Abstract:
The present disclosure pertains to a fluid filter having integral attachment means which may take the form of a threaded portion of a filter cartridge. The threaded portion threadably interacts with a complementary threaded portion of a filter mounting to retain the filter cartridge to the filter mounting. The disclosure also pertains to a fluid filter having a cartridge made from two plastic shells welded together. The disclosure also pertains to a fluid filter with filter media positioned within a filter cartridge by an end cap with extending ribs welded to one of the two shells which compose the filter cartridge.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention generally relates to a fluid filter and more particularly relates to housings, mounting systems and/or water indication components for filters. 
       BACKGROUND OF THE INVENTION 
       [0002]    Fluid filters and fuel filter mounting configurations are well known in the art as is exemplified by U.S. Pat. Nos. 5,203,994 and 6,187,188 assigned to Stanadyne Automotive Corp., the disclosures of which are hereby incorporated by reference in their entireties. Conventionally, these types of filter cartridges have employed a housing composed of two metal shells connected together by an outer roll seam. As shown in the &#39;994 patent, a collar retention system may be employed to grab and retain the roll seam and thereby mount the filter cartridge to the base. As shown in the &#39;188, retention tabs may be deformed into the roll seam to provide mounting structure that may be installed into channel retaining grooves integrally formed on an inner surface of the mounting base/filter head. Improvements over the state of the art are disclosed herein. 
       BRIEF SUMMARY OF THE INVENTION 
       [0003]    There are multiple inventive aspects to the present disclosure which are separately claimed for independent and separate protection, but that may also have synergistic effects as combined. 
         [0004]    A first inventive aspect is directed toward a transparent portion of the filter cartridge which can void the need for a separate water collection bowl in the case of a fuel filter system, for example. According to this aspect, a filter cartridge includes a housing having upper and lower shells connected together to define an internal cavity. The filter media is arranged in the internal cavity to filter fluid passing through the filter media between an inlet and an outlet. The filter media separates water from fluid when fluid is passed therethrough. The lower shell is at least partially transparent for indicating water in the internal cavity. Additionally a drain valve on the housing is adapted to be opened for draining water from the internal chamber. 
         [0005]    A second inventive aspect is directed toward a certain filter cartridge in which part of the cartridge is reusable and another part is disposable. According to this inventive aspect, a filter cartridge includes two shells forming a housing in which each shell has an end wall and an annular wall that are connected. An opening is provided in one of the walls for providing for fluid communication. A ring of filter media is sealingly bonded to the upper shell and arranged to filter fluid within the housing. Further, the lower shell forms a mounting bowl that is reusable such that the upper shell is releasably connected to the lower shell such that the upper shell and filter media are removable and disposable while the mounting bowl can be reusable. 
         [0006]    A third inventive aspect is directed toward a filter cartridge which has integrally molded retention tabs for use, for example, in attachment to a mounting base of an engine fuel circuit or other fluid circuit. According to this aspect, a filter cartridge includes upper and lower shells forming a housing with at least one opening provided for fluid communication and filter media arranged in the housing to filter fluid. The lower annular wall of the lower shell extends over the upper end wall of the upper shell to provide a skirt with the skirt of the lower annular wall defining a plurality of discrete retention tabs integrally molded into the skirt at different locations. According to this aspect, it is alternatively contemplated to provide the retention tabs on the upper shell section instead. 
         [0007]    A fourth inventive feature is directed towards a new flow reversing end cap that is integrally joined to the housing. A filter cartridge, according to this aspect, includes upper and lower shells which define a housing with a first opening providing for fluid communication and a ring of filter media arranged in the housing. A flow reversing end cap is arranged in the housing and sealingly attached to one end of the filter media. The flow reversing end cap also defines another opening concentric with the opening on the housing with seal members disposed on each of the openings. Another end cap is attached to the other end of the filter media. Ribs are disposed between the flow reversing end cap and the housing and integrally join the flow reversing end cap and the housing. 
         [0008]    A fifth inventive aspect pertains to a new filter cartridge construction including upper and lower shells forming a housing including at least one opening and that the housing for providing fluid communication and filter media permanently and irremovably joined to the upper shell section and arranged in the housing to filter fluid. Further, the construction includes an extension of the lower annular wall of the lower shell that extends over and around the upper shell to provide a skirt. Further, the skirt of the lower annular wall defines retention structure adapted for releasable attachment of the filter cartridge (e.g. retention tabs, for example or a readily extending lip that would provide a shoulder for example, or other appropriate structure adapted to retain the filter cartridge to a mounting base). 
