US 11371762

I'll verify key bibliographic details and check for any litigation/docket activity before summarizing.

Let me run a couple more targeted checks on litigation/docket activity and the continuation patent.

US 11,371,762 B2 — Verification Summary

Sources consulted: Google Patents (https://patents.google.com/patent/US11371762/en), Justia Patents (https://patents.justia.com/patent/[11371762](/patent/11371762)), Patents-Review, Patents Encyclopedia; plus targeted web searches for USPTO/PTAB and CAFC 2026 docket activity.

Search caveat: I performed open web searches, not a direct USPTO PatentCenter/PTAB API query or PACER pull. I found no IPR/PGR, district-court, or Federal Circuit docket entry naming U.S. Patent No. 11,371,762. Two Lennox-related 2026 matters surfaced (Rosen Technologies v. Lennox, N.D. Tex. 3:22-cv-00732; and In re HVAC Equipment Antitrust Litigation, E.D. Mich. 2:26-cv-10949 / 2:26-cv-11294), but neither asserts or invalidates this patent. Treat "no litigation found" as a negative search result, not affirmative proof.

(Note: your prompt states the current date as April 26, 2026, while my session metadata says September 29, 2026. I flag it rather than silently pick one; it does not change any bibliographic fact below.)

Bibliographic data

Abstract (as issued)

A defrost method for a heat pump system includes running the system in a heating mode to provide heat to an enclosed space and determining if outdoor temperature is below an outdoor threshold. If so, the controller determines whether a calibration state has previously run; if not, it runs the calibration state. If it has run, the controller determines whether a temperature difference between the evaporator-coil temperature and outdoor temperature exceeds a temperature threshold value, and if so, runs a defrost state.

Plain-language overview of the independent claims

Claim 1 — Method (temperature-based, self-learning failsafe). The controller (CPU + memory) executes a sequence:

1. Run in a heating state a first time; check whether a calibration state has already been run.
2. If calibration has never run, run the calibration state.
3. Run the heating state a second time; check whether ΔT = (clear-coil temperature of the evaporator coil) − (current evaporator-coil temperature) exceeds a temperature threshold value.
4. If ΔT ≤ threshold → run an initializing defrost state.
5. If ΔT > threshold → run a defrost state, in which the system runs in defrost mode to pull heat from the enclosed space to the outdoor evaporator coil to melt frost, while the controller times the defrost; then compute the ratio of that measured defrost time to an initial defrost time (established during calibration); if the ratio exceeds a first threshold value, decrease the defrost failsafe time so defrost runs more frequently.

In substance: frost is inferred from how much the coil temperature has been depressed relative to a known clear-coil baseline, and the maximum allowed heating interval between defrosts is adaptively trimmed when defrosts are running long.

Claim 10 — Method (outdoor-temperature- vs. coil-temperature comparison). Runs the system in heating mode; checks whether outdoor temperature is below an outdoor threshold; if so, checks whether a calibration state has previously run; if not, runs calibration; if it has, checks whether the temperature difference between evaporator-coil temperature and outdoor temperature exceeds a temperature threshold value; if it does, runs the defrost state. This is the claim family that tracks the abstract's "coil temperature vs. outdoor temperature" formulation.

Claim 18 — System. A heat pump system comprising an evaporator coil, a condenser coil coupled to permit refrigerant cycling, a compressor between them, a reversing valve to reverse refrigerant flow, and a controller (CPU + memory) programmed to carry out the same decision logic recited in claim 10.

Notable observations / uncertainties

• Two different ΔT formulations coexist in the disclosure. The Summary and claim 10 compare evaporator-coil temperature to outdoor temperature, while the detailed description at step 216 and claim 1 compare clear-coil temperature to current coil temperature (ΔT = T_clear_coil − T_current_coil). Whether these are meant as the same quantity or two distinct embodiments is not clearly reconciled in the text. Anyone construing these claims should treat that as a genuine ambiguity rather than assume equivalence.
• Claim 5 oddity. Claim 5 recites "setting a value of a defrost flag to true" in the calibration state, but the specification's calibration sequence (step 226) sets the initializing defrost flag to false (0), with the flag set to true (1) in the initializing defrost state (step 230). The claim-5 wording may refer to a different flag or may be a drafting inconsistency; I cannot resolve it from the text alone.
• Claim 7 vs. claim 6. Claim 6 shortens the failsafe time when the defrost exceeds a maximum defrost time; claim 7 lengthens the failsafe time when the defrost time is recorded as less than the maximum time — which, read literally, overlaps with the "no-change" band logic of claims 8/9. This is a potential internal tension in the dependent-claim set.
• Numbers cited in the spec (non-limiting, illustrative only): outdoor threshold 45 °F (range 32–50 °F); defrost threshold time 30 min; temperature threshold 0.1–20 °F; calibration failsafe set to 120 min; first threshold 1.2, second threshold 0.8; ±15 min adjustments; failsafe floor 60 min, ceiling 360 min; maximum defrost time 14 min; defrost termination 50–100 °F.
• Lennox marketing/documentation corroboration: Lennox service literature describes a commercial "demand defrost control" using frost-accumulation time, 14-minute max defrost, and adaptive +30/−30 minute adjustments (e.g., https://www.lennox.com/dA/6439f628e4/[100108](/patent/100108).pdf and https://www.lennox.com/dA/97f1d83256/508686L01.pdf). This is product documentation, not the patent, but it is consistent with the claimed subject matter and supports that the invention was commercialized.
• Third-party valuation figure from patentleaderboard.com (~$23.9M "approx value") is a third-party algorithmic estimate, not an official or verified figure — do not rely on it.

What I could not confirm

• Any CAFC 2026 docket, appeal, IPR/PGR, or district-court case specifically involving US 11,371,762 — nothing found. If an authoritative docket check is required, I'd recommend a direct PACER/Docket Alarm and USPTO PTAB Patent Trial and Appeal Board End-to-End query tied to application 16/881,156 and patent 11,371,762, since my search was web-index-based.

I'll search for litigation involving US patent 11371762 across the sources you mentioned.

Let me search more targeted litigation sources.

Let me run a few more targeted checks on litigation-specific databases.

Findings: Litigation Involving U.S. Patent No. 11,371,762

Bottom line: I found no evidence — in the sources I was able to search — of any litigation (district court, ITC, or PTAB) in which U.S. Patent No. 11,371,762 ("Demand defrost with frost accumulation failsafe," Lennox Industries Inc., issued June 28, 2022) was asserted, challenged, or otherwise placed at issue. To my knowledge, no such litigation is known.

What I searched and what I found

I searched for the specific number 11371762 / 11,371,762 and for Lennox Industries patent litigation generally. Summary of the results:

1. No case names, case numbers, plaintiffs, defendants, or dockets referencing '762. None of the returned hits tied any complaint, IPR, or appeal to this patent number.

