This chapter deals with double patenting arising from the filing of a divisional application; for double patenting arising from internal priority see T 1423/07.
The principle of the prohibition of double patenting is based on the idea that the applicant has no legitimate interest in proceedings that give rise to the grant of a second patent in respect of the same subject-matter for which he already holds a patent. There is therefore nothing objectionable in the established EPO practice that amendments to divisional applications are objected to and refused, when the same subject-matter is claimed in the amended divisional application as in a pending parent application or a granted parent patent. However, this principle could not be applied with a view to preventing the filing of identical applications, because that would infringe the prevailing principle that an assessment of the EPC requirements is made on the basis of the final version put forward (G 1/05 and G 1/06, OJ 2008, 271 and 307, point 13.4 of the Reasons).
In T 118/91 and T 80/98, care was taken to avoid any risk of double patenting by ensuring that the subject-matter of the divisional application differed from that of the parent application. In T 118/91, in particular, the board stated that it could find nothing to support the contention that features forming part of the subject-matter of the divisional application could not be the subject of a dependent claim in the parent application. The board agreed with the Guidelines that, as a general rule, one application may claim its own subject-matter in combination with that of the other application. This approach does not lead to "double patenting" in its normal sense. In this particular case, the board was satisfied that any danger of "double patenting" had been eliminated by extensive restriction of the claims in the divisional application.
In T 58/86 it was decided that the independent claims in a divisional application impermissibly exceeded the disclosed content of the original application, an essential feature of the relevant subject-matter of the original application being omitted in each of them. Reinstating this feature would have resulted in subject-matter that was already protected in the original application.
In T 587/98 (OJ 2000, 497) the examining division, relying on the Guidelines prohibiting "conflicting" claims, had refused a European patent application, filed as a divisional application, on the grounds that its subject-matter overlapped with that of the parent application and that in the overlapping region the same subject-matter was claimed; as legal basis for the refusal it invoked Art. 125 EPC. The board held that Art. 125 EPC was not applicable to the case at issue since this article required "the absence of procedural provisions in the Convention" but the provisions governing divisional applications were self-contained and complete. In addition a prohibition of "conflicting" claims in the wide sense applied by the examining division would be a matter of substantive law rather than a matter of procedure - and Art. 125 EPC was not applicable to substantive law. The board also found that there was no express or implicit provision in the EPC which prohibited the presence in a divisional application of an independent claim - explicitly or as a notional claim arrived at by partitioning of an actual claim into notional claims reciting explicit alternatives - which was related to an independent claim in the parent application (or patent, if it had already been granted) in such a way that the "parent" claim included all the features of the "divisional" claim combined with an additional feature.
In T 307/03 (OJ 2009, 422) the board understood T 587/98 to have found that there was no basis in the EPC prohibiting "conflicting claims" within the meaning of the guidelines; it could not follow T 587/98 on this point. The board in T 307/03 relied on Art. 60 EPC 1973, concerning the fundamental right to a patent, to deduce the principle of the prohibition of double patenting, and did not seek to import a principle of procedural law solely under Art. 125 EPC 1973. The board emphasised that the principle of the prohibition of double patenting, namely that the inventor (or his successor in title) has a right to the grant of one and only one patent from the EPO for a particular invention as defined in a particular claim, can be deduced from Art. 60 EPC 1973. Once a patent had been granted, this right to a patent had been exhausted and the EPO was entitled to refuse to grant a further patent to the inventor or his successor in title for the subject-matter for which he had already been granted a patent. Furthermore, a double patenting objection can also be raised where the subject-matter of the granted claim is encompassed by the subject-matter of the claim later put forward, that is where the applicant is seeking to re-patent the subject-matter of the already granted patent claim, and in addition to obtain patent protection for the other subject-matter not claimed in the already granted patent. In particular, where the subject-matter which would be double patented is the preferred way of carrying out the invention both of the granted patent and of the pending application under consideration, the extent of double patenting cannot be ignored as de minimis. To avoid the objection of double patenting the claims of the pending application should be confined to other subject-matter that is not already patented, to allow the examination procedure to focus on whether a claim to this other subject-matter meets the requirements of the EPC.
