Abstract:
A filter element is provided that has a generally cylindrical configuration and that defines a longitudinal axis and a radial direction. The filter element comprises a center tube that defines a central reservoir and that includes annular filter media surrounding the center tube and the central reservoir, an open end joined to the center tube disposed along the longitudinal axis, the open end including an opening allowing fluid to flow from the central reservoir to the outside of the filter element, and a closed end joined to the center tube opposite the open end disposed along the longitudinal axis, the closed end including an end cap comprising a body that defines an attachment pocket and an air pocket that surrounds the attachment pocket.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates generally to a drain for a housing. More specifically, the present disclosure relates to a liquid filter housing drain with an integral air vent. 
       BACKGROUND 
       [0002]    Liquid filter drains are known for draining filter housings of accumulated contaminants. In diesel engines, for example, a fuel line filter is used to separate out water and debris. These contaminates accumulate in a lower portion of the filter housing. 
         [0003]    For example,  FIG. 1 , which is taken from U.S. Pat. No. 8,157,997, the contents of which are incorporated by reference herein for all purposes in its entirety, illustrates a canister filter system  1  having a base  10 , a canister  20 , and a filter element  30 . The general construction and use of a canister filter system is understood by those of ordinary skill in this art. Thus, all the details of the construction and use of canister filter system  1  need not be explained here. The canister filter system  1  may be used to filter fluids such as diesel or gasoline or other liquid fuels, lubrication oil, hydraulic fluid for hydraulic power systems, transmission fluid, or even possibly intake air for an engine. The canister filter system  1  may also be used as a fuel/water separator filter. The canister filter system  1  with the features described herein could be adapted by those of ordinary skill in this art to serve many different purposes and suit many other applications. 
         [0004]    The base  10  includes an inlet channel  11  for fluid inlet into the canister filter system  1 , and an outlet channel  12  for fluid outlet from the canister filter system  1 . The base also includes base threads  13 . Other attachment structure than threads may be used. 
         [0005]    The canister  20  includes an open end  21  and a closed end  22 . Adjacent the open end  21  are canister threads  23  which can be engaged with base threads  13  to hold the canister  20  to base  10 . Threads are one example of engagement structures which may be included on the base  10  and canister  20  to form a releasable engagement. Other engagement structures may be used as will be recognized by those of ordinary skill in this art. 
         [0006]    The filter element  30  may take many different forms to suit a particular application. In the illustrated embodiment, the filter element  30  is well suited for filtering fuel or lubrication oil. The filter element  30  may include annularly arranged filter media  31  circumferentially surrounding a central reservoir defined by center tube  32 . Axial ends of filter media  31  are sealed by end plates. Open end plate  33  defines an axial open end of filter element  30 . The open end plate  33  is termed “open” because it includes an opening  35  for allowing passage of fluid to outlet channel  12  from the central reservoir defined by center tube  32 . Closed end plate  34  defines an axial closed end of filter element  30 . The closed end plate  34  is termed “closed” because it prevents any fluid outside the filter element  30  adjacent axial end of filter media  31  from flowing unfiltered into center tube  32 . Open end plate  33  and closed end plate  34  may each be joined to the center tube  32  via welding, adhesives, etc. Alternatively, several or all of center tube  32 , open end plate  33 , and closed end plate  34  may be constructed as unitary components. 
