In Re Tanaka, 640 F.3d 1246

Tanaka appeals a Board decision holding that a reissue adding only narrower claims while retaining all original claims is not a proper § 251 error correction.
The '991 patent covers an alternator pulley with a one-way clutch; Tanaka filed a reissue to broaden claim 1, later proceeding with unamended original claims 1-7 and adding dependent claim 16.
Examiner rejected claims 1-7 and 16 as non-correctible under § 251; the Board affirmed, concluding Tanaka sought a hedge against possible invalidity rather than a valid § 251 error.
This court reverses, holding that adding dependent claims while retaining original claims is consistent with longstanding reissue precedent and § 251’s remedial purpose.
The court holds a patent can be partly inoperative due to omission of a narrower dependent claim, and distinguishes no-defect reissues from the present petition.
Dissent by Judge Dyk argues the majority misreads precedent and would allow reissue where all original claims remain.

Issue	Plaintiff's Argument	Defendant's Argument	Held
May a reissue add a narrower dependent claim while preserving all original claims under § 251?	Tanaka: allowed as hedge against possible invalidity of original claims.	PTO: not proper because it does not correct an error under § 251 and retains all original claims.	Yes; reissue proper under § 251.
Does omission of a narrower dependent claim render a patent partly inoperative warranting reissue?	Tanaka argues omission can render inoperative; narrower claims clarify scope.	PTO: omission does not render patent partly inoperative since dependent claim subsumed by independent claim.	Omission can render patent partly inoperative; reissue permissible.
Is the Board bound by older cases that did not squarely decide whether retaining original claims with added narrow claims is proper for reissue?	Tanaka asserts long-standing practice supports the approach.	PTO argues those cases do not squarely address the issue.	No; the court can decide merits, recognizing longstanding precedent supports the approach.
Does the public policy concern about hedge reissues undermine § 251's remedial purpose?	Public has interest in preventing hedges limiting patent scope.	Equitable intervening rights and longstanding practice mitigate concerns.	Remedial purpose and stare decisis support the hedge-declared approach.

In re Handel, 312 F.2d 943 (1963) (hedge against possible invalidity; implied proper purpose for reissue)
In re Muller, 417 F.2d 1387 (1969) (properly define invention narrowly; species vs. original claims)
Hewlett-Packard Co. v. Bausch & Lomb, Inc., 882 F.2d 1556 (Fed. Cir. 1989) (assumed hedge practice; did not decide on omission of narrow claims)
Gage v. Herring, 107 U.S. 640 (1883) (reissue not proper absent correction of an error in the original claims)
Pall Corp. v. Micron Separations, Inc., 66 F.3d 1211 (Fed. Cir. 1995) (each claim is a separate statement of the patented invention)