Patent Publication Number: US-6213083-B1

Title: Fuel shutoff system

Description:
This application is a continuation-in-part of application Ser. No. 08/780,338, filed Jan. 8, 1997, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to the field of internal combustion engines and, more particularly, to internal combustion engines that utilize fuel shutoff systems upon engine shutdown. 
     BACKGROUND OF THE INVENTION 
     Internal combustion engines are used in a variety of applications, such as lawn mowers, generators, pumps, snow blowers, and the like. Such engines often have carburetors wherein fuel received from a fuel source is mixed with air and supplied to a combustion chamber for ignition. The fuel mixture is drawn from the carburetor into the combustion chamber due to a low pressure created in the combustion chamber by the rotation of the engine. The products of combustion are then expelled from the combustion chamber into the exhaust manifold during the exhaust stroke of the engine. 
     An operator of an engine may shut the engine down by grounding the electrical ignition system, thereby causing the spark plug to cease firing. After shutdown, the engine does not immediately stop rotating. During the continued rotation or coasting of the engine after ignition shutdown, unburned fuel and air are drawn from the carburetor into the combustion chamber, and expelled into the exhaust system. 
     The continued draw of unburned fuel into the combustion chamber and exhaust manifold after engine shutdown causes problems. Fuel is wasted, and unburned fuel is released into the environment, thereby increasing exhaust emissions. Additionally, the muffler or muffler with catalytic converter often get very hot, and the unburned fuel may ignite when it contacts these components, thereby causing backfiring or afterburning. Backfiring and afterburning can shorten the useful life of the catalytic converter and of the muffler itself. Likewise, the presence of unburned fuel in the combustion chamber may cause dieseling. 
     To alleviate these problems, fuel shutoff mechanisms have been devised to control the flow of fuel after ignition shutdown. For instance, U.S. Pat. No. 5,301,644 to Olmr discloses a fuel shutoff mechanism which includes a solenoid valve. However, the &#39;644 system, as well as other apparatus which use solenoids, typically require a battery to function. The addition of a battery to engines adds to the weight and cost of the engine. Additionally, solenoids, or other electric actuating devices, are expensive and are expensive to replace. In the small utility engine industry, for example, the additional cost, weight, and complexity are very undesirable. 
     Other fuel shutoff devices, such as the one disclosed in U.S. Pat. No. 5,092,295 to Kobayashi, use the throttle of the engine to act as a fuel blocker upon engine shutdown. This is done by adding structure which overrides the governor of the engine and closes the throttle valve upon shutdown. The problem with these devices, however, is that they are complex, and must be added onto and may disturb the delicate balance of the engine governor. 
     Yet other devices, such as U. S. Pat. No. 4,510,739 to Dluhosch, use a fuel shutoff valve which stops the flow of fuel into the fuel bowl. The disadvantage of these devices is that a substantial amount of fuel remains in the fuel bowl after the engine ignition is shut down, and can still be drawn into the combustion chamber and exhaust system after shutdown. 
     SUMMARY OF THE INVENTION 
     The invention is a fuel shutoff system that solves the problems of the prior art. More particularly, the invention includes a fuel shutoff system that is usable on engines without a battery, and is reliable, simple and less expensive than electrically operated solenoids. Additionally, the fuel shutoff operates without interfering with the engine governor, and effectively blocks the fuel flow downstream of the fuel bowl on engine shutdown. 
     One aspect of the invention is a fuel shutoff system for an internal combustion engine, wherein the engine has a carburetor with a fuel bowl, an intake valve, and a fuel conduit between the fuel bowl and the intake valve. The invention includes a blocking member for selectively blocking the fuel conduit downstream of the fuel bowl to substantially prevent passage of fuel to the intake valve, and a manually-operable control for actuating the blocking member. In each embodiment, the engine includes a throttle and a fuel metering device, and the blocking member is distinct from the throttle and the fuel metering device calibration. 
     In one embodiment of the invention, the engine includes a carburetor having a fuel nozzle, and the fuel shutoff system includes a mechanically operated blocking member for selectively blocking fuel from flowing from the fuel bowl into the fuel nozzle. In one form, the blocking member is selectively positioned adjacent the fuel nozzle in a first position wherein the blocking member blocks the fuel from flowing into the fuel nozzle, and in a second position wherein the blocking member allows the fuel to flow into the fuel nozzle. By blocking the fuel flow downstream of the fuel bowl, restarting the engine is simplified. The fuel bowl does not have to be refilled before starting. 
     In another embodiment of the invention, the engine has a passageway through which a gas (the fuel/air mixture) may pass to an intake valve of the engine, and the engine has a throttle valve disposed in the passageway. The blocking member is disposed in the passageway and can be selectively positioned in a first open position, and in a second closed position upon engine shutdown to substantially block the flow of gas or fuel/air mixture to the intake valve and to the combustion chamber. 
     Another aspect of the invention is an ignition grounding device for grounding the ignition system of the engine wherein the fuel shutoff system and the grounding device are both actuated by the same mechanical operation. 
     An important feature and advantage of the invention is that the invention reduces the amount of unburned fuel which is wasted and released into the environment since all fuel flow is shut off upon engine shutdown. 
