US 4558326

I'll search for litigation and docket information on this specific patent number, then summarize.

Let me try additional targeted searches.

US Patent 4,558,326 — Analyst Summary

Search scope note: I searched for this specific number (no fuzzy/near-number matches returned) across general web indexes, Espacenet bibliographic/INPADOC records, SumoBrain, FreePatentsOnline and Google Patents. I re-checked specifically for CAFC / district court litigation records tied to 4558326 and found none. I cannot confirm or deny any 2026 CAFC docket activity from an authoritative court source; the CAFC docket database was not directly reachable in these searches, so treat "no litigation found" as a search-result finding, not a certification.

Bibliographic data

Prior art cited: US 4,123,761 (Kimura, 1978) and US 4,376,283 (Kimura, 1983); foreign: JP 55-53570 (4/1980) and JP 56-113464 (9/1981).

Abstract (as printed)

In an ink jet recording apparatus of the ink-on-demand type, the recording ink is forcibly sent from a pressure chamber in the recording head to nozzles which jet the recording ink onto a recording medium. An ink cartridge is a closed-up rigid body having an opening therein which permits gas to flow in and out of the rigid body. The rigid cartridge body contains a flexible ink container bag which contains recording ink. A pressurized gas supply is connected to the ink cartridge body in communication with the opening thereof for increasing the pressure inside the ink cartridge body and for thereby increasing the pressure of the ink in the flexible container bag due to flexing of the bag under increased pressure. A cap made of elastic material is coupled to the cartridge body so as to be connected to the ink container bag in a liquid-tight manner to supply recording ink from inside the ink container bag to the recording head under pressure to purge the recording head of bubbles and of ink previously contained therein.

Plain-language overview of the independent claims

Claim 1 — Method (independent). A method of ink jet recording used with an ink-on-demand head plus a cartridge made of a rigid body housing a flexible, yieldable ink bag. The method has two selective steps:

• a purging step: during a non-recording period, force gas (via gas pressurizing means) through the cartridge body's opening into the rigid body, raising the pressure inside the body; that pressure makes the flexible bag yield, pressurizing the ink so it flows into the recording head and flushes bubbles/foreign matter out; and
• a venting step: selectively open that same opening to atmosphere so no purging occurs (i.e., normal hydrostatic-pressure recording operation).

In short: pressurize the rigid housing's air space to squeeze the soft inner ink bag and blow the head clean; vent the housing to stop.

Claim 2 — Apparatus (independent). An ink jet recording apparatus (ink-on-demand head with pressure chamber and nozzles) with a cartridge of a flexible-portion ink bag inside a rigid body, characterized by:

1. the cartridge body being a closed-up, substantially rigid body with at least one opening permitting gas to selectively flow in and out;
2. a pressurizing gas supply that selectively feeds gas through the opening to raise the body's internal pressure, which raises pressure around the outside of the bag and thereby pressurizes the ink via flexing of the bag;
3. an elastic cap coupled liquid-tight to the bag for delivering ink to the head under that pressure to purge it of bubbles and previously contained ink; and
4. means for selectively venting the opening to prevent purging.

In short: a hard outer shell with a gas port + a soft inner ink bag + an elastic outlet cap + a vent — indirect pressurization of the ink through the gas blanket, rather than squeezing the cartridge or pumping liquid ink.

Dependent claims (3–14) — quick map

• 3 — pressurizing gas supply is an air pump
• 4 — air pump + coupling means to the cartridge opening
• 5 — air pump + control valve controlling gas conduction/exhaust
• 6 — manual blower + coupling means
• 7 — heating chamber (thermal expansion of gas) + coupling means
• 8 — pressurizing gas supply comprises a liquefied gas
• 9 — gas supply attachably/detachably coupled to a conduction-and-exhaust opening
• 10 — cartridge body has a gas conduction opening and a separate gas exhaust opening
• 11 — pressurizing means located inside the cartridge to pressurize the ambient gas around the bag
• 12 — that internal pressurizing means is a liquefied gas (FIG. 12 self-contained cartridge)
• 13 — that internal pressurizing means is a contractible/expandable pressure chamber with a closable outside-air opening (FIGS. 13/14 manual blower / bellows)
• 14 — depends on claim 4: air pump + coupling means and a control valve

The specification discusses additional implementations not separately claimed as independent subject matter, including a liquefied-gas container with control valve (FIGS. 6–9), a sealed cartridge loading chamber arrangement (FIGS. 3, 8, 10–11), recovery of expelled ink via a cleaning roller/waste receiver/suction system (FIGS. 2, 15), and an integrated linear-actuator-driven diaphragm air pump performing suction and pressurization simultaneously (FIGS. 16–17).

Points of uncertainty / caveats

• Litigation: No CAFC or district court records for this patent number appeared in any search. I have no authoritative basis to state this patent was ever asserted, and absence of hits is not proof of no litigation (older patents are often poorly indexed in free databases).
• Assignee: The name of record at issuance is Konishiroku Photo Industry Co., Ltd.; Google Patents reports the current assignee as Konica Minolta, Inc. based on recorded reassignments (Konica Corporation, 1989). I state both rather than treating them as identical.
• Claim text above is taken from a secondary database (SumoBrain) that reproduces the granted claims and is consistent with the granted PDF front matter (14 claims, 19 figures). Where a discrepancy exists between databases (e.g., the law firm), I have deferred to the printed patent.
• Date context: All status information is as retrieved on the search date; the patent's 20-year term ended September 6, 2003, so it is not in force today.

I'll search for litigation involving US patent 4558326.

Let me try more targeted searches.

Let me search additional litigation-specific sources.

Litigation Search: US Patent 4,558,326

Summary of Findings

No litigation involving US Patent 4,558,326 could be confirmed. My searches of patent-litigation resources (CourtListener/RECAP, Unified Patents-style aggregators, and general web searches) returned no cases naming this patent as an asserted patent. I cannot report plaintiff, defendant, jurisdiction, case number, filing date, or outcome because I found no such record.

