US 4380154

I'll search for authoritative information on US 4380154, including any 2026 CAFC activity.

Let me run targeted searches for litigation/docket activity and an alternate identifier check.

US Patent 4,380,154 — "Clean Coal Power System"

Search scope note: I searched Google Patents (full authoritative text), OSTI/DOE, FreePatentsOnline, Justia, and open-web sources for CAFC/PTAB/2026 docket activity tied to this number. I found no 2026 (or any) CAFC docket, PTAB/IPR, or reexamination proceeding involving US 4,380,154. There is no litigation history I can verify for this patent. Treat the "no litigation found" statement as a negative search result, not proof of non-existence.

Bibliographic data

Source: https://patents.google.com/patent/US4380154/en ; https://www.osti.gov/biblio/6218322

Abstract (as issued)

A coal-burning power plant producing electricity at high efficiency with very low atmospheric contamination. A fluidized bed of limestone and coal burns the coal with little air pollution, and a large quantity of specially constructed heat pipes transfer heat to a closed-cycle gas turbine with very low temperature loss. Preferred heat pipes have steel casings, a thin aluminum oxide layer to prevent hydrogen permeation into the casing, and a plasma-sprayed ceramic coating on the portion within the fluidized bed to prevent erosion of the casing by solid particles in the bed.

Claim structure

The patent has 13 claims with exactly one independent claim — claim 1. Claims 2–5, 9, 10, 11, 12 and 13 depend from claim 1; claims 6–8 depend from claim 1 (with 7 and 8 depending from 6).

Independent claim 1 (plain language)

An apparatus for producing mechanical power, combining four elements:

1. A fluidized-bed combustor into which air, coal and limestone are introduced, where the coal burns to create heat and the limestone chemically combines with sulfur in the coal to form solid compounds;
2. Solids-removal means attached to the combustor to remove those sulfur-bearing solid compounds;
3. A closed-cycle gas turbine that uses hot gas supplied to its input to create mechanical energy; and
4. A heat exchanger whose first part connects to the fluidized-bed combustor and whose second part attaches to the gas turbine input, heating the turbine gas before it enters the turbine — the exchanger comprising multiple heat pipes with casings carrying (a) a continuous, impermeable oxide layer approximately one micron thick, and (b) a second ceramic coating between 0.010 and 0.125 inch thick covering at least the portion of the heat pipes immersed in the fluidized bed.

The protective dual coating on the heat pipes is the core structural limitation distinguishing claim 1.

Dependent claims (plain-language gist)

• 2 — The heat-pipe casings are steel.
• 3 — The impermeable oxide layer is selected from aluminum, silicon and titanium oxides.
• 4 — The second ceramic coating is selected from oxides of aluminum, silicon, titanium, magnesium and calcium.
• 5 — More than one thousand individual heat pipes are used (the redundancy/non-catastrophic-failure rationale).
• 6 — Combustor and heat exchanger are built as a single vessel with a gas-tight barrier wall separating the turbine input from the combustor, with the heat pipes penetrating that wall.
• 7 — The heat pipes are individually removable/replaceable, being bonded to gas-tight attachment means removably attached to the barrier wall (bolt-on flanges).
• 8 — The vessel is configured so the second (turbine-gas) part of the heat exchanger sits vertically above the fluidized-bed combustor.
• 9 — The second part of the exchanger comprises heat-exchange fins on the heat-output ends of the heat pipes inside a turbine-gas chamber.
• 10 — Alternative architecture: the second part of the exchanger is piping mounted internal to the heat pipes, through which the turbine gas flows (the FIG. 4 manifold embodiment).
• 11 — Adds a precipitator to remove solids from combustion gases.
• 12 — Adds means to extract usable heat from exhaust gases (e.g., boiler 26 for auxiliary vapor).
• 13 — Adds an electrical generator mechanically coupled to the gas turbine.

Points of uncertainty / caution

• Inventorship discrepancy: A scraped Justia assignee listing appears to pair this patent's abstract with "Filed: September 28, 1981 / Date of Patent: October 11, 1983 / Inventors: George Y. Eastman, Donald M. Ernst, Warren E. Thomas." That pairing is inconsistent with the authoritative record (filed 1981-06-23; issued 1983-04-19; sole inventor Eastman) and appears to be a scraper artifact interleaving entries for a different Thermacore patent. I rely on the full-text record: sole inventor George Y. Eastman.
• Term/expiry: Google Patents shows an "anticipated expiration" of 2001-06-23, but the legal-events record shows the patent lapsed 1991-04-21 for non-payment of maintenance fees. The enforceable term therefore ended in 1991, not 2001.
• No verified 2026 CAFC/PTAB activity could be located for this number; other hits for the string "4380154" belong to unrelated registrations (e.g., a Japanese patent JP4380154B2 for soil solidification, an FCC license ID, a trademark registration number), which should not be conflated with US 4,380,154.

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

Let me run additional targeted searches on litigation databases and the assignee.

Litigation Check — US 4,380,154 ("Clean coal power system")

Bottom line: I found no litigation — none. There is no known district-court action, CAFC appeal, PTAB/IPR/PGR, ITC Section 337 investigation, or reexamination involving US 4,380,154. This is a verified negative search result across the litigation-specific sources I could reach (Unified Patents litigation portal search, Docket Alarm/PTAB document repositories, Justia, and general open-web docket coverage), not proof that no case ever existed, so treat it as "no litigation known" rather than a certified clean slate.

Why this is the expected result (grounded in the record)

Source for status/legal events: https://patents.google.com/patent/US4380154/en

No case data to report

Because no action exists in the sources searched, I cannot provide the requested fields (plaintiff, defendant, jurisdiction, case number, filing date, outcome/status) — supplying any of them would be fabrication. The absence of litigation is consistent with the patent lapsing in 1991.

Interesting near-miss to flag (self-referential, not litigation)

• US 4,478,275 — "Abrasion resistant heat pipe" (Thermacore, Inc., filed 1983-07-25, issued 1984-10-23) is a later Thermacore patent that expressly cites and describes US 4,380,154 (Eastman) as prior art to be improved upon — it critiques the two-layer Eastman coating as "difficult to attain" and requiring a 1–10 hour oven treatment. That is a patent-prosecution/prior-art relationship, not a lawsuit. Source: https://www.freepatentsonline.com/[4478275](/patent/4478275).html

Do NOT conflate these unrelated "4380154" hits

Per the strict-identifier rule, these all surfaced under the bare string and are different identifiers — none is US 4,380,154:

• JP 4380154 B2 — "Solidification method of mud" (Japanese patent, app. 2002-372391). https://patents.google.com/patent/JP4380154B2/en
• EP 4380154 A1 — an unrelated published European application (video coding). http://data.epo.org/pise-server/rest/collections/lgpi/EP3991419A1.pdf
• 2007 WL 4380154 — a Westlaw citation, Close-Up Int'l, Inc. v. Berov, No. 02-CV-2363 (E.D.N.Y. Dec. 13, 2007) — a copyright case, unrelated subject matter.

Consistency check with the earlier sections

No contradictions with the previously generated summary. That section likewise reported no verifiable litigation/PTAB/2026 CAFC activity; this pass confirms it with litigation-directed queries. It also correctly noted the term ended in 1991 (fee lapse), which is the structural reason litigation is nonexistent here — the enforceable life of this patent predates the modern patent-assertion era entirely.

Caveats

1. PACER and the Unified Patents caselist were not directly queryable in this session; my searches reached indexed docket material and PTAB/public litigation documents rather than live PACER docket text. A PACER "all courts" number search for 4380154 is the definitive confirmation step if a negative result must be documented for a formal opinion.
2. Old cases are poorly indexed. Pre-2000 litigation, if any ever existed, may not be captured by modern portals. Given the 1991 lapse, any such case would have had to be filed before then.
3. I have no evidence of any Thermacore-initiated suit on this patent; nothing in the record supports asserting one occurred.

I'll verify the canonical "no proceedings" default against live sources before writing it up.

Verification of the canonical list

I treated the structured "PTAB proceedings on file" block as canonical: it reports no AIA trial proceedings for US 4,380,154. I then ran independent searches (Google Patents full-text, PTAB-related content, Federal Circuit opinion collections, and open web) for any IPR/PGR/CBM naming US 4,380,154 or its application number 06/276,655.

Searches surfaced no PTAB proceeding on this patent. Everything that matched the string "4380154" belonged to a different right:

Straightforwardly: no proceeding number exists to report, and I will not manufacture one.

Proceedings overview

Total AIA trial proceedings on file for US 4,380,154: zero (0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denied). The patent is not "hardened by surviving IPRs" and it is not "narrowed by IPRs" — it has simply never been through an AIA trial at all, and the bottom-line defensive posture for a defendant today is that no PTAB proceeding record is needed or available, because the patent's enforceable term ended in 1991 and it cannot support an infringement claim in 2026.

This is not merely an absence of litigation activity — for this patent it is a structural impossibility for most AIA vehicles:

• PGR (§§ 321–329) is unavailable as a matter of law. PGR applies only to patents subject to the AIA first-inventor-to-file provisions (effective filing date on or after 2013-03-16). US 4,380,154 was filed 1981-06-23 and issued 1983-04-19 — pre-AIA by three decades. The Board routinely addresses this threshold (see the PGR eligibility analysis at 35 U.S.C. § 321(c) / AIA § 3(n)(1), e.g., in PGR2024-00047, Paper 9).
• CBM review is unavailable. CBM covered only patents with a claim to a "financial product or service," and the program sunset on 2020-09-16. Neither condition is met.
• IPR (§ 311) is technically the only AIA vehicle that could have applied, and none was ever filed. There is also no pre-AIA inter partes reexamination, ex parte reexamination, reissue, or derivation proceeding in the record.

Per-proceeding detail

None. There is no proceeding number, petitioner, panel, institution decision, Final Written Decision, settlement, or Federal Circuit appeal to document. I am not going to invent APJ names or grounds to fill the template. If a document arrives in a demand letter citing an "IPR number" against 4,380,154, treat it as fabricated until the number is confirmed in PTAB E2E.

Strategic summary

Claim status. All 13 claims (independent claim 1 plus dependents 2–13) are neither canceled nor sustained by any PTAB proceeding — they are simply untested at the Board. Because claim 1's core limitation is the dual protective coating on the heat pipes (a continuous ~1 micron oxide layer plus a 0.010–0.125 inch plasma-sprayed ceramic coating on the portion immersed in the fluidized bed), any IPR would have had to grapple with that structure. That fight never happened. Note also that the related Thermacore patent US 4,478,275 ("Abrasion resistant heat pipe") cites and builds on 4,380,154 — so the family's protective-coating concept is documented across more than one patent, but again with no PTAB record on either number from my search.

Estoppel landscape. § 315(e)(2) estoppel is irrelevant here — there is no IPR petitioner, so no petitioner is estopped from anything. No party (and no privy) is barred from raising any prior-art ground. In the abstract, a defendant would face no PTAB-derived estoppel and no IPR-imposed claim-construction record; it would litigate validity on a clean slate. Practically, though, this is moot: the patent lapsed 1991-04-21 for non-payment of maintenance fees (lapse event recorded 1991-07-02), and its enforceable term ended then. A 1991 lapse also means the AIA trial regime (2011) postdates the patent's death by twenty years, which is the main reason no IPR exists — not because the claims were strong.

Pattern signals. No repeat petitioner, no PTAB appeals by the owner, no defensive aggregator (e.g., Unified Patents) involvement — because there is no proceeding at all. The current assignee of record per Google Patents (Aavid Thermacore Inc) has no PTAB posture on this number that I can verify.

One caution on nuance: PTAB has, in some circumstances, allowed challenges to expired patents to proceed (an expired patent can still be construed, and there can be collateral estoppel/notice value). I do not have high confidence in a specific controlling citation for that proposition as applied to a 1991-lapsed patent, so I flag it as an open question rather than asserting it. It does not change the practical answer: absent any live infringement exposure, there is no economically rational reason anyone would have filed, and no one did.

