US 4999225

I'll search for this specific patent number across the requested sources.

US Patent 4,999,225 — Analyst Summary

Search scope note: I ran targeted searches against Google Patents/USPTO-derived records and open web sources for the literal identifier "4999225" / "4,999,225." I found no CAFC 2026 docket entry, appeal, or litigation record referencing this patent, and no USPTO PatentCenter "reexamination/PTAB" activity. Any assertion of active 2026 CAFC involvement would be unsupported. (Unrelated hits for "4999225" — e.g., a Chinese trademark registration number 4999225 and JP 4999225 B2 — are different IP rights and were excluded.)

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Bibliographic Data

Discrepancy flagged (not auto-corrected): Google Patents lists the US priority date as 1989-01-05 (same day as filing). The EP family record for EP-0375931-A2 lists a priority date of 1988-12-28 — the same date the US assignment was recorded. I do not have authoritative confirmation of which date governs for priority purposes, so I am reporting both as found rather than reconciling them.

Source: https://patents.google.com/patent/[US4999225A](/patent/US4999225A)/en ; https://pubchem.ncbi.nlm.nih.gov/patent/EP-0375931-A2

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Abstract (as issued)

A method for producing a dense and tenacious coating with a thermal spray gun including a nozzle member and a gas cap. The gas cap extends from the nozzle and has an inwardly facing cylindrical wall defining a combustion chamber with an open end and an opposite end bounded by the nozzle. An annular flow of a combustible mixture is injected at a pressure of at least two bar above atmospheric pressure from the nozzle coaxially into the combustion chamber. An annular outer flow of pressurized air is injected from the nozzle adjacent to the cylindrical wall. Powder particles having a heat-stable, non-fusible component and a heat-softenable component, entrained in a carrier gas, are fed axially from the nozzle into the combustion chamber. An annular inner flow of pressurized air is injected from the nozzle into the combustion chamber coaxially between the combustible mixture and the powder-carrier gas. Upon combusting the annular mixture a supersonic spray stream containing the powder is propelled through the open end to produce a coating.

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Plain-Language Overview of the Independent Claims

Claim 1 — Full apparatus-specific process (the "preferred gun" claim).
Using a gun whose gas cap forms a combustion chamber closed at the rear by the nozzle face and open at the front, the method requires all of the following, together:

1. Inject an annular flow of combustion gas + oxygen coaxially into the chamber at a steady pressure of at least 2 bar above atmospheric.
2. Inject an annular outer flow of pressurized non-combustible gas (air) next to the chamber wall, radially outside the combustible mixture.
3. Feed axially into the chamber, in a carrier gas, powder of polymer particles with heat-stable non-meltable cores and heat-softenable surfaces.
4. Inject an annular inner flow of pressurized gas coaxially between the combustible mixture and the powder/carrier stream.
5. Combust the mixture so a supersonic spray stream (carrying the material in finely divided form) exits the open end.
6. Aim the stream at a substrate to form a coating.

Note (literal reading): the claim body's final step refers to "the heat fusible material in finely divided form," even though the fed powder is defined as having non-meltable cores — an internal wording inconsistency in the granted text, quoted as-is.

Claim 2 — Broader combustion-chamber process with a metal component.
Using a gun with a tubular member defining a combustion chamber having an open end that propels combustion products at supersonic velocity:

• Inject combustion gas + oxygen into the chamber at a steady pressure of at least 2 atmospheres above ambient;
• Feed powder whose particles have both a heat-stable non-meltable polymer component and a metallic component;
• Combust to produce a supersonic powder-laden stream through the open end;
• Direct it at a substrate to coat it;
• wherein the polymer is thermoset grains that become surface heat-softenable by the spray stream (i.e., only the surface is modified/softened; the core remains non-meltable).

Claim 5 — Broadest "combustion chamber means" claim.
Using a gun with combustion-chamber means and an open channel that propels combustion products at supersonic velocity:

• Feed through the open channel powder particles comprising a heat-stable non-meltable polymer;
• Inject and combust combustion gas + oxygen in the chamber at a pressure sufficient to produce a supersonic powder-laden stream through the channel (no explicit numeric pressure floor, unlike claims 1 and 2);
• Direct the stream at a substrate to form a coating;
• wherein the polymer is again thermoset grains that are surface heat-softenable by the spray stream.

Dependent claims at a glance

• 3 (on 2): pressure sufficient to yield ≥8 visible shock diamonds with no powder feed.
• 4 (on 3): combustion gas selected from propylene or methylacetylene-propadiene ("MPS").
• 6 (on 1): polymer grains comprise poly(paraoxybenzoyl)ester.
• 7 (on 6): grains consist essentially of poly(paraoxybenzoyl)ester.
• 8 (on 6): grains consist essentially of a copolyester of poly(paraoxybenzoyl)ester.
• 9 (on 6): powder further comprises aluminum or aluminum-base alloy powder.
• 10 (on 5): powder particles further comprise metallic particles.

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Technical Gist

The patent's core insight is that HVOF/supersonic combustion spraying (not plasma, not low-velocity flame spray) can successfully deposit materials that will not melt — non-meltable minerals (SiC, BN, graphite, diamond, AlN, etc.) composited with a meltable metal, and thermoset polymers (e.g., EKONOL™ poly(paraoxybenzoyl)ester, Xydar™ copolyester) whose surface alone becomes heat-softenable in the flame. Examples report ~85% deposit efficiency for a 30% polyester / 70% Al-12Si blend vs ~65% typical for plasma-sprayed 40% powder, with ~1% uniform porosity (vs ~5% non-uniform), R15y hardness 78–83 (vs 65–75), and retained, uniformly distributed SiC in nickel-clad SiC coatings. The gun itself (annular combustible stream + outer air sheath + inner air sheath around an axial powder feed) is described in the earlier, related US 4,865,252 (Rotolico/Sala), which this patent leans on for apparatus support.

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Certainty / Limitations

• Bibliographic and claim data above are drawn from the authoritative full text and the Google Patents record — high confidence.
• The priority-date discrepancy (1989-01-05 vs 1988-12-28) is unresolved in the sources I retrieved.
• The patent is expired (lapsed 2003); it cannot be asserted, so a CAFC 2026 appeal concerning it is implausible. If you are looking for 2026 Federal Circuit activity, please supply a docket number or party name — I could not locate any such proceeding tied to the literal number 4,999,225, and I will not infer one.

I'll research this systematically. Let me run several targeted searches.

Let me try more targeted searches on litigation databases and specific case records.

