T 354/04 – Beware of Incomplete Standards

Claim 1 of the [new main] request read:

1. Use of a melt composition to make man-made vitreous fibres which are shown to be biodegradable in the lung wherein the composition has an analysis, measured as weight of oxides, which includes

Si02: 32 to below 45%

[…]

Other Elements 0 to 8%,

and wherein […] the composition has a melt viscosity at 1400°C of 10 to 70 poise, calculated according to Bottinga and Weill, American Journal of Science volume 272, May 1972, page 455-475 […] 

[…] Claim 1 is silent about the nature of the “other elements”. Only the description of the patent in suit contains a non-exhaustive list of “other elements” that “can be present in the composition in any amount that does not detract from the desired properties and which does not exceed 8%”: P2O5, B2O3, BaO, ZrO2, MnO, ZnO and V2O5 are specifically mentioned. With regard to the amounts of these “other elements”, it is indicated in the description that “each of the other elements is normally present in an amount of not more than 2%, except that P2O5 and/or B2O3 may be present in larger amounts”. Moreover, it is expressly mentioned that that “preferably, there is 1 to 8% ... P2O5 and 0 to 5% B2O3”. [6.2]

Claim 1 is restricted to the use of those melt compositions […] which meet the requirement of a melt viscosity value falling within the recited numerical range, the value to be considered being the viscosity value calculated according to the BW model described in [document] C28. [6.3]

[…] The question that must be answered in the first place is […] whether the person skilled in the art, considering the contents of the patent in suit and of C28, as well as common general knowledge on the filing date of the patent in suit, was actually in a position to calculate the viscosities of melt compositions having analyses throughout the ranges indicated in claim 1. [7.8]

[…] C28 describes a model for predicting instead of measuring the viscosities of multi-component silicate melts. At first glance C28, which is praised as the authoritative reference in viscosity calculations, appears to describe a simple calculation of the viscosity of multi-component melts requiring not much more than filling in available data in the formula (1):

wherein η is the viscosity, Xi is the mole fraction of the i-th component, Di is a constant associated with component i over a restricted range (in terms of mole percent SiO2) of composition, and each temperature has a particular set of Di constants.

When trying to apply the calculation model of C28 to the compositions embraced by the compositional ranges in claim 1, the skilled person is however confronted with difficulties due to a lack of data and to gaps in the information provided in C28. The teaching in C28 is incomplete insofar as the BW model as set out therein is not fully applicable to all the compositions as defined in present claim 1. [8]

[The compositional ranges in claim 1 include, inter alia, compositions comprising relatively high amounts of ZrO2 or P2O5.] As far as ZrO2 and P2O5 are concerned, C28 does not report any of the Di values needed for the calculation. The straightforward viscosity calculation according to formula (1) of C28 is thus not possible for the compositions comprising up to 8 weight % ZrO2 or P2O5. [8.1]

The authors of C28 indicate that in some cases, estimated or approximated Di values of certain components may be used in the calculation when the required Di values are not tabulated. However, C28 contains no guidance whatsoever having regard to approximations or estimations that could be applied in the case where a composition contains ZrO2 in more than just a negligible amount, let alone in a higher amount of up to 8% by weight. [8.2]

[...] C28 does not contain theoretical considerations which could be considered as a basis for enabling the skilled person to make appropriate, scientifically sound estimations of the Di values for ZrO2 and for P2O5 in amounts of up to 8 % by weight. [9.3]

To fill these gaps in C28, the skilled person could only speculate about appropriate estimations based on considerations not addressed in C28, and the viscosity calculated would thus depend on speculative Di values. In other words, depending on the specific underlying assumptions adopted by the skilled person, the estimations would not in any case give the same result. Under these circumstances, for the board, the skilled person would have to grope in the dark because he is not in a position to calculate the viscosity of these compositions as required by claim 1, i.e. based on the information comprised in C28, the patent and common general knowledge alone. [10.2]

In order to be able to calculate viscosity values according to the model of C28 for the compositions referred to under point 6.2.5, the skilled person would thus first have to investigate experimentally the quantitative impact of specific components such as ZrO2 and P2O5 on the viscosity of multi-component silicate melts in the SiO2 mole fraction range(s) concerned. The investigations necessary for obtaining the correct Di values or for checking the validity of an approximation not disclosed in C28 involve high temperature melt viscosity measurements, the evaluation of the data and cross-checking how they fit with the BW model. [11.3]

Neither the patent in suit nor C28 contain more specific instructions on how viscosity measurements and evaluations required for determining the results to be used in the BW model for P2O5 or ZrO2 in compositions as defined in claim 1 could be carried out. Moreover, a calibration of the measured data against C28 or patent data is not possible since these two documents do not contain examples of compositions comprising ZrO2 or P2O5 in amounts of up to 8 % by weight. The skilled person is thus forced to develop its own research program. For the board, there are however limitations to what can be expected from the skilled person. [11.6]

The board thus concludes that the experimental and evaluative work required from the skilled person represents an undue amount of experimentation in the sense of decision T 435/91. The skilled person would actually be forced to generate all necessary data in order to be in a position to calculate the viscosities of melt compositions having analyses throughout the full ranges indicated in claim 1. This undue amount of experimentation requires more than routine means and manipulations and requires more than merely common general knowledge. The skilled person cannot be expected to embark on the scientific research programme required for testing the validity of given approximations and/or for finding the correct Di values for the calculation of the parameter value which is needed for identifying those amongst the compositions falling within the compositional ranges of claim 1 which are actually the ones to be used according to the invention. Or, in other words, it is not up to the skilled person to overcome the limitations of the patent in suit and fill gaps left by the patentee in the information. [11.8]

The patent does not disclose the invention as claimed in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art (A 100(b)). [13]

Consequently, the main request cannot be allowed. [14] 

The moral of this story: When you have to refer to a standard for defining the way in which some claimed parameters are determined, do not forget to check that the standard is applicable in a straightforward manner to all embodiments that are covered by the claim.

To read the whole decision, click here.