US 11371758

I'll search for this specific patent number across USPTO and litigation sources.

Let me check litigation/PTAB records and the USPTO record specifically.

US 11,371,758 B2 — Summary

Sources used: Google Patents full text (https://patents.google.com/patent/US11371758B2/en, which is the authoritative text supplied to me), plus targeted searches of web-indexed USPTO/PTAB/CAFC material. I did not obtain a direct USPTO PatentCenter or Patent Public Search record, so bibliographic details below are grounded in the Google Patents record for this exact number.

Bibliographic data

Abstract (as published)

A refrigeration cycle apparatus includes a refrigerant circuit, by pipes, connecting a compressor, a flow switching device, a first heat exchanger, an expansion device, and a second heat exchanger. As refrigerant to be circulated through the refrigerant circuit, any one of a refrigerant having saturated gas temperature under standard atmospheric pressure that is higher than that of R32 and a refrigerant mixture mainly composed of the refrigerant is used. The refrigerant circuit includes an internal heat exchanger configured to exchange heat between the refrigerant flowing through a refrigerant-inlet side of the second heat exchanger and the refrigerant flowing through a refrigerant-outlet side of the second heat exchanger.

Technical field / problem

Directed to refrigeration (e.g., air-conditioning) cycles using a flammable, low-GWP refrigerant — the specification emphasizes R290 (propane) and mentions R1270, R1234yf, R1234ze, R454A/C, R455A, R448A, R463A, R1123, and CO₂-containing refrigerants. The stated problem: these refrigerants (saturated gas temperature at standard atmospheric pressure higher than that of R32) have low pressure/density, so pressure loss in the extension pipe — especially in cooling mode where the indoor heat exchanger is the evaporator — materially degrades performance. Making the refrigerant leave the evaporator fully superheated avoids pipe pressure loss but causes dryout/distribution losses in the evaporator. The disclosed internal (refrigerant-to-refrigerant) heat exchanger between the second heat exchanger's inlet and outlet sides lets refrigerant leave the evaporator in a two-phase state while arriving at the compressor suction as superheated gas, and also reduces charge amount.

Independent claim 1 — plain language

A refrigeration cycle apparatus comprising a refrigerant circuit (pipes connecting compressor → flow switching device → first heat exchanger → expansion device → second heat exchanger), where:

• The circulating refrigerant is one whose saturated gas temperature at standard atmospheric pressure is higher than R32's, or a mixture mainly of such a refrigerant.
• The circuit has an internal heat exchanger exchanging heat between refrigerant in a first passage connected to the second heat exchanger's inlet and refrigerant in a second passage connected to its outlet.
• A first extension pipe connects the first passage to the expansion device; a second extension pipe connects the second passage to the flow switching device.
• The compressor, flow switching device, and first heat exchanger are in a heat-source-side unit; the second heat exchanger and internal heat exchanger are in a load-side unit (i.e., split indoor/outdoor architecture with interconnecting extension pipes).
• A bypass mechanism is provided so that refrigerant leaving the second heat exchanger's outlet bypasses the internal heat exchanger during operation in which the second heat exchanger acts as a condenser.
• The bypass mechanism specifically comprises (a) a bypass pipe connecting the second heat exchanger's refrigerant inlet and outlet, (b) a first check valve on the bypass pipe, and (c) a second check valve at an inlet of the internal heat exchanger.

(The bypass-mechanism limitation corresponds generally to the "bypass mechanism 120" of Embodiment 3 and its check valves 122/123.)

Dependent claims 2–7 — plain language

• Claim 2: the refrigerant is flammable.
• Claim 3: the second heat exchanger uses a flat multiway tube (with multiple internal holes) plus an attached fin (microchannel-type construction).
• Claim 4: an expansion mechanism (pipe, capillary tube, or expansion valve) is placed between the internal heat exchanger and the second heat exchanger's refrigerant inlet, in the evaporator-direction flow (Embodiment 2).
• Claim 5: three temperature sensors plus a controller — one in the heat-exchange area of the second heat exchanger, one at its refrigerant outlet (evaporator direction), one between the internal heat exchanger and the flow switching device; the controller runs the evaporator operation based on the sensed temperatures.
• Claim 6: the internal heat exchanger is a double-pipe heat exchanger or a plate heat exchanger.
• Claim 7: during evaporator operation, refrigerant at the second heat exchanger's outlet is in a two-phase state and refrigerant at the inlet of the second extension pipe is in a superheated gas state.

Litigation / CAFC check (as requested)

I searched for the literal number 11371758 alongside litigation terms (CAFC, Federal Circuit, docket, PTAB, IPR, district court, 2026) and alongside the patent's title/assignee/inventor. I found no record of any Federal Circuit appeal, PTAB/IPR proceeding, or district court action involving US 11,371,758. The only litigation-adjacent hits were unrelated patents and orders that happened to match my search terms.

Uncertainty note: absence of results in a web search is not a guarantee of no litigation. There may be district court cases or a CAFC docket that simply is not web-indexed or that I could not retrieve. I also did not directly query the USPTO Patent Public Search, PatentCenter, or the CAFC docket system; I recommend verifying there if litigation status is material.

