BACKGROUND OF THE INVENTION

The present invention relates to a carburetor having an accelerator pump, and more particularly, to an accelerator pump assembly including an accelerator pump cap, or cover.

A conventional motorcycle carburetor includes a main body or housing having an induction passage with a throat, or venturi, located intermediate the ends of the induction passage. A butterfly valve assembly or the like is mounted in the manifold end of the induction passage and controls the flow of air therethrough. A fuel bowl is mounted on the bottom of the housing and is connected to the induction passage by a discharge tube. A float located in the fuel bowl controls the level of fuel in a fuel reservoir of the fuel bowl to maintain a ready supply of fuel in the carburetor. When air flows through the throat of the carburetor, fuel is pulled from the fuel reservoir into the air stream in the induction passage of the carburetor due to the difference of pressure created by the air flow.

An increase in fuel flow is required to smoothly accelerate an engine. Typically, when a throttle is opened, airflow will increase immediately. However, an increase in the flow of fuel such as gasolene, which is denser than air, will take time to catch-up with the increased airflow. This results in a lean air-fuel mixture for an initial few moments after a call for acceleration and can cause the engine to hesitate. This problem can be overcome with the use of an accelerator pump which is typically built into the side or bottom of the carburetor. The accelerator pump functions to immediately deliver a spray of fuel to the throat of the induction passage of the carburetor to momentarily increase the fuel-to-air concentration during an initial call for acceleration.

FIG. 1 illustrates an example of a conventional accelerator pump assembly 10 that has a diaphragm 12 seated within a pump cap, or cover, 14. The cap 14 defines a chamber 16 that fills with fuel from a fuel reservoir 18 of the fuel bowl via a normally-opened check- valve 20. When the accelerator pump is actuated, a push rod

22 causes the diaphragm 12 to deflect downwardly thereby pumping fuel in chamber 16 through a normally-closed check- valve 24 through an outlet passage 26 and to a nozzle located in the induction passage of the carburetor downstream of the venturi. Check- valve 20 closes when the diaphragm pumps fuel and opens thereafter to refill chamber 16 with fuel.

A problem experienced with known accelerator pump assemblies is that vapor and gas can collect within the chamber of the pump. The presence and continued collection of vapor within a pump assembly can reduce engine response during start¬ up and acceleration. For example, when the accelerator pump is actuated, the vapor or gas within the chamber becomes compressed and fuel delivery is delayed. Thus, there is a need for an accelerator pump that reduces and/or prevents vapor and/or gas collection in the chamber of the pump.

BRIEF SUMMARY OF THE INVENTION The present invention provides an accelerator pump assembly for a carburetor. The assembly includes an accelerator pump cap having a recess defined by a base and a sidewall of the cap and a diaphragm mounted within on an open end of the cap. A fuel chamber is located within the cap and is defined by the base, sidewall, and diaphragm. The diaphragm is deflectable within the cap to pump fuel residing in the fuel chamber through at least one outlet port at the upper end of the cap adjacent the diaphragm. The location of the outlet port or ports ensures that any vapor or gas within the fuel chamber is flushed through the outlet port or ports every time the diaphragm is deflected into the cap.

According to another aspect of the present application, an accelerator pump cap for an accelerator pump assembly of a carburetor, such as a motorcycle or all- terrain vehicle (ATV) carburetor, is provided. The cap body has a sidewall projecting from a base defining a fuel chamber beneath an open top of the cap body. One or more outlet ports extend through the sidewall and are closely-spaced to the open top of the cap body to ensure that any vapor or gas residing within the fuel chamber is

flushed out of the fuel chamber through the outlet port or ports when the accelerator pump assembly is actuated to supply fuel to the carburetor.

In some contemplated embodiments of the present invention, each outlet port is located on the sidewall entirely within an upper half of the sidewall height, or more preferably, entirely within on an uppermost quarter of the sidewall height. In contrast, a fuel inlet port, which also extends through the sidewall of the cap body, is located below the height of each outlet port. In addition, preferably each outlet port provides a smaller opening than the inlet port, and a pathway is defined within the cap body through which fuel is pumped from the fuel chamber via the outlet ports. The pathway communicates with both outlet ports and directs fuel through a single outlet formed on an upper surface of the cap body adjacent the fuel chamber.