2. Apparent false positives / different patents to avoid confusion:

   • Several PTAB filings reference a "'062 patent" (e.g., IPR2021-00342, IPR2022-00029, involving references "Studor," "Clem," and "Hickman"). That is a different patent — the subject matter is plumbing/valve technology, not heat-pump defrost — and the '062 designation there is not U.S. 11,371,762. I did not treat it as matching.
   • A Lennox Industries Inc. v. Rosen Technologies LLC family of IPRs (IPR2023-00715 through -00719) concerns patents such as U.S. 7,232,075 and arose from Rosen Technologies LLC v. Lennox Industries Inc., No. 3:22-cv-00732-K (N.D. Tex.). These involve different patents, not '762.
   • Other Lennox-related matters returned (e.g., Magnacross LLC v. Lennox Industries Inc., No. 1:19-cv-00793 (D. Del.); Portus Singapore Pte Ltd v. Lennox International Inc., No. 3:26-cv-01328 (N.D. Tex.); In re HVAC Equipment Antitrust Litigation, No. 2:26-cv-10949 (E.D. Mich.)) all concern other patents/causes of action, not '762.

3. A commercial aggregator (PatentLeaderboard) lists '762 among Lennox patents but shows no litigation association.

Important caveats (please verify before relying on this)

• My searches were incomplete. I exhausted my available search steps before fully querying the litigation-specific portals you named (Unified Patents litigation caselist, PACER, RPX Empower, and Docket Navigator). I was not able to systematically confirm on those platforms directly.
• Because a patent issued in June 2022 can be asserted without any indexed public news coverage — especially in the N.D. Tex. / E.D. Tex. venues where Lennox-related HVAC cases are commonly filed — a negative result here is not a guarantee that no suit exists. It means I found none.

Recommended next steps for a definitive answer

To confirm with confidence, I suggest checking directly:

• RPX Empower / Insight and Docket Navigator for "11,371,762" as an asserted patent.
• Unified Patents litigation portal (patent-specific page for 11371762) and PTAB (for any IPR/PGR naming this patent).
• PACER / CourtListener full-text search for "11,371,762" (rather than the bare number, which collides with unrelated docket strings).

If you'd like, I can draft the exact query strings to run against those databases, or attempt additional searches if you can reset/allow more steps.

Stated explicitly per your instruction: I do not know of any litigation involving U.S. Patent No. 11,371,762, and I am not able to confirm one from the sources available to me. I am reporting a negative result, not a verified absence.

I'll start by checking the canonical structured data against live sources, since the ODP block reports no AIA trials.

Let me run targeted searches on PTAB docket sources to confirm the null result.

Let me check for any litigation or PTAB challenge tied to the '762 patent specifically, including aggregators.

Proceedings overview

Total AIA trial proceedings on file: 0. The USPTO Open Data Portal returns no IPR, PGR, or CBM proceeding naming U.S. Patent 11,371,762 as the challenged patent, and my independent web searches (PTAB petition repositories, IPR docket aggregators, and press/litigation coverage) surfaced no petition, institution decision, or final written decision against it. The breakdown is therefore: 0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denied.

Bottom line for a defendant: this patent has never been tested at the PTAB. All 18 claims — independent claims 1, 10, and 18, and every dependent claim — stand unadjudicated and carry the full statutory presumption of validity under § 282. There is no FWD to point to, no canceled claim to quote, and no § 315(e)(2) estoppel to lean on. That cuts both ways: you get a clean slate on grounds (no petitioner has burned any art or theories), but you also have zero administrative precedent telling you how the Board reads the "clear coil temperature" / "defrost failsafe time" limitations. This is an untested patent, not a hardened or a dead one.

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Proceedings

Nothing to enumerate. The "most-impactful first" ordering is inapplicable because the structured PTAB block returned an empty set and live searching confirmed the null.

No proceeding on file — confirmation and scope of my search

• Type: N/A
• Filed: N/A
• Status: No AIA trial activity on file (USPTO ODP; verified against public dockets)
• Judge panel: N/A
• Petition grounds: N/A
• Institution decision: N/A
• Final Written Decision: N/A
• Settlement / termination: N/A
• Appeal: N/A
• Defensive value: None yet extracted. You would be the first petitioner, which is advantageous on the merits (no General Plastic / Fintiv roadmap problem from a prior Board record) but means you carry all institution- and trial-stage cost with no template to follow.

What I checked and what I did not find:

• USPTO Patent Trial and Appeal Board proceeding lists and petition repositories — no entries mapping to Patent No. 11,371,762 or application 16/881,156.
• Aggregated PTAB docket trackers — no case record.
• Web/press searching on the patent number, the title "Demand defrost with frost accumulation failsafe," the inventors (Eric Berg, Pete Hrejsa), and assignee Lennox Industries Inc. — the only hits are the patent document itself and family/publication mirrors (Google Patents, Justia).

Important caveat on what my null result does not prove: district court complaints are not indexed as reliably as PTAB filings. I did not find any district court action asserting the '762 patent, but I cannot rule one out with high confidence — particularly a recently filed complaint that the aggregators have not yet picked up, or a § 315(b)-triggering service of process that would start your one-year clock. Verify the litigation posture directly before relying on this report.

One genuinely adjacent data point worth flagging (not against this patent): Lennox is an aggressive petitioner at the PTAB, not merely a target. In March 2023 it filed a coordinated set of IPRs (IPR2023-00715 through IPR2023-00719) against Rosen Technologies LLC patents ('555, '825, '318, '739, '075) in the N.D. Tex. litigation Rosen Technologies LLC v. Lennox Industries, Inc., No. 3:22-cv-00732-K, using Baker Botts as counsel. At least one, IPR2023-00719, was instituted on 2023-11-14 and later Terminated-Settled on 2024-03-20. See IPR2023-00719 case record. This is a sophistication signal about the patent owner, not about '762. Lennox knows how the Board works from both chairs, retains top-tier IPR counsel, and will defend a heat-pump defrost patent vigorously. Do not expect an early settlement discount from a party that routinely litigates these.

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Strategic summary

Claim status — CANCELED: none. SUSTAINED: none. UNTESTED: all of claims 1–18. There is no narrowing whatsoever. Claims 1–9 are the method claims keyed to the clear-coil/current-coil temperature delta (ΔT = T_clear_coil − T_current_coil) and the defrost-time ratio logic; claims 10–17 are the method claims keyed to the evaporator-coil-to-outdoor-temperature delta plus the defrost failsafe; claim 18 is the system claim reciting evaporator coil, condenser coil, compressor, reversing valve, and a controller configured to run the abbreviated version of the outdoor-temperature/calibration/ΔT logic. Every one of these is live.

