By Reinhardt Schuster and Clemens Rübel

I. Introduction

On March 12, 2002, the German Federal Supreme Court has rendered four judgements, thus clarifying a judicial field where there has been repeated legal uncertainty for a long time. The Federal Supreme Court had not rendered any decision on this topic since the last fundamental amendment to the German Patent Act in 1981 which included, above all, an amendment to the regulation of the scope of protection of a patent in accordance with the shortly before enacted European Patent Convention (EPC).

Since the publication of a judgement of the District Court Düsseldorf of March 22, 2001 led to fierce discussions among experts (compare a report from the authors in MIP, Patent Year Book 2002, p. 21), the judgements of the Federal Supreme Court had been awaited impatiently in professional circles.

The Federal Supreme Court has rendered not only one decision on this topic, but four on one single day: The judgements led to a final result which is quite similar to the one found in the District Court decision. Its reasoning, however, is different. In comparison to former Federal Supreme Court rulings before 1981 concerning the interpretation of claims containing numerical data, these judgements proceed from a smaller scope of protection.

II. The new Federal Supreme Court judgements

All four judgements have been rendered in cases in which numerical ranges had been claimed and in which the attacked embodiment was always slightly outside of the literally claimed range. Thus, in these cases only non-literal infringement was in question.

At the beginning, all four cases deal abstractly with the problem how patent claims can be interpreted when the case in question involves data bordering on the limits of the claimed numerical ranges. Therefore, they all deal with potential patent infringement according to the Doctrine of Equivalents.

For this reason, the Federal Supreme Court examines didactically the scope of protection of a patent according to this doctrine: It holds that the scope of protection is fundamentally determined by the terms of the claims. Description and drawings are to be used for the interpretation of the technical terms used in the claims as well as for the clarification of the meaning and the extent of the invention described therein. Hereby, the meaning has to be ascertained which the person skilled in the art allocates to these terms in the relevant technology.

The scope of protection extends beyond the literally claimed scope also to equivalents, if (1) the problem of the invention is solved by amended but objectively equally functioning means, (2) a person skilled in the art is able to find the amended means as equally functioning due to his expert knowledge with a view to the claim language, and (3) the considerations the person skilled in the art needs to make in this respect should be orientated to such extent at the terms of the technical teaching defined in the patent claim that the person skilled in the art considers the different embodiment with the modified means as an equivalent solution to the literally claimed solution.

The particular aspect of these judgements is that the Doctrine of Equivalents is also applicable to patent claims with numerical data. According to the new German Patent Law (after 1981), numbers in patent claims can be and are to be interpreted, although the scope for interpretation seems now to have become smaller in comparison to the old law, when such data were considered only as exemplary determination while not excluding to a reach outside the claimed ranges.

The Supreme Court concedes that numbers as such are unambiguous, whereas general terms formulated in words require a certain abstraction with respect to the object named. However, when used in different context, identical numbers can describe different facts. In this sense, numbers can be and need to be interpreted, too. Thus, every patent writes its own dictionary and needs interpretation, also with respect to numbers in the claims.

For reasons of legal certainty regarding patent claims that include numbers, the application of the doctrine of equivalence should in such cases be carried out with much more thoroughness than in cases in which numerical ranges are not concerned, the Supreme Court says. The applicant of a patent with numerical data has special reason and responsibility to consider the consequences of the formulation of the claims regarding the scope of the requested patent protection. Yet the person skilled in the art considers a certain unclearness within the normally permissible variations or tolerances as compatible with the technical meaning of the object described. There are, however, some numerical data which the person skilled in the art understands as having to be observed literally: The so-called "critical values". Due to the principle of legal certainty, these values cannot be interpreted above the claimed range, i.e. if interpreted otherwise, the sense of the claims would be left. The below case study of these four important cases of the Supreme Court will show, in which situations the Court assumes such "critical values", excluding the coverage of not exactly and literally covered data and ranges. Here, the interpretation of "critical values" by the Court corresponds to the third "Catnic" question: "Would the reader skilled in the art nevertheless have understood from the language of the claim that the patentee intended that strict compliance with the primary meaning was an essential requirement of the invention?" If yes, the variant is outside the claim.

III. The four decisions

In all four judgments, a methodologically instructive, general and abstract formulation of criteria under examination of cases with numerical data for the doctrine of equivalents is in each single case followed by a detailed examination of the facts with respect to these criteria.

1. Plastic Pipe Piece "Kunststoffrohrteil"

The invention concerned is a plastic pipe which contains a special coating absorbing noise. A soundproof state is reached by including a barium sulfate filler in the thermoplastic material, so that the piece of plastic pipe reaches a weight of at least 8 kg/m2 and a density of 1.8 to 2.7 g/cm3. The inventive idea has the advantage to reach a sound-proof state with comparably thin walls. The attacked embodiment has a weight of more than 8 kg/m2 and a density of 1.6 g/cm3 with a wall thickness of 5.6 mm. All the other features correspond literally to the patent claims. The claims indicate no numerical value for the wall thickness, but the above mentioned values for the width and the density are mentioned in claim 1. Considering these facts, the person skilled in the art realizes that the crucial point of the invention is that the piece of pipe has a certain weight per surface unit. He further understands that, even when leaving the claimed range of density, the wanted inventive weight per surface unit can nevertheless be obtained by amending the thickness of the wall. The range of density is left towards a lower grade, which is compensated by a slight thickening of the wall. This is self-explaining, since patent claim 2 of the patent-in-suit says that the lower range of density is preferred, and it can be taken from disclosed preferred embodiments that a wall thickness of 7 mm is still considered as sufficient. For this reason, the technical teaching in the attacked embodiment was considered by the Supreme Court an equivalent to the patented solution.

