US 5992986

I'll search for this specific patent and any current litigation/docket activity, then summarize.

US 5,992,986 — "Ink supply apparatus"

Important scope note on my search: I could not directly query the USPTO PatentCenter/PTAB or the CAFC 2026 docket systems from this session; my searches were general public-web searches. US 5992986 surfaces reliably on Google Patents, Justia, and FPO, and the patent's own prosecution/assignment history is legible. I found no CAFC 2026 docket entry, appeal, or IPR involving US 5992986. That is a negative finding from limited searching, not proof of absence. Treat any litigation-status statement as unverified.

Also, per your instruction, I am not auto-correcting the number: the identifier you gave, 5992986, matches US 5,992,986 exactly.

Bibliographic data (from the patent text)

Abstract (verbatim)

"An ink supply apparatus includes a carriage on which a printer head arrangement including a printer head is mounted to an alignment plate and an ink reservoir arrangement including an ink reservoir is mounted to a frame pivotably connected to the alignment plate to permit access to the printer head arrangement. A conduit connects an inlet of the printer head to an outlet of the ink reservoir. The outlet of the ink reservoir is located directly behind the inlet of the printer head when the frame is pivoted to a normal operating position to minimize surges in the conduit and thereby prevent leakage out of or air ingestion into the nozzles of the printer head. The ink supply apparatus is particularly well suited for use in ink jet printers where multiple printer heads are used and printing occurs in two directions of travel of the carriage."

Plain‑language overview of the independent claims

Claim 1 — Ink supply apparatus for a moving carriage.
Requires: (a) a track along a first axis; (b) a carriage that moves both directions along that track; (c) a print‑head arrangement on the carriage, with one or more print heads, each having an ink inlet and at least one nozzle; (d) an ink reservoir arrangement pivotally mounted on the carriage behind the print‑head arrangement so it can move relative to the print heads (for service access); (e) each reservoir has an outlet, and a conduit runs from each reservoir outlet to the matching print‑head inlet; and — the load‑bearing limitation — (f) for each reservoir/print‑head pair, the reservoir outlet and the print‑head inlet lie on a second axis perpendicular to the track axis. That alignment (outlet "directly behind" inlet) is what the specification says cancels the fore/aft ink surge when the carriage reverses, avoiding nozzle leakage or air ingestion.

Claim 7 — Multi‑head / multi‑reservoir apparatus with stepped ink levels.
Builds on the same track/carriage/perpendicular‑axis concept, but adds: multiple print heads; a like number of reservoirs, one per head; the heads mounted discretely (individually) on the carriage; all reservoirs interconnected to one another; and the reservoirs filled to different ink levels along a third (vertical) axis perpendicular to both the track axis and the outlet‑to‑inlet axis. Dependents 8–11 add staggered nozzle heights and a pump/sensor fill scheme (fill the highest reservoir, ink cascades down; a level sensor in the lowest reservoir stops the pump).

Claim 22 — Carriage for an ink jet printer (apparatus‑subcombination claim).
Requires: a plate and a frame mounted to the plate; a print‑head arrangement on the plate (one or more heads, each with an inlet and at least one nozzle); an ink reservoir arrangement pivotally mounted on the frame; and conduits connecting each reservoir outlet to the corresponding head inlet. Notably, claim 22 does not recite the perpendicular‑axis alignment; that limitation appears in dependent claim 23.

What the patent is really about (one paragraph)

The invention targets high‑speed, wide‑web, production ink‑jet printing where the carriage carries several print heads per color (preferably three, staggered) and prints in both travel directions. Two problems are addressed: (1) refilling while printing — reservoirs are ganged so a single fill port cascades ink through weirs to set each reservoir's level, with a thermistor‑pair level sensor shutting off the pump; and (2) ink surge / nozzle leakage on carriage reversal — solved by aligning each reservoir outlet with its print‑head inlet on an axis perpendicular to the carriage track, so equal and opposite ink surges on either side of the frame's pivot cancel out. Supporting features include a vent hole with an air‑permeable plug, and a pressurized‑gas purging arrangement (≈15 psi) that blows ink out of the nozzles at a maintenance station.

Uncertainty flags

• Assignee chain: original assignee Raster Graphics, Inc.; a collateral assignment to Silicon Valley Bank is recorded; the current listed assignee is Océ Display Graphics Systems, Inc. That assignment history is from the patent's public record as displayed, and I have not independently confirmed present‑day ownership (e.g., whether it passed to Canon Production Printing or another successor).
• No 2026 CAFC activity located — verify against the Federal Circuit's public docket if litigation status matters.
• Status: the record shows "Expired – Lifetime" with an anticipated expiration of 1997‑03‑12 + 20 years = 2017‑03‑12, so the patent is past term.

Sources: https://patents.google.com/patent/US5992986/en ; https://patents.justia.com/patent/5992986

I'll search litigation-focused sources for this specific patent number.

Let me run more targeted litigation searches.

Answer: No litigation involving US 5,992,986 was located

Bottom line: Based on the searches I was able to run, I found no known litigation, PTAB proceeding, ITC investigation, or CAFC appeal in which US Patent No. 5,992,986 is identified as an asserted patent (or as the subject of a validity challenge). I have no plaintiff, defendant, jurisdiction, case number, filing date, or outcome to report for this patent. This is a negative finding from limited searching, not proof of absence, and I flag the verification gaps explicitly below.

This is consistent with — and reinforces — the earlier-generated section of this analysis, which likewise located no CAFC 2026 docket entry, appeal, or IPR for this patent. I found no contradiction between the two.

What I searched, and what I got

Why the absence is plausible

• The patent is long expired. The Google Patents record shows legal status "Expired – Lifetime" with an anticipated expiration of 1997‑03‑12 + 20 years = 2017‑03‑12. An expired, pre‑AIA‑era patent in a niche industrial wide-format inkjet field is an unlikely candidate for current assertion.
• No post-issuance challenge appears in the record. The Google Patents "Family / Cited By / Citations" sections for US 5,992,986 list prior-art citations, forward citations, and family members (WO 1998/040217 A1), but contain no litigation or PTAB entries. Google Patents does surface litigation for many patents when it has such data; its absence here is weak corroboration.
• Assignee context. Original assignee Raster Graphics, Inc.; collateral assignment to Silicon Valley Bank (recorded 1998‑08‑07); change of name to Océ Display Graphics Systems, Inc. (recorded 2004‑12‑01, effective 2002‑05‑27). I did not find any infringement action brought by Raster Graphics or Océ Display Graphics Systems naming the '986 patent. (Note: whether the chain has since passed to Canon Production Printing or another successor remains unverified — see the uncertainty flags in the earlier summary.)

Verification steps I could not complete (and you should)

The strict‑rule instruction requires that I not present unverified negative findings as certainty. The following sources are the ones that would definitively answer this, and I was unable to query them in a structured, reliable way from this session:

1. Unified Patents Portal — Litigation caselist: https://portal.unifiedpatents.com/litigation/caselist (filter by patent number 5992986). This is the most direct test.
2. Unified Patents Portal — PTAB caselist: https://portal.unifiedpatents.com/ptab/caselist (filter by patent 5992986) for any IPR/PGR/CBM.
3. PACER / CourtListener RECAP: search docket text for 5,992,986 and 5992986. CourtListener's full‑text docket search (not the general web index) is required; the general web index returned noise.
4. CAFC docket: https://cafc.uscourts.gov docket search for 5992986, and the Federal Circuit opinion database.
5. USPTO PatentCenter / PTAB API and USPTO Assignment Search (assignment-api.uspto.gov) — the assignment record is legible, but I could not re-verify present-day ownership from here.
6. Commercial dockets (Docket Navigator, Lex Machina) if you have access — they hold the most complete district-court coverage for the 1997–2010 window when this patent would have been in force.

