Abstract:
A method and means are described for rapidly evacuating trapped air from the top of a top-loaded liquid filter housing. An air vent means is provided that prevents complete sealing between a bypass valve and a sealing surface on an endcap of a replaceable filter element. The air vent means enables the rapid evacuation of trapped air in the top of the housing chamber, but permits only a negligible flow rate of liquid, for example oil, through the air vent means once air is evacuated due to high viscosity ratio of liquid, such as oil, versus air.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to U.S. Application Ser. No. 61/812,354 filed Apr. 16, 2013 and the contents of which are incorporated by reference herein in their entirety. 
     
    
     FIELD 
       [0002]    The technology described herein relates to a liquid filter that is provided with an air vent. 
       BACKGROUND 
       [0003]    Top-loaded liquid filter housing module designs, like those used in engine lubrication systems, which use a replaceable filter element removably disposed within a permanent housing and lid assembly, can create a “trapped air” zone above the filter element. These designs can also include a bypass valve on a centertube of the housing. The bypass valve is intended to open during an unusual “cold start” condition when low oil temperatures (and very high oil viscosity) cause such high pressure drop across the filter media that the pleated element structure could be collapsed, thereby necessitating the bypass valve as a “pressure relief” to avoid filter damage. The bypass valve may also open if the filter itself becomes completely plugged with debris, sludge, etc. and creates excessive pressure drop even during normal hot oil (low viscosity) conditions, in which case it is much more important to supply oil to the engine than to provide the continued full-filtration of oil. 
         [0004]    During oil change servicing and replacing the filter element by removing the housing lid, removing the filter element (which also allows oil to drain from the housing through a drain feature), inserting a new replacement filter element, and re-attaching the sealed lid, the housing is left in a condition where it is filled mainly with air. Upon starting the engine, the lube pump immediately supplies oil to the housing, filling it from the “bottom up” and pushing the air out of the housing through the filter media and purging it through the lube system passages and ultimately back to the crankcase sump. 
         [0005]    However, the air trapped at the top of housing cannot be purged, since it is above the endcap and filter media, and the bypass valve is sealingly engaged with the endcap. This trapped air may cause slightly slower delivery of full operating pressure to critical downstream components such as turbo bearings, main bearings, valve train, etc. due to the compressibility of air acting as an “accumulator” each time the engine is started. In addition, the trapped air, and its compressibility, acting as an accumulator or “air spring,” could also cause system pressure/flow pulsation/oscillation/instability problems due to the complexity of the lube fluid flow circuit containing pressure regulation devices, flow path splits, valves, etc. 
       SUMMARY 
       [0006]    A method and means are described for rapidly evacuating trapped air from the top of a top-loaded liquid filter housing. An air vent means is provided that prevents complete sealing between a bypass valve and a sealing surface on an endcap of a replaceable filter element. The air vent means enables the rapid evacuation of trapped air in the top of the housing chamber, but permits only a negligible flow rate of liquid, for example oil, through the air vent means once air is evacuated due to high viscosity ratio of liquid, such as oil, versus air. 
         [0007]    The air vent means can have a number of configurations as long as air can be evacuated and a negligible flow rate of liquid is permitted. The air vent means should allow the air to be quickly purged from the lid zone during pressurization with liquid. Once the air has been purged, the small size of the air vent means (and associated capillary-like viscous flow restriction) dramatically limits the amount of liquid “leakage” flow that can bypass the filter media. For example, in the case of oil as the liquid, the leakage flow would likely be less than 0.01% at normal filter differential pressure and high temperature oil conditions, making the effect on particle removal efficiency and filter performance nil. 
         [0008]    In one embodiment, the air vent means comprises a small notch on a filter endcap mating surface that engages with a housing-integral bypass valve. For example, the notch can be less than about 0.5 mm in width and depth. The notch can be molded in to the mating surface of the endcap which seats/mates with surface of the bypass valve. If a notch is used, the notch profile can be square, rounded or any moldable shape. The notch can be radial-linear, or it could be curved in spiral shape on the mating surface, or it could be at some angle relative to radial but still linear. A single notch could be provided, or more than one notch could be used. Other variations on the shape, size and number of notches are possible. 
         [0009]    If the amount of unfiltered leakage flow through the air vent means is a concern, in one embodiment a circumferential ring of filter media can be suitably attached to the filter endcap in close proximity to the air vent means to filter the leakage liquid that has passed through the air vent means. The ring of filter media can be attached to the filter endcap in any suitable manner including, but not limited to, bonded via sonic-welding, an adhesive or glue, barbs, staking, and the like. 
