Abstract:
Length-adjustable filter cartridges are provided which in preferred embodiments include at least one length-adjustable end cap attached to an end of a generally cylindrical filter body. The length-adjustable end cap most preferably includes an annular stationary ring member which is attached to one end of the filter body, and a moveable connection member slideably received within said annular stationary ring member so as to be moveable longitudinally relative thereto. A seal is formed between the stationary ring member and the moveable connection member so as to seal against fluid leakage yet permit relative axial movement (length adjustment) therebetween. In use, the filter cartridges may be adapted to fit conventional standardized bag filter cartridge housings even though the physical size and/or geometries of the metal support basket thereof is non-standard. That is, a filter cartridge having the length-adjustable end cap of the present invention may be positioned within a standard sized bag filter cartridge housing, whereby the length-adjustable end cap may be longitudinally moved until the filter cartridge length corresponds substantially to that of the surrounding metal support basket in which it is placed. As such, the bottom end cap of the filter cartridge is ensured to be supported by the metal basket to prevent it from rupturing during normal use.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to the field of filter cartridges. More particularly, the present invention relates to filter cartridges which are length-adjustable.  
         BACKGROUND AND SUMMARY OF THE INVENTION  
         [0002]    Manufacturers of industrial disposable rigid filter cartridges have for many years essentially standardized filter cartridge diameter and length dimensions and geometries. As a result, the filter cartridges produced by virtually every manufacturer is capable of being employed in another manufacturer&#39;s cartridge housing. Nonetheless, there still exists a need for non-standardized filter cartridges to be provided to the industry. For example, the standardized filter cartridge geometry may not be entirely sufficient for use in large filtration installations and/or to filter heavily contaminated fluids. While higher capacity filter cartridge geometries can be envisioned, their commercial acceptance is limited due to the costs associated with the replacement of existing filter cartridge housings designed for use with the conventional standardized filter cartridge geometries.  
           [0003]    Bag filters have, to some extent, solved some of the issues presented by filter cartridges with respect to more rigid filter cartridges. In this regard, a bag filter is essentially a closed-end pouch made of a filter material (e.g., a felt or nonwoven material). The bags are installed in perforated rigid metal baskets which serve to support the bag against the inlet pressure of the fluid to be filtered. In this regard, the bag filters are positioned such that the fluid flows into the open top of the bag and then through the bag wall (i.e., an inside-out flow path) and the outer supporting metal basket. Some advantages of employing bag filters is that the bags offer ease of installation and all the contaminant is trapped inside the bag allowing for ease of disposal. Disadvantages of bag filters include their relatively low surface area and limited types of filter media (e.g., most commercial bag filters are formed of a needle punched felt material).  
           [0004]    Most forms of conventional rigid metal baskets in which bag filters are employed include an open top having a seal flange for dependently supporting the bag filter, a generally cylindrical perforated side wall portion and a conical or rounded bottom wall region. The seal flange is essentially standardized among bag filter manufactures, but the axial length of the side wall portion varies from one manufacturer to another. Since the fluid flow though conventional bag filter systems is inside-out, any commercially successful more rigid disposable filter cartridge that is provided as a high filter capacity replacement for conventional bag filters must have its bottom supported physically by the surrounding perforated side wall of the metal basket. However, since the effective axial length of the cylindrical perforated side wall can, and often does, vary from one manufacturer to the next, no currently available cartridge design can universally be supplied to the entire market.  
           [0005]    Therefore, what has been needed in this art are filter cartridges that are suitable for use with standardized bag filter housings (more particularly, with the varying length support baskets thereof), yet be capable of providing enhanced fluid filtration capabilities as compared to conventional bag filters. The present invention is directed towards fulfilling such needs.  
           [0006]    Broadly, the present invention is embodied in length-adjustable filter cartridges. In especially preferred forms, the present invention is embodied in filter cartridges having a generally cylindrical filter body which includes a fluid-filtration media, and at least one length-adjustable end cap attached to an end of the filter body. The length-adjustable end cap most preferably includes an annular stationary ring member which is attached to one end of the filter body, and a moveable connection member slideably received within said annular stationary ring member so as to be moveable longitudinally relative thereto. A seal is formed between the stationary ring member and the moveable connection member so as to seal against fluid leakage yet permit relative axial movement (length adjustment) therebetween.  
           [0007]    In use, the filter cartridges of the present invention may be adapted to fit conventional standardized bag filter cartridge housings even though the physical size and/or geometries of the metal support basket thereof is non-standard. That is, a filter cartridge having the length-adjustable end cap of the present invention may be positioned within a standard sized bag filter cartridge housing, whereby the length-adjustable end cap may be longitudinally moved until the filter cartridge length corresponds substantially to that of the surrounding metal support basket in which it is placed. As such, the bottom end cap of the filter cartridge is ensured to be supported by the metal basket to prevent it from rupturing during normal use.  
