My invention is similar to a patent in what they do except mine folds up and is portable. Patentable?

On the surface, your change sounds like it sufficiently distinguishes your invention from the other for patentability purposes.

However, the patent that describes the other invention may claim far more than what the patent owner actually sells as his contraption. In other words, to determine if your invention is patentable, a patent attorney will have to compare your invention to the patent claims that cover the other invention -- not to the contraption that the patent owner sells. Moreover, the other invention may have been patentable precisely because it did NOT fold. You won't know unless your patent attorney does a "prior art" search and evaluates that invention and all related inventions.

You need to speak with a patent attorney. Also, buy the book "Patent It Yourself" for background information on patents -- do not file your own patent application.

Your question is fact specific and a full qualified analysis would be required to answer, but you haven't given me enough information to tell you your invention is not patentable.

Speaking to a more general point, nearly every invention is an improvement of existing technology. The key to patentability is often whether that improvement would have been obvious at the time the invention was made. Your patent attorney will be able to assist you in analyzing obviousness and other matters concerning patentability.

Also, as noted above, do not ignore the importance of getting a clearance opinion if you plan on making, using or selling an improvement of existing technology. The existing patents might cover your invention, despite the improvements.

Best of luck!

I would advise you to speak to an attorney. I am a patent attorney and am licensed to practice in Florida. Please call me for a free consultation.

Clark Wilson