Germany: The Interpretation of Patent Claims in Germany
Legal development and current case law

I. Historical development of the principles of patent law in Germany

Before the era of the German Patent Act 1981, which after a number of changes is in its current version valid today, the principles for determining the scope of protection of a patent were subject to a development of interaction of granting practice, legal doctrines and jurisdiction.

The first German patent act of 1877 did not yet prescribe any special wording in the patent claim for the delimitation of the scope of protection. In the practice of the time, however, the inclusion of patent claims after the description was soon being established. Thus the patent act of 1891 already included the legal basis for this practice which read: "The patent claim shall indicate what (as being patentable) is to be protected." In these years, the Reichspatentamt already determined in the granting procedure the "subject matter of the invention" as well as the "scope of protection".

The so-called Hartig's doctrine demanded that the delimitation of what was not to fall under the protection was to take place in the patent claim. A claim had to be consist of a descriptive term, an indication of the features regarded as being essential, and a formulation of the invention in one single sentence, as well as with a clear definition of what is delimitating the novelty of the subject matter of the invention from the prior knowledge. Isay found in his later teaching, that it was an impossible task to assign to the patent claim in the granting procedure the delimitation of the scope of protection. Only in an infringement procedure the court was to establish the scope of protection, based on the objective state of the art and independent of the claim wording. This was the birth of the so-called "dual doctrine" about the subject matter of the invention on the one hand and the scope of protection on the other. The Imperial Court followed this opinion with its decision of Feb. 9, 1910, with longtime repercussions on the German legal practice.

There followed a time, until the thirties, of a judicial patent interpretation practice which was partly independent of the claims and, at the same time, a granting practice which did not discern the essence of the invention from the application files.

Towards the end of the thirties, the jurisdiction set up additional criteria for delimitating the scope of protection under the aspect that the exclusivity right granted to the inventor was not to reach further than adequate as far as the benefit of the public was concerned. The scope of protection was to be concluded from the patent claim, and the description as well as the drawings had to be consulted to clarify the technical sense of the claim. Not the patentee's view was decisive for the technical sense of the claim, but the average skilled person's imagination of the invention on the day of application.

In later years the Imperial Court took to a more differentiated view of the scope of protection, which was later followed by the Supreme Court. Under the so-called "triple division theory" one differentiated between

• the "immediate subject" (limited to the pure wording of the claims; the off-limits rest of the protected invention);
• the "subject matter" of the invention (to be derived from the claim wording, with consideration of the description, the general knowledge, the skilled person's knowledge of the state of the art which was to be taken as an irrefutable presumption, and the so-called "smooth" equivalents to which belonged the smooth technical equivalents as well as the smooth legal equivalents of the patent law;)
• the "general inventive thought" (constituting the essence of the invention, which in some cases can only be discerned by abstracting from the patent file - derivable from the claim wording and sufficiently disclosed in the description.)

In this context, the judge in the infringement proceedings had primarily to deal with the interpretation of the investigated subject matter of the invention. In individual cases it may have become necessary, because of opposing state of the art detrimental to novelty, to limit the scope of protection of the patent to its immediate subject matter (wording of the claims). In other cases, the general inventive thought had to be examined in order to answer the question of patent infringement by the special form of the attacked embodiment.

The determination of the scope of protection of a patented invention, according to § 6 German patent act of 1968, was still characterized by the "triple division theory". The wording of § 6 PatG 1968 (according to which the effect of the patent extended to the subject matter of the invention) was deemed a sufficient basis, delimitating, on the one hand, the the competence of the patent office and, on the other hand, the competence of the nullity court as well as the competence of the civil (infringement) courts. This concept has governed the jurisdiction of the Federal Supreme Court until lately.

For determining the "subject matter of the invention" according to the "triple division theory", one had to start with the patent claims. Only such technical teaching belonged to the subject matter of the invention which the skilled person could derive, with the knowledge of the day of priority, from the sense of the patent claims and without further reflection, while taking the description, the drawings as well as the general knowledge into consideration. For investigating the subject matter of the invention - contrary to the earlier jurisdiction - not the whole state of the art was to be assumed as being known to the skilled person. The interpretation of the patent claims according to the state of the art was only allowed to the extent in which this was stated in the patent file or could be counted to the specialist knowledge of the skilled person. According to the then predominant opinion, the state of the art was not appropriate - such as it was assumed to be present in the fictive knowledge of the skilled person for the examination of novelty.

