Opportunity For Equivalents In Claim Amendments

It is commonly held that the doctrine of equivalents is lost when claim amendments are made during patent prosecution. That is, any claim amendment that is made during patent prosecution surrenders or gives up elements which are equivalent to those elements claimed in the amendment. Surrender of the doctrine of equivalents places the burden on the patent Applicant, and the patent practitioner representing the Applicant, to carefully consider any amendments to the claims prior to issuance of the patent (when such occurs). This principle is neatly summed up in the rulings on the following two cases. In re Zletz, 893 F.2d 319, 322, 13 USPQ2d 1320, 1322 (Fed. Cir. 1989) (manner of claim interpretation that is used by courts in litigation is not the manner of claim interpretation that is applicable during prosecution of a pending application before the PTO). Sage Prods., Inc. v. Devon Indus., Inc., 126 F.3d 1420, 1425, 44 USPQ2d 1103, 1107 (Fed. Cir. 1997) (patentee who had a clear opportunity to negotiate broader claims during prosecution but did not do so, may not seek to expand the claims through the doctrine of equivalents, for it is the patentee, not the public, who must bear the cost of failure to seek protection for this foreseeable alteration of its claimed structure). What does this mean for the patent practitioner? The claims as originally filed in a non-provisional patent application have full use of the doctrine of equivalents. In an infringement proceeding, any claim that is granted as originally filed covers not only the literal elements in the claims but the equivalents of those elements. But, an amended claim loses the equivalents. So, the patent practitioner should exercise caution and prudence when amending claims. Usually, a claim is amended during patent prosecution to clarify the meaning of a claim element, or to narrow or broaden the extent of a claim element in light of art that is cited by the Examiner. As the Sage ruling above warns us, we have the opportunity to negotiate broader claims during prosecution. If we don't take advantage of this opportunity to establish a desired breadth of any claim element amended, we give up that broader breadth. Some examples may illuminate. In an electronics patent application, suppose the claim as originally filed recites MOS transistors. But, the specification teaches that bipolar transistors could also be used in a circuit, as could relays, etc. If the claim as originally filed is...