US 11255538

I'll search for authoritative information on this patent number, including any 2026 CAFC docket activity.

Initial searches returned mostly irrelevant results. Let me run more targeted queries.

Let me do a final targeted check for any litigation or PTAB proceedings involving this patent.

US Patent 11,255,538 — Verification Summary

I ran multiple searches against patent databases, Google Patents/Justia/FPO mirrors, general litigation reporting, and Federal Circuit 2026 decision round-ups. No CAFC 2026 docket entry, appeal, IPR, or district-court litigation involving U.S. Patent No. 11,255,538 surfaced in any search. The only records found are prosecution/grant records and third-party citation records. I am stating that as an absence of findings in the sources I could reach, not as a certified negative — I cannot query PACER or the Federal Circuit docket directly with the tools available, so if an appeal or suit exists, my searches did not surface it.

Also, per the "interpret literally" rule: I did not find any result for a different but similar number, and I have not substituted any other patent number here.

---

Bibliographic data (matches the full text supplied)

Sources: https://patents.google.com/patent/US11255538/en; https://patents.justia.com/patent/11255538; https://www.wikidata.org/wiki/Q125019074; https://iprdb.com/content/[US11255538B2](/patent/US11255538B2)

Note on the "2037-04-20" expiration: this does not equal 20 years from the 2018-10-18 filing. It is consistent with expiry running 20 years from the 2016-02-05 parent filing (2036-02-05) plus a patent term adjustment, and the OCR of the printed front page in one search result shows the string "440" adjacent to "under 35 U.S.C." — suggestive of a 440-day PTA. This is my inference, not an authoritative statement; I did not retrieve a USPTO Patent Term Adjustment determination document.

Note on a name variant: one assignment record in the Google Patents legal-events table reads "Assignors: SHMELEV, VLADIMIR, YASYLYK, NIKOLAY," while the patent front page and all other records list Nikolai Vasilik. I am flagging the discrepancy rather than correcting it. One assignment record also spells an inventor "DAIVD KALENSKY."

---

Abstract (as printed)

Methods and devices for gas mixture combustion on a surface of a permeable matrix are provided which produce or result in surface stabilized combustion (SSC) with increasing amounts of radiation energy emitted by the matrix surface and decreasing concentrations of pollutant components in the combustion products. The gas mixture is fed to a burner that includes a permeable matrix material having a first thermal conductivity and configured to preheat the combustible gas mixture as it travels through the matrix. The burner includes a plurality of thermal elements having a thermal conductivity higher than and disposed in thermal transfer communication with the matrix base material. The permeable matrix base material forms a combustion surface with at least a portion of the thermal elements exposed above the combustion surface. The gas mixture is combusted at or near exit pores and channels formed at the permeable matrix material combustion surface.

---

The invention in one paragraph

The patent addresses premixed radiant infrared burners that burn fuel/air on the surface of a permeable metal matrix (metal foam, porous metal, or pressed metal wire — e.g., FeCrAl/FeCrAlY "chromal" foam). The core addition over the parent is thermal elements (plates, rods, bars, rings, fins) made of a higher-thermal-conductivity material — stainless/heat-resistant steel, graphite, chromium, iron, iridium, lithium, nickel, Inconel®/Hastelloy®-type alloys — placed in thermal transfer contact with the matrix, with portions protruding above the combustion surface. These elements recuperate heat from the combustion products conductively, convectively, and radiatively and push it back into the matrix body, which preheats the incoming gas mixture, raises the radiating surface temperature, widens the stable combustion range, and cuts NOx and CO. In the reported experiments the surface temperature rose by up to ~200 K, radiation flux density by up to 1.7×, stable power density range extended from 20–70 W/cm² to 15–100 W/cm², and CO dropped up to 3×.

---

Plain-language overview of the independent claims

Claim 1 — Method of burning a combustible gas mixture

Steps:

1. Feed the combustible gas mixture into a burner having (a) a permeable matrix base material that is specifically a metal foam, porous metal, or pressed metal wire material forming a combustion surface, and (b) multiple thermal elements in thermal transfer communication with the matrix, where at least a portion of the thermal elements are in contact with the matrix and exposed above the combustion surface. The matrix has a first thermal conductivity; the thermal elements must have a higher thermal conductivity than the matrix.
2. Preheat the mixture as it passes through the permeable matrix.
3. Combust the preheated mixture at or near the exit pores and channels at the combustion surface, and in the spaces between the thermal elements that are exposed above that surface.

The final clause ties it together: the preheating must include combustion heat transferred to the matrix base material through the thermal transfer communication with the thermal elements. So the thermal elements are not merely a radiant screen sitting above a burner — they are the heat-recovery path into the matrix body, and combustion must occur at/between them.

Claim 10 — Radiant infrared premixed gas burner (apparatus)

Two required parts:

• A permeable matrix base material limited to metal foam, porous metal, or pressed metal wire, having a first thermal conductivity, providing surface stabilized combustion when the mixture exits through its pores/channels, and configured to preheat the mixture as it travels through the matrix.
• Multiple thermal elements in thermal transfer contact with the matrix, with at least a portion exposed above the combustion surface, having a thermal conductivity higher than the matrix, and configured to transfer thermal energy of the surface stabilized combustion back to the matrix for that preheat.

Note this claim is drafted widely — it does not require the thermal elements to penetrate the matrix (that is claim 12), and it does not require a coating (that is claim 18). The material limitations on the matrix ("metal foam material, porous metal material, or a pressed metal wire material") are, however, expressly recited.

Claim 19 — Radiant infrared premixed gas burner with IR-transparent coating

Claim 19 restates the claim 10 architecture (permeable matrix base material with first thermal conductivity, configured to preheat; thermal elements in thermal transfer communication, exposed above the combustion surface, higher thermal conductivity, configured to transfer combustion thermal energy to the matrix for preheat) and adds the coating requirement: at least a portion of a downstream surface of the matrix and of the exposed thermal elements is coated with a material having a lower thermal conductivity than the matrix and optically transparent to IR radiation, where the coating is a ceramic, the coating thickness is 10–500 microns, and the matrix base material is a metal.

⚠️ Verification caveat on claim 19: the authoritative text supplied to me is truncated mid-sentence — it ends at "the thermal elements having a thermal conductivity higher than t". The remainder above is reconstructed from the Justia full-text rendering (https://patents.justia.com/patent/11255538), which shows claim 19 as an apparatus claim differing from claim 18 in that it places the IR-transparent coating on both the downstream matrix surface and the exposed portions of the thermal elements, with the ceramic/10–500 micron/metal-matrix limitations. Treat the tail of claim 19 as not fully verified against the source I was given; it should be confirmed against the issued patent PDF or Patent Center before being relied on.

---

Dependent-claim structure (for context, not repeated here)

• Claims 2–9 depend from claim 1: partial disposal of a thermal element in the matrix (2); matrix material list — chromal, kanthal, heat-resistant steel, carbides of titanium/aluminum/iron/chromium/yttrium (3); thermal-element material list (4); element forms — plates, rods, bars, rings, fins (5); element-to-element spacing 2–60 mm (6); base end flush with upstream surface and extending 1–15 mm beyond the downstream surface (7); the coated-surface embodiment with conductivity ratio 3–10, ceramic coating 10–500 microns, metal matrix (8); coating on the exposed thermal elements too (9).
• Claims 11–18 depend from claim 10: fuel inlet, oxidizer inlet, mixer (11); element partially in the matrix (12); placement options — penetrating, flush with upstream surface, protruding beyond downstream surface (13); matrix 5–30 mm thick and elements 0.1–5 mm thick (14); element forms and 2–60 mm spacing (15); protrusion height 0.5–5× the inter-element distance (16); cylindrical matrix with planar elements extending radially (17); IR-transparent coating on at least a portion of the downstream matrix surface and thermal elements (18).

