Improving an Existing Device

You are allowed to improve on existing patents.

You will have the same problems that the original patent holder does in defending his claim/claims.

Hiring a patent attorney is expensive. Hiring an attorney to go after "infringers" is more expensive.

"no brainres" may not be accepted as a an, "improvement on an existing device"

Document every detail and have a competent witness attest. Dates are critical.

I'd check the US Patent Office web site.

Good Luck!

Don't companies like Novellas and BASF specialize in this sort of thing... So it must be legal somehow.

A possible way to "test the waters" to see if an idea could earn money is to obtain a provisional patent. This gives you protection for one year while you look for a assignee (buyer of your idea). The United States Patent Office (USPTO) costs for this is minimal. In general the protection goes away if you do not apply for a regular patent within one year. The 20 year patent term starts with the relied upon provisional patent.

Usually improvements to someone else's idea is patentable. Lynlynch is correct in that "no brainers" may not be able to be patented because they may be considered to have "obviousness" by the USPTO.

In general, only the original assignee or inventor (many other details) can revise their own patent (called a reissue) but this does not prevent someone else from getting a new patent on their specific improvement.

You might go the USPTO web site www.uspto.gov and look at their general information on the highlighted words: provisional patent, assignee, obviousness, and reissue.