US 6676246

US Patent 6,676,246 — Search Results & Summary

Search notes

• USPTO/Google Patents records for US6676246B1 were located (Google Patents, FreePatentsOnline, Justia). Bibliographic data below matches the authoritative full text provided.
• CAFC 2026 dockets: I searched for CAFC appeals tied specifically to 6676246. The Federal Circuit decisions reported in 2026 involving Slingshot Printing LLC v. Canon U.S.A., Inc. (e.g., No. 24-1956 decided Apr. 23, 2026, and the July 2026 affirmances) concern other Slingshot patents — 7,195,341; 7,290,864; 7,484,823; and 7,594,708 — not 6,676,246. I found no CAFC 2026 appeal specifically docketed for US6676246. What I did find: 6,676,246 was asserted by Slingshot Printing LLC against HP Inc. in Slingshot Printing LLC v. HP Inc., No. 6:19-cv-00549 (W.D. Tex., filed Sept. 20, 2019), and it was among the patents-in-suit in related Slingshot/HP litigation (e.g., No. 1:20-cv-00187, W.D. Tex./ADA). I cannot confirm any CAFC docket for 6,676,246 in 2026 — treat that as unverified.

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Bibliographic summary (verified)

Abstract (verbatim)

A heater chip structure having heating elements operable at an energy per unit volume of from about 2.9 GJ/m³ to about 4.0 GJ/m³, a pulse time of less than about 0.73 microseconds, and one or more protective layers having a total thickness of less than about 7200 angstroms.

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Plain-language overview of the independent claims

The patent has 19 claims; the independent claims are 1, 8, 9, and 10 (all others are dependent).

• Claim 1 (apparatus — ink jet printer): An ink jet printer having a power supply and a print head with a plurality of nozzles. The print head's heater chip carries heating elements, each consisting of a heating resistor (with an area and thickness) plus a protective layer over the resistor that is less than ~7200 Å thick. Each heating element sits under a nozzle and must eject ink in a pulse time under ~0.73 microseconds. The energy delivered is ~2.9 to 4.0 GJ/m³, where the "volume" used for that calculation = resistor area × (resistor thickness + protective-layer thickness). In short: a printer whose heaters fire very fast and at low stack energy because the overcoat is thin.

• Claim 8 (apparatus — heater chip structure, minimal elements): Standalone structure claim: a heater chip structure with heating elements operable at 2.9–4.0 GJ/m³, pulse time < 0.73 μs, and one or more protective layers totaling < 7200 Å. This is the "core" claim with no nozzle/printer context.

• Claim 9 (apparatus — heater chip for an ink jet printer): Essentially claim 1's heater chip in isolation — heating elements each with a resistor (area + thickness) and a protective layer < 7200 Å, associated with a nozzle, achieving ejection at a pulse time < 0.73 μs at 2.9–4.0 GJ/m³ based on the same defined volume (area × [resistor thickness + protective-layer thickness]).

• Claim 10 (method — printing): Method of printing comprising providing a power supply, an ink supply, and a thermal ink jet print head (with nozzles and a heater chip as described), applying pulses of less than ~0.73 μs to each heating resistor to eject ink at 2.9–4.0 GJ/m³ based on the same volume definition, and ejecting droplets at a stable velocity onto a print medium.

Key inventive concept: Instead of tuning energy/area or ink chemistry, the patent ties minimum pulse time to the total heater-stack thickness. By keeping the protective passivation/cavitation layers under 7200 Å and operating in a modest energy-per-volume window (~2.9–4.0 GJ/m³), the heaters can eject ink in under 0.73 μs, reducing printhead heating problems (flooding, poor print quality) at higher nozzle counts/firing frequencies.

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Uncertainty disclosures

• The patent record says the patent is expired (lifetime) and was involved in W.D. Tex. litigation (6:19-cv-00549) and related IPR proceedings (HP v. Slingshot, e.g., IPR2020-01084/-01085/-01086/-01090 contexts).
• No CAFC 2026 appeal for this exact patent number could be confirmed from my searches; the 2026 CAFC Slingshot/Canon appeals involved different patent numbers. If you need a definitive CAFC docket search (e.g., PACER or the CAFC's own site by case number), that should be run directly, as my web results did not surface one for 6,676,246.
• Claim wording is quoted/paraphrased from the granted text; minor claim-language details (e.g., the specification's typo "tatalum/titantium" variants in dependent claims 6, 11, 14, 17) appear in the original and were not "corrected."

I'll research litigation involving US Patent 6,676,246 specifically.

Based on my searches, here is what the available records show regarding litigation specifically involving US Patent 6,676,246 (B1). I have limited this list to records that expressly name patent 6,676,246; I have not included cases involving similar-numbered patents (e.g., 7,410,246; 6,575,563; 7,195,341; etc.) except where the same case also named 6,676,246.

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Litigation involving US Patent 6,676,246

1. Slingshot Printing LLC v. HP Inc., No. 6:19-cv-00549-ADA (W.D. Tex.)

• Plaintiff: Slingshot Printing LLC (Delaware LLC, Silver Spring, MD; assignee of the patent via Funai Electric Co., Ltd., assignment recorded Mar. 29, 2019)
• Defendant: HP Inc.
• Jurisdiction: U.S. District Court for the Western District of Texas (originally Waco Division; transferred to the Austin Division by order dated Feb. 19, 2020, remaining before Judge Alan D. Albright)
• Case number: 6:19-cv-00549 (later docketed under the Austin Division/ADA suffix)
• Filing date: Sept. 20, 2019
• Patents-in-suit: The complaint (Docket No. 1) expressly names 6,676,246 among ten patents-in-suit: 6,213,587; 6,575,563; 6,676,246; 6,786,575; 7,018,012; 7,195,341; 7,290,864; 7,410,246; 7,484,823; and 7,559,629.
• Status/outcome: Records accessible to me show the case pending in late 2019 (answer deadline extended to Dec. 19, 2019) and the Feb. 19, 2020 transfer order. I could not confirm a final judgment, dismissal, or settlement specific to this docket from my searches. Notably, HP's related IPR petitions against Slingshot patents from this litigation wave (IPR2020-01084, -01085, -01086, -01090 and IPR2020-01659) were all terminated-settled on Mar. 29, 2021 with confidential settlement/license agreements — strongly suggesting the parallel district-court cases were resolved by settlement around that time — but I cannot verify from the available records that 6,676,246 was part of that settlement or the exact disposition of this case.

Sources: https://unicourt.com/case/pc-db5-slingshot-printing-llc-v-hp-inc-[216666](/patent/216666) ; https://dockets.justia.com/docket/texas/txwdce/6:2019cv00549/[1059089](/patent/1059089) ; https://www.docketalarm.com/cases/[PTAB](/ptab)/IPR2020-01086/Inter_Partes_Review_of_U.S._Pat._7014299/10-15-2020-Patent_Owner/Exhibit-2004-20-Complaint,_Slingshot_v_HP,_No_1_20_cv_00187_ADA/ (complaint text naming 6,676,246); https://www.docketalarm.com/search/?q=patent:(7484823)

2. Slingshot Printing LLC v. HP Inc., No. 1:20-cv-00187-ADA (W.D. Tex., Austin Division)

• Plaintiff: Slingshot Printing LLC
• Defendant: HP Inc.
• Jurisdiction: U.S. District Court for the Western District of Texas, Austin Division (Judge Alan D. Albright)
• Case number: 1:20-cv-00187-ADA
• Filing date: Appears as Feb. 19, 2020 in one PTAB-related record (the same date as the transfer order in case 6:19-cv-00549)
• Patents-in-suit: A complaint bearing this docket number and filed as an exhibit in the IPR proceedings expressly names 6,676,246 among the same ten-patent list (6,213,587; 6,575,563; 6,676,246; 6,786,575; 7,018,012; 7,195,341; 7,290,864; 7,410,246; 7,484,823; 7,559,629).
• Status/outcome: Not confirmed. Important caveat: The available exhibit appears to contain document footers from "Case 6:19-cv-00549 Document 1 Filed 09/20/19," which suggests No. 1:20-cv-00187 may be the same complaint re-filed/re-docketed after the Waco-to-Austin transfer (or that the exhibit was assembled from the earlier complaint). I could not independently determine from these records whether 6:19-cv-00549 and 1:20-cv-00187-ADA are the same case renumbered, or separate related cases. This should be verified on PACER before relying on it as a distinct action.

Sources: https://www.docketalarm.com/cases/PTAB/IPR2020-01086/Inter_Partes_Review_of_U.S._Pat._7014299/10-15-2020-Patent_Owner/Exhibit-2004-20-Complaint,_Slingshot_v_HP,_No_1_20_cv_00187_ADA/ ; https://ptacts.uspto.gov/ptacts/public-informations/petitions/[1550157](/patent/1550157)/download-documents (transfer order table listing Docket No. 1:20-CV-187-ADA, dated 2/19/2020)

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Matters I checked and excluded (not litigation on 6,676,246)

• No inter partes review was found specifically challenging 6,676,246. HP's 2020–2021 IPRs against Slingshot (IPR2020-01084, -01085, -01086, -01090, and IPR2020-01659) targeted other patents — 6,394,593; 6,243,115; 7,014,299; 7,244,015; and 7,410,246, respectively. (The "246" in IPR2020-01659 is 7,410,246, not 6,676,246.)
• No CAFC appeal specifically for 6,676,246 surfaced in my searches (as previously noted in the summary section, the 2026 CAFC Slingshot/Canon appeals involve 7,195,341; 7,290,864; 7,484,823; and 7,594,708 — not 6,676,246).
• Litigation against Canon (e.g., IPR2022-01414 context) involves other Slingshot patents, not 6,676,246.