---

Bottom line on the docket question

• Litigation/CAFC 2026: nothing found. No 2026 Federal Circuit opinion, appeal, or docket entry naming US 11,255,538 appeared in searches of Federal Circuit 2026 decision summaries and general patent-litigation coverage. I cannot rule out a pending matter that simply is not indexed in the sources I searched.
• PTAB: no IPR/PGR involving this patent was found. I could not directly query the PTAB API, so this is likewise an absence-of-evidence finding.
• Everything above concerning the patent's content is grounded in the full text you supplied plus the Google Patents/Justia/Wikidata/IPRDB records cited; the one place with a genuine gap is the ending of claim 19.

I'll search for litigation involving US patent 11255538 across patent litigation sources.

Let me search additional litigation-specific sources.

Let me do a few more targeted searches for case dockets and any assertion.

Litigation Search Results — U.S. Patent No. 11,255,538

Bottom line: I found no evidence of any litigation involving U.S. Patent No. 11,255,538. No case could be identified in any court or tribunal.

What I searched

• General web searches for "11255538" combined with litigation, lawsuit, and complaint terms.
• Patent-litigation-oriented queries (Unified Patents-style aggregation, CourtListener/RECAP references, ITC/CAFC references).
• Assignee-focused queries (Gas Technology Institute / GTI Energy, the patent's owner) paired with infringement/litigation terms.

What the searches returned

The only results tied to the number 11255538 were non-litigation references:

• Google Patents / FreePatentsOnline / Patents-Review / Wikidata — bibliographic and full-text records of the patent itself ("Radiant infrared gas burner," Gas Technology Institute; inventors Aleksandr Kozlov, David Kalensky, Mark Khinkis, Vladimir Shmelev, Nikolai Vasilik; filed 2018-10-18; granted 2022-02-22; adjusted expiration 2037-04-20; current assignee listed as GTI Energy).
• Unrelated documents that merely happen to cite the patent, or that contain the numeral string "11255538" in a completely different context (e.g., a genomic coordinate range "11224332..11255538" in a PKM-gene patent — clearly not this patent).

The one litigation-flavored results returned (e.g., Gas Technology Institute v. Rehmat, and a DISH/Sling fitness-streaming claim-construction chart) were false positives — they concern the same corporate plaintiff family or an unrelated number, and do not involve U.S. Patent No. 11,255,538.

Required case-by-case table

Important caveats and confidence level

• Confidence: moderate-to-high that no litigation exists as of the search date, but not certain. This is a niche, recently issued (Feb. 2022) industrial-combustion patent held by a non-practicing research institute, which is the type of asset that is rarely asserted. That is consistent with finding nothing.
• Search-tool limitation: My live searches exhausted their step budget before I could query dedicated litigation databases directly (e.g., the Unified Patents litigation portal, PACER/RECAP docket searches keyed to the exact patent number, or Docket Navigator). Those sources are the proper place to run a definitive "no hits" confirmation, and I was unable to complete that step. A null result here therefore means "not found in the searches I ran," not a verified global negative.
• No auto-correction applied: I interpreted "11255538" literally as U.S. Patent No. 11,255,538 throughout and excluded near-miss numbers (e.g., other gas-burner patents such as US 10,281,140 B2 or US 10,488,039 B2, and unrelated similarly numbered documents).

Recommended next step for a definitive answer

If you need a certified "no litigation" result, run the exact string "11,255,538" (and the bare form 11255538) through:

1. Unified Patents litigation portal — https://portal.unifiedpatents.com/litigation/caselist
2. PACER / CourtListener RECAP docket search.
3. The USPTO Patent Assignment / PatentCenter "Litigation" tab for the patent, which surfaces any district-court or ITC challenges.

None of the sources I reached contradicted one another on this point, so I have no basis to revise the training-data expectation that this patent has not been asserted.

I'll verify the structured "no proceedings" signal against the open web before committing to an answer.

Nothing relevant surfaced. Let me run narrower queries on the patent owner and the parent patent.

Let me try litigation-side and docket-aggregator angles, since asserted patents are what attract IPRs.

Proceedings overview

Zero AIA trial proceedings are on file for US 11,255,538 — the structured USPTO Open Data Portal block returns no IPR, PGR, or CBM for this patent, and independent web searches across PTAB petition records, PTAB docket aggregators, and Federal Circuit/CourtListener returned no petition, institution decision, FWD, or appeal naming either US 11,255,538 or its parent US 10,488,039 — leaving the patent in an untested, un-hardened posture: every one of its 19 claims is live, no claim has ever been canceled, and no statutory estoppel (§ 315(e)) has been triggered by anyone, which means the full § 102/§ 103 prior-art field (limited to patents and printed publications) remains available to a defendant filing first.

---

No proceedings to report

I am not going to manufacture proceeding numbers to fill the section template. There are none. What follows is what I actually verified and why the absence is reliable.

Canonical source (controlling): The "PTAB proceedings on file" block supplied with this task states the USPTO ODP API returns no AIA trial proceedings for this patent as of the most recent ingest. That is the authoritative list, and I have treated it as such.

Corroborating search angles I ran and what they returned:

Why the absence is credible rather than a data gap:

1. No assertion campaign found. IPRs follow demand letters and complaints. I found no district court action, no ITC investigation, and no publicly reported assertion of US 11,255,538 or its parent. The patent has the profile of a research institution's portfolio asset (GTI Energy / Gas Technology Institute, Des Plaines, IL), not a litigated patent.
2. The patent is young relative to its family. US 11,255,538 issued 2022-02-22 from application 16/164,368 filed 2018-10-18 and is a continuation-in-part of application 15/016,469 (filed 2016-02-05, issued as US 10,488,039). Post-issuance AIA challenges would be expected only after an assertion creates a defendant with standing, a motive, and a § 315(b) clock.
3. The claim set is apparatus/method-narrow and metal-matrix specific (metal foam / porous metal / pressed metal wire matrix plus thermally-conductive elements, e.g., claim 1, claim 10, claim 19), which historically attracts design-around more than validity challenge in an industry — industrial/residential gas burners — that is not a hotbed of IPR-for-hire activity (no Unified Patents-style defensive aggregator is in the chain here).

Residual uncertainty I will flag rather than paper over: the ODP structured block covers AIA trials (IPR/PGR/CBM). It does not by itself rule out an ex parte reexamination or a reissue, which are not AIA trials. The Google Patents legal-events record for US 11,255,538 shows only assignments, publication, grant, and maintenance/expiration-status entries — no reexamination certificate — so I found no evidence of one, but I did not independently confirm reexam status through the USPTO reexam database. Treat a reexam check as a to-do, not as a settled negative.

---

Strategic summary

Claim status — everything is untested. US 11,255,538 has 19 claims. Independent claim 1 (method of burning a combustible gas mixture on a metal foam / porous metal / pressed-metal-wire permeable matrix with thermal elements exposed above the combustion surface), independent claim 10 (radiant infrared premixed gas burner apparatus), and independent claim 19 (a second apparatus claim, whose text is truncated in the published record) are all live and never adjudicated. Dependent claims 2–9 (depending from claim 1) and 11–18 (depending from claim 10) are likewise all intact. There is no canceled claim, no sustained claim, and no substitute claim on the record — the "survived two IPRs and is hardened" narrative and the "claims 1–5 are dead" narrative are both false. Nothing has been narrowed by the PTAB.

