The improved device of the present invention is used in connection with an air filter for internal combustion engines. It is particularly useful for application to turbo-charged diesel engines on trucks, tractors and industrial and marine applications. The device indicates and locks itself in position when the air filter has become so loaded with contaminants that the supply of air required by the engine for its operating efficiency is not being drawn through the filter and that the filter therefore requires cleaning or replacement. It also locks itself in various positions so as to provide a continuous indication as to how much useful remains in the air filter before it should be cleaned or changed.
Heretofore, flag, gauge or warning light indicators have been used to indicate when an air filter is filled with dust or other contaminants which restrict the air flow to the engine but do not give gradual fixed readings from a clean to a dirty filter condition. Many operators unnecessarily and improperly clean or change an air filter element rather than take a chance of having a warning signal appear even though the filter is not full of contaminants. Over-servicing prevents a normal dust build-up from filtering out the fine particles that lodge in the pores of the filter paper element of, for example, a dry air filter. This shortens the life of the filter element and more frequent cleaning is needed, which increases the risk of filter element damage and improper installation. A hole as small as 1/16" can pass enough dust to ruin an engine within eight hours of operation. Most air cleaners are designed to retain a certain amount of dust until 25" of vacuum is reached. At that point the air filter is full and is incapable of taking any more dust without a rapid increase in vacuum downstream of the filter elements. The high vacuum can pull dust through the filter element and may even pull particles of the filter element and oil from the engine crank case into the combustion chamber, particularly with turbo-charged diesel engines. Such dust, contaminants or lack of oil may ruin the engine in a relatively short time.
With the flag or switch type indicators or with a continuously reading or dial gauge, it is virtually impossible to ascertain how much capacity is left in the air filter when the engine is shut down or turned off. Furthermore, dial type gauges vary the indication of vacuum depending on the load on the engine while the engine is in operation. The load and the engine air flow may be highest when the operator of the vehicle may not be able to readily visually observe the gauge or indicator. When less load is placed on the engine, an erroneous gauge reading may be indicated. When the engine is stopped completely, the gauge or indicator does not continue to indicate the true condition of the air filter as when the engine was under maximum load condition. Therefore, the maintenance personnel or the driver of the vehicle may not know the true condition of the air filter at the end of a run, since operators rarely maintain a log of readings of the air filter indicator. To make such an observation, the engine must be restarted and preferably operated with a dynamometer to simulate maximum load conditions. Such procedures take considerable time and expense and if not done frequently, may result in the engine dangerously operating with an overloaded air filter.
Furthermore, the ideal situation when a dial type gauge is used is for the operator of the engine to monitor and log and report maximum readings. It is difficult to train operators to follow such procedures, and many times the operator neglects to do so, with resultant poor engine operation.
In addition, more fuel is used to maintain horsepower at above 20" of vacuum, and if cleaning the air filter does not reduce the vacuum below 20", the filter element should be replaced to avoid frequent cleaning and to save fuel.
The device herein gives a gradual reading from a clean filter condition to a dirty filter condition and automatically locks into the highest clogged air flow condition (that is, dirty filter condition) experienced during engine operation so that it may be read after shutdown and may also be monitored during engine operation.
Furthermore, after cleaning or replacement, it is easy to reset the indicator and it will then assume a position away from a danger line on the indicator showing how much air filter use is left. Obviously air filters should be replaced when there is not much filter capacity left after cleaning.
The device herein is designed to give a continuous, progressive reading to indicate the build-up of contaminants within the air filter and to indicate the condition of the filter through eliminating guess work as to the time when cleaning or replacement of an air filter is approaching because the condition of the filter is indicated by the movement of an indicating member with respect to a visible scale. Furthermore, the indicating device indicates the condition of contamination of the air filter progressively and locks itself into its highest vacuum indicating position, whereby regardless of whether or not the engine to which it is attached is operating, there is a positive indication of the condition of contamination of the air filter and an indication to the extent to which the air filter is still useful.
Indicators for registering the restriction present in air filters have been utilized heretofore and are the subject matter of patents such as U.S. Pat. Nos. 3,068,831 Witchell, 3,443,365 Lee and 3,465,707 Kashiwaba. The indicators disclosed in these patents lock themselves into position only when they have indicated a restriction in the air filter which indicates that the filter life is expended. Such high restriction may occur at a time unknown to the operator of the vehicle, particularly when intent on driving, for example, when passing another vehicle on a hill and he will, therefore, not be aware of the degree to which the air filter is contaminated. There is no progressively locked indication of contamination as in the case of the device of the present invention.
Other prior patents in this field are Nelson U.S. Pat. Nos. 3,939,457 and 4,033,733. However, the devices disclosed in these prior Nelson patents do not include the progressive locking feature of the present invention.
It is therefore an object of the invention to provide a contamination indicating device for an air filter for internal combustion engines, which device provides a positive indication of the increasing contamination of the air filter by having the contamination indicating member therein progressively lock itself into various indicating positions and to maintain the indication of the highest amount of contamination even in the absence of operation of the engine.