         [0007]    Fluid to be filtered enters from the inlet channel  11  and flows to the annular cavity  28  between canister  20  and filter media  31 . The fluid then passes into and through filter media  31 , then into center tube  32  through the perforations shown therein in  FIG. 1 . The fluid exits center tube  32  through open end plate  33  and opening  35  into the outlet channel  12 . The open end plate  33  and closed end plate  34  help define the fluid channels into and out of filter media  31 , preventing any fluid from flowing directly to outlet channel  12  and bypassing filter media  31 . First and second annular seals  38  and  39  may advantageously be included on filter element  30  and also help define and seal fluid passageways into and out of filter element  30 . First annular seal  38  may be included on the open end plate  33  around opening  35  and adjacent the axial open end of filter element  30  to help seal the inlet channel  11  from the outlet channel  12 . Second annular seal  39 , larger in diameter than first annular seal  38 , may be formed circumferentially around the open end plate  33  to provide the seal between canister  20  and base  10 , or in other words provides a seal to prevent fluid in inlet channel  11  from leaking out of the joint between canister  20  and base  10 . First and second annular seals  38 ,  39  may be integrally formed with open end plate  33 , or attached with adhesives or other methods, as is known in this art. When first and second annular seals  38 ,  39  are integrally formed on or included on open end plate  33 , proper replacement of these seals is assured when the filter element is replaced at proper intervals. Otherwise, a technician may fail to properly replace the seals at appropriate intervals, which could result in leakage out of the system, or leakage within the system allowing unfiltered fluid to bypass the filter element  31  and lead to contamination. 
         [0008]    The filter element may have a generally cylindrical configuration that defines a longitudinal axis and a radial direction. Other configurations are possible. 
         [0009]    A drain is typically disposed at the bottom of the filter housing and opened via some type of threaded connection. However, the filter assembly and filter line connected to the filter assembly is generally otherwise a closed system. Without a vent to replace outgoing fluid and contaminants with air, the contaminants either do not flow out of the housing or, if they do, they exit the drain inefficiently in spurts. 
         [0010]    For example,  FIG. 2  which is taken from U.S. Pat. Application Publication No. 2015/0202552, the contents of which are incorporated by reference herein for all purposes in its entirety, is a cross-sectional view taken axially through a filter housing assembly  100  with a drain valve assembly  102  in an open conformation, that is similar in nature to that disclosed in  FIG. 1  although not exactly the same. The filter itself includes a porous filtering medium  150  and defines central chamber or space  152 . As shown in  FIG. 2 , the drain valve assembly  102  is opened in response to the threaded stem portion  104  being unmated with the threaded filter portion  106 . To open the drain valve assembly  102 , the valve stem  104  may be rotated via a user or other service technician rotating a knob  108 . The knob  108  is affixed to the valve stem  104 . 
         [0011]    Once the drain valve assembly  102  is opened, a series of passages for the release of fluid and the ingress of air are opened between the interior of the housing or canister  110  and the outside. These opening includes a drain outlet  112  disposed at the end of the second end  114 . To facilitate collecting the fluid as well as an incidental amount of fuel, the drain outlet  112  includes a fitting  116  for a tube  118 . In this regard, the filter housing assembly  100  is often disposed within the body of a machine and relatively close to the power source of the machine. In order to prevent fluid from the drain outlet  112  spilling into the machine or onto the power source, the tube  118  may be fitted to the fitting  116  and run to a desired location such as a waste receptacle. To help secure the tube  118  to the fitting  116 , the fitting  116  may include one or more barbs  120  or other such structure such as ridges, grooves, or the like. 
         [0012]    To continue, the body  122  has an axial passage  90  disposed therethrough. The axial passage  124  has a divider  126  disposed axially along at least a portion thereof. The divider  126  separates the axial passage  124  into an outlet passage  128  and a vent passage  130 . In various examples, the divider  126  extends the entire length of the axial passage  124  or a portion of the length of the axial passage  124 . In the particular example shown, the divider  126  extends a portion of the length of the axial passage  124  and stops at about the beginning of the fitting  116 . However, in general, the divider  126  does extend past a vent side passage  132  the axial passage  124 . This vent side passage  132  is configured to allow air into the vent passage  130  while reducing or preventing liquid from exiting out of the vent side passage. It is an advantage that this vent side passage  132  is distinct from the drain outlet  112  because fitting the tube  118  to the fitting  116  may otherwise reduce the ability of vent gases to travel back up through the drain outlet  112 . 
