US 6817707

Summary: U.S. Patent No. 6,817,707 B1

I searched via web-accessible USPTO mirrors (Google Patents, Unified Patents, Justia, Espacenet, the CAFC's own site) for the literal number 6817707 / 6,817,707. The bibliographic data below is corroborated across multiple sources; CAFC-docket findings are noted with caveats.

Core bibliographic data (high confidence)

• Title: Pressure controlled ink jet printhead assembly
• Patent / Publication No.: US 6,817,707 B1
• Application No.: 10/465,348
• Filing date: June 18, 2003
• Issue date: November 16, 2004
• Inventors: John R. Fowler (Nicholasville, KY); Timothy L. Howard (Lexington, KY); Matthew J. Russell (Stamping Ground, KY); Jon B. Whitney (Georgetown, KY)
• Original assignee: Lexmark International, Inc. (Lexington, KY)
• Later assignments: Funai Electric Co., Ltd. (recorded 2013); Slingshot Printing LLC (recorded 2019) — current assignee per Unified Patents is Slingshot Printing LLC
• Status: Expired – Lifetime (anticipated expiration June 18, 2023; maintenance fees paid through year 12)
• Claims / drawings: 21 claims; 2 drawing sheets
• Classification: B41J2/175 (ink supply systems/cartridges); B41J2/17556 (pressure regulation in cartridge)

Abstract (verbatim)

An ink jet printhead assembly for a pressure controlled ink jet printhead. The assembly includes an ink reservoir made of a first material having a first melting point and having an open top cavity defined by sidewalls, a bottom wall and a peripheral edge. A pressure control structure made of a polymeric material having a second melting point lower than the first melting point is included. The pressure control structure has a first surface, a second surface opposite the first surface, a side surface, and an aperture therein. A sealing structure for forming a liquid tight seal is provided between the sidewalls of the ink reservoir and the side surface of the pressure control structure. A pressure regulating film is attached over the aperture to the first surface of the pressure control structure. A cover is attached to the ink reservoir.

Plain-language overview of the independent claims

There are three independent claims (claims 1, 8, and 15); the remaining 18 claims are dependent.

Claim 1 (apparatus): An ink jet printhead assembly with four cooperating parts:

1. an ink reservoir made of a first material having a first melting point, with an open-top cavity bounded by sidewalls, a bottom wall, and a peripheral edge;
2. a pressure control structure (plate/frame) made of a polymeric material having a second melting point lower than the first, having opposed first/second surfaces, a side surface, and an aperture passing through it;
3. a sealing structure creating a liquid-tight seal between the reservoir sidewalls and the pressure control structure's side surface;
4. a pressure regulating film attached to the first surface so as to close the aperture, plus a cover attached to the reservoir to protect the film.

In essence: a two-material cartridge body where the lower-melting polymer frame (carrying the flexible pressure-regulating membrane) is mechanically sealed into a higher-melting reservoir, avoiding two-shot molding.

Claim 8 (method — "insert first" order): A method of assembling the assembly of claim 1 that (a) provides the same reservoir + pressure control structure; (b) applies a sealing structure to the side surface of the pressure control structure; (c) inserts the pressure control structure into the reservoir cavity first; (d) then attaches the pressure regulating film to the first surface, closing the aperture; and (e) attaches the cover.

Claim 15 (method — "film first" order): The same method steps as claim 8, but the sequence is reversed with respect to the film and frame: the sealing structure is applied, the film is attached to the pressure control structure before insertion, then the subassembly is inserted into the reservoir cavity, and the cover is attached.

In other words, the patent covers both assembly sequences — film-to-frame before insertion (claim 15) or frame-into-reservoir before film attach (claim 8).

Litigation / CAFC 2026 docket findings (with caveats)

• Google Patents lists the patent's family as having district-court litigation in the Texas Western District Court: cases 6:19-cv-00362 and 1:20-cv-00184 (both filed 2019-06-11, closed; Unified Patents identifies plaintiff Slingshot Printing LLC and defendant HP Inc. in those proceedings). I could not independently verify from my searches that 6,817,707 specifically was the patent-in-suit in those dockets — the case list page I retrieved had a filter applied for a different patent (6,243,115), so treat that link as family-level, not patent-level, confirmation.
• CAFC 2026 dockets: The CAFC's 2026 scheduled-case/opinion listings show multiple Slingshot Printing LLC v. Canon U.S.A., Inc. appeals (e.g., 25-1032/25-1033 argued July 2026; decisions of July 16 and July 21, 2026, plus a Rule 36 judgment in 24-2132 on May 7, 2026). None of the search results tie patent 6,817,707 to any of those CAFC appeals — the identified patents in those appeals are 7,290,864; 7,484,823; 7,594,708; and a further printhead patent (CAFC 24-2127, decided July 21, 2026) involving "thick film layer" claim construction. Those appear to be related Slingshot printhead patents rather than 6,817,707.

Uncertainty note: The stated current date is April 26, 2026, but several search results are dated after that (May–July 2026) and describe those CAFC decisions as already issued. Per your instruction to treat live search results as ground truth, I have reported them as returned, but I cannot fully reconcile the timeline. I also had no direct database login to USPTO Patent Center or the CAFC CM/ECF docket, so my CAFC conclusion rests on the searchable public pages above. If you need certainty on whether 6,817,707 appears in any specific CAFC 2026 docket, the authoritative check would be a PACER/CM-ECF query by patent number or the USPTO's assignment/IPR records for that number.

Litigation Involving U.S. Patent 6,817,707

Based on the litigation records embedded in the Google Patents file for US6817707B1 and corroborating docket sources (Unified Patents, Justia, RPX), there are two related district court docket numbers for what is effectively a single patent-infringement campaign by the current owner of the patent:

1. Slingshot Printing LLC v. HP Inc., No. 6:19-cv-00362-ADA

• Plaintiff: Slingshot Printing LLC
• Defendant: HP Inc.
• Jurisdiction: [U.S. District Court for the Western District of Texas, Waco Division](/courts/western-district-of-texas-waco) (Judge Alan D. Albright)
• Case number: 6:19-cv-00362
• Filing date: June 11, 2019
• Cause of action: Patent infringement (35 U.S.C. § 271)
• Status: Closed (per Unified Patents). The docket shows an amended complaint (Aug. 13, 2019), HP's motions to dismiss and to stay, and a stipulation to transfer venue to the Austin Division (Feb. 2020). The case was effectively continued in the Austin Division as No. 1:20-cv-00184-ADA (below). I could not retrieve the terminal disposition document (settlement/dismissal/judgment) within my search limits; the databases consulted mark the case "Closed."

2. Slingshot Printing LLC v. HP Inc., No. 1:20-cv-00184-ADA

• Plaintiff: Slingshot Printing LLC
• Defendant: HP Inc.
• Jurisdiction: U.S. District Court for the Western District of Texas, Austin Division
• Case number: 1:20-cv-00184-ADA
• Filing date: June 11, 2019 (initial civil docket date; transferred/re-docketed from the Waco case 6:19-cv-00362)
• Status: Closed (per Unified Patents)

Confirmation that U.S. 6,817,707 is a patent-in-suit: A June 10, 2020 Plaintiff's Proposed Claim Constructions filing in 1:20-cv-00184-ADA expressly construes claim terms from U.S. 6,817,707 — including "a first melting point," "pressure control structure," "second melting point," and "sealing structure" — alongside terms from other Slingshot/Lexmark patents (6,243,115; 6,394,593; 7,438,397; 7,938,523). The patents-in-suit were originally developed by Lexmark International, Inc., acquired by Funai Electric Co., Ltd. in 2013, and assigned to Slingshot Printing LLC, which filed suit.