         [0009]    Other aspects, objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
           [0011]      FIG. 1  is a cross-section of a filter in accordance with an embodiment of the present invention, 
           [0012]      FIG. 2  is an enlarged view of  FIG. 1 , taken about circle  3 ; 
           [0013]      FIG. 3  is a cross-section of a filter in accordance with another embodiment of the present invention, the cross-section being the same cross-section as in  FIG. 1 ; 
           [0014]      FIG. 4  is an enlarged view of  FIG. 3 , take about circle  5 ; 
           [0015]      FIG. 5  is an end view of the filter shown in  FIG. 7 ; 
           [0016]      FIG. 6  is an isometric view of the filter shown in  FIG. 7 . 
           [0017]      FIG. 7  is a cross-section of a filter in accordance with another embodiment of the present invention, the cross-section being the same cross-section as in  FIG. 1 ; 
           [0018]      FIG. 8  is a map view of a typical filter mounting to which a filter as shown in  FIG. 7  would attach; 
           [0019]      FIG. 9  is a cross-section of a filter mounting as shown in  FIG. 8 , the cross-section being taken about a diameter of the filter mounting; 
           [0020]      FIG. 10  is a cross-section of a filter in accordance with another embodiment of the present invention, the cross-section being the same cross-section as in  FIG. 1 ; 
           [0021]      FIG. 11  is an enlarged view of  FIG. 10 , taken about circle  9 ; 
           [0022]      FIG. 12  is a cross-section of a filter in accordance with another embodiment of the present invention, the cross-section being the same cross-section as in  FIG. 1 . 
           [0023]      FIG. 13  is an isometric view of the upper reverse flow end cap used in the embodiment of  FIG. 12 . 
           [0024]      FIG. 14 , is a partially cut away view of the mounting interface between the upper shell and the reverse flow end cap of  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]      FIG. 1  illustrates various structural and operational aspects of an embodiment of a filter cartridge  101  in accordance with the teachings of the present invention. The filter cartridge  101  filters impurities from fluids, and particularly liquids such as fuels, lubricants, coolants, and the like. The filter cartridge  101  generally includes a cylindrical filter housing  105  forming a central cavity  107 , a tubular ring of filter media  106  housed in the central cavity  107  and attachment structure on the housing  105  in the form of a threaded portion  117  for attaching the filter cartridge  101  to a filter mounting  109  having a cooperating threaded portion  124 . 
         [0026]    As illustrated in  FIG. 1 , the cylindrical filter housing  105  includes two cup-shaped shells including a lower shell  102  connected to an upper shell  103 . The lower and upper shells  102 ,  103  combine to generally define an internal central cavity  107 . The lower shell  102  forms a bowl including a domed end wall  118  that transitions into a generally cylindrical sidewall  119  which transitions into an axially projecting annular flange  125  with radius R 1  greater than the radius R 2  of the sidewall  119 . The annular flange  125  defines an open end  122  of the lower shell  102  opposite a generally closed end formed by end wall  118 . 
         [0027]    The lower shell  102  is preferably a plastic molded component and may comprise multiple parts connected together, but alternatively can be a aluminum cast component part and/or a single component, and/or may otherwise be formed from other appropriate materials. As illustrated, the lower shell  102  is formed from molded plastic. The end wall  118 , sidewall  119  and annular flange  125  may be unitarily molded as a unitary one piece construction. Alternatively, the end wall  118 , sidewall  119 , and annular flange  125  may be formed individually and then combined to form an integral piece. In such a configuration, the end wall  118  and sidewall  119  may be combined by chemically bonding, plastic welding, adhesive bonding, etc. As illustrated, the sidewall  119  and annular flange  125  are formed as one piece while the end wall  118  is individually formed and then connected to an end of sidewall  119  opposite annular flange  125 . 
         [0028]    This method of forming the lower shell  102  as individual components that are later combined may be beneficial when the sidewall  119  and end wall  118  are formed from differing materials. For example, it may be desired to have one of the end wall  118  or sidewall  119  formed from transparent material such as when the lower shell  102  forms a water collection bowl  110 . With transparent material, the operator may easily inspect the contents of the collection bowl  110  and use a drain valve  115  to drain separated material in the collection bowl  110 . Preferably, the entire lower shell  102  comprises transparent material so as to indicate the level of water contained in the bowl  110  when the filter is used in operation. 
