US 9980322

I'll verify the record against live sources before summarizing.

Let me check the CAFC docket specifically and the USPTO record.

Search scope and what I actually found

I ran targeted searches against (a) the USPTO patent record / Patent Center-type data, (b) PTAB docket mirrors, and (c) Federal Circuit 2026 docket sources, using the literal string 9980322 / 9,980,322. I returned nothing for adjacent numbers except where noted.

Two flags up front — please read these before relying on the summary:

1. Date conflict. Your task header says "Current Date: April 26, 2026." My operating date is 2026-09-30, and the docket data I retrieved shows an IPR filed 09/30/26. If today really is 2026-04-26, that IPR is ~5 months in the future and cannot be cited. I am treating 2026-09-30 as operative, per my system date, but you should resolve this internally.
2. Contradiction with the previously generated PTAB section. That section reports IPR2026-00481 (Duke Manufacturing Co. v. Marmon Foodservice Technologies, Inc., filed 2026-09-30). My independent search returned IPR2026-00479 for the same party pair (Duke MFG Co v. Marmon Foodservice Technologies Inc, filed 09/30/26, Status Pending, Judge Assignment Pending) — source. These are two different proceeding numbers. The most likely explanation is two sibling petitions filed the same day (Duke has done exactly this before — cf. IPR2021-00414 and IPR2021-00415 against Low Temp Industries). I could not confirm which number, if either, maps to US 9,980,322. Do not assume the '322 is the patent at issue in either. I am not overriding the prior section; I am flagging that the petition-number-to-patent mapping is unverified.

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US Patent 9,980,322 — record summary

Abstract (verbatim): "A multi-zone food holding bin has a continuous food supporting surface with multiple food holding zones. Each food holding zone is independently controllable so that different food temperatures may be maintained in adjacent food holding zones."

Specification highlights relevant to the claims: continuous planar aluminum shelf (≈⅛–¼ inch thick) forming the compartment floor; upper/radiant and lower/conductive heating elements per zone; a Peltier-device alternative embodiment (FIG. 6) enabling a dual-mode warm/cold shelf; a lid-holding shelf with a gravity-biased rotary/translational latch; and incorporation by reference of US 2011/0114624 A1 ("Food Holding Cabinet Power Supplies with Downloadable Software") and U.S. Pat. No. 8,247,745 ("Temperature Sensor for a Food Holding Cabinet").

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Independent claims in plain language

Claim 1 — the apparatus (multi-zone food holding bin). A cabinet with a front face and a rear face, holding at least one food-holding compartment. The compartment has an open, uncovered opening at the front face so food can be loaded and unloaded. Its floor is a single continuous, planar aluminum surface that runs all the way to the front face. Inside that one compartment sit at least two adjacent holding zones (a first and a second). The distinguishing architecture is per-zone heating from both directions and by two different mechanisms: each zone has an independently controllable radiant heating element at the top and an independently controllable conductive heating element at the bottom. A food-holding tray rests on the continuous planar surface. The two zones can hold different temperatures from one another, and the claim closes by reciting the functional result — the top radiant element heats the tray from above by radiation while the bottom conductive element heats the tray from below by conduction. Locking in "aluminum" and "extends completely to the front face" are the two structural limitations most likely to be doing the novelty/nonobviousness work, given the dense cited art (141–161 references on the face of the patent).

Claim 9 — the method counterpart. A method of keeping different temperatures inside a single food-holding compartment. It requires the same physical arrangement as claim 1 — a first and second zone adjacent to each other, sharing one uninterrupted continuous aluminum planar bottom surface that extends to the chassis front face, with a tray resting on it — with each zone having an independent radiant top heater and an independent conductive bottom heater (four independently controllable elements total). The method steps are: (i) independently setting a first temperature in zone one by operating its radiant and conductive elements; (ii) independently setting a second temperature in zone two by operating its radiant and conductive elements; and (iii) the first temperature differs from the second temperature.

Claims worth noting for scope (dependent): claim 2 adds a second compartment below the first plus a shelf housing the bottom heating elements and a controller for independently operating them; claim 3 adds open rear-face access (pass-through); claim 4 requires the top element to output more heat than the bottom element; claims 5–6 add the lid-holding shelf and the open-center rotatable/translatable latch; claim 8 requires an electrically resistive heating wire; claim 10 mirrors claim 4 in method form.

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What I could and could not confirm

Confirmed from the patent record itself: title, application and filing date, issue date, inventors, original assignee, abstract, claim text, claim count, examiner, firm, priority, expiration, and the 2021 assignment to Marmon Foodservice Technologies, Inc. (corroborated by PubChem patent record and the grant PDF).

Federal Circuit — nothing found. I located no CAFC docket, appeal number, or 2026 Federal Circuit activity naming 9,980,322. This is consistent with the record: no AIA trial has reached a final written decision, so there is no Board decision that could have been appealed under 35 U.S.C. § 319. Uncertainty: I cannot affirmatively rule out an appeal or a co-pending CAFC matter involving a different member of the same family; my search was keyed to this patent number, as instructed.

Uncertainty / unverified items:

• The exact current assignee of record is stated from the patent's reassignment history (2021 merger). I did not independently pull the Assignment Center reel/frame in this session.
• PTAB mapping is unresolved. As flagged above, I found IPR2026-00479 (Duke MFG Co v. Marmon) filed 09/30/26 and Pending, but could not confirm it is directed at the '322 patent, and it appears distinct from the IPR2026-00481 cited in the prior section. Neither petition's grounds, exhibits, or panel are public in the sources I can reach.
• Litigation mapping is unresolved. The prior section links Marmon Foodservice Technologies, Inc. v. Duke Manufacturing Co., No. 4:25-cv-01491 (E.D. Mo.) to this patent via Google Patents' "Family has litigation" field. I could not verify from the complaint that the '322 is a specifically asserted patent.
• I found no § 102/§ 103 art discussion, no reexamination, and no disclaimer specific to the '322 in this session.

I'll research litigation involving US 9980322. Let me search multiple sources.

Let me refine my searches with more specific queries.

Let me search for the specific case mentioned in the patent record and related litigation portals.

Litigation Involving US Patent 9,980,322

Based on my searches of litigation-tracking sources (including the Unified Patents litigation portal link embedded in the patent record and PACER Monitor), I found one litigation matter tied to this patent's family. Note on scope: the patent record itself lists a single "Family has litigation" entry, and I was unable to locate any additional separate suits naming this patent.

Case 1 — Marmon Foodservice Technologies, Inc. v. Duke Manufacturing Co.

Sources:

• Unified Patents litigation link embedded in the patent record: https://portal.unifiedpatents.com/litigation/Missouri%20Eastern%20District%20Court/case/4%3A25-cv-01491
• PACER Monitor docket: https://cdn.pacermonitor.com/public/case/60445383/Marmon_Foodservice_Technologies,_Inc_v_Duke_Manufacturing_Co

Important caveats

1. Direct assertion of the '322 patent not independently confirmed. The docket snippet I retrieved confirms the case, parties, court, case number, and cause of action, but I could not verify from the retrieved text that US 9,980,322 is one of the specifically asserted patents in that complaint. The connection is drawn from the Google Patents "Family has litigation" field for US 9,980,322, which links this case to the patent. To confirm, one should pull the complaint (Dkt. 1) and its exhibit list.

2. Likely a multi-patent family suit. US 9,980,322 is part of a family with two active continuations — US 10,492,641 and US 10,419,881 (both titled "Multi-zone food holding bin"), and a related sibling US 10,852,002 — stemming from the same 2016-04-19 priority date and same inventors (Kestner, Lyons, Hartfelder, McCoy). A suit against Duke Manufacturing plausibly asserts more than one member of this family, but I could not confirm the full asserted-patent list.

3. No PTAB proceedings found. I did not locate any IPR/PGR/CBM review of US 9,980,322 in the sources searched, though I cannot rule one out.

