Patentability - Infringement

Infringement

The fact that an invention is patentable or even patented does not necessarily mean that use of the invention would not also infringe another patent. The first patent in a given area might include a broad claim covering a general inventive concept if there is at that point no relevant prior art. Later, a specific implementation of that concept might be patentable if it is not disclosed in the earlier patent (or any intervening prior art), but nevertheless still falls within the scope of the earlier claim (covering the general concept). The later inventor must, therefore, obtain a license from the earlier inventor to be able to exploit their invention. At the same time, the earlier inventor might want to obtain a license from the later inventor, particularly if the later invention represents a significant improvement in the implementation of the original broad concept. In this case, the two enter into a cross license.

Thomas Edison's thin carbon filament light bulb was a patentable improvement over the earlier patented Woodward and Evans thick carbon filament light bulb. Thomas Edison bought the Woodward patent for $US 5,000 before he began his development work so that Woodward would not be able to sue him for patent infringement after Edison became commercially successful.