Carburetor with controlled fast idle cam

Claim 1

A carburetor having an induction passage open at one end to air and adapted to be connected at its other end to the intake manifold of an internal combustion engine, a spring closed throttle valve mounted for rotation across the passage to control flow of air and fuel therethrough, an air movable choke valve unbalance mounted in the induction passage above the throttle valve and movable between a closed position and open positions by the flow of air thereagainst to control the air flow past the choke valve, a rotatable fast idle cam having a cam surface operatively engageable by a lever rotatable with the throttle valve, the fast idle cam being journalled for a free rotation by gravity on a shaft on which is secured a choke lever connected to the choke valve, the choke lever having a one-way interconnection with the cam permitting free rotation of the choke lever relative to the cam in a choke valve opening direction while restricting rotation of the cam past the choke lever in the same direction, a first chamber containing a bimetallic temperature responsive coiled spring connected to the choke valve lever biasing the choke valve closed and the fast idle cam in the same direction towards a highest fast idle position with a force that increases with decreases in temperature from a predetermined level, engine temperature sensitive heating means adjacent the coiled spring for warming the spring as a function of changes in engine temperature level to permit progressive opening of the choke valve and movement of the fast idle cam towards a lower fast idle speed position, a second chamber contiguous with the first chamber and having a common wall defined by a heat insulating gasket, a second bimetallic temperature responsive spring cantilever mounted in the second chamber so as to be insulated from the heating means in the first chamber with the free end of the second spring flexibly projecting into the path of movement towards the lower fast idle speed position of a pin projecting from the fast idle cam so as to be engagable by the pin below predetermined temperature levels to restrict further movement of the pin and cam in the choke valve opening direction even though permitted by an opening movement of the choke valve and choke lever, to prevent engine stalling at lower temperature levels occasioned by an opening of the choke valve and throttle valve position than is dictated by the temperature conditions, the second spring being movable from a first position at low temperatures projecting into the path of movement of the pin to a second position at higher temperatures withdrawn from the path of movement of the pin, and a heater element associated with the second spring heating the second spring and effecting a faster movement of the second spring from the first to second positions than would normally occur by exposure of the first spring to the engine temperature sensitive heating means or ambient temperature conditions alone.