US 5808282

I'll search for this specific patent across the sources you mentioned.

Let me confirm whether there's any litigation or Federal Circuit activity tied specifically to this patent number.

US 5,808,282 — "Microwave sintering process"

Scope note: I searched specifically for patent number 5,808,282. Searches for "828"-ending numbers surface many unrelated patents (e.g., 7,456,828; 9,807,828; 7,267,828; 6,425,828; and the '828 patent in M-3 & Assocs. v. Cargo Sys.). Those are not this patent and are excluded below. Note also that some third-party documents cite this patent with the assignee name garbled as "Microwave Corp." for Microwear Corp. (e.g., DE102004021016A1).

Bibliographic data

Source: Google Patents US5808282; see also Justia and FreePatentsOnline.

Prosecution chain: This patent is a continuation of Ser. No. 08/443,176 (filed 1995-05-17), itself a continuation of Ser. No. 08/220,840 (filed 1994-03-31), both abandoned. Related family members sharing the 1994-03-31 priority include US 5,736,092 ("Microwave sintering process"), US 5,874,377 ("Sintered silicon nitride product"), EP 0752979 B1, JP H09510950A, KR 100226807B1, CA 2124093C, WO 1995/026940 A1, AU 2064595A, DE 69510541T2 and AT E181720T1.

Abstract (verbatim)

"A microwave susceptor bed useful for sintering ceramics, ceramic composites and metal powders is disclosed. The susceptor bed contains granules of a major amount of a microwave susceptor material, and a minor amount of a refractory parting agent, either dispersed in the susceptor material, or as a coating on the susceptor material. Alumina is the preferred susceptor material. Carbon is the most preferred parting agent. A sintering process using the bed and novel silicon nitride products produced thereby are described."

Independent claim (claim 1) in plain language

Claim 1 is the sole independent claim, and it claims an apparatus/assembly, not a method:

• A microwave heating assembly for heating or sintering a material, comprising:
  • A. a bed of granules made of:
    • (a) a major amount of a microwave susceptor selected from alumina, zirconia, thoria, or mixtures of these; and
    • (b) less than about 10% by weight of a refractory parting agent, either dispersed within the susceptor material or applied as a coating on it; and
  • B. the material to be heated or sintered surrounded by those granules, where that material is a ceramic or a metal material.

In substance: put the workpiece in a free-flowing granular bed whose granules are mostly a microwave-coupling refractory oxide plus a small amount of a refractory "parting agent" that keeps the granules from fusing to each other at sintering temperature. The granules trap heat and stay pourable so the bed collapses around the workpiece as it shrinks, while remaining porous enough for a protective gas (e.g., nitrogen) to flow through.

Dependent claims 2–7 in plain language

• Claim 2 — limits the parting agent to carbon, molybdenum disulphide, silicon carbide, or zirconia.
• Claim 3 — narrows to the preferred pair: susceptor is alumina, parting agent is carbon.
• Claim 4 — numerical limits for that pair: alumina about 90–98 wt%, carbon about 2–10 wt%.
• Claim 5 — granule size about 0.5–3 mm (depending from claim 4).
• Claim 6 — granule size about 500 microns to 10 mm (depending from claim 1).
• Claim 7 — granule size about 0.5–3 mm (depending from claim 1).

Technical context from the specification (non-claim)

• The bed is deliberately granular/free-flowing (agglomerates/pellets, e.g., made in a disc/drum pelletizer with a polyvinyl alcohol binder, or by extrusion), with porosity preferably >30%, most preferably ~50%, so it is permeable to flowing gas — contrasted with prior packed powder beds that occlude oxygen and cannot be purged.
• Preferred susceptor: alumina (hydrated alumina couples from room temperature to >2000 °C; alpha alumina couples well above ~400 °C). If alpha alumina is used, the parting agent can be chosen to provide coupling up to ~400 °C.
• Workpieces may be embedded directly in the bed (preferred), placed on top, or housed in a microwave-transparent crucible (alumina or quartz) inside the bed.
• Reported results: silicon nitride sintered to 3.2 g/mL ≈ 98.5% theoretical, light grey (Rock-Color Chart N7–N8) with acicular grains ~0.3 µm diameter / 1–2 µm long, versus commercial material at ~1–3 µm × 10–20 µm and N2–N3 (dark grey/black); aluminum nitride to 3.18 g/mL (~97%); Al₂O₃/TiC composite to 4.00 g/mL (~95%). Example 9 (carbon-only bed) is a comparative showing inferior densification (<70%, and ~78% with a graphite crucible).
• The specification also states the invention "broadly extends to" a sintering process and to a novel sintered silicon nitride product; those aspects are pursued in sibling family members rather than in the claims of this patent.

Litigation / CAFC docket check

I found no 2026 (or other) CAFC docket entry, IPR/PGR, or district-court case specifically involving US 5,808,282 in the sources searched. Searches for "828" in Federal Circuit material returned only unrelated patents. I cannot rule out an unindexed or non-public proceeding, but on the available evidence there is no active Federal Circuit appeal naming this patent, consistent with its Expired – Lifetime status (20-year term from the 1994-03-31 priority; anticipated expiration 2014-03-31).

Confidence / uncertainty

• Bibliographic data, the abstract, and all seven claims are taken from the authoritative full patent text and are high-confidence.
• Legal status is expressly an assumption on the source page ("The legal status is an assumption and is not a legal conclusion").
• The assignee listing is internally inconsistent across sources: Google Patents shows "Original Assignee: Microwear Corp" and current assignees Thermicedge Corp / Indexable Cutting Tools of Canada Ltd, while FreePatentsOnline lists Microwear Corporation. The assignment record also shows two same-day (1997-09-08) transfers (Thermicedge → Microwear) that I did not independently verify against the recorded assignment documents.
• I did not independently verify the family-member data against USPTO/EPO registers beyond the aggregator pages cited.

I'll search for litigation involving US patent 5808282 across patent litigation databases and court records.

Let me search more targeted litigation databases for this patent and its related entities.

Litigation Search Results for U.S. Patent No. 5,808,282

Bottom line: I found no publicly recorded litigation — neither district court infringement actions, ITC § 337 investigations, nor Federal Circuit/PACER appeals — involving U.S. Patent No. 5,808,282 ("Microwave sintering process").

What I searched

I ran targeted queries against web-accessible patent litigation sources, including:

• General litigation-oriented queries pairing the number with "litigation," "lawsuit," and "infringement complaint"
• PACER/CourtListener-style docket text ("5808282 courtlistener docket," "case number district court infringement")
• The number in quotation marks and with comma formatting ("5,808,282") to reduce false positives from unrelated IDs

What came back

The searches returned only non-litigation references to the number 5,808,282:

None of these are court records. No case caption, docket number, plaintiff, or defendant associated with the patent appeared.

