Patent Abstract:
A carburetor for a gas powered internal combustion engine having a plurality of pressure reducing stages for reducing the pressure of the gas phase in a liquified petroleum gas storage bottle prior to the mixing of the gas phase of the liquified petroleum gas with ambient air.

Full Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of our prior patent application Ser. No. 12/462,310, filed Aug. 3, 2009. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the carburetor art and more particularly to a carburetor for a liquified petroleum gas, such as propane, powered internal combustion engine for providing a multi-stage pressure reduction of the gas phase of the liquified petroleum gas contained in a liquified petroleum gas storage bottle which contains both the liquid phase and the gas phase of the liquified petroleum gas and metering the amount of the gas for mixing of the gas with ambient air before introduction of the gas/air mixture into the internal combustion engine. 
     2. Description of the Prior Art 
     Carburetors of various configurations have heretofore been utilized in connection with providing metered amounts of fuel with air, at either ambient pressure or supercharged, to provide a fuel/air mixture before introducing the fuel/air mixture into, for example, the intake manifold of an internal combustion engine for distribution of the fuel/air mixture to the cylinders of the internal combustion engine. While the advent of direct fuel injection of the fuel into the cylinders of the internal combustion engine has decreased the use of carburetors for many liquid fuel, such as gasoline, powered devices, there are still many applications wherein a carburetor may be economically advantageous utilized. 
     In gasoline powered internal combustion engines, utilizing a carburetor to mix the gasoline with the air, in general the liquid gasoline is mixed with the air in the carburetor and the liquid gasoline/air mixture flows from the carburetor into an intake manifold of the internal combustion engine. From the intake manifold the liquid gasoline/air mixture is introduced into the individual cylinders of the internal combustion engine. In each cylinder, some or all (depending on the type of engine) of the liquid gasoline is converted into the vapor stage where a spark plug ignites the mixture to provide the power stroke of the piston in the cylinder. The carburetor is generally connected in gas flow communication to the intake manifold so as to be substantially heat isolated from the intake manifold and the internal combustion engine since heating the carburetor might cause the gasoline to convert into the vapor phase in the carburetor which would “vapor lock” the carburetor and prevent the introduction of the desired metered amount of flow of liquid gasoline for mixing with the ambient air. 
     One present use of carburetors, however, is in the field of gas phase powered internal combustion engines wherein the fuel is the gas phase of a liquified petroleum gas. The containers of the liquified petroleum gas contain both liquid phase and gas phase of the liquified petroleum gas which, for example may be propane. The pressure of the gas phase of the liquified petroleum gas in the container may be on the order of 150 pounds per square inch and, as such, the pressure must be reduced before the metered amount of gas may be mixed with the air to provide the desired mixture of gas/air for introduction into the cylinders of the internal combustion engine. In the prior art a separate pressure regulator has generally been utilized to provide the desired reduction in the gas pressure. However, a separate pressure regulator has often introduced complications in the design of the fuel system for such gas powered internal combustion engines. One such complication is the instance of the liquid being introduced into the regulator. In such instances, generally the liquid phase will convert into the gas phase. In so converting to the gas phase, the regulator will be cooled as the liquid absorbs heat from the structure of the regulator and the performance of the regulator will be erratic. Should such introduction of liquid of the liquid phase into the carburetor continue long enough, there will be no conversion of the liquid phase to the gas phase and the liquid phase of the liquified petroleum gas will remain in the regulator. Since the internal combustion engine is designed to operate on the gas phase, and not the liquid phase, as the fuel in the fuel/air mixture, the engine would cease functioning until the gas phase in the correct metered amount is mixed with the air. 
     Thus, there has long been a need for a fuel system for gas powered internal combustion engines wherein both the pressure regulation of the gas, the metering of the gas flow and the combining of the metered gas flow with the air is accomplished in a single unit before introduction of the gas/air mixture into the intake manifold of the engine. Further, in providing such a combination pressure regulator and metering of the gas phase into the air flow in the desired ratio, such single should insure that only gas phase of the fuel is introduced with the ambient air to provide the desired gas/air mixture even though some liquid phase may enter the unit. That is, even if liquid phase enters the unit, the unit must provide that only gas phase is ultimately mixed with the ambient air to provide the desired gas/air mixture for the engine and liquid phase does not enter the engine. 
     Accordingly, there has long been a need for a carburetor for use in a gas powered internal combustion engine that incorporates both the pressure regulation of the gas as well as the metering of the pressure regulated gas into the air flow to provide the desired gas/air ratio mixture for introduction into the intake manifold of the internal combustion engine. 
     Accordingly, it is an object of the present invention to provide a combination pressure regulator and carburetor for use in a gas powered internal combustion engine. 
     It is another object of the present invention to provide a combination pressure regulator and carburetor for use in a gas powered internal combustion engine that minimizes or eliminates any flow of liquid phase of the fuel into the intake manifold of the engine. 
     It is yet another object of the present invention provide a combination pressure regulator and carburetor for use in a gas powered internal combustion engine wherein the carburetor is positioned in relationship to the internal combustion engine to receive heat therefrom so as to convert any liquid introduced therein into the gas phase. 
     It is still another object of the present invention to provide a combination pressure regulator and carburetor for use in a gas powered internal combustion engine in which the gas phase of the liquified petroleum gas is metered into the air flow in the desired amount to provide a gas/air mixture corresponding to the operating condition of the internal combustion engine. 
     It is still another object of the present invention provide a combination pressure regulator and carburetor for use in a gas powered internal combustion engine which may be mounted on the intake manifold or in close proximity thereto so as to absorb heat therefrom. 