     Another feature and advantage of the invention is that the fuel shutoff, particularly at the fuel nozzle, enables the engine to be transported with fuel and oil without the fuel passing through the engine into the crankcase, thereby avoiding oil dilution and hydraulic lock. 
     Another feature and advantage of the invention is that the fuel shutoff, particularly at the fuel nozzle, enables the engine to be transported with fuel without the fuel flowing into the carburetor during transport, thereby avoiding the potential for engine flooding. 
    
    
     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. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a lawn mower including an internal combustion engine incorporating one embodiment of the present invention. 
     FIG. 2 is a partial side view of an internal combustion engine depicting a first embodiment of the present invention. 
     FIG. 3 is a cross sectional side view of a carburetor used in the first embodiment. 
     FIG. 3A is an enlarged partial view of FIG.  3 . 
     FIG. 4 is a cross sectional front view of the carburetor in FIG.  3 . 
     FIG. 5 is another cross sectional view of the carburetor in FIG.  3 . 
     FIG. 6 is a schematic view of the first embodiment in the run position. 
     FIG. 7 is a schematic view of the first embodiment in the stop position. 
     FIG. 8 is a partial side view of a blocking member used in a second embodiment of the invention, shown in partial section, depicting a rotatable lever arm interconnected with the blocking member. 
     FIG. 9 is a schematic view of a control lever used in a third embodiment of the invention, depicting a bowden wire directly connected to the control lever. 
     FIG. 10 is a perspective view of a push pull motion type lever-bowden cable assembly of a fourth embodiment of the invention. 
     FIG. 11 is a cross sectional side view of a carburetor according to a fifth embodiment of the invention, depicting a blocking member in the gas passageway. 
     FIG. 12 is a schematic view of a control lever of the fifth embodiment, in the run position. 
     FIG. 12A is an exploded side view of the blocking member according to the fifth embodiment, depicted in the run position. 
     FIG. 13 is a schematic view of the control lever of the fifth embodiment of the invention, in the shutoff position. 
     FIG. 13A is an exploded side view of the blocking member according to the fifth embodiment, depicted in the shutoff position. 
     FIG. 14 is a partial side view of an internal combustion engine depicting a sixth embodiment of the present invention. 
     FIG. 15 is a partial cross-sectional view of a carburetor used in the sixth embodiment of the invention. 
     FIG. 16 is a partial side view of an ignition ground switch that may be used in the sixth embodiment of the invention. 
     FIG. 17 is a side view of the push/pull motion type lever-link arm assembly used in the sixth embodiment of the invention. 
     FIG. 18 is a top cross-sectional view of the push/pull knob, taken along line  18 — 18  in FIG.  17 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 through 18 illustrate a number of embodiments of the present invention. Each of the illustrated embodiments of the invention is used with an internal combustion engine having a carburetor and a combustion chamber. In FIGS. 2 and 3, engine  12  has a gas passageway  19  through which gas (the fuel/air mixture) may pass to an intake valve (not shown) of the engine  12 . Carburetor  14  has a carburetor body  18  having a throat  20  extending therethrough, and a fuel bowl  22  secured to carburetor body  18  by a carburetor bowl mounting screw  23 . Throat  20  has a throttle valve  28  and a choke valve  30  disposed therein. Throat  20  also has a reduced diameter portion or venturi  32  disposed therein, and one end which is interconnected with an intake manifold (not shown) in fluid flow communication with an intake valve (not shown). Gas passageway  19  includes throat  20  of carburetor  14  and the intake manifold (not shown). The intake valve (not shown) regulates the flow of air and fuel into a combustion chamber  16 . 
     The illustrated embodiments (see FIG. 4) also include a fuel feed line  24  that acts as a passageway for fuel to flow from a fuel tank (not shown) to carburetor  14 , and into fuel bowl  22 . Carburetor  14  has a float  26  which floats on fuel in fuel bowl  22  and actuates a valve  27  which blocks fuel from flowing into the fuel bowl  22  when fuel bowl  22  is full. A fuel nozzle  34  extends from fuel bowl  22  to venturi  32 , having one end  34   a  in fuel bowl  22 , and another end  34   b  in venturi  32 . Fuel nozzle  34  has multiple apertures for air  36  disposed in the side thereof The fuel nozzle  34  also includes at least one, and possibly more, fuel supply jets  35  that supply fuel to the end  34   a . As will be described below, the fuel nozzle  34  acts as a high speed fuel circuit when fuel exits at end  34   b . Fuel nozzle  34 , throat  20 , and the intake manifold (not shown) comprise a fuel conduit between fuel bowl  22  and the intake valve (not shown). When engine  12  is running, fuel flows from the fuel tank (not shown), through the fuel feed line  24 , into the fuel bowl  22 , up through at least a portion of the fuel nozzle  34 , into the gas passageway  19 , into the intake manifold (not shown), through the intake valve (not shown), and into combustion chamber  16 . 
     As best seen in FIG. 5, an air bleed circuit  38  is disposed in the carburetor body  18 . The air bleed circuit  38  communicates with an idle and transition fuel circuit  78  adjacent the fuel nozzle  34 . The idle and transition fuel circuit  78  also comprises part of the fuel conduit and communicates with the nozzle  34  at the bottom-most aperture  36 . Fuel enters at nozzle end  34   a  and can get to the intake valve via the nozzle  34 , the idle and transition fuel circuit  78  or a combination of both. 
