Continuation Applications and Their Affect on the Public Availability of Material Disclosed (But Not Claimed) in Patents

It is generally assumed that inventions claimed in a patent application are available to the public if a patent application is abandoned, after the patent expires, or if a patent lapses due to the applicant’s failure to pay maintenance fees. In addition, it is assumed that subject matter disclosed but not claimed in a patent application has been “dedicated to the public” and is therefore available for public use.

In some circumstances however, an expired (or abandoned) patent does not mean that the material claimed in the patent is available for public use. Similarly, when a patent application claims only a subset of the subject matter disclosed in the specification, it does not necessarily mean that the unclaimed subject matter is available for public use.
Why?
A continuing patent application, (also called a “continuation” or “continuation application”) may have been filed that has overlapping claims with the expired or lapsed patent, or that claims subject matter left unclaimed in the parent. (See What is a continuation application? for a description of the different types of continuations.) Alternatively, there may be a pending foreign-filed application that claims the same material as the expired or abandoned patent.

Due to the widespread use of continuation applications in the U.S. and to a lesser extent in other countries, it is important to determine if there are any pending continuation applications before assuming that subject matter claimed in an expired or abandoned patent is available for public use. If the application has been published in the U.S., you can check to see if there are any continuation applications by visiting PAIR at the USPTO.  See also How to View Continuity Data in PAIR.