What the Searches Did Return

• Google Patents (authoritative text): US 4,558,326 — "Purging system for ink jet recording apparatus," inventors Yoshiaki Kimura and Yasuhiko Tanaka. Priority date 1982-09-07, filed 1983-09-06, granted 1985-12-10. Original assignee Konishioku Photo Industry Co., Ltd. (later Konica Corporation, now Konica Minolta). Legal status: Expired – Lifetime, with anticipated expiration 2003-09-06.
• Espacenet INPADOC (FR/DE portal): Only prosecution/assignment/ maintenance-fee events appear (e.g., assignment to Konica Corporation recorded 1989-09-22; fee payments through the 12th year). No litigation events are listed.

Important Caveat — a Same-Number Red Herring

One search surfaced a reference to a "'326 Patent" in Intellectual Ventures I LLC v. American Airlines, Inc. (E.D. Tex., 4:24-cv-00980). Per your strict rule, I am not treating that as US 4,558,326. On its face this appears to be a different patent: the IV complaint deals with software/technology patents and references companion patents such as a "'469 Patent" and a "'582 Patent," which is inconsistent with a 1985 Konica ink-jet hardware patent. I did not obtain a patent number or confirmation tying it to 4,558,326, so I will not assert any connection.

Confidence and Limitations

• High confidence that the patent expired for failure to maintain (anticipated expiration 2003-09-06), meaning any infringement action would have had to be filed well before that date. This is consistent with the absence of any modern docket hits.
• Cannot rule out older, pre-electronic, or non-digitized litigation (e.g., 1980s–1990s district court suits that were never indexed in modern databases such as CourtListener/Unified Patents). I found no evidence of such suits, but my search was not exhaustive of paper-era records.
• I did not reach PACER directly or the Unified Patents case list before exhausting my search steps, so this should not be read as a definitive negative from those specific sources.

Bottom Line

Based on available online litigation records, there is no known litigation involving US Patent 4,558,326. If you need a definitive negative, the next step would be a direct PACER docket search and a commercial litigation database (e.g., Darts-IP, Lex Machina) covering 1985–2003, since any suit would necessarily antedate the patent's 2003 expiration.

I'll verify the structured data against public sources before writing anything.

Let me run a few more targeted checks before concluding.

PTAB Proceedings — US 4,558,326 ("Purging system for ink jet recording apparatus")

Proceedings overview

Zero AIA trial proceedings are on file. The structured USPTO Open Data Portal block states plainly that no AIA trial proceedings exist for this patent, and targeted web searches for "4,558,326" / "US4558326" combined with IPR / PGR / CBM / PTAB / petitioner terms returned no proceedings of any kind. The count is 0 active, 0 invalidated, 0 sustained, 0 settled, 0 institution-denied.

The bottom-line defensive posture is therefore not "hardened patent" or "canceled claims" — it is the third thing, and the strongest one available: the patent is expired and structurally incapable of ever having had an AIA trial. US 4,558,326 issued 1985-12-10, carries a priority date of 1982-09-07, was filed 1983-09-06, and its anticipated expiration is 2003-09-06. The AIA trial regimes did not exist until 2012-09-16 (IPR/CBM) and 2013-03-16 (PGR). There is a nine-year gap between this patent's death and the birth of the forum that would have judged it. If you are receiving a demand letter citing this patent today, the demand is defective on its face: an expired patent has no enforceable claim, and no IPR is needed — or possible — to establish that.

No proceedings to enumerate

Because the canonical list is empty, there is no "most-impactful first" ordering to perform and no FWD, panel, settlement, or appeal to report. I will not manufacture one. For completeness, here is what each of the requested data fields resolves to:

Why there can be no proceeding — three independent bars

This is worth stating explicitly, because "no proceedings" is often read as "nobody bothered." That is the wrong read here.

1. Expiration (the dispositive bar). Per the structured data and confirmed on the Google Patents record, US 4,558,326 reached its anticipated expiration on 2003-09-06 (20 years from the 1983-09-06 filing; the alternative 17-years-from-grant measure would have run out even earlier, on 2002-12-10, and the 20-year measure controls). Maintenance fees were paid through the 12th year (FPAY event, 1997-05-29), so the patent did not lapse early — it ran its full statutory term and then expired. A patent owner cannot assert an expired patent; a defendant cannot be enjoined or mulcted in damages for practicing a claim that no longer exists. No PTAB petition was ever necessary.

2. Temporal bar. 35 U.S.C. §§ 311(c) and 321(c) and their AIA effective dates mean inter partes review and post-grant review petitions could not be filed before 2012-09-16. This patent expired nine years earlier.

3. Subject-matter bar (for CBM). AIA § 18 Covered Business Method review was limited to patents claiming a method or apparatus "used in the practice, administration, or management of a financial product or service." US 4,558,326 claims an ink-jet purging/cartridge apparatus (CPC B41J2/16526, B41J2/1721, B41J2/175). It is not a CBM-eligible patent under any reading. PGR is independently unavailable because the patent's 1983 priority date is decades before the 2013-03-16 PGR cutoff.

Strategic summary

Claim status. No claim of US 4,558,326 has been adjudicated by the PTAB, so there is no "canceled vs. sustained vs. untested" breakdown in the AIA sense. The authoritative claim set runs at least to claim 14 (claims 12 and 13 depend from claim 11, and claim 14 depends from claim 4, per the patent's own claim text). Every one of those claims — independent and dependent alike — is expired and unenforceable, and none is "untested" in any way that matters to a defendant. There is no surviving claim set to narrow around, because there is no live patent to assert.

Estoppel landscape. § 315(e)(2) estoppel is irrelevant here: it attaches only to petitioners who have been through an IPR, and there have been none. That cuts in the defendant's favor — you are not boxed out of any prior-art ground, because no prior art has ever been "reasonably raised" in a PTAB proceeding on this patent. If you nonetheless want the art for a different purpose — e.g., to invalidate a later, live patent that claims priority to or cites US 4,558,326 as a parent or backdrop — you are free to use it. Note that US 4,558,326 is itself heavily cited as prior art by later ink-cartridge patents (e.g., US 7,144,104 (Brother) expressly cites it and JP-A-S59-59457 as the purging-system background; KR100524843 cites it as the "welded ink container bag" reference). Its real modern function is as a § 102/§ 103 reference against other people's patents, not as an assertion vehicle.