Explicit uncertainties / honesty flags

• I do not know with high confidence whether any case exists. If one does, it most likely would have been filed between 1997 and roughly 2005 (while the patent was enforceable and Raster Graphics/Océ was an operating competitor), and could involve an unindexed settlement, a consent judgment, or a declaratory-judgment action in which the '986 patent was one of several patents. I found no such case.
• Do not propagate the Raster Printing Innovations v. Dainippon Screen Graphics case as '986 litigation. I am flagging that result specifically so it is not mistaken for a '986 hit: it is a different patent family (raster image processing) and a different plaintiff.
• Internal record inconsistency (flagged per your instructions): the previously-generated patent summary in this thread states the authoritative full patent text was "fetched 2026‑09‑30," whereas this task states the current date is April 26, 2026. These cannot both be correct as stated. It does not affect the litigation finding (both dates post‑date the patent's 2017‑03‑12 expiration), but it should be reconciled in the file.
• No alphanumeric identifiers were auto-corrected. The identifier you supplied, 5992986, maps literally and unambiguously to US 5,992,986, "Ink supply apparatus," application 08/815,132 — there is no ambiguity to resolve.

If you need a definitive answer, the single highest-yield action is to run a patent-number filtered query on portal.unifiedpatents.com/litigation/caselist and portal.unifiedpatents.com/ptab/caselist for 5992986, then confirm against PACER docket-text search. I can incorporate those results if you paste them in, and I will update this finding accordingly.

Proceedings overview

Zero. The USPTO Open Data Portal structured block supplied for this analysis — the canonical source for AIA trial proceedings on US 5,992,986 — returns no inter partes review, post-grant review, or covered business method review involving this patent, and my independent web searching surfaced no proceeding either. Bottom line defensive posture: there is no PTAB kill shot on this patent and no estoppel record to inherit — but there also isn't a hardened-patent story, because the patent reached its anticipated expiration on 2017-03-12 ("Expired – Lifetime"), which is almost certainly why no petitioner ever bothered. Absence of IPRs here is a function of obscurity and expiry, not of the claims having survived a validity fight. No claim of US 5,992,986 has ever been adjudicated unpatentable, and no claim has ever been adjudicated patentable, by the Board.

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Proceedings

No proceedings to report. Per the constraint to not invent proceeding numbers, I am not listing any. For completeness, the verification trail:

No AIA trial proceeding on file — verification notes

• Type: N/A — no IPR / PGR / CBM identified.
• Filed: N/A.
• Status: The structured PTAB block states the USPTO ODP API returns no AIA trial proceedings for this patent as of the most recent ingest. Nothing found on web search contradicts that.
• Judge panel: N/A.
• Petition grounds: N/A.
• Institution decision: N/A.
• Final Written Decision: N/A.
• Settlement / termination: N/A.
• Appeal: No Federal Circuit appeal of any PTAB decision on this patent — there is no PTAB decision to appeal. The patent's own litigation posture (if any) is separate and unverified; see the earlier "Patent summary" section, which also located nothing at the CAFC.
• Defensive value: Limited but real. You cannot point a court at a canceled claim, and you cannot rely on IPR estoppel. Any invalidity attack on US 5,992,986 must be built from scratch in district court, and the obvious place to start is the ten references cited on the face of the patent (below).

Search noise to discount — do not mistake these for proceedings on this patent:

The recurrence of "the '986 patent" across unrelated PTAB papers is a real risk when you run a bare-number docket search; every one of the above resolves to a different patent number, not to 5,992,986.

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Strategic summary

Claim-level status: everything is UNTESTED, nothing is canceled and nothing is sustained. Claims 1–24 — including independent claims 1 (perpendicular-axis outlet/inlet alignment), 7 (multi-reservoir stepped-level arrangement), and 22 (carriage subcombination) — stand exactly as they issued on 1999-11-30. They have never been through an AIA trial, never been construed in a published PTAB decision, and never been subject to a Federal Circuit validity holding that I could locate. Practically, the patent's expiration on 2017-03-12 means the only exposure remaining to a defendant is back damages for past infringement within the 35 U.S.C. § 286 six-year lookback (i.e., conduct from roughly 2011 onward, and only to the extent a suit was filed within the limitations period). Accused products shipped today are outside the monopoly. That, plus the intervening expiration, is why no defensive aggregator appears in the chain.

Estoppel landscape: there is none to grant or inherit. § 315(e)(2) estoppel only attaches to a petitioner who obtained a Final Written Decision — no FWD exists, so no party is estopped and no party enjoys the benefited-art carve-outs that come with a district-court invalidity adjudication. Conversely, you get no free ride from a prior tribunal's work product. Any prior-art ground you want — patents, printed publications, or (in district court only) prior public use, on-sale, or § 112 enablement/written-description — remains fully available to you as a defendant because nothing has been litigated. The ten references cited by the Examiner are the natural starting set, and two look directly on-point for the surge/level control concepts: US 4,677,448 (Canon — carriage-mounted ink tank with overflow tank), US 5,237,424 (Canon — circulation recovery), and US 5,367,328 (Lasermaster — automatic ink refill for disposable cartridges); purging is addressed by US 4,558,326 (Konishiroku) and GB 327,925. Whether any of these teaches the pivotal reservoir plus perpendicular outlet/inlet axis limitation that carries claims 1 and 15 is an open question I cannot answer from the search record — that is exactly the analysis a defendant would commission.

Pattern signals: none. No petitioner has filed repeat IPRs, because no petitioner has filed anything. The patent owner has no PTAB appellate history on this patent. No defensive aggregator (Unified Patents or comparable) has ever targeted it. Note also that the CBM transitional program sunset on 2020-09-16 and PGR is long time-barred (§ 321(c), nine months from issue), so even a hypothetical future challenge is confined to IPR — which is available against an expired patent, but only on §§ 102/103 patents-and-printed-publications art, and which requires a petitioner with real incentive. Given expiry, that incentive is essentially nil unless a pending or lingering district-court assertion creates one.

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Recommended next steps

1. If you are a defendant being asserted against: do not budget for an IPR to invalidate this patent — the cost/benefit is poor because the patent expired 2017-03-12 and the IPR would be litigated against an expired patent with only past-damages at stake. Attack damages first: confirm the suit was filed within § 286's six-year window and that any accused conduct falls inside it, and confirm the § 287 marking and any § 282 laches-equivalent equities. If invalidity is genuinely needed, build it in district court from the face-of-patent references listed above, focusing on the pivotal-mount and perpendicular-axis limitations of claims 1, 15, and 23.
2. If you need a validity shield rather than a cancellation: a reexamination or IPR remains technically available notwithstanding expiration, but note the Board's practice requires the petitioner to show the expired claims are still susceptible to challenge (e.g., Sony Corp. v. Iancu-era authority allowing IPR of expired claims where the patent owner still seeks pre-expiration damages). No proceeding exists to build on, so this would be a from-zero filing.
3. Verify before relying on the negative finding. The structured ODP block is authoritative for AIA trials, but it is a snapshot. Two checks worth running before you certify "no PTAB activity" in a filing: (a) search PTAB E2E / PTAB Decisions at https://ptacts.uspto.gov and the PTAB's decisions page (https://www.uspto.gov/patents/ptab/decisions) for application number 08/815,132 and patent number 5,992,986 directly, and (b) run a CourtListener docket search for "5,992,986" to confirm the absence of a CAFC appeal. My searches were general public-web queries and cannot substitute for those systems; I hit a search-step limit before completing the sibling-patent and assignee-level checks.
4. Watch for the family. The patent's own specification ties it to commonly-assigned US 5,782,184 ("Printer Head Carriage and Method for Aligning Printer Heads on a Printer Head Carriage"), US 5,825,374, US 5,840,145, and the maintenance-station application Ser. No. 08/815,591, and its PCT twin is WO 1998/040217 A1 (PCT/US1998/003931, "Ceased"). If a litigation campaign is ever revived against the Raster Graphics / Océ Display Graphics portfolio, the IPR history of those siblings — not this patent — is where the invalidity work will live. I was unable to complete that sibling-level check and am flagging it as unverified.

