Unity of Invention

Unity of invention is a requirement in international patent applications under the Patent Cooperation Treaty (PCT) and in most national/regional patent systems outside the United States. Under PCT Rule 13, an international application must relate to 'one invention only or to a group of inventions so linked as to form a single general inventive concept.' The single inventive concept is the technical feature (or combination of features) that defines the contribution over the prior art. If claims are not all linked by a single inventive concept, the application lacks unity of invention — and the International Searching Authority (ISA) or International Preliminary Examining Authority (IPEA) will search only one of the claimed inventions (applicant's choice or default to first).

Unity analysis under PCT Rule 13 involves: (1) Identify the 'special technical features' — the technical features that make a contribution over the prior art; (2) Determine whether those special technical features are the same across all claimed inventions; if yes, unity exists; if no, there are distinct inventive concepts and unity is lacking. The analysis proceeds claim-by-claim: if independent claims 1 and 5 each require the same novel technical feature (e.g., a specific catalyst), they share a single inventive concept even if they cover different products. But if claim 1's novel feature is A and claim 5's novel feature is B (a completely different advance), they lack unity unless A and B are both necessary to define a single broader inventive concept.

When the ISA determines a PCT application lacks unity, it: (1) Searches only claims belonging to the first inventive concept (or the concept the applicant pays additional search fees for); (2) Issues a lack of unity objection in the International Search Report (ISR) or Written Opinion; (3) Invites the applicant to pay additional search fees for each additional invention (protest procedure available if applicant disagrees). Options for applicant: (a) Pay additional fees to search all inventions and decide later which to pursue in each country; (b) Accept the search as is and file divisional applications in each national/regional phase for the non-searched claims; (c) Protest the lack-of-unity decision (ISA Director reviews; fees refunded if protest upheld). In national phase, lack of unity objection is addressed under each country's rules — some countries require divisionals, others allow more claims to be examined.

UNITY OF INVENTION (PCT/EPO/most countries): focuses on whether all claims share a single inventive concept — the novel technical contribution. Claims pass unity if they all depend on the same inventive concept, even if they cover different categories (product, process, use). The inventive concept test is the link. U.S. RESTRICTION REQUIREMENT (35 U.S.C. § 121): the USPTO can require the applicant to elect one of several distinct and independent inventions for prosecution in one application. U.S. restriction is broader — it can require restriction between species of a genus, between a product and its manufacture process, or between a device and its use, even when they share an inventive concept. The two tests are similar but not identical: a unity objection in EPO is not automatically a restriction requirement in the U.S., and vice versa. In U.S. divisional practice, a divisional filed to avoid restriction in the U.S. gives the patent owner two patents on the same overall disclosure.

In PCT practice, claims to a product AND a method of using that product CAN satisfy unity of invention if there is a technically novel product that defines the inventive concept, and the method of use is dependent on that novel product. Example: a new chemical compound (novel) + a method of treating disease using that compound — unity is typically present because the single inventive concept (the novel compound) links both claims. But: if the product is known prior art and only the method is novel, unity may be lacking between the product and method claims because the product itself is not the novel contribution. The USPTO's restriction practice is more likely to require restriction between product and method even when EPO/PCT would find unity.