Executive Intellectual Property Bulletin

DISTRICT COURT APPLIES 35 USC 112 TO LIMIT

SCOPE OF CLAIMED METHOD STEP

Altech Controls v. EIL Instruments, 44 USPQ2d 1890 (SD Tex. June 6, 1997)

Altech Controls, a recently published decision from the U.S. District Court Southern District of Texas, applies 35 USC 112 ¶6 to limit the literal scope of the claimed method step "selectively energizing and deenergizing compressors in response to the respective increase capacity signals and the decrease capacity signals..." to structural equivalents of the selection strategy disclosed in the patent specification. The claim so-limited was ruled not to cover the binary-logic selection strategy employed by EIL Instruments, a competing maker of commercial refrigeration systems accused of infringement. The decision, among the first to construe methods under the constraints of ¶6, affects not only infringement analyses and design-around strategies for existing patents, but also patent-making practices generally.

Background: 35 USC 112 ¶6 allows inventors to define or claim features of their inventions as a "means" or "step" for performing a function without literally reciting structure, material, or acts in the claim itself for performing the function. However, ¶6 also limits the protective scope of these claimed features to the corresponding structure, material, or acts described in the specification and their structural equivalents. For example, one may claim an element of an invention as "a means for fastening two boards." Literally, this language encompasses screws, nails, glue, clamps, indeed anything that could serve the fastening function. Yet, ¶6 requires courts to look to the specification to determine its legal scope. If the specification only discloses screws for this function, ¶6 would exclude non-structural equivalents, glue for instance, from the scope of the claim, leaving a potential way for someone to design around the patent. Thus, many patent attorneys who once used means language as a matter of course now use it only sparingly, if at all.

In recent years, courts have ruled that some claims using means language were outside ¶6 and still other that did not were within ¶6, leaving some practitioners confused about whether any given claim triggers ¶6. For apparatus claims, it is understood that claims having functional language without corresponding structure or material for achieving the function fall under ¶6. Also understood is that using "means" in any claim raises a legal presumption that the claim falls under ¶6. However, beyond the nebulous notion that reciting a step plus function without supporting acts triggers ¶6, little is known about construing method claims under ¶6 (OI Corp v. Tekmar, 42 USPQ2d 1777). Thus, cases, such as Altech Controls, which purport to apply ¶6 to method claims promise to be instructive.

Case Analysis: In Altech Controls the court conducted a special pre-trial hearing, known as a "Markman" hearing, to construe the claims as understood around the application filing date (p.1894). Among many issues was whether the claimed "step of selectively energizing and deenergizing compressors" fell under ¶6 and, if so, whether the corresponding first-on-first-off (FIFO) selection procedure in the specification, the only selection strategy disclosed, was structurally equivalent to EIL's binary-logic technique (p.1893). The FIFO procedure entailed turning on the longest inactive compressor or turning off the longest running compressor to increase or decrease cooling capacity. The court ultimately found that ¶6 applied, because use of "step" terminology in the claim raised a ¶6 presumption, analogous to the presumption attached to "means" language, which was unrebutted in the prosecution history and because the step language was materially identical to means language in other claims (p.1897).

In performing the structural equivalency analysis to determine if Altech's FIFO selection procedure encompassed EIL's binary selection technique, the court leaned heavily on two factors: prosecution history estoppel and the literal claim language. During prosecution, Altech had repeatedly invoked the FIFO procedure to gain allowance, essentially precluding, or estopping, Altech from later expanding the claim to cover more (p.1901). Additionally, the claimed step language itself didn't allow turning on or off two or more compressors at a time to change capacity, and thus precluded it from covering EIL's binary compressor control strategy, which entailed activating and deactivating specific compressor combinations (p.1899).

Although the court's reliance on prosecution history estoppel and on the literal claim language ultimately adds little to our understanding about the construction of method claims under ¶6, the case does illustrate that practitioners should eschew use of "step" terminology in method claims if they wish to avoid a presumption that ¶6 applies and the prospect of courts trying to apply it. Furthermore, during prosecution, it's better to argue how the claimed invention itself distinguishes from prior art, rather than how structures or processes in the specification do.

If you have questions or comments, please contact bulletin author Eduardo Drake or any other attorney at Schwegman, Lundberg & Woessner.