Why this is consistent with the record

The patent's own front-page data (via Google Patents) shows "Expired – Lifetime," with anticipated expiration 2014-03-31. The patent issued 1998-09-15 from application 08/848,018 (a continuation of 08/443,176, which was itself a continuation of 08/220,840, priority 1994-03-31). An expired patent cannot support prospective injunctive relief and typically falls out of active assertion campaigns, which aligns with the absence of litigation records.

Limitations and caveats

• I could not directly query the Unified Patents litigation portal or PACER as live structured databases in this session; my results derive from indexed web/court-document sources rather than a certified docket search.
• "No results found" here means no publicly indexed litigation surfaced, not a guarantee that no suit ever existed. Settlement-only, sealed, or very old paper dockets may not be web-indexed.
• The related family members — US 5,736,092 and US 5,874,377 (same priority date, same inventors), plus EP 0752979 B1, CA 2124093 C, and WO 1995/026940 A1 — were also not shown as being involved in any litigation in these results, but I did not run a dedicated separate litigation search on each.

Recommendation

For a definitive confirmation, the following should be checked directly (which would require access I don't have in this session):

1. USPTO Patent Center / Assignment records for the '282 patent — already show the chain Westaim Technologies → Thermicedge Corp. → Microwear Corp. → Indexable Cutting Tools of Canada Ltd., but litigation is not recorded there.
2. PACER docket search on the patent number and on assignees Microwear Corp., Thermicedge Corp., Westaim Technologies, and Indexable Cutting Tools of Canada Ltd.
3. Unified Patents litigation portal and Westlaw/LexisNexis docket databases.

If you'd like, I can next attempt searches keyed to the assignee names or the sibling patent numbers (5,736,092 and 5,874,377), which sometimes surface suits the patent-number query misses.

I'll start by verifying the structured block's default against live sources, then check for any older or unindexed proceedings and related litigation/appeals.

The structured block's default is holding up. Let me confirm with targeted searches on the patent owner chain and litigation history.

PTAB Proceedings — US 5,808,282 ("Microwave sintering process")

Proceedings overview

Total AIA trial proceedings on file: 0. The canonical structured list from the USPTO Open Data Portal returns no IPR, PGR, or CBM proceeding for US 5,808,282 — no active proceedings, no claims invalidated, no claims sustained through trial, no settlements, and no institution denials. My independent web searches also surfaced no proceeding naming this patent, its owners (Microwear Corp. → Thermicedge Corp. → Indexable Cutting Tools of Canada Ltd.), or its inventors (Apte / Morris). The bottom-line defensive posture for a defendant is therefore "unhardened but untested": the patent has never been through an AIA trial, so there is no IPR record to borrow — but there is also no claims-canceled silver bullet, and the patent is expired, which changes the practical calculus entirely.

Critical threshold fact that dominates everything below: the '282 patent reached its anticipated expiration on 1994-03-31 + 20 years = 2014-03-31, and Google Patents/ODP lists it as "Expired - Lifetime." A defendant facing an assertion today is almost certainly looking at a letter that post-dates expiry and cannot support a § 271(a) infringement claim for post-expiry conduct. Before investing in invalidity work, confirm the assertion isn't limited to pre-2014-04-01 conduct (recovery looks back only 6 years under § 286) — that, not the PTAB record, is the gate.

Proceedings

None. There is no proceeding to report.

Per your operating instruction, the structured ODP block is canonical and controls: no PTAB activity on file. I found nothing in web search that contradicts it. Rather than pad this section with invented numbers, here is what I checked and what I explicitly disconfirmed.

What I searched and found (i.e., did not find):

False positives you should not be misled by (I hit all of these and confirmed they are different patents):

• US 7,588,828 (Nanoco Technologies) — Samsung v. Nanoco, IPR2021-00183/-00186. Different patent, different art (quantum dots).
• A joystick/handheld-controller " '828 patent" in PTAB filings (e.g., petition papers at ptacts.uspto.gov referencing an '828 patent with claim 17 "display mode selection means") — a post-2003 filing; not US 5,808,282.
• US 6,066,584 (CeramTec campaign, IPR2015-00398 / -00424 / -01328 / -01504) — alumina ceramic art, superficially adjacent to the '282 subject matter but a different patent and patent owner.
• Family members that are not the '282 patent: US 5,736,092 and US 5,874,377 (same 1994-03-31 priority; the '377 covers the sintered silicon nitride product claims), EP 0 752 979 B1, CA 2 124 093 C, KR 100226807 B1, JP H09510950 A, WO 1995/026940 A1. If you are being asserted against those patents, run a fresh PTAB check on each — my null result covers only US 5,808,282.

Why no Federal Circuit appeal exists: a CAFC appeal requires a Final Written Decision to appeal from. With zero instituted trials, there is no FWD, no appeal docket, and nothing on CourtListener for this patent. I found none.

Caveat on confidence: My searches are not a substitute for a direct PTAB E2E / Patent Trial and Appeal Board Endpoint query, and the ODP block itself notes the index may lag. I rate "no AIA trial proceedings" as high confidence given the concordance of the ODP block and my null searches, but I did not have direct PTAB E2E API access in this session. A five-minute check on PTAB E2E (https://ptacts.uspto.gov) and on CourtListener's docket search before you rely on this in a filing is cheap insurance.

Strategic summary

Claim status: all 7 claims are UNTESTED (never construed, never canceled, never confirmed). The patent has one independent claim (claim 1 — a microwave heating assembly comprising a granular bed of a major amount of alumina/zirconia/thoria susceptor plus <10 wt% refractory parting agent, surrounding a ceramic or metal work piece) and dependent claims 2–7, which narrow to specific parting agents (carbon, MoS₂, silicon carbide, zirconia), the alumina+carbon embodiment at 90–98 wt% / 2–10 wt%, and granule sizes of 0.5–3 mm and 500 µm–10 mm. Because no IPR ever ran, there is no narrowing amendment, no adverse claim construction, and no PTAB-record admission to exploit. There is likewise no claim you can safely disregard as canceled. Note also that claim 1's own file history is unusually favorable to a defendant on one point: the specification expressly concedes that a carbon-only susceptor bed reaches only ~70% theoretical density and a graphite crucible only ~78% (Example 9) — useful invalidity/§ 112 and written-description ammunition if the patentee ever tries to read claim 1 broadly onto a plain carbon bed.

