T 0497/91 30-06-1992

Reasons for the Decision

1. The appeal is admissible.

2. The novelty of the claimed lock for moulds was not disputed by the Appellant and is recognised by the Board; no further argument is necessary, therefore, in this respect (Article 54 EPC).

3. The prior art portion of Claim 1 is based upon document D1, which was considered as the starting point of the invention in the previous proceedings. However, this document was published on 25 October 1984, that is to say after the priority date of the present patent. In order to see if this priority date is still valid for the whole subject-matter of Claim 1, as required by Article 88(3) EPC, the Board has examined whether all the features of the contested Claim 1 could be found in the English translation of the Japanese priority document relating to the present invention. The last feature of Claim 1 is not found in any of the claims of this priority document, but an implicit disclosure of it appears on page 4, lines 18- 22. Thus, in the opinion of the Board, the claimed priority date of the present invention is still valid for Claim 1, and, consequently, document D1 does not constitute state of the art as defined in Article 54 EPC combined with Article 89 EPC.

4. During the oral proceedings, it was agreed that the closest prior art is described in the description of the patent in suit, column 1, lines 5-11. An example of this closest prior art is described in document E7.

According to this closest prior art, a lock for locking the moulds of an injection moulding apparatus comprises motor means and a transmission mechanism. The transmission mechanism operates a toggle mechanism, the links of which are brought into a straightened state, thereby locking the moulds. A hydraulic mechanism is used as the driving motor.

The Board agrees with the Appellant that, when a toggle mechanism is used, it is to be assumed that the links of this mechanism, when they are completely extended, are "in a straightened state". The Board has considered the Appellant's offer to file additional evidence as to the meaning of the term "Strecklage", which is currently used in the German documents, but has concluded that such evidence is not necessary, since this expression corresponds to the term "straightened state". In the closest prior art, therefore, it is also to be assumed that the links are in a straightened state when the moulds are closed.

5. In the light of this closest prior art, the technical problem underlying the patent in suit is to be seen in providing a similar lock, which overcomes the disadvantages of hydraulic means and which, in the locking position, prevents the moulds and the links of the toggle mechanism from being moved by means of a low energy consumption, when, for example, vibrations occur.

According to the disputed patent, this technical problem is solved by providing an electrical servo motor as driving means and by supplying this motor with a current lower than the normal operating current, when the moulds are locked, so that the links are kept in the straightened state.

6. The Board is satisfied that this problem is effectively solved. Although the opposition and the appeal were not based on the ground that there was insufficiency of disclosure (Article 100(b) EPC), the Appellant argued several times that features, such as the level of the low current, the moment of its application, or the means of stopping the links, were missing and that it was not possible to solve the problem on the basis of the disclosed features. The Board has considered of its own motion under Article 114(1) EPC the Appellant's arguments concerning insufficiency, but has found however that these arguments are not convincing and that, in the opinion of the Board, the features of Claim 1 adequately disclose the solution of the invention. The Board does not see any reason to unduly limit the scope of the claim by giving the level of the low current and the moment it is applied. A person skilled in the art, receiving the teaching of applying a lower current as soon as the links are "in the straightened state", is able to determine the kind of electrical motor which can fulfil the claimed requirements, that is to say with a normal current, move the links towards the locking position, the motor being then "stopped" (see the description), meaning that it no longer rotates, and supplied with a low current, which is sufficient "to hold" the links in position. No stopping means for the links are needed, since there is already a physical abutment because of the moulds, which are closed.

7. Document E1 is an old document, filed in 1929. It concerns a simple press for plastic products, having a die moving up and down to press into a given shape a plastic material lying on the working surface of the press. Once the die has reached its lower pressing position, it must be maintained under pressure for a certain time. The object of this prior art is to avoid the disadvantages of hydraulic driving means and, to this end, an electrical motor is used, rotating a spindle by means of a gear transmission, thus moving a nut in a longitudinal direction to displace the joint point of a toggle mechanism, thereby moving the die. Switching means are provided on the path of the nut to stop the motor at both extreme positions of the die. This document teaches that, as soon as the die has reached its lower position which corresponds to the higher pressure, the current is switched off and that the die remains in its locking position, since the motor is quickly stopped by means of a brake.

8. As seen, a brake is mentioned in this prior art, but its only function is to bring the motor to a standstill as quickly as possible. That it moreover helps to hold the links in position is not disclosed in this document. Therefore, the assertion of the Appellant that this prior art teaches the need for mechanical means to hold the links in position is not supported by the provision of a brake, which in this prior art has in fact another function. Lines 55-57 in the right-hand column of page 2, mentioned by the Appellant as a further basis for his assertion, indicate only that, when driving belts are used, instead of an electrical motor, the switches are replaced by mechanical means, which disconnect the belts. Such an indication is quite remote from a hint to provide mechanical means for holding the links or for providing the electrical motor of the invention with a low current.

9. The problem of holding the links when the die has reached its end position in order to press the plastic material is not even envisaged in document E1. It is only stated that this position is held because of the quick stopping of the motor, and nothing more. The man skilled in the art, reading this document, does not receive any suggestion for providing means to keep the links in position, when vibrations or the like occur. There is not even a teaching that there could be a problem with controlling the locking position of the die. Faced with the problem of the present invention, the man skilled in the art therefore has no reason to turn his attention to this prior art.

10. If he does so nevertheless, this document also gives him no suggestion for the solution itself, since it teaches to switch the motor off. The solution of the contested invention is based moreover on the observation that a little power is needed to hold the links when they are in a straightened state, and it is only for this main reason that a motor with a low current can be used. Document E1 gives absolutely no hint in this direction, so that the skilled person has no reason from this prior art to continue to supply current to the motor when the links have reached their straightened position, since it would be wasteful. The solution of the present invention must be regarded as a consequence of the above-mentioned observation. Of course, it is well-known that the links of a toggle mechanism, when they are in a straightened state, need little power to be held in position, but the use of this knowledge to solve the problem underlying the present invention is not suggested. Because of this link between the particular solution of the present invention and the said observation, which is the basis for this solution, the Board considers that an inventive step would be recognised in the corresponding feature of Claim 1, even if the teaching of mechanical means for holding the links, such as a brake, had been given by the prior art, because with such mechanical means a particular position of the links is not needed.

11. Since no other document among those mentioned during the proceedings suggests this solution, and since the Appellant has given no other reason why it should occur to the skilled man to operate the motor under a low current when the moulds are locked instead of switching the current off, this particular feature of Claim 1 implies an inventive step, so that the whole granted claim meets the requirements of Articles 52 and 56 EPC. Claim 1 being the only independent claim, the granted patent, therefore, is to be maintained.