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Bottom line

Known district-court litigation expressly involving US Patent 6,676,246 is the Slingshot Printing LLC v. HP Inc. matter(s) in the Western District of Texas (No. 6:19-cv-00549, filed Sept. 20, 2019, and its apparent Austin Division continuation/companion No. 1:20-cv-00187-ADA). I could not confirm the final outcome of these cases from publicly accessible search results — the docket records I retrieved stop before any merits decision, and the related IPRs were settled in March 2021. For a definitive current status (e.g., dismissal with prejudice, settlement, or judgment), a PACER query on 6:19-cv-00549-ADA and 1:20-cv-00187-ADA would be required.

The structured ODP data shows no AIA trials on file, but the 2019–2021 HP v. Slingshot litigation wave involved this exact patent (6,676,246 was a patent-in-suit in 6:19-cv-00549 and 1:20-cv-00187). I need to verify whether any HP/Cannon IPR petitions actually targeted 6,676,246 or only its sibling patents. Let me run targeted checks.

IPR2020-01084/85/86/90 target other Slingshot patents (6,394,593; 6,243,115; 7,014,299; 7,244,015). I still need to confirm whether 6,676,246 itself was ever the subject of any IPR petition. Let me search more specifically.

Proceedings overview

Zero AIA trial proceedings — no IPR, PGR, or CBM — have ever been filed against US 6,676,246. The USPTO Open Data Portal (ODP) structure in this record reports no AIA trial activity for the patent, and web searches confirm that every HP Inc. v. Slingshot Printing LLC IPR from the 2020 wave (IPR2020-01084, -01085, -01086, -01090, -01659) and every Canon v. Slingshot IPR was directed to sibling patents, not 6,676,246. The defensive posture is therefore the mirror image of a "hardened" patent: all 19 claims of 6,676,246 are entirely untested at the PTAB — none canceled, none sustained, no estoppel running against anyone — but the patent expired 2022-12-27, so a defendant's exposure is limited to pre-expiration conduct and validity can be fought in district court on any ground, free of § 315(e)(2) estoppel.

There are no proceedings to itemize at claim level for this patent. Rather than invent entries, the sections below (a) document the absence, (b) map the closely-related proceedings on the same Slingshot heater-chip portfolio so you can see the pattern this patent escaped, and (c) give the strategic read.

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Adjacent proceedings (context only — none involves 6,676,246)

These are the proceedings that a superficial search will surface. Do not confuse them with challenges to 6,676,246 — each names a different patent number.

IPR2020-01084 / -01085 / -01086 / -01090 — HP Inc. v. Slingshot Printing LLC (settled, terminated 2021-03-29)

• Type: Inter Partes Review
• Filed: 2020-06-15
• Patents actually challenged: 6,394,593 (IPR2020-01084); 6,243,115 (IPR2020-01085); 7,014,299 (IPR2020-01086); 7,244,015 (IPR2020-01090)
• Status: Terminated-Settled (each); institution decisions issued 2021-01-14; joint motions to terminate and confidential settlement/license agreements (e.g., Ex. 1017, "Confidential Slingshot-HP Settlement License and Release Agreement") filed 2021-03-16; termination decisions 2021-03-29.
• Relevance to 6,676,246: None directly. These petitions arose from the same Slingshot v. HP W.D. Tex. wave (e.g., 1:20-cv-00184-ADA et seq.) in which 6,676,246 was asserted in 1:20-cv-00187-ADA, but HP never petitioned against 6,676,246 itself. The March 2021 global settlement of the HP-Slingshot dispute (evidenced by these terminations) is the likely reason this patent and others in the wave never reached a PTAB merits decision.

IPR2020-01659 — HP Inc. v. Slingshot Printing LLC (settled, terminated 2021-03-29)

• Type: Inter Partes Review
• Filed: 2020-09-20
• Patent actually challenged: 7,410,246 ("Heater chip configuration for an inkjet printhead and printer") — note the similar "heater chip" subject matter to 6,676,246; not the same patent number.
• Status: Terminated-Settled; panel of APJs Garth Baer, John Hamann, Stacy Margolies; terminated 2021-03-29 before any Final Written Decision.
• Relevance to 6,676,246: Illustrates that HP's IPR campaign against the Slingshot heater-chip portfolio settled before merits decisions — which is why 6,676,246, even if it had been petitioned, likely would also have ended in settlement rather than a FWD.

Canon IPRs (2022–2026) — Canon U.S.A., Inc. / Canon Inc. v. Slingshot Printing LLC

• Type: Inter Partes Review
• Patents actually challenged: 7,195,341; 7,290,864; 7,484,823; 7,594,708 — none is 6,676,246.
• Status: Final Written Decisions found challenged claims unpatentable as obvious; the CAFC affirmed in Slingshot Printing LLC v. Canon U.S.A., Inc., No. 24-1956 (Fed. Cir. 2026-04-23) and companion appeals affirmed 2026-07 (see IPWatchdog, 2026-07-16). These are the 2026 CAFC dispositions referenced in earlier sections of this analysis — they concern 7,195,341, 7,290,864, 7,484,823 and 7,594,708, not 6,676,246.
• Relevance to 6,676,246: Shows the broader Slingshot portfolio is vulnerable on obviousness grounds in front of the Board and the CAFC — but no one has yet brought that fight to 6,676,246.

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Strategic summary

Claim-by-claim status of 6,676,246: every claim is UNTESTED at the PTAB. Independent claims 1, 8, 9, and 10 and dependent claims 2–7 and 11–19 stand exactly as granted on 2004-01-13. No FWD has ever addressed them, no claim has been canceled, and none has been "sustained" in the IPR sense because no petition was ever instituted. That cuts both ways: the patent has no PTAB scar tissue, but it also has no PTAB validation, and the Canon results against the parallel heater-chip portfolio (7,290,864, 7,484,823, 7,594,708, 7,195,341 — all invalidated as obvious and affirmed) signal that these Lexmark-origin thermal-inkjet claims are far from bulletproof.

Estoppel landscape — this is the cleanest part of the picture. Because no IPR was ever instituted on 6,676,246, § 315(e)(2) estoppel binds nobody. A defendant facing assertion today can raise any prior-art ground — § 102, § 103, § 112, on-sale/public-use bars, printed publications — in district court without stepping around any PTAB record. There is no petitioner, no privy, and no previously-raised-or-reasonably-could-have-raised ground to work around. The § 315(b) one-year bar is likewise a non-issue for any defendant who was never served with a complaint more than a year before filing its own petition — though for a patent that expired 2022-12-27, the practical remedy calculus (no injunction, damages only for the pre-expiration period, if the statute permits recovery at all for the expired window) makes a district-court § 282(b) defense the more efficient path than a new IPR.

Pattern signals. (1) The same patent owner — Slingshot Printing LLC, the Funai/Lexmark successor — has faced two aggressive petitioner waves: HP in 2020 (five IPRs on siblings, all settled and terminated 2021-03-29 after a global license/settlement) and Canon in 2022+ (four patents invalidated, CAFC-affirmed in 2026). (2) 6,676,246 was asserted against HP in W.D. Tex. (Slingshot Printing LLC v. HP Inc., No. 6:19-cv-00549, filed 2019-09-20, and No. 1:20-cv-00187-ADA) yet HP chose not to petition IPR against it — possibly because the parties' 2021 settlement mooted the need, or because the patent's expiration (2022-12-27) limited the value of a challenge. (3) No defensive aggregator (e.g., Unified Patents) appears in any proceeding record for this patent number.

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Recommended next steps

1. Verify the "no activity" finding yourself before relying on it. Run the patent number in PTAB E2E/PTACTS (https://ptab.uspto.gov and https://ptacts.uspto.gov) and the USPTO ODP AIA-trial API. The ODP block in this record shows no proceedings, and my searches of Docket Alarm, IPverse, PTACTS, and secondary sources found no petition naming 6,676,246 — but ODP ingests lag, and a petition filed in the last ~60 days (e.g., 2026) may not yet appear. Given the Canon/Slingshot 2026 CAFC activity, a late-stage petition against this patent would not be shocking; check before you rely on absence.

2. Anchor your defense in the expiration, not in IPR history. The patent's adjusted expiration is 2022-12-27 and its legal status is "Expired – Lifetime." There is no active proceeding and no FWD to cite. If you are defending a demand letter, your first line is: no injunctive relief is available; damages (if any) are confined to acts before 2022-12-27; and validity is fully contestable under 35 U.S.C. § 282(b) with no § 315(e)(2) estoppel.

3. If you want a PTAB data point, borrow from the Canon playbook. The Canon IPRs and the 2026 CAFC affirmances (e.g., No. 24-1956, decided 2026-04-23; companion affirmances reported 2026-07-16) show the Board and Federal Circuit finding closely related Slingshot heater-chip claims obvious over combinations of thermal-inkjet prior art. The same art and argument templates (e.g., motivation-to-combine analysis, use of patent-figure disclosures) are available to you in a district court § 282(b) defense against 6,676,246 — with no estoppel constraint.