Pattern signals. No petitioner has filed against this patent, so there is no repeat-petitioner pattern, no joinder activity, and no defensive aggregator (Unified Patents or similar) in the chain — none of which is surprising for a 1983-priority patent that expired in 2003. The only Board-adjacent activity my search surfaced is Ex parte Harshbarger, Appeal No. 97-2943 (Application 08/319,174), in which the examiner relied on "Kimura" — this patent — as prior art in an ex parte appeal about priming an ink-jet print head. That is a pre-AIA ex parte prosecution appeal, not an AIA trial, and not a proceeding against this patent. It is, however, useful confirmation that the "Kimura" reference has a documented track record of being applied as prior art.

Assignees of record: originally Konishioku Photo Industry Co., Ltd., reassigned to Konica Corporation effective 1987-10-21 (recorded 1989-09-22), with the current-assignee field listing Konica Minolta Inc. None of these entities has asserted this patent in an AIA forum.

Recommended next steps

If you are a defendant and the patent has claims invalidated: it does not, and that is not the argument to make. The correct and far cheaper argument is expiration.

• Do not file an IPR. A petition against US 4,558,326 would be dismissed as moot — the patent expired on 2003-09-06, and the Board does not cancel expired claims to grant a petitioner relief it already has. Filing would be a waste of fees and could invite a fee-shifting argument.
• Cite the expiration record. Anchor on the Google Patents legal-status entry ("Expired - Lifetime," anticipated expiration 2003-09-06) and the maintenance-fee history (12th-year FPAY paid 1997-05-29, with no lapse — the term was fully served, not prematurely abandoned). There is no FWD to link to, because there is none; link the expiration record instead: https://patents.google.com/patent/US4558326/en
• Rebuttal to any citation-based demand. If a plaintiff cites US 4,558,326 to argue your later ink-cartridge product infringes an unexpired patent's claims, US 4,558,326 is more likely to help you than hurt you — it is a 1983-priority printed publication whose purging-by-pressurized-cartridge disclosure is squarely § 102(b) art against many post-1985 claims. Brother's own US 7,144,104 had to distinguish "columns 11–13" of this patent to get its claims allowed.
• No trial-stage milestones to track. There is no pending proceeding, so no institution deadline, no oral hearing date, and no one-year FWD due date to diarize. The absence of PTAB activity is expected here and is not a signal that the patent is somehow robust — it is a signal that the patent has been dead for over two decades.

Caveat on sourcing. The structured ODP block is the canonical list and it is empty; my web searches corroborated empty. I could not access PTAB E2E or CLS-based litigation dockets directly within this session, so if the patent were somehow tied to a non-AIA, non-Midland proceeding (e.g., an ITC investigation or an ex parte reexamination request), that would not show up in an AIA-trial search and I have no evidence one exists. Treat the AIA-trial answer as firm and the "no other proceedings ever" answer as strongly supported but not exhaustively docket-verified.

I'll start by verifying what I can against live sources before reconstructing the chain.

Found the reel/frame numbers via INPADOC. Let me verify the reel/frame specifics and check for any litigation or NPE involvement.

I could not open the Assignment Center UI directly (it is a JavaScript/session application and my fetches did not return its records), so the reel/frame data below comes from the Espacenet INPADOC legal-status feed, which mirrors the USPTO assignment filings, cross-checked against the Google Patents legal-events block on the patent page. The correspondent-of-record field was not present in either reachable source, so I have left it as "not retrievable" rather than guessing. Treat every correspondent statement below as expressly unverified.

Inventors

Both men assigned "ASSIGNORS INTEREST" to Konishiroku by instrument executed 1983-09-02, four days before the 1983-09-06 US filing — a routine pre-filing employee assignment, not a symptom of anything.

Departure pattern: no evidence of either inventor departing within 12 months of filing. Circumstantially, a "Kimura" appears as sole inventor on later ink-jet patents in the same technical line (US4604633, "Ink-jet recording apparatus," 1986; US5155502, "Ink-jet cartridge," 1992), which is consistent with continued Konica employment — but I have not verified the assignee on those two, so this is background color, not a finding. No fire-sale precursor here.

Original assignee

Konishiroku Photo Industry Co., Ltd., 26-2, Nishishinjuku 1-chome, Shinjuku-ku, Tokyo, Japan — a corporation of Japan (address as recorded in reel 004171/0870).

• Line of business: photographic film, cameras, photographic processing equipment, photocopiers, fax machines and laser printers. It was the oldest Japanese camera maker (founded 1873 as a photographic-materials shop).
• Product embodying the claims: the patent is an ink-on-demand ink-jet purging architecture — a flexible ink bag inside a rigid, gas-pressurized cartridge shell. Konica did commercialize ink-jet/office-imaging hardware in this era, and the claimed architecture (pressurized bag-in-shell cartridge) is the approach later adopted across the industry, but I cannot confirm a specific shipping Konica product reading on these claims, so I decline to assert one.
• Current status: Konishiroku renamed itself Konica Corporation in 1987 (same corporate person, name change only). Konica then merged with Minolta on 2003-08-05 to form Konica Minolta Holdings, Inc., now Konica Minolta, Inc. No dissolution, no bankruptcy. Note: Google Patents renders the "Original Assignee" field as Konica Minolta Inc. — that is a normalization artifact of the successor name; the patent face and the 1983 assignment both say Konishiroku Photo Industry Co., Ltd.

Assignment timeline

Two recorded assignments, both corporate housekeeping. There is no third-party transfer of any kind.

• 1983-09-02 (executed) / recorded 1983-09-06 — Reel 004171/0870

  • Conveyance: Assignment ("ASSIGNMENT OF ASSIGNORS INTEREST")
  • Assignor: Kimura, Yoshiaki and Tanaka, Yasuhiko (jointly)
  • Assignee: Konishiroku Photo Industry Co., Ltd., No. 26-2, Nishishinjuku 1-chome, Shinjuku-ku, Tokyo, Japan, a corporation of Japan
  • Correspondent: not retrievable from the reachable sources. Not assumed.
  • Context: ordinary employee-to-employer invention assignment, executed immediately before the US filing — not an acquisition.

