Auxiliary fuel and air supply in a carburetor

An auxiliary fuel and air supply apparatus for a diaphragm carburetor with a fuel and air mixing passage having a throttle valve located therein downstream of an air intake opening of the fuel and air mixing passage, the apparatus comprising:

• a bore having a fuel and air mixing valve disposed therein defining in part a valve actuation chamber and a separate fuel and air mixing chamber communicating with the fuel and air mixing passage at a location downstream of the throttle valve;
• a fuel chamber;
• a fuel passage having an upstream end in communication with the fuel chamber and a downstream end in communication with the fuel and air mixing chamber;
• an air passage having an upstream end in communication with the fuel and air mixing passage at a location upstream of the throttle valve and further having a downstream end in communication with the fuel and air mixing chamber;
• a return fuel passage having an upstream end in communication with the valve actuation chamber;
• a purge passage in communication with the valve actuation chamber;
• and
• a fuel chamber purge apparatus including a purge bulb at least partially surrounding a purge valve having an inlet in communication with the fuel chamber and an outlet in communication with the valve actuation chamber via the purge passage, wherein upon actuation of the purge bulb fluid pressure moves the fuel and air mixing valve to communicate the fuel and air mixing passage with the air and fuel passages.

A diaphragm carburetor comprising:

• a body;
• an air inlet in the body;
• a fuel and air mixture outlet in the body;
• a fuel and air mixing passage through the body between the air inlet and the fuel and air mixture outlet;
• a throttle shaft carried by the body, extending across the fuel and air mixing passage, and including a passage therein;
• a throttle valve disposed in the fuel and air mixing passage between the air inlet and fuel and air mixture outlet and carried by the throttle shaft;
• an auxiliary fuel and air mixing chamber carried by the body;
• a fuel metering assembly carried by the body and defining a fuel chamber;
• an auxiliary fuel inlet passage in communication with the mixing chamber and the fuel chamber to supply fuel to the mixing chamber;
• an auxiliary air inlet passage in communication with the auxiliary fuel and air mixing chamber and the fuel and air mixing passage at a location upstream of the throttle valve to supply air to the auxiliary fuel and air mixing chamber;
• an auxiliary fuel and air outlet passage in communication with the auxiliary fuel and air mixing chamber and the fuel and air mixing passage at a location downstream of the throttle valve to supply a mixture of fuel and air from the auxiliary fuel and air mixing chamber to the fuel and air mixing passage;
• a valve carried by the body in the auxiliary fuel and air mixing chamber defining in part a valve actuation chamber and being movable to a closed position and an open position to control flow of an auxiliary air and fuel mixture from the auxiliary fuel and air mixing chamber to the fuel and air mixing passage, wherein the valve includes at least one passage therein in communication with the passage in the throttle shaft;
• a fuel chamber purge passage in communication with the mixing chamber;
• and
• a fuel chamber purge apparatus carried by the body and in communication with the fuel chamber and the fuel chamber purge passage and being operable to move the valve to the open position, wherein the fuel chamber purge apparatus includes a purge bulb and a purge valve having an inlet and an outlet, such that repeated depression and release of the purge bulb draws fuel from the fuel chamber through the inlet of the purge valve and into the purge bulb, and expels fuel from the purge bulb through the outlet of the purge valve, into the valve actuation chamber thereby moving the valve, and ultimately out of the carburetor through a return fuel passage.