Nothing new under the sun. The vast majority of famous inventions are improvements of some kind. The lightbulb improved upon existing technologies (as did almost all of Edison's inventions). Alexander Graham Bell's invention was filed as an "Improvement in Telegraphy" and George Westinghouse's famous patent was for an "Improvement in Steam-Power Brake Devices."
So, if you improve on an existing invention (or expired patent), you may be able to acquire a patent for your improvement, but not for the underlying prior art. This article and this article both explain the distinctions. So to the extent you can separate and identify the improvement, you may be able to acquire a patent on that.