Estoppel landscape is essentially empty — for everyone. § 315(e)(2) estoppel arises only against petitioners who were parties to an instituted IPR, and no one was. So no potential defendant is currently barred from raising any prior-art ground against the '282 patent. The entire prior-art field is open: the pre-1994 references cited on the face of the patent (e.g., US 4,144,911 to Nishitani/Nippon Steel, US 4,307,277 to Mitsubishi, US 4,960,709 to Kimrey, US 5,072,087 to Apte/Alcan, CA 2,000,109 and CA 2,001,062 to Apte et al., and the Tiegs/Kiggans silicon-nitride microwave literature listed as "Other References"), plus anything else you can find. That said, because the patent is expired, the practical question is not "can we invalidate" but "is there a live damages theory at all."

Pattern signals: none. No serial petitioner, no patent-owner appeal aggressiveness, no aggregator in the chain. The assignment history (Microwear → Westaim Technologies → Thermicedge → Microwear → Indexable Cutting Tools of Canada Ltd. in 2000) is ordinary corporate housekeeping, not litigation-driven activity. Combined with the 2014-03-31 expiry and the absence of any AIA challenge even during the 2012–2014 window when IPRs became available, the portrait is of a patent that was never a serial-assertion vehicle. In the microwave-sintering field it is cited mainly as background art — e.g., a Harper International technical deck markets the "Powder Bed process [USP 5808282]" as its own commercialized technology, and DE 102004021016 A1 cites it as prior art on multi-layer insulation/powder-bed design. That is a signal of technological relevance, not enforcement relevance.

Recommended next steps

1. If you are a defendant: do not lead with invalidity. Lead with the run-out. The patent's 20-year term ended 2014-03-31, and it is recorded as "Expired - Lifetime." Ask the asserting party to identify (a) the specific accused acts, (b) their dates, and (c) the statutory basis for recovery on post-2014-04-01 conduct. If the demand letter cites claims 1–7 for ongoing or recent activity, the letter is meritless on its face and you should respond with a § 285 fee posture, not a licensing negotiation. Confirm this before spending another dollar: Google Patents US5808282 (legal status: Expired - Lifetime; anticipated expiration 2014-03-31).
2. If the assertion is limited to pre-expiry conduct (e.g., a stale damages claim under § 286's 6-year lookback, reaching conduct back to ~2020 — which cannot exist here), verify with the PTAB and then build the invalidity case from scratch. There is no IPR estoppel against you, so the full pre-1994 art landscape is available. Start with the 30 references cited on the patent's face and the Apte/Alcan prior patents (US 5,072,087; US 5,012,220), which are the same inventor's own earlier microwave-heating work and therefore prime § 102(b)/§ 103 material and potential double-patenting/obviousness-type-double-patenting fodder against the '282 and its '092/'377 siblings.
3. If you are asserted on a family member (US 5,736,092; US 5,874,377; EP 0 752 979 B1; CA 2 124 093 C), treat that as a separate research task. The '377 in particular carries product claims ("sintered silicon nitride characterized by >95% theoretical density, fine grains <1 µm diameter / <5 µm length, colour not darker than light grey") that are the kind of product-by-property claim vulnerable to § 112(b) indefiniteness and § 102 anticipation arguments — but I have no PTAB data on it and did not search it to that depth here.
4. There is no pending deadline to track. With zero active proceedings, there is no institution-decision date, no oral-hearing date, no statutory one-year FWD due date, and no POP or CAFC briefing schedule. Nothing is running.

Primary sources to cite/verify:

• PTAB E2E (proceeding search): https://ptacts.uspto.gov
• CourtListener (any '282 CAFC appeal — expect none): https://www.courtlistener.com
• Google Patents record with legal status, assignment chain, and family: https://patents.google.com/patent/US5808282/en

Confidence and limits: (i) The "zero proceedings" conclusion rests on the structured ODP block plus concordant web searches; I did not query PTAB E2E directly. (ii) I did not locate any FWD, institution decision, or settlement because none appears to exist — I have not invented any proceeding numbers, panels, or dispositions. (iii) Judge panel information, claim-level outcomes, and estoppel facts are absent by definition where no trial was instituted, and I have not filled those gaps with speculation.

I'll research the assignment record and related entities before drafting. Let me run several searches.

Assignment & Ownership Analysis — US 5,808,282 ("Microwave sintering process")

Verification entry point: USPTO Assignment Center · Google Patents legal events for US5808282 · Google Patents full text

Data-quality note up front: I was able to retrieve the reassignment events (dates, assignor/assignee, conveyance type) from Google Patents' legal-events feed, which mirrors the USPTO assignment database. I was not able to retrieve the underlying reel/frame numbers or the correspondent of record (the filing attorney/agent) for these records — those fields are not exposed in the sources I could reach, and I will not invent them. Every place below where a reel/frame or correspondent would normally appear is flagged as not retrievable. Treat the dates below as the recording/posting dates surfaced by the legal-events feed; execution dates are typically the same or slightly earlier but are not separately shown.

Inventors

Unusual-pattern check: The instruction to look for "all inventors departing within 12 months of filing" is not assessable here — no employment or departure records are exposed in the retrieved data. One timing observation is notable, however: the application that issued as this patent (Ser. No. 08/848,018) was filed 1997-04-28, but the inventors' assignment of rights was not recorded until 1997-07-08 — roughly three years after the 1994-03-31 priority filing and only after a chain of continuations. That gap is consistent with rights being consolidated inside a corporate group rather than a normal at-filing inventor assignment, and it foreshadows the 1997 corporate shuffle described below. This is an observation about timing, not a departure finding.

Original assignee

Microwear Corp — named as assignee on the face of the issued patent (Google Patents "Original Assignee" and "Current Assignee" both list Microwear Corp; current assignees also include Thermicedge Corp and Indexable Cutting Tools of Canada Ltd).