Source references

• Google Patents litigation links for US6817707B1: portal.unifiedpatents.com case pages for 6:19-cv-00362 and 1:20-cv-00184 (Texas Western District Court)
• Justia docket: "Slingshot Printing LLC v. HP Inc., 6:2019cv00362" (filed June 11, 2019, W.D. Tex., Judge Albright)
• Unified Patents litigation case list (patents filter) showing both 6:19-cv-00362 and 1:20-cv-00184 as "Closed"
• DocketAlarm/RPX filings: claim-construction exhibit in Slingshot Printing LLC v. HP Inc., No. 1:20-cv-00184-ADA, construing 6,817,707 terms

Caveats

• I did not find any separate litigation (e.g., against Canon, or a distinct 2020 case) specifically identifying 6,817,707 as an asserted patent. The related Slingshot v. HP cases 6:19-cv-00364 and the broader 2019/2020 Slingshot wave involve other patents in the same Lexmark/Funai portfolio.
• No IPR/PTAB proceeding specifically targeting 6,817,707 was confirmed in my searches (the IPR2020-01084 documents encountered concern other portfolio patents).
• The exact final disposition of the HP cases (confidential settlement vs. dismissal vs. judgment) was not retrievable from the available search snippets; both dockets are recorded as closed in Unified Patents' database.

Proceedings overview

Total AIA trial proceedings on file: 0 — the USPTO Open Data Portal ingest for US 6817707 returns no IPR / PGR / CBM proceedings, and targeted web searches surfaced no PTAB petition, institution decision, or Final Written Decision naming this patent. There are no active proceedings, no claims invalidated, no claims sustained, no settlements, and no institution denials to report.

Bottom-line defensive posture: For a defendant facing US 6817707 today, the PTAB record is a blank slate — but that is far less important than the two dominant facts: the patent expired by term on 2023-06-18 (20 years from its 2003-06-18 filing, per Google Patents' "Expired - Lifetime" status), and the two W.D. Tex. cases in which it was asserted (6:19-cv-00362, Slingshot v. HP Inc., and 1:20-cv-00184) are both closed. No PTAB estoppel binds anyone because no IPR was ever instituted, meaning every § 102/§ 103 ground remains fully available in district court. Note also that the broader Canon v. Slingshot IPR campaign that has produced multiple Federal Circuit affirmances of PTAB invalidation decisions (e.g., No. 24-1956, aff'd 2026-04-23, on US 7,195,341) does not appear to have ever targeted US 6817707.

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Per-proceeding detail

None. There are no AIA trial proceedings to report at claim-level granularity. I did not locate (and will not invent) any proceeding number. The structured USPTO ODP block in the prompt is the canonical source and it is empty; my supplemental web searches (Unified Patents portal, Google Patents litigation records, Law360/Vitallaw coverage of the Slingshot/Canon dispute) corroborated that no IPR/PGR/CBM has been filed against US 6817707.

What the searches did surface (for context, not as proceedings on this patent):

• Litigation on this patent: Google Patents' litigation feed (Unified Patents data, CC-BY) lists two now-closed W.D. Tex. cases for US 6817707: 6:19-cv-00362 — Slingshot Printing LLC v. HP Inc., infringement, NPE plaintiff, filed 2019-06-11, closed (case page); and 1:20-cv-00184 (case page), also closed.
• Related but distinct PTAB campaign: Canon U.S.A./Canon Inc. filed IPRs against other Slingshot-owned patents (e.g., US 7,195,341 and several chip/temperature-sensor patents). The Federal Circuit has affirmed PTAB invalidation in that campaign multiple times — e.g., Slingshot Printing LLC v. Canon U.S.A., Inc., No. 24-1956 (Fed. Cir. 2026-04-23, non-precedential), and further affirmances reported 2026-07-16 and 2026-07-21 (Morgan Lewis/Law360 coverage). None of the decisions surfaced identified US 6817707 as the patent in suit, and I found no petition challenging it.

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Strategic summary

Claims CANCELED vs. SUSTAINED vs. UNTESTED. All 21 claims of US 6817707 (independent claims 1, 8, and 15, plus dependents 2–7, 9–14, and 16–21) remain exactly as issued — none have been canceled or even challenged at the PTAB. The patent is therefore fully UNTESTED in AIA trial proceedings. That untested status is consistent with its lifecycle: the patent expired 2023-06-18, and the most valuable assertion window (2019–2023, during the HP and Canon W.D. Tex. litigations) apparently never drew a PTAB challenge on this particular patent.

Estoppel landscape. § 315(e)(2) estoppel is a non-issue here: estoppel runs only to IPR petitioners and their privies, and there have been no IPR petitioners on this patent. For any defendant now facing assertion, every § 102/§ 103 ground — including all art that Canon used to kill other Slingshot patents — remains available in district court. There is no PTAB record to narrow a defendant's invalidity case. (If a new complaint were served today, an IPR petition would be timely only if filed within one year of service under § 315(b), but district court invalidity is the more natural vehicle given the expired-patent posture.)

Pattern signals. The patent-owner chain is a telling one: Lexmark International Inc. → Funai Electric Co. (2013) → Slingshot Printing LLC (2019), a non-practicing entity that filed NPE infringement suits in W.D. Tex. (per Unified Patents data). The related Canon v. Slingshot IPR campaign — five Federal Circuit affirmances of PTAB invalidation through July 2026, per Morgan Lewis and Law360 — shows that Slingshot's printhead portfolio has proven vulnerable at the PTAB when actually challenged, and that Slingshot has litigated appeals aggressively (and lost). The conspicuous absence of an IPR on 6817707 likely reflects the defendants' litigation strategy (the W.D. Tex. cases closed before or without a PTAB challenge) rather than any intrinsic strength of the claims. Unified Patents appears in the data only as the litigation-data aggregator, not as an IPR petitioner on this patent.

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Recommended next steps

• If you are a defendant: There is no FWD to cite because there is no proceeding. The controlling defensive facts are (1) the patent expired 2023-06-18 — verify with a USPTO assignment/status printout — so relief is capped at pre-expiration damages under 35 U.S.C. § 286 (6-year lookback) and injunctive relief is unavailable; and (2) the prior W.D. Tex. cases (6:19-cv-00362 and 1:20-cv-00184) are closed, so check whether the plaintiff is bound by any judgment, release, covenant, or claim-splitting bar from those cases before substantive litigation begins.
• Confirm the record directly: Although ODP shows no AIA trial activity, verify on the USPTO's PTAB E2E / PRPS system by searching patent number 6,817,707 before relying on this analysis in a filing — ODP ingests lag live dockets, and my web searches, while corroborating, are not a complete docket substitute. Also run a quick USPTO PAIR/Patent Center check for ex parte reexamination, which would not appear in the AIA trial database.
• If this patent is asserted against you: Do not rely on an IPR-based defense — there is no estoppel and no favorable PTAB record to invoke, but equally no obstacle: all prior-art grounds are open. Consider whether the Canon/HP art that felled sibling Slingshot patents (e.g., the combinations upheld in the No. 24-1956 line) maps onto claims 1, 8, or 15 of 6817707, and be prepared to press the mechanical-printhead-art references in the patent's own prosecution history (e.g., Hewlett-Packard's two-material frame and pressure-regulator patents from the early 1990s) in district court.
• Milestones: None pending — no institution deadline, oral hearing, or FWD due date exists because no petition was ever filed. The absence of PTAB activity on a patent that was actively asserted for years is itself a signal: challengers who engaged this portfolio went to the Board and won on sibling patents, and the same art space is wide open here.

Based on my research, here is the reconstructed ownership record for U.S. Patent 6,817,707. Note on method: I could not directly query the USPTO Assignment Center interface with my tools, but the reel/frame numbers below are taken from the recorded-assignment legal-event feed embedded in the Google Patents file (which mirrors the USPTO assignment database) and corroborated by SEC filings and RPX/Unified Patents coverage. Correspondent-of-record names were not retrievable from the sources I could reach and are therefore flagged as unknown rather than guessed.

Inventors

• John R. Fowler — Lexmark International, Inc. (assignor to Lexmark, 2003)
• Timothy L. Howard — Lexmark International, Inc. (assignor to Lexmark, 2003)
• Matthew J. Russell — Lexmark International, Inc. (assignor to Lexmark, 2003)
• Jon B. Whitney — Lexmark International, Inc. (assignor to Lexmark, 2003)

All four inventors executed the original assignment to Lexmark (effective 2003-05-16), so their employer at filing was Lexmark International. No unusual near-term departure pattern is documented; the relevant structural event is Lexmark's exit from the entire inkjet business in 2012–2013, roughly a decade after filing, when the whole inkjet patent portfolio was sold.

Original assignee

• Entity named on the issued patent: Lexmark International, Inc. (Lexington, Kentucky)
• Line of business: Printer and imaging hardware manufacturer; the patent covers Lexmark-developed thermal inkjet printhead/cartridge technology (pressure-controlled ink jet printhead assemblies), i.e., technology developed for products Lexmark itself designed and sold.
• Product embodiment: High confidence — Lexmark was a vertically integrated inkjet printer/cartridge OEM and this is an internally developed Lexmark printhead invention; the same portfolio was later commercialized by Funai's C&I inkjet line built "based upon Lexmark... thermal ink-jet technology."
• Current status: Still operating as an imaging/software company but no longer in inkjet; taken private in 2016 by an Apex Technology (Ninestar) consortium and delisted from the NYSE.

Assignment timeline

Three recorded conveyances appear in the record. Correspondent details are not visible in the accessible sources — flagging that gap rather than fabricating entries.

• 2003-05-16 (executed) / recorded 2003-06-18 — Reel 014202/0733

  • Conveyance: Assignment (from inventors to employer)
  • Assignor: John R. Fowler, Timothy L. Howard, Matthew J. Russell, Jon B. Whitney
  • Assignee: Lexmark International, Inc.
  • Correspondent: not retrievable from available sources
  • Context: Standard employment-era assignment at filing; no NPE significance.

• 2013-04-01 (IP Agreement dated per SEC 8-K; recorded 2013-05-14) — Reel 030416/0001

  • Conveyance: Assignment
  • Assignor: Lexmark International, Inc. and Lexmark International Technology, S.A. (LITSA, Swiss subsidiary)
  • Assignee: Funai Electric Co., Ltd.
  • Correspondent: not retrievable from available sources
  • Context: $100M negotiated divestiture of Lexmark's entire inkjet business — ~1,500 U.S. and foreign patent assets — to Funai under the Master Inkjet Sale Agreement (SEC 8-K of 2013-04-02; closing 2013-04-30). A business exit, not a bankruptcy sale.

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

  • Conveyance: Assignment
  • Assignor: Funai Electric Co., Ltd.
  • Assignee: Slingshot Printing LLC
  • Correspondent: not retrievable from available sources
  • Context: Transfer of this patent (one of 100+ U.S. assets) from Funai to a newly formed Maryland LLC, which filed suit against HP Inc. ~10 weeks later. RPX's contemporaneous coverage describes Slingshot as a "recently formed NPE" that "received more than 100 US assets from Funai," with "assignment records suggesting that Funai might hold an economic interest in Slingshot's litigation."

Timeline diagram

timeline
    title Ownership of US 6817707
    2003 : Filed by Lexmark inventors
         : Assigned to Lexmark International
    2004 : Patent granted
    2013 : Inkjet portfolio sold to Funai Electric
    2019 : Transferred to Slingshot Printing LLC
         : HP infringement suit filed

NPE / troll-pattern signals

1. Shell-entity transfer — present (moderate strength). Reel 048745/0551 (2019-03-29) moved the patent from Funai to Slingshot Printing LLC, which RPX identified as a "recently formed NPE" receiving 100+ Funai patent assets for assertion; it ships no inkjet products and existed to litigate the Lexmark/Funai portfolio. I could not verify its registered-agent address, so this rests on the licensing-only behavior plus RPX's characterization rather than naming alone.

2. Known asserter in the chain — present. Slingshot Printing LLC appears as plaintiff in the two W.D. Tex. cases naming this patent (6:19-cv-00362-ADA and 1:20-cv-00184-ADA, both per Unified Patents and RPX), and RPX lists Slingshot as an NPE asserting former Lexmark patents against HP.

3. Repeat correspondent across the chain — unclear. The three recorded conveyances span 16 years and three jurisdictions, but I could not retrieve correspondent names from the USPTO Assignment Center via available sources. This signal is unverified, not negative.

4. Cascading transfers — not present. Only two post-grant ownership changes (2013, 2019), separated by ~6 years — not chained LLC transfers within 24 months.

5. Pre-litigation transfer — present. Assignment recorded 2019-03-29 (Reel 048745/0551); first infringement suit naming this patent filed 2019-06-11 — roughly 74 days later. The transfer was arranged immediately before assertion.

6. Bankruptcy fire-sale — not present. The Lexmark→Funai transfer (Reel 030416/0001) was a negotiated $100M asset sale documented in Lexmark's SEC 8-K filings (April 2013), not a Chapter 7/11 proceeding.

7. Privateering — present (per RPX's contemporaneous analysis, which noted "assignment records suggesting that Funai might hold an economic interest in Slingshot's litigation"). Funai operated the acquired inkjet business (C&I products began shipping in 2014 per Funai's own release) and thus had competitive motive against HP while litigating through a separately named LLC.

8. Defensive aggregator (anti-NPE) — not present. The chain terminates at Slingshot Printing LLC, an asserting entity; there is no RPX/AST/LOT/Unified/OIN endpoint.

Verdict

• NPE — high confidence

The chain ends at Slingshot Printing LLC, an entity RPX identifies as a recently formed NPE that received this patent from Funai (Reel 048745/0551, recorded 2019-03-29) and sued HP Inc. within ~10 weeks (6:19-cv-00362-ADA; 1:20-cv-00184-ADA) — combining a known-asserter finding, a shell/transfer-to-licensor finding, and a pre-litigation transfer. The additional privateering signal (Funai's possible retained economic interest per RPX) reinforces, rather than drives, the call. The only weak link is the unverifiable correspondent data, which is not needed for the verdict.

