The doctrine of equivalence is commonly used to interpret the scope of an invention in patent and utility model litigation case law.
This doctrine expresses that when determining the scope of a patent (or utility model), a claimed feature may be replaced by a different one that performs the same or substantially the same function in the same or substantially the same manner with the same or substantially the same effect. In a recent utility model case, the Metropolitan Appeal Court explained that equivalency may not be extended to features that were not available before the priority date due to the lower level of the state of the art.
Another common interpretation of the doctrine of equivalence also widely used in litigation cases is that by replacing a claimed feature with an equivalent feature, the scope of a patent (or utility model) may not be extended so that prior art solutions fall into the scope of the patent (or utility model) concerned.
This limitation seems to be somewhat softened, at least in view of a recent opinion of the Industrial Property Expert Board of the Hungarian Intellectual Property Office in connection with a patent infringement case. The expert board has no decisive role in patent infringement litigation proceedings before the courts; however, its position can be taken into account by the court and parties often like to request such an opinion before or during the lawsuit.