GB703916A - Improvements in two stroke crank case compression otto cycle internal combustion engines with scavenging air pumps - Google Patents

Abstract

703,916. Two-stroke engines; cylinder ports and passages; lubricating; regulating; valves. SCHNURLE, A. Oct. 30, 1950 [Oct. 31, 1949], No. 26353/50. Classes 7(2) and 7(6) In an engine suitable for motor vehicles scavenging air from a pump is supplied to a working cylinder through ports located between an exhaust outlet and inlets for fuel-air mixture drawn from a carburetter, compressed in the corresponding crankcase and admitted therefrom to the cylinder through ports controlled by the crankshaft counterweights acting as valves as they rotate. As applied to a twin-cylinderengine, fuel-air mixture from a carburetter 28, Fig. 3, is drawn through a common inlet passage 17 into separate crankcases 9, 10, Fig. 1, and scavenging air is supplied' by a double-acting pump 30 driven from a crankshaft eccentric 15. The air flowsthrough passages (not shown) to scavenging ports 24, Fig. 2, situated between exhaust ports 22 and ports 26 connected by transfer passages 27, Fig. 6, to the crankcases 9, 10, the arrangement being such that both air and mixture streams scavenge the cylinders by the reverse loop method but that the air acts as a buffer between the mixture and the exhaust gases. Each crankshaft counterweight 14, Fig. 6, is shaped to co-act as a rotary valve with the corresponding passage 27 and prevent entry of mixture to the cylinder until the working pistons h a v e reached or passed bottom dead-centre. The cylinders 1, 2, Fig. 1, have a common cover 5 provided with combustion chambers 6 and sparking plugs 19. Throttle valves 29, 35, Fig. 3, controlling mixture and air respectively are linked by a rod 36 for conjoint control, the valve 35 being placed in a conduit leading to an inlet port 33 supplying air alternately to either side of the piston 30. A bore 2 connects the passage 17 and the space 20 containing the eccentric 15 so that mixture is pumped to and from the space and, as the mixture used contains one part of oil to twenty-five parts of fuel, lubrication of the pump drive is thus effected.