Abstract:
An air filter restriction sensor assembly for use on an engine, such as a small gas engine provides a simple on/off system with remote indicating to notify the operator of the air restriction. More specifically, the air restriction in the air intake line of the engine creates a vacuum which pulls on a plunger mechanism until the mechanism contacts a switch, such as a membrane switch, and activates the switch. The switch can be electrically connected to an indicator device, such as a light-emitting diode, which is readily visible to the operator to notify the operator of the air restriction.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This Non-Provisional Application claims benefit to U.S. Provisional Application Ser. No. 60/600,981 filed Aug. 12, 2004 and U.S. Provisional Application Ser. No. 60/618,299 filed Oct. 13, 2004. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to air filter restriction sensor assemblies, and more particularly to such assemblies for use in small gas engines. 
     BACKGROUND OF THE INVENTION 
     It is known that small gas engines are used on equipment and vehicles such as lawn mowers, lawn tractors, and the like. When used on lawn mowers, for example, the engines are exposed to the environment where they may be subject to debris, dirt, moisture, or other contaminants. To maintain the proper functioning of the gas engine, air filters are used to screen and filter the air that is taken in by the engine and more specifically the carburetor of the engine. In many applications, the air filter is concealed from view and therefore when dirt or debris is on the filter, thereby restricting the air flow, this condition is not readily apparent to the operator. 
     To overcome this problem, known engines sometimes include a sensor mechanism to detect if the dirt or debris on the air filter is restricting the air flow to the engine. As the air filter on the engine becomes dirty and the air flow becomes restricted, vacuum is increased in the air intake line of the engine downstream from the air filter. Conventionally, the vacuum created by the air restriction is detected by a spring-loaded sensor device, a micro-switch, or both, that show the operator the state of the air filter restriction. The springs or micro-switches, however, wear out over time, can give false readings from the engine vibration, or can be difficult to calibrate. 
     The present invention is directed at improving upon known air filter restriction sensor assemblies and in particular air filter restriction sensor assemblies for small gas engines. 
     SUMMARY OF THE INVENTION 
     The present invention is directed towards an air filter restriction sensor assembly for use on an engine, such as a small gas engine. With the invention, a simple on/off system is provided whereby the vacuum created in the air intake line created by the air restriction in the air filter pulls on a plunger mechanism until the mechanism contacts a membrane switch and activates the switch. The switch is adapted to send out an electrical signal that can be electrically connected to an indicator device, such as a light-emitting diode (“LED”), which is readily visible to the operator to notify the operator of the air restriction, a control module, such as an engine on/off switch, or any desired electrical operation. 
     An advantage of the teachings and principles of the invention is that there are no springs or switches that can wear out over time or give undesirable false readings from the engine vibration. An additional advantage is the membrane switch can be easily calibrated to activate under a desired contact pressure. Yet another advantage of the invention is the membrane switch is sealed so the fuel and any other contaminants coming from upstream to the carburetor will not adversely affect the performance of the invention. This invention also has the advantage of not requiring a manual reset like the prior art. Also, the invention has remote indicating in the form of an LED which permits the invention to be mounted directly to the air intake line and yet the operator will be able to readily monitor the condition of the air intake line. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of an exemplary air filter restriction sensor assembly of the present invention. 
         FIG. 2  is a cross-section view of the sensor assembly of  FIG. 1 . 
         FIG. 3  is cut-away bottom view of the sensor assembly of  FIG. 1 . 
         FIG. 4  is an exploded view of the sensor assembly of  FIG. 1 . 
         FIG. 5  is an exploded view of an alternative embodiment of an air filter restriction sensor assembly. 
         FIG. 6  is a cut-away side view of the sensor assembly of  FIG. 5 . 
         FIG. 7  is a cross-section view of the sensor assembly of  FIG. 5  taken at line  7 — 7 . 
         FIG. 8  is an exploded view of another alternative embodiment of an air filter restriction sensor assembly. 
         FIG. 9  is a cross-section view of yet another alternative embodiment of an air filter restriction sensor assembly. 
