Abstract:
Each cap of a pair of end caps mounted on opposed ends of a conventional radial flow cylindrical filter element of a filter cartridge includes a circular sleeve extending axially from the filter element for penetrably receiving a supporting stud and for maintaining an O-ring seal therebetween. The area of one of the end caps radially outwardly of its circular sleeve is greater than the corresponding area of the other end cap to cause fluid to be filtered to pressure bias the filter cartridge toward the other end cap and to positionally retain the filter cartridge within its housing. A positioning member extending into the filter element from one of the end caps receives and stabilizes sleeve for a u/v lamp disposed within the filter element to kill any microorganisms present and to oxidize any organic matter subjected to the emitted ultra-violent radiation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 09/706,964 filed on Nov. 6, 2000, now abandoned. In addition, this application claims priority to the subject matter disclosed in a U.S. provisional patent application entitled “EK FILTER” filed Jan. 12, 2000 and assigned Ser. No. 60/175,797 directed to an invention made by the present inventors. 
     The present application describes apparatus related to an usable with the inventions described in U.S. Pat. No. 5,266,215 issued Nov. 30, 1993 and U.S. Pat. No. 5,540,848 issued Jul. 30, 1996, and U.S. Pat. No. 5,709,799 issued Jan. 20, 1998 which patents are assigned to the present Assignee and incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to mountings for filter cartridges and, more particularly, to seals for sealing opposed ends of a filter element of a filter cartridge that accommodate for axial movement of the filter cartridge without compromising the seals. 
     2. Description of Related Art 
     Filter cartridges have been in use for decades to filter with a cylindrical filter element a fluid flowing radially therethrough. Usually, the fluid flow through the filter element is from its external surface to its internal surface. Thereafter, the fluid is exhausted axially from one end. Each opposed end of the filter element include a compressible annular cap mating with an annular knife edge of a housing. Each annular knife edge forms a seal with the respective end cap as a function of the compression therebetween imposed by the housing and the elasticity and resiliency of the filter element. Over a period of time, the end caps tend to acquire a set and the pressure against the corresponding annular knife edge diminishes to the point where the seal is compromised. 
     The resiliency and elasticity of the filter element providing a bias against the opposed annular knife edges diminish over a period of time or through deterioration caused at least in part by interaction with the fluid being filtered. The loss of resiliency and elasticity compromises the bias force against the opposed annular knife edges. The pressure differential on opposed sides of each annular knife edge increases as the filter element becomes more and more clogged. Such increase in pressure differential, coupled with the compromised sealing bias, will cause leakage. The resulting leakage will contaminate the previously filtered fluid with potentially disastrous results. 
     The previously known solution to extend the filtering life of a filter cartridge has been that of increasing the pressure bias of the annular knife edges on the opposed ends of the filter element. At best, this solution increases the life of the sealing function of the annular knife edges for a limited period of time. 
     Another problem with conventional filter cartridges is that tolerances of filter cartridges from different manufacturers are not the same. Thus, a presumably standard sized filter cartridge may not fit a housing for such filter cartridge sufficiently well to maintain a seal for a reasonable period of time before being affected by the above described modes of deterioration. 
     SUMMARY OF THE INVENTION 
     A housing for a filter cartridge includes a cylinder having a closed bottom for receiving the filter cartridge and a top threadedly engageable with the open end of the cylinder to close the housing. An inlet proximate to the bottom of the cylinder introduces fluid to be filtered to the exterior surface of the filter cartridge and an outlet in axial alignment with the filter cartridge extends through the top for discharge of the filtered fluid. An end cap on the filter cartridge includes a circular sleeve for receiving a stud extending inwardly from the bottom of the cylinder and an O-ring disposed therebetween serves as a seal to prevent inflow of unfiltered fluid into the axial center of the filter cartridge. A similar end cap is disposed at the other end of the filter cartridge, its circular sleeve circumscribes a hollow stud defining the outlet and an O-ring disposed between the stud and the circular sleeve prevents mixing of the filtered and unfiltered fluids. The use of the O-rings between the respective circular sleeves and studs accommodates axial translation of the filter cartridge without compromising the respective seals. By having the surface area radially external of the circular sleeve of one of the end caps greater than that of the other end cap provides a pressure bias induced by the inflowing unfiltered fluid to urge the filter cartridge in the direction of the end cap with the lesser area subject to the inflowing unfiltered fluid. Upon axially stacking two or more filter cartridges, an O-ring is placed intermediate overlapping circular sleeves of adjacent cartridges to maintain the seal at the junction of the filter cartridges to preclude mixing of the filtered and unfiltered fluids. 