Estoppel landscape — nothing is estopped, which cuts both ways. Because no IPR was ever instituted against any party, no § 315(e)(2) estoppel attaches to anyone. A defendant is free to file an IPR on any § 102/§ 103 ground, and the usual "you should have raised that in your IPR" trap does not exist on this patent yet. But the sword is double-edged: a defendant who is the first to file gains no estoppel against later defendants, and — critically — a defendant facing active litigation must clear § 315(b)'s one-year bar running from service of the complaint, and cannot build a validity case on prior art beyond patents and printed publications (§ 311(b)) in the IPR forum. Two timing features matter here:

• The CIP priority question is the most interesting live validity lever. The specification's CROSS REFERENCE section states this application "is a continuation-in-part application" of 15/016,469 (filed 2016-02-05). The subject matter that gives the patent its novelty — the thermal conductive elements / recuperators penetrating the matrix — including the specific numeric ranges in claims 6, 7, 14, 15 and 16, may be new matter added in the CIP, supported only by the 2018-10-18 filing. If so, those claims are entitled only to an effective filing date of 2018-10-18, which opens a window of intervening prior art from 2016-02-05 through 2018-10-18. This is a priority/§ 102 analysis a defendant should run against the parent's disclosure before drafting any petition; the Google Patents record itself labels the 2015-02-09 priority date an "assumption" and not a legal conclusion.
• § 325(d) risk is real but manageable. The specification's own Background of the Invention narrates and describes several prior-art burner architectures (SSC on iron-chromium-aluminum alloy particles; a woven ceramic fiber sleeve on a perforated metal carrier; a thick ceramic-fiber/polymer layer on a corrosion-resistant mesh screen; a reverberatory screen above the matrix; a two-layer matrix of differing permeability). If any of those correspond to references the Examiner actually considered, a petition grounded on them invites discretionary denial under § 325(d). Art that the Examiner did not consider — particularly 2016–2018 publications on volumetric/porous-media combustion with internal heat recuperation — is the cleaner path.

Pattern signals. No petitioner has filed anything, so there is no serial-filer pattern to report. The patent owner has not pursued PTAB appeals (nothing to appeal), and there is no defensive aggregator such as Unified Patents in the chain. Ownership is notable for diligence purposes: the assignment records show the current assignee as GTI Energy, originally Gas Technology Institute, and the reassignment history includes an assignment from the Semenov Institute of Chemical Physics of the Russian Academy of Sciences with inventors Shmelev and "Yasylyk, Nikolay" (the face of the patent lists the inventor as "Nikolai Vasilik" — a name discrepancy worth noting in any chain-of-title or standing analysis). A § 315 standing or real-party-in-interest question involving the Semenov Institute is a legitimate diligence item if this patent is ever asserted.

---

Recommended next steps

If you are a defendant and the patent has been asserted against you:

1. There is no FWD to link to and no invalidated claim to quote. Do not represent to a court or to opposing counsel that any claim of US 11,255,538 has been canceled — it has not. Your defense is a validity challenge you build from scratch, or non-infringement.
2. Calendar § 315(b) immediately. You have one year from service of the complaint to file an IPR. Because the assertion would be the first, this is a clean-slate filing with no § 315(e) estoppel and no § 325(d) history to overcome beyond the prosecution record.
3. Run the CIP priority analysis first. Compare claims 6, 7, 14, 15, and 16 (the spacing, thickness, and protrusion ranges) against the 15/016,469 parent disclosure. If the thermal-element geometry is CIP new matter, scouting prior art in the 2016-02-05 → 2018-10-18 window is likely your highest-yield effort and may not require the Board to reach the merits of the 2015 priority date at all.
4. Pull the full prosecution file for application 16/164,368 from USPTO PatentCenter and build a § 325(d) map before selecting art. Nothing is estopped, but the Board can still deny institution if your references are substantially the same as what the Examiner already weighed.
5. Confirm the negative independently. Docket Alarm / PTAB E2E for the patent number and for the parties; CourtListener for any CAFC appeal; and the USPTO reexamination database for any ex parte reexam, which the ODP AIA-trial block would not show.

If no assertion has been made yet (the more likely state):

Say it plainly — there is no PTAB activity on this patent, and that absence is itself the signal. A patent that has never attracted an IPR is one that has not been seriously litigated; GTI Energy appears to hold US 11,255,538 as a portfolio asset rather than a licensing weapon. The practical consequences: (a) there is no PTAB record to mine for claim constructions, expert admissions, or narrowed claim scope — the only public record is the specification and prosecution history; (b) there is no forum estoppel protecting you or constraining the patent owner; and (c) if you are evaluating a freedom-to-operate or design-around question on a radiant infrared permeable-matrix burner, the most valuable public artifact is not a PTAB decision but the experimental-support section of the specification (pp. 12A/12B prototype, FIGS. 13–15B), which fixes the claimed performance envelope — matrix thickness 5–30 mm, thermal-element thickness 0.1–5 mm, element spacing 2–60 mm, protrusion 5–15 mm, stable combustion 15–100 W/cm² — and therefore draws the boundaries of any design-around.

Primary public sources for verification: US 11,255,538 on Google Patents · US 2019/0049108 A1 (pre-grant publication) · USPTO PTAB E2E / PTAB Decisions · USPTO PatentCenter for application 16/164,368 · CourtListener for any CAFC appeal.

Assumption flagged: the ODP "no proceedings" result is treated as controlling per the task instructions. Should a recently-filed petition surface that the ODP ingest has not yet indexed, the analysis above changes materially only as to the new proceeding itself — the "no estoppel, all 19 claims live" posture would still hold until an FWD issues.

I'll research the assignment record before writing anything.

Ownership Reconstruction — US 11255538 B2 ("Radiant infrared gas burner")

Scope note / data limitation (read first). The chain below is built from the legal-events and assignee data embedded in the authoritative full text of US 11255538 (Google Patents, fetched 2026-09-24) plus corroborating public sources. I was not able to retrieve the USPTO Assignment Center detail records (reel/frame numbers and the recorded correspondent attorney/firm) for this patent in this session — my searches returned no reel/frame-level data, and Google Patents' mirrored legal-events table does not display reel/frame or correspondent fields. I have therefore left every reel/frame and correspondent field marked "not retrieved" rather than inventing values. Anything below that appears without a reel/frame citation is date-and-party-level only and should be re-verified at the Assignment Center search page before being relied on in a prosecution or litigation context:

• https://assignmentcenter.uspto.gov/
• https://assignment.uspto.gov/patent/index.html (search 11255538)
• Google Patents legal events: https://patents.google.com/patent/US11255538/en

---

Inventors

Unusual patterns — findings:

1. Split-inventor / dual-employer filing. Two of five inventors are Moscow-based and their rights did not flow directly to GTI. The record shows a two-step chain: Shmelev + Yasylik (Vasilik) → Semenov Institute of Chemical Physics → Gas Technology Institute (both steps dated 2018-12-04). This is a US–Russian institutional collaboration, not a corporate-employee filing.
2. Name-variant risk. The same inventor appears as "Nikolai Vasilik" (patent front page / Wikidata) and "YASYLYK, NIKOLAY" (assignment record). Any chain-of-title opinion must reconcile these spellings; this is a genuine title-diligence flag, not a cosmetic one.
3. No evidence of inventor departure within 12 months of filing. I found no source establishing that any inventor left GTI within 12 months of the 2018-10-18 CIP filing. Unclear — not determinable from available records.

---

Original assignee

Gas Technology Institute (Illinois not-for-profit corporation), Des Plaines / Chicago, IL — named on the issued patent, and current assignee of record shown on Google Patents as GTI Energy.

• Line of business: Energy research, development, demonstration and technology transfer. GTI describes itself as having produced "nearly 500 products, 750 licenses, and more than 1,200 associated patents" (APGA Research Foundation profile), i.e. its core commercial model is licensing and sponsored R&D, not manufacturing burner hardware.
• Corporate history: GTI is the successor to the Institute of Gas Technology (IGT). The 2009 N.D. Ill. opinion in Cement-Lock v. Gas Technology Institute records that "IGT now operates under the name GTI." In 2021 GTI renamed itself GTI Energy (Power Progress, "New name, scope for Gas Technology Institute").
• Product embodying the claims: No commercial radiant-infrared burner product traceable to this patent was identified. The patent's own examples are laboratory prototypes (Chromal foam matrices with stainless-steel plates; test data in FIGS. 13–15B). No evidence of a shipped product.
• Current status: Operating — a going-concern nonprofit research organization (GTI Energy). Not dissolved, not in bankruptcy. No Chapter 7/11 proceeding found.
• Prior litigation posture (context, not this patent): GTI appears in the docket as a defendant in Cement-Lock LLC v. Gas Technology Institute, No. 1:05-cv-00018 (N.D. Ill.) and as plaintiff in Gas Technology Institute v. Rehmat and Goyal v. GTI — all fiduciary-duty/RICO/trademark disputes over the Cement-Lock technology, none of them patent infringement assertions involving US 11255538.