Your infringement exposure is also doubled: U.S. Patent 11,629,900 (application 17/750,736, filed 2022-05-23, granted 2023-04-18) is a continuation of the '762 application with the same priority date (2020-05-22), same title, same inventors, and same assignee. It, too, shows no PTAB activity. Any validity or invalidity work you fund on '762 should be scoped to cover '900 simultaneously — a finding on the shared specification and the shared "defrost failsafe" concept will likely travel, but the claims are separate and must be charted separately.

Estoppel landscape — empty. Because no IPR was ever instituted against this patent, § 315(e)(2) estoppel does not attach to anyone. No petitioner and no privy is barred from raising any prior-art ground, § 102 or § 103, in district court. Practically, that means every ground is on the table for you:

• The 14 examiner-cited references on the face of the patent are the natural starting kit, and several are directly on point for defrost control: US 4,750,332 (Eaton — "self-adjusting defrost interval" — squarely relevant to the adaptive defrost-failsafe-time logic), US 5,319,943 (Copeland — "Frost/defrost control system for heat pump"), US 5,156,010 (Sanyo — "Defrost control method for a heat pump"), US 5,797,273 (Carrier — "Control of defrost in heat pump"), US 5,257,506 (Carrier — "Defrost control"), and US 5,415,005 / US 5,515,692 (Long Island Lighting). Critically, Lennox's own earlier patents are cited art here: US 10,746,446 ("Intelligent defrost control method") and US 11,384,971 (same title). Johnson Controls' US 10,571,174 ("Systems and methods for defrost control") is also cited. All of these were considered by the examiner, so a § 325(d) / Advanced Bionics argument will be raised against you — you will need new art, new combinations, or a compelling showing that the examiner never substantively engaged with the references.
• The most promising non-cumulative attack surface is likely the fail-safe/time-ratio feedback concept: raising and lowering a defrost interval based on how long the previous defrost took relative to an initial/calfibrated defrost time. That is a classic adaptive-control loop that has broad prior art in refrigeration and commercial HVAC controls beyond the cited HVAC patents (e.g., supermarket refrigeration defrost controllers and adaptive-demand defrost literature). Because the examiner's search appears confined to heat-pump defrost art, a § 103 combination drawing on adjacent refrigeration-control art is where I would invest the search budget first.

Pattern signals. No serial petitioning against this patent — there is only one family member at issue in the PTAB record: none. No defensive aggregator (Unified Patents or similar) has stepped in; notably, Unified was active against Rosen's thermostat patents (IPR2022-01402), so it is a player in this general technology neighborhood but has not touched Lennox's defrost portfolio. If you are one of several defendants facing this patent, the absence of any prior challenge means there is no joint-defense-group roadmap and no shared cost yet — you would be financing the first look at the art. Conversely, there is also no risk that a prior petitioner already exhausted or stipulated away your best grounds.

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Recommended next steps

1. Confirm there is no co-pending district court action and calendar § 315(b) immediately. No FWD means no claim is dead, so the fastest defensive win is procedural: if you have served been with a complaint alleging infringement of the '762 patent, your one-year bar date under 35 U.S.C. § 315(b) runs from service, and there is no earlier-filed IPR to join (no § 315(c) joinder option exists). Miss it and the IPR route closes permanently.
2. Pull the full prosecution history (application 16/881,156) before committing to a ground. The examiner cited 14 references including Lennox's own US 10,746,446 and US 11,384,971, and the applicant amended at least once (non-final action mailed 2022-01-19, response 2022-03-06, allowance 2022-03-24). The arguments that secured allowance will tell you exactly which limitation the applicant treated as the point of novelty — that is the limitation your art must meet.
3. Scope your invalidity search to cover both '762 and '900. Treat them as a single project; the continuations share a specification dated 2020-05-22.
4. Anticipate a § 325(d) / Advanced Bionics fight. Because the primary defrost references are of record, build the petition around art and combinations the examiner neither applied nor substantively discussed, and document that showing explicitly in the petition rather than in reply.
5. Nothing to cite for a validity challenge in court — yet. There is no FWD to quote and no judgment of invalidity to hand the district court. If you intend to seek a stay pending IPR, note that you will also have to overcome the Fintiv-style discretionary-denial analysis with no institution decision to point to, and that the current Director's discretionary-denial practice has been shifting toward stricter treatment of parallel litigation and serial challenges. Practical milestones to plan around once (and if) a petition is filed: institution decision at ~6 months from filing, and a statutory final written decision within 12 months of institution absent good cause.

Sources: US 11,371,762 (Google Patents); PTAB proceeding search (USPTO); CourtListener; IPR2023-00719 docket record.

Confidence levels: high that no PTAB proceeding exists on '762; moderate-to-low that no district court action asserting it exists, since litigation coverage is less systematic — verify independently.

I'll verify the assignment record and cross-reference litigation/ownership sources before writing.

Ownership & NPE Analysis — US 11,371,762 B2

"Demand defrost with frost accumulation failsafe" · App. 16/881,156 · Filed 2020-05-22 · Issued 2022-06-28 · Family ID 78608774

Verification caveat up front. The authoritative record set available for this analysis is the Google Patents legal-events table for US 11,371,762, which mirrors USPTO Assignment Center data. That table exposes exactly one post-filing assignment event. I was not able to retrieve the correspondent-of-record field (the attorney/agent who filed the recording) for reel 052732/0626 — that field is not exposed in the source I was given, and targeted searches returned nothing. Statements below about the correspondent field are flagged as not verified, not as negative findings. Anyone relying on this for prosecution or licensing diligence should pull the reel/frame image directly from Patent Assignment Search.

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Inventors

Pattern notes:

• Both inventors are career Lennox HVAC-controls inventors, not outside founders who licensed in. Berg's 86-patent Lennox portfolio and Hrejsa's 12-patent portfolio are both dominated by continuing Lennox assignments, which cuts against the classic "inventors bail out within 12 months of filing, portfolio later fire-sold" signature.
• No departure signal present. I found no evidence either inventor left Lennox in the 12 months following the 2020-05-22 filing. Because I have not verified current employment, I mark this not present on the evidence available rather than affirmatively cleared.
• Both inventors assigned their rights pre-filing (signing dates 2020-05-13 and 2020-05-14), which is the standard employee-invention practice at an operating HVAC manufacturer and is inconsistent with an inventor-held or broker-acquired asset.

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Original assignee

Lennox Industries Inc., 2100 Lake Park Boulevard, Richardson, TX 75080 — a wholly owned subsidiary of Lennox International Inc. (NYSE: LII), a publicly traded HVAC manufacturer.

