T 2143/21 27-09-2023

Reasons for the Decision

1. The appeals are admissible.

2. Background

The invention is directed at a high pressure fuel feed pipe for a direct injection engine. It more specifically relates to the fuel pipe end structure where a connection head is brazed to an end of the steel pipe, cf. para [0001] of the granted patent. The steel pipe has a reduced diameter portion (drawn portion or drawn stage in the claim language) at its end. The drawn portion is inserted and brazed in the connection head. The invention is aimed at preventing stress concentration at the pipe's brazing area, cf. paras. [0008]-[0009]. To this end, the steel pipe end structure geometry must be within certain parameters, cf. Figures 1 and 2 of the patent, all defined in relation to the pipe regular diameter D. Thus, the diameter of the drawn portion D1 must satisfy 0.8D <= D1 <= 0.9D; the drawn portion must have a minimum straight (constant diameter) length L1 outside the connection head of L1 >= 0.06D; and the axial length L2 of the tapered (Fig. 1) or double tapered (Fig. 2)portion, has a minimum with L2 >= 0.14D. Finally, the combined length L1+L2 has an upper limit of L1+L2 <= 1.5D. A minimum free straight pipe length L1 outside the connection head (L1 >= 0.06D), in combination with pipe diameters satisfying 0.8D <= D1 <= 0.9D, is said to result in the reduction of stress concentration at the brazing area. The double-stage drawn portion of the second embodiment is further said to provide a stress dispersion effect on the fuel pipe and thus to further prevent stress concentration, cf. para [0013].

3. New main request - Admission

This new main request was filed by the appellant proprietor during the oral proceedings before the Board. It is therefore an amendment to the proprietor's case and its admission at the discretion of the Board, Art 13(2) RPBA. According to this rule, the Board should in principle not take such an amendment into account unless there are exceptional circumstances which have been justified with cogent reasons by the party concerned.

Asked by the Chairman during the oral proceedings, the appellant proprietor refrained from giving any reasons for the late filing of this request. The Board also sees no apparent reason for filing such a request at this late stage of the proceedings. The new request seeks to overcome the finding of lack of novelty by further amending claim 1 that was already part of the contested decision, see sections 12 and 13 finding lack of novelty of claim 1 of the previous amended main request over D1.

In the light of the above, the Board decided not to admit the new main request into the proceedings, Art 13(2) RPBA.

4. First auxiliary request - Inventive step

4.1 The appellant opponent contests the opposition division's positive conclusion of inventive step for claim 1 of this request which is identical to granted claim 2 starting from D1 in combination with common general knowledge, cf. impugned decision section 15. Granted claim 2 differs from granted claim 1, which is deleted from this request, in that it has a two stage drawn portion with L2 now defining the axial length of the two-stage drawn portion,see figure 2, not that of a one-stage drawn portion, see figure 1, as in granted claim 1. Otherwise, all parameters and the claimed ranges are identical.

4.2 It is undisputed that Figure 2 of document D1 discloses a terminal structure of a high-pressure fuel pipe with a connection head 132 brazed to an end of a fuel pipe 124A in the sense of the contested claim. The known fuel pipe has a drawn portion (portion inserted in connection head 132) and a main fuel pipe body with larger diameter. In the claim wording the insertion portion diameter is D1 and the main pipe portion diameter or pipe diameter is D.

4.2.1 The appellant proprietor submits that the structure disclosed by Figure 2 of D1 does not satisfy the claimed proportions of 0.8D <= D1 <= 0.9D and L1 >= 0.06D. They do not dispute that values for L2 and L1+L2 relative to the fuel pipe diameter D can be inferred from D1 and these are within the ranges claimed in the final two features of claims 1 and 2.

For ease of understanding, Figures 1 and 2 of the patent specification which include definitions of L1, D and D1 for the respective embodiments are represented below.

FORMULA/TABLE/GRAPHICFORMULA/TABLE/GRAPHIC

4.2.2 The question whether and, if so, which dimensions could be inferred from D1 was discussed and decided in the context of the original main request, later withdrawn. The reasons for which the Board held that dimensions could be inferred from D1 hold also for claim 1 of present auxiliary request to the extent it claims the same parameter values.