• Primary line of business: This is not a licensing vehicle. The patent's own commercial context (cutting tools) and the corporate chain tie Microwear into the Westaim Technologies / Thermicedge group, an advanced-materials and ceramic cutting-tool business. The group's technology was commercialized as microwave-sintered silicon nitride, aluminum nitride and Al₂O₃/TiC ceramic inserts — i.e., the very products embodied in the claims (see Examples 4, 5 and 8, which report RNGN-45/T6 turning inserts outperforming Kennametal KY-2000, Newcomer and Sandvik grades on gray cast iron).
• Did they ship a product embodying the claims? Yes, downstream of Microwear. The terminal holder, Indexable Cutting Tools of Canada Ltd., sells silicon nitride, white ceramic and whiskered ceramic inserts that press releases expressly describe as "produced using patented microwave sintering technology." (GWS Tool Group acquisition release: https://www.gwstoolgroup.com/gws-tool-group-announces-acquisition-of-indexable-cutting-tools-of-canada-inc/ ; see also https://ctemag.com/news/gws-tool-group-acquires-indexable-cutting-tools-canada/)
• Current status: The original group has been reorganized/divested. Microwear Corp itself no longer appears as an independent operating brand. Indexable Cutting Tools of Canada Ltd. operated in Welland, Ontario and Edmonton, Alberta for "more than 50 years"; it was acquired by GWS Tool Group (Tavares, FL) on 2021-06-01 (Gowling WLG advised Indexable: https://gowlingwlg.com/fr/insights-resources/client-work/2021/gws-tool-group-acquires-indexable-cutting-tools). Whether the US patent assets were expressly conveyed in that share/asset purchase is not confirmed by the retrieved sources — the last USPTO-recorded assignment still names Indexable.
• Patent term: Expired 2014-03-31 (20 years from the 1994-03-31 priority date). Legal status: "Expired – Lifetime."

Assignment timeline

Four (4) post-filing reassignments are recorded. No security agreements, mergers, changes of name, licenses, releases, or corrections are recorded — the chain is exclusively straight "ASSIGNMENT OF ASSIGNORS' INTEREST" conveyances.

1. Recorded 1997-07-08 — Reel NNNNNN/NNNN — not retrievable

• Conveyance: Assignment (Assignment of Assignors' Interest)
• Assignor: Larry Roy Morris; Prasad Shrikrishna Apte (the inventors)
• Assignee: Westaim Technologies, Inc.
• Correspondent: not retrievable — cannot run the repeat-correspondent test (see signal 3).
• Context: Consolidation of the inventors' rights into the Westaim corporate group — the first corporate owner of record.

2. Recorded 1997-09-08 — Reel NNNNNN/NNNN — not retrievable

• Conveyance: Assignment
• Assignor: Westaim Technologies Inc.
• Assignee: Thermicedge Corporation
• Correspondent: not retrievable
• Context: Internal reorganization — transfer from the parent to the group's cutting-tool operating entity.

3. Recorded 1997-09-08 — Reel NNNNNN/NNNN — not retrievable

• Conveyance: Assignment
• Assignor: Thermicedge Corporation
• Assignee: Microwear Corporation
• Correspondent: not retrievable
• Context: Internal reorganization on the same day as link 2 — a second intra-group hop, taking the patent to the entity that would appear as assignee on the issued patent (1998-09-15).

4. Recorded 2000-09-28 — Reel NNNNNN/NNNN — not retrievable

• Conveyance: Assignment
• Assignor: Microwear Corporation
• Assignee: Indexable Cutting Tools of Canada Limited
• Correspondent: not retrievable
• Context: Divestiture / business sale — the microwave-sintered ceramic insert business passes to the operating manufacturer Indexable, where the technology was actually practiced and productized.

If a verification pass at the Assignment Center returns reel/frame and correspondent data, those are the four records to reconcile — I found no evidence of any fifth record.

Timeline diagram

timeline
    title Ownership of US 5808282
    1994 : Priority application filed
    1995 : First continuation filed
    1997 : Inventors assign to Westaim Technologies
         : Westaim assigns to Thermicedge
         : Thermicedge assigns to Microwear
    1997 : Current application filed
    1998 : Patent issues to Microwear
    2000 : Microwear sells to Indexable Cutting Tools
    2014 : Patent expires
    2021 : Indexable acquired by GWS Tool Group

NPE / troll-pattern signals

Family context (relevant to any assertion question): This patent is one of three US members of the same 1994-03-31 priority family — US 5,736,092 (sintering process) and US 5,874,377 (sintered silicon nitride product), both also "Expired – Lifetime," plus EP 0752979 B1, CA 2124093 C, JP H09510950 A and KR 100226807 B1. The family covers both process and product (US 5,874,377 claims the sintered silicon nitride product directly), i.e., it was structured for normal commercial protection of a manufacturing line — consistent with an operating-company portfolio rather than a licensing shell.

Verdict

Operating-company assertion — with an explicit caveat on the "assertion" limb.

Justification: The complete recorded chain — inventors → Westaim Technologies, Inc. (rec. 1997-07-08) → Thermicedge Corporation (rec. 1997-09-08) → Microwear Corporation (rec. 1997-09-08) → Indexable Cutting Tools of Canada Limited (rec. 2000-09-28) — consists entirely of corporate operating entities, and the terminal holder manufactures ceramic inserts that press materials describe as "produced using patented microwave sintering technology." There is not one shell-entity transfer, known-asserter assignee, or defensive-aggregator terminus in the chain; the only pattern with any NPE flavor, the three transfers inside ~3 months in 1997, is textually explained as an intra-group reorganization inside a single corporate family. The caveat: the phrase "assertion" in this verdict label is not evidenced — I found no infringement litigation involving US 5,808,282, and the patent expired 2014-03-31. Read the verdict as "practicing-entity-owned, non-NPE chain," not as confirmation of enforcement activity.

Two items to close out at the Assignment Center: (a) the four reel/frame numbers, and (b) the correspondent of record on each — the latter is needed to convert signal 3 from unclear to a definitive call, and to confirm the 1997-09-08 same-day double transfer was in fact signed by a single group attorney.

I'll research this patent and its cited prior art, and ground the analysis in searchable sources.

I have the patent's own citation list. Let me characterize the key cited references.

Prior-Art Analysis — US 5,808,282 ("Microwave sintering process")

1. Identification of the patent (literal)

Source of record: https://patents.google.com/patent/US5808282/en ; front-page "References Cited" list also mirrored at https://www.freepatentsonline.com/[5808282](/patent/5808282).html and https://patents.justia.com/patent/5808282

Critical date. Because the earliest effective filing date in the chain is 31 March 1994, §102 prior art must predate that date (subject to any §102(b) one-year bar at 1993-03-31 for the 1994 filing). References granted after 1994-03-31 can only qualify under §102(e) if their own U.S. filing date precedes the applicant's invention date.

Claim 1 (the only claim that matters for anticipation). Literally:

"1. A microwave heating assembly … comprising: A. a microwave heating bed of granules comprising a. a major amount of a microwave susceptor material selected from the group consisting of alumina, zirconia, thoria and mixtures thereof; and b. an amount less than about 10% by weight of a refractory parting agent either dispersed with the susceptor material or as a coating on the susceptor material; and B. the material to be heated or sintered surrounded by the granules, which material is selected from the group consisting of ceramics and metal materials."

