CABINET CHAILLOT

T0063/22 – sufficiency of disclosure and correction of error

Art. 83 EPC, Rule 139 EPC, T 380/05, G 1/03, sufficiency of disclosure, correction of error

The appeal lies from the opposition division's decision to revoke the patent because the underlying invention was not sufficiently disclosed.
The subject-matter of claim 5 contains the following method step:
"a casting step for casting a molten metal of the aluminum alloy in which 1000 <= t/L <= 4000 is satisfied, where t is the thickness of an ingot (mm) and L is an amount of cooling water per unit time and unit ingot length (liter[sic]/minute·mm)"
The significance of the feature "unit ingot length" is disputed (the "disputed feature").
Method claim 5 is dependent on product claim 1. Product claim 1 requires the superplastic-forming aluminium alloy plate to have intermetallic compounds with an equivalent circle diameter of 5 to 15 µm, in a density of 50 to 400 pieces/mm**(2), a feature further referred to as the claimed particle density.
The claimed particle density is achieved by adjusting the process so as to fulfill the condition 1000<=t/L<=4000. If the parameter t/L is outside of this range, the claimed particle density is not achieved.
Use of the correct parameter t/L is therefore essential for achieving the claimed particle density, which in turn is responsible for the advantageous surface properties after forming and the superplastic-forming properties of the product as claimed. If the claimed particle density is not achieved, the macroscopic effects the patent aims to achieve cannot be obtained. An unclear definition of this parameter amounts in the present case to a lack of sufficient disclosure (in accordance with T 380/05, with reference to G 1/03).
The only sentence in paragraph [0033] which uses the disputed feature reads:
"In the invention, the indicator of the cooling rate represented by t/L is 1000<=t/L<=4000, preferably 3000<=t/L<=4000, where t is the thickness of the ingot produced (mm) and L is the amount of cooling water per unit time and per unit length of ingot thickness (unit ingot length) (liter[sic]/minute·mm)."
The skilled person is thus taught that the feature unit ingot length is identical to the feature unit length of ingot thickness.
The skilled person would at most recognise an unfortunate choice of wording but they would not realise that there was a need for a different interpretation or correction.
It is not accepted that the feature unit length of ingot thickness actually referred to the ingot circumference, as alleged by the appellant. There is no basis in the patent in suit for completely changing the meaning of this term, e.g. by deleting the word "thickness" and purposively interpreting the remaining part as referring to the ingot circumference.
The requirements of Rule 139 EPC are also not fulfilled because it is not apparent that nothing else could have been intended, nor what could have been intended instead.
The appellant alleges to have made an invention. They use the parameter t/L to describe the invention. This parameter is an unusual parameter.
It is not apparent from the patent in suit that this unusual parameter is derived from parameters t and L found in the prior art, as alleged by the appellant. The patent in suit provides a definition for both t and L. There is nothing to prompt the skilled person to find an alternative definition in the prior art.
It is precisely in the case of claimed subject-matter relying on a newly formulated and, hence, unfamiliar parameter to define the solution of a technical problem by which a relevant effect is achieved, that the applicant or patentee, who has the duty of making a full and fair disclosure of his invention to the public (Article 83 EPC), is under a particular obligation to disclose all the information necessary to define the new parameter not only (i) in a formally correct and complete manner such that its values can be obtained by a person skilled in the art without undue burden, but also (ii) in a manner which reliably retains the validity of the parameter for the solution of the technical problem for the application or patent in suit as a whole in the sense that the values routinely obtained will not be such that the claimed subject-matter covers variants incapable of providing the relevant effect or, therefore, of solving the associated technical problem.
If, for a specific geometry of the casting equipment and a specific amount of cooling water per minute, the parameter L is calculated with the ingot thickness instead of the ingot circumference, the numerical result for L is higher by the quotient of the circumference and the thickness. In order to meet the condition 1000<=t/L<=4000, the flaw in the calculation of L must be offset. This can be done by reducing the amount of cooling water per minute by this factor, to only a fraction of the amount required to provide the claimed particle density. The desired effect concerning particle density and, as a consequence, the impact on the surface properties will, however, not be achieved.
Identifying the correct cooling conditions in order to obtain the required properties amounts to a major research project.
The appeal is dismissed.

 

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