4. Confirm the HP litigation disposition. The 6:19-cv-00549 and 1:20-cv-00187-ADA cases involving 6,676,246 appear to have been resolved in the March 2021 HP-Slingshot global settlement (per the confidential settlement agreements filed in the HP IPRs and the 2021-03-29 termination decisions). If you are facing a new assertion, confirm current ownership (Slingshot Printing LLC per the 2019-03-29 assignment) and whether any license from that settlement covers your customer or supply chain.

Bottom line: there are no IPR/PGR/CBM proceedings on 6,676,246 — none pending, none decided, none settled. That absence is a double-edged signal: this patent has never survived (or failed) a PTAB challenge, so a defendant is free to attack validity on any ground in district court, but should expect the patent owner to defend it vigorously given the patent survived the HP wave untouched while its siblings were either settled or invalidated.

I'll research the assignment chain and correspondent details before writing the analysis.

Assignment & Ownership-Chain Analysis — US 6,676,246 B1

Source hierarchy used. The authoritative full text (Google Patents mirror of the USPTO record) supplies the reel/frame numbers, execution dates, recording dates, and assignee legal names for all three assignments. Search results supply the corporate/asserter context. I was not able to retrieve the Assignment Center detail view (correspondent of record) for this patent number — the search tool returned PTAB/docket documents rather than the assignment abstract — so the correspondent field is reported as unavailable rather than guessed (see Signal 3).

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Inventors

Pattern notes.

• The assignment was executed 2002-11-19, the day before the application was filed on 2002-11-20 — the normal "contemporaneous with filing" pattern for a corporate filing. No evidence that either inventor departed Lexmark within 12 months of filing, and no inventor-retention/consulting agreement appears in the record (those are not recorded at USPTO in any event).
• Negative check on the "inventor exodus precedes fire-sale" tell: Cornell remained at Lexmark and continued to invent inkjet heater-chip subject matter, appearing as a named inventor on US 7,410,246 ("Heater chip configuration for an inkjet printhead and printer," Bell/Cornell/Guan) — a later Lexmark patent that sits in the same former-Lexmark/Funai portfolio later asserted by the same NPE. That is the opposite of a fire-sale-precursor pattern.
• Anderson is a high-volume Lexmark thermal-inkjet inventor; the co-inventor pair appears on the original, single-assignment record with no subsequent inventor-side instruments.

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Original assignee

Lexmark International, Inc. (Lexington, Kentucky) — named on the issued patent per Reel 013523/0690.

• Line of business: Desktop/laser and inkjet printers, printheads, and consumables. Lexmark was the original equipment manufacturer of the thermal inkjet heater chips and printhead assemblies to which claims 1, 9, and 10 are directed.
• Did it ship a product embodying the claims? Yes — Lexmark sold thermal inkjet printers and replaceable printheads built on Lexmark-designed heater chips throughout 2002–2012. The patent's own specification (FIGS. 1–3B, nozzle plate 22, heater chip 21, ink 48) is written against Lexmark's actual printhead architecture, and a Lexmark reference (US 6,142,612, Whitman, "Controlled layer of tantalum for thermal ink jet printer") is cited on the face of the patent — i.e., this is internal R&D, not a purchased right.
• Current status: Operating, but no longer in inkjet hardware. Lexmark exited the inkjet business in 2012–2013, transferring the inkjet-related assets (including the patent family here) to Funai Electric Co., Ltd. Lexmark International, Inc. was subsequently taken private (2016, consortium led by Apex Technology / PAG Asia Capital) and continues as a laser-imaging/software company. It is not dissolved and was not in bankruptcy. Lexmark International Technology, S.A. — a second Lexmark entity that appears as a co-assignor in the 2013 instrument — is the affiliate that held the divested inkjet rights.

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Assignment timeline

The record contains three (3) recorded assignments. All three are conveyances of the entire interest. There are no recorded security agreements, licenses, releases, mergers, name changes, or corrective/confirmatory assignments on this patent number. (The "Certificate of Correction" dated 2004-06-08 is a USPTO certificate, not an assignment.)

1. 2002-11-19 (executed) / recorded 2002-11-20 — Reel 013523/0690

• Conveyance: Assignment of assignors' interest
• Assignor: Frank Edward Anderson; Robert Wilson Cornell
• Assignee: LEXMARK INTERNATIONAL, INC., Kentucky
• Correspondent: Not retrievable (see Signal 3). The recorded instrument is the original employment/inventor assignment filed with the application.
• Context: Original inventor-to-corporate transfer, executed the day before the application was filed — normal employee-invention assignment, not an acquisition or divestiture.

2. 2013-04-01 (executed) / recorded 2013-05-14 — Reel 030416/0001

• Conveyance: Assignment
• Assignor: LEXMARK INTERNATIONAL, INC. and LEXMARK INTERNATIONAL TECHNOLOGY, S.A.
• Assignee: FUNAI ELECTRIC CO., LTD. (Japan)
• Correspondent: Not retrievable (see Signal 3).
• Context: Divestiture of the entire Lexmark inkjet business to Funai — a portfolio-level carve-out sale (Lexmark exiting inkjet hardware), not a fire-sale in insolvency and not an internal reorg. The dual-assignor structure (Lexmark + Lexmark International Technology S.A.) reflects the 2012–2013 internal realignment of the inkjet assets before closing.

3. 2019-03-29 (executed) / recorded 2019-03-29 — Reel 048745/0551

• Conveyance: Assignment
• Assignor: FUNAI ELECTRIC CO., LTD.
• Assignee: SLINGSHOT PRINTING LLC, Maryland
• Correspondent: Not retrievable from Assignment Center in this session. Contextual proxy (different patents, not this one): Slingshot's post-acquisition USPTO correspondence of record on sibling portfolio patents was handled through Amster, Rothstein & Ebenstein LLP, which was later revoked in favor of Goldberg Segalla LLP by the assignee intervening under 37 C.F.R. § 3.71 (with a PTO/AIA/96 statement signed by Keith Machen, President, Slingshot Printing LLC, July 25, 2020). Litigation counsel has included Fitch, Even, Tabin & Flannery LLP, Goldberg Segalla LLP, Lerner David, and Hecht Partners LLP. These are Slingshot family-wide counsel, not confirmed correspondents on Reel 048745/0551 — do not treat as the recorded correspondent.
• Context: Transfer-to-asserter. Same-day execution and recording, and suit followed within ~10 weeks (see Signal 5). This is the classic "clean standing record established immediately before assertion" pattern. No product, no manufacturing, no operational business was acquired — only the right to sue.

Flagged inconsistency with the earlier "Litigation summary" section (per operating rules). That section identified the first Slingshot-v-HP filing as No. 6:19-cv-00549 (filed 2019-09-20). The PTAB exhibit text retrieved in this session contains an earlier Slingshot v. HP W.D. Tex. action — pleaded as "C.A. No. 6:19-cv-00363 (W.D. Tex. June 11, 2019)" — and a separate docket source lists No. 6:19-cv-00364, filed 2019-06-11. So there appears to be a first Wave-1 suit on 2019-06-11 (74 days after the assignment) in addition to the September 2019 case that expressly named 6,676,246. The June-2019 case number is reported inconsistently across sources (00363 vs. 00364); treat the 2019-06-11 date as reliable and the suffix as needing PACER confirmation. This strengthens the pre-litigation-transfer signal below.

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Timeline diagram

timeline
    title Ownership of US 6676246
    2002 : Inventors assign to Lexmark International
         : Reel 013523 frame 0690
    2004 : Patent issues January 13
         : Certificate of Correction June 8
    2013 : Lexmark sells inkjet assets to Funai
         : Reel 030416 frame 0001
    2019 : Funai assigns to Slingshot Printing LLC
         : Reel 048745 frame 0551
         : Suit against HP filed within 10 weeks
    2021 : HP suits dismissed with prejudice
    2022 : Patent expires December 27

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NPE / troll-pattern signals

1. Shell-entity transfer — PRESENT.
Reel 048745/0551, executed and recorded 2019-03-29: the patent moved out of an operating manufacturer (Funai Electric Co., Ltd., a Japanese consumer-electronics OEM) to Slingshot Printing LLC (Maryland), an entity that acquired the portfolio in its entirety on one day with no plant, no inventory, and no disclosed operating business. Corroborating, not name-based, evidence: (a) RPX's Empower reporting ties Slingshot to "more than a dozen patent assertion entities, typically named according to a 'slingshot and stones' or 'David and Goliath' theme," linked via public records to York Eggleston and Keith Machen — Machen signing as President of Slingshot Printing LLC on the PTO/AIA/96 statement dated 2020-07-25; (b) the entity's only visible conduct after acquisition is litigation. Timing corroborates purpose: assignment 2019-03-29 → first suit ~2019-06-11.

2. Known asserter in the chain — PRESENT.
The current assignee, Slingshot Printing LLC, is a documented repeat plaintiff: Slingshot Printing LLC v. HP Inc. (W.D. Tex., first filed 2019-06-11; later No. 6:19-cv-00549 and the Austin-Division wave, dismissed with prejudice 2021-03-24/04-01 under a Settlement, Release and License Agreement) and Slingshot Printing LLC v. Canon U.S.A., Inc. / Canon Solutions America, Inc. (E.D.N.Y. No. 2:22-cv-00123, filed 2022-01-07; No. 22-cv-1852; plus W.D. Tex. No. 6:20-cv-00048). Slingshot is expressly not on the classic Acacia / Marathon / IV / Wi-LAN / Conversant name lists, but it is independently surfaced by RPX and by IPWatchdog's litigation roundup as a litigation-funded campaign entity (IPWatchdog lists the 2:22-cv-00123 filing as "Slingshot Printing LLC [Keith Machen & York Eggleston]"), and its principal, York Eggleston, is publicly associated with Catapult IP Innovations Inc., the BlackBerry patent-acquisition SPV. That is the functional equivalent of a "known asserter" finding.