Claims 2 (parting agent = carbon, MoS₂, SiC, zirconia), 3 (alumina + carbon), 4 (90–98 wt% alumina, 2–10 wt% carbon), 5/7 (granules 0.5–3 mm), 6 (granules 500 µm–10 mm) are all additive limitations on claim 1.

2. Method and caveats

I worked from the citation list printed on the face of US 5,808,282 itself (the "References Cited" / "Patent Citations" set), which is the USPTO-recorded IDS/examiner citation set, supplemented by live lookup of individual references.

Two honest limitations:

• I did not obtain the Patent Center file history / examiner's "Notice of Allowance" reasons, so the §102/§103 mapping below is my own infringement-style element-by-element reading, not a quotation of the examiner's rejections.
• Where I could not retrieve and read the full text of a cited reference, I say so explicitly rather than asserting content.

Overall conclusion up front: On the references cited on the face of the patent, no single reference appears to disclose every element of claim 1, so the record does not show a clean §102 anticipation of claim 1. The exposure is concentrated in (a) §102/§103 against claim 1's granular susceptor-bed element, driven by Holcombe (US 4,880,578 / US 4,810,846), Kimrey (US 4,963,709), and the Apte/Alcan family (US 5,072,087; CA 2,000,109; CA 2,001,062; CA 2,028,067; WO 91/05747), and (b) §103 against claims 3–4 (alumina + carbon) and claims 5–7 (granule size), which read on well-known refractory-grain practice.

3. The cited references, one by one

A. Strongest candidates (§102/§103 exposure on claim 1)

US 4,880,578 A — Holcombe, Dykes & Meek (U.S. DOE)

• Method for heat treating and sintering metal oxides with microwave radiation; filed 1988-08-08; granted 1989-11-14.
• Description: encloses a compact of a poorly-coupling oxide (alumina, yttria, silica, magnesia, calcia) in a housing/capsule formed of a low-density oxide that couples at low temperature — zirconia, hafnia, or combinations, in the form of fibers, powders, hollow spheroids or granules — which heats by microwave, transfers heat to the compact until it self-couples, then acts as thermal insulation. Alumina bricks/caskets provide extra insulation. Verified at https://patents.google.com/patent/[US4880578A](/patent/US4880578A)/en and the PDF (patentimages).
• §102 potential: This is the single most damaging reference for the susceptor half of claim 1. It discloses granules of a microwave susceptor material (zirconia) surrounding the material to be sintered. If the examiner read "housing … granules" as the "bed of granules" of claim 1(a) and the encased compact as "the material … surrounded by the granules" of claim 1(B), then claim 1 turns on the refractory parting agent (<10 wt%, dispersed or coating). That element is absent from Holcombe. So: §102 as to claim 1 = likely no; §103 = yes, when combined with any reference teaching carbon/SiC/zirconia as an anti-sticking/parting agent in a granular refractory bed (e.g., US 5,214,010, US 4,666,775, or the JP ceramic-art references below).
• Anticipation of dependent claims: Holcombe does not disclose carbon as a parting agent (claim 2/3), the 90–98/2–10 wt% ranges (claim 4), or the 0.5–3 mm / 500 µm–10 mm granule sizes (claims 5–7).

US 5,072,087 A — Apte et al. (Alcan International)

• Process for heating materials by microwave energy; filed 1988-10-06; granted 1991-12-10.
• Description: the assignee/inventor's own earlier process for heating bodies in a packed powder bed of microwave susceptor material. This is the archetype of the "packed powder bed" approach the patent's Background criticises (no gas permeability, bed sinters, ceramic loses contact on shrinkage, need for different beds for oxides vs. non-oxides).
• §102 potential: Because it is the inventors' own earlier bed process, it is the most relevant art on the bed concept, and it shares the same inventive entity lineage — a §102(b)/§103 problem for the broad concept, but it teaches powder, not granules, and it does not disclose a minor refractory parting agent to keep the bed free-flowing. No full §102 anticipation of claim 1; strong §103 art.

US 5,016,220 A — Apte et al. (Alcan International)

• Process and apparatus for heating bodies at high temperature and pressure utilizing microwave energy; filed 1988-02-16; granted 1991-04-23.
• Description: microwave heating of bodies under high temperature/pressure (hot-isostatic-type) using microwave energy — same inventor family, same Alcan programme. Cited in the PDF/DE literature as one of the known coaxial-coupling/high-pressure microwave applicator patents.
• §102 potential: Apparatus/process for microwave heating, not a granular parting-agent bed. No anticipation of claim 1; background/§103 only.

CA 2,001,062 A1 — Prasad Shrikrishna Apte

• Method of heat-treating unstable ceramics by microwave heating and susceptors used therefor; filed 1989-10-19; laid open 1991-04-19. (The corresponding WO publication WO 91/05747 A1, published 1991-05-02, appears in the FPO foreign-reference list.)
• Description: microwave heat-treating of unstable ceramics (e.g., nitrides) with susceptors — the inventors' prior packed-susceptor-bed work described in the Background of US 5,808,282, including the use of silicon nitride/SiC/boron carbide-type susceptors and getters.
• §102 potential: Directly on point as to the problem (protecting unstable ceramics during microwave sintering) and to susceptor beds. But it teaches a packed powder bed with in-situ atmosphere-generating constituents, not a free-flowing granular bed with an inert refractory parting agent. No anticipation of claim 1 as a whole; highly material §103 art (indeed, close enough that the patent's own Background devotes a paragraph to disclaiming it).

CA 2,028,067 A1 — Robert Murray Kimber

• Method of heat-treating unstable ceramics by microwave heating and susceptors used therefor; filed 1990-10-19; laid open 1992-04-20.
• Description: companion Alcan/Kimber application on susceptors for microwave heat-treating of unstable ceramics.
• §102 potential: Same analysis as CA 2,001,062. §103 art; not a complete §102 reference.

CA 2,000,109 A1 — David Nelson Mitchell

• Process for heating materials by microwave energy; filed 1989-10-03; laid open 1991-04-03.
• Description: the Alcan process for microwave heating of non-susceptor materials in a powder bed of susceptor materials such as sub-alpha alumina (this is the disclosure the Background of US 5,808,282 cites by name and date). The corresponding disclosure appears as EP 0 363 193 A2, whose text defines "susceptor"/"non-susceptor" and describes mixing/embedding the body in susceptor powder, conventional magnetron + resonant cavity equipment, containers of microwave-transparent material, and temperatures up to ~2,500 °C.
• §102 potential: Discloses the susceptor-powder-bed-around-the-workpiece concept in the same material class (alumina). It does not disclose granules or a refractory parting agent. §103 art; not a full §102 anticipation.

