Abstract:
A carburetor having a plurality of orifices at different locations adjacent to the sidewall of the airflow passage therethrough and connecting passages communicating the orifices with a fuel source, such that different airflow conditions through the airflow passageway will generate different negative pressure conditions in the respective orifices and connecting passages, such that fuel will be drawn to the airflow passageway through the orifice or orifices and connected passage or passages with the greatest negative pressure conditions therein, a primary operational result being fuel delivery capable of rapidly changing corresponding to rapidly changing airflow conditions in the airflow passageway corresponding to changing operating conditions.

Description:
This application is a divisional application of patent application Ser. No. 09/242,032, filed Feb. 5. 1999, now U.S. Pat. No. 6,149,140, which is a national stage application of International Application No. PCT/US98/11754, filed Jun. 5, 1998, and which claims the benefit of provisional application No. 60/048,907, filed Jun. 6, 1997, 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to carburetors for internal combustion engines, and more particularly, to primary and secondary fuel delivery circuits therefor and methods for the operation and installation of same. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a carburetor including a chamber for receiving and holding fuel, a sidewall forming a passageway for the flow of air therethrough having an inlet opening and an outlet opening and a constricted portion therebetween further includes a plurality of orifices at different locations adjacent to the sidewall in communication with the air flow passageway, and connecting passages connecting the orifices with the fuel chamber. The various orifices are positioned at different locations in the air flow passageway such that different air flow conditions through the air flow passageway will generate different negative pressure conditions in the respective orifices and connecting passages, such that fuel will be drawn to the air flow passageway through the orifice or orifices and connecting passage or passages with the greatest negative pressure conditions therein, the operational result being fuel delivery capable or rapidly changing corresponding to rapidly changing air flow conditions in the air flow passageway corresponding to changing operating conditions. 
     According to another aspect of the present invention, the carburetor has a primary fuel delivery circuit including a primary fuel passage extending from the fuel holding chamber to a primary fuel delivery orifice located in communication with the air flow passageway. At least one secondary fuel delivery circuit is providing including at least one orifice in communication with the air flow passageway adjacent to the carburetor sidewall. At least one connecting passage communicates the at least one orifice with the primary fuel delivery circuit. In operation, different air flow conditions through the air flow passageway will generate different negative pressure conditions in the various orifices, under some air flow conditions fuel being drawn into the primary fuel delivery circuit by the negative pressure conditions and exiting into the air flow passageway through the orifices and connecting passageways having the greater negative pressure conditions therein, the fuel delivery characteristics being rapidly changeable corresponding to changing air flow conditions. 
     The circuitry according to the present invention can be easily and readily installed on a wide variety of known carburetor construction, and in new carburetor constructions. 
     In operation, it has been observed that the fuel exiting the orifices into the air flow passageway is in a highly vaporized state, which in combination with the ability of the fuel delivery to rapidly change corresponding to changes in air flow conditions, provides enhanced engine performance and response. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric representation of pertinent aspects of a typical carburetor including a conventional primary fuel delivery circuit and a plurality of secondary fuel delivery circuits according to the present invention; 
     FIG. 2 is an isometric representation of the carburetor of FIG. 1 showing fuel delivery through the primary fuel delivery circuit thereof; 
     FIG. 3 is another isometric representation of the carburetor of FIG. 1 showing fuel delivery through the secondary fuel delivery circuits of the present invention under low air speed operating conditions; 
     FIG. 4 is another isometric representation of the carburetor of FIG. 1 showing fuel delivery through the primary fuel delivery circuit and the secondary fuel delivery circuits of the present invention under higher air speed operating conditions; 
     FIG. 5 is an isometric representation of a prior art carburetor including a conventional primary fuel delivery circuit and a secondary fuel delivery circuit according to the present invention; 
     FIG. 6 is an isometric representation of the carburetor of FIG. 5 including an alternative secondary fuel delivery circuit according to the present invention; 