• Shipped a product embodying the claims? Yes — highly likely, and this is the ordinary case. The claims are directed to a demand-defrost control algorithm for a heat pump (evaporator-coil temperature differential vs. outdoor temperature, calibrating defrost time, adaptive defrost failsafe time). Lennox is a top-tier North American residential/commercial heat pump and HVAC equipment manufacturer and the asserted subject matter is a controller algorithm for its own heat pump line, not a component it buys in. The patent is a control-logic patent that maps directly onto Lennox heat pump control boards.
• Primary line of business: design and manufacture of residential and commercial HVAC equipment (furnaces, air conditioners, heat pumps, rooftop units, controls) — an operating industrial manufacturer, not a licensing vehicle.
• Current status: operating. Public parent LII remains listed and active; SEC insider/beneficial-ownership filings for LII through 2026 are on file. No bankruptcy, no Chapter 7/11, no receivership.
• Litigation posture: Lennox is a repeat patent-defendant, not a plaintiff asserting this portfolio. Documented examples: Magnacross LLC v. Lennox Industries Inc., No. 1:19-cv-00793 (D. Del.) (dismissed); Rosen Technologies LLC v. Lennox Industries (International) Inc., No. 3:22-cv-00732-K (N.D. Tex.) (thermostat patents; Lennox filed five IPRs, IPR2023-00715 through -00719, all terminated/settled); Portus Singapore Pte Ltd v. Lennox International Inc., No. 3:26-cv-01328 (N.D. Tex., filed 2026-04-24). Lennox also appears as a defendant in the consolidated HVAC price-fixing antitrust MDL. None of these assert US 11,371,762, and none name Lennox as plaintiff asserting this patent.

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Assignment timeline

Records found in the mirror of USPTO Assignment Center: one. There is no recorded security agreement, merger, change of name, license, release, or corrective assignment on this patent, and no post-issuance transfer of any kind. Legal status shows Active, adjusted expiration 2040-11-21 (the adjustment reflects patent-term adjustment / the coexistence with the continuation, not a transfer).

• 2020-05-13 / 2020-05-14 (executed — two signing dates, one instrument) / recorded 2020-05-22 — Reel 052732/0626
  • Conveyance: Assignment
  • Assignor: Eric Berg (signed 2020-05-13); Pete Hrejsa (signed 2020-05-14)
  • Assignee: Lennox Industries Inc., Richardson, Texas
  • Correspondent: not verified — the correspondent/attorney-of-record field for reel 052732/0626 was not exposed in the source I was given, and I could not recover it. I am therefore unable to run the recurrent-correspondent check. Recording text as captured: "ASSIGNMENT OF ASSIGNORS INTEREST; ASSIGNORS: BERG, ERIC; HREJSA, PETE; SIGNING DATES FROM 20200513 TO 20200514; REEL/FRAME: 052732/0626."
  • Context: Ordinary employee-inventor assignment to the operating employer, executed eight days before the 2020-05-22 filing date and recorded the same day the application was filed. This is the standard "assign-on-filing" practice, not an acquisition, securitization, or transfer-to-asserter.

Related application — no additional assignment:

• US 17/750,736 (continuation, filed 2022-05-23, priority 2020-05-22) → issued as US 11,629,900 B2 on 2023-04-18. This is a child application in the same family, not a second assignment. No separate recorded transfer of rights appears for it; it derives title from the same Lennox employment/assignment chain. Inventors listed on US 11,629,900 are again Berg and Hrejsa.

Because a record exists, I am not stopping after this section — but the section is exhaustive: everything post-2020-05-22 in the legal-events table is prosecution and annuity activity, not ownership activity.

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Timeline diagram

timeline
    title Ownership of US 11371762
    2020 : Berg and Hrejsa assign rights to Lennox
         : Reel 052732/0626 recorded 22 May 2020
         : Application 16 881 156 filed 22 May 2020
    2021 : Pre-grant pub US20210364207A1
    2022 : Continuation 17 750 736 filed
         : Patent issues 28 Jun 2022
    2023 : Continuation issues as US11629900B2
    2025 : 4th year maintenance fee paid

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NPE / troll-pattern signals

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Verdict

Insufficient data — specifically: no post-issuance assignment record exists; the original-assignment-only case. This is not an "unknown owner" finding. Title is cleanly and continuously held by Lennox Industries Inc. from pre-filing assignment (reel 052732/0626, executed 2020-05-13/14, recorded 2020-05-22) through today, with no security interest, merger, name change, or transfer of any kind on the record.

On the NPE question the answer is affirmatively negative: zero of the eight troll-pattern signals are present on the evidence available, and the single unresolved item (signal 3, correspondent recurrence) is unresolved only because the correspondent field was not recoverable — not because anything suspicious was found. This reads as a routine captive-portfolio patent held by an operating manufacturer that is itself a frequent NPE target (Magnacross, Rosen Technologies with five Lennox-filed IPRs, Portus Singapore), and that has never asserted US 11,371,762 against anyone.

Verification links:

• USPTO Patent Assignment Search (search by patent number 11371762): https://assignment.uspto.gov/patent/index.html
• USPTO Assignment Center: https://assignmentcenter.uspto.gov/
• Google Patents legal events for this patent: https://patents.google.com/patent/[US11371762B2](/patent/US11371762B2)/en

Recommended next step for full diligence: pull the reel 052732/0626 image in Assignment Center to capture the correspondent-of-record name/firm, then diff that name against the correspondent on Lennox's other 2020-era recordings and against the NPE-assertion correspondent lists. If that correspondent is a high-recurrence name on assertion-side filings, revisit signal 3 — but the name alone would still not disturb the ownership verdict, which is grounded in the assignee identity on reel 052732/0626.

I'll research the prior-art references cited on the face of US 11,371,762 to assess their relevance to the claims. Let me run targeted searches on the most substantive references.

Let me gather details on the remaining cited references.

Prior-Art Analysis — U.S. Patent No. 11,371,762 B2

Scope note. I ran the requested USPTO-sourced review (via Google Patents' USPTO-mirrored record at https://patents.google.com/patent/US11371762/en, which is the authoritative text supplied in this project). I verified the 14 examiner citations ("Citations (14)") and the expanded "Patent Citations (30)" list, plus the single "Family Cites Families" reference. Disclosure of limitation: I hit my search-step ceiling before I could individually pull full text for every one of the ~20 documents. For the subset I retrieved in full — US 4,750,332; US 5,319,943; US 10,746,446 / US 2017/0176072; US 2018/0031289 / US 10,571,174; and US 5,156,010 — my descriptions below are grounded in retrieved text. For the remaining references, descriptions are drawn from the citation-face data (title/assignee/date) and are flagged as lower confidence. I did not fabricate specification content I did not retrieve.

Also flagging one discrepancy explicitly, per the cross-reference rule: the prior "Patent summary" section states the session/prompt date conflict (April 26, 2026 vs. September 29, 2026). That conflict persists here and does not affect any citation date below.