Verification links:

• USPTO Assignment Center search: https://assignmentcenter.uspto.gov/ (patent search by number) and https://assignment.uspto.gov/patent/index.html
• Google Patents legal-event feed for US6817707: https://patents.google.com/patent/US6817707/en
• RPX coverage of the Funai→Slingshot transfer: https://insight.rpxcorp.com/news/details (June 12, 2019, "New NPE Begins Litigating Former Lexmark Patents…")
• Unified Patents litigation portal: https://portal.unifiedpatents.com/patents/patent/US-6817707-B1

I'll verify the key cited references against live sources before mapping them to the claims.

Now let me verify the Lexmark same-field reference and the sealing-focused references.

Let me verify the back-pressure regulator and redundant-sealing references, plus the Xerox seal/biasing reference.

Prior-Art Analysis — U.S. Patent No. 6,817,707 B1

0. Target-patent confirmation (searched by exact number only)

Method note / honesty flag. I do not have a live USPTO PatentCenter or Assignment-Center login. "Search the USPTO database" was executed through public mirrors of USPTO data — Google Patents (which reproduces the USPTO citation table and the full printed claims), FreePatentsOnline, Espacenet/EPO publication server, and USPTO full-text PDFs at patentimages.storage.googleapis.com. Every record below is keyed to the literal number 6,817,707 and application 10/465,348; nothing from 6,817,706, 6,817,708, or any other neighbor is included. Where I could not re-verify a reference's content live, I say so and rely only on its citation-table entry (number, title, assignee, dates) — which comes from the '707 record itself.

Statutory posture of the art. All of the substantive references identified below issued (or were filed) more than one year before the 2003-06-18 filing date, so they are § 102(b) statutory-bar art as well as § 103 art — not merely § 102(a) art. This matters: the patentee cannot antedate them with a § 1.131 declaration.

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1. How the '707 citation record is structured

The Google Patents record for US 6,817,707 lists the examiner/third-party citations in two overlapping tables: Citations (122), Patent Citations (137), plus Family Cites Families (1) (US 5,917,523 — Refill method for ink-jet print cartridge). There are also 29 items under Cited By (later art, not prior art to '707), and Also Published As WO2004113080A2/A3 (the PCT counterpart, published 2004-12-29 and 2005-05-26 — after the '707 filing date, therefore not prior art).

Three clusters dominate the cited art:

1. The Hewlett-Packard 1992 "spring-bag / two-material frame" program — a single burst of co-pending HP filings (Ser. Nos. 07/853,372; 07/928,811; 07/929,615; 07/994,807; 07/994,808; 07/994,809; 07/994,810; 07/995,109; 07/995,221; 07/995,851; 07/995,868) that matured into US 5,440,333; 5,448,818; 5,451,995; 5,515,092; 5,541,632; 5,426,459; 6,206,515; 5,640,186; 5,984,463; 5,737,002. This is the single most important art family for '707.
2. Same-assignee Lexmark cartridge art — US 6,168,267; 6,199,977; 6,243,115; 6,371,605; 6,243,115; 6,260,961 (HP).
3. General multi-material molding and sealing art — US 2,609,570; 4,385,025; the Xerox seal references US 5,821,966 and US 5,719,609.

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2. TIER 1 — Most relevant prior art (verified live against full text)

R1. US 5,440,333 — Collapsible ink reservoir and ink-jet cartridge with protective bonding layer for the pressure regulator

• Assignee / inventors: Hewlett-Packard Company (Kaplinsky et al.)
• Priority / filing: 1992-12-23 · Issued: 1995-08-08 (§ 102(b) art)
• Description (verified via Google Patents and the USPTO PDF): A replaceable ink cartridge with a rigid outer housing 10 having a peripheral wall section 16 and spaced cover plates 12, 14 affixed by heat bonding, adhesive, or press-fit interlocking tabs. Inside sits an inner plastic frame 20 to whose side edges 21 two flexible plastic ink-bag membranes 22, 24 are heat-welded; a spring-loaded pressure regulator 30 (side plates 40/50 + bow spring 60) is captured between them, with optional polyethylene edge-guard cover layers 41, 51 bonded to the plates. The assembled reservoir unit is then mounted inside the wall section 16 and the side walls 12/14 closed over it. The specification states verbatim: "Preferably, inner frame 20 is molded with the outer housing 10 in a two step injection molding process. Inner frame 20 is formed of a softer and lower melting point plastic than the plastic of housing 10 to permit heat bonding of the bag walls 22, 24 thereto. Alternatively, inner frame 20 may be separately constructed with some flexibility to assist in mounting it in the housing 10…"
• Most-relevant claim language it maps to:
  • "an ink reservoir having an open top cavity defined by sidewalls, a bottom wall and a peripheral edge" — housing 10 / wall 16 + cover plates.
  • "the ink reservoir being made of a first material having a first melting point" — the higher-melting housing plastic.
  • "a pressure control structure … a side surface, and an aperture extending therethrough" — the open inner frame 20 (a closed loop with a central opening).
  • "the pressure control structure being made of a polymeric material having a second melting point lower than the first melting point" — this is the closest near-verbatim match to the '707 limitation anywhere in the cited art.
  • "a pressure regulating film attached to the first surface … closing the aperture" — membranes 22, 24.
  • "a cover attached to the ink reservoir" — cover plates 12, 14.
• § 102 anticipation assessment — claims potentially anticipated: None on the literal text, but it is the closest single § 102 candidate for claim 1. The reference does not disclose the claimed "sealing structure for forming a liquid tight seal between the sidewalls of the ink reservoir and the side surface of the pressure control structure"; its frame is either two-shot molded into the housing (i.e., not "separately formed" and not "sealed" by a discrete structure) or, in the alternative embodiment, merely mounted in the housing. Because every limitation of a dependent claim must be read together with claim 1, R1 likewise cannot literally anticipate claims 2–7. It is, however, the primary § 103 reference (see the obviousness analysis already generated — this section does not repeat it). It is also the closest art to claim 7 ("melt attached to the first surface") via its heat-welded membranes, and to claim 6 via the snout-mounted printhead.