     When the engine  12  is idling, the throttle valve  28  substantially blocks the throat  20 . Atmospheric pressure air enters the air bleed circuit  38  through restrictor  80 , flows through the air bleed circuit  38  due to the lower pressure created by the engine  12  and exits through the (see FIGS. 3 and 5) idle circuit aperture  82  in the passageway  19 . As the air passes over the idle and transition circuit  78 , fuel is drawn upward, via the commonly known venturi effect, into the idle and transition circuit  78  where it mixes with air flowing through the air bleed circuit  38  and exits through the idle aperture  82 , which is on the engine side of the closed throttle valve  28 . 
     When the throttle valve  28  begins to open for higher engine speed or the application of a load, transition apertures  84  (FIG. 3) are exposed. The transition apertures  84  also communicate with the idle and transition circuit  78 . As the engine speed increases, the pressure differential in the air bleed circuit  38  increases, which draws the air through the air bleed circuit  38  faster, which in turn draws more fuel upward into the idle and transition circuit  78 . The fuel exits through the idle aperture  82  and the transition apertures  84  to provide the increased amount of fuel necessary to accommodate the higher operational speed. 
     As the throttle valve  28  opens more, for even higher engine speeds, the pressure differential becomes great enough that air passes through the venturi  32 , and over the nozzle end  34   b  in the direction of the arrow shown in FIG.  3 . Fuel is now drawn upward through the nozzle  34  and eventually ceases to be drawn upward through the idle and transition circuit  78 . When this occurs, the fuel passes only through the nozzle  34  and exits only at end  34   b . This is referred to as the high speed fuel circuit. At one point, however, fuel is drawn up both the high speed fuel circuit and the idle and transition circuit  78 . 
     The amount of fuel drawn into the idle and transition circuit  78  can be adjusted by a fuel metering device. As shown in FIGS. 4 and 5, the fuel metering device is an air adjustment screw  86  that adjusts the air flow through the air bleed circuit  38 . The air adjustment screw  86  includes a needle end  88  that extends into the idle aperture  82 . As the air adjustment screw  86  is manually turned, the needle end  88  can be inserted or retracted from inside the idle aperture  82 . By changing the size of the idle aperture  82 , the pressure differential in the air bleed circuit  38  is changed. This allows the manufacturer or user to adjust the amount of fuel drawn into the idle and transition circuit  78 . As such, the air adjustment screw  86  acts as a fuel metering device for adjusting the air/fuel mixture. In the illustrated embodiment, the air adjustment screw  86  is capped with a limiter cap  90  that limits the adjustability of the screw  86 . Limiter caps are commonly used due to governmental engine emissions standards. 
     Each of the illustrated embodiments in FIGS. 1 through 18, as described below, also includes a blocking member for selectively blocking the fuel conduit downstream of the fuel bowl to substantially prevent the passage of fuel to the intake valve. The blocking member is distinct from both the throttle valve  28  and the fuel metering device. 
     FIGS. 1 through 7 illustrate a first embodiment of the present invention. Referring to FIGS. 2 through 7, a blocking member or plunger  40  is located in fuel bowl  22  adjacent to an input end  34   a  of fuel nozzle  34 . Plunger  40  is selectively movable between a stop position in which plunger  40  blocks the flow of fuel into fuel nozzle  34 , as shown in FIGS. 3A and 7, and a run position in which plunger  40  does not block the flow of fuel into fuel nozzle  34 , as shown in FIGS. 3 and 6. Plunger  40  is preferably in the shape of a truncated cone for better sealing with the input end  34   a  of fuel nozzle  34 . Additionally, plunger  40  is preferably made of material such as a metal, plastic or rubber that is insoluble in and impervious to fuel. 
     Although the blocking member has been depicted and described as a plunger blocking the input end of the fuel nozzle, it is apparent that the blocking member may have a different shape (eg. a plate, or sphere), and that it could be placed at the output end of the fuel nozzle or in a slot in the nozzle between the input and output ends. 
     As shown in FIGS. 2,  6  and  7 , plunger  40  in the first embodiment is selectively movable between the stop or blocking position, and the run or non-blocking position through the use of a bowden cable  42  interconnected with a lever assembly  52 . Bowden cable  42  has one end  42   a  attached to plunger  40  and extends from plunger  40  through an aperture  43  drilled through carburetor bowl mounting screw  23 . Bowden cable  42  then extends to and has a second end  42   b  interconnected with an actuating lever assembly  52 . 
     Plunger  40  is directly attached to one end  42   a  of bowden cable  42 , and in one embodiment, plunger  40  and bowden cable  42  are at least partially made of metal, and bowden cable  42  is attached by soldering or other means to plunger  40 . A tight seal is created between bowden cable  42  and carburetor bowl mounting screw  23 , such that fuel cannot leak from fuel bowl  22  through aperture  43  in carburetor bowl mounting screw  23 . An O-ring  45  or other similar means is used to create such a seal. In the first embodiment, the O-ring  45  may be supplied by National O-Ring, 11634 Patton Road, Downey, Calif. 90241. 
