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Imagine you’re surfing on a beautiful day at Malibu. As youstart riding a wave, a portion of the wave in front of you shoots up and throwsyou flying into the air, causing you to land hard on the sand below. Now imagine you’re litigating a patent case and using thedoctrine of equivalents as a primary line of attack against the allegedinfringer. While trying your case, the doctrine of equivalents is removed fromconsideration by the court, leaving you no basis for proving infringement. Seemimpossible? It isn’t, and familiarity with a recent line of cases may help you”shoot the curl,” so to speak. The doctrine of equivalents has been slowly whittled awayduring the past 50 years since its inception in Graver Tank v. Linde AirProducts Co. Prosecution history estoppel, the all-elements rule and priorart limitations all place significant restrictions on the application of thedoctrine of equivalents. More recently, the doctrine of “patent drafterestoppel” has provided an additional limitation. The U.S. Court of Appeals for the Federal Circuit’sdecision in Sage Products v. Devon Industriesarguably began the recenttrend toward patent drafter estoppel. The latest in this line of patent drafter estoppel cases is FinControl Systems Pty Ltd. v. OAM Inc. The Fin Control Systemscasedeals with a technology for permitting easy insertion and removal of surfboardfins. Since the technology was introduced into the surfing market, manysurfboard and surfboard accessory manufacturers, such as alleged infringer OAM,have attempted to copy the technology because of its widespread commercial success. Since Fin Control Systems (FCS) holds a patent on thetechnology, it began systematically enforcing the patent against others in theindustry. ( See Surfco Hawaii v. Fin Control Systems Pty. Ltd.) In partbecause of the doctrine of patent drafter estoppel, FCS was prevented fromenforcing the patent against OAM, though differences between the OAM system andthe patent claims were arguably not substantial. In a nutshell, patent drafter estoppel restricts theapplication of the doctrine of equivalents where the patent drafter has addedlimitations, particularly structural limitations, to the claims duringprosecution that are overly restrictive. The test for patent drafter estoppel is whether the patentdrafter would have “reasonably foreseen” the limiting potential ofthe particular claim language. If the restrictive nature of the claimlimitation was reasonably foreseeable to the patent drafter during theprosecution of the application, the court will prevent the patentee from usingthe doctrine of equivalents to expand its claim scope. An interesting aspect of the doctrine of patent drafterestoppel is that it prevents application of the doctrine of equivalents even incases where there is no prosecution history, and it thus provides allegedinfringers an additional point of argument for avoiding patent infringementwhere the drafter of the asserted patent has not covered reasonably foreseeablealterations of the claimed device or process. SAGE PRODUCTS The Federal Circuit’s decision in Sage Productsarguably began the recent trend of patent drafter estoppel. Although the courtcited an earlier decision in Conopco Inc. v. May Department Stores Co.for its central holding, it is assumed for purposes of this discussion that SageProductswas an important development in doctrine of equivalents law, as ithas been frequently cited in the past five years. Sagedealt with patents on disposal containers formedical waste. The plaintiff alleged infringement of two of its patents, andthe defendant counterclaimed for infringement of its own patent. The DistrictCourt found none of the patents infringed by the respective containers, and theFederal Circuit affirmed. The Federal Circuit’s analysis with respect to one ofSage’s patents (U.S. Pat. No. 4,779,728) is particularly important. Claim 1 of the 728 patent describes a container thatincludes a “first constriction extending over [a] slot” formed at thetop of the container body. The defendant produced a container that had twoconstrictions that were formed below a slot formed in the container body. TheFederal Circuit found that the Devon container could not literally infringe theSage claim because the Devon container did not include a constriction that wasformed “over” a slot at the top of the container body. The court thenturned to the doctrine of equivalents. CLAIM LIMITATIONS The Federal Circuit applied the”function/way/result” test to the Sage claim and found that althoughthe Devon container may meet the test, Sage was prevented from asserting thedoctrine of equivalents on the basis of certain limitations in the claim. Thecourt opined the following: “For a patentee who has claimed an invention narrowly,there may not be infringement under the doctrine of equivalents in many cases,even though the patentee may have been able to claim more broadly. If it wereotherwise, the claims would be reduced to functional abstracts, devoid ofmeaningful structural limitations on which the public could rely.” Therefore, the court found that because the patentee hadincluded the limitation “first constriction extending over [a] slot”in the claim, it was prevented from expanding the scope of the claims with thedoctrine of equivalents to cover containers, such as Devon’s, that included aconstriction beneath the slot. The court saw