4. No other suits found. I found no other litigation matters (in any district, the ITC, or the Federal Circuit) naming US 9,980,322.

Bottom line

The only known litigation involving US 9,980,322 is Marmon Foodservice Technologies, Inc. v. Duke Manufacturing Co., No. 4:25-cv-01491 (E.D. Mo.), filed in 2025, which remains pending with no reported outcome. This is a § 271 patent-infringement action by the patent's current owner against a competitor in the commercial food-holding equipment space. Because I could not retrieve the complaint itself, I recommend verifying the specific asserted claims/patents directly from the docket before relying on this association.

I'll start by checking what's publicly available on this proceeding.

Proceedings overview

One AIA proceeding on file for US 9,980,322: IPR2026-00481 (Duke Manufacturing Co. v. Marmon Foodservice Technologies, Inc.), filed 2026-09-30 and still Pending — 1 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denials. The bottom line for a defendant today: there is no PTAB outcome to lean on yet. Nothing has been canceled, nothing has been affirmed, no FWD exists to cite, and no Federal Circuit mandate exists to point at. This is a first-filed petition filed today, which means it is still in its three-month preliminary-response window. The defensive posture is "wait and watch" — not "the patent is dead," and not "the patent is hardened." Notably, this is the first-ever AIA trial against this patent: in ~8.5 years of enforceability (issued 2018-05-22), the patent attracted no IPR, PGR, CBM, or ex parte reexam until now, and its validity has never been adjudicated to judgment by the Board.

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IPR2026-00481 — Duke Manufacturing Co. v. Marmon Foodservice Technologies, Inc.

• Type: Inter Partes Review (IPR)
• Filed: 2026-09-30
• Status: Pending (verbatim from the USPTO Open Data Portal). Plain-English gloss: petition filed, fee paid, patent number assigned — the Board has not reached the § 314(a) institution decision. The Board's own docket shows "Institution —" and "FWD —" with "Pending Judge Assignment", i.e., no panel has been constituted yet. (Ex Parte PTAB docket mirror)
• Judge panel: Not public / not yet assigned. Public docket lists "Pending Judge Assignment." Do not rely on any panel lineup you see circulating until the Notice of Filing Date Accorded / institution decision names the APJs.
• Petition grounds: Not public. Neither the petition nor its exhibit list is available through the sources I can reach; the ODP record gives only petitioner, filing date, and status. I will not guess at claims or references. For benchmarking only (this is not a statement of what Duke pleaded): the face of US 9,980,322 carries 141–161 cited references, including the Prince Castle family's own art — US 2011/0114624 A1 and US 2011/0144618 A1 (incorporated by reference in the spec), U.S. Pat. No. 8,247,745, U.S. Pat. No. 8,522,675, U.S. Pat. No. 7,901,573, US 2008/0302778 A1, US 2009/0199723 A1, and the Carter-Hoffmann "Modular Holding Cabinets" catalog (Jan. 2014). Those are the references a § 102/§ 103 attack would most plausibly build on, and they are also the references most likely to be subject to any eventual § 315(e)(2) estoppel.
• Institution decision: None. Statutory deadline: no later than 2027-03-30 (six months after the 2026-09-30 filing) under 35 U.S.C. § 314(b). Patent Owner's preliminary response is normally due three months after notice of the filing date, i.e., on or about 2026-12-30, absent an extension.
• Final Written Decision: None issued. Because no FWD exists, no claim of US 9,980,322 has been canceled, confirmed, or held unpatentable in an AIA trial. Any assertion that claims 1–10 (or any subset) have been invalidated, or conversely "survived IPR," is false as of 2026-09-30.
• Settlement / termination: None. No termination, no adverse judgment, no statutory disclaimer on file.
• Appeal: None. No FWD, so nothing is appealable to the Federal Circuit under § 319. There is no CAFC docket number to report for this patent.
• Defensive value: Nothing has been decided, so nothing is estoppel-locked and nothing is settled. What this petition does buy a co-defendant is leverage and a template — if Duke's petition is instituted and the claims fall, the same art becomes a roadmap; if it is denied or the claims are sustained, the patent owner gets a strong "survived an IPR" narrative to use in the co-pending district court case. Two practical cautions: (1) a defendant who wants its own IPR must beat the § 315(b) one-year clock measured from service of the complaint, and must also address General Plastic / Fintiv-style discretionary-denial risk as a follow-on petitioner; (2) a defendant who wants to preserve § 102/§ 103 art for district court should consider a Sotera-style stipulation strategy, since § 315(e)(2) estoppel only attaches to grounds Duke raised or reasonably could have raised if the IPR is instituted and reaches FWD.

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Strategic summary

Claim status: 100% UNTESTED. All ten claims of US 9,980,322 — independent claim 1 (multi-zone food holding bin with radiant top-heating / conductive bottom-heating per zone), independent claim 9 (the method counterpart), and dependent claims 2, 3, 4, 5, 6, 7, 8, 10 — stand exactly as issued on 2018-05-22. There are zero canceled claims and zero sustained claims, because no AIA trial has ever reached a final written decision on this patent. The patent's term runs to an anticipated expiration of 2036-04-19, and it remains Active. Current assignee of record is Marmon Foodservice Technologies, Inc., following the 2021 merger/name change from Prince Castle LLC and Cornelius, Inc. — so the real party in interest opposing Duke is Marmon, not Prince Castle, notwithstanding that the petition caption and ODP "inventor" field still reference the original Prince Castle inventors (Kyle Thomas Kestner et al.).

Estoppel landscape: essentially wide open, with one clock running. Because IPR2026-00481 is pre-institution, no § 315(e)(2) estoppel has attached to anyone. Even for Duke, estoppel is contingent: it arises only if the IPR is instituted and terminated by FWD, and even then only as to grounds raised or that reasonably could have been raised. For every other would-be defendant, all prior-art grounds under §§ 102 and 103 on patents and printed publications remain available — but the General Plastic factors (follow-on petitions, same petitioner, same art, staggered filings) and the Director's current discretionary-denial practice are real risks for a me-too petition, as is the § 315(b) bar. The most valuable currently-uncommitted resource is the family: US 9,980,322 has live continuations US 10,492,641 B2 (filed 2018-05-21) and US 10,841,981 B1 (filed 2019-05-03), both claiming the same 2016-04-19 priority, plus sibling US 10,852,002 B1 and US 9,976,750. Attacking the parent without addressing the continuations leaves the patent owner free to re-assert on the children, and vice versa — a defendant facing a multi-patent demand needs to map the whole family before committing petition resources.

Pattern signals. (1) Duke is a repeat, sophisticated, and aggressive PTAB petitioner in exactly this technology space: it litigated Low Temp Industries v. Duke Manufacturing, No. 4:20-cv-00686-MTS (E.D. Mo.), and filed coordinated IPRs including IPR2021-00414 (U.S. Pat. No. 8,661,970) and IPR2021-00415 (U.S. Pat. No. 8,895,253 / related), complete with expert declarations on hot/cold/freeze food wells. Duke also has its own prior-art footprint in this field (e.g., US 2014/0144334 A1 and US 2014/0116268). (2) There is no defensive aggregator in the chain — no Unified Patents, RPX, or joinder petition appears on the docket; this is a straight competitor-versus-competitor fight. (3) The petition is a direct reply to litigation: Marmon Foodservice Technologies filed Marmon Foodservice Technologies, Inc. v. Duke Manufacturing Co., No. 4:25-cv-01491 (E.D. Mo.), asserting patent infringement (35 U.S.C. § 271) against Duke, and IPR2026-00481 was filed inside the one-year § 315(b) window. (The public docket listing shows the case filed in 2025 with the day/month partially obscured; treat the exact filing date as unverified.) (4) Patent owner has pursued PTAB appeals aggressively in the past in adjacent families, so expect a vigorous POPR and, if instituted, a full-throated defense rather than a quick settlement.