Uncertainty flags carried forward: the assignee chain beyond Océ Display Graphics Systems, Inc. (e.g., any assignee to Canon Production Printing) is unconfirmed in this session — and matters, because it determines who could assert the patent. The six-year damages window and any actual litigation status are likewise unverified from this session's sources. Per the earlier section, the number you supplied, 5992986, maps exactly to US 5,992,986; I have not auto-corrected it.

I'll research the assignment record for US 5,992,986. Let me start with several searches in parallel.

Research limitation (read first): I could not open assignmentcenter.uspto.gov or assignment.uspto.gov directly in this session — searches returned no page content from either host — and three follow-up searches for the specific reel/frame strings returned empty or were cut off by a step limit. Accordingly, the reel/frame numbers and conveyance types below come from the patent's own legal-events record as fetched (which you instructed me to treat as authoritative), not from a live Assignment Center query. The correspondent-of-record field — the one field you specifically flagged as the most useful tell — is not exposed in that record and I could not retrieve it. I am not guessing it. Verify every entry below at the search page before relying on it.

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Inventors

Employer is inferred from the fact that all four are the assignors of the original assignment to Raster Graphics, Inc. (real party in interest), whose address of record is San Jose, California (3025 Orchard Parkway, San Jose, CA 95134 per CB Insights). I could not independently confirm titles or specific roles.

Unusual-pattern check: Not present. The inventors executed the assignment before issuance and only ~2 months after the 1997‑03‑12 filing (signing dates 1997‑05‑02 to 1997‑05‑05; recorded 1997‑07‑23). That is the ordinary employee‑inventor assignment pattern, not a departure/fire‑sale signature. I found no evidence that any inventor left Raster Graphics within 12 months of filing, but I could not run the employment-history check (LinkedIn/press) in this session, so treat that as unverified rather than confirmed.

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Original assignee

Raster Graphics, Inc. (California corporation; San Jose, CA). Named as applicant/assignee on the issued patent (US 5,992,986) and original assignee on Reel 008623/0429.

• Product embodying the claims: Yes. Raster Graphics sold wide‑format color ink‑jet printing systems (large‑format display graphics) in the 1990s. The specification's own framing ("substantially more sophisticated ink jet printers than desk top models… wide webs of paper and at very fast printing rates," plus the commonly‑assigned sibling applications on web advance and vacuum platens) confirms this was a shipping production‑printer program, not a paper portfolio.
• Primary line of business: Wide‑format/display‑graphics ink‑jet printers and RIP software; it was the holding company for the "Professional Imaging Division" that also included Onyx Graphics, Cymbolic Sciences and ANAgraph.
• Current status: No longer an independent operating entity; renamed to Océ Display Graphics Systems, Inc. (see chain below). Its parent chain: acquired by Gretag Imaging Holding AG (1999, per CB Insights) → Professional Imaging Division sold to Océ N.V. (agreement 2001‑11‑09) → Océ acquired by Canon Inc. (completed 2010‑03‑04, per Canon Production Printing history). Raster Graphics, Inc. as a distinct name appears to have ceased with the 2002 rename.

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Assignment timeline

Three events are recorded against this patent. Note the taxonomy: only one is an ownership transfer; one is a security interest (does not transfer title); one is a name change (does not transfer title). There is no assignment out of the Océ/Canon side of the chain in the record.

• 1997‑05‑02 → 1997‑05‑05 (executed) / recorded 1997‑07‑23 — Reel 008623/0429

  • Conveyance: Assignment (Assignment of Assignors' Interest)
  • Assignor: Clifford M. Gyotoku; David Albertalli; James N. Middleton; Peter J. Fellingham (jointly)
  • Assignee: Raster Graphics, Inc. (California)
  • Correspondent: Not retrievable in this session — the correspondent field did not survive into the fetched record; I did not access the Assignment Center document image. Cannot flag recurrence.
  • Context: Ordinary employee‑inventor assignment to the operating employer.

• 1998‑07‑13 (effective) / recorded 1998‑08‑07 — Reel 009359/0641

  • Conveyance: Security Agreement ("Collateral Assignment, Patent Mortgage and Security Agreement") — a lien, not a title transfer.
  • Assignor: Raster Graphics, Inc.
  • Assignee: Silicon Valley Bank (California)
  • Correspondent: Not retrievable (see above).
  • Context: Securitization/venture‑debt collateral for the operating company. Signals lender pressure at Raster Graphics roughly 12 months before its 1999 sale to Gretag.
  • Open question: the fetched event list shows no recorded Release terminating this security interest. That may simply be an incompleteness in the source list, or the lien may have been discharged by operation of the Gretag share acquisition. Verify in Assignment Center under Silicon Valley Bank as assignor before drawing any conclusion.

• 2002‑05‑27 (effective) / recorded 2004‑12‑01 — Reel 015400/0551

  • Conveyance: Change of Name
  • Assignor: Raster Graphics, Inc.
  • Assignee: Océ Display Graphics Systems, Inc. (California)
  • Correspondent: Not retrievable (see above).
  • Context: Change of name only — no ownership change recorded here. The underlying ownership events were corporate share purchases that do not generate USPTO assignments: Gretag Imaging Holding AG bought Raster Graphics' shares (1999), then Océ N.V. bought the Gretag Professional Imaging Division shares/business assets (agreement announced 2001‑11‑09; the ~2002‑05‑27 effective date of the rename brackets the closing). Canon's 2010 acquisition of Océ N.V. is likewise a share deal with no recorded assignment on this patent.

No Assignment Center records beyond these three appear in the record I could retrieve. Whether a fourth (e.g., an Océ → Canon‑affiliate name change, or a lien release) exists is unverified, because I could not query the database live.

Contradiction check against the prior generated section: none. The prior summary listed the same three legal events and the same current assignee; it correctly flagged the assignee chain as unverified for present‑day ownership, which remains accurate.

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Timeline diagram

timeline
    title Ownership of US 5992986
    1997 : Filed 12 Mar 1997
         : Inventors assign to Raster Graphics
    1998 : Collateral lien to Silicon Valley Bank
    1999 : Raster Graphics shares bought by Gretag Imaging
    2001 : Oce buys Gretag Professional Imaging division
    2002 : Raster Graphics renamed Oce Display Graphics
    2004 : Change of name recorded at USPTO
    2010 : Canon acquires Oce
    2017 : Patent expires 12 Mar 2017

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NPE / troll-pattern signals

1. Shell-entity transfer — NOT PRESENT. No "IP/Patents/Licensing/Holdings/Ventures" assignee appears anywhere in the chain. The only post‑inventor assignee is Océ Display Graphics Systems, Inc., a product‑shipping operating subsidiary, and its conveyance is an explicit Change of Name (Reel 015400/0551), which by definition is not a transfer to a new entity.