thefirst-constriction-extending -over-the-slot language as a “clear structurallimitation” upon which the public has a right to rely in conducting itsbusiness activities. Obviously, if the Sage claim had been drafted broadly — toexclude the over-the-slot limitation — the claim would have been literallyinfringed by the Devon container. However, the fact that the limitation waspresent prevented both literal infringement and infringement under the doctrineof equivalents. In a sense, the doctrine of equivalents, although applicable,was essentially thrown out by the court because the patent drafter had draftedthe claims too narrowly. The court noted: “A skilled patent drafter wouldforesee the limiting potential of the ‘over the slot’ limitation. … If Sagedesired broad patent protection for any container that performed a functionsimilar to its claimed container, it could have sought claims with fewerstructural encumbrances … as between the patentee who had a clear opportunityto negotiate broader claims but did not do so, and the public at large. It isthe patentee who must bear the cost of its failure to seek protection for this foreseeablealteration. … Because this issued patent contains clearstructural limitations, the public has a right to rely on those limits inconducting its business activities” [emphasis added]. The court was apparently stating that it would not use thedoctrine of equivalents to expand the scope of claims that could have beendrafted more broadly at the time of prosecution to cover foreseeablealterations. It also appears that the fact that the claims at issue containedclear structural limitations was important to the court. This places a heavy burden on the patent drafter to chooseclaim language carefully and to take extreme care in identifying possiblealternative designs at the time of prosecution. A patent drafter who does nottake such care in drafting his claims may wind up eliminating the remedy of thedoctrine of equivalents for its client. OTHER CASES The Federal Circuit has decided several other cases usingthe foreseeability rationale of Sage Products. For example, in ZodiacPool Care Inc. v. Hoffinger Industries Inc., the Federal Circuit appliedthe function/way/result test to the defendant’s vacuum device and found thatsince the plaintiff’s claim included clear structural limitations, a finding ofinfringement under the doctrine of equivalents would reduce the claims tonothing more than “functional abstracts.” In Antonious v. Spalding & Evenflo Companies Inc.,the court found that the limitation “formed and attached solely to saidrear wall” for a weight in a golf club head could not cover under thedoctrine of equivalents a similar weight that was attached to both a rear walland another member, or “peripheral mass,” within the club head. Thecourt cited Sage Productsin deciding that “to find equivalence inthis circumstance would thus remove entirely the limitation ‘formed andattached solely to said rear wall’” from the claim. Similarly, in Ethicon Endo-Surgery Inc. v. U.S. SurgicalCorp., the Federal Circuit found that the limitation “a lockoutmechanism connected to said longitudinal slots” for a surgical staplerprevented a finding of infringement under the doctrine of equivalents where theaccused infringer’s stapler lockout mechanism was not directly connected to thestapler’s longitudinal slots. The court clarified that the rationale of Sage Productswas not an excuse to ignore the doctrine of equivalents, but rather stood forthe proposition that claim limitations cannot be ignored in a doctrine ofequivalents analysis. More recently, in Vehicular Technologies Corp. v. TitanWheel International Inc., the Federal Circuit noted the patent drafter’schoice of the phrase “consisting of,” rather than the broader phrase”comprising,” is a factor to be considered in determininginfringement under the doctrine of equivalents. The judge’s concurrence tookthe majority opinion one step further. While citing Sage Products, the judge opined that adoctrine of equivalents analysis — either a function/way/result or an”insubstantial differences” test — need not be performed where thepatent drafter has chosen terms (e.g., “consisting of”) for which he shouldhave reasonably foreseen the limiting potential. Another recent case dealing with patent drafter estoppel is MooreU.S.A. Inc. v. Standard Register Co. In Moore, the Federal Circuitpositively confirmed that patent drafter estoppel is a viable defense to a chargeof infringement under the doctrine of equivalents while affirming a finding ofnon-infringement. The court also referred to “the inherent narrowness ofthe claim language” as warranting little, if any, range of equivalents.The court stated: “We cannot agree with any of Moore’s theories oninfringement by equivalents. If our case law on the doctrine of equivalentsmakes anything clear, it is that all claim limitations are not entitled to anequal scope of equivalents. Whether the result of the all limitations rule,prosecution history estoppel, or the inherent narrowness of claimlanguage.” In the latest case, Fin Control Systems, the issuewas a system for providing detachable fins to the bottom of a surfboard. FCSdeveloped and patented a first system for providing detachable fins, whichincluded two plugs disposed in the surfboard for receiving each fin. Thealleged infringer, OAM, had developed its own system that included a single,bone-shaped plug for receiving each fin. U.S. Patent