T 0636/99 10-04-2002

1. Admissibility of the appeal

1.1. Lack of novelty and lack of inventive step were the grounds on which the opposition was based. In addition to document D1 an alleged public prior use consisting in the delivery of a rotary-anode X-ray tube of the type MRC200 by Philips Medizin Systeme GmbH was also cited as prior art. This alleged public prior use was substantiated in the statement of grounds of opposition as to its date (between November 1989 and April 1990), its object (the MRC200 tube represented by the drawing of D2) and its circumstances (delivery to the Duke University, Durham, U.S.A.); a witness was also offered to confirm the details of the prior use (see the statement of grounds of opposition, page 1). Moreover, the appealed decision states, inter alia, that the subject-matter of claim 1 as amended (present main request) is novel and involves an inventive step over the prior use.

1.2. The documents (D4 to D8, D10) and arguments presented in the statement of grounds of appeal likewise relate to an alleged public prior use, consisting in the delivery of a rotary-anode X-ray tube of the type MRC200 by Philips Medizin Systeme GmbH to the Duke University, Durham, U.S.A. in 1989. It is also argued there that the subject-matter of claim 1 according to the main request, i.e. as amended during the opposition oral proceedings, lacks novelty and inventive step in view of said prior use.

1.3. The prior use was presented and the witness offered in the statement of grounds of opposition, meeting the requirements of Rule 55c EPC within the period of time defined in Article 99(1) EPC. Amended claim 1, as found allowable by the opposition division, was filed during oral proceedings before the opposition division. It was in response to this that the appellant/opponent filed the new documents (D4 to D8, D10), which all relate to the same alleged prior use. In these circumstances, there is no reason for rejecting them as being filed late.

1.4. In view of the foregoing, the respondent's allegations that the grounds of appeal are based on fresh grounds and on fresh facts, and that the appeal is unconnected with the reasons given in the appealed decision, do not appear to be supported by the facts. Consequently, the Board judges that the appeal complies with the requirements mentioned in Rule 65(1) EPC, and is therefore admissible.

2. Proprietor's main request

2.1. Claim 1 according to the main request includes the features specified in granted claim 1 in combination with, inter alia, the feature "a lubricant storage chamber (22) for receiving the lubricant and communicating with the first bearing gap (G)" which is taken from granted dependent claim 8 or granted dependent claim 11.

2.2. The application as filed discloses only two alternative embodiments of the tube: in the first embodiment the internal shaft of the tube forms its stationary structure and in the second its rotary structure. According to the description and the figures as filed, the lubricant storage chamber is always formed along the centre axis of the internal shaft of the X-ray tube. Granted claim 8 identifies the lubricant storage chamber as formed in the stationary structure (i.e. according to the first embodiment), but is appended to granted claim 1 only through dependent claim 7 which identifies this structure as having a columnar structure rotatably inserted in the rotary structure. In a similar way, granted claim 11 identifies the lubricant storage chamber as formed in the rotary structure (i.e. according to the second embodiment), but is appended to granted claim 1 only through dependent claim 10 which identifies this structure as having a columnar structure inserted in the stationary structure. Granted claims 7, 8, 10 and 11 are respectively identical to dependent claims 8, 9, 11 and 12. of the application as filed. None of the other claims of the application as filed mentioned the location of the lubricant storage chamber. The Board has found no disclosure in the application as filed of the concept of a lubricant storage chamber, when present, being formed elsewhere than in the internal shaft of the X-ray tube.

2.3. The respondent has argued that a lubricant storage chamber was not recited in the originally filed claim 1 and that, according to the description, the tube of the invention is not explicitly restricted to a lubricant storage chamber located in its internal shaft and the location of this storage chamber has no significant technical influence on the operation of the tube. However a claim does not disclose everything falling within its scope, so this argumentation does not prove that a tube with a lubricant storage chamber located in the structure receiving the internal shaft was disclosed in the application as filed.

