A U.S. patent application is automatically published 18-months after the earliest effective filing date unless a Nonpublication Request is included with the patent application filing papers. A patent application for an invention is required to be published if it is subject to a foreign patent application or an international patent application – or if the applicant intends to file such a non-U.S. patent application.
Neustel Law Offices has published a detailed article called Patent Application Publication which provides additional information regarding the publication of patent applications including publication strategies.