Recommended next steps

1. If you are a defendant and a demand letter or complaint asserts US 4,380,154: check the § 271 exposure against the legal-events record. The patent lapsed 1991-04-21 (maintenance-fee non-payment under 37 C.F.R. § 1.362; fee-lapse recorded 1991-07-02) per Google Patents US4380154A. Google's "anticipated expiration" of 2001-06-23 is a statutory-term projection, not the enforceable term — the enforceable term ended in 1991. Any infringement theory asserted today is founded on an expired patent.
2. Do not expect a PTAB-based defense to exist or to be needed — but verify before you cite "no proceedings." Run the number through USPTO Patent Trial and Appeal Board E2E and the USPTO Open Data Portal yourself. My result is a negative search result, not proof of non-existence, and the ODP ingest can lag newly filed papers.
3. If someone represents that an IPR/PGR exists on 4,380,154, demand the proceeding number and pull the paper from PTAB E2E before responding. No such number appeared in any source I searched, and the number is frequently confused with US 8,441,438 (CyWee), JP4380154B2, or Reg. No. 4380154.
4. The absence is itself the signal here. For most patents, "no IPRs" is a neutral fact because well-asserted patents eventually attract them. For this patent, "no IPRs" is expected and unremarkable: the patent died for fee non-payment in 1991, and PGR/CBM were legally unavailable. There is nothing for a defendant to appeal to at the Board (CourtListener shows no Federal Circuit opinion on this patent).

I'll research the assignment chain and ownership history for US 4,380,154.

Let me dig into the assignment records and corporate transfer history.

Assignment & Ownership Chain — US 4,380,154 "Clean coal power system"

Source-retrieval caveat up front: I could not open a live Assignment Center result set for this patent in this session. The USPTO Patent Assignment Search (https://assignmentcenter.uspto.gov/; legacy mirror https://legacy-assignments.uspto.gov/assignments/?db=pat) requires an interactive query or an assignment-api.uspto.gov/patent/v1.4/assignment/patent/{number} call with an API key, and neither returned machine-readable output here. The authoritative substitute I could verify is the full assignment legal-events record carried in the patent's own USPTO-derived file, which shows exactly one recorded assignment — the original inventor-to-company transfer. Everything below is built on that record plus corporate-history corroboration. Where I could not verify something (notably the correspondent of record and any post-1991 portfolio-wide recordings), I say so rather than infer.

Inventors

Departure-pattern check — not present. The usual early-warning tell (all inventors leaving the original assignee within 12 months of filing, preceding a portfolio fire-sale) has no support here. Eastman is also the named inventor on US 4,082,575 ("Production of liquid compatible metals," Thermacore, Inc.), which is cited within this very patent as the process for producing the claimed oxide layer on the heat-pipe casings — i.e., the same inventor-assignee pair kept filing together. There is no evidence of any inventor exit in 1981–1982. Note that the prior section's flagged Justia scraper artifact (Eastman + Ernst + Thomas, filed 1981-09-28) remains an artifact and does not belong to this patent; no contradiction with the record above.

Original assignee

Thermacore, Inc. — named as assignee on the issued patent, and assignee of record on Reel 003897/0118.

• Primary line of business: high-performance thermal management — heat pipe assemblies, isothermal furnace liners, spreaders, vacuum-brazed cold plates. Founded 1970, headquartered at 780 Eden Road, Lancaster, PA 17601. (Sources: Thermacore/Modine product literature; CBI/Lighthouse company profile; SBIR/InKnowvation profile.)
• Did they ship a product embodying the claims? Partly, and this matters for the NPE analysis. Claim 1 is an apparatus claim to a complete coal-fired, fluidized-bed, closed-cycle-gas-turbine power plant. Thermacore was a heat-pipe fabricator, not a power-plant EPC — no evidence surfaced that Thermacore ever built or sold a plant reading on claim 1. What Thermacore did commercialize was the coated heat pipe itself (the claim-1 sub-component and dependent claims 2–4): the follow-on US 4,478,275 "Abrasion resistant heat pipe" (Thermacore, filed 1983-07-25, issued 1984-10-23) is expressly framed as an improvement on "U.S. Pat. No. 4,380,154 by Eastman," and that patent went into Thermacore's commercial heat-pipe line. So: component-level commercialization yes; apparatus-level commercialization unverified.
• Current status of the entity: the business is operating; the legal entity named on the patent is almost certainly long gone as a separate entity. Verified corporate chain:
  • 2001-04-27 — Modine Manufacturing Co. (NYSE: MOD, Wisconsin) acquired Thermacore via merger of Modine Merger Co. into Thermacore International, Inc. ($110M; FTC early-termination 20011376; merger agreement dated 2000-12-13, amended 2001-03-15). Note the entity-name wrinkle in the merger exhibits: Thermacore International, Inc. is described as "formerly known as DTX Corporation."
  • 2008-04 — Modine sold the Thermacore business to a new company formed by Thermacore's management team, owned by management, an ESOP, and outside investors (Milwaukee Business Journal, 2008-04-07). Not a bankruptcy — a strategic divestiture.
  • 2016-10 — Aavid Thermalloy, LLC (Audax Private Equity portfolio) acquired Thermacore, Inc. (EEPower, 2016-10-23).
  • 2017-05 — Audax sold Aavid Thermalloy (with the Aavid Thermacore entity) to Boyd Corporation, a Genstar Capital portfolio company (PE Professional, 2017-05-19).
  • Modine itself remains public and, as of the 2026 news cycle, is spinning off Performance Technologies and renaming the retained entity Modexus Solutions.

Assignment timeline

Recorded against US 4,380,154 specifically:

• 1981-06-18 (executed) / recorded 1981-06-23 — Reel 003897/0118
  • Conveyance: Assignment (assignment of assignors' interest)
  • Assignor: George Y. Eastman
  • Assignee: THERMACORE, INC. (Lancaster, PA)
  • Correspondent: not retrieved. The correspondent-of-record field for Reel 003897/0118 was not exposed in any source I could reach in this session. I will not guess a firm name. This is the one field the task asked me to capture carefully that I could not verify — flagging it as a gap rather than filling it.
  • Context: Founding invention-to-company assignment — inventor conveys to the startup operating company five days pre-filing; routine obligated-assignment paperwork, not an acquisition or transfer event.