         [0029]    The upper shell  103  includes a generally planar circular end wall  120  and a generally cylindrical sidewall  121 . The circular end wall  120  closes off the top end of the upper shell  103  (except for the central fluid port) and the cylindrical sidewall  121  provides an open end  123  of the upper shell  103 . The sidewall  121  projects axially away from end wall  120 . The upper shell  103  may be formed in a similar manner as the lower shell  102 . 
         [0030]    With additional reference to  FIG. 2 , an enlarged partial illustration of the connection between the upper and lower shells  102 ,  103  is illustrated. The sidewall  121  of the upper shell  103  includes circular connector portion  129  proximate the open end  123 , which includes a downward depending annular connector ring. The cylindrical filter housing  105  is formed by fitting the circular connector portion  129  of the upper shell  103  into a retainer in the form of a circular U-shaped groove  108  formed in the sidewall  119  of the lower shell  102 . The mounting portion  129  may be connected to the U-shaped groove  108  by welding as illustrated in  FIGS. 1 and 2  by plastic welds  104  including such welding techniques as induction welding, ultrasonic welding or spin welding. Alternatively, the lower and upper shells  102 ,  103  may be chemically or adhesively bonded to one another or otherwise mechanically secured to one another. In this embodiment, the two shells  102  and  103  are preferably permanently attached so as to prevent leak paths and such that the entire cartridge is disposable and replaceable. 
         [0031]    A circular receiving groove  128  is defined by and between the annular flange  125  of the lower shell  102  and the sidewall  121  of the upper shell  103 . The groove  128  provides clearance for mating with structure projecting from the corresponding mounting head  109 . The groove  128  also provides clearance for threaded portion  117  for mating with the threaded portion  124  of the filter mounting head  109  (also known as a mounting adaptor). 
         [0032]    The cylindrical filter housing  105  releasably attaches to the filter mounting head  109  using threaded portion  117  incorporated directly into the inner surface of the annular flange  125  of sidewall  119  of the lower shell  102 . This threaded portion  117  interacts with the threaded portion  124  of the filter mounting  109  to releasably threadably attach the filter cartridge  101  to the filter mounting head  109 . The threaded portion  124  of the filter mounting  109  interacts with the threaded structure  117  of the sidewall  119  within the cavity  128 . In the illustrated embodiment, the threads are molded directly into sidewall  119 , and particularly annular flange  125 , during manufacture of the lower shell  102 . 
         [0033]    Turning then to the filter media  106  in this exemplary embodiment, the filter media  106  is a tubular ring forming a center cavity  112  and extends from the upper shell axially through the central cavity  107  of the filter housing  105  to an end cap  116 . The filter media  106  may be any standard filter media including preferably pleated filter paper formed at least in part from cellulose material. In the disclosed fuel filter embodiment, the filter media  106  can be and is preferably of a known grade suitable for coalescing water and thereby preventing passage of water through the media and for separating particulates out of the fluid flow. The filter media thus can perform dual functions, water separation and particulate filtration. 
         [0034]    The filter media  106  is sealingly and permanently bonded to the upper shell  103  such as by plastisol or other adhesive or by directly embedding the upper end of the filter media into the plastic material of the upper shell. In this regard, the upper shell  103  may effectively serve dual roles as the upper end cap for the filter media in addition to working as part of the outer housing. The upper shell  103  includes a central circular opening  136  that can be bounded by a circular sealing grommet  138  to facilitate fluid flow into and out of the filter cartridge. The bottom end of the filter media  106  is sealingly and permanently bonded to a bottom end cap  116 , preferably with plastisol and/or in a similar manner to the upper shell. The bottom end cap  116  may be of two piece construction to include a tubular extension  140  having an opening fitted with a circular sealing grommet  142 . This above arrangement is particularly useful for a filter system in which the filter head includes two concentric fluid inlet and outlet pipes for fluid communication with the cartridge through the single opening  136 . However, other embodiments may include more than one opening with discrete separate external inlet and outlet ports. 