     SUMMARY OF THE INVENTION 
     The above and other objects of the present invention are achieved, in a preferred embodiment thereof in a carburetor having a body member. The body member has first walls defining a first stage pressure regulating chamber. The first stage pressure regulating chamber may have, in one preferred embodiment of the present invention useful for operation of, for example, a lawn mower, a volume of about 1.6 cubic inches and the first walls may have an area on the order of 11.1 square inches. The first stage pressure regulating chamber has first stage gas inlet port walls defining a first stage gas inlet port into the first stage pressure regulating chamber. The first stage gas inlet port is adapted to be connected to a liquified petroleum gas container which may contain, for example, propane. The liquified petroleum gas container has both the liquid phase and the gas phase of the liquified petroleum gas therein. The gas phase of the liquified petroleum gas is desired for use as the fuel in a gas/fuel mixture for powering an internal combustion engine. The pressure of the gas phase or liquid phase in the liquified petroleum gas container may be on the order of 150 pounds per square inch. The first stage gas inlet port allows the flow of the gas phase or the liquid phase from the liquified petroleum gas container into the first stage pressure regulating chamber. According to the principles of the present invention, the first stage pressure regulating chamber has a comparatively large volume and a comparatively large surface area which aids in ensuring the conversion of any liquid phase of the liquified petroleum gas being converted into the gas phase of the liquified petroleum gas. In a preferred embodiment of the present invention which may be utilized, for example, on a lawn mower, the first stage volume may be on the order of 1.6 cubic inches and the surface area of the first walls of the first stage may be on the order of 8.7 cubic inches. 
     A first stage diaphragm for regulating gas pressure in the first stage pressure regulating chamber is sealingly mounted in the first stage pressure regulating chamber and is mounted for diaphragm movement towards and away from said first stage gas inlet port. A first stage metering lever pivotally mounted in said first stage pressure regulating chamber and has a first end for movement towards and away from the first stage gas inlet port and a second end spaced from the first end and connected to the first stage diaphragm. A first stage pivot pin is provided in the first stage pressure regulating chamber and the first stage metering lever is pivotally mounted on the first stage pivot pin at a location thereon that is intermediate the first end and the second end thereof. The first end of the first stage metering lever is aligned with the first stage gas inlet port. 
     For movement of the diaphragm towards the first stage gas inlet port the first end of the first stage metering lever is moved away from the first stage gas inlet port to allow the flow of the gas into the first stage pressure regulating chamber. For movement of the diaphragm away from the first stage gas inlet port, the first end of the first stage metering lever is moved into sealing relationship with the first stage gas inlet port to prevent the flow of gas into the first stage pressure regulating chamber. The first stage pressure regulating chamber diaphragm has an inner surface facing the first stage pressure regulating chamber and an outer surface opposite thereto. 
     A first stage diaphragm cap is mounted on the body member to cover the first stage diaphragm. A pressure plate is mounted on the first stage diaphragm on the opposite side thereof from the side of the first stage diaphragm facing the first stage pressure regulating chamber. A resilient means such as a first stage coil spring has a first end in contact with the pressure plate and a second end in regions adjacent the first stage diaphragm cap. 
     A screw member has a first end threadingly mounted in the first stage diaphragm cap and the first end of the screw member is accessible from regions external the body member and the second end of the first stage coil spring bears against the diaphragm pressure plate. The first stage coil spring biases the first stage diaphragm towards the first stage gas inlet port. The first end of the screw member projects to regions external the body member and a control knob is mounted on the first end of the screw member to rotate the screw member and thereby move the first stage diaphragm towards or away from the first stage gas inlet port. When the control knob is rotated in a first direction the first stage diaphragm is moved away from the direction of the first stage gas inlet port thereby causing the first end of the first stage metering lever to block the first stage gas inlet port and prevent the flow of gas into the first stage pressure regulating chamber. When the control knob is rotated in the opposite directions the first stage diaphragm is moved away from the first stage gas inlet port the first end of the first stage metering lever is moved away from the first stage gas inlet port to allow the flow of gas through the first stage gas inlet port and into the first stage pressure regulating chamber. 
     As the gas phase, gas phase and liquid phase mixture or liquid phase flows into the first stage pressure regulating chamber any liquid phase introduced into the first stage pressure regulating chamber is converted in the first stage pressure regulating chamber of the carburetor to the gas phase. The pressure of the gas on the first stage diaphragm tends to move the diaphragm away from the first stage gas inlet port. The amount of movement of the first stage diaphragm under the pressure of the gas in the first stage pressure regulating chamber that is sufficient to cause the first end of the first stage metering lever to block the first stage gas inlet port is controlled by the biasing force exerted on the diaphragm by the first stage coil spring. The pressure of the gas in the first stage pressure regulating chamber which causes the movement of the first end of the first stage metering lever to block the first stage gas inlet, port is less than the gas pressure of the gas in the liquified petroleum gas storage bottle. The gas pressure in the first stage pressure regulating chamber during operation of the internal combustion engine may be in the range of 10.0 to 50.0 pounds per square inch. The first stage pressure regulating chamber has a volume that, for some applications, may, as noted above, be on the order of 1.6 cubic inches though greater or smaller volumes may be provided for particular applications. 