• 1987-10-21 (effective date) / recorded 1989-09-22 — Reel 005159/0302

  • Conveyance: recorded under the Assignment (AS) event code; the free-form text reads "RELEASED BY SECURED PARTY; ASSIGNOR: KONISAIROKU PHOTO INDUSTRY CO., LTD." — i.e. a release/name-change filing in favour of the successor, not an arm's-length transfer
  • Assignor: Konisairoku [sic] Photo Industry Co., Ltd. (the misspelling is as recorded; it is the same entity)
  • Assignee: Konica Corporation, Japan
  • Correspondent: not retrievable from the reachable sources. Not assumed.
  • Context: internal reorganisation / change of corporate name only. Two independent indicia support this: (i) Konishiroku formally adopted the Konica Corporation name in 1987, which matches the 1987-10-21 effective date precisely; and (ii) the identical reel/frame 005159/0302 is cited as the ownership record on unrelated Konishiroku cases such as US4618569 and US4449792 — a single portfolio-wide bulk recording covering the whole Konishiroku docket, exactly what a corporate rename produces and what a portfolio sale does not.

No further assignments of record. In particular, there is no recorded assignment to Konica Minolta; Konica Minolta's listed ownership is by corporate succession through the 2003 Konica–Minolta merger, not by a recorded instrument. Maintenance fees were paid at years 4 (1989-04-03), 8 (1993-05-26) and 12 (1997-05-29, FPAY), and the patent reached its anticipated expiration on 2003-09-06 — i.e. it ran to full term and has been expired for roughly 23 years.

Timeline diagram

timeline
    title Ownership of US 4558326
    1982 : Japan priority applications filed
    1983 : Inventors assign to Konishiroku Photo Industry
    1985 : US 4558326 issues
    1987 : Konishiroku renamed Konica Corporation
    1989 : Name change recorded reel 005159 0302
    2003 : Konica merges with Minolta
    2003 : Patent term expires

NPE / troll-pattern signals

1. Shell-entity transfer — not present. The only two assignees of record are Konishiroku Photo Industry Co., Ltd. and Konica Corporation, both large Japanese operating manufacturers (Konica employed ~4,935 people in 1987; ~17,319 in 2002). Neither is an LLC, neither has an "IP / Holdings / Ventures" name, and no registered-agent-service address appears (reels 004171/0870 and 005159/0302).

2. Known asserter in the chain — not present. Neither recorded assignee appears on any of the listed NPE rosters (Acacia, Marathon, IV, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Erich Spangenberg entities), and the chain never leaves Japanese corporate ownership.

3. Repeat correspondent across the chain — unclear. This is the one signal I genuinely cannot close out: the correspondent of record is not exposed in the INPADOC feed or the Google Patents legal-events block, and I could not reach the Assignment Center's record view to read it off reels 004171/0870 and 005159/0302. I am not going to infer a correspondent from thin air. Note that even if a single firm appears on both frames, that would be weak evidence here, because both frames are intra-corporate Japanese housekeeping filings, not transfers to unrelated parties.

4. Cascading transfers — not present. Two recorded instruments across forty years, separated by roughly four years (1983 → 1987), with no chained LLCs and no shared-principal pattern. Nowhere near the "multiple transfers in <24 months" threshold.

5. Pre-litigation transfer — not present. No assignment of record within 6 months of any suit, because there is no suit. See the litigation note below.

6. Bankruptcy fire-sale — not present. Konishiroku/Konica never filed Chapter 7 or 11. Konica merged with Minolta in 2003; Konica Minolta later exited the photo-imaging business (its digital SLR line went to Sony), but that 2006 transaction post-dates this patent's 2003-09-06 expiration, so no Kodak/Nortel/Polaroid-style asset sale could have swept this patent up.

7. Privateering — not present. No transfer to any third party at all, so no proxy asserter was armed. There is no SEC-disclosed or EFF/Patent Progress-reported transfer.

8. Defensive aggregator (anti-NPE) — not present. The chain terminates at Konica Minolta (operating company), not at RPX, AST, LOT Network, Unified Patents or OIN. The patent was neutralised by expiry, not by purchase into a defensive pool.

Litigation check: a search for infringement actions naming US4558326 returned only patent-family and citation references (e.g. the JP priority filings JP-A-59-59457 and the family member cited as prior art in EP 0921005 and EP 1466739) — no district-court or ITC case, and no RPX/Unified Patents asserter entry. I flag that as negative evidence from a search, not a certified PACER clearance.

Verdict

Insufficient data — read affirmatively: no NPE activity is evidenced, and none is possible now.

The entire recorded chain is two instruments: the inventors' pre-filing assignment to Konishiroku Photo Industry on reel 004171/0870 (executed 1983-09-02, recorded 1983-09-06), and a release/rename record into Konica Corporation on reel 005159/0302 (effective 1987-10-21, recorded 1989-09-22) that was filed portfolio-wide across the Konishiroku docket — the same reel/frame appears on unrelated Konishiroku patents such as US4618569 and US4449792. Zero of the eight NPE signals is present, the sole unresolved point is the un-retrievable correspondent field, and the patent expired 2003-09-06 after maintenance fees were paid through year 12, so it has been unassertable for over two decades. A "troll" verdict here would require a transfer that simply does not exist on the record.

Verification links: USPTO Assignment Center search (search patent number 4558326) · Google Patents legal events for US4558326 · Espacenet INPADOC legal status for US4558326

I'll research US patent 4558326 and its cited prior art references.

Let me verify the cited references and pull the front-page "References Cited" data.

Let me identify the second US reference on the front page (4,376,283) and check the German counterpart's search report.

Prior-Art Analysis: US 4,558,326 — “Purging system for ink jet recording apparatus”

Note on sources/method: I could not open a USPTO PatentCenter/PAIR page within my search budget; the citation data below is taken from the face of the patent itself (the printed "References Cited" block, read from the patentimages.uspto/Google-hosted copy of the granted document) cross-checked against Espacenet and Google Patents bibliographic records. I flag every place where a fact is unverified rather than inferred.

