One-piece cranks, like you commonly see on cheap American bikes and lower-end bmx bikes are "Ashtabula" cranks. The flat-bladed forks found on the old Schwinns are known as "Ashtabula forks", too.
Why? Well, for one thing, the older versions on the Schwinns were made in Ashtabula, Ohio, by the Ashtabula Bicycle parts Company. Their parts were so prevalent, back in the day, that the name Ashtabula became the generic name for such parts, much like "Kleenex" became the generic for facial tissue.
An odd little footnote in bicycling history: Ashtabula built one of the earliest (some say the first) complete bmx bikes available, in the mid-1970s.
While we now think of Ashtabula parts a cheap and heavy, but the actual "Ashtabula" parts were well-known for high quality and durability, back in the day. Of course, they were also heavy like a boat anchor...