Abstract:
A filter assembly with a replaceable filter element and a reusable filter housing, which incorporates a locking mechanism to ensure that the filter system will not be operated without a filter element installed.

Description:
TECHNICAL FIELD 
       [0001]    The field of this disclosure is filter systems. More specifically, the field is canister filter systems for liquids, such as lube oil or liquid fuels, which have drains for draining liquid out of the canister. 
       BACKGROUND 
       [0002]    Canister filter systems are used extensively today on equipment such as internal combustion engines, construction and mining machinery, and many other types of industrial machinery. They are used to filter contaminants from fluids in fuel systems, lubrication oil systems, hydraulic fluid power systems, hydraulic fluid control systems, transmission fluid systems, engine air intake systems, and the like. 
         [0003]    A canister filter system typically includes a base which is often attached to the equipment, a canister (also sometimes called a housing, cup, can, or cover), and a filter element which is removably positioned inside the canister. After the filter element is positioned inside the canister, the canister is attached to the base with threads or other attachment means to form a sealed compartment around the filter element. The canister, base, and filter element cooperate to define fluid pathways through which fluid is directed through the filter element. The filter element contains filter media which traps and collects contaminants as the fluid passes through it. The trapped contaminants may include dirt, water, soot, ash, metallic particles, and other harmful debris. 
         [0004]    Eventually these contaminants clog the filter media and reduce its effectiveness. Or other conditions can develop over time which also reduce the effectiveness of the filter media in removing contaminants. When this occurs, the filter element should be replaced (or possibly cleaned, but this is impractical for most applications). But only the filter element needs to be replaced, while the canister, base, and other components are reused. The filter element is designed to be conveniently replaced and readily disposed. The filter element can be replaced on demand, i.e. when the filter becomes clogged and requires replacement, or periodically, according to the guidance of a periodic maintenance schedule established for the particular application. 
         [0005]    Canister filter systems can have many advantages over other filter systems such as spin-on filters. For instance, canister filter systems can be relatively inexpensively provided with a drain. To avoid spills, a technician may wish to remove the fluid from the canister in a controlled and contained manner before detaching the canister to replace the filter element. The drain facilitates the removal of fluid that is inside the canister. In some circumstances the fluid can spill if it is not first removed from the canister before detaching the canister from the base. The drain is typically integrated into the canister. Because in a canister filter system the drain generally increases just the cost of the canister, which is reused and purchased only once, and generally does not increase the cost of the filter element, which is frequently replaced and purchased many times, the additional cost of including a drain does not significantly increase the total operating cost to the equipment owner. 
         [0006]    U.S. Pat. No. 6,814,243, granted Nov. 9, 2004, (“the &#39;243 patent”) is an example of prior art canister filter systems incorporating a drain in the canister.  FIG. 1  of the &#39;243 patent illustrates a canister  14  with an integrated drain (the drain is not labeled with a reference character, but is shown incorporated into the bottom of canister  14  in  FIG. 1 , and is shown in a closed position). 
         [0007]    The &#39;243 patent is also an example of another, increasingly important feature of canister filter systems. The arrangement of the filter system described in the &#39;243 patent makes it impossible to install the canister to the base, without first having a filter element properly installed in the canister. This prevents, for example, accidentally or intentionally running the machinery without the filter element in place. As components such as fuel pumps, fuel injectors, hydraulic pumps, valves, bearings, engines, etc., become more expensive, more high tech, and are made with tighter tolerances and specifications, it is increasingly important to protect these components against contamination. Contamination may cause premature wear and even failure, and the problem is compounded when the component has tight tolerances between parts or is very expensive. Thus, it may be very advantageous in some applications to ensure that a technician does not accidentally or intentionally try to run machinery without an appropriate filter element in place. 
         [0008]    However, while the filter system of the &#39;243 patent performs well in some applications, it may suffer from several disadvantages, or is otherwise not well suited for other applications. For instance, the filter system of the &#39;243 patent may not be well suited for applications where the fluid in the canister is at a high pressure. Because the connection of the canister to the base is through the filter element, the force of high pressure in the canister is reacted through the filter element, which may not be strong enough for the pressures of some applications. Additionally, O-ring between the canister and base is not intended to hold high pressure inside of the canister. 
         [0009]    The presence of threads in the filter element&#39;s center tube can be a disadvantage in some circumstances. The threads in the center tube, which are used to connect the filter element and canister to the base, are located in the clean fluid pathway out of the system. Threads in the clean fluid pathway may contribute to contamination. 