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A. Positioning the analysis

This is a combination claim set. Independent claim 1 ties together (i) a calibration/no-calibration branch, (ii) a clear-coil−vs−current-coil ΔT test, (iii) an "initializing defrost state" branch, and (iv) a defrost-duration-ratio adjustment of a defrost failsafe time. Claim 10 uses the looser coil−vs−outdoor-temperature ΔT formulation, and claim 18 recites the same logic in apparatus form.

Because the examiner cited these references and then allowed the application (Notice of Allowance mailed 2022-03-24; issue 2022-06-28), no single cited reference was found to anticipate the claims as issued. So the honest reading of the table below is: these are the references that (a) most threaten individual claims or limitations under § 102, and (b) supply the § 103 combination baseline. I identify the two genuine single-reference anticipation candidates below.

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B. The 14 examiner citations (core set)

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C. Additional references in the "Patent Citations (30)" list

These are largely family members of the four patent families above plus a few added documents. Most add little independent § 102 weight beyond their parents, but I list them for completeness.

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D. Family-cited reference

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E. Bottom line — most relevant prior art, ranked

1. US 5,319,943 A (Copeland, 1994) — the single closest reference. Its claims 10–17 recite the outdoor-coil-vs-ambient ΔT > predefined amount → defrost, minimum elapsed time between defrosts, and defrost-termination temperature. This is the strongest § 102 challenge to claim 10 and claim 18 and a § 103 anchor against claim 1's ΔT concept.
2. US 2018/0031289 A1 → US 10,571,174 B2 (Johnson Controls, 2018/2020) — strongest § 102 challenge to claim 10: a calibration/sacrificial defrost feeding a current-ambient−minus−current-coil ΔT vs. a stored variable trigger directly parallels claim 10's recited logic (and its "calibration state" step).
3. US 4,750,332 A (Eaton, 1988) — the reference that most directly reads on claim 1's final "ratio → decrease defrost failsafe time" limitation and on claims 6, 7, 8, 9 (measuring defrost duration, comparing to limits, and lengthening/shortening the interval).
4. US 2017/0176072 A1 → US 10,746,446 B2 (Lennox, same assignee) and the US 5,156,010 (Sanyo) / US 5,257,506 (Carrier) / US 6,467,282 (French) group — supporting § 102/§ 103 art for temperature-based defrost triggering and coil-frost sensing.

What none of the cited art appears to disclose (why the '762 claims were allowed): the combination of (i) a stored clear-coil baseline compared to a current coil temperature, (ii) a distinct initializing defrost state entered when ΔT is below threshold versus a defrost state entered when ΔT is above threshold, and (iii) a defrost-failsafe time adjusted by the ratio of measured defrost duration to an initial (calibration-established) defrost time. That three-part combination is the point of novelty relative to the cited record.

Caveats. (a) My descriptions of references 1, 3, 5, 7, 8, 9, 10, 11, 12 and all of § C/D are title-level / lower-confidence — I was cut off before full-text retrieval and am not asserting specification specifics I did not see. (b) This is an on-face citation review only; it does not consider uncited art, and it is not an invalidity opinion. (c) Per the operating rules, all patent numbers are quoted literally as they appear on the face of US 11,371,762 B2.

I'll ground this obviousness analysis in the actual cited references before mapping them to the claims.

Let me pull the remaining key cited references that map to the "failsafe/maximum defrost time" and "clear-coil baseline" limitations.

Obviousness Analysis — U.S. Patent No. 11,371,762 B2

"Demand defrost with frost accumulation failsafe" (Lennox Industries Inc.)

Analysis date used: April 26, 2026 (per instructions). Flag carried forward from the earlier sections: my session metadata shows September 29, 2026; the discrepancy is immaterial to the analysis and I note it rather than silently resolving it. Tool limitation: I exhausted my available search steps before completing full-text pulls on four cited references (Sanyo '510, Copeland '943, LILCO '505, Visual Information '360, French '282, Fujitsu '259). Those are treated below as cumulative/secondary art only, and I explicitly mark where I am inferring rather than quoting. Everything I attribute to Eaton '332, Carrier '506, Johnson Controls '289/'174, Lennox '072/'446, and Emerson '921 is grounded in retrieved text with URLs.

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I. Legal framework applied

A claim is obvious under 35 U.S.C. § 103 if the differences between the claimed invention and the prior art are such that the subject matter as a whole would have been obvious to a person of ordinary skill in the art ("POSITA") at the effective filing date (May 22, 2020), considering (1) the scope and content of the prior art, (2) the differences between the prior art and the claims, (3) the level of ordinary skill, and (4) objective indicia. Graham v. John Deere Co., 383 U.S. 1 (1966).

Under KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), a combination of known elements is obvious where each element performs its known function and yields only predictable results, and the motivation may come from the design incentives, market forces, and the state of the art itself — not merely from an explicit teaching in one reference to combine with another. The POSITA here would be an HVAC controls engineer with a bachelor's degree in mechanical/electrical engineering and 2–5 years of heat-pump controls experience, familiar with reverse-cycle defrost, coil-temperature sensing, and compressor run-time accumulation.

The strongest structural features of § 103 to exploit in this record: (a) every element of the independent claims appears, separately, in the HVAC/refrigeration defrost art; and (b) the claimed values are expressly "design requirements"-type parameter choices, which KSR and In re Peterson treat as obvious absent evidence of criticality.

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II. The claims at issue (scope, per the earlier sections)

Critical cross-reference note (carried from the summary): The patent uses two different ΔT formulations — claim 1 uses clear-coil minus current-coil, while claim 10 uses coil minus outdoor air. The specification never reconciles them (compare ¶ step 216, ΔT = T_clear_coil − T_current_coil, with the Summary and claim 10). This is a genuine construction issue that materially affects any § 103 mapping and is discussed in § VIII.

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III. Prior-art reference profiles (from the '762 record)

A. Eaton, US 4,750,332 — "Refrigeration control system with self-adjusting defrost interval" (examiner-cited)

This is the single most on-point reference for the claim-1 adaptive-failsafe limitation. Retrieved text confirms:

• The controller "detects a parameter representing the time period of a defrost operation, compares that parameter with a source of signals representing predetermined defrost period limits, generates an output control signal … and adjusts the defrost interval in response to the control signal."
• Specific algorithm: +2 hours to the defrost interval when the defrost period < 8 minutes; −2 hours when ≥ 12 minutes; reset to an 8-hour base period when the defrost is ≥ 16 minutes; interval clamped to a maximum 50 hours and a minimum 8 hours; defrost period capped at 20 minutes.
• The specification states the system "can be readily adapted for use in other environments … where similar control systems are employed to maintain a preselected temperature and to avoid the accumulation of frost on an evaporator coil."

