Patent classifications are used by patent offices to assign patent applications, issued patents and utility models to technical areas and thus make them retrievable. All technical areas are covered.
The patent classifications are assinged upon filing a patent and during the examining process by the examiners. The first assigned classes are shown in the patent document. Classes can be amended during the examination process if new aspects are added or if the first assignment was incomplete or wrong. These amendments are reported by the patent offices and are available in databases, such as the DOCDB of the European Patent Office.
The most important patent classifications are the International Patent Classification (IPC) and the Cooperative Patent Classification (CPC)
Patent offices worldwide use the IPC. There are approximately 70 000 different IPC codes for different technical areas.
The CPC is an extension of the IPC and includes approximately 250 000 classification entries.
More on IPCMore on CPC