B. §102(e)-type references (granted after the 1994-03-31 priority date but filed before it)

US 5,321,223 A — Kimrey, Holcombe & Dykes (Martin Marietta Energy Systems)

• Method of sintering materials with microwave radiation; filed 1991-10-23; granted 1994-06-14. Full PDF: patentimages (US5321223.pdf).
• Description: sintering of poorly-coupling ceramics (incl. alumina, silicon nitride, AlN, sialons) by coating the compacted article with carbon / blending with a carbon-residue-forming organic, so the carbon improves microwave coupling; sintering to ≥95% theoretical. Verified.
• §102 significance: This is the closest art to claim 1(b) ("…or as a coating"), but the carbon coating is on the article to be sintered, not on the susceptor granules, and there is no granular susceptor bed. No §102 anticipation of claim 1; it is the best §103 reference for the "carbon as coating" language. Note the §102(e) timing: granted 1994-06-14 — after the priority date, so it is only available as §102(e) art if its filing (1991-10-23) predates the applicant's invention date, which it does.

US 5,449,887 A — Martin Marietta Energy Systems

• Thermal insulation for high temperature microwave sintering operations and method thereof; filed 1993-03-25; granted 1995-09-12.
• §102 significance: Granted well after the 1994-03-31 priority date, so not §102(a)/(b) art. It is only available, if at all, as §102(e) art (filed 1993-03-25, before priority) and/or as §103 art. Directionally it concerns microwave-transparent insulation (aluminosilicate/ceramic-fibre blanket) around a microwave-sintering load — relevant to the Figures 1–3 insulation (18) but not to the granular parting-agent bed.

US 5,401,450 A — Nissan Motor (from the "Family Cites Families" sub-list)

• β-silicon nitride sintered body and method of producing same; 1995-03-28.
• §102 significance: Granted after the priority date; only potentially §102(e) art. Relevant only to the fine-grained β-Si₃N₄ product characteristics discussed elsewhere in this family (the sister patent US 5,874,377, Sintered silicon nitride product), not to the bed claim.

C. Purely background / obviousness-type references (no §102 anticipation of any claim)

D. Foreign patent citations

E. Non-patent literature cited on the face of the patent

4. Bottom line

1. The USPTO-recorded citation set for US 5,808,282 consists of 30–31 patent citations (≈22 US grants plus JP, CA, GB and one anomalous EP item) plus at least three non-patent publications, as printed on the patent's face. I confirm the patent number literally as US 5,808,282 and did not return or substitute any similar number.

2. No cited reference, taken alone, discloses every element of claim 1. The two elements that repeatedly save claim 1 are (i) the bed being granules (free-flowing, gas-permeable, collapsible) rather than a packed powder or a fibre/solid housing, and (ii) the refractory parting agent at <10 wt%, dispersed in or coated on the susceptor granules.

3. The references with realistic §102 exposure are:

   • US 4,880,578 (Holcombe) — discloses granules of zirconia microwave susceptor surrounding the material to be sintered → arguably §102 against the susceptor half of claim 1; defeated only by the parting-agent limitation.
   • US 5,072,087 (Apte/Alcan) and the CA 2,000,109 / CA 2,001,062 / CA 2,028,067 / WO 91/05747 family — disclose the susceptor powder-bed-around-the-workpiece concept in the same material class but as packed powder, not granules.
   • US 5,321,223 (Kimrey/Holcombe) — the closest art to the "or as a coating" language of claim 1(b), but carbon-coated workpieces, not coated granules (and only §102(e)-timing available: filed 1991-10-23, granted 1994-06-14).

4. Claims 2, 3, 4 are the weakest link. Alumina-plus-carbon refractory practice was well known (e.g. US 5,214,010, Indresco, dense alumina-carbon slidegate plates; JP S60-71571, Harima Ceramic, refractory nozzle grain) and carbon's dual role as coupling aid and anti-sticking agent was known (US 5,321,223; US 4,666,775). A §103 combination of Holcombe (zirconia/alumina granules as susceptor) + a refractory-grain anti-sticking teaching (Indresco / JP '571 / Kennecott '775) + Kimrey '223 (carbon coating) is the strongest obviousness case in the record against claims 1–4.

5. Timing flags for the record:

   • US 5,449,887 (granted 1995-09-12) and US 5,401,450 (1995-03-28) post-date the 1994-03-31 priority date and are not §102(a)/(b) art; they qualify, if at all, only under §102(e) (filed 1993-03-25 and earlier respectively).
   • EP 1,597,998 A2 (2005, LG dishwasher door lock) is not prior art on any theory and is almost certainly a citation-list/OCR artefact, most likely a collision with GB 1,597,998 A (Special Metals, 1981).
   • The family/related patents US 5,736,092 (Microwave sintering process) and US 5,874,377 (Sintered silicon nitride product) share the same 1994-03-31 priority and are siblings, not prior art — they should not be cited against claims 1–7.

Caveat I want on the record: items 3, 5, 7–9, 11, 14–22 and 23–26 in section C/D above are characterised from the citation record, the abstract-level description, and (for US 4,880,578, US 4,810,846, US 4,963,709, US 5,321,223) the full text; for the remaining peripheral items I relied on title/assignee/date metadata. If you need each §102 conclusion hardened, the next step is pulling the full PDFs of US 4,666,775, US 5,188,273, US 5,194,408 and US 5,214,010 and the file-history rejections from Patent Center.

I'll ground the key prior-art references from the patent's citation lists before building the § 103 analysis.

Obviousness Analysis — U.S. Patent No. 5,808,282 ("Microwave sintering process")

Analyst note on scope: This section builds on the litigation summary already generated. That summary found no recorded litigation and noted the patent is Expired–Lifetime (anticipated expiration 1994-03-31 priority + 20 yrs). Nothing in this § 103 analysis contradicts it. One cross-reference worth flagging up front: the product claims (sintered silicon nitride per se — density, grain size, colour) live in sibling US 5,874,377, not in the '282. The '282 claims (7 total) are directed to an apparatus (a "microwave heating assembly" comprising a granular bed) and optionally to granule size ranges. That claim-scope fact materially shapes the obviousness case below.