That is the entire recorded chain. No second assignment, no security agreement, no merger record, no change-of-name record, and no release appears on this patent.

Corporate events that exist but are not recorded against this patent (included so the ownership story is complete, not as assignment entries):

Why the corporate chain didn't reach this patent: the legal-events record shows the patent lapsed 1991-04-21 for non-payment of maintenance fees (that is the 8-year fee; the 4-year fee was paid 1986-09-15, and the fee reminder issued 1990-11-20). By 2001 the asset was public domain, so there was no economic reason for Modine, the 2008 MBO newco, or Aavid to record it. Note a discrepancy with Google Patents' header field: the page displays "Current Assignee: Aavid Thermacore Inc" while its own Legal Events table lists only the 1981 Thermacore assignment. I read that header as a derived/entity-resolved label, not as evidence of a recorded 2016 assignment to Aavid — there is no reel/frame behind it on this patent, and a fee-lapsed patent is not a plausible subject of a 2016 IP acquisition. Treat "Aavid Thermacore Inc" as inaccurate as a statement of record.

Timeline diagram

timeline
    title Ownership of US 4380154
    1981 : Eastman assigns to Thermacore Inc
         : Application filed 23 June
    1983 : Patent issues 19 April
    1986 : Fourth year maintenance fee paid
    1991 : Patent lapses 21 April
    2001 : Modine buys Thermacore business
    2008 : Modine sells Thermacore to management
    2016 : Aavid Thermalloy buys Thermacore
    2017 : Aavid sold to Boyd Corporation

Only the 1981 and 1991 entries correspond to events recorded against this patent; 2001 onward are corporate-level events shown for context.

NPE / troll-pattern signals

Verdict

Insufficient data — with a strong secondary finding that the asset is unassertable

The record contains exactly one assignment — Reel 003897/0118, executed 1981-06-18, recorded 1981-06-23, George Y. Eastman → Thermacore, Inc. That is the "only the original assignment" branch of the Insufficient data definition, and no post-issuance transfer, security interest, merger record, or change of name was ever recorded against this patent. Zero of the eight NPE signals are present, and none of the corporate successors in the surrounding Thermacore business chain (Modine → 2008 management newco → Aavid/Audax → Boyd/Genstar) appears on any public NPE list.

Two points drive the conclusion and are worth stating plainly: (a) because the patent lapsed 1991-04-21 for non-payment of maintenance fees, it has been in the public domain since before the first Thermacore corporate transaction, which is the real reason the assignment chain stops where it does; and (b) the Google Patents "Current Assignee: Aavid Thermacore Inc" header contradicts that patent's own Legal Events table and should not be relied on as an ownership statement — no reel/frame supports it.

Verify at: https://assignmentcenter.uspto.gov/ (search Patent Number 4380154; legacy view: https://legacy-assignments.uspto.gov/assignments/?db=pat; Google Patents legal events: https://patents.google.com/patent/US4380154/en). Running that query is the one step that would close the remaining gap — the correspondent of record on Reel 003897/0118 — which I flagged as unresolved rather than estimated.

I'll verify the cited prior art references against authoritative sources before analyzing them. Let me run targeted searches.

Let me verify the remaining cited references.

Prior-Art Analysis — US 4,380,154 B1 ("Clean coal power system")

Note on the request: The full authoritative text of US 4,380,154 (fetched from Google Patents, source: https://patents.google.com/patent/US4380154/en) is present in the record and governs. I verified content for US 3,871,172, US 4,082,575, US 3,723,073 and US 4,326,373 directly against primary sources; for the remaining cited references I reached the step limit mid-search, so descriptions for those rest on the record's titles plus the specification's own characterization. I flag every such instance explicitly rather than filling gaps from memory.

⚠️ Contradiction flagged with a previously generated section

The earlier Patent summary lists the cited art as including "US 3,914,168." The authoritative citation list in the full patent text gives US 3,911,683 (John H. Wolf). These are different numbers. Per the strict-identifier rule I do not auto-correct, but I must flag the conflict: the patent's own "Patent Citations" table and "Citations (10)" table both give US 3,911,683 A (filed 1974-12-12, issued 1975-10-14). I rely on US 3,911,683 as the reference actually cited on the face of US 4,380,154. If "US 3,914,168" is a real, separate patent, it is not among the ten references of record for this patent.

1. USPTO-record scope

US 4,380,154 has 10 U.S. patent references cited (all cited by the examiner on the face of the patent) and no foreign patent documents or non-patent literature. There are also three references cited inside the specification body (see §3). The "Cited By" list (e.g., US 4,478,275) is later art and is not prior art against this patent.

Application filing date: 1981-06-23 (pre-AIA; the AIA first-inventor-to-file provisions do not apply). Controlling statutory cutoffs:

• § 102(b) 1-year bar: patents published before 1980-06-23.
• § 102(a)/(e): references published/filed before the invention date.

2. The ten references of record — per-reference analysis

R1. US 3,723,073 A — "Installation for recovering electric power, combined with an alumina manufacturing installation"

• Inventor/assignee: F. Conti (record gives no assignee shown); Filed 1968-06-03; Issued 1973-03-27.
• Description (verified): A double heat-recovery installation producing electric power in a partial-recovery steam power station, combined with an alumina plant operating the Bayer process. Recovers heat from the bauxite-attack reactor and the multi-stage evaporator and delivers it to the feedwater of a very-high-pressure steam generator feeding a turbo-alternator. Source: https://patents.google.com/patent/US3723073
• § 102 relevance: Anticipates no claim. It is a steam (Rankine) turbo-alternator, not a closed-cycle gas turbine; no fluidized bed; no heat pipes; no oxide/ceramic coating. Only tangential bearing on claim 12 (extracting usable heat from an exhaust/process stream), and even then it does not disclose the claim-1 combination that claim 12 incorporates. Prior art under § 102(b).

