Abstract:
A display provides an indication of the remaining useful life of a filter element by providing a visible level of fluid in the display corresponding to the remaining useful life. The fluid level is adjusted by a valve responsive to a pressure differential across the filter element. An increasing pressure differential produces an increased fluid level in the display. The display may be provided with markings indicating that a particular fluid level in the display corresponds to the need to change a filter cartridge containing the filter element.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/715,777, filed Sep. 9, 2005, the contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to fluid systems having a filtration device in which restriction of the filtration device can be determined by measurement of pressure. More specifically, the invention relates to devices for indicating whether a fluid filter requires replacement. 
     2. Description of the Related Prior Art 
     Fluid systems requiring filtration apparatus are an integral part of the automotive and heavy equipment industries. Engine systems, hydraulic systems and various other collateral systems require fluids such as air, oil, fuel and coolants to be at least partially contained and directed to their functional end points. For instance, in engine systems utilizing diesel fuel, extremely high-pressure pumps are utilized. These pumps have very close tolerances and may be easily damaged or disabled by particulate laden fuel. In addition, the fuel injectors of these engines are configured to deliver a spray of fuel in a specifically designed pattern. Interference with the passages, orifices or other structures of the injectors may result in a decrease in engine efficiency and/or damage to the engine itself. Most of the above-described fluid systems, including most diesel fuel systems, require at least one filter to be present. 
     In diesel fuel systems, a primary fuel filter is arranged between the fuel storage compartment and the high-pressure fuel pump. Fuel delivery systems for diesel engines typically include a fuel supply pump for delivery of partially pressurized fuel to the high-pressure pump. These fuel supply pumps can be arranged in the fuel storage compartment or close to the high-pressure pump. When arranged in the fuel storage compartment, the supply pump pressurizes the fuel supply line leading to the high-pressure pump. When arranged close to or as part of the high-pressure pump, the supply pump creates negative pressure in the supply line between the fuel storage compartment and the supply pump. 
     Depending on such things as preventative maintenance scheduling, fluid quality, operating conditions and the like, filters become restricted or clogged at various rates. Filter occlusion may adversely impact system efficiency and in some cases may damage or destroy system components. In other cases restriction of the filter can result in filter failure which may allow highly contaminated fluid to reach portions of a high pressure pump or fuel injection system, resulting in extremely high repair costs for those devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view through an exemplary filter assembly in combination with an exemplary embodiment of a liquid visual display according to aspects of the present invention; and 
         FIGS. 2A through 2C  are exterior elevation views of a filter assembly incorporating an exemplary liquid visual display according to aspects of the present invention showing visual indications of filter life by liquid levels in the display. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred embodiment of the liquid visual display according to aspects of the present invention will now be described with reference to  FIGS. 1-2C  wherein like numerals refer to similar parts. 
     The liquid visual display  10  is configured for attachment to a filter assembly  12 .  FIGS. 1-2C  illustrate the liquid visual display attached to the base  14  of the filter assembly  12 . The base  14  is the portion of the filter assembly  12  configured to define a filter receptacle and removably receive a disposable filter cartridge  16 . The filter base  14  defines fluid communication pathways  18 ,  20  from a fuel storage compartment or fuel tank to the filter cartridge  16  and from the filter cartridge  16  toward the high-pressure pump, respectively. The filter base  14  circulates unfiltered fuel through a filter element  15  contained in the received filter cartridge  16  before routing the filtered fuel into the flow pathway  20  toward the high-pressure pump. Together, the filter base  14  and filter cartridge form a filter assembly, the construction and function of which are well known. 
     The liquid visual display  10  is configured to sense a pressure differential across the filter element  15  and provide a visual indication of that pressure differential in the form of a fluid level visible in a transparent dome  22 . According to aspects of the present invention, a low fluid level in the dome  22  corresponds to a low-pressure differential across the filter element, indicating a large proportion of filter life remaining as shown in  FIG. 2A . A high level of fuel in the transparent dome  22  is indicative of little or no fuel life remaining and is produced by a corresponding high-pressure differential across the filter element as shown in  FIG. 2C . 
     The variable fluid level in the dome is accomplished by a valve  36 , which interacts with a float  42  via a spring  40 . As best seen in  FIG. 1 , the dome  22  is secured to the top or header portion of a filter base  14  in a vertical orientation. An air bleed  24  having an extended stem  26  is threadably engaged through the top of the dome  22  and extends downwardly to sealingly communicate with the fuel inlet passage  18 . The stem  26  of the air bleed  24  includes an axial passage  28  and a transverse orifice  30  close to the top of the dome  22 . The axial passage  28  and transverse orifice  30  communicate the pressure in the fuel inlet passage  18  with the interior of the dome  22 . A valve seat/float guide  32  sealingly engages a fuel outlet conduit  34 , which communicates with the fuel outlet passage  20  from the filter. A valve  36  carries a sealing member  38  positioned beneath the valve seat and exposed to the pressure of the fuel outlet passage  20 . 
