Carburetor throttle valve positioner

Claim 1

A carburetor throttle valve positioner comprising, in combination, an engine carburetor having an induction passage open to ambient essentially atmospheric pressure at one end and adapted to be connected to an engine intake manifold at the opposite end so as to be subject to engine vacuum varying in level from ambient atmospheric pressure at engine shutdown to a maximum subatmospheric pressure level during engine deceleration operating conditions, a throttle valve rotatably mounted across the passage and movable from an essentially closed position to an engine idle speed position and beyond to a wide open throttle position, and return, for controlling flow through the passage, and control means to move the throttle valve to and between its positions, the control means including a vacuum controlled servo having a hollow shell with a flexible diaphragm dividing the shell into two chambers, a movable plunger connected to the diaphragm and operatively engaged with the throttle valve, conduit means connecting each of the chambers to engine intake manifold, a vacuum reservoir in one of the conduits and a flow restricting means between the reservoir and the manifold vacuum connection for delaying decay of vacuum level in the reservoir upon decay of manifold vacuum, first spring means biasing the plunger towards an open beyond idle speed throttle valve first position, and second spring means biasing the plunger in the opposite direction to oppose the first spring means and position the throttle valve to an engine idle speed second position below a predetermined intake manifold vacuum level, an increase in the manifold vacuum level acting on the diaphragm above the predetermined level overcoming the force of the second spring means to move the plunger to the first position, a decay of manifold vacuum level responsive to engine shutdown conditions permitting reservoir vacuum temporarily to move the plunger and throttle valve towards a third throttle valve closed position, subsequent decay in the reservoir vacuum permitting return of the plunger and throttle valve to the second position by the spring means.