           [0008]    These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.  
       
    
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS  
       [0009]    Reference will hereinafter be made to the accompanying drawings, wherein like reference numerals throughout the various FIGURES denote like structural elements, and wherein;  
         [0010]    [0010]FIG. 1 is a cross-sectional view of a conventional bag filter housing system in which an exemplary length-adjustable filter cartridge in accordance with the present invention is positioned;  
         [0011]    [0011]FIG. 2 is an elevational view of an exemplary length-adjustable filter cartridge embodying the present invention;  
         [0012]    [0012]FIG. 3 is an enlarged cross-sectional view taken along line  8 - 8  in FIG. 1 which more specifically depicts the length-adjustable top end cap associated with the filter cartridge depicted in FIG. 8; and  
         [0013]    [0013]FIG. 4 is an enlarged cross-sectional view of another top end cap that may be associated with another exemplary embodiment of the length-adjustable filter cartridge in accordance with the present invention;  
         [0014]    [0014]FIG. 5 is a side elevational view of another exemplary embodiment of a length-adjustable filter cartridge in accordance with the present invention;  
         [0015]    [0015]FIG. 6 is a top end perspective view thereof;  
         [0016]    [0016]FIG. 7 is a bottom end perspective view thereof;  
         [0017]    [0017]FIG. 8 is a cross-sectional elevational view of the filter cartridge depicted in FIG. 5, as taken along line  8 - 8  therein;  
         [0018]    [0018]FIG. 9 is a schematic representation of the pressure conditions exerted on the top end cap of the filter cartridge embodiment depicted in FIGS.  5 - 8 ; and  
         [0019]    [0019]FIG. 10 is an exemplary graphical plot which depicts the pressure conditions exerted on the top end cap of the filter cartridge embodiment depicted in FIGS.  1 - 5 ; 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    Accompanying FIG. 1 depicts a cross-sectional view of a conventional bag filter housing system  10  in which an exemplary length-adjustable filter cartridge  100  (see FIGS.  2 - 3 , for example) in accordance with the present invention is positioned. In this regard, the housing system  10  includes a generally cylindrical housing wall  10 - 1  having an annular support flange  10 - 2  which establishes upper and lower interior chambers  10 - 3 ,  10 - 4 , respectively. The upper and lower interior chambers  10 - 3 ,  10 - 4  communicate with inlet and discharge ports  10 - 5 ,  10 - 6 , respectively. Fluid to be filtered will thus enter the housing  10  at a pressure P 1  via the port  10 - 5 , pass through the filter media of the filter cartridge  100  so as to remove particulate matter therefrom, and then be discharged from the housing  10  at a pressure P 2  less than P 1  via the port  10 - 6 .  
         [0021]    The top of the housing  10  is closed by a lid  10 - 7  by means of conventional swing bolt assemblies  10 - 8 . Removal of the lid  10 - 7  will thus allow access to the interior of the housing  10  so that the filter cartridge  100  may be replaced periodically. It will be observed in this regard that the top annular seal  114  of the cartridge  100  is dependently supported by the annular support flange  10 - 2  of the housing  10 . Also, it will be observed that the upper rim of the internal rigid perforated support basket  10 - 9  is dependently supported by the support flange  10 - 2  of the housing  10 . Thus, since the inlet pressure P 1  of the fluid entering the upper interior chamber  10 - 3  is greater than the discharge pressure P 2  of the filtered fluid being discharged from the lower interior chamber  10 - 4 , the seal  14  of the filter cartridge  121  will be pressed into sealing contact with the support flange  10 - 2  and the upper rim of the support basket  10 - 9  thereby preventing fluid leakage therearound.  
         [0022]    Accompanying FIGS. 2 and 3 depict one preferred embodiment of a disposable filter cartridge  100  in accordance with the present invention. In this regard, the filter cartridge  100  is most preferably comprised of a generally cylindrical filter body  112  provided with suitable filter media  114  defining an interior space  116 . A bottom end cap  118  is physically attached to (e.g., by heat-welding, adhesives, solvent bonding or like techniques) the filter media  114  at the lower end of the filter cartridge body  112  so as to close the interior space  116  at that end. A length-adjustable end cap assembly  120  is physically attached to the opposite end of the filter body  112  by similar means.  