     Bowden cable  42  has an outer sheath  44  and an inner wire  46 . Inner wire  46  is slightly longer than outer sheath  44 , and is attached to plunger  40  on one end  46   a  and to an actuator lever  49  on the other end  46   b . The outer sheath  44  surrounds the inner wire  46  and has an end  44   a  nearest the plunger  40  that is locked into position by a jam nut  48  which is attached to carburetor bowl mounting screw  23 . The end  44   b  of the outer sheath  44  that is interconnected with the actuating lever assembly  52  is locked into position by a bowden cable clamp  50 . One suitable bowden cable  42  is supplied by Capro Inc., 300 South Cochran, Willis, Tex. 77378. 
     As shown in FIGS. 6 and 7, the major components of actuating lever assembly  52  include actuator lever  49 , a control lever  60 , and a mounting plate  59 . 
     In FIGS. 6 and 7, actuator lever  49  includes a first pivot  54 , a return spring  56 , and an engagement arm  58 . First pivot  54  mounts actuator lever  49  to bowden cable clamp  50 , which is in turn mounted to mounting plate  59 . First pivot  54  allows actuator lever  49  to pivot between a run position as illustrated in FIG. 3, and a stop position as illustrated in FIG.  7 . Because actuator lever  49  is interconnected with plunger  40  via bowden cable  42  when in the run position, actuator lever  49  pulls bowden cable  42  so that plunger  40  is in a non-blocking position. When in the stop position, actuator lever  49  pushes bowden cable  42  so that plunger  40  is in the blocking position. 
     Actuator lever  49  is moved between the run and the stop positions through the selective engagement of engagement arm  58  with control lever  60 . Engagement arm  58  acts as a lever to pivot actuator lever  49  between the run and stop positions. Return spring  56  is interconnected between actuator lever  49  and bowden cable clamp  50 , and returns actuator lever  49  to the run position when engagement arm  58  is not engaged with the control lever  60 . In an alternate embodiment, actuator  49  may be spring biased to the closed or off position so that the engine may be transported without fuel spillage. 
     As shown in FIGS. 6 and 7, control lever  60  is preferably a rotary motion lever that has a handle or tab  62 , and a second pivot  64 . Of course, other types of levers may be used. 
     Second pivot  64  mounts control lever  60  to mounting plate  59  and allows for rotary motion of control lever  60  in relation to mounting plate  59 . Control lever  60  has one portion  60   a  that is interconnected with a governor spring  66 , another portion  60   b  which is selectively engageable with an ignition ground switch  68 , and another portion  60   c  that is selectively engageable with engagement arm  58 . 
     Governor spring  66  is interconnected between a governor arm  67  and control lever  60  and acts to adjust the speed of engine  12  (FIG. 2) as control lever  60  is rotated. As control lever  60  is rotated in a clockwise direction, as illustrated in FIG. 3, governor spring  66  is tightened, throttle valve  28  (FIG. 3) is moved to a more open position, and the engine runs faster. As control lever  60  is rotated in a counter-clockwise direction, as illustrated in FIG. 7, governor spring  66  is loosened, throttle valve  28  (FIG. 3) is moved to a more closed position, and the engine runs slower. Therefore, control lever  60  is a manually-operable control that controls both the throttle valve  28  and the blocking member or plunger  40 . 
     In fixed speed applications, such as generators and the like, the throttle position is often not manually-controllable. In these applications, control lever  60  would only control the blocking member, and governor spring  66  would not be interconnected with control lever  60 . 
     Ignition ground switch  68  is interconnected with an ignition wire  70 , and selectively grounds the ignition system (not shown) of engine  12  (FIG. 2) to stop the engine. The fuel shutoff system of the present invention should stop the engine without the ignition ground switch. When control lever  60  engages ignition ground switch  68 , ignition ground switch  68  grounds the ignition system, and the engine stops. In the preferred embodiment, the ignition ground switch  68  may be supplied by Fastex Division, 195 Algonquin Road, Des Plaines, Ill. 60016. 
     Control lever  60  only engages ignition ground switch  68  and engagement arm  58  when it is in the fully counter-clockwise position illustrated in FIG.  7 . Therefore, the ignition system is grounded and plunger  40  is moved to the blocking position only when control lever  60  is in the fully counter-clockwise position. Plunger  40  is fully closed and ignition ground switch  68  are actuated at substantially the same time by control lever  60 . 
     Referring again to FIGS. 6 and 7, two adjustable stops  72  and  74  are on mounting plate  59 , and limit the rotary motion of control lever  60 . First stop  72  stops the control lever  60  in an engine run position, as illustrated in FIG.  3 . Second stop  74  stops control lever  60  in an engine stop position, as illustrated in FIG.  7 . 
