Patent ID: 6571755
Filing Date: 2003-06-03
Classification: F02B

Abstract:
A two stroke reciprocating engine having head mounted inlet and exhaust valves and an external pump for charging the cylinders, wherein:the external pump is a reciprocating positive displacement pump having a respective pumping chamber for groups of at least two cylinders of the engine, each pumping chamber having a displacement swept by its pumping piston which is greater than the swept cylinder displacement of each cylinder of the engine; the pump is secured to a mounting on the engine adjacent the cylinders whereby the outlet from the pump is located closely adjacent the inlets of the engine; the crank pins of the engine's crankshaft are arranged at angular spacings of 360Â° divided by the number of cylinders in the group; the crank pins for each group of cylinders are arranged at angular spacings of 360Â° divided by the number of cylinders in the group; step-up drive means is provided for driving the pump from the engine, the step-up being in the ratio of the number of cylinders in each group of cylinders of the engine per pumping chamber; relatively short feed passages are provided through transfer manifolding interconnecting the outlet from each pumping chamber to the inlets of the group of cylinders to be fed thereby, and the connection between the engine and the pump and the operation of the inlet and exhaust valves of the engine are timed such that: the or each pumping piston leads alternate ones of the power pistons fed thereby to their respective Top Dead Centre (TDC) positions; the inlet valve to each power cylinder to be fed opens before Bottom Dead Centre (BDC) and closes before TDC, and the outlet valve from the fed power cylinder opens before BDC and closes before TDC.