         [0013]    To continue, the outlet passage  128  is open at an inlet  134  disposed at the first end  136 , at the drain outlet  112  and at a first side passage  138 . The vent passage  130  is closed at the first end  136  in order to help direct the flow of vent gases into the housing  110  via a second side passage  140  as shown by a plurality of air flow arrows  142 . The vent passage  130  is also open at the drain outlet  112  and the vent side passage  132 . In operation, unscrewing the valve stem via the knob  108  unthreads the threaded stem portion  104  from the threaded filter portion  106 . As the valve stem  104  moves downward or outward from the housing  110 , the upper seal  144  is opened and the first and second side passages  138  and  140  are drawn down into the lower portion of the housing  110  where the fluid has collected. 
         [0014]    Gravity works to urge the fluid into the first and second side passages  138  and  140  and a small vacuum pressure then draws air into the vent side passage  132 , up the vent passage  130  and out the second side passage  140  to enter the housing  110  as shown by the air flow arrows  142 . The replacement vent air then allows the fluid to continue flowing into the first side passage  138 , down the outlet passage  128  and out the drain outlet  112  as shown by a plurality of fluid flow arrows  142 . Of note, if vent gas is available to be drawn up from the drain outlet  112 , this vent gas is drawn up along the vent passage  130  as shown by the air flow arrows  146 . In addition, at all times and particularly near the end of the draining process, the second side passage  140  and vent passage  130  are available for draining fluid. This dual functionality of the vent passage  130  is self-regulated in response to the amount of vent gas needed to replace outgoing fluid and increases the efficiency with which the fluid exits the housing  110 . While air is flowing into the housing, the liquid and its contaminants flow out of the housing. This flow is designated by arrows  148 . 
         [0015]    However, it has been found that the design of  FIG. 3  still needs further improvement in order to break the vacuum to facilitate drainage. It should be noted that at no time does the space around the threaded portion of the stem  104  have substantial fluid communication with the interior of the housing as ledge  154  of the stem portion  104  never drops below the bottom end plate  156 . This is prevented as the bottom ledge  158  of the drain assembly abuts the housing  110  first. 
         [0016]    Other different ways of providing the necessary venting have been previously devised. One such example is the use of removable plugs at the top of the base of the filter assembly. However, this design has two drawbacks. First, this design does not allow for the efficient draining of higher viscosity liquids such as diesel fuel. Also, the drain time can be very slow as there is no way of breaking the vacuum when the liquid flows out of the closed system. 
         [0017]    Another solution has been to add a vent plug to the filter base but this adds additional cost. In the field, maintenance technicians often loosen a fluid line that is attached to the filter base to provide venting. However, this may inadvertently lead to a technician forgetting to reattach the fuel line, which can result in a leak. 
         [0018]    For all the above reasons, it is desirable to develop a better method for venting a filter housing than has been previously devised. 
       SUMMARY OF THE DISCLOSURE 
       [0019]    A filter element is provided that has a generally cylindrical configuration and that defines a longitudinal axis and a radial direction. The filter element comprises a center tube that defines a central reservoir and that includes annular filter media surrounding the center tube and the central reservoir, an open end joined to the center tube disposed along the longitudinal axis, the open end including an opening allowing fluid to flow from the central reservoir to the outside of the filter element, and a closed end joined to the center tube opposite the open end disposed along the longitudinal axis, the closed end including an end cap comprising a body that defines an attachment pocket and an air pocket that surrounds the attachment pocket. 
         [0020]    A canister filter system is provided that comprises a canister that includes an open end and a closed end, a drain that penetrates through the closed end of the canister and that includes attachment structure and a filter element that has a generally cylindrical configuration and that defines a longitudinal axis and a radial direction. The filter element comprises a center tube that defines a central reservoir and that includes annular filter media surrounding the center tube and the central reservoir, an open end joined to the center tube disposed along the longitudinal axis, the open end including an opening allowing fluid to flow from the central reservoir to the outside of the filter element, and a closed end joined to the center tube opposite the open end disposed along the longitudinal axis, the closed end including an end cap comprising a body that defines an attachment pocket and an air pocket that surrounds the attachment pocket. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a perspective cross-sectional view of a filter assembly that includes a filter base, canister, filter element and a drain as is known in the art. 