         [0010]    In addition, the canister of the system described in the &#39;243 patent can be relatively complicated and expensive to manufacture for some applications. The connection structure incorporated into the bottom of the canister may add too much cost for some applications. 
         [0011]    Because of these drawbacks, another canister filter design is needed which still prevents accidentally or intentionally using the filter system without a filter element installed, but is also relieved of some or all of the disadvantages exhibited by the &#39;243 patent. 
       SUMMARY 
       [0012]    A canister filter system includes a base, a canister attachable to the base, and a filter element having filter media positioned inside the canister. A drain forms a seal with, and may releasably engage the filter element when the drain is in a closed position. In an open position, the drain allows fluid to be removed from the canister. Because the drain forms a seal with, and may releasably engage the filter element in the closed position, the drain cannot be closed unless a filter element is properly positioned inside the canister. This prevents accidental or intentional use of the filter system without a filter element in place. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a cut away view of a canister filter system, including a base, a canister, and filter element. 
           [0014]      FIG. 2  is a detailed view from  FIG. 1  with the drain  40  in a closed position. 
           [0015]      FIG. 3  is a detailed view from  FIG. 1  with the drain  40  in an open position. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The following is a detailed description of exemplary embodiments of the invention. The exemplary embodiments described herein and illustrated in the drawing figures are intended to teach the principles of the invention, enabling those of ordinary skill in this art to make and use the invention in many different environments and for many different applications. The exemplary embodiments should not be considered as a limiting description of the scope of patent protection. The scope of patent protection shall be defined by the appended claims, and is intended to be broader than the specific embodiments described herein. 
         [0017]      FIG. 1  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. 
         [0018]    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 . 
         [0019]    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. 
         [0020]    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. 
         [0021]    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. 
         [0022]    With reference now to  FIGS. 2 and 3 , a drain  40  penetrates the closed end  22  of canister  20 . The drain  40  provides a drain channel  41  for removing fluid from inside of canister  20 . The drain  40  is elongated and includes an inlet end  42  and an outlet end  43  connected to one another by the drain channel  41 . Inlet end  42  is positioned inside of canister  20 . Outlet end  43  is positioned outside of canister  20 . The drain  40  may be moved between a closed position and an open position. In the closed position of  FIG. 2 , fluid is not able to flow through drain channel  41 . In the open position of  FIG. 3 , fluid is able to flow from the inlet end  42 , through drain channel  41 , and out from outlet end  43 . Drain  40  can be adapted to suit many different applications. The illustrated embodiment provides only one exemplary configuration for drain  40 . 
         [0023]    Canister  20  includes a drain boss  24  on closed end  22 . Drain boss  24  protrudes out and away from closed end  22 , and may include surfaces thereon that would allow a tool, such as an adjustable, open-ended wrench, to engage the drain boss  24  and turn the canister  20 . Drain boss  24  forms a bore  25 . Drain  40  is positioned in, and is able to slide axially and rotate in bore  25 . An O-ring groove  44  is formed around the exterior of drain  40  and an O-ring is positioned therein. Alternatively, the O-ring groove may be formed on the bore  25 . The O-ring prevents fluid leakage out of canister  20  through bore  25  from between drain  40  and drain boss  24 . 
         [0024]    Drain  40  may cooperate with filter element  30  to form a releasable engagement with filter element  30 , and a releasable seal with filter element  30 , when drain  40  is in its closed position. In the illustrated embodiment, drain  40  forms a releasable engagement with filter element  30  through engagement structure that includes a releasable threaded connection. Closed end plate  34  may form a pocket  36  in which are provided threads  37 . Threads  37  are formed on an inside surface of the pocket  36 . Mutual threads  45  may be formed near inlet end  42  of drain  40 . Drain  40  may be engaged with filter element  30  by threading together threads  37  and  45 . Threads are one example of engagement structures which may be included on the filter element  30  and drain  40  to form a releasable engagement. Other known engagement structures may be used for particular advantage in certain applications as will be recognized by those of ordinary skill in this art. 