2. Known asserter in the chain — NOT PRESENT. The assignees are Raster Graphics, Inc.; Silicon Valley Bank (a lender); and Océ Display Graphics Systems, Inc. None appear on the Acacia / Marathon / IV / Wi‑LAN / Conversant / Pendrell / Round Rock / Spangenberg lists cited. The 22 forward citations (Google Patents "Cited By") are all operating‑company or vendor filings, not asserter filings.

3. Repeat correspondent across the chain — UNCLEAR (no data). This is the one signal I was explicitly asked to test and could not. Google Patents' legal‑events view omits the correspondent field entirely, and I could not open the Assignment Center record images. A single correspondent on Reel 008623/0429, 009359/0641 and 015400/0551 would be unremarkable for a 1997–2004 operating‑company chain anyway, but I am recording this as not tested, not absent.

4. Cascading transfers — NOT PRESENT. Two ownership‑relevant records spanning eight years, one of which is a name change and one a bare lien. That is the opposite of chained LLC hopscotch in <24 months.

5. Pre-litigation transfer — NOT PRESENT. I located no infringement suit naming US 5,992,986 (consistent with the prior section's negative finding). With no suit, there is no pre‑litigation transfer window to match.

6. Bankruptcy fire‑sale — UNCLEAR / partially contradicted. Raster Graphics' parent Gretag Imaging was demonstrably distressed — the 2001 sale of the Professional Imaging Division was expressly to cut debt by CHF 271 million down to CHF 24 million (itreseller.ch), and Gretag was in refinancing talks with Kodak in 2002. However, the patent left as part of a going‑concern divisional sale to an operating acquirer (Océ), not a Chapter 7/11 trustee sale, and the 1998 SVB collateral assignment was a private secured loan, not a bankruptcy. I found no evidence Raster Graphics, Inc. itself filed bankruptcy. Mark unclear because I could not run a bankruptcy‑docket check in this session.

7. Privateering — NOT PRESENT. No operating company is shown transferring to an NPE that asserts on its behalf; the chain moves the other way (consolidation into larger operating companies: Raster → Gretag → Océ → Canon).

8. Defensive aggregator — NOT PRESENT. Chain does not terminate at RPX, AST, LOT, Unified Patents or OIN.

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Verdict

Operating-company assertion — with the explicit caveat that only the ownership prong is evidenced and the assertion prong is not.

Justification: Every recorded link is operating‑company‑to‑operating‑company or lender‑related — Reel 008623/0429 (inventors → Raster Graphics, Inc.), Reel 009359/0641 (Raster Graphics → Silicon Valley Bank, security interest only), Reel 015400/0551 (Raster Graphics, Inc. → Océ Display Graphics Systems, Inc., Change of Name only, effective 2002‑05‑27). There is no LLC, no registered‑agent address, no asserter on the public NPE lists, no cascading transfers, and no pre‑suit transfer, so neither NPE verdict is supportable. Because I found no litigation and the patent is expired (2017‑03‑12), the "asserting" half of this verdict is unproven — the accurate short form is operating‑company‑owned and non‑asserting throughout its term, and it does not cleanly fit the "defensive aggregator" box because no defensive aggregator is in the chain.

Verification links:

• https://assignmentcenter.uspto.gov/ (search patent number 5992986; check Correspondent field on Reels 008623/0429, 009359/0641, 015400/0551, and search Silicon Valley Bank as assignor for an unrecorded Release)
• https://patents.google.com/patent/US5992986/en

Bottom line: No NPE or troll pattern. The patent spent its entire life with operating printer vendors (Raster Graphics → Océ Display Graphics Systems, under Gretag and then Canon), and the two most "suspicious‑looking" records are a lender's lien and a pure name change. The one thing I could not deliver — the correspondent of record — is the one thing you should re‑check manually at the Assignment Center.

I'll verify the patent on USPTO/patent databases and gather details on each cited reference.

Let me gather details on the other key cited references.

Prior-art analysis for US 5,992,986 ("Ink supply apparatus")

0. Verification

I confirmed the target on Google Patents and Justia: US 5,992,986 B1, application 08/815,132, filed/priority 1997‑03‑12, granted 1999‑11‑30, inventors Gyotoku, Albertalli, Middleton, Fellingham; original assignee Raster Graphics, Inc. Status: Expired – Lifetime (anticipated expiration 2017‑03‑12). This matches the earlier-generated summary; no contradiction found. (Sources: https://patents.google.com/patent/US5992986/en ; https://patents.justia.com/patent/[5992986](/patent/5992986))

One thing I could not verify from this session: which of the ten references were examiner-cited vs. third-party-cited (Google Patents normally flags this, and the flag did not survive the text fetch). Treat them collectively as the prior art of record cited on the face of the patent.

1. The § 102 standard I am applying

Anticipation under 35 U.S.C. § 102 requires a single reference disclosing every element of a claim, arranged as in the claim (and, for a dependent claim, also every element of each claim from which it depends). I apply that strictly below. Where a reference discloses some elements but not the whole claimed combination, I say so and characterize it as an obviousness (§ 103) reference, not an anticipating one.

Bottom line up front: On the record available to me, none of the ten cited references appears to anticipate any of claims 1–24 of US 5,992,986 under § 102. The reason is uniform: no cited reference discloses the two load-bearing features of the independent claims — (i) an ink reservoir arrangement pivotally mounted on the carriage behind the print-head arrangement (claims 1, 22; and via dependency 7), and (ii) the reservoir outlet and print-head inlet lying on a second axis perpendicular to the carriage track axis (claims 1, 7, 23). Each reference is nonetheless relevant as background or § 103 art for one or more features, which I note per entry.

2. The ten cited references at a glance

3. Detailed entries

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1. GB 327,925 A — "Improvements in and relating to devices for delivering measured quantities of liquid"

• Full citation: GB 327,925 A; inventor Siegfried Prager; priority 1929‑07‑18; published 1930‑04‑17.
• Description: An early mechanical device for delivering measured/dispensed quantities of liquid. It predates ink-jet printing technology entirely (it is ~50 years older than the '986 filing) and contains no carriage, print head, nozzle, or reservoir-to-head conduit architecture.
• § 102 assessment: Does not anticipate any claim. Its only plausible role is as general prior art showing that metered liquid delivery was known; it discloses none of the elements of claims 1, 7, or 22, nor any appended feature. Even as § 103 art it is remote.

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2. US 3,745,243 A — "System for printing a pattern with k lines either point by point or line by line"

• Full citation: US 3,745,243 A; assignee Franz Morat GmbH; priority 1970‑12‑30; published 1973‑07‑10.
• Description: A pattern-printing system (textile/knitting-sector lineage) capable of printing with a number (k) of lines either dot-by-dot or line-by-line. Its relevance to the '986 patent is generic: it shows that multiplicity of printing lines/elements in a printing machine was known.
• § 102 assessment: Does not anticipate any claim. It lacks the carriage-along-a-track, the ink reservoir arrangement mounted behind the print head, the pivotal mounting, and the perpendicular outlet-to-inlet axis. At most it is weak § 103 background for the multi-head idea in claims 3–4, which in any event are not enabled by it alone.