---

Assignment timeline

Four recorded conveyances appear, all in a ~3-week window in late 2018, all naming Gas Technology Institute as assignee. Two of them run through the Semenov Institute rather than directly from the inventor. Reel/frame and correspondent were not retrievable in this session — shown as [not retrieved] rather than estimated.

• 2018-11-13 (executed) / recorded 2018-11-13 — Reel [not retrieved]/[not retrieved]

  • Conveyance: Assignment
  • Assignor: KALENSKY, DAIVD [sic]; KOZLOV, ALEKSANDR
  • Assignee: GAS TECHNOLOGY INSTITUTE
  • Correspondent: [not retrieved] — cannot assess recurrence
  • Context: Original employment assignment — US-based GTI inventors convey their rights to their employer in the application that became this patent.

• 2018-11-13 (executed) / recorded 2018-11-13 — Reel [not retrieved]/[not retrieved]

  • Conveyance: Assignment
  • Assignor: KHINKIS, MARK
  • Assignee: GAS TECHNOLOGY INSTITUTE
  • Correspondent: [not retrieved] — cannot assess recurrence
  • Context: Original employment assignment — filed separately from the Kalensky/Kozlov instrument, same day, same assignee.

• 2018-12-04 (executed) / recorded 2018-12-04 — Reel [not retrieved]/[not retrieved]

  • Conveyance: Assignment
  • Assignor: SEMENOV INSTITUTE OF CHEMICAL PHYSICS OF RUSSIAN ACADEMY OF SCIENCES
  • Assignee: GAS TECHNOLOGY INSTITUTE
  • Correspondent: [not retrieved] — cannot assess recurrence
  • Context: Institutional cross-border conveyance — the Russian academy institute passes the Moscow inventors' rights to GTI, completing the chain.

• 2018-12-04 (executed) / recorded 2018-12-04 — Reel [not retrieved]/[not retrieved]

  • Conveyance: Assignment
  • Assignor: SHMELEV, VLADIMIR; YASYLYK, NIKOLAY [Vasilik]
  • Assignee: SEMENOV INSTITUTE OF CHEMICAL PHYSICS OF RUSSIAN ACADEMY OF SCIENCES
  • Correspondent: [not retrieved] — cannot assess recurrence
  • Context: First link of the two-step foreign chain — inventors convey to their employer-institute, which then conveys upstream to GTI.

• No post-issuance assignment is recorded. The patent issued 2022-02-22; the grant, the 2037-04-20 adjusted expiration and the "Active" status are all consistent with title remaining with the original assignee.

• Name change, not a recorded assignment: Google Patents lists current assignee GTI Energy, reflecting the 2021 renaming of Gas Technology Institute. No reassignment record for the change of name appears in the legal events — treat as a change of name to be confirmed by a USPTO 37 CFR 3.21/3.23 name-change record or by corporate documentation, not as a transfer of title.

---

Timeline diagram

timeline
    title Ownership of US 11255538
    2015 : Provisional filed 2015-02-09
    2016 : Parent application filed 2016-02-05
    2018 : CIP application filed 2018-10-18
         : Kozlov Kalensky Khinkis assign to GTI
         : Semenov Institute assigns to GTI
         : Moscow inventors assign to Semenov
    2021 : Gas Technology Institute renamed GTI Energy
    2022 : Patent issued 2022-02-22

---

NPE / troll-pattern signals

1. Shell-entity transfer — NOT PRESENT. Every recorded conveyance runs toward Gas Technology Institute (assignee on all four 2018-11-13 and 2018-12-04 entries). No "IP / Holdings / Licensing / Ventures" LLC appears anywhere in the chain. GTI is an Illinois not-for-profit research organization, not a single-purpose Delaware or Texas LLC, and no registered-agent-service address appears in the record. Caveat: GTI's business model is licensing-intensive (self-reported 750 licenses from 1,200+ patents), so it is a non-manufacturing patent holder — but that is a research-institute licensing model, not a shell-entity transfer, and no evidence of product-less assertion by GTI on this patent exists.

2. Known asserter in the chain — NOT PRESENT. No assignee in the chain matches any entity on the supplied list (Acacia, Marathon, Intellectual Ventures, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation Corp, Spangenberg entities). Searches surfaced no RPX or Unified Patents high-frequency-plaintiff listing for Gas Technology Institute or GTI Energy. GTI's public litigation footprint is fiduciary/RICO/trademark litigation in which GTI was largely a defendant (Cement-Lock v. GTI, N.D. Ill. 1:05-cv-00018).

3. Repeat correspondent across the chain — UNCLEAR (not assessable). The correspondent-attorney field for all four 2018 records was not retrievable in this session. Because recurrence is the whole signal, I will not speculate: a single appearance would not be a finding anyway, and I have zero appearances to count. This is the single most important field to pull from Assignment Center before drawing any conclusion.

4. Cascading transfers — NOT PRESENT. Four records in 21 days, but all are inventor/employer-to-company originations feeding one assignee; there is no chain of successive LLC-to-LLC transfers, no shared correspondence addresses, no common-principal pattern, and no transfer in under 24 months between distinct assignees. The only two-step hop (Semenov Institute → GTI) is an intra-collaboration title cleanup, completed the same day as the inventors' conveyance to the Institute.

5. Pre-litigation transfer — NOT PRESENT. No infringement suit naming US 11255538 was found. The recorded assignments date to 2018, roughly 3 years and 2 months before issuance (2022-02-22), which is the opposite of a within-6-months-of-suit transfer. The 2018 filings are consistent with ordinary pre-issuance prosecution housekeeping (and, plausibly, with the international collaboration needing its foreign-institute leg documented).

6. Bankruptcy fire-sale — NOT PRESENT. No Chapter 7/11 proceeding involving Gas Technology Institute or GTI Energy was identified; GTI Energy is an operating nonprofit as of the rename announcement.

7. Privateering — NOT PRESENT. No operating-company-to-NPE transfer exists in this chain; the terminal owner is the original research organization, and no third-party assertion on GTI's behalf was surfaced.

8. Defensive aggregator (anti-NPE) — NOT PRESENT. The chain does not terminate at RPX, AST, LOT Network, Unified Patents or OIN. It terminates at the original not-for-profit assignee. (Inverse condition: the patent has not been neutralized by a defensive aggregator.)

---

Verdict

Insufficient data.

The only recorded conveyances are the original 2018-11-13 and 2018-12-04 assignments, which move title from the five inventors — three directly and two via the Semenov Institute of Chemical Physics — to the original assignee, Gas Technology Institute, with no post-issuance transfer and no recorded name-change assignment (the GTI Energy name reflects the 2021 rename per Power Progress). Not one of the eight NPE signals is affirmatively present, and the two signals that could change the picture — the recorded correspondent on the four 2018 records and any reel/frame confirmation of the Semenov two-step — could not be retrieved from the USPTO Assignment Center in this session, so I have marked them "[not retrieved]" rather than infer them. On the present record this reads as a clean, retained-by-original-owner chain at a nonprofit research institute, but the honest classification given the missing reel/frame and correspondent fields is Insufficient data, not NPE and not defensive-aggregator. Verify at https://assignmentcenter.uspto.gov/ (search 11255538) and https://assignment.uspto.gov/patent/index.html.

I'll search for the specific patent and its cited prior art references.

Let me dig deeper into the specific cited references for this patent.

Let me try to retrieve the actual front-page references cited for this patent.

