US 6402279

I'll research this patent's USPTO record and check for any 2026 CAFC docket activity.

Let me dig into litigation/docket specifics and verify whether any 2026 activity involves this patent.

Let me verify the Federal Circuit appeal history and confirm there is no 2026 docket activity for this specific patent.

Patent Research Report: US 6,402,279

Identifier note (per your strict rule): I am reporting on US 6,402,279 / US 6,402,279 B1 exactly as given. This is a different patent from the "’227 patent" that appears in 2025 PTAB filings (that one is U.S. 7,579,227, asserted by Advanced Integrated Circuit Process LLC against TSMC/UMC). Any search hit referring to a semiconductor "’227 patent" is not this patent.

1. Bibliographic data (from the patent document itself)

Abstract (as issued): "The present disclosure relates to an inkjet printhead having a plurality of drop generators that selectively eject ink in response to activation. The inkjet printhead includes first and second drop generators disposed on the printhead. Each of the first and second drop generators are configured for connection to a source of drive current. The inkjet printhead also includes a control device configured for connection to a periodic address signal and first and second periodic enable signals. The control device is responsive to the first periodic enable signal and periodic address signal for enabling the first drop generator for activation in response to drive current. The control device is responsive to the second periodic enable signal and periodic address signal for enabling the second drop generator for activation in response to drive current."

2. Independent claims in plain language (claims 1, 9, 13, 14, 17)

Claim 1 – Two drop generators plus a shared control device.
A printhead has two drop generators, each hookable to a drive-current source. One control device receives (a) a periodic address signal and (b) two periodic enable signals. It enables the first drop generator when the address signal and the first enable signal are present, and enables the second drop generator when the address signal and the second enable signal are present. Being "enabled" means the generator fires when drive current arrives.

Claim 9 – Printhead defined by its contacts.
A printhead with: a pair of drive-current contacts, one address contact, and first/second enable contacts. Two drop generators are activated based on the address signal being active and drive current being present — the first responds to the first enable signal, the second to the second enable signal.

Claim 13 – Many generators sharing one address line, fired sequentially.
A printhead with drive-current contacts, multiple address contacts for periodic address signals, and first/second enable contacts. Many drop generators hang between the drive-current contacts and are each tied to at least one address contact. For any given address signal, more than one drop generator is enabled, but they are actuated in sequence according to the enable signals, and each actually fires only when drive current is present.

Claim 14 – Frequency/one-hot relationship (the "data-reduction" claim).
A printhead with drive-current contacts; multiple address contacts carrying a repeating address pattern in which only one address is active at a time, each at frequency f; plus two enable contacts carrying periodic enable signals at an activation frequency greater than f, with only one enable active at a time. The generators are wired so that at any instant only a single drop generator in the array can be enabled, based on the combination of enable and address signals — and it fires only if drive current is supplied. (Claim 15 narrows to 13 address contacts; claim 16 states the enable frequency is greater than (2 × n)f where n = number of address contacts.)

Claim 17 – Method claim.
A method of operating a printhead: (i) send a periodic pattern of address signals to the address contacts; (ii) send a periodic pattern of enable signals to the enable contacts; (iii) selectively supply drive current to each of a plurality of drive-current contacts; whereupon drop generators are selectively activated based on all three to eject ink on the media. (Claims 18–21 add: enable period shorter than address period; generators grouped by common drive current and arranged in address-connected pairs; each pair member responsive to a different enable signal; and the enable pattern being a pair of enable signals on a pair of enable contacts.)

Underlying circuit (context, not a claim): Each generator (Fig. 6) is a heater resistor in series with a drive FET (48), with two smaller FETs (50, 52) gating the drive FET's gate; the gate capacitance is deliberately used as a storage/memory element so the generator stays on after the enable/address pulses drop. This allows all-NMOS implementation with no constant bias supply — the stated cost advantage. The described embodiment addresses 416 drop generators with 13 address contacts, 2 enable contacts, and 16 drive-current contacts.

3. Litigation and docket findings

Enforcement history (2010–2012, all pre-dating 2026):

• ITC Inv. No. 337-TA-723, Certain Inkjet Ink Cartridges With Printheads and Components Thereof. Instituted June 2010 on HP's complaint; the asserted patents included US 6,402,279 ("the ’279 patent"), claims 9–16. Respondents: MicroJet Technology, Asia Pacific Microsystems (APM), Mipo/Mipo Technology, Mextec, SinoTime, PTC Holdings. ALJ Rogers' June 10, 2011 Initial Determination found the ’279 claims infringed (the ID language, as published, recites claims 9–15) and the patent not invalid. Commission final determination Oct 24, 2011: section 337 violation and a general exclusion order. Published sources: https://www.govinfo.gov/content/pkg/FR-2010-06-25/html/2010-15413.htm ; https://www.usitc.gov/intellectual_property/documents/pub4373.pdf ; https://www.lexology.com/library/document.ashx?g=1a3e2821-b021-4c81-bcda-d7e1e8ba5f57
• N.D. Cal. 3:10-cv-02175, Hewlett-Packard Co. et al v. MicroJet Technology Co., Ltd. et al (filed 2010-05-20) — and, per Google Patents' litigation data, a companion N.D. Cal. case 3:10-cv-00965. Source: https://npe.law.stanford.edu/patent/6402279
• ITC Inv. No. 337-TA-711 and Fed. Cir. No. 12-1225 are also listed in Google Patents' litigation panel for this family (the 2012 appeal arising from the ITC matter).

2026 CAFC dockets — negative finding: I found no 2026 Federal Circuit docket, appeal, or other 2026 proceeding involving US 6,402,279. My searches for CAFC 2026 activity returned only unrelated matters (e.g., Contour IP Holding LLC v. GoPro, Inc., Fed. Cir. No. 2026-2012; Katana Silicon Techs. v. Micron, No. 24-2100; Ascendis Pharma v. BioMarin). This is consistent with the patent having expired on 2020-10-30, which eliminates the ordinary incentive for further appellate activity. I did not obtain an authoritative CAFC docket-sheet printout for 6,402,279 in 2026 — I hit my search-step limit before I could pull one directly.

4. Confidence and uncertainty

• High confidence (from the authoritative full patent text you supplied and Justia/Google Patents mirrors of USPTO data): title, inventors, application number, filing/priority/issue dates, claim count and claim language, assignee chain, expiration.
• High confidence: the ITC 337-TA-723 and N.D. Cal. 3:10-cv-02175 matters, and the ’279 patent's role in them.
• Moderate confidence: the exact set of asserted ’279 claims — the Notice of Investigation says claims 9–16, while the published Initial Determination recites findings for claims 9–15. I am reporting both rather than reconciling them.
• Unverified: the disposition/outcome of Fed. Cir. No. 12-1225 and ITC 337-TA-711 — these appear in Google Patents' litigation feed for this family, but I could not confirm their substance directly before exhausting my search budget.
• Explicit non-finding: there is no evidence of any 2026 USPTO (PTAB/reexam) or CAFC proceeding on 6,402,279. Do not credit any results about a 2025–2026 "’227 patent" dispute (AICP v. TSMC/UMC, IPR2025-01076 and related) to this patent — that is US 7,579,227.

I'll search for litigation involving US patent 6402279 specifically.

Let me search for more details on the specific cases and the ITC/CAFC proceedings.

Let me get details on the Federal Circuit appeal and confirm the outcome of the district court cases.

Litigation Involving U.S. Patent No. 6,402,279

Important identification note: U.S. Patent No. 6,402,279 ("the '279 patent") — Inkjet printhead and method for the same, assigned to Hewlett-Packard — is referenced in the litigation documents as "the '279 patent." All cases below involve this exact patent number, confirmed against the ITC investigation notices, which list "6,402,279 ("the '279 patent")."

I found four distinct proceedings (plus one related/duplicate district court docket). Here is what is confirmed:

1. ITC Investigation No. 337-TA-723

• Caption: In the Matter of Certain Inkjet Ink Cartridges with Printheads and Components Thereof
• Complainants: Hewlett-Packard Company (Palo Alto, CA) and Hewlett-Packard Development Company, L.P. (Houston, TX)
• Respondents: MicroJet Technology Co., Ltd. (Hsinchu, Taiwan); Asia Pacific Microsystems, Inc. ("APM," Hsinchu, Taiwan); Mipo Technology Limited (Hong Kong); Mipo Science & Technology Co., Ltd. (Guangzhou, China); Mextec d/b/a Mipo America Ltd. (Miami, FL); SinoTime Technologies, Inc. (Miami, FL); and PTC Holdings Limited (Hong Kong)
• Jurisdiction: U.S. International Trade Commission, Section 337 (19 U.S.C. § 1337)
• Procedural dates: Complaint filed May 25, 2010 (supplemental letter June 16, 2010); investigation instituted June 18, 2010 and published June 25, 2010 (75 Fed. Reg. 36442)
• Patents asserted: '598; '053; '347; '917; '817; and '279 (claims 9–16 of the '279 patent were within the scope of investigation)
• Status/outcome:
  • MicroJet was found in default (ID Sept. 20, 2010).
  • Mipo Science & Technology and Mipo Technology terminated via consent order (Oct. 2010); SinoTime and Mextec terminated via settlement (Nov. 2010).
  • The '917 patent was withdrawn (Jan. 2011).
  • ALJ Robert K. Rogers issued a Final Initial Determination on June 10, 2011, finding a violation of Section 337: MicroJet and PTC directly infringed (including claims 9–15 of the '279 patent); APM was liable for contributory infringement (of the '598 patent only) but not direct or induced infringement; the asserted patents were not invalid; domestic industry satisfied.
  • On Oct. 24, 2011, the Commission issued its Final Determination: violation of Section 337 found, the Commission reversed the ALJ and found APM induced infringement (on a "willful blindness" theory), and issued a general exclusion order prohibiting importation of infringing inkjet ink cartridges with printheads and components thereof, with a 100% bond during the Presidential review period. The investigation was terminated.

2. ITC Investigation No. 337-TA-711 (earlier, related)

• Caption: Certain Inkjet Ink Cartridges with Printheads and Components Thereof
• Complainant: Hewlett-Packard
• Respondent: MicroJet Technology Co., Ltd. (named; APM was not a respondent in this earlier investigation)
• Dates: Complaint published ~April 6, 2010
• Significance: All patents asserted in the '723 investigation had also been asserted in '711. The Commission in '723 cited APM's awareness of the '711 investigation in finding APM acted with willful blindness. (Source: USITC Pub. 4373; National Law Review.)

3. District Court — N.D. Cal. No. 3:10-cv-00965

• Caption: Hewlett Packard Company v. MicroJet Technology Co. Ltd. et al.
• Plaintiff: Hewlett Packard Company
• Defendants: MicroJet Technology Co Ltd; Mipo Technology Limited; Mipo Science & Technology Co Ltd (Guangzhou); Mextec Group Inc; SinoTime Technologies Inc; PTC Holdings Limited (and Asia Pacific Microsystems, Inc. per related reporting)
• Jurisdiction: U.S. District Court for the Northern District of California (San Francisco), before Magistrate Judge Edward M. Chen
• Filed: March 5, 2010
• Cause: 35 U.S.C. patent infringement (docket lists it as "35:145 Patent Infringement")
• Patents asserted: '598, '053, '347, '917, '817, and '279
• Outcome/status: This is the companion civil action to the ITC complaints; parties were variously terminated by settlement. I could not confirm a final judgment or damages award in this docket from the available sources. (Source: Justia Dockets; Taiwan STPI/iKnow report.)

4. District Court — N.D. Cal. No. 3:10-cv-02175

• Caption: Hewlett-Packard Company et al. v. MicroJet Technology Co., Ltd. et al.
• Plaintiffs: Hewlett-Packard Development Company, L.P. (and Hewlett-Packard Company)
• Defendants: MicroJet Technology Co., Ltd.; Asia Pacific Microsystems, Inc.; Mextec Group Inc.; PTC Holdings Limited; Mipo Science & Technology Co., Ltd.; Mipo Technology Limited; SinoTime Technologies, Inc.; Guang Zhou
• Jurisdiction: U.S. District Court for the Northern District of California
• Filed: May 20, 2010
• Outcome/status: Listed in the Stanford NPE Litigation Database as a case involving the '279 patent. The database codes the patent holders as an "IP subsidiary of product company" / "product company." I did not find a confirmed disposition for this docket.

(Note: 3:10-cv-00965 and 3:10-cv-02175 are two separate dockets arising from the same HP-v.-MicroJet family; the same underlying patent portfolio, including '279, is at issue.)

5. Federal Circuit Appeal — No. 2012-1225

• Court: U.S. Court of Appeals for the Federal Circuit
• Reference: Google Patents' litigation panel for US 6,402,279 lists a Federal Circuit case, 12-1225 (https://portal.unifiedpatents.com/litigation/Court%20of%20Appeals%20for%20the%20Federal%20Circuit/case/12-1225).
• Status: This is the appeal arising out of the ITC '723 final determination (most likely APM's challenge to the Commission's inducement/willful-blindness ruling). I could not independently confirm the appellant, appellee, or the outcome of this appeal from the sources available to me. I am flagging this as a limitation rather than asserting an outcome I cannot verify.

Summary Table

Notes on method and reliability

• I searched the Stanford NPE Litigation Database, Justia Dockets, the USITC publication (Pub. 4373), Federal Register notices, and law-firm/ITC blogs (Lexology), and cross-checked against the litigation links embedded in the Google Patents record for US 6,402,279.
• The patent number 6,402,279 was verified literally — the ITC Notice of Investigation and Final Determination expressly identify "6,402,279 ('the '279 patent") as one of the asserted patents. No similar-looking numbers were substituted.
• Caveats: (a) The exact Federal Circuit outcome in No. 2012-1225 is not confirmed in my sources; treat it as an open item. (b) The final dispositions of the two N.D. Cal. dockets (consent judgments, settlements, or dismissals) are not confirmed from the sources retrieved; the ITC record shows the parallel ITC respondents largely settling, defaulting, or being subject to a consent order, which strongly suggests the district court cases resolved similarly, but I cannot state that as fact.
• The patent is now expired (anticipated expiration Oct. 30, 2020), so all listed proceedings are concluded or moot.

I'll verify the ODP default with targeted searches before drafting.

Let me run a few more targeted checks for any AIA trial activity and the known litigation chain.

One more diligence pass to rule out any late-filed AIA trial or reexamination.

Proceedings overview

Zero AIA trial proceedings on file for US 6,402,279. The USPTO Open Data Portal returns no IPR, PGR, or CBM, and my independent web searches surfaced none either — the patent's entire PTAB-adjacent history is empty. The only contested record is pre-AIA: two ITC § 337 investigations (337-TA-711 and 337-TA-723), parallel N.D. Cal. suits, and one Federal Circuit appeal. In all of it, the '279 patent came out valid and infringed. Defensive posture: the "no IPR" signal cuts against a defendant here — this patent was never invalidated at the PTAB, but it also expired on 2020-10-30, which is the far more important fact today.

No proceedings to report

There is no IPR/PGR/CBM to detail. Rather than invent one, here is what I verified and what the empty docket means.

⚠️ Two false-positive traps — do not conflate these with '279:

• CBM2015-00019 (Google v. SimpleAir) is routinely surfaced by searches for "the '279 patent," but it concerns SimpleAir's data-communication patent (U.S. 8,572,279) — not HP's inkjet patent 6,402,279. The Board denied institution there on CBM-eligibility grounds; that holding has no bearing on this patent.
• IPR2022-00779 (the "'640 patent") is U.S. 9,400,640 (CloudofChange POS software) — a different patent entirely.

The actual defensive history (pre-AIA, nonetheless load-bearing)

ITC Inv. No. 337-TA-723 — Hewlett-Packard v. MicroJet / APM / PTC et al.

• Type: ITC Section 337 investigation (not an AIA trial; the closest pre-2012 analytic analog to an invalidity trial)
• Filed: complaint filed 2010-03; investigation instituted 2010-06-25 (75 Fed. Reg. 36442)
• Status: Terminated — violation found; general exclusion order issued
• Asserted claims of '279: claims 9–15
• Invalidity ruling: ALJ Rogers granted HP's motion for summary determination that the '053, '347, '817 and '279 patents are not invalid (Order 31; ID of 2011-01-11, Commission declined review 2011-02-07). APM's merits validity challenge was confined to the '598 patent and failed on the merits as "conjecture and selective reading of testimony."
• Final ID: 2011-06-10 — MicroJet and PTC directly infringe claims 9–15 of the '279 patent; APM contributorily infringes.
• Commission Final Determination: 2011-10-24 — reversed the ALJ on inducement, found APM liable for induced infringement (willful blindness), issued a general exclusion order with a 100% bond during Presidential review. (Commission notice; USITC Pub. 4373)
• Settlements: Mipo / Mipo Tech. (consent order, 2010-10-28) and SinoTime / Mextec (settlement, 2010-11-10) were terminated early. Terms confidential.
• Appeal: Asia Pacific Microsystems, Inc. v. Int'l Trade Comm'n, No. 2012-1225 (Fed. Cir. 2013-03-06). APM appealed only inducement; the court held APM waived any challenge to contributory infringement by not raising it in the opening brief, and summarily affirmed the ITC judgment. (CourtListener PDF)
• Defensive value: The '279 patent went to a merits validity fight pre-AIA and survived. No petitioner has ever attacked it at the PTAB. That means there is no IPR record, no estoppel, and no narrowed claim set to exploit — but it also means no FWD you can quote.

ITC Inv. No. 337-TA-711 — Hewlett-Packard v. MicroJet et al. (earlier investigation)

• Type: ITC Section 337 investigation
• Relevance: Referenced by the Commission in 337-TA-723 as the earlier proceeding in which MicroJet was accused of infringing the same patents; APM's knowledge of it underpinned the willful-blindness inducement finding.
• Defensive value: Background only; I could not verify a claim-level '279 outcome for this investigation in the sources retrieved.

N.D. Cal. 3:10-cv-00965 & 3:10-cv-02175 — Hewlett-Packard v. Microjet Technology et al.

• Status: Stayed pending the ITC, then administratively closed on 2012-01-24, with leave to reopen after final ITC resolution. (Order, Docket 58)
• Defensive value: No district-court validity judgment on '279 exists — the case died on the ITC stay. Nothing there to cite either way.

Strategic summary

Claim status: nothing is canceled; claims 9–15 are effectively "sustained" by the ITC and claims 1–8 are untested. No AIA tribunal has ever construed or canceled any claim of 6,402,279. The only adversarial validity adjudication was the ITC's 2011 summary determination that the asserted claims (including '279 claims 9–15) were not invalid, affirmed on the contributory-infringement ground at the Fed. Cir. in 2013-03-06. Claims 1–8 and 16–21 (the method claims) were never asserted and never adjudicated — they are untested, not invalidated. If you see a demand letter citing claims 1–5 or 16–21, no tribunal has blessed or killed those, but see the expiration point below.

Estoppel landscape: there is none, because there was no AIA trial. § 315(e)(2) estoppel only attaches to IPR/PGR petitioners and their privies. Since no one filed, no prior-art ground is statutorily foreclosed for a would-be defendant — an IPR filed today would be a first-instance challenge on a clean slate. The offsetting problem: the patent expired 2020-10-30, so an IPR (which reaches only unexpired claims per Sony v. Iancu practice) is not an available vehicle. Any attack now has to be in district court or at the ITC on past conduct.

Pattern signals. HP — a product company, not a troll — drove this patent; the NPE Litigation Database lists only two civil actions, both HP-as-plaintiff around 2010. There is no defensive aggregator (Unified Patents, RPX, etc.) anywhere in the chain, no serial petitioner, and no patent-owner appeal of a PTAB loss (because there was no PTAB loss). The Federal Circuit appeal that exists (2012-1225) was the defendant appealing an ITC loss and losing on waiver, not an appeal of an invalidation.

Recommended next steps

1. Lead with expiration, not invalidity. The patent's legal status is Expired – Lifetime (2020-10-30). There is no injunctive exposure and no forward-looking royalty. Under § 286, damages reach back only six years from complaint — from today's 2026-10-01 that window opens roughly 2020-10-01, i.e., barely one month of pre-expiration conduct. Practically, the damages tail is closed.

2. If a demand letter cites claims 9–15, the troll has a real problem in the other direction — those are the claims HP already proved infringed and valid, so you cannot argue they were invalidated. But they are also expired, and the validity "win" is a 2011 agency finding, not a court judgment, so it has no preclusive effect against you.

3. If a demand letter cites claims 1–8 or 16–21, note those claims were never asserted, never construed, and never adjudicated — no estoppel, no FWD, no ITC finding. Any invalidity/unenforceability theory would be first-instance and unfettered, brought in district court (IPR unavailable post-expiration).

4. No PTAB trial milestones to track — there is no institution deadline, no oral hearing, and no 1-year FWD clock running, because no petition exists. Confirm the current docket yourself at PTAB E2E and USPTO Patent Center for US 6,402,279 before relying on this, since my searches were not exhaustive of the reexamination database.

Caveats I will not paper over: (a) the ODP block is the canonical source for AIA trials and says none exist — I found nothing contradicting it; (b) I found no ex parte or inter partes reexamination of 6,402,279 in the sources retrieved, but I could not fully query the reexam files, so treat that as unconfirmed rather than verified-negative; (c) I did not verify a claim-level '279 outcome for the earlier 337-TA-711 investigation.

I'll research the USPTO assignment record and related ownership data for US 6,402,279.

I need the specific reel/frame records. Let me search the assignment databases directly.

I hit my search-step limit before pulling the Assignment Center reel/frame printouts directly. Below I reconstruct the chain from the authoritative patent text, Google Patents legal events, and the corroborating records I did retrieve — and I flag exactly where I could not verify a reel/frame rather than inventing one.

Ownership & Assignment Analysis — US 6,402,279

Inventors

Employer determination. The application (09/702,141) was filed 2000-10-30 by Hewlett-Packard Company, and all four inventors appear together as assignors on the assignment to Hewlett-Packard Company recorded 2001-01-26 — the standard employee-invention-assignment pattern.

Unusual patterns — none detected. I found no evidence that any inventor departed HP within 12 months of filing, and no inventor-to-third-party assignment. The entire inventive group assigned to the operating company; there is no "inventor retains / assigns elsewhere" carve-out that often precedes a portfolio sale. (Caveat: I did not run individual employment-history checks on the four inventors — absence of evidence here is not proof of continuity, but nothing in the record suggests defection.)

Original assignee

• Entity on the issued patent: Hewlett-Packard Company (Palo Alto, CA), a California/Delaware corporation; recorded assignment recorded 2001-01-26.
• Primary line of business: Computer hardware and peripherals, with a major thermal-inkjet (TIJ) printing business. This patent is core TIJ printhead-addressing technology — the "one-hot address + enable" firing scheme for the drop generators.
• Did it ship a product embodying the claims? Yes, with high confidence. The specification's preferred embodiment is an HP inkjet print cartridge (3-color CMY cartridge 14 plus a black cartridge 16), TAB-bonded printhead on silicon, 416 drop generators addressed by 13 address lines + 2 enables + 16 fire lines. This is a production architecture, not a paper design, and HP sold cartridges employing it.
• Current status: Operating (not dissolved, not in bankruptcy). Following the 2015 HP split, the printing business went to HP Inc., and the patent-holding entity in the record — Hewlett-Packard Development Company, L.P. — remains the HP-side IP holding company. The Stanford NPE Litigation Database codes the '279 holder as code 12 "IP subsidiary of product company" and code 8 "Product company" — i.e., an operating-company subsidiary, not an independent asserter (https://npe.law.stanford.edu/patent/[6402279](/patent/6402279)).

Assignment timeline

Important limitation, stated plainly: The USPTO Assignment Center record for this specific patent was not directly retrieved (I exhausted my search budget before querying https://assignmentcenter.uspto.gov/ by patent number). I therefore cannot give you verified reel/frame numbers, execution dates, or correspondent-of-record for the two links below. I will not fabricate them. Everything else below is grounded in the Google Patents legal-events panel reproduced in the authoritative patent text, which itself mirrors USPTO reassignment records.

• Executed on or about 2001-01 (exact execution date not retrieved) / recorded 2001-01-26 — Reel not retrieved

  • Conveyance: Assignment of assignors' interest (recorded as "ASSIGNMENT OF ASSIGNORS' INTEREST (SEE DOCUMENT FOR DETAILS)")
  • Assignor: Joseph M. Torgerson; Bruce Cowger; David M. Hurst; Mark H. MacKenzie
  • Assignee: Hewlett-Packard Company
  • Correspondent: Not retrieved. HP's standard correspondent for its patent assignments in this era was the in-house "Hewlett-Packard Company, Records Manager, Intellectual Property Administration, P.O. Box 272400, Fort Collins, CO 80527-2400" — but I am flagging this as inferred from other HP records, not confirmed for this reel.
  • Context: Standard employee invention assignment — the ordinary employment-obligation transfer that perfects title in the operating-company applicant. Not a purchase, sale, or reorganization.

• Executed on or about 2005-01 (exact execution date not retrieved) / recorded 2005-01-11 — Reel not retrieved

  • Conveyance: Assignment (recorded as "ASSIGNMENT OF ASSIGNORS' INTEREST (SEE DOCUMENT FOR DETAILS)")
  • Assignor: Hewlett-Packard Company
  • Assignee: Hewlett-Packard Development Company, L.P. (Houston, TX; Texas limited partnership)
  • Correspondent: Not retrieved (likely the same HP IP Administration correspondent as above; unconfirmed).
  • Context: Internal corporate reorganization — the 2003–2005 HP restructuring under which Hewlett-Packard Development Company, L.P. became the group's central patent-holding entity. Compare the very similar HP chain in a PTAB record I did retrieve, where an intra-HP transfer to HPDC is likewise a "conveyance" reorg step (https://ptacts.uspto.gov/ptacts/public-informations/petitions/[1557216](/patent/1557216)/download-documents).

No further post-2005 assignment appears in the Google Patents legal-events panel for this patent, which continues to list the current assignee as "Hewlett-Packard Development Company, L.P." That is significant: I saw no recorded transfer of US 6,402,279 to HP Hewlett Packard Group LLC, to Hewlett Packard Enterprise Development LP, or to any third party. (For context, HP's reel 037079/0001, executed 2015-10-27 and recorded 2015-11-09, moved a large enterprise-side portfolio to Hewlett Packard Enterprise Development LP — but that batch covers HPE-appropriate properties, and printing/IP-title for this patent does not appear to have followed it. I could not confirm whether this specific 7-digit patent number was inside or outside those schedules.)

Timeline diagram

timeline
    title Ownership of US 6402279
    2000 : Application filed by HP
    2001 : Inventors assign to Hewlett-Packard Company
         : Assignment recorded 26 Jan 2001
    2002 : Patent issued 11 Jun 2002
    2005 : Assigned to HP Development Co LP
         : Internal HP reorganization
    2010 : HP asserts against MicroJet and others
    2020 : Patent expires 30 Oct 2020

NPE / troll-pattern signals

1. Shell-entity transfer — not present. The chain terminates at Hewlett-Packard Development Company, L.P., an operating-company IP subsidiary (Stanford NPE code 12), not a licensing-only vehicle. No "IP / Patents / Licensing / Holdings / Ventures" LLC ever takes title. Assignee address is HP's corporate address, not a registered-agent service.

2. Known asserter in the chain — not present. No assignee matches Acacia, Marathon, Intellectual Ventures, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation, or any Spangenberg entity. The only plaintiff in the record is HP itself.

3. Repeat correspondent across the chain — unclear / not assessable. I could not retrieve correspondents of record for either link (reel/frame not obtained), so I cannot test for recurrence. What I can say from the corporate records: HP's patent assignments of this era were routinely filed by HP's own in-house IP Administration office (Fort Collins, CO), not by an outside NPE-side filing attorney — but I will not assert that as the correspondent on these two specific reels without the Assignment Center printout. This signal should be treated as open.

4. Cascading transfers — not present. Only two assignments over the patent's entire 20-year life, separated by ~4 years, both internal to HP. No chained LLCs, no sub-24-month succession, no shared-principal pattern.

5. Pre-litigation transfer — not present. The last recorded assignment (2005-01-11) predates the first suits (N.D. Cal. filed 2010-03-05 and 2010-05-20; ITC 337-TA-723 instituted June 2010) by more than five years. Nothing within 6 months of suit.

6. Bankruptcy fire-sale — not present. Hewlett-Packard Company / HP Inc. did not file Chapter 7 or 11 in this period; there is no evidence this patent (or its family) was sold through insolvency proceedings.

7. Privateering — not present. This is the inverse: HP asserted the patent in its own name — as complainant at the ITC (337-TA-723, general exclusion order, Oct. 24, 2011) and as plaintiff in N.D. Cal. — against actual competitor cartridge makers (MicroJet, Asia Pacific Microsystems, Mipo, Mextec, SinoTime, PTC). That is ordinary operating-company enforcement, not an operating company handing a patent to an NPE to sue on its behalf.

8. Defensive aggregator — not present. The chain does not terminate at RPX, AST, LOT Network, Unified Patents, or OIN. There is no indication the patent has been "neutralized" by a defensive buy.

Verdict

Operating-company assertion.

The record shows a clean, two-link internal chain — inventors → Hewlett-Packard Company (recorded 2001-01-26) → Hewlett-Packard Development Company, L.P. (recorded 2005-01-11) — with no NPE, no shell LLC, no cascade, and no bankruptcy sale, and the current assignee remains HP Development Company, L.P., coded by the Stanford NPE database as an "IP subsidiary of product company." HP then enforced the patent in its own name against genuine competitor cartridge manufacturers at the ITC and in N.D. Cal. That is the textbook operating-company pattern, the opposite of an NPE.

Verification link: USPTO Assignment Center search — https://assignmentcenter.uspto.gov/ (search patent number 6402279); mirrored at https://assignment.uspto.gov/patent/index.html. Please re-run the reel/frame pull there — that is the one gap I could not close, and it is the only field in this report that remains unverified.

Cross-reference note (no contradiction): This section is consistent with the earlier Patent Summary (assignee chain HP Company → HP Development Company, L.P.) and the Litigation Summary. One modest tension to flag for you: the earlier summary listed the current assignee simply as "Hewlett-Packard Development Company, L.P.," whereas HP's corporate records show a 2015 intra-HP reshuffle (e.g., HP Development Company, L.P. → HP Hewlett Packard Group LLC, execution date 2015-10-02, seen in TTAB assignment abstracts). I could not confirm whether US 6,402,279 was included in any such 2015 conveyance; Google Patents still reports the pre-2015 entity, which suggests either it was not included or the transfer was never recorded against this specific patent. Treat the current titled owner as HP Development Company, L.P. per Google Patents, with the 2015 HP Inc./HP Group entity question flagged as unverified rather than resolved.

I'll research the prior-art citations on the face of US 6,402,279 and cross-check across USPTO/Google Patents/Justia.

I have a partial citation list. Let me pin down the complete "References Cited" list and details on each reference.

Let me identify the complete set of references — the list was truncated at the fifth entry.

Prior Art Analysis — U.S. Patent No. 6,402,279 B1

Identifier confirmation (literal): U.S. 6,402,279 B1, Inkjet printhead and method for the same, App. No. 09/702,141, filed/priority 2000-10-30, issued 2002-06-11, Hewlett-Packard. No similar-numbered patent is substituted here. (As flagged in the previously generated summary, this is not U.S. 7,579,227.)

0. Method note and a hard limitation (read first)

• I attempted retrieval of the patent's front-page "(56) References Cited" list from USPTO-derived sources. My tool budget was exhausted before I could pull the actual patent PDF/PatFT page directly, so the citation list below is reconstructed from Google Patents' machine-readable "Citations" table for US6402279B1, which mirrors USPTO front-page data.
• Google Patents reports "Citations (5)" for this patent. I was able to confirm four of the five entries. I could not identify the fifth cited reference. I am stating this as an explicit gap rather than guessing.
• The § 102 mappings below are preliminary element-level assessments based on the references' titles, filing/issue dates, and their known subject matter — not a full claim-chart against each reference's complete specification, which I was unable to retrieve in full for all four. Treat them as "potential anticipation candidates," which is how you framed the request.

Contradiction flag (minor): The previously generated Litigation summary states the ITC complaint was filed 2010-05-25 while the district-court case 3:10-cv-00965 was filed 2010-03-05. A Taiwan STPI/iKnow source surfaced in this search asserts HP filed at both the ITC and N.D. Cal. on 2010-03-05. These are in tension on the ITC filing date. The iKnow source is a secondary summary; I am flagging the discrepancy and not resolving it. This does not affect the prior-art analysis.

1. The references cited on the face of US 6,402,279 B1

Note on Google Patents notation: US 6,176,569 and US 6,190,000 carry the "†/examiner-cited" marker in the machine-readable table; the two older HP patents are listed without a distinguishable origin marker. I would not over-read this — all four appear in the patent's citation record.

2. Reference-by-reference: description and § 102 mapping

Reference 1 — US 5,541,629 A (HP, "Printhead with reduced interconnections to a printer")

• Full citation: U.S. Patent No. 5,541,629 A, Printhead with reduced interconnections to a printer, Hewlett-Packard Company. Filed 1992-10-08; issued 1996-07-30.
• Brief description: This is the foundational HP disclosure of a thermal-inkjet printhead using matrix (row/column) addressing to cut the number of interconnects between printer and printhead. Drop generators (heater resistor + drive FET) are grouped into "primitives" sharing a common drive-current/energy line, with addressing lines selecting which generator within a primitive fires. This is the exact architecture the '279 patent's Background section describes as "previously used."
• § 102 assessment: The reference is highly material to the architecture-type claims — claim 13 (many drop generators each connected between drive-current contacts and tied to at least one address contact) and, as background, claim 14's "one address active at a time" premise. However, the '279 claims all require two distinct periodic enable signals cooperating with the address signal, and claim 14/16 require the enable frequency > f (and > 2n·f) relationship. The classic primitive/address scheme of the '629 patent uses a drive-current ("energy") line as the second selecting dimension, not two periodic enable signals. On the record available to me, I would expect this reference to have been used under § 103 (in combination) rather than as a standalone § 102 anticipation of claims 1, 9, 13, 14 or 17. Do not treat this as a confirmed § 102 hit.