1. The patent being analyzed (literal identifiers as printed)

Claim scope that the prior art must be measured against:

• Claim 1 (method): purging step = selectively forcibly conducting a gas, during a non-recording period, by a gas pressurizing means, through at least one opening of the ink cartridge body and into the cartridge body, raising the internal pressure so that the yieldable portion of an ink container bag yields, pressurizing the ink so it flows into the head and purges bubbles; plus selectively opening that opening to atmosphere to prevent purging.
• Claim 2 (apparatus): closed-up substantially rigid cartridge body with at least one gas opening; pressurizing gas supply means; elastic cap coupled liquid-tight to the bag; means for selectively venting the opening.
• Claims 3–14 (dependent): air pump; pump + coupling means; pump + control valve; manual blower + coupling; heating chamber + coupling; liquefied gas; attachable/detachable coupling; separate gas-conduction and gas-exhaust openings; pressurizing means inside the cartridge; liquefied gas inside the cartridge; contractible/expandable pressure chamber with closeable air opening; claim 4 + control valve.

2. Prior art cited on the face of US 4,558,326 (the authoritative list)

The printed "References Cited" block contains four documents — two U.S. patents and two Japanese published applications:

⚠️ Database caveat: Some aggregator pages (e.g., Google Patents' automated "Patent Citations" block) attach US 4,170,016 and US 4,223,322 to this number. Those two documents appear as citations of a different, related Konishiroku patent (US 4,276,554, "Ink jet mechanism for purging and activating"), not of US 4,558,326. The face-of-patent list above (4 documents) is the controlling citation set. I note the discrepancy rather than silently reconciling it.

2.1 — U.S. 4,123,761 (Kimura et al.)

• Full citation: U.S. Patent 4,123,761, Method of purging ink passages of an ink jet recording device, inventors Yoshitaki Kimura, Masanori Kawai, Takashi Hatano; assignee Konishiroku Photo Industry Co., Ltd.; Appl. No. 802,673, filed Jun. 2, 1977; JP priority Jun. 7, 1976 (51-66894); patented Oct. 31, 1978; 14 claims. (DE 2,725,761 A1, publ. Dec. 15, 1977, is the German counterpart.)
• Brief description: Purging of a drop-on-demand (Kyser-type, U.S. 3,946,398) printhead by applying purge pressure to the ink in an ink supply source, holding an automatic valve wide open, and establishing a one-directional ink flow toward the orifice to carry bubbles and impurities out — optionally combined with a suction means at the nozzle face (including relative positioning of suction-tube edge to the nozzle face, FIG. 7/8). One embodiment (FIG. 3) uses an elastic balloon as the ink supply source.
• Prior-art status: Printed/patented Oct. 31, 1978 — well before both the Sep. 7, 1982 JP priority and the Sep. 6, 1983 U.S. filing → pre-AIA § 102(b) art (and § 102(a) as to the filing date). Same inventor and same assignee as US 4,558,326 (a self-citation; not "by another" for § 102(a)/(e) purposes, but fully available as a § 102(b) printed publication).
• Which claims it could potentially affect: It is the closest cited reference as to the purging step concept of claim 1 (forcing ink under pressure through pressure chambers/nozzles to expel bubbles) and as to the general environmental context of claim 2 (ink-on-demand head; pressure chamber; nozzles). However, it does not appear to disclose the structural core of claims 1–2: a rigid cartridge body with at least one gas opening, a flexible/yieldable ink container bag housed in it, gas pressurizing means conducting gas into the cartridge body, an elastic cap coupled liquid-tight to the bag, and selective venting of the opening to atmosphere. Pressure in 4,123,761 is applied to the ink itself in the supply source (elastic balloon / potential energy) — not to a gas space surrounding a bag. My assessment: not a § 102 anticipation of claim 1 or claim 2 as a whole; it is the principal § 103 (obviousness) reference.

2.2 — U.S. 4,376,283 (Kimura)

• Full citation (as verified): U.S. Patent 4,376,283, inventor Kimura, issued March 1983 (aggregators show "1983-03-15"; Google's automated table shows "1983-03-01"), U.S. classification 346/140 PD — the same class/subclass as reference #1 and as the field of search of US 4,558,326.
• Brief description: ⚠️ Unverified within my search budget. I retrieved the citation entry as printed on the face of US 4,558,326 (inventor/date/class only) but could not confirm this patent's title or disclosure. I will not guess it. The class (346/140 PD, drop-on-demand printheads) and the shared inventor indicate a closely related Konishiroku drop-on-demand ink-jet disclosure.
• Prior-art status: Its issue date (March 1983) falls between the earliest JP priority (Sep. 7, 1982) and the U.S. filing (Sep. 6, 1983). Its filing date is presumably earlier (unverified) and, if earlier than the applicant's invention date, it is potentially pre-AIA § 102(e) art based on its U.S. filing date. Because the named inventor appears to be the same individual (Kimura), a "by another" § 102(e) analysis, and any commonly-owned § 103(c) exception, would need to be checked against the actual inventive entity and chain of assignment. Which claims it could affect: cannot be mapped without verifying its disclosure — flagged as a research gap.
• Action item: If you need a definitive § 102 mapping for this reference, pull the US 4,376,283 front page and claims directly from USPTO PatentCenter/Google Patents.

2.3 — JP 55-53570 (Japanese O.P.I. Publication No. 53570/1980), April 1980

• Full citation: Japanese Patent Publication Open to Public Inspection (Kokai) No. 53570/1980 (cited in the body of US 4,558,326 as "Japanese Patent O.P.I. Publication No. 53570/1980 and the like"; listed as foreign patent document 55-53570, 4/1980).
• Brief description (per the patent's own characterization): A pressure chamber having an electrically driven pump is placed in the middle of the ink supply system between ink tank and recording head; the pump raises flow quantity/pressure and sends ink toward the nozzles to expel bubbles and foreign matter.
• Prior-art status: Published April 1980 — a foreign printed publication more than one year before the U.S. filing → pre-AIA § 102(a)/(b) art as to the U.S. filing date.
• Which claims: It is the reference the applicants themselves use to define prior-art technique (2) (see column 1 of the specification). It addresses pump-in-the-ink-line purging and therefore bears on the purging function recited in claim 1, but it discloses no gas pressurization of a rigid cartridge body surrounding a flexible bag, no elastic cap, and no selective venting. Not anticipatory of claims 1 or 2; relevant to the § 103 framing and to the "expensive liquid pump" problem the invention solves.

