Ordinary meaning can limit features in claims to the features’ purpose and principal use, according to the Federal Circuit’s recent decision in Asetek Danmark A/S v. CMI USA Inc., No. 16-1026 (Fed. Cir. 2016).

The patents-in-suit are directed to systems and methods for cooling the “central processing unit (CPU) or other processing unit of a computer system” using cooling liquid.  The patents describe a system with an upper and lower chamber referred to as a “pump chamber” and “thermal exchange chamber,” respectively.  At issue was the accused infringer’s theory that the prior art’s disclosure of a “sucking channel” was a “thermal exchanger” as required by the claims because the sucking channel “exchanges some heat.”

As colorfully illustrated and explained at page 12 of the Slip Opinion, that argument won’t do:

No ordinary meaning or claim construction requires appellants’ conclusion that Koga’s “sucking channel” is a “thermal exchange chamber” simply because it exchanges some heat.  No meaning of the claim phrase precludes its limitation only to devices with certain device-defining characteristics such as purpose and principal use, excluding other structures that occasionally or in minor ways produce the same result—any more than a bedside plugin radio must be considered a room radiator because it unavoidably gives off some heat.

The Court’s opinion is necessarily limited to the facts at hand.  Nevertheless, this claim construction principle may help guard against the possibility of an Examiner or litigant offering a claim interpretation that would encompass structures that are not realistically comparable to the claimed invention.