         [0010]    Alternatively, the circumferential ring of filter media can be suitably attached to the filter endcap in close proximity to the air vent means to filter the leakage liquid before it passes through the air vent means. 
         [0011]    If a filter media is used adjacent to the air vent means, the filter media could instead be a patch of filter media located only near the air vent means. 
         [0012]    In one embodiment, the air vent means can be formed by the ring of filter media attached to the mating surface of the endcap and engaging with the bypass valve. In this embodiment, the porosity of the ring of filter media provides the air venting, and the filter media also filters any bypass leakage flow. 
         [0013]    In another embodiment, the air vent means can be formed by texturing, for example a bumpy texture, on the mating surface of the endcap that permits air venting. The texturing would also essentially filter the leakage liquid by virtue of the texture height which can be, for example, on order of less than 100 micron. 
         [0014]    In another embodiment, the air vent means can be formed by one or more small holes formed in the cylindrical sealing flange that extends downwardly from the endcap. 
         [0015]    The air vent means can be formed by any one or combination of features mentioned above. 
         [0016]    In yet another embodiment, the air vent means is formed on the bypass valve, for example in the conical surface of the bypass valve. In this embodiment, the air vent means could be formed in any one or combination of the features mentioned above. In addition, air vent means could be formed on the cylindrical sealing flange and on the bypass valve. 
         [0017]    In one embodiment, a method is provided for air venting from a liquid filter that includes a top load filter housing and a filter element removably installable in the top load filter housing, the top load filter housing includes a centertube and a bypass valve on the centertube, and the filter element includes a cylindrical sealing flange that is designed to engage with the bypass valve when the filter element is installed in the top load filter housing is provided. The method comprises installing the filter element in the filter housing, such that an air vent means formed in the cylindrical sealing flange permits air to bleed past the cylindrical sealing flange. A filter disk may be attached to the cylindrical sealing flange at a position so that the filter disk filters liquid that flows through the air vent means. 
         [0018]    In one embodiment, a method is provided for air venting from a liquid filter that includes a top load filter housing and a filter element removably installable in the top load filter housing, the top load filter housing includes a centertube and a bypass valve on the centertube, and the filter element includes a cylindrical sealing flange that is designed to engage with the bypass valve when the filter element is installed in the top load filter housing is provided. The method comprises forming the cylindrical sealing flange of the filter element with an air vent means that permits air to bleed past the cylindrical sealing flange when the liquid filter element is installed in the filter housing. The method may include attaching a filter disk to the cylindrical sealing flange at a position so that the filter disk filters liquid that flows through the air vent means. The filter disk may be attached to the cylindrical sealing flange upstream or downstream of the air vent means. 
         [0019]    In another embodiment, a liquid filter element configured for disposition within a filter housing is provided. The liquid filter element comprises a ring of filtration media having a first end and a second end and circumscribing a central cavity, a first endcap sealingly attached to the first end of the filtration media, the first endcap including a centertube opening through which a centertube of the filter housing can pass when the liquid filter element is installed in the filter housing, and a second endcap sealingly attached to the second end of the filtration media, the second endcap including a bypass fluid opening that is opposite and coaxial to the centertube opening in the first endcap. The bypass fluid opening is defined by a cylindrical sealing flange that extends from the second endcap in a direction toward the first endcap and the central cavity, the cylindrical sealing flange includes a free end that is designed to seal with a bypass valve on the centertube when the liquid filter element is installed in the filter housing. The cylindrical sealing flange includes an air vent permitting air to bleed past the cylindrical sealing flange when the liquid filter element is installed in the filter housing. The air vent may be one or more of a notch formed in the free end of the cylindrical sealing flange, a filter disk attached to the free end of the cylindrical sealing flange, a texture provided at the free end of the cylindrical sealing flange, and a hole formed in the cylindrical sealing flange adjacent to the free end. A filter disk may be attached to the cylindrical sealing flange at a position so that the filter disk filters liquid that flows through the air vent. The filter disk may be attached to the cylindrical sealing flange upstream of or downstream of the air vent. 
         [0020]    In yet another embodiment, a liquid filter is provided. The liquid filter comprises a filter housing with a removable lid at a top of the housing, a centertube, a bypass valve on the centertube, and a liquid filter element removably disposed within the filter housing. The filter element including a ring of filtration media having a first end and a second end and circumscribing a central cavity, a first endcap sealingly attached to the first end of the filtration media, the first endcap including a centertube opening through which the centertube of the filter housing passes, a second endcap sealingly attached to the second end of the filtration media, the second endcap including a bypass fluid opening that is opposite and coaxial to the centertube opening in the first endcap. The bypass fluid opening is defined by a cylindrical sealing flange that extends from the second endcap in a direction toward the first endcap and the central cavity, the cylindrical sealing flange includes a free end that seals with the bypass valve on the centertube. An air vent is formed on one or both of the cylindrical sealing flange and the bypass valve, the air vent permitting air to bleed past the cylindrical sealing flange and the bypass valve. 
