This invention relates to the double-acting scavenging pump and the air-supply pumps of a two-stroke cycle slow-combustion engine which pumps have hitherto been driven independently of each other.
According to this invention the scavenging pump driven by a separate crank is arranged in such a manner that the pressure of one or more stages of the air-supply pump, arranged concentrically with the scavenging pump cylinder, considerably reduces , or even entirely neutralises the momenta or accelerations of the pump pistons.