Thursday, 11 February 2010

T 567/08 – Ambiguity Kills The Cat

Readers interested in major and surprising decisions only should not read on. The present decision is not revolutionary at all, but it contains a very thorough discussion of an ambiguous amendment that led the patentee into the “inescapable trap” between A 123(2) and A 123(3). In particular the question of whether the existence of particular interpretations that would make the amendment allowable can change the fate of the claim is discussed in detail.

[...] The subject-matter of claim 1 as granted is defined in part using the term “base footprint”, which is not disclosed in the original disclosure but was introduced during examination and held to add subject-matter in the decision under appeal. [3.1]

The decisive issue now is whether the addition of this term represents an amendment of the type addressed in G 1/93 [12] namely an “undisclosed technical feature limiting the scope of protection of the granted patent in comparison with the application as filed”. Such a “limiting extension” adds subject-matter contrary to A 123(2) but at the same limits the scope of protection vis-à-vis what could have been claimed, so that its removal infringes A 123(3). Only if there is a basis in the application as filed for replacing such subject-matter without violating A 123(3) can it be remedied. On the other hand, if the limitation merely excludes part of the potential protection of the application as filed, without providing a technical contribution to the subject-matter of the claimed invention, it does not add subject-matter and the opposition ground under A 100(c) does not prejudice maintenance of the patent.

G 1/93 makes its findings in the light of the overall purpose of A 123(2)(3), namely to create a fair balance of interests between patentee (or applicant) and competitors and third parties. [3.2]

Original disclosure

It is uncontested that the term “base footprint” is not expressly disclosed in the application as filed. In granted claim 1 a rear sidewall extends beyond the “base footprint” to effectively form the shoulder (though not defined as such in the claim). The relevant parts of the original disclosure dealing with the location of the shoulder are to be found on page 12, in the first paragraph, (“the shoulder ... extends to at or near a theoretically plane extending vertically upwards rear the first end (the base) of the container” and in as filed claim 8 (“the shoulder ... extends to at or near a theoretical plane which extends vertically above the circumference of the first end”). [4.1]

“The first end” and “base” are used, it would appear, as synonyms on page 12. In a further passage […] the two terms are again used interchangeably: “the container has a first, closed end which … has a planar surface, enabling it to stand upright. The planar surface may be completely flat or comprise a flat rim and an inwardly domed area. The base often has a diameter ...”. This passage also offers a definition, if somewhat grammatically flawed, of what is meant by the first end/base. It focuses on the flat surface on the bottom end of the container including any domed area contained within it and corresponds to what the [patent proprietor] reads as “base” and “base footprint”:

It is noted that this definition excludes the rounded edge of the container bottom lying outward of and connecting to the flat surface. On the side of the shoulder this edge is shown as relatively prominent and not negligible. [4.2]

With this definition in mind, page 12, first paragraph, and claim 8, can then be read as teaching to locate the shoulder beyond a plane extending vertically from the circumference of this flat surface. [4.2]

Added subject-matter

Claim 1 was amended upon grant to require the support (forming the shoulder) to lie “beyond the base footprint”. The term “footprint” can have various meanings, and its use in conjunction with “base” is open to interpretation, as the debate to date has shown. [5.1]

If “footprint” is understood, as does the [patent proprietor], in the sense of a “tyre footprint”, meaning “the area of contact between a tyre and the ground” (Oxford English Dictionary or OED), it corresponds to the contact surface of the container bottom end on the underlying surface. The circumference thereof corresponds to that of the base or first end as defined above, and the requirement in granted claim 1 could then be read as equivalent to that understood from the text (where “the support/shoulder extending beyond the circumference” will be understood as meaning that it extends beyond the plane extending vertically from the circumference). [5.2]

On the other hand, the term can be read analogously to “footprint of a personal computer”, denoting the “area of a surface taken up by a microcomputer on a desktop” (OED) and formed by the downward projection onto the surface of the PC. This reading would allow for more complex, non planar base shapes - such as with an outer rounded edge - the downward projection of which then forms the “footprint”. In this interpretation “base footprint” includes for example the rounded edge onto the underlying surface:

The area is larger than that of the contact surface above, and its circumference further outward. Thus interpreted, granted claim 1 requires the support/shoulder to lie further outward than if it is interpreted as in the previous paragraph. [5.3]

Both interpretations represent common usage, as illustrated by the citations from the OED. Moreover, they fit within the context of the entire contents, i.e. there is no contradiction between this claim wording and description and figures of the patent specification, the relevant parts of which … are unchanged with respect to the originally filed description. These passages encompass also shoulders that extend further outward , e.g. those beyond the boundary of the base projection rather than of the contact surface. [5.4]

The second interpretation however is more specific than the teaching derivable from the original disclosure. It adds new, more precise information on the location of the shoulder, which is not derivable from the original application. Moreover, in the context of the problem of stability this information is technically significant; by defining a more limited range of possible shoulder positions it provides a technical contribution to the invention. In its second interpretation the feature of the “base footprint”, and bearing in mind G 1/93 [headnote II], thus adds subject-matter extending beyond the content of the application as filed, contrary to the requirements of A 123(2). [5.6]

This possible interpretation gives the proprietor an unwarranted advantage and is damaging to the legal security of third parties. It does not matter that the claim can also be read in such a way that it does not add subject-matter. The fact that in one reasonable interpretation of the claim it does do so is decisive. The legal certainty of a claim that, by introduction of an undisclosed ambiguous term, is amended to have multiple reasonable interpretations, is thus compromised when one of those interpretations relates to added subject-matter.

The Board thus concurs with the finding of the decision under appeal, that the corresponding opposition ground of A 100(c) is prejudicial to the patent as granted. [5.7]

Limitation of scope of protection

The first interpretation of “base footprint” as synonymous to contact surface clearly does not per se result in a limitation of the scope of the original disclosure. However, reading the term in its second sense, claim 1 as granted only protects containers with supports/shoulders that extend further outward, beyond the wider area. A shoulder, which lies between the contact surface boundary and that of the whole base projection,

does not fall within granted claim 1’s scope, though by virtue of the original application’s disclosure of the contact surface boundary as lower limit it could have been. According to the second interpretation of “base footprint” this amendment to claim 1 at grant thus limits the scope of the claim in comparison to the application as filed and published. It is again stressed that this second interpretation is consistent with description and figures, and it is thus a valid construction of claim scope when the claim is read in light of the description and figures in accordance with A 69(1). [6.1]

As demonstrated above, but for the prohibition of A 123(3), subsequent amendment of claim 1 by removing the term “base footprint” would result in embodiments, which before amendment did not infringe the patent, after amendment infringing it.

Here again the fact that there is at least one reasonable, contextually consistent reading of the term that results in a limitation of scope, among a number of possible readings that do not, is decisive. The ambiguity of the undisclosed amendment adds to, rather than mitigates the legal uncertainty surrounding the rights deriving from the patent. In this regard, the Board notes that if it were to construe an ambiguous undisclosed term in a manner favourable to the Proprietor (i.e. in a way that does not add subject-matter and limit scope) it would act against the principle of a fair balance of interests underlying A 123(2)(3). In its view the Proprietor should not be able to reap any benefit from the fact that an added undisclosed feature is ambiguous, with regard to an added undisclosed feature that is not. [6.2]


As follows from the above, the amendment of claim 1 pertaining to “base footprint” adds subject-matter, but limits the scope of protection in comparison to the application as filed and published. The Board concludes that it is a “limiting extension” in the sense of G 1/93. [7] 

To read the whole decision, click here.