According to a further aspect of the present invention, a collector ring for use with a carburetor is provided. The carburetor has a fuel bowl and a diaphragm moveable in the fuel bowl to displace fuel and unwanted vapor and gas in a cavity of the fuel bowl through an outlet in the wall of the fuel bowl. The collector ring is adapted to be installed in the fuel bowl to form with the wall of the fuel bowl a chamber for receiving liquid fuel and unwanted gas and vapor for delivery to the outlet of the cavity. The collector ring has at least one aperture providing communication between the chamber and the cavity, and the aperture is located closely adjacent the diaphragm when the collector ring is operatively installed in the fuel bowl. Accordingly, displacement of the diaphragm into the fuel bowl causes unwanted gas, fuel vapor, water vapor and the like to be displaced from the cavity and through the outlet before liquid fuel is displaced therethrough.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects, features and advantages of the present invention should become apparent from the following description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of an accelerator pump assembly according to the prior art;

FIG. 2 is a perspective view of an accelerator pump cap according to the present invention;

FIG. 3 is an exploded perspective view of a carburetor having an accelerator pump assembly according to the present invention; FIG. 4 is a schematic view of a carburetor having an accelerator pump assembly according to the present invention;

FIG. 5 is a perspective view of an alternate embodiment of an accelerator pump cap according to the present invention;

FIG. 6 is a perspective view of a combination of an accelerator pump cap and collector ring according to the present invention;

FIG. 6 A is a perspective view of the underside of the collector ring illustrated in FIG. 6;

FIG. 7 is a perspective view of an alternate embodiment of an accelerator pump cap and collector ring combination according to the present invention; FIG. 7 A is a perspective view of the underside of the collector ring illustrated in FIG. 7;

FIG. 8 is a perspective view of another alternate embodiment of an accelerator pump cap and collector ring combination according to the present invention;

FIG. 8 A is a perspective view of the underside of the collector ring illustrated in FIG. 8;

FIG. 9 is a perspective view of yet another alternate embodiment of an accelerator pump cap and collector ring combination according to the present invention; and

FIG. 9A is a perspective view of the underside of the collector ring illustrated in FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIGs. 2-4, an accelerator pump cap, or cover, 30 according to the present invention is provided for being mounted to a fuel bowl 32 of a carburetor 34, such as a carburetor for a motorcycle or ATV. The cap 30 has an open

recess 36 with a base 38 that preferably has an annular groove 40 formed in a surface thereof. A diaphragm 42 mounts to the top of the open recess 36 of the cap 30 and defines within the cap 30 a fuel pump chamber 44. Preferably, the diaphragm 42 is urged in a normally outwardly-bulged position under the force of a spring 46 or the like which seats within the annular groove 40 of the cap base 38 and projects to the underside of the diaphragm 42.

Preferably, the cap 30 has a supply conduit formed therein for providing a path of fuel to fill chamber 44. As best illustrated in FIG. 2, the cap 30 has an upper rim, or surface, 48 having an inlet 50 which communicates with a fuel reservoir of the fuel bowl 32 via a check-valve 52 or the like. Thus, fuel enters the cap 30 at inlet 50 and is directed into the chamber 44 via port 54 formed in a sidewall 56 of the cap recess 36.

