How Inventive! (No. 13)

When was the helicopter invented?  Setting aside the classic example of Leonardo da Vinci's drawings (because he apparently never attempted to make a working device?), how long ago was the helicopter patented?  In 1907, J.N. Williams applied for his "Flying Machine" patent, U.S. Patent 1,023,233.  The following year, the venerable Thomas Edison applied for U.S. Patent 970,616, also titled "Flying Machine".

Figure 1 from U.S. Patent 1,023,233:

Figure 1 from U.S. Patent 970,616: