Liquid visual display

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.

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.

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.

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.