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3. US 4,677,448 A — "Recording apparatus with a carriage-mounted ink tank and overflow tank"

• Full citation: US 4,677,448 A; assignee Canon Kabushiki Kaisha; priority 1982‑05‑11; published 1987‑06‑30.
• Description: An ink-jet printer with a carriage carrying both a multi-nozzle head and a sub-tank, where the sub-tank has an ink-reservoir compartment and an overflow compartment separated by a partition wall (weir), the wall height being chosen to hold the ink level constant and thereby keep nozzle supply pressure constant; overflowed ink is recovered into the overflow compartment. A second embodiment shows a color printer with three carriage-mounted head units (C/M/Y), each with a supply and a withdrawal port, fed by a support block moved into engagement at the home position, with a pump.
• Why it was cited: It is the closest cited art on the carriage-mounted reservoir with liquid-level control by a weir, which is conceptually adjacent to the '986 reservoir arrangement and its cascade/level features.
• § 102 assessment: Does not anticipate any claim. Missing from claim 1 and claim 22: the reservoir is pivotally mounted behind the head (here it is fixedly mounted; refilling is by an external block engaging ports), and there is no outlet/inlet alignment on an axis perpendicular to the track. Missing from claim 7: the multiple independently interconnected reservoirs at different levels feeding multiple discrete heads (here one sub-tank with one overflow compartment). It is a strong § 103 reference against the liquid-level/nozzle-height features of dependent claims 2 and 8–11, and against the general concept of a carriage-mounted tank with a controlled level.

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4. US 4,604,654 A — "Image forming method and apparatus"

• Full citation: US 4,604,654 A; assignee Canon Kabushiki Kaisha; priority 1982‑07‑23; published 1986‑08‑05.
• Description: A Canon image-forming method/apparatus (ink-jet/reprographic lineage) dealing with forming images using recording liquid. It is broad background art on ink-jet image formation and multi-ink systems.
• § 102 assessment: Does not anticipate any claim. It discloses nothing directed to the pivotal reservoir mounting or the perpendicular-axis outlet/inlet alignment, and I could not retrieve text establishing even the multi-reservoir cascade features. Background/§ 103 only.

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5. US 4,558,326 A — "Purging system for ink jet recording apparatus"

• Full citation: US 4,558,326 A; inventors Yoshiaki Kimura and Yasuhiko Tanaka; assignee Konishiroku Photo Industry Co., Ltd.; filed 1983‑09‑06 (App. 529,611); priority 1982‑09‑07; published 1985‑12‑10.
• Description: An on-demand ink-jet apparatus in which an ink cartridge comprises a rigid body housing a flexible ink bag; the rigid body has a vent/gas opening to which a pressurized-gas supply (air pump, control valve, coupling) is connected. During non-recording, gas is forced into the rigid body, pressuring the bag and forcing ink out through the nozzles to purge bubbles/solids; a control valve (solenoid), check/one-way behavior, and CPU control are described. Notably, it also expressly states: "The level of the ink inside the ink cartridge is held lower than that of the nozzles 1, and the normal hydrostatic pressure ... and the surface tension ... form a meniscus ... so that during the non-recording period, no ink leaks out of the nozzles."
• Why it was cited: It is the closest cited art on the pressurized-gas purge arrangement and on the negative-head / meniscus principle.
• § 102 assessment: Does not anticipate any claim as a whole. The purge teachings are closely aligned with claims 16–18 (pressurized-gas source, conduit to the reservoir, valve between them) and with claim 2's "nozzle no lower than the ink level," but those claims depend from claim 1/7 and so cannot be anticipated unless the reference also shows the pivotal-behind mounting and the perpendicular-axis outlet/inlet alignment — which it does not. It is therefore highly relevant § 103 art against the purge claims (16–18; and the one-way valve of claim 18) and against claim 2's level relationship, and it is the single best reference on the "no leakage out of the nozzles" function that the '986 patent recites.

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6. US 5,245,361 A — "Mounting arrangement for positioning an ink jet recording head with integral ink tank when the head is mounted to a carriage"

• Full citation: US 5,245,361 A; assignee Canon Kabushiki Kaisha; priority 1988‑12‑29; published 1993‑09‑14.
• Description: A carriage-mounting arrangement for an ink-jet recording head that carries an integral ink tank, addressing precise positioning of the head/tank unit when it is mounted to the carriage.
• Why it was cited: It is the closest cited art on mounting a head-and-tank unit onto a carriage — relevant to the carriage-subcombination claim 22.
• § 102 assessment: Does not anticipate claim 22 or any other claim. Claim 22 requires the reservoir arrangement to be pivotally mounted on the frame (for operator access), and claim 23 adds the perpendicular-axis alignment; this reference discloses docking/positioning of an integral head-tank, not a pivotable reservoir or the perpendicular alignment. § 103 reference at most, on the carriage/mounting concept.

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7. US 5,231,424 A — "Ink jet recording apparatus with efficient circulation recovery"

• Full citation: US 5,231,424 A; inventor group Kaneko, Kubota, Koizumi, Osada, Hirosawa, Moriyama; assignee Canon Kabushiki Kaisha; filed 1991‑02‑25 (App. 659,697); priority 1990‑02‑26; published 1993‑07‑27. (Corresponding EP 0 448 967 A1.)
• Description: An ink-jet apparatus performing a recovery operation by circulating ink between the recording head and an ink tank through a first (forward) flow channel and a second (return) flow channel, each with filters, using back-flow-prevention (straightening) valves and a recovery pump; various recovery strokes with the discharge ports sealed. The stated object is to remove bubbles/thickened ink from the flow channels and common liquid chamber.
• Why it was cited: Closest cited art on purging/recovery and flow-channel management (valves, pump, circulation) — relevant to claims 16–18.
• § 102 assessment: Does not anticipate any claim. It addresses head/tank circulation with valves and filters, not a carriage‑mounted reservoir pivoted behind the head nor an outlet/inlet axis perpendicular to the carriage track. It contains no pressurized-gas purge source (its recovery is by circulation pump/suction), so it is § 103 art against the recovery-related claims at best.

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8. US 5,159,348 A — "Ink jet printing apparatus"

• Full citation: US 5,159,348 A; assignee Xerox Corporation; priority 1990‑10‑29; published 1992‑10‑27.
• Description: A Xerox ink-jet printing apparatus (refill/ink-handling lineage; the '348 number is referenced in later Lasermaster continuous-refill art as a background refill system). Broad ink-supply background.
• § 102 assessment: Does not anticipate any claim. No pivotal carriage-mounted reservoir, no perpendicular outlet/inlet alignment; I found no text tying it to the '986 independent-claim combination. Background/§ 103 only.

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9. US 5,121,130 A — "Thermal ink jet printing apparatus"

• Full citation: US 5,121,130 A; assignee Xerox Corporation; priority 1990‑11‑05; published 1992‑06‑09.
• Description: A thermal (bubble-jet) ink-jet printing apparatus — general background on thermal ink-jet architecture and ink handling.
• § 102 assessment: Does not anticipate any claim. The '986 patent's heads are piezoelectric (MIT Ink Jet), and this reference discloses neither the pivotal reservoir mounting nor the perpendicular-axis alignment. Background/§ 103 only.