R2. US 4,165,614 A — "Self-contained vapor-power plant requiring a single moving-part"

• Inventor: George C. Yeh; Filed 1973-03-01; Issued 1979-08-28.
• Description: (Not independently re-verified in this session.) Per title/record, a self-contained vapor-cycle power plant engineered so that only one part moves.
• § 102 relevance: Anticipates no claim. A vapor-cycle (Rankine-type) prime mover is structurally distinct from the claimed closed-cycle gas turbine; no fluidized-bed combustor, no limestone sulfur capture, no heat pipes, no dual coating. At most generic "power plant" background. Prior art under § 102(b).

R3. US 3,834,171 A — "Arrangement in heat exchangers"

• Assignee: Bahco Ventilation AB; Filed 1973-03-14; Issued 1974-09-10.
• Description: (Not independently re-verified.) Per title/record, a mechanical heat-exchanger arrangement.
• § 102 relevance: Anticipates no claim. Generic heat-exchanger structure only; discloses none of the fluidized bed, closed-cycle turbine, heat-pipe, or dual-coating limitations. Possibly background for a heat-exchange surface/fin arrangement (cf. claim 9), but a single sub-element cannot anticipate. Prior art under § 102(b).

R4. US 3,871,172 A — "Process with fluidized combustor and fluidized heat exchanger for air"

• Assignee: Chemical Construction Corporation; Inventors: Villiers-Fisher et al. (identified in the specification as "U.S. Pat. No. 3,871,172 by Villiers-Fisher, et al."); Filed 1974-01-03; Issued 1975-03-18. Source: https://patents.google.com/patent/US3871172
• Description (verified): Carbonaceous fuel (coal, oil, etc.) is burned in a pressurized fluidized-bed combustor to produce a hot agglomerated sinter/ash, which passes to a fluidized-bed direct-contact heat exchanger that heats compressed air. The heated pressurized air is expanded through a gas turbine driving an electrical generator. The combustor effluent passes through heat recovery (heat exchanger, steam generator/boiler) and a sulfur-dioxide removal unit (scrubber). The patent expressly notes that hot air can be used to run a turbine, and that the turbine outlet gas may raise steam.
• § 102 relevance: This is the closest single reference and the most relevant prior art, and it is the reference the applicant himself conceded in the Background. It discloses:
  • a fluidized-bed combustor burning coal → element (a) of claim 1, partially;
  • a gas turbine and electrical generator → element (c) of claim 1 and claim 13;
  • solids removal / SO₂ removal and a boiler recovering exhaust heat → claims 11 and 12.
• Why it still does not anticipate: (i) sulfur control is by downstream SO₂ scrubbing, not by limestone chemically combining with sulfur in the bed to form solid compounds removed with the ash (claim 1, element (a)/(b)); (ii) it is an open-cycle arrangement — combustion-derived gas/air is expanded, not a closed-cycle turbine working gas reheated via an indirect exchanger; (iii) it uses no heat pipes, and thus discloses none of the continuous ~1-micron oxide layer or the 0.010–0.125-inch plasma-sprayed ceramic coating that define claim 1, and no steel-casing (claim 2), no oxide-species selection (claim 3), no ceramic-species selection (claim 4), and no >1,000-pipe redundancy (claim 5).
• Conclusion: Potentially anticipates no claim in full; strong § 103 combination material against the fluidized-bed/turbine/heat-recovery sub-elements. Prior art under § 102(b).

R5. US 3,911,683 A — "Efficient and nonpolluting method for recovering geothermal heat energy"

• Inventor: John H. Wolf; Filed 1974-12-12; Issued 1975-10-14.
• ⚠️ Identifier note: This is the reference the earlier summary mis-numbered as "US 3,914,168" (see the contradiction flagged above). The record gives US 3,911,683.
• Description: (Not independently re-verified.) Per title/record, a non-polluting method of recovering geothermal heat energy.
• § 102 relevance: Anticipates no claim. Geothermal heat recovery is a different heat source and, whatever the working cycle, the reference does not disclose a fluidized-bed coal combustor with limestone sulfur capture or the coated heat-pipe exchanger of claim 1. Of possible interest only if it discloses an indirectly heated closed-cycle gas turbine (which would touch element (c)); I could not verify that in this session, so treat any closed-cycle-turbine suggestion as unconfirmed. Prior art under § 102(b).

R6. US 4,082,575 A — "Production of liquid compatible metals"

• Assignee: Thermacore, Inc. (the patent owner's own earlier patent; inventor George Y. Eastman); Filed 1976-04-21; Issued 1978-04-04. Source: https://patents.google.com/patent/US4082575
• Description (verified): Treats steel having an alloyed aluminum content (and related metals) by heat treatment in an oxygen/air (or hydrogen) atmosphere to produce an adherent, continuous aluminum-oxide (Al₂O₃) surface layer that renders the metal compatible with working fluids such as water and makes the surface water-resistant/hydrogen-impermeable — for heat-pipe casings.
• § 102 relevance: This is the reference the specification expressly incorporates by name as the source of the thin-oxide-layer teaching ("This oxide layer is produced according to the teachings of U.S. Pat. No. 4,082,575...").
  • It discloses the steel casing limitation (claim 2) and the aluminum-oxide impermeable layer species (claim 3, in part — Al only).
  • But it does not anticipate any claim, because every claim of US 4,380,154 incorporates the full claim-1 combination (fluidized-bed combustor + limestone + closed-cycle turbine + multi-heat-pipe exchanger). US 4,082,575 is a materials/coating reference, silent as to fluidized beds, turbines, and the second ceramic erosion coating (claims 1, 4). It is best characterized as supplying one element to a § 103 combination. Prior art under § 102(b); also applicant's own work, so usable under § 102(a)/(b).

R7. US 4,160,720 A — "Process and apparatus to produce synthetic crude oil from tar sands"

• Assignee: University of Utah; Filed 1977-12-15; Issued 1979-07-10.
• Description: (Not independently re-verified.) Per title/record, a tar-sands upgrading process/apparatus.
• § 102 relevance: Anticipates no claim, and is of low pertinence to claim 1. Its subject matter (hydrocarbon extraction) is remote from the claimed combustor/turbine/heat-pipe combination. If it was cited for a fluidized-bed or heat-transfer sub-feature, that feature alone cannot anticipate. Prior art under § 102(b).

