During prosecution and after a patent is granted, ownership rights in the application or patent may change as a result of an assignment. The USPTO Glossary defines an assignment as “a transfer of ownership of a patent application or patent from one entity to another”.
Under 37 C.F.R. § 3.11, [a]ssignments of applications, patents, and registrations, and other documents relating to interests in patent applications and patents… will be recorded in the Office” with the Assignments Recordation Branch. Once an assignment is recorded (via the USPTO’s Electronic Patent Assignment System, or EPAS), ownership information affected thereby is available to the public and is searchable.
The USPTO’s assignment search database, also known as Assignments on the Web (AOTW), includes all recorded patent assignments submitted to the USPTO since August 1980, and is searchable by assignment, correspondent, assignor, assignee, patent numbers and invention title. Searching the database for a particular property (i.e., patent application or patent) will produce a listing of the entire chain of title (i.e., transfer of ownership from the inventors to the current owner and any owners in between) for that property. Unfortunately, copies of assignment documents are not available electronically and need to be ordered through a vendor or directly from the USPTO for a fee.