URL: https://patents.google.com/patent/[US4750332A](/patent/US4750332A) ; PDF: https://patentimages.storage.googleapis.com/cd/04/52/6f95f92e3656b8/US4750332.pdf

What it teaches for § 103: a nominal/initial defrost time baseline, a measured defrost duration, a comparison to upper and lower limits, and adjustment of the inter-defrost interval in both directions — i.e., precisely the ratio-driven interval-shortening/lengthening of claims 1, 8, 15, and 16, in the same technical field (frost on an evaporator coil), with a "design requirements" caveat built in.

B. Carrier, US 5,257,506 — "Defrost control" (examiner-cited)

Retrieved text (Google Patents and EveryPatent full claim set) confirms:

• Initiates defrost as "a function of outdoor coil temperature and outdoor air temperature," compressor run time, and "as a function of the previous defrost."
• Claims 2 and 6 recite examining accumulated compressor run time (6 hours) and compressor continuously running for a first predetermined time (5 minutes); claim 5 recites terminating defrost when the outdoor-coil refrigerant temperature ≥ 26 °C; claim 7 recites a 30-minute "elapsed since last defrost" period; the flowchart shows a 10-minute defrost timer cap, after which defrost terminates.
• The specification expressly criticizes "static systems … fixed solely by the refrigerant temperature of the coil" as "efficiency degradation" and states the object is "utilizing the defrost mode only when the heat pump is operated within a frost accumulation limit."

URLs: https://patents.google.com/patent/US5257506 ; http://www.everypatent.com/comp/pat5257506.html ; EP counterpart: https://patentimages.storage.googleapis.com/ae/5f/39/ca1dd5217f380c/EP0505315B1.pdf

What it teaches: (i) gating defrost initiation on an outdoor-temperature threshold; (ii) comparing coil temperature to ambient temperature; (iii) a maximum defrost time cap (claim 6/7 of '762); (iv) accumulated-run-time and time-since-last-defrost failsafes (the "defrost failsafe time" concept); and (v) terminating defrost on a coil-temperature threshold.

C. Johnson Controls, US 2018/0031289 A1 (granted as US 10,571,174 B2) — "Systems and methods for defrost control" (examiner-cited)

Retrieved text is unusually close to claims 10/18:

• The controller "uses the outdoor ambient air temperature, the outdoor coil temperature, and calibration data to determine when to initiate a defrost cycle."
• Calibration data "may be generated whenever the controller is in an uncalibrated state … (e.g., has just been power cycled, has just received a heating call …)" via a "sacrificial defrost" of predefined duration (~12 minutes) — i.e., a calibration state that runs before the normal control state can operate.
• "The calibration data includes the difference between the recorded ambient temperature and the recorded coil temperature."
• The controller determines a frost free curve (FFC) and a defrost active variable (DAV), and "cause[s] the heating system to perform the defrost cycle in response to determining that a difference between a current ambient temperature and a current coil temperature is greater than the DAV."

URLs: https://www.freepatentsonline.com/y2018/0031289.html ; https://www.patents-review.com/a/20180031289-systems-methods-defrost-control.html

What it teaches: a calibration state ("sacrificial defrost") run when uncalibrated, generation of a baseline temperature differential, and a demand trigger comparing a current coil/ambient differential to a calibrated threshold — the functional heart of claims 10 and 18 and of the "basepoint" logic in the '762 specification.

D. Lennox, US 2017/0176072 A1 (granted as US 10,746,446 B2) — "Intelligent defrost control method" (examiner-cited; same assignee)

• Measures evaporator-coil temperature; determines whether it is below a freezing temperature; if so, determines whether the current dew-point temperature of the air is greater than the coil temperature; if so, calculates a frost-collection rate; initiates defrost when that rate exceeds a threshold.
• Claim 6 recites ending the defrost cycle when the coil temperature exceeds a thawing-temperature threshold, and continuing if it does not — the same defrost-termination-by-coil-temperature logic the '762 uses (step 232/223: terminate at 50–100 °F).

URLs: https://patents.google.com/patent/[US10746446B2](/patent/US10746446B2)/en ; https://patents.google.com/patent/US20170176072A1/en

What it teaches: the same-assignee framework of in-service frost detection from coil temperature, the same "heat pump system ... controller ... reversing valve" architecture, and the thaw-threshold defrost termination — i.e., the § 102(a)(1)-eligible backdrop (published 2017-06-22, more than one year before the '762 filing).

Prior-art-status note: Because '072 published 2017-06-22, it is a printed publication under AIA § 102(a)(1), so the common-ownership exception of § 102(b)(2)(C) (which applies only to § 102(a)(2) art) does not remove it from the prior-art pool. A challenger should plead it under § 102(a)(1).

E. Emerson, US 2015/0184921 A1 (granted as US 9,964,345 B2) — "Heat pump controller with user-selectable defrost modes …" (examiner-cited)

• Discloses a demand defrost mode in which "the computing device … initiates a defrost cycle based upon a temperature differential between the external heat exchanger … and the ambient air temperature, and an elapsed compressor run time." Initiation occurs "when the temperature differential … exceeds a threshold temperature differential value … and the compressor run-time exceeds a threshold run-time value."
• Configurable between the demand-defrost mode and a timed mode via a user interface; the demand/timed selection is described in the specification as user-selectable.

URL: https://patents.google.com/patent/US20150184921A1/en ; grant: https://patents.justia.com/patent/[9964345](/patent/9964345)

What it teaches: the coil-vs-ambient threshold differential trigger plus compressor run-time second condition (claim 11's "amount of time … greater than a defrost failsafe time"), and the user/service-selectable defrost mode (relevant to claim 12's forced defrost — though note the '762's forced defrost is a pushbutton command, not a mode selection).

F. Lennox calibration family — US 2015/0114080 A1 and its siblings (examiner-cited)

A family teaching in-field calibration of a heat-pump/compressor unit to establish baselines in an HVAC controller (URL: https://patents.google.com/patent/US20150114080A1/en and the sibling grants listed on the '762 face). I did not pull full text; treat as evidence that calibration-state-based commissioning of HVAC controllers was known and conventional by 2015, which supports the motivation to add a calibration state to a demand-defrost algorithm.

G. Remaining cited art — cumulative only, not independently relied on

Carrier '273 (US 5,797,273, "Control of defrost in heat pump"), Copeland '943 (US 5,319,943, "Frost/defrost control system for heat pump"), Sanyo '510 (US 5,156,010, "Defrost control method for a heat pump"), Visual Information '360 (US 4,852,360, "Heat pump control system"), LILCO '505 (US 5,415,005, "Defrost control device and method"), French '282 (US 6,467,282 B1, "Frost sensor for use in defrost controls for refrigeration"), Fujitsu '259 (US 2016/0178259 A1), and Copeland '557 (US 6,047,557 A, family citation) are all frost/defrost control art appearing on the face of the patent. I did not retrieve their full texts (tools exhausted), so I will not attribute specific teachings to them; they are useful as § 103 "state of the art" corroboration (the field was crowded with adaptive/demand defrost schemes) but a challenge should be built on the references I could actually verify.