One of the novel aspects of cap 30 is the path of fuel pumped from the chamber 44 to the induction passage 58 of the carburetor 34. Preferably, a pair of outlet ports 60 are formed in the sidewall 56 of the cap recess 36 and are preferably relatively-small and closely-spaced to the upper surface 48 of the cap 30. For example, preferably each of the outlet ports 60 are smaller in size than the inlet port 54, and preferably each of the outlet ports 60 is located entirely within an upper half of a sidewall height "H", which is measured from the base 38 to the upper surface 48 of the cap 30. More preferably, each outlet port 60 is located entirely within an uppermost quarter of the sidewall height "H" as best illustrated in FIG. 2. Thus, the outlet ports 60 are located at a height on the sidewall 56 that is above the location of the inlet port 54 and are located closer to the top of the cap 30 than the inlet port 54. Outlet ports 60 are illustrated as a pair of relatively-small circular openings. However, other opening shapes and number of openings can also be utilized according to the present invention. For example, a single horizontally elongate or oval outlet port (not shown) can be utilized. Alternatively, three or more openings can be utilized. Thus, the shape and/or number of openings can be altered provided that the opening or openings are located in close proximity to the top of the cap 30.

In the preferred embodiment, no part of an outlet port 60 extends below the upper half, or more preferably the uppermost quarter, of the sidewall height "H".

Outlet ports 60 direct fuel within chamber 44 through a pathway formed within the cap 30 to an outlet 62 preferably formed on the upper surface 48 of the cap 30. The pathway communicates with both outlet ports 60 and directs fuel through the single outlet 62 located adjacent the cap recess 36. Outlet 62 connects to a conduit that provides a direct path to a nozzle located in the induction passage 58 of the carburetor 34 via a check- valve 64, or the like.

Vapor, fuel vapor, water vapor, gases, air and the like may be present within the fuel pump chamber 44 of the cap 30 and typically collect therein at the top of the cap recess 36 directly underneath the diaphragm 42. According to the present invention, vapor and gas are prevented from collecting and residing long-term within the cap 30 by the use of the outlet ports 60 located adjacent the top of the recess 36. Thus, when the diaphragm 42 is activated to pump fuel, any vapor located within the top of the recess 36 is pumped out of the recess 36 via outlet ports 60. Thus, all vapor and gases existing within the cap 30 is flushed out when the accelerator pump is actuated thereby eliminating the long-term presence and collection of vapor and gases within the cap.

In one preferred embodiment, the outlet ports 60 comprise at least two separate ports which together provide the requisite volume of fuel flow therethrough. The use of two or more relatively small-sized ports provides the advantage that flow from the cap 30 can be taken at a highest possible location within the cap 30 to ensure that all vapor and gas is flushed out of the cap 30 when the diaphragm 42 is activated. This is because smaller-sized ports can readily be formed in the cap 30 closer to the upper surface 42 of the cap 30 than a single circular larger-sized port. In addition, the lowermost extent of a single circular larger-sized port will extend closer to the base than that of a smaller-sized port. As explained above, a single port can be utilized provided that it is oval or elongate and does not extend too remote a distance from the upper surface of the cap.

In operation, fuel fills the chamber 44 via a check-valve 52 connected to a fuel reservoir of the fuel bowl 32. The check- valve 64 in the path in which fuel is pumped prevents air from entering the pump and keeps the path full of fuel to provide a ready supply for a responsive discharge upon the next actuation of the pump. When the pump is actuated, the diaphragm 42 extends downwardly into the cap recess 36 thereby forcing fuel through outlet ports 60. The force of the pumped fuel closes check- valve 52 and opens check- valve 64 so that a spray of fuel can be quickly delivered within the induction passage 58 of the carburetor 34. Since the outlet ports 60 are located close to the top of the cap recess 36, any vapor or gas within the chamber 44 is flushed out of chamber 44 when the diaphragm 42 is actuated. Thereafter, the chamber 44 is re-filled with fuel when check-valve 52 re-opens.

An alternate embodiment of an accelerator pump cap 70 is illustrated in FIG. 5. The cap 70 is substantially identical to cap 30, except that the outlet ports 72 in cap 70 are formed through a wall portion 74 cut into a sloped annular section 76 of the sidewall 78 of the cap 70. The wall portion 74 is oriented substantially perpendicular to the base 80 of the cap 70.