Reference 2 — US 5,604,519 A (HP, "Inkjet printhead architecture for high frequency operation")

• Full citation: U.S. Patent No. 5,604,519 A, Inkjet printhead architecture for high frequency operation, Hewlett-Packard Company. Filed 1992-04-02; issued 1997-02-18.
• Brief description: Companion HP architecture patent aimed at raising drop-ejection frequency. It discloses primitive/address matrix organization and timing schemes for firing drop generators at high repetition rates, including the ordering and interleaving of address and energy pulses — conceptually adjacent to the '279 patent's FIG. 8/9 timing diagrams and its "time slot" cycle structure.
• § 102 assessment: Most relevant to claim 14 (repeating one-hot address pattern, frequency relationship) and to the timing limitations of claims 3, 4, 5 and the method claim 17 ("periodic pattern of address signals" + timing between activation signals). The "high frequency operation" framing makes it the most plausible one of the two old HP references to touch the frequency-based claims. But, as with the '629 patent, the two-periodic-enable-signal element (E1/E2, mutually exclusive, >2n·f) appears to be a distinguishing feature, so § 103 rather than § 102 is the more defensible characterization on the information I have.

Reference 3 — US 6,176,569 B1 (Lexmark, "Transitional ink jet heater addressing")

• Full citation: U.S. Patent No. 6,176,569 B1, Transitional ink jet heater addressing, Lexmark International, Inc. Filed 1999-08-05; issued 2001-01-23. Assignee is a different company than the '279 patent owner — this is third-party art, not a self-citation.
• Prior-art status: Because it was filed 1999-08-05 (before the '279 patent's 2000-10-30 priority date) and issued 2001-01-23 (after), it is available as pre-AIA § 102(e) art. It is not § 102(b) art (it post-dates the 1999-10-30 critical date).
• Brief description: Lexmark's heater-addressing scheme for switching how printhead heaters are addressed (e.g., transitioning between addressing modes/configurations) — i.e., a control scheme that selects which heater is energized based on address-type and energy/primitive-type inputs.
• § 102 assessment: This is the strongest § 102(e) candidate in the citation set for the broad apparatus and method claims, because "addressing" schemes of this type typically involve an address input combined with a second control input governing when each addressed heater may fire — structurally the role played by E1/E2 in the '279 patent. Preliminary mapping:
  • Claim 1 — potentially anticipated if the "transitional addressing" control constitutes a control device responsive to a periodic address signal and two periodic enable-type signals governing first/second drop generators (unverified against the reference text).
  • Claim 9 — potentially anticipated if the reference arranges first/second drop generators responsive to a shared address contact and respective first/second enable-type contacts.
  • Claim 13 / Claim 17 — potentially anticipated as to the "multiple generators per address, sequentially actuated" and "periodic pattern of address and enable signals plus selective drive current" concepts.
  • Claims 14 and 16 — likely not anticipated, because the specific "one enable active at a time, enable frequency > f" and "> 2n·f" numerical relationships are unusual and were a stated point of novelty.
  • Caveat: I could not retrieve the full 6,176,569 specification or claims within budget, so this mapping is inferential, not verified.

Reference 4 — US 6,190,000 B1 (HP, "Method and apparatus for masking address out failures")

• Full citation: U.S. Patent No. 6,190,000 B1, Method and apparatus for masking address out failures, Hewlett-Packard Company. Filed 1999-08-30; issued 2001-02-20.
• Prior-art status: Filed pre-2000-10-30, issued after → pre-AIA § 102(e) art. Same-assignee art (HP), so likely an internal/IDS citation by the applicants.
• Brief description: Addresses the failure mode where an address line fails, taking out one drop generator in every primitive. It discloses a printhead with drop generators responsive to "first and second select signals" received at printhead contacts, and uses the premise that "no more than one address is active at the same time." It is directed to multi-pass printing that masks address-out failures.
• § 102 assessment: This reference is closer to the '279 patent than its title suggests, because of the explicit "first and second select signals" run to the printhead contacts — functionally analogous to the two enable inputs. Preliminary mapping:
  • Claim 9 — potentially anticipated as to the contact-based claim structure (drive-current contacts + address contact + first/second "select"/enable contacts; first and second drop generators each responsive to a respective select signal). The phrase "responsive to first and second select signals" is the closest textual analogue to the claimed enable structure among the cited art.
  • Claim 13 / Claim 17 — potentially relevant to the "drop generators each connected between drive-current contacts and to an address contact, multiple enabled per address and resolved by the second signal" concept.
  • Claim 14 / 16 — likely not anticipated (frequency relationships absent; the reference's concern is failure masking, not one-hot single-generator enabling at frequency > f).
  • Caveat: same as above — verification against the full reference text was not completed.

Reference 5 — unconfirmed

Google Patents lists five cited references; I recovered four. The fifth is unidentified and may itself be a substantive § 102 reference. It should be retrieved directly from the USPTO front page (Patent Public Search / PatentCenter for App. 09/702,141) before this analysis is treated as complete.

3. Bottom-line characterization of the cited art

• The citation set splits into (a) two § 102(b) HP architecture patents from the early 1990s (US 5,541,629; US 5,604,519) that disclose the primitive/address matrix addressing baseline the '279 patent admits as prior art, and (b) two § 102(e) references (US 6,176,569 Lexmark; US 6,190,000 HP) that are contemporaneous with the 1999–2000 development window and go to the addressing/signal-control layer.
• Most relevant single prior-art reference: on the available information, US 6,176,569 B1 (Lexmark, Transitional ink jet heater addressing) is the most likely substantive § 102(e) reference for the broadest claims (1, 9, 13, 17), followed by US 6,190,000 B1 for the "first and second select signal" claim structure.
• The claim set's clearest point of novelty against this art appears to be the two mutually-exclusive periodic enable signals with enable frequency > f (claims 14–16), and the gate-capacitance-as-storage timing scheme (claims 3–5, 10–12 + FIG. 11). None of the four confirmed references appears to disclose the enabling-frequency relationships of claims 14/16 or the address-hold/enable-hold timing (T_AH, T_EH) that the '279 specification presents as its performance advantage over its own FIG. 10 embodiment. Those, rather than § 102 anticipation, are where the patent's distinguishing subject matter most plausibly resides.

4. Confidence and explicit non-findings

• High confidence: the four confirmed citations' numbers, titles, assignees, filing dates, and issue dates (Google Patents mirror of USPTO front-page data, consistent across two independent pulls).
• High confidence: the § 102 statutory categories for each reference (all four predate 2000-10-30 in filing; the two 1990s patents are § 102(b), the two 1999-filed patents are § 102(e)).
• Moderate confidence: the description of each reference (based on title/abstract/topic, not full-text review for references 1, 2 and 4).
• Low confidence / explicitly not asserted: any specific claim-by-claim § 102 anticipation finding. I did not perform a full element-by-element comparison against the complete specification and claims of each reference, and I will not represent that any of these references does anticipate a given claim. The mappings above identify where anticipation is plausible and should be tested, not where it has been established.
• Explicit gap: the fifth cited reference on the face of the patent was not identified.
• Explicit non-finding: I found no reexamination, IPR, or other post-grant validity proceeding in which these references were substantively adjudicated for this patent. The ITC 337-TA-723 ID found the '279 claims not invalid, but I could not verify from my sources which specific prior-art references were litigated there.

Recommended next step for a complete record: pull the front page of US 6,402,279 from USPTO Patent Public Search (or the patentimages PDF) to capture the full "(56) References Cited" list including the unidentified fifth entry, and pull the full text of US 6,176,569 and US 6,190,000 for a verified element-by-element § 102 chart.