     FIG. 7 is a plan view of the main body to metering block surface of a typical Holley brand carburetor showing installation of the secondary fuel delivery circuits of FIGS. 5 and 6 therein according to the present invention; 
     FIG. 8 is a graphical representation of torque versus RPM for an engine utilizing a carburetor including the secondary fuel delivery circuit of FIG. 6; and 
     FIG. 9 is a graphical representation of horsepower versus RPM for the engine using the secondary fuel delivery circuit of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings more particularly by reference numbers wherein like numerals refer to like parts, FIG. 1 is an isometric representation of a typical carburetor  10  including a conventional prior art primary fuel delivery circuit  12 , and secondary fuel delivery circuits  14  and  14 A according to the present invention. Carburetor  10  includes a body portion (mostly not shown for clarity) which includes a sidewall portion  16  defining an air flow passageway  15  extending between an inlet opening  18  and an outlet opening  20 , sidewall  16  forming a constricted portion  22  intermediate inlet opening  18  and outlet opening  20 . Carburetor  10  includes a throttle plate  29  located in passageway  15  downstream of constricted portion  22 , throttle plate  29  being mounted on a shaft  27  for rotation therewith for controlling the airflow through the passageway in the conventional manner. Generally, carburetor  10 , minus secondary fuel delivery circuits  14  and  14 A, is representative of numerous known commercially available carburetors used for internal combustion engines for a wide range of devices such as automobiles, motorcycles, aircraft, watercraft, off road sport vehicles, and other internal combustion engine powered devices. Carburetor  10  additionally includes a chamber for receiving and holding fuel (deleted for clarity) in communication with a fuel tube No.  1 A or a fuel tube No.  2 A (shown in dotted lines) of primary fuel delivery circuit  12 . Primary circuit  12  further includes a cross over tube  76 A which communicates fuel tube No.  1 A or No.  2 A with a booster tube  34  of the primary circuit, which booster tube  34  communicates with a primary fuel delivery orifice  38  located in a booster  36  in the air flow passageway. 
     Referring to FIG. 2, under normal operating conditions of primary fuel delivery circuit  12 , fuel represented by the arrow  30  flows into fuel tube No.  1 A or No.  2 A where it collects represented by the shaded area. Note here that the primary difference between fuel tubes No.  1 A and No.  2 A is that fuel tube No.  1 A includes a parallel emulsion tube having cross over passages for introducing air represented by the arrow  32  from atmosphere into the fuel collected in the tube No.  1 A. As air flows through the carburetor air flow passageway  15  and booster  36  (the air flow being represented by the arrows  35 ) a negative pressure condition is generated in primary fuel delivery orifice  38  and in booster tube  34 . This negative pressure condition is communicated from booster tube  34  to fuel tube No.  2 A or through cross over tube  76 A to fuel tube No.  1 A to cause fuel to be drawn into and through booster tube  34  (shown by additional shading and large arrows), where the fuel exits through primary fuel delivery orifice  38  into booster  36 , where air flow  35  mixes with the fuel and carries it through air flow passageway  15  into the internal combustion engine (not shown), the amount of fuel drawn through the primary circuit roughly corresponding to the degree of air flow through air flow passageway  15 . 
     Again referring to FIG. 1, secondary fuel delivery circuit  14  includes a connecting passage  75  having one end in communication with booster tube  34  and an opposite end in communication with a connecting passage  77 , which connecting passage  77  communicates with a fuel delivery orifice  28 F on sidewall  16  in communication with air flow passageway  15  upstream of throttle plate  29 . 
     Secondary fuel delivery circuit  14 A similarly includes a connecting passage  82  having one end in communication with booster tube  34  and an opposite end in communication with a connecting passage  98 , which in turn communicates with connecting passages  80  and  81 . Connecting passage  81  in turn communicates with orifice  28 A at an upper position on sidewall  16  in communication with air flow passageway  15 . Connecting passage  98  communicates with orifice  28 B at a first intermediate position on sidewall  16  in communication with air flow passageway  15 . And, connecting passage  80  communicates with orifices  28 C and  28 D at lower positions on sidewall  16  in communication with air flow passageway  15 . Each of the orifices  28 A- 28 F is located upstream of throttle plate  29 . The different locations of orifices  28 A- 28 F in communication with air flow passageway  15  is an important feature of the present invention as it has been found that air flow characteristics through air flow passageway  15  will differ at different locations in the air flow passageway. By placing orifices of a fuel delivery circuit at different locations where correspondingly different air flow characteristics are anticipated, better fuel delivery more responsive to changing air flow conditions reflecting engine demand and other conditions can be achieved. 
