In Germany, too, it has become established to assess the inventive step on the basis of the problem-solution approach. Advantages of the invention on the one hand and disadvantages of the prior art on the other play a central role. It is assumed that the person skilled in the art wishes to avoid known disadvantages. The BGH recently dealt with the following question: Can a solution be considered non-obvious and thus inventive if it is associated with foreseeable disadvantages?
The patent claim of the patent in suit relates to a “belt tensioner drive” which essentially consists of two worm gears connected in series. Each of the two worm gears has a 90° deflection, so that the drive axis and output axis of the belt tensioner drive are ultimately parallel to each other.
The invalidity attack is mainly based on two citations: One (D3) shows the exact same sequence of two worm gears in a retractor. However, this gear is used for the purpose of loosening the belt to a certain extent. Compared to the patent in suit, there was therefore only a different, quasi opposite purpose.
The other citation (D2) relates to a belt tensioner, but with a combination of crown gear and worm gear. In other words, while the invention used a worm gear in the first place, the citation used a crown gear instead.
The German Federal Patent Court declared the Patents null and void. It was known to the person skilled in the art that crown wheel gears have the disadvantage that they generate noise. At the same time, the skilled person was aware that other reversing gears, such as worm gears, do not have this disadvantage. The skilled person therefore had reason to search for gearbox solutions that did not have this disadvantage. Since citation D2 already provided for a worm gear as the second gear, it was reasonable to expect that the skilled person would also use a worm gear as the first gear.
The patent proprietor appealed against this to the BGH. However, the BGH confirmed that the patent in suit is not inventive. In its reasoning, the BGH stated the following, among other things.
The advantage of the worm gear, namely self-locking against a torque from the belt reel to the electric motor, is known from the belt tensioner counter position (D2).
In addition, D3 shows the skilled person the principle of using two worm gears as 90° deflection gears in order to achieve a parallel arrangement of belt reel and electric motor with low noise. The skilled person can recognize that the arrangement of an electric motor, two worm gears and a belt reel can achieve the function of belt tensioning. It is only necessary to reverse the polarity of the electric motor in order to change the direction of rotation and thus produce belt tensioning instead of belt slack.
As the skilled person was aware of the disadvantageous noise development of crown wheel gears, he had reason to further develop the belt tensioner known from D2 in such a way that the noise emissions are reduced. He received suggestions on how such an improvement could be realized in the prior art according to D3.
The patent proprietor’s objection that the use of two worm gears instead of just one would result in a higher reduction ratio and that the application in accordance with the patent was therefore not obvious does not apply. The fact that the electric motor has to rotate at a higher ratio with two worm gears is in no way mentioned as a difficulty in the patent in suit. Nor does it specify how this disadvantage is to be overcome. It is therefore the case that the Patents tacitly accepts this disadvantage.
If the examples of solutions proposed by the inventor ignore the existing disadvantages or difficulties and simply accept them, then it cannot be argued that the person skilled in the art would have recognized these difficulties and would not have considered the corresponding disadvantageous solution.
As a further objection to obviousness, the patent proprietor submitted the following: In the citation it is mentioned that self-locking should be aimed for and various other measures are mentioned as a solution, but not the use of a second worm gear. It was therefore more obvious for the skilled person to choose one of these other measures for noise reduction.
This objection also does not apply according to the BGH. If the skilled person considers several alternatives to solve a problem, several of them may be obvious. In principle, it is irrelevant which of the alternative solutions the skilled person would consider first (i.e. the most obvious).