Findings: Litigation Involving U.S. Patent No. 4,999,225

No litigation is known or found involving U.S. Patent No. 4,999,225.

I searched for this specific patent number across litigation-oriented sources (including the Unified Patents litigation portal, and general web/patent-citation index searches) and found zero district court actions, CAFC appeals, ITC Section 337 investigations, or PTAB proceedings naming this patent.

What the searches actually returned (and why each is not litigation on '225)

Important caveat on the "Sulzer Metco" connection

U.S. 4,999,225 was assigned to The Perkin-Elmer Corporation (recorded 1988-12-28), then to Sulzer Metco (US), Inc. (merger recorded 1996-08-13), and today the recorded current assignee is Oerlikon Metco US Inc. So the corporate chain is real — but I found no court case in which any of these entities asserted '225. I did not, however, exhaustively query every PACER docket under each successor's name, so I cannot rule out a never-indexed or very short-lived suit with certainty.

Legal-status context (from the patent record)

• Filing date: 1989-01-05; granted: 1991-03-12; priority: 1989-01-05
• Anticipated expiration: 2009-01-05
• Actual status: Expired – Fee Related. Maintenance fee reminder mailed 2002-09-25; lapsed for failure to pay maintenance fees on 2003-03-12 (37 CFR 1.362)

Because the patent lapsed in March 2003 — roughly six years before its nominal 2009 term — any infringement action would necessarily have had to be filed before lapse (plus the six-year § 286 damages lookback). That narrows the window considerably, and no suit within it appears in the sources searched.

Bottom line

There is no known litigation involving U.S. 4,999,225. I am reporting this as a negative finding based on the searches available; I cannot certify an absolute negative, since no search can prove the absence of an unindexed or sealed action. If you need a certified-clear answer, the definitive step would be a PACER/Unified Patents docket search filtered on the exact patent number "4999225" (not similar numbers), plus a check of the Westlaw/Lex Machina Litigation Analytics record under assignees Perkin-Elmer, Sulzer Metco (US), and Oerlikon Metco US.

Proceedings overview

Total AIA trial proceedings on file for US 4,999,225: 0 (zero). The structured "PTAB proceedings on file" block — sourced from the USPTO Open Data Portal — returns no IPR, PGR, or CBM proceeding for this patent, and independent web searching surfaced no petition, institution decision, FWD, or Federal Circuit appeal naming US 4,999,225 as the challenged patent. Because there is no proceeding to break down by status (active / claims invalidated / claims sustained / settled / institution denied), the useful "bottom line" is a different one: there is nothing for a defendant to lose to IPR estoppel, and nothing for the patent owner to point to — because the patent itself lapsed for failure to pay maintenance fees on 2003-03-12, more than nine years before AIA trials existed. Any demand letter citing this patent today is citing a dead, unenforceable right; the PTAB record is empty because there was never anything worth challenging.

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No AIA trial proceedings

There is no proceeding to caption in the {PROCEEDING_NUMBER} — {Petitioner} v. {Patent Owner} format, and I will not manufacture one. The findings that support that conclusion, and the non-PTAB facts that matter more:

• Canonical source: USPTO ODP structured block returned "no AIA trial proceedings." This is the authoritative list for this task and it is empty.
• Independent verification: Web searches for US4999225 IPR, "4999225" PTAB, "4,999,225" inter partes review, and PTAB E2E-style queries returned no PTAB paper, trial number, or docket entry referencing US 4,999,225. The only third-party citations of this patent I could find are patentability citations by examiners in later, unrelated applications (e.g., EP 1 431 413 A3 cites "US 4 999 225 A (ROTOLICO ANTHONY J ET AL)" as a category-Y reference against claims 12–18), not PTAB challenges. (EP1431413A3)
• Structural reason the list is empty: IPR/PGR/CBM practice began 2012-09-16. Per the Legal Events on the patent's Google Patents record, the patent expired 2003-03-12 ("PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362"; "Lapse for failure to pay maintenance fees," effective 2003-03-12). Its nominal 20-year term from the 1989-01-05 filing would have run to 2009-01-05 — it never got there. There was no live patent in existence when the AIA trial regime opened.
• Assignee chain (for completeness): Perkin-Elmer Corp. → Sulzer Metco (US), Inc. (merger, effective 1996-07-02) → current listed assignee Oerlikon Metco US Inc. No defensive aggregator (Unified Patents, RPX, etc.) appears anywhere in the chain, and no litigation-driven IPR campaign is visible because no assertion campaign appears to exist.
• Non-US proceedings: The family has a European counterpart, EP0375931B1 (granted 1996-01-10), which appears in the "Similar Documents" cluster on the Google Patents page. I have not verified its EPO Register status (post-grant opposition/lapse) and I am not asserting an EPO opposition occurred. Flag it as unverified rather than treat it as a parallel proceeding.

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Strategic summary

Claim status: all ten claims are UNTESTED and none is CANCELED — but "untested" here means "unreachable," not "hardened." Claims 1–10 were never subjected to an AIA trial, so there is no FWD narrowing, no certificate canceling claims, and no surviving-claim list to hand a defendant. What does exist is a maintenance-fee lapse: under 35 U.S.C. § 41(b) and 37 C.F.R. § 1.362, the patent expired as of 2003-03-12 for failure to pay maintenance fees. The consequence for a defendant is much better than an IPR win, because there is no residual claim scope to route around and no reissue/reexam apparatus that was exercised to revive it. Compare: an IPR that kills claims 1–5 still leaves claims 6–10 alive to be asserted. Here nothing is alive.

Estoppel landscape: § 315(e)(2) is a non-issue in both directions. No petitioner ever filed, so no petitioner (or privy) is estopped from raising any § 102/§ 103 ground — but no defendant needs estoppel relief either, because there is no tribunal and no enforceable claim to defend against. If you nonetheless want the invalidity record for a stray assertion, the art is fully available: the patent's own front-page citations (Bleakley US 2,317,173; Poorman US 2,714,563 / 2,964,420; Peck US 3,741,792; Browning US 4,416,421; Dittrich US 3,254,970; Longo US 3,655,425 / 3,723,165; Economy US 3,784,405; Metco US 3,530,892, US 3,617,358) plus the applicant's own admissions about the copending application that matured as US 4,865,252 are all unencumbered by any estoppel or IPR record. See the citation tables on the Google Patents page.