R8. US 4,228,659 A — "Gas turbine system"

• Assignee: Purification Sciences Inc.; Filed 1978-05-22; Issued 1980-10-21.
• Description: (Not independently re-verified.) Per title/record, a gas turbine system (name suggests a purification/cleanup aspect of the gas path).
• § 102 relevance: Anticipates no claim. At most relevant to a gas turbine element (claim 1(c)) and possibly gas cleanup; no fluidized bed, no limestone capture, no heat pipes, no coating. Prior art: because issue (1980-10-21) is after the § 102(b) cut-off (1980-06-23), it is not § 102(b) art; it can be § 102(a) art (patented before applicant's invention) and/or § 102(e) art (U.S. filing 1978-05-22, before applicant's 1981-06-23 filing).

R9. US 4,249,594 A — "High efficiency furnace"

• Assignee: Southern California Gas Company; Filed 1979-02-28; Issued 1981-02-10.
• Description: (Not independently re-verified.) Per title/record, a high-efficiency furnace (heat-exchange heating appliance).
• § 102 relevance: Anticipates no claim. A furnace/heat-exchanger improvement; discloses none of the coal fluidized bed, closed-cycle turbine, or coated heat-pipe combination. Possible background for heat-exchange structure (cf. claims 9/12) only. Prior art: issued after 1980-06-23, so not § 102(b); potential § 102(a) and/or § 102(e) (U.S. filing 1979-02-28).

R10. US 4,326,373 A — "Integrated gas turbine power generation system and process"

• Assignee: General Electric Company; Filed 1980-05-29; Issued 1982-04-27 (issue date is after the filing date of US 4,380,154). Source: indexed under F02C 3 (Google Patents sitemap).
• Description: (Not independently re-verified beyond title/classification.) An integrated gas turbine power generation system and process.
• § 102 relevance: Anticipates no claim. Relevant only to the gas turbine / power-generation element (claim 1(c); claims 12–13 peripherally). Critically, its U.S. filing date (1980-05-29) precedes US 4,380,154's filing (1981-06-23) while its publication date (1982-04-27) is later — the classic posture for pre-AIA § 102(e) prior art (a U.S. application/patent by another filed before the applicant's invention). This is the most likely reason the examiner cited it, and it is the correct statutory hook to check.

3. References cited in the specification body (not in the face-of-patent list)

4. Which claims does any reference actually anticipate?

Applying the § 102 test (a single reference must disclose every limitation of the claim, arranged as claimed):

Because claims 2–13 all depend (directly or through claim 6) from claim 1, no reference discloses all limitations of any claim; the dependent-claim analysis therefore terminates at claim 1 in every case.

Bottom line: None of the ten references anticipates any claim of US 4,380,154 under 35 U.S.C. § 102. The references are best understood as § 103 combination material: R4 (fluidized-bed combustor + turbine + heat recovery) supplies the process skeleton; R6 (steel/Al-oxide heat-pipe casing) supplies the permeation-barrier coating; and the novelty resides in (a) indirect heat transfer to a closed-cycle turbine via multiple heat pipes, and (b) the dual coating — a ~1-micron continuous impermeable oxide layer plus a 0.010–0.125-inch plasma-sprayed ceramic erosion layer over the fluidized-bed-immersed portion — the latter being the true point of novelty and the limitation no cited reference addresses.

5. Most-relevant prior art, ranked

1. US 3,871,172 (Villiers-Fisher et al., Chemical Construction Corp.) — fluidized-bed combustor + gas turbine + heat recovery; the reference the applicant conceded in the Background. § 102(b).
2. US 4,082,575 (Thermacore/Eastman) — steel heat-pipe casing with aluminum-oxide impermeable layer; the source of the claim-3 oxide teaching. § 102(b).
3. US 4,326,373 (General Electric) — integrated gas-turbine power generation; § 102(e) candidate (U.S. filed before, published after).
4. US 4,228,659 (Purification Sciences) — gas turbine system; § 102(a)/(e) candidate.
5. US 4,249,594 (SoCal Gas) and US 3,834,171 (Bahco Ventilation) — heat-exchange/furnace structure; § 102(a)/(e) and § 102(b) respectively.
6. US 3,723,073, US 3,911,683, US 4,165,614, US 4,160,720 — peripheral (heat recovery, geothermal, vapor power, tar sands); § 102(b), but no anticipation of any claim.

6. Caveats

1. Only four references were content-verified in this session (US 3,871,172, US 4,082,575, US 3,723,073, plus confirmation of US 4,326,373's date/class). Descriptions for US 4,165,614, US 3,834,171, US 3,911,683, US 4,160,720, US 4,228,659 and US 4,249,594 rely on the record's titles and the specification; I did not read their full texts, so their element-level disclosures should be re-checked against full documents before being relied on in any opinion.
2. Identifier conflict flagged, not corrected: the earlier summary's "US 3,914,168" vs. the record's US 3,911,683 — the patent's own tables give 3,911,683.
3. Ser. No. 169,659 — the resulting patent number is unconfirmed; do not assume an issued number.
4. "Anticipates" is used strictly: given the dependency structure, my finding is that no cited reference anticipates any claim; the strongest genuine challenge would be a § 103 combination of R4 + R6 (+ optionally R10), and even that combination does not reach the second ceramic coating limitation of claim 1 or claims 4.

I'll verify the subject matter of the examiner-cited prior-art references before mapping them to the claims.

Now let me verify the remaining examiner-cited references and the state of the heat-pipe/fluidized-bed art circa 1981.

Obviousness Analysis — US 4,380,154 ("Clean Coal Power System") under 35 U.S.C. § 103

Bottom line up front. Claim 1 is a combination of four elements, three of which are squarely in the pre-1981 prior art and one of which (the duplex protective coating on the heat-pipe casings) is disclosed in the inventor's own earlier § 102(b) patent. The strongest prima facie case is US 3,871,172 (Villiers-Fisher) + US 4,228,659 (Lowther) + US 3,834,171 (Johansson) + US 4,082,575 (Eastman), with the outer plasma-sprayed ceramic layer supplied by the fluidized-bed refractory art (e.g., US 4,249,594) or by Official Notice. The weakest link in any rejection is the numerical thickness ranges (~1 micron; 0.010–0.125 inch), for which I found no express pre-1981 disclosure.

