Answer:
An improvement of an existing invention is itself an invention, and can be patented like any other invention. Contact a patent practitioner (patent agent or patent attorney) for assistance. The United States Patent and Trademark Office has lists and addresses of patent practitioners in every state. Avoid companies that advertise they will "help you get a patent."
First answer by ID1676503483. Last edit by Embram. Contributor trust: 3 [recommend contributor recommended]. Question popularity: 3 [recommend question].