     FIG. 1 illustrates a remotely operated version of the first embodiment in combination with a lawn mower  92 . The lawn mower  92  includes a handle  94  having a remote primer  93 , which is pushed to inject raw fuel into the carburetor throat  20  prior to starting, a throttle lever  95 , which opens and closes the throttle valve  28  to affect engine speed, and a deadman lever or switch  96  as is commonly known. The deadman switch  96  is coupled to the actuator lever assembly  100  illustrated in FIGS. 3 and 3A. A bowden cable  98  preferably couples the deadman switch  96  to the actuator assembly  100 , however other methods of coupling may be employed. Actuator assembly  100  includes a fixed member  102 , fixed to the engine  12 , and a movable member  104 , movable relative to fixed member  102 . Preferably, the movable member  104  pivots about pivot point  106  to actuate the plunger  40  either by pulling it down to the run position, or by pushing it up to the stop position. When the deadman lever  96  is held in the run position, the bowden cable  98  is taut. The sheath of the bowden cable  98  is fixed to the movable member  104  causing the actuator lever assembly  100  to be in the run position as shown in FIG.  3 . When the deadman switch  96  is released, the bowden cable  98  slacks inside the sheath and the actuator lever  100  pivots to the stop position in FIG.  3 A. Bowden cable  98  can also be interconnected to an ignition grounding switch (not shown), but this need not be the case. 
     Variations of the remotely operated embodiment shown in FIG. 1 can also be utilized with generators, pumps, snow blowers and the like. In the case of generators for example, the engine controls are often remotely located from the engine on a frame. The fuel shutoff device can also be remotely actuated using a push/pull knob, as described below with respect to FIG. 10, or any other suitable actuation device. 
     FIG. 8 illustrates a blocking member or plunger  140  and a mechanical actuating means used in a second embodiment of the invention. As in the first embodiment, plunger  140  is located in a fuel bowl  122  adjacent to an intake end  134   a  of a fuel nozzle  134 . Plunger  140  is selectively movable between a first, stop position in which plunger  140  blocks the flow of fuel into fuel nozzle  134  (shown in phantom in FIG.  8 ), and a second, run position in which plunger  140  does not block the flow of fuel into fuel nozzle  134  (shown by the solid lines in FIG.  8 ). 
     Although blocking member  140  has been depicted and described as a plunger  140  blocking input end  134   a  of fuel nozzle  134 , it is apparent that blocking member  140  may have a different shape (eg. a plate), and that it could be placed at the output end  134   b  (FIG. 8) of fuel nozzle  134  or in a slot in the fuel nozzle between input end  134   a  and output end  134   b  (FIG.  8 ). 
     Plunger  140  in FIG. 8 is selectively movable between the stop or blocking position, and the run or non-blocking position through the use of a connecting member  142  interconnected with a rotating actuating lever assembly  152 . Connecting member  142  has one end  142   a  attached to plunger  140 , and extends from plunger  140  through an aperture  143  drilled through the center of the carburetor bowl mounting screw  123 . Connecting member  142  then extends to and has a second end  142   b  interconnected with a rotating actuating lever assembly  152 . 
     A tight seal is created between connecting member  142  and carburetor bowl mounting screw  123 , such that fuel cannot leak from fuel bowl  122  through aperture  143 . As in the first embodiment, an O-ring  145  or other similar means is used to create such a seal. 
     Carburetor bowl mounting screw  123  has an internally threaded bore  125  therein, and the actuating lever assembly  152  includes a threaded member  144  which is threaded into threaded bore  125 . One end  144   a  of threaded member  144  is connected to connecting member  142 , and the other end  144   b  of threaded member  144  is connected to a lever arm  149 . When lever arm  149  is rotated such that the pitch of the thread in threaded bore  125  advances threaded member  144  further into threaded bore  125 , plunger  140  is advanced towards the intake end  134   a  of fuel nozzle  134  via connecting member  142 . When plunger  140  contacts or substantially contacts the intake end  134   a  of fuel nozzle  134 , plunger  140  blocks or substantially blocks the flow of fuel into fuel nozzle  134 , and is therefore in the stop or blocking position. 
     As lever  149  arm is rotated such that the pitch of the thread in threaded bore  125  moves threaded member  144  further out of threaded bore  125 , plunger  140  is moved away from intake end  134   a  of fuel nozzle  134  via connecting member  142 . When plunger  140  is not in contact or substantial contact with intake end  134   a  of fuel nozzle  134 , plunger  140  does not block or substantially block fuel from flowing into fuel nozzle  34 , and is therefore in the run or non-blocking position. 
     FIG. 9 illustrates an actuating lever assembly  252  used in a third embodiment of the invention. In the actuating lever assembly  252  of the third embodiment, a bowden cable  242  is directly attached to a rotary motion control lever  260  via an adjustment bolt  280 . Adjustment bolt  280  is attached to control lever  260  at an elongated opening or adjustment slot  282  in the control lever  260 . For calibration of the embodiment, the attachment point of bowden cable  242  to control lever  260  can be adjusted by repositioning adjustment bolt  280  in adjustment slot  282 . By repositioning the attachment point of bowden cable  242  to control lever  260 , the movement of bowden cable  242  in relation to the movement of control lever  260  is adjusted. Additionally, the end  244   a  of an outer sheath  244  of bowden cable  242  is held in position by a second jam nut  250  which is connected to the mounting plate  259 , rather than by a bowden cable clamp  50  (FIGS. 6 and 7) as in the first embodiment. 
     The actuating lever assembly  252  in the third embodiment also includes an ignition ground switch  268  interconnected with an ignition wire  270 , an adjustable stop  272 , and a second pivot  264 , which are similar to the corresponding components discussed above in the first embodiment. 