2.4. Consequently the Board judges that claim 1 of the main request contravenes Article 123(2) EPC.

3. Proprietor's first auxiliary request

Claim 1 according to the first auxiliary request results from the deletion of the feature "a lubricant storage chamber (22) for receiving the lubricant and communicating with the first bearing gap (G)" recited in claim 1 of the main request. The deletion of this feature from claim 1, which would widen the scope of claim 1 and put the opponent, who is the sole appellant, in a situation worse than if he had not appealed, is not acceptable because of the rule against the reformatio in peius (G 9/92, OJ EPO 1994, 875). The Board is aware that according to G 1/99, OJ EPO 2001, 381, an exception to this principle may be made in circumstances where the patent as maintained in amended form would otherwise have to be revoked as a direct consequence of an inadmissible amendment held allowable by the opposition division in its interlocutory decision. However, this exception does not apply to the present case because it is possible to remedy the situation by amending claim 1 to specify the particular arrangement which is disclosed in the application as filed (see fourth auxiliary request, below).

4. Proprietor's second and third auxiliary requests

The subject-matter of claims 1 according to the second and third auxiliary requests is not restricted to an X-ray tube comprising a lubricant storage chamber (22) provided in an internal shaft of the tube. Thus for the same reasons as given for the main request (see supra 2.2. and 2.3), the subject-matter of these claims extends beyond the original content of the application in contravention of Article 123(2) EPC.

5. Fourth auxiliary request - Admissibility of the amendments

The subject-matter of claim 1 according to the fourth auxiliary request is restricted to an X-ray tube comprising a lubricant storage chamber (22) provided in an internal shaft of the tube being one of said stationary structure (15) and rotary structure (12). The Board is satisfied that this claim does not contravene Article 123(2) or (3) EPC.

6. Fourth auxiliary request - Novelty

6.1. The appellant submits that the subject-matter of claim 1 according to the fourth auxiliary request is not novel in view of the X-ray tube of the type MRC200 (construction drawings D4a to D4f) which according to him was delivered to the Duke University, Durham (USA) in 1989 (D5 to D6). According to the proprietor this MRC200 tube does not have the following features of claim 1 according to the fourth auxiliary request:

(i) a lubricant storage chamber provided in an internal shaft of the tube,

(ii) an annular groove being a large-capacity annular space for decreasing gas pressure when bubbles produced in the bearing reach the annular space, and

(iii) the grooves in that bearing section communicating directly with the annular groove are arranged to flow back toward the bearing lubricant accumulated in the annular groove when the tube is operating.

6.2. Having regard to feature (ii), the appellant argues that the construction drawings (D4) show an annular space provided in the bearing of the MRC200 tube between the ring block ("Druckscheibe": D4e; part 5 in the drawing D4a, "SR-Lager Zus.") and the left hand transition between the shaft and its radial flange ("Spiralrillenachse": D4b; part 1 in the drawing "SR-Lager Zus.") that corresponds to the large-capacity annular space (25) for decreasing gas pressure when bubbles produced in the bearing reach the annular space, as recited in the claim. The appellant reinforces this argument by referring to document D9 and deducing therefrom that bubbles produced in the bearing of the MRC200 tube can expand in this annular space because it is much wider than the bearing gap formed between the rotary and stationary structure of the bearing.

6.3. As pointed out by the proprietor, this prior art annular space is formed by a 0.30 mm + 0.1x45 chamfer at the anode side end of the 27.2 mm centre hole of the ring block (Druckscheibe) and by an undercut (Freistich) on the shaft (Spiralrillenachse) at the non-anode side transition between the shaft and the radial flange (D4b: Einzelheit X).

6.4. Assuming for the sake of argument, without deciding, that the MRC200 tube is prior art in the meaning of Article 54 EPC, the Board considers that undercuts and chamfers, which are usually provided by sinking the inevitably slightly rounded transition between a shaft and an integral flange thereon so as to avoid unwanted mechanical contact and allow the thrust bearing to rotate freely, form part of the general knowledge of the skilled person. Moreover the depth (0.2 mm) and the angles (8 and 15 ) of the undercut shown in the drawings (D4b: Spiralrillenachse, Einzelheit X) correspond almost exactly to those of the examples of undercuts according to DIN 509 (D11). Accordingly, in the opinion of the Board, unless told otherwise, the skilled man will simply assume that the construction details of the annular space of the thrust bearing referred to by the appellant are provided for avoiding unwanted contact between the ring block and the flange. It would not occur to him that the annular space serves any other purpose.

6.5. According to the patent in suit (see published patent specification: from column 1, line 54 to column 2, line 11; column 5, lines 2 to 9) the annular groove (25) should be sufficiently large so that the gas pressure of the bubbles (or gas) produced in the bearing when the tube is assembled or while the tube is operating decreases when the bubbles reach the annular space without expelling the metal in this space. The Board thus shares the proprietor's view that the definition of the annular groove in claim 1 is a functional definition and not a mere structural one.

