Heating of combustible mixture generators for internal combustion engines

In a combustible mixture generator for an internal combustion engine, said generator including a tubular wall defining a main mixture flow path, a main throttle element mounted downstream of said wall, fuel metering means for metering fuel into said flow path near the upstream end thereof within said tubular wall, and heat exchanger means incorporated in said wall over at least a part of the length thereof, said heat exchanger means including means defining an annular heating water chamber, water inlet means adjacent one end of said chamber and water outlet means adjacent the other end of said chamber, the improvement comprising water ducting connected to said inlet and said outlet for connection to a cooling water circuit of said engine, said ducting containing thermally controlled valve means which is adapted to open at elevated temperatures, said heat exchanger means being situated higher than said cooling water circuit whereby the level of said cooling water when said valve means is closed and said cooling water circuit of said engine is shut down is below said heat exchanger means, and said heat exchanger means including an internal wall bounding said main mixture flow path, said internal wall comprising electric resistance heating material, and said heat exchanger means further comprising electrical leads connected to said electric resistance heating material and adapted for connection to an electrical supply, and a thermally controlled electric control device in said leads, said electric control device being controlled in dependence upon the temperature of said cooling water, whereby said electric resistance heating material is heated electrically when said cooling water temperature is below a predetermined value and said material is disconnected from said supply when said cooling water temperature is above said value.