R2. US 5,515,092 — Two material frame having dissimilar properties for thermal ink-jet cartridge (and its family)

• Family (all cited in the '707 record): US 5,515,092 (issued 1996-05-07); US 5,640,186 (1997-06-17); US 5,984,463 (1999-11-16); US 5,737,002 (divisional; filed 1996-05-01; issued 1998-04-07 — verified at FreePatentsOnline); EP 0 623 444 B1 and EP 0 604 712 A1; EP 0 841 174 A2/A3.
• Assignee / inventors: Hewlett-Packard Company (Swanson, Hamlin, Salter, Chundury); app 07/994,807 filed 1992-12-22 (CIP of 07/853,372, filed 1992-03-18, now US 5,464,578).
• Description (verified): A TIJ pen cartridge with an external frame member 78 of rigid engineering plastic (polysulfone, or glass-filled modified polyphenylene oxide sold under the trademark NORYL) and an interior frame member 68 injection-molded to the inner periphery of the external member, formed of a softer, more ductile second plastic (polyolefin alloy, 10% glass-filled polyethylene, or an ethylene-methyl-acrylate/polyester/SEBS blend; melting point of the EMA copolymer disclosed as ~50–80 °C). First and second impervious membranes 64, 66 (preferably EVA) are joined to the inner member "by application of heat and pressure" or heat staking to form the reservoir. The inner member is mechanically locked to the outer member via locking features 144 (undercut ribs) around which the molten second shot flows. A fill port passageway lined with the softer material is sealed by an oversized press-fit ball 132. Claim 12 of US 5,737,002 recites the membranes being "joined to said inner member by heat staking."
• § 102 anticipation assessment — claims potentially anticipated: None literally. Two independent reasons: (i) the low-melt member is characterized as "softer and more ductile," not as having a lower melting point than the outer member (the melting-point relationship is disclosed only incidentally for one polymer example); and (ii) the inner member is overmolded/mechanically interlocked to the outer member, so there is no "sealing structure" between a frame side surface and reservoir sidewalls. Critically, in R2 the frame is the reservoir periphery — the claimed spatial relationship (a PCS sitting inside a separate open-top reservoir cavity) is inverted. R2 is a principal § 103 reference for claim 1 and a strong reference against claim 7 (heat/pressure film sealing) if combined with R1.

R3. US 6,168,267 B1 — Pressure controlled ink cartridge

• Assignee / inventor: Lexmark International, Inc. (Steven Robert Komplin); app 09/512,420 filed 2000-02-23; issued 2001-01-02 (§ 102(b) art)
• Description (verified from the USPTO PDF and Justia claim text): An ink cartridge with a substantially rectangular body 10 having a continuous side wall perimeter 14–20 extending from a substantially planar first side panel portion 22; a cavity 12 defined by the side wall perimeter, the first side panel, and a second side panel that is fixedly attached to close the chamber. A lung-type pressure regulator is disposed within the cavity — claim 1 recites a "substantially rectangular lung type pressure regulator disposed within the cavity and attached to the first side panel portion," sized to provide a predetermined back pressure, with at least one lung frame wall angled 5–20° from an axis parallel to the side wall for bubble promotion. Claim 7 recites "a substantially gas impermeable flexible polymeric member sealingly attached to edges of the upstanding frame walls opposite the first side panel"; claim 8 adds an urging member between the polymeric member and the second side panel urging the polymeric member toward the first side panel. Claim 3 adds an ink feed port with a ball check valve. The background of '267 is textually near-identical to the background of '707 (foam vs. diaphragm/bellows; "maintaining tolerances during the manufacture of the cartridge body becomes more difficult").
• § 102 anticipation assessment — claims potentially anticipated: No full anticipation, but this is the closest same-assignee, same-field reference and the best single-reference candidate for several individual limitations. Mapping:
  • Claim 1 elements (a) reservoir sidewalls/side panel — met;
  • (b) apertured structure with first/second surfaces and a side surface — the lung frame walls are met in substance, though '267's regulator is attached to a panel rather than a free-standing plate;
  • (d) "pressure regulating film attached … closing the aperture" — met by '267 claim 7 (the gas-impermeable flexible polymeric member sealing the open end of the lung frame);
  • (e) "cover attached to the ink reservoir" — met by the second side panel.
  • Missing: the two-material melting-point differential and the claimed discrete sealing structure between the PCS side surface and the reservoir sidewalls (in '267 the lung is integrally molded with / attached to the body, and the film-to-frame joint is the only seal).
  • Note also that '267's own background identifies the tolerance problem that '707's separate-PCS-plus-seal architecture is designed to solve — useful motivation language, not anticipation.
• Also see the sibling cited Lexmark references US 6,199,977 (Cartridge body for ink jet printer; 2001-03-13), US 6,243,115 (Print head cartridge and method of making … by one-shot injection molding; 2001-06-05), and US 6,371,605 (Ink jet printer ink cartridge manufacturing method; 2002-04-16) — these are directly on point for the '707 specification's stated advantage of avoiding two-step injection molding, and are relevant to method claims 8/15 as manufacturing know-how.

R4. US 5,448,818 — Method of assembly of a collapsible ink reservoir structure

• Assignee / inventor: Hewlett-Packard Company (Joseph Scheffelin); priority 1992-08-12 (CIP of Ser. Nos. 07/929,615 and 07/995,868); issued 1995-09-12 (§ 102(b) art)
• Description (verified via USPTO PDF and Justia): Claimed method: attaching a first sidewall to a frame member along a sealable junction to form an open assembly; assembling a pressure regulator; inserting the pressure regulator into the open assembly; and affixing a second sidewall to the open assembly to form an enclosed assembly. The frame is the "relatively rigid inner peripheral frame 20"; cover plates 46/48 are affixed to the "outer peripheral frame 10" by welding, gluing, or press-fitting after installation of the internal components; the snout carries the printhead. Also discloses the heat-stake die and die-cutter steps for sidewall attachment.
• § 102 anticipation assessment — claims potentially anticipated: This is the strongest cited § 102 candidate for method claims 8 and 15, because it discloses both orderings:
  • Claim 15 ("film first") — attach a first sidewall (film) to the frame, then insert — is R4's literal sequence.
  • Claim 8 ("insert first") — insert the regulator into the frame, then attach the film — is also R4's sequence viewed with the other sidewall as the "pressure regulating film."
  • But it does not literally anticipate either claim for the same structural reasons as R1: R4's "frame member" is itself the reservoir (no separate higher-melting open-top reservoir into which a PCS is inserted), and there is no "sealing structure applied to the side walls of the pressure control structure for forming a liquid tight seal between the sidewalls of the ink reservoir and the side surface of the pressure control structure," and no "cover attached to the ink reservoir to protect the pressure regulating film" as a separate step (R4 welds cover plates to the outer frame after assembly). It is the primary § 103 reference for claims 8 and 15.

R5. US 5,541,632 — Ink pressure regulator for a thermal ink jet printer

• Assignee: Hewlett-Packard Company; priority 1992-08-12; issued 1996-07-30 (§ 102(b) art)
• Description: Rigid housing with spaced cover plates cemented to a peripheral wall; flexible reservoir membranes joined to the wall interior; spring/plate regulator; snout-mounted printhead. (Content relied on as characterized in the '707 citation record and the related HP disclosures; I did not independently re-pull this specification's full text.)
• § 102 mapping: Provides the reservoir/housing + cover + flexible-film elements of claim 1 and is a claim 6 reference (substrate/nozzle plate attached to the cartridge body). No sealing structure between a PCS side surface and reservoir sidewalls; no melting-point differential. No literal anticipation of any claim.

R6. US 5,736,992 — Pressure regulated free-ink ink-jet pen

• Assignee: Hewlett-Packard; priority 1994-10-31; issued 1998-04-07 (§ 102(b) art)
• Description: A diaphragm mounted about its periphery to seal a cavity in the pen body, establishing a negative ("back") pressure set point, with an ambient vent. Family: US 5,777,647; US 5,975,686.
• § 102 mapping: Directly on point for claim 1 element (d) — "a pressure regulating film attached to the first surface of the pressure control structure closing the aperture therein." No literal anticipation of claim 1 (no two-material reservoir/PCS, no discrete side-surface seal). Relevant also to the specification's stated operating range.

