Within the framework of Art. 123(2) and Art. 82, Rule 137(5), first sentence, 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 further defines an element that was already a feature of the original main claim or makes a contribution to the effect(s) of the features 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), first sentence, should be raised in these circumstances, even though an additional search may be required (see C‑IV, 7.3).
If amended claims are directed to subject-matter which has not been searched 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 allowable.
In other words, in order to assess whether or not amended claims fulfil the requirements of Rule 137(5), first sentence, the examining division needs to establish first whether or not the subject-matter to which they relate has or should have been searched (see B‑III, 3.5) and second whether or not an objection of lack of unity would have been raised if the amended claims had been present in the set of claims on file at the time of the search.
As a consequence, an objection under Rule 137(5), first sentence, will normally arise if the applicant attempts to replace a technical feature contained in a claim with a technical feature taken from the description and having an effect unrelated to the effect(s) of the features of the originally claimed invention(s).
The situation described above is different from amendments corresponding to an invention originally claimed but not searched under Rule 64, or Rule 164(1) or Rule 164(2), which are dealt with in H‑II, 6.2.
Rule 137(5), first sentence