Patent ID: 6851664

Claim:
A self-relieving choke valve system for a carburetor of a combustion engine comprising: a body of the carburetor; a fuel-and-air mixing passage defined by the body; a choke valve disposed within the fuel-and-air mixing passage, the choke valve having a closed position and being movable to an open position when the engine is running; a vacuum motor having a housing carried by the body, a vacuum chamber, an actuator communicating with the vacuum chamber and movable relative to the housing in response to a vacuum applied to the vacuum chamber, and a mechanical linkage operably connecting the choke valve with the actuator; a vacuum source derived from the engine and producing a vacuum signal when the engine is running which communicates with the vacuum chamber, wherein the actuator moves upon communication of the vacuum signal with the vacuum chamber to move the choke valve into the open position; wherein the vacuum source is located in the fuel-and-air mixing passage downstream of the choke valve; a throttle valve of the carburetor disposed within the fuel-and-air mixing passage downstream of the choke valve: a first tap of the vacuum source located downstream of the throttle valve when in an idle position; wherein the vacuum chamber is constructed and arranged to communicate with the first tap at least when the combustion engine is running at low engine rpms; a venturi of the carburetor disposed within the fuel-and-air mixing passage between the choke valve and the throttle valve; a second tap of the vacuum source located in the venturi; wherein the vacuum chamber is constructed and arranged to communicate with the second tap at least when the combustion engine is running at high engine rpms; a conduit between the housing of the vacuum motor and the body of the carburetor for communicating of the vacuum signal to the vacuum chamber, the conduit having a first leg communicating the first tap with the vacuum chamber and a second leg communicating the second tap with the vacuum chamber; and a check valve in the first leg, wherein the check valve is yieldably biased closed when the engine is running at high rpms and opened by the vacuum signal from the first tap when the engine is running at low rpms and the throttle valve is substantially closed.