Pattern signals: there are none, and the absence is diagnostic rather than suspicious. A patent that is asserted gets IPRs — usually several, usually within 12 months of service under § 315(b). This patent shows zero petitions across a 30+ year post-issuance history, zero PTAB activity, and no Federal Circuit docket traffic attributable to it. The most likely explanations are the ones the record actually supports: it was a 1989 Perkin-Elmer/Metco process patent in a niche (HVOF/supersonic combustion spray of non-meltables) where the practicing entity was the assignee itself, not a licensor enforcing against third parties, and it was dropped for non-payment in 2003. There is no troll, no aggregator, and no revocation-of-enforceability fight to inherit.

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Recommended next steps

• If you are a defendant receiving an assertion of US 4,999,225: do not build an IPR. IPR of an expired patent is generally disfavored/moot, and here it is affirmatively pointless. Instead, put the legal-status record in front of the other side: quote the Legal Events entries showing "2003-03-12 LAPS — Lapse for failure to pay maintenance fees" and "PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362," available on the Google Patents legal-events panel and confirmable at USPTO Patent Center and EPAS/Patent Maintenance. An expired-for-nonpayment patent cannot support an infringement claim, and continued assertion after notice of the lapse is the kind of conduct that supports a § 285 fee motion.
• Because there is no PTAB activity, there are no trial milestones to track — no institution-decision deadline, no oral hearing, no statutory one-year FWD clock. Nothing is pending at the Board for this patent, so there is no scheduling order to diarize.
• Claim-level citation caution: any document that tells you "claims 1–5 were canceled in IPR" or "the patent survived IPR" is wrong about this patent. The correct statement is: no PTAB proceeding exists; the patent expired 2003-03-12 for non-payment of maintenance fees. If you need a citable negative-artifact report, the USPTO PTAB Decisions page and PTAB E2E/PTACTS search (https://ptacts.uspto.gov/) both return nothing for patent number 4,999,225 as of 2026-09-30.
• Unverified item to clear if it matters: EP0375931B1 (the EP member of this family) — check the EPO Register for opposition history and lapse if your matter has European exposure. I have not confirmed that record and am not representing that an opposition exists.

I'll research the assignment record systematically, cross-referencing the patent's legal events with corporate history and asserter directories.

Let me research the inventors, the recorded correspondent of record, and cross-check asserter directories.

Ownership Reconstruction — U.S. Patent No. 4,999,225

Preliminary note on sources. The USPTO Assignment Center UI (https://assignment.uspto.gov/patent/index.html; https://assignmentcenter.uspto.gov/) is a JavaScript application that cannot be scraped from here, so I worked from the machine-readable assignment/legal-events record mirrored on Google Patents for this patent, cross-checked against SEC-equivalent corporate sources and the prior litigation findings. The indexed record exposes reel/frame, conveyance, assignor, assignee, and dates, but does not expose the correspondent of record for either entry. I therefore cannot report a correspondent name, firm, or address for this chain — and I will not invent one. I flag this explicitly below rather than guess.

No contradiction with the previously generated litigation summary: that section found zero litigation naming '225, which is consistent with the clean, non-asserted ownership chain reconstructed here.

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Inventors

Three named inventors, all residents of Long Island, N.Y., all working for the assignee's Metco Division of The Perkin‑Elmer Corporation, Westbury, N.Y.:

The specification itself ties the inventors to the Metco product line — the examples specify a "Metco Type DJ™ Gun sold by The Perkin‑Elmer Corporation, Westbury, N.Y." and "Metco 601NS / 301NS / 310NS" powders — confirming the Metco Division as employer/worksite.

Unusual-pattern check — NOT present. There is no evidence of a post-filing inventor exodus preceding a portfolio sale. To the contrary, Rotolico and Kushner continued to file applications assigned to Perkin‑Elmer after '225, e.g. U.S. 5,059,095 (filed 1989‑10‑30, Kushner/Rotolico/Nerz/Saia) and U.S. 5,122,182 (filed 1990‑05‑02, Dorfman/Kushner/Rotolico/DelRe/Novinski). That is a "stayed with the assignee" pattern, not a fire-sale precursor.

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Original assignee

The Perkin‑Elmer Corporation, a New York corporation, Norwalk, Conn. (recorded as such in the 1988 assignment; the Metco operating unit was in Westbury, Long Island).

• Products embodying the claims: Yes, demonstrably. The patent's own examples spray the claimed method on the Metco Type DJ™ HVOF gun with Metco 601NS (polyester/aluminum abradable), 301NS (nickel‑chrome‑iron clad with Al + BN) and 310NS (aluminum‑graphite) powders — commercial Perkin‑Elmer/Metco products. This is an operating company selling the practice of the claims, not a paper holder.
• Primary line of business: Diversified instrumentation; by the early 1990s Perkin‑Elmer was refocusing on analytical instruments/biotechnology, with Metco (~$100M+ 1993 sales) as a non-core surface‑technology division.
• Current status: Operating (not dissolved, not bankrupt). Metco was divested — see the timeline. The parent continued as an analytical-instruments/life-sciences business; the divestiture was a strategic "recentering," not a bankruptcy fire‑sale. (Corporate descendants of the PerkinElmer instruments business persist today; I am not tracing that genealogy further, as it is not an ownership link to '225.)

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Assignment timeline

Two recorded conveyances touch this patent. Both are ordinary corporate documents; neither is an NPE transfer.

• 1988‑12‑27 (executed) / recorded 1988‑12‑28 — Reel 005014/0947

  • Conveyance: Assignment (Assignment of Assignors' Interest)
  • Assignor: Anthony J. Rotolico; Burton A. Kushner; Amr Aly (joint inventors) — reel/FRAME 005014/0947 recorded in the legal-events table; Executed 1988‑12‑27
  • Assignee: The Perkin‑Elmer Corporation, a corp. of New York
  • Correspondent: not exposed in the indexed record — not determinable from available sources. (The Assignment Center record would carry this field; the Google Patents mirror does not. No inference drawn.)
  • Context: Initial inventor-to-employer assignment, executed before the 1989‑01‑05 filing date — the standard "assign-before-file" practice, not a monetization event.

• 1996‑07‑02 (executed) / recorded 1996‑08‑13 — Reel 008126/0066

  • Conveyance: Merger
  • Assignor: The Perkin‑Elmer Corporation
  • Assignee: Sulzer Metco (US), Inc. (New York)
  • Correspondent: not exposed in the indexed record — not determinable from available sources. Same caveat as above; no repeat-correspondent analysis possible on this chain.
  • Context: Internal corporate reorganization implementing Sulzer's 1994 acquisition of the Metco Division. Note the lag: the deal was announced 1994‑02‑23 and cleared by the FTC in October 1994, but the U.S. merger instrument wasn't executed/recorded until 1996 — a two-year administrative tail, still purely an intra‑corporate record cleanup.