     FIG. 10 illustrates yet another actuating lever assembly  352  used in a fourth embodiment of the invention. In the fourth embodiment, actuating lever assembly  352  includes a remote control lever  360  which is a push/pull motion type lever. Control lever  360  includes a push/pull knob  362 , a connecting member  342 , and a stop  372 . Connecting member  342  may be connected to a bowden cable  342 , which in turn is interconnected with the blocking member  40  (FIGS.  3  and  7 ), or connecting member  342  may be connected directly to blocking member  40  (FIGS.  3  and  7 ). When the push/pull knob  360  is pulled out in relation to the stop  372 , blocking member  40  (FIGS. 3 and 7) is positioned such that it does not block the fuel flow in the fuel conduit, and the embodiment is in the run or non-blocking position. When the push/pull knob  362  is pushed-in in relation to the stop  372 , blocking member  40  (FIGS. 3 and 7) is positioned such that it blocks the fuel flow in the fuel conduit, and the embodiment is in the stop or fuel blocking position. 
     In the fourth embodiment, an ignition ground switch  68  (FIGS. 2 and 6) is also interconnected with the actuating lever assembly  352 . The ignition ground switch  68  (FIGS. 2 and 6) may be interconnected with the actuating lever assembly  352  via bowden cable  342 , or may be directly attached to actuating lever assembly  352 . When the push/pull knob  360  is pushed-in to the stop position, the ignition ground switch  68  (FIGS. 2 and 6) is actuated, and grounds the ignition system of the engine. 
     FIGS. 11 through 13A depict a fifth embodiment of the present invention. As best shown in FIG. 11, a blocking member or fuel/air mixture blocking valve  440  is disposed in a gas passageway  419  of the engine  12  (FIG.  2 ). A throttle valve  428  and a choke valve  430  are also disposed in the gas passageway  419 , and are distinct from blocking member  440 . Air flows through the gas passageway  419  in the direction of the arrows in FIGS. 11,  12 A and  13 A. In FIG. 11, a spacer block  490  is located between the carburetor  414  and the intake manifold (not shown). Spacer block  490  has a hollow bore  421  therethrough, and is positioned such that hollow bore  421  is included in gas passageway  419 . Carburetor throat  420 , having a venturi  432 , is also part of the gas passageway  419 . Fuel blocking valve  440  is disposed within hollow bore  421  of spacer block  490 . 
     Fuel blocking valve  440  is selectively movable between a first, stop position in which blocking valve  440  blocks the flow of the air/fuel mixture in gas passageway  419 , as illustrated in FIG. 13A, and a second, run position in which blocking valve  440  does not block the flow of the air/fuel mixture in gas passageway  419  as illustrated in FIG.  12 A. Fuel blocking valve  440  is preferably in the form of a butterfly valve, and is sized such that when in a blocking position, fuel blocking valve  440  blocks, or substantially blocks, the flow of the air/fuel mixture through gas passageway  419 . (FIG.  13 A). 
     Fuel blocking valve  440  in the fifth embodiment is selectively movable between the blocking position and the non-blocking position through the use of an actuating lever assembly  452  interconnected with fuel blocking valve  440 . Referring to FIGS. 12 and 13, the major components of actuating lever assembly  452  include a control lever  460 , an actuator cam  449 , a cam spring  442  and a mounting plate  459 . 
     As depicted in FIGS. 12 and 13, control lever  460  is a rotary motion lever that has a handle or tab  462 , and a second pivot  464 . Of course, other types of levers may be used. Control lever  460  has one portion  460   a  that is interconnected with a governor spring  466 , another portion  460   b  which is selectively engageable with an ignition ground switch  468 , and another portion  460   c  that is selectively engageable with actuator cam  449 . As control lever  460  is rotated so as to engage actuator cam  449 , actuator cam  449  is rotated in a clockwise direction, as shown by arrow  451 . 
     In the fifth embodiment, there is a direct mechanical link between actuator cam  449  (FIGS. 12 and 13) and fuel blocking valve  440  (FIGS.  12 A and  13 A). The link may be a shaft, a rack and pinion apparatus, or gears, as is well known in the trade. Other embodiments of the invention may link actuator cam  449  and fuel blocking valve  440  through the use of a bowden cable, or other similar means. 
     As actuator cam  449  is rotated in a clockwise direction through engagement with control lever  460 , fuel blocking valve  440  is moved from a non-blocking to a blocking position via the direct mechanical link between fuel blocking valve  440  and actuator cam  449 . The use of actuator cam  449  allows for efficient switching of fuel blocking valve  440  between the blocking and non-blocking positions. Due to the profile of cam surface  449   a  of the actuator cam  449 , once speed control lever  460  engages actuator cam  449 , a small amount of angular movement of control lever  460  results in a large amount of angular movement of fuel blocking valve  440 , thereby reducing the amount of control lever movement needed to actuate fuel blocking valve  440  into a blocking position. By comparing FIGS. 12 through 13A, it is apparent that a rotation of cam  449  of less than 45 degrees from the open position (FIG. 12) to the closed position (FIG. 13) results in a 90 degree rotation of fuel blocking valve  440  from the open position (FIG. 12A) to the closed position (FIG.  13 A). Fuel blocking valve  440  is spring loaded so that fuel blocking valve  440  remains in the fully open or non-blocking position when control lever  460  is not engaging actuator cam  449 . 
