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

A device for regulating the intake air temperature of an internal combustion engine which is equipped with a carburetor in its air intake system, an air filter upstream of the carburetor, and, leading to the air filter, a cold air intake duct for raw air of ambient temperature, a warm air intake duct for preheated raw air coming from an exhaust stove or the like, and a duct junction through which the two intake ducts open into a raw air mixing duct which connects them to the air filter, the duct junction having associated therewith an air flow proportioning valve which, in a first end position, opens the cold air duct while closing the warm air duct and, in a second end position, closes the cold air duct, while opening the warm air duct, the air temperature regulating device comprising in combination:

• a pneumatic actuator operatively connected to the air flow proportioning valve in such a way that negative air pressure supplied to the actuator will move the valve in the direction towards said second end position, in opposition to a return spring biasing the valve towards said first end position;
• a vacuum line supplying negative air pressure to the pneumatic actuator from a point downstream of the carburetor;
• a temperature-controlled pressure relief valve arranged in the vacuum line, at a point at which a temperature-responsive element of the relief valve is exposed to the proportioned flow of raw air which moves from the duct junction to the carburetor, the relief valve being so adjusted that an increase in the temperature of the proportioned flow of raw air progressively increases the opening of a relief port in the vacuum line, thereby correspondingly reducing the negative pressure which is being supplied to the pneumatic actuator, with the result that the return spring will shift the air flow proportioning valve more towards said first end position;
• a position-adjustable stop cooperating with the air flow proportioning valve so as to block the return-spring-induced valve movement in the direction towards the first end position, at varying distances from said end position;
• and
• temperature-responsive stop positioning means, including a temperature-responsive element which is exposed to raw air of ambient temperature.