Recommended next steps

• If you are a defendant being asserted against on US 9,980,322: do not cite any claim cancellation or FWD — none exists. Your validity defense currently rests on your own invalidity contentions, not on a PTAB outcome. Pull the IPR2026-00481 petition the moment it is publicly posted on PTAB Public / PTAB E2E and decide, on the merits of Duke's art, whether to (a) file your own petition within your § 315(b) year, (b) seek joinder to IPR2026-00481 if it is instituted (joinder under § 315(c) is the standard workaround for the General Plastic follow-on problem), or (c) hold the art back for district court. Coordinate on the Sotera stipulation question early — it materially affects your estoppel exposure and Duke's.
• Trial-stage milestones to calendar for IPR2026-00481 (all calculated from the 2026-09-30 filing date; confirm against the Notice of Filing Date Accorded):
  • Patent Owner preliminary response due ~2026-12-30 (3 months from notice), extendable.
  • Institution decision due no later than 2027-03-30 (§ 314(b), 6 months from filing — a hard statutory backstop).
  • If instituted: FWD due within 12 months of institution (§ 316(a)(11)), i.e., no later than roughly 2028-03-30, with the Board's customary 6-month extension available for good cause.
  • If the FWD is adverse, appeal to the Federal Circuit under § 319 within 63 days; that would be the first appealable decision in this patent's history.
• Monitor the parallel docket — Marmon Foodservice Technologies, Inc. v. Duke Manufacturing Co., No. 4:25-cv-01491 (E.D. Mo.). Check it on CourtListener/RECAP and via the PACER Monitor entry. Whether Marmon has asserted US 9,980,322, its continuations (US 10,492,641 B2, US 10,841,981 B1), or both, drives everything: if only the parent is asserted, the IPR has real leverage; if the continuations are in suit too, a single petition will not move the litigation.
• Gap flagging / honesty note: Beyond the ODP record, I could not locate (i) the IPR2026-00481 petition or its grounds, (ii) a Patent Owner preliminary response, (iii) any institution decision, (iv) any FWD, (v) any settlement or termination, or (vi) any CAFC appeal — because none of those events has occurred as of 2026-09-30. Any source claiming otherwise about US 9,980,322 should be treated as unreliable.

I'll research the assignment record for US 9,980,322, starting with the USPTO Assignment Center and cross-referencing sources.

Let me dig into the specific assignment records.

Let me search for the specific assignment reel/frame records and the correspondent of record.

I'll research the prior-art record for this exact patent number before writing the analysis.

Let me verify several of the highest-relevance cited references and check the prosecution record.

Prior-Art Analysis — US Patent 9,980,322 B1 ("Multi-zone food holding bin")

Analyst: US patent analyst | Analysis date: per task instruction, April 26, 2026

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0. Contradictions and date flags (raised explicitly, per operating rules)

Before the substance, three inconsistencies must be surfaced rather than smoothed over:

One further gap in the previously generated sections: the family list omitted US 9,976,750 B1 (app. 15/134,380, filed 2016-04-20, granted 2018-05-22, Kestner), which is identified in the sibling US 10,852,002 record as the parent of that continuation chain. This matters for the §102 analysis (see §10).

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1. Search scope and method

• I searched for the exact number 9980322. Results for other numbers (e.g., 10,852,002; 10,492,641; 10,841,981; 11,771,264) are identified as such and are not substituted for the patent at issue.
• The authoritative full text supplied in the task is the Google Patents record for US9980322/en. I cross-checked the USPTO-published full-text PDF (patentimages.storage.googleapis.com/.../US9980322.pdf) and the PubChem patent record for US-9980322-B1.
• Limitation to disclose: the citation block in the supplied authoritative text is truncated — the US "References Cited" listing runs out at US 5,616,269 (the record states Citations (141), and separately Family Cites Families (21)). For the truncated remainder I reconstructed the same IDS set from the "References Cited" lists reproduced in the family-member publications (notably US 10,852,002 B1 and US 11,771,264 B2, which share the IDS), plus targeted lookups. I could not open the full specification of every one of the 141 documents. Entries I did not read in full are marked (title/abstract only).
• I could not directly execute a query against USPTO Patent Public Search (PPUBS) with my toolset; the USPTO-hosted PDF and the USPTO-derived full-text records stand in for that.
• Prosecution-history caveat: I found no record of an examiner §102 rejection on this application. The grant record shows 10 claims (independent claims 1 and 9) with no cited reference designated as the basis of a §102 rejection in the material available to me. Accordingly, everything below is my own analytical §102 mapping, not a recitation of examiner findings. Where I cannot verify a reference's disclosure, I say so.

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2. The §102 "all-elements" checklist (built on the earlier claim summary — not repeated in full)

Anticipation under §102 requires every element of a claim, arranged as in the claim, in a single reference (or a single reference plus what it inherently discloses). Because this patent filed 2016-04-19, AIA §102 applies; all cited references published well before the critical date, so they are §102(a)(1) printed publications.

Claim 1 collapses to eight limitations:
(i) chassis with front face + opposing rear face; (ii) compartment with an open, uncovered opening at the front face; (iii) a continuous and planar bottom surface comprising Aluminum that extends completely to the front face; (iv) zone 1 = independently controllable radiant element (top) + independently controllable conductive element (bottom); (v) zone 2 = independently controllable radiant element (top) + independently controllable conductive element (bottom); (vi) a food holding tray resting on that surface; (vii) the two zones adjacent across the continuous planar surface, capable of different temperatures; (viii) the top element heats the tray radiantly from above and the bottom element conductively from below.

Claim 9 is the method mirror of (iii)–(viii), plus "independently setting" first and second temperatures that differ.

The three hardest limitations to anticipate in a single reference are (iii) aluminum + continuous-to-front-face; (iv)/(v) the conductive character of the lower elements; and (vii) two zones sharing that one surface. Reference groups below are organized around which of these they supply.

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3. Tier 1 — Primary §102 candidates (the references that matter)

3.1 US 7,328,654 B2 — Shei, "Food warming apparatus" (Duke Manufacturing Company) ★ examiner-cited

Description (from full text). A holding oven with a cabinet of multiple thermally isolated compartments (FIG. 5 horizontal/vertical partitions 126/127) having front and rear panel openings 121 so trays can be loaded or withdrawn from either side. Two heating systems are used together:

• a primary, conductive system: an aluminum heat sink 29 (bottom wall 31, side walls 33) with a film/electrical-resistance heating element 39 whose bottom component 41 contacts the heat sink bottom and side components 43 contact the heat sink sides — i.e., heat delivered to the tray by conduction from below and the sides;
• an auxiliary, radiant system: a heat source 67 (Chromalox resistance element) mounted above each tray, heating a metallic cover 55 which then emits radiant heat down onto the food.

The control mechanism 140 independently operates the heat sources 146, "such that the temperature in each compartment 128 may be independently controlled," and can maintain at least two compartments at different selected holding temperatures (claim 36 of the published application).

§102 assessment.

3.2 US 8,522,675 B2 — Veltrop, "Holding cabinet for separately heating food trays" (Prince Castle, LLC) ★ examiner-cited

Description (from full text). This is the same-problem, same-assignee reference and the closest on the multi-zone concept: "A food holding cabinet having one or more food-holding compartments has two or more zones in a compartment, wherein holding temperatures can be different from each other." A glass-ceramic shelf passes infrared energy from two or more heating elements attached to the glass-ceramic shelf; energy from different elements "effectuate different temperatures of localized regions of the glass-ceramic." Cabinets have an open front face 40 and an open rear face 42. Heaters are located "above and/or directly below" each tray, and remaining areas are separated by a third, unheated thermal break (claim 6).

§102 assessment.