     It is therefore a primary object of the present invention to provide seals at opposed ends of a filter cartridge that do not depend upon resiliency and elasticity of the filter element. 
     Another object of the present invention is to provide seals for a filter cartridge that accommodate axially translation of the filter cartridge without compromising the respective seals. 
     Yet another object of the present invention is to provide sealing elements at opposed ends of a filter cartridge to permit use of a single or axially stacked filter cartridges within a housing without compromising the seals necessary to prevent mixing of filtered and unfiltered fluids flowing through the housing. 
     A further object of the present invention is to provide a housing for a filter cartridge which does not compress the filter cartridge to establish seals to control flow of the fluid to be filtered therein. 
     A yet further object of the present invention is to provide an end cap for a filter cartridge which positionally maintains an ultra-violet lamp assembly in fixed position therewithin. 
     A still further object of the present invention is to provide an axially translatable filter cartridge disposed in sealed relationship within a housing for supporting an ultra-violet lamp assembly therewithin. 
     A still further object of the present invention is to bias a filter cartridge toward one end of an enclosing housing as a function of the pressure of the inflowing fluid to be filtered. 
     A still further object of the present invention is to provide an inexpensive filter cartridge and housing having seals not affected by deterioration of the resiliency and elasticity of the filter element. 
     A still further object of the present invention is to provide a method for sealing a filter cartridge within a housing. 
     The and other objects of the present invention will become apparent to those skilled in the art as the description thereof proceeds. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be described with greater specificity and clarity with reference to the following drawings, in which: 
     FIG. 1 illustrates a cross section of a conventional filter cartridge, housing and attendant seals used in the prior art; 
     FIG. 2 illustrates a cross section of a conventional prior art filter cartridge and housing for supporting a UV lamp assembly within the filter cartridge; 
     FIG. 3 illustrates a cross section view of a filter cartridge and housing incorporating the present invention; 
     FIG. 4 illustrates translation and bias of a filter cartridge in response to pressure differentials induced by a fluid to be filtered; 
     FIG. 5 illustrates axially stacked filter cartridges within a housing; 
     FIG. 6 is a plan view of a bottom end cap; 
     FIG. 7 is a cross sectional view taken along lines  7 — 7 , as shown in FIG. 6; 
     FIG. 8 is a plan view of a top end cap; and 
     FIG. 9 is a cross sectional view taken along lines  9 — 9 , as shown in FIG.  8 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a conventional prior art filter cartridge  10  mounted within a representative housing  12 . The filter cartridge includes a cylindrical filter element  14  having annular end caps  16 ,  18 . Usually, these end caps are identical and each of the end caps is formed of a rubber-like resilient material. Housing  12  includes an inlet  30  for introducing a fluid to be filtered about the external surface of the filter cartridge. As represented by arrows  32 , the fluid to be filtered flows through filter element  14  into an axial cavity  20  within the filter cartridge. The filtered fluid flows through the axial cavity  20 , as represented by arrows  34 , and through outlet  36 , as represented by arrow  38 . An annular knife edge  40  is formed on bottom  42  of housing  12  to compressively engage a corresponding surface of end cap  16 . Upon such engagement, a seal is formed therebetween to prevent flow of unfiltered fluid from inlet  30  therebetween into axial cavity  20 . A similar annular knife edge  44  extends downwardly from top  46  of housing  12  to compressively engage end cap  18 . Upon such engagement, a seal is established to prevent flow past the end cap of unfiltered fluid into axial cavity  20 . An annular space  48  is disposed about filter cartridge  10  and the corresponding wall of housing  12  to distribute the inflowing unfiltered fluid along the length of the external surface of the filter cartridge. Top  46  may be threadedly engaged with the rest of housing,  12 , as illustrated. An O-ring  50 , or the like, may be used to effect a seal between the top and the housing. 
