IP Courses Lecture Site

A company has several identical patents for epilators in Europe. The patented epilator consists of a handle, a motor with a rotating axis, and a coil spring arranged on the rotating axis. The coil spring is bent at one point so that the coils on the outside of the spring are spread apart and those on the inside are compressed. This mechanism allows hairs to enter the spread coils and be pulled into the compressed areas by the rotation of the spring and finally pulled out. The patent claim therefore covers an epilator with a coil spring that can grip and remove hairs due to its bend. The infringer wants to use the principle of the epilator, but attempts to circumvent the patent by using a rubber roller instead of the coil spring. This rubber roller has radial incisions that are spread apart and compressed on the opposite side when rotated – similar to the coil spring. The function of the rubber roller is therefore comparable to that of the coil spring: it grips the hairs in the incisions and pulls them out by compressing the incisions due to the rotation. The patent holder does not want to tolerate this modification.

Equivalent patent infringement is an extension of patent protection. It applies in cases where the patent claims are not literally fulfilled, but the patented invention is circumvented by minor modifications. Patent claims are normally formulated precisely and must be interpreted when assessing infringement. This often leads to situations in which the object of the infringement does not formally constitute a patent infringement because one or more features of the patent claim are not fulfilled. This can result in a seemingly marginal deviation ruling out infringement, even though the actual invention has been adopted almost identically.

In the past, German patent law was committed to the so-called general concept of invention, in which the scope of protection of a patent was not rigidly aligned with the patent claims. Rather, it was assumed that all objects corresponding to the essence of the invention should also be covered by patent protection. However, this broad interpretation was rejected because it was difficult for third parties to predict.

In order to combat unfair circumvention of the invention, equivalent patent infringement was introduced. This applies if the infringing object does not literally correspond to the patent claim, but differs only in one feature that is considered too simple or obvious a circumvention of the patent.

For equivalent patent infringement to exist, a feature of the patent claim must first be missing from the infringing object, i.e., it must not be literally fulfilled. The decisive factor is then whether this feature is replaced by a so-called substitute means that achieves the same technical effect. This substitute means must not merely represent a completely different solution, but must fulfill three criteria: equal effect, obviousness, and equivalence.

In the specific case of the epilator, this is evident from the fact that the patent claim expressly requires a coil spring. The infringer does not use this, but replaces it with a rubber roller with radial incisions. This means that the feature “coil spring” specified in the claim is missing. However, the rubber roller performs the same function as the coil spring: it spreads out, grips the hairs and pulls them out again when compressed. The rubber roller is therefore a substitute that replaces the coil spring. This substitution must be examined in terms of equivalent effect, obviousness and equivalence.

The first criterion for equivalent patent infringement is equivalent effect. This involves examining whether the substitute used in the infringing product achieves the same technical effect as the feature specified in the patent claim. The decisive factor is whether the function is performed identically and thus the inventive achievement has the same effect. If the substitute performs the same task with the same success, this criterion is considered to be fulfilled.

In the case of the epilator, it had to be examined whether the rubber roller had the same technical effect as the coil spring. The question was whether both components performed the same function, namely gripping and pulling out hair. The courts found that the rubber roller achieved the same effect as the curved coil spring due to its radial incisions when rotating: In both cases, hairs were picked up in spread-out areas and pulled out when compressed. The rubber roller thus fulfilled the criterion of equivalent effect.

The second criterion of equivalent patent infringement concerns obvious interchangeability. This involves examining whether the modification was recognizable to the skilled person as an obvious technical alternative on the filing date of the patent. The replacement means must not represent a surprising or independent further development, but must be considered by the skilled person, based on their expertise and the known technology, as an obvious possibility for fulfilling the claimed function. Only then can it be included in the scope of protection of the patent.

In the epilator case, it was examined whether replacing the coil spring with a rubber roller was an obvious modification. The courts concluded that this was the case: both components fulfilled the same function of gripping and pulling out hair, and the rubber roller represented a technically obvious alternative for a person skilled in the art. If, on the other hand, the rubber roller had represented a surprising and independent technical solution, the criterion would not have been met and there would have been no equivalent patent infringement.

The third criterion for equivalent patent infringement is equivalence. This involves examining whether a person skilled in the art, after reading the entire patent specification, would assume that the alternative means – in this case, the modified component – should also be covered by the scope of protection of the patent. The decisive factor is whether the patent holder has deliberately limited the protection to the selected feature with the specific wording of the claim or whether the modification appears to be equivalent. If the patent specification makes it clear that only a very specific solution is claimed, an extension to other means may be ruled out.

In the case of the epilator, the question arose as to whether a person skilled in the art would gain the impression from reading the patent specification that a rubber roller was also covered by the protection. Some courts denied this, as the patent specification referred exclusively to a coil spring, thus giving the impression that the patent holder had deliberately claimed only this solution. Other courts, however, considered the roller to be equivalent, as it performed the same function and saw no indication that the scope of protection had been deliberately narrowed. Depending on the assessment of this equivalence, the patent infringement was affirmed or denied.

Another corrective factor in assessing equivalent patent infringement is the objection of free prior art. The basic idea is that a patent holder should not be granted more protection through the concept of equivalence than he was entitled to at the time of filing the application. If the modification chosen by the infringer was already part of the prior art or represented an obvious technical solution, it may not be subsequently brought under patent protection. Otherwise, equivalence would lead to an impermissible extension and deprive the general public of something that was already freely available. For this reason, the equivalence test always examines whether the modified solution was known or obvious to a person skilled in the art from the prior art. If this is the case, it cannot be included in the scope of protection as equivalent.