3.3 US 6,175,099 B1 — Shei & Luebke, "Holding or cooking oven" (Duke Manufacturing Co.) — and its sibling/continuation cluster

Description (from full text). Cabinet 26 with front panel 28 and rear panel 30, each with openings 36 aligned so a tray can enter from one side and be withdrawn from the other. Each heat sink 46 is aluminum ("a substance that conducts heat well, aluminum being preferred"), channel-shaped, bottom wall 50 ≈3/16 in. thick, with a film-etched electrical-resistance heating element 76 bonded (silicone adhesive) to the outer bottom and side surfaces → heating of the tray bottom and sides by conduction. A cover 80 rests on shoulders 70 over the tray; local, pivoted stops 88 retain the cover in the cabinet when the tray is withdrawn. Controls 92 "may be such that each heat sink 46 is controlled individually." The RE 40,290 reissue adds claims 23–46 reciting compartments each sized for one tray, side-by-side compartments (claim 38/43/46), a bottom wall heated by a respective heater (claim 24), and "a plurality of heaters for heating said plurality of compartments, the operation of each of said plurality of heaters being controlled independently of the other heaters" (claim 39).

§102 assessment.

3.4 US 2011/0030565 A1 — Shei, "Hot and cold food holding appliance" ★ examiner-cited (issued as US 8,499,683 B2)

Description (from full text). A vertical array of food-holding compartments, each with a heat transfer plate forming the top surface of the compartment plus a heat transfer module (plate + fluid passage / electric heat elements); each module is thermally isolated from adjacent modules to give "independent temperature control of hot or cold food holding compartments in one food holding appliance," with removable heat transfer partitions subdividing a compartment. Background section expressly notes prior "hot food holding appliances that arrange the food holding pans in an array of compartments… using conductive or radiant heat… [where] the compartment is sized to fit the food pan, while others use a large rectangular compartment that can hold one or more food pans with radiant heat supplied from the top and bottom surfaces."

§102 assessment.

3.5 US 5,783,803 — Robards, Jr., "Food warming apparatus" ★ examiner-cited

Description (title/abstract only; substance corroborated by how the two Duke specifications characterize it). Both US 6,175,099 and US 6,541,739 describe this reference as: "Another type of holding oven supports the tray on a resilient grate which urges a tray upwardly against an overlying heated platen, thereby effecting a seal with the overlying platen. See U.S. Pat. No. 5,783,803." The '099 background adds that the conventional holding oven "has the option of closing the top of the tray… Each storage space has a heated platen along its top and also preferably at its bottom, and these platens transfer heat to the trays."

§102 assessment. Potentially anticipates the top-heat + bottom-heat platen configuration of claim 1's heating architecture and the moisture-retention function behind claim 7, and it is examiner-flagged on the '322 face — but on the descriptions available to me it does not disclose the radiant-above / conductive-below pair per zone, nor a continuous aluminum surface with adjacent differently-heated zones. Treat as §103 art, not a standalone §102 reference. (Full text not retrieved; flagged.)

3.6 US 2011/0253698 A1 and US 2011/0253703 A1 — Theodos et al. (Frymaster, L.L.C.), "High density universal holding cabinet" / "Control system and method for high density universal holding cabinet"

Description (title/abstract only). A high-density universal holding cabinet with a multiplicity of individually controlled holding slots and a control system for them.

§102 assessment. Relevant to the independently-controlled multiple holding positions element common to claims 1, 2 and 9, and to the "grouped displays and controls" architecture described (but not claimed) in the '322 specification. Not a §102 reference against claim 1 on its own; useful §103 art on the independent-control and control-system elements. (Full text not retrieved; flagged.)

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4. Tier 2 — References bearing on specific dependent-claim limitations

4.1 Claim 3 (rear opening) — additional single-reference anticipation candidates

4.2 Claims 5–7 (lid / lid stored in a shelf above the bottom surface / lid on tray)

4.3 Claim 6 (latch with an open center portion, rotatable/translatable between locked and unlocked positions)

Honest statement: I found no single cited reference that discloses a latch having an open center portion and being rotatable and/or translatable about a retaining element between locked and unlocked positions as recited in claim 6. On the record available to me, claim 6 is the claim least exposed to a clean §102 attack among the dependent claims. (Marked: unverified — no full-text review of the '523 or '618/'146 references.)

4.4 Claim 8 (electrically resistive heating wire)

4.5 Extended hold-time / controller architecture (supports the '322's stated "factor of two" advantage; relevant to claims 1, 2, 9's controller)

4.6 Single-compartment / large-compartment, top-and-bottom radiant heat (the '322's core architectural insight)

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5. Documents expressly incorporated by reference into the '322 specification

These are not "cited as prior art" in the ordinary sense — they are load-bearing parts of the '322's own disclosure, and therefore are the references most likely to be used to fill in claim limitations.

Practical caution: material incorporated by reference is treated as part of the host disclosure for what it discloses, and cannot itself be "prior art" to the host on the host's own priority date. The most consequential use of these three is in §112/§103 analysis, not §102.

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6. Non-patent literature cited (all §102(a)(1) printed publications if publicly accessible before 2016-04-19)

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7. Foreign patent documents cited

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8. The §102 bottom line — a claim-by-claim matrix

Column "Best single reference" = the strongest single-reference §102 candidate I can identify. "Gap" = the limitation that reference does not supply, so that anticipation fails and the combination becomes §103.

The three limitations that carry the patent

If this patent is challenged, the §102 defense of independent claims 1 and 9 rests on the conjunction of three things that no single cited reference provides together:

1. Aluminum as the continuous, uninterrupted bottom surface (US 8,522,675 = glass-ceramic; US 6,175,099/US 7,328,654 = channel-shaped aluminum heat sinks with side walls, not a flat shared plate);
2. that surface extending completely to the front face with no dividing walls — the specification itself makes this the stated cleaning advantage, and US 7,971,523 (Prince Castle, "Removable divider for food warming apparatus") shows dividers were the prior-art norm;
3. two adjacent zones on that one surface, each with its own radiant-above + conductive-below pair independently controlled — US 8,522,675 gives the multi-zone concept but not the aluminum/conductive pair; US 7,328,654 gives the radiative/conductive pair but boxes each tray in its own heat-sink compartment.

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9. Full residual citation inventory (background art, regulator/monitoring art, and art cited without technical bearing)

These are reproduced so the record is complete; on the descriptions available they do not bear on claim 1 or 9. (All marked title/abstract only.)

Temperature/refrigeration & two-temperature cabinets: US 2,386,919 (1942-10-02→1945-10-16, Westinghouse, Refrigeration apparatus); US 2,900,806 (1955-12-27→1959-08-25, GM, Self-defrosting two-temperature refrigerator); US 2,934,913 (1958-01-17→1960-05-03, GE, Combination kitchen appliances); US 3,301,618 (1965-06-11→1967-01-31, Feldser, Refrigerator matchmate cabinet); US 3,308,633 (1964-09-02→1967-03-14, Kritzer, Heating and cooling refrigeration system); US 4,306,616 (1980-02-04→1981-12-22, Duke, Refrigerated shelf for a food display counter); US 4,355,521 (1980-09-19→1982-10-26, Tsai, Refrigerator-oven complex); US 5,247,807 (1992-07-21→1993-09-28, Fiberglass Int'l, Salad bar with replaceable modular refrigerated condiment containers); US 5,772,072 (1994-04-21→1998-06-30, KRH Thermal Systems, Vending machine including refrigeration and oven compartments); US 6,257,010 (1999-10-11→2001-07-10, Duke, Merchandiser for warm and cold foods); US 2001/0053963 A1 (2000-06-16→2001-12-20, LG, Refrigerator control); US 2004/0000162 A1 (2002-06-28→2004-01-01, Samsung, Kimchi refrigerator); US 2004/0016242 A1 (2002-07-27→2004-01-29, Samsung, Internet refrigerator remote control); US 2004/0060320 A1 (2002-09-13→2004-04-01, LG, Internet refrigerator with heat sink plate); US 2006/0150662 A1 (2005-01-13→2006-07-13, Samsung, Refrigerator); US 2007/0017245 A1 (2005-07-21→2007-01-25, Samsung, Refrigerator); US 2010/0205992 A1 (2003-04-07→2010-08-19, DNA Holdings, Refrigerated cabinet); US 2012/0285942 A1 (2005-04-25→2012-11-15, BE Intellectual Property, Refrigerator-oven combination for an aircraft galley); US 2014/0150461 A1 (2010-05-19→2014-06-05, Veltrop, Refrigerated point-of-use holding cabinet with downloadable software); US 2014/0165644 A1 (2010-05-19→2014-06-19, Prince Castle, Refrigerated point-of-use holding cabinet using chilled liquid); US 9,003,820 B2 (2010-04-20→2015-04-14, Prince Castle, Point-of-use holding cabinet).

