Abstract:
An air filter restriction indicating device communicating with the supply of air passing from an air filter to the air intake of an internal combustion engine. The indicating device senses a decrease in the supply of air drawn through the air filter by the engine based upon changes in the amount of vacuum in the negative side of the air supply, the amount of restriction being indicated by the movement of an indicating device. Improved means included in the indicating device senses the movement of the indicating device and progressively locks the indicating device into various indicating positions as the vacuum increases due to an increased restriction of the filter, so that the maximum reading of restriction achieved during engine operation remains visible to the operator or maintenance personnel even after the engine is turned off. Further, an electronic signal is sent to a dashboard mounted signaling device, such as a light or buzzer, to indicate to the vehicle operator that air filter maintenance is required.

Description:
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&#39;s air filter. 
     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 turbocharged diesel engines on trucks, tractors and industrial and marine applications. The device indicates and locks itself in position, and activates a signaling device on the vehicle dashboard, 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 to provide a continuous indication as to how much useful life remains in the air filter before is should be cleaned or changed. 
     The use of a gauge to monitor the filtering ability of a vehicle&#39;s air filter is known in the art. However, the prior art combination of such a gauge with a switch to positively actuate a dashboard indicator light of the filter&#39;s condition, without flickering or giving an otherwise unclear signal, based on the status of the gauge, is new in the art. In particular, the dashboard light signal could sometimes light before the gauge actually reached “redline,” or the point at which the air filter required replacement. Further, the dashboard light signal could flicker or not remain lit after the gauge had reached redline. The mere presence of the gauge and dashboard indicator will in most cases cause the driver of the vehicle to rely on the signal being given. However, if a signal is unclear, or gives a false indication that the filter is not yet in need of replacement, serious engine damage could result. 
     Earlier patents in this area include U.S. Pat. No. 4,369,728, issued to Nelson on Jan. 25, 1983, and U.S. Pat. No. 4,445,456, issued to Nelson on May 1, 1984. However, the signal in the vehicle and the gauge near the engine would not always agree with each other using these prior art devices. Further, the dashboard light would not always remain on until the filter was serviced and the gauge reset. Also, as disclosed, these switches were relatively expensive to manufacture and assemble. 
     Additionally, prior art indicators have not always been easy to fully reset, sometimes resulting in a gauge that may give a false, premature signal that an air filter requires replacement. This may in turn result in unnecessary filter maintenance. 
     SUMMARY OF THE INVENTION 
     The switch gauge of the present invention signals when the air filter of an internal combustion engine requires servicing or replacement by measuring the performance of the filter by measuring the vacuum in the air intake 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 air flow condition experienced during engine operation so that it may be read after shutdown and may also be monitored during engine operation. Furthermore, the device actuates a dashboard mounted light or other signaling device to alert the vehicle operator that the filter has become dirty and requires maintenance or replacement. 
     An object of the invention is to provide a gauge for indicating that an air filter for a vehicle with an internal combustion engine requires replacement. A further object of the invention is to provide such a gauge that also provides a visual signal to the driver of the vehicle while the vehicle is operational and being driven. 
     It is a further object of the invention to provide such a gauge that is easily reset after each filter change. 
