wall of the opening  36  to flex slightly to allow the ring to be slid downwardly over the product water tube neck  20 , until the rib snaps into the annular groove  38 . To prevent rotation of the retaining ring  30  relative to the product water tube  14 , the rib  37  may be secured in the groove by solvent bonding, sonic welding, or other means. One alternate means of preventing rotation would be to provide barrier ribs in the annular groove  38  corresponding in position to the notches  40  in the center opening of the ring. The interrupted ends of the annular rib  37  would engage such barrier ribs and inhibit relative rotation between the ring and the tube.  
         [0031]    The outside surface of the lower retaining ring portion  33  is sealed to the upper end of the outer cover  16  of the filter cartridge, with a tape-like sealing wrap  41 . The sealing wrap comprises one part of a multi-component brine seal, the other components of which will be described hereinafter.  
         [0032]    The upper portion  32  of the retaining ring  30  has a cylindrical outer surface  42  in which is formed a circumferential annular groove  43  in which is seated an O-ring  44 . On diametrically opposite sides of the cylindrical outer surface  42 , are outwardly extending lugs  45 . The lugs  45  are adapted to be received in slots  46  formed in the upper end of the tubular body  47  of the brine ring  31 . The brine ring body  47  has a cylindrical inner surface  48  that is engaged by the  0 -ring seal  44  as the retaining ring on the cartridge  10  slides into the tubular body  47  of the brine ring  31 . Once the lugs  45  are received in the slots  46 , the filter cartridge  10  is rotated slightly on its axis (in a counterclockwise direction with respect to the housing  11  in FIG. 4), causing the lugs  45  to enter undercut portions  50  in the slots  46 . The filter cartridge is then locked against axial withdrawal from the housing. The O-ring  44  provides a second or intermediate component of the multi-component brine seal.  
         [0033]    The threaded cylindrical boss  28 , depending downwardly from the underside of the manifold  29 , includes a smaller diameter central sleeve  51  which receives the upper end of the cylindrical neck  20  of the filter cartridge when the housing containing the cartridge is threaded onto the boss  28 . The tight seal between the cartridge neck  20  and the sleeve  51  provided by the double O-ring seal  22  causes the filter cartridge to hang up and resist axial withdrawal from the sleeve  51  when the housing is removed, as for filter cartridge replacement. However, with the lugs  45  on the retaining ring locked in the undercut portions  50  of the brine ring slots  46 , the filter cartridge will be removed axially along with the housing. By locking the retaining ring  30  to the product water tube  14  (by entry of the annular rib  37  into the annular groove  38  in the neck portion  20  of the product water tube) the axial force resisting movement of the upper end of the neck  20  from the central sleeve  51  is borne by the neck and the retaining ring. In prior art constructions, where the retaining ring is not connected directly to the product water tube, the axial force is borne by the upper end of the wound filter membrane  13  which bears against the underside of the retaining ring. This could cause damage to the relatively fragile membrane or, if there is relative axial movement between the ring and the membrane, the portion of brine seal provided by the sealing wrap  41  might be disturbed.  
         [0034]    The tubular body  47  of the brine ring  31  has an outer cylindrical surface  52  and is provided at its lower end with a number of circumferentially spaced, radially extending connecting tabs  53 . The connecting tabs serve to space the brine ring radially inwardly from the inner surface of the housing side wall  25  and to provide surfaces for attaching the brine ring to the inside of the housing. Preferably, there are four connecting tabs  53  which are joined to the upper end of the housing side wall just below the threaded upper end portion  27 . The connecting tabs  53  may be secured to the wall by sonic welding, solvent bonding or any other convenient means. The upper end of the brine ring body  47  extends upwardly from the connection points and into the upper end portion  27  of the housing. When the housing is threaded onto the end cap boss  28 , the brine ring  31  extends into the interior of an annular cylindrical wall portion  54  in the boss  28 . The cylindrical wall portion  54  has a cylindrical inner surface  55  which is engaged by a pair of O-rings  56  carried in annular grooves  57  formed in the outer cylindrical surface  52  of the brine ring. These O-rings  56  provides a liquid tight seal that forms the third component of the multi-component brine seal.  