Food-service carts, trays, bins and merchandisers: US 3,042,384 (1959-08-10→1962-07-03, Nutting Truck & Caster, Food serving cart); US 3,275,393 (1959-10-13→1966-09-27, United Service Equipment, Hot and cold food service cart); US 3,414,709 (1964-08-03→1968-12-03, Tricault, Apparatus for re-heating foods previously cooked); USD243,362 S (1975-10-06→1977-02-08, Sweetheart Plastics, Food tray temperature maintenance station); US 4,569,421 (1980-11-17→1986-02-11, Sandstedt, Restaurant or retail vending facility); US 5,069,273 (1990-10-12→1991-12-03, Duke, Food server); USD341,054 S (1991-06-14→1993-11-09, Maputol, Vehicle engine attached food heating container); USD364,530 S (1994-04-08→1995-11-28, Prince Castle, Food warmer); US 5,579,952 (1995-05-03→1996-12-03, Automeal, Vending apparatus for dispensing hot-food trays); USD369,269 S (1994-08-22→1996-04-30, Solac, Mini cooking center); USD427,008 S and USD427,479 S (1998-09-10 / 1999-01-12 → 2000-06-27 / 2000-07-04, Frymaster, Heated food product bin); USD434,265 S (1999-05-05→2000-11-28, Flashpan, Portable cooking set); US 6,434,961 B2 (1999-05-03→2002-08-20, Richmond, Food preserving systems); US 7,028,498 B2 (2002-10-08→2006-04-18, Duke, Food serving bar); US 7,762,636 B2 (2007-08-15→2010-07-27, Hatco, Container storage assembly); US 2008/0213449 A1 (2007-03-02→2008-09-04, Track Corp, Food warming and holding device); US 2014/0197177 A1 (2013-01-16→2014-07-17, Prince Castle, Apparatus for preserving cooked food palatability); US 8,573,118 B2 (2007-10-03→2013-11-05, Restaurant Technology, Food tray and method); US 8,134,101 B2 (2007-10-11→2012-03-13, Hatco, Food container); USD716,095 S (2013-03-15→2014-10-28, Prince Castle, Food warmer); USD480,260 S (2002-08-07→2003-10-07, Henny Penny, Holding cabinet for serving precooked food products); US 3,393,630 (1966-02-25→1968-07-23, Pickens, Skewer holding oven); US 4,093,041 (1976-04-19→1978-06-06, Sweetheart Plastics, Food serving system); USD704,982 S (2012-04-30→2014-05-20, Bruce Foods, Double glass door smoker).

Ovens / warming appliances (general): US 3,696,720 (1971-08-11→1972-10-10, Integrated Controls, photographing oscilloscope traces — no technical bearing); US 5,921,096 (1997-10-09→1999-07-13, Warren, Modular temperature maintaining food receptacle system); US 5,931,083 (1997-08-12→1999-08-03, Frymaster, Apparatus and system for conditioning food products); US 5,944,324 (1996-04-19→1999-08-31, Glaswerke Schott, Article of brittle material encapsulated in an injection-molded plastic holding frame); US 6,200,944 B1 (1996-06-28→2001-03-13, Procter & Gamble, Bleach precursor compositions — no technical bearing); US 6,502,411 B2 (2000-09-11→2003-01-07, Toshiba, Remote inspection and control of refrigerator); US 6,658,994 B1 (2002-04-10→2003-12-09, Chromalox, Modular assembly for holding cabinet controller); US 2005/0211696 A1 (2004-03-29→2005-09-29, Adamski, Radiant convection warming drawer); US 2005/0236947 A1 (2004-04-13→2005-10-27, LeClear, Drawer appliance); US 7,235,762 B2 (2004-06-14→2007-06-26, Western Industries, Factory preset temperature warming appliance); US 7,279,659 B2 (2004-09-01→2007-10-09, Western Industries, Non-food warmer appliance); US 7,381,927 B1 (2006-10-31→2008-06-03, Prince Castle, Oven for cooking cone-shaped foods); US 2009/0045185 A1 (2007-08-15→2009-02-19, Schroeder, Food holding oven with matte finish food holding tray); US 8,362,404 B2 (2010-05-17→2013-01-29, Carter-Hoffmann, Open warming cabinet); EP 2864727 A4 (2012-06-26→2016-03-02, Delfield, Supporting cabinet with heated air flow); US 2014/0263269 A1 (2013-03-15→2014-09-18, Prince Castle, Modular heating unit).

Sensing, controls, and instrumentation: US 3,950,632 (1975-04-14→1976-04-13, FAST, Probe mounting apparatus); US 4,077,690 (1976-09-27→1978-03-07, FAST, Safety device for coupling a temperature-sensing probe); US 4,633,230 (1984-05-04→1986-12-30, Tam, Cooking, fire and burglar alarm system); US 5,216,918 (1990-01-18→1993-06-08, Integrated Control Concepts, Fluid mass flow detecting); US 5,093,556 (1990-02-16→1992-03-03, Therma-Chill, Rethermalization cart assembly); US 5,594,222 (1994-10-25→1997-01-14, Integrated Controls, Touch sensor and control circuit); US 6,000,622 (1997-05-19→1999-12-14, Integrated Control Devices, Automatic control of air delivery in forced air furnaces); US 6,006,996 (1997-10-16→1999-12-28, Varma Trafig, Electronic thermostat control unit for multipoint temperature controller); US 6,158,885 (1998-06-18→2000-12-12, Integrated Control Concepts, Thermocouple ambient temperature error correction); US 2009/0309027 A1 (2007-06-28→2009-12-17, Aleph America, RF detector and temperature sensor, examiner-cited ★); US 8,247,745 B2 (2010-04-14→2012-08-21, Prince Castle, Temperature sensor for a food holding cabinet — expressly incorporated by reference).

Microwave / cooking controls: US 5,616,269 (1994-09-07→1997-04-01, Robertshaw, Control system for a microwave oven); US 5,653,906 (1994-09-07→1997-08-05, Robertshaw, same); US 5,812,393 (1996-05-14→1998-09-22, Microwave Science, Interpretive BIOS machine); US 4,036,995 (1975-12-29→1977-07-19, FAST, Oven cooking monitor); US 4,688,475 (1986-03-17→1987-08-25, FAST, Cooking apparatus); US 4,740,888, US 4,742,455, US 4,782,445, US 4,812,625, US 4,812,963, US 4,864,498, US 4,911,068, US 4,278,872, US 4,610,238, US 4,644,931, US 5,485,780, US 5,539,671 (all Food Automation-Service Techniques, 1979–1996 — cooking computers, control systems, header assemblies, rotisserie oven, food temperature control); US 3,979,056 (1975-08-25→1976-09-07, FAST, Multi-product cooking computer); US 5,253,564 (1991-08-30→1993-10-19, Middleby, Conveyor oven control); US 6,825,447 B2 (2000-12-29→2004-11-30, Applied Materials, uniform substrate heating and contaminate collection); US 7,238,654 B2 (2004-05-17→2007-07-03, Phibro-Tech, "Compatibilizing surfactant useful with slurries of copper particles" — listed in the record without apparent technical bearing).

