U.S. patent law is complex. Simply referring to the U.S. system as "first to invent" rather than "first to file" probably adds more confusion than elucidation to the discussion.
Assuming that a U.S. patent application satisfies all the other requirements for a patent, section 102 of the patent code states that a "person shall be entitled to a patent unless ...." Section 102 has six subsections, each giving a different reason that a person should NOT get a patent. Subsections (a), (b), (f) and (g) are most relevant to this discussion.
102(a) blocks the applicant from getting a patent if the invention was publicly known
* before the applicant invented it. So if I invented something on July 7, 2003, any publication, public use, etc. before July 7, 2003 should stop me from getting a patent. Note that since I didn't develop the invention before July 7, 2003, there is no way I could have publicly disclosed the invention before July 7, 2003. So there is nothing the inventor can do that will block there patent based on 102(a).
102(b) focuses on the date of the patent application** rather than the date of invention. If my invention was publicly known* more than one year before I applied for the patent, then I should not get a patent. So if I applied for a patent on September 1, 2005, but anyone - including me - publicly disclosed the invention before September 1,
2004, that should block my patent application.
102(f) is easy: "he did not himself invent the subject matter sought to be patented"
102(g) relates to the situation where two different people apply for a patent on the same subject matter; in certain situations an "interference" proceeding may be held. In the interference the person that first applied
** for the patent is generally assumed to be the first inventor and entitled to the patent. But if the second person that applied for a patent can prove that he invented first and meets certain other requirements, the second applicant may get the patent rather than the first applicant.
- publicly known - is defined somewhat differently for (a) and (b). ** application date is the earlier of the actual application date or the date of the U.S. priority application. A provisional application may provide a priority date; but a document disclosure does not.
I hope this clarified more than it confused
Richard Tanzer Patent Agent