In this case the opponent filed an appeal after the Opposition Division had maintained the opposed patent in amended form.
Claim 1 of the main request before the Board read:
A vertical position control system which receives input signals including selected altitude (hs), selected vertical speed (ĥs), current altitude (h), and current vertical speed (ĥ), the control system including(a) a command processor (24) that computes a command trajectory in terms of a commanded altitude (hc) and a commanded vertical speed (ĥc);(b) a first combining unit (26) operatively connected to an output of said processor and for combining current altitude (h) with commanded altitude (hc) to produce a differential commanded altitude signal (∆hc);(c) a first multiplier (29) operatively connected to an output of said first combining unit for converting the differential commanded altitude signal (∆hc) into a proportional pitch attitude command (∆θc);(d) a smoothing integrator (62) operatively connected to an output of said first multiplier and having an output representing pitch attitude command (θc),(e) a second combining unit (68) operatively connected to a combination of the output of said integrator and the output of said first multiplier for combining the pitch attitude command (θc) and a current pitch attitude (θ) to form a pitch attitude error (Eθ), and(f) a second multiplier (72) operatively connected to the output of said second combining unit for filtering the pitch attitude error,characterized in that the command processor includes a filter having a damping ratio which is variable, the filter being dependent on a feedback component resulting from the intermediate commanded vertical speed (ĥ’c) and the intermediate commanded vertical altitude (h’c) wherein the intermediate commanded vertical speed (ĥ’c) is multiplied by a factor including the damping ratio which may be set to any desirable constant or may be a variable calculated at the time of engagement or other convenient time to adjust the response of the control system in relation to a respective flight maneuver.
The crucial question before the Board was whether this claim complied with the requirements of A 123(3). If so, the patent proprietor was stuck in the inescapable trap.
[2.1] The present case concerns the conflict between A 123(2) and (3) EPC which was considered in decision G 1/93 of the Enlarged Board of Appeal (EBA). In G 1/93 […] it is stated that
“If a European patent as granted contains subject-matter which extends beyond the content of the application as filed within the meaning of A 123(2) and which also limits the scope of protection conferred by the patent, such patent cannot be maintained in opposition proceedings unamended, because the ground for opposition under A 100(c) prejudices the maintenance of the patent. Nor can it be amended by deleting such limiting subject-matter from the claims, because such amendment would extend the protection conferred, which is prohibited by Article 123(3) EPC. Such a patent can, therefore, only be maintained if there is a basis in the application as filed for replacing such subject-matter without violating A 123(3)”.
[2.2] In the present case the wording of claim 1 of the granted patent “the command processor includes a filter having a damping ratio which is variable dependent on a feedback component” (which feature the OD held to infringe A 123(2)) was amended to “the command processor includes a filter having a damping ratio which is variable, the filter being dependent on a feedback component” (board’s emphasis). It has to be decided whether this amendment extends the scope of protection, since, in accordance with A 123(3),
“The European patent may not be amended in such a way as to extend the protection it confers”.
[2.3] Considering the wording of claim 1 from a linguistic point of view, it is clear to the board that the phrase “dependent on a feedback component” in the granted version of claim 1 is associated with the word “variable” which immediately precedes it. As it is not disputed that the term “variable” refers to the damping ratio (indeed, this aspect is retained in the amended version), it follows that claim 1 as granted requires, in a linguistic sense, a damping ratio that is variable dependent on a feedback component.
[2.4] It is not in dispute that that the description provides no support for a damping ratio that is variable dependent on a feedback component.
The extent of protection conferred by a claim feature not consistent with the description was considered in decision T 1018/02. In accordance with decision T 1018/02 [3.8],
“… the description cannot be used to give a different meaning to a claim feature which in itself imparts a clear, credible technical teaching to the skilled reader. This also applies if the feature has not been initially disclosed in the form appearing in the claim. Otherwise third parties could not rely on what a claim actually states (cf. A 69(1): The terms of the claims determine the extent of protection whereas the description is only used to interpret the claims) and A 123(2) would become meaningless in respect of amendments to the claims”.
[2.5] In order to determine whether the claim feature in itself imparts a clear, credible technical teaching, it is necessary, in the board’s view, to examine whether (a) the feature as claimed is in itself meaningful and plausible from a technical point of view, and (b) there is, prima facie, any inherent incompatibility with the remaining features of the claim.
[2.6] The technical plausibility of a damping ratio which is variable dependent on a feedback component is in the board’s view not in doubt. The respondent argued at the oral proceedings (OPs) that such a measure would be “unusual”, leading the skilled person to conclude that this was not the intended meaning. However, in the board’s view, whether or not a feature is in common use cannot in itself be a factor leading the skilled person to doubt its meaning.
