In 1966, Holless Wilber Allen invented "Compound Bow" with triangular wheels / cams. He was then granted a patent right in 1969.
I actually heard it was earlier than 1966, like the 40's, and the inventor could not get a patten.
The compound bow, on the other hand, has a pulley and cable system that makes holding weight much easier. A compound bow is simply a machine that stores energy, supplied by the shooter, then releases that energy into an arrow.