Patent Claims Including Numerical Data - Scope of Protection and Doctrine of Equivalents

by Reinhardt Schuster and Clemens Rübel

I. Introduction

In a landmark decision (Chimney Pipe Case), rendered on March 22, 2001, the District Court Düsseldorf, statistically the most frequented first instance Court for patent infringement proceedings in Germany and even in Europe, had to decide on the scope of protection of a patent which limited its scope by numbers in its claims. Here, the Court had to balance important principles against each other when deciding whether the scope of protection also covers embodiments which lie outside of the range indicated by these numbers: The principle of rewarding the inventor with an adequate scope of protection versus certainty of the law in view of the specific claim language. This area of conflict regularly comes up with decisions in the field of the doctrine of equivalents.

II. The doctrine of equivalents

1. The Principle of rewarding the inventor versus certainty of the law

The entire patent law is based on the economic policy consideration that the inventor should be rewarded for his contribution to technical progress by granting a patent and protecting his invention during the (limited) time of the term of his patent. It should be worthwhile for the inventor to disclose as quickly as possible his invention to the public, instead of using it secretly on his own, or leaving the patent unused. In form of a monopoly lasting for a certain period of time, the inventor obtains the economic value of his invention. The scope of this monopoly, however, has to be determined precisely, because competitors have to know the borderline which limits their right to manufacture without entering into conflicts with patents, and from where on they have to ask the inventor for a license or develop and use alternative technologies. The certainty of the law, on the other hand, is as important for the functioning of the economy as the rewarding of the inventor. A precise borderline, limiting the scope of protection, is therefore desirable.

Thus, a limitation of the patent protection to the wording as literally claimed would be very desirable in accordance with the spirit of the certainty of the law. However, it would be easy to circumvent the wording of the patents by changing infringing embodiments in such a way that the embodiment would differ only slightly from the wording of the claims without giving up the principles and advantages of the invention, so that the holder of the patent would not receive his fair reward. The inventor, on the other hand, would like to have everything protected which was published by the patent, including the description and drawings.

2. Applicable law for the scope of protection

The European Patent Law and the literally corresponding German Law try to find a harmonizing compromise in providing that "the extent of the protection conferred by a (European) patent or a (European) patent application shall be determined by the terms of the claims. Nevertheless, the description and drawings shall be used to interpret the claims". The protocol to the interpretation of Art. 69 EPC which is, according to Art. 164 (1) EPC, part of the EPC and applicable to European as well as national patents, again precises the compromise found in Art. 69 EPC:

Art. 69 should not be interpreted in the sense that the extent of the protection conferred by a European patent is to be understood as that defined by the strict, literal meaning of the wording used in the claims, the description and drawings being employed only for the purpose of resolving an ambiguity found in the claims. Neither should it be interpreted in the...