3. Repeat correspondent across the chain — UNCLEAR (data gap).
I could not extract the correspondent of record for Reels 013523/0690, 030416/0001, or 048745/0551 from the Assignment Center/assignment.uspto.gov abstract in this session. The three filings are 17 years apart and were necessarily handled by three different agents of record (Lexmark's in-house IP department — Customer No. 21972, "Lexmark International, Inc. Intellectual Property Law Department, 740 West New Circle Road, Lexington, KY" — is the Lexmark-side address seen on unsigned POA documents in the family; Amster Rothstein & Ebenstein LLP appears on Slingshot-side family documents; Goldberg Segalla LLP superseded it in 2020). Because the signal requires recurrence on the assignment instruments themselves, and I have no correspondent data on those instruments, I mark this UNCLEAR and expressly decline to convert family-wide counsel into a finding. To close it, pull the three reel/frame records directly in Assignment Center.

4. Cascading transfers — NOT PRESENT.
Three transfers over ~16.5 years (2002 → 2013 → 2019). There is no <24-month chain of successive LLC-to-LLC hops, no shared registered-agent address between consecutive assignees, and no common principals between Lexmark, Funai, and Slingshot. The two ownership exits (2013, 2019) are both portfolio-level, but they are six years apart and each has an independent commercial rationale.

5. Pre-litigation transfer — PRESENT.
Reel 048745/0551 was executed 2019-03-29. The first Slingshot v. HP suit followed on 2019-06-11 (~74 days), and the case expressly naming 6,676,246 among the patents-in-suit, No. 6:19-cv-00549, was filed 2019-09-20 (~175 days). Both are within six months of the assignment. This is the defining pattern the signal targets: title was cleaned up immediately before assertion, establishing a clean standing record and a Texas filing posture.

6. Bankruptcy fire-sale — NOT PRESENT.
No Chapter 7/11 records, no court-ordered sale, no assignment "via court proceeding" instrument appears for either the 2013 or 2019 link. Lexmark's divestiture to Funai was a going-concern asset sale during Lexmark's solvent operation; Funai's 2019 assignment to Slingshot is recorded as a plain assignment with no bankruptcy provenance (no "Order Approving Sale" or trustee signature on the recorded instrument). The patent's own legal-events block shows only routine maintenance-fee payments (2007-07-13 yr 4; 2011-07-13 yr 8; 2015-07-01 yr 12) — consistent with a maintained, monetization-tracked asset, not an abandoned estate asset.

7. Privateering — UNCLEAR (and, on the better reading, NOT PRESENT).
Classic privateering requires the operating company to transfer to an NPE that then asserts on the operating company's behalf against its competitors while the operating company keeps selling. Here Funai had already exited the inkjet hardware business before the 2019 transfer; it did not retain a back-end license/royalty interest on the face of the recorded instrument, and the targets (HP, then Canon) were not Funai's live competitors at that point. The more accurate characterization is a straight portfolio monetization sale to an NPE, not privateering. I mark it UNCLEAR only because a revenue-share or retained interest could exist in an unrecorded side agreement, which I cannot rule out from the public record.

8. Defensive aggregator (anti-NPE) — NOT PRESENT.
The chain terminates at Slingshot Printing LLC, an asserter, not at RPX, AST, LOT Network, Unified Patents, or OIN. There is no neutralizing entity anywhere in the chain. (Inverse note: the patent did survive the HP wave untouched — HP petitioned IPRs against sibling patents 6,394,593 / 6,243,115 / 7,014,299 / 7,244,015 / 7,410,246 and never against 6,676,246 — but the March 2021 stipulated dismissals with prejudice were a settlement/license, not a defensive aggregation.)

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Verdict

NPE — high confidence.

Three independent strong signals converge on the same entity and the same window. (1) Shell-entity transfer: Reel 048745/0551 (executed and recorded 2019-03-29) moved the entire right from operating manufacturer Funai Electric Co., Ltd. to Slingshot Printing LLC, a Maryland licensing vehicle with no products, whose President Keith Machen is publicly tied by RPX to a family of "slingshot and stones"-themed assertion entities alongside York Eggleston. (2) Known asserter: Slingshot is a documented repeat plaintiff (HP, W.D. Tex. 2019–2021; Canon, E.D.N.Y. from 2022-01-07) and is indexed as a litigation-funded campaign in RPX and IPWatchdog reporting. (3) Pre-litigation transfer: suit followed the 2019-03-29 assignment within ~74 days (first HP filing ~2019-06-11) and the case expressly naming 6,676,246 within ~175 days (No. 6:19-cv-00549, 2019-09-20) — squarely inside the six-month window, evidencing that the chain was arranged to enable assertion. The intermediate Reel 030416/0001 (2013-04-01 / 2013-05-14, Lexmark + Lexmark International Technology S.A. → Funai) is an ordinary corporate divestiture and is not itself an NPE signal; it is the upstream event that placed an operating company's heater-chip portfolio into monetization hands. Caveat: the chain is now economically spent — the patent expired 2022-12-27 and all HP cases were dismissed with prejudice in March/April 2021, so any remaining exposure is pre-expiration, damages-only conduct.

Verify at: USPTO Assignment Center — search patent number 6676246 (mirror: assignment.uspto.gov); Google Patents US6676246B1 legal events.

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Verification gaps to close before relying on this

1. Correspondent of record on all three reels/frames — the one Assignment-Center field I could not retrieve; pull each record individually (this is the single highest-value follow-up for Signal 3).
2. Whether No. 6:19-cv-00363 and No. 6:19-cv-00364 are the same or duplicative June-2019 filings, and whether 6,676,246 was pleaded in the June-2019 case or only in the September-2019 case (affects the tightness of the "10 weeks" pre-litigation-transfer finding, though not the finding itself).
3. Funai's post-2019 corporate status (I did not confirm any insolvency, and found no bankruptcy provenance on the recorded instrument; do not assume one).
4. Any unrecorded license/royalty-back retained by Funai in the 2019 sale — would move Signal 7 from UNCLEAR toward privateering if it exists.

I'll verify the patent record and pull details on each cited reference before mapping them to the claims.

I have strong verification on several key references. Let me verify the remaining cited references.

§ 102 Prior-Art / Anticipation Analysis — US 6,676,246 B1

Search scope notice. All results below are for US 6,676,246 B1 only. I excluded look‑alike numbers that surface in the same Slingshot/Lexmark (ex‑Funai) portfolio — including 7,410,246 ("Heater chip configuration…"), 7,014,299, 6,575,563, 6,467,864, 6,890,062, 6,394,593, and 7,195,341 — none of which is the patent in suit here.

Two flags before the analysis:

1. Date conflict. This task states "Current Date: April 26, 2026," but the system date is 2026‑09‑23, and the previously generated Obviousness section relies on CAFC decisions dated July 16, 2026. Those cannot post‑date a task set on April 26, 2026. I flag the contradiction rather than silently reconcile it; nothing in the § 102 analysis below turns on either date.
2. A number‑conflation trap I found and rejected. A PTAB petition excerpt appears in search results discussing "the '246 patent" with claims 1, 6, and 24 and a companion "'951 Patent," combining Feinn in view of Prasad. That cannot be US 6,676,246, which has only 19 claims (verified in the authoritative text) and no claim 24. That petition concerns a different "‑246" patent. I have not imported any of its content into this analysis.

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1. The patent being tested (verified)

The three parameters that decide everything. Every independent claim requires a combination:

• (P1) protective layer(s) over the resistor with total thickness < about 7200 Å;
• (P2) a firing pulse time < about 0.73 µs;
• (P3) delivered energy 2.9–4.0 GJ/m³, computed on a defined volume = resistor area × (resistor thickness + protective‑layer thickness).

Claim 8 is the broadest (structure only: "operable at" 2.9–4.0 GJ/m³, "pulse time of less than about 0.73 microseconds," and "one or more protective layers … less than about 7200 angstroms"). Claims 1 and 9 add the nozzle, the resistor area/thickness, and the express volume metric. Claim 10 adds the method steps and "stable velocity."

Critical dependency rule. Claims 2–7 depend from claim 1; claims 11–13 from claim 8; claims 14–16 from claim 9; claims 17–19 from claim 10. Under § 112(d), each dependent claim incorporates all limitations of its base claim. Therefore a reference can only anticipate a dependent claim if it also anticipates the corresponding independent claim. Since no reference below discloses P1+P2+P3 together, no cited reference anticipates any of the 19 claims. The rest of this document supplies the element‑by‑element proof and identifies the closest calls.

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2. Anticipation framework applied

• Single‑reference rule. Anticipation requires one reference disclosing every claimed element "arranged as in the claim." Net MoneyIN v. VeriSign; Scripps Clinic. Two references that together disclose P1+P2+P3 is a § 103 case, not § 102.
• "About" ranges. A reference value falling inside an "about"‑modified claimed range can anticipate. Titanium Metals Corp. v. Banner, 778 F.2d 775 (Fed. Cir. 1985). This makes P1 (a thickness ceiling) far easier to read onto a reference than P2/P3.
• Functional language is still a limitation. "Operable at 2.9–4.0 GJ/m³" and "pulse time of less than about 0.73 µs" must be disclosed or inherently present in the reference. Where a reference states its own operating pulse width, that express value controls.
• § 102(e) subset. Pre‑AIA § 102(e) art = US patents/applications "by another" filed before the '246 invention date, regardless of publication. Two cited references are § 102(e)‑only (see below).

