T 500/11 – You May Pick It

Claim 1 of the auxiliary request before the Board read:

1. Method for the production of trichlorosiliane by reaction of silicon with HCl gas at a temperature between 250° and 1100°C, and an absolute pressure of 0.5 – 30 atm in a fluidized bed reactor, in a stirred bed reactor or in a solid bed reactor, characterised in that the silicon supplied to the reactor contains between 550 and 10 000 ppm chromium. (my emphasis)

Claim 1 as granted (and of the main request) was identical, only the lower limit of the chromium content was different (50 ppm). However, the Board had found this claim to lack novelty over document D1, which disclosed a range of 5 to 200 ppm.

In what follows, the Board examines compliance of the auxiliary request with A 123(2):

[3.1] The amendment in claim 1 at issue corresponds to the restriction of the range “between 50 to 10000 ppm of chromium” by the lower end value of 550 ppm. It is uncontested that there is a literal basis for this specific value in example 3 of the patent in suit, however not in combination with the other features of amended claim 1 under dispute.

[3.2] [The opponent] argued that the amendment consisted of an inadmissible intermediate generalisation in the sense of T 962/98, because the feature 550 ppm Cr was inextricably linked to the other features of the process according to example 3 – namely the type of reactor, the pressure and temperature, the particle size and the contact time – and thus this specific value could not be arbitrarily extracted from its context. [The opponent] referred also in this respect to paragraph [0003] of the patent which disclosed that the “selectivity and reactivity will depend strongly on the process temperature when silicon and HCl is reacted”. This would make clear that the temperature was a feature which was inextricably linked to the selectivity to TCS.

[3.3] The question to be answered now is whether the feature “550 ppm Cr” is inextricably linked to the other features defined in Example 3 of the patent in suit.

The board observes in this respect that there is no doubt that not only the concentration of chromium has an influence on the selectivity of TCS but also other parameters too, such as e.g. the particle size, the pressure, the temperature, and the contact time in the reactor. All these features however are parameters which may be varied individually and each of these variations would necessarily lead to a different result on the selectivity to TCS.

If the feature “550 ppm chromium” was inextricably linked to specific other parameters of Example 3, this would mean that the selectivity to TCS would only be achieved in the definite combination of “550 ppm chromium” with the specific other parameters of example 3. This however is manifestly not the case here.

Moreover, according to paragraph [0020] of the patent in suit, the addition of chromium to silicon is described very generally as improving the selectivity to TCS in the reaction of silicon with gaseous HCl.

It follows from the above considerations that the different parameters, and in particular those in Example 4, can be varied independently one from another and that there is no reciprocal relationship, which would imply that the concentration of chromium is part of an entanglement in which a variation of the other parameters is not allowed.

[3.4] The question at issue was already addressed in several decisions, in particular in T 273/10 or T 962/98, to which the board refers in the following paragraphs.

[3.4.1] According to T 962/98 [2.5], an intermediate generalisation would be admissible if the skilled person could recognise without any doubt from the application as filed that the characteristics taken from a working example were not closely related to the other characteristics of the working example and applied directly and unambiguously to the more general context.

[3.4.2] In decision T 273/10 [14.2-3], a claim amended by inclusion of a bundle of features extracted from a specific embodiment had been found allowable because the bundle of features proposed as an amendment comprised all the features essential for the performance of the invention. Further, according to T 273/10, those features of the embodiment which did not contribute to solving the problem underlying the invention did not have to be part of the claimed subject-matter resulting from the amendment.

[3.4.3] In the case at issue, as explained in point [3.3] above the aim of the invention – namely increasing the selectivity to TCS – is merely achieved by addition of selected amounts of chromium to silicon and thus this feature is not “closely related to the other characteristics of the working example and applies directly and unambiguously to the more general context” as required in T 962/98.

[3.4.4] The present decision is also in line with decision T 273/10 since the proposed amendment comprises the feature essential for the performance of the invention, namely a certain amount of chromium, and moreover those features of the embodiment which do not contribute to solve the problem underlying the invention are not part of the claimed subject-matter resulting from the amendment.

[3.5] It follows from the above considerations that the gain of selectivity is solely due to the presence of chromium in the silicon feedstock, and that the picking out of the value 550 ppm from the working example 3 is therefore plainly acceptable in the case at issue, with the consequence that claim 1 of this request meets the requirements of A 123(2).

Dependent claims 2 to 6, which have a basis in the corresponding dependent claims 2 to 6 of the application as filed, also meet the requirements of A 123(2).

I for one am not very comfortable with the fact that isolated values taken from examples may become boundaries of claimed ranges, which I consider to be a completely new teaching, but there seems to be some consensus that this is alright.

Should you wish to download the whole decision, just click here.

The file wrapper can be found here.