           [0022]      FIG. 2  is front sectional view of a drain design used with a filter assembly similar to that shown in  FIG. 1  as is known in the art. 
           [0023]      FIG. 3  is front sectional view of an endcap for a filter element and a drain assembly according to an embodiment of the present disclosure. 
           [0024]      FIG. 4  is an enlarged detail view showing the collection funnel with the hose attachment of the drain assembly of  FIG. 3  with more clarity. 
           [0025]      FIG. 5  is a top perspective view of the collection funnel of  FIG. 4  shown in isolation from the drain assembly. 
           [0026]      FIG. 6  is a top oriented perspective view of the drain assembly of  FIG. 3  with the collection funnel removed showing the openings of the liquid drain passages, the openings of the air vent passages, and the partition that separates them clearly. The drain assembly is shown in a closed configuration. 
           [0027]      FIG. 7  is an enlarged detail view of one of the openings of the liquid drain passages of  FIG. 6 . 
           [0028]      FIG. 8  is a bottom view of the drain assembly of  FIG. 6 . 
           [0029]      FIG. 9  is a perspective view of the stem member isolated from the drain assembly of  FIG. 6 . 
           [0030]      FIG. 10  is an enlarged sectional view of the drain assembly of  FIG. 6  to more clearly show the bottom surface of the barrel member of the drain assembly. 
           [0031]      FIG. 11  is a sectional view of the drain assembly of  FIG. 6  in an open or draining configuration. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    Focusing now on  FIG. 3 , an embodiment of an end plate or end cap  200  and filter drain assembly  202  according to one embodiment of the present disclosure is shown in a closed configuration. The filter element has a generally cylindrical configuration that defines a longitudinal axis L and a radial direction R. The end cap  200  includes an attachment pocket  204  at its furthermost extent in the axial direction along the longitudinal axis L of the filter element. The body includes a nominal wall  206  that forms the attachment pocket  204  of the end cap  200  jogs in the radial direction R of the filter element, forming an air pocket  208  that surround the stem member  210  and barrel member  212  of the drain assembly  202 . The air pocket  208  is not substantially filled by any component of the drain assembly even when the drain assembly is in the closed configuration. Put another way, the air pocket is at least partially empty and is not filled with a component or a fluid other than air when the drain is in the closed configuration. 
         [0033]    Focusing closely at the end cap, it includes a body that includes a nominal wall  206  that defines an attachment pocket  204  and an air pocket  208  that surrounds the attachment pocket  204 . The air pocket  208  is partially defined by a base surface  214  that begins at the termination of the thread profile  216  and extends in an outwardly radial direction R and terminates a predetermined distance such that this termination point  218  is substantially aligned radially with the outside surface  220  of the attachment portion of the end cap  200 . The length  222  of the base surface  214  measured in the radial direction R may be at least 75% of the nominal wall thickness. 
         [0034]    Similarly, the nominal wall of the end cap jogs a distance in the radial direction that is at least as great as the nominal wall thickness  206  as the wall transitions from the attachment pocket  204  to the air pocket  208 . This results in the inside surface  224  of the air pocket being positioned further away from the longitudinal axis L in the radial direction R than the outside surface  220  of the wall that is adjacent the threaded portion of the end cap. The wall then extends from around the air pocket in a downward axial direction along the longitudinal axis L of the filter element and terminates in a bottom end plate  226 . 
         [0035]    Furthermore, the depth of the air pocket  208  in the axial direction along the longitudinal axis L is greater than the amount of protrusion  228  of the barrel member  212  of the drain assembly past the bottom end plate  226  of the end cap  200 . Furthermore, this amount of protrusion  228  is less than the distance  230  from the ledge or stop  232  of the barrel member  212  to an abutment feature  234  of the canister  236  when the drain is in the closed configuration. This is advantageous when opening the drain assembly as will be discussed in more detail later herein. 