Gap in the indexed record (flagged, not assumed): Google Patents lists Oerlikon Metco US Inc. as current assignee, but no third assignment event appears in the legal-events table. The Sulzer→Oerlikon Metco transition was the 2014‑01‑31 announced / 2014‑06‑02 closed division sale to Oerlikon. Because no reel/frame is surfaced for that step, I treat "Oerlikon Metco US Inc. is the recorded current owner" as the host-provided current-assignee field only — I did not find an assignment recording evidencing it and will not cite one.

No other assignments (security agreements, licenses, change-of-name, releases) appear for '225.

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Timeline diagram

timeline
    title Ownership of US 4999225
    1988 : Inventors assign to Perkin Elmer 005014 0947
    1989 : Application filed 1989 Jan 5
    1991 : US 4999225 granted 1991 Mar 12
    1994 : Metco division sold to Sulzer
    1996 : Merger recorded to Sulzer Metco US 008126 0066
    2003 : Lapsed for unpaid maintenance fee
    2014 : Metco sold to Oerlikon

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NPE / troll-pattern signals

Additional negative fact bearing on all signals: the patent lapsed for non‑payment of maintenance fees on 2003‑03‑12 (37 CFR 1.362), roughly six years before its anticipated 2009‑01‑05 term. This both (a) evidences that no assignee was monetizing the patent post‑2003, and (b) closes any assertion window — further inconsistent with an NPE play.

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Verdict

Defensive / non-asserting — with an explicit definitional caveat: the chain terminates at an operating manufacturer (Oerlikon Metco US Inc., successor via Sulzer Metco (US), Inc.), not at a formal defensive aggregator such as RPX/AST/LOT/Unified. Of the available labels, "non‑asserting" is the operative and correct descriptor; the "defensive aggregator" prong does not apply.

Justification: the only two recorded conveyances are Reel 005014/0947 (1988‑12‑27, inventors → Perkin‑Elmer, the standard assign-before-file) and Reel 008126/0066 (executed 1996‑07‑02, Perkin‑Elmer → Sulzer Metco (US), Inc. by merger); both are ordinary corporate events between named operating companies, with no shell entity, no known asserter, no cascading transfers, and no pre-suit transfer. The patent was commercialized by its original owner (Metco Type DJ gun and 601NS/301NS/310NS powders in the specification), was never asserted, and lapsed for fee non‑payment in 2003 — a textbook non‑NPE, non‑asserting operating-company chain.

Verification link: search patent number 4999225 at https://assignment.uspto.gov/patent/index.html (records: reel 005014/0947 and reel 008126/0066). To close the two open items — the correspondent of record on each reel, and whether a Sulzer → Oerlikon assignment was recorded but not indexed — run the exact-number query in Assignment Center and, if needed, pull the reel images directly.

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Two cross-reference flags for the file:

1. Priority-date discrepancy (minor). The U.S. record and Google Patents give priority/filing 1989‑01‑05, but the EPO/PubChem entry for the EP counterpart EP 0 375 931 A2 lists a priority date of 1988‑12‑28. This is likely an EPO-database convention quirk, but since the brief says to flag contradictions: the U.S. chain (assignment executed 1988‑12‑27, filed 1989‑01‑05) is internally consistent and I treat 1989‑01‑05 as controlling for the U.S. patent.
2. Current-assignee field vs. recorded event. As noted, "Oerlikon Metco US Inc." is supplied by the host as current assignee but has no corresponding assignment entry in the legal-events table — do not treat it as reel/frame‑grounded without the Assignment Center pull.

I'll research the cited prior-art references for US 4,999,225. Let me run targeted searches.

Let me gather details on the remaining cited references.

Prior-Art Analysis — US 4,999,225

Scope/reliability note: My live tool calls returned Google Patents and Espacenet/patent-mirror records rather than an independent PatentCenter page for the literal string "4999225," and I hit the tool-step limit before completing every planned query. The record I retrieved is consistently the same document, and the citation list below is corroborated by the authoritative full text supplied. I did not auto-correct the number: "4999225" resolves to US 4,999,225 A (leading zero dropped by citation convention). No results for similar numbers are included.

The patent itself (for the identification step):

• US 4,999,225 A — "High velocity powder thermal spray method for spraying non-meltable materials"
• App. No. US 07/290,928; filed 1989-01-05; granted 1991-03-12
• Inventors: Rotolico, Kushner, Aly; original assignee Perkin-Elmer Corp; current assignee Oerlikon Metco US Inc.
• 10 claims, independent claims 1, 2, 5; status Expired–Fee Related (lapsed 2003-03-12)
• URL: https://patents.google.com/patent/[US4999225A](/patent/US4999225A)/en

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The prior art of record (11 U.S. patent citations)

All 11 face-of-patent citations published before 1989-01-05, so each qualifies as prior art at least under 35 U.S.C. § 102(b) (printed publication more than one year before filing). There were no non-patent-literature citations listed. The "Cited By" documents (e.g., EP 0555195, US 5,269,980, WO 03/051528, etc.) are forward citations and are not prior art to '225.

Corroborating sources: patent face + Google Patents citation list (https://patents.google.com/patent/US4999225A/en); US 3,784,405 PDF (https://patentimages.storage.googleapis.com/dd/0a/0f/37305d6fb3c35b/US3784405.pdf); US 4,416,421 text (Espacenet US4416421A); US 3,723,165 PDF (https://patentimages.storage.googleapis.com/57/a0/f1/5a479de2914dcf/US3723165.pdf).

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§ 102 anticipation analysis, reference by reference

Legal standard applied: A claim is anticipated under § 102 only if a single reference discloses every limitation, arranged as in the claim. References cited together to reconstruct the invention are § 103 (obviousness) art, not § 102 art. Because the '225 claims are method claims requiring a supersonic combustion spray stream at a steady pressure of at least two bar/atmospheres above ambient combined with a non-meltable-component powder, I assessed each reference against that full combination.

1. US 2,317,173 (Bleakley) — most relevant to claims 1, 2, 5 (structure), but does NOT anticipate.
Bleakley discloses the closest flow geometry to claim 1: axial powder feed into a chamber, an annular combustion-gas flow, and a coaxial outer air sheath along the chamber wall, with the stream exiting an open chamber end. However, it is an atmospheric/low-velocity "melting chamber" device; it lacks (a) supersonic discharge, (b) the ≥2-bar steady chamber pressure, (c) the inner coaxial gas sheath (claim 1), and (d) any non-meltable/thermoset polymer powder. No complete anticipation of any claim; significance is § 103 (claim 1's three-flow architecture).

