T 0015/81 (Eddy-current testing device) 28-07-1981
I. The European patent application No. 79 102 888.9 filed on 9 August 1979 and published on 16 April 1980, with priority of 28 August 1978 claimed from a previous application filed in the Federal Republic of Germany, was refused by decision of the Examining Division of the European Patent Office dated 7 April 1981. That decision was based on claims 1-5 filed on 29 May 1980 and still effective, of which claim 1, with the characterising portion additionally subdivided by letter, reads as follows: "Eddy-current testing device for tubes of heat exchangers with a bundle of U-shaped tubes, wherein a probe unit having two toroidal coils positioned across the tube's axis and embedded in a coil-carrying member, said probe unit being attached to a flexible pushing arrangement, is pushed into a tube in the bundle, said pushing arrangement comprising two longitudinally connected parts, the part adjacent to the probe unit being thinner than the tube and ringed by rounded centering elements, whereas the other part is designed as a push tube, characterised in that (a) one part of the pushing arrangement is likewise designed as a push tube (b) is more flexible than the first-mentioned push tube and (c) is of a length roughly the same as that of the longest bend to be inspected by the probe in the bundle of U-shaped tubes."
II. The reasons given for the refusal were that in view of the prior art disclosed by GB-A-1 488 833 the subject-matter of claim 1 did not involve an inventive step as specified by Art. 56 EPC and thus could not be allowed. Consequently, related claims 2-5 could not be allowed either, since they presupposed the admissibility of claim 1. Neither was there anything in their features which could be regarded as meriting a patent.
III. On 30 April 1981 the applicant lodged an appeal against that decision, paying the fee for appeal and filing a Statement of Grounds at the same time. In his communication of 3 June 1981 the rapporteur of the Board of Appeal subsequently introduced DE-A 1-2 635 537, cited in the search report, into the proceedings. In the oral proceedings held on 28 July 1981 at the request of the appellant, the latter requested that the decision refusing the application be set aside and the patent granted on the basis of the documents filed on 29 May 1980, as an alternative with the insertion of a descriptive portion, filed on 30 April 1981, after line 27 in column 2. ......
From the reasons for the decision
1. The appeal complies with Articles 106 to 108 and Rule 64 EPC and is therefore admissible.
2. Novelty: ...... The subject-matter of the application, as set out in effective claim 1, proves to be new. (Reasoning here omitted)
3. Inventive step: The question now to be examined is whether the invention involves an inventive step. According to column 2, lines 6-11 of the effective description, the aim of the application is to reduce, compared with the devices specified, in DE-A 1-2 635 537, the forces needed to manoeuvre the probe unit and push tube around bends, so as to enable a proper inspection to be carried out even in bends with very small radii of curvature. According to the penultimate and last paragraphs on page 3 and the first paragraph on page 4 of DE-A 1- 2 635 537, the aim of the invention which it describes is to prevent the deficiencies encountered in eddy-current probes when passed through "bent", non-circular or encrusted sections, by seeking to reduce - like the subject of the application - coefficients of friction between the probe and the internal wall of the tube (and thus inevitably the pushing forces too) as compared with known devices. Since the elimination of deficiencies and achievement of improvements is a constant preoccupation in technical circles, the aims set by the present application cannot be regarded as comprising anything inventive. As the examination for novelty showed, the only difference between the subject-matter of the application according to claim 1 and the subject-matter according to claim 1 of DE-A 1-2 635 537 with a helical spring (10) as elastic member, consists in fitting a push tube (feature (a)), instead of the helical spring (10), between the less flexible section (6) of the pushing arrangement and the coil-carrying member (8), and in stipulating the length of the more flexible section (feature (c)). When operating apparatus according to DE-A 1-2 635 537 with a helical spring fitted, a skilled person will undoubtedly discover that there are certain deficiencies in the deformation behaviour of a helical spring. One deficiency, for example, is the ease with which such a spring deforms lengthwise, making it difficult to position the probe accurately in the tube. If a designer working on the development of such apparatus does not possess the technical knowledge to overcome such difficulties, he can be