A history question about planar drivers

The Magnepan web site states that Magnepan founder Jim Winey developed the magnetic planar speaker and founded the company in 1969.

He had heard and liked electrostatic speakers, but as an engineer at 3M at the time, he thought there might be a way to drive the film magnetically instead of electrostaticly. He quit 3M, started Magnepan, and patented the product.

There is a link on the Magnepan website to a SoundStage! article on the company and discusses the product's history.

I believe that a speaker using the electrostatic approach came before the magnetic cone speaker. We are talking about the early years of the last century.

Yes, the design of electrostatic speakers is much older. There were experimental models in the Bell labs back in the 1920s.

Janszen tweeters were available in the early 1950s and Peter Walker came out with the Quad in the mid 1950s.

That's very interesting - especially that electrostatics predated what are now "conventional" cone drivers.

Another thing that caught my eye is that the planar magnetic design was originated by Jim Winey in 1969, yet Infinity, Apogee, and others were creating planar magnetic designs long before his initial patent should have expired.

Perhaps because he was working at 3M at the time prevented him from successfully completing the patent (the Magnepan factory tour does not explicitly state so), or perhaps it's a bit more complicated than that and his patent was narrow enough in scope that the other companies got around it.