2. US 2,714,563 & 3. US 2,964,420 (Poorman) — relevant background only.
Detonation-wave spraying discloses high-velocity impact and short dwell time (concepts the '225 spec invokes), but detonation is not a steady supersonic combustion stream and no non-meltable polymer is disclosed. No anticipation of claims 1, 2, 3, 4, 5.

4. US 3,254,970 (Dittrich) — relevant to the POWDER limitation of claims 1, 2, 5 and to claims 9/10, not anticipating.
It discloses a non-meltable refractory core clad with metal — i.e., the "heat-stable non-meltable core + heat-softenable surface" particle concept. But it is a product patent; it does not disclose the claimed supersonic, ≥2-bar spray method. At most it bears on the powder element of claims 1/2/5 and the metal-component limitations (claims 9, 10). No § 102 anticipation.

5. US 3,530,892 (Metco) — apparatus detail only.
A cylindrical valve plug for gas control. Discloses no powder or spray-method limitation. Not anticipatory of any claim.

6. US 3,617,358 (Dittrich) — powder-making method.
Agglomeration/spray-drying of multi-component powder relates only to how the powder element of claims 1/2/5 (and claims 9/10) is made. Not anticipatory.

7. US 3,655,425 (Longo & Patel) — most relevant to the mineral-composite powder of claims 1, 2, 5 and claim 10.
Ceramic-clad flame-spray powder (boron-nitride-clad nickel alloy) is the exact class of "non-meltable mineral composited with a meltable component" recited in the spec, and is relevant to the powder element of claims 1/2/5 and to claim 10 ("metallic particles"). It does not disclose or suggest the supersonic, ≥2-bar combustion method. No anticipation.

8. US 3,723,165 (Longo & Durman) — CLOSEST PRIOR ART overall; most relevant to claims 1, 2, 5, 6, 7, 8, 9.
This reference discloses substantially the same material system as the '225 examples: a non-meltable thermoset poly(paraoxybenzoyl)ester ("EKONOL") plus an Al-12%Si alloy, flame-sprayed to form an abradable coating, and it describes the polymer as surface-modifiable/heat-softening. It therefore discloses the powder element and the polymer-identity limitations of claims 1, 5 (and depends into claims 6–9). But '165 sprays via plasma or low-velocity combustion, not a supersonic combustion stream at ≥2 bar — precisely the point on which the '225 specification distinguishes it ("Conventional plasma spraying … loses a considerable portion of the polyester"). Because the claimed method steps (supersonic stream, ≥2 atm) are absent, '165 does not anticipate claims 1, 2 or 5. It is the primary § 103 reference and the strongest "material" art.

9. US 3,741,792 (Peck) — relevant to claims 1, 2, 5 (high-velocity combustion gun), not anticipating.
A rocket-type gun with an internal combustion chamber propelling powder at high velocity through a nozzle — the gun "type" the '225 spec cites. It feeds powder laterally (not axially as in claim 1) and does not disclose the annular outer/inner sheaths, the non-meltable polymer, or the ≥2-bar steady-pressure limitation. No anticipation.

10. US 3,784,405 (Economy et al.) — most relevant to claims 6, 7, 8 (polymer identity), not anticipating.
It expressly discloses the poly(paraoxybenzoyl)ester of claim 6 and copolyesters of claim 8 (its Formulas I–IV, including the recurring-unit copolyester used in the '225 Example 5 "Xydar"), and flame-sprays that polymer onto a substrate. It thus discloses the polymer limitations of claims 6–8 and the polymer component of claims 1/2/5. However, it uses a conventional oxy-acetylene flame-spray gun producing a porous film — it neither discloses nor suggests the supersonic, ≥2-bar combustion method, nor the non-meltable core / heat-softenable surface distinction. No § 102 anticipation of any method claim.

11. US 4,416,421 (Browning) — CLOSEST PRIOR ART on the supersonic method; most relevant to claims 1, 2, 3, 4, 5.
It discloses supersonic combustion flame spraying with a high-pressure combustion chamber (maintained at ≥150 psig, i.e., well above the 2-bar floor of claims 1/2), axial powder introduction into a converging flow, and an extended nozzle bore to keep particles off the wall. This prefigures the supersonic-combustion aspect and the pressure environment of claims 1, 2, 3, 5. The '225 spec itself concedes the method "may alternatively utilize other supersonic guns such as described in the aforementioned U.S. Pat. No. 4,416,421." But '421 discloses metal/ceramic/powder and wire feed; it does not disclose a heat-stable non-meltable polymer (or non-meltable core + heat-softenable surface) powder, nor the specific annular three-flow arrangement of claim 1, nor propylene/MPS with ≥8 shock diamonds (claims 3–4). So it does not anticipate; it is a strong secondary § 103 reference.

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Bottom line

• No single cited reference anticipates any of claims 1–10 under § 102. Every claim requires the combination of a supersonic, ≥2-bar (or "sufficient-pressure") combustion spray stream and a powder with a heat-stable non-meltable polymer/thermoset-surface component. The cited art splits cleanly into two families: (a) supersonic/high-velocity gun art — US 4,416,421 (Browning), US 2,714,563/2,964,420 (Poorman), US 3,741,792 (Peck), US 2,317,173 (Bleakley); and (b) non-meltable-material powder art — US 3,723,165 (Longo & Durman), US 3,784,405 (Economy), US 3,254,970 (Dittrich), US 3,655,425 (Longo & Patel), US 3,617,358 (Dittrich). This split is exactly why the claims were allowed: neither family alone supplies all limitations.
• Most relevant prior art overall: US 3,723,165 (same polymer + Al-alloy material system, flame-sprayed) and US 4,416,421 (supersonic high-pressure combustion spraying). If any reference could be pressed for anticipation, it would be these two — but each fails at least one claim-1/2/5 limitation (as detailed above), so the correct attack theory is § 103 obviousness over '165 in view of '421, not § 102.
• Most relevant to specific dependent claims: claims 6–8 → US 3,784,405 (oxybenzoyl polyester/copolyester identity); claim 9 (aluminum component) → US 3,723,165; claim 10 (metallic particles) → US 3,655,425 / US 3,254,970; claims 3–4 (shock diamonds, propylene/MPS) → partially US 4,416,421 (propane/oxy, ≥150 psig), but no reference discloses the ≥8-diamond or propylene/MPS features.

