Measuring and testing – Simulating operating condition – Marine
Reexamination Certificate
1999-06-30
2001-09-18
McCall, Eric S. (Department: 2855)
Measuring and testing
Simulating operating condition
Marine
C116S266000, C116S276000, C073S715000
Reexamination Certificate
active
06289726
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a mechanical filter gauge for determining the filtering capability of a vehicle filter, and in particular to a mechanical gauge for measuring and displaying the functionality of a vehicle's fuel filter.
The improved device of the present invention is used in connection with a fuel filter for internal combustion engines. It is particularly useful for application to trucks, particularly fleet trucks where a reduction in fuel filter changes can lead to significant cost savings. Formerly, to save costs, preexisting air filter gauges, such as those disclosed in U.S. Pat. Nos. 4,369,728 and 4,445,456, were modified to serve as fuel filter gauges, in order to minimize tooling costs and to utilize familiar technology. However, these gauges proved relatively costly, due to the materials needed to withstand fuels.
Prior art fuel filter gauges are also larger than necessary. The vacuum range of a plugged fuel filter is about five times higher than for an air filter. This translates into piston forces which are five times higher in the larger size prior art fuel gauge. The additional requirement of handling 20 psi back pressure creates excessive forces in the existing gauge causing damage.
Prior art fuel filter gauges also required felt filters in the base in the area of the reset button. However, these felt filters can be inadvertently mispositioned, resulting in leaks. The felt filters could also leak and freeze if the fuel filter gauge was mounted with the push button reset gauge in an upward position.
Certain fuel systems include two fuel filters, thereby requiring two fuel filter gauges. These systems have the first filter located prior to a ten psi electric in-line fuel pump, for example, with the second filter positioned between this electric pump and the engine driven pump located adjacent to the engine. The fuel filter gauge located after the first filter but before the first pump will be exposed to suction vacuum only, typically up to 10 in.Hg as the first filter plugs. The second fuel filter gauge attached to the fuel system after the second fuel filter will be exposed to pressure up to 10 psi or the pressure level the in-line electric pump is capable of producing. The second gauge will eventually respond to vacuum created by the engine driven pump when filter restriction due to plugging is great enough to block flow from the in-line pump. Thus the fuel filter gauges must withstand both pressure and vacuum, which has proven problematic for prior art fuel filter gauges. Back pressure can occur in two pump fuel systems and during initial pressurization testing for leaks in the fuel system at the assembly plant. The lock pin mechanism of prior art fuel filter gauges had difficulty withstanding the back pressure force and the prior art diaphragm could reverse fold against the edges of the metal diaphragm retainer causing a cut therefrom and a resulting leak.
A gauge of this type preferably indicates the condition of the fuel filter and locks itself in position, permitting determination of the condition of the fuel gauge even when the vehicle engine is not running. In the prior art, however, lock pin forces were concentrated at points that were prone to overload, distortion and breakage at high operating temperatures.
Additionally, prior art indicators have not always been easy to fully reset, due in part to poor leverage, high lock force, and high reset spring force, sometimes resulting in a gauge that may give a false, premature signal that a filter requires replacement. This may in turn result in unnecessary filter maintenance.
The fuel filter gauge of the present invention overcomes difficulties described above and affords other features and advantages heretofore not available.
SUMMARY OF THE INVENTION
The fuel filter gauge of the present invention indicates when the fuel filter of an internal combustion engine requires replacement by measuring the performance of the filter by measuring the vacuum in the fuel system of the vehicle. The device gives a gradual reading from a clean filter condition to a dirty filter condition and automatically locks into the highest clogged fuel flow condition experienced during engine operation so that it may be read after shutdown and may also be monitored during engine operation.
An object of the invention is to provide a gauge for indicating that a fuel filter for a vehicle with an internal combustion engine requires replacement. It is a further object of this invention to provide such a gauge that is reliable over a long period of time despite constant exposure to engine fuel.
It is a further object of the invention to provide such a gauge that is relatively smaller in size, thereby reducing material costs. Reduction in size also results in a smaller diameter diaphragm which greatly reduces the piston effective area and the associated calibration spring force by the square of the diameter.
It is a further object of the invention to provide such a gauge that is easily reset after each filter change. It is a further object that this fuel filter gauge be relatively small in size, and made of relatively inexpensive materials to minimize manufacturing costs. It is an important operating objective of this invention that the fuel filter gauge be capable of handling at least 20 psi back pressure.
It is a further object of the invention that a breather filter design be employed that eliminates the need for a felt filter. It is also an object of the invention that the fuel filter gauge be positionable with the push button reset switch in an upward position without risk of damage from outside contaminants entering the lock mechanism of the fuel filter gauge.
It is yet a further object of the invention that the fuel filter gauge be capable of locking itself in position when the engine is turned off, indicating the status of the fuel filter even after the engine has stopped running. An additional objective of this invention is to provide a fuel filter gauge that is easy to reset when a used filter has been replaced.
It is yet a further object of this invention to provide a fuel filter gauge capable of withstanding both pressure and vacuum forces. It is also an object that the internal locking mechanism and diaphragm assembly of the gauge must be able to withstand the pressure reversals and forces encountered in the fuel system.
Other objects and advantages of the invention will become apparent from the following detailed description and from the appended drawings in which like numbers have been used to describe like parts throughout the several views.
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Berry, III Charels Henry
Ferris Gregory Matthew
Manross Jerry Lee
Metcalf Michael Dean
Sidler Laverne Lee
Engineered Products Co.
McCall Eric S.
Oppenheimer Wolff & Donnelly LLP
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