T 0888/90 (Sub-combination) of 1.7.1992

Summary of Facts and Submissions

I. European patent application No. 86 304 441.8 (publication No. 0 206 638) was refused by a decision of the Examining Division for the reasons that the subject-matter of Claim 1 did not include all of the features necessary to achieve the desired result and consequently did not meet the requirements of clarity under Article 84 EPC.

II. The appellant lodged an appeal against this decision on 27 October 1990, paying the fee for appeal and submitting a statement of grounds in due time.

III. In a communication dated 19 November 1991, the Board informed the appellant of its provisional opinion that the subject-matter of Claim 1 was still lacking clarity. It was suggested that Claim 1 under dispute be amended so as to include additional structural features for assisting the fluid to be directed preferably through the filter element.

IV. In a reply received on 31 March 1992, the appellant submitted two new sets of amended claims according to the main request and to the first subsidiary request, respectively.

Claim 1 according to the main request reads:

"1. A liquid-gas bubble separator comprising: a container (11), having an inlet (41), an outlet (43), and a flow channel (47), extending between the inlet (41) and the outlet (43);

a filter element (21) in said container (11) between the inlet (41) and the outlet (43), said filter element (21) permitting the passage of the liquid and inhibiting the passage of the gas bubbles;

vent means (49), leading from the interior of the container (11) to the exterior of the container (11) for exhausting the gas bubbles from the container (11); and

a bypass passage (71) allowing liquid to bypass the filter element (21), if the filter element (21) becomes blocked, characterised in that the filter element (21) extends only part way across the flow channel (47) and the bypass passage (71) is formed by part of the flow channel (47) around the filter element (21), the inlet (41) being arranged to direct incoming flow toward the filter element (21)."

V. The appellant requests:

- that the decision under appeal be set aside,

- that the case be remitted to the first instance to continue with the prosecution on the basis of either set of Claims 1 to 10 as filed on 31 March 1992 (main or first subsidiary request), and

- that the appeal fee be reimbursed.

Reasons for the Decision

1. The appeal is admissible.

2. Amendments (main request)

The Board is thus satisfied that the claims according to the main request meet the requirements of Article 123(2) EPC, in view of additional limitations. As to the omission of an essential feature, as objected to by the Examining Division, the matter is dealt with below with respect to the clarity of Claim 1.

3. Clarity and support

3.1 In the decision to refuse the patent application, the Examining Division submitted that Claim 1 in the version as rejected was lacking clarity for the reason that an essential feature was missing.

According to the Examining Division, Claim 1 failed to provide means for the production of a swirling flow, so as to prevent forward flow through the bypass passage as long as the filter remains unblocked.

Thus, by omitting the last feature stated in Claim 1 as originally filed, i.e. "means responsive to flow through the container when the filter element is clean for recirculating a portion of the fluid that passes through said filter element back through the bypass passage to the upstream side of the filter element to essentially close the bypass passage to forward flow", the appellant had, according to the Examining Division, deprived Claim 1 of a feature deemed to be necessary to the solution when considering the technical problem recognised from the application in respect of the prior art.

This objection is obviously based on Article 84 EPC taken together with Rule 29(1) and (3), according to which the main claim must be supported by the description and must state the essential features of the invention, so as not to be so broad that it goes beyond the invention but not so narrow as to deprive the applicant of a just reward for the disclosure of his invention (Guidelines for Examination, C.III.6.2).

3.2 The omission of a feature in a combination may mean that a claim is merely relating to a sub-combination of an invention. It is the view of the Board that such a sub-combination with no function other than that of an intermediary building block for providing an inventive full combination may also be patentable in principle, if expressly presented as such for that purpose in the application as filed and it otherwise satisfies all conditions for patentability. Such sub-combinations are analogous to intermediate compounds in a chemical synthesis, which have no other functions either and could also be patented in principle.

Thus the principle that claims must contain all essential features also prevails in such cases, as long as the function so provided by the less complex structure to build up the more complex structure is accepted as a proper technical effect.