     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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of an air intake system for an internal combustion engine incorporating the switch gauge of the present invention; 
     FIG. 2 is a perspective view of the indicating device of the present invention; 
     FIG. 3 is an exploded view of the indicating device illustrated in FIG. 2; 
     FIG. 4 is a vertical section view of the indicating device taken along line  4 — 4  of FIG. 2; 
     FIG. 5 is a partial section view similar to FIG. 4, showing the lockpin in the locking position; 
     FIG. 6 is a close-up view of the area shown in the broken circle of FIG. 5; 
     FIG. 7 is a view similar to FIG. 6, showing the lockpin in the locking position; 
     FIG. 8 is a horizontal section view taken along line  8 — 8  of FIG. 5; 
     FIG. 9 is a perspective view of a switch terminal; 
     FIG. 10 is a partial side view of a normally open leaf switch; 
     FIG. 11 is a partial side view of an alternative embodiment showing a normally closed switch; 
     FIG. 12 is a plan view of an alternative embodiment of the terminal/switch assembly; 
     FIG. 13 is a perspective exploded view of the alternative embodiment of the terminal/switch assembly shown in FIG. 12; and 
     FIG. 14 is a partial side view of the base cap assembly showing the alternative embodiment of the terminal/switch assembly shown in FIG.  12 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference to the drawings, and in particular to FIG. 2, switch gauge of the present invention is generally indicated by reference numeral  10 . Switch gauge  10  includes a preferably transparent housing  12 , a base cap  14 , a calibration spring  16  and an indicator cup  18 . Housing  12  includes a preferably generally cylindrical attachment member  20  for attachment to air intake system  22  of a vehicle&#39;s internal combustion engine, preferably via a tube  24 , as shown in FIG.  1 . 
     Referring to FIG. 1, switch gauge  10  is shown schematically attached to a vehicle&#39;s air intake system  22 , and also electrically attached to a signal means  26 . Signal means  26  and switch gauge  10  are both powered by a power source  28 , preferably the vehicle&#39;s battery. Signal means  26  is preferably a light mounted on the dashboard of the vehicle to provide an indicator to the driver of the vehicle, although other indicators, or combinations of indicators, such as a buzzer, a voice message, or a text message, could also be used to achieve the same result. 
     Referring to FIGS. 3 and 4, the key components of switch gauge  10  also include the flexible diaphragm  30  and the lockpin  32 . Lockpin  32  in turn is pivotally attached to and projecting upwardly from base cap  14 . In particular, the base portion  34  of lockpin  32  engages reset button  36 , which in turn is actuated by flexible reset cover  38 . Reset spring  40  bears against base cap  14  to bias reset button  36  away from base cap  14 , in turn ensuring positive contact between optional reset actuator  42  of reset cover  38  and base portion  34  of lockpin  32 . Reset button  36  includes a bearing surface  44  which reset spring  40  bears against. It is preferred that base portion  34  of lockpin  32  include a groove along a portion of the diameter thereof (not shown) to permit compression thereof during fitment with reset button  36 . Base portion  34  also includes a flat surface  46  which bears against a mating flat inner surface  48  on reset button  36  to insure proper positioning of the two components relative to one another. During assembly, it is also preferable to apply a small amount of adhesive to ensure the permanent retention of base portion  34  within the opening of reset button  36 . 
     Lockpin  32  includes several teeth  50  along one side thereof. Teeth  50  are intended for engagement with lock ring  52 . In addition to providing permanent attachment of indicator cup  18  to flexible diaphragm  30 , lock ring  52  includes an opening  54  in the center thereof through which passes lockpin  32 . As shown in FIGS. 4 and 5, the configuration of lockpin  32 , combined with the effect of reset spring  40 , results in a bias of lockpin  32  generally in the direction of the edge thereof having teeth  50 . In other words, the edge of lockpin  32  having teeth  50  tends to bear against central opening  54  of lock ring  52 . 
     Calibration spring  16  bears against the upper, inside surface of housing  12  on one end, and against indicator cup  18  on the other. Nipple member  56  of housing  12  engages tube  24 , which in turn intersects air intake  22 , which carries air from air inlet F, which encloses the air filter (not shown). As the air filter becomes dirty from extended use, the amount of air passing through it decreases, although the vehicle&#39;s internal combustion engine continues to draw air at a steady rate. As the amount of air passing through the filter decreases, there is a corresponding decrease in the air pressure and a resulting vacuum in air intake system  22 , resulting in a vacuum inside of the nipple member  56  and the corresponding inwardly projecting inner chamber  58  within housing  12 . As this vacuum increases, the negative air pressure gradually overcomes the force of calibration spring  16 , and indicator cup  18  is drawn upwards, or toward nipple member  56 . As indicator cup  18  is drawing toward nipple member  56 , the edge of central opening  54  engages teeth  50  of lockpin  32 . Thus, even after the vehicle&#39;s engine is turned off, indicator cup  18  is maintained in its prior position. 