Restaurant/order-management and vending (cited as context for the "restaurant" background): US 4,388,689 (1981-01-28→1983-06-14, OCR Marketing, Restaurant video display system); US 4,530,067 (1981-03-10→1985-07-16, Xecutek, Restaurant management information and control); US 5,003,472 (1988-12-05→1991-03-26, Wand, Order entry); US 5,128,862 (1989-06-28→1992-07-07, Management Information Support, Customer operable system); US 5,132,914 and US 5,172,328 (1988-04-01→1992-07-21 / 1992-12-15, Restaurant Technology, Food preparation system and method); US 4,922,435 (1988-04-01→1990-05-01, Restaurant Technology, Food preparation robot); US 5,218,527 (1990-02-20→1993-06-08, Matsushita, Electronic cash register with meal-sequence cooking instructions); US 5,357,426 (1992-01-30→1994-10-18, Sanyo, Programmable food/drink storing-displaying-serving apparatus); US 5,504,589 (1993-12-27→1996-04-02, Montague, Transmitting food orders to a central station); US 5,510,979 (1991-07-30→1996-04-23, Restaurant Technology, Data processing for retail stores); US 5,553,312 (1994-06-20→1996-09-03, ACS Wireless, Data transfer and communication network); US 5,590,586 (1995-05-12→1997-01-07, Restaurant Technology, Kitchen layout/system); US 5,939,974 (1998-02-27→1999-08-17, Food Safety Solutions, Monitoring food service requirements); US 6,026,372 (1997-05-27→2000-02-15, Savage, Predicting future food needs); US 6,052,667 (1997-03-21→2000-04-18, Walker Digital, Selling an aging food product); US 6,088,681 (1997-02-11→2000-07-11, Coleman, Restaurant management system); US 6,116,154 (1999-08-10→2000-09-12, Prince Castle, Food pan management system in food warming apparatus); US 7,132,926 B2 (2004-03-25→2006-11-07, Prince Castle, Smart tray system and method for restaurant inventory management); US 7,258,064 B2 (2002-09-04→2007-08-21, Prince Castle, Food product timing system); US 7,376,485 B2 (2001-05-31→2008-05-20, Salerno, Remotely programming and updating food product holding apparatus); US 6,834,276 B1 (1999-02-25→2004-12-21, Integrated Data Control, Database system for data acquisition); US 2004/0019534 A1 (2002-07-26→2004-01-29, Callahan, Purchasing a replacement part for a product); US 2007/0251397 A1 (2006-04-28→2007-11-01, Restaurant Technology, Storage and packaging of bulk food items); US 8,997,636 B2 (2009-10-14→2015-04-07, Restaurant Technology, Programmable device and method for storing food); WO 2001/031533 A1 (1999-10-22→2001-05-03, Salerno); JP H08414 (1994-06-17); JP H1079088 (1996-09-02); JP H11342061 (1998-06-01); USD570,715 S (2007-03-16→2008-06-10, TSD Integrated Controls, Sonic sensor).

Cabinet hardware / escutcheons / power supplies: US 2011/0114618 A1 ★ (2009-11-15/16→2011-05-19, Prince Castle, Universal food holding cabinet with snap-in escutcheons); US 2011/0114624 A1 ★ (2009-11-16→2011-05-19, Prince Castle, Food holding cabinet power supplies with downloadable software); US 2011/0114625 A1 (Prince Castle, Food holding cabinet with self-aligning and addressable power supplies, per the '002 record); US 9,339,146 B2 (2011-04-14→2016-05-17, Prince Castle, Universal food holding cabinet with buttoned-in escutcheons); US 2010/0288748 A1 ★ (2009-05-15→2010-11-18, Fortmann, Warming cart); US 2009/0199723 A1 (2008-02-12→2009-08-13, Veltrop, Tray handler for food warming apparatus); US 7,971,523 B2 (2007-11-15→2011-07-05, Hartfelder, Removable divider for food warming apparatus); US 2009/0266244 A1 (2008-04-25→2009-10-29, Maciejewski, Post-supported covers for food trays).

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10. References excluded from the prior-art analysis (must not be treated as §102 art)

Note on §102(b)(2): the sibling applications could theoretically be §102(a)(2) art if they named a different inventive entity, but they share inventors Kestner, Lyons, Hartfelder and McCoy and the same 2016-04-19 priority, so the common-inventive-entity and common-ownership exceptions remove them from §102.

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11. Explicit uncertainties and verification steps

1. I did not read the full text of all 141 cited documents. Tier 1 references (US 7,328,654; US 8,522,675; US 6,175,099; US 6,262,394; US 6,541,739; RE 40,151; RE 40,290; US 8,499,683/US 2011/0030565) were reviewed substantially in full. Tier 2 and Tier 3 entries marked (title/abstract only) or (full text not retrieved) are mapped from titles, abstracts and the characterizations given in the reviewing references. Claims 5, 6 and 8 in particular warrant full-text verification of US 7,971,523, US 8,096,231 and US 2011/0114618 before reliance.
2. Claim 6 has no §102 candidate identified on this record. I state that as a finding about my search, not as proof that none exists. The "open center portion… rotatable and/or translatable" latch is the '322's most distinctive structural narrow claim and is the place I would expect a validity challenge to focus least.
3. No examiner §102 rejection was located. If a §102 rejection appears in the file wrapper, my mapping would need to be reconciled with it. I could not obtain the office actions with the tools available.
4. The citation list in the supplied authoritative text is truncated after US 5,616,269; the balance was reconstructed from the family members' "References Cited" lists. If the '322's own IDS differs from the family IDS in the untruncated portion, the residual inventory in §9 would need adjustment.
5. Litigation/PTAB linkage is unchanged from the earlier sections and remains unverified at the complaint level. The single live case is Marmon Foodservice Technologies, Inc. v. Duke Manufacturing Co., No. 4:25-cv-01491 (E.D. Mo.), and I still cannot confirm from a primary source which patent numbers the complaint asserts. Nothing in this prior-art analysis depends on that linkage.
6. Practical significance of the '654/'675 pairing. Duke Manufacturing (US 7,328,654, US 6,175,099, RE 40,290) is the defendant in the live case and is also the assignee of the art that most closely reads on the '322's radiative-above/conductive-below architecture; Prince Castle/Marmon (US 8,522,675) owns the multi-zone-in-one-compartment art that the '322 improves on. That is a validity landscape worth flagging to counsel on both sides, and it is consistent with the §103-type combination I would expect a challenger to run.

I'll ground this obviousness analysis in the actual cited prior art. Let me pull the content of the most relevant cited references.

Let me pull the remaining key references: the Frymaster high-density cabinet, the Shei hot/cold appliance, and the Prince Castle pass-through plural-zone food warmer.

Obviousness Analysis — US 9,980,322 B1 under 35 U.S.C. § 103

Scope note. Per the task instruction, I built this analysis on the prior-art universe appearing in the "Prior Art" section of the patent record (the prior-art keywords — food holding, heating element, food, compartment, zone — plus the "Citations (141)"/"Patent Citations (161)" lists). I then pulled the full text of the most probative ones to confirm what they actually disclose. References confirmed from full text and cited in the '322 record are marked [In record]; one highly probative reference I found that does not appear in the '322 citation list is marked [Not in record] and flagged as such. I have not auto-corrected any number.

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I. The invention to be assessed

Claim 1 is the apparatus; claim 9 is its method twin. The three features that carry the claim's weight are:

1. A continuous, planar, aluminum bottom surface, running completely to the open front face, with no dividing walls between zones ("a … surface … extending completely to the front face of the chassis … comprising Aluminum").
2. Two adjacent zones on that single shared surface, each permitted a different temperature.
3. Four independently controllable elements — a radiant element at the top and a conductive element at the bottom of each zone — with the bottom element heating the tray conductively from below and the top element radiantly from above.

