In German court decisions as well as in the German patent literature it has been a generally accepted position that product claims on the one hand and process claims on the other hand represent distinct claim categories; and that product patents (containing only product claims) and process patents (containing only process claims) are distinct patent categories. The applicant is free to choose the appropriate claim category or categories; a patent may contain product claims, process claims or both. However, after grant this choice is binding on the patentee, and a change of category from a product patent to a process patent (and vice versa) is considered to be inadmissible because it involves an extension of the protection conferred (Benkard, Patentgesetz – Gebrauchsmustergesetz, 9th Edition 1993, pages 141, 501, 686 and 710).
The Boards of Appeal of the European Patent Office take a different position in that regard: "A change from a product claim to a claim for a process of manufacturing the product is generally seen as unproblematical" (Case Law of the Boards of Appeal of the European Patent Office, 4th Edition 2001, page 221). According to Decision T 54/90 a: "product claim covers all methods for making the same; when it is replaced by a process claim directed to a single method it does not extend the protection conferred thereby" (Reasons for the Decision, 3.2).
Thus, the European Patent Office in opposition proceedings allows a change of patent category which may have the consequence that the German part of the European patent is invalid. Patentees should be aware of the risk that national courts in nullity proceedings may find that a change of patent category from a product patent to a patent for a process for manufacturing the product involves an inadmissible extension of the protection conferred by the patent. The German Federal Patent Court did not yet have an opportunity to consider that question.