     Thus, the valve  36  and its sealing member  38  are positioned between the interior of the dome, which is exposed to the fuel inlet pressure and the outlet conduit which is exposed to the fuel outlet pressure. The fuel outlet pressure will always be less than the fuel inlet pressure, with the result that the valve  36  and its sealing member  38  will be exposed to downward force in the illustrated embodiment. The valve  36  is biased toward an upward or sealed position by a spring  40  engaged between a head of the valve and a spring seat molded in a float  42 . 
     The float  42  is configured to substantially fill the interior of the dome  22 , thereby minimizing the free volume inside the dome. The float  42  is substantially cylindrical in configuration and includes an axial hole  44  to accommodate the valve seat/float guide  32 . The float  42  also includes an off axis hole  46  to accommodate the stem  26  of the air bleed  24 , the transverse orifice  30  of the air bleed  24  communicates with the off axis hole  46  in the float  42  which also communicates with the interior of the dome. The buoyancy characteristics of the float  42  and the spring force of the spring  40  are selected so that the valve  36  is pulled away from its sealed position (downwardly in the Figures) when the pressure differential between the inlet passage  18  and outlet passage  20  (across the filter element) reaches a predetermined level. 
     Unseating the valve  36  allows air to be drawn from the interior of the dome into the fuel outlet passage  20  and permits fluid to be drawn into the dome through the axial passage  28  and transverse orifice  30  of the air bleed  24 . Fluid entering the interior of the dome  22  exerts an upward buoyant pressure on the float  42 , which increases the upward bias on the valve  36 , re-seating the valve. Thus, the float  42 , spring  40  and valve  36  interact to provide a variable seating force on the valve  36  in response to the fluid level in the dome. The transverse orifice  30  is positioned such that fluid entering the dome cannot return to the fluid inlet  18 . This, the level of fluid in the display reflects a maximum pressure differential across the filter element and not the pressure differential at any given moment in time. It will be apparent to those skilled in the art that the pressure differential across the filter element will vary according to the operating conditions of the system. It is the maximum pressure differential across the filter element that is most relevant to the remaining service life of the element. 
     As the filter  16  becomes occluded with particulate matter, the pressure differential across the filter element will rise, exerting increasing pressure on the valve  36  and its sealing member  38 . An increasing pressure differential will again unseat the valve  36 , permitting more fluid to enter the interior of the dome. Higher fluid levels in turn exert a greater buoyant force on the float  42 , compressing the spring  40  and increasing the upward sealing force on the valve  36 . 
       FIGS. 2A-2C  illustrate the appearance of the liquid visual display  10  corresponding to various filter conditions.  FIG. 2A  shows a low level of fluid in the dome, corresponding to a low-pressure differential across the filter element or approximately 100% of filter life remaining.  FIG. 2B  illustrates an intermediate level of fluid in the dome, indicative of an increased pressure differential across the filter element corresponding to approximately 50% of filter life remaining.  FIG. 2C  illustrates a high level of fluid in the dome, corresponding to a relatively high-pressure differential across the filter element, indicating little or no filter life remaining. The liquid visual display may be provided with colored bars or other indicia correlating the level of fluid in the dome with the relative filter life or need to change the filter. 
     The pressure differential corresponding to the fluid level in  FIG. 2A  is approximately 1-2 inches of mercury. The pressure differential corresponding to the fluid level in  FIG. 2C  is approximately 7-10 inches of mercury. 
     An alternative configuration would eliminate the spring between the float and valve so that the valve is biased by the float alone. 
     The liquid visual display as illustrated in  FIGS. 1-2C  is configured to function in either a pressurized or vacuum fluid delivery line. A pressurized fluid delivery line is one in which the filter assembly is located between the supply pump and the high-pressure pump. A vacuum or suction fuel supply system is one in which the filter assembly is located between the fuel supply and the supply pump. The liquid visual display is configured to detect a true pressure differential between the fuel inlet and fuel outlet of the filter assembly, since it communicates with both of these pressures. 
     While a preferred embodiment of the foregoing invention has been set forth for purposes of illustration, the foregoing description should not be deemed a limitation of the invention herein. Accordingly, various modifications, adaptations and alternatives may occur to those skilled in the art without departing from the spirit and the scope of the present invention.