When I tracked down the history of the hairpin legs I may have stopped before the story ended. I think that is the complete story of the two-rod hairpin legs, but as is often the case with design, where one story ends another begins.
From the original description on the patent, it seems the original intent of the three-pin hairpin leg was for tables.
The invention relates to a furniture leg construction and, more particularly, to a table leg construction having a leg secured to a mounting plate and a U-shaped reinforcing brace connected to the leg and mounting plate for reinforcing the plate.
An object of the invention is to provide a new and improved furniture leg.
Another object of the invention is to provide a tubular leg having a hairpin-shaped reinforcing brace with it ends connected to the mounting plate for the leg rearwardly and the sides of the upper end of the leg and having its midportion secured to the rear of the leg intermediate the midportion and lower end of the leg.The original two-rod hairpin leg doesn't have a patent, so this might be the first time "hairpin" is used as a defining design element in a patent.
Richard G. Reineman holds a dozen or so other patents, mostly for furniture, more specifically mostly for chair designs. He designed and patented the first one-piece plastic chair in 1960 and his name is also attached to one of the most-used pool table designs out there. But beyond that, there's not much info about Reineman to be found. (Or at least that I can find.)
The three-rod hairpin leg has move far beyond being just a table leg. It can be found on pretty much any furniture item that need legs, although come to think of it, the table still does seem to be the most popular. Perhaps the appearance of added stability made it a more obvious choice for furniture that needed to support a significant amount of weight.