The focus of our discussion today will be on the various types of limitations in a patent claim, including structural, functional, and intended use claim limitations, and how they differ from one another.
What is a structural claim limitation?
A structural claim limitation is a type of limitation found in patent claims that restrict the claimed invention to a specific physical structure or arrangement of components. It describes the specific configuration, shape, composition, or other physical characteristics of the claimed invention, and helps to distinguish it from other similar or related inventions.
An example of a structural claim limitation is “an apparatus for filtering water comprising a cylindrical filter element and a filter housing having an inlet and an outlet, wherein the cylindrical filter element is positioned within the filter housing between the inlet and the outlet.” The emphasized limitations specify the physical structure (i.e., filter element, filter housing, inlet, and outlet) of the claimed apparatus, including the specific shape (i.e., cylindrical) and location of its components (i.e., between).
In an apparatus claim, the structure of the apparatus must be recited. Patent examiners primarily look to the structural elements of the claim to determine whether the claim is patentable. The question they are asking is whether the prior art discloses such structure.
A simple format to write an apparatus claim is:
An apparatus comprising:
Element 1;
Element 2; and
Element 3.
What is a functional claim limitation?
A functional claim limitation is a type of limitation found in patent claims that define the claimed invention in terms of its functional characteristics or features, rather than its physical structure or components. It describes what invention does, rather than what the invention is.
An example of a functional claim limitation is “a software program for organizing and displaying digital photographs, wherein the program is configured to automatically group photographs by date, time, and location.” The emphasized limitation does not describe the physical structure or components of the software program, but rather its function or purpose, which is to organize and display digital photographs in a specific way. The limitation specifies the functional features of the program, such as its ability to group photographs based on date, time, and location.
Functional claim limitations do provide patentable weight to a claim. However, the interpretation of functional claim limitations is so broad that the function is easily found within the prior art. In particular, if a prior art reference is capable of performing a such function that prior art reference is said to disclose such function. This is true even if the prior art reference does not perform such a function.
As such, you might wonder why anyone might want to recite functional limitations in a claim. The purpose of functional limitations is to provide context and link the structural elements together.
A simple format to include functional limitations in an apparatus claim is:
An apparatus comprising:
Element 1 for [insert function of element 1];
Element 2 for [insert function of element 2]; and
Element 3 for [insert function of element 3].
What is an intended use limitation?
An intended use claim limitation is a type of limitation found in patent claims that define the claimed invention in terms of its intended use or purpose. It specifies the problems or needs the invention is designed to solve, and the context in which it is intended to be used. An intended use claim limitation is used to provide context for the patent claim.
Examples of intended use limitations are shown above. In the example “an apparatus for filtering water,” the intended use of the apparatus is filtering water. Also, in the example “a software program for organizing and displaying digital photographs,” the intended use is organizing and displaying digital photographs. The distinction between functional limitations and intended use limitations is that intended use limitations describe an end result, not how something is performed.
Intended use limitations are typically not given any patentable weight unless some structural differences are imposed by the use or result on the structure of material recited in the claim. In general, intended use limitations are used to give context and focus the examiner’s attention on the field of the invention. Oftentimes, during the examination, the examiner will use prior art in a totally different field and apply them to the claimed invention. In order to prevent the examiner from doing so, it’s helpful to recite the intended use of the invention in the preamble of the claim.
A simple format to include intended use limitations in an apparatus claim is:
An apparatus for [insert intended use of apparatus], the apparatus comprising:
Element 1 for [insert function of element 1];
Element 2 for [insert function of element 2]; and
Element 3 for [insert function of element 3].