According to the board in T 1423/07, Art. 60 EPC provides no basis for refusing a European application for double patenting. The purpose of Art. 60 EPC is only to define to whom the right to a European patent belongs. Art. 60 EPC could not be interpreted such that the inventor or his successor in title had a right to the grant of one and only one patent from the EPO for a particular invention, with the consequence that claims comprising subject-matter included in the claims of an already granted patent of the same applicant were refused no matter whether or not the applicant had a legitimate interest in the grant of the subsequent application.
In T 1391/07, the board noted that the practice of prohibition of "double patenting" was confined to patents and applications relating to the same invention as defined by the subject-matter of the corresponding claims and therefore confined to claims conferring notionally the same scope of protection. It saw no basis for extending this practice to cover claims not defining the same subject-matter but conferring - as in the case before it - a scope of protection overlapping with each other only partially in the sense that some, but not all of the embodiments notionally encompassed by one of the claims would also be encompassed by the other one of the claims. In particular, the lack of legitimate interest of an applicant in obtaining two patents for the same subject-matter - as invoked by the Enlarged Board of Appeal in decisions G 1/05 and G 1/06 (see above) - cannot be invoked when the scopes of protection conferred by the respective subject-matters overlap only partially with each other as there is no manifest objective reason to deny the legitimate interest of the applicant in obtaining a protection different from - although partially overlapping with - that of the parent patent already granted. Accordingly, the board concluded that the mere fact that the scope of protection notionally conferred by the claim in suit would partially overlap with that of the granted parent patent did not prejudice the grant of a patent (see also T 877/06, T 1491/06).
According to the board in T 936/04, "double patenting" is not a ground of opposition. It is, however, within the discretion of the departments of the EPO to raise the objection in opposition or opposition appeal proceedings against proposed amended claims, but this should be done only in clear cases. The purpose behind the principle of the prohibition of double patenting is to avoid unnecessary duplication of effort, and not to impose on the departments of the EPO an obligation to make a complex comparison between the case before them and the claims that may have been granted in some other proceedings. In the case at issue, at the time of the decision by the opposition division, a patent had not yet been granted on the divisional application. For this reason alone the opposition division was correct to disregard the objections of double patenting raised before it. At that stage it would only be a matter for the Examining Division, in the proceedings on the divisional application before it, to avoid double patenting by again allowing claims already granted in the parent patent.
In T 1708/06 the board held that, notwithstanding the question of whether the principle of the prohibition on double patenting applied under the EPC, the two applications did not relate to the same invention and so the issue of "double patenting" did not arise.
In T 2402/10 the respondent raised an objection of double patenting, since claim 1 had been amended during the opposition/appeal proceedings in such a manner that its scope fully encompassed the scope of the claims of the patent granted from the grand parent application. The board recalled the well-established case law that a principle of prohibition of double patenting existed on the basis that an applicant had no legitimate interest in proceedings leading to the grant of a second patent for the "same subject-matter" (G 1/05, OJ 2008, 271; G 1/06, OJ 2008, 307; see also T 1391/07, T 877/06, T 1708/06, T 469/03). In the case at issue, claim 1 contained technical features not required by any claim of the patent granted from the grant parent application. Since the patent granted from the grant parent application and the patent in suit claimed different subject-matter, the question of double patenting could not arise. The board noted that the respondent also referred to the headnote of T 307/03, according to which a double patenting objection could also be raised where subject-matter of the granted claim was encompassed by the subject-matter of the claim later put forward. The board, however, saw this as no reason to depart from the mandatory requirement of "same subject-matter" invoked in decisions G 1/05 and G 1/06 and in the established case law.