Intended use and functional claiming is a common topic of interest because the lines of demarcation are somewhat blurred yet the difference in outcomes can be extreme. For example, intended use limitations essentially disappear in a validity analysis, meaning claims may stand or fall based on whether or not a certain limitation is, or is not, intended use.

Control systems are an area where intended use issues often arise as many control system inventions relate to a combination of system components arranged in a certain way, as well as how those components are controlled and/or operated. An example of how these issues play out in a real case can be seen in this recent Raytheon appeal (Appeal 2021-004831 Application 15/809,150) related to control of a gas turbine engine.

Claim 1 on appeal is reproduced below, with the limitations at issue underlined for emphasis:

1. A gas turbine engine comprising:
a fan rotor;
a compressor aft of said fan rotor;
a combustor aft of said compressor;
a turbine section aft of said combustor, said turbine section configured to drive said compressor section and said fan rotor;
a cooling air system comprising, an input connected to a compressed air tap, an output connected to at least said turbine section, and a heat exchanger having a first path and a second path, wherein the first path is disposed between said input and said output;
a valve and a propulsor disposed along a lower pressure cooling air path, wherein said h eat exchanger second path is in fluid communication with at least a portion of said lower pressure cooling air path, wherein said valve is configured to control flow within said heat exchanger second path;
said valve and said propulsor being controlled such that at ground idle of the gas turbine engine, said valve will be closed and said propulsor will be off at least at some times and at take off said valve will be open, and said propulsor will be on; and
wherein a gear reduction is positioned between a fan drive turbine rotor in said turbine section and said fan rotor.

The cited art used to reject claim 1 operated differently at idle and take off (essentially, the opposite to what was claimed). However, if the underlined features are merely intended use, the deficiency of the prior art is irrelevant. Thus, the issue came down to whether or not the underlined aspect was merely intended use.

Raytheon argued that the features are positively recited and required that the valve and propulsor are being controlled, which can only occur if the prior art has a controller programmed in the same manner. Raytheon cited Typhoon Touch Techs., Inc. v. Dell, Inc., 659 F.3d 1376 (Fed. Cir. 2011) and Dell, Inc. v. Acceleron, LLC, 818 F.3d 1293 (Fed. Cir. 2016) as support for the assertion that the language at issue in claim 1 requires more than the mere capability of operating as recited.

The PTAB was not moved by this argument.

Appellant’s argument regarding intended use is unavailing because the claims at issue in Typhoon Touch and Dell recited structure that performed the functional limitations in the claims, whereas, in contrast, Appellant’s claim recites, in passive voice, “said valve and said propulsor being controlled such that,” followed by the intended result of the control. Contrary to Appellant’s argument, claim 1 does not recite a control,or a controller, programmed in a particular manner

InTyphoon Touch and Dell, the claims recited memory and a processor for executing instructions (to carry out some operation), and a microcontroller with connectivity to remotely pole a CPU, respectively. Instead of specifying structure that performs the recited function, Raytheon’s claim 1 on appeal:

leaves open the question of what (or even who) controls the valve and propulsor ‘such that at ground idle of the gas turbine engine, said valve will be closed and said propulsor will be off at least at some times and at take off said valve will be open, and said propulsor will be on.’ As the ‘operation at idle and take off’ limitation does not modify structure, we agree with the Examiner that this limitation amounts to mere intended use of the structure actually recited in claim 1. Consequently, Appellant’s argument regarding intended use fails to identify Examiner error.

When a system or device claim merely specifies how various elements will operate or merely specifies resulting effects, there is opportunity for the Office, or an accused infringer, to argue that such features are merely intended use and thus not necessary to be disclosed by invalidating prior art. Thus, when drafting, particularly in the control systems arena, there are benefits to including sufficient structure, such as specifically reciting a controller programmed to carry out the operations needed, to distinguish the prior art.