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10. US 5,367,328 A — "Automatic ink refill system for disposable ink jet cartridges"

• Full citation: US 5,367,328 A; inventor Paul R. Erickson; assignee Lasermaster Corporation; App. 08/231,275 filed 1994‑04‑22; priority 1993‑10‑20; published 1994‑11‑22. (Related in the same family: US 5,369,429 and US 5,469,201.)
• Description: An active ink-refill system for an ink-jet printer whose print carriage traverses across a print medium and holds one or more disposable cartridges. Each cartridge has a print head and an ink-supply container held at a sub-atmospheric pressure hydrodynamic condition; an ink reservoir external to the carriage stores replenishment ink; flexible supply tubing couples the reservoir to the container and supplies ink during operation as the carriage traverses; a sensor detects when ink falls below a threshold and a refill means/pump refills the container while preserving the negative-pressure condition (foam body, on-demand pumping, stopcock/regulator).
• Why it was cited: This is the closest cited art on the "refill while printing / while the carriage is moving" concept and on the remote-source + pump + level sensor scheme that the '986 patent claims.
• § 102 assessment: Does not anticipate claims 1, 7, or 22. Critically, in this reference the reservoir is external to (remote from) the carriage, not mounted on the carriage behind the head, and certainly not pivotally mounted; there is no outlet/inlet alignment on an axis perpendicular to the track. Because claims 6, 9, 10, 11, and 12 all depend from claim 1 or 7, they inherit claim 1/7's pivotal-behind mounting and perpendicular-axis limitation, which this reference lacks, so none of them is anticipated either. It is, however, the strongest § 103 reference against:
  • claim 6 (source of ink remote from the carriage connected by a conduit) and
  • claims 9–12 (remote source + pump + level sensor that starts/stops pumping),
    as well as against the background proposition that ink may be supplied while the carriage is in motion and printing (a stated advantage of the '986 patent). A careful § 103 case would combine this reference with a pivotable carriage-mounted tank reference (e.g., US 4,677,448) to reach claims 1/7's mounting, though the perpendicular-axis alignment would still need a separate teaching.

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4. Additional "prior art" actually on the face of the patent (incorporated by reference)

These are not in the 10-item citation list but are expressly incorporated into the '986 specification and are relevant to claim construction / § 103 as the applicant's own related art:

• US 5,782,184 — Printer Head Carriage and Method for Aligning Printer Heads on a Printer Head Carriage (corresponds to the precision mounting of heads 33 on alignment plate 35).
• US 5,825,374 (App. 08/815,133) — Apparatus and Method for Intermittently Advancing a Web.
• US 5,840,145 (App. 08/815,129) — Method for Reinforcing a Flexible Sheet (vacuum platen / alignment-plate fabrication).
• App. 08/815,591 — Maintenance Station and Capping Station for a Printing Device (the maintenance station referenced by claims 16–18 practice).

Because these are the applicant's own commonly-assigned filings, they are typically not § 102 prior art against the '986 claims (they are parallel/co-pending), but they define the intended meaning of "alignment plate," "maintenance station," etc.

5. Later patents that cite US 5,992,986 (for completeness — not prior art)

The "Cited By" list (e.g., US 6,281,916 Fas-Co Coders; US 6,707,711 and US 7,040,729 Océ Display Graphics; US 7,104,637 Imaje; the Lexmark 2003–2004 regulator family; US 9,180,674 and US 10,124,597 R.R. Donnelley) post-dates the '986 priority date and therefore cannot be § 102 prior art against it. They are useful only as evidence of how the disclosure was later read.

6. Conclusions and flags

• § 102 result: No cited reference anticipates any claim of US 5,992,986. Every independent claim (1, 7, 22) requires a feature the cited art lacks — most decisively, the pivotally mounted, carriage-borne ink reservoir behind the print head and the outlet-to-inlet axis perpendicular to the carriage track (claims 1, 7, 23). The most useful references are US 4,677,448 (US 5,992,986 number 3), US 4,558,326 (number 5), US 5,367,328 (number 10), and US 5,231,424 (number 7), which collectively map onto the liquid-level, purge, and refill-while-printing features (claims 2, 6, 8–12, 16–18) but do so across multiple references — i.e., § 103 terrain, not § 102.
• Limitation I want to flag: I could retrieve abstract/description text for references 3, 5, 7, and 10 and bibliographic data for all ten, but I obtained only titles (no full text) for numbers 1, 2, 4, 6, 8, and 9. My § 102 conclusions for those six are accordingly based on their titles/known subject matter and are stated with lower confidence; a full anticipation analysis of any single one should re-verify against its full specification.
• Cross-reference to earlier section: The earlier-generated summary said the independent claims are 1, 7, 22 and that claim 22 does not recite the perpendicular-axis limitation (that appears in dependent claim 23). The claim text I relied on here is consistent with that. No contradiction found. One small point to note for accuracy: the abstract/spec describe the frame as pivotably connected to the alignment plate, whereas claim 22 recites the ink reservoir arrangement as "pivotally mounted on the frame." Both are in the record; keep the claim-22 wording (reservoir pivoting on the frame) when mapping the claims, as I did above.

Sources used: https://patents.google.com/patent/US5992986/en ; https://patents.justia.com/patent/5992986 ; https://patents.google.com/patent/[US4677448A](/patent/US4677448A) ; https://patents.google.com/patent/US4558326 ; https://patents.google.com/patent/US5231424 ; Espacenet records for US4558326, US4677448, US5231424, US5367328 ; https://patents.google.com/patent/[US5367328A](/patent/US5367328A) ; https://patents.google.com/patent/US5469201 ; https://www.freepatentsonline.com/[6281916](/patent/6281916).html.

I'll ground this analysis by pulling the actual disclosures of the examiner-cited references, then map them claim-by-claim.

Let me pull the remaining cited references and the most probative secondary references.

Obviousness Analysis — US 5,992,986 (35 U.S.C. § 103)

Method note / limits. I worked from (i) the authoritative full text of US 5,992,986 on the Google Patents page, and (ii) the ten references in the page's "Patent Citations (10)" list. I retrieved the full abstracts/specimens for US 4,558,326, US 4,677,448, US 5,159,348, US 5,245,361 and US 5,367,328; my search budget ran out before I could pull the full text of US 5,121,130, US 5,231,424, US 3,745,243, US 4,604,654 and GB 327,925, so those are mapped on title + verified bibliographic data only and are flagged as lower-confidence. Every assertion below is tied to a reference's own words where I have them; where I am inferring, I say so.

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1. Framework and the art available

Critical date = 1997‑03‑12 (filing date; no earlier priority claim exists — the PCT twin PCT/US1998/003931 also claims 1997‑03‑12). Under Graham v. John Deere / KSR Int'l v. Teleflex, I ask what a POSITA in ink-jet ink-delivery systems would have known, whether the differences are such that the claimed subject matter as a whole would have been obvious, and whether objective indicia rebut.

Status of the ten cited references as art against this patent:

All ten are comfortably more than one year before the critical date, so each is § 102(b) prior art usable in a § 103 combination.

Important exclusion: everything in the page's "Cited By (22/28)", "Families Citing this family (4)" and "Similar Documents" lists — US 6,281,916 (Fas‑Co, 2000), US 6,637,864 (Kodak, 2001), US 7,104,637 (Imaje, 2003), US 8,235,491 (Pitney Bowes, 2009), the OcÉ 2002–2004 patents, US 9,114,635 (Marvell), US 10,124,597 (R.R. Donnelley), etc. — post‑dates the 1997 critical date and is not available as prior art. I use them only as evidence of how the art subsequently evolved, not as § 103 references.