     
    
    
     Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  depicts an exploded view of an exemplary embodiment of an air filter restriction sensor assembly of the invention. The air filter restriction sensor assembly  10  generally includes a top housing  12 , a plunger  18 , a switch  20 , a diaphragm  22 , a plunger disc  24 , and a housing  26  that defines a nozzle end  28 . 
     The top housing  12 , in one embodiment, is formed by two housing halves  14  and  16 . The housing  12  includes an integral hinge such as living hinge (not shown). The first housing half  14  includes a snap-arm  32  that may be used to snap-fit the first housing half  14  to a slot  34  formed in the second housing half  16 . The housing halves  14 ,  16  are snap-fit together after the other components of the assembly  10  are properly mounted together and within the top housing  12 . The assembled top housing  12  defines a rim  13  that extends around the periphery of the housing. As discussed below, the housing  26  will snap-fit to the rim  13  of the housing  12 . The housing  12  further defines at least one slot  15  through which will extend electrical leads  46  of the switch  20 . The slot  15  may be sized and shaped to match the shape of the lead  46  or any other type of lead used with the assembly. 
     The housing halves  14  and  16  further define interior walls  42  and  44 , respectively. The walls  42  and  44  extend radially toward the center of the housing  12 . When assembled, the walls  42  and  44  define a central opening  45  ( FIG. 2 ) through which is mounted the plunger  18 . The central opening  45  aligns and centers the plunger  18  relative to the housing  12  as the plunger  18  moves within the assembly, as discussed below. The walls  42  and  44  will also separate the assembly into chambers  52  and  54  ( FIG. 2 ). 
     The plunger  18  or plunger member may be embodied in many forms and configurations and is meant to include any reciprocating moving part that facilitates the air restriction sensing of the invention. The plunger  18  or plunger member defines, in one aspect, a web-shaped body  19  on which is mounted an elastomer member  30 . The body  19  is web-shaped to reduce the mass of this part so that engine vibration and other outside forces such as rocks or bumps encountered from a rough lawn, for example, have less adverse effect on the assembly. One skilled in the art will appreciate that other shapes and configurations of the body  19  are possible. The elastomer member  30  in the exemplary embodiment is over-molded onto the plunger  18  and more specifically onto the web-shaped body of the plunger  18 . Other techniques for mounting, attaching, or connecting the elastomer member  30  are possible. The elastomer member  30  can be rubber or any suitable thermoplastic material. In use, as the plunger  18  moves within the assembly as a result of air restriction in the air filter, the plunger  18  will cause the elastomer member  30  to contact and activate the switch  20 . Testing has shown that the switch  20  responds better to contact by a softer object, such as the elastomer member  30 , as opposed to contact by a harder object, such as a solid plastic disc. However, both techniques and configurations for contacting the switch  20  may be used with the present invention. 
     The plunger  18  further defines a plunger support post  33  that is configured between the body  19  and a plunger head  34 . As installed, the plunger support post  33  will pass through the opening  45  formed by the inner walls  42 ,  44 , and through an opening  21  in the switch  20 . The plunger  18  not only-defines the plunger head  34 , but also defines opposing hinge fingers  36  that are formed onto the head  34 . The hinge fingers  36  are flexible and serve to permit the plunger  18  to be snap-fit through an opening  37  in the diaphragm  22  and to a central opening  27  in the plunger disc  24 . The hinge fingers  36  thus mount the diaphragm  22  and plunger disc  24  to the head  34 . 
     The switch  20  defines a disc-shaped body and includes at least one lead  46  that, once assembled, will extend out of the housing  12  for electrical connection to a battery, an LED, or some other device or component. The switch  20  also defines the opening  21  through which will extend the support post  33  of the plunger  18 . In an exemplary embodiment, the switch  20  may be a membrane switch, such as a switch described in U.S. Pat. No. 5,401,922. The switch  20  is activated when a predetermined force is exerted on the switch from the elastomer member  30 , which is being pulled into contact with the switch  20  from the vacuum created in the chamber  54 , as described below. 