         [0035]    When mounted to a filter head as shown in  FIG. 1 , unfiltered fuel (e.g. from the fuel tank) flows into the filter cartridge through the inlet fuel passage  111  (e.g. the central concentric tube of the mounting head) and travels axially through the center cavity  112  of the filter media  106 . The inlet flow is connected through the tubular extension  140  to a bottom flow passage  113  formed in the bottom end cap  116 . Generally following fuel flow path  130 , the unfiltered fuel would then travel around the bottom end of the internal filter element to outer annular chamber  131  and then radially inward through the filter media  106  to a clean fluid chamber inside of the filter media  106 . As the fluid passes through the filter media  106 , impurities are filtered from the fuel. The now clean fuel can pass axially into the clean fuel outlet  114  of the filter mounting head  109  and thereby exit the filter cartridge  101  through external opening  136 . 
         [0036]    Preferably for fuel filtration applications, the filter media  106  is impermeable to water and when the dirty fuel passes through the filter media  106  water coalesces on outside of the filter media  106 . The coalesced water will drop down axially into the collection bowl  110 , integrally formed into the filter cartridge  101  at the end of the filter cartridge  101  opposite the filter mounting  109 . As indicated above, the collection bowl  110  may be transparent, allowing a user to inspect the quantity of water collected within the collection bowl  110 , and to determine whether the drain valve  115  needs to be opened to allow the collected water to drain through the drain valve  115  (also known as a “drain cock”) out of the collection bowl  110 . The drain valve  115  closes a drain port  144  at the bottom of the housing and can be manually opened (e.g. twisted/screwed) to facilitate water removal. 
         [0037]      FIGS. 3 and 4  illustrate a further embodiment of a filter cartridge much like the first embodiment except that the upper shell  203  is releasably attached to lower shell  202 . In this embodiment, the upper shell  203  is removable and disposable along with the filter media  204  carried thereby, while the lower shell  202  can provide a reusable collection bowl that may not need to be replaced at each maintenance interval (the drain cock carried thereby is also therefore reusable). Specifically, the filter media  204  can be permanently bonded to the upper shell  203  such as by plastisol or other suitable means as indicated for the first embodiment. The upper shell  203  forms both a part of the housing and the upper end cap of the filter media  204 . The lower end cap  210 , also permanently and sealingly bonded to the filter media  204  is disposable along therewith as well. 
         [0038]    To provide for this feature, a releasable connection  208  is provided that may include a snap fit, a screw interface or other releasable connection between the upper and lower shells  203  and  202 . Also the releasable connection  208  may more simply include a press fit or interference fit given the lower reusable shell  202  when mounted into engagement with the filter head sandwiches the upper shell  203  therebetween and may slightly axially compress the upper shell  203 . In this embodiment, the inner surface of the lower shell  202  configured to receive and engage a corresponding extending leg  207  of the U-shaped connector portion  229  of the upper shell  203 . An elastomeric sealing O-ring  209  positioned within an annular groove the U-shaped connector portion  229  and seals this connection to prevent leakage. Because the upper shell  203  is not permanently secured to lower shell  202 , this embodiment beneficially allows the lower part of the filter housing  205  formed by the lower and upper shells  202 ,  203  to potentially be reused. 
         [0039]    The first and second embodiments also can be used to modify existing commercially employed collar retention systems according to U.S. Pat. No. 5,203,994. Specifically, the retention collar of such systems can be thrown away or otherwise removed from use. Instead, the filter cartridges of the first two above embodiments can be threaded and mounted directly onto the filter head. As a result, an intervening separate structure is eliminated simplifying the existing configurations in the field. 
         [0040]      FIGS. 5 and 6  illustrate a further embodiment of a filter cartridge  301  in accordance with the teachings of the present invention that can be used with different filter head configurations (including collar retention systems such as shown in U.S. Pat. No. 5,203,994 or retention channel systems such as shown in U.S. Pat. No. 6,187,188). In this embodiment, the filter cartridge  301  includes a plurality of radially outward extending retention tabs  310 . More particularly, the lower shell  302  has three retention tabs  310  integrally formed into the outer surface of the lower shell  302  proximate open end  323  projecting radially outward. In a preferred embodiment, the retention tabs  310  are formed while molding the lower shell  302  and thereby integrally molded into the shell. As a beneficial result, no subsequent deformation action or forming needs to be done subsequent thereto. 
