Editing Patentability (section)

== Infringement ==

The fact that an invention is patentable or even patented does not necessarily mean that use of the invention would not also [[patent infringement|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). This means that the later inventor must 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 [[Henry Woodward (inventor)|Woodward]] and [[Mathew Evans|Evans]] thick carbon filament light bulb. Thomas Edison bought the Woodward patent for $5,000 US before he began his development work so that Woodward would not be able to later sue him for patent infringement after Edison became commercially successful.