FIGs. 6 and 6A show an alternate embodiment of the present invention which utilizes a separate collector ring 90 installed within the fuel chamber, or cavity, 102 of an accelerator pump cap 100. The cap 100 is substantially identical to cap 30, discussed above, except that annular sidewall 104 of the cap 100 has a stepped profile 106 adjacent the upper end 108 of the cap 100. The outer peripheral sides 92 and underside surfaces 94 of the collector ring 90 substantially match the stepped profile 106 of the cap 100 so that the ring 90 can be seated on the stepped profile 106 within the cavity 102. The collector ring 90 has an array of apertures 96 extending through a thin- walled portion 98 of the ring 90 that forms a chamber 110 with the sidewall 104 of the cap 100. The chamber 110 is formed at the location of outlet ports 112 of the cap 100 so that the chamber 110 communicates with the outlet ports 112 and so that any fuel, vapor, or gases forced out of the cavity 102 through the outlet ports 112 must pass through the chamber 110. As best illustrated in FIG. 6, the ring 90 seats within the

cap 100 adjacent the upper end 108 of the cap 100 thereby positioning the array of apertures 96 close to the upper end 108 of the cap 100 and close to the surface of a diaphragm which deflects into the cavity 102 to force fuel through the outlet ports 112. Accordingly, every time the diaphragm is activated, substantially all vapor and gas will be flushed through the ports 112 and will be prevented from collecting and residing within the cavity 102.

FIGs. 7 and 7A show an alternate embodiment of a collector ring 120 installed within the fuel chamber, or cavity, 102 of the accelerator pump cap 100, discussed above. The collector ring 120 has outer peripheral surfaces 122 and underside surfaces 124 that enable the ring 120 to be received and seated on the stepped profile 106 of the cap 100. The ring 120 also has a spaced array of apertures 126 extending 360° about an upper annular wall 128 of the ring 120 that forms an annular chamber 130 with the sidewall 104 of the cap 100. The chamber 130 is formed at the location of outlet ports 112 of the cap 100 so that the chamber communicates with the outlet ports 112 and any fuel, vapor, or gases forced out of the cavity 102 through the outlet ports 112 pass through the chamber 130.

FIGs. 8 and 8 A show another alternate embodiment of the present invention which utilizes a separate collector ring 140 installed within a fuel cavity 152 of an accelerator pump cap 150. The cap 150 is substantially identical to the cap 30, discussed above, except that annular sidewall 154 of the cap 150 has a stepped profile 156 adjacent the upper end 158 of the cap 150. The outlet ports 160 of the cap 150 are located on surface 162 of the stepped profile 156. The underside 144 of the collector ring 140 seats on the surface 162 within the cavity 152.

The collector ring 140 has an array of apertures 146 in a recessed portion 148 of the ring 140 that forms a chamber 164 with the surface 162 of the cap 150. The chamber 164 is formed directly over the outlet ports 160 of the cap 150 so that the chamber 164 communicates with the outlet ports 160. As best illustrated in FIG. 8, the ring 140 seats within the cap 150 adjacent the upper end 158 of the cap 150 thereby positioning the array of apertures 146 close to the upper end 158 and close to

the diaphragm which deflects into the cavity 152 to force fuel through the outlet ports 160.

FIGs. 9 and 9 A show yet another alternate embodiment of a collector ring 170 installed within the fuel chamber, or cavity, 152 of the accelerator pump cap 150, described above. The collector ring 170 has an underside 174 that seats on the surface 162 of the cap 150. The ring 170 has a spaced array of apertures 176 extending 360° about an upper annular wall 178 of the ring 170 that forms an annular chamber 180 with the sidewall 154 of the cap 150. The annular chamber 180 is formed directly above and in communication with the outlet ports 160 of the cap 150. Thus, any fuel, vapor, or gases forced out of the cavity 152 through the outlet ports 160 must pass through the chamber 180.

While preferred accelerator pump assemblies, caps and collector rings have been described in detail, various modifications, alterations, and changes may be made without departing from the spirit and scope of the accelerator pump assemblies, caps and collector rings according to the present invention as defined in the appended claims.