2. Cutting Knife I, II "Schneidmesser I, II"

These two cases concern patents that claim special devices of cutting knifes which, among other features, encompass an angle of 10° to 22°, preferably 16°, and further encompass with their longitudinal axes a sharp angle to the corresponding radius of the basic body which amounts to 9° to 12°.

In the decision Cutting Knife I, however, the attacked embodiment has only an angle of 8°40'. For the invention, the Supreme Court found, it is only crucial that the cutting knife always penetrates at first with the radial interior end of the cutting edge into the object to be cut. A flat penetrating of the cutting edges into the object would result in soft cutting. These effects also appear when a slightly sharper angle is applied, a fact which the person skilled in the art manages to notice, as the Supreme Court has found. However, if a special range is given in a patent claim and if no clue can be found in the patent specification that the claimed values are only meant to be understood as an example, the person skilled in the art is generally not expected to consider whether the invention could also be executed by applying other values than the values claimed. This does not apply if the divergence from the claimed range is, as in this case, so small (only 20') that it remains within the frame of the corresponding German industry norm for the generally permissible variation in angle measuring. Here, a certain unclearness is compatible with the technical sense of the numerical data, and for this reason the attacked embodiment is considered an equivalent to the claimed device, the Supreme Court held.

The case Cutting Knife II is, however, different to Cutting Knife I. It concerns another angle named in claim 1 of the patent: "angle of 10° to 22°, preferably 16°". The attacked embodiment is similar to the patented device, but shows at this point an angle of 25°. This value is, according to the Federal Supreme Court, so much larger than the preferred value for an equal solution (16°) that the person skilled in the art would not consider the attacked embodiment as equivalent when reading claim 1. It is no longer compatible with the sense of the patent claims, since, after examining the device, the person skilled in the art would further come to the result that the claimed range of the angle is crucial for achieving the solution supplied by the invention of the patent, and therefore the keeping of the claimed ranges is of considerable importance. Thus, according to the German Federal Supreme Court, it seems to be excluded that experts would consider a scope beyond the claimed range as protected by the patent because such a scope of protection could no longer be related with the sense of the patent claim.

3. Custodiol II

This judgement concerns a medical solution for avoiding damages of the heart and kidneys. It contains eleven different components, among which the amount of 10 +/- 2 mmol/l magnesium chloride is claimed. The accused embodiment has only 4 mmol/l.

In this case, the Federal Supreme Court has denied patent infringement mainly for one reason: The divergence of the value in the attacked embodiment with respect to the patent claim is too large. The person skilled in the art does no longer relate such an embodiment to the claimed numerical range. He/she would not find this solution, even if it is of equal effect to the claimed solution.

IV. Summary

The new judgements of the Federal Supreme Court differ from the jurisprudence of the old law as well as from the judgement of the District Court Düsseldorf of last year mainly in their reasoning but not in their final result. Instead of abstractly invoking and using the principle of certainty of the law as the most pertinent criterion for examining and limiting the scope of protection, the Court examines more closely the criteria developed in former decisions with regard to the Doctrine of Equivalents and, different to the judgement of the District Court Düsseldorf, it needs no further newly developed criteria. In contrast to judgements before 1981, it is closer orientated towards the patent claims. The patent claims no longer serve only as a guide line for the determination of the scope of protection, but are the decisive basis for it. As a result, this leads to a more limited scope of protection under the Doctrine of Equivalents, but does not foreclose this doctrine for patents claiming numerical ranges.

As rule of thumb, the following can be concluded from these decisions: The more important the observation of the numerical ranges named in the claims is for the solution of the problem of the patent and the nearer the ideal value for the solution is to the edge of the numerical range (which was left), the larger is the range of tolerance along the limit of the numerical range. As a consequence, in these cases, a comparatively larger extension of the numerical range falls within the scope of protection than in other cases. This rule of thumb finally corresponds to the result of the aforementioned Düsseldorf judgement as well as to the court rulings under the old German Patent Act, although the tolerance range has generally become smaller and is intended to be used more responsibly. However, this is only a rule of thumb and does not prevent lawyers from thoroughly examining and arguing the applicability of the criteria of the Doctrine of Equivalents, which was confirmed by the Supreme Court to patent claims including numerical data.

One thing is sure: By these four detailed, deliberately rendered and reasoned judgements by the German Federal Supreme Court on this topic, legal uncertainty concerning the determination of the scope of protection of patents with numerical data has been reduced considerably.

© Reinhardt Schuster and Clemens Rübel

The authors are attorneys-at-law with the Intellectual Property Law firm Bardehle Pagenberg Dost Altenburg Geissler Isenbruck which has offices in Munich, Düsseldorf, Mannheim, Heidelberg, Paris, Alicante, Shanghai.

First published with Managing Intellectual Property / IP-Litigation Yearbook, 2002

The content of this article does not constitute legal advice and should not be relied on in that way. Specific advice should be sought about your specific circumstances.