Internal-combustion engines of the reciprocating type wherein the working piston is permanently connected with the main driving-shaft of the engine in which a combustible mixture is burned within the working cylinder thereof and the resulting gases cooled and condensed, thereby producing a more or less perfect vacuum within the said working cylinder, whereupon
atmospheric pressure acts upon the said working piston to move it through a working stroke. The pressure of the atmosphere may be the only force acting upon the working piston, or the engine may be so designed that the combustible gases upon being ignited generate pressure which also acts upon the said working piston.