     The integrity of the seal at each of end caps  16  and  18  is a function of the degree to which annular knife edges  40  and  44  compress the corresponding end cap. Initially, such seal is usually very effective. This seal depends upon several variables: the resiliency of the end caps to maintain compressive engagement with the corresponding annular knife edge, the resiliency of filter element  14  to bias the end caps against their respective annular knife edges, and, the properties of the fluid being filtered to induce deterioration of the resilience of the filter cartridge components. 
     FIG. 2 illustrates a filter cartridge  10  and housing  12  similar to that shown in FIG.  1  and representative of prior art embodiments. That is, it includes annular knife edges  40 ,  44  sealingly cooperating with annular end caps  16 ,  18 . In some applications, an ultra-violet lamp is disposed within the filter cartridge to irradiate with ultra-violet radiation filtered fluid flowing into axial cavity  20 . To protect the ultra-violet lamp, a sleeve  60  is disposed within axial cavity  20  in general radial alignment with filter cartridge  10 . This sleeve houses the ultra-violet lamp and may be made of quartz or similar material transparent to ultra-violet radiation. An annular spacer  62 , or the like, may be employed to maintain the displacement between sleeve and the filter cartridge. Necessarily, the sleeve is sealed by O-ring  64  or the like mounted in annular groove  66  in bottom  42  of housing  12 . Usually, no support is provided between sleeve  60  and the interior surface of the filter cartridge. The outflow of the filtered fluid, as represented by arrows  68 , occurs intermediate sleeve  60  and the adjacent surface of the filter cartridge. 
     Referring to FIG. 3, there is illustrated a filter cartridge  70  and housing  72  constructed in accordance with the present invention. The filter cartridge includes a filter element  74  of a hollow cylindrical shape and having a pair of annular end caps  76 ,  78 ; reference is also made to FIGS. 6,  7 ,  8  and  9  illustrating the end caps. End cap  76  includes a rim  80  for encircling the filter element, which rim extends from an annular flange  82 . The flange may include ribs  84  or other projections for engaging the material of filter element  74  to retain the end cap in place. A circular sleeve  86  extends from annular flange  82  to define a cylindrical space therewithin. End cap  78  includes the same elements as end cap  76 . However, the main difference between the two end caps is that circular sleeve  94  of end cap  78  is of greater diameter than that of circular sleeve  86  of end cap  76 . Thereby, the amount of surface area of annular flange  82  radially external to circular sleeve  86  is less for end cap  78  than it is for end cap  76 . 
     Housing  72  includes a cylinder  96  defining a compartment  98  for receiving filter cartridge  70 . It also includes an inlet  100  for introducing fluid to be filtered. A circular in cross section support or stud  102  extends upwardly from bottom  104  of cylinder  96  to penetrably engage aperture  106  in annular flange  82 . As shown in FIG. 3, the diameter of circular sleeve  86  of end cap  76  is greater than the diameter of stud  102 . An O-ring  108  is disposed about stud  102 . Circular sleeve  86  encircles and sealingly engages O-ring  108  to effect a seal between end cap  76  and stud  102 . As shown in FIGS. 6 and 7, circular sleeve  86  may be segmented with segment  87  extending radially inwardly to retain O-ring  108  within the circular sleeve. By inspection, it will become evident that filter cartridge  70  may translate along its axis of rotation to some extent and O-ring  108  will accommodate such translation without compromising the seal between the circular sleeve and the stud. The extent of translation possible is, of course, a function of the width of circular sleeve  86 , the height of stud  102  and the relative position of end cap  76  with the stud. 
     Top  110  is threadedly engaged with cylinder  96  by threads  112  to secure the top to the cylinder and retain filter cartridge  70  therebetween. The junction between the top and the cylinder is sealed by O-ring  114  to prevent leakage through the junction. Top  110  includes a circular stud  116  extending downwardly into the space defined by circular sleeve  94  of end cap  78 . The diameter of stud  116  is less than the internal diameter of circular sleeve  94  to permit placement of an O-ring  118  therebetween and effect a seal. An outlet  120  is disposed in top  110  to accommodate outflow of filtered fluid, as represented by arrow  130 . 
     A fluid to be filtered is introduce through filter  100  and flows into annular space  122  disposed between cylinder  96  and the external surface of filter element  74 . The fluid to be filtered then flows through the filter element, as depicted by arrows  124 . The filtered fluid entering axial space  126  flows toward outlet  120 , as depicted by arrows  128  and through the outlet, as depicted by arrow  130 . 
