It is settled case law that the admissibility of amendments depends, among other things, on whether the amended claims converge with or diverge from the subjectmatter previously claimed, i.e. whether they develop and increasingly limit the subject-matter of the independent claim of a main request in the same direction and/or in the direction of a single inventive idea, or whether they entail different lines of development because, for instance, they each incorporate different features (T 240/04, T 1685/07, T 980/08, T 1589/08, T 1690/08, T 1969/08, T 162/09).
In T 1685/07, the auxiliary requests, which had not been filed until after the summons to oral proceedings, said completely different things. The board ruled that, when deciding whether to admit new requests first introduced during the appeal proceedings, it was particularly important to ascertain whether the applicant or patent proprietor submitting more than one request was following a consistent line of defence in its various requests and not, particularly towards the end of the proceedings, using a "screen" of different versions of claims to create, for both the other party and the board of appeal, an obscure and unacceptable procedural situation in which they were obliged to select from a multiplicity of varying versions the one which could in the final analysis be valid.
In T 1750/08 the board admitted the auxiliary request because the amendment as a further limitation of a feature that underlaid the opposition division's decision to maintain the patent in amended form and that was already central to the discussions in the appeal (converging request).