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3. Master table — the 26 references cited on US 6,676,246

Dates are filed (earliest priority) → issued/published, as recorded in the patent's citation tables. References marked ★ were cited by the examiner (the remaining 24 were applicant/IDS citations). "Anticipates?" = does it disclose P1+P2+P3 in one reference?

(#25 and #26 are family/publication duplicates of #5 and #16 respectively. #18 is the publication of #17.)

Note the asterisks. Only two references bear the examiner's asterisk: US 6,142,612 (#15) and US 6,491,377 (#24). The examiner independently located exactly the two references I identify as the substantive heater‑stack/energy art — the rest are IDS background.

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4. Element‑by‑element analysis of the substantive references

A. US 6,491,377 B1 — Cleland et al. (Hewlett‑Packard) ★ — closest reference

• Full citation: US 6,491,377 B1, "High print quality printhead," Hewlett‑Packard Co. Filed 1999‑08‑30; issued 2002‑12‑10.
• § 102 basis — express caution: Issued 2002‑12‑10, twenty days after the '246 filing date (2002‑11‑20). It therefore cannot be § 102(a) or § 102(b) art. It qualifies only under pre‑AIA § 102(e) as a US patent granted on an application filed 1999‑08‑30, by another, before the '246 invention date. (See the correction already flagged in the Obviousness section for the sibling mis‑dating of US 6,331,049.)
• Description (verified against the patent): A substrate carrying a multiplicity of heater resistors at ≥ 6 resistors/mm², each ≥ 70 Ω, with "an overlaying passivation thermal barrier characteristic adjusted to enable ejection of an ink drop of less than 6.5 ng with an energy impulse equal to or less than 1.4 µJ." Claim 5 recites the passivation layer is "less than 5000 Å." The specification expressly states that protective layers "tend to increase the inherent turn‑on energy," and that as resistors are fired at higher frequency and greater density, "there must be a reduction in the amount of energy input to the printhead."
• Anticipation verdict — NO.
  • P1 (< 7200 Å): YES (passivation < 5000 Å, claim 5) — the only element this reference supplies outright.
  • P2 (< 0.73 µs): NOT DISCLOSED. No pulse duration is stated. This is fatal to § 102; converting 6,491,377's ≤ 1.4 µJ into a sub‑0.73 µs pulse time is arithmetic a challenger must perform — i.e., a § 103 argument, not anticipation.
  • P3 (2.9–4.0 GJ/m³): NOT DISCLOSED. No energy‑per‑unit‑volume (let alone the '246's peculiar volume metric) appears.
  • Claims 1, 8, 9, 10 all fail on P2/P3; every dependent claim fails with them.
• Best use: the primary § 103 reference, not a § 102 reference.

B. US 6,331,049 B1 — Hewlett‑Packard ★ — strongest teaching on the mechanism

• Full citation: US 6,331,049 B1, "Printhead having varied thickness passivation layer and method of making same," Hewlett‑Packard Co. Filed 1999‑03‑12; issued 2001‑12‑18. Prior art under § 102(a) and § 102(e) — issued 2001‑12‑18 is less than one year before 2002‑11‑20, so not § 102(b). (This is the same date‑hook error the prior Prior Art section made and the Obviousness section corrected; I confirm the correction.)
• **Description (verified against the patent, US 6,331,049 B1 and EP 1 034 932 A):
  • The passivation layer is relatively thin (121) over the ink expulsion element (112) "to reduce the energy required to expel ink," and relatively thick (122) over the circuitry (150) to prevent capacitive coupling.
  • Express quantification: "Thinning the passivation layer from 0.75 microns to 0.38 microns achieves a TOE reduction of approximately 22%," and it "may be reduced below 0.38 microns, for example, to 0.2 microns or below."
  • Background asserts the governing relationship verbatim: "TOE is related to passivation layer thickness in that the thicker the passivation layer, the more energy required to expel a drop of ink."
  • Stack: Si₃N₄ passivation (thin region ~0.2 µm) + Ta protection/cavitation layer 124 applied to ~0.6 microns.
• Anticipation verdict — NO. This is the sharpest point in the whole analysis:
  • P1 (< 7200 Å): arguably NOT even disclosed. The '246 counts the cavitation (Ta) layer inside the "protective layer 40" and therefore inside the thickness denominator (see Claim 1: thickness measured "from the top surface 38a of the heater resistor 38 to the outermost surface 40a of the protective layer 40"). Under that metric 6,331,049's heater stack is roughly 0.2 µm + 0.6 µm ≈ 8,000 Å — above the 7,200 Å ceiling. A patent owner can defeat even this element on the reference's own numbers.
  • P2 (pulse time): NOT DISCLOSED. No pulse width stated.
  • P3 (GJ/m³): NOT DISCLOSED. No energy‑density value stated; only a percentage TOE reduction.
• Best use: § 103 — it is the reference that supplies the motivation and mechanism (thin the protective stack over the heater → lower energy) that the '246 claims to have discovered.

C. US 6,142,612 A — Whitman (Lexmark) ★ — same corporate origin; the "teaching‑away" reference

• Full citation: US 6,142,612 A, "Controlled layer of tantalum for thermal ink jet printer," Lexmark International, Inc. Filed 1998‑11‑06; issued 2000‑11‑07. Prior art under § 102(b) (issued more than one year before the '246 filing).
• Description (verified against the patent and EveryPatent/Justia mirrors):
  • Optimizes the sputtered tantalum outermost protective layer over a Si₃N₄ / SiC / Ta stack using an I‑Optimal regression design; the optimum Ta thickness is about 9,000 Å (≈ 50% thicker than previously used), chosen for cavitation/resistor life.
  • Expressly frames the trade‑off the '246 claims to have "discovered": "as the thickness of the protective layers is increased, it is more difficult to heat the ink through the protective layers because the protective layers impede the dissipation of heat. Accordingly, as the total thickness of the protective layers has increased, it has previously been suggested to use current pulse of long times (widths)… Longer pulse widths imply a lower power density to the heater. Lower power density has been correlated to lower print quality."
  • FIG. 4 plots drop volume vs. current pulse width for standard vs. optimized‑thickness heads.
• Anticipation verdict — NO.
  • P1 (< 7200 Å): NOT disclosed — in fact contradicted. The reference's optimum Ta layer alone (≈ 9,000 Å) exceeds the claimed 7,200 Å ceiling before any Si₃N₄/SiC is counted.
  • P2 (< 0.73 µs): NOT disclosed. The reference speaks of long pulse widths as the prior remedy; it does not state a sub‑0.73 µs value.
  • P3: NOT disclosed.
• Best use: § 103 for the mechanism (thickness ↔ pulse width/power density), while acknowledging it cuts against the claimed ceiling — the honest "teaching away" problem discussed in the Obviousness section.

D. US 6,139,131 A — Hewlett‑Packard — the reference that states a pulse time, and it is the wrong one

• Full citation: US 6,139,131 A, "High drop generator density printhead," Hewlett‑Packard Co. Filed 1999‑08‑30 (US 09/386,028); issued 2000‑10‑31. § 102(a)/(b)/(e) — issued more than one year before 2002‑11‑20.
• Description (verified against the specification and claims): A high‑density thermal inkjet printhead with ≥ 6 heater resistors per mm², each adapted to eject a drop with an energy pulse between 1.0 and 1.4 µJ (claim 13); claim 8 recites the drive pulse "lasting a duration of between 1.31 µsec and 1.5 µsec"; method claim 14 supplies 10.7–10.9 V for 1.3–1.5 µsec. Background states that as resistors are fired at higher frequency and packed more densely, "there must be a reduction in the amount of energy input to the printhead."
• Anticipation verdict — NO, and it is affirmative evidence against anticipation.
  • P1 (< 7200 Å): NOT disclosed. No protective‑layer thickness is claimed or specified.
  • P2 (< 0.73 µs): NOT disclosed — expressly contradicted. The reference's only stated pulse durations are 1.31–1.5 µs, i.e., roughly 2× the claimed ceiling. Because it states its own operating pulse width, there is no room for an inherent‑disclosure argument on P2.
  • P3: NOT disclosed in GJ/m³ (and 1.0–1.4 µJ is lower than the '246's implied operating point on the same stack volumes).
• Best use: § 103 context (pulse width as the design variable for density/frequency) and, defensively, as a reference establishing what the art's actual operating pulse widths were.

E. US 6,244,682 B1 — Hewlett‑Packard — the TOE methodology reference

• Full citation: US 6,244,682 B1, "Method and apparatus for establishing ink‑jet printhead operating energy from an optical determination of turn‑on energy," Hewlett‑Packard Co. Filed 1999‑01‑25; issued 2001‑06‑12. § 102(b) (issued more than one year before 2002‑11‑20).
• Description: A method/apparatus for optically detecting the turn‑on energy of a printhead and setting the operating energy accordingly — i.e., the art's standard technique for driving a heater at its minimum reliable energy. (Confidence: title/abstract‑level; I was cut off before a full‑text verification of this reference, so I do not assert specific numerical values from it.)
• Anticipation verdict — NO. Supplies neither P1, nor P2, nor P3 numerically. Best use: § 103 — evidence that setting heater energy to the minimum reliable value was routine practice.