The concept of the protection of the "general inventive thought" consisted in providing legal protection for all those embodiments of the teaching of the patent which were putting to use the essence of the teaching disclosed in the patent claims, but which were not encompassed within the scope of protection of the "subject matter of the invention". Since only derivations of the scope of protection of the "subject matter of the invention" were encompassed by the claimed technical means for solving the patent's problem - which were obvious to the skilled person as being of equal effect without further consideration - one only had to fall back on the "general inventive thought" if a) the attacked embodiment showed not all the criteria which were, according to the claim wording, deemed necessary by the inventor for the solution of the problem (compare so-called protection of elements and protections of sub-combinations).

II. Patent interpretation regarding applications after 1978 (German Patent Act of 1981)

1. Legal basis

The current legal basis for the determination of the scope of protection are § 14 German Patent Act (Bundespatentgesetz BPatG) and, in identical wording, Art. 69 (1) European Patent Convention (EPC):

Concerning additional interpretation - also of § 14 German Patent Act - the Protocol on the Interpretation of Art. 69 says:

According to the supplemented Art. 2 No. 1 of the Munich Revision File to the EPC of Nov. 29, 2000, the revised Protocol on the Interpretation explicitly states in Art. 2, that in the future

These principles of interpretation which are applicable to all patent applications filed since January 1^st, 1978 and to the ensuing patents thereof, are in principle not contravening to the principles for identifying the scope of protection applied prior to 1978. Also today there is still a differentiation being made, in the framework of identifying an act of infringement, between the "subject matter of an invention" (content or technical teaching) and "the scope of protection". In the 80ies, the German Federal Patent Court ruled, that the subject matter, the clearity of which the examiner had to see to, is to be governed by the terminological definition of its content. In the granting procedure, in principle only this subject matter but not its extent of protection is to be defined, encompassing a scope of as yet not existing solutions of identical or similar nature.

The Patent Office establishes the subject matter of the patent to which the courts are bound in infringement suits. Insofar as the content is unclear, the interpretation of the patent claim regarding the determination of the "subject matter of the invention" is conducted in Germany according to the principles of interpretation set forth in §§ 133, 157 of the Civil Code (BGB), according to which a legally relevant declaration (of intent) or a kind of special law (the patent claim being comprehended as such) is treated. This means that the judge in the infringement suit is meant to find out the true intent of the patentee at the priority date, that is how the public comprehended in good faith the content of the claim. The measure for this is the average knowledge of the skilled person at whom the declaration is addressed. Regarding the practice field, the technical branch of industry is relevant to which the technical problem to be solved applies.

For the interpretation, only the average skilled person's knowledge at the date of priority and the state of the art as expressed in the patent specification may be taken into account. The average skilled person's knowledge does not constitute the whole state of the art. Only such state of the art that is known to the average skilled person is to be taken into account with the interpretation of the subject matter. Any technical knowledge obtained at a later date as well as older, later published patent applications are also not part of the "average knowledge". The content of the patent grant files is not considered in principle, since the intent of the applicant is of no relevance, except in case the files contain delimitating declarations or renunciations of the applicant. Technical terms can be interpreted according to the state of the art if explanations hereto are missing in the patent specification. Not the terminology of the scientific teaching is decisive, but the language used by the professional circles at whom the patent specification is addressed. Therefore, the skilled person's view on the technical sense is relevant. With an investigation of the subject matter of the invention, an expansion to equivalents is not allowed.

What was (and still is) termed in practice as "interpretation of the patent claim" is, in most cases, not an interpretation of the declaration of intent of the patentee for clarification of the subject matter of the invention, but his attribution of the scope of protection of a patent. While the subject matter of the invention is gained by an interpretation of a declaration in a manner common in Civil Law, the scope of protection has to be specifically established and attributed. In German legal practice it has been stressed again and again that every patent and utility model is entitled to the widest conceivable scope of protection. This extent is situated in the area between the disclosure of the patent specification and the state of the art. The upper limit should be set, according to general opinion, by the entitlement of third parties to adequate legal security. This balance of interest between a maximum reward for the inventor, on the one hand, and legal security for thirds on the other, is also implied in the sense of the Protocol on the Interpretation of Art. 69 EPC (see above, last sentence).