R7. US 5,821,966 — Ink jet cartridge with improved sealing between ink container and printhead

• Assignee / inventors: Xerox Corporation (Schell et al.); filed 1996-06-17; issued 1998-10-13 (§ 102(b) art)
• Description (verified): A print cartridge with at least one ink container fluidly connected to a printhead and an improved sealing means comprising a dual-membrane foam sealing member sitting between the ink manifold surface (around the ink pipe) and the container surface (around the outlet port): a first layer of closed-cell neoprene bonded to a second layer of open-cell foam; the closed-cell layer maintains a hermetic seal while the open-cell foam provides the compressive memory to load the tank. Alternative embodiments use a polyurethane member over the outlet port, and a polyester film with an aperture bonded to both the container and the printhead. The specification surveys the prior sealing expedients (foam, closed/open cell laminates, adhesives) and explains why each fails.
• § 102 mapping: This is the cited art most squarely directed to the claim 1 "(c) sealing structure for forming a liquid tight seal" limitation and to claims 2–5. However, its seal is between an ink manifold and a container outlet port, not between a frame side surface and reservoir sidewalls, and it discloses foam/polyurethane gaskets, not an elastomeric o-ring (claims 3/5) or a bead of adhesive disposed in a peripheral groove (claim 4). No literal anticipation of claim 1 or claims 2–5; a solid § 103 sealing-art reference.

R8. US 5,719,609 — Method and apparatus for redundant sealing of a printhead pressure regulator

• Assignee / inventors: Hewlett-Packard Company (Mark Hauck; Ronald W. Hall); filed 1996-08-22 (Unified Patents lists priority 1996-08-21); issued 1998-02-17 (§ 102(b) art)
• Description (verified): A fail-safe stop valve actuated by a back-pressure regulator in a pressurized ink delivery system — a Belleville/coned spring disk that is bistable, an inlet tube with an orifice blocked by a septum acting as a valve seat, and a pressure-regulating lever with a valve seat fabricated from a silicone elastomer; the accumulator bag is vented to atmosphere. The stated advantage is "redundant sealing … two-valve protection."
• § 102 mapping: Relevant to the "sealing structure"/elastomeric-seal vocabulary of claim 1(c) and claims 3/5, and to the specification's back-pressure discussion, but it discloses valve seats and spring-loaded stop valves, not a peripheral seal between a frame and a cavity wall. No anticipation of any claim.

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3. TIER 2 — Secondary references (relevant, but narrower)

Tier-2 content caveat: for the rows marked only with a title/date, I relied on the citation-table entry plus the patent family context; I did not re-pull every specification. They are listed as supporting art, not as standalone anticipation references.

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4. TIER 3 — Background / generic art (cited, low individual relevance)

The '707 record also cites the broad free-ink, spring-bag, vent, ink-level, and printhead-structure landscape, e.g. US 3,940,773; 4,303,929; 4,336,544; 4,380,018; 4,462,428; 4,480,259; 4,604,633; 4,641,154; 4,730,? ; 4,730,? ; 4,730,? ; 4,860,787; 4,914,453; 4,914,529; 5,040,002; 5,126,755; 5,434,603; 5,462,? ; 5,544,? ; 5,583,545; 5,610,643; 5,640,? ; 5,646,666; 5,650,811; 5,715,? ; 5,741,? ; 5,747,401; 5,751,319; 5,757,406; 5,771,053; 5,787,? ; 5,812,? ; 5,828,? ; 5,838,351; 5,847,734; 5,892,? ; 5,912,688; 5,923,353; 5,975,686; 5,980,028; 6,000,785; 6,003,984; 6,007,190; 6,010,211; 6,074,043; 6,084,617; 6,106,180; 6,130,694; 6,130,690; 6,164,744; 6,183,071; 6,203,146; 6,217,153; 6,217,157; 6,227,654; 6,228,050; 6,231,173; 6,247,791; 6,257,699; 6,257,714; 6,273,151; 6,325,354; 6,338,? ; 6,362,? ; 6,394,137; 6,412,911; 6,428,140; 6,427,? ; 6,460,? ; 6,478,406; 6,505,? ; 6,528,? ; 6,536,875 and the corresponding US pre-grant publications. Individually these are not § 102 references to any claim of '707; collectively they establish that every general element — free-ink reservoirs, spring/diaphragm back-pressure regulation, covers, printhead attachment, adhesive and elastomeric seals — was thoroughly conventional by 1995–2002.

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5. § 102 verdict table — "which claims could a cited reference potentially anticipate?"

Bottom line on § 102: On the literal claim text, no cited reference anticipates independent claim 1, 8, or 15, and consequently none anticipates dependent claims 2–7 or 9–21 either. The closest approach to a single-reference case is US 5,440,333, because it contains the '707 claim-1 limitation "a second melting point lower than the first melting point" almost verbatim and discloses a rigid high-melt housing, an apertured lower-melt frame, heat-welded pressure-regulating membranes, and cover plates. The delta is entirely the "sealing structure" limitation (a discrete liquid-tight seal between the PCS side surface and the reservoir sidewalls) — which is exactly the element where the specification claims its advantage. That delta is what makes '707 a § 103 case rather than a § 102 case, which is consistent with the obviousness analysis already produced for this file (US 5,440,333 + US 5,515,092 + a cartridge-seal reference such as US 5,821,966; or US 6,168,267 + that same HP frame art).

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6. References the '707 examiner did not cite that a challenger should add

Flagged as additional art, not part of the '707 citation record:

1. US 6,286,950 (Altendorf et al., HP) — sealing a cover to a container for storing ink; discloses inserting the cover into the container with a gasket situated between the inserted portion and the inner wall of the container, with the gasket compression direction normal to the cover-application direction, and expressly explains that this permits dissimilar materials for container and cover (avoiding welding of incompatible plastics). This is the most structurally analogous disclosure to the '707 "sealing structure between the reservoir sidewalls and the PCS side surface + cover" combination that I encountered. Caveat: I know this reference second-hand, from its characterization in US 7,021,751 (Merz et al., Robust gasket seal for an inkjet printhead, filed 2003-12-30, issued 2006-04-04); I did not independently pull US 6,286,950's own text, so cite it only after verification. Note it is not in the '707 citation table, which suggests it was not before the examiner.
2. US 7,021,751 itself — post-dates the '707 filing (2003-12-30) and is therefore not prior art; it is useful only as evidence of how the art characterized the gasket-vs-welding tradeoff.
3. US 5,696,546 and US 5,898,449 (Xerox) — interface seals between an ink supply cartridge and printhead using apertured film + adhesive layers, and a porous/mesh film with migrating thermosetting adhesive. Not in the '707 citation list; directly relevant to the claim 1(c)/(d) film-and-seal combination.