F. US 5,726,690 A — Hewlett‑Packard — pulse‑width ↔ drop‑volume linkage

• Full citation: US 5,726,690 A, "Control of ink drop volume in thermal inkjet printheads by varying the pulse width of the firing pulses," Hewlett‑Packard Co. Filed 1991‑05‑01; issued 1998‑03‑10. § 102(b).
• Description: Varies the firing‑pulse width to control ejected drop volume; treats pulse width and delivered energy as linked, controllable design variables. (The long 1991→1998 pendency indicates a continuation/divisional chain; the priority date shown is the earliest. § 102(b) applies on either date since the grant is 1998.)
• Anticipation verdict — NO. No thickness, no sub‑0.73 µs value, no GJ/m³ value. Best use: § 103 context.

G. US 5,682,185 A (HP) — energy‑measurement scheme

• Full citation: US 5,682,185 A, "Energy measurement scheme for an ink jet printer," Hewlett‑Packard Co. Filed 1993‑10‑29; issued 1997‑10‑28. § 102(b).
• Description: In‑printer measurement of the energy delivered to firing resistors. Anticipation verdict — NO (no P1/P2/P3). Best use: § 103 — establishes that per‑pulse energy was a measured, controlled quantity in the art.

H. US 6,227,640 B1 / US 2001/0008411 A1 — Hewlett‑Packard (Maze) — same disclosure, two documents

• Full citations: US 6,227,640 B1, "Variable drop mass inkjet drop generator," HP, filed (priority) 1994‑03‑23; issued 2001‑05‑08, § 102(b); and its published application US 2001/0008411 A1, published 2001‑07‑19, § 102(b). Do not count these as two independent references — they are one disclosure.
• Description: A drop generator whose ejected drop mass is varied (e.g., by pulse modulation).
• Anticipation verdict — NO as to every claim of the '246 (no thickness, no pulse time, no energy density). Best use: background/§ 103.

I. US 5,742,307 A (Xerox)

• Full citation: US 5,742,307 A, "Method for electrical tailoring drop ejector thresholds of thermal ink jet heater elements," Xerox Corp. Filed 1994‑12‑19; issued 1998‑04‑21. § 102(b).
• Description: Electrically trimming individual heater elements to normalize their drop‑ejection threshold. Anticipation verdict — NO (thresholds, not stack thickness or pulse width).

J. US 6,318,845 B1 (Canon) — date‑hook note

• Full citation: US 6,318,845 B1, "Ink‑jet printing apparatus and method for varying energy for ink ejection for high and low ejection duties," Canon K.K. Filed 1998‑07‑10; issued 2001‑11‑20.
• § 102 basis: Issued 2001‑11‑20, exactly the one‑year § 102(b) boundary. Because § 102(b) requires the reference be published more than one year before filing, I treat this as § 102(a)/(e) art rather than § 102(b). (Immaterial to outcome.)
• Description: Varies ejection energy with print duty. Anticipation verdict — NO.

K. Remaining general printhead‑construction references — all NO

These supply the conventional thermal‑inkjet context (heater resistor + dielectric passivation + Ta cavitation layer + nozzle/orifice plate, and conventional drive/fabrication methods) but disclose none of P1, P2, or P3 in the claimed combination:

(Descriptions for the Canon/Fujitsu/Hitachi entries above are title/abstract‑level from the patent's own citation tables; I did not verify each full text, so I state only what the title reliably supports.)

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5. Claim‑by‑claim § 102 verdict

The two structurally "closest" independent claims fail for the same reason:

• Claim 8 needs only a thin‑stack structure with the stated operating window. US 6,491,377 supplies the thin layer (< 5000 Å) and low energy (≤ 1.4 µJ) but states no pulse time and no GJ/m³ value. That gap is bridgeable only by calculation — § 103, not § 102.
• Claims 1/9/10 additionally require the express volume metric and a nozzle; even US 6,331,049, the best structural fit, appears to sit above the 7200 Å ceiling once its ~0.6 µm Ta cavitation layer is counted, exactly as the '246 counts it.

The dependent‑claim material/geometry lists do not rescue a § 102 case. Claims 6, 7, 11, 12, 14, 15, 17, 18 recite conventional materials (SiN, SiC, Ta, TiW, DLC, Si‑DLC, TaB, TiN, Ti, WSi; TaAl, TaN, TaAl:N, Ta+TaAl) and claims 3, 13, 16, 19 recite conventional dimensions (300–1100 µm²; 500–1500 Å). Those elements are abundantly disclosed across the Canon/HP/Lexmark art — but because each of those claims incorporates its base claim's P1/P2/P3 limitations, none can be anticipated by a reference that does not also anticipate the base claim.

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6. Conclusions

1. No cited reference anticipates any claim of US 6,676,246. The claims are defined by a three‑parameter operating envelope (thin protective stack + sub‑0.73 µs pulse + 2.9–4.0 GJ/m³ on the patent's own volume metric). The cited art, at most, discloses one of those parameters at a time — and in two instances (US 6,142,612's ~9,000 Å Ta; US 6,139,131's 1.31–1.5 µs pulses) the reference states a value on the wrong side of the claimed boundary.

2. The substantive prior art is exactly the two examiner‑cited references. The examiner starred only US 6,491,377 (Cleland/HP) and US 6,142,612 (Whitman/Lexmark) — the thin‑passivation/high‑density/low‑energy printhead and the reference that expressly ties protective‑layer thickness to pulse width and power density. Both are § 103 references; neither is a § 102 reference.

3. Statutory‑hook corrections (consistent with the earlier Obviousness section). US 6,491,377 is prior art only under § 102(e) — it issued 2002‑12‑10, after the 2002‑11‑20 filing. US 6,331,049 is § 102(a)/(e), not § 102(b) — it issued 2001‑12‑18, less than one year before filing. US 6,318,845 sits exactly on the § 102(b) boundary and is best treated as § 102(a)/(e).

4. If a § 102 argument is to be attempted at all, it can only be pitched at claim 8 as the broadest claim, and only by arguing that US 6,491,377's < 5000 Å passivation + ≤ 1.4 µJ design inherently fires in under 0.73 µs at 2.9–4.0 GJ/m³. That argument requires (a) an express, uncontested volume‑metric calculation on 6,491,377's disclosed geometry and (b) an inherency showing that the reference's structure necessarily operates in the claimed window — i.e., it collapses back into a § 103/§ 112 analysis. I would not expect it to succeed as pure anticipation.

5. Consistency with the prior sections. This analysis is consistent with — and supplies the § 102 foundation for — the previously generated Obviousness section, which reached § 103 on US 6,491,377 + US 6,142,612 + US 6,331,049 (+ US 6,139,131 / US 5,726,690) and flagged that no IPR was ever instituted on this patent so that any § 282(b) district‑court ground bears no § 315(e)(2) estoppel. The one point I would add for a litigator: because the anticipation case is essentially unavailable, the entire invalidity exposure of US 6,676,246 runs through § 103, and its resolution will turn on expert testimony about whether a PHOSITA would have selected the specific < 0.73 µs / 2.9–4.0 GJ/m³ operating point with a reasonable expectation of success — a topic on which the specification supplies no criticality data.

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Verification links: US 6,676,246 — https://patents.google.com/patent/US6676246/en ; US 6,491,377 — https://patents.google.com/patent/US6491377 ; US 6,331,049 — https://patents.google.com/patent/US6331049 ; US 6,142,612 — https://patents.google.com/patent/US6142612 ; US 6,139,131 — https://patents.google.com/patent/US6139131 . USPTO Patent Center / Assignment Center should be used to confirm the citation tables natively.

Search limitation disclosure: I reached the tool-call limit before running focused verifications on US 5,726,690, US 6,244,682, US 5,682,185, US 6,042,221, and the Canon/Fujitsu/Hitachi references. Descriptions for those entries are title/abstract-level from the patent's own citation record and are labelled accordingly; none of them is a candidate anticipation reference, so the missing verification does not affect the § 102 conclusions.

§ 103 Obviousness Analysis — US 6,676,246 ("Heater construction for minimum pulse time")

Statutory framework. Application filed Nov. 20, 2002; issued Jan. 13, 2004. Pre-AIA 35 U.S.C. § 103 applies. All grounds below assume an invention date no earlier than the filing date (no priority or conception evidence in the record) and rely on references that qualify as prior art under pre-AIA § 102(a), (b), or (e) as noted for each.

One correction to the earlier Prior Art section (flagged per operating rules). That section classified US 6,331,049 as "§ 102(b) art." That is incorrect: US 6,331,049 published Dec. 18, 2001, which is less than one year before the Nov. 20, 2002 filing date (the § 102(b) bar date was Nov. 20, 2001). US 6,331,049 nonetheless qualifies as prior art under § 102(a) (published before the invention date) and § 102(e) (US application filed Mar. 12, 1999, by Hewlett-Packard, another, before the '246 invention date). This does not change the analysis but corrects the statutory hook. Similarly, US 6,491,377 published Dec. 10, 2002 — after the '246 filing date — so it is prior art only via § 102(e) (HP application filed Aug. 30, 1999), not § 102(a)/(b). All other references used below are § 102(b) art as dated in the Prior Art section.

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I. The claim scope to be attacked

Independent claims: 1, 8, 9, 10. Dependent: 2–7, 11–19.

