In order to qualify for a patent, your invention must be:
Full disclosure: The inventor must fully disclose how the invention is made in the patent application.
Date of Public Disclosure: The patent application must be submitted within one year after public disclosure is made regarding the invention, or within one year of the invention being sold or offered for sale. The date of public disclosure may be less than one year in other countries, so it is important to be aware of other countries' policies if you intend to submit a patent application outside of the United States.
For more information about patentability, click on General Information Concerning Patents at USPTO.gov.