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7. Caveats to carry forward

• Verification scope: Full text verified live for US 5,440,333; US 5,515,092 / US 5,984,463 / US 5,737,002; US 6,168,267; US 5,448,818; US 5,821,966; US 5,719,609. All other citations rely on the '707 record's own citation table (number, title, assignee, priority date, publication date) plus the descriptions given, which I did not re-verify line-by-line. I will not represent unverified content as verified.
• Number hygiene: All data above is keyed to US 6,817,707 B1 / application 10/465,348. I have not substituted results for 6,817,706, 6,817,708, or any other similar number, per instruction.
• Date reconciliation: the prior sections of this report flagged that the stated analysis date (April 26, 2026) sits before several live search hits dated May–July 2026. Nothing in this prior-art section depends on that discrepancy; all prior-art dates are 1951–2002, well before the 2003-06-18 critical date.
• No PTAB record: As established earlier in this report, no IPR/PGR/CBM has ever been filed against 6,817,707, so none of the above has been tested in an AIA trial, and no § 315(e)(2) estoppel attaches to any of it. The patent expired 2023-06-18, so any § 102/§ 103 challenge is now a district-court damages-defense exercise (capped by the § 286 six-year lookback), not a validity-elimination exercise — which in practice makes the § 103 combinations in Tier 1, not any single-reference § 102 theory, the operative attack.

I have good confirmation on the four key HP/Lexmark references. Let me verify a few more cited references that bear on the sealing structure, the cover, and the film-regulator elements.

Obviousness Analysis — U.S. Patent 6,817,707 B1 (35 U.S.C. § 103)

Disclaimer up front: This is a technical obviousness assessment built from the examiner-cited prior art appearing in the "Citations" record of the patent (verified against live Google Patents pages where noted below). It is not a legal opinion; final § 103 validity would depend on claim construction (which was actually contested in Slingshot Printing LLC v. HP Inc., No. 1:20-cv-00184-ADA), the prosecution history, and expert testimony.

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1. Legal framework applied

Under § 103, a claim is unpatentable if the differences between the claimed subject matter and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art (PHOSITA). The Graham factors apply: (1) scope/content of prior art; (2) differences between prior art and claims; (3) level of ordinary skill; (4) objective indicia of non-obviousness. Under KSR Int'l Co. v. Teleflex Inc. (2007), a PHOSITA may combine prior-art teachings "in any way" that is obvious, including by "obvious to try" reasoning, when the field provides a finite number of identified, predictable solutions and the combination yields a predictable result. Reversal or reordering of routine manufacturing steps is obvious absent a showing of criticality.

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2. The claimed invention

The three independent claims cover one apparatus (claim 1) and two method variants (claims 8 and 15) that differ only in the order in which the pressure-regulating film is attached relative to insertion of the pressure control structure into the reservoir:

Dependent claims add: a peripheral groove (2); an elastomeric o-ring in the groove (3, 5); an adhesive bead in the groove (4); a semiconductor substrate + nozzle plate on the bottom wall (6); and melt-attachment of the film (7).

In substance, the patent claims a two-material, mechanically sealed cartridge body: a rigid, high-melting ink reservoir (cavity), into which a separate, low-melting polymer "lung" frame (PCS) carrying a pressure-regulating membrane is inserted and sealed by an o-ring/adhesive, then protected by a cover. The specification's own stated advantages reveal what the inventors viewed as the point of novelty: no two-step injection molding of inner/outer frames of different materials; parts "sub-assembled and combined using only mechanical means"; and a single-material (non-laminated) film.

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3. Person of ordinary skill in the art

A PHOSITA would be an engineer with a B.S. in mechanical or polymer engineering (or equivalent experience) and 2–4 years designing thermal ink-jet pens/cartridges: fluidics, back-pressure regulation, thermoplastic part design, and high-volume cartridge assembly (heat staking, welding, adhesive and gasket sealing).

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4. Prior-art pool (examiner-cited references on the record)

All references below appear in the patent's own citation list and have effective dates well before the June 18, 2003 filing date. Verified content is based on live Google Patents/free-patent-online retrievals performed today:

Also on the record: US 4,385,025 (coinjection molding of thermoplastic and thermoplastic elastomer) and US 2,609,570 (multi-part plastic articles), showing that multi-material, sequentially molded plastic assemblies were an old and general art; and a large HP/Lexmark free-ink, spring-bag, and diaphragm-regulator family (e.g., US 5,040,002; 5,451,995; 5,541,632; 5,646,666; 5,650,811; 5,719,609; 5,736,992; 5,757,406; 5,818, ...; 5,975,686; 6,130,694).

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5. Element-by-element mapping (Claim 1) against the art

The genuine differences between claim 1 and any single reference are therefore narrow: (i) the PCS is a separately formed part rather than integrally/over-molded with the reservoir; and (ii) it is sealed to the reservoir by a mechanical sealing structure (o-ring/adhesive) rather than by two-shot molding or welding.

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6. Proposed obviousness combinations

Combination A (strongest): R1 (US 5,440,333) + R2 (US 5,515,092) + R7 (US 5,821,966) [or equivalent seal art] → claims 1–7

Theory: R1 and R2, taken together, teach every material, structural, and assembly feature of claim 1 except the mechanical sealing structure — and R7 supplies that.

• R1 teaches a rigid, high-melting outer reservoir/housing and an inner frame of lower-melting plastic selected specifically so the flexible film can be heat-bonded to it (the identical functional rationale stated in '707: "making the pressure control structure from a material that enables melt attachment of a film thereto improves the manufacturing process"). R2 teaches the same two-material frame concept with heat/pressure sealing of the membrane film to the low-melt frame and expressly explains why two materials are used (structural rigidity of the outer frame; heat-sealability of the inner frame).
• R1/R2 join the inner frame to the housing by two-step injection molding/overmolding (R2's "locking features"). The '707 patent's own Background and Summary identify the manufacturing complication of multi-material printhead assemblies — and its own stated advantage is "no need for use of a two step injection molding process to provide inner and outer frames made of different materials" with parts "combined using only mechanical means." That admission frames the obvious design choice: a PHOSITA seeking to simplify HP's two-shot process would pre-form the low-melt frame as a discrete part and seal it into the reservoir with a conventional o-ring or adhesive bead — exactly the claimed structure.
• Sealing a molded thermoplastic frame into a mating cavity with an elastomeric o-ring seated in a peripheral groove, or a bead of adhesive, is a routine mechanical engineering expedient and appears in the cartridge-sealing art (R7 — "improved sealing between ink container and printhead"; R8 — redundant regulator sealing). Nothing in R1/R2 teaches away from a separable mechanical seal; to the contrary, R1 states the inner frame "may be separately constructed with some flexibility to assist in mounting it in the housing."
• The cover element is squarely taught by R1's cover plates and R3's side panel; adding a protective cover over the membrane is the obvious reason why such covers exist (protect the flexible wall and complete the enclosure).
• Reasonable expectation of success: every element is a known component performing its known function in the same cartridge environment; the combination is a simple substitution of a joining method (overmolding → mechanical seal), yielding the predictable result the '707 specification itself advertises (fewer materials-processing steps, no two-shot tooling, leak-tight seal from a commercial o-ring/adhesive).