Observations worth flagging

1. Claim 1 vs. specification mismatch (possible claim-construction issue): claim 1 recites the second check valve "provided at an inlet of the internal heat exchanger," whereas the specification (Embodiment 3) describes second check valve 123 as provided "between an outlet of the first passage 100a of the internal heat exchanger 100 and the second-heat-exchanger liquid port 11." Those are not obviously the same location; this could matter for infringement/support analysis.
2. Cited-by: two BMIL Technologies, LLC patents — US 12,313,318 B2 and US 12,313,319 B2 (both filed 2022-08-12, published 2025-05-27, "Low GWP cascade refrigeration system") — cite this patent.
3. Prosecution history available: the record lists extended European search report (2021-03-05), the ISR (2018-06-19), and a JP office action (2021-07-06) — useful if you need the file wrapper, though a U.S. file wrapper was not retrieved.

I have not disclosed any confidential or non-public client information in this summary (none was provided to me).

I'll search for litigation involving US patent 11371758 across patent litigation databases.

Let me search more targeted patent litigation databases and case-law sources.

Let me check the Unified Patents litigation portal and other litigation trackers directly.

Findings: Litigation Involving U.S. Patent No. 11,371,758

Result: No litigation found.

After searching patent-litigation resources (Unified Patents litigation portal, CourtListener/RECAP, Justia federal docket archives, and general web sources), I found no record of any district court lawsuit, ITC investigation, or PTAB proceeding (IPR/PGR) involving U.S. Patent No. 11,371,758 — either as an asserted patent or as a patent challenged in a validity proceeding.

Because no case exists to report, I cannot supply the requested per-case fields (plaintiff, defendant, jurisdiction, case number, filing date, status). There are no cases to list.

Supporting context from the search

• No litigation hits for "11371758." Searches combining the number with "litigation," "lawsuit," "infringement," "court case," and "Unified Patents litigation" returned only:
  • The Google Patents page for US11371758B2 itself;
  • Unrelated cases that merely contain similar-looking numbers (e.g., IPR2017-01892 on U.S. 8,577,358; a Moderna v. Pfizer docket citing IPR2023-01358; a docket citing U.S. 12,133,078; a "113 patent" in a DYMO/Sanford matter), and
  • Litigation-tracker articles about entirely different patents (Muvox/Apple/Amazon on 11,899,713).
• None of these involve 11,371,758 — they are number collisions, and the strict rule to interpret identifiers literally means none of them should be conflated with the patent at issue.

Patent profile (for confidence in the negative finding)

• Patent: US 11,371,758 B2, "Refrigeration cycle apparatus"
• Inventor: Shin Nakamura
• Assignee: Mitsubishi Electric Corporation
• Application: US 16/976,273 (PCT/JP2018/015225, filed 2018-04-11; published as US20200408445A1)
• Grant date: 2022-06-28; anticipated expiration: 2038-04-11; legal status: Active
• Family/parallel versions: WO2019198175A1, EP3779326B1, JPWO2019198175A1, ES2966611T3, CN111801535B

The Google Patents "Cited By" listing for this patent shows only two third-party citations of the patent document — US 12,313,318 B2 and US 12,313,319 B2 (both Bmil Technologies, LLC, "Low GWP cascade refrigeration system," 2025) — which are citations, not litigation, and do not indicate any suit.

Important caveats on this negative finding

1. Absence of evidence is not conclusive proof of absence. A litigation-tracker search reflects only what is publicly indexed at the time of the search; very recent filings, settlements, or state-court/foreign actions may not yet appear, and some dockets are behind paywalls (PACER full-text, Docket Navigator) that I could not access directly.
2. This is a Mitsubishi Electric apparatus patent granted in mid-2022, a category that historically sees relatively little assertion activity compared with NPE-type patents, which is consistent with (but not proof of) the lack of litigation.
3. I cannot verify a definitive "no cases exist" conclusion for the reasons above. If a conclusive litigation clearance is required, it should be run against a commercial litigation database (Docket Navigator, Lex Machina, or a full PACER docket search across all districts) and against the USPTO PTAB docket directly.

If you can point me to an alternative source (e.g., a specific docket number or a Unified Patents portal URL), I can attempt to verify it against that source.

I'll start by verifying the structured data against live sources before writing anything.

Let me run a few more targeted checks, including litigation and any post-grant challenges.

Let me do a final round of targeted checks to be thorough about any litigation or post-grant challenge.

Proceedings overview

Total AIA trial proceedings on file for US 11,371,758: zero (0). Breakdown: 0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denials. The USPTO Open Data Portal returns no AIA trial proceedings for this patent as of the most recent ingest, and independent web searching surfaced no IPR, PGR, or CBM naming US 11,371,758 or its international counterpart WO2019/198175 / EP3779326. The bottom-line defensive posture: there is no PTAB record to work from — claims 1–7 are wholly untested at the Board, all seven claims stand unamended, and no petitioner has triggered any § 315(e) estoppel. That cuts both ways: the patent has not been "hardened" by surviving an IPR, but it also means zero claim-cancellation leverage exists today. A defendant's validity attack starts from a clean slate, and so does Mitsubishi's enforcement position.

No proceedings to report

I checked the structured ODP block (canonical source: no AIA trial proceedings), then searched for practitioner-level traces (docket aggregators, PTAB petition documents, litigation dockets, and Mitsubishi's own PTAB footprint). Nothing tied to this patent. Per the operating rules, I will not invent a proceeding number to fill the template — the per-proceeding subsections are left empty on purpose.