         [0036]    Focusing now more on the drain assembly of  FIG. 3 , it includes a barrel member  212  that is concentrically disposed about the stem member  210  and a funnel member  238  that is attached to the barrel member  212 . All of these components share the same longitudinal axis and radial direction as the filter element and the end cap as already described. The barrel member  212  defines vent passages  240  that surround the central or longitudinal bore of the barrel member and liquid flow passages  242  that surround the vent passages  240  in a concentric spatial relationship. The stem member  210  includes an attachment end  244  that in this case is a threaded end that extends from a shaft portion  246  that extends into the central bore of the barrel member  212 . The stem member  210  defines a retaining groove  248  near its bottom end for receiving a retaining member  250  of the barrel member  212  as will be discussed shortly. The free end  252  of the shaft  246  of the stem member  210  stops short of a concave surface  254  proximate the end  256  of the barrel member  212  that is opposite the end  258  that is adjacent the attachment end  244  of the stem member. Other attachment structures for the stem and the associated attachment pocket of the end cap other than threads are possible. 
         [0037]    The spatial relationship between the vent passage  240  and the liquid flow passage  242  may be described as being spaced away from the longitudinal axis L along the radial direction R on the same side of the longitudinal axis L, that is to say, the vent passage  240  and the liquid flow passage  242  are adjacent each along the same radial direction R that extends from the longitudinal axis L. Also, the vent passage  240  is positioned between the longitudinal axis L and the liquid flow passage  242  along a radial direction R. Other arrangements are possible. Also, designs that are not symmetrical or that use one or more vent passages and one or more liquid flow passages are considered to be within the scope of the present disclosure. 
         [0038]    Furthermore, the canister  236  may define a liquid reservoir  260  and the liquid flow passage  242  may be positioned between the vent passage  240  and the liquid reservoir  260  in the radial direction R on the same side of the longitudinal axis L. 
         [0039]    A funnel member  238  is attached to the bottom portion of the drain assembly. More specifically, the funnel collection member  238  includes at least one and preferably four apertures on its side surface (only two are shown in  FIG. 3 ), that serve dual purposes. First, they provide a catch point for the snap portions  262  of the barrel member  212  to retain the funnel member  238  onto the barrel member  212 . Second, these apertures provide side vent passages  264  that allow the ingress of air to the vent passages from the environment. A barbed connection or other hose attachment structure  266  is provided at the bottom of the funnel member to allow the attachment of a hose for draining fluid. Ribs  268  are also shown that extend from the interface with the barrel member down toward the main outlet passage  270  of the funnel member. The top surfaces of the ribs  268  prevent downward movement of the barrel member  212  further into the funnel member  238  but allow enough space for the snap members  262  of the barrel member  212  to engage the surfaces that define the aperture  264  of the funnel member  238 . 
         [0040]    An upper seal  272  between the drain assembly and the end cap of the filter element is provided that prevents the leaking of air into the liquid reservoir located at the bottom of the canister. Of course, the opposite is also true, that is to say, the upper seal prevents the seeping of liquid into the air pocket. The lower seal  274  prevents the leaking of air from the environment into the liquid in the canister while also preventing the leaking of liquid from the canister to the environment. 
         [0041]    It should be noted that other than the adjustment to the end cap and the drain assembly, the construction of all the embodiments herein are similar to some of those known in the art including those discussed above with reference to  FIGS. 1 and 2 . Therefore, the embodiments discussed herein with respect to the drain assembly below and the end cap above may be used with some of the filter assemblies and filter elements known in the art including those discussed with reference to  FIGS. 1 and 2  above and may have some of the same features. 
         [0042]      FIG. 4  shows more clearly that snap features  250  are included that are disposed in the central bore of the barrel member  212  that engage the retaining groove  248  of the stem member  210 . The barrel member  212  defines at least one vent passage  240  and at least one liquid flow passage  242  and the funnel member  238  defines one side vent opening  264  and the liquid flow passage  242  is positioned between the side vent opening  264  and the vent passage  240  along the radial direction R. The funnel member  238  is configured to collect the flow from a plurality of liquid flow passages  242  of the barrel member  212  when they are present. 
