Nonobvious Prior Art Claims

Dear Rich: Say there is a known prior art that currently has a patent pending and I file for a provisional stating claims with which I believe are nonobvious to the prior art. [Hi Readers. Before we lose you in a torrent of inventor-speak, allow us to provide a short translation.  This inventor has come up with something that he believes to be new and not obvious (nonobvious) to those in the field of invention. (These two standards --  new and nonobvious -- are the basis for getting a patent.) Another inventor has filed a patent application for a related invention (the "patent pending" reference).  In summary, the inventor doesn't believe his invention is substantially similar to the existing technology in that patent application (or "prior art"). What follows are his questions and our answers.
1. Can they accuse me of infringement and take me to court? The other inventors cannot sue you for patent infringement until their patent is granted. If 18 months have passed since the other inventors filed a patent application and the application has been published, they can notify you about the application and then sue you for any infringements that occurred after notification. (We've discussed that previously here). In either case, the actual lawsuit cannot be filed until the patent is granted. Whether the inventor succeeds obviously depends on whether you guessed right about the prior art.
2. Can I sell during my provisional status and if or when do I have to stop selling because there is a known prior art with a patent pending status? You can sell any time you want but if you sell your invention and it infringes, you'll be liable once the other patent is granted.
3. If this invention which I believe is nonobvious to the prior art shows that it has commercial value, but there's a known prior art, is it worth filing a non-provisional after 8-12 months? We're kind of going around in circles. If you have commercial potential and you're concerned about infringement (or issues of prior art) you should bring in a patent attorney to provide an opinion before you waste your money or time on the pursuit. Keep in mind that whether you're right or wrong about the prior art, the other inventor can come after you if there's enough of a case to get in court. And then you'll be spending money on a court battle when you could be devoting the time and money to some other great new idea.
4. If my invention is non-obvious to the prior art will a patent be issued and do I still have to license the basic idea of the prior art? If your invention is new, nonobvious and meets all the patent requirements, you're entitled to a patent. Keep in mind, these determinations are tied to the interpretation of the patent claims, explained here.) If the invention doesn't infringe, do you have to license rights from the other inventor? No.
5. I read in your book that changing something small may be considered as a novelty and may be considered patentable (if I am correct). If so, do you have to go to court to prove that, or can the examiner just approve it, and when a patent is issued to the nonobvious then you are protected? In some cases, small changes are enough to get a patent, in other cases, no. If an examiner feels the application is sufficient, you'll get your patent. Alas, that patent can always be challenged and then you may have to deal with two battles, a patent reexamination and a court case.