Hybrid drive train concept

This is dated Dec 15, 1972 and signed by George E Swartz.  This is very close to the Prius drive train that came along 25 years later.  There are two electric motors, two differentials and a small battery pack.  Motors are used as motors or generators.  M1 is two quadrant motor generator and M2 is four quadrant motor generator and two directions.  IC engine is run at mostly constant RPM.  This is a dual mode small bus application where the vehicle runs on a powered guideway, or on city streets.  On the guideway, battery charging is available from the power rail.  The IC engine can be used for emergency power or "get home" ability when electric power fails.  Off guideway, the two electric motors act via the differential as a variable speed transmission and a reverse motion transmission, just as in the Prius.  This was the best paper design that I could come up with compared to conventional drive trains, considering low weight, small size, efficiency, low fuel use, and low pollution.  The disadvantages I considered were high development cost and control system complexity.  This is from some old papers I was in the process of throwing out.  I didn't think this was worth a patent search at the time and probably others had come up with the same conclusions as I did, but just the same, this is a pretty early hybrid design.