Abstract:
A fuel filter for an engine includes a housing having an interior space and is assembled into a fuel flow path between a source of fuel and the engine. The housing includes a passageway which has an inlet aperture which is used to control the delivery of fuel to either the engine or back to the source of fuel. The housing also includes a return-fuel passageway which is in flow communication with the interior space and is adapted to couple to the source of fuel. A filter cartridge is installed within the housing and includes an end cap with an air vent tube having an inlet opening. The air vent tube is designed so as to assemble into the passageway, so as to plug the inlet aperture. Once the inlet aperture is plugged by the air vent tube, the flow entrance to the passageway is raised from the inlet aperture to the inlet opening of the air vent tube. The plugging of the inlet aperture by the air vent tube allows fuel to be delivered to the engine. When the air vent tube is not assembled into the inlet aperture, fuel is drained back to the source and does not reach the engine. The fuel filter further includes a pressure-regulated control valve which is installed within the return fuel passageway and is activated by the internal pressure within the housing. This valve permits excess fuel to be returned to the source of fuel.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates in general to a fuel filter and a fuel filtering system for use with a vehicle, wherein the fuel filter is located “downstream” from a fuel pump. More specifically, the present invention relates to the design of a fuel filter which is used within a fuel filtering system and which includes a pressure-controlled, spring-biased, internal valve that enables the automatic draining of excess fuel back to either the fuel tank or to a suction-side primary filter. The fuel filter of the present invention includes a water-separation capability such that accumulated water is automatically drained with excess fuel by means of the internal valve, thereby precluding the need for a separate water-drain mechanism. The design of the present invention also precludes the need to prompt the user to activate or open any separate water-drain mechanism in order to periodically drain the accumulated water from the interior of the fuel filter housing. 
     Fuel filters and fuel filtering systems have been used in the automotive field and related vehicle and equipment fields for a number of years. The structural configurations of these earlier fuel filters and fuel filtering systems have included a number of design variations and improvements, all in an effort to try and solve certain design shortcomings. The present invention is no different in this regard. Certain disadvantages and shortcomings of existing fuel filter and fuel filtering system designs have been considered by the present inventors and the present invention provides structural design improvements in order to overcome and/or improve upon those disadvantages and shortcomings. One concern with fuel filtering systems is whether unfiltered fuel can be delivered to the fuel injectors or other critical engine components which utilize the fuel for combustion. Since small particulate matter can be detrimental to the long term efficacy of the fuel injection equipment (FIE), filtering of the fuel is particularly important for vehicles which use modern, high pressure FIE. When the filtering media cartridge is not installed in the filter housing, it would be an improvement to be able to prevent fuel flow to the FIE. The present invention provides this capability by means of a unique drain passageway which is wide open whenever the filtering media cartridge is removed. 
     Another concern with fuel filters which have a screw-on or snap-on cap, cover or lid is the entrapment of air inside of the fuel filter housing. As fuel is delivered to the fuel filter, the trapped air can only exit by passing to the engine or injectors or by flowing back to the fuel tank. Since the trapped air is at the top of the fuel volume within the filter housing, its most likely exit path is to flow with the fuel to the FIE and combustion cylinder. Accordingly, trapped air can interfere with the smooth and continuous delivery of fuel to the engine. It would therefore be an improvement to be able to route the trapped air back to the fuel tank. The present invention provides this capability by a unique air vent tube which cooperates with the aforementioned drain passageway. 
     Another concern with fuel filters and fuel filtering systems which include a water-separation capability is when and how to drain the accumulated water. Since the separated water typically accumulates at the base of the fuel filter housing, below the fuel, the most common approach is to provide a separate water drain valve. Release or activation of the water drain valve can be manual or automatic. With manual draining, the user has to remember to periodically open the drain valve in order to drain the accumulated or collected water. While automatic drain systems are frequently based on the water level and the electronic sensing of that water level, these designs still necessitate a separate drain valve and associated hardware and electronics. These drain systems also involve the addition of hardware, components and electronics outside of the filter housing which can in turn interfere with other engine components. 
     The fuel which is pumped to the fuel filter is delivered at a flow rate which is greater than the usage rate of the engine. This means that there is excess fuel which has to be returned to a point in the flow loop which is upstream of the fuel filter, such as to the fuel tank or to the fuel pump, for example. The present invention provides a design improvement to this task by incorporating a pressure-regulated drain valve that automatically drains both excess fuel and accumulated water whenever the internal pressure within the filter housing exceeds a predetermined level. This automatic draining of accumulated water precludes the need for any external components, hardware or electronics. The design of the present invention also precludes the need for the user to remember to periodically activate or release the water drain valve. 