Note on dates. The task header says "Current Date: April 26, 2026"; the operating context I was given says 2026-09-27. Nothing in this analysis turns on the difference; both postdate every reference and every event discussed.

1. Governing legal framework

• The application was filed 1981-06-23 and issued 1983-04-19 — three decades pre-AIA. Pre-AIA § 103(a) governs, with the Graham v. John Deere, 383 U.S. 1 (1966) four-factor framework (scope/content of art; differences; PHOSITA level; secondary considerations).
• KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007) supplies the operative obviousness gloss and applies to pre-AIA patents: a combination is obvious where (i) the elements were known, (ii) there was an identifiable reason to combine, and (iii) the combination did no more than the prior art predicted.
• Reasoning must be articulated — In re Kahn, 441 F.3d 977, 988 (Fed. Cir. 2006); MPEP §§ 2141–2144. The motivation may come from the references themselves, the nature of the problem, or common knowledge (MPEP 2144.01).
• Numerical ranges: In re Woodruff, 919 F.2d 1575 (Fed. Cir. 1990); In re Peterson, 315 F.3d 1325 (Fed. Cir. 2003); Wm. Wrigley Jr. Co. v. Cadbury Adams USA LLC, 683 F.3d 1356 (Fed. Cir. 2012) (overlapping/close ranges → prima facie obviousness; no unexpected results shown).
• "Obvious to try" with a finite number of identified, predictable solutions: In re O'Farrell, 853 F.2d 894 (Fed. Cir. 1988).

Level of ordinary skill. A mechanical/thermal-systems engineer (B.S. + several years) in utility-scale combustion and heat-transfer equipment, familiar with (a) fluidized-bed combustion, (b) closed-cycle/Brayton turbine plant design, (c) heat-pipe theory and construction, and (d) high-temperature coatings for coal-service components. This is a high-skill, cross-disciplinary artisan — which cuts toward obviousness, because the four fields here were each individually mature by 1981.

2. The prior art of record, with statutory basis

Dates below are taken from the patent's own "Citations" table and confirmed by reference to the documents where I could retrieve them. I flag the § 102 subsection each reference can support.

Two important catalogue corrections to keep in mind:

1. The "Cited By" list is not prior art. Everything in the Cited By table — US 4,492,085 (GE, filed 1982-08-09), US 4,478,275 (Thermacore, filed 1983-07-25), US 5,687,570 / 5,799,490 (Ormat), DE 10 2015 213863 (TU Dresden), etc. — postdates 1981-06-23. Those can support the state of the art / commercial-context narrative and later-claim obviousness, but cannot be used under § 103 against this patent's claims. Do not let a rejection be built on them.
2. The examiner cited nearly all of the pieces. US 3,871,172, 3,834,171, 4,082,575, 4,228,659, 4,249,594 and 4,326,373 all appear on the face of the patent. Whatever basis the allowance rested on, it was not ignorance of these references. The reasonable inference is that allowance turned on the duplex coating limitations and/or the specific combination, which is exactly where a § 103 challenge should be aimed (and, correspondingly, where the patent's validity is strongest).

3. Claim 1 element-by-element mapping

4. Ground 1 (primary): the "clean-coal + heat-pipe + coated-casing" combination

Formal statement

Claims 1–4, 6–9 and 11–13 are obvious over Villiers-Fisher (US 3,871,172) in view of Johansson (US 3,834,171) and Eastman (US 4,082,575), further in view of Lowther (US 4,228,659).

Identification of the differences

Villiers-Fisher alone discloses elements (a), (b), and a turbine-driven generator, plus downstream heat recovery — but it uses direct-contact fluidized heat exchange to heat the turbine working fluid, is open-cycle, and has no heat pipes and no coated casings. Johansson supplies the heat-pipe-array/partition-wall architecture. Lowther supplies the closed-cycle, indirectly-heated turbine. Eastman supplies the oxide coating and its process.

Articulated reasons to combine (this is where the case is strong)

1. The reference itself states the problem the invention solves. Villiers-Fisher: "the ash loadings are still above the levels allowable for existing gas turbines." That is an express, in-art recognition that a barrier between the abrasive combustion products and the turbine is needed. A heat-pipe array spanning a partition wall is a known barrier that transfers heat without mixing the streams.

2. The specification concedes the motivation. The patent states the correspondence between limestone-FB optimum temperature (1500–1700 °F) and closed-cycle gas turbine optimum temperature (1400–1700 °F) "has been widely observed and is the subject of active development work." An applicant's own admission of what the art was already pursuing is powerful § 103 evidence (MPEP 2144.01; In re Kahn).

3. The specification concedes the design rationale for the heat-pipe architecture — high thermal conductance, negligible temperature loss, self-contained sealed elements, non-catastrophic single-element failure, and (unlike a shell-and-tube exchanger) no single-membrane puncture that lets ash into the turbine or working gas out. Under KSR, "a court must ask whether the improvement is more than the predictable use of prior art elements according to their established functions." A heat pipe used to transfer heat across a partition is precisely its established function in Johansson.

4. Eastman (US 4,082,575) supplies both the reason and the mechanism for the coating. It teaches that steel is desirable for heat-pipe casings ("low cost, strength, ease of forming, corrosion resistance") but that a bare steel casing is attacked by the working fluid/steam with hydrogen evolution that "blocks operation of the heat exchange cycle," and that a continuous oxide layer solves it. A PHOSITA seeking a durable steel heat pipe in high-temperature water vapour/combustion service would apply 4,082,575 for its stated purpose — and the reference is the same inventor's own § 102(b) patent, cited in the specification as the source of the process.

5. Predictable result. No new function is performed by any element in the combination; the assembly is a series arrangement of known heat-transfer components.

Claim-by-claim under Ground 1

5. Ground 2: attacking the outer ceramic coating specifically

Claim 1 (the (g) limitation) and claim 4 are obvious over Villiers-Fisher + Johansson + Eastman further in view of Southern California Gas (US 4,249,594) and/or the general knowledge in the fluidized-bed refractory art.

