T 0676/89 26-03-1991

1. The appeal is admissible.

2. Novelty It is undisputed by all the parties that none of the documents cited nor the prior use asserted by the Appellants during the Opposition proceedings before the first instance relates to a naval ground mine. Consequently, the subject-matter of Claim 1 is novel with respect to such evidence.

The prior use which has been newly asserted by Appellant (01) during the Appeal proceedings has not been included into the consideration of novelty for reasons which will be set out later in this decision.

3. Closest state of the art The Respondent has explicitly acknowledged in the description of the patent in suit, (cf. column 1, lines 16 to 58) and confirmed in his letter dated 25 April 1990, page 1, last paragraph, that a naval ground mine comprising the features in the pre-characterising part of Claim 1 has been known before the priority date of the patent in suit. Although no printed document has been cited in this respect, a modular ground mine comprising all the features enumerated in the first part of Claim 1 and described in column 1, lines 16 to 58, of the description, can, therefore, be considered as constituting the closest prior art.

4. Problem and solution

4.1. The description of the patent in suit, (cf. in particular column 1, lines 25 to 58) states that naval ground mines in general, and hence also the modular ground mine which forms the closest prior art described above, must be capable of withstanding extremely rough handling. Therefore with this known modular design, the strong joint of the modules is achieved by the simple expedient of providing a flange at each end of each module, and of bolting through the flanges.

The patent in suit suggests that a major disadvantage of this known modular ground mine consists in that its bulky protruding flanges provide a regular pattern which render such mine clearly identifiable by modern sonar devices. Consequently, the patent in suit maintains to solve the problem of detection by providing a connection between the modules which is undetectable by a sonar but nevertheless constitutes an adequately strong joint.

4.2. Although not mentioned by the patent in suit, the protruding flanges of the closest prior art mine also bring about another problem which is as serious as the problem mentioned above and recognisable by a person skilled in the art.

The historical development of naval war shows, see for instance the above-mentioned book by Ledebur, (pages 52, 83 and 84), that naval ground mines have for a long time, and to an increasing extent, been launched via the torpedo tubes of submarines and surface crafts. In these cases their shape, at least with respect to the diameter, has to fit into the torpedo tubes. This requirement, however, constitutes a rather tough restriction of size for ground mines which are intended to reliably destroy their target when this passes in a certain distance and therefore need to have a higher explosive power than those weapons which are constructed to explode on direct contact.

Consequently, if a known modular ground mine with protruding flanges were adapted in diameter to fit into a torpedo tube, the person skilled in the art would immediately realise that the flanges would provide an empty space between the torpedo tube and the surface of the ground mine which could have been better used for additional explosives. Moreover, the protruding flanges would impede the convenient and quick loading of the mine into the torpedo tube for launching.

These two disadvantages immediately call for a removal of the protruding flanges and for the creation of a less obtrusive surface.

4.3. The problem indicated under point 4.2, as well as the one under 4.1, is simultaneously solved by the features specified in Claim 1. Consequently, the solution of either of these independent problems also results in the solution of the other. In particular, the measure that "the ring has a radially outer surface which conforms substantially without discontinuity to the peripheral contour of the casing" at least in the region of the connection of the modules favours the launchability of the mine through a torpedo tube but simultaneously makes it less identifiable by a sonar.

5. Inventive step

5.1. The problem of launchability of a ground mine via a torpedo tube specified under 4.2 above is a well known desideratum in relation to any known ground mine, see Ledebur above. It may be that torpedoes and naval ground mines give rise to different problems as soon as they have left their common launching device, which problems then require independent constructional solutions. As far as the behaviour within a torpedo tube is concerned, the main body of a ground mine has to meet the same requirements as the main body of a torpedo which is intended to be slidably launched through the same torpedo tube. The Board is, therefore, convinced that a mutual exchange of technical information between the fields of torpedoes and of naval ground mines, as far as problems caused by the common launching device are concerned, is daily routine for the skilled designers in these fields.

5.2. The designer of a modular ground mine who wants to modify a known ground mine (with protruding flanges) to make it launchable through a torpedo tube and therefore to create a continuous cylindrical surface of its main body at least in the region of this connection will, consequently, also inform himself in the field of torpedoes about how flanges protruding from the surface can be avoided whilst a firm connection between adjacent modules can be nevertheless maintained.

5.3. In the course of his search the person skilled in the art would have found document (D2). This document discloses a torpedo the main body of which is composed of the module sections (20, 30, 40, 50). Each section is provided with a spigot on an end face (15a, 15b) thereof with an radially outwardly directed lip. According to column 2, in particular last paragraph, adjacent sections are connected by a ring (60) having a radially outer surface which conforms substantially without discontinuity to the peripheral contour of the sections at least in the region of the said end face thereof. The radially inner surface (65) of the ring is adapted to embrace and hold together the lips on the spigots of adjacent end faces of the two module sections to be connected. The ring (60) is capable of being divided into distinct segments (6A, 6B, 6C) to permit assembly of the torpedo and being provided with fastening means in form of screws (62) whereby the ring segments can be firmly held together.

Consequently, the modular torpedo disclosed in (D2) comprises the same relevant features as the modular naval ground mine according to Claim 1.

5.4. A person skilled in the art trying to solve the problem of making a known modular ground mine launchable through a torpedo tube, as specified in paragraph 4.2 above, in the knowledge of document D2 would arrive at a naval ground mine comprising the features of Claim 1.

Using his modified ground mine, the person skilled in the art would readily accept as a favourable extra (bonus) effect that it is also less detectable by sonar devices than were previous mines. This property cannot, however, render inventive the otherwise obvious design (cf. T 21/81, OJ EPO 1983, 15).

5.6. The subject-matter of Claim 1 is therefore lacking an inventive step.

6. In the course of the Appeal proceedings the Appellant (01) has asserted, for the first time, a further prior use of a modular ground mine which, according to the contention by this party, would have affected the novelty of the subject- matter of Claim 1. The facts and evidence delivered by the Appellant, however, could not remove the considerable doubts of the Board, whether the circumstances of the asserted use were such as to render this use public. The matter was, in any case, irrelevant in view of the above conclusion.