I would like all inventors to understand that an international search is a critical part of all GOOD Patent Searches. If something has been patented anywhere in the world at any time in history, you will not be granted a U.S. patent. If the product was not patented but available to the public, it is considered part of the public domain and, again, you will not be granted a U.S. patent.
For example, I had a client who was trying to patent a type of metal hinged glove. There was no prior art (previously granted patents), but there was evidence of metal hinged gloves in history (in fact, ancient history – i.e., “knights in shining armor”). Because of the introduction of the metal hinged glove in the medieval times, the concept of the hinged glove had become part of the public domain and thus could not be patented. The “knights in shining armor” were never even in the U.S. But it doesn’t matter!
We frequently find similar products patented in other countries. In order to make good business decisions, you need a patent search that includes the international search even if you don’t plan to manufacture or sell outside of the U.S.