Dickinson's A Short History of The Steam Engine makes it clear that the concept of the uniflow engine reached back to Montgolfier and Jacob Perkins (who patented the idea) and Leonard Jennett Todd (Patent No.
According to Dickinson's A Short History of The Steam Engine, the concept of a uniflow engine can be traced back to Montgolfier and Jacob Perkins, who patented it.  Leonard Jennett Todd also holds a patent for this design.