     Referring to FIGS. 5-7, as the air filter becomes more dirty, further reducing air flow through the air intake system, calibration spring  16  gradually becomes increasing compressed, as indicator cup  18  is drawn closer to nipple member  56 , until lockpin  32  no longer extends into central opening  54  of lock ring  52 . Then, as illustrated in FIG. 5, teeth  50  no longer engage central opening  54  of lock ring  52 , but rather reset spring  40  urges the distal end of toothed portion  60  of lockpin  32  into contact with the tapered lower surface  62  of lock ring  52 . Lock ring  52  also includes a circumferentially projecting skirt  64  that prevents the distal end of toothed portion  60  of lockpin  32  from sliding past the edge of lock ring  52 , which in turn, as shall be shown, ensures the simple, reliable resetting of switch gauge  10 . As shown in FIG. 7, lock ring skirt  64  extends sufficiently far enough from tapered lower surface  62  to permit additional compression of calibration spring  16  due to the vacuum in air intake system  22  without lockpin  32  sliding past the edge lock ring skirt  64 . 
     When positioned as shown in FIG. 5, reset spring  40  biases lockpin  32  such that the lower surface of switch actuator  66  of lockpin  32  bears down on leaf  68  of normally open switch  70 , pushing it against contact  74 , closing the circuit illustrated in FIG. 1, resulting in the activation of signal means  26 , such as the illumination of a dashboard indicator light. Normally open switch  70  is illustrated in FIG.  10 . FIG. 11 shows an alternative embodiment, normally closed switch  72 , also employing a leaf  68  which bears against contact  74 . 
     Referring to FIGS. 8-10, leaf  68  is shown as part of switch assembly  76 , which includes terminals  78 , and connecting strips  80  forming lockpin guiding slot  82 . Connecting strips  80  meet to form a distal anchoring portion  84 . Leaf  68  is preferably attached as by being mechanically staked to the base portion  86  of switch assembly  76 . Base portion  86  and anchoring portion  84  are attached to base cap  14  as by ultrasonic stakes  88 , including one mounted on support post  89  (see FIG.  4 ). Base cap  14  includes posts  90 ,  92  projecting upwardly therefrom to assure proper positioning of switch assembly  76  thereon. Base cap  14  also includes a connector tunnel  93  through which connection of an output line to switch terminals  78  for activation of signal means  26  is accomplished. 
     Referring to FIGS. 12-14, an alternate and preferred embodiment of a switch assembly  94  is illustrated, using the same switch leaf  68  as switch assembly  76 . Used with switch assembly  94  is a slightly modified base cap  96 . Base cap  96  preferably includes generally horizontally disposed pockets  98  for receiving first and second retention members  100 ,  102 . The preferably triangularly configured receiving pockets  98 , and the corresponding retention members  100 ,  102 , also serve to assure that switch assembly  94  is accurately and consistently positioned on base cap  96 . Base cap  96  also preferably includes first and second projecting rib portions  104 ,  106 , with a breather port  108  positioned within first projecting rib portion  106 . Projecting rib portions  104 ,  106  help to limit the side to side motion of lockpin  32  in base cap  96 . Rib portions  104 ,  106  also help align switch actuator portion  66  of lockpin  32  with the leaf  68  of switch assembly  94 . Angled surfaces  110 ,  112  of rib portions  104 ,  106 , respectively, also assist with proper assembly of lockpin  32  in base cap  96 . 
