Compound internal combustion and external combustion engine

Claim 1

A compound engine comprising at least one internal combustion cylinder having an inlet and an outlet and one external combustion cylinder having an inlet and an outlet, each of said cylinders having a reciprocable piston therein coupled to a common utilization output shaft, heat exchanger means associated with said external combustion cylinder for transferring heat to a space in said cylinder above said piston in said external combustion cylinder, means for transferring hot exhaust gases exhausted from said internal combustion cylinder during its exhaust cycle to said heat exchanger means, means for introducing a heat expandable gas through the inlet of said external combustion cylinder into said space above said piston in said external combustion cylinder whereby heat transferred by said heat exchanger means to said space during passage of said exhaust gases through said heat exchanger means causes cooling of said exhaust gases and expansion of said heat expandable gas in said space imparting motive power to said piston in said external combustion cylinder and to said common utilization output shaft in addition to motive power applied to said shaft by said piston in said internal combustion cylinder during conventional expansion cycles in said internal combustion cylinder, means for exhausting said heat expandable gas after expansion in said combustion cylinder to the inlet of said internal combustion cylinder, and means for exhausting said cooled exhaust gases to the ambient, wherein said expandable gas after expansion is exhausted to said inlet of said internal combustion engine cylinder during a return stroke of the piston associated with said external combustion cylinder effectuated simultaneously with a downstroke of the piston associated with said internal combustion cylinder, and wherein said heat exchanger means comprises an annular chamber disposed above and in communication with said external combustion cylinder, whereby a portion of said expandable gas is displaced into said annular chamber during upstroke of the piston associated with said external combustion cylinder in the course of a compression cycle in said external combustion cylinder.