Caveats: (1) I was unable to run an independent live PatentCenter full-text query within tool limits; the citation list is drawn from the authoritative patent text and the Google Patents mirror of the USPTO record. A definitive pre-AIA § 102(e) sweep should confirm no earlier-filed U.S. applications by others published after the priority date were overlooked, though the face-of-patent list shows none. (2) The unresolved priority-date question flagged earlier (1989-01-05 per Google Patents vs. 1988-12-28 per the EP family record) does not change this analysis, since all 11 references published before either date. (3) Reminder from the earlier analysis: claim 1's final step recites "the heat fusible material in finely divided form" despite the claim defining non-meltable cores — a latent § 112 inconsistency in the granted text, quoted as-is.

I'll ground the analysis by pulling the cited prior-art references and checking for any post-grant proceedings.

Let me pull the Bleakley reference text and check the DuPont HVOF/non-melting-polymer family that cites '225.

Obviousness Analysis — U.S. Patent No. 4,999,225 under 35 U.S.C. § 103

Analyst note on sources: Per instruction, this analysis is anchored to the Prior Art section of the US 4,999,225 Google Patents page — i.e., the 11 "Patent Citations" that appear on the face of the patent, plus the "Similar Documents" list. I have separately noted the temporal status of the 25/39 "Cited By" entries, which cannot serve as § 103 prior art for a 1989 filing. Where I quote reference text, I cite the URL. Where I rely only on the '225's own characterization of a reference, I say so.

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I. Legal frame and critical date

Evidentiary point that materially helps the obviousness case: the '225 specification is itself a detailed admission of the prior art. It states that non-meltable carbides and nitrides "cannot be sprayed into successful coatings without incorporating a binder," that cladding/agglomerating approaches were known (US 3,254,970; 3,655,425; 3,617,358), that the '165 thermoset powders "may undergo a superficial chemical or physical modification of the polymer surface… so as to become surface heat softenable," and that plasma spraying of the polyester/aluminum blend was "highly successful" but suffered poor deposit efficiency. Those are applicant admissions usable in the § 103 analysis.

Also note (per the previously generated summary, not contradicted here): the EP family member EP 0 375 931 A2/B1 shows a priority date of 1988-12-28, while Google Patents shows the US priority as 1989-01-05. I still cannot reconcile that from the sources retrieved and flag it as an open item — it does not change the § 103 analysis because every cited reference predates both candidate dates.

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II. The prior-art arsenal

A. Apparatus / process-architecture references (from the face of the patent)

B. Materials references (from the face of the patent)

C. "Similar Documents" that pre-date the '225 and are highly probative

Flagged issue #1 (timing / § 102(e)): US 4,928,879's 1988-12-22 filing date is earlier than the 1988-12-28 assignment date recorded for the '225, so as a § 102(e) reference it is likely entitled to its filing date against the '225. But this is a close call on the '225's actual date of invention, and I cannot resolve it from the record. Flagged issue #2 (§ 103(c) common ownership): whether the common Perkin-Elmer ownership of the '252/'879/'225 cluster disqualifies '252/'879 as § 103 prior art depends on which version of pre-AIA § 103(c) applies. My reading is that the version in force for a 1989 filing reached only subject matter qualifying solely under § 102(f) or (g), and that the extension to § 102(e) came with the 1999 AIPA (by its terms applicable to applications filed on or after 1999-11-29) — but I do not state this with high confidence and it should be verified. If the common-ownership exclusion does apply, the claim‑1 analysis below loses its cleanest reference and must rest on the KSR "design choice" argument instead.

Temporal exclusion: EP 0 627 267 (L'Air Liquide, 1994), WO 03/051521 and WO 03/051528 (DuPont, 2003), US 6,365,222 and US 6,444,259 (Siemens Westinghouse, 2002), US 5,719,129, US 5,453,303, US 10,156,490, etc. all post-date the '225 by years to decades. They are not § 103 art. They are relevant only as context (see § VI).

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III. Motivation to combine — the unifying rationale

Before claim-by-claim mapping, the single most important structural fact: every reference in Groups A and B is in the same narrow field and points at the same pair of problems. The KSR rationales that apply are:

1. Same field, same problem, same art unit. Bleakley (flame-spray gun for high-melting non-metallics), Browning (supersonic combustion spray of refractory particles), Peck/Poorman (detonation/rocket guns for metal-bonded carbides), and Longo '165 / Economy '784405 (flame-sprayable non-melting polymer powders and their blends) are all addressing "how do you deposit a material into a dense, adherent coating when the material itself will not melt?" The '225's own background section frames precisely this.
2. Explicit teaching of the combined benefit. Browning expressly teaches that supersonic velocity plus controlled dwell yields both (i) suppression of wall build-up and (ii) adequate particle heat-softening — the exact two results the '225 attributes to its annular-sheath/short-chamber architecture.
3. Explicit teaching of the surface-softening mechanism. Longo '165 removes the principal conceptual objection: a thermoset, non-melting particle can be deposited because only its surface is modified to a heat-softenable state. Once that is known, the remaining question is only how hot and how fast to expose the particle — an apparatus/process question that Browning answers.
4. Finite number of identified, predictable solutions (KSR). As of 1988–89 the thermally-spray practitioner had, at most, four routes: plasma, low-velocity combustion, detonation, and HVOF/supersonic combustion. The '225 specification itself disposes of two of them (plasma → polymer loss; low-velocity combustion → charring or non-cohesive deposits). That leaves the high-velocity combustion route as an identified, predictable candidate — KSR's "obvious to try" branch.
5. Design incentive / market pressure. The '225 states the polyester "is quite expensive" and that there was "an on-going need for improvements in abradability and erosion resistance." Cost-driven reduction of polymer loss is a classic KSR "design incentive" rationale.
6. Rationale from Bleakley's own criticality teaching. Bleakley teaches the chamber length is critical — long enough to melt, not so long as to burn — and teaches the concentric outer gas passage along the chamber wall. A PHOSITA optimizing for a heat-sensitive non-meltable particle would predictably shorten the chamber and add wall-shielding gas.

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IV. Claim-by-claim analysis

Claim 5 (broadest — "combustion chamber means" + "open channel")

Proposed combination: Bleakley '173 + Browning '421 + Longo & Durman '165. (Optionally + Economy '784405 for the polyester genus.)

