Patent ID: 8020377

Claim:
Apparatus for producing hot gas comprising: a) a first elongated wall portion having a shape like an oval having an inward curve on one side and defining a first bend at one end thereof and a first outlet at the other end thereof; b) a second elongated wall portion having a shape like an oval within the first elongated wall portion and having an inward curve on one side spaced from the inward curve of the first wall portion, and defining a second bend juxtaposed to the first bend, and having a receiving space juxtaposed to the outlet, the inward curve of said second wall portion terminating spaced from the receiving space, said second elongated wall portion being juxtaposed to and spaced inwardly from the first wall portion to define a first continuous combustion chamber therebetween extending from the receiving space to the outlet; c) a third elongated wall portion extending from a point juxtaposed to the space within the second bend to a point between the receiving space and the termination of the inward curve of said second wall portion wherein said third elongated wall portion includes a terminal portion that is bent back toward the termination of the inward curve of the second wall portion to subtend an acute angle, said terminal portion including a baffle terminating spaced from the first wall portion to define a gap therebetween, d) said third wall portion juxtaposed to and spaced inwardly from the second wall portion to define a continuous by-pass passage therebetween that extends from the receiving space to the space at the second bend, and said third wall portion being spaced outwardly from the inward curve of said second wall portion to define a second combustion chamber that extends from an inlet at the space at the second bend to a second outlet at the termination of the inward curve of the second wall portion; e) a first plate fixed to the lateral edges of the wall portions on one side thereof, and a second plate fixed to the lateral edges of the wall portions on the other side thereof to enclose the spaces between the wall portions with the wall portions extending between the plates; f) a fuel inlet mounted on one of the plates terminating in an ignition device for introducing fuel into the space at the second bend to produce combustion gases in the second combustion chamber and, g) an air inlet mounted on one of the plates for introducing combustion air into the receiving space wherein introduced air is divided by the third wall portion (1) to flow through the by-pass passage into the second combustion chamber and (2) to flow via said gap into the first continuous combustion chamber wherein it merges with combustion gases emerging from said second combustion chamber and diverted by said baffle into said second combustion chamber.