     Referring now to FIG. 3, fuel delivery to air flow passageway  15  by primary fuel delivery circuit  12  and secondary fuel delivery circuits  14  and  14 A for lower air flow conditions corresponding to low speed throttle conditions and low engine demand, is shown by shading and large black arrows. As can be seen, fuel  3 O enters primary fuel delivery circuit  12  from the fuel holding chamber (not shown) where it accumulates in fuel tube No.  1 A (or No.  2 A). The fuel is then drawn through cross over tube  76 A into booster tube  34  wherein the fuel travels through connecting passages  75  and  82 . From connecting passages  75  and  82 , the fuel travels into connecting passages  77  and  98 , and exits into air flow passageway  15  through orifices  28 B and  28 F, which generate the highest negative pressure or vacuum signals under this air flow condition. Here, it has been observed that the fuel exiting orifices  28 B and  28 F is at a high degree of vaporization, which significantly contributes to enhanced performance provided by the secondary fuel delivery circuits  14  and  14 A of the present invention. 
     FIG. 4 shows the fuel delivery characteristics of primary delivery circuit  12  and secondary fuel delivery circuits  14  and  14 A, shown by shading and large black arrows, under higher air flow conditions corresponding to greater engine demand. Here, fuel  30  again enters fuel tube No.  1 A (or No.  2 A) from which it is drawn into booster tube  34 . Some of the fuel then exits through primary fuel delivery orifice  38  into air flow passageway  15  through booster  36 . Also, and importantly, additional fuel is drawn from booster tube  34  into connecting passage  75  where the fuel then flows through connecting passage  77  and orifice  28 F into air flow passageway  15 . Still further, fuel is also drawn through connecting passage  82  into connecting passage  98  where the fuel exits into air flow passageway  15  through orifice  28 B. Here it should be noted that under these conditions the negative pressure conditions at orifice  28 B can be sufficiently strong to reverse flow in the other orifices, that is, to draw air from air flow passageway  15  into orifices  28 A,  28 C, and/or  28 D, through connecting passageway  80  and  81  into connecting passage  98  where the air mixes with the fuel and exits back into air flow passageway  15  through orifice  28 B as shown. Again, the fuel exiting orifices  28 B and  28 F is highly vaporized, which provides the above discussed advantages. 
     It is important to recognize when studying the operation of secondary fuel delivery circuits  14  and  14 A that all of the interconnected connecting passages are directly influenced by the strongest overriding circuit. That is, the negative pressure conditions in the portion of the fuel delivery circuits wherein the negative pressure signal or signals are strongest can cause fuel delivery through the circuit portions with weaker negative pressure signals to stall and even reverse, as illustrated in FIG. 4, so as to supply additional fuel an/or air to the stronger portions of the circuit. Also, it is also important to note that prior to the reversal of the flow in the circuit portions, the circuits can be in an equilibrium state charged with fuel which enables them to become the stronger circuits virtually instantaneously as air flow changes such that the circuits can be said to essentially have a “self-seeking” feature which enables them to deliver the fuel to the orifice or orifices where the vacuum signal is strongest. Still further, and importantly, the fuel delivery orifices  28 A- 28 F can be placed in various locations throughout the air flow passageway  15  and are not restricted by the shape of sidewall surface  16 , although placing orifices  28 A- 28 F on surfaces having optimal air flow characteristics may provide certain advantages. 
     Referring to FIG. 5 an isometric representation of a typical prior art carburetor  100  including a conventional prior art primary fuel delivery circuit  12  as discussed above and a secondary fuel delivery circuit  14 B according to the present invention. Carburetor  100  includes a typical prior art idle fuel circuit including an idle adjusting screw  101 , an idle port  102  for discharging fuel into the airflow passageway of the carburetor, an idle inlet  103  which receives fuel through an idle supply passage  105 A, and an idle transfer passage  104  which communicates fuel from the idle circuit to an intermediate circuit  105 . Secondary fuel delivery circuit  14 B includes a connecting passage  75  and a connecting passage  108  for communicating booster tube  34  with intermediate circuit  105 , which has the resultant effect of converting the existing intermediate fuel delivery orifice into the equivalent of secondary fuel delivery orifice  28 F as indicated. To illustrate, normal fuel flow is shown by the thin black arrows separately through booster tube  34  into the airflow passgeway and through passage  105 A to the idle fuel circuit, some of the fuel exiting through idle orifice  102  and some flowing through transfer passage  104  to the intermediate fuel circuit. Fuel flow through the new secondary fuel delivery circuit  14 B is shown by the heavy black arrows as flowing from booster tube  34  through transfer passage  75  to transfer passage  108  which provides fuel to the intermediate circuit, such that the orifice thereof is utilized as a secondary fuel delivery orifice  28 F. 