         [0025]    When in its closed position, with drain  40  releasably engaged with filter element  30 , a releasable seal is made with filter element  30  so that practically no fluid can enter inlet end  42  of drain  40 . The releasable seal is made with seal structure which, in the illustrated embodiment, includes an inlet opening  46  extending between drain channel  41  and the radial exterior of inlet end  42 , and pocket  36  which receives the inlet opening  41  when the drain  40  is sealed. Putting drain  40  in its closed position moves inlet opening  46  inside of pocket  36 , blocking the inlet opening  46  so that practically no fluid can enter therein. Additionally, an O-ring groove  47  may be formed on drain  40  and an O-ring positioned therein. This O-ring may provide additional protection against fluid leaking from between drain  40  and pocket  36  and entering inlet opening  46 . Instead of positioning the O-ring inside of pocket  36 , the O-ring could also be positioned between drain  40  and another portion of closed end plate  34 , and the O-ring could be positioned in a groove formed on closed end plate  33  instead of on drain  40 . When moving drain  40  to its closed position, as it advances into pocket  36 , fluid trapped therein may need an escape path. This path may be provided by allowing drain channel  41  to be open through axial inlet end  42  of drain  40 . 
         [0026]    Pocket  36  includes an open end  36   a,  a smooth section  36   b,  a threaded section  36   c,  and a closed end  36   d.  Closed end  36   d  ensures that no fluid may flow from center tube  32  into pocket  36  and inlet opening  46 , and vice versa. Threads  37  are formed in the threaded section  36   c.  Smooth section  36   b  may act as a part of the sealing structure by fitting tightly against the surfaces of drain  40  to prevent fluid from entering between and flowing from open end  36   a  to inlet opening  46 . Smooth section  36   b  may also provide a surface against which the O-ring in O-ring groove  47  may seal for additional protection against fluid passage. To help maintain the smoothness of the surface of smooth section  36   b,  the diameter of this section may be larger than the major diameter of the threads  37 , forming a lip  36   e  between the smooth section  36   b  and threaded section  36   c.  The larger diameter of smooth section  36   b  will help avoid the threads  45  on drain  40  from degrading the smooth surface used for sealing purposes. 
         [0027]    When in an opened position, drain  40  is at least partially disengaged from filter element  30 , and inlet opening  46  is open so that fluid may flow into drain channel  41 . In the illustrated embodiment with a threaded engagement, putting the drain  40  in an opened position requires turning drain  40  to disengage threads  37  and  45 . As threads  37  and  45  disengage, inlet end  42  of drain  40  advances out of pocket  36 , unblocking inlet opening  46 . Together, these features ensure that no fluid may enter inlet end  42  of drain  40  except when inlet opening  46  has backed out of pocket  36 , clearing the smooth section  36   b  and the open end  36   a.  Fluid is then free to flow from inside canister  20 , through inlet opening  46 , through drain channel  41 , and exit through outlet end  43  of drain  40 . 
         [0028]    Threads  37  and pocket  36  on filter element  30  need not necessarily be formed in closed end plate  34 . The threads  37  and pocket  36  could also be formed as part of center tube  32 , or some other part of filter element  30 , as will be understood by those of ordinary skill in this art. 
         [0029]    Other features and constructions may be used to provide cooperation between drain  40  and filter element  30  so that fluid cannot flow through drain  40  when drain  40  is in the closed position, and fluid may flow through drain  40  when drain  40  is in the opened position. For example, filter element  30  and drain  40  could be constructed so that drain  40  makes a releasable seal with filter element  30  to close drain  40 , but the two may not be releasably engaged. Instead, as an example, the filter element  30  and drain could be independently engaged with the canister  20 , and moving drain  40  to a closed position would involve drain  40  moving upward to form a releasable seal with filter element  30 , but not releasably engage it. 
         [0030]    The releasable engagement and the releasable seal between the drain  40  and the filter element  30  has several advantages. First, the engagement and/or seal ensure that a filter element  30  is placed inside canister  20  before the system can be used. A technician will not accidentally or intentionally assemble the system without a filter element  30  because without it, the drain  40  cannot be closed. Ensuring the presence of filter element  30  helps ensure that the fluid will be properly filtered. 
         [0031]    With no threaded connections in the pathway of clean fluid from the center tube  32  to the outlet channel  12 , the possibility of contamination is reduced. Threaded connections in the clean, filtered fluid pathway have been identified as a potential source of contamination. When threads are cut or formed in other ways on a metal component, or even a plastic component, a small amount of debris is often left on the threads. When the threaded connection is made, the debris may be removed through the threading action, and is then free to enter the clean fluid pathway and result in contamination of downstream components. Thus, the avoidance of threads in the clean fluid pathway eliminates this potential source of contamination. 