• US 4,249,594 teaches fluidized beds as heat-exchange media and, importantly, that ceramic materials are used in the stages having the highest temperatures — i.e., the art already chose ceramics for the hottest, most aggressive region of a fluidized-bed exchanger.
• It was and is elementary that a fluidized bed of limestone/ash is abrasive, and that plasma-sprayed refractory oxide coatings (alumina in particular) are applied to FB boiler tubes and internals to resist that abrasion. This is exactly the proposition the later Thermacore patent US 4,478,275 ("Abrasion resistant heat pipe," 1984) was written to address, and its criticism of the Eastman duplex coating was that it was difficult to attain, not that the concept was unknown — a concession-style admission that supports the § 103 framing.
• Under In re Kahn and MPEP 2144.01, the nature of the problem itself ("prevent erosion of the heat pipe casing by the solid particles within the bed," per the abstract) can supply the motivation.

Weakness: I could not retrieve a single pre-1981 reference of record that expressly states a 0.010–0.125 inch ceramic coating thickness, or an ~1 micron oxide thickness. Without such a reference, the examiner must argue the ranges are the product of routine optimization (In re Peterson; Pfizer; Wrigley) or rely on Official Notice. That is a rebuttable position but a contested one. See § 6.

6. Where an obviousness attack is weakest — and how a patent owner would respond

A rigorous § 103 opinion has to state the counter-case.

1. The numerical ranges. "approximately one micron" and "between 0.010 and 0.125 inch" are the only genuinely specific quantitative limits in claim 1. No reference of record discloses either. A patent owner will argue the inventor discovered a criticality: a layer thin enough to remain continuous, adherent and thermally transparent, yet thick enough to survive the erosive bed. Whether that is critical or merely routine is a question of fact on which the record is thin. Note, however, the specification's own statement that the one-micron oxide "has no significant effect on the heat transfer between the heat pipe and the fins" — which reads as an absence of a surprising property, undermining the criticality argument.

2. The duplex-coating combination as a whole. A patent owner will argue no reference suggests stacking a diffused sub-micron oxide permeation barrier under a thick plasma-sprayed abrasion coating on the immersed portion only. Counter: 4,082,575 supplies layer one for an articulated reason (hydrogen permeation) and the FB refractory art supplies layer two for a different articulated reason (erosion); KSR allows combination where each element performs its own known function.

3. Closed-cycle limitation. Villiers-Fisher is open-cycle. A rejection built only on Villiers-Fisher + Johansson + Eastman fails on element (c). The Lowther reference (US 4,228,659) is therefore mandatory, and it is only § 102(e) art (effective 1978-05-22, published 1980-10-21). If the applicant were able to swear behind 1978-05-22 (a Rule 131-type showing for pre-AIA practice), that reference would drop out. I have no evidence that any such showing was or could be made; absent evidence of an earlier invention date, § 102(e) applies.

4. Common-ownership disqualification does not help here for 4,082,575 — but only because it qualifies under § 102(b) (issued 1978-04-04, more than a year before 1981-06-23). That is a critical point in both directions: the applicant's own earlier patent is prior art against him because of the one-year grace cutoff. Conversely, if a rejection were premised on a copending, commonly owned Eastman/Thermacore application — e.g., U.S. Ser. No. 169,659, which the specification cites alongside 4,082,575 — pre-AIA § 103(c) could disqualify it. I could not verify the status, filing date, or content of Ser. No. 169,659; do not build a rejection on it without confirming its file history.

5. Secondary considerations. No objective evidence of non-obviousness appears on the face of the record. There is no verified commercial-success or licensing narrative, and no nexus evidence. The patent's 1991-04-21 lapse for non-payment of maintenance fees is not itself an obviousness fact, but it is the reason no objective-indicia record was ever developed.

6. Anti-hindsight caution. The particular combination — heat pipes immersed in a limestone FB feeding a closed-cycle Brayton loop, with a duplex coating — is genuinely unusual for its date. A careful examiner or challenger must show that the references, not the applicant's disclosure, supply the bridge. Here they largely do: Villiers-Fisher's express "ash loadings above allowable" statement and the specification's admission that the FB/closed-cycle temperature correspondence was "widely observed and … the subject of active development work" are the two strongest such bridges in the record.

7. Provisional conclusion

Recommended rejection architecture if this is for a validity opinion or a reexamination-style challenge: lead with Villiers-Fisher + Lowther + Johansson + Eastman (4,082,575) on claims 1–4, 6–9, 11–13; add US 4,249,594 and/or Official Notice for the outer ceramic-layer thickness; attack claim 5 as KSR scaling; and treat claim 10 separately, since it is the one claim for which I could not construct a grounded combination from the art of record.

8. What I could not verify (stated explicitly)

• US 4,326,373 (GE) — full text not retrieved. Its "integrated gas turbine power generation system" characterization comes from the patent's own citation table and is provisional. It is § 102(e)-only art (US filing 1980-05-29), so its availability depends on the applicant's invention date.
• U.S. Ser. No. 169,659 — cited in the specification alongside US 4,082,575 as a source of the oxide-coating process. I could not confirm whether it issued, its filing date, or its content. Under pre-AIA § 103(c) it may be disqualified as commonly owned art, but that conclusion is unverified.
• US 4,230,173 (Eastman) surfaced in a third-party EP search report as heat-pipe art. I did not confirm its dates or content and have not relied on it. If it is Eastman's own work it is likely disqualified (own work, and common ownership) — but verify before citing.
• No pre-1981 reference of record discloses the 0.010–0.125 inch or ~1 micron thicknesses. This is a verified gap in the art of record, not an absence of such art in the world; a full search (fluidized-bed erosion-coating literature, e.g., plasma-sprayed alumina on FB boiler tubes, 1975–1981) could close it and materially strengthen the case.
• I found no litigation, PTAB, or reexamination record on this patent in the earlier passes of this analysis, and nothing in this § 103 pass changes that. Validity here is an academic/portfolio question, not a live-controversy one: the patent lapsed 1991-04-21 for maintenance-fee non-payment.