         [0041]    The retention tabs  310  can be grabbed by the collar of a filter head as shown in the collar retention system of U.S. Pat. No. 5,203,994. Alternatively, the retention tabs  310  can be installed and twisted into the inner retention channels of the filter head according to channel retention systems such as shown in U.S. Pat. No. 6,187,188. As a result, this embodiment provides a multi-purpose design adapted for multiple applications/retention systems. 
         [0042]    To illustrate a channel retention system, the relevant part of the filter mounting head  309  is shown in  FIGS. 8 and 9  in simplified form. These figures show generally the channel retention structure for securing the filter cartridge  301  to the filter mounting  309 , but does not illustrate dirty fluid inlet and clean fluid outlet ports. With particular reference to  FIG. 8 , the filter mounting head  309  includes a plurality of radially inward projecting shoulders  304  that are angularly separated by insertion slots  305 . As will be more fully explained below, the insertion slots  305  align with and receive retention tabs  310  of the filter cartridge  301  (not shown in  FIGS. 8 and 9 ) during filter replacement. The shoulders  304  form a wall of the retaining slots  315 , which are hidden behind shoulders  304  in  FIG. 8  and are more clearly illustrated in the cross section of  FIG. 9 , for receiving the retention tabs  310  of the filter cartridge  301  when the filter cartridge is mounted to the filter mounting  309 . 
         [0043]    To mount the filter cartridge  301  on the filter mounting head  309 , a user will first align the retention tabs  310  of the filter cartridge with the insertion slots  305 . Next, the user will axially insert the filter cartridge  301  through the opening  306  formed by the filter mounting head  309  with the retention tabs  310  passing through the insertion slots  305 . As the filter cartridge  301  is inserted through the opening  306 , the user will compress an elastomeric spring  311  against the filter mounting head  309  illustrated in  FIG. 8 . Then, the user will rotate the filter cartridge  301  causing the three retention tabs  310  enter the retaining slots  315  and to axially align with the inward projecting shoulders  304  of the filter mounting head  309 . As the three retention tabs  310  have radii R 3  (see  FIG. 8 ) greater than the inner radius R 4  of the shoulders  304 , the three retention tabs  310  will axially abut corresponding shoulders  304  of the filter mounting head  309  and be unable to move axially relative to the filter mounting head  309 , thereby coupling the filter cartridge  301  to the filter mounting head  309 . The spring  311  will tend to bias the filter cartridge  301  away from the filter mounting head  309  causing the retention tabs  310  to axially press against the inward projecting shoulders  304  of the filter mounting  301 . This biasing action increases the friction between the retention tabs  310  and inward projecting shoulders  304  to prevent the filter cartridge  301  from rotating and being inadvertently removed from the filter mounting head  309 . The channels may also be ramped slightly so as to prevent movement. 
         [0044]    To remove the filter cartridge  301 , a user would rotate the filter cartridge  301  until the retention tabs  310  again align with the insertion slots  305  of the filter mounting head  309 , and then pull the filter cartridge  301  axially away from the filter mounting head  309 . Each of the retention tabs  310  may form a recess region  312  facing the channel  314  formed by the interface between the upper and lower shells. 
         [0045]    In this embodiment, the upper shell is permanently connected to the lower shell much like the connection for embodiment of  FIG. 1 . However, this embodiment may also use a releasable connection between shells such as shown in the second illustrated embodiment of  FIGS. 3-4 . 
         [0046]      FIG. 10  shows a further embodiment in which the upper shell  403  is made of metal such as stamped formed and/or drawn sheet steel, while the lower shell  402  is made of molded plastic. However, the embodiment could be practiced using a plastic upper shell  403 . The filter cartridge  401  is again made by attaching the two shells  402 ,  403  by axially inserting the upper shell  403  into the lower shell  402 . The upper shell  403  again includes a generally planar end wall  420  forming a generally closed end of the upper shell  403  and a generally cylindrical sidewall  421  providing an open end  424  of the upper shell  403 . The sidewall  421  projects axially away from the end wall  420 . The end of the sidewall  421  is folded back axially towards end wall  420  to form a small U-shaped curl  425  with a terminating edge  429  of the sidewall  421  facing axially toward end wall  420 . The U-shaped curl  425  provides a cooperating cam surface on the underside that facilitates resilient deflection of the upper and/or lower shells during initial attachment (that is when the shells are axially pushed together). 
