Intellectual Property Directions

Catching a patent infringer is like hunting for rabbits with a snare - not that I’ve ever done that. Make the loop of the snare too small and your prey will not fit in but make it too large and you may catch more than you expected. In the IP world, too limited a claim allows the infringer to design around your patent but enlarging your claim scope with the doctrine of equivalents may ensnare some prior art, invalidating your (enlarged) claim. Both the hunter and the hunted should learn the lesson of prior art ensnarement.

The doctrine of equivalents (DOE) is supposed to help patent holders by expanding the effective scope of a claim beyond the literal words in the claim. Without a DOE, inventors would have to claim every insignificant variation of their invention explicitly to prevent a clever infringer from using a minor substitution of a functionally equivalent part as a work-around of the patent.

Even with the DOE we often see a series of dependent claims enumerating small variations in an element claimed broadly in the independent claim: “…where the light source of claim 1 is a laser”, “where the light source of claim 1 is a light emitting diode”,…”is a incandescent source”, “…is a candle”. Just imagine the burden on the inventor if there were no DOE.

Of course, under the DOE the patent holder must argue to the court why the claim should effectively be broadened and, in doing so, opens the “new”, broader claim to the court’s examination for obviousness or anticipation based on the prior art, some of which may not have been before the patent examiner. During this judicial process the patent holder’s arguments may open the snare so large as to “catch” some prior art and in the process, to mix a metaphor, end up hoisting the patent holder by his own petard.

The lesson for patent holders is to be judicious before asserting the DOE; the lesson for those who want to design around a patent is to start building your prior art defenses as part of your design around.

This entry was posted on Monday, July 27th, 2009 at 3:51 pm and is filed under Broadening, doctrine of equivalents. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.