T 0089/06 16-02-2007

1. The patent relates to equipment to enable a vessel to act effectively as an offshore oil or gas production platform. Production risers extend from wells on the sea bed and are connected to tubes which pass upwards through a turret mounted on the vessel. In order to permit the vessel to turn to face into the wind direction (cf. "weathervaning" in the claims) whilst the risers remain stationary the turret is rotatably mounted on the vessel by means of a bearing. Larger numbers of risers potentially require larger diameter turrets to accommodate the corresponding tubes, which would result in larger bearings and less storage space on the vessel. The present patent aims to permit a larger number of tubes to be accommodated without increasing the size of the bearing. The independent claims relate to two aspects which permit improved access to the respective ends of the tubes by providing more space. Claim 1 concerns the size of the lower imaginary circle on which the lower ends of the tubes lie and claim 10 (as granted) concerns vertical spacing of the upper ends of the tubes. The single disclosed embodiment includes both aspects.

Formal admissibility of the requests

Main request

2. Claim 1 according to this request, claim 1 as granted, differs essentially from the claim on which it is based, claim 1 as originally filed, by inter alia deletion of the requirement that the upper ends of the tubes are "at least about as high as said bearing".

2.1 As set out in the original application, the problem relates to accommodating additional tubes within the turret without increasing the size of the bearing and therefore the space through which the tubes can pass. Claim 1 as originally filed contained features concerning the first aspect of the solution to this problem, cf. 1 above, and specified that the upper ends of the tubes were at least about as high as the bearing. This was clearly a limitation wholly consistent with the disclosed problem since the size of the bearing would only restrict the space available to accommodate tubes which reach to a height at which the size of the bearing limits the space available.

2.2 The patent proprietor argues that in the single embodiment the lower ends of one group of tubes 62 are on an imaginary circle larger than the inner diameter of the bearing although their upper ends do not reach as high as the bearing and that this provides a basis for deleting the feature from the claim. This line of argument overlooks the fact that, as explained in more detail in point 7.1 below, the original application is directed to two related but nevertheless distinct ideas, concerned with working space requirements around the lower ends and the upper ends of the tubes respectively. It is only the second of these ideas which specifically requires the division of the tubes into groups the upper ends of which terminate at different heights (see original independent claims 5, 8 and 10). The first idea on the other hand can be implemented with a single group of tubes and where that is the case it is apparent that the location of the upper ends of the tubes must then be such that their radial positioning is restrained by the size of the bearing. Otherwise the requirement of present claim 1 that the diameter of the imaginary circle on which the lower ends of the tube are located is larger than the inner diameter of the bearing becomes devoid of any genuine technical significance.

2.3 The patent proprietor further argues that the deleted feature is implicitly contained in present claim 1 in as far as it specifies that the tubes extend between the turret upper and lower portions lying respectively above and below the sea surface. The board cannot agree because there is no clear definition of the upper and lower portions of the turret relative to the height of the bearing.

2.4 The absence from claim 1 according to the present request of the feature that the upper ends of the tubes are "at least about as high as said bearing" therefore extends the subject-matter of the patent beyond the content of the application as originally filed (Article 100(c) EPC) and the request fails.

First auxiliary request

3. In claim 1 also according to this request the feature that the upper ends of the tubes are "at least about as high as said bearing" is absent. This request therefore fails for the same reasons as the main request.

Second auxiliary request

4. Claim 1 according to this request has been amended to include the feature whose absence led to the failure of the main and first auxiliary requests, cf. 2 above. However, it differs from claim 1 as originally filed in as far as the feature that the diameter of the imaginary upper circle is no greater than the bearing inside diameter has been replaced by the feature that the diameter of the imaginary upper circle is smaller than the imaginary lower circle diameter.

4.1 Present claim 1 specifies that the group of tubes each inclines at a plurality of degrees so higher locations along the tubes lie closer to the central axis of the turret. It automatically follows from this that the diameter of the upper imaginary circle must be smaller than that of the lower imaginary circle. The introduced feature therefore is tautologous but does not in itself lead to objection under Article 100(c) EPC. However, as a result of the deletion of the feature that the diameter of the upper imaginary circle is no greater than the bearing inside diameter, the possibility is introduced that the tubes do not pass through the bearing. Such a possibility is contrary to the concept according to the invention of accommodating more tubes without increasing the diameter of the bearing, cf. 1 above.

