(under subclass 39) Two-cycle internal-combustion engines in which the combustible mixture, or both the constituents thereof, is supplied to the working cylinder under pressure materially greater than atmospheric pressure, such supply beginning at the beginning of the working stroke and continuing for a determinate portion thereof, the combustible mixture being ignited either at constant pressure as it enters the cylinder or at constant volume after the whole charge has been supplied thereto, in either case without recompression in the working cylinder. The combustible mixture or the constituents thereof may be supplied directly to the working cylinder without preliminary storage or may be supplied to suitable reservoirs interposed between the compressing means and the working cylinder and within which a considerable volume of combustible mixture, or its constituents, is stored. Engines in this subclass in which ignition takes place after the whole charge has been supplied to the working cylinder differ from those in ... which work upon a two-stroke cycle, only in the degree of compression to which the charge is subjected before ignition, and as some of the engines in the subclass above mentioned are provided with a supply-pump for forcing air through a charge-forming device to the cylinder of the engine the combustible mixture thus produced is necessarily supplied to such engines under some pressure. However, where the structure and operation of the device as a whole clearly indicate that the pressure under which the charge is supplied is so slight as to be sufficient only to insure its flow into the working cylinder the engine is classified in subclass 39. In engines working on the two-cycle pump-compression cycle the whole charge properly
mixed to form a combustible mixture may be compressed by a single pump or the air and combustible may be compressed by separate pumps to be mixed on their way to the working cylinder or after such constituents have entered thereinto.
SEE OR SEARCH THIS CLASS, SUBCLASS:
61, for double-acting engines working on the two-stroke pump-compression cycle.
495+, and 590+, for oil-engines operating upon a cycle similar to that defined by this definition.