2.4 — JP 56-113464 (Japanese O.P.I. Publication No. 113464/1981), September 1981

• Full citation: Japanese O.P.I. Publication No. 113464/1981 (listed as foreign patent document 56-113464, 9/1981), cited in the specification as Japanese Patent O.P.I. Publication No. 113464/1981.
• Brief description (per the patent's own characterization): Prior-art technique (3) — a cap is placed closely over the nozzle points and the bubbles/foreign matter are sucked out with a suction pump from the nozzles.
• Prior-art status: Published September 1981 → foreign printed publication predating the filing; pre-AIA § 102(a)/(b) art as to the U.S. filing date.
• Which claims: Bears on the "purge the recording head from bubbles or the like along with the ink thereinside" functional language of claim 1 and on the venting/atmosphere-management concept, but it teaches the opposite mechanism (negative pressure at the nozzles) and contains no cartridge-gas-pressurization, no flexible-bag-in-rigid-body structure, and no elastic cap. Not anticipatory of claims 1 or 2. Note that claim 10 (separate gas-conduction and gas-exhaust openings) and claims 3–7 (pump/coupling/valve/blower/heating chamber) find no counterpart in this reference.

3. Family-level citations (NOT citations against US 4,558,326 — flagged separately)

The German counterpart DE 3332273 A1 (Konishiroku; publ. Mar. 8, 1984; same priority Sep. 7, 1982) belongs to the same INPADOC family (JP 59-45160, 59-48162, 59-54566, 59-59455, 59-59456, 59-59457; JP 57-156085 etc.). The "Family Cites Families" list surfaced from that family record includes JPS522780B2; JPS491287U; AT320304B; SE371901B; JPS51118511A; DE2610518C3; DE2704735C2. These are search-report/family-level documents, not the examiner's prior-art citations against US 4,558,326, and I have not verified their subject matter. Treat them as leads only.

Separately, Espacenet reports ~163 forward-citing documents ("Cited By") — this is subsequent art citing US 4,558,326 (earliest: US 4,516,134, May 7, 1985), which is not prior art to it and is outside the scope of your request.

4. Bottom line

1. The complete face-of-patent prior-art list for US 4,558,326 is four documents: U.S. 4,123,761; U.S. 4,376,283; JP 55-53570 (4/1980); JP 56-113464 (9/1981).
2. No cited reference appears to be a clean § 102 anticipation of independent claim 1 or independent claim 2. Each lacks at least one element of the claimed combination — critically, the gas pressurization of a closed rigid cartridge body housing a flexible ink container bag, plus the selective opening of that body to atmosphere to inhibit purging. The cited art instead purges either by pressurizing ink in the supply source (US 4,123,761), by an in-line liquid pump (JP 55-53570), or by suction at the nozzles (JP 56-113464).
3. U.S. 4,123,761 is the strongest reference and is best characterized as a § 103 reference (same inventor, same assignee, same purge objective, different pressure-application mechanism); it is also § 102(b) art as of Oct. 31, 1978.
4. Open verification gaps (stated explicitly rather than guessed): (a) the title and disclosure of U.S. 4,376,283, and hence whether it can be asserted under § 102(e) and against which claims; (b) whether the inventive entity of U.S. 4,376,283 is identical to that of US 4,558,326 (affects "by another" and § 103(c) analyses); (c) the disclosure content of the two JP Kokai documents, which I have characterized only as the patent itself characterizes them, not from the primary Japanese texts.
5. Dependent-claim note: Claims 8 and 12 (liquefied gas as pressurizing means), 6 (manual blower), 7 (heating chamber), and 10 (separate conduction/exhaust openings) recite subject matter that does not appear in any of the four cited documents, so the cited art does not reach them even on a § 103 theory without additional references.

Primary grounding URLs: https://patents.google.com/patent/US4558326/en ; https://patentimages.storage.googleapis.com/ee/2b/c7/69afdc3c55218e/US4558326.pdf (face-page "References Cited"); https://patents.searchlight.law/doc/US4558326 ; https://be.espacenet.com/publicationDetails/inpadocPatentFamily?CC=US&date=19851210&NR=[4558326A](/patent/4558326A)&KC=A&FT=D&DB=EPODOC ; https://patentimages.storage.googleapis.com/6f/93/b2/78403fef64d45a/US4123761.pdf ; https://patentimages.storage.googleapis.com/1b/ea/ba/5b7d45d893a53c/US4223322.pdf.

I'll ground this analysis in the actual record before reasoning — pulling the claim set and verifying the two Japanese prior-art publications named in the description.

I now have the full claim set and the cite list. Let me verify the two U.S. references cited on the face of the patent, since they materially affect the §103 analysis.

Obviousness Analysis — U.S. Patent 4,558,326 (35 U.S.C. § 103)

0. Record basis, and what I could and could not verify

Patent under analysis: U.S. 4,558,326, "Purging system for ink jet recording apparatus," Kimura et al., filed 1983-09-06, JP priority 1982-09-07 through 1982-09-29, granted 1985-12-10, expired 2003-09-06. Source: https://patents.google.com/patent/[US4558326A](/patent/US4558326A)/en (PDF: https://patentimages.storage.googleapis.com/ee/2b/c7/69afdc3c55218e/[US4558326](/patent/US4558326).pdf).

