Device for 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 equipped with a carburetor in its air intake system and an air filter upstream of the carburetor;

• the device including 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;
• the device further including:
• 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, a pneumatic valve actuator with an actuator return spring, a drive connection between the valve means and the moving member of said valve actuator, a vacuum line leading from a point downstream of the carburetor to said valve actuator and so connected to it that the negative pressure in the vacuum line displaces said moving actuator member against the actuator return spring, in the sense of opening the warm air intake duct closing the cold air intake duct, and, in said vacuum line, a thermostat-controlled relief valve arranged at a location where its thermostatically sensitive element is exposed to the temperature of the air flow downstream of the intake duct junction and responds to a temperature increase by progressively opening a relief port in the vacuum line to lower the negative pressure therein and to reset the valve means in the direction of closing the warm air intake duct;
• and the device still further including abutment means in the drive connection between said valve actuator member and the valve means, for limiting the return movement of the actuator member and drive connection, and a longitudinally expanding and contracting wax thermostat exposed to the raw air of ambient temperature and forming a portion of said drive connection, whereby an ambient temperature level below a predetermined value causes the wax thermostat to contract to such an extent that the fully returned actuator member and drive connection, as positioned by said abutment means, maintains the valve means in a position in which the warm air intake duct remains partially opened;
• the improvement in said device comprising:
• an adjustable threaded connection between the moving member of the pneumatic valve actuator and the wax thermostat, which connection makes it possible to permanently increase or decrease the effective length of the drive connection.