Scope note and verification caveat (please read first)

I ran searches against Google Patents (including the USPTO-hosted full text mirrored there) and secondary aggregators. I was not able to retrieve the complete, officially verified front-page "(56) References Cited" list for US 11,255,538 B2 — my search session hit its step limit before I could pull the granted-patent PDF front page or the USPTO Patent Center "References Cited" tab. What follows is therefore built from (a) fragments of the US 11,255,538 B2 "References Cited" table that surfaced in a document reproducing that patent, (b) the confirmed citation lists of the closely related family members, and (c) prior art expressly discussed in the patent's own Background section. I flag confidence level for each item rather than fabricate numbers. Per your standing rule, I have not auto-corrected any identifier.

---

1. Identification of the patent (no correction of identifiers)

Key § 102 threshold issue created by the CIP status: the effective filing date is 2015-02-09 for subject matter carried over from 15/016,469, but 2018-10-18 for any new matter first added in 16/164,368 (e.g., the specific "thermal element" configurations of FIGS. 6–11). Any reference dated between those two dates is § 102(a)(1)/(a)(2) art only against claims not supported by the parent — this is the single most important date question for any anticipation analysis here.

---

2. Prior art references identified

2.1 Family member — cited but not § 102 prior art

2.2 References recovered from the "References Cited" table attributed to US 11,255,538 B2 (partial, OCR-scrambled — confidence noted)

A document purporting to reproduce the US 11,255,538 B2 front page ("References Cited") shows a long list of U.S. patent numbers with issue months/inventor surnames. The table's columns are scrambled in the reproduction, so only a subset can be mapped with confidence:

2.3 Confirmed burner prior art from the patent's own Background section and the companion family citations

These are the references the specification itself characterizes as known art (no patent numbers are given in the text for most, so I attribute them by subject matter and by the citation lists of the sibling documents):

2.4 Post-priority but potentially citable under § 102(a)(2) only for new matter

• US 2015/0276217 A1 (Clearsign Combustion Corp., pub. 2015-10-01) and US 2016/0230984 A1 (Clearsign, pub. 2016-08-11) — burners with a perforated flame holder and entrainment distance. These appear in citation chains surrounding this family. If the thermal-element claims are found to be supported only by the 2018-10-18 CIP disclosure, these publications could be § 102(a)(2) art against them; if the 2015-02-09 priority holds, they are not.

---

3. Bottom-line § 102 assessment

1. No single reference located discloses all elements of independent claim 1 or claim 10. The distinguishing limitation across the whole field retrieved is the combination of (a) a metal-foam/porous-metal/pressed-wire matrix forming a combustion surface, together with (b) a plurality of higher-thermal-conductivity thermal elements in contact with the matrix and exposed above the combustion surface, wherein (c) combustion occurs between the exposed elements.
2. The strongest § 102 candidate is US 5,641,282 (flame support rod structure, GRI, 1997): it discloses rods protruding above a radiant burner face and supporting/stabilising the flame. It is the best § 102(a)(1) challenge to claims 1, 5, 6, 10, 15 and 16 — dependent on whether its rods are in thermal transfer contact with, and conductively recuperate heat into, the matrix body (the patent's stated point of novelty). If they are merely flame holders, it is § 103 art rather than § 102 art.
3. US 5,147,201 (Xiong) and US 5,476,375 (Khinkis) are the strongest art for the matrix-side limitations (permeable matrix, porous-phase/surface-stabilised combustion, preheat, low NOx/CO) — relevant to claims 1 and 10, but they appear to lack the exposed thermal elements that distinguish the claims.
4. US 4,643,667 (IGT) is the closest art for the coating limitations of claims 8 and 18 (low-conductivity layer over a high-conductivity layer), though it is a two-layer porous plate rather than a coating on a metal foam.
5. US 2016/0230986 A1 / US 10,488,039 B2 is not § 102 art against this patent (same family, same inventors/assignee), and the examiner's citation of it in prosecution would have been for § 112/priority purposes, not anticipation.

---

4. What I could not verify (stated explicitly)

• The complete and exact front-page § 56 reference list of US 11,255,538 B2. My retrieval returned a column-scrambled reproduction; several numbers (e.g., 5,137,583; 5,165,887; 5,170,504) and roughly two dozen inventor surnames were legible but not reliably mappable to issue dates, patent numbers, titles or claims. I have therefore declined to assign § 102 anticipation mappings to them.
• Whether the examiner issued any § 102 or § 103 rejection during prosecution of 16/164,368, and which references were applied. That requires the USPTO Patent Center / IFW "References Cited" and office-action history, which I could not open.
• The full text of claim 19 (truncated in the source I retrieved) and the full text of claim 11's antecedent basis — relevant if you want element-by-element mapping against US 5,641,282.
• I did not auto-correct any identifier; where a number appeared only in a scrambled reproduction I have marked it as unverified rather than substituting a plausible alternative.

Sources used

• https://patents.google.com/patent/US11255538/en (authoritative full text supplied in the prompt)
• https://iprdb.com/content/[US11255538B2](/patent/US11255538B2) (bibliographic confirmation: App. US16/164,368; pub. 2022-02-22)
• https://patents.google.com/patent/US20160230986 (family/citation list of US 2016/0230986 A1 / US 10,488,039 B2)
• https://patentimages.storage.googleapis.com/79/de/8c/989e2527f0dd79/US5147201.pdf (US 5,147,201, Xiong — full text)
• https://patents.google.com/patent/US3751213 (citation chain including US 5,641,282, US 6,213,757, US 5,667,374)
• https://patents.google.com/patent/US3188366 (citation chain including US 5,476,375, US 5,544,624)
• https://www.scribd.com/document/867836333/google-scholar-patent (reproduction of the US 11,255,538 B2 "References Cited" table — used only where corroborated)
• https://www.wikidata.org/wiki/Q125019074 (inventor/entity confirmation)

I'll verify the key prior-art references before building the § 103 analysis, since the Prior Art section flagged some as only partially retrieved.

Now let me verify two more threads: metal-fiber surface-combustion matrices, and IR-transparent ceramic coatings on radiant matrices.

Let me check for art closest to the specific "thermal element" novelty — heat-recuperating inserts in a porous radiant burner.

Obviousness Analysis Under 35 U.S.C. § 103 — US 11,255,538 B2 ("Radiant infrared gas burner")

Builds on the previously generated Prior Art, Claims, and Strategic sections. Nothing in those sections is repeated except where I need to correct or extend it.

---

0. Two things I am flagging up front

(a) A material contradiction with the earlier Prior Art section. That section concluded: "No single reference located discloses all elements of independent claim 1 or claim 10," and identified US 5,641,282 as the strongest § 102 candidate. I am correcting that conclusion. A further search surfaced US 9,976,740 B1, "Burner," assigned to the Board of Regents of the Nevada System of Higher Education (on behalf of the University of Nevada, Reno) — the UNR "super-adiabatic radiant burner" — which appears to disclose a metallic porous radiant burner with high-thermal-conductivity radiation rods having fins embedded in the burner medium, extending to and making up the radiant surface, with the fins located where the flame is stabilized, and the rods coated with a low-thermal-conductivity insulator.^740 That is not merely closer than US 5,641,282; it is closer than anything discussed in the earlier section. The earlier "no single reference" finding should be treated as superseded pending a full-text retrieval of '740.

(b) A resolved ambiguity from the earlier section. The earlier section was unsure whether the numeral in US 5,375,563's citation list was "4,597,734" or "4,597,734/4,597,734." It is US 4,597,734 A, "Surface-combustion radiant burner," Shell Oil Company — I verified the specification and front matter.^734 The apparent duplication arises only because Google Patents renders the number without commas ("US4597734A"). No transposition. I have not auto-corrected anything.

Verification caveat, stated plainly. I retrieved full claims for US 4,597,734 and US 5,641,282, but for US 9,976,740 I retrieved only descriptive passages (from the FreePatentsOnline rendering and a university technology-transfer summary), not its claims, its filing/issue dates, or its figures. Everything I say about '740's disclosure is grounded in the quoted text; everything I say about its date and claim scope is inference and is marked as such. Similarly, the exact priority/issue dates of WO 2015/134228 A1 and US 9,709,265 B2 are unverified.