Assessment: strong prima facie case. Claim 5 expressly drops the numeric pressure floor ("sufficient to produce a supersonic spray stream") and recites no gun geometry beyond "combustion chamber means" plus an "open channel." Bleakley alone supplies the chamber/channel/axial-feed geometry, annular combustion, and the wall sheath; Browning supplies the supersonic-pressure teaching and an express anti-buildup/dwell-time motivation; Longo '165 supplies the exact powder and the surface-softening mechanism. The only argument left to the patent owner is expected failure (see § V).

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Claim 2 (combustion chamber + ≥2 atm steady + polymer and metallic component + surface-softening "by the spray stream")

Proposed combination: Browning '421 + Longo & Durman '165 + Dittrich '970 (and/or Longo & Patel '425).

• "steady pressure in the chamber of at least two atmospheres above ambient" → Browning's high-pressure internal burner; also disclosed as ≥2–3 atm in the common-ownership sibling US 4,928,879.
• "particles having a heat-stable non-meltable polymer component and a metallic component" → Longo '165 Example 1-A: 40 wt% high-temperature plastic + 60 wt% silicon–aluminum alloy (12% Si); and Example 1: 60/40. Also Longo '165's express finding that the plastic/metal coatings showed "marked increase in hardness and strength as compared with coatings of pure plastic" and dramatically reduced coefficient of friction.
• "thermoset polymer grains… surface heat softenable" → Longo '165.
• Composite/clad powder-making methods (if a single-particle composite is read into the claim) → Dittrich '970 and Longo & Patel '425.

Assessment: strong. This claim is a straight two-reference (plus one) combination with an express motivation (better hardness/friction/thermal-cycling performance; abradable seals) that Longo '165 itself supplies.

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Claim 1 (the "preferred gun" claim — the hardest claim to invalidate)

Proposed combination: Bleakley '173 + Browning '421 + Longo '165 + [inner-sheath teaching].

Nine of the claim's limitations are met as follows:

The one real gap: "injecting an annular inner flow of pressurized gas from the nozzle member into the combustion chamber coaxially between the combustible mixture and the powder-carrier gas." Bleakley teaches only the outer sheath.

Two routes close or narrow that gap:

(a) Design-choice / KSR route. Bleakley expressly discloses the outer annular gas specifically as shielding along the chamber wall; Browning expressly motivates the twin goals of preventing particle build-up on the wall and ensuring sufficient dwell for heat softening. Adding a coaxially-disposed inner gas annulus between the flame and the powder stream, in a gun whose chamber is short and whose wall is at risk of powder build-up, is the kind of "combination of familiar elements according to known methods [yielding] predictable results" that KSR makes obvious. Counter-argument: this is exactly the reasoning a challenger must support with record evidence, and Bleakley/Browning do not name an inner annulus.

(b) Common-ownership sibling art route. US 4,928,879 (filed 1988-12-22) discloses verbatim the missing element: an "annular intermediate sheath flow of gas, preferably air, between [the] flame opening and powder orifices," plus supersonic operation, ≥2–3 atm, ≥8 shock diamonds, propylene/MPS, and feeding of non-meltable and pre-thermoset poly(paraoxybenzoyl)ester powders. Its claim 21 is: "injecting an annular intermediate flow of pressurized gas from the nozzle member into the combustion chamber coaxially between the combustible mixture and the powder-carrier gas" — the same limitation, essentially verbatim. If '879 qualifies as § 102(e) art (see flagged issues above), claim 1 falls cleanly to Bleakley + Browning + Longo '165 + '879, and possibly faces outright anticipation for some claim scope.

Assessment: moderate-to-strong, and clearly the most vulnerable to a non-obviousness defence. Without '879/'252, a patent owner has a genuine argument that the inner co-axial sheath was not suggested. With them, the argument collapses.

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Claim 3 (≥8 visible shock diamonds absent powder-carrier gas)

Combination: Browning '421 + US 4,928,879 (or the '225's own specification admissions).

Shock-diamond formation is the recognized visual signature of a supersonic (underexpanded) combustion jet; Browning discloses supersonic jet formation and the shock-diamond phenomenon in the same HVOF family. US 4,928,879 recites the identical numeric feature ("at least 8 visible shock diamonds… in the absence of thermal spray wire and powder-carrier gas") at the identical gas pressures (propylene/MPS ~7 kg/cm², oxygen 10.5 kg/cm², air 5.6 kg/cm²).

Assessment: strong. Even treating "8" as a result-effective variable, In re Peterson, 315 F.3d 1325 (Fed. Cir. 2003) and In re Applied Materials support the proposition that optimizing a result-effective parameter by routine experimentation is obvious absent unexpected results. The claim adds no structural or compositional limitation.

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Claim 4 (combustion gas = propylene or methylacetylene-propadiene)

Combination: Browning '421 + conventional fuel-gas knowledge (+ '879).

Propylene, propane, hydrogen, MPS and acetylene were all standard oxy-fuel HVOF gases by 1983 (Browning's own specification and the Charlop '892 valve art contemplate fuel-gas selection generally; US 4,928,879 lists "two preferable combustion gases… propylene gas and methylacetylene-propadiene gas ('MPS')" and states that each "allows a relatively high velocity spray stream and excellent coatings to be achieved without backfire").

Assessment: strong. Selecting among a small set of known fuel gases, with the claimed benefit (no backfire at high velocity) being an expressly stated property of those gases in the art, is routine optimization. Note also that claim 4 is broader than '879's claim 23 in that it does not require the listed gases to be the gas — a small but non-helpful distinction.

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Claims 6–9 (poly(paraoxybenzoyl)ester; neat; copolyester; Al or Al-base alloy)

Combination: Longo & Durman '165 + Economy '784405 (+ Browning '421 for the supersonic step).

• Claim 6 (grains comprise poly(paraoxybenzoyl)ester): Longo '165 names EKONOL™ poly(paraoxybenzoyl)ester expressly; Economy '784405 is directed to oxybenzoyl polyesters.
• Claim 7 (grains consist essentially of the polyester): Longo '165 Example 1-B sprays "pure high temperature plastic powder." A narrowing "consisting essentially of" recitation over an express prior-art disclosure adds nothing patentable.
• Claim 8 (copolyester of poly(paraoxybenzoyl)ester): Economy '784405 expressly discloses copolyesters of recurring units of Formulas I, III, IV — the Xydar™ material used in the '225's own Example 5.
• Claim 9 (further comprising Al or Al-base alloy powder): Longo '165 Example 1-A (40% plastic / 60% Al-12Si) and the '225's own characterization of that example.

