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Continuation Drafter
Continuation practice · Tier E

The parent's file history follows the claim, not the family

Maquet v. Abiomed

Changing the claim language between family members is a real defence against inherited disclaimer, and silence in response to an examiner's notice of allowance generally is not a disavowal.

How to read the ledger below. Each numbered point carries the kind of evidence behind it. ESTABLISHED is stated in the authority's own text, with a locator. IMPLEMENTED is the rule as the authority actually applied it. OBSERVED is carried by a source outside this one. ASSUMED is the drafter's inference, flagged as such and not the authority speaking. Quotations are checked against a cached copy of the primary source by script.

In one paragraph

The Federal Circuit vacated and remanded in Maquet Cardiovascular v. Abiomed on 21 March 2025, rejecting three claim constructions that had narrowed a continuation using prosecution statements made in two earlier patents of the same family, one the parent and one four generations back. The prosecution history of a related patent is relevant only where it addresses a limitation in common with the patent in suit, and the court refused to extend the doctrine to patents that merely share subject matter, because a patentee is free to claim an invention differently in later applications. On one term the claims were too dissimilar for the earlier history to matter at all. On another the language was virtually identical so the earlier history did apply, and the court still found no disavowal, because silence after an examiner notice of allowance is generally not a disclaimer and broad statements in an inter partes review preliminary response that never named the claim are not clear and unmistakable.

Reader summary

The district court construed three terms in a continuation by importing limitations from prosecution arguments made in two earlier patents in the same family, one the parent and one four generations back. The Federal Circuit rejected all three constructions.

The rule it applies is not new but is stated crisply. A related patent's prosecution history is relevant if it addresses a limitation in common with the patent in suit. Where the limitations differ, an applicant's disclaimer as to one claim is not assumed to reach another, because a patentee is free to claim an invention differently in later applications. The court refuses to widen this to shared subject matter, which is what the accused infringer asked for.

The two halves of the decision are worth separating because they fail for different reasons.

For one term, the claims were not sufficiently similar at all, so the parent's prosecution history was simply irrelevant and importing a negative limitation from it was legal error.

For another, the court agreed the claim language was virtually identical, so the ancestor's prosecution history WAS relevant. It still found no disclaimer, because what the patentee had actually done was stay silent after an examiner's notice of allowance, and later make broad statements in an inter partes review preliminary response that never mentioned the claim at all. Neither is clear and unmistakable.

That second half is the more useful one. It shows both gates operating: relevance, then disavowal, and a patentee can win at either.

Why this matters when you are drafting

A continuation does not inherit the whole family's file history. Claims 5, 6 and 8. It inherits arguments about limitations its claims share. The comparison is limitation to limitation, not patent to patent.

Claim language is the unit of analysis, not subject matter. Claim 9. The court declined to widen the doctrine, and it named the argument it was refusing. That refusal is the most citable thing in the opinion.

Different language in the continuation is a real defence. Claims 7 and 10. Where the continuation claims something the parent's prosecuted claims did not recite, or omits a positional or structural requirement they contained, the parent's disclaimer does not follow.

But similarity is not the end of it. Claims 11 and 12. Where the language is virtually identical the earlier history comes in, and then the question is whether anything in it was a clear and unmistakable disavowal. Two gates, two chances.

Silence during prosecution is generally safe, and volunteering is where risk lives. Claim 13. Not responding to a notice of allowance did not create disclaimer. What creates disclaimer is affirmative characterization.

Post-grant statements reach back into claim construction. Claim 14. Anything said in an inter partes review preliminary response is intrinsic-record material for construing claims, and the court left open how far that reaches across family members. Treat post-grant advocacy about a parent as capable of affecting a child.

Depth of the family does not limit the reach. The district court used a great-great-grandparent's prosecution. Nothing in the opinion cuts off relevance by generation; what cuts it off is the limitations comparison.