One near-miss worth flagging so you don't mistake it for activity on this patent: third-party aggregator data shows IPR2023-00957 and IPR2023-00997 (TCL Communication Technology v. Mitsubishi Electric, filed 2023-06-02, both "Terminated-Settled"). Those are Mitsubishi cases, but there is no indication in the sources I reviewed that either challenges US 11,371,758 — different technology (telecom/display, not refrigeration) and different patent numbers. Treat them as unverified and not attributable to this patent. I could not confirm the challenged patent numbers, so do not cite them as this patent's IPR history.

Strategic summary

Claim status: all seven claims are UNTESTED at the PTAB. Nothing has been canceled, nothing has been confirmed. As granted on 2022-06-28, the patent has one independent claim (claim 1) and six dependent claims: claim 2 (flammable refrigerant), claim 3 (flat multiway tube + fin — the FIG. 11 structure), claim 4 (expansion mechanism between the internal heat exchanger and the second-heat-exchanger liquid port — Embodiment 2's expansion mechanism 110), claim 5 (three temperature sensors + controller executing the evaporator operation on temperature data), claim 6 (double-pipe or plate internal heat exchanger), and claim 7 (two-phase at the second heat exchanger outlet, superheated gas at the second extension pipe inlet). A defendant being asserted against today faces the full set, because no claim has been narrowed or killed by an adjudicative body.

Estoppel landscape: none exists. Because no IPR or PGR was ever instituted, § 315(e)(2) estoppel is a non-issue — no petitioner, and no privity chain, is barred from raising any § 102/§ 103 ground in district court or the ITC. Equally, there is no IPR-driven prosecution history narrowing to exploit beyond the ordinary file wrapper. That means an inter partes challenge is fully available to you: IPR is the only AIA vehicle left, because PGR required filing within nine months of grant (2022-06-28 → window closed 2023-03-28), and CBM is unavailable (this is a mechanical refrigeration patent, not a "financial product or service," and CBM sunset for new petitions long ago). Any IPR you file has no § 315(b) one-year bar unless you have already been served with a complaint on this patent — which is the trigger to watch.

Pattern signals: too little data to detect a pattern, which is itself informative. Mitsubishi Electric is an operating company, not a defensive aggregator or NPE; there is no Unified Patents-type entity in the chain. Japan-based industrials of Mitsubishi's size typically see PTAB activity only after they assert a patent or a competitor's product launch collides with it, and there is no public record I could find of this patent being asserted in district court. Two further signals worth noting: (i) the patent sits in live technical territory — the family includes EP3779326B1 (granted 2023-11-29) and JP/ES/WO members — so non-US challenges (e.g., EPO oppositions) may exist even where US AIA trials do not; and (ii) it has already been cited by later low-GWP refrigerant patents (US12313318B2 and US12313319B2, BMIL Technologies, both granted 2025-05-27), which tells you the claim space is commercially relevant to cascade refrigeration and that forward-citation art is accumulating.

Recommended next steps

The plain answer: there is no PTAB activity on this patent. Say that to the client without hedging. The absence is a real signal — well-asserted patents eventually attract IPRs, and this one was granted 2022-06-28 and has no public assertion history, so no one has yet had a § 315(b) trigger to file. If your client has just received a demand letter or complaint, that is likely the first assertion, and the IPR clock is now running on the complainant's side.

• Preserve your IPR rights immediately. If you have been served with a complaint alleging infringement of US 11,371,758, the § 315(b) one-year bar starts on the date of service of the complaint (or on service of a complaint alleging infringement of the same patent, for privies). Calendar it. Because there is no prior petitioner, you are not burdened by anyone else's estoppel.
• Do not treat this patent as "hardened." With no institution decision and no FWD, there is nothing to quote. Any statement to the contrary — that claims were "sustained" or that Mitsubishi "prevailed" — would be fabrication. The claim set's only validity evidence is the examiner's allowance on 2022-06-28 over the 30 references of record (notably JP2001227822A, US20170299241A1, US20160223239A1, US20120199326A1, and the search report cited in the ODP record).
• Interrogate the claim-1 structure early. Granted claim 1 recites a bypass mechanism (bypass pipe joining the second heat exchanger's inlet to its outlet, a first check valve on the bypass pipe, and a second check valve "at an inlet of the internal heat exchanger"). That combination pulls together the Embodiment 1 internal-heat-exchanger concept with Embodiment 3's bypass plumbing (reference signs 120, 121, 122, 123), while Embodiments 1 and 2 as described omit it. This is a strong hint that claim 1 was narrowed during prosecution to overcome art. Confirm against the file wrapper at USPTO PatentCenter (application 16/976,273) and pull the pre-grant publication US20200408445A1 to compare claim 1 as filed against claim 1 as granted — a claim-1 argument over the "second check valve provided at an inlet of the internal heat exchanger" limitation, and prosecution-history estoppel on the bypass feature, may be your cheapest non-infringement or § 112 path. This is an observation about claim drafting, not a finding — verify it in the file history before relying on it.
• Non-PTAB routes remain open and unencumbered. With no estoppel and no Board record, ex parte reexamination and district-court invalidity defenses carry no § 315(e) consequences and can be pursued in parallel.
• Track the primary sources for anything filed after this analysis. Monitor the USPTO PTAB End-to-End (E2E) system and the PTAB Decisions portal for new filings against 11,371,758, and CourtListener / the Federal Circuit docket for any appeal or co-pending litigation that would precede an IPR. Patent-assignment and family records: Google Patents US11371758B2, family members EP3779326B1 and WO2019198175A1.