         [0035]    An annular slot  58  is formed in the boss  28  between the outer threaded surface and the annular cylindrical wall  54 . A brine outlet port  60  is formed in the bottom of the annular slot  58  and extends upwardly through the body of the manifold  29  to a suitable drain connection. Similarly, an untreated water inlet port  61  is formed in the body of the header and opens into the space within the boss  28  between the annular cylindrical wall  54  and the sleeve  51 . The center web  35  of the retaining ring  30  is provided with a number of flow openings  62  so that untreated water entering the interior space is directed into the untreated water inlet end  23  of the filter cartridge  10 . As a result of membrane separation, the larger volume brine flow leaves the filter cartridge  10  through the bottom brine water outlet  24 , while the treated water (also referred to as membrane permeate or product water) moves radially inwardly through the holes  15  in the product water tube  14  and then upwardly through a product water outlet  63  defined by the neck  20  of the product water tube  14 . The downwardly depending sleeve  51  defines a product water port  64  in the header  29 .  
         [0036]    Referring particularly to FIGS.  1 - 3 , the three part brine seal is comprised of the inner sealing wrap  41 , the O-ring  44  and the pair of O-rings  56 . These combine to provide fluid separation between the incoming untreated water entering the system via inlet port  61  and the brine flow exiting the system via outlet port  60 . Brine flow from the outlet end  24  of the filter cartridge passes upwardly through the open space between the outside of the cartridge and the inside wall of the housing, through the spaces  65  defined by the brine ring connecting tabs  53  (see FIG. 6), into the annular slot  58  and through the brine outlet port  60 . Treated water leaving the system via the product water port  64  may be directed into a flow control module  66  mounted in the manifold header  29 . The module may be of the type described in the above identified co-pending application.  
         [0037]    Finger tabs  67  extending upwardly from the center web  35  of the retaining ring  30  facilitate manual insertion of the cartridge  10  into the housing and rotation of the cartridge to cause the locking lugs  45  to move into the undercut portions  50  in the slots  46  in the brine ring  31 . It should be noted that, if any relative rotation of the filter cartridge with respect to the housing occurs during the process of threading the upper end portion  27  of the housing onto the boss  28 , such that the lugs  45  may tend to back out of the undercut portions  50 , reverse rotation will occur when the housing is unthreaded and the lugs will move back into the undercut portions. Thus, the filter cartridge will remain locked in the housing as it is removed from the header such that the entire assembly can be removed together. Referring to FIGS. 3 and 7, the finger tabs  67  are preferably provided with openings for receipt of the hooked ends of a handle  68  to facilitate removal of the cartridge from the housing for replacement. The handle  68  is preferably sized such that it may nest within the upper ring portion  32  of the retaining ring  30  while the cartridge is installed and operating. The handle may optionally be constructed as a pull ring formed as an integral part of the retaining ring  30 .  
         [0038]    An alternate embodiment of a brine ring in accordance with the present invention is shown in FIGS.  8 - 10 . The brine ring  110  is similar in construction to the brine ring  31  of the previously described embodiment, except that it is attached to the inner wall of the housing with a snap-in connection. Thus, the brine ring  110  includes a tubular body  111  defined by inner and outer generally cylindrical walls  112  and  113 , respectively. The outer cylindrical wall  113  near the upper end of the tubular body is provided with a pair of annular O-ring grooves  114  for receipt of the O-rings that seal against the cylindrical inner surface of the end cap boss as described with respect to the previous embodiment. Also in a manner similar to the FIG. 5 assembly, the upper edge of the tubular body  111  is provided with attachment slots  115  for receipt of attachment lugs on a retaining ring (not shown).  
