If a patent says something is “essential,” then it must be so

To help a patent attorney prepare a patent application, inventors often provide a copy of a manuscript for an upcoming technical journal, research publication or white paper. The manuscript often goes into great detail to explain what features of the invention are essential, critical, or otherwise important to achieve certain results.

Then the patent attorney guts all of that language and produces a document that describes nothing with certainty, and that suggests everything is an option.

Why does this happen?

A recent opinion from the U.S. Court of Appeals for the Federal Circuit helps to explain the reasoning behind this.

A basic tenet of patent law is that the scope of the patent is defined by the patent’s claims. The detailed description serves as an instruction manual for how to make and use the invention, while the claims define the boundaries of the patent rights that cover the invention.  In order to infringe the patent, someone has to make, use or sell a product or process that contains all elements of at least one of the claims.

Ordinarily, when evaluating a patent infringement case, a court is not supposed to read words into the claims that aren’t already there. A court can use the detailed description to understand what the claim terms mean.  However, in most cases a court should not add features to a claim (and thus narrow the scope of the claim) if those features aren’t expressly recited in the claim.

The recent Federal Circuit decision, X2Y Attenuators, LLC v. Int’l Trade Commission, highlights an exception to this rule:  if the detailed description describes an element as “essential,” then the court may interpret it as being so — even if the claims don’t include that element.

In the X2Y Attenuators case the patent covered a structure for reducing electromagnetic interference in electrical circuits. The claims covered a structure with four electrodes.  The claims also described the positioning of certain electrodes in a way that caused certain pairs of the electrodes to be physically shielded from each other. The detailed description also said that a common conductive pathway electrode was “an essential element of all embodiments or connotations of the invention.” Because of this language, the court concluded that one could only infringe the patent if one were to make, use or sell a product with a common conductive pathway electrode, even though the patent claims did not specifically recite that element. In particular, the court noted:

we have held that labeling an embodiment as “essential” may rise to a disavowal.

One of the first questions I typically ask an inventor when talking about a new invention is whether he or she has been through the patent process before. If the answer is “no,” then I try to prepare the inventor for the fact that the patent application’s description may soften some of the inventor’s absolute statements.

It’s important to recognize that what’s “essential” to achieve the best possible practical implementation of an invention may not always be “essential” for the purpose of patentability.  The X2Y Attenuators case helps illustrate what happens when a patent application confuses the difference between the two.