     There are second walls in the body member defining a second stage pressure regulating chamber. The second stage pressure regulating chamber has a second stage gas inlet port providing a gas flow passage into said second stage pressure regulating chamber. Gas flow passage walls are provided between the first stage gas outlet port and the second stage gas inlet port to allow the flow of gas from the first stage pressure regulating chamber into the second stage pressure regulating chamber. A second stage diaphragm is sealingly mounted in the second stage pressure regulating chamber for regulating gas pressure in said second stage pressure regulating chamber and is mounted for movement towards and away from said second stage gas inlet port. 
     A second stage metering lever is pivotally mounted in the second stage pressure regulating chamber and is connected to the second stage pressure regulating chamber diaphragm in manner similar to the mounting of the first stage metering lever and has a first end for movement towards and away from the second stage gas inlet port and a second end spaced from the first end and a pivot pin connection pivotally engaging a second stage pressure regulating chamber pivot pin for providing pivotal mounting thereof intermediate the first end and the second end. Movement of the second end of the second stage metering lever is selectively moved into and out of blocking relationship to the second stage gas inlet port for corresponding movement of the second stage diaphragm away from and towards the second stage gas inlet port to regulate the flow of gas into the second stage pressure regulating chamber to provide a gas pressure in the second stage pressure regulating chamber at a gas pressure lower than the gas pressure in the first stage pressure regulating chamber. The regulated pressure of the gas in the second stage pressure regulating chamber may be on the order of 0.5 pounds per square inch. 
     For a carburetor having a first stage pressure regulating chamber with the above set forth dimensions, the second stage pressure regulating chamber may have a volume of 0.4 cubic inches and may have a surface area on the order of 7.5 square inches. 
     The second stage pressure regulating chamber diaphragm has an inner surface facing the second stage pressure regulating chamber and an outer surface opposite thereto. A second stage pressure regulating chamber diaphragm cap is mounted on the carburetor body member over the second stage pressure regulating chamber diaphragm. A second stage pressure plate is attached to the outside face of the second stage pressure regulating chamber diaphragm A second stage pressure regulating chamber resilient means such as a coil spring is mounted between an face of the second stage pressure regulating chamber diaphragm opposite the face thereof facing the second stage pressure regulating chamber and the second stage pressure regulating chamber diaphragm cap for biasing the second stage pressure regulating chamber diaphragm towards the second stage gas inlet port for selectively blocking the second stage pressure regulating chamber gas inlet port to prevent the flow of gas into the second stage pressure regulating chamber. For the condition of the gas pressure in the second stage pressure regulating chamber greater than a predetermined value, the second stage pressure regulating chamber diaphragm is moved away from the second stage pressure regulating chamber gas inlet port and the second end of the second stage pressure regulating chamber metering lever blocks the second stage gas inlet port to prevent the flow of gas into the second stage pressure regulating chamber In general, for most operating conditions of the internal combustion engine all of the fuel flowing from the second stage regulating chamber will be in the gas phase and not the liquid phase. 
     The body member has third walls defining a metering chamber. The metering chamber has a metering chamber gas inlet port providing a gas flow passage into the metering chamber for accepting a gas flow from said second stage pressure regulating chamber gas outlet port. The metering chamber has a metering chamber gas outlet port for allowing the flow of gas from the metering chamber. A metering chamber diaphragm is sealingly mounted at the metering chamber for regulating the gas flow in the metering chamber and is mounted for movement towards and away from the metering chamber gas inlet port. A metering chamber gas flow lever is pivotally mounted in the metering chamber and has a first end for movement towards and away from the metering chamber gas inlet port and a second end spaced from said first end. The second end of the metering chamber gas flow lever is operatively in contact with the metering chamber diaphragm. A pivot pin is provided in the metering chamber and the metering chamber gas flow lever has a pivotal connection to the pivot pin at a point intermediate the first end and the second end thereof. 
     A metering spring is provided having a first end bearing against the second end of the metering chamber gas flow lever and as second end bearing against the third walls of the body member to urge the first end of the metering chamber gas flow lever into contact with the metering chamber diaphragm. Movement of the metering chamber diaphragm towards the metering chamber gas inlet port moves the first end of the metering chamber gas flow lever away from the metering chamber gas inlet port and movement of the metering chamber diaphragm away from the metering chamber gas inlet port moves the first end of the metering chamber gas flow lever towards the metering chamber gas inlet port. 
     A needle member is operatively connected to the second end of the metering chamber gas flow lever and moves therewith. The gas pressure in the metering chamber may be in the range of atmospheric to a small vacuum pressure depending on the speed and load of the internal combustion engine to which the carburetor is attached. For the condition of the gas pressure in the metering chamber greater than a preselected value the needle member is moved into the metering chamber gas inlet port to block the flow of gas into the metering The gas pressure in the metering chamber is less than the gas pressure in the second stage pressure regulating chamber. 
     A metering chamber diaphragm cap is mounted on the body member and bears against the outside face of the metering chamber diaphragm. The metering chamber has a third gas volume less than second gas volume of the second stage pressure regulating chamber. For the application wherein the second stage pressure regulating chamber has the above specified volume of about 1.0 cubic inches, the metering chamber may have a volume on the order of 0.4 cubic inches. 
     The body member has fourth walls defining a throttle bore. The throttle bore has an ambient air inlet port for allowing the flow of ambient air from regions external the body member into the throttle bore. The throttle bore also has an outlet port which may be connected to the inlet manifold of the internal combustion engine to be powered by the liquified petroleum gas. 
