The Poor Man's Patent is a Myth
One of the undying myths of Patent World is that there is such a thing as a Poor Man's Patent. If you've never heard of it, the poor man's patent involves writing out a description of your invention and mailing that description to yourself. The transmission of this description through the mail and the cancelling of the postage by the Post Office is supposed to establish a date of invention for you. That way if someone steals your invention or comes along and invents it independently, you have "proof" that you invented it first. The proof is in the sealed envelop and the date the postage was cancelled.How To Conduct a Patent Search
you can do a patent search online. The U.S. Patent and Trademark Office (1790 - Present) and Delphion (1974 - Present) both provide free online databases. You can searching using keywords or phrases that describes your invention. Look for common terms describing the invention and its function, effect, end-product, structure, and use. The results will list the title and number of all patents related to your keywords (l976 forward only). The title link will take you to the full text of the patent. You will not be able to do a complete search online for a pre-1976 patent unless you know the exact patent number. With online patent be sure to examine other referenced patents that the inventor has listed.What You Can Patent
A patent provides you with the right to keep others from making and selling your invention for up to 20 years. The most common type of patent, a utility patent, protects rights in new and useful processes, machines and other things. These patents also can protect rights in non-obvious improvements made to existing things. To determine if your invention is patentable, you must first research all previous patents and other publicly disclosed inventions to ensure that no one else has already patented something similar. Because this process can be difficult and complicated, the U.S. Patent and Trademark Office recommends hiring a registered patent attorney to conduct the search for you.The Do-It-Yourself Patent Search
If you decide to do the patent search yourself, you have several search methods available: The USPTO (United States Patent Trade Office) Public Search Facility. The USPTO operates a Patent Public Search Facility located in Alexandria, Virginia. Here every U.S. patent granted since 1790 may be searched and examined. Many inventors like to make at least one pilgrimage to the Patent Public Search Facility. It's located fewer than 15 minutes from National Airport by taxi; Metro Rail serves it off the Blue and Yellow lines, King Street Station; and several hotels are within walking distance, so it's easy to get to and around.What is reissue?
Patent law states "On taking up an application for examination or a patent in a reexamination proceeding, the examiner shall make a thorough study thereof and shall make a thorough investigation of the available prior art relating to the subject matter of the claimed invention." This means that prior art could disqualify your application for a patent.