4.2 It follows from the foregoing that the opposition ground according to Article 100(c) EPC is valid in respect of claim 1 according to this request which therefore fails.

Third auxiliary request

5. Claim 1 according to this request specifies that the tubes are "substantially straight". The term 'substantially' is commonly used in patents in order to denote that the property to which this refers is to be considered as present but subject to normal deviations. Indeed, it is used in this way in present claim 1 which specifies that the turret is supported for rotation about an axis which is "substantially vertical". However, the term has no universally accepted meaning and its influence on the clarity of a claim must be considered on the facts of the particular case. The present description paragraph [0018] states in respect of the single embodiment that the tubes are "preferably substantially straight in that the top and bottom of each tube preferably extend within 15º of each other and more preferably within 10º of each other". It is thus evident that the term "substantially straight" is defined in the description of the patent specification in a manner which is not consistent with the way it would normally be understood in the context of a claim. Indeed, the term "substantially" has two different meanings within the one claim. This leads to an unacceptable lack of clarity in the definition of the matter for which protection is sought. Furthermore is to be noted that the claim also specifies that the tubes are inclined to the axis at "a plurality of degrees" which in the embodiment is 7º, 9º or 11º depending on the group. However, if each "substantially straight" tube may exhibit a 15º angular misalignment a nominal inclination of from 7º to 11º would result in a tube which in fact at least partly upwardly deviates away from the central axis, in contradiction to the requirement in the claim that the inward inclination results in higher locations along the tubes lying closer to the axis. It follows that the introduction into the claim of the term "substantially straight" renders the claim unclear (Article 84 EPC), for which reason the request fails.

Fourth auxiliary request

6. All of the objections which led to the failures of the earlier requests are overcome by the amendments made in claim 1 according to this request. Nevertheless, one objection by the opponents remains, that the term "about" which has been introduced into claim 1 results in a lack of clarity (Article 84 EPC).

6.1 As set out above, the problem addressed by the patent is to permit an increase in the number of tubes which can be accommodated in a turret without increasing the size of the bearing. Accordingly, present claim 1 specifies that the tubes have upper ends lying at least about as high as the bearing. It is clear to the skilled person that the solution taught by the patent is applicable to tubes which extend not just to the height of the immediate proximity of the bearing but also ones which have their upper ends at a somewhat lower height at which the size of the bearing still acts as a significant restriction. It is this which is reflected in the word "about" which therefore does not cause any lack of clarity.

6.2 In the light of the foregoing the board finds that claim 1 according to the fourth auxiliary request is formally admissible. No formal objections were raised by the opponents against present claim 8 or any of the dependent claims. The claims according to this request therefore form the basis of the further considerations set out below.

Sufficiency of disclosure - Article 100(b) EPC

7. The patent contains two independent claims, an apparatus claim 1 which relates generally to the arrangement of the lower ends of the tubes relative to the turret and claim 8 (according to the fourth auxiliary request which forms the basis of the present consideration, see 6.2 above), a method claim which relates generally to the arrangement of the upper ends of the tubes relative to the turret. A single embodiment is described which contains both of the arrangements. The opponents do not dispute that the disclosure of the patent is sufficient for the skilled person to put into effect the subject-matter of each of the independent claims either individually or in combination. However, they argue with reference to decisions T 5/99, T 632/01 (both not published in OJ EPO) and T 409/91 (OJ EPO 1994, 653) that the requirement of sufficiency of disclosure is satisfied only if the problem is solved over the entire claimed range. In particular, they argue that if the system according to claim 1 were put into effect there would remain a problem with accommodating the upper ends of the tubes. Similarly, they argue that if the method according to claim 8 were put into effect there would remain a problem with accommodating the lower ends of the tubes.

7.1 The core of the opponents' argument is that there is a single problem which is solved by the present patent and that this requires the presence of the features of both claims 1 and 8. However, this argument implies that in order to accommodate any larger number of tubes within a bearing of a particular size it would be necessary to provide the claimed features at both the upper and lower ends. There is no evidence that this would be the case. An increase in the number of tubes would result in a reduction of the free space around both the upper and lower ends of the tubes and incorporation of the features according to claims 1 and 8 would provide more space at both ends. However, it is entirely plausible that when the number of tubes accommodated in a turret having a bearing of a certain size is increased the features of claim 1 may be employed to provide more space around the lower ends of the tubes whilst the space available around the upper ends would be reduced but nevertheless remain within acceptable limits. A corresponding argument is applicable in respect of the features of claim 8. It would rest with the skilled person to decide whether the restricted access resulting from an increase in the number of tubes would justify employing the claimed solutions at the upper end, the lower end or both.