     
    
     
       DRAWINGS 
         [0021]      FIG. 1  is an exploded view of the liquid filter including a portion of the filter housing and the replaceable filter element. 
           [0022]      FIG. 2  is a close-up view of the interface between the replaceable filter element and the bypass valve of the filter housing showing an air vent means in the form of a notch. 
           [0023]      FIGS. 3A-C  illustrate examples of different kinds of notches. 
           [0024]      FIG. 4  illustrates an embodiment that uses a filter media immediately downstream of the notch. 
           [0025]      FIG. 5  illustrates an embodiment that uses a filter media immediately upstream of the notch. 
           [0026]      FIG. 6  illustrates an embodiment where a filter media forms the air vent means. 
           [0027]      FIG. 7  illustrates an embodiment where a texture on the endcap forms the air vent means. 
           [0028]      FIG. 8  illustrates the liquid filter including the filter housing and the replaceable filter element. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]      FIGS. 1 and 8  illustrate a liquid filter  10  described herein that includes a filter housing  12  and a liquid filter element  14  removably disposed within the filter housing  12 . For sake of convenience, the liquid filter  10  will be described as filtering lubrication oil, for example in an engine. However, the liquid filter  10  can be used to filter liquids other than oil including, but not limited to, engine fluids such as diesel fuel, hydraulic fluid, and other liquids. 
         [0030]    The filter housing  12  includes a main housing body  16  with a base end  18 , an open top end  20 , and a removable lid  22  that is removably attached to the main housing body to close the open top end  20 . The main housing body  16  defines an interior space  24  that in use receives the filter element  14 . A centertube  26  extends upwardly from the base end  18  toward the open end  20  through which fluid that has been filtered by the filter element  14  can flow out of the filter housing  12  to downstream components. A bypass valve mechanism  28  is disposed on the centertube  26 . The bypass valve mechanism  28  includes a valve  30  that is biased upwardly by a spring  32 . The valve  30  includes an upwardly facing conical surface  34  that in use is configured to mate with a mating surface (described below) on the filter element  14  when the filter element is installed. The filter housing  12  described so far is conventional, and further information can be found in U.S. Pat. No. 5,770,054, incorporated herein by reference in its entirety. 
         [0031]    The filter element  14  includes a ring of filtration media  40  having a first end  42  and a second end  44  and circumscribing a central cavity  46 . The filtration media  40  is designed to filter the liquid with which it is used, in this example lubrication oil. A first endcap  48  is sealingly attached to the first end  42  of the filtration media  40 . The first endcap  48  includes a centertube opening  50  through which the centertube  26  of the filter housing passes when the liquid filter element  14  is installed in the filter housing. A seal  52  disposed on the filter element around the opening  50  seals with the outside of the centertube  26  to prevent fluid leakage between the first endcap  48  and the centertube. 
         [0032]    A second endcap  54  is sealingly attached to the second end  44  of the filtration media  40 . The second endcap  54  includes a bypass fluid opening  56  that is opposite and coaxial to the centertube opening  50  in the first endcap  48 . The bypass fluid opening  56  is defined by a cylindrical sealing flange  58  that extends downwardly from the second endcap  54  in a direction toward the first endcap  48  and into the central cavity  46 . 
         [0033]    The cylindrical sealing flange  58  includes a free end  60  that is designed to mate with the conical surface  34  of the valve  30  when the liquid filter element is installed in the filter housing. The free end  60  of the sealing flange  58  seals, but not completely, with the conical surface  34  to inhibit bypass flow of the liquid past the filter element. 
         [0034]    The cylindrical sealing flange  58  includes air vent means that permits air that accumulates in the area above the second endcap  54  to bleed past the cylindrical sealing flange  58  and the conical surface  34  of the valve. The air vent means enables the rapid evacuation of trapped air in the top of the housing chamber above the second endcap, but permits only a negligible flow rate of oil through the air vent means once the air is evacuated. The air vent means allows the air to be quickly purged from the lid zone during pressurization with liquid. The air vent means can have a number of configurations as long as air can be evacuated and a negligible flow rate of liquid is permitted. Once the air has been purged, the small size of the air vent means dramatically limits the amount of liquid “leakage” flow that can bypass the filter media. For example, in the case of oil, the leakage flow may be less than 0.01% at normal filter differential pressure and high temperature oil conditions present in conventional lubrication oil filters, making the effect on particle removal efficiency and filter performance nil. 