         [0043]    Looking now at  FIG. 5 , it illustrates a top perspective view of the funnel member  238 . The funnel member  238  includes a first end  276  that defines an opening that is configured to be in fluid communication with the stem member  210  and the barrel member  212 , a second end  278  that includes hose attachment structure  266 , and a side wall that extends from the first end to the second end. Ribs  268  are disposed in the interior of the funnel member  238  that abut the barrel member  212  as the funnel member  238  is attached to the barrel member  212 . 
         [0044]      FIG. 5  also shows more clearly the construction of the windows or apertures  264  that serve the dual purposes of retaining the funnel member  238  onto the barrel member  212  and to provide a source of venting air, in other words, they also act as vent openings. A plurality of these is shown but it is contemplated that only one may be needed in some embodiments. On top of each window  264 , a depression  280  is provided that fixes the relative angular position of the funnel member to the barrel member. Once the snaps of the barrel member are aligned with these depressions, there is a natural resistance to any rotation of the funnel member relative to the barrel member as the funnel member is snapped onto the guide member. Once the snaps are in place in the windows, any rotation of the funnel member is imparted to the barrel member as the snaps push on the sides of the windows. This, in turn, provides some rotation to the stem member in a manner that will be discussed later herein. Also, the depressions may aid in molding the windows successfully into the funnel member. 
         [0045]      FIG. 6  shows a perspective view of the drain assembly  202  without the funnel member. The stem member  210  includes a central or longitudinal bore  282  that may provide additional venting as will be discussed in more detail later herein. A raised partition  284  separates the vent passages  240  from the liquid passages  242  in the barrel member (see also  FIG. 7 ). The partition  284  includes alternating straight sections  286  and curved sections  288  along the perimeter of the partition. The partition creates an obstruction that helps the vent passages from being filled with liquid during the draining process as will be shown more clearly later herein. The elevation of the air paths above the liquid drain paths creates a hydrostatic pressure differential between the air and the liquid. The liquid flow passages  242  have an alternating pattern of large and small passages that form a circular array about the longitudinal axis of the drain assembly. Alternatively, this may be described as having two liquid flow passages  242  that are adjacent to each other that are defined by differently configured perimeters. The maximum dimension  290  of the small passages is less than the maximum dimension  292  of the large passages. As a result, the smaller rectangular passages  242 ′ alternate between acting as air or liquid passages while the larger trapezoidal passages  242 ″ exhibit full flow fluid only. 
         [0046]    As shown, six vent passages  240  are provided while twelve liquid passages  242  are provided (see also  FIG. 8 ). The stem member  210  and barrel member  212  are shown to be separate members made by an injection molding process but it is contemplated that they could be made as one piece or by another process, etc. The number and configuration of any of the passages may be altered as desired. For example, the perimeter of the liquid flow passages may be circular or have any suitable polygonal shape, etc. 
         [0047]    The spatial relationship of the vent passages  240  and liquid flow passages  242  may be described as follows. As already mentioned, the barrel member  212  is concentrically disposed about the stem member  210 . A plurality of vent passages  240  form a circular array about the longitudinal axis L and a plurality of liquid flow passages  242  form a circular array about the array of vent passages and the longitudinal axis L. There are also a plurality of liquid flow passages  242  and vent passages  240  that are spaced away from the longitudinal axis L along the same radial direction R that extends from the longitudinal axis L. 
         [0048]    The configuration of the barrel member  212  may also be described as having a first end  258  that is proximate the threaded end  244  of the stem  210  and a second end  256  that is arranged in an opposing fashion to the first end along the longitudinal axis L. The partition  284  extends from the first end and an anti-capillary flow feature is present on the second end as will be described in more detail shortly. The first end of the barrel member defines one or more entrances for the liquid flow passage(s) (located where reference numerals  242 ′ and  242 ″ point in  FIG. 6 ) and one or more exits for the vent passage(s) (located where reference numerals  240  point in  FIG. 6 ) and a partition  284  extends from the first end and separates the entrance of one liquid flow passage from the exit of the vent passage. The vent passages and liquid flow passages of the barrel member all run solely along the longitudinal axis L. This helps to allow fluid to drain from the air pocket when the drain is opened and closed as there is no tendency for the liquid to sit in a horizontal or radial oriented bore that may leak back into the air pocket. 