     The body member has fifth walls defining a gas flow passage providing communication between the gas outlet port of the metering chamber and the throttle bore to allow the flow of gas from metering chamber into the throttle bore for mixing with the ambient air to provide an gas/air mixture having the desired ratio of liquified petroleum gas to ambient air required to power the internal combustion engine at a flow rate required for the particular operating condition of the internal combustion engine between, for example, idle to full throttle thereof. For a carburetor having the gas volumes specified above for the first stage pressure regulating chamber, the second stage pressure regulating chamber, and the metering chamber it has been found that the gas flow through the carburetor at idle is on the order of 18 cubic inches per minute and the gas flow through the carburetor at full throttle is on the order of 152 cubic inches per minute. 
     The carburetor has sixth walls in said body member defining a gas/air mixture outlet port for allowing the flow of the gas/air mixture to regions external said body member for connection into an inlet manifold of the internal combustion engine. 
     The carburetor has seventh walls in said body member and the seventh walls define a throttle control chamber providing communication with the throttle bore. A throttle slide is movably mounted in the throttle control chamber for reciprocating motion therein. A throttle needle is connected to the throttle slide for movement therewith. The throttle needle has a needle end for selective movement into and out of the gas inlet port of the throttle bore for controlling the flow of gas into said throttle bore from said metering chamber from full flow to partially blocking the flow of gas into to the throttle bore for the condition of the throttle needle partially blocking the gas inlet port of the throttle bore. A throttle cable or linkage is operatively connected to the throttle slide for moving the throttle slide in the throttle control chamber. A remote end of the throttle cable extends through a throttle cap to regions external the body member and the remote end of the throttle cable may be connected to the throttle mechanism of the internal combustion engine. 
     A throttle slide spring is positioned in the throttle cap for biasing the throttle slide toward the position wherein the throttle needle may project into the gas inlet port of the throttle bore to control the flow of gas to either block the flow of gas from the metering chamber gas outlet port partially or not at all depending on how far the needle projects into the throttle bore inlet port of the throttle bore. In some applications it may be desired to provide a limitation on how far the throttle needle projects into the throttle bore gas inlet port. For example, it may be advantageous in use of the internal combustion engine to selectively limit the travel of the throttle needle to a position corresponding to the idle speed of the internal combustion engine. To provide such a limitation, a throttle control pin may be threadingly mounted on the body member and have a first end that may project into the throttle bore so as to limit the movement of the throttle slide to a position where the throttle needle is partially extended into the gas outlet port of the metering chamber at the idle speed of the internal combustion engine. 
     In preferred embodiments of the present invention, the throttle needle is threadingly attached to the throttle slide so adjustments may be made to provide a desired range of gas/air mixtures for various operating conditions of the engine. In general, the position of the throttle needed relative to the throttle slide is made once at the factory manufacturing the carburetor to adjust the position as necessary because of manufacturing tolerances. The throttle slide and the throttle needle always move together. The engine speed is determined by the position of the throttle slide in the throttle bore which controls the amount of air flowing in the throttle bore and the position of the throttle needle in the metering chamber gas outlet port. For each position of the throttle slide in the throttle bore there is a corresponding position of the throttle needle in the gas flow outlet port of the metering chamber so as to provide the desired gas/fuel ratio for the corresponding engine speed. 
     In those applications of the present invention utilizing a carburetor having the dimensions above set forth, it has been found that the internal combustion engine may have a power on the order of 3 to 6 horsepower but the dimensions may be appropriately scaled for internal combustion engines having a power of, for example, 0.5 to 20 horsepower. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The above and other embodiments of the present invention may be more fully understood from the following detailed description taken together with the accompanying drawing wherein similar reference characters refer to similar elements throughout and in which: 
         FIG. 1  is a front view of the carburetor according to the principles of the present invention; 
         FIG. 2  is a view of the carburetor shown in  FIG. 1  along the view line  2 - 2  of  FIG. 1 ; 
         FIG. 3  is a view of the carburetor shown in  FIG. 1  along the view line  3 - 3  of  FIG. 1 ; 
         FIG. 4  is a view of the carburetor shown in  FIG. 1  along the view line  4 - 4  of  FIG. 1 ; 
         FIG. 5  is a sectional of the carburetor shown in  FIG. 1  along the section line  5 - 5  of  FIG. 3 ; 
         FIG. 6  is a sectional view of the carburetor shown in  FIG. 1  along the section line  6 - 6  of  FIG. 1  showing the carburetor at about an idle speed of the internal combustion engine; 
         FIG. 7  is a sectional view of the carburetor shown in  FIG. 1  similar to  FIG. 6  showing the carburetor at about a ¾ speed of the internal combustion engine; 
         FIG. 8  is a view of the carburetor shown in  FIG. 1  along the view line  8 - 8  of  FIG. 1 ; 
         FIG. 9  is a partial a sectional view as indicated on  FIG. 5  at detail B of a metering chamber gas flow control arrangement in the open position useful in the practice of the present invention; 
         FIG. 10  is a partial a sectional view similar to  FIG. 9  of a metering chamber gas flow control in the closed position useful in the practice of the present invention; 
         FIG. 11  is a partial sectional view as indicated on  FIG. 5  at detail A showing an idle adjustment screw useful in the practice of the present invention; 
         FIG. 12  is a partial sectional view showing indicated on  FIG. 5  at detail C showing the attachment of a lever to a diaphragm and the lever allowing gas flow through the gas outlet port useful in the practice of the preset invention; 
         FIG. 13  is a partial sectional view similar to  FIG. 12  showing the attachment of a lever to a diaphragm and the lever sealing the gas outlet port useful in the practice of the preset invention; and, 
         FIG. 14  is a block diagram showing the preferred attachment arrangement of the carburetor of the present invention to the inlet manifold of an internal combustion engine. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the Figures of the drawing and in particular to the sectional view of  FIG. 5 , there is shown a preferred embodiment generally designated  10  of the present invention of a carburetor  12  according to the principles of the present invention. The carburetor  12  has a body member  14 . The body member  14  has first walls  16  defining a first stage pressure regulating chamber  18 . The body member  14  also has first stage gas inlet walls  20  defining a first stage gas inlet port  22 . The first stage gas inlet port  22  is adapted to be connected to a liquified petroleum gas container indicated at  24  which contains both the liquid phase and the gas phase of the liquified petroleum gas therein and the liquified petroleum gas may, for example, be propane. The gas phase of the liquified petroleum gas flows out of the liquified petroleum gas container  24  as indicated by the arrow  26  into the first stage gas inlet port  22  and into the first stage pressure regulating chamber  18 . Depending upon the operating conditions of the carburetor  12 , some of the liquid phase or a mixture of the liquid phase and gas phase of the liquified petroleum gas may also enter the first stage pressure regulating chamber  18 . Any liquid phase of the liquified petroleum gas that flows into the first stage pressure regulating chamber is converted by the heat absorbed from the walls  16  of body member  14  of the carburetor  12  to the gas phase. The pressure of the gas phase and/or the liquid phase of the liquified petroleum gas in the liquified petroleum gas container  24  may be on the order of 150 pounds per square inch. 