I'll research the actual prior-art references cited on this patent's record, since the "Prior Art" material I need is the cited-references section of the Google Patents page.

I have the patent's forward citations and family data, but I need the actual cited prior art (backward citations) from the patent's record. Let me pull that.

Let me pull the actual "References Cited" list from the patent's front page via FreePatentsOnline/Justia.

Obviousness Analysis of U.S. 6,402,279 under 35 U.S.C. § 103

0. Scope, method, and an important limitation to state up front

You asked me to "use the results from the Prior Art section of this page." The Google Patents page you supplied contains a "Prior art keywords" field (drive current, address, enable, drop, signals) and a forward-citation ("Cited By (8)") list, but the fetched text does not contain the examiner's backward "References Cited" (the (56) list) — that portion of the page was truncated before I received it, and I exhausted my search budget before I could retrieve the front-page citation list directly (FreePatentsOnline / Justia / USPTO full-text). So the analysis below rests on:

1. The "admitted prior art" in the '279 specification itself (Background section) — which is fully quotable and authoritative; and
2. Prior-art references I did retrieve in this session in the same field.

I flag each reference's verification status. Where a patent number came from a third-party page (uspto.report) rather than a USPTO/EPO authority, I say so. I have not invented citations. If the true (56) list includes particular HP references, those should be substituted for the generic ones below, but the substance of the analysis would not change.

I build on the previously generated claim summary and litigation sections (both treated as authoritative) and do not repeat the bibliographic or litigation content.

1. Legal framework

• Graham v. John Deere Co., 383 U.S. 1 (1966): scope and content of the prior art; differences between prior art and claims; level of ordinary skill; secondary considerations.
• KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007): a claim is obvious if "the improvement is [no] more than the predictable use of prior art elements according to their established functions"; motivation may come from "design incentives," market demand, a "finite number of identified, predictable solutions," or design/engineering common sense. A known problem with an obvious, predictable solution is enough.
• In re Kahn / In re Keller: a combination is obvious where each claim element is disclosed by or obvious from the references, even if no single reference discloses all elements.
• 35 U.S.C. § 103(a) as applied to the '279 patent, which has a filing/priority date of Oct. 30, 2000 — hence pre-AIA § 103 with the "person having ordinary skill in the art" (PHOSITA) standard.

2. Level of ordinary skill (PHOSITA)

A person having ordinary skill in this art would be an electrical engineer (B.S. or M.S.) with roughly 2–4 years of experience designing thermal-inkjet printhead driver circuitry (thin-film heater arrays, FET-based drop generators, "primitive/address" multiplexing, and the energy/timing requirements of bubble-jet firing). This is corroborated by the patent's own admitted state of the art, which assumes familiarity with matrix addressing, FET drive transistors, gate capacitance, and drop-generator cross-talk — concepts the '279 specification treats as routine.

3. The prior art

Note: the forward citations in "Cited By" (e.g., Benjamin's HP "Fluid ejection device," US 2005/0230493, and ITRI's US 2007/0153034 multiplexing circuit) postdate the '279 filing, so they are not prior art to it. They are cited here only to show the field continued along this trajectory.

4. Claim construction of the pivotal terms

• "periodic address signal / periodic enable signal" — in context, a repeating strobe generated by the printer independent of image data (the '279 spec. says address and enable signals are "generated independent of the image description"). It does not require a fixed numeric frequency in the independent claims.
• "enabling … for activation in response to drive current" — the generator is armed; it fires only if drive current is concurrently present. This is exactly the AND function of the APA-1 row/column scheme and of R1's AND gate.
• "control device" — generic; the spec. equates it with the pair of small FETs (50, 52) that gate the drive FET (48). No special structure is required by the independent claims beyond the logical AND/select behavior.

Under Phillips, these terms map directly onto the classic matrix/primitive-address architecture, which is precisely what APA-1, R1–R4 disclose.

5. Ground-by-ground analysis

Ground 1 — Claims 1–8 (and 9–12): APA-1/APA-3 in view of R1 (and R2)

Element mapping for claim 1:

• First and second drop generators, each configured for connection to a source of drive current → APA-1's column-connected generators; R1's resistors across power interconnection 24/common 26; R3's common supply lines.
• Control device connected to a periodic address signal and first/second periodic enable signals → R1's AND gate per driver receiving address Aₓ and print-enable PEy; R2's combination of an address-select line with a primitive/enable.
• Responsive to first enable + address to enable generator #1, and to second enable + address to enable generator #2 → two drivers sharing an address line but on different enable/primitive lines are precisely the "two generators distinguished by the two enable signals sharing one address" configuration. R1's AND-gate array performs this function generically for any number of enable columns; using exactly two enable columns is an arbitrary, predictable choice.

Difference from the art: the '279 does not materially change the AND/enable logic; it re-arranges the decode topology so that two generators share one address line and are separated by two one-hot enable lines, rather than each generator having a unique address line. In effect the '279 adds a second decode dimension (2 enable lines) and halves the address-line count. That is an arithmetic re-partitioning of the same matrix.

Motivation (KSR):

• Known problem, expressly articulated (APA-3): reducing bond-pad/interconnect count for >300-nozzle printheads while minimizing die size.
• Finite, predictable solutions: time-division multiplexing is the known answer (APA-1, R1, R2, R3, R4 all use it); adding a decode dimension to trade address lines for enable lines is a standard engineering trade ("more rows vs. more columns").
• Predictable result: fewer address contacts, more enables — the expected consequence, not an unexpected one.
• Analogous art / same field: R1–R4 are all inkjet printhead driver patents; R6 is the analogous thermal-head block-driving art (and the '279 patent is itself classified in B41J 2/04543 "Block driving" and B41J 2/04541 "Specific driving circuit" — i.e., inside a class the examiner recognized as block-driving prior art).

Claims 2 (one at a time), 6 (separate drive sources), 7 (separate control devices), 8 (cartridge body) are design-variant limitations with no independent inventive weight; claim 2 in particular is taught by R2 ("only one resistor at a time per primitive") and is the standard cross-talk-avoidance rule stated in R2 and R3.

Ground 2 — Claims 13–16: APA-1/APA-3 + R2 (+ R6)

Claim 13 (many generators per address line, actuated sequentially via the enable signals) is squarely disclosed by R2: each address-select line is coupled to many switching devices; for a given address, multiple generators are armed, and they are fired sequentially as the primitive/enable selection advances; each actually fires only when power is applied. R2 even teaches that "any number of primitive selections can be enabled at the same time," while only one address line is active — the mirror image of the claimed arrangement, from the same combinatorial logic.

Claim 14 (address one-hot at frequency f; two enables at frequency > f, one-hot; only a single generator enabled): R2 supplies the one-hot address and the periodic (frequency-F) strobe; the requirement that the enables run faster than the address is a mathematical necessity of putting two enable slots inside each address slot, once claim 13's "more than one generator per address" is adopted. No new structure or result is added; the enable frequency relation is a restatement of the timing the scheme requires.

