Boasting about Preferred Rectifiers

The plots below demonstrate how a sensor's alternating current (AC) output signal, after a mechanical shock or a loud bang, is converted into pulsating direct current (DC) by half- and full-wave rectifiers:

A detected sensor signal will be proportional to the total shaded area in its rectifier plot. Clearly, a detector using a full-wave rectifier will be more sensitive.

In a sensor patent, a claim element for "rectifying" an AC signal didn't refer to any particular type of rectifier. The patent's specification did emphasize that a full-wave rectifier is far superior to a half-wave rectifier, and disclosed only embodiments with full-wave rectifiers. But "incorporated by reference" into the patent was a related, abandoned application disclosing a half-wave rectifier in its preferred embodiment.

When the patent owner sued for infringement of that claim, the defendant argued that it wasn't infringing because the patent "taught away" from the half-wave rectifier used in its sensor. After it was pointed out in deposition that incorporating the abandoned application brought a half-wave rectifier within the scope of the claim term "rectifying," the case settled.

The case might have ended sooner had the patent specification explicitly disclosed both the preferred full-wave rectifier and the admittedly less-effective half-wave rectifier.