Device for automatically controlling the intake air temperature of a carburetor-equipped internal combustion engine

A device for controlling the intake air temperature of an internal combustion engine which is equipped with a carburetor in its air intake system and an air filter upstream of the carburetor, and which has a raw air mixing duct leading into the air filter from an intake duct junction formed by a cold air intake duct through which is taken in raw air of ambient temperature and a warm air intake duct through which is taken in preheated raw air coming from an exhaust stove, for example, and valve means associated with said intake duct junction for adjusting the relative flows of raw air through said cold air intake duct and warm air intake duct by progressively opening one duct while at the same time closing the other duct, said air temperature controlling device comprising in combination:

• a pneumatic valve actuator with an actuator return spring;
• a drive connection between the valve means and said valve actuator;
• a vacuum line leading from a point downstream of the carburetor to said actuator, the line being so connected thereto that the negative pressure supplied by said line moves the actuator against the actuator return spring, in the sense of opening the warm air intake duct and closing the cold air intake duct;
• a thermostat-controlled relief valve arranged in the vacuum line, at a point where its thermostatically sensitive element responds to the temperature of the mixed intake air flow, said valve being so adjusted that an increase in temperature of the mixed air flow progressively increases the opening of a relief port in the vacuum line, thereby correspondingly reducing the negative pressure which is being supplied to the valve actuator, thus resetting the valve means in the direction of closing the warm air intake duct;
• thermostatically responsive means in the drive connection between the valve means and the valve actuator for increasing and decreasing the effective length of said connection, when the temperature of the air flowing through the cold air intake duct increases or decreases, respectively, so that a rise in the ambient temperature results in a resetting of the valve means in the direction of closing the warm air intake duct;
• and
• abutment means arranged in said drive connection, in opposition to said actuator return spring and at a point of said connection which is located operatively between the actuator and the thermostatically responsive means, for stopping the actuator return movement in a position in which the effective length of the drive connection, as determined by a comparatively high ambient temperature level, causes the valve means to close the warm air intake duct, and in which the effective length of the drive connection, as determined by a comparatively low ambient temperature level, causes the valve means to partially open the warm air intake duct.