• Claim 8 (broadest): a heater chip structure having heating elements "operable at an energy per unit volume of from about 2.9 GJ/m³ to about 4.0 GJ/m³," "a pulse time of less than about 0.73 microseconds," and "one or more protective layers having a total thickness of less than about 7200 angstroms." Note what claim 8 does not require: no nozzle, no ink, no resistor area/thickness, no defined volume metric, no power supply, no "stable velocity." Two of the three limitations are purely functional ("operable at …," "a pulse time of …").
• Claims 1 and 9: add a power-supply context (claim 1) and, materially: each heating element = resistor (area, thickness) + overlying protective layer < 7200 Å; the element has a "volume … determined by the area of the heater resistor multiplied by the sum of the thickness of the heater resistor and the thickness of the protective layer"; ink is ejected through an associated nozzle in a pulse time < 0.73 μs; and the energy delivered per that defined volume is 2.9–4.0 GJ/m³.
• Claim 10 (method): the same structure, plus applying pulses < 0.73 μs at 2.9–4.0 GJ/m³ and ejecting droplets "at a stable velocity."
• Dependent claims: resistor thickness 500–1500 Å (2, 3, 13, 16, 19); resistor area 300–1100 μm² (3, 13, 16, 19); protective layer 1000–7200 Å (4); multi-layer overcoat (5); conventional overcoat material lists — SiN, SiC, Ta, TiW, DLC, Si-DLC, TaB, TiN, Ti, WSi (6, 11, 14, 17); conventional resistor material lists — TaAl, TaN, TaAl:N, Ta+TaAl (7, 12, 15, 18).

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II. The person of ordinary skill in the art (PHOSITA)

A design or process engineer with (i) a bachelor's degree in electrical engineering, materials science, or chemical engineering and 2–5 years of experience developing thermal inkjet printheads; (ii) working knowledge of thin-film resistor and passivation/cavitation layer deposition (materials, thicknesses, stress, adhesion); (iii) familiarity with heater drive electronics, turn-on energy (TOE), pulse-width control, and firing-frequency/nozzle-density tradeoffs; and (iv) access to the standard thermal-inkjet literature (e.g., the HP, Canon, Lexmark patent corpus and the Lloyd & Taub chapter in Output Hardcopy Devices). This is a mature, crowded field by 2002 — as the '246 specification's own background and the sheer density of the cited art (26 listed references, largely HP/Canon/Lexmark thermal-inkjet heater patents spanning 1983–2002) confirm.

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III. The claimed "invention" as the specification frames it — and the admissions that help the challenger

The specification discloses no new material, no new device architecture, and no new drive scheme. Its entire contribution is a parameter window:

"it has been discovered that the required pulse time for satisfactory operation of an ink jet heater is generally a function of the heater stack thickness and is generally independent of the heater area and ink composition" … "relatively low pulse times and improved printer performance may be achieved by constructing the heater chip to limit the thickness of the protective layers and applying only relatively low power to the resistors." (Detailed Description; emphasis added)

Three points matter for § 103:

1. The patentee concedes the governing physical relationship (stack thickness → pulse time) and disclaims any dependence on area or ink. That relationship is precisely what the closest prior art already teaches (see § IV below). The claims merely package the consequence of a thin stack as functional limitations.
2. All materials are conventional and the specification says so — "the invention is not limited to any particular material or combination of materials in the protective layer"; the passivation/cavitation materials are the industry-standard SiN/SiC/Si-DLC/DLC/Ta set; resistor materials are the industry-standard TaAl/TaN family.
3. No criticality data. The specification contains no comparative examples, no data showing that 0.73 μs or 7200 Å or 2.9–4.0 GJ/m³ are critical boundaries, and no showing of unexpected results. The values are stated as design windows. That is the classic profile of a claim vulnerable under KSR as an obvious optimization of result-effective variables.

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IV. The closest prior art (from the record's cited references, confirmed against the underlying patents)

Primary reference — US 6,491,377 B1 ("High print quality printhead," HP; examiner-cited; § 102(e), app. filed Aug. 30, 1999)

Confirmed from the patent itself:

• Claim 1: a printhead with heater resistors at a density ≥ 6 resistors/mm², each ≥ 70 Ω, "having an overlaying passivation thermal barrier characteristic adjusted to enable ejection of an ink drop of less than 6.5 ng with an energy impulse equal to or less than 1.4 μJ."
• Claim 5: "the passivation layer has a thickness of less than 5000 Å."

This single patent discloses a high-nozzle-density, high-frequency-class printhead with (i) a protective (passivation) layer under the claimed 7200 Å ceiling (indeed under 5000 Å) and (ii) expressly low-energy operation (≤ 1.4 μJ), targeting the same problem the '246 patent says it solves — high nozzle density requiring short address times and low energy to avoid printhead heating artifacts.

Secondary reference — US 6,142,612 A ("Controlled layer of tantalum for thermal ink jet printer," Lexmark/Whitman; examiner-cited; § 102(b)/(e), filed Nov. 6, 1998)

A Lexmark patent (same corporate origin as the '246) addressing the exact variable the '246 patent claims to have discovered. It optimizes the sputtered tantalum cavitation-layer thickness over a Si₃N₄/SiC/Ta stack and, per the Prior Art section, "explains that thicker overcoats otherwise force longer pulse widths and lower power density, degrading print quality." In other words, the art's own language teaches the stack-thickness ↔ pulse-width relationship on which the '246 claims rest. Its specific Ta optimum (~9000 Å) lies above the '246's 7200 Å total ceiling, which a patent owner will call "teaching away" (see § VIII), but its explicit framing of overcoat thickness as the pulse-width control variable is the intellectual bridge to the '246 claims.

Tertiary reference — US 6,331,049 B1 ("Printhead having varied thickness passivation layer," HP; § 102(a)/(e), filed Mar. 12, 1999)

Confirmed from the patent: the passivation layer is made "relatively thin over the ink expulsion element to reduce the energy required to expel ink" and thick over circuitry; "TOE is related to passivation layer thickness in that the thicker the passivation layer, the more energy required"; a reduction "from 0.75 microns to 0.38 microns achieves a TOE reduction of approximately 22%," with thicknesses "reduced below 0.38 microns, for example, to 0.2 microns or below" (2000 Å). This is an express teaching that thinning the passivation over the heater element alone — while keeping it thick elsewhere — cuts TOE, and it quantifies the relationship. A 0.2 μm passivation over a ~0.1 μm resistor yields a sub-7200 Å (indeed ~3000 Å) heater stack.

Context references for pulse-time / firing-frequency engineering

• US 6,139,131 A (HP, § 102(b)/(e), filed Aug. 30, 1999): high-drop-generator-density printhead (432 generators; 1200-dpi-class) with matrix addressing and explicitly engineered firing intervals; defines pulse time t_PW = 1.4 μs ± 0.1 with dead time for thermal recovery — i.e., it treats pulse width as the design variable for increasing nozzle count and firing frequency, the very context of the '246 background.
• US 5,726,690 A (HP, § 102(b)): drop-volume control by varying firing-pulse width; teaches that shorter pulse widths improve ejection dynamics and that TOE shifts with pulse width (~0.5 μJ/μs) — i.e., pulse width and energy are linked, controllable variables.
• US 6,244,682 B1 / 6,227,640 B1 (HP): operating-energy selection (turn-on energy) and variable-drop-mass generators — showing energy is set to the minimum reliable value, per TOE methodology.
• US 4,719,478; 4,936,952; 4,968,992; 5,580,468; 6,042,221; 6,315,853 (Canon); 5,831,648 (Hitachi Koki); EP 0 490 668; EP 1 078 757; JP 06-320729: general heater-resistor + protective-layer construction and driving methods using the same conventional SiN/SiC/Ta stacks and TaAl-family resistors.

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V. Proposed § 103 combinations and claim mapping

Ground 1 (strongest): US 6,491,377 + US 6,142,612 (+ US 6,331,049, + US 6,139,131 as needed) → claims 1, 8, 9, 10

Ground 2: US 6,331,049 + US 6,491,377 (+ US 6,142,612) → claims 1, 8, 9, 10

Same mapping, with 6,331,049 as the primary: it is the reference that most directly teaches the spatially selective thinning of the passivation layer over the heater element to reduce expulsion energy, expressly acknowledging (and solving) the countervailing reliability problems of thin passivation by keeping the layer thick over circuitry. Combining 6,331,049's thin-over-heater architecture with 6,491,377's high-density, high-resistance, low-energy heater design and with 6,142,612's pulse-width/overcoat-thickness teaching yields the same claimed structure and operating window.

Ground 3 (against claim 8 in particular): 6,491,377 or 6,331,049 "alone + PHOSITA knowledge"

Claim 8's minimal elements — a thin-stack (< 7200 Å) heater chip operable at low energy density and sub-0.73 μs pulses — track 6,491,377 (or 6,331,049) plus the admitted stack-thickness/pulse-time relationship. A challenger can argue claim 8 is obvious over 6,491,377 in view of the PHOSITA's routine practice of setting pulse width to the minimum reliable value for the stack (TOE methodology per 6,244,682/5,726,690), with the < 0.73 μs and 2.9–4.0 GJ/m³ figures being nothing more than the measured operating point of the disclosed thin-stack device.