     The diaphragm  22  defines a disc-shaped body having a crown-shaped periphery, more easily seen in  FIG. 2 . The crown-shaped periphery provides the disc-shaped body with a resiliency or springiness. The diaphragm  22  also defines the opening  37  that is centrally positioned on the diaphragm. The opening  37  permits the hinge fingers  36  to pass through the diaphragm and mount to the plunger disc  24 . The diaphragm may be made of a rubber or elastomeric material. It should be understood that the diaphragm  22  may also be any plunger moving member that will cause movement of the plunger  18  under the conditions of a vacuum or restricted air flow. 
     Referring to  FIG. 2 , in use, and upon the creation of a vacuum in the chamber  54 , the diaphragm  22  is adapted to move the plunger  18  and accompanying elastomer member  30  into contact with the switch  20 . The diaphragm  22  is positioned between the top housing  12  and the housing  26  to provide an air tight seal in the chamber  54  and to permit a vacuum to form in the chamber  54  in the event of air restriction in the air intake line. The chamber  52 , where the switch  20 , web-shaped body  19  of the plunger, and elastomer member  30  are positioned, is not sealed and therefore will be open to the atmosphere. With this configuration, a vacuum will not form in chamber  52 , thereby permitting the plunger  18  and more specifically the web-shaped body  19  containing the elastomer member  30  to move toward or away from the switch  20 . In a small engine application, for example, where the nozzle end  28  of the assembly  10  is connected to the air intake line, if the air filter becomes plugged or obstructed, a vacuum will form in the chamber  54  such that the diaphragm  22  pulls the plunger  18  and accompanying elastomer member  30  into contact with the switch  20 , thereby activating the switch  20 . The switch will, in turn, activate a remote indicator, such as an LED, to notify the operator of the condition. 
     Referring to  FIGS. 2–4 , the housing  26  forms part of the chamber  54  and defines the nozzle end  28 . The nozzle end  28  further defines a passageway  29  that permits air to pass in and out of the chamber  54 . In one exemplary application, the nozzle end  28  is connected to the air intake line between the air filter and the carburetor of a small gas engine. As stated above, as air is restricted in the air intake line, the vacuum will be increased in the chamber  54  due to its connection to the intake line via the nozzle end  28 . 
     The housing  26  also defines a plurality of spaced apart hinges  50  that are configured to snap onto the rim  13  formed in the top housing  12 . The number and spacing of hinges  50  may vary. It should be understood, however, that other suitable structures can be used to join the housing  26  with the top housing  12 . 
     The plunger disc  24  provides the connection point between the plunger  18  and the diaphragm  22 . The plunger disc  24  defines in one aspect, a web-shaped body  25  that, similar to the web-shaped body  19  of the plunger  18 , will reduce the mass of this part. The plunger disc  24  defines the opening  27  ( FIG. 1 ) that receives the hinge fingers  36 . The hinge fingers  36  secure the plunger disc  24  to the plunger  18 . Alternatively, the plunger  18  could connect directly to the diaphragm  22 . While the preferred connection is through the use of the plunger disc  24 , both connections are contemplated with the invention. 
     During operation, the vacuum created in the chamber  54  from the air restriction in the air intake line pulls the diaphragm  22  towards the nozzle end  28 . The diaphragm  22  acts on the plunger disc  24  which is secured over the diaphragm, and moves the plunger disc  24  as well as the connected plunger  18  toward the nozzle end  28 . This movement, in turn, causes the connected elastomer member  30  to come in contact with the switch  20  and thus activate the switch. As indicated earlier, the switch  20  may then activate a remote indicator, such as an LED, to notify the operator of the air restriction condition. 