What the authority establishes

  1. [ESTABLISHED, the disposition] "we hold that the district court erred in construing the "guide mechanism" term in claim 1 of the '783 patent and the "guide wire" terms in claims 1 and 24 of the same patent." (P. 24.) The court rejected the constructions, vacated the judgment as to that patent, and remanded.
  1. [ESTABLISHED, the standard for disclaimer] Where the patentee has "unequivocally disavowed a certain meaning to obtain his patent, the doctrine of prosecution disclaimer attaches and narrows the ordinary meaning of the claim congruent with the scope of the surrender." (P. 12.) And the doctrine "precludes patentees from recapturing through claim interpretation specific meanings disclaimed during prosecution." (P. 12.)
  1. [ESTABLISHED, how high the bar is] When "the prosecution history is used solely to support a conclusion of patentee disclaimer, the standard for justifying the conclusion is a high one." (P. 12.) A patentee is bound only by a disavowal that is "clear and unmistakable." (P. 13.) The quotation begins after a bracketed alteration in the source, per hazard 9.
  1. [ESTABLISHED, ambiguity defeats it] Where "the alleged disavowal is ambiguous, or even amenable to multiple reasonable interpretations, we have declined to find prosecution disclaimer." (P. 13.)
  1. [ESTABLISHED, and this is the family rule] "The prosecution history of a related patent can be relevant if, for example, it addresses a limitation in common with the patent in suit." (P. 13.)
  1. [ESTABLISHED, the converse, which is the actual holding] "if the limitations at issue are dissimilar, we generally cannot accept, without more support, that an applicant's disclaimer with respect to one claim would be equally applicable to another claim." (P. 13.) And the court quotes Ventana that "prosecution disclaimer generally does not apply when the claim term in the descendant patent uses different language." (P. 14.)
  1. [ESTABLISHED, why, and this is the sentence a continuation practitioner should keep] "This is because a patentee is free to take a different approach to claiming an invention in subsequent patents, either by adding limitations or by altering the claims' format." (P. 14.)
  1. [ESTABLISHED, the requirement stated as a requirement] "for prosecution disclaimer to apply, the related patents must have limitations in common to support the inference that the patentee's earlier arguments are also applicable to the claim limitations of the patent-in-suit." (P. 14.)
  1. [ESTABLISHED, the extension the court refused] Abiomed argued disclaimer applies "despite differences in the claim language, when patents share" common subject matter (P. 15.), and the court answered: "The law of prosecution disclaimer, however, does not extend this far, and we make no such extension today." (P. 15.) A tribunal "must instead focus on the claim language, and differences in such language, when determining whether the prosecution history of an earlier, related patent is relevant for construing a later claim." (P. 15.)
  1. [ESTABLISHED, the first term, which failed the relevance gate] Claim 1 of the patent in suit and the earlier prosecuted claims of its parent "are not sufficiently similar such that the prosecution history of the latter would be relevant when construing the former." (P. 14.) The district court had imported a negative limitation from the parent's prosecution, which "was legal error." (P. 14.)
  1. [ESTABLISHED, the second term, which PASSED the relevance gate] Comparing the guide-wire language across generations, "both claims contain the exact same guide wire limitation, and that the remainder of the claims are virtually identical except with two minor differences." (P. 18.) So the ancestor's prosecution history "is relevant when construing claim 1 of the '783 patent." (P. 18.)
  1. [ESTABLISHED, and it still failed the disavowal gate] "despite the similarity of claim limitations, the intrinsic record shows that Maquet did not make a clear and unmistakable disavowal." (P. 18.)
  1. [ESTABLISHED, silence is not disavowal] An "applicant's silence in response to an examiner's notice of allowance will generally not rise to a clear and unmistakable claim disavowal." (P. 19.) Here the patentee "never responded to the second notice of allowance and never made any affirmative statement about" the reference the examiner discussed. (P. 19.)
  1. [ESTABLISHED, statements in an inter partes review can create disclaimer, but must meet the same bar] "Statements made by a patent owner during an IPR proceeding can be relied on to support a finding of prosecution disclaimer during claim construction." (P. 19.) Such statements "must be" both clear and unmistakable. (P. 20.) The ones here were "broad and vague statements" that "do not refer to any particular claim in the '728 patent, let alone a claimed "guide wire."" (P. 20.)
  1. [ESTABLISHED, the question the court expressly did NOT answer] Whether statements made about an EARLIER, related patent during an inter partes review can support disclaimer when construing a LATER patent in district court is "slightly different" from what Aylus decided, and "We need not answer this question given that Maquet made no clear and unmistakable claim disavowal". (P. 20.) An open question, flagged as open.
  1. [ESTABLISHED, the review standard] The court would "review the district court's claim construction de novo because it was based entirely on an intrinsic evidence determination about the meaning of the prosecution history, and not on any evidence about extra-patent understandings of language or about other facts." (P. 13.) No deference, which is why this reversal was available.
  1. [IMPLEMENTED, the two-gate structure] Claims 5 through 12 together mean a disclaimer argument across family members must clear two independent gates: the limitations must be common enough for the earlier history to be relevant, and the earlier statement must itself be a clear and unmistakable disavowal. The opinion demonstrates a loss at each gate on different terms of the same patent, which is why it is worth reading whole.
  1. [ASSUMED, drafter's inference, flagged as such] Claim 7 makes claim drafting in a continuation a lever on inherited disclaimer: language deliberately different from the parent's is harder to bind with the parent's arguments. The opinion does not offer this as strategy, and it cuts both ways, since different language also weakens any argument that the parent's prosecution supports the later claim. It follows from claims 6 and 7 read against the outcome in claim 10.

Quotations, verified against the source

All from the Federal Circuit's opinion. Page locators computed from the docket stamp.