An occasion for the establishment of the scope of protection is, as a rule, the alleged case of infringement. For establishing the scope of protection of a patent, in particular, in the framework of an assessment by the court of an infringing act, the patent claims and, in particular, the claim features need to be determined in detail. The content of the invention gained by way of interpretation - in case the wording of the patent claims is unclear according to the principles of interpretation set forth in the Civil Law (see above) - is the lowest and untouchable limit of the patent claims to which the judge in the infringement suit is bound. In Germany, where infringement (specialized chambers of the Regional Civil Courts) and nullity suits (Federal Patent Court) are separate procedures, the judge in the infringement suit cannot scrutinize the "subject matter of the patent" as defined in the claims, for novelty, inventive step and, as the case may be, industrial applicability in order to reach below this lowest limit of protection. However, as soon as the subject matter of the patent is left in direction of the scope of protection, a comparison with the claimed extent and the state of the art is allowed and necessary (see below II 2b). It is not legally regulated to what extent - in the framework of the interpretation of the patent claims and claim features with regard to the subject matter of the invention and the scope of protection - the general knowledge or the submitted or objective state of the art is to be taken into account for the findings of the court. This gap has up to now only been filled by judicial law, which will be explained in more detail below.

Also the new case law is continuing the decade-old principle of interpretation of patent claims: Firstly, in the framework of investigating the subject matter of the invention in the patent specification and the technical terms used therein, as well as for clarifying the importance and the reach of the invention, one has to start from the basis of how the average skilled person comprehends these technical terms with consideration of the description and the drawings, and what he concretely associates with them and with the described inventive idea. Here, the general knowledge of the skilled person of the respective technical field as well as the state of the art submitted in the patent specification are decisive for an assessment. Any state of the art not communicated in the patent specification, however, is to be taken into account only if it can be assigned to the general knowledge of the skilled person. The patent file can nevertheless create "its own dictionary" which has a priority status with regard to the consideration of the general technical language, the teaching of the patent being limited in this context to those wordings which the state of the art known to the average skilled person is allowing to be technically realizable and which this person is taking into consideration.

For the assessment of the central question in an infringement suit, whether the invention protected by the patent is being illegally used, firstly the content of the patent claims is to be established, on the basis of the above explained understanding of the skilled person, that is the sense attributed to the wording of the claims by the average skilled person, with support of the description and drawings (§§ 133, 157 German Civil Code). The infringement court has to make factual assessments about the subject matter of the invention disclosed in the patent specification, which are, according to current case law, subject to unlimited re-assessment in the appeal procedure.

The establishment of the subject matter of the invention, which is traditionally characterized by problem and solution, in particular, the answer to the question of how the average skilled person understands the patent specification (expert's opinion), is admitted to evidence. Thus the question of patent infringement can be answered differently depending on the result of the taking of evidence about the understanding of the average skilled person with regard to the subject matter of the patent-in-suit.

a) Identical use

A use according to the claim wording or an interpretation in the sense of the wording is an identical use of the claimed teaching of the patent-in-suit by the attacked embodiment and thus falls clearly within the scope of protection and constitutes a patent infringement. This corresponds to the principles of interpretation of Art 69 (1) EPC, according to which the scope of protection of a patent is determined by the content of the patent claims, for the interpretation of which the description and the drawings are to be consulted. Of decisive importance here is the view of the skilled person, the determination of the content of the claims depending on his comprehension, including the terms used therein. This also applies to the determination of any scope reaching further than the protection conveyed by the sense of wording in the patent claims.

However, in practice there are more cases (needing a more differentiated judgement), with the attacked embodiment not making use of the technical teaching designated by the claim features according to the literal wording or sense, but showing one or several features of the patent claim in, for instance, modified or incomplete form.

b) Equivalents

It corresponds to the yearlong jurisdiction on equivalence (= teaching of equal values in patent law) that the scope of protection of a patent encompasses also such embodiments which do not fully realize the features to the solution claimed in the patent or which realize them by other means in conjunction with additional means, this being an expression of a principle common in European law. The following four criteria have been established by the German Federal Supreme Court:

(1) equal effect with regard to the problem solved

(2) subject matter of the invention / the patent claims as a framework of orientation

(3) their comprehension by the skilled person

(4) distance to the state of the art

which will be explained in further detail:

(1) Accordingly, embodiments deviating from the wording of the patent claims or not corresponding to their literal sense can fall within the scope of protection, if the attacked embodiment shows - while following the concept of solution designated in the claims - a technically equal effect. A simple conformity of the technical result does not suffice to meet this criterion. The starting point for examining an equivalent infringement is a comparison of the problem solutions offered by the patent's embodiment and by the attacked embodiment. If the technical solutions are different, there is no equivalence. The concrete problem of the patent must be solved by the attacked embodiment. For establishing whether the attacked embodiment is showing an equal effect and is following the same path to the solution as the patent, the comprehension of the skilled person is again decisive, just as it is for the establishment of the subject matter of the invention.