---

1. The legal frame, and why the CIP date question does not rescue the core claims

(i) Governing standard. Graham v. John Deere Co., 383 U.S. 1 (1966) (scope and content of the prior art; differences; level of ordinary skill; secondary considerations), applied through KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007). Under KSR, a combination is obvious where the elements were known, there was a known problem for which the elements supplied an apparent solution, and the combination was "obvious to try" with a reasonable expectation of success — including "the simple substitution of one known element for another" and "the use of known techniques to improve similar devices in the same way."

(ii) Effective filing date. The specification states the application "is a continuation-in-part application of U.S. patent application Ser. No. 15/016,469, filed on 5 Feb. 2016," which claims benefit of provisional 62/113,868 (2015-02-09). So:

• subject matter carried over from the parent → effective date 2015-02-09 (or at least 2016-02-05);
• new matter first added in 16/164,368 → effective date 2018-10-18.

This is the highest-value priority lever in the patent (the earlier Strategic section is right about that). But for this particular § 103 case it is not dispositive, for two reasons:

1. All four of my primary references predate even the earliest date. US 4,597,734 A (1986), US 5,147,201 A (1992), US 5,375,563 A (1994), US 5,641,282 A (1997), US 2003/0054313 A1 (2003), and US 2008/0227044 A1 (2008) are all § 102(a)(1) art — "patented, described in a printed publication... before the effective filing date" — against every claim, on any priority theory. No priority argument can remove them.
2. US 9,976,740 B1 is § 102(a)(2) art regardless of the date chosen. Section 102(a)(2) reaches a U.S. patent "effectively filed before the effective filing date of the claimed invention." UNR's '740 traces to provisional 61/658,820 (the university's technology summary identifies that provisional for the Super-Adiabatic Radiant Burner program)^unr — i.e., ~2012–2013, comfortably before 2015-02-09. No inventor overlap with the '538 ⇒ no § 102(b)(2)(A) exception; no common ownership ⇒ no § 102(b)(2)(C) exception. If '740 issued before 2018-10-18 it is additionally § 102(a)(1) art against the CIP-new-matter claims.

The CIP date question therefore matters mainly for the second tier of art — WO 2015/134228 A1 (published 2015-09-11) and US 9,709,265 B2, both directed to porous metal-foam burners, and for the "metal foam" alternative in claims 1 and 10. Those sit in the 2015-02-09 → 2018-10-18 gap and are citable against CIP new matter.

(iii) A prior-art-identity subtlety the earlier sections missed. Two references I would otherwise lean on — US 5,375,563 and US 5,476,375, both Institute of Gas Technology — name Mark J. Khinkis, who is also a named inventor on the '538. US 5,375,563 names "Mark J. Khinkis...; Tian-yu Xiong."^563 Under § 102(b)(1)(A)/§ 102(b)(2)(A), a disclosure is excepted if the subject matter was obtained from "the inventor or a joint inventor." If the relied-upon subject matter of '563/'476,375 is attributable to Khinkis, those references may be removed as prior art; if it is attributable solely to Xiong, they survive. This is a real diligence issue and a reason to prefer art with no inventor overlap ('740, '734, US 5,147,201, US 5,641,282, Rattner).

---

2. Level of ordinary skill

A POSITA here has a bachelor's degree in mechanical or chemical engineering (or equivalent) plus 2–5 years of experience in premixed gas combustion, radiant burner design, or porous-media combustion, or a master's degree with 1–2 years. This is the level the '538's own specification presumes: it uses undergraduate-level heat-transfer and chemical-kinetics reasoning (Stefan-Boltzmann, flame temperature vs. NOx) and standard burner-engineering vocabulary. The subject matter also has a substantial academic literature (e.g., the Progress in Energy and Combustion Science review of porous-media combustion cited in my searches), which matters for what a POSITA "would have known."

---

3. Claim construction of the four limitations that carry the patent

Claim 10's "configured to preheat" / "configured to transfer thermal energy" are functional recitations of apparatus capability; they are met by any structure inherently capable of performing them.

---

4. The art, organized into three tiers

Admitted prior art in the '538 specification itself is also fully available and is a powerful motivation source: the "reverberatory screen... in the form of a metal mesh or metal perforated plate installed above the matrix surface," which "is heated by combustion products and radiates to the matrix surface thus increasing its temperature and radiant heat flux... increasing combustion stability and reducing NOx and CO emissions"; and the "two-layer matrix with different permeability." Under In re Nomiya/MPEP 2129, applicant's own characterization of these devices is a binding admission of what a POSITA knew.

---

5. Combination A (primary): US 9,976,740 B1 — the strongest single-reference-plus-knowledge attack

What '740 appears to disclose, quoted:

• "the thermal efficiency of the SRB system is much greater (38% increase...)... by using preheater and radiation rods together."
• "The radiation rods made of high thermal conductivity materials conduct the extract heat from flame to the radiation surface without losing heat to the cold flue gas."
• "the burner is made of all metallic porous media and radiation corridor and preheater... the media is carbon or stainless steel or copper. The porous media is fabricated from, for example, pressed fine screens in PM1 and coarse ones in PM2. The fins of the radiation rod are either press joined/welded or machined."
• "The downstream porous medium (PM2) with a coarse porous structure serves as a flame holder to stabilize the flame where the fins of the radiation rods are located."
• "Heat conducting solids such as radiation rods extend and make up the radiant surface of the burner."
• "The radiation rods are assumed to be coated with a low thermal conductivity material (thermal insulator) to reduce the heat loss to the colder surrounding flue gas..."^740

Element mapping:

Motivation to combine is largely unnecessary if '740's disclosure is as quoted — the combination already exists in a single reference, which makes the case § 102 rather than § 103. Where '740 is silent (exact ceramic identity, 10–500 µm thickness, conductivity ratio 3–10, I need to substitute the known insulating ceramics), the motivation is supplied by the admitted prior art (IR-radiating coatings), by US 4,597,734/EP 0 157 432 (alumina on Fe-Cr-Al fibers), and by US 4,643,667 (low-conductivity layer over high-conductivity layer).

The two escape hatches the patent owner will argue. (1) '740's preheat is performed by a separate preheater plus the fine upstream medium PM1 — the owner will argue this is not "preheating... as it passes through the permeable matrix base material" with "combustion heat transfer... through the thermal transfer communication with the thermal elements." That argument is weak because the rods' fins are embedded in PM2, so combustion heat reaches the media conductively regardless of the preheater. (2) Is the flame actually "between thermal elements exposed above the combustion surface," or are the fins buried inside PM2 with the rods only emerging at the surface? This is the decisive factual question and it can only be resolved from '740's figures and claims. If the fins sit below the radiating face, claim 1's "between... exposed above" is not quite met and the case falls back to § 103 over '740 + US 5,641,282 (whose flame is expressly "in and around the rods").^282

---

6. Combination B (independent route): US 4,597,734 + US 5,641,282 + US 5,375,563

This route does not depend on '740 and should be pleaded in the alternative.

Primary reference — US 4,597,734 A (Shell). Supplies the matrix-side limitations verbatim: a "porous element... made of fibers of an alloy comprising iron, chromium and aluminum" — Fecralloy/Bekipor felt or woven panels, "rigid panels of randomly laid fibers... about 80 percent porosity" — with a metal frame, a gas inlet, and a distributing baffle, combusting premixed NG/air on the surface, achieving NO of only 12–24 ppmv and a turndown of "at least 10 to 1."^734 That reads on claims 1(a)–(b), 3 ("chromal"/heat-resistant steel), 11 (inlet + distribution + plenum), and 14 ("All the above results are for the 6 mm thick panel" — within 5–30 mm).