     A first stage diaphragm  28  is sealingly mounted on the body member  14  in the first stage pressure regulating chamber  18  and provides diaphragm type movement towards and away from the first stage gas inlet port  22 . As utilized herein, “diaphragm movement” refers to that type of movement of a diaphragm wherein the diaphragm is mounted along the edges and the center of the diaphragm moves in response to forces exerted on the diaphragm. A first stage metering lever  30  is pivotally mounted on pivot pin  32  contained in the first stage pressure regulating chamber  18 . The first stage metering lever  30  has a first end  34  that moves towards and away from the first stage gas inlet port  22  and a second end  36  spaced from the first end  34  coupled to the first stage diaphragm  28 . The pivot pin  32  is intermediate the first end  32  and second end  34  of the first stage metering lever  30  so that movement of the diaphragm  18  towards the first stage gas inlet port  22  in the direction of the arrow  158  ( FIG. 13 ) causes the first end  34  of the first stage metering lever to be retracted from the first stage gas inlet port  22  and movement of the first stage diaphragm  28  away from the first stage gas inlet port  22  in the direction of the arrow  160  ( FIG. 13 ) causes the first end  34  of the first stage metering lever  34  to move towards the first stage inlet port  22  until sufficient such movement of the first stage diaphragm  28  causes the first end  34  of the first stage metering lever  30  to seal the first stage gas inlet port  22  thereby preventing the flow of liquified petroleum gas or liquid phase thereof into the first stage pressure regulating chamber  18 . The first stage diaphragm  28  has an inner face  28   a  facing the first stage pressure regulating chamber  18  and an outer face  28   b  opposite thereto. 
     A first stage diaphragm cap  38  is mounted on the body member  14  by, for example mounting screws  170  ( FIG. 13 ) to cover the first stage diaphragm  18 . A pressure plate  40  is mounted on the outer face  28   b  of the first stage diaphragm  18 . A resilient means such as coil spring  42  has a first end  42   a  bearing against the pressure plate  40  and a second end  42   b  in regions adjacent the first stage diaphragm pressure cap  38 . A screw member  44  is provided that has a first end  44   a  that threadingly engaging the first stage diaphragm cap  38  as indicated at  46 . The second end  42   b  of the coil spring  42  bears against the pressure plate  40 . The first end  44   a  of screw means  44  can extend to regions external the carburetor  12  and a control knob  48  is coupled to the first end  44   a  of the screw means  44  to rotate the screw means  44 . As the screw means  44  is rotated by the control knob  48  in a first direction, the first stage diaphragm  28  is moved towards the first stage gas inlet port  22  and as the screw means  44  is rotated by the control in a second direction opposite the first direction the diaphragm  28  is moved away from the gas inlet port  22 . 
     As shown in greater detail on  FIG. 13 , as the gas phase, gas phase and liquid phase mixture or liquid phase of the liquified petroleum gas flows into the first stage pressure regulating chamber through the first stage gas inlet port  22 , any liquid phase is converted to the gas phase and the pressure of the gas on the first stage diaphragm  28  causes the first stage diaphragm  28  to move in the direction of the arrow  160  away from the first stage gas inlet  22  thereby causing the first end  34  of the first stage metering lever  30  to move towards the first stage gas inlet port  22  until a preselected pressure is reached and at that preselected pressure the first end  34  of the first stage metering lever  30  moves into sealing relationship with the first stage gas inlet port  22  thereby preventing the flow of gas into the first stage pressure regulating chamber. The amount of movement of the first stage diaphragm  28  which will cause the sealing of the first stage gas inlet port  22  is controlled by the amount of pre-loading bias on the first stage diaphragm by the coil spring  42  and the gas pressure in the first stage pressure regulating chamber. As the first stage diaphragm  28  moves toward the first stage gas inlet port  22  in the direction of the arrow  158  ( FIG. 12 ) the first end  34  of the first stage metering lever  30  moves away from the first stage gas inlet port  22  allowing the flow of gas phase and/or liquid phase of the liquified petroleum gas from container  24  to flow into the first stage pressure regulating chamber  18 . In some applications of the present invention it may be advantageous to vent the outer face  28   b  of the first stage diaphragm  28 . To accomplish such venting, an aperture  28   a  is provided in the diaphragm cap  28  to allow communication of the volume between the outer face  18   a  and the diaphragm cap  28  to be exposed to ambient air at the ambient air pressure. 