In its latest decision, the Federal Supreme Court states "while continuing hitherto existing jurisdiction, that with an embodiment deviating from the sense of the patent claims, a use falling within the scope of protection can be established, if the skilled person can identify with the help of his specialist knowledge - on the basis of considerations tying on to the sense of the claims of the protected invention - the modified means, which were used in the attacked embodiment. The aspect of an appropriate protection for the inventor's accomplishment, on the one hand, and the precept of legal security on the other, are both demanding that the sense of the patent claims to be investigated constitutes not only the starting point but also the authoritative basis for the establishment of the scope of protection".

The Federal Supreme Court emphasizes, that these principles are harmonizing with the Protocol on the Interpretation of Art. 69 EPC, which is, according to consistent case law, also to be subjected to the interpretation of § 14 German Patent Act and which, according to Art. 2, No. 1 of the Munich Revision Act to the EPC, shall explicitly enact in the later revised Protocol, that with the establishment of the scope of protection such elements are to be taken into account which are equivalents of the elements cited in the patent claims.

(2) Since the equivalence is orientated after the subject matter of the invention, the latter is primarily and principally to be established (via problem-solution), and, as the case may be, to be interpreted (see above) and to be emanated from (i.e. not from its equivalents).

(3) Thus the scope of protection encompasses also such means, which are not explicitly cited by the inventor/patentee for the solution of the problem, but which were obvious to the skilled person as being of equal effect. By way of the concept of equivalence, such embodiments can be included in the scope of protection, which, at the date of priority, could be identified from the content of the patent claims by the skilled person without inventive effort. However, such embodiments, which the average skilled person can only recognize after detailed consideration as being of equal effect, cannot be included in the scope of protection. In this context, the comprehensive ability of the skilled person (specialist skill) is decisive, the comprehension of the practically trained expert weighing more than that of a scientist.

(4) An embodiment that deviates from the patent claims in its elements contributing to the solution is, therefore, only covered by the scope of protection (and constitutes an infringement) if it can only be discerned via the technical teaching of the patent-in-suit. The attacked embodiment deviating in its elements does not constitute a use according to the patent, if this embodiment could be derived from the state of the art. This is because the protection conveyed by the patent law does not extend to an embodiment deviating from the claimed literal wording or from the sense of the wording, such embodiment having been priory known (§ 3 German Patent Act) or having been obvious (§ 3 German Patent Act) in the state of the art at the date of priority.

In an infringement suit, the objection of the free state of the art can legitimately be made, if the attacked embodiment is attacked as an equivalent use. Because of the different competence of the nullity instances and the infringement courts, the objection that the embodiment does not constitute a patentable invention with regard to the state of the art - and, therefore, does not constitute an infringement - is not admitted in cases of identical patent infringement.

Thus a differing, equivalent embodiment that is to be included in the scope of protection must be identified by the skilled person as being obviously derivable from the technical teaching of the patent. Yet, at the same time, this equivalent embodiment is neither to be priory known, nor can it be obvious in the state of the art. For this delimitation to the state of the art, the whole state of the art has to be taken into consideration.

The state of the art at the date of priority is essential for answering the question of infringement in the area of equivalents, or for determining the scope of protection disclosed in the patent file. In a fundamental decision, the Federal Supreme Court has already found that, for the determination of the scope of protection vis-a-vis embodiments with equal effect, the whole state of the art has to be considered, not only the state of the art of the patent file or the state of the art that may comprise the general knowledge of the skilled person. Only for the investigation of the meaning (breath) of the terms used in the patent specification (in the framework of determining the subject matter of the invention), the disclosed state of the art and the general knowledge of the skilled person shall be considered exclusively. The scope of protection encompasses, at first, an unknown area between the subject matter or the content of the invention on the one hand, and the limit which is shown by the technical state of the art on the other - since what belongs to the prior art cannot be part of the scope of protection. A later-found state of the art can thus, on the one hand, enlarge the equivalent scope, but it can also diminish the scope of protection of the patent.

c) Numerical indications and measurements

Already the Supreme Court of the German Reich (Reichsgericht) had determined, that numbers indicated in the patent claim are to be comprehended with regard to the nature of the invention, this meaning the problem and solution concept of the inventive idea, in particular, with regard to the envisaged purpose or the aimed-at effect. As a rule, a limiting attribution of the indicated measurements can be assumed, if they are stipulated in the patent claim as high and low end values. Any broader interpretation of the scope of protection based on the explanations of the patent description is hereby excluded in principle.