         [0039]    A number of integral connector tabs  116  extend outwardly from the brine ring outer wall  113  and are positioned equally spaced around the circumference of the brine ring body  111 . The connector tabs terminate in generally flat outer end faces  117 . The brine ring  110  is adapted to be inserted and connected to the same housing  11  used with the previously described embodiment. The inner cylindrical wall  109  of the housing  11  is provided with a shallow annular groove  118  which can be conveniently milled or otherwise cut into the cylindrical surface  109 . The groove  118  is positioned just below the upper edge of the cylindrical wall  109  such that it is separated from the upper edge by a narrow inner wall band  119 . The shallow annular groove  118  need only be cut to a depth in the range of about 0.020 to 0.040 inch (0.5 to 1.0 mm). The outer end faces  117  of the connector tabs  116  define a cylindrical surface that is slightly greater than the diameter of the cylindrical inner wall  109  of the housing immediately adjacent the groove, and just slightly less than the diameter of the shallow annular groove  118 . Furthermore, the tubular body  111  of the brine ring is thin enough that it will deflect slightly and enough to permit the outer ends of the connector tabs to be moved past the inner wall band  119  and snap into the shallow annular groove  118 . Though not welded or otherwise bonded to the inside wall surface  109  of the housing, the snap-in attachment of the brine ring  110  is intended to be permanent.  
         [0040]    In use, the brine ring  110  is first installed in the housing by flexing the tubular body  111  slightly and causing the connector tabs to enter the annular groove  118 . The filter cartridge ( 10  in FIG. 4 with the attached retaining ring  30 ) is then inserted axially through the cylindrical interior of the brine ring and into the housing until the O-ring seal ( 44  in FIG. 5) on the cartridge engages the inner cylindrical wall  112  of the ring  110  (and the lower end of the cartridge bottoms in the housing). The entire assembly is then attached to the threaded end cap ( 12  of FIG. 2), all in a manner previously described.  
         [0041]    The inherent flexibility of the tubular brine ring  110  provides sufficient deflection for insertion and snap-in attachment of the ring into the housing  11 . Although the brine ring may be removed, if necessary, it is intended to be left in place once installed in the housing. When the filter cartridge  10  is replaced, the entire housing assembly is removed from threaded connection to the end cap  12 , the retaining ring  30  removed from locking engagement with the upper end of the brine ring, and the filter cartridge and retaining ring pulled axially out of the housing and through the brine ring.  
         [0042]    Referring to FIGS. 11 and 12, a modified brine ring  120  is similar in construction to the snap-in brine ring  110  shown in FIGS.  8 - 10 . Thus, modified brine ring  120  includes a tubular body  121  defined by inner and outer generally cylindrical walls  122  and  123 , respectively. The outer cylindrical wall  123 , near the upper end of the tubular body, is provided with a pair of annular O-ring grooves  124 , as described and for the same purpose as the previously described FIG. 8 embodiment. As also previously described with respect to the other embodiments, the upper edge of the tubular body  121  is provided with attachment slots  125  for receipt of attachment lugs  45  on a retaining ring (see FIGS. 4 and 5). In this embodiment, a number of integral connector tabs  126  extend outwardly from the brine ring outer wall  123 , equally spaced around the circumference of the brine ring body  121 . In this embodiment, the connector tabs  126  are positioned at a location lower than the corresponding connector tabs  116  of the embodiment of FIGS. 8 and 10. A number of stabilizing tabs  127  extend integrally from the outer cylindrical wall  123  of the tubular body in an arrangement aligned with and spaced vertically above the connector tabs  126 .  
         [0043]    Referring particularly to FIG. 12, the brine ring  120  is adapted to be mounted inside the same housing  11  used with the previously described embodiments. The cylindrical inner wall  129  of the housing  11  is provided with a shallow annular groove  128  which may be identical dimensionally to the annular groove  118  of FIG. 8, but which is cut into the housing wall  129  at a position axially lower than in the previously described embodiment. The outer end faces  130  of the connector tabs  126  define a cylindrical surface that is slightly greater than the diameter of the cylindrical inner wall  129  of the housing immediately adjacent the groove, but just slightly less than the diameter of the annular groove  128  itself. On the other hand, the outer end faces  131  of the stabilizing tabs  127  define a cylindrical surface that is equal to or just very slightly smaller than the diameter of the cylindrical inner wall  129  of the housing above the annular groove  128 . With this construction, the brine ring  120  is inserted into the housing until the connector tabs  126  snap into the annular groove  128 . The following stabilizing tabs  127  engage the inner wall of the housing with a light press or close tolerance slip fit, such that the outer faces  131  of the tabs  127  provide a stabilizing abutment against the housing wall. This helps assure that the brine ring  120  does not deflect in use in a direction transverse to its axis.