     Ignition ground switch  468  in the fifth embodiment is similar to ignition ground switch  68  (FIGS. 6 and 7) discussed above in the first embodiment. Additionally, the structure relating to the governor spring  466  and its attachment between governor spring  467  and control lever  460  in the fifth embodiment is substantially the same as in the first embodiment discussed above. As in the first embodiment, the governor spring is not attached to control lever  460  in most fixed speed applications. 
     The operation of the fifth illustrated embodiment of the invention is best shown by comparing FIGS. 12 and 12A with FIGS. 13 and 13A. FIG. 12 and 12A, in combination, illustrate the fifth embodiment of the invention in the run, non-blocking and non-grounding position. Control lever  460  is in a position such that it does not engage actuator cam  449 . In this position, actuator cam  449  is held in a run position by cam spring  442 . Fuel blocking valve  440  remains in a non-blocking position, thereby allowing the air/fuel mixture to flow through gas passageway  419  and to the intake valve. In this position, control lever  460  does not engage ignition ground switch  468 , so the ignition system of the engine is not grounded. Additionally, governor spring  466  is pulled, thereby moving throttle valve  28  into a more open position, making the engine  12  run faster. 
     The phantom lines in FIGS. 12 and 12A illustrate the fifth embodiment in a slow run position, with throttle valve  28  partially closed, fuel blocking valve  440  in a non-blocking position, and ignition ground switch  468  and actuator cam  449  not actuated by control lever  460 . The solid lines in FIGS. 12 and 12A illustrate the fifth embodiment in the fast run position, with control lever  460  engaging stop  472 , throttle valve  428  more open, fuel blocking valve  440  in a non-blocking position, and ignition ground switch  468  and actuator cam  449  not actuated by control lever  460 . 
     FIGS. 13 and 13A illustrates the fifth embodiment of the invention in the stop, blocking and grounding position. Control lever  460  is rotated as far counter-clockwise as possible so that control lever  460  engages actuator cam  449 . In this position, control lever  460  engages actuator cam  449  such that fuel blocking valve  440  is rotated to the blocking position, thereby substantially blocking the air/fuel mixture from flowing through gas passageway  419  into the intake valve. Control lever  460  engages ignition ground switch  468 , so that the ignition system of the engine is grounded. Additionally, governor spring  466  is loosened thereby moving throttle valve  428  into a fully open position. 
     Control lever  460  only engages ignition ground switch  468  and actuator cam  449  when it is in or substantially close to the fully counter-clockwise position illustrated in FIG.  13 . Therefore, ignition ground switch  468  is actuated and fuel blocking valve  440  is in the blocking position only when control lever  460  is in the fully counter-clockwise position. Actuator cam  449 , and therefore fuel blocking valve  440  as well as ignition ground switch  468 , are actuated at substantially the same time by control lever  460 . 
     FIGS. 14 through 18 illustrate a mechanical actuating means used in a sixth embodiment of the invention using a link arm lever assembly  552 . As shown in FIG. 15, plunger  540  is located in a fuel bowl  522  adjacent to an intake end  534   a  of a fuel nozzle  534 . Plunger  540  is selectively movable between a first, stop position in which plunger  540  blocks the flow of fuel into fuel nozzle  534  (shown in phantom in FIG.  15 ), and a second, run position in which plunger  540  does not block the flow of fuel into fuel nozzle  534  (shown by the solid lines in FIG.  15 ). 
     Although blocking member  540  has been depicted and described as a plunger  540  blocking input end  534   a  of fuel nozzle  534 , it is apparent that blocking member  540  may have a different shape (eg. a plate), and that it could be placed at the output end  534   b  of fuel nozzle  534  or in a slot in the fuel nozzle between input end  534   a  and output end  534   b.    
     Plunger  540 , as shown in FIG. 15, is selectively movable between the stop or blocking position, and the run or non-blocking position through the use of a connecting member  542  interconnected with a link arm lever assembly  552 . Connecting member  542  has one end  542   a  attached to plunger  540 , and extends from plunger  540  through an aperture  543  drilled through the center of the carburetor bowl mounting screw  523 . Connecting member  542  then extends to and has a second end  542   b  interconnected with the link arm lever assembly  552 . 
     A tight seal is created between connecting member  542  and carburetor bowl mounting screw  523 , such that fuel cannot leak from fuel bowl  522  through aperture  543 . As in the first embodiment, an O-ring  595  or other similar means is used to create such a seal. 
     The link arm lever assembly  552  includes a generally L-shaped link arm  545  having a first end  545   a  and a second end  545   b . The second end of link arm  545   b  is interconnected with the second end of connecting member  542   b . As shown in FIG. 12, the second end of link arm  545   b  and the second end connecting member  542   b  are interconnected by an interconnecting member  547 . In the alternative, the link arm  545  and the connecting member  542  can be interconnected by other interconnecting means known in the art, such as welding, or may be integrated together into a single part. 
     As shown in FIG. 14, a guide member  549  is attached to engine  12  by guide member retainer bracket  551 . Guide member  549  is an elongated tube having an elongated bore  549   c  extending therethrough about axis  563 . Guide member  549  has a first end  549   a  and a second end  549   b . Link arm  545  extends through and is slidably engaged with bore  549   c  from second end  549   b  to first end  549   a  about axis  563 . 