4.2.3 The proprietor submits that the drawings of D1 are of schematic nature. No specific sizes or proportions can thus be derived from them.

These arguments are however not convincing.

4.2.4 It is readily apparent when considering the figures of D1 in the context of the whole disclosure that the figures 1-3 of D1 are not mere schematic drawings (defined as "an illustrative figure which gives an outline or general scheme of an object" (OED)). D1 is concerned with details of a high pressure fuel fitting, and how to provide a metal-to-metal seal that allows for a limited amount of axial misalignment. In that context, the shape and relative dimensions of the contact surfaces are central. The figures are intended to illustrate the core concepts of this fitting and may thus be taken to be much more representative than a purely schematic drawing. This is borne out by their level of detail and the fidelity of representation of the shapes of the different elements described so that figures 1-3 can be considered much closer to a technical drawing (defined as "a precise and detailed drawn representation or plan" (OED)). Though exact measurements may not be possible (no scale is shown), it can certainly be used to infer relative dimensions of the different elements.

4.2.5 The Board is also not convinced by the appellant proprietor's arguments that the figures' measurements of D1 contradict the teaching of its description. Figure 2 shows a circle with a substantially constant radius and thus represents a "generally spherical-shaped exterior surface 132 having a single, constant radius", as is described in para [0022] of D1. The manual three point method using a compass to find the centre of circle used by the proprietor is not accurate enough to prove that this is so. Using the Windows 10 Snip & Sketch tool, for example, a more accurate determination of the cross-sectional shape of exterior surface can be made and it is found to be circular as expected for a "generally spherical" surface as stated in D1, see screen-shot below. The figure in the screen-shot shows a circle fitting practically perfectly the cross-section of the spherical surface in Fig. 2. The Board adds that the Snip & Sketch tool is a standard, well known feature of the Windows operating system, and has been so at least from Windows 10 onwards. Insofar as the appellant proprietor is unfamiliar with the tool, instructions as to its use are freely available on the Internet. Insofar as the appellant proprietor's query at the oral proceedings before the board as to its functioning is meant to question or call into doubt its accuracy, such doubts, leaving aside the fact that they are late, constitute nothing more than unsubstantiated allegation and must fail.

FORMULA/TABLE/GRAPHIC

Using the same Snip&Sketch tool the angle theta of Figure 2 is found to be 83°. This again does not contradict para [0025] of D1 where it states "[F]or example... can be about 80 degrees" (emphasis added).

4.2.6 Thus, within the minor tolerances inherent in any reproduction, the skilled person can directly infer from the figures of D1 approximate proportions, as those defined in claim 1. Taking the values measured by the appellant proprietor themselves for Figure 2, cf. grounds of appeal p. 8, and expressing them with the same significance, i.e. the same number of significant figures or decimal places, for the purpose of comparison to the same number of decimal places as in the contested claim, it can be concluded that this figure anticipates the disputed features:

- D1 (measured by the appellant proprietor) = 0.771D, expressed with the same significance as in the claim 1, i.e. with one significant figure or one decimal place D1 = 0.8D corresponding the lower value of the claimed range 0.8D <= D1 <= 0.9D

- L1(measured by the appellant proprietor) = 0.057D, expressed again with a single significant figure or decimal place L1 = 0.06D, corresponding again to minimum of the claimed range L1 >= 0.06D.

4.2.7 Upheld claim 1 corresponding to granted claim 2 differs from the known structure in that the drawn portion is a two stage drawn portion, with the relevant range requirements now referring to L2 as the length of the two stage drawn portion. In granted claim 1, now deleted, it referred to L2 as the axial length of the one stage drawn portion. Otherwise, all range requirements are the same as in granted claim 1. If L2 is defined generally as the axial length of the drawn portion, whether one or two stage, then, as explained above, D1 is already seen to disclose values within all claimed ranges, none of which are new also for claim 1 of the auxiliary request.

