Interesting tidbit:

 In 1947, the U.S. government filed suit against the Phillips Screw Company and
seventeen manufacturers of Phillips screws and drivers alleging anti-competitive
practices dating back to 1933. They were charged with patent pooling, cartel
practices, price-fixing, and the suppression of competing technologies. The
case, United States v. Phillips Screw Co., was tried in the U.S. District Court
of Northern Illinois (Chicago). The case was concluded in 1949 with a consent
decree that dissolved the patent pool, likely making it difficult to protect the
collection of patents that the company relied upon to protect its intellectual
property. In any case, unlicensed companies had earlier begun to produce similar
competing designs, some of which were convinced to buy into the licensing
agreement. Other manufacturers, however, said that their designs were not based
on the Phillips design, but on the older, unprotected Frearson design. In the
same year, a final refinement was patented on the Phillips drive system by an
engineer from the American Screw Company; that patent expired in 1966.