Claim set (verified, 14 claims): https://www.sumobrain.com/patents/us/Purging-system-ink-jet-recording/4558326.html and https://be.espacenet.com/publicationDetails/claims?CC=US&NR=[4558326A](/patent/4558326A)

References cited on the face of the patent (the "Prior Art" record you asked me to use):

Critical date / legal framework. Filed 1983-09-06, so pre-AIA § 103 governs. Both Japanese publications are more than one year before the filing date and are therefore § 102(b) statutory bars. US 4,123,761 (1978) is likewise a § 102(b) bar. US 4,376,283 issued 1983-03-08 — less than one year before the filing date and after the earliest JP priority date of 1982-09-07; its status as § 102(a)/(e) art in the U.S. turns on facts (its U.S. filing date, and whether the applicants could antedate it) that I have not verified. I therefore do not rest any conclusion on it.

1. The claim set, and why the preamble admissions matter

• Claim 1 — method: selectively forcing gas through the cartridge body's opening during a non-recording period to raise pressure inside the cartridge body, causing a yieldable portion of the ink bag to yield, pressurizing the bagged ink so it flows to the head and purges bubbles; and selectively opening the opening to atmosphere to prevent purging.
• Claim 2 — apparatus in Jepson ("the improvement comprising") format: admitted preamble = ink-on-demand head + ink cartridge of an ink container bag having a flexible portion housed in an ink cartridge body; improvement = closed-up substantially rigid body with a gas opening, pressurizing gas supply means, elastic cap in liquid-tight coupling, and means for selectively venting.
• Dependent claims — 3 air pump; 4 air pump + coupling; 5 air pump + control valve; 6 manual blower + coupling; 7 heating chamber + coupling; 8 liquefied gas; 9 attachable/detachable coupling to the opening; 10 two separate openings (gas in, gas out); 11 pressurizing means inside the cartridge; 12 that means = liquefied gas; 13 that means = contractible/expandable pressure chamber with closeable air opening; 14 = claim 4 + control valve.

Two admissions in the specification are decisive to the § 103 posture:

1. The specification states that "as the ink supply means … there is usually used an airtight ink cartridge … comprised of a highly hermetically sealed bag or container containing ink … provided attachably and detachably in a cartridge receiving position." That is the claim 2 preamble, admitted.
2. It states the cartridge body "is of a closed-up structure except for the vent hole 7, and usually … air freely flows through the vent hole in and out of the cartridge body." That is claim 1's "selectively opening said at least one opening … to the atmosphere to prevent a purging operation," admitted.

The claims' only genuine point of novelty is therefore narrow: using the gas headspace between bag and rigid body as the pressure-transmitting medium for a purge, plus specific choices of pressure source. Everything else in claim 2 is conceded.

2. The core combination — claims 1, 2, 9, 10 (and 3–5, 14)

Combination A: US 4,123,761 (primary) + admitted flexible-bag cartridge (secondary) + JP 55-53570.

What each provides. US 4,123,761 supplies every functional element of the purge method except the gas: purging by elevating supply pressure, valve control, unidirectional flow from supply toward the orifice, and performance "at least upon purging operations" (i.e., outside normal recording). JP 55-53570 supplies an electrically driven pump in the ink supply path to expel bubbles, with a control valve and a separate suction pump for the expelled ink — i.e., the "purge by pump pressure" approach the patent itself identifies as prior art. The admitted cartridge supplies the rigid body, the flexible bag, the opening, the normally-open vent, and the detachable mounting.

Motivation to combine — supplied by the applicant's own problem statement. The specification identifies exactly three deficiencies in the art:

• mechanical squeezing of the tank "is lacking in the pressure accuracy as well as in the pressure stability … it is difficult to apply a given constant pressure regardless of the residual quantity of the ink in the tank";
• the in-line pressure pump "requires an expensive pump for liquid use, so that it becomes a problem in respect of cost";
• nozzle suction "requires a complex and expensive apparatus and also requires a high accuracy due to the mutual relation between the sucking rate and the ink supply rate."

Recited problem (i) is a direct, explicit teaching to a POSITA to pressurize in a way that is independent of ink volume. Applying a gas pressure to the outside of a conformable bag is the textbook answer to that problem, and it simultaneously answers (ii) because an ordinary air pump/blower replaces a liquid-handling pump, and (iii) because no capping/suction apparatus is needed to expel ink (the prior art already taught capturing the expelled ink — US 4,123,761 claim 14; JP 55-53570's suction pump; JP 56-113464's cap-and-suck).

Predictability. The claimed advantages (a) constant pressure regardless of residual ink, (c) uniform pressure on the ink, and (d) no localized over-force that could rupture the bag are not unexpected results — they are the direct, predictable consequence of applying a uniform gas pressure to a conformable container (Pascal's principle plus a flexible membrane). No new mechanism, timing sequence, or material is required. The claim 2 "means for selectively venting" is satisfied by the admitted vent hole; "substantially rigid body" by the admitted cartridge body; the "elastic cap" by the admitted cap 8/connector 9 structure described as prior art in FIG. 1.

Rationale category. This is the paradigm "combination of known elements according to known methods yielding predictable results," reinforced by "simple substitution of one known pressurizing element (gas source) for another (mechanical squeeze or liquid pump)" and "use of a known technique (gas-pressurizing a collapsible liquid container) to improve a similar device in the same way."

Dependent claims. Claim 3 (air pump) — commodity fluid-handling selection; JP 55-53570 already shows a pump plus valves in a purge circuit. Claim 4/5/14 (coupling means; control valve) — the art shows both (the patent's own FIG. 1 coupling 14 and O-ring 17, and JP 55-53570's valves 5/12). Claim 9 (attachable/detachable coupling) — compelled by the admitted detachable cartridge. Claim 10 (two separate openings) — an obvious design choice once gas flow through the headspace is contemplated; it converts a fill-and-vent cycle into a flow-through purge, and the reference of record already uses separate supply and discharge paths (JP 55-53570, ink supply passage vs. ink discharge passage).

Assessment: claims 1, 2, 3, 4, 5, 9, 10, 14 all appear obvious over Combination A, with claims 3–5, 9, 10, 14 additionally obvious as mere design selections.

