Kemnetz: HW 04/04

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  • rewriting of dependent*1307 claims into independent form coupled with the cancellation of the original independent claims creates a presumption of prosecution history estoppel,
    • estoppel: a series of legal and equitable doctrines that preclude "a person from denying or asserting anything to the contrary of that which has, in contemplation of law, been established as the truth, either by the acts of judicial or legislative officers, or by his own deed, acts, or representations, either express or implied.
  • On remand, the United States District Court for the District of Delaware barred Honeywell from asserting the doctrine of equivalents.
  • Because Honeywell did not show that the alleged equivalent was unforeseeable at the time of the narrowing amendment or that the narrowing amendment bore no more than a tangential relation to the alleged equivalent, this court affirms.


  • technology to control airflow surge in auxiliary power units (gas turbine engines often used in the tail end of the aircraft). APUs generate electricity for the aircraft, must be controlled against surges (airflow through the compressor is too low) which can damage the APU.
  • has a "set point" = minimum flow to avoid surges
  • a set of adjustable inlet guide vanes that open and close like Venetian blinds and regulate the amount of ambient air drawn into the load compressor
  • flow-related parameter measures airflow out of the compressor and a comparison is made btwn the actual flow conditions (flow-related parameter) and the desired flow conditions.
  • APU determines proper setting of the surge bleed valve


  • the applicant separated system claims from the method claims and they issued in 2 different claims
  • the claims on appeal have to include IGVs, but the original independent claims did not reference IGVs
  • Honeywell said Sundstrand's APS 3200 infringed claims, but Honeywell didn't mark it's product with the '893 patent and since both patents were the same tangible product, Honeywell should have marked the product
  • a jury found Sundstand infringed claims in '893 and '194 under doctrine of equivalents
  • on appeal the court vacated the judgment of infringement and remanded it
  • on remand the district court said:
    • the alleged equivalent would have been unforeseeable at the time of the narrowing amendment
    • the rationale underlying the narrowing amendment bore no more than a tangential relation to the equivalent in question
    • there was some other reason suggestion that the patentee could no reasonably have been expected to have described the alleged equivalent

  • under the doctrine of equivalents: "a product or process that does not literally infringe upon the express terms of a patent claim may nonetheless be found to infringe if there is ‘equivalence’ between the elements of the accused product or process and the claimed elements of the patented invention."
  • the doctrine of equivalents prosecution history estoppel prevents a patent owner from recapturing with the doctrine of equivalents, subject matter surrendered to acquire the patent
  • Foreseeability: an equivalent is foreseeable if one skilled in the art would have known that the alternative existed in the field of art as defined by the original claim scope, even if the suitability of the alternative for the particular purposes defined by the amended claim scope were unknown
    • the EQUIVALENT ELEMENT: “the use of (1) a static pressure differential (i.e., DELPQP), which can be indicative of surge only if the APU is experiencing low flow, in combination with (2) IGV position, which is indicative of whether the APU is experiencing low flow or high flow, to detect surge.”
    • according to timeline, Sundstrand began using IGV position to control airflow within 2 months of observing the double solution problem --> IGV solution may have been known and foreseeable in the art.
    • honeywell argues: in the 1982-83 time frame surge control systems did not use IGVs for surge control
    • it was a known or foreseeable thing to use IGV position to determine whether the flow was high or low (several prior art references in the record support this)

Petitioner's Reply Brief:

  • an attack on the doctrine of equivalents
  • an expansion of the scope of prosecution history estoppel (which they found)


  • a claim limitation was never added, amended, or objected during prosecution
  • the court's decision will limit the permissible range of equivalents for a large percentage of issued patents and will create new forms of estoppel not authorized by the Court
  • they imposed improper burdens on the doctrine of equivalents

Imposing an Expansive and Unwarranted New Type of Prosecution History Estoppel

  • the decision changes the law in 2 ways: directly contrary to statute and another restriction on equivalency
  • can only use estoppel when a claim amendment results in narrowing the claims and surrendering subject matter
  • "another nail in the DoE's coffin"
  • the costs for filing patent applications will increase dramatically
  • examination of the patent application will be complex b/c of the numerous independent claims
  • people are going to avoid dependent claims

In re-writing from dependent to independent:

  • Honeywell just rewrote the dependent claims to independent claims and didn't make any other changes so prosecution history estoppel should not have been applied
  • Honeywell didn't replace the cancelled claims with a new claim that added a limitation b/c the asserted claim had the same scope in both application and issue patent.
  • it was a cosmetic change
  • the Court didn't follow precedent, has been held in numerous cases that rewriting a dependent claim in independent form is not a substantive modification that changes the scope of the claim

“this new rule will simply drive patent applicants away from dependent claims and away from the accepted protocol of presenting successively narrowed dependent claims for examination.” App. 26a (Newman, J., dissenting). This result is contrary to the intent of Congress, which sought to encourage the use of dependent claims with reduced filing fees ( see App. 30a), and contrary to the sound administration of patent prosecution. As Judge Newman predicted, “[t]his new rule will simply raise the cost and increase the difficulty of patent examination.”

  • under the decision, any time there is a cancellation of a claim during prosecution, the claims that issued would necessarily be considered replacement claims and subject to NO EQUIVALENTS OF ANY KIND
  • it's unbounded estoppel
  • a dramatic increase in the burden on a patentee to prevent equivalent infringements
  • the decision prevents Honeywell from recovering for infringement on a separate claim that was never rejected or narrowed during prosecution.