     Referring to  FIGS. 5–7 , in another exemplary embodiment, an air filter restriction sensor assembly  78  includes a housing  79  ( FIG. 6 ) that includes two housing halves—a first housing half  80  that is aligned with a second housing half  82 . To assemble the sensor assembly, the internal components of the sensor assembly are positioned in the first housing half  80 , and the second housing half  82  is then aligned with and placed over the first housing half  80 . Each housing half defines a tongue and groove connection  83  that is used to join the two housing halves. The first and second housing halves are then ultrasonically welded together along the tongue and groove  83  to create a hermetic seal. The hermetic seal will pemit a vacuum to form inside chambers  86  and  87 . 
     Similar to the above embodiment, the assembled housing  79  defines a nozzle end  84  that may be connected to the air intake line. The housing  79  also defines two inside walls  102 ,  104  that form an opening  100 . 
     Referring to  FIGS. 5 and 6 , the sensor assembly  78  also includes a plunger or plunger member  88  that defines a flat face  90 . The vacuum created in the chamber  86  will pull against the flat face  90  of the plunger  88 . The plunger  88  also defines a shaft  92  that is joined to a contact pad or surface  94 . The contact pad or surface  94  defines a face  96  that in operation will contact a switch  98 , such as a membrane switch, and activate the switch  98 . The shaft  92  of the plunger  88  is configured to extend through the hole  100  formed by the two inside walls  102 ,  104  in the housing to keep the face  90  and contact pad  94  of the plunger  88  concentric to the housing  79 . In this configuration, the plunger  88  is permitted to move back and forth relative to the housing  79 . With this configuration, when the vacuum in the chamber  86  (caused by the air restriction) pulls on the face  90 , the vacuum will also pull the plunger  88  until the contact pad  94  contacts the switch  98  and activates the switch. Similar to the above embodiment, the switch may electrically connect to other components, such an LED or other remote indicator. In an exemplary application, the switch may be electrically connected in series between the battery on a lawn tractor, for example, and the LED that will be mounted on the tractor where the operator can see it, for example, on the tractor&#39;s dashboard. The LED will light when the switch  98  is closed as a result of the sensor assembly  78  detecting the air restriction in the air intake line between the air filter and the carburetor, thereby alerting the operator of this condition. 
     The switch  98  may be mounted to the inside walls  102 ,  104  on the side opposite the nozzle end  84 . In the exemplary embodiment and as illustrated in  FIG. 7 , the membrane switch  98  will be split at  106  so that the switch  98  may be placed around the shaft  92  of the plunger  88 . As indicated, the switch  98  may be connected to other components. The electrical wires to achieve this connection will be fed out through a hole, not shown, in the housing. If required, the hole can be hermetically sealed. 
     Referring to  FIG. 8 , another exemplary embodiment includes a cylindrical-shaped plunger  110  having a face  112  that will contact the switch  98 . With this embodiment, the plunger  110  is positioned in the chamber  87  formed by the housing halves  80  and  82  and the inner walls  102  and  104 . The plunger  110  will be positioned adjacent to the switch  98 , which will seat on, or adhere to, the inner walls  102  and  104 . Similar to the above embodiment, an opening  100  is formed by the inner walls  102  and  104 . The remaining features and aspects of this embodiment are similar to the embodiment described above. With the embodiment depicted in  FIG. 8 , as a vacuum is created in the chamber  86 , the vacuum will pull on the plunger  110  through the opening  100  and the opening in the switch  98 , as illustrated in  FIG. 8 . This pulling force will cause the plunger  110  to either contact or further contact the switch  98  and activate the switch  98 . 
     Referring to  FIG. 9 , in another exemplary embodiment, an o-ring  108  may be used to seal the chamber  86 . The o-ring may be positioned between the plunger  88  and the inner walls of the housing halves  80  and  82 . In this embodiment, the chamber  87  is not hermetically sealed. Rather the chamber  87  is open to the atmosphere. Thus, the o-ring  108  may be used to seal the chamber  87  to permit a vacuum to form in the chamber  86 . When a vacuum is created in the chamber  86 , the plunger  88  will activate the switch in the manner described above. 
     Variations and modifications of the foregoing are within the scope of the present invention. It should be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art. 
     Various features of the invention are set forth in the following claims.