T 0153/91 09-09-1993

1. The appeal complies with the requirements of Articles 106 to 108 and Rules 1(1) and 64 EPC; it is, therefore, admissible.

2. Formal admissibility of the amended documents

Granted Claim 1 was directed to a closure cap defined both by structural features and features relating to the method by which the cap is produced. Present Claim 1 on the other hand is directed to a method of making a cap, that cap having all of the structural features specified in granted Claim 1. When, as in the present case, an invention resides in a combination of structural and method features, and those method features, here the use of a particular pre-heating temperature range and heating by means of electromagnetic radiation in a particular frequency range, are of interest only from the process point of view and leave no impact on the structure of the finished product, then a method claim is clearly more suitable for reflecting the totality of the invention. A change of category of claim is in these circumstances not in principle objectionable under Article 123(3) EPC (see for example Decision T 5/90, not published).

Although this general viewpoint was fully accepted by the Appellants at the oral proceedings they did, however, argue that the replacement of the reference in granted Claim 1 to exposing the plastisol to "microwave energy" by the reference in present Claim 1 to electromagnetic energy having a frequency of 10 to 200 MHz unallowably extended the scope of protection of the claim since, in their view, the term "microwave energy" would have been understood by the skilled person as being electromagnetic energy having a frequency of 300 to 300,000 MHz. Having regard to column 4, lines 32 to 45 of the patent specification where it is stated that preferably "microwave energy" of a frequency of 10 to 200 MHz, specifically 27.10 to 27.15 MHz, is to be used it is however clear that the term "microwave energy" as found in granted Claim 1 was not intended to have the restricted, now generally accepted meaning of radiation with a frequency of 300 to 300,000 MHz. Indeed, it is apparent from the evidence submitted by the parties, for example Webster's Third New International Dictionary from 1971 and Entwurf DIN IEC 27 (Co) 48 from 1980, that at the relevant time of drafting the patent application in particular the lower end point of the range was not well defined. Accordingly, this amendment of Claim 1 represents a clear restriction and not an extension of its scope and is not objectionable.

Present Claim 1 has further been restricted with respect to granted Claim 1 by the definition of the closure cap as being made of polypropylene, cf. for example originally filed Claim 1.

Lastly, the reference in granted Claim 1 to heating the plastisol until it is "completely molten", which in the circumstances would make no technical sense, has been replaced by a reference to complete fluxing of the plastisol which is the generally accepted term in the relevant art, cf. for example document (b), page 1, lines 11 to 20.

The amendments made to the dependant Claims 2 and 3 and the description do not go beyond those necessary to bring these into line with the terms of Claim 1 and to indicate the most relevant state of the art.

There are, therefore, no objections to the amended documents under Articles 123(2) and (3) EPC.

3. State of the Art

3.1. Document (v) relates to the in situ fluxing of a conventional plastisol gasket material in a plastics closure cap. Since at the temperatures of 150 C to 170 C required for fluxing the plastics material of the closure cap would be subject to degradation, eg. softening or blistering, it is proposed selectively to heat the plastisol gasket material by microwave radiation in the frequency range of 300 to 300,000 MHz.

3.2. In document (u) it is proposed to flux plastisol gasket material in a polyolefin closure cap by exposing it to radiation in the frequency range of 1 to 200 MHz, the specific example given being 27.12 MHz. To this end the plastisol should comprise a plasticiser having specific dielectric properties. The exposure time lies between 30 and 60 seconds.

3.3. In document (b) reference is made to the method proposed in document (v) to the effect that the microwave heating of the plastisol gasket material led to overheating in the interior thereof and consequential degradation. It is accordingly proposed to pre-heat the closure cap and plastisol gasket material by conventional means such that at the time of microwave heating the closure is at a temperature preferably between 5 C and 35 C below its melting point. In the specific example given with a polypropylene cap having a melting temperature of 165 C the cap is heated to about 135 C to 140 C before being exposed to microwave heating at 850 watts for 1 to 1¼ minutes.

3.4. Document (l) relates to a polypropylene closure cap with a plastisol gasket cured by exposure to microwave radiation in conjunction with mild heating. The closure cap shown in Figure 4 comprises a pilfer-proof device in the form of a ring attached to the side wall of the cap by frangible bridges, the ring engaging under a locking collar disposed around the neck of the container. The gasket is disposed in an annular space bounded by an outer undercut and an inner axially extending rib. In the closure cap shown in Figure 2 the annular space for receiving the gasket is bounded by inner and outer undercuts.

3.5. Document (c) relates in general terms to the use of radiation in the frequency range of 5 to 30 MHz in the curing of polyvinyl chloride resin foams.

3.7. The other documents cited in the course of the opposition proceedings are less relevant than those analysed above and do not need to be considered here in detail. Furthermore, in view of the concession made by the Respondents with respect to the implicit teaching of document (l) (see below) it is not necessary to go into the alleged public prior use of the process disclosed in document (b) with respect of closure caps having pilfer- proof devices.

4. Novelty and inventive step

4.1. The closest state of the art on which the preamble of Claim 1 is based is to be found in document (l). At the oral proceedings the Respondents conceded that the reference in this document to curing the plastisol gasket material by exposure to microwave radiation "in conjunction with mild heating" would be understood by the skilled person as a reference to recently commercialised "Darawave" process as described in document (b), the "mild heating" therefore being a pre- heating step as proposed there. Of the prior art documents cited, document (l) is the only one which specifically discloses, in relation to the Figure 4 embodiment, the in situ fluxing of a plastisol gasket in a closure cap having a pilfer-proof device of the form defined in the preamble of Claim 1. As that fluxing is achieved by exposure to microwave radiation, i.e. in the frequency range of 300 to 300,000 MHz as disclosed in document (b), rather than radiation in the frequency range of 10 to 200 MHz as specified in the characterising clause of Claim 1, it is apparent that the subject-matter of that claim is novel.