3. Second-tier claims — 6, 7, 8

• Claim 6 (manual blower + coupling). Substitution of a hand-squeezed elastic bulb for the air pump. Squeeze-bulb dispensing is notoriously old and well known in fluid handling (atomizer bulbs, priming bulbs, blood-pressure bulbs). The specification's own justification — "effectively used for recording apparatus of which the purge operation can be made sufficiently with a relatively small pressure" — recites the reason to make the substitution, i.e., motive. Likely obvious over Combination A in view of that general knowledge.
• Claim 7 (heating chamber + coupling). Raising pressure in a sealed gas volume by heating is elementary physics. The motivation (eliminate the pump and any electrically operated valve; simpler structure, easier maintenance) is stated in the specification and is a recognized cost/simplicity trade-off. Heat-resistant materials are a routine engineering constraint, not an inventive contribution. Likely obvious, though the prior art of record does not show heating used as a purge pressure source, so the examiner's allowance is more understandable here.
• Claim 8 (liquefied gas). Using a liquefied propellant (butane, propane, CO₂, halogenated hydrocarbons — all recited in the specification) to pressurize a container is the classic aerosol/bag-on-valve technology. Substituting a self-pressurizing propellant for a pump is a known substitution for a known purpose with a predictable benefit (high pressure available instantly, no pump). Likely obvious over Combination A plus analogous dispensing art — the strongest such art being bag-in-can/aerosol dispensing, which is reasonably pertinent to the problem of expelling liquid from a collapsible inner container.

4. Third-tier claims — 11, 12, 13 (pressurizer inside the cartridge)

These are the patent's most defensible claims, because the prior art of record locates all pressurizing/sucking hardware on the apparatus side (JP 55-53570's pumps and valves; JP 56-113464's suction pump; the specification's own coupling means 14/72).

Still, the § 103 case is strong on design-choice/self-containment reasoning: the admitted art already makes the cartridge attachably and detachably interchangeable, and it is a recognized design objective to make a consumable more self-contained so the apparatus needs no plumbing, coupling, or sealing (the specification itself argues "(e) the structure is so simple that the operation can be made without fail" and "(f) the overall cost can be reduced"). Placing the pressurizer inside the replaceable cartridge is the natural way to achieve that goal. Claim 12 (internal liquefied gas) and claim 13 (internal contractible/expandable chamber with a closeable air opening) are then the same two substitutions already addressed in § 3, merely relocated — claim 13 in particular is a bellows/squeeze-chamber, i.e., claim 6's manual blower mounted on the cartridge body, which is exactly how the specification's FIG. 13–14 embodiments are described.

Assessment: claims 11–13 are obvious but contestable; they would likely survive on the record as it stands (no cited reference shows an on-cartridge pressurizer) and fall only with additional analogous art showing self-pressurizing or self-contained dispensers.

5. The best non-obviousness arguments, and the rebuttals

1. "All prior art purging acted on the ink, not on the gas around the ink." True of the four cited references. Rebuttal: the claim does not require any new purge physics; it requires a known purge function performed with a known pressurizing technique (gas on a collapsible container), and the applicant's own stated problem — constant pressure independent of residual ink — supplies the reason to move the pressure application point from the liquid to the gas. Under the TSM-era standard then controlling (and equally under the predictable-results line), an explicit problem statement in the specification is itself evidence of the direction of the art.
2. "The references are non-analogous / different purge philosophies (suction at the nozzles vs. pressure at the tank)." Rebuttal: US 4,123,761 expressly combines pressure-side purging with suction at the orifice in one document (claim 14), and JP 55-53570 combines a pressure pump with a suction pump — the two "philosophies" are the same field of endeavour, and the references are from the same small community of ink-jet purge developers.
3. "Unexpected results: no rupture, uniform pressure." Rebuttal: these are the inherent, predictable consequences of uniform gas pressure on a flexible membrane, and the specification offers no comparative test data against the mechanical-squeeze or liquid-pump approaches. Attorney argument reciting advantages (a)–(f) is not evidence of unexpected results.
4. Common ownership / same inventors. US 4,123,761 and US 4,376,283 are the same inventors'/assignee's earlier work. That does not remove them as § 102(b) art (US 4,123,761), but it is relevant background colour: the patentee's own prior development had already taught pressure-side purging, so the increment here is a pressurizing-medium substitution.

6. Secondary considerations (Graham factor 4)

Nothing in the record supports a non-obviousness finding. The patent contains no comparative data, no evidence of commercial success, no evidence of copying, no evidence of failure of others, and no evidence of a long-felt-but-unmet need framed around the claimed gas-pressurization feature. The only "evidence" is the specification's list of advantages, which are (a) legal argument and (b) largely inherent in the structure. If a challenger were to develop evidence that the industry continued to suffer ink-level-dependent purge pressure, that could cut the other way — but that is not in this record.

7. Bottom line

Overall: the strongest single-line attack is US 4,123,761 in view of JP 55-53570 and the applicant's admitted vented flexible-bag cartridge, optionally further in view of JP 56-113464 and analogous bag-in-can/aerosol dispensing art. The claimed subject matter largely consists of known purge function + known cartridge structure + a known pressurizing technique, combined to produce results the specification itself describes as the goal rather than as a surprise. The claims most likely to withstand a § 103 challenge on this record are 7 and 11–13, and they would be vulnerable to additional analogous art not cited on the face of the patent.

8. Explicit caveats

• This is a retrospective/hypothetical analysis: the patent expired 2003-09-06.
• I was unable to retrieve the substantive disclosure of JP 56-113464 and US 4,376,283 in this session. I relied, for JP 56-113464, on the characterization given in the patent's own "Prior Art" section; for US 4,376,283 I relied only on its identifying data, and I have not treated it as supplying any teaching. Any conclusion resting on those two documents should be re-verified against their full texts.
• I did not review the file history or any reexamination/validity proceeding for US 4,558,326, so I cannot confirm what the examiner considered or why the claims were allowed. The pre-AIA TSM framework would have governed at allowance, which is a materially stricter framework for a "substitution" rationale than post-KSR practice.
• No representation is made about the validity or infringement of any claim; this is a technical obviousness assessment, not a legal opinion.