1. Governing standard and level of ordinary skill

• Law: Pre-AIA 35 U.S.C. § 103(a) applies (priority 1994-03-31; filed 1997-04-28). The framework is Graham v. John Deere (scope/content of prior art; differences; PHOSITA level; secondary considerations) as refined by KSR Int'l v. Teleflex, 550 U.S. 398 (2007).
• PHOSITA (as of March 1994): a materials/ceramic engineer with an M.S. (or B.S. plus several years) in ceramic processing, with 2–5 years' hands-on experience in microwave sintering at 2.45 GHz, familiar with susceptor/heating-aid practice, kiln furniture and refractory bedding materials, and the dielectric-loss literature (Sutton; Holcombe/Meek/Janney at ORNL; Alcan).
• Critical claim-construction observation: Claim 1 recites (i) a "bed of granules," (ii) a "major amount" of alumina/zirconia/thoria susceptor, (iii) "<10% by weight" of a refractory parting agent, dispersed or coated, and (iv) the workpiece "surrounded by the granules." It does **not** recite the features that the specification uses to distinguish the invention: free-flowing character, >30%/≈50% porosity, gas permeability, collapse with workpiece shrinkage, or a flowing protective atmosphere. The claims are therefore broader than the disclosed invention, and that breadth is the single biggest vulnerability. Under KSR, the obviousness inquiry is directed to what is claimed, not to the commercial embodiment.

2. The prior-art record actually relied on (from the "Prior Art" section of the page)

2.1 Substantively relevant references (verified content)

2.2 Citation-list artifacts to exclude from any obviousness theory

The page's "Patent Citations (31)" table contains entries that cannot be prior art to a 1994 patent and/or are off-topic, apparently from family-level or re-use mapping:

• "EP1597998A2 — LG Electronics — Dishwasher and door locking device" (2004‑05‑20) — chronologically impossible as prior art to the '282; the EP number appears to have been re-used/coincidentally matched. (A GB 1,597,998 to Special Metals, "Method of [improving] the susceptibility of a material to microwave energy heating," is the substantively relevant number and appears in the "Family Cites Families" list.)
• JPS 53‑44930 (ACF Industries, "Valve operating device for expandable gate valve," 1978), JPS 56‑30834 (Sanyo, "Molding method of model," 1981), JPS 60‑71571 (Harima Ceramic, "Nozzle refractories for molten metal vessel," 1985) — subject matter unrelated to microwave sintering; do not use.
• Duplicate listings: the page prints the same references twice under "Citations (30)" and "Patent Citations (31)"; count each reference once.

Flagged internal contradiction (per the cross-reference instruction): the '282 specification states that "Canadian Patent Application 2,000,109 of Apte et al., laid open on Apr. 3, 1991, describes a microwave sintering process… in a powder bed of susceptor materials such as sub-alpha alumina." The citation table on the same page attributes CA 2,000,109 to David Nelson Mitchell / Alcan, "Process for heating materials by microwave energy," with the same 04/03/1991 laid-open date (corresponding to US 5,072,087). These cannot both be right. Taken literally, CA 2,000,109 = Mitchell/Alcan; the specification's attribution to "Apte et al." is likely a drafting error, and the Apte bed described in the background is CA 2,001,062. This matters because the specification's characterisation of its own prior art is an admission usable against it.

3. Primary § 103 combination and element-by-element analysis

Combination A (strongest): Holcombe '578 + Holcombe '130 + General Mills '408, optionally + Alcan '541 + Indresco '010

Rationale to combine (KSR factor (a) — known elements arranged according to known methods; factor (c) — improvement of a similar device in the same way):

• '578 and '130 are the same technology lineage (DOE/ORNL → Martin Marietta) addressing the same problem in the same way; '130 is a later refinement that expressly carries forward '578's "low-density metal-oxide housing" concept but replaces the rigid housing with a container of refractory-oxide granules and a coated workpiece. A PHOSITA seeking to load/unload, conform to irregular workpieces, and reuse the heating medium would substitute a pourable granular bed for a rigid low-density housing as a predictable design choice (KSR factor (b) — simple substitution of one known element for another).
• '408 and '223 supply the why for the "<10 wt% refractory parting agent" limitation: '408 expressly warns that a fully densified/vitrified susceptor loses microwave activity, so a PHOSITA engineering a reusable susceptor bed is directly taught to limit inter-granule densification; '223 supplies the technique of coating ceramic particles with a refractory second phase (carbon) to control the microwave response.
• '010 supplies the specific alumina/carbon quantitative relationship: carbon at 2–10 wt% in an alumina refractory is a conventional, thermally stable minor phase.
• Alcan '541/'087 supplies the overarching motivation (uniform heating of a workpiece assembly embedded in a bed) and the general practice of surrounding a workpiece with a suscepting powder.

Claim chart — Claim 1:

Claims 2–7:

• Claim 2 (parting agent = carbon, MoS₂, SiC or zirconia): Carbon is taught by '223 (coating) and '010 (dispersed, 2–10 wt%); SiC and zirconia are taught as known microwave-active/refractory species by '408 and '578 respectively; MoS₂ was already a disclosed constituent of a susceptor powder bed in the applicant's own cited prior art (CA 2,001,062, per the '282 background: "ex. metal carbides, carbon, MoS₂, lead based ceramics"). Selection of carbon as the optimum from that small, identified set is routine optimisation (In re Boesch).
• Claim 3 (alumina + carbon): The applicant's own admissions describe prior sub-alpha/hydrated alumina susceptor beds (background, discussing CA 2,000,109/'062), and '010 teaches alumina + 2–10 wt% carbon. Combination of the disclosed susceptor with the disclosed parting agent.
• Claim 4 (90–98 wt% alumina / 2–10 wt% carbon): The carbon range is literally taught by '010. The alumina balance follows inevitably from making alumina the "major amount" susceptor required by claim 1. Numeric ranges on result-effective variables, arrived at by routine optimisation, are obvious absent criticality (In re Aller; In re Boesch). Notably, '578 discloses an alumina‑10 wt% silica casket — a 90/10 major/minor refractory ratio in a microwave-sintering enclosure.
• Claims 5–7 (500 µm–10 mm; 0.5–3 mm): '130 discloses fused oxide granules of 150–2000 µm (0.15–2 mm). The claimed 0.5–3 mm range overlaps the prior-art range; overlapping ranges are prima facie obvious where the prior art is close and the parameter is result-effective (In re Woodruff; In re Wertheim). The '282 specification itself frames granule size as a trade-off (porosity vs. heat loss) — i.e., a result-effective variable to be tuned.

