Ladas & Parry Guide to European Patent Office Practice

7. Claims to Priority

Any claim to priority and the country in which the priority-founding application was filed must be stated at the time of filing the application. [81] Multiple priority claims are permitted and a single claim may have more than one priority date. [82]

7.1 Validly claimed convention priority

In the summer of 1994, the Enlarged Board of Appeal made it clear that, for claims not entitled to the earliest claimed priority date, any publication of the subject matter of the earliest filed convention application that occurred before the priority date of the claim was citable against it, notwithstanding the fact that priority was claimed.[83] There are difficulties in reconciling this decision with both the provision of the EPC that a claim can have more than one priority date, and with Article 4B of the Paris Convention.[84] In the example given in the opinion, it was made clear that the claim that was held to be subject to attack was directed to a "different invention" from that disclosed in the application from which priority was claimed. So far as the Paris Convention was concerned, it was asserted that it is generally agreed that Article 4B applies only if the claim in question is to the same invention as that of the priority document. The effect of this decision is that unless the European application is identical with an application from which priority is claimed, there may be danger in permitting the publication of the contents of the basic application during the convention year between filing the original application and filing in the EPO.

The question of what is a validly claimed convention priority came up in Preprogenia/Collaborative. [85] It was held that for priority to be established, "the subject matter of the claims of the European application must be clearly identifiable in the documents of the previous application as a whole. Identical wording is not required. However, if any essential element of the invention for which a European patent is sought is missing, there is no right to priority." The Board agreed that in some cases features might be implied, so long as the implication was "direct and unambiguous," but matter that was omitted, and only recognized as being essential later, could not be implied as being present.

In Hepatitis B/Biogen a claim to a recombinant DNA molecule capable of coding for a particular protein was found to be supported by a priority document notwithstanding the fact that the priority document lacked any data on production of the protein in question.[86] The English Court of Appeal reached an exactly contrary decision on the same patent in Biogen v. Medeva. [87] The EPO agreed, however, that a claim to a specific amino acid sequence is not supported by a priority document in which a sequence was given but differed in three amino acids out of a total of 527, even though following the teaching given the desired product could have been obtained. In the Board's view, the structure set out in the claim was part of its essential technical content and since this was not present in the priority document, priority could not validly be claimed from such document. [88]

In Snack Food/Howard, [89] the question arose as to whether priority could properly be claimed when the invention as claimed was more limited than the disclosure of the priority document. The claims of the European application required at least 5% oil or fat. The priority document made no specific mention of a 5% fat limit, although mention was made of the amount of fat being less than 20%, for example 8 to 20%. The Appeal Board concluded that from the technical point of view the limitation of the amount of fat was not an essential part of the invention. In its view the invention in fact related to the use of bran in the product. The invention, "is not concerned with the inclusion of oil or fat in the product at all." In light of this, the Appeal Board concluded that the claims were properly entitled to convention priority, although specific features of the claim found no exact support in the priority document. The Board noted that:

...in general the mere addition of a technical feature to a claim will always limit the extension of protection and may or may not change the nature of the claimed invention. This is entirely a question of fact in each case and depends upon the relationship of the additional technical feature to the previous technical features of the claim.

Similarly in Waste Compactor/Justamente[90] the Board observed that:

It is necessary to give some flexibility to the requirement of identity of invention between the two applications. ... Consequently some features claimed in the European application need not be explicitly mentioned in the previous application whose priority is claimed , provided that the skilled person is able, purely on the basis of his knowledge or by performing simple operations to carry out the invention, to infer these features from the prior application. [91]

This approach is, however, a two-edged sword, as was shown by the case of Air Products and Chemicals/Priority. [92] In this case there had been an initial United States application filed more than 12 months before the filing of a European application. Subsequently, a second United States application was for limited protection within the disclosure of the initial U.S. application. A European application was also filed within one year of the filing of the second U.S. application, which claimed priority therefrom. The EPO Board of Appeals likened the limitation effected in the second U.S. application over the first to a disclaimer. On this basis, it concluded that because priority could have been claimed from the first U.S. application, but was not, no valid claim could be made to priority from the second U.S. application, which was not "the first application for protection of the same invention," as is required by the Paris Convention. The Board noted that a different conclusion would have been reached had the first U.S. application been abandoned with no rights outstanding. This was not, however, the factual situation in the present case.