No. 5,464,359, assigned to FCS and titled”Surf Fin Fixing System,” discloses and claims a “surfcraft” (e.g., surfboard) with removable fins. The fins include tabs at alower portion thereof that fit into plugs disposed in the surfboard. The finsare secured in the plugs by screws, which are inserted at angled positions withrespect to the sides of the tabs. As mentioned previously, the OAM system includes a single,bone-shaped plug for receiving each fin of the surfboard. A cruciform slot isformed at each end of the bone-shaped plug for receiving cruciform tabs formedon the fins. Screws may be inserted in front of and behind the cruciform slotsof the bone-shaped plug to further secure the fin. Claim 13 of the 359 patent describes the screws of the FCSsystem by saying that “releasable means laterally engaging” the tabsof the fins. Claim 13 also describes the screws as being disposed in a”passage” extending to a “side wall” of the plug. As notedpreviously, the OAM system also includes screws for securing the fins to thesurfboard; however, the screws in the OAM system are inserted at positions infront of and behind the fins instead of engaging the fins “laterally”on the “sides” of the fins. The District Court determined that the terms “laterallyengaging” and “side wall” in Claim 13 meant a screw that engagesa fin “from the sides.” After making this determination, the DistrictCourt concluded that the OAM fin system could not literally infringe the systemclaimed in the 359 patent because the screws in the OAM system engaged therespective fins from the front and back and not from the sides. The District Court also found that there could be noinfringement under the doctrine of equivalents because to make any otherdetermination would read the patentee’s “laterally engaging” and”side wall” limitations out of the claim. The District Court citedthe Federal Circuit’s holding in Sage Products, and the foreseeabilityrationale, in finding no infringement under the doctrine of equivalents. The Federal Circuit affirmed the District Court holding withrespect to both literal infringement and infringement under the doctrine ofequivalents. With respect to the doctrine of equivalents, the court opined: “We also affirm the district court’s conclusion thatthere can be no infringement under the doctrine of equivalents because applyingthe doctrine to find infringement in this case would improperly read the’lateral’ and ‘side’ limitations out of Claim 13. Here the patentee limitedClaim 13 to lateral engagement, and, as correctly interpreted, lateralengagement must necessarily exclude engagement from the front or the rear withrespect to the surfboard orientation.” Thus, in accordance with the patent drafter estoppelrationale, the Federal Circuit found in Fin Control Systemsthat thepatentee could not cover under the doctrine of equivalents that which it couldhave covered by appropriately drafting the claims of the patent. Put anotherway, means of engagement other than lateral engagement were foreseeable to thepatent drafter at the time of prosecution, and, therefore, such alterationscannot be covered by the doctrine of equivalents. Accordingly, even though the only difference between the OAMsystem and the claimed FCS system was the point at which the screws wereinserted, OAM was still held to have not infringed the 359 patent because ofthe doctrine of patent drafter estoppel. CONCLUSION The line of cases from Sage Productsto FinControl Systemsmakes it clear that accused infringers may have the additionaldefense of patent drafter estoppel to a charge of patent infringement. Asopposed to prosecution history estoppel, the doctrine of patent drafterestoppel may be used even when one is charged with infringement of claims thatsailed through the U.S. Patent Office without creating any prosecution history. Additionally, a patent drafter estoppel defense may beraised in situations where prosecution history estoppel may not apply — whereamendments have been made to overcome � 112 rejections. Finally, patent drafter estoppel may be used in conjunctionwith prosecution history estoppel as an alternative defense to a charge ofpatent infringement in cases where the patent drafter has apparently overlookeda foreseeable equivalent in drafting his claims. Under the circumstances, patent drafters should use cautionwhen crafting claims and when introducing limitations during prosecution. Ofcourse, one cannot foresee every possible alternative embodiment or everypossible infringer at the time of prosecution; however, the patent draftershould be mindful of the limiting nature of structural limitations andseriously consider whether the limitations are required by the prior art. The doctrine of equivalents is a powerful remedy, and theprudent patent drafter should take all necessary steps to ensure that thisremedy is not lost because of inappropriate claim drafting. Darius C. Gambino is an associate in the intellectualproperty department of Duane Morris, www.duanemorris.com/. He focuses his practice in patent prosecutionand litigation (mechanical and electrical arts), licensing agreements,copyright ownership and trademark protection. Richard A. Paikoff is a partnerin the intellectual property department of Duane Morris. He focuses hispractice in patent prosecution and litigation (chemical arts), licensingagreements, copyright ownership and trademark protection.

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