According to the most recent opinion of the Federal Supreme Court, the above explained principles for determining the scope of protection are also to be applied if a patent claim contains numerical indications and measurements. Here, a distinctly stricter judgement is necessary, according to the cited decisions of the Federal Supreme Court, compared to the legal practice before 1978 (for example, the Supreme Court of the German Reich found it to be doubtful to assume a patent infringement for a measurement of 17,1% when a range of 8-14% was stated). Accordingly, numerical indications and measurements form a part of the reliability of the patent claim as an important basis for the determination of the scope of protection. They shall help to determine and, therefore, also delimitate the object to be protected by the patent. It is now prohibited to view such indications as being of lesser reliability or to understand them merely as an example-like fixation of the protected technical teaching as it was deemed to be possible according to the case law before Art. 69 EPC came into effect.

Moreover, in its latest decision, the Federal Supreme Court has stated the following:

Transgressions above or below the claimed scope are not to be seen as a priori falling out of the scope of protection of the patent. Numerical indications and measurements are, in principal, interpretable, as any other part of a patent claim. What is of importance here, is how the skilled person understands such indications in the whole context of the patent claim, and, in order to further explain this context, the descriptions and the drawings are to be taken into consideration as well. The skilled person will not always assign the same fixed meaning to numerical indications and measurements. But he/she will, as a rule, allow for such indications a higher degree of clearness and unambiguity as might be the case with verbally described elements of the technical teaching. Numbers as such are unambiguous, whereas linguistically formulated general terms show a certain abstraction as to the object they designate. For this reason, features concretized by numerical indications and measurements can be attributed, from the viewpoint of the skilled reader, with such a meaning, that the objective inventive result will be delimitated more precisely and, as the case may be, more narrowly than it would be the case with a verbal circumscription.

Since it is the business of the patentee to state what he wants to have protected, the reader of the patent specification can assume, that the patentee's intention is mirrored also in the fact that he included numerical indications in his formulation of the claims. This is all the more so, because with numerical indications, the patentee has special reason to be aware of the consequences which the claim formulation has with regard to the limits of the protection he seeks. For this reason, an unambiguous numerical indication principally and definitely determines and delimitates the protected object - the transgression of which cannot, as a rule, be assessed as falling within the claimed range (object). On the other hand, this does not exclude, according to the Federal Supreme Court, that the skilled person is seeing a certain unclearness - for example, a common tolerance - as being consistent with the technical sense of a numerical indication. Thus the House of Lords admitted in the Catnic decision, that with a claim feature directed at a right angle, deviations of 6 to 8 degrees can be regarded as still being consistent with the assumption of a use of the protected teaching.

In a different context, however, the same angle may depict itself to the skilled person as an exact unchangeable value. This would be the case, if the skilled person determines, that it is a "critical" value. How a certain numerical indication or measurement will be finally understood is, therefore, a question of the judicial assessment of the skilled person's understanding of the individual case.

In the cited decisions the Federal Supreme Court further explains: The same principle as for the determination of the technical sense of the patent claim applies also to the determination of a scope of protection that reaches beyond the latter: numerical indications and measurements included in the claim are limiting the protected object with their specified values. In the framework of the determination of the scope of protection, it is not allowed to abstract from the sense of numerical indications. An embodiment found by the skilled person can be understood as being equivalent in the sense of the patent claim only if it achieves just that very effect which, according to the skilled person's understanding, is attributed to the numerical delimitation of the claim feature.

In the decision Custodiol I, the Federal Supreme Court judged the deviation between the portion of magnesium chloride of 4 mmol/l used in the medicament (for which a supplementary certificate of protection had been requested) and the portion of magnesium chloride specified in the basic patent as being substantial. It was deemed to be substantial, because the concentration in the medicament corresponded to only 50% of the minimal concentration as cited in claim 1) of the patent, and because only a relatively small range of tolerance of an average of 20% was previewed therein (in comparison to 50-80% for other obligatory ingredients). Any notions regarding equivalence were rejected on the grounds of these grave deviations.

The decision Custodiol II confirms this opinion of a substantial deviation. Additionally, the Federal Supreme Court rejected the reasoning of the lower instance, that the inventive step of the teaching of the patent-in-suit consisted exclusively of an addition of á-Ketogluterate, and that the concentration of the known ingredients, such as magnesium chloride, did not matter to the skilled person.