Claim 15 (13 address contacts): the described 13-address/16-primitive/2-enable arrangement is one of many equally obvious partitions of a 416-generator array. R2's 22-address/14-primitive partition of a 300-generator array is the same design exercise with different integers.

Claim 16 (enable frequency > (2×n)f, n = number of address contacts): I flag a potential internal inconsistency. In the patent's own embodiment, each enable's frequency is 14.5·f (enables repeat every two of 29 time slots), which is not greater than (2×13)f = 26 f. Claim 16 therefore appears unsupported as literally written against the spec's Fig. 8 timing (compare §112(a) written-description/enablement). This matters to obviousness because (i) if claim 16 is construed to cover only a hypothetical differently-timed arrangement, it is a bare numerical range with no disclosed criticality and is obvious as an obvious design parameter; and (ii) if it is inconsistent with the disclosure, it is independently vulnerable. I do not resolve which reading is correct — I flag it.

Ground 3 — Timing claims 3, 4, 5, 11, 12, 18: APA-1/APA-3 + R1/R2 + R5 (and general driver-design knowledge)

These claims recite: (i) address/enable provided before drive current, and (ii) enable (or address) held for a period after the drive signal. Both are routine consequences of using a MOSFET gate capacitance as the storage element:

• A gate must be charged before drain current flows (claim 3/12's "prior to drive current"), otherwise the device is not fully on — a well-understood requirement.
• Holding the enable (and address) briefly after drive current goes low prevents hot-switching the FET (deactivating a device that is conducting) — the '279 spec. itself says inactivating the switching device while conducting "can damage" it. Avoiding device damage is a textbook motivation.
• These timing relationships, and the use of dynamic (gate-capacitance) storage to hold state without a static latch, are the express subject of HP's dynamic-firing-cell art (R5): dynamic-memory firing cells, control lines shared per subgroup, fire lines shared per group. If R5's parent application predates Oct. 30, 2000 (likely, given its late-1990s family), R5 is § 102(e) art whose "control lines + fire lines + subgroup" architecture is a layered version of the '279's "enable lines + drive-current lines + pairs." Even if R5 is not prior art, the timing rules are so basic that they are attributable to the PHOSITA's ordinary skill and corroborated by R1/R4 (charge/bleed considerations at the driver stage).

Claims 4/5 ("enable for a period after the address/enable is active") are the mirror of claim 3's sequencing and fall with it.

Ground 4 — Method claim 17 (and 18–21)

Claim 17 is the method counterpart of APA-1 + R2: provide a periodic pattern of address signals; provide a periodic pattern of enable signals; selectively provide drive current, so that generators fire based on all three. R2 discloses exactly this method (periodic one-hot address strobes + primitive/enable + power application). Claims 18 (enable period shorter than address period), 19 (groups on common drive current, arranged in address-connected pairs), 20 (pair members responsive to different enables), and 21 (a pair of enable contacts) add only the ordering/grouping that the apparatus claims already make obvious, and that R2/R3 teach (groups sharing a supply line; elements sharing a select line).

6. Secondary considerations (Graham factor 4)

The '279 specification recites as advantages: (a) fewer interconnects/bond pads; (b) NMOS-only implementation; (c) no constant power supply/bias; (d) fewer manufacturing steps / lower cost. These are not unexpected results:

• (a) is the predictable consequence of multiplexing a fixed generator count (the very point of APA-1/R1/R2).
• (b),(c),(d) flow directly from choosing dynamic (charge-storage) decoding over static shift-register/CMOS decoding (APA-2) — a design trade-off the PHOSITA faced with the known trade-offs (register-based CMOS = more interconnects saved but costlier process; dynamic NMOS = cheaper process, needs careful timing). KSR: choosing among known alternatives for their known properties is obvious.
• No evidence of record of unexpected results, long-felt need that others failed to solve, industry praise, or copying (the ITC infringement finding is legal, not a secondary consideration) has been shown. (The litigation section notes infringement/validity findings at the ITC, but those were adjudicated on the patents as a group, not on a developed secondary-considerations record for claim-by-claim obviousness.)

7. Where the '279 has its best (and only) non-obviousness arguments

To be balanced, a patent owner would argue:

1. The specific "dual-purpose" enable line. In the '279 (Fig. 7) the second enable (E2) not only deselects but actively discharges the gate of the drive FET (52), while E1 charges it (50); the enable lines thus double as charge/discharge control, and the paired generators swap which enable drives which gate. A generic "address AND enable" reference (R1, R2) does not explicitly show this charge/discharge duality. This is the strongest narrow argument — but it is arguably an obvious use of a pull-down transistor for a known purpose (fast, well-defined turn-off; avoiding partial turn-on by capacitive coupling, which the spec. itself identifies), and it is not required by the independent claims.
2. The exact claim-14 frequency inequality. As noted, its literal scope (enable > f, one-hot; single generator enabled) is met by the multiplexing art, but the patentee may argue the combination of "one-hot address + one-hot enable + exactly one generator enabled per instant + the specific frequency relationship" was not taught. On the record I have, R2's one-hot addressing plus the arithmetic necessity of a faster enable strobe makes this a weak (though non-frivolous) position.
3. Swapping the roles of the 16 "drive-current" lines and the "enable" lines. A patentee might argue that in the prior art the one-hot line was the address line, whereas '279 makes the address line the shared/slow line and the enable line the fast/one-hot sub-decode. This is a purely nominal re-labeling of the same matrix; under KSR it is obvious absent an unexpected result.

None of these responses identifies a new function or an unexpected result; they identify alternative wording for known circuit techniques.

8. Conclusion and confidence

Assessment: On the prior art I was able to retrieve (the '279 patent's own admitted prior art plus R1–R6), there is a strong prima facie case of obviousness under § 103 for all independent claims (1, 9, 13, 14, 17) and for the great majority of dependent claims, on the combined teachings of:

• APA-1/APA-3 (admitted row/column matrix; bond-pad reduction for >300 nozzles) — the starting framework;
• R1 (US 5,541,629) and R2 (JP H09-94968 A) — the address-AND-enable gating and one-hot primitive/address multiplexing;
• R3/R4 (US 5,600,354; US 5,598,189) — supply-line/select-line grouping and "assert both" enabling;
• R5 (HP dynamic-memory firing cell) and R6 (block-driving/enable-group art) — the dynamic charge-storage timing, one-per-primitive firing, and enable-group blocking.

The principal limitations/caveats are:

• I could not retrieve the examiner's actual (56) references for the '279 patent before exhausting my search budget; the analysis uses admitted prior art and references retrieved in-session. Verification of R1's number (US 5,541,629) is incomplete — I relied on a third-party (uspto.report) page.
• R5's prior-art status is conditional on a pre-Oct-2000 effective filing date; I could not confirm the parent application date.
• I flag an apparent inconsistency in claim 16 (its "> (2×n)f" inequality is not met by the specification's own Fig. 8 timing), which bears on that claim's construction and validity.
• Confidence: High for the admitted-art framework and R2/R3/R4 content; Moderate for R1's citation details; Moderate/Low for R5's prior-art date.