Art. 123(3) EPC is directly aimed at protecting the interests of third parties by prohibiting any broadening of the claims of a granted patent, even if there should be a basis for such broadening in the application as filed (G 1/93, OJ 1994, 541). In accordance with the general intention of Art. 123(3) EPC, there should be legal certainty for the activities of third parties trusting that the protection conferred by a patent can only be restricted, but not extended (T 1149/97).
The object of Art. 123(3) EPC is to prevent any procedural situation where an act which does not infringe the patent as granted becomes an infringing act as a result of an amendment after grant (see T 1149/97, T 1898/07 referring to T 59/87 date: 1988-04-26, OJ 1988, 347 and T 604/01).