     To accommodate uses wherein an ultra-violet lamp is disposed within filter cartridge  70  to irradiate and kill microorganisms in the fluid flowing out of filter element  74  and to oxidize any organic matter that may be present, a positioning member  140  may be incorporated in end cap  78 . The positioning member extends downwardly within cylindrical space  142  interior of filter element  74 . It includes a circular shroud  144  that may support a plurality of radially inwardly extending ribs  146 . These ribs, or the interior surface of the shroud, may be canted inwardly toward the upper end, as illustrated. An aperture  148  is centrally disposed within end cap  78  internal of the shroud to accommodate flow of the fluid through the shroud and into outlet  120 . 
     FIG. 4 illustrates a filter cartridge  70  and housing  72  as shown in FIG. 3 with the addition of a sleeve  150  extending upwardly from bottom  104  of the housing. The sleeve is of ultra-violet transmissive materials, such as quartz. An ultra-violet lamp is mounted interior of the sleeve to irradiate the water flowing out of filter element  74  into annular space  152  intermediate the filter element and sleeve  150 . The upper end of the sleeve is rounded, as illustrated, and nests within shroud  140  against ribs  146 , which ribs help stabilize the sleeve within the housing. Circular sleeve  86  of end cap  76  extends about sleeve  150  in spaced relationship therewith to accommodate O-ring  108  placed therebetween to form an effective seal to prevent unfiltered fluid from entering annular space  152 . Thus, sleeve  150  acts in the manner of a support for the filter cartridge. As discussed above, the area of annular flange  82  is Greater than the area of annular flange  90  of end cap  78 . Even though the pressure of the unfiltered fluid acting upon each of annular flanges  82 ,  90  is essentially the same, the force acting upon end cap  76  is greater than the force acting upon end cap  78  due to the differences in area. Such greater force acting upon end cap  78  will urge filter cartridge  70  along sleeve  152  toward top  110 , as depicted by arrows  154 . This force positionally biases the filter cartridge toward top  110  and will result in maintaining the integrity of the seal provided by O-ring  118  intermediate circular sleeve  94  and stud  116 . That is, the seal attendant top  110  is maintained both statically and dynamically. 
     Referring to FIG. 5, there is shown a further embodiment of the present invention wherein multiple filter cartridges are stacked end to end. Housing  160  is formed of cylinder  162  and top  164  secured to the cylinder in the manner described above. Cylinder  162  is of sufficient length to accommodate two or more filter cartridges. In the embodiment illustrated, two filtered cartridges ( 70 A,  70 B) are mounted end to end within housing  160 . End cap  76  of lower filter cartridge  70 A is mounted on stud  102  of bottom  104 , as described above. Similarly, end cap  78  of the upper filter cartridge  70 B is mounted upon stud  116  of top  164 , as described above. End cap  78  at the upper end of lower filter cartridge  70 A includes a circular sleeve  94  which is of greater diameter than circular sleeve  86  extending from end cap  76  located at the bottom of the upper filter cartridge  70 B. The annular space between circular sleeves  86  and  94  is filled with an O-ring  166  to effect a seal therebetween. Thereby, the unfiltered fluid entering through inlet  100  is precluded from flowing into cylindrical space  168  within each of filter cartridges  70 A,  70 B. Flow through circular space  168  into outlet  120  is accommodated by aperture  148  in end cap  76  of lower filter cartridge  70 A, aperture  106  in end cap  76  of upper filter cartridge  70 B and aperture  148  in end cap  78  of the upper filter cartridge. As discussed above, any contraction or expansion of the filter elements of either or both of filter cartridges  70 A,  70 B after a period of use may result in axial displacement of the circular sleeves relative to one another or an circled stud. Since an intervening O-ring may roll or slide to accommodate such displacement, the sealing effect of the O-rings is not compromised. 
     While the invention has been described with reference to several particular embodiments thereof, those skilled in the art will be able to make the various modifications to the described embodiments of the invention without departing from the true spirit and scope of the invention. It is intended that all combinations of elements and steps which perform substantially the same function in substantially the same way to achieve the same result are within the scope of the invention.