Confidence statement: I am highly confident there is no AIA trial proceeding on US 11,371,758 as of 2026-09-30, based on the ODP structured block plus multiple corroborating searches. I could not, however, rule out a very recently filed petition that no public index has ingested yet, nor a foreign (EPO/JP) opposition. If the client has a live docket number, that is the fastest way to confirm the § 315(b) date.

I'll research the assignment record and ownership context for US 11,371,758 before writing up the analysis.

Let me check for any litigation, assertion activity, and SEC-level ownership changes involving this patent or its owner.

Let me verify the assignment record details and check the patent's current status directly.

Ownership & Assignment Analysis — US 11,371,758 B2

Patent: "Refrigeration cycle apparatus" · App. 16/976,273 (35 U.S.C. §371 national stage of PCT/JP2018/015225) · Filed/priority 2018-04-11 · Granted 2022-06-28 · Anticipated expiration 2038-04-11 · CPC F25B 40/00, 13/00, 39/00, 41/22, 41/30, 49/02, 5/02

Source of record: Google Patents legal-events panel (https://patents.google.com/patent/[US11371758B2](/patent/US11371758B2)/en), which mirrors the USPTO Assignment Center record. Note on method: the USPTO Assignment Center UI itself was not reachable from this environment during this run, so the reel/frame, conveyance, and dates below are taken from the Google Patents legal-events mirror. The correspondent of record on the reel is not exposed in that mirror and could not be confirmed — see signal 3.

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Inventors

Pattern notes: No unusual pattern. There is a single inventor of record, so the "all inventors departed within 12 months" fire-sale tell cannot arise and is not observed. The inventor's assignment was executed ~2020-07-10, i.e., at §371 national-stage entry (roughly two years after the 2018-04-11 PCT filing) — this is the normal formality timing for a national-stage case, not a departure signal. No evidence of inventor departure, and Nakamura continued filing Mitsubishi Electric applications in this technology area through at least 2023 (e.g., WO/2024/224637, filed 2023-04-28).

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Original assignee

Mitsubishi Electric Corporation (7-3, Marunouchi 2-chome, Chiyoda-ku, Tokyo 100-8310, Japan).

• Primary line of business: Diversified electrical/electronics manufacturer; the relevant segment here is HVAC & refrigeration (room air conditioners, commercial refrigeration, heat pumps) and building systems.
• Product embodiment: Yes, plausibly and materially. The claims are directed to a refrigeration cycle using a refrigerant whose saturated-gas temperature at atmospheric pressure is higher than R32's, with an internal heat exchanger between the inlet and outlet sides of the second (load-side) heat exchanger. Mitsubishi Electric commercially ships air conditioners designed around low-GWP refrigerants in exactly this family (R32 equipment, and R290/R1234yf-oriented development for the European F-gas market), and the specification's payload (FIG. 7–10 refrigerant-property data, flat multiway tubes) tracks the company's production heat-exchanger line. No product-marking survey was performed, so treat "ships products embodying the claims" as a reasonable inference from the company's product line, not a verified claim-charting result.
• Current status: Operating. A large, publicly listed, going-concern Japanese corporation. No bankruptcy, dissolution, or acquisition of the assignee is shown anywhere in the record.

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Assignment timeline

Only one recorded assignment exists for this patent. There are no security interests, mergers, name changes, licenses, releases, or corrections of record.

• 2020-07-10 (executed) / recorded 2020-08-27 — Reel 053616/0595
  • Conveyance: Assignment (Assignment of Assignors' Interest)
  • Assignor: NAKAMURA, Shin (individual inventor)
  • Assignee: MITSUBISHI ELECTRIC CORPORATION
  • Correspondent: Not exposed in the Google Patents legal-events mirror; not confirmed. For general context only (not a finding on this reel), Mitsubishi Electric's US patent prosecution in this technology family is routinely handled by Posz Law Group, PLC (that firm appears as the "Attorney, Agent, or Firm" on at least one related Mitsubishi Electric patent, US 10,627,175). I could not verify whether Posz — or anyone else — is the correspondent on reel 053616/0595, so do not rely on this as the recording attorney.
  • Context: In-house formality / employer capture. The lone inventor's rights were conveyed to his employer at §371 national-stage entry. This is the ordinary inventor-to-employer assignment, not an acquisition, fire-sale, securitization, or transfer to an asserter.

Nothing else is recorded. There is no post-issuance assignment. The chain terminates at the original operating-company assignee, which means (absent a non-recorded transfer) Mitsubishi Electric Corporation still owns the patent.

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Timeline diagram

timeline
    title Ownership of US 11371758
    2018 : PCT filed by Mitsubishi Electric
         : Priority date 11 Apr 2018
    2020 : Inventor assignment recorded
         : Reel 053616 frame 0595
    2022 : Patent granted to Mitsubishi Electric
    2038 : Anticipated expiration

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NPE / troll-pattern signals

Assessed against the single recorded link (reel 053616/0595) and the absence of any other recording.

1. Shell-entity transfer — Not present. The only assignee is Mitsubishi Electric Corporation, a large operating manufacturer at a real corporate headquarters (Marunouchi, Chiyoda-ku, Tokyo). No "IP / Holdings / Licensing / Ventures" LLC, no registered-agent service address, no single-purpose entity appears anywhere in the chain.

2. Known asserter in the chain — Not present. Neither the original assignee nor any recorded assignee matches the named NPE lists (Acacia, Marathon, Intellectual Ventures, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, etc.). The two "Cited By" hits (US 12,313,318 and US 12,313,319, both BMIL Technologies, LLC, 2025) are forward citations to this patent in later refrigeration patents — they are not assignments of US 11,371,758 and do not put an NPE in this patent's chain. Do not conflate them.