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VI. Motivation to combine — KSR analysis

Same field, same problem, complementary teachings. All principal references are thermal inkjet printhead patents addressing heater/passivation stack design, energy, and firing density. KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), requires no explicit "suggestion"; the combination is of known elements with predictable results, driven by a recognized design need:

1. The problem was known and shared. The '246 background describes it: as nozzle count and firing frequency rise, "the time available to address all nozzle hole positions … decreases," and thick insulating protective layers "increase the amount of energy that must be applied … [and] correspondingly … the pulse time." That is not a novel problem statement — it is the same problem 6,142,612 (thick overcoats → longer pulses, lower power density → degraded quality), 6,331,049 (passivation thickness ↑ ⇒ TOE ↑), 6,491,377 (dense, low-energy, thin-passivation design), and 6,139,131 (dense-array pulse-time engineering) each address.
2. The combination is of complementary, non-competing solutions. 6,331,049 and 6,491,377 push toward thin passivation for low energy; 6,142,612 explains why thickness is the pulse-width lever (even though its own lifetime-optimized Ta choice is thick). A PHOSITA seeking short pulses at high frequency reads the thin-stack references and 6,142,612's mechanism together and arrives at: thin protective stack (< 7200 Å, indeed ~2000–5000 Å), low pulse energy, sub-microsecond pulse width. That is precisely the claimed combination.
3. The results were predictable. The patentee's own admission that pulse time is a function of stack thickness (independent of area and ink) means the claimed pulse-time result follows mechanistically from the thin-stack structures already in 6,491,377/6,331,049. There is no new physics, no new material, and no new circuit in the '246 patent.
4. Portfolio context is probative. The PTAB and the Federal Circuit have now repeatedly held closely related Slingshot (ex-Lexmark) thermal-inkjet chip claims unpatentable as obvious over combinations of ordinary thermal-inkjet patents — e.g., Slingshot Printing LLC v. Canon U.S.A., Inc., No. 24-1956 (Fed. Cir. Apr. 23, 2026) (claims of 7,195,341 obvious over Torgerson US 6,412,917 + Bruce US 7,240,997); the July 16, 2026 affirmances (7,290,864 obvious over US 7,722,144/7,278,703/6,582,062; 7,484,823 and 7,594,708 obvious over "Benjamin" + "Giere'673," including US 7,384,113/6,612,673). Those are different claims (substrate layout, bondpad routing, temperature sensing), but they confirm the Board's and CAFC's treatment of this exact patent family's incremental, parameter/layout-driven claims in a mature field. Nothing about 6,676,246's claim scope — which is more functional and less structural than those — places it on stronger ground. (Sources: https://www.cafc.uscourts.gov/opinions-orders/24-1956.OPINION.4-23-2026_2681303.pdf; https://ipwatchdog.com/2026/07/16/cafc-affirms-two-ptab-obviousness-rulings-in-canon-printhead-patent-disputes/.)

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VII. Dependent claims

• Resistor thickness 500–1500 Å and area 300–1100 μm² (claims 2, 3, 13, 16, 19): conventional thin-film resistor dimensions. TaAl-family resistors of ~1000 Å and heaters of ~10⁻¹¹–10⁻⁹ m² are pervasive in the cited Lexmark/HP/Canon stack art (6,142,612; 6,331,049; 6,042,221) and are implicit in 6,491,377's resistor-density and drop-size disclosures. A PHOSITA choosing dimensions for a 6.5-ng drop generator would land in these ranges as a matter of routine scaling.
• Protective layer 1000–7200 Å (claim 4): directly overlaps 6,491,377 claim 5 (< 5000 Å) and 6,331,049's 2000–3800 Å thin regions; ranges that merely overlap or bracket disclosed values are classically obvious.
• Multi-layer overcoat (claim 5): 6,142,612's Si₃N₄/SiC/Ta stack and 6,331,049's passivation + protection/cavitation layer 124 are multi-layer.
• Material-list claims (6, 11, 14, 17 — SiN, SiC, Ta, TiW, DLC, Si-DLC, TaB, TiN, Ti, WSi; and 7, 12, 15, 18 — TaAl, TaN, TaAl:N, Ta+TaAl): every listed material was a known passivation/cavitation or resistor material in the art (SiN/SiC/Ta appear in 6,142,612 and 6,331,049; DLC/Si-DLC in the '246's own disclosure as alternatives; TaAl/TaN throughout the Canon/Lexmark art). The claims recite "one or more materials selected from the group" — i.e., picking any one conventional material from a closed list of known-function materials, with no unexpected property shown, is obvious (cf. In re Applied Materials, 692 F.2d 1289 (Fed. Cir. 1982) — selecting from a finite list of known alternatives with predictable results).

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VIII. The honest counter-analysis — where the § 103 case is weakest (and what a patent owner would say)

1. The < 0.73 μs number is below every exemplified pulse width in the closest art. 6,139,131 operates at 1.4 μs ± 0.1; 5,726,690 demonstrates ~1.5–3.5 μs. No cited reference demonstrates stable-velocity ejection at sub-0.73 μs. The challenger's best answer is mechanistic (thin-stack thermal time constant ~0.2–0.5 μs) plus the admitted stack-thickness/pulse-time relationship — but if the patent owner can produce evidence that sub-0.73 μs pulses with the claimed thin stacks produced unexpectedly stable ejection (the "stable velocity" limitation of claims 1 and 10), the ground weakens. No such evidence appears in the specification, however, and the claimed range reads like a design point, not a critical boundary.
2. The 2.9–4.0 GJ/m³ window with the claim-defined volume metric (resistor area × [resistor + protective-layer thicknesses]) appears in no reference. The metric itself is an unusual accounting convention (counting the protective layer in the energy-density denominator). A challenger must argue the metric is arbitrary and that the physical requirement — enough energy to superheat a thin stack + adjacent ink to nucleate a bubble — is what the window actually describes. The numbers check out against 6,491,377's ≤ 1.4 μJ only if one assumes representative heater geometry (my estimate: ~700 μm², ~6000 Å stack → ≈ 3.3 GJ/m³), which is consistent with, but not expressly disclosed in, the reference. A rigorous case would need expert testimony linking 6,491,377's operating energy to the claim's volume metric.
3. 6,142,612 can be characterized as teaching away. Its optimized Ta layer is ~9000 Å — a thicker protective layer than the '246's 7200 Å ceiling, chosen for cavitation lifetime. A patent owner will argue the art's own Lexmark reference pointed away from the claimed thin stacks. The answer is that 6,491,377 and 6,331,049 point toward thin stacks for low-energy operation, so the combination supplies the direction 6,142,612 lacks; and 6,142,612 is used for its mechanism (thickness ↔ pulse width), not its thickness value. Under KSR, a reference need not be the "best" embodiment to contribute a teaching, and a PHOSITA is not barred from combining a thinner-stack teaching with a reference that explains the underlying tradeoff.
4. Functional-claim-format risk. Because claims 1, 8, 9, and 10 are drafted substantially in functional terms ("operable at," "pulse time of," "energy … ranges from"), the obviousness case converges on whether the claimed operating window is an "intended use" or "result-effective variable" optimization. That is favorable to the challenger where, as here, the specification admits the controlling variable (stack thickness) and supplies no criticality data.
5. No secondary considerations in the record. There is no evidence of long-felt need, industry copying, commercial success, licensing, or unexpected results tied to the claimed ranges. The patent expired in 2022 and was asserted only through the settled HP wave and by an NPE — none of which supplies objective indicia of non-obviousness.

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IX. Bottom line

Claims 1, 8, 9, and 10 of US 6,676,246 present a colorable-to-strong § 103 case under the Graham/KSR framework, with the strongest ground being:

US 6,491,377 (thin passivation < 5000 Å; dense, low-energy, ≤ 1.4 μJ heaters) in view of US 6,142,612 (expressly teaching that protective-layer thickness controls pulse width/power density) and US 6,331,049 (expressly teaching selective thinning of passivation over the heater element to cut TOE, quantified down to 0.2 μm), optionally with US 6,139,131 / US 5,726,690 for the pulse-width-as-design-variable and firing-frequency context.

The claimed protective-layer ceiling (< 7200 Å) is expressly satisfied (indeed exceeded in the thinning direction) by 6,491,377 and 6,331,049; the pulse-time and energy-density limitations are functional consequences of the known thin-stack/low-energy design point, with the patentee's own specification conceding that pulse time is a function of stack thickness and independent of area and ink. The dependent claims add only conventional materials and dimensions that pervade the cited art.

The genuine litigation risk for a challenger is concentrated in two places: (i) proving that a PHOSITA would have arrived at the specific < 0.73 μs pulse time and the 2.9–4.0 GJ/m³ window (on the claim's unusual volume metric) with a reasonable expectation of success — which will turn on expert testimony and the absence of any criticality data in the '246 specification; and (ii) overcoming the "teaching away" argument built on 6,142,612's ~9000 Å Ta optimum — which is best answered by using 6,142,612 only for its mechanism and relying on 6,491,377/6,331,049 for the thin-stack direction. The parallel PTAB/CAFC record invalidating the related Slingshot heater-chip patents as obvious (No. 24-1956, decided Apr. 23, 2026; companion affirmances July 16, 2026) is a meaningful signal that claims of this type, from this portfolio, in this art, do not typically survive § 103 scrutiny. Because no IPR was ever instituted on 6,676,246, a defendant may raise this § 103 case on any references in district court under § 282(b) with no § 315(e)(2) estoppel, limited to the pre-Dec. 27, 2022 damages window given the patent's expiration.