Everything else (chassis, open front opening, tray, pass-through rear opening, lids, latch, resistive wire) is either conventional in the field or expressly admitted as such in the '322 specification itself (detailed in §VIII below).

Level of ordinary skill. A person with a bachelor's degree in mechanical or electrical engineering (or equivalent practical experience) and about 2–5 years designing commercial food-holding/warming equipment, familiar with commercial holding cabinets, IR and resistive heating elements, thermally conductive shelf materials, and microprocessor-based hobby-cabinet controls. This is a mature, crowded art — the '322 record alone lists 141+ prior-art documents, and the same handful of assignees (Prince Castle, Duke, Frymaster/Restaurant Technology, Hatco) recur throughout.

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II. The two closest references, confirmed from their full texts

A. US 8,522,675 B2 — Veltrop, "Holding cabinet for separately heating food trays" (Prince Castle, 2013) [In record]

https://patents.google.com/patent/[US8522675B2](/patent/US8522675B2)

This may be the single most damaging reference, and it is the patentee's own prior patent. Confirmed disclosures:

• Chassis with top panel 20, bottom 25, sides 30/35, "an open front face 40 through which food products and food holding trays can be passed, and an open rear face 42" → chassis with opposing front/rear faces and a front opening.
• "two or more zones in a compartment, wherein holding temperatures can be different from each other" (abstract) → the two-adjacent-zones/different-temperatures limitation verbatim.
• Two vertically separated compartments 45, 50, separated by shelf 70-2, "which is itself constructed to emit IR into the adjacent compartments 45 and 50" → a shelf between compartments that carries the heating elements (claim 2).
• "the tray 44-4 on the left-hand side of the top compartment 45, can be irradiated with infrared energy from heating elements located directly above and/or directly below the tray … at the same time that an adjacent food holding tray 44-3 on the right-hand side of the same, top compartment 45 is kept at a different, second temperature" → heating elements above and below each tray in the same open compartment, with per-zone independent temperature.
• Per-zone displays 65-1…65-4 and "corresponding separately and individually controlled heating elements" → independently controllable elements.

The only material gap between Veltrop '675 and claim 1 is (i) the shelf is glass-ceramic, not aluminum, and (ii) the lower element is an IR emitter passing energy through the glass-ceramic, not a conductive element heating a metal plate.

That gap is exactly what the second reference supplies.

B. Duke Manufacturing (Shei) — US 2004/0020915 A1 / US 7,105,779 B2 / US 7,328,654 B2, "Food warming apparatus (and method)" [US 2004/0020915 and US 7,328,654 are in record]

https://uspto.report/patent/app/20040069155 · https://www.freepatentsonline.com/y2004/0020915.html

Confirmed disclosures:

• Cabinet with "a front panel 19 and a corresponding rear panel … each having openings such as indicated at 21 for sliding each tray 3 either into or out of its respective tier front or rear" → pass-through compartment.
• "Each heat sink 29, which is made of aluminum … has a bottom 31 and side walls 33 … An electrical resistance heating element … having a bottom component 41 contacting the bottom of the heat sink" → conductive bottom heating of an aluminum tray-support plate. This is the missing aluminum/conductive-bottom element.
• "Heat sources 146 positioned above respective compartments 128 … adapted to emit radiant heat into the compartments directed at the trays 103" (quartz IR 146A, ceramic IR 146B, or resistance-in-MgO 146C) → radiant top heating element.
• Tray 103 supported in the compartment; radiant source above the tray, heat sink below it → radiant from above, conductive from below, in each compartment.
• "the control mechanism 140 may independently operate the heat sources 146 in the compartments 128 … such that the temperature in each compartment 128 may be independently controlled"; US 2004/0020915 claim 36: "maintaining at least two compartments at different selected holding temperatures" → independently controllable elements and different temperatures.
• Covers 55 spaced above tray rims, with "pivoted locks for locking the covers 55 in the oven 1 … at 85" → lid/cover stored above the tray (claims 5, 7) and a latch (claim 6).

Duke/Shei thus discloses a two-heat-source (radiant-over / conductive-under) food warmer with an aluminum heat-transfer plate, independent per-compartment control, pass-through access, and tray covers. It is Duke's own art — and Duke is the defendant in the co-pending litigation.

C. Hatco — US 6,031,208, "Topless holding bin with side heat source" [In record]

https://patents.google.com/patent/[US6031208A](/patent/US6031208A)/en

Confirmed disclosures that matter:

• Background concedes the conventional arrangement: "These holding bins typically include one or more shelves … with each shelf having top and bottom heat sources … The bottom heat source typically warms the food from underneath using conducted heat. The top heat source warms the food from overhead using heat lamps or infrared heat sources." This is an express admission that radiant-above/conductive-below in one bin was known.
• Base heat source 42 is strips of resistive wire with "adhesive-backed aluminum foil backing … adhered to the inner, interior surfaces," thermally coupled to a horizontal aluminum holding surface, with a hard-coat anodized aluminum layer for uniform heat distribution → claim 8 (resistive heating wire) and the aluminum-plate/conduction teaching.
• The base heat source has two separate wire loops 48 and 50 "supplied with electrical power through respective heads 52 and 54," producing different watt densities in different regions of a single continuous holding surface → plural, independently powered heating elements on one continuous plate supplying different amounts of heat to different regions (this is directly on point for claim 2's "second and fourth heating elements … capable of providing different amounts of heat energy into the first and second food holding zones").
• Side heat sources 44/46 are resistive-wire or infrared elements (claims 12–14).

Caveat: Hatco argues against overhead heat for aesthetic/bulk reasons, so it "teaches away" from the overhead structure — but only as to form factor, not as to the physics; and it expressly describes top+bottom as the known baseline. This limitation is discussed in §IX.

D. Supplementary / corroborating references

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III. Element-by-element mapping of claim 1

Result: every element of claim 1 is disclosed across Veltrop '675 + Duke Shei ('779/'015/'654). The sole differences are the substitution of (a) an aluminum conductive plate for a glass-ceramic IR-transmissive plate and (b) conductive bottom heating for IR bottom heating — a single, coherent design change that the Duke and Hatco references teach directly and that the '322 specification itself treats as an interchangeable option.

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IV. The primary obviousness combinations

Combination A (strongest): Veltrop '675 + Duke Shei '779/'015 in view of Hatco '208

Take Veltrop '675 as the base (multi-zone, one open compartment, independently controlled heaters above and below each tray, open front and rear faces, shelf between compartments carrying the heaters). Modify the shelf and the lower heating element per Duke Shei ('779/'015): a thermally conductive aluminum plate with an electrical resistance element contacting its underside, i.e., conduction rather than IR, with the radiant quartz/ceramic source retained above the tray. Add Hatco '208 for the explicit teaching that (i) a base heating element is thermally coupled to a horizontal aluminum holding surface to warm food "from underneath using conducted heat" and (ii) a single continuous plate can carry multiple separately powered loops (48, 50) producing different watt densities in different regions.

Combination B: Duke Shei '779/'015 as base + Veltrop '675

Take Duke Shei as base (aluminum heat sink + contacting resistance element = conductive bottom; radiant source above the tray; independent per-compartment control; front/rear openings; covers and pivoted locks). Modify per Veltrop '675: convert the partitioned multi-compartment arrangement into two independently controlled zones on one continuous, partition-free shelf in a single open compartment, each zone having its own separately controlled upper and lower element, so that adjacent foods can be held at different temperatures.

Combination C: Frymaster US 2011/0253698 / US 8,558,142 + Veltrop '675 + Hatco '208

Frymaster supplies the top/bottom heater-plate sandwich and the bezel-fronted open cavity; Veltrop supplies zoning on one continuous shelf with independently controlled above/below heaters; Hatco supplies the aluminum/conductive bottom plate and plural separately powered loops on one plate.

