Legal Definitions - functional limitation

In patent law, a functional limitation refers to defining an invention by what it does or its intended purpose, rather than by its specific physical structure, components, or how it achieves that purpose.

While not inherently invalid, patent examiners scrutinize claims that rely heavily on functional limitations because they can be overly broad. Such claims might inadvertently cover every possible way to achieve a particular function, even methods not conceived or described by the inventor, potentially hindering future innovation by others.

• Example 1: Software Invention

  Imagine an inventor applies for a patent describing their invention as "a computer program for efficiently compressing data files." This is a functional limitation because it defines the invention solely by its outcome (efficient data compression) rather than by the specific algorithms, data structures, or processing steps it uses to achieve that compression. A patent examiner might question this claim's breadth, as many different computer programs could achieve efficient data compression using various, distinct methods.

• Example 2: Mechanical Device

  Consider a patent application for a new type of engine. If the inventor claims "a mechanism for converting thermal energy into rotational motion," this would be a functional limitation. It describes the engine's fundamental purpose but doesn't specify the unique arrangement of pistons, turbines, combustion chambers, or other components that make this particular engine novel. Such a broad claim could potentially cover all types of heat engines, from steam engines to internal combustion engines, making it too encompassing.

• Example 3: Chemical Composition

  Suppose an inventor develops a new material. If their patent claim states "a composition of matter effective for preventing corrosion on metal surfaces," this is a functional limitation. It describes the material by its desired effect (corrosion prevention) rather than by its specific chemical formula, molecular structure, or the precise combination of elements and compounds that give it that property. This claim could be challenged for being too broad, as countless different chemical compositions might prevent corrosion.