4.3 The appellant proprietor argues that this sole difference of a two-stage drawing rather than one stage drawing produces a dispersion effect of stresses acting on the fuel pipe, cf. paras. 0013, 0025 and 0035 of the patent specification, which would be different from the effect of one stage drawing. This effect would be apparent from the example 3 of a two-stage specimen described in paragraphs 0033-0035, when compared to the one-stage embodiments of examples 1 and 2 of the preceding paragraphs 0027-0032.

4.3.1 However, the Board is unable to see such a special effect in the two stage drawing per se. "Dispersion of stress" is another way of stating that stress concentration is avoided or reduced. This effect is described in paragraphs 0013, 0025 and 0034 as an effect that is over and above that resulting from spacing the drawn portion from the brazing by a minimum distance L1 >= 0.06D. That feature prevents stress concentration in the drawn portion due to brazing, see paragraph 0013, lines 47 to 49, one of the main problems addressed by the patent, paragraph 0009, but, as explained above, is already disclosed in D1.

4.3.2 Thus, the two stage drawing is meant to further reduce or avoid stress concentration in the drawing area compared to the one step drawing embodiment. In the Board's understanding, however, further reduction of stress concentration is only possible if the two stage drawing is over a greater length compared to single step drawing. If drawing length L2 and start and end diameters D and D1 are the same, stress distribution will be more gradual and spread out, i.e. less concentrated, in single step drawing. In two step drawing, for the same drawing distance L2 stress will be less evenly distributed and more concentrated around the two steps, at least one of which must have a taper angle (theta2,theta3) larger than one step taper theta1 for the same drawing length, thus resulting, if anything, in more localized and thus greater stress concentration.

4.3.3 The patent does not state anywhere, let alone in claim 2, that the drawing length L2 is larger than for one step drawing. Claim 2 rather includes the very same constraints and ranges for all parameters, in particular those relating to the length L2 of the drawn portion, as in claim 1. It is also not apparent from the examples that the drawing length would be larger for two step drawing. Though example 3 of paragraph 0033 to 0035, which is meant to illustrate the dispersion effect of two stage drawing, gives values for L2 (6mm), no such values are given for the two single stage examples 1 and 2 discussed in the previous paragraphs. Nor is the dispersive effect quantified in any way, so that no meaningful comparison between the two modes can be made.

Last but not least, the known terminal structure of D1 has parameter values within the claimed ranges, see sections 4.2.1 to 4.2.6 above, and thus in particular has a drawing portion length L2 which is the same as claimed.

4.3.4 The Board adds that it thus does not agree with the decision, section 15.2, where it is generally stated that the two-stage drawing or diameter change involves less material deformation in each step and thus less stress is generated. This is so, if at all, only if the drawing is effected over a larger distance L2.

4.3.5 The Board therefore considers that there is no conclusive evidence for associating any special effect with the two-stage drawing alone over and above that associated with the known one-stage drawing of D1. Absent any other technical effect, the Board therefore considers that the effect of this difference is merely to provide an alternative to a single stage drawing.

4.4 The Board has no compelling reason to believe that the skilled person would not be familiar with multi-step tube drawing, as argued by the appellant proprietor. The skilled person in this case is an engineer designing high pressure fuel injectors who must have a good knowledge of metal workpiece forming processes such as for example tube drawing in all its variants. That they must have knowledge in this area is evident already from D1 which, as explained above, indisputably shows drawn tube sections in the figures 1 to 3. When seeking to provide an alternative to the one-stage drawing of D1, the skilled person would draw on their knowledge of drawing and thus consider also multi-stage drawing, for example two-stage drawing, as an obvious alternative to the single stage drawing disclosed in D1.

4.5 Consequently, the Board holds that, contrary to the conclusions of the opposition division, the subject-matter of upheld claim 1 does not involve an inventive step, Art 56 EPC.

5. In conclusion, the appellant proprietor's main request is not admitted. The Board finds that the decision was wrong in affirming inventive step for the upheld claim and therefore must be put aside. Consequently, taking into consideration the amendments made by the appellant-proprietor, the patent and the invention to which it relates do not meet the requirements of the Convention and the patent must be revoked pursuant to Article 101(3)(b) EPC.