     The first end of link arm  545   a  extends from the first end of guide member  549   a  and is interconnected with a push/pull motion type lever  560 . The lever  560  includes a push/pull motion knob  562 , and a stop  572 . Referring to FIG. 17, knob  562  is rotatably mounted on first end  545   a  such that knob  562  can generally rotate about axis  563 . Knob  562  is a generally disc shaped member having a top edge  562   a  and a bottom edge  562   b . A locking member  566  is mounted to the bottom edge  562   b , and extends horizontally therefrom. 
     As shown in FIG. 17, the first end of guide member  549   a  acts as the stop  572  for lever  560 . In other embodiments, a separate stop member can be employed. 
     Referring to FIG. 14, a locking bracket  568  is mounted to the engine  12  substantially adjacent to knob  562 . Bracket  568  is a generally C-shaped member having a first arm  570 , a second arm  572  and a web  574  interconnecting arms  570  and  572  respectively. First arm  570  is attached to the engine  12 . Second arm  572  has a top surface  576  having a recess  578  therein as shown in FIGS. 17 and 18. 
     As shown in phantom in FIGS. 14 and 15, as the push/pull knob  562  is pulled out in relation to the stop  572 , plunger  540  is advanced towards the intake end  534   a  of fuel nozzle  534  via link arm  545  and connecting member  542 . When plunger  540  contacts or substantially contacts the intake end  534   a  of fuel nozzle  534 , plunger  540  blocks or substantially blocks the flow of fuel into fuel nozzle  534 , and is therefore in the stop or blocking position. As shown in FIGS. 17 and 18, and as shown in phantom if FIG. 14, the knob  562  can then rotated about axis  563  such that locking member  566  is engaged with locking bracket  568  and fits within recess  578 . In this position, the plunger  540  is held substantially in the stop position. 
     To unlock the locking member, the knob is rotated such that locking member  566  does not engage the locking bracket  568 . As shown in FIGS. 14 and 15, as the push/pull knob  562  is pushed-in in relation to the stop  572 , plunger  540  is moved away from intake end  534   a  of fuel nozzle  534  via link arm  545  and connecting member  542 . When plunger  540  is not in contact or in substantial contact with intake end  534   a  of fuel nozzle  534 , plunger  540  does not block or substantially block fuel from flowing into fuel nozzle  534 , and is therefore in the run or non-blocking position. 
     FIG. 16 depicts an ignition ground switch that may optionally be used with the sixth embodiment discussed above. In FIG. 16, ignition ground switch  668  is interconnected with the link arm lever assembly  652 . In FIG. 16, the ground switch assembly includes an elongated tube shaped guide member  649  having an elongated bore  649   c  extending therethrough about axis  663 . The guide member includes a second end  649   b . The ground switch assembly may also include an interior surface  651  of bore  649   a  being coated with a non-conductive layer  653 . Non-conductive layer  653  can be made of rubber or plastic, or any other non-conductive material known in the art. Link arm  645  extends through and slidably engages the non-conductive layer within bore  649   c  about axis  663 . 
     The ignition ground switch  668  includes an upper portion  680  and a lower portion  682 . Upper portion  680  includes an upper ground clip  684  attached to the second end of guide member  649   b . An upper engagement member  686  made of conductive material is attached to upper ground clip  684  and extends substantially horizontally from guide member  649 . The conductive material can include conductive metal known in the art, such as iron, steel, aluminum, and copper, or may include other conductive material. A ground wire  687  is connected to the engagement member  686  and extends to a grounding point  689 . 
     Lower portion  682  includes a lower ground clip  688  made of substantially non-conductive material attached to link arm  645 . Lower ground clip  688  is attached to link arm  645  at a point below guide member  649  such that when link arm  645  is in the stop or blocking position, the lower ground clip  688  nearly engages the second end  649   b  of guide member  649 , and when link arm  645  is in the run or non-blocking position, the lower ground clip  688  is spaced substantially from the second end  649   b  of guide member  649 . A substantially L-shaped lower engagement member  690  made of conductive material is attached to lower ground clip  688 . Lower engagement member  690  has a first, horizontally extending portion  691 , and a second vertically extending portion  693 . The conductive material can include conductive metal known in the art, such as iron, steel, aluminum, and copper, or may include other conductive material. An ignition wire  692  is connected to the engagement member  690 . 
     As shown in FIG. 16, when the link arm lever assembly  652  is in the stop or blocking position, the vertically extending portion  693  of lower engagement member  690  engages the upper engagement member  686 , and grounds the ignition system of the engine. When the link arm lever assembly  652  is in the run or non-blocking position, the vertically extending portion  693  of lower engagement member  690  does not engage the upper engagement member  686 , and the ignition system of the engine is not grounded. 
     While several embodiments of the present invention have been shown and described, other embodiments will be apparent to those skilled in the art and are within the intended scope of the present invention. The present invention includes any manually-operated means for blocking the flow of fuel or an air/fuel mixture, downstream of the fuel bowl and upstream of the engine intake valve upon engine shutdown. Therefore, the scope of the present invention is to be limited only by the following claims.