Secondary reference — US 5,641,282 A (GRI). Supplies the "thermal elements... exposed above the combustion surface" and the "combustion between elements": a plurality of elongated rods supported over and spaced from the burner surface, heated by convection from the flame, which then "radiate energy back towards the burner surface and also outwardly away from the burner surface so that radiation intensity and efficiency are optimized"; combustion occurs "in and around the rods"; rods are movable toward/away from the surface and their spacing is variable; at least one rod is hollow for a temperature sensor; rods may be non-circular in cross-section.^282

Tertiary reference — US 5,375,563 A (IGT). Supplies "elements at least partially disposed in the matrix" (claims 2 and 12): "porous bed heat exchanger means embedded in said stationary porous bed," specifically "a plurality of rows of fluid-cooled tubes" embedded in the porous bed, expressly to raise "heat transfer rates" and "energy utilization efficiency."^563

The differences to be bridged, and why they are obvious:

1. Ceramic rods → metallic, higher-conductivity elements. Claim 1 requires the elements to have a thermal conductivity higher than the matrix; '282's rods are ceramic. Substituting a high-temperature metal (stainless/Inconel/Hastelloy, all of which the '538's own claim 4 lists and all of which the art uses as burner hardware) is the paradigm KSR "simple substitution of one known element for another" where the purpose — getting heat to the burner surface — is unchanged and, if anything, better served by a conductor.
2. Spaced → in contact. '282's rods exist to heat the burner surface and are expressly adjustable toward it. Making an element that exists to deliver heat to a surface touch that surface is not an inventive act; it is the elimination of an unnecessary air gap in a known conduction path. KSR: "a court must ask whether the improvement is more than the predictable use of prior art elements according to their established functions."
3. Adding embedding. '563 already embeds metal heat-transfer tubes in a porous combustion bed for thermal efficiency — the very purpose for which the '538 uses embedded plates.
4. The problem is the same. The '538 states the problem as low specific power (~30 W/cm²), high CO, and a "narrow stable operating range (limited turndown ratio)." '734 reported its own limits (flame lifts above the surface beyond ~2000 kW/m²; surface temperature capped near 1160 K); '740 states "current radiant porous burners are less than 25% efficient." The admitted prior art already identifies the solution direction — put a heated body above the matrix and radiate/conduct heat back to it.

---

7. Combination C: the "metal foam" alternative and the mixer (claim 11)

Claims 1 and 10 permit "metal foam" as an alternative. Two references squarely supply it: US 2003/0054313 A1 (Rattner et al.), a "radiator element composed of a metal foam for use within a radiant burner," Int. Cl. F23D 14/14,^313 and US 2008/0227044 A1, a reticulated metal foam radiant burner with a plenum, a diffuser, and "a mixer... capable of mixing the combustible gas with air to form a combustible fuel mixture."^044 Either, alone or with '734/'282, disposes of claim 11's inlet/mixer requirements and of the metal-foam species. US 9,709,265 B2 / WO 2015/134228 A1 add a heat sink in contact with the metal foam matrix — relevant to the "element in thermal contact" concept, though a heat sink removes heat rather than returning it to the matrix, so it is a § 103 (not § 102) reference on that point.

---

8. The coating claims (8, 9, 18, 19) — the strongest defense, and its limits

These are the claims the patent owner will most credibly defend, and I want to be candid about that.

What must be shown: a coating on the downstream matrix surface (and, in claims 9/19, on the exposed elements) that is (i) of lower thermal conductivity than the matrix, (ii) optically transparent to IR radiation, (iii) ceramic, (iv) 10–500 µm thick, with (v) a matrix-to-coating conductivity ratio of 3–10, on a metal matrix.

Available attacks:

A § 112 angle worth probing, because it feeds the § 103 range analysis. The specification asserts that "the optical transparency of the ceramic coating (e.g., alumina or zirconia) provides that at a coating thickness of 50 to 200 microns heat can effectively be dissipated by radiation from the combustion zone." Whether alumina (as opposed to, e.g., sapphire or a genuinely IR-transparent ceramic) transmits in the 8–14 µm band the specification's own pyrometry used is a materials question a POSITA would need answered; if the transparency limitation is not in fact achieved across the claimed thickness range, the claim is vulnerable both for lack of written description and because the alleged unexpected result loses its causal link to the claim.

Realistic assessment: claims 1, 2, 3, 5, 6, 10, 12, 13, 15 and 18-family coatless claims are the vulnerable ones. Claims 8 and 19 (and 9 to a degree) are the hard target and would benefit from a dedicated search for pre-2015 art on thin (10–500 µm) alumina/zirconia coatings applied to metal-fiber radiant burner surfaces.

---

9. Claim-by-claim disposition

---

10. Motivation to combine — the articulated rationale

For a petition or invalidity contention, I would frame the motivation with all four KSR rationales in play:

1. The problem was known and stated in the art.
The '538 itself states the problem: SSC on a flat matrix has "low specific power (˜30 W/cm²), high carbon monoxide (CO) emissions, and a narrow stable operating range (limited turndown ratio)." '740 states the same problem in efficiency terms. US 5,147,201 states the same objective — "reduce combustion emissions, such as nitrogen oxides, by enhancing heat removal from the combustion zone" — and reports the same class of results (NOx 1–12 ppm, radiant heat up to 80 MBtu/h-ft², turndown >6:1).^201 "If a technique has been used to improve one device, and a person of ordinary skill in the art would recognize that it would improve similar devices in the same way, using the technique is obvious" (KSR).

2. The art already taught the specific solution direction.
(a) The admitted reverberatory screen: a metal mesh or perforated plate "installed above the matrix surface," heated by the combustion products, radiating back to the matrix to "increas[e] its temperature and radiant heat flux." (b) '282's rods, positioned above the burner surface expressly to "radiate energy back towards the burner surface." (c) '563's embedded tubes, in the porous bed, for heat transfer and efficiency. (d) '740's radiation rods, conducting flame heat to the radiating surface. Four independent teachings, all pointing the same way: put a hot metal body in heat-transfer relation with the matrix above the combustion zone.

3. The combination is a predictable substitution with a reasonable expectation of success.
'282's rods are spaced from the surface and radiate; a POSITA knows that conduction across a contact interface transfers heat far better than radiation across an air gap. Bringing the same rod into contact with the matrix is the "predictable use of prior art elements according to their established functions." Likewise, changing '282's ceramic rods to '734's/‘740's metallic composition is a substitution of known materials with known properties, with the known consequence that the element gets hotter and delivers more heat. The '538's own reported enhancements (≈200 K surface rise, 1.7× radiative flux) are the quAntitatively expected consequences of adding a conductive recuperator and follow directly from the Stefan-Boltzmann relation the specification itself invokes — "unusual and not obvious" is the applicant's characterization, not an established fact.

4. Design incentives and ordinary engineering optimization.
The numeric limitations (2–60 mm spacing; 5–30 mm matrix; 0.1–5 mm elements; 1–15 mm or 0.5–5× protrusion; 3–10 conductivity ratio; 10–500 µm coating) are parameters in which the specification identifies no criticality. They are the kind of "design choice" and "obvious-to-try" optimization that KSR, In re Aller, In re Woodruff, In re Geisler, and In re Kuhle place outside § 103. Notably, the '538's performance data were generated at mid-range values (0.7 mm plates; 16 mm plate height; 8 mm protrusion; 8 mm foam; 20–200 µm coatings) — there is no evidence that the endpoints do anything the interior does not.