[2.7] Further, in the board’s view, there is in the present case no inherent incompatibility with the remaining features of claim 1.
Although claim 1 as granted later stipulates that the damping ratio “may be set to any desirable constant or may be a variable calculated at the time of engagement or other convenient time”, it is perfectly possible, in the board’s view, that the setting of the damping factor to a desirable constant (e.g. a choice of one value amongst a set of constants) or to a calculated variable can be made dependent on the feedback component, e.g. such that a different constant/variable is used during different phases of the maneuver.
The respondent argued that the correct interpretation of the claim was that once the damping ratio is set to a desirable constant or a calculated variable, it remains fixed at the same value throughout the maneuver, this being entirely incompatible with a dependency of the damping ratio on a feedback component.
However, the board observes that claim 1 does not require that the damping ratio remain fixed throughout a maneuver. On the contrary, it provides that the damping ratio may be “a variable calculated at the time of engagement or any other convenient time” (board’s underlining). Claim 1 therefore embraces changing the value during a maneuver.
[2.8] The remaining arguments of the respondent put forward at the OPs can be summarised as follows:
(i) Claim 1 is ambiguous, in that it has two possible meanings. The first meaning is that the damping ratio is dependent on a feedback component, the second being that the filter itself is dependent on the feedback component. The skilled person has to read the claim with a mind desirous of understanding. He would therefore appreciate that there is an inconsistency between a damping ratio which is variable dependent on a feedback component and the later feature that the damping ratio may be set to a constant. In resolving this inconsistency, the skilled person would come to the only true interpretation of the granted claim which is that it is not the damping ratio which is dependent on a feedback component, but the filter itself. Since the amendment relates to taking only one of the two possible meanings of granted claim 1, the scope of protection has not been extended.
(ii) In order that the command processor produce output values of commanded altitude and commanded vertical speed, the skilled person would know that the feedback component must be fed back to the filter input rather than be used to control the damping ratio.
[2.9] Re (i): As explained above, the board disagrees that the claim is either linguistically or technically ambiguous in the sense that the feature “a filter having a damping ratio which is variable dependent on a feedback component …” has more than one meaning.
Re (ii): Claim 1 does not exclude that the feedback component is fed back to the filter input as well as being used to control the value of the damping ratio.
The board therefore finds these arguments of the respondent unconvincing.
[2.10] The board concludes that claim 1 as granted was limited in the sense that the damping ratio was variable dependent on a feedback component. As claim 1 of the main request no longer includes such a limitation, the board concludes that protection conferred by the patent has been extended, contrary to A 123(3).
[2.11] In the impugned decision, the OD relied on decisions T 190/99 and T 749/03 as well as T 108/91 and T 438/98, all of which had been cited by the patent proprietor during opposition proceedings. The [patent proprietor] referred again to these decisions in the written phase of these appeal proceedings. In the light of these decisions, the OD concurred with the view of the proprietor that, having regard to A 123(3) EPC, it was “possible to amend a granted claim to replace an inaccurate technical statement, which is evidently inconsistent with the totality of the disclosure of the patent, with an accurate statement of the technical features” [board’s note: this corresponds to the headnote of T 108/91].
The OD stated further that
“The only sensible interpretation of claims 1 and 7 [as granted] in view of the disclosure in the patent specification implies that it is the filter which is dependent on the feedback component: with such a reading, the claims are not only clear and consistent in themselves but also clear and consistent with the totality of the disclosure of the patent”.
It concluded that A 123(3) was not infringed by claim 1 of the present main request.
[2.12] As already stated, the board agrees that in the present case “a damping ratio which is variable dependent on a feedback component” has no basis in the description. However, the board has explained above […] why it is not possible to use the description to give another meaning to this feature than the one deriving from the wording used in the claim.
Moreover, the board observes that T 190/99 [2.3.4] adopts the standpoint of the earlier decision T 108/91. With regard to T 108/91, it is noted that the feature in question, the deletion of which, in that board’s view, did not contravene A 123(3), was considered to run against the implicit technical objective of the invention (cf. point [2.2]). Without going into whether this is still a valid approach in the light of the later-published decision G 1/93, the board notes that this aspect does not apply to the present case, since varying the value of the damping ratio dependent on a feedback component does not prima facie run counter to the aim of improving the flight response of the aircraft. T 749/03 also concerns a different situation to the present case in that, in the case at issue in T 749/03, certain features could only be made sense of by reference to the description and drawings (cf. point [2.2.9]). Finally, in decision T 438/98 the amendment concerned the correction of an obvious clerical error (cf. point [3.1.3]). Therefore the board disagrees with the view of the OD and the appellant as to the relevance of these decisions to the present case.
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