Piston reciprocating compressed air engine

A reciprocating piston type compressed air operated engine, comprising:

• (a). a crankshaft and a valve operating camshaft,
• (b). two power cylinders each having a piston operably connected to the crankshaft to move together in the cycle of operation of the engine, one being operable on an admission-compression-work-exhaust cycle and the other being operable on a work-exhaust-admission-compression cycle,
• (c). first and second reservoirs for air under pressure each of which is connected to one of the power cylinders, and a third reservoir for air under pressure connected to both of the two reservoirs,
• (d). a transfer cylinder connected to both of the power cylinders and to the third reservoir, and having a piston connected to the crankshaft for movement opposite to the movements of the power cylinder in the cycle of operation of the engine, and a piston connected to the crankshaft,
• (e). a fourth source of air under pressure powered externally to the engine, and connections from the source to the power cylinders and to the third reservoir and being operable during the operating cycle of the engine to remove air from the power cylinders on their exhaust stroke and supply air under pressure to the third reservoir,
• (f). and valve means operated by the camshaft for supplying air under pressure from the first and second reservoirs to the power cylinders, then exhausting air alternately from the power cylinders to the transfer cylinder assisted by air under pressure from the fourth source, and for transferring air under pressure from the transfer cylinder to the third reservoir and thence to the first and second reservoirs and thence to the power cylinders.