expected to consult the relevant prior art for components which perform the same function and are better able to meet the requirements. Thus, GB-A-1 488 833 provides the teaching that a flexible push tube connecting the probe unit with the distant pushing means be used to push the probe forward in curved sections of the U-shaped tube. The replacement of the helical spring (10) in a device according to claim 1 of DE-A 1-2 635 537 by a tube, in order to exploit readily apparent technical advantages of such a tube, is therefore to be regarded as an obvious step for a skilled person. The difference resulting from feature (a) is thus lacking in inventive step supportive of a patent. As regards feature (c), there are only two ways in which to perform a full inspection of a U-bend - either by moving the probe round the whole of the bend from one leg if the flexible part is of suitable length (feature (c)), or by moving it along each of the two legs in turn, inspecting just over half the bend in each operation (method according to GB-A-1 488 833). Of the two methods, the one to be chosen will be clear from the simplest consideration of the particular circumstances. For example, where inspecting a U-bend accessible from one side only, a skilled person will not leave one half of the bend uninspected but will naturally make the flexible section long enough to pass through the entire bend, especially as lines 123-127 on page 3 of GB-A-1 488 833 already draw his and his colleagues'attention to the principle of selecting the length of the flexible section to suit the radii of curvature of the tube to be inspected. Since however it is not the "radii of curvature" which are being inspected, but the bends of the tube, this passage is to be interpreted as teaching that the length of the more flexible part be suited to the length of the bend. Again, no-one using such apparatus will perform two half-bend inspections in succession, just because that is the method indicated in GB-A-1 488 833, if he finds that the probe can be moved round the whole of the bend without risk of damage. Therefore, feature (c) does not involve an inventive step. Furthermore, instead of supporting the solution which features (a) and (b) are said to provide, feature (c) in fact counteracts it, since the longer the flexible section is, the greater the friction and thus the pushing forces required. ... thus, the method which GB-A- 1 488 833 mentions of inserting the probe unit into a tube by suspending it from a lifting head (Fig. 1) represents but one possibility, and moreover one in which the probe also requires pushing forces, namely the weight of the device. Neither is there the slightest apparent obstacle to prevent the person conducting the inspection from using muscle power to push this known probe into the tube, because of the tube's position for instance. Furthermore, the information content disclosed by DE-A1- 2 635 537 is not impaired by the fact that the ratio (inferable only from the Figures) of the tube's internal diameter to the length of the resilient member is in the order of 1:2 or 1:3, from which the appellant concludes that these known devices are suitable for inspecting short bends only. The role of Figures, it may be said, is purely to clarify the principles of a device's construction. Their purpose is not to provide particular details of dimensions or relative proportions. Therefore, it can naturally be assumed that in practical embodiments of test devices according to DE-A 1-2 635 537, the length of the resilient member will be adapted to test conditions, e.g. is suited to an inspection of U-shaped tubes such as indicated in line 6 on page 2. It is not correct either to say that until the subject of the application had been created it had not been possible to inspect U-shaped heat exchanger tubes with radii of curvature of 5-6 cm and internal diameters of 2 cm. For example, the passage from line 128 on page 3 to line 3 on page 4 of GB-A 1 488 833 indicates that the test device described therein had been successfully used for examining U-shaped tubes with those very dimensions. ... Claim 1 is not allowable, because, as demonstrated, its subject-matter does not involve an inventive step (Articles 52 and 56 EPC).
4. As regards the dependent claims: The dependent claims 2-5 related to claim 1 are not allowable either, since their outcome is contingent on the admissibility of claim 1. Furthermore, the Board cannot find any patentable features in the features of the sub-claims. Thus, the feature of claim 2 is apparent from GB-A-1 488 833 (reference sign 9 in Fig. 1) or from DE-A1- 2 635 537 (reference sign 7 in Fig. 1). The features of the other sub-claims clearly do not go beyond such measures as are available to the skilled person for achieving greater flexibility of the push tube 12.
For these reasons, it is decided that:
The appeal is dismissed