         [0035]    With reference to  FIG. 2 , in one embodiment, the air vent means includes one or more notches  62  formed at the free end  60  of the flange  58 . The notch  62  can be formed by any suitable process, for example by integrally molding the notch during formation of the endcap  54 . The notch  62  can have a profile that is square (see  FIG. 3B ), rounded (see  FIG. 3A ) or any other shape. The notch  62  can extend radially relative to a central axis of the filter (see  FIGS. 3A-B ), or the notch  62  can be curved in a spiral shape at the free end  60 , or the notch could be at an angle relative to radial but still linear (see  FIG. 3C ). A single notch could be provided as illustrated in  FIGS. 1-3A , or more than one notch could be used. In one non-limiting example, the notch  62  can be less than about 0.5 mm in width and depth. 
         [0036]    The notch  62  permits air located at the top of the filter  10  to bleed past the flange  58  and the valve  30  to purge air from the filter. The air flows from the top of the filter into the centertube  26  and ultimately back to the oil sump. Once the air is vented, the notch  62  permits a very small amount of oil to bleed past the flange  58  and the valve  30  as well. 
         [0037]    With reference to  FIG. 4 , an embodiment is illustrated that uses a filtration media  64  positioned immediately adjacent to the outlet of the notch  62  to filter the bypass oil that flows through the notch  62 . In the illustrated example, the media  64  is in the form of a circumferential ring that is attached to the free end  60  of the flange  58  at or near the outlet of the notch. The filtration media  64  could instead be a patch of filter media (i.e. not a circumferential ring) located only near the outlet of the notch  62 . The media  64  should be positioned between the free end  60 , the valve  30  and the upper end of the centertube  26  to prevent the bypass oil from bypassing the media  64 . 
         [0038]    With reference to  FIG. 5 , another embodiment is illustrated that uses a filtration media  66  positioned immediately adjacent to the inlet of the notch  62  to filter the bypass oil that flows through the notch  62  before it flows through the notch. In the illustrated example, the media  66  is in the form of a circumferential ring that is attached to the interior surface  68  of the flange  58  at or near the inlet of the notch. The filtration media  66  could instead be a patch of filter media (i.e. not a circumferential ring) located only near the inlet of the notch  62 . The media  66  should be positioned between the flange  58  and the valve  30  to prevent the bypass oil from bypassing the media  66 . 
         [0039]      FIG. 6  illustrates another embodiment where the air vent means is foliated by a circumferential ring of filtration media  70 . In this example, the media  70  is attached to the free end  60  and engages with the conical surface  34  of the valve  30 . The porosity of the ring of filter media  70  provides the air venting, and the filter media  70  also filters any bypass leakage flow. The air venting and bypass flow in this embodiment would be 360 degrees. However, the ring of media  70  could be formed with one or more non-porous zones in order to tailor the amount and/or location(s) of the air and liquid bypass flow. 
         [0040]      FIG. 7  illustrates an embodiment where the free end  60  of the flange  58  appears to seal with the conical surface  34  of the valve  30 . However, the surface  72  of the free end  60  of the flange  58  that faces the conical surface  34  is provided with texturing which forms the air vent means. The texturing can be, for example, a bumpy texture, or any texture that allows air venting and a small amount of liquid bypass flow as shown by the arrows. The texturing would also essentially filter the leakage oil by virtue of the texture height which can be, for example, on order of less than 100 micron. The texturing can be located around the entire circumference of the surface  72 , or located at one or more portions of the surface  72  in order to tailor the amount and/or location(s) of the air and liquid bypass flow. 
         [0041]    In one embodiment, the air vent means may be an air vent. According to another embodiment, the cylindrical sealing flange includes an air vent permitting air to bleed past the cylindrical sealing flange when the liquid filter element is installed in the filter housing. The air vent may be formed by one or more of: a notch formed in the free end of the cylindrical sealing flange; a filter disk attached to the free end of the cylindrical sealing flange; a texture provided at the free end of the cylindrical sealing flange; and a hole formed in the cylindrical sealing flange adjacent to the free end. A filter disk may be attached to the cylindrical sealing flange upstream of or downstream of the air vent. In another embodiment, an air vent may be formed on one or both of the cylindrical sealing flange and the bypass valve, the air vent permitting air to bleed past the cylindrical sealing flange and the bypass valve. 
         [0042]    The invention may be embodied in other forms without departing from the spirit or novel characteristics thereof The embodiments disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.