3. Repeat correspondent across the chain — Not present / unclear. With only one recorded link, recurrence is definitionally impossible, and the correspondent name on reel 053616/0595 could not be read from the mirror used here. No finding either way.

4. Cascading transfers — Not present. No series of chained assignments exists; the single assignment is dated 2020-07-10 and is the inventor-to-employer formality.

5. Pre-litigation transfer — Not present. No infringement suit naming US 11,371,758 was located in the searches performed, so there is no assignment within 6 months of any first suit (the only assignment predates issuance by ~23 months and is an employer capture).

6. Bankruptcy fire-sale — Not present. Mitsubishi Electric Corporation is an operating going concern; no Chapter 7/11 proceeding, no §363 sale, and no sale-in-bankruptcy recording exists for this patent.

7. Privateering — Not present. No transfer to any third party, NPE or otherwise, that could assert on Mitsubishi Electric's behalf. The patent has never left the operating company's ownership on the record.

8. Defensive aggregator (anti-NPE) — Not present. The chain does not terminate at RPX, AST, LOT Network, Unified Patents, or OIN. Continuation in the original manufacturer's hands is not neutralization via a defensive aggregator; it is simply retained operating-company ownership.

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Verdict

Insufficient data (per the rubric's "only the original assignment" branch) — with the affirmative finding that the chain terminates at the original operating-company assignee.

The entire recorded chain is a single inventor-to-employer assignment: NAKAMURA, Shin → Mitsubishi Electric Corporation, executed 2020-07-10, recorded 2020-08-27, reel 053616/0595. There is no post-issuance assignment, no LLC transfer, no known asserter, no cascading chain, no pre-litigation transfer, and no defensive-aggregator terminus — so zero NPE signals are present, and the verdict "NPE" of any confidence level is affirmatively excluded. The honest characterization is a standard operating-company-owned patent (Mitsubishi Electric, an operating HVAC manufacturer) that has never been separated from its original owner of record; I default to "Insufficient data" only because the rubric keys that label to a chain with no records beyond the original assignment, and I could not verify the reel-level correspondent or run a full litigation/PTAB docket sweep from this environment.

Verification link: https://assignmentcenter.uspto.gov/ (search patent number 11371758; also indexed at https://assignment.uspto.gov/patent/index.html). Please confirm reel 053616/0595, its correspondent of record, and the absence of any later recording before relying on this for a clearance or standing opinion.

Caveats: (a) The correspondent on reel 053616/0595 was not readable from the mirror used and is unverified; the Posz Law Group reference is context about Mitsubishi's prosecution counsel generally, not a confirmed recording agent. (b) Absence of recorded assignments does not conclusively prove current ownership — unrecorded transfers are possible, though 35 U.S.C. §261 limits their effect against third parties.

I'll research this systematically. Let me start by verifying the patent in USPTO databases and then examine each cited reference.

Let me research the key cited references in detail.

Prior-Art Analysis — U.S. Patent No. 11,371,758 ("Refrigeration cycle apparatus")

Analyst note: Per the working rule, I interpret the patent number, its application/priority data, and all citation identifiers literally. I did not auto-correct any identifier. The authoritative source is the full patent text you supplied (fetched from Google Patents). Where I relied on title/abstract/examiner-citation metadata rather than full reference text, I say so explicitly.

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1. Identification of the patent (USPTO)

I could not open a live USPTO PatentCenter/PatFT record within the search budget; the internal consistency of the Google Patents bibliographic data (application number, PCT, family, grant date) corroborates the USPTO-facing record. If a ceremony-grade verification is required, confirm at PatentCenter for application 16/976,273.

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2. Independent claim 1 — element breakdown (the anticipation targets)

The specification's own art is claim 1, which is a combination claim. Its elements are:

• (A) Refrigerant circuit by pipes connecting: compressor → flow switching device → first heat exchanger → expansion device → second heat exchanger.
• (B) Refrigerant = one whose saturated gas temperature at standard atmospheric pressure is higher than that of R32 (≈ higher than −52 °C; spec names R1234yf −29 °C, R1234ze −19 °C, R454A/C, R455A, R448A, R463A), or a mixture mainly thereof.
• (C) Internal heat exchanger exchanging heat between a first passage connected to the second-HX refrigerant inlet and a second passage connected to the second-HX refrigerant outlet.
• (D) First extension pipe connecting the first passage and the expansion device.
• (E) Second extension pipe connecting the second passage and the flow switching device.
• (F) Compressor, flow switching device, first HX in a heat-source-side unit.
• (G) Second HX and the internal heat exchanger in a load-side unit.
• (H) Bypass mechanism causing refrigerant leaving the second-HX outlet to bypass the internal HX in the flow direction used when the second HX is a condenser.
• (I) Bypass mechanism comprises: bypass pipe connecting the second-HX inlet to the second-HX outlet; a first check valve on the bypass pipe; and a second check valve at the inlet of the internal heat exchanger.

Dependent claims: 2 (flammable refrigerant); 3 (flat multiway tube + fin); 4 (expansion mechanism between internal HX and second-HX inlet during evaporator operation); 5 (three temperature sensors + controller); 6 (internal HX is double-pipe or plate HX); 7 (during evaporator operation, second-HX outlet is two-phase and second-extension-pipe inlet is superheated gas).

Elements (C)–(I) are the true novelty core. Any reference asserted under §102 must disclose all of (A)–(I).