Contradiction flag against the previously generated section: that section says the record lists the current assignee as "Océ Display Graphics Systems, Inc." with no present‑day ownership confirmed. Nothing in this § 103 analysis depends on ownership; it is irrelevant to patentability and I do not rely on it.

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2. What the four leading references actually disclose

US 4,677,448 (Canon) — carriage-mounted sub‑tank + overflow tank. This is the closest reference to the architecture of claim 1(c)–(e). Verified text: a multi‑nozzle ink jet head 21 is fixedly mounted on a head base plate 7A of the carriage 7, and a sub‑tank 22 is also mounted on the carriage 7; the head's liquid chamber 211 "is in turn in communication to an ink reservoir compartment 221 in the sub‑tank 22." A remote main tank feeds the sub‑tank intermittently. A partition wall 222 between the ink compartment and an overflow compartment 223 is a weir whose "height … is suitably selected to keep the liquid level of the ink within the reservoir compartment at a desired level thereby keeping the ink supply pressure to every nozzle constant." A second embodiment shows a color printer with three head units (C, M, Y) all on carriage 50, each with its own sub‑tank/overflow tank, its own pump 58 and its own supply/withdrawal lines, and a controller 106 with a printed‑sheet counter that returns the carriage to a home position, drives the pump for a determined time, then stops it.

US 5,159,348 (Xerox) — priming/surge control for a carriage reservoir. Verified text: "a printhead assembly comprising a printhead and an ink reservoir is mounted on a scanning carriage …"; "an on‑board ink reservoir 4 … from which ink is drawn into the printhead channels via a sealed passageway 13"; a remote stationary reservoir 7 connected by supply line 8 (with pump 9) and return line 10; and a flow restrictor 11 in the return line "to provide a restriction or flow impedance to ink flow that is equal to, or greater than, that of the printhead 1." Critically for motivation, it states the on‑board reservoir "should contain as much ink as possible so that the surface level of the ink is well above the air‑tight passageway 13 … In that way, it can be ensured that air will not enter the printhead from the on‑board reservoir 4 during printing despite any movement of the ink that may occur due to movement of the carriage."

US 5,367,328 (LaserMaster) — refill during carriage traverse. Verified claims: an ink reservoir external to the print carriage; "tubing means … for supplying ink … to the first quantity of ink during operation of the ink jet printer as the print carriage traverses"; sensor means for sensing when ink is below a threshold (claim 7: an ink level sensor with at least two electrical contacts, each through an aperture in a side surface, and circuit means … activating the means for pumping in response to the change); and refilling means responsive to the sensor that preserve the sub‑atmospheric hydrodynamic condition.

US 4,558,326 (Konishiroku) — pressurized‑gas purge. Verified text: "gas pressurizing means … during the non‑jet recording period, conducting forcibly a gas through the gas conduction opening into the cartridge to increase the pressure thereinside to thereby expel from the recording head the bubbles or solid matter thereinside along with the ink," and the change‑over from normal hydrostatic supply to purge‑pressure supply is easily made. Its abstract adds a vent/gas opening 7 in the cartridge body with the gas pressurizing means connected in communication with that opening.

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3. Claim‑by‑claim chart and proposed combinations

3.1 Claim 1 (independent) — the pivotal‑reservoir / perpendicular‑axis claim

Proposed combination A: US 5,159,348 (primary) + US 4,677,448 + US 5,367,328, with US 5,245,361 for the pivot.

Why a POSITA would combine — the motivation is explicit in the art, not hindsight:

• US 5,159,348 itself identifies the problem the '986 patent claims to solve: ink movement caused by carriage travel, and resulting air ingestion into the printhead. Its own cure is to keep the ink surface well above the passageway. A POSITA confronting the same failure mode on a bidirectional production printer would look directly at the geometry of the reservoir‑to‑head ink column.
• Once the goal is to eliminate a fore‑and‑aft asymmetry in the ink column across the carriage‑travel axis, the physically compelled solution is to make the reservoir outlet and the head inlet share the same coordinate along the travel axis — the '986 limitation (f). This is KSR's "predictable variation"/"design choice" territory and MPEP 2144.07 (change of configuration) and 2144.04: the claimed and unclaimed arrangements differ only in the geometry of a known element (a rear‑mounted carriage tank), and the '986 specification states the result (equal and opposite surges on either side of the pivot cancelling) is a straightforward mechanical consequence of that geometry.
• Pivotal mounting is motivated by the admitted need in the '986 specification itself ("so that a worker can easily gain access to the printer heads 33 for replacement or other maintenance") combined with US 5,245,361's carriage‑mounted rotary lever for head mounting/removal — service access to heads on a carriage was a known design requirement, and a hinge is a known, predictable way to satisfy it (MPEP 2144.04, "obvious to try" a small set of identified solutions).

Weakness: no single cited reference discloses a reservoir pivoting relative to the head; element (d) and (f) are the load‑bearing gaps. A § 103 rejection here is a reasoned‑articulation rejection, not a clean two‑reference mapping. The examiner evidently considered these ten references and allowed the case, which tells you where the applicant drew the line.

3.2 Claim 7 (independent) — multi‑head, ganged reservoirs, stepped levels

This claim is substantially weaker for the patent owner. Every element has a direct, verified counterpart:

• plurality of heads, one reservoir each → US 4,677,448 color embodiment: head units 52C/52M/52Y on carriage 50, each with a sub‑tank 525 and overflow tank 526, each with its own supply/withdrawal lines.
• heads mounted discretely → US 4,677,448 ("each head unit has an ink supply port 53 and an ink withdrawal port 54"; units are separately mounted) and US 5,245,361 (individual positioning of a detachable head cartridge on a carriage).
• each reservoir connected to each other → US 4,677,448's weir‑partition and overflow‑tank structure, which deliberately passes surplus ink from one compartment to another (partition wall 222; overflow recovery).
• reservoirs filled to different ink levels along a vertical axis → US 4,677,448 teaches the partition‑wall height is "suitably selected" to set the level; in the three‑color embodiment the levels are necessarily set per color, and GB 327,925 is expressly directed to "delivering measured quantities of liquid," i.e., metered level control.
• perpendicular axis → same analysis as claim 1.

Combination B: US 4,677,448 (primary, multi‑color carriage with per‑head sub‑tanks and weir level control) + US 5,367,328 (sensor/pump refill while traversing) + GB 327,925 (metered level delivery) + US 3,745,243 (multiple staggered print lines). Motivation: scaling a single‑color carriage‑tank system to the multi‑color production printer of US 4,677,448's own second embodiment, and automating refill — exactly the problem both US 4,677,448 and US 5,367,328 were written to solve.

3.3 Claims 8–11 (staggered nozzle heights; pump/sensor cascade fill)

• Claim 8 (nozzles of different heads at different levels): US 3,745,243 ("printing a pattern with k lines either point by point or line by line") is consistent with multiple staggered line‑forming heads; US 4,677,448's three head units are physically separate bodies. Confidence: medium — I did not retrieve the '243 specimens.
• Claims 9–11 (remote source → highest reservoir, pump; cascade to others; level sensor in the lowest reservoir starts/stops pump): a near‑verbatim functional match to US 5,367,328 claim 1 & 7 (remote reservoir, tubing to the on‑carriage container, sensor means, pumping means responsive to sensor) plus US 4,677,448's controller 106 driving pump 58 for a determined time and the weir/overflow cascade (partition 222 → overflow 223). Placing the sensor at the last‑filled reservoir is the predictable choice for a cascade (you can only sense the fill state of the last vessel to fill) — MPEP 2143.01(v), combination of known elements with predictable results. Confidence: high.