     During operation, the gas pressure of the liquified petroleum gas in the first stage pressure regulating chamber is less than the pressure of the liquified petroleum gas phase in the liquified petroleum gas container  24 . The operating pressure of the liquified petroleum gas in the first stage pressure regulating chamber may be in the range of 10.0 to 50.0 pounds per square inch. The first stage pressure regulating chamber  18  also has a first stage gas outlet port  18   a . In one particular application of the principles of the present invention in the embodiment  10 , the volume of the first stage pressure regulating chamber may be on the order of 1.6 cubic inches. 
     The body member  14  has second walls  50  defining a second stage pressure regulating chamber  52 . The second stage pressure regulating chamber  52  has walls  54  defining a second stage gas inlet port  54  which receives gas from the first stage gas outlet port  18   a  in the first stage pressure regulating chamber  18 . The body member has walls  56  defining a gas flow passage channel  58  extending from the first stage gas outlet port  18   a  which provides gas flow communication to allow the flow of gas from the first stage pressure regulating chamber  18  into the second stage gas inlet port  54  and into the second stage pressure regulating chamber  52 . 
     A second stage pressure regulating chamber diaphragm  60  is sealingly mounted on the body member  14  for regulating the pressure in the second stage pressure regulating chamber  52  in a manner similar to the mounting of the first stage diaphragm  28  described above. The second stage pressure regulating diaphragm  60  has an inner face  60   a  facing the second stage pressure regulating chamber and an outer face  60   b  opposite thereto. A second stage metering lever  62  is pivotally mounted by pivot pin  64  in the second stage pressure regulating chamber  52  and the second stage metering lever  62  has a first end  66  which is movable into and out of sealing relationship with second stage gas inlet port  54 . A second end  68  of the second stage metering lever  62  is attached to the second stage pressure regulating chamber diaphragm as indicated at  70  in the same manner as described above for the first stage metering lever  30 . Movement of the first end  66  into and out of sealing relationship with the second stage inlet port  54  is controlled by the corresponding movement of the second stage pressure regulating chamber diaphragm  60  away from and towards, respectively, the second stage gas inlet port  54  in a manner similar to the action of the first stage metering lever  30  described above. The pressure of the gas in the second stage pressure regulating chamber  52  is on the order of 0.5 pounds per square inch. For a carburetor embodiment  10  in which the volume of the first stage pressure regulating chamber  18  is on the order of 1.6 cubic inches as described above, the volume of the second stage pressure regulating chamber  52  is on the order of 1.0 cubic inches. 
     A second stage pressure regulating chamber diaphragm cap  70  is mounted on the carburetor body  14  by screws  170  over the second stage pressure regulating chamber diaphragm  60 . A second stage pressure regulating chamber resilient means such as the coil spring  72  has a first end  72   a  bearing against the second stage pressure regulating chamber diaphragm cap  70  and a second end  72   b  bearing against a pressure plate  74  which is mounted on the outer surface  60   b  of the second stage pressure regulating chamber diaphragm  60 . The coil spring  72  urges the second stage pressure regulating chamber diaphragm  60  towards the second stage gas inlet port  58 . For the condition of the gas pressure in the second stage pressure regulating chamber  52  above a preset second stage pressure regulating chamber value, the second stage pressure regulating chamber diaphragm  60  is moved away from the second stage gas inlet port  54  causing the first end  66  of the second stage metering lever  62  to block the second stage gas inlet port  54  thereby preventing the further flow of gas into the second stage pressure regulating chamber  52 . The pressure of the gas in the second stage pressure regulating chamber  52  is controlled by the pressure of the gas therein and the biasing force exerted on the second stage pressure regulating chamber diaphragm  60  by the coil spring  72 . The operation of the second stage pressure regulating chamber diaphragm  60  and second stage metering lever is the same as described above in connection with the first stage pressure regulating chamber diaphragm  28  and first stage metering lever  34  and as illustrated in the detail showing on  FIGS. 12 and 13 . 
     The carburetor body  14  has third walls  80  defining a metering chamber  82 . The metering chamber  82  has a metering chamber gas inlet port  84  that is in gas flow communication with the second stage pressure regulating chamber  52  to allow the flow of gas from the second stage pressure regulating chamber  52  into the metering chamber  82 . The metering chamber  82  also has a gas outlet port  86  to allow the flow of gas from the metering chamber  82 . The metering chamber  82  and the structure associated therewith serves the primary purpose of metering the flow of gas phase liquified petroleum gas into the metering chamber  82 . 
     A metering chamber diaphragm  88  is sealingly mounted to the carburetor body  14  at the metering chamber  82  for regulating the gas pressure in the metering chamber  82  and is mounted for movement towards and away from the metering chamber gas inlet port  84 . As shown on  FIG. 5  and in more detail on  FIGS. 9 and 10 , there is provided a metering chamber gas flow lever  90  having a first end  90   a  operatively connected to a metering needle  94 . The metering chamber gas flow lever  90  has a second end  90   b  operatively connected to the metering chamber diaphragm  88 . A biasing spring  200  has a first end  200   a  abutting the third walls  80  which define the metering chamber  82 . The biasing spring  200  has a second end  200   b  which abuts against the second end  90   b  of the metering lever  90  in regions adjacent to the location of the operative contact between the metering chamber diaphragm  88  and the metering chamber gas flow lever  90 . The biasing spring biases the metering chamber diaphragm in the direction of the arrow  210  ( FIGS. 9 and 10 ). The metering needle  94  has a first end  94   a  aligned with the metering chamber gas inlet port  84  and, with the movement of the metering chamber diaphragm  88 , moves into and out of the metering chamber gas inlet port  84  to selectively block and allow the flow of gas into the metering chamber  82  as illustrated in detail on  FIGS. 9 and 10 . The metering chamber diaphragm  88  has an inner face  88   a  facing the metering chamber  82  and an outer face  88   b  opposite thereto. 