  • "unequivocally disavowed a certain meaning to obtain his patent, the doctrine of prosecution disclaimer attaches and narrows the ordinary meaning of the claim congruent with the scope of the surrender." (P. 12.)
  • "precludes patentees from recapturing through claim interpretation specific meanings disclaimed during prosecution." (P. 12.)
  • "the prosecution history is used solely to support a conclusion of patentee disclaimer, the standard for justifying the conclusion is a high one." (P. 12.)
  • "clear and unmistakable." (P. 13.)
  • "the alleged disavowal is ambiguous, or even amenable to multiple reasonable interpretations, we have declined to find prosecution disclaimer." (P. 13.)
  • "review the district court's claim construction de novo because it was based entirely on an intrinsic evidence determination about the meaning of the prosecution history, and not on any evidence about extra-patent understandings of language or about other facts." (P. 13.)
  • "The prosecution history of a related patent can be relevant if, for example, it addresses a limitation in common with the patent in suit." (P. 13.)
  • "if the limitations at issue are dissimilar, we generally cannot accept, without more support, that an applicant's disclaimer with respect to one claim would be equally applicable to another claim." (P. 13.)
  • "prosecution disclaimer generally does not apply when the claim term in the descendant patent uses different language." (P. 14.)
  • "This is because a patentee is free to take a different approach to claiming an invention in subsequent patents, either by adding limitations or by altering the claims' format." (P. 14.)
  • "for prosecution disclaimer to apply, the related patents must have limitations in common to support the inference that the patentee's earlier arguments are also applicable to the claim limitations of the patent-in-suit." (P. 14.)
  • "are not sufficiently similar such that the prosecution history of the latter would be relevant when construing the former." (P. 14.)
  • "was legal error." (P. 14.)
  • "despite differences in the claim language, when patents share" (P. 15.)
  • "The law of prosecution disclaimer, however, does not extend this far, and we make no such extension today." (P. 15.)
  • "must instead focus on the claim language, and differences in such language, when determining whether the prosecution history of an earlier, related patent is relevant for construing a later claim." (P. 15.)
  • "both claims contain the exact same guide wire limitation, and that the remainder of the claims are virtually identical except with two minor differences." (P. 18.)
  • "is relevant when construing claim 1 of the" (P. 18.)
  • "despite the similarity of claim limitations, the intrinsic record shows that Maquet did not make a clear and unmistakable disavowal." (P. 18.)
  • "applicant's silence in response to an examiner's notice of allowance will generally not rise to a clear and unmistakable claim disavowal." (P. 19.)
  • "never responded to the second notice of allowance and never made any affirmative statement about" (P. 19.)
  • "Statements made by a patent owner during an IPR proceeding can be relied on to support a finding of prosecution disclaimer during claim construction." (P. 19.)
  • "broad and vague statements" (P. 20.)
  • "do not refer to any particular claim in the" (P. 20.)
  • "slightly different" (P. 20.)
  • "We need not answer this question given that Maquet made no clear and unmistakable claim disavowal" (P. 20.)
  • "we hold that the district court erred in construing the" (P. 24.)

Tensions and open questions

How similar is similar enough is not defined. Claim 8 requires limitations in common; claim 11 finds two minor differences tolerable while claim 10 finds a different set of differences disqualifying. Between the two lies a judgment the opinion does not reduce to a test.

Claim 15 is an express reservation and it matters for family practice. Whether an inter partes review statement about a parent can narrow a child's claims is undecided. A practitioner should assume it might.

The court's refusal in claim 9 rests partly on a non-precedential decision being non-precedential. Advanced Cardiovascular is described as such, and the court reads it as consistent anyway. The strength of the refusal for a future panel is therefore mostly in the reasoning, not in the distinguishing.

Nothing addresses disclaimer running the other way. Everything here is about an earlier patent's history narrowing a later claim. Whether a later patent's prosecution can bear on an earlier one is not raised.

The judgment as to one patent was left undisturbed and this record says nothing about it. Maquet did not challenge the non-infringement judgment on the other patent.

What this record does and does not cover

The prosecution-disclaimer standard, the limitations-in-common requirement, all three claim-term analyses, the inter partes review discussion and the disposition were read end to end.

What was NOT read closely, and is therefore outside what this record can support: the technology, the full prosecution histories, the prior art, and the district court proceedings. This record says nothing about whether the accused device infringes on the corrected constructions, because the case was remanded, nor about the patent whose judgment was left undisturbed. Aylus is known here only through this opinion's use of it.

Currency

This record was verified against its primary source on 2026-08-15. That is a fidelity check: the quotations, locators and attribution are accurate to that source. Whether the authority has since been narrowed, distinguished, abrogated or reversed has not been checked here. Confirm it still stands before relying on it.