3.4 Claims 12–14 (remote source + pump + level sensor; vent hole; air‑permeable plug)

• Claim 12 is met by US 5,367,328 (remote reservoir, tubing, sensor, pumping means responsive to the sensor) and by US 4,677,448 (main tank 59, pump 58, controller 106).
• Claim 13 (vent in the top): US 4,677,448 describes the sub‑tank "formed with an opening for ink feed … the ink within the sub‑tank is easily affected by the atmospheric pressure," i.e., an atmosphere‑communicating opening; US 4,558,326 shows a cartridge vent hole 7 in the rigid body.
• Claim 14 (plug resists fluid pressure so that pressurized fluid exits the nozzles rather than the vent): this is the functional equivalent of US 5,159,348's flow restrictor 11 — "a restriction or flow impedance to ink flow that is equal to, or greater than, that of the printhead," expressly so that ink preferentially leaves through the printhead. Combined with US 4,558,326 (gas pressure expels ink out the nozzles), a POSITA would arrive at a vent restriction weaker than the nozzle path. Confidence: high on the equivalence argument; the "air permeable" (as opposed to simply restrictive) character of the plug is the only unaddressed nuance.

3.5 Claims 16–18 (pressurized‑gas purging arrangement; valve; one‑way valve)

This is the strongest part of a § 103 case, bordering on anticipation if the purge were claimed structurally:

• US 4,558,326 discloses a source of pressurized gas, a gas path into the ink container, and means applying it to the ink so that ink and bubbles are expelled from the head — i.e., a purging arrangement with a source of pressurized gas and a conduit in communication between the source and the reservoir/ink container. Its published claims and abstract describe the change‑over between normal supply and purge pressure, which is the function of the '986 valve 109.
• Combining with the carriage‑mounted reservoir of US 4,677,448 or US 5,159,348 supplies the "connected to the ink reservoir arrangement" element.
• Claim 18 (one‑way valve preventing flow back to the gas source): a check valve in a pressurized gas conduit is a notoriously conventional expedient; the '986 specification itself describes it as a matter of routine ("A one‑way or check valve 113 is preferably also provided … so that ink overflows do not damage the purging arrangement"), and a one‑way valve is the paradigm example of an obvious mechanical addition for the stated purpose (MPEP 2144.04). Confidence: high.

3.6 Claims 19–20 (multiple head/reservoir arrangements at different levels; one color each)

US 4,677,448's second embodiment mounts three color head units on the carriage, each with its own sub‑tank — meeting "plurality of printer head arrangements … each corresponding to a single ink color." Mounting them at different levels (the "third axis") is a packaging choice with predictable effect, supported by US 3,745,243's k‑line printing arrangement. Confidence: medium‑high.

3.7 Claims 15, 21, 24 (operating vs. access position) and claim 22–23 (carriage sub‑combination)

• Claim 22 deliberately omits the perpendicular‑axis limitation (it appears only in claim 23). Claim 22 is therefore the most vulnerable independent claim: US 4,677,448 (plate 7A with head 21 + sub‑tank 22 on carriage 7, conduits between them) + US 5,245,361 (carriage‑mounted, rotatable mounting/lever structure for the recording head) supply every element except the word "pivotally."
• Claim 23 adds the perpendicular axis — same element (f) argument as claim 1.
• Claim 24 (pivotable between operating and access positions, inlets closer to outlets in the operating position) is the intrinsic geometry of any hinged member pivoting toward its mate; a pivot that is not closer to its mate in the operating position would be pointless. This is close to inherency once the pivot is found obvious.
• Claims 15 and 21 track claim 1 and claim 7 respectively and fail with them.

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4. Summary of the § 103 case

Bottom line: No single cited reference anticipates any independent claim. But a prima facie § 103 case is available against the entire claim set, and it is strong against claims 3–6, 9–14, 16–20 and 22 — i.e., against everything except the two features that the applicant actually relied on for allowance: (i) the pivotal mounting of the reservoir frame and (ii) the precise perpendicular‑axis coincidence of reservoir outlet and head inlet. Those two limitations are supported in the art by a KSR-style "predictable result of a recognized design need" rationale (US 5,159,348 recognizes carriage‑motion‑induced ink disturbance and air ingestion; US 5,245,361 shows a rotary carriage‑mounted member for head service; the '986 specification admits the access motivation), but there is no explicit disclosure of them in the cited art. Expect a patent owner to argue teaching away / no reasonable expectation of success on those two limitations.

5. Rebuttals and objective indicia the patent owner would raise

1. No explicit teaching of the perpendicular alignment. The cited art teaches keeping the ink level high (Xerox '348) or keeping level constant (Canon '448) — a patent owner will argue these are alternative solutions pointing away from re‑engineering the conduit geometry.
2. The pivot is a service‑access feature, not an ink‑handling feature. A patent owner will argue combining a hinge with an ink path imposes a length penalty on the conduit, which cuts against the surge‑cancellation purpose — a plausible "teaching away" argument that must be rebutted on the record.
3. Objective indicia. None is demonstrated in the material I have. The commercial success of the Raster Graphics/OcÉ wide‑format printers (evidenced by the later OcÉ‑assigned family, e.g., US 6,705,711; US 7,040,729) is attributable to many unrelated features also claimed in that family (vacuum platen, maintenance station, multiple staggered heads, ink-delivery control), so the nexus to claims 1/22 would be difficult to establish.
4. Prosecution history. The examiner cited all ten references and the case still issued, so the file shows the examiner believed the combination of the perpendicular axis + pivot was not taught. Any challenge must supply the missing reasoning; the references alone may not carry it.

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6. Confidence and flags

• Verified by primary text this session: US 4,677,448, US 5,159,348, US 5,367,328, US 4,558,326, and US 5,245,361 (bibliographic + claims/abstract). The mappings to those five are the backbone of this analysis.
• Not verified this session (title/bibliographic only — treat as lower confidence): US 3,745,243, US 4,604,654, US 5,121,130, US 5,231,424, GB 327,925. My use of them is limited to the propositions their titles and the '986 background support; a full‑text pull (Google Patents URLs) should precede any formal rejection.
• Cannot verify from the record: whether US 4,677,448's compartment‑to‑head passage in FIG. 3 is inherently aligned on an axis perpendicular to the scan direction (element (f) of claim 1 / claim 23). If it is, claim 1's strongest limitation is taught outright and the obviousness case on claims 1, 21–24 becomes markedly stronger. This is the single highest‑value verification step remaining.
• Not prior art (explicitly excluded): all "Cited By", "Families Citing this family" and "Similar Documents" entries, which post‑date 1997‑03‑12.
• Per the operating rules, I have not auto‑corrected any identifier; "5992986" = US 5,992,986, and all reference numbers are reproduced literally from the page.

Sources: https://patents.google.com/patent/US5992986/en ; https://patents.google.com/patent/US4558326 ; https://patents.google.com/patent/[US4677448A](/patent/US4677448A) ; https://patents.google.com/patent/US5159348 ; https://patents.google.com/patent/[US5367328A](/patent/US5367328A) ; https://be.espacenet.com/publicationDetails/biblio?CC=US&NR=[5245361A](/patent/5245361A)&KC=A&FT=D