         [0049]    Other features of the drain assembly can also be seen in  FIG. 6  including the upper and lower seals  272 ,  274  that are positioned on either side of the ridge that provides a stop  232  for limiting the movement of the drain assembly relative to the filter element when closing the drain assembly and the canister when opening the drain assembly. Four snap features  262  are provided (only three are shown in  FIG. 6 ), that are used to snap on the funnel member. Depressions or cut-outs  294  are provided directly beneath the snap features that facilitate the molding of those features. 
         [0050]      FIG. 8  shows the bottom of the barrel member  212  and stem member  210 . The concave surface  254  that is proximate to the vent and fluid passages  240 ,  242  of the barrel member and that defines the perimeters of the entrances of the vent passages (where reference numerals  240  point in  FIG. 8 ) and exits of the fluid passages (where reference numerals  242 ′ and  242 ″ point in  FIG. 8 ) can also be seen. The perimeter of the shaft portion  246  of the stem member  210  has a hexagonal configuration but other configurations are possible. The hexagonal perimeter  296  mates with a partially complimentary perimeter of the central bore of the barrel member, that serves as drive structure  298 . This perimeter includes undulations that tangentially contact the surfaces of the hexagonal perimeter of the shaft of the stem member and that provide clearance areas proximate the corners where these surfaces meet. These clearance areas also serve as the air vent passages  240  and are partially defined by a circular perimeter. Other configurations are possible. The lower seal  274 , ridge  232 , snap features  262  and associated cut-outs  294  for those snap features of the barrel member can also be seen. The snap features  250  the barrel member that engage the retaining groove of the stem member can also be slightly seen. 
         [0051]    Referring now to  FIG. 9 , the stem member  210  may be seen in a perspective view in isolation. The hexagonal perimeter  296  of the shaft portion  246 , the threaded portion  244 , the retaining groove  248 , and the exit of the longitudinal bore  282  can be seen. The central or longitudinal bore  282  is concentric with the longitudinal axis L but this may not be true for other embodiments. 
         [0052]      FIG. 10  shows an enlarged sectional view of the drain assembly with the funnel member removed. The concave surface  254  proximate the ports of the liquid and vent passages  242 ,  240  can be seen. The concave surface helps to keep drain liquids from blocking the air vent passages. Without this feature, capillary action may allow a portion of the draining liquid to flow towards the air vent passages. More viscous liquids may frequently block or restrict the air vent passages. As a result, the liquid may drain in an undesirable stop/start fashion. The concave shape discourages the capillary flow toward the air vent passages and creates a continuous flow of liquid. 
         [0053]    Any surface may serve this end provided some change in elevation or height is achieved between the liquid flow passages and the vent air passages. Another feature that discourages or limits the capillary flow from the exit of the liquid flow passage toward the entrance of the vent passages such as partitions or ribs, etc. may also be used. When a changed in elevation is used, it is desirable that the lowest point  300  of the entrance of the vent passage is higher along the longitudinal axis L than the highest point  302  of the exit of the liquid flow passage. A snap feature  250  of the barrel member  212  engaging the retaining groove  248  of the stem member  210  can also be seen. 
       INDUSTRIAL APPLICABILITY 
       [0054]    In practice, the drain assembly is rotated until it reaches a closed configuration as shown in  FIG. 3  via the threaded connection between the end cap  200  of the filter element and the stem  210  of the drain assembly. After enough time has passed or enough contaminates have settled at the bottom of the liquid reservoir  260  of the canister  236  necessitating draining, the drain assembly  202  is rotated in the opposite direction until its stop ledge  232  hits an abutment feature  234  of the canister  236  as shown in  FIG. 11 . This rotation is created by grabbing the funnel member  238  shown in  FIG. 3  manually and turning the entire assembly. This may be facilitated by providing knurling on the outer surface of the funnel member for grip. Alternatively, a tool interface such as a hexagonal feature may be added to the outside surface of the funnel member to help make this rotation. 