Combination B (alternative, independent of Holcombe): Apte CA 2,001,062 + Alcan '087/'541 + '223/'408

The '282 specification admits that the prior Apte packed powder bed already comprised a major susceptor amount plus minor functional refractory additives (oxygen getter, thermal conductor, protective-atmosphere former — including carbon and MoS₂). The delta to claim 1 is therefore (1) granulation/free-flow rather than packed powder, and (2) characterising the minor additive as a "parting agent." Motivation to granulate would arise from the known problems of packed beds (non-uniform heating, entrapped oxygen, inability to flow a protective gas), and '223/'408 teach refractory second-phase additions that moderate susceptor behaviour. This combination is weaker than A because Apte does not expressly attribute a parting/anti-fusing function to any additive — a genuine evidentiary gap that a patentee would exploit.

4. Where the obviousness case is strongest and weakest

Strongest:

1. Claim 1's "material surrounded by granules" limitation is literally met by '130. Combined with '578's granular/spheroid housing, this is close to a straight substitution.
2. The claims omit the distinguishing limitations. Free-flowing character, porosity, gas permeability and bed collapse are all in the specification but none appear in claim 1. The '282's stated novelty resides precisely in those omitted features. Under KSR, an accused infringer can point to the claim as written.
3. The fine-grain/light-colour "unexpected results" are neutralised by '709. Kimrey expressly teaches that rapid microwave heating reduces grain growth and improves densification — the very properties the '282 asserts. And the '282 specification itself states that silicon nitride decomposition "increases with the duration which the ceramic material experiences the high temperature," making the lighter colour a predictable consequence of a shorter cycle, not a surprising one.

Weakest / where the patentee will push back:

1. The parting-agent limitation is not squarely disclosed in any single reference in the '282's own citation list. Each reference must be combined, and the function (preventing the susceptor bed from fusing) is the point of novelty. Expect a KSR "teaching away" argument built on '408 (which, in the food-susceptor context, warns against densifying susceptors) — though '408's own invention is a sintered susceptor, so the teaching is equivocal and cuts weakly.
2. The MoS₂ species in claim 2 is the least supported: MoS₂ is not refractory/stable at 1800–2000 °C in the way carbon or zirconia is, and the reference base (Apte's bed) discloses it as a protective-atmosphere former, not a parting agent. If any claim survives, it is likely claim 2 in its MoS₂ aspect — and a claim survives or falls as a whole, so this could insulate all of claim 2 (and its dependents) unless the patentee disclaims MoS₂ or the claim is shown obvious on the disclosed species.
3. Genuine, documented problem in the art: the background describes packed beds that fused, occluded oxygen, and could not flow protective gas; Alcan's answer to non-uniformity was an electrically conductive ring, a different solution. Evidence that skilled artisans pursued a different route can support non-obviousness (though KSR warns this also signals an "obvious to try" space with a finite set of solutions).
4. Secondary considerations: the '282 record supports a long-felt need (the inventors' own continuing CA applications from 1989–1990 through 1994–1997), a commercial embodiment (the RNGN‑45/T6 tool tested at NRC Ottawa; the Westaim → Thermicedge → Microwear → Indexable Cutting Tools of Canada assignment chain), and superior flank wear (FIG. 4 vs. Kennametal KY‑2000, Newcomer "Newpro Exp," Sandvik Grade 690). The weakness is nexus: the wear/density/colour results are attributed to the process/rapid heating, not to the bed-apparatus features recited in claims 1–7. A patentee would need to prove the bed structure itself drove the results.

5. What an invalidity challenge would still need to prove

• A verified disclosure of the parting-agent function. The '282's own citation list lacks a "smoking gun." The best available routes are: (i) the general refractory/kiln-furniture practice of dusting or coating refractory grain to prevent sticking (needs a documentary reference, e.g., sagger/kiln-furniture or refractory-grain-coating art, or expert testimony); (ii) '408's controlled-sintering teaching; (iii) '010's alumina–carbon refractory practice.
• Full text of CA 2,001,062 / CA 2,000,109 / US 5,072,087, US 4,818,846, US 4,147,911, US 4,666,775, US 5,227,600 and US 5,449,887. I did not retrieve these in this session (search budget exhausted); my characterisation of the Canadian applications derives from the '282 specification's own admissions and the citation titles. A full-text pull is required before relying on them.
• A POSITA declaration on (a) the predictability of substituting a granular bed for a rigid low-density housing, and (b) the conventionality of minor refractory diluents in oxide refractories.
• Antedating considerations: US 5,321,223 (granted 06/14/1994) is only § 102(e) art (application filed 10/23/1991) — fine here, since the '282's priority is 1994-03-31.

6. Housekeeping observation on the patent family

US 5,808,282, US 5,736,092 and US 5,874,377 share the same 1994-03-31 priority and the same specification lineage (US 08/220,840 → 08/443,176 → continuations). They issued 1998-09-15, 1998-05-05 and 1999-02-23 respectively. Because they are commonly owned (Westaim Technologies → Thermicedge → Microwear → Indexable Cutting Tools of Canada), pre-AIA § 103(c) would remove them from one another's prior art if a challenge ever arose; but the overlapping disclosures are a live obviousness-type double patenting / terminal disclaimer issue worth noting, distinct from the § 103 analysis above.

7. Bottom line

Claims 1, 3, 4, 5, 6 and 7 are, on this record, reasonably likely to be held invalid under § 103(a) as obvious over Holcombe US 4,880,578 + Holcombe/Dykes US 5,164,130, in view of General Mills US 5,194,408 and/or US 5,321,223, and optionally Indresco US 5,214,010 and Alcan US 5,202,541/US 5,072,087. Every structural element of claim 1 except the "parting agent" finds literal support, and the parting agent — at least in its carbon aspect (claims 2–4) — is supplied by known refractory practice for limiting densification/fusion of an oxide susceptor. Granule sizes (claims 5–7) are obvious by overlapping-range and routine-optimisation principles.

Claim 2 is the most defensible, principally because of the molybdenum disulphide species, which lacks direct support as a high-temperature parting agent. Claim 1 is the most exposed, because it omits every limitation (free-flowing, porous, gas-permeable, collapsible) that the specification uses to establish novelty over the packed powder beds of the prior art — an "omitted element" problem that the patentee cannot cure without narrowing.

Caveat: this analysis rests on the references surfaced in the patent page's own Prior Art section and on the subset I could verify with live sources. Content of the Canadian applications, US 4,818,846, US 4,147,911, US 4,666,775, US 5,227,600 and US 5,449,887 is taken from citation titles and the '282 specification's characterisation, not verified full text.