Once a patent application is filed, it enters the "prosecution" stage, during which it is examined (usually after considerable delay) by the assigned Patent Examiner, who often challenges the originally-filed claims using various rejections, some of which can be based on alleged prior art references.  Via the Patent Attorney's skilled amendment, rebuttal, and/or negotiation with the Examiner, the application can eventually emerge as an issued patent.

Along the way, the application might be amended and/or re-filed (keeping the benefit of its original filing date).  In some cases, a final decision of the Examiner might be appealed, if appropriate.  In a minority of situations, the client might decide to abandon further prosecution of the application.  There are numerous other possibilities, thereby making a detailed explanation of the prosecution stage rather long and tedious.

The general process for prosecuting a U.S. patent application is:

1. The USPTO checks the filed application for compliance with numerous formalities.
2. Once all formalities are met, the USPTO sends the application to an "Art Unit", which assigns it to one of its many Examiners.
3. After a substantial delay (typically 9 to 30 months while the Examiner addresses a mountain of earlier-filed applications), the Examiner performs a search for prior art publications (typically published patents and patent applications) that reasonably relate to the claims of the filed application.
4. The Examiner prepares and mails an "Office Action" explaining why the Examiner believes the claims to be unpatentable.
5. The Patent Attorney reviews the Office Action, and with input from the inventors (if necessary), carefully prepares a Response to the Office Action. The Response might rebut the Examiner's approach, amend the specification, drawings, and/or claims; and/or present legal and/or technical arguments challenging the Examiner's position. Any written communication with the USPTO is carefully scrutinized to avoid providing potential "ammunition" to later opponents of the patent (whether licensees or litigants).
6. Typically, after several rounds of Office Actions and Responses, the Examiner becomes comfortable with the claims and issues a "Notice of Allowance and Issue Fee Due".
7. Assuming that the allowed claims and reasons for allowance are acceptable, the required Issue Fee is paid.  Quite frequently, a follow-up patent application is filed that claims subject matter described in the earlier application, but not captured by the allowed claims.  This "continuation" application should be filed no later than the date the Issue Fee is paid on the allowed "parent" application.
8. The USPTO issues, publishes, and mails a United States Patent, complete with gold seal and red ribbon.

For more information, check out our FREE guide, "Empowering Intellectual Property – Step 5 – Secure".