     The improvements of the present invention represent novel and unobvious advances in the state-of-the-art for fuel filters and fuel filtering systems. 
     SUMMARY OF THE INVENTION 
     A fuel filter for an engine according to one embodiment of the present invention comprises a housing having an interior space and being constructed and arranged to be assembled into a fuel flow path between a source of fuel and the engine, the housing including an integral flow passageway having a flow inlet aperture and being adapted for flow connection to the source of fuel. Included as part of the fuel filter is a fuel filter cartridge which is installed within the housing and includes an end cap with an air vent tube which has an inlet opening and an exit opening. The air vent tube is assembled into the integral flow passageway so as to plug the flow inlet aperture such that the flow entrance to the integral flow passageway is changed from the flow inlet aperture to the inlet opening of the air vent tube. By positioning the inlet opening of the air vent tube near the upper end of the filter housing, fuel is able to be delivered to the engine only when the filter cartridge is properly installed. 
     One of the objects of the present invention is to provide an improved fuel filter. 
     Related objects and advantages of the present invention will be apparent from the following description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a fuel filter according to a typical embodiment of the present invention. 
     FIG. 2 is a side elevational view in full section of the FIG. 1 fuel filter as assembled. 
     FIG. 3 is a diagrammatic illustration of a fuel filtering system which includes the FIG. 1 fuel filter according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
     Referring to FIG. 1, there is illustrated as an exploded view, a fluid filter  20  which is configured according to a preferred embodiment of the present invention. The fluid in this preferred embodiment is fuel. Fuel filter  20  includes, as some of its primary components, a main housing  21 , filter element  22 , standpipe  23 , centertube  24 , upper end cap  25 , lower end cap  26 , and cover  27 . Also included as part of the construction of fuel filter  20  is a seal  31 , plug  32 , latch  33 , and mounting bracket  34 . Bracket  34  is preferably an integral or unitary part of main housing  21 . 
     The main housing  21  is a unitary casting and is configured with fuel outlet ports  40  and  41 , fuel inlet port  42  and excess fuel return port  43 . These various ports are configured as hollow passageways with a generally cylindrical geometry. In the preferred embodiment of the present invention, the disclosed fuel filter  20  is used in conjunction with a V-8 engine and the fuel injectors are grouped with four injectors in the left bank and the remaining four injectors in the right bank. One outlet port  40  delivers fuel to the left bank of injectors and the other outlet port  41  delivers fuel to the right bank of injectors. Threaded fluid fittings  44 ,  45 ,  46  and  47  are threaded into the ends of the corresponding ports as illustrated and serve to facilitate the connection of the required fluid conduits (not illustrated) to the four ports. Fitting  44  is assembled into port  40 , fitting  45  into port  41 , fitting  46  into the fuel inlet port  42 , and fitting  47  into the fuel return port  43 . A pressure-regulated drain valve  50  is assembled into the hollow interior of return port  43  prior to assembly of fitting  47 . 
     The interior of the main housing  21  is configured to include a fuel drain passageway  51 . A cooperating air vent tube  52  which fits into passageway  51 , is included as part of the upper end cap  25 . The details of the overall construction of filter  20  are also illustrated in FIG. 2, and the overall fuel filtering system for filter  20  is diagrammatically illustrated in FIG.  3 . 
     Since much of what is illustrated as comprising the construction of fuel filter  20  will be known to a person of ordinary skill in the art, the focus of the present invention is directed to two areas which constitute two of the more important aspects of the present invention. As illustrated, the main housing  21  is a unitary casting and the fuel drain passageway  51  is cast as part of the inner wall  53  of the main housing. Passageway  51  extends from upper ledge  54  downwardly to its point of intersection  55  with return port  43 . There is flow communication between return port  43  and passageway  51 . Return port  43  which extends into the base  56  of housing  21  includes a first (threaded) portion  57  which receives fitting  47  and a second portion  58  which receives drain valve  50 . Connecting fluid passageway  59  establishes a fuel flow path from the hollow interior of housing  21  to the innermost end  61  of inner portion  58 . This flow path allows excess fuel and accumulated water in the interior of housing  21  to flow through passageway  59 , around drain valve  50 , out the threaded portion  57  of excess fuel port  43 , through fluid fitting  47  and back upstream to either the fuel tank  64  or to the primary fuel filter  65  (see FIG.  3 ). Region  60  is intended to diagrammatically represent the assembly of the standpipe  23  into the housing base and the telescoping receipt of the centertube  24  by the standpipe  23 . Since this is a typical construction technique for fluid filters, additional details are not necessary. 