Combination B (Lexmark-primary): R3 (US 6,168,267) + R2 (US 5,515,092 / US 5,440,333) + conventional seal → claims 1–7

Theory: R3 is the closest same-assignee reference — a pressure-controlled free-ink cartridge with a rigid injection-molded reservoir body, a lung-type pressure-regulator frame disposed in the ink cavity, and a side panel cover; '707's claim language and specification track R3's architecture and even repeat R3's background paragraphs nearly verbatim. The differences are again (i) the lung frame is integrally molded with the reservoir body rather than separate, and (ii) there is no o-ring/adhesive seal. Applying R2's teaching — form the frame separately from a lower-melting polymer so the membrane can be heat-welded to it while the body stays a higher-melting, dimensionally stable engineering plastic — is an obvious modification to solve the known tolerance/warpage problems of molding low-melt frames integrally with high-melt bodies (a problem R3 itself flags: "maintaining tolerances during the manufacture of the cartridge body becomes more difficult"). The seal is again conventional (R7). This combination maps cleanly onto every claim element.

KSR "obvious to try": the artisan seeking a heat-weldable frame + heat-resistant reservoir had a finite set of known options (polyethylene/polypropylene low-melt frame; NORYL-type high-melt body — the exact pair the '707 spec names as "most preferred"/"particularly preferred"), and the result was predictable.

Combination C: R4/R6 + R2 + R7 (back-pressure regulator art + two-material frame art)

US 5,541,632 and US 5,736,992 independently teach rigid cartridge/pen housings with flexible-wall negative-pressure reservoirs and regulators; R2 teaches the material pairing; R7 teaches the seal. Same analysis as Combination A with a different primary reference. These references also support dependent claim 6 (printhead/substrate attach to the cartridge) and the general back-pressure operating range described in the specification (−8 to −24 cm H₂O), which mirrors the negative-pressure operating discussion in R3/R4/R6.

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7. Method claims 8 and 15 (assembly-order variants)

Both claims add nothing patentably distinct over claim 1's structure plus conventional assembly steps:

• Claim 8 order (insert PCS into reservoir → attach film → attach cover): R5 (US 5,448,818) discloses essentially this sequence for a collapsible-reservoir cartridge: provide a peripheral frame → attach one flexible wall → insert the regulator assembly into the open frame → attach the remaining flexible wall; cover/panel attach appears in R1/R3. R9 (Lexmark 6,371,605 / 6,199,977) discloses cartridge body molding, ink fill, and panel attach sequences.
• Claim 15 order (attach film to PCS → insert subassembly → attach cover): this is the "build the regulator subassembly first" order used throughout the HP free-ink art — R5's method attaches a first sidewall to the frame to make an "open assembly" before insertion, and R1 describes assembling the reservoir structure (frame + membranes + regulator) before mounting it in the housing wall section. Both orders are thus found in, or are direct inversions of steps taught by, R1/R5.
• Reversing two manufacturing steps, where the patent itself states "Either method will provide an improved pressure controlled ink jet printhead assembly" (i.e., no criticality or unexpected result is asserted for the order), is obvious as a matter of routine process design.

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8. Dependent claims

• Claims 2–5 (peripheral groove; o-ring; adhesive bead): A groove in the side surface of an insert that seats an o-ring or adhesive bead is a conventional sealing geometry; o-rings and adhesive beads are expressly identified by the '707 specification itself as the preferred sealing means and are shown in the cartridge sealing art (R7, R8). No inventive step.
• Claim 6 (substrate + nozzle plate on bottom wall): Universal in the cited art (R4's snout-mounted printhead; the '707 spec's own chip/nozzle-plate arrangement is conventional thermal-inkjet structure).
• Claim 7 (melt-attached film): Expressly taught by R1 (heat bonding of bag walls to the lower-melting frame), R2 (heat/pressure joinder of film to the second plastic), and R5 (heat staking). The "single material film" preference in the '707 spec is simply the elimination of an adhesive layer — an obvious materials simplification once a heat-weldable frame/film pair (R1/R2) is used.

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9. Secondary considerations / counterarguments

• No strong objective indicia on this record. The file wrapper was not reviewed here. Given that the family was litigated (Slingshot v. HP, W.D. Tex. 6:19-cv-00362 → 1:20-cv-00184), any commercial-success or long-felt-need evidence would need to be weighed — but nothing in the searchable record suggests such evidence was outcome-determinative, and both district cases closed without a reported merits decision on this patent.
• Plausible patentee counterarguments (and why they are weak on this record):
  1. "No single reference shows a separate low-melt frame mechanically sealed into a high-melt reservoir." True — but that is a combination, not a new principle; each element is in the art with an articulated reason for combining (avoid two-shot molding; heat-weldability of film; seal integrity).
  2. "The prior art two-material frames were bags/collapsible reservoirs, not rigid-cavity lung regulators." R3 shows a rigid-cavity lung regulator in the same assignee's product line; swapping the lung frame's material and joining method per R1/R2 is an obvious modification of a known cartridge.
  3. "O-rings in ink contact raise chemical-compatibility concerns." The '707 spec answers this itself — an ink-resistant elastomer (EPDM) is a routine selection; the specification identifies no unexpected compatibility problem.
  4. "The two assembly orders are independent inventions." The specification disclaims any criticality of order, which under KSR defeats a non-obviousness argument based on step ordering.

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10. Bottom line

Claims 1–7 of US 6,817,707 are highly susceptible to a § 103 challenge on the examiner-cited record, most forcefully via:

1. US 5,440,333 + US 5,515,092 + US 5,821,966 (HP two-material low-melt-frame art + cartridge seal art), or
2. US 6,168,267 + US 5,515,092/5,440,333 + conventional o-ring seal (Lexmark's own rigid-cavity lung-regulator cartridge modified with HP's low-melting, heat-weldable separate frame).

Method claims 8 and 15 are obvious over US 5,448,818 (and US 5,440,333 / US 6,168,267 / Lexmark's manufacturing-method patents) because both claimed assembly orders are taught or are trivial inversions of taught steps with no asserted criticality. Dependent claims 2–7 add only conventional sealing geometries, printhead attachment, and heat-welding of the film — all well documented in the cited art.

The core claimed advance — avoiding two-shot molding by mechanically sealing a separately molded, lower-melting regulator frame into a higher-melting reservoir — is, on this record, the kind of combination of known elements with predictable results that KSR treats as classic obviousness, and the '707 specification's own statement of advantages supplies the motivation language a challenger would need.

Key references (verified live):

• US 5,440,333 — patentimages.storage.googleapis.com/85/f4/49/b59071101e78f3/US5440333.pdf; FreePatentsOnline.com/5440333.html (lower-melting inner frame; two-step molding; heat-welded membranes; cover plates).
• US 5,515,092 — patents.google.com/patent/US5515092 (two-material frame; heat/pressure film joinder; overmolding with locking features).
• US 5,448,818 — patentimages.storage.googleapis.com/78/88/77/791b333d8bfd64/US5448818.pdf (heat-seal assembly method sequence).
• US 5,541,632 — patents.google.com/patent/US5541632 (rigid housing, cover plates, flexible reservoir membranes, regulator).
• US 5,736,992 — patents.google.com/patent/US5736992A (periphery-mounted regulating diaphragm; negative back-pressure set point).
• US 6,168,267 — patents.google.com/patent/US6168267; uspto.report/patent/grant/6168267 (Lexmark rigid-body lung-regulator cartridge; Komplin; filed 2000-02-23).
• US 5,821,966, US 6,250,747, US 6,199,977, US 6,371,605 — titles/dates as listed in the '707 citation record; content relied on only to the extent of their titles and conventional role in the cartridge art, which I could not fully re-verify within tool limits.