Patent drafters sometimes turn to “means-plus-function” language to claim an invention based on its function rather than its underlying structure. The ruling by the U.S. Court of Appeals for the Federal Circuit in Robert Bosch, LLC v. Snap-On, Inc. serves as a good reminder that means-plus-function language, in and of itself, may not satisfy the definiteness requirement.
Robert Bosch LLC owns a patent for a diagnostic tester that determines whether a motor vehicle’s computerized control unit needs to be reprogrammed. The tester is made of a “program recognition device” and a “program loading device.”
Bosch sued Snap-On Inc. for infringement of the patent. The district court found that the terms “program recognition device” and “program loading device” were indefinite, making the patent itself invalid. Bosch appealed.
Road to indefiniteness
According to U.S. patent statutes, a patent must conclude with one or more claims specifically pointing out and distinctly claiming the invention at issue — definiteness. In assessing the definiteness of Bosch’s patent, the Federal Circuit focused on Section 112(f) of the statutes.
Under that statutory section, a patentee can recite a portion of a claim in a patent application as a means, or a step, for performing a particular function (for example, a means for fastening), but without reciting any structure corresponding to the recited means. These “means for” claims, however, are sufficiently definite only if the patent specification describes some corresponding structure for performing the recited function (for example, a nut and bolt) — in which case the patent is deemed to cover that structure and its equivalents.
To determine whether a claim limitation invokes Sec. 112(f), a court must first decide whether the limitation is drafted in a means-plus-function format. The use of the term “means” or “step” and inclusion of functional language triggers a rebuttable presumption that Sec. 112(f) governs the construction of the claim term. If so, the court attempts to interpret the claim limitation by identifying corresponding structures, material or acts in the patent specification to which the claim term will be limited. If the court is unable to identify any such structures, the court deems the claim indefinite and the patent invalid.
All function, no structure
The appellate court found that the trial court had erred in presuming that “program recognition device” is a means-plus-function recitation based solely on the use of the phrase “by means of” in the relevant patent claim. But the appellate court concluded the error was harmless because the term invoked Sec. 112(f) without the presumption. Likewise, the court found that “program loading device” invoked 112(f).
Both terms, the court said, invoked Sec. 112(f) because they only described functions and, even when construed in light of the patent specification, failed to provide sufficiently definite structure to someone skilled in the relevant art. The specification’s lack of structure corresponding to the claimed functions, however, also led the court to conclude the claim phrases were indefinite.
More than words
When looking to satisfy the definiteness requirement under Sec. 112(f), patentees must not focus solely on whether a claim limitation is expressed as means-plus-function. Without reference to a corresponding structure in the specification, such claims will likely fail.