     The pressure-regulated drain valve  50  includes a hollow valve plunger  68  which has a grooved or fluted outer body  69  and a closed base  70 . Also included as part of valve  50  is spring  71  which fits within the hollow interior of valve plunger  68  and a fixed support plate  72 . Circular support plate  72  is press fit into position within inner portion  58  and functions to fix the position of (one end of) spring  71  and in effect, the position of the drain valve  50 . The spring length and spring constant are selected so as to establish the fluid pressure which will cause the valve plunger  68  to move to the left in the FIG. 2 illustration, which is a direction toward the outer surface of housing  21 . 
     Inner portion  58  is counter-bored in order to create valve seat surface  75  which has a conical geometry. Valve plunger  68  is configured with an abutment flange  76  which has a conical surface  77  with a size, shape and overall geometry which is designed to seat on valve seat surface  75  in a sealed or liquid-tight manner. It should be understood that the axial distance between the fixed position of support plate  72  and surface  75  relative to the location of closed base  70  and the length of spring  71  creates a continuous spring force on the inner surface  70   a  of base  70  and this pulls the conical surface  77  of flange  76  tightly against valve seat surface  75 . As described, the drain valve  50  is in a normally-closed position due to the action of spring  71 . The valve is movable to a flow-enabling position due to the internal pressure. 
     In operation, when the excess fuel and any accumulated water reach a fluid pressure greater than approximately 45 psi, as seen by the exposed end  70   b  of base  70  which is positioned adjacent the edge of passageway  59 , the valve plunger  68  moves in the direction of fitting  47  which in the illustration of FIG. 2, is to the left. This movement of the valve plunger  68  lifts surface  77  off of surface  75 . Since the outer body of the valve plunger  68  includes full length grooves, the fuel and any water present adjacent base  70  on the interior of the main housing, is able to flow through the grooves and then through the separation between surfaces  77  and  75 . At this point, the fuel and any water pass through drain holes in plate  72 . From here the fuel and any water is able to flow out of the filter housing by means of excess fuel return port  43  and threaded fluid fitting  47 . The predetermined pressure setting of 45 psi, which is the threshold level which needs to be exceeded in order to open the drain valve, is controlled primarily by the spring constant of spring  71  and by the surface area of the exposed circular end  70   b  of base  70 . While there may be a slight counter-acting pressure on the side of the valve plunger  68  which is opposite to passageway  59 , any flow-through fuel passageway  51  more likely flows directly out through port  43  and fitting  47 . If this flow is rapid enough, a small venturi-effect can actually be created on this opposite side of the pressure-regulated drain valve  50 . If a venturi-effect is created, there would actually be a small pressure drop in this location. However, the magnitude of any venturi-effect and thus, the magnitude of any pressure drop, is believed to be negligible in view of the minimum flow volume and the minimal flow rate of fuel through passageway  51  when the fuel filter is fully assembled and functioning within the fuel filtering system  79  of FIG.  3 . 
     If the fuel filter element  22  is not installed within the remainder of fuel filter  20 , it is preferred that fuel not be delivered to the engine. In this way, any small particulate matter that might otherwise interfere with the fuel injectors is prevented from reaching the injectors. Since the fuel pump  80  can be operated whether or not a fuel cartridge is installed, any such safety mechanism or safety feature would preferably be incorporated directly into the fuel filter. According to the present invention, the fuel drain passageway  51  is integrally cast as part of the unitary main housing  21  and allows fuel to drain by way of port  43  once the fuel level in the housing reaches the height of ledge  54  which defines the upper inlet opening  82  of passageway  51 . Once the fuel reaches the level of ledge  54 , it is able to flow into the inlet opening  82  and from there down through passageway  51  in the direction of the base and to the point of intersection  55  between passageway  51  and portion  58 . Any fuel which is going to be delivered to the two banks of fuel injectors, must rise to a level above ledge  54 . However, any fuel at that level, assuming that the air vent tube  52  is not installed, is routed to the excess fuel return port  43 , thereby preventing any unfiltered fuel from ever reaching the injectors as unfiltered fuel. 
     When the air vent tube  52  is inserted into inlet opening  82  and into passageway  51 , the flow opening  82  is closed (i.e. plugged) and the fuel level within the main housing is then above to rise above ledge  54  to a level that allows the fuel to be delivered to the fuel injectors. The insertion of tube  52  into opening  82  effectively raises the flow inlet location for passageway  51  to a location which is closer to cover  27 . Inlet opening  52   a  is located adjacent to cover  27  as is illustrated. While tube  52  is open at its top  83  (i.e. inlet opening  52   a ) and at its free (lower) end  84 , the opening  85  at end  84  is quite small and noticeably smaller in diameter than the remainder of the hollow interior of tube  52 , including the opening  52   a  at top  83 . The size of opening  85  freely permits air which has little or no measurable viscosity to flow and escape from the interior of the fuel filter. However, the more viscous fuel, at least compared to air, has a difficult time in freely passing through the smaller opening  85 . Consequently, any fuel which might be present at the open top  83  of tube  52  and thereby drain through tube  52  and ultimately through passageway  51 , is of a minimal amount compared to the substantially larger volume of fuel delivered to the fuel filter by the fuel pump  80 . The large volume of fuel which is handled by the fuel filter is sufficient to fully supply the fuel injectors and allow the excess to drain by way of the pressure-regulated drain valve  50 , notwithstanding that there might also be some minor or minimal flow by way of air vent tube  52  and fuel drain passageway  51 . 
