Patent Infringement—The Doctrine of Equivalents Revisited

In the United States, if literal patent infringement is avoided through failure to satisfy each element of a recited patented claim, there is an opportunity to consider infringement under the doctrine of equivalents. The doctrine of equivalents, in essence, states that if someone avoids literal infringement but has made an insubstantial departure from the claimed invention they can be held liable as an infringer. In effecting this analysis, one compares the claim with the alleged infringing conduct, element by element. If someone has accomplished substantially the same function in substantially the same way to achieve substantially the same result, there can be infringement under the “doctrine of equivalents.” This doctrine was discussed in detail in the August 2002 article in this series.

One restriction on the doctrine of equivalents occurs through prosecution history estoppel, also known as file wrapper estoppel. This means that if, during the prosecution of the patent application, one has made a claim amendment to overcome a defect or rejection based upon issues of patentability, the doctrine of equivalents cannot be employed with respect to that claim.

A line of cases handed down by the Court of Appeals for the Federal Circuit (CAFC) has made it more difficult to employ the doctrine of equivalents. In the Honeywell case, the CAFC ruled that a common practice employed during prosecution of a U.S. patent application can result in the doctrine of equivalents not being available.

Suppose that a first patent, Claim 1, recited a method of establishing a unitary rectangular frame member by providing four elongated framing members and securing each end of each frame member to an end of another frame member to establish the frame structure. Further assume that a dependent claim, Claim 2, recited the method of Claim 1 wherein the frame ends are secured adhesively. A dependent claim must be read as if it contains all of the recitals of the claim or claims from which it depends and, in addition, adds one or more recitals. As a result, in the present example, Claim 2 could have been written originally as an independent claim with all of the features of Claim 1 plus the added recital of Claim 2 or it could have been written as presented in the form of dependent claim.

In the Honeywell case, the CAFC ruled that if one were to, in this context, cancel Claim 1 and rewrite Claim 2 so as to present it in independent form to render it allowable, this would be regarded as an amendment to Claim 2, which would create prosecution history estoppel and preclude the use of the doctrine of equivalents. For example, if one were to self-bond plastic frame elements at corners, it could be said that “adhesively” meant that a separate adhesive must be used and, therefore, there was no literal infringement, but that the self-bonding under the doctrine of equivalents resulted in infringement. Under the court ruling, such an approach would not be available.

It is difficult to obtain claim allowance by a narrowing amendment relating to patentability while preserving the right to employ the doctrine of equivalents. For example, if Claim 2 had originally been written as an independent claim, it presumably would have been allowable and there would have been no amendment to Claim 2. As Claim 1 would have been rejected and cancelled, however, the doctrine of equivalents would not have been available for Claim 2. This is true even though, in principle, the recitals of Claim 1 were present in Claim 2 from the outset due to the dependency.

Amending Claim 1 by introducing the limitation of Claim 2 would not solve the problem as this would amount to an amendment to a rejected claim which would, under the law prior to the Honeywell case, preclude application of the doctrine of equivalents.

Under these circumstances, what can an applicant do to minimize the impact of this ruling? First, one can make sure that the broadest claims are realistically targeted toward the broadest scope of the invention as contrasted with being overly broad. This will reduce the likelihood of having to narrow or cancel the broadest claim. Obtaining a patentability search prior to preparing the application can help provide guidance in this context.

Another approach would be to imaginatively disclose in the specification and expressly claim by way of dependent claims alternate approaches which might otherwise be embraced by the doctrine of equivalents. For example, if a further dependent claim in the hypothetical example recited “securing the frame elements through self-bonding,” this would provide a basis for assertion of literal infringement.

It will be appreciated, therefore, that during initial drafting of the disclosure and the original claims, one should keep in mind the additional potential problems presented by the CAFC case.

Arnold B. Silverman is a member of the Intellectual Property Department and a member of Eckert Seamans Cherin & Mellott, LLC in Pittsburgh, Pennsylvania.

For more information, contact A.B. Silverman at Eckert Seamans Cherin & Mellott, LLC, 600 Grant Street, 44th Floor, Pittsburgh, Pennsylvania 15219 (412) 566-2077; fax (412) 566-6099; e-mail abs@escm.com.