Carburetor temperature responsive throttle plate positioner

Claim 1

An engine idle speed control for the throttle plate of 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, and a spring closed throttle plate mounted for rotation across the passage to control flow of air and fuel therethrough, the control including a lever operatively connected to the throttle plate for rotation therewith, a fast idle cam rotatably mounted for cooperation with the lever, the cam having a stepped contoured peripheral surface engaged by the lever during the closing movement of the throttle plate, the surface consisting of a series of circumferentially contiguous stepped faces of progressively changing radial extension with respect to the axis of the cam, the faces being separately engagable with the lever so as to progressively change the closed position of the throttle lever as a function of the rotative position of the cam to thereby control the idle speed positions of the throttle plate as a function of the movement of the cam, a temperature responsive element connected to the fast idle cam and movable in response to the attainment of predetermined temperature levels to rotate the cam, a shaft rotatably mounting a bellcrank-like lever, the latter lever having a finger-like portion pivotably mounted at one end, the portion being swingable to a position between the lever and cam surface during engine off conditions to cam the lever away from the cam surface incrementally to increase the degree of opening of the throttle plate for starting purposes in direct proportion to the increase in throttle opening afforded by the particular cam face that would be engaged by the lever for the prevailing temperature level, spring means acting on said finger-like portion biasing the portion to a position between the lever and cam face, and engine vacuum responsive servo means operable in response to a predetermined engine manifold vacuum level acting thereon to withdraw the movable means against the spring means bias to permit return of the lever against the cam face and return of the throttle plate to a less open position and one that is dictated by the radial extent of the particular face of the cam surface presented for engagement by the lever in accordance with the prevailing temperature level.