It cannot, however, be assumed that assemblies ab ovo directly and unequivocally imply their own sub-combinations, since a plurality of such kinds of entities may be envisaged with various scopes in their definitions. Thus without express disclosure in this respect, including the particular use, the support for such claims would be inadequate (Article 84 EPC). Neither should such subject-matter arbitrarily be generated by amendment after the filing date against Article 123(2) EPC, in the absence of an express presentation.

In the present case the sub-combination in question was in no stage presented as an intermediary building block type of subject-matter and the claim would therefore go beyond the content of the disclosure in this respect.

3.3 However, there is, of course, a further possibility, which recognises that the omitted feature is inessential to the function actually disclosed in the application. The Board does not share the conclusions of the Examining Division to the contrary in this respect for the following reasons:

In view of the state of the art cited in the introductory part of the description (cf. pages 1 and 2) it follows that the technical problem underlying the present application is to provide an improved liquid-gas bubble separator having a filter element and a bypass passage allowing the flow of liquid to bypass the filter element automatically, i.e. without assistance of any manual operation or the use of any mechanical bypass valve, when the filter becomes blocked.

As was rightly observed by the appellant in his response received on 31 March 1992, the basic idea of the solution is that filter 21, inlet 41, and bypass passage 71 are so arranged in relation to each other that fluid from the inlet is directed first to the filter rather than the bypass passage such that, when the filter is not blocked, the fluid flows through the filter to the outlet 43; fluid will not normally pass to the outlet via the bypass passage unless the filter is blocked.

To achieve this result, the necessary means must comprise the particular positioning of the filter element within the container as well as the preferential guiding of the fluid flow toward the filter in normal operating conditions.

3.4 The characterising features of Claim 1 according to the main request meet these requirements since they specify that:

(a) the filter element 21 extends only part way across the flow channel 47;

(b) the bypass passage 71 is formed by part of the flow channel around the filter element, and

(c) the inlet 41 is arranged to direct incoming flow toward the filter element.

Since, in addition, as mentioned in the precharacterising portion of Claim 1, said filter element extends between the inlet and outlet of the container and permits the passage of the liquid, there cannot be any doubt that the fluid will preferably flow through the filter which offers a flow resistance smaller than that provided by the bypass passage, as long as the filter remains unclogged.

Therefore, the Board is satisfied that the solution as claimed is clear and complete and, consequently, meets the requirements of Article 84 and Rule 29(1) and (3) EPC.

3.5 The arguments brought forward by the Examining Division (cf. point 3.1 above) are not convincing since, although the fluid through the bypass passage may be controlled by a means for recirculating a portion of the filtered fluid through the bypass passage, this can obviously be made in different ways; for example, by creating a swirling or a vortex-like flow within the filter element or a slight negative pressure in the bypass passage (cf. the description, page 4, line 14, to page 5, line 7).

Further, as convincingly set out by the appellant in his response along with Annex 1 received on 31 March 1992, other arrangements than the configuration of the described embodiment can be directly imagined for ensuring that the fluid does not flow through the bypass passage with the filter element in the unclogged condition. Recirculation of filtered fluid by inducing a lower pressure at the upstream end of the bypass passage is neither necessary nor essential to force the fluid to flow first through the filter element. The same result can be achieved by gravity if the inlet 41 is provided above the filter element at the top of the container as illustrated in Annex 1, Figures C, D or G. In any case, it is sufficient to consider that according to feature (c) of Claim 1 "the inlet 41 is arranged to direct incoming flow toward the filter element".

Therefore, in the Board's opinion, there is no need unduly to restrict the scope of the main claim to a particular embodiment as long as the general solution according to Claim 1 has neither been seriously contradicted nor challenged on account of the teachings of the cited prior art documents during a further substantive examination.

ORDER

For these reasons it is decided that:

1. The decision under appeal is set aside.

2. The case is remitted to the first instance for further prosecution on the basis of Claims 1 to 10 according to the main request, as specified in point V above.

3. ...