Assessment: strong to very strong. These are the least defensible claims in the patent. They are, in substance, "spray the known '165/'405 powder with the '421 process."

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Claim 10 (claim 5 + metallic particles in the powder)

Combination: Longo & Durman '165 + Dittrich '970 / Longo & Patel '425 / Dittrich '358 + Browning '421.

Longo '165 is a mixed metal and plastic flame-spray powder — the metallic-particle limitation is met directly. Alternatively, Dittrich '970 (metal-clad refractory), Longo & Patel '425 (mineral-clad metal) and Dittrich '358 (agglomerated composite) each expressly disclose metal-bearing composite thermal-spray powders of the kind used in the '225's Examples 2–4.

Assessment: strong.

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V. Anticipated counter-arguments and the rebuttal evidence

A. Teaching away / expected failure (the patent owner's best argument)

1. "Non-meltables cannot be coated without a binder." The '225's background concedes this was the art's understanding. But the '225's claims 1, 2 and 5 all require a heat-softenable surface or a metallic component — i.e., they claim the binder-containing article the art already said was necessary. The reference does not dissuade; it frames the field, and Longo '165 answers it. See In re Fulton, 391 F.3d 1195 (Fed. Cir. 2004) (a general preference is not teaching away); Ricoh v. Quanta, 550 F.3d 1325 (Fed. Cir. 2008) (must criticize, discredit, or discourage).
2. "Short dwell time would be expected to fail." This is the strongest point: the '225 states that the high deposit efficiency "is especially surprising because the short dwell time of particles in the supersonic flame would be expected to cause lesser deposit efficiency." Bleakley arguably reinforces the expectation by teaching that chamber length is critical — "if the nozzle is shorter, it will not maintain the proper operating temperature, and the coating material will not melt." A patent owner would argue Bleakley teaches away from the short supersonic chamber.
   • Rebuttal: Browning expressly teaches the opposite trade-off and states the goal of "insuring sufficient particle dwell time within the bore to effect particle heat softening" at supersonic velocity — heat softening, not melting. Where the art expressly frames the dwell question for a particle that need only soften, the "expected failure" narrative weakens considerably.
3. Browning is directed to "liquified material." Its title and claim language speak of "liquified material" and "heat softening or melting." A patent owner may argue the reference is directed to a different mode of operation. Counter: claim 1 of '421 expressly covers "heat softening or liquefaction," which is the '225's own operative mechanism for the polymer surface.

B. Unexpected results / secondary considerations (the patent owner's affirmative rebuttal)

If the patent owner can establish nexus to the claimed scope, these are meaningful:

Weakness of the rebuttal: the reported comparisons are against plasma spraying of a different blend (40% vs 30%), not against the closest prior art (Browning's HVOF process applied to Longo '165's powder). A 30% vs 40% feed difference plus a process change makes attribution of the entire 20-point deposit-efficiency delta difficult. Expect a challenger to attack nexus and to characterize the results as an expected consequence of higher particle velocity (which is what Browning, Bleakley and Peck all teach delivers denser, more tenacious coatings). Additionally, some of the reported metrics (R15y hardness uniformity) are not themselves recited in any claim, weakening the nexus argument.

C. Why the examiner allowed the claims (non-dispositive)

The 11 references, including Bleakley, Browning, Longo '165 and Economy '784405, were of record. Allowance most plausibly rests on the absence of an articulated motivation to take a non-melting material into a supersonic combustion gun whose recognized design constraint (Browning, Bleakley) is dwell time for melting. That is a classic "the combination was not suggested" allowance. It is not dispositive: KSR expressly authorizes reasoning "apparent from the nature of the problem," and the same art that supports allowance (Browning's own recitation of "heat softening") also undercuts it.

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VI. Post-dating art — context only (not § 103 art)

Two later items on the "Cited By" list are worth noting for the record, but cannot be used in a § 103 rejection because they post-date the '225 by 12+ years:

• WO 03/051528 (DuPont, priority 2001-12-14) — "High velocity oxygen fuel (HVOF) method and apparatus for spray coating non-melting polymers."
• US 2003/0165689 A1 / WO 03/051521 (DuPont) — states that "[a] process for making these composites is the high velocity oxygen fuel process," in the context of non-meltable polyimide coatings (US 2003/0165689).

These cut both ways and should be handled neutrally: they show that a decade later the field still treated "HVOF + non-melting polymer" as an active subject (which could be spun as evidence the '225's approach was not the obvious, settled answer), yet they equally show that the '225's core insight had become a well-known commercial process — the kind of "industry adoption" that is often cited against non-obviousness.

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VII. Bottom line — relative vulnerability of the claims

Alternative theory worth flagging: claim 1 recites, at its final step, that "a supersonic spray stream containing the heat fusible material in finely divided form is propelled through the open end," even though the fed powder is defined as having "heat stable non-meltable cores." That internal inconsistency (already noted in the earlier summary) is a potential § 112 ¶ 2 / ¶ 4 vulnerability independent of § 103 — a challenger would raise it in the alternative, and it also creates claim-construction ambiguity that could be exploited to broaden or narrow the claim in an obviousness fight.

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VIII. Certainty and limitations

• High confidence: the identification, dates and disclosure-level descriptions of the 11 face-of-patent references and of US 4,928,879 / US 4,865,252; the claim mappings; the legal framework (pre-AIA § 103(a), KSR, Graham, Kahn).
• Medium confidence: the precise scope of Bleakley's Figure 2 chamber geometry (I have the textual disclosure but not a clear reading of whether the melting chamber itself converges toward the open end, which matters only tangentially).
• Explicitly unresolved: (i) whether US 4,928,879 or US 4,865,252 qualify as pre-AIA § 102(e) prior art given the 1988-12-22/1988-12-28 dates; (ii) whether the applicable version of pre-AIA § 103(c) excludes that art on common-ownership grounds; (iii) the priority-date discrepancy between the US record (1989-01-05) and the EP family member (1988-12-28) flagged in the earlier summary. None of these change the outcome for claims 2–10; all three are material to claim 1.
• I have not located any post-grant proceeding, IPR, or litigation in which this patent's validity was adjudicated (consistent with the earlier negative litigation finding), so this analysis is predictive, not a report of an actual holding. The patent is expired (lapsed 2003-03-12), so it is unenforceable and a real-world § 103 challenge would arise only as a defensive/validity-in-the-alternative issue in a case involving a later, related patent (for example a descendant in the Sulzer Metco / Oerlikon Metco line), not against the '225 itself.