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3. Cited references — full citation, dates, description, and claim relevance

The Google Patents front page presents two overlapping citation tables: a "Citations (27)" list and a "Patent Citations (30)" list. The 30-item list is the more complete examiner-facing set (it adds EP 1947405 A1, US 2010/0058800 A1, and JP 5991989 B2). The table below covers the 30-item set (unioned with the 27-item set). Code categories: X = single-reference novelty/§102 candidate; Y = §103 combination candidate; A = background only.

Note: the Google Patents "Families Citing this family" list (CN 106642791 A, CN 118265878 A, US 2025/0067463 A1, US 2024/0392178 A1) are forward citations, not prior art against US 11,371,758, and are excluded from the §102/§103 analysis above.

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4. Ranked short list — references closest to anticipation

Tier 1 (closest to §102 anticipation of claim 1):

1. US 4,030,315 A (Borg-Warner, 1977-06-21). Discloses, in one reverse-cycle heat pump: a reversing valve (element A/F); a heat exchanger 24 having first and second independent fluid paths exchanging heat between the hot liquid leaving the condenser (the "second HX" of the patent's cooling/heating counterpart) and the suction gas leaving the evaporator (element C); field-connected line sections 32A/34A functioning as extension pipes to a split heat-source/load assembly (elements D, E, F, G); and an automatic bypass of the heat exchanger using check valves (elements H, I; claim 4 recites first and second capillaries with first and second check valves). This is the single reference that most nearly reads on all of claim 1. The core §102 vulnerability/defense is element (H): the direction/mode of bypass in US 4,030,315 (HX used in heating, bypassed in cooling) is inverted relative to the claimed "bypass in the flow direction used when the second HX is a condenser," so a strict §102 read may fail and the reference may instead support §103. Also reads on claim 6.

2. US 2016/0223239 A1 (Trane, 2016-08-04). An indoor (load-side) unit with an indoor liquid/suction heat exchanger plus a metering device having a check valve and/or bypass configuration. Maps to elements (C), (G), (I). Newer than the 2018 priority? No — published 2016-08-04, i.e., it is prior art (before the 2018-04-11 filing), though its own priority (2015-01-31) is also before filing. Candidate for claims 1 and 6.

3. US 2015/0276271 A1 (Lennox, 2015-10-01). A reversible cycle in which a cycle-enhancement line (counterflow internal heat exchange) is connected through first/second entrance and exit lines, each carrying a one-way (check) valve, letting a one-way enhancement function in both modes. Maps to elements (C)–(I) and reflects the exact check-valve-gated internal-HX topology. Candidate for claims 1 and 6.

Tier 2 (strong §103 combination material):

• US 5,987,907 A; US 2005/0039897 A1; US 2012/0199326 A1 — internal-HX structure (claims 1, 6).
• JP 2001-227822 A (the specification's own Patent Literature 1) and JP 2011-043279 A / US 2017/0299241 A1 / US 2014/0290292 A1 (Mitsubishi Electric) — same-field refrigeration-cycle architecture (claims 1, 6, 7).
• FR 2916835 A1 (Valeo) — evaporator + internal exchanger packaged as one module (claims 1, 6).

Tier 3 (dependent-claim anchors):

• Claim 2 (flammable / low-GWP refrigerant): US 2010/0326095 A1 (Arkema); US 2013/0325732 A1 (Mexichem).
• Claim 3 (flat multiway tube + fin): US 2017/0343288 A1 (Carrier); US 2018/0112897 A1 (Daikin); US 2015/0096311 A1 (Modine).
• Claim 4 (expansion mechanism between internal HX and second-HX inlet): JP 2003-194432 A (Matsushita); JP 2012-132578 A (Panasonic); JP 2009-250592 A (Daikin).
• Claim 5 (three temperature sensors + controller): US 2009/0013700 A1 (Unezaki); US 2010/0005831 A1 (Carrier); US 2010/0131115 A1 (Bum Suk Kim).
• Claim 6 (double-pipe or plate HX): US 2005/0039897 A1 (Muto); US 2012/0199326 A1 (Visteon); JPH 05141811 A (Nippondenso); US 4,030,315 A.
• Claim 7 (two-phase at outlet / superheated at second-extension-pipe inlet): US 5,987,907 A; US 2014/0290292 A1 / JP 5991989 B2 (Mitsubishi Electric); JP 2001-227822 A.

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5. Non-patent literature cited

From the citation record:

• Extended European Search Report dated 2021-03-05, EP Application No. 18914807.5.
• International Search Report of the ISA dated 2018-06-19, PCT/JP2018/015225 (with English translation).
• Office Action dated 2021-07-06, JP Patent Application No. 2020-512993 (with English translation).

These are prosecution documents, not §102 prior art in their own right, but the ISR and EESR search reports are the best source for an examiner's own "X/Y" categorization and should be pulled in full if a rigor-grade anticipation opinion is needed.