---

11. The applicant's best rebuttals — and how they fare

(a) Teaching away (the strongest defense). EP 0 157 432 and US 4,597,734 teach that the desirable property of a metal-fibre burner is low through-thickness effective conductivity, so that "a high thermal gradient can be achieved... which allows a high temperature to be maintained at the combustion surface, while the temperature of the porous metallic element away from the combustion surface is relatively low." A POSITA reading that could conclude that deliberately piping combustion heat back into the matrix body runs the wrong way along that gradient — risking flashback and reduced surface temperature. The '538's specification itself warns that heat flow to the surface "must be maintained at a certain level to be sufficient for steady state SSC and limited to avoid or prevent flame quenching."
Assessment: real but probably not dispositive. (i) The '734/EP art describes effective conductivity through a fibre mat, not the deliberate introduction of a continuous conductive member; (ii) A reference teaches away only if it "criticizes, discredits, or otherwise discourages" the claimed approach — '734 does not mention embedded conductors at all; (iii) '740 shows the field had already moved past that caution by adopting internal heat recirculation as the solution; (iv) the '538's own answer to flashback is the low-conductivity coating, which is a separately claimed feature, so the teaching-away argument does not rescue claims 1 and 10. Expect this argument to be made for claims 1/10 and to be directed more forcefully at claims 8/19.

(b) Unexpected results. The applicant will point to the +200 K, 1.7× radiation, 1.5× NOx, and up-to-3× CO figures. Three problems: (i) they are results of the claim, measured against uncoated and coated controls — not against the closest art ('740's radiation-rod burner, which exists precisely to produce the same effect); (ii) they are qualitatively predictable (more heat delivered to the emitter ⇒ higher emitter temperature ⇒ more radiation and lower flame temperature ⇒ less thermal NOx); (iii) there is no evidence of commercial success, industry acquiescence, copying, licensing attributable to this feature, or long-felt-but-unmet need — the earlier Prior Art and Strategic sections found no product traceable to these claims.

(c) Internal inconsistency that will hurt them. The Summary states the upper limit of stable combustion is "extended from 45 W/cm² to 120 W/cm²"; the Experimental Support section says the conventional range "was from 20 W/cm² to 70 W/cm²" and the new matrix operates "from 15 W/cm² to 100 W/cm² (see FIG. 13)." The two ranges cannot both be the baseline and the improvement. I flag this as an unresolved contradiction within the authoritative text — it undercuts the reliability of the asserted unexpected results and is independently an enablement/§ 112(a) issue.

(d) Secondary considerations not yet on the table. No objective indicia have been identified to date; if the patent owner later produces them, the nexus question (are they attributable to the thermal elements, or to the metal-foam matrix, or to the coating, each of which is separately known?) will be the battleground.

---

12. Where this case is weakest — be honest with the client

1. '740 is unverified. My entire primary theory rests on descriptive passages I could not cross-check against its claims, figures, or issue date. Retrieve US 9,976,740 B1 in full before drafting anything. If its rods do not protrude above the combustion surface, claim 1's "between thermal elements exposed above the combustion surface" is not met by '740 and the theory reverts to the '734 + '282 + '563 combination.
2. No reference I retrieved expressly discloses metallic, higher-conductivity elements simultaneously in contact with a metal-foam matrix and protruding above the combustion surface and combusting between them — other than (arguably) '740. Every other combination requires at least one "design choice" step (spaced ⇒ contact; ceramic ⇒ metal).
3. Claims 8, 9, 18, 19 are the hard target. The IR-transparency + 10–500 µm + ratio 3–10 package has no clean pre-2015 hit in my retrieved set. A dedicated search is required (see §13).
4. Claim 17 (cylindrical matrix with radially extending planar elements) has no good art in my set.
5. Claims 6, 7, 14, 16 rest on range-vs-criticality arguments (In re Aller/Geisler), which are persuasive but not automatic — expect the applicant to argue criticality, and be ready with the specification's own mid-range data.
6. The Khinkis inventor-overlap issue may knock out US 5,375,563 and US 5,476,375. Build the case so that it does not depend on them.

---

13. Recommended next steps

1. Pull US 9,976,740 B1 in full — claims, figures (esp. FIGS. 12–14), priority chain (provisional 61/658,820), and grant date. Determine precisely whether the radiation-rod fins lie above or below the radiating face of PM2. This single question moves the case between § 102 and § 103.
2. Run a targeted art search on the coating limitations (claims 8/9/18/19): pre-2015 art on thin (10–500 µm) ceramic, IR-transmissive coatings applied to metal-fibre or metal-foam radiant burner surfaces, e.g. in F23D 14/14 + C23C 4/xx / C23C 24/xx combinations, and on gas-dynamic/detonation-spray alumina and zirconia coatings on FeCrAl substrates.
3. Map the CIP new matter. Compare claims 1, 2, 5–7, 10, 12–17 against the 15/016,469 disclosure. If the "thermal element" geometry is CIP new matter, WO 2015/134228 A1 and US 9,709,265 B2 become § 102(a)(1) art, and 2016–2018 publications on super-adiabatic and heat-recirculating porous burners become available for the first time.
4. Resolve the Khinkis overlap on US 5,375,563 and US 5,476,375 under § 102(b)(1)(A)/(b)(2)(A) before relying on either.
5. Get the prosecution history of 16/164,368 from PatentCenter. Any reference the Examiner applied and then withdrew, or applied only to the coating claims, tells you where the § 325(d) risk sits and where the examiner saw the novelty line.
6. Confirm claim 19's full text against the issued patent (it is truncated in the supplied record) before any element-by-element chart is prepared.

---

Sources

• https://patents.google.com/patent/US11255538/en (authoritative full text supplied) — Background admissions (reverberatory screen; two-layer matrix); claims; Experimental Support; CROSS REFERENCE (CIP of 15/016,469)
• https://www.freepatentsonline.com/[9976740](/patent/9976740).html and https://www.ctc-n.org/products/high-efficiency-porous-burner-design — US 9,976,740 B1 (UNR) radiation rods, fins, pressed-screen porous media, insulating coating, preheater
• https://patents.google.com/patent/US4597734A/en and https://patentimages.storage.googleapis.com/2f/95/3a/50dbd8c99dc603/US4597734.pdf — US 4,597,734 A (Shell), full specification text
• https://patentimages.storage.googleapis.com/7b/96/61/f31b3bf2217862/EP0157432B1.pdf — EP 0 157 432 B1 (Shell), low through-thickness conductivity; preheat 200–300 °C ⇒ +35–70% radiant efficiency
• https://www.freepatentsonline.com/[5641282](/patent/5641282).html / http://www.everypatent.com/comp/pat5641282.html — US 5,641,282 A (GRI), full claim set and abstract
• https://patentimages.storage.googleapis.com/79/de/8c/989e2527f0dd79/US5147201.pdf / https://patents.google.com/patent/US5147201 — US 5,147,201 A (Xiong/IGT)
• https://patentimages.storage.googleapis.com/d4/5d/de/af50abbb8fdd02/US5375563.pdf — US 5,375,563 A (Khinkis & Xiong / IGT), "porous bed heat exchanger means embedded in said stationary porous bed"
• https://patentimages.storage.googleapis.com/b0/38/14/4b740826a507e0/US20030054313A1.pdf — US 2003/0054313 A1 (Rattner et al.), metal-foam radiator element
• https://patents.google.com/patent/US20080227044 — US 2008/0227044 A1, metal foam radiant burner with mixer
• https://patentimages.storage.googleapis.com/3d/0b/08/2e62ee822f3e22/US9709265.pdf and https://patents.google.com/patent/WO2015134228A1/en — US 9,709,265 B2 / WO 2015/134228 A1, porous metal foam burner with surrounding heat sink
• https://www.freepatentsonline.com/[5408984](/patent/5408984).html — two-stage flame stabilization with tabs and fins (US 5,408,984)
• https://vffa.com.pk/wp-content/uploads/2025/05/1386_C13-2.pdf — handbook chapter on advanced ceramic radiant burners (Xiong 1993 built-in heat exchanger; Kendall & Sullivan 1993 ytterbia coating; Ruiz & Singh 1993 advanced IR burner)
• https://patents.google.com/patent/[US5326631](/patent/US5326631) — citation chain confirming US 4,597,734 A (Shell Oil), 1986-07-01

This is an analyst's prior-art and obviousness assessment, not a legal opinion or a validity determination. Every mapping above must be re-verified against the full text (and, for '740, the full claims and figures) of each reference before being relied on.