7.2 The decisions T 5/99 and T 632/01 (both supra) cited by the opponents deal with the requirements of sufficiency of disclosure in accordance with the EPC. However, in both decisions it was found that the respective disclosures were deficient to the extent that the meaning of essential terms in the claims was not able to be determined. This is not so in the present case and the opponents have not suggested otherwise. Those decisions therefore are not relevant to the present case. In decision T 409/91 (supra) it was found that the skilled person would not be able to put into effect the subject-matter over the whole range as claimed because it was known from neither the disclosure nor the relevant common general knowledge how to produce a particular property falling within the scope of the claims, cf. reason 2. Contrary to the present opponents' assertions also this decision is not relevant to the present case because, as the opponents admit, the skilled person is able to put into effect the subject-matter as claimed.

7.3 On the basis of the foregoing the board finds that the objection under Article 100(b) EPC is not valid.

Inventive step - Article 56 EPC

8. The opponents made no attack during appeal on inventive step of the subject-matter of the independent method claim (claim 8 according to the fourth auxiliary request) and the board agrees with the findings of the opposition division in this respect. It is therefore necessary to consider inventive step only in respect of claim 1.

9. The board and the parties are in agreement that the closest state of the art is known from D1 and that this discloses all features of claim 1 except that the tubes have lower ends lying on an imaginary lower circle which is of a diameter that is at least 10% greater than the bearing inside diameter.

9.1 The disclosure of D1 relates generally to the provision of tubes on the turret and through which the risers pass. The tubes are inclined at an angle which is essentially the same as the natural angle of the riser. The turret is mounted on a bearing of a type which all parties agree to be one which presents no significant obstacles to being manufactured to any chosen large diameter and, as shown in D1, the inner diameter of the bearing is indeed greater than the diameter of the imaginary circle defined by the lower ends of the tubes. Nevertheless, the skilled person would be unwilling to enlarge the bearing when attempting to accommodate additional tubes because the additional space requirement would reduce the vessel's payload. The cited documents are silent as regards the problem of providing sufficient space around the lower ends of the tubes when an increased number of them is to be used without increasing the size of the bearing.

9.2 The opponents argue that the claimed feature that the diameter of the imaginary lower circle is at least 10% greater than the inner diameter of the bearing would be the obvious result of simply reducing the size of the bearing. However, this view is based on ex post considerations since it bears no relation to the problem to be solved which is not to reduce the size of the bearing but to increase the number of tubes without increasing the size of the bearing. Even if the skilled person were to attempt to reduce the diameter of the bearing in the system according to D1 which proposes that the inclination of the tubes be according to the natural angle of the risers and therefore essentially fixed, the imaginary lower diameter would be reduced similarly and the result would not be the subject-matter of present claim 1.

10. Another approach by the opponents is to consider D7 as disclosing the closest state of the art and to argue that its combination with the disclosure of D1 renders the subject-matter of claim 1 obvious. D7 in its embodiment of figure 9 discloses a system generally according to claim 1 but wherein the tubes are located parallel to the central axis of a cylindrical turret. The opponents argue that the skilled person faced with the problem of increasing the number of risers which may be used with the D7 system and finding that this would result in too little space at the lower ends would employ the inclined arrangement according to D1 to provide that additional spacing. However, D1 is totally silent about any benefits of extra space at the lower ends of the tubes so the skilled person would receive no encouragement to combine the teachings for that reason. It is feasible that the skilled person might combine the teachings of D7 and D1 in order to provide inclined tubes in the system of D7. However, in so doing he would still have no incentive to extend the imaginary lower circle beyond the confines of the turret which in both D1 and D7 are defined by the respective inner diameters of the bearings.

11. On the basis of the above considerations the board concludes that the subject-matter of claim 1 involves an inventive step. Since the subject-matter of claims 2 to 7 contains all features of claim 1 the same conclusion applies also to those claims.