     Turning to FIG. 6, the carburetor  100  is shown including conventional prior art primary fuel delivery circuit  12 , and another secondary fuel delivery circuit  14 C according to the present invention. Circuit  14 C includes transfer passage  75  as above which passes through a plug  107  having an intersecting passage  77  communicating with a secondary fuel delivery orifice  28 F. Circuit  14 C additionally includes a connecting passage  82  formed therein communicating with a secondary fuel delivery orifice  28 B as shown. Again, conventional fuel delivery is shown by thin black arrows wherein fuel is supplied to the idle and intermediate fuel circuits through passage  105 A. Fuel delivery through secondary fuel delivery circuit  14 C is through connecting passages  82  and  75  to delivery orifices  28 B and  28 F. 
     Turning to FIG. 7, a main body to metering block gasket surface  200  of a typical prior art Holley brand carburetor  202  is shown including modifications to provide both secondary fuel delivery circuits  14 B and  14 C according to the present invention therein. Here, the number  7  corresponds to the passageway through booster tube  34  of primary fuel delivery circuit  12  of the carburetor embodiment  100  discussed above. The secondary circuits are added to the carburetor by forming a groove in the main body to metering block gasket surface  200  which will form connecting passage  75  when the corresponding gasket (not shown) is placed thereover; forming a connecting passage  77  in the main body  204  in communication with connecting passage  75 ; forming a groove in the main body to metering block gasket surface  200  in connection with connecting passage  75  which will form connecting passage  82  when the gasket is placed on the surface; and forming an orifice  28 B in the main body  204  communicating with connecting passage  82  and the air flow passageway through the carburetor (not shown), and an orifice  28 F communicating connecting passage  77  with the air flow passage (also not shown). With this relatively simple and easy modification, a Holley brand carburetor such as the one shown in FIG. 5 will typically boost both the horsepower and torque of an internal combustion engine on which it is used by a significant amount. 
     The above modifications to carburetor  202  can be made using conventional machining practices. Also, such modifications can be made at the time of manufacture of the main body  204  by casting passages  75 ,  77  and  82 , and the orifices  28 B and  28 F into the body when it is cast, or by later machining any of the passages and/or orifices therein in a subsequent operation. 
     FIG. 8 is a graphical representation of torque versus revolutions per minute (RPM) an engine using a Holley brand carburetor modified to include the secondary fuel delivery circuit  14 C of FIG. 6 above, compared to the same Holley brand carburetor model without the new secondary fuel delivery circuit. Here, the curve  300  represents the torque versus RPM curve for the engine with the modified carburetor including circuit  14 C, and the curve  302  represents the engine with the unmodified carburetor. It can be see that torque is increased throughout an RPM range of between 5800 and 7000 by approximately 20 lb/ft with the modification. 
     FIG. 9 is a graphical representation of horsepower versus RPM for the same carburetors, the curve  304  representing horsepower versus RPM for the carburetor including the modifications  14 C, the curve  306  representing horsepower versus RPM for the unmodified carburetor. As can be seen, the modified carburetor provides approximately 20 more horsepower over the range of 5800 to 7000 RPM. Both the horsepower increase and torque increase over the RPM range shown is important, as that is the RPM range most used by the tested engines, which are stock car engines. 
     Thus there has been show and described herein a novel invention of carburetor with primary and secondary fuel delivery circuits and methods of operation and installation of the same which fulfill all of the objects and advantages set forth therefore. It will be apparent to those skilled in the art, however, that many changes, modifications, variations and other uses and applications for the subject invention are possible. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention, which is limited only by the claims which follow.