     The configuration of switch assembly  94  preferably includes the fastening of flexible switch leaf  68  as by a rivet  114  to second retention member  102 . Leaf  68  is preferably gold plated. Projecting from an affixed to first retention member  100  is contact  116 , which is preferably made of platinum. Since they provide the two terminal components of switch assembly  94 , it is important that retention members  100 ,  102  are not in contact with each other following assembly. To this end, each is inserted through a spaced opening  118 ,  120 , respectively, in terminal housing  122 , permitting the extension of terminal portions  124 ,  126  of retention members  100 ,  102 , respectively, therefrom. Also projecting outwardly from terminal housing  122  is retention tab  128  for retaining terminal housing to base cap  96 , as shown in FIG.  14 . 
     As may be seen with reference to FIGS. 2 and 4, also shown is a label liner  130  preferably included inside of housing  12 , label liner  130  preferably having delineations  132  indicating the condition of the air filter. Delineations  132  preferably indicate levels of vacuum in intake system  22 , with a clear marking, preferably in red, indicating when the level has reached a point that the air filter requires maintenance or replacement. 
     In use, switch gauge  10  may be installed in any orientation that is convenient to the particular application being contemplated, given the various space limitations and the like that may be encountered in various vehicle engine compartments. However, upon installation, an electrical connection is formed between switch gauge  10  and a power supply  28 , and then with a signal indicator  26  of some sort, such as a light or buzzer, preferably located on the dashboard of the driving compartment of the vehicle. The electrical connection is formed by plugging into the switch terminals  78  of base cap assembly  14 , or terminal portions  124 ,  126  of base cap assembly  96 . The respective terminals are accessible through connector tunnel  93 . 
     When first installed, switch gauge  10  has indicator cup  18  in the position indicated in FIGS. 2 and 4. As the air filter in air inlet F becomes dirtier over time through ongoing use, air flow through intake system  22  is impeded, resulting in a vacuum in the system, which is indicated by the position of indicator cup  18  as it gradually rises to the position indicated in phantom in FIG.  4 . As indicator cup  18  gradually rises to the position indicated in phantom in FIG. 4, it is retained in position even when the engine is turned off by the latching of central opening  54  of lock ring  52  on the teeth  50  of lockpin  32 . As the force of calibration spring  16  is overcome resulting in its gradual compression, the central cylinder  134  of preferably brightly colored indicator cup  18  is drawn into housing inner chamber  58 . Upon reaching this position, as shown in FIG. 5, the toothed portion  60  of lockpin  32  is fully withdrawn from central opening  54  of lock ring  52 , whereby the force of reset spring  40  urges switch actuator  66  of lockpin  32  to depress switch leaf  68 . Depressing switch leaf  68  causes the actuation of normally open switch  70 , or normally closed switch  72 , or switch assembly  94 , depending on which is installed in switch gauge  10 . Actuation of the switch results in activation of signal means  26 . The configuration of lock ring  52 , including especially the tapered surface  62  and the presence of skirt  64 , assures that switch leaf  68  remains depressed, and signal means  26  remains activated, until the air filter is cleaned or replaced, and switch gauge  10  is reset even if the engine is stopped and restarted several times. 
     To reset switch gauge  10 , simply depress reset cover  38  on base cap  14  or  96 . Depressing reset cover  38  brings reset actuator  42  into contact with the sloped surface  136  of reset button  36 , overcoming the bias of reset spring  40 , and centering lockpin  32  on central opening  54  of lock ring  52 . Tapered lower surface  62  of lock ring  52  helps assure that the distal end of toothed portion  60  of lockpin  32  is guided to central opening  54  of lock ring  52 . As soon as lockpin  32  passes through central opening  54 , calibration spring  16  biases indicator cup  18  away from attachment member  20 . It should be understood, however, that attachment member  20  need not always be positioned as shown on housing  12 , and that its position herein is relied on for convenience. 
     Those skilled in the art will further appreciate that the present invention may be embodied in other specific forms without departing from the spirit or central attributes thereof. In that the foregoing description of the present invention discloses only exemplary embodiments thereof, it is to be understood that other variations are contemplated as being within the scope of the present invention. Accordingly, the present invention is not limited in the particular embodiments which have been described in detail therein. Rather, reference should be made to the appended claims as indicative of the scope and content of the present invention.