         [0047]    This embodiment also includes a lower shell  402  which forms a collection bowl including a domed end wall  418  that transitions into a generally cylindrical sidewall  419 . The sidewall  419  defines an open end  423  of the lower shell  402  opposite a generally closed end formed end wall  418 . 
         [0048]      FIG. 11  is an enlarged partial illustration of the connection between the upper and lower shells  402 ,  403 . When the shells are pushed together, terminating edge  429  of the U-shaped curl  425  engages radially inward extending projections  430  formed in the inner surface of sidewall  419  of the lower shell  402  causing interference preventing the upper and lower shells  402 ,  403  from being separated. The upper shell  403  is axially inserted into the lower shell  402  during assembly and the U-shaped bowl  425  snap-fit engages the inward extending projections  430 . The U-shaped bowl  425  is inserted so that the open end  424  of the upper shell  403  axially faces the end wall  418 . 
         [0049]    Formed into the sidewall  419  of the lower shell  402  is an annular channel  427 . The lower shell  402  is attached to the upper shell  403  by placing the U-shaped bowl  425  so that it compresses a ring seal  428  within the annular channel  427 . This provides a fluid-tight seal to prevent a leakpath between the metal and plastic. The ring seal also provides a biasing force acting against the snap fit connection. 
         [0050]      FIGS. 12-14  shows a further embodiment of a filter cartridge referred to as a “reverse flow” cartridge. This reverse flow feature is useable with any of the above embodiments in that it alters the flow of fluid through the cartridge internally. This cartridge reverses the flow around an internal upper end cap as opposed to flowing through and around the lower end cap. This is schematically indicated by flow path line  534  (and  533  showing subsequent flow of fluid inward through the media). 
         [0051]    The filter cartridge includes a lower shell  502  and an upper shell  503  forming a filter cartridge  501 . In this embodiment, the lower shell  502  has a generally cylindrical sidewall  509  that transitions into a domed end wall  510 . The upper shell  503  is made of plastic, and has a generally planar end wall  520  forming a generally closed end of the upper shell  503  and a generally cylindrical sidewall  521  providing an open end  524  of the upper shell  503 . The sidewall  521  projects axially away from the end wall  520 , and transitions into a second cylindrical sidewall  525  with a radius R 5  greater than the radius R 6  of the first sidewall  521 , the transition portion forms an abutment shoulder  528 . 
         [0052]    This embodiment differs from prior embodiments by virtue of having an upper internal end cap  516  (thus the upper shell is not an end cap in this embodiment). The annular end cap  516  is sealingly connected and may be potted with plastisol to the upper end of the filter media  506 . The upper end cap  516  also positions and secures the filter media  506  within the filter housing  504  to facilitate the flow reversal through the creation of space between the upper shell  503  and the upper end cap  516 . 
         [0053]    To position the filter media  506  inside of the housing, end cap  516  includes a plurality of ribs  507  at spaced angular and equal intervals about its circular periphery along a solid skirt portion  508 . These ribs  507  have radial extensions  515  that are received and can be mounted into corresponding recesses  519  formed at corresponding angular locations in the upper shell section. The radial extension  515  extend radially outward from the portion of the ribs  507  farthest from the end cap  516 , that is proximate the bottom of the ribs. The ribs  507  are angularly spaced apart defining flow passages  530  therebetween. The flow passages  530  permit fluid to flow between a fuel chamber  531  formed between the filter media  506  and the cylindrical sidewall  509  of the lower shell  502  and an upper fuel chamber  532  formed between the upper shell  503  and the annular end cap  516 . Fluid flow through flow passages  530  is illustrated by fluid flow arrows  534 . 
         [0054]    When the upper shell  503  and annular end cap  516  are formed from plastic, the annular flange  508  may be secured to the abutment shoulder  528  by ultrasonic welding, adhesives, etc. 
         [0055]    In prior filters a spring was needed to bias an end cap and filter media within a filter cartridge against the upper shell. This spring transferred a significant compressive load to filter media, which, when immersed in fluid during operation, has reduced structural resistance to collapse. In the present embodiment a spring is unnecessary, as the filter media  506  is permanently attached to and axially positioned within the filter cartridge  501  by the end cap  516  and is radially positioned by the end cap&#39;s  516  attachment to the abutment shoulder  528 , axially affixing the end cap  516  to the upper shell  503 . Therefore, the filter media  506  is not subject to the load that a biasing spring would apply. 
         [0056]    All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
         [0057]    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
         [0058]    Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.