According to established case law, a product claim confers protection to all processes for making that product, such that the replacement of a claim directed to a product by a claim directed to a specific process or method for making that product does not extend the protection conferred thereby (T 674/02 with reference to T 54/90, T 28/92, T 468/97, T 554/98; see also T 191/90, T 762/90, T 153/91, T 601/92, T 646/98, T 425/02, T 1139/06).
In T 423/89 the change in category from a product-by-process claim to a manufacturing process claim was admissible. In T 402/89, however, the board pointed out, in passing, certain difficulties in interpreting the term "protection conferred".
In T 5/90 the patent was granted with a claim in the form "a product having product features x and product-by-process features characteristic of process steps y". This claim, however, turned out not to be novel. The patentee finally claimed "a process of making a product having product features x by using process steps y and process steps z". The board interpreted such a claim as covering the process steps only in so far as a product having product features x actually resulted. This was called a process-limited-by-product claim by the board. The direct product of this process would also be protected under the provisions of Art. 64(2) EPC 1973, but such product inevitably fell within the scope of the product claim originally granted. The board regarded a process-limited-by-product claim of this type as clearly complying with the requirements of Art. 123(3) EPC 1973 because it would only be infringed if the product fell within the originally granted product claim and in addition the particular form of manufacture using process steps z was used (see also T 562/04).
In T 20/94 the patent as granted exclusively comprised process claims for preparing a product. In the form as amended it comprised a product claim relating to the product per se. The board stated that the protection conferred by a claim directed to a process for preparing a product covered a product directly obtained by that process (Art. 64(2) EPC 1973), but it was not protected when obtained by any other process. However, the protection conferred by a claim directed to a product per se was absolute upon that product. The product claim thus conferred protection on that product regardless of the process by which it was prepared. The appellant attempted to overcome this objection by formulating the product claim as amended in the form of a product‑by‑process claim using the term "directly obtained". The board did not agree with this line of argument, stating that a product‑by‑process claim was interpreted as a claim directed to the product per se, since the only purpose of referring to a process for its preparation was to define the subject‑matter for which protection was sought, which was a product. Thus amended claim 1 in the case in question contravened Art. 123(3) EPC 1973.
In T 1206/01 the board pointed out that according to the established case law of the boards of appeal a product claim conferred protection on the claimed product, regardless of the process or method by which it was prepared. Therefore a change of category from a granted product claim to a process claim restricted to one or more methods of preparing the product did not extend the protection thereby conferred.