         [0055]    As the drain assembly  202  is rotated to reach its draining or open configuration as shown in  FIG. 11 , the upper seal  272  will drop below the bottom member  226  of the end cap  200 , allowing a relatively large volume of air to exit the air pocket  208  immediately to break the vacuum and start the draining of liquid through the drain assembly. The close proximity of the air pocket to the vent passage  240  and liquid draining passage  242  is helpful in creating the proper flow. As shown in  FIG. 11 , once the drain assembly bottoms out on the abutment feature  234  of the canister  236 , a small gap  304  is created that allows the flow of air, designated by arrows  306  into the liquid reservoir at the bottom of the canister. At the same time, liquid may flow, represented by arrows  308 , from the liquid reservoir a very short distance to the liquid flow passage  242  without blocking the air vent passage  240  due in part to the partition  284 . 
         [0056]    More specifically, drain  202  includes a stop  232  that is configured to contact the end cap  200  when closed (see  FIG. 3 ) and contact the canister  236  when opened (see  FIG. 11 ) and the distance  230  from the stop to the canister along the longitudinal axis L when in the closed configuration (see  FIG. 3 ) is more than the distance  228  from the stop to the entrance of a fluid flow passage along the longitudinal axis (see  FIG. 3 ). As shown in  FIG. 11 , the difference between the distances defines a gap  304  between the drain and the end cap measured along the longitudinal axis L. Also, the height  310  of the partition measured along the longitudinal axis L from the stop member to the top of the partition is greater than the distance  230  from the stop member to the canister when the drain is in the closed configuration. As a result, the partition and exits of the vent passages always remain up in the air pocket even when the drain is in the open configuration as illustrated in  FIG. 11 . Hence, these passages are not blocked as liquid flows down into the liquid flow passages. 
         [0057]    In particular, the following spatial relationship between the air pocket  208  and the air vent passage  240  and the liquid flow passage  242  is useful. The air pocket is in direct fluid communication with the liquid flow drain passage, the liquid reservoir to be drained, and the air vent passage once the drain assembly is rotated into an open or draining configuration. Also, the air vent passage is in communication with the air pocket at a point that is above the liquid reservoir and the liquid drain passage along the longitudinal axis L. The liquid drain passage is located closer to the liquid reservoir to be drained than the air vent passage along the radial direction R. 
         [0058]    Also, when the stem member  210  is fully retracted from the threaded portion  204  of the end cap  200 , the central bore  282  of the stem member may also provide additional air venting as it is in fluid communication with the air pocket  208 . This may be achieved by providing a groove  312  through the threads so that there is fluid communication between the attachment pocket  204  and the air pocket  208 . Alternatively, the stem could be configured to be backed all the way out of the attachment pocket  204  as shown in  FIG. 2 . This central bore may not be necessary in all embodiments but may be useful for those embodiments that are used with high viscosity fluids. Conversely, when the bore of the stem is able to provide enough venting, it is contemplated that the vent passages of the barrel member may be omitted. 
         [0059]    It will be appreciated that the foregoing description provides examples of the disclosed assembly and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated. 
         [0060]    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. 
         [0061]    It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the apparatus and methods of assembly as discussed herein without departing from the scope or spirit of the invention(s). Other embodiments of this disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the various embodiments disclosed herein. For example, some of the equipment may be constructed and function differently than what has been described herein and certain steps of any method may be omitted, performed in an order that is different than what has been specifically mentioned or in some cases performed simultaneously or in sub-steps. Furthermore, variations or modifications to certain aspects or features of various embodiments may be made to create further embodiments and features and aspects of various embodiments may be added to or substituted for other features or aspects of other embodiments in order to provide still further embodiments. 
         [0062]    Accordingly, this disclosure 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 disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.