If amended claims are directed to subject-matter which has not been searched (e.g. because it only appeared in the description and the Search Division did not find it appropriate to extend the search to this subject-matter, see B-III, 3.5) and which does not combine with the originally claimed and searched invention or group of inventions to form a single general inventive concept, such amendments are not admissible.
In practice, within the framework of Art. 123(2) and Art. 82, Rule 137(5) should be construed as permitting any limitation of searched subject-matter which is unitary with the originally claimed subject-matter, irrespective of whether the technical feature(s) used for the limitation has/have been searched.
Thus, the addition to a claim of a technical feature which makes a contribution to the effect(s) of the originally claimed invention(s) and which was expressly not searched but was disclosed in the context of the invention in the application as filed (usually in the description) will not result in an amended claim lacking a single general inventive concept with respect to the originally claimed invention(s). Consequently no objection under Rule 137(5) should be raised in these circumstances, even though an additional search may be required.
However, where features taken from the description and pertaining to a different inventive concept than the original claim are added to the claim, an objection under Rule 137(5) may be raised. It may occur that the description of the application contains a further general inventive concept, distinct from that underlying the main claim and its dependent claims, if any, but not clearly identified or declared as such in the description. In such a case, if the subject-matter of the main claim based on the first inventive concept is amended, any amendment of the claim pertaining exclusively to said further inventive concept could justify an objection of lack of unity "a posteriori" (see T 1394/04).
Therefore, an objection under Rule 137(5) will normally arise if the applicant attempts to replace a technical feature contained in a claim with a different technical feature taken from the description.
Similarly to this case, but in contrast to the situation discussed above (where the added technical feature makes a contribution to the effect(s) of the originally claimed invention(s)), an objection under Rule 137(5) would also arise if a technical feature taken from the description which has an effect unrelated to the effect(s) of the originally claimed invention(s) were added to a claim, except where the amendment does not result in a change in the general inventive concept. Such a situation could arise for instance if the original claims included a broad claim, the subject-matter of which was not new or did not involve an inventive step, but also included other claims defining one or more inventions, and a technical feature from the description which had an effect not mentioned in the original claims was added to that broad claim, such that there is lack of unity between the new limited claim and the claims originally present.
If an objection under Rule 137(5) is to be raised, the applicant should be informed that he may continue to pursue such subject-matter only in the form of a divisional application under Art. 76, provided that at least one of the periods provided for in Rule 36(1)(a) and Rule 36(1)(b) has not yet expired (see A-IV, 1.1.1, A-IV, 184.108.40.206 and A-IV, 220.127.116.11).
If a communication from the Examining Division does not raise an objection as to lack of unity under Art. 82, but rather raises an objection as to the admissibility of an amendment according to Rule 137(5), this does not cause the period for the filing of a divisional application according to Rule 36(1)(b) to start, or to start again if a unity objection has been raised before in examination proceedings (see A-IV, 18.104.22.168). Consequently, in such a case, if the period provided for in Rule 36(1)(a) has already expired and, if a unity objection has been raised before in examination proceedings, the period provided for under Rule 36(1)(b) has also expired, it will not be possible for the applicant to file a divisional application. If no such objection under Rule 137(5) is raised, the Examining Division should consider performing an additional search (see C-IV, 7.2).