The subject-matter of Claim 1 is distinguished from the teachings of document (l) by two features relating to the structure of the closure cap and two features concerned with the parameters of the gasket fluxing operation as such.

The first of the features relating to the cap is that the annular space for receiving the plastisol material is bounded by both an inner and an outer undercut, whereas in the Figure 4 embodiment of document (l) only an outer undercut is provided. It is however known from Figure 2 of document (l) as well as document (i) to secure the attachment of the gasket to the closure cap by providing inner and outer undercuts in the claimed manner so that this feature cannot in itself be considered as contributing anything of inventive significance to the claimed subject-matter.

The remaining three characterising features of Claim 1 are all measures which are concerned with the technical problem of providing an energy-efficient and cost- effective method of equipping pilfer-proof polypropylene closure caps with in situ fluxed plastisol gaskets.

From a reading of the whole of document (b) it is apparent that the skilled person is being encouraged to use pre-heating temperatures which bring the plastisol close to the melting temperature of the closure cap, preferably 10 to 5 C therebelow, of page 2, lines 50 to 54. The minimum pre-heating temperature specifically mentioned is to 35 C below the melting point of the cap, that is for a polypropylene cap with a melting point of 165 C a pre-heating temperature of 130 C. Thus it is stated at page 3, lines 23 to 26 that a "closure temperature of more than 35 C below the melting point of the closure, i.e. typically below 130 C for polypropylene, is unlikely to be useful for conventional plastisols. For a plastisol of a lower fusion point a lower closure temperature is possible". However, the disadvantageous properties of such low fusion point plastisols are clearly described on page 1, line 59 to page 2, line 15 of the document. Accordingly, even on the assumption that the skilled person with the knowledge of document (b) would recognise the potential benefits of pre-heating the closures by conventional means when using lower frequency radiation in the range of 1 to 200 MHz as suggested by document (u), thereby to reduce the length of time exposure to the radiation is required, there is nothing which could encourage him to use pre-heating temperatures in the range of 50 to 110 C as stated in the present Claim 1.

It is however apparent that by using these lower temperatures the energy requirements for pre-heating will be reduced and the rate of throughput through the heating oven can be increased since the closure caps will more quickly reach the desired temperature. This latter effect is further enhanced by the 20 to 50% reduction of thickness in the end wall of the closure cap in the region of the gasket, as required by present Claim 1, thus improving heat transfer to the plastisol.

It is true that in the embodiments of Figures 3 and 4 of document (l) the end wall is slightly thickened centrally and decreases in thickness towards its periphery. This is stated to allow better flow of plastics material in the mould and also to resist "doming" under pressure. In the embodiment of Figure 2 however it can be clearly seen that the end wall is considerably thicker in the region of the gasket than centrally thereof. Thus the skilled person receives no impetus from this document to decrease the end wall thickness at the gasket to the extent required by present Claim 1 and is not taught that any such reduction could be beneficial with respect to the gasket fluxing operation.

It is also known from a number of documents cited in the opposition proceedings to improve the mechanical anchorage of the gasket to the closure cap by providing dimples or other small recesses in the bottom of the channel in which the gasket is located. These recesses cannot however be considered as an end wall thickness reduction within the meaning of present Claim 1.

Having regard to the above the Board comes to the conclusion that the method defined in present Claim 1 cannot be derived in an obvious manner from the state of the art and accordingly constitutes a patentable invention (Article 56 EPC). This claim together with Claims 2 and 3 dependent thereon and the amended description therefore constitute a suitable basis for maintenance of the patent in amended form.

5. Procedural questions

At the end of the oral proceedings before the Opposition Division on 25 October 1990 the latter announced its intention to maintain the patent in amended form on the basis of the amended Claim 1 submitted at those proceedings and set a two month time limit for the filing of an amended description. This was received on 29 October 1990 and communicated to the Appellants with an official letter dated 8 November 1990. With a fax dated 13 November 1990 (confirmed by letter received on 22 November 1990) the representative of Appellants indicated that there were aspects of the acknowledgement of prior art with which his clients would not be in agreement and that he was seeking their instructions. The interlocutory decision of the Opposition Division to maintain the patent in amended form was issued on 7 December 1990 before the receipt on 12 December 1990 of a fax from the Appellants (confirmed by letter received on 14 December 1990) setting out their objections to the introductory description of the amended patent specification.

The Appellants argue that the procedure adopted by the Opposition Division deprived them of their opportunity to comment on the amended description submitted by the Respondent on 29 October 1990. That assertion may on the face of it appear justified. It must, however, be pointed out that apart from a re-ordering and adaptation to the terms of the claim accepted at the oral proceedings the main substance of the amended description, in particular the evaluation of the teachings of document (b) which is the only aspect criticised in the Appellants' letter received on 14 December 1990, is to all extents and purposes identical to that of the granted patent specification. It cannot therefore be said that the Appellants did not have any opportunity to comment on this matter and indeed, as is clear from their submissions made in writing and during the oral proceedings before the Opposition Division, it is apparent that they had already clearly expressed their dissatisfaction with what they believed to be a misleading interpretation of the true content of document (b).

Thus, although it might have been more apposite for the Opposition Division to await a further submission from the Appellants once the fax of 13 November 1990 had been received, the procedure followed by the Opposition Division does not constitute a substantial procedural violation since the right of the Appellants to be heard according to Article 113(1) EPC had been adequately safeguarded.