     A pivot pin  96  is mounted in the metering chamber  82  and the metering chamber gas flow lever  90  is mounted on the pivot pin at a point between the first end  90   a  and second end  90   b  thereof for pivotal movement thereon. 
     A metering chamber diaphragm back up plate  98  is coupled to the carburetor body  14  and bears against the outer face  88   b  of the metering chamber diaphragm  88 . The metering chamber diaphragm back up plate  98  has an aperture  98   a  having a preselected area which allows ambient atmospheric air at the ambient air pressure to act upon the outer face  88   b  of the metering chamber diaphragm  88 . The outer face  88   b  of the metering chamber diaphragm  88  is exposed to ambient air pressure because of the aperture  98   a  in diaphragm back up plate  98 . The biasing spring  200  tends to move the metering chamber diaphragm  88  in the direction of the arrow  210  ( FIGS. 9 and 10 ) thereby tending to move the first end  94   a  of the metering needle  94  into engagement with the metering chamber gas inlet port  84 . For the condition of the first end  94   a  of metering needle  94  fully engaging the metering gas chamber inlet port  84  as shown on  FIG. 10  the flow of gas into metering chamber  82  is blocked. For the condition of the gas pressure in metering chamber  82  decreasing to a predetermined value lower than the atmospheric air pressure, the force of the atmospheric air pressure on the outer face  88   b  of the metering diaphragm  88  becomes sufficient to overcome the force of the gas pressure on the inner face  88   a  of the metering diaphragm  88  and the force of the biasing spring  200 , the metering chamber diaphragm  88  moves in the direction of the arrow  190  ( FIGS. 9 and 10 ) thereby opening metering chamber gas inlet port  84  to allow the flow of gas into metering chamber  88  as shown in  FIG. 9 . 
     The a bearing plate  88 ′ may, if desired, be coupled to the inner face  88   a  of the metering chamber diaphragm  88  to provide additional support for the action of the diaphragm  88  against the second end  90   b  of the metering lever  90 . 
     The metering chamber  82  has a volume, for a carburetor having the dimensions as above set forth, in the range of 0.4 cubic inches. The gas pressure in the metering chamber  82  for the carburetor having the dimensions and gas pressures as above described is on the order of atmospheric to a partial vacuum depending on the speed and load conditions of the internal combustion engine to which the carburetor  14  is operatively connected. 
     As shown on  FIGS. 5 ,  6  and  7 , the carburetor body has fourth walls  100  defining a throttle bore  102 . As described below in greater detail, the throttle bore  100  has an air inlet port  104  and a gas/air outlet port  106  and the gas outlet port  106  is adapted to be connected to the intake manifold of an internal combustion engine for delivering thereto a gas/fuel mixture having a preselected gas to air ratio for the particular operating conditions of the internal combustion engine. 
     The carburetor body has fifth walls  108  defining a gas flow passage  110  which provides gas flow communication between the metering chamber  82  and the throttle bore  102  to allow the flow of gas from the metering chamber  82  into the throttle bore  102 . The diameter of the throttle bore  102  is smaller than the air inlet port  104  and the gas/air outlet port  106 . This creates a venturi when air flow is drawn through the throttle bore  102  by the suction applied by the internal combustion engine. As the flow of air passes into the reduced diameter throttle bore  102 , the speed of the airflow increases and the pressure decreases. The now lower than ambient air pressure present in the throttle bore  102  is connected by the metering chamber outlet passage  110  to the metering chamber  82 . The greater atmospheric pressure present on the metering chamber diaphragm outer surface  88   a  causes the metering chamber diaphragm  88  to move towards the metering chamber inlet port  84 , which in turn causes the metering chamber needle  94  to lift from the metering chamber gas inlet port which allows the flow of liquefied petroleum gas into the metering chamber  82 . The flow of gas continues into the metering chamber outlet port  110  and thus into the throttle bore  102 . The gas mixes with ambient air in the throttle bore  102  to provide a gas/air mixture with the desired ratio of liquified petroleum gas to air required by the internal combustion engine at a flow rate required by the particular operating conditions of the internal combustion engine. For a carburetor having the dimensions and configurations as above described, it has been found that the gas flow through the carburetor from the gas inlet port  22  to the throttle bore  102  may be on the order of 18 cubic inches per minute at idle to a gas flow rate on the order  152  cubic inches per minute for the internal combustion engine at full throttle. 
     As shown on  FIGS. 6 and 7 , there are sixth walls  110  in the throttle inlet port  102  defining the gas/air mixture outlet port  106  for introduction of the gas/air mixture into the inlet manifold of an internal combustion engine to be powered by the liquified petroleum gas. 
