>>512388694 (OP)
They invented relatively minor changes, which were perhaps improvements over existing products or perhaps not.
Around 80% of patents are just slightly different ways of doing something that someone else already invented. Maybe they're better, maybe not, the ONLY requirement to get a patent is that it be DIFFERENT. So, for example, the hillbilly who invents a cat brush that has an integrated flea powder dispenser in it has just as valid of a patent as Shuji Nakamura, the inventor of the first commercially viable blue LED.
As far as "underrepresented", if anything they get overpromoted. I've seen tee-shirts proclaiming that blacks invented all sorts of crap, and when I looked up some of the names I found that the basic inventions had been made by whites years or even decades earlier -- the black guys just happened to come up with some minor change.
The only black inventor I'm aware of who came up with something significant was Lonnie Johnson, who invented the Super Soaker squirtgun.