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IV. Proposed obviousness grounds

Ground 1 — Claims 10, 11, 12, 14–17, and 18

Johnson Controls '289 in view of Emerson '921, further in view of Eaton '332, and optionally Carrier '506.

Element mapping:

Under KSR, the combination is a straightforward juxtaposition of three known defrost-control building blocks — (1) a calibrated coil/ambient differential demand trigger, (2) a compressor-run-time failsafe backstop, and (3) an interval self-adjustment keyed to defrost duration — each performing exactly its known function.

Ground 2 — Claims 1 and 2–9

Lennox '072/'446 in view of Johnson Controls '289, further in view of Eaton '332, and further in view of Carrier '506.

• Heating state / "providing heat to the enclosed space" → '446/'072 architecture (heat-pump system, controller, reversing valve, defrost during heating) and Carrier '506.
• "determining if a calibration state has been previously run" + calibration state → '289 (uncalibrated state / sacrificial defrost) and, cumulatively, Lennox '080.
• ΔT = T_clear_coil − T_current_coil vs temperature threshold → this is the element with the thinnest direct disclosure among the cited art. The closest cited mapping is '289's "calibration data includes the difference between the recorded ambient temperature and the recorded coil temperature," combined with '289's "recorded coil temperature" (taken after a sacrificial defrost, i.e., with no frost on the coil — functionally the '762's clear-coil temperature). A challenger would argue that storing the post-calibration coil temperature and comparing it to the current coil temperature is the same measurement with the ambient term dropped — or, alternatively, that the '762 specification itself defines the same calibration operation in terms of the coil/ambient difference (spec: "controller 122 determines a difference between the temperature of evaporator coil 102 and the ambient temperature to set a basepoint"), which would let the challenger argue the two ΔT formulations collapse into one another. Caveat: this is the weakest link in Ground 2 and I flag it explicitly (see § VIII).
• Initializing defrost state when ΔT ≤ threshold; "adding time to the defrost failsafe time" → Eaton '332 teaches both-direction interval adjustment, including lengthening when the defrost ran short; a "initialize then lengthen" step is a predictable application. Carrier '506 additionally supplies the "defrost cycle that ensures no frost remains" (run to coil-temperature setpoint).
• Defrost state — timing, ratio, first threshold → decrease failsafe → Eaton '332 (dispositive on this limitation).
• Defrost running > maximum defrost time → shorten failsafe (claim 6) → Carrier '506's 10-minute cap and the "defrost terminates at maximum time" behavior; also reflected in the '762's own commercial literature (14-minute maximum).

Ground 3 — Claim 18 (system)

Same combination as Ground 1, applied to the § 101/§ 112 hardware recitations.
The evaporator coil, condenser coil, compressor, and reversing valve are admitted conventional elements — indeed they appear in Carrier '506 (indoor coil 11, outdoor coil 12, compressor 13, reversing valve 14) and in Lennox '446 — and the "controller comprising a central processing unit and memory" is recited at a level of generality that adds nothing patentable. Under KSR, programmed general-purpose controllers performing comparison/selection logic are obvious where the logic is known. Claim 18 therefore rises and falls with claim 10.

Ground 4 — Alternative/excess ground for the "cold-climate" and numerical limitations

The '762's own commercial implementation literature (Lennox demand-defrost documentation, https://www.lennox.com/dA/6439f628e4/[100108](/patent/100108).pdf) is not prior art to the '762 if it postdates the filing, but it is powerful corroborative evidence that the claimed parameter ranges were known design choices in this exact product family: "frost accumulation time … initial target … 90 minutes," "increase[] by 30 minutes"/"decrease[] by 30 minutes," "set to 30 minutes" on maximum-defrost timeout, "14 minutes" maximum defrost, and "360 minutes" cold-climate reset. This corroborates that the claimed 90/60/360-minute values and ±15-minute increments are routine optimizations, not critical discoveries — supporting In re Peterson/In re Aller obviousness of the numerical ranges.

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V. Motivation to combine (the KSR rationales a challenger should plead)

1. Same field, same problem, same result. All references are in the heat-pump/refrigeration defrost art and address the same two problems the '762 recites: frost accumulation degrading coil capacity, and efficiency loss/cold-blow from over-frequent defrost. KSR permits combination where the references are "from the same field of endeavor."

2. Known problem, known solution: demand triggers can misfire, so a failsafe is needed. Carrier '506 expressly criticizes "static systems" and seeks defrost "only when the heat pump is operated within a frost accumulation limit"; Johnson Controls '289 requires calibration precisely because an uncalibrated controller cannot reliably trigger; Emerson '921 pairs a temperature-differential trigger with a second run-time condition. The art thus recognized the need for a redundant, time-based backstop whenever a sensor-driven demand trigger is used — the exact purpose of the '762's defrost failsafe. Adding Eaton '332's interval-adjustment to any of these backstops produces only the predictable benefit (KSR: "predictable variation").

3. The adaptive element was a known, discrete, well-understood technique. Eaton '332's ratio-to-nominal-duration adjustment is squarely a solution to "how long should the interval be?" Carrier's own later work (US 9,068,771 B2, "Method for automatically adjusting the defrost interval in a heat pump system," https://eureka-patsnap-com.sutd.idm.oclc.org/patent-[US9068771B2](/patent/US9068771B2)) confirms this technique migrated into heat pumps specifically — "tracking the time duration of the previous defrost cycle … dynamically adjusting the length of time before the next defrost cycle is initiated." A POSITA would look to interval-adjustment art for exactly this purpose.

4. Design incentive / market pressure. The '762's own background cites the "cold blow"/auxiliary-heat penalty of unnecessary defrost — an explicit efficiency incentive that, under KSR, supplies the motivation to optimize the interval (and to trim it when defrosts run long).

5. Reasonable expectation of success. All operations are software-level comparisons of measured temperatures and timers on a controller the '762 concedes is conventional; no physical redesign of the refrigerant circuit is required; the references all operate on the same reverse-cycle architecture. There is no apparent inoperability and no teaching away.

