with simple crankcase pumps, i.e. with the rear face of a non-stepped working piston acting as sole pumping member in co-operation with the crankcase

Full Title

Engines characterised by provision of pumps for charging or scavenging > Engines with reciprocating-piston pumps; Engines with crankcase pumps > with simple crankcase pumps, i.e. with the rear face of a non-stepped working piston acting as sole pumping member in co-operation with the crankcase