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6. Caveats and confidence

1. §102 vs §103 designation is preliminary. The examiner "cited-by-examiner" flags on many rows are the only signal of which references were considered material; the Google Patents tables do not publish the examiner's X/Y/A categories for this patent. The true categorization lives in the U.S. file wrapper (Form 892 / examiner's search) and in the EP EESR for EP 3779326 — neither of which I could open in full within the search budget.
2. Full text not verified for every reference. I obtained substantive text for US 4,030,315 A, US 2016/0223239 A1, and US 2015/0276271 A1 (via Google Patents / FreePatentsOnline / Patents-Review/FPO excerpts). For the remaining ~27 rows, the descriptions are drawn from the citation-table titles/assignees and general knowledge; they should be confirmed against the reference full text before being asserted as §102 art.
3. Element (H) is the pivot. No reference I examined discloses the literal claimed mode-direction of bypass (bypass of the second-HX condenser-outlet path). US 4,030,315 A is structurally closest but appears to invert that direction. This is exactly the kind of nuance that converts a would-be §102 reference into a §103 reference.
4. No litigation/validity challenge found (consistent with the previously generated litigation section). The previous litigation section lists "Cited By" as US 12,313,318 B2 and US 12,313,319 B2 (Bmil Technologies). The full patent text additionally shows a "Families Citing this family" list (CN 106642791 A; CN 118265878 A; US 2025/0067463 A1; US 2024/0392178 A1). These are not in contradiction — one is a "Cited By" (patents citing 11,371,758) and the other is a family-level forward-citation list — but the two lists should not be conflated.
5. Next steps for a definitive prior-art opinion: (a) pull the Form 892 / examiner's search from PatentCenter for app. 16/976,273; (b) pull the EESR for EP 18914807.5 and the ISR for PCT/JP2018/015225; (c) obtain full text of US 4,030,315 A, US 2016/0223239 A1, and US 2015/0276271 A1 to run a formal element-by-element §102 chart against claim 1; (d) run the same chart for dependent claims 2–7 against the Tier-3 anchors.

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Bottom line: The two most relevant prior-art references for US 11,371,758 are US 4,030,315 A (Borg-Warner, 1977) — a reverse-cycle heat pump with an internal (condenser-liquid/suction-gas) heat exchanger, check valves, and automatic bypass in a split system, reading on most of claim 1 including the extension-pipe and unit-split elements — and, among the modern art, US 2016/0223239 A1 (Trane, 2016) and US 2015/0276271 A1 (Lennox, 2015), which disclose check-valve-gated internal-heat-exchange loops on the load side of a reversible cycle. Given the inverted bypass mode, US 4,030,315 A is best characterized as a §103 (Y) combination anchor for claim 1 and a §102 candidate for claim 6, rather than a clean single-reference anticipation of claim 1.

I'll ground the key prior-art references before building the obviousness analysis.

Let me verify a few more of the cited references relevant to dependent claims 3–4 and the refrigerant-selection element.

Obviousness Analysis — US 11,371,758 B2 under 35 U.S.C. § 103

Patent: US 11,371,758 B2, "Refrigeration cycle apparatus" (Mitsubishi Electric; inventor Shin Nakamura; app. US 16/976,273; filed/priority 2018-04-11; granted 2022-06-28).
Scope of this section: the references listed in the "Prior Art" portions of the record (27 examiner citations, 30 patent citations incl. duplicates, 3 non-patent citations, 8 "Family Cites Families" references, and the Patent Literature 1 reference cited on the face of the specification). Per the operating rules, patent numbers are read literally; no citation is conflated with a similar-looking number.

Analyst's caveat up front: I retrieved full or near-full descriptive text via search only for a subset of the cited references (notably US 2016/0223239 A1, US 2015/0276271 A1, US 2018/0112897 A1, US 5,987,907 A, US 2017/0299241 A1). For the remainder I have only bibliographic data and titles from the citation list supplied in the patent text. Where I rely on a reference whose disclosure I did not verify, I say so explicitly. I have not fabricated any quotation from an unverified reference.

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1. Legal framework applied

• Graham v. John Deere, 383 U.S. 1 (1966): scope/content of prior art, differences, PHOSITA level, secondary considerations.
• KSR Int'l v. Teleflex, 550 U.S. 398 (2007): a combination is obvious where the improvement is "the predictable use of prior art elements according to their established functions," and an explicit teaching-suggestion-motivation is not required. A finite number of identified, predictable solutions is sufficient.
• MPEP § 2143 factors: teachings that a combination was "known to have been used" or "obvious to try," design incentives, market/regulatory pressure, and "obviousness of a chemical/physical property."
• In re Keller / In re Merck: a reference may be combined for what it fairly teaches; all elements need not be found in a single reference.

PHOSITA level (assumed): a bachelor's degree in mechanical engineering (or equivalent) with 2–5 years of experience in vapor-compression HVAC product design, familiar with split-system architecture, internal/suction-line heat exchangers (SLHX/LSHX), reversing valves, and low-GWP refrigerant transitions.

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2. Claim 1 decomposed into limitations

Limitation 1.7 is the narrowest structure and the likely point of novelty (see §7 below).

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3. Primary reference: US 2016/0223239 A1 (Trane International, "Indoor Liquid/Suction Heat Exchanger") — cited by examiner

Verified disclosure (freepatentsonline.com/y2016/0223239.html; patents-review.com/a/20160223239):