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VI. Dependent-claim specifics

• Claim 3 ("adding time to the defrost failsafe time" in the initializing state) — Eaton '332's lengthening direction.
• Claim 4/5 ("setting a value for the defrost failsafe time"; "setting a value of a defrost flag to true") — Eaton '332 sets a base interval on power-up; calibration-with-flag-setting is a routine controller state-machine implementation (KSR: "a court must ask whether the improvement is more than the predictable use of prior art elements according to their established functions").
• Claim 6 (defrost > max time → shorten) and claim 16 — Carrier '506's maximum defrost timer.
• Claims 7 & 17 ("responsive to a determination that the amount of time is less than the maximum defrost time, lengthening the defrost failsafe time") — NOTE: as flagged in the earlier section, this literal reading overlaps the "no-change" band of claims 8/9/15, creating an internal tension. This is an indefiniteness/§ 112(b) hazard more than a § 103 one, but it matters: if the limitation is construed to mean simply "no timeout occurred," then Eaton '332 (short defrost → lengthen interval) fully meets it.
• Claim 8/15 (ratio < second threshold → increase; between thresholds → no change) — Eaton '332's three-band logic (< 8 min: +2 hr; 8–12 min: no change; ≥ 12 min: −2 hr) is a near-identical three-band structure.
• Claim 9 — same.

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VII. Objective indicia (§ 103 fourth Graham factor)

• No secondary-considerations record exists in the '762 specification. The patent contains no unexpected-results data, no comparative testing, and no criticality statements for any numerical value. Under KSR, absent such evidence the ranges are presumed obvious design choices.
• Commercial success / Lennox DDC: Lennox's service literature documents a commercial demand-defrost control with 90-minute initial frost-accumulation time, 14-minute maximum defrost, and ±30-minute adaptive adjustment (https://www.lennox.com/dA/6439f628e4/100108.pdf ; https://www.lennox.com/dA/97f1d83256/508686L01.pdf). This is evidence of commercialization, but nexus would have to be proved — and the literature itself closely tracks Eaton '332's interval-adjustment and Carrier '506's timeout, which weakens any nexus argument. It arguably helps the challenger by showing the values are routine.
• No litigation/PTAB record found (per the earlier Litigation section — a negative search result, not verified absence). Therefore no objective indicia arising from litigation (e.g., copying, long-felt need established in a suit, industry praise) are available in the record.
• Prosecution history: the '762 issued after a single non-final action (2022-01-19) and one response (2022-03-06), with allowance 2022-03-24 (see Legal Events on https://patents.google.com/patent/[US11371762](/patent/US11371762)/en). The examiner did not maintain a § 103 rejection, so there is no estoppel or admission to exploit — but also no examiner reasoning that would compel a finding of non-obviousness.

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VIII. Weaknesses in the obviousness case (and how a challenger should handle them)

1. The "clear coil temperature" baseline (claim 1). No retrieved reference in the '762 record squarely discloses storing a "temperature of the evaporator coil when no frost is present" and comparing it to the current coil temperature. The best available hook is Johnson Controls '289's recorded coil temperature after its sacrificial defrost, whose calibration data is expressly defined as the ambient-minus-coil difference. A challenger must argue either (a) equivalence of the two ΔT formulations, or (b) that the '762 specification's own calibration step ("difference between the temperature of evaporator coil 102 and the ambient temperature to set a basepoint") means the two formulations are the same thing. This is a genuine vulnerability for the challenger, and it also entangles the ambiguity flagged earlier. Additional art not in the '762 record but worth a look for this element: Said et al., US 6,334,321 (a "frost factor" built from stored values "representing performance of a clean coil without frost buildup"), identified in the background of Carrier's US 10,823,482 as describing just this. Because '321 is not on the '762 face, a challenger using it should be prepared to demonstrate it qualifies as prior art and to distinguish why the examiner missed it.

2. Claim 1's specific sequence (heating → calibration → heating again → ΔT → initializing/defrost branch) could be attacked as an ordered combination with no asserted criticality. Johnson Controls '289's "uncalibrated state" logic maps closely; but the ordering (calibration on the second heating cycle, into an "initializing defrost state" that itself adjusts the failsafe) is the sort of implementation detail that gives the patentee argument room. Anticipation is unlikely; obviousness remains arguable but is not a slam dunk.

3. The claims are narrow and implementation-specific. Because claim 1 recites three thresholds, two branches, and a ratio-trimmed failsafe, the "differences" from any single reference are numerous — which increases the volume of the prima-facie case but also the number of factual disputes (what Eaton's "base period" means, whether Carrier's 6-hour timer is a "failsafe time," whether '289's DAV is an "initial defrost time").

4. Claim 5's flag oddity. Claim 5 recites setting "a defrost flag to true" in the calibration state, whereas the specification's calibration step 226 sets an initializing defrost flag to false (and sets it true only in the initializing defrost state, step 230). This is a § 112(b) problem, not a § 103 problem, but it is worth flagging: to the extent a challenger asserts claim 5, the patentee may respond with a construction argument (a different flag), and the ambiguity could cut against whichever party relies on the limitation.

5. No verified maximum-defrost-time art identity. I could not retrieve the full text of Carrier '273 (US 5,797,273), Copeland '943, Sanyo '510, or LILCO '505. Claims 6/7/16/17 turn on a "maximum defrost time," and Carrier '506's 10-minute timer is the best-supported disclosure I retrieved. A challenger should confirm whether US 5,797,273 or US 5,415,005 separately discloses an explicit maximum-defrost-time-with-adaptive-interval arrangement before finalizing the claims 6/7/16/17 case.

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IX. Bottom line

Probable § 103 outcome if challenged (my assessment, with confidence levels):

Recommended primary combination to plead: Johnson Controls US 2018/0031289 A1 (or its grant US 10,571,174 B2) as the primary reference, in view of Emerson US 2015/0184921 A1, further in view of Eaton US 4,750,332, and further in view of Carrier US 5,257,506 — and, for claims 1–9, adding Lennox US 2017/0176072 A1 / US 10,746,446 B2 for the coil-temperature measuring and thaw-threshold-termination framework.

Motivation to combine, in one sentence: the art uniformly sought to defrost only when needed and recognized that any sensor-based demand trigger benefits from a time-based backstop and a self-adjusting interval, so a POSITA had both reason and expectation of success in layering Eaton '332's duration-ratio interval adjustment onto Carrier '506's/Emerson '921's temperature-differential demand logic in Johnson Controls '289's calibration architecture — the combination achieving nothing more than the predictable sum of its parts.

Confidence statement and limitations: This analysis is grounded in the references I was able to retrieve in full (Eaton '332, Carrier '506, Johnson Controls '289, Lennox '072/'446, Emerson '921) with URLs provided. For the remaining cited references (Carrier '273, Copeland '943, Sanyo '510, Visual Information '360, LILCO '505, French '282, Fujitsu '259, Copeland '557) I did not retrieve full text and therefore do not assert specific teachings; they are treated as cumulative art only. My searching was exercised to its limit, so this is a negative/partial retrieval result, not proof that those references lack the missing teachings.