         [0023]    As is perhaps more clearly seen in FIG. 3, the bottom end cap  118  most preferably includes an arcuate central wall  118 - 1  which protrudes into the interior cartridge space  116  and a series of integral radial support ribs  20 - 2 . The arcuate central wall  118 - 1  and support rigs  118 - 2  collectively serve to enhance the structural integrity of the filter cartridge body  112  at its lower end so that it may withstand the inlet pressures P 1  associated with the inlet fluid entering the interior cartridge space  116 .  
         [0024]    The length-adjustable top end cap assembly  120  includes an annular stationary ring member  122  which is physically attached (e.g., by heat welding, adhesives, solvent bonding or like techniques) to the end surface of the filter media  114 . A seal ring  124  is fixed to an inner annular region of the stationary ring member  122  so as to be coaxially positioned with respect to the inner space  116 .  
         [0025]    A moveable connection member  126  includes a lower cylindrical neck portion  128  and an upper annular flange portion  130 . Most preferably, the neck and flange portions  128 ,  130  are formed as a unitary (one-piece) structure and provided with cross-supports  131  so as to increase the structural integrity of the same while yet retaining an opening which communicates with the interior space  116  of the filter cartridge  100 . The neck portion  128  is received within, and is slideable with respect to, the annular stationary ring member  122  as shown by the arrows A I  in FIGS. 2 and 3 in sealing contact with the seal ring  124 . Thus, the entire connection member  126  is slideable along the longitudinal axis of the filter cartridge  100  so that the flange portion  130  thereof may be moved towards and away from the stationary ring member  122  (i.e., as shown by the phantom lines in FIG. 3). During such sliding movement, however, a fluid seal is maintained between the exterior surface of the neck portion  126  and the seal ring  124 .  
         [0026]    An annular stop surface  132  protruding radially outwardly from the terminal end of the neck portion  128  so as to provide limit to the movement of the moveable member  126  and thereby define a maximum separation distance between the flange portion  130  and the stationary ring member  122  (i.e., as shown by the solid lines in FIG. 3). Thus, upon contact between the annular stop surface  132  and the seal ring  124 , a maximum longitudinal dimension of the filter cartridge  100  will ensue. Conversely, upon contact between the flange portion  130  and the stationary ring  122 , a minimum longitudinal dimension of the filter cartridge will ensure. As a result, the embodiment of the filter cartridge  100  as shown in FIGS. 3 and 4 may be adapted to fit conventional support baskets  10 - 9  provided within typical bag filter housing systems  10  as described previously. That is, the filter cartridge  100  having the length-adjustable end cap  120  as described above, may be positioned within a perforated support basket  10 - 9  of a housing system  10 , whereby the length-adjustable end cap may be longitudinally moved until the lower end cap  118  thereof is physically supported by the basket  10 - 9  in a manner described previously.  
         [0027]    Yet another possible length-adjustable filter cartridge  200  is depicted in accompanying FIG. 4. In this regard, the filter cartridge assembly  200  is provided with a length adjustable top end cap assembly  220 . The filter cartridge  200  may be provided with the same bottom end cap  118  as described previously with respect to FIGS. 2 and 3.  
         [0028]    The top end cap assembly  220  most preferably includes a cylindrical stationary ring member  222  which extends upwardly from an annular base member  224 . The base member  224  is itself physically attached (e.g., by heat welding, adhesives, solvent bonding or like techniques) to the end surface of the filter media  214 . Integral cross-support rods  225  are provided so as to provide internal support for the base  224 , yet allow essentially unimpeded fluid flow therethrough.  
         [0029]    A moveable connection member  226  includes a lower cylindrical neck portion  228  and an upper annular flange portion  230 . Most preferably, the neck and flange portions  228 ,  230  are formed as a unitary (one-piece) structure so as to increase the structural integrity of the same. The neck portion  228  is received within, and is slideable with respect to, the annular stationary ring member  222 . In this regard, the upper lip  240  of the stationary ring  222  is outwardly biased so as to form a flexible fluid-tight seal with the neck portion  228 .  
         [0030]    Accompanying FIGS.  5 - 8  depict another preferred embodiment of a length-adjustable filter cartridge  300  that may be employed in the exemplary housing system  10  described above with reference to FIG. 1. Specifically, as shown therein, the filter cartridge  300  is generally comprised of a generally cylindrical filter body  312  provided with suitable filter media  314  defining an interior space  316  (see FIG. 8).  
         [0031]    A length-adjustable end cap assembly  320  is physically attached to the filter media  314  at the upper end of the cylindrical filter body  316 . A bottom end cap  118  may be provided with cartridge  300  in a manner similar to that described above with respect to FIGS.  2 - 3 .  