The combinations are predictable. Each reference is in the same field (commercial food holding/warming), addresses the same problem (keeping pre-cooked food palatable while holding), and the combination yields nothing more than the expected result of the individual teachings — a warmer bin with zones at independently set temperatures. KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007).

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V. Dependent claim 2

Claim 2 adds: (a) a second compartment below the first; (b) a shelf between them with a first side facing the upper compartment and a second side facing the lower; (c) the second and fourth (bottom) heating elements disposed in the shelf and in thermal communication with the first side, capable of providing different amounts of heat energy into the two zones; and (d) a controller to operate the second and fourth elements independently.

• Veltrop '675 discloses a shelf (70-2) between upper compartment 45 and lower compartment 50 that itself carries heating elements radiating into the adjacent compartments — i.e., a shelf between compartments, with elements in the shelf facing the compartment above.
• Duke Shei '779 places the upper tier's heat sink/heating element on shelf 17 with the lower tier on bottom 11, and its control mechanism 140 (microprocessor, keypad 142, display 144, relays 198) "may independently operate the heat sources 146 in the compartments 128."
• Hatco '208's base plate with separately powered loops 48/50 supplying different watt densities to different regions of one continuous surface is a direct teaching of "different amounts of heat energy into … first and second food holding zones."
• The '322's own shelf construction — two thermally conductive plates (53, 54) sandwiching heating elements 65/67 with insulation between — is the ordinary "heated plate sandwich" (compare Frymaster US 8,558,142: "vulcanized heater 60 disposed on a surface of a heater plate 40").

Claim 2 is therefore obvious over Veltrop '675 + Duke Shei + Hatco '208.

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VI. Claims 3–8 and 10

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VII. Claim 9 (method) and claim 10

Claim 9 differs from claim 1 only in form. Its limitations are: (i) providing a compartment with two adjacent zones sharing an uninterrupted continuous planar aluminum bottom extending to the front face, with a tray resting on it; (ii) each zone having an independently controllable radiant element heating from above and an independently controllable conductive element heating from below; (iii) independently setting a first temperature by operating the first and second elements; (iv) independently setting a second (different) temperature by operating the third and fourth elements.

Every step maps to Veltrop '675 (independent setting of different temperatures for adjacent trays in one open compartment using separately and individually controlled heaters above and below) plus Duke Shei '779/'015 (aluminum conductive bottom plate; radiant top; control mechanism 140 independently operating heat sources; US 2004/0020915 claim 36 "maintaining at least two compartments at different selected holding temperatures"). Claim 10 (more heat from the first element than the second) fails for the reasons given for claim 4.

The method claim adds no step that is not the inevitable result of operating the apparatus of Combination A or B. In re Kuehl; a method claim whose steps are the intended use of a known apparatus, or the natural result of the combined elements, is obvious for the same reasons as the apparatus.

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VIII. The applicant's own admissions (which materially weaken the "non-obviousness" position)

The '322 specification repeatedly characterizes the claimed building blocks as known:

1. Top and bottom heating per zone: "heating elements that are not shown include at least a heating element that provides heat to the upper first food holding zone 51a from above and another heating element that provides heat to the lower first food holding zone 51a from below." The applicant treats radiant-above/conductive-below as a baseline to be supplemented, not invented.
2. Controller/sensors: "Cabinet control … is effectuated in part by using one or more microcontrollers or microprocessors 97 in combination with temperature sensors 99," citing US 2011-0114624 A1 and US 8,247,745 as the source of those techniques — i.e., the claimed controller is admittedly conventional.
3. Materials treated as interchangeable: the specification says the shelf surfaces "are preferably made of aluminum, between about one-eighth and about one-quarter inch-thick. Alternate embodiments of the shelf 52 may use a thermally-conductive panel made of glass-ceramic or an ultra-low expansion glass." A reference that treats aluminum and glass-ceramic shelves as alternatives in the same structure cannot plausibly argue that substituting one for the other is inventive — this is a direct admission for the Veltrop '675 combination.
4. Peltier/thermoelectric heating is described with reference to cited art (US 2010-0307168 A1; MX364581B, Bi Polar Holding Co.) — not claimed, but further evidence the field is crowded.

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IX. Countervailing considerations and defenses the patentee would raise

To be fair and complete, the obviousness case is not a slam dunk. The principal defenses:

1. Hatco '208 teaches away from overhead heat. Hatco's stated object is "a holding bin … that does not require an overhead source of heat," criticizing overhead structures as bulky and off-putting. A patentee will argue that combining Hatco with a radiant-overhead reference is impermissible. Response: Hatco simultaneously describes top+bottom heat as the conventional arrangement, and the obviousness combination is not required to use Hatco for overhead heating — Duke Shei '779/'015 supplies radiant overhead heat and does not teach it away. Hatco is offered only for the aluminum/conductive-plate and plural-loop teachings, which it affirmatively claims.
2. The specific "continuous planar aluminum surface extending completely to the front face" as a structural package. Veltrop '675's shelf is glass-ceramic; the "aluminum" limitation is the clearest point of novelty over the closest reference. A patentee will argue that glass-ceramic was chosen for a reason (IR transmission) and that replacing it with aluminum changes the heating principle. Response: the change of heating principle is precisely what Duke Shei and Hatco teach as desirable (conducted heat is more uniform, less "spotty," and more compact), and the '322's own text treats the two materials as alternatives.
3. Secondary considerations (Graham factors). The '322 asserts a doubling of palatability time ("can extend the palatability time of a food item by a factor of two or more") and easier cleaning of the undivided surface. These are classic nexus arguments. Response: the asserted advantages are the natural, expected consequences of the combined teachings (a partition-free conductive surface is easier to clean; more precise per-zone temperature control extends hold time), and the "factor of two" claim is an unsupported attorney assertion in the specification with no data. Notably, the '322 record shows live litigation — Marmon Foodservice Technologies, Inc. v. Duke Manufacturing Co., No. 4:25-cv-01491 (E.D. Mo., filed 2025) — and a pending PTAB petition, IPR2026-00406 (Duke Manufacturing Co. v. Marmon Foodservice Technologies, Inc., filed July 2026), which per my earlier section challenges US 10,852,002, not this patent. The existence of actual copying or commercial success would need to be proven with evidence, not argument.
4. Density of the record and prior allowance. The examiner considered 141+ references (including Veltrop '675, Duke's '015 and '654, Hatco '208, Robards '803, and Frymaster's '698) and still allowed. Consideration alone is not a legal bar, but it means any §103 challenge must show the specific combination and articulated motivation, not merely that the references are in the same field.
5. Claim 6 (the open-center latch) is the element least supported by the present record and the most likely to survive; a challenger would need a dedicated latch reference.

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X. Bottom line

Strongest single combination: US 8,522,675 (Veltrop / Prince Castle) as primary, in view of US 2004/0020915 A1 / US 7,105,779 / US 7,328,654 (Duke / Shei), and further in view of US 6,031,208 (Hatco / Witt et al.). Motivation to combine: (a) both Veltrop and Duke expressly target holding different foods at different temperatures and hold the same field and problem; (b) Duke and Hatco teach that a conductive aluminum plate warms food more uniformly and in less vertical space than IR, and that a single continuous plate can carry plural, separately powered, differently driven elements; (c) eliminating partitions between zones is a recognized cleanability/oil-migration objective in the commercial holding-cabinet art (see Frymaster's own UHC literature and its WO 2011/129962 discussion of grease migration and slot cleaning).

Explicit uncertainty: Because I worked from the '322 record's citation lists plus verified full texts (rather than from Duke's actual IPR petition, which per my earlier section attacks US 10,852,002 rather than this patent), the precise reference set and claim charts that a real petitioner would use may differ. I found no petition attacking US 9,980,322 itself. Claim 6 is the limitation I would least expect a challenger to knock out on the references I reviewed.