6.6. Even if the structure of the tube, and particularly its internal structure, was visible to a skilled person having access to an X-ray tube of the type MRC200, it would not have been possible for him to deduce the assembling method or the effect achieved when the bearing is rotating, from an inspection of the disassembled bearing.

6.7. Although the width of the bearing gap formed between the rotary and stationary structures of the bearing (20 My) is much smaller than the dimensions of the annular groove formed by combination of the undercut and chamfer referred to by the appellant, this groove cannot be unambiguously recognized as a "large-capacity space" because its capacity is small in comparison with that of other cavities of the bearing, in particular the cavity formed between the stationary structure and the right hand side of the radial flange (D4b: Spiral-rillenachse). The appellant thus has not convinced the Board that it is directly derivable from the drawings D4, or from the bearing itself, that the annular groove referred to by the appellant is such as to decrease gas pressure when bubbles produced in the bearing reach the annular space.

6.8. Having regard to feature (iii), it has not been proved that the spiral grooves of the thrust bearing of the MRC200 tube communicate with the annular groove. On the contrary, "Ansicht Z" of D4e shows that the area occupied by the spiral grooves stops well short of the annular space.

6.9. The teaching of document D1 or D9 cannot be considered in combination with the MRC200 tube in determining novelty of the bearing because the tube and the construction drawings contain no clear reference to these documents.

6.10. Consequently, the Board judges that the subject-matter of claim 1 according to the fourth auxiliary request is novel within the meaning of Article 54 EPC.

7. Fourth auxiliary request - Inventive step

7.1. Starting from the MRC200 tube, the objective problem underlying the present invention can be seen as providing means for decreasing the gas pressure of the bubbles produced when the tube is assembled or during its operation and for preventing lubricant from leaking in the vacuum envelope of the tube. This corresponds to the technical problem identified in the patent in suit (see column 1, line 44 to column 2, line 18).

7.2. This problem is solved by providing the tube with an annular groove being a large-capacity annular space for decreasing gas pressure when bubbles produced in the bearing reach the annular space, and by arranging the grooves in that bearing section communicating directly with the annular groove to flow back toward the bearing lubricant accumulated in the annular groove when the tube is operating.

7.3. The appellant refers to D9 which discloses an X-ray tube which has got a large-capacity annular space (15) formed by the combination of an undercut (Freistich) on the shaft (8) in the boundary transition region between the radial bearing (11b), which is provided with a helical groove, and the axial thrust bearing (14), which is provided with a spiral groove, and a bevelling of the bearing housing (9) opposite the undercut (15) for decoupling these bearings from each other to avoid movement of lubricant between them. According to the appellant, it would be obvious to the skilled man to consider applying the same combination of features at the vacuum side of the flange of the bearing of the MRC200 tube to obtain the same effect.

7.4. However, the annular space (15) of D9 is on the other side of the flange and it is not obvious that the effect provided by it would be obtained at the transition of the spiral groove of the thrust bearing and the vacuum-side (lower) end of the shaft of the MRC200 tube because this end of the shaft is not provided with a helical groove (which is only on the anode-side end of the shaft), nor is it separated from the stationary structure by the same gap as is the anode-side end of the shaft. A reduction of gas pressure when bubbles reach the annular space is neither disclosed nor suggested in D9. Accordingly, the skilled person would not be led by D9 to form a large-capacity annular space at the transition between the vacuum-side end of the shaft and the corresponding thrust bearing section of the MRC200 tube because he would not expect this to solve the technical problem. Since a solution to this problem is neither disclosed nor suggested in any other piece of cited prior art or by the general knowledge of the skilled man, the Board considers that the subject-matter of independent claim 1 according to the fourth auxiliary request involves an inventive step within the meaning of Article 56 EPC.

8. Under these circumstances it is not necessary to decide whether the delivery of the MRC200 tube to the Duke University in 1989 made the details of the bearing available to the public before the priority date of the patent in suit.

9. In the Board's judgement, taking into account the amendments according to the fourth auxiliary request the patent in suit and the invention to which it relates satisfy the requirements of the Convention. The description and drawings do not require amendment.