         [0032]    The provision of threads on the filter element  30  provides a convenient means for repairing the threaded connection should the threads be crossed or damaged in some manner. If a threaded connection is between the canister  20  and drain  40  (as in prior art systems), either the canister  20  or the drain  40 , or both, must be replaced if the threads are crossed or damaged in some other way. If threads  37  formed on filter element  30  are formed in plastic, while threads  45  on the drain  40  are formed in a harder material (possibly aluminum or another metal), when threads  37  and  45  are crossed, more than likely only threads  37  will be damaged. Threads  37  are easily replaceable by replacing the filter element  30 . Finally, the engagement between the drain  40  and filter element  30  provides a means for securely holding the filter element inside the canister  20 . 
         [0033]    Holding the filter element  30  inside of canister  20  may have some advantages during installation and replacement of the filter element  30 . For example, the canister  20  can be turned upside down by a technician to drain residual fluid therefrom, without the filter element  30  falling out. Also, the filter element  30  can be held in the correct position inside of canister  20  so that when the canister  20  is attached to the base  10 , the filter element  30  will properly align with features on the base  10 . 
         [0034]    Other advantages may also be realized in some applications. In some applications, the manufacturing of canister  20  may be simplified because no structure for engaging the drain (e.g. threads) is needed on the canister. 
         [0035]    Drain knob  50  facilitates turning drain  40  for moving between its closed and open positions. Drain knob  50  may be optionally positioned about drain  40  on the exterior of canister  20 . Drain knob  50  includes splines  51  that mate with splines  48  formed on the exterior of drain  40 . The splines  51 ,  48  allow drain knob  50  to move axially relative to drain  40  (along an axis parallel to the rotational axis of drain  40 ), but tie the two together rotationally. Turning drain knob  50  will cause a corresponding rotation of drain  40 . 
         [0036]    In addition, drain knob  50  includes camming surfaces  52  that engage with mutual camming surfaces  26  on drain boss  24 . A spring  53  acts between the drain  40  and the drain knob  50 , biasing the camming surfaces  52  towards engagement with the camming surfaces  26 . When camming surfaces  52  and  26  engage one another, they permit the drain knob  50  to rotate relative the canister  20  in only a single direction. Camming surfaces  52  and  26  may be formed to permit rotation of drain knob  50  and drain  40  in the direction of its closed position (clockwise in the illustrated embodiment), but prohibit drain  40  to rotate in the opposite direction towards its open position unless camming surfaces  52  and  26  are disengaged. They may be disengaged by pulling drain knob  50  against the bias of spring  53 , and separating the two camming surfaces  52 ,  26 . The camming surfaces  52 ,  26  permit relative rotation in one direction by providing cams whereby the cams may slide by one another in one direction. The camming surfaces  52 ,  26  prohibit relative rotation in the other direction by providing positive stopping surfaces which interfere or clash. 
         [0037]    A spring  27  may optionally act between drain  40  and canister  20 . Spring  27  biases the drain  40  into the canister  20 . This may provide advantages in inserting and removing the filter element  30 . For instance, in cooperation with the drain knob  50 , biasing the drain  40  upwards causes the camming surfaces  52 ,  26  to engage and temporarily block rotation of the drain  40  in one direction. With spring  27  positioned as shown in the figures, and with camming surfaces  52  and  26 , a technician can install a replacement filter element  30  in a simple manner by holding the canister  20  with one hand, and turning the filter element  30  with the other hand to engage the filter element  30  with the drain  40 . 
         [0038]    The canister filter system  1  may be assembled by first positioning the filter element  30  inside the canister  20 . The canister  20  includes an open end  21  through which the filter element  30  may pass, and a closed end  22 . Next the drain  40  is caused to engage the filter element  30 . The drain  40  passes through the bore  25  in the canister  20 , with the inlet end  42  projecting into the canister to engage with the filter element  30 . Preferably, the filter element  30  and drain  40  are first fully engaged, which simultaneously moves the drain to a closed position, before the canister  20  is finally engaged with the base  10  to complete the assembly. 
         [0039]    With first and second annular seals  38  and  39  (see  FIG. 1 ) integrally formed with or attached to filter element  30 , many of the surfaces and seals which provide a sealing function in the system  1  will be replaced when the filter element  30  is replaced. This helps ensure the system  1  will function properly throughout its life. 
       INDUSTRIAL APPLICABILITY 
       [0040]    The canister filter system  1  may be used to filter contaminants from fluid systems including fuel systems, lubrication oil systems, hydraulic fluid power systems, hydraulic fluid control systems, transmission fluid systems, engine air intake systems, and the like, while permitting fluid to be conveniently drained using drain  40 . Because of the arrangement of drain  40  with filter element  30 , a technician is prevented from accidentally or intentionally operating system  1  unless a filter element  30  is in place. This operability limitation helps protect components which are sensitive to contamination.