     The carburetor has seventh walls  112  defining a throttle control chamber  114 . A throttle slide  116  is mounted for sliding movement in the throttle control chamber  114  in the directions indicated by the double ended arrow  118 . A throttle needle  120  is mounted on the throttle slide  116  for reciprocating motion therewith in the directions indicated by the double ended arrow  118 . The throttle needle  120  has a needle end  120   a  for selective movement into and out of a gas inlet port  124  to meter the flow of gas into the throttle bore from full flow wherein the first end of the needle  120   a  is retracted from the gas inlet port  124  to a position where the first end  120   a  of the needle  120  partially blocks the aperture in the insert  128  to reduce the flow of gas into the throttle bore  102  at an idle speed of the internal combustion engine. The taper of the needle end  120   a  of the throttle needle  120  is shaped to partially block the aperture in insert  128  at any position of between fully open throttle slide  116  and a fully closed position to provide the metering function of the correct gas/air ratio for the specific internal combustion engine at any engine speed or load. The throttle needle  120  is threadingly attached to the throttle slide  116  as indicated at  119  for movement therewith. By rotating the throttle needle at the threading engagement  119 , an adjustment of the gas/air ratio is achieved. A throttle cable  130  is operatively connected to the throttle slide to move the throttle slide in the direction indicated by the upper arrow  118   a  when the contact ball  132  engages the upper end  116   a  of the throttle slide  116 . A throttle cap  140  is threadingly connected to the carburetor body  14  as indicated at  142  and a throttle spring  144  is mounted in the throttle cap  140  and has a first end  144   a  bearing against the upper end  116   a  of the throttle slide  116  and a second end  144   b  bearing against the throttle cap  140  to bias the throttle slide  116  in the direction of the second arrow  118   b.    
     In some applications of a carburetor according to the principles of the present invention, it may be desirable to provide a throttle slide movement limitation  220  on the travel of the throttle slide  116  towards the gas inlet port  124  to thereby limit the penetration of the throttle needle  120  into the gas inlet port  124 .  FIG. 11  illustrates the details of the throttle slide movement limitation  220 . As shown thereon, there are walls  222  in the body member  14  in regions adjacent the throttle bore  102  defining a limitation chamber  224 . A control needle  226  threadingly engages the body member  14  as indicated at  228 . The control needle  226  has a first end  226   a  that may be moved into the throttle bore  102  as indicated by the dotted line showing at  230  by rotating the adjustment end  226   b  of the control needle  226 . For the first end  226   a  of the control needle  226  projecting onto the throttle bore as shown by the dotted line, the throttle slide  116  engages the first end  226   a  and thus downward movement of the throttle slide  116  is stopped at a predetermined position corresponding to the desired minimum opening of the gas inlet port  128 . A control needle spring  244  is positioned in the limitation chamber  224  and abuts the body member  14  and the second end  226   b  of the control needle  226  to bias the control needle  226  outwardly. 
     The carburetor  12  may be provided with flanges  240  having apertures  242  therethrough which may be utilized for attachment of the carburetor to the internal combustion engine as desired. 
       FIG. 14  illustrates a block diagram showing the preferred mounting relationship between the carburetor, an intake manifold and an internal combustion engine. As shown on  FIG. 14 , a carburetor  150 , which may be the same as carburetor  12  described above, receives ambient air indicated by the arrow  180  and gas phase/liquid phase liquified petroleum gas such as propane, as indicated by the arrow  182 . The carburetor  150  converts any liquid phase liquified petroleum gas entering the carburetor  150  into the gas phase thereof and mixes the gas phase with the ambient air in a preselected gas to air ratio and provides the gas/air mixture at the outlet thereof, as indicated by the arrow  184 , as described above for the operation of carburetor  12 . The carburetor  150  is mounted on or in close proximity to an intake manifold  152  of an internal combustion engine  154  so as to be in heat receiving relationship thereto. That is, in the preferred embodiments of the present invention the carburetor such as the carburetor  150 , which may be the same as carburetor  12 , shown in the block diagram of  FIG. 14 , is in heat receiving relationship to the internal combustion engine  154  so that the carburetor  150  receives heat by any or all of the heat transfer modes of radiation, conduction and convection from the engine and/or and structural parts thereof and/or and accessories thereof. The heat received by the carburetor  150  supplies the necessary energy to convert any liquid phase of the liquified petroleum gas which enters the first stage pressure regulator chamber of the carburetor into the gas phase. The intake manifold  152  directs the gas/fuel mixture as shown by the arrow  186  to the cylinders  154   a  of the internal combustion engine  154  which may be connected to any desired device (not shown) to provide the operation thereof. 
     As noted above, the diaphragms  40 ,  60  and  88  are sealingly mounted on the body member  14 .  FIGS. 9 ,  10  and  11  illustrate a preferred sealing arrangement. The diaphragms are provided with a knife edge that bears against the body member  14  and the force of the back up plates bearing against the diaphragms provides the desired sealing engagement. However, other sealing arrangements may be utilized as desired in particular applications. 
     Although specific embodiments of the present invention have been described above with reference to the various Figures of the drawing, it should be understood that such embodiments are by way of example only and merely illustrative of but a small number of the many possible specific embodiments which can represent applications of the principles of the present invention. Various changes and modifications obvious to one skilled in the art to which the present invention pertains are deemed to be within the spirit, scope and contemplation of the present invention as further defined in the appended claims. While the particular embodiments and applications of the present invention have been above described and illustrated, the present invention is not limited to the precise construction and arrangements disclosed. Those persons knowledgeable in the art may also conceive of certain modifications, changes and variations in the precise details of the embodiments disclosed above for adaptation of the principles of the present invention to various applications to suit particular circumstances or products to be formed. The invention is therefore not intended to be limited to the preferred embodiments depicted, but only by the scope of the appended claims and the reasonably equivalent apparatus and methods as described herein.

Technology Classification (CPC): 5