     The fit of tube  51  into opening  82  of passageway  51  only needs to be reasonably close such that if there is any leakage flow through this interface, it is of minimal volume so as to not affect the rising fuel level and a sufficient supply of fuel to the fuel injectors. The tube  52  is an integral part of the unitary upper end cap  25  which is securely and fixedly attached to the upper end of the filter element  22 . Consequently, as the filter element  22  with its centertube  24  assembled and with both end caps attached, is inserted onto standpipe  23 , care must be taken to align the air vent tube  52  with the housing  21  so that the air vent tube  52  fits into and plugs opening  82 . In order to facilitate this assembly, alignment indicia (not illustrated) are provided (preferably marked) on the upper surface  86  of the upper end cap  25  and on the upper edge  87  of the main housing  21 . These marked alignment indicia simply need to be circumferentially aligned so as to be in the same radial line and once this is done, the tube  52  will be accurately aligned with opening  82  for direct and interference-free insertion of tube  52  into opening  82  upon the axial movement of the filter cartridge onto the standpipe  23 . The assembly of the two end caps and the centertube to the filter element  22  creates the referenced filter cartridge. 
     As the cover  27  is assembled onto the upper open end  88  of the main housing  21 , it is possible for air to be trapped. The pressure head created by this trapped air could interfere with the assembly of the cover, as well as create a pressure on the residual fuel and force some of this fuel to drain. Activation of the fuel pump would then push this trapped air through to the injectors which would delay the delivery of fuel. By including the air vent tube  52  as part of the present invention, a portion of this trapped air is able to escape by way of tube  52  and passageway  51  to port  43 . While some air may still be trapped, a substantial portion is initially vented. Then as the fuel level rises, the remainder of the trapped air or at least the majority of it, is able to escape from the interior of the main housing in the same manner. As a consequence of this unique air vent tube and its interface with the passageway  51 , most all of the trapped air is vented back to the fuel tank (or possibly to the primary fuel filter) and only a very minimal amount of air, if any, is actually seen by the fuel injectors. In the preferred embodiment, the open end  88  of the housing is internally threaded and the cover  27  is externally threaded for threaded assembly into the open end. 
     Referring to FIG. 3, the fuel filtering system  79  associated with fuel filter  20  is diagrammatically illustrated. System  79  includes, in addition to fuel filter  20 , a fuel tank  64 , primary fuel filter  65 , and fuel pump  80 . The fuel is contained within tank  64  and is pulled through the primary fuel filter  65  by the action of pump  80 . The suction force of pump  80  pulls the fuel through the filter  65  and then with a positive pressure, pushes the fuel through fuel filter  20 . The excess fuel return port  43  by way of fitting  47 , is connected to the fuel tank  64 , such that excess fuel, accumulated water, and possibly some air, is returned to the fuel tank  64 . The requisite fuel for the engine is pumped to the two banks of injectors as denoted by arrow  89 . 
     Depending on the overall temperature of the fuel which is delivered to the primary fuel filter from the tank, it is possible for the fuel to wax-up on the surface of the filter cartridge of the primary fuel filter  65 . Since work is done on the excess fuel which is returned to the fuel tank, its temperature will be elevated. System  79  is designed so that the temperature of the fuel on the inlet side of the primary fuel filter  65  can be sensed and depending on the fuel temperature, the returned fuel can either be routed back to the fuel tank or to the primary fuel filter or both. As is illustrated, there is a diverter valve  90  which is in communication with the temperature sensing probe on the inlet side of the primary fuel filter. Valve  90  is configured to direct either all of the returned fuel to the primary fuel filter or only a portion of it, with the remainder being directed back to the fuel tank, depending on the temperature of the fuel on the inlet side of filter  65 . In operation, if the temperature sensed on the inlet side of the primary fuel filter suggests that the fuel may be experiencing some degree of thickening or waxing-up, then by diverting some or all of the warmer returned (excess) fuel, the problem attributed to the lower temperature fuel can be alleviated. By introducing the warmer returned fuel directly to the primary fuel filter, it is intended to lower the viscosity of the fuel at that point, allowing freer flow through the primary fuel filter. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.