Temperature supplemental pulldown mechanism for carburetor automatic choke

Claim 1

An automatic choke system for use with a carburetor having an air/fuel induction passage and an unbalance mounted, air movable, choke valve mounted for variable movement across the passage to control airflow through the passage, first engine temperature responsive spring means operably connected to the choke valve urging the choke valve towards a closed position with a force increasing as a function of decreases in the temperature of the spring means from a first predetermined level, a choke pulldown servo sensitive to engine manifold vacuum for operatively moving the choke valve towards an open position in opposition to the spring means, and second ambient temperature responsive bimetal coil spring means between the servo and choke valve for controlling the opening of the choke valve as a function of ambient temperature changes from a second predetermined level, the ambient responsive spring having an inner end secured to a shaft and an outer end movable circumferentially in response to the coiling and uncoiling of the ambient spring in response to ambient temperature changes, means connecting the outer end of the ambient spring to the pulldown servo, and a lever fixed to the shaft, the lever having first and second legs extending in opposite directions, one leg extending in a direction to be engaged at times and moved by abutment means on the servo upon operation of the servo, the second leg being movable in a path containing the choke valve and moving alternately in response either to movement of the lever by the abutment means or in response to ambient temperature changes effecting rotation of the shaft to operatively engage the choke valve to move it to an open pulldown position, the degree of pulldown opening of the choke valve varying as a function of the ambient temperature level.