 Prior to the Patent Act of 1952, the Congress required only novelty and utility for issuance of patent, and never created any statutory requirement of nonobviousness.However, the U.S. Supreme Court, in the case of "Hotchkiss v. Greenwood", invalidated a patent on the grounds that it involved only a substitution of materials rather than any real innovation.The "Hotchkiss" court effectively added the requirement of nonobviousness, and it had been left to the judiciary to determine whether the patent involved non-obvious invention.