         [0032]    The length-adjustable end cap assembly  320  includes a generally cylindrically configured stationary ring member  324  integrally joined to and extending upwardly from an annular base  326 . Most preferably, the stationary ring member  324  and annular base  326  are formed as a unitary (one-piece) structure with one another. Integral cross-support rods  326 - 1  are provided so as to provide internal support for the base  326 , yet allow essentially unimpeded fluid flow therethrough. The ring member  324  is most preferably supported by radially extending buttresses  328  integrally jointed to the ring member  324  and the base member  326 .  
         [0033]    A moveable connection member  330  is slideably and coaxially received within the stationary ring member  324  and includes a lower cylindrical neck portion  332  and an upper annular support flange portion  334  transversely oriented relative to the central axis of the neck portion  332  (and the filter body  312 ). An annular elastomeric seal element  334 - 1  (see FIG. 8) may positioned around the perimetrical edge of the support flange portion  334  so as to enhance its sealing functions. The neck portion  332  includes an annular recess which receives an O-ring seal  332 - 1  therein so as to provide sliding sealing contact with a facing interior cylindrical surface of the stationary ring member  324 . The moveable connection member  330  and the stationary ring member  324  are thus moveable axially relative to one another so that the effective axial length of the filter cartridge  300  may be varied between a lesser axial length (i.e., as shown in solid line in FIG. 8) and a greater axial length (i.e., as shown in phantom line in FIG. 8). As such, the bottom end cap  118  of the filter cartridge  300  can virtually be assured of being supported at the lower end of the rigid perforated basket  10 - 9  within the housing  10  as has been previously described.  
         [0034]    The relative position of the stationary ring member  324  as shown in FIGS.  5 - 8  provides essentially for a balanced pressure condition (i.e., as between the inlet and discharge fluid pressures P 1  and P 2 , respectively) to be exerted on the annular base member  26 . As a result of such a pressure balanced condition, there is less of a tendency for the base member to separate from the filter body  16  (as might tend to occur under relatively extremely high differential pressure (ΔP) conditions between the pressures P 1  and P 2  of the inlet and discharge fluids, respectively. Such pressure balancing is depicted schematically in FIG. 9 and graphically in FIG. 10.  
         [0035]    As is shown in FIG. 9, the inner annular segment  326  of the base member  326  is subjected to a greater pressure condition P 1  as compared to the outer annular segment  3260  of the base member  326  due to the pressure drop (ΔP) through the filtration media  314  of the filter body  312 . By positioning the stationary ring member  324  substantially midway along the radial dimension of the annular base member  326 , therefore, substantially equalized pressure conditions as between the inner and outer annular segments  326   i ,  326   o , respectively, can be achieved. This attribute of the present invention is shown graphically in FIG. 10 as substantially equal shaded areas between the P 1  and P 2  pressure conditions and the pressure drop curve ΔP. Since the shaded areas are substantially equal they substantially cancel each other, thereby resulting in an essentially balanced pressure condition to exist. As such, the filter cartridge  300  is especially usefully employed in those applications where relatively extremely high ΔP conditions are required, although it may likewise be used over virtually all other lesser ΔP conditions, if desired.  
         [0036]    Most preferably, the moveable connection members  126 ,  226  and  330  are provided as a component part of the filter cartridges  100 ,  200  and  300 , respectively, when the filter cartridges are supplied to the end user. As such, these connection members  126 ,  226  and  330  are most preferably made of a plastics material that may be recycled and/or otherwise disposed when the filter cartridge has been spent. However, it is entirely conceivable that the moveable connection members  126 ,  226  and  330  may be provided as a one-piece reusable component structure formed of a durable material (e.g., stainless steel). When provided as a reusable component, therefore, the connection members  126 ,  226  and  330  may thus be separated from a spent filter cartridge by the end user and reinserted into a fresh filter cartridge having the other structural components as described previously.  
         [0037]    Virtually any filtration media conventionally employed to filter fluids may be employed as the filtration media in the filter cartridges according to the present invention. Thus, for example, the filtration media may be comprised of a non-woven mass of melt-blown polymeric fibers formed, for example, from thermoplastic polymers, preferably polyolefins such as polypropylene, polyethylene and the like. Especially preferred filter media for filter cartridges are those as described more fully in commonly owned U.S. Pat. No. 5,591,335 and U.S. application Ser. No. 09/358,886 filed on Jul. 22, 1999 (now U.S. Pat. No. ______), the entire content of each being expressly incorporated hereinto by reference. Alternatively (or additionally) the filter media may be comprised of pleated sheets of non-woven or woven filter materials which are, in and of themselves, highly conventional in the fluid filtration art.  
         [0038]    Therefore, while the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.