• An A/C system with an outdoor unit and an indoor unit; the Liquid/Suction Heat Exchanger (LSHX) 230 is located in the indoor unit 202 — this reads directly on limitations 1.3 and 1.5 (internal HX mounted in the load-side unit).
• The LSHX is "coupled between an outdoor heat exchanger … and an indoor metering device … on a so-called 'liquid' line" and "between an indoor heat exchanger … and a compressor … on a so-called 'vapor' line" — i.e., the two passages straddle the second HX's liquid (inlet) side and vapor (outlet) side, exactly the 1.3 relationship, with the interconnecting lines being the extension pipes of 1.4.
• The system is expressly described as optionally a heat pump with a reversing valve in the outdoor unit, with flow reversed in heating mode — limitation 1.1's flow switching device and the split-unit framing of 1.5.
• Critically for 1.6: "the HVAC heat pump system may comprise a plurality of check valves, solenoid valves, and/or any other suitable configuration of valves that would effectively remove the LSHX 230 from the fluid circuit during operation in the heating mode … Additionally, the HVAC heat pump may also comprise a bypass line and/or a plurality of bypass lines that operate in conjunction with the valves to remove the LSHX 230 from the fluid circuit when the HVAC heat pump system is operated in the heating mode."
• The reference discloses a superheat sensor 240 downstream of the LSHX and a controller adjusting the indoor metering device based on sensed superheat — relevant to claim 5.

Mapping: In the heating mode of Trane's heat pump, the indoor heat exchanger is the condenser. Therefore Trane's "remove the LSHX from the fluid circuit during heating mode" is the same mode condition recited in limitation 1.6 ("during an operation in which the second heat exchanger is used as a condenser"). Trane thus teaches the function of 1.6 and discloses the bypass line + check valves genus of 1.7.

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4. Secondary reference: US 2015/0276271 A1 (Lennox Industries, "Reversible heat pump with cycle enhancements") — cited by examiner

Verified disclosure (patents-review.com/a/20150276271; freepatentsonline.com/y2015/0276271):

• The reference's stated problem is precisely the one the '758 patent must solve: "One-way cycle enhancements function optimally only when refrigerant flows through them in one direction. Conventionally, a reversible heat pump optimally benefits from one-way cycle enhancements in only one direction of refrigerant flow."
• The disclosed "cycle enhancement apparatus" has first/second side entrance lines and first/second side exit lines, each with a one-way (check) valve oriented so that flow is directed to/bypass around the enhancement, plus "a cycle enhancement line … having a cycle enhancement between the entrance portion and the exit portion."
• The enhancement is expressly described as a counterflow heat exchanger 302, and for FIG. 4 "Counterflow heat exchanger 302 may be a plate or coaxial tube" (relevant to claim 6), exchanging heat between the cool (liquid) line and the suction line — i.e., a liquid/suction internal heat exchanger — while the four check valves automatically shunt refrigerant around it in the reverse mode.
• The reference is framed around CO₂/transcritical systems and generally improving effective, reversible cycle enhancements.

Mapping: Lennox supplies the explicit structural teaching missing from Trane: an internal heat exchanger interposed in a refrigerant line, with check-valve-based bypass plumbing that automatically removes the enhancement depending on flow direction/mode — the exact structural idea of limitations 1.6 and 1.7(a)–(b). The two references come from the same field (residential/light-commercial reversible heat pumps), address the same problem (efficiency penalty of a one-directional cycle enhancement in a reversible circuit), and their combination is a textbook KSR combination of known elements performing their established functions.

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5. Remaining limitations and supporting references

5.1 Refrigerant selection (1.2) — low-GWP, R32-replacement fluids

Argument: Limitation 1.2 is a functional recitation of a known chemical selection rather than a structural difference. Where the prior art (Arkema, Mexichem) discloses the low-GWP fluids and the field was under regulatory pressure to move off R410A/R32, selecting a fluid whose saturation temperature at atmospheric pressure exceeds R32's is the "predictable use of prior art elements according to their established functions." The specification itself concedes the whole benefit narrative is a known physical-property consequence ("Compared with R32, these refrigerants have a low pressure at the same saturated gas temperature, a low density, a significant refrigerant pressure loss to a circulation amount …"). A PHOSITA selecting among the finite list of identified R32-alternatives (R1234yf, R1234ze, R454A, R454C, R455A, R448A, R463A, R1123, R290, R1270) has the requisite motivation and a reasonable expectation of success. This is the strongest obviousness argument on 1.2, but it is also the limitation the examiner is most likely to have treated as satisfied by the art, so it is not where the case turns.

5.2 Split-system/extension-pipe architecture (1.1, 1.4, 1.5)

US 2017/0299241 A1 (Mitsubishi Electric, "Refrigeration cycle apparatus") — verified via search — discloses a heating unit (outdoor) / cooling unit (indoor) split connected by liquid-side crossover piping and gas-side crossover piping, with valves and check valves on the crossover piping. That is squarely the extension-pipe + unit-split structure of 1.4/1.5, and additionally evidences that check-valve-bearing crossover piping in split systems was well known. Also relevant background: US 5,987,907 A (Mitsubishi Denki) discloses a main circuit with a bypass piping having an opening/closing mechanism bypassing at least one of the compressor, condenser, throttle and evaporator — a generic bypass-around-a-component teaching.

5.3 Flat multiway tube + fin (claim 3)

US 2018/0112897 A1 (Daikin, "Heat exchanger and air conditioner") — cited by examiner and verified: discloses a heat exchanger with "a plurality of flat tubes … in each of which a plurality of refrigerant channels are formed; and fins joined to the flat tubes," exchanging heat between refrigerant in the channels and air. That is limitation-for-limitation the claim-3 structure. US 2017/0343288 A1 (Carrier, "Multi-pass and multi-slab folded microchannel heat exchanger") provides further microchannel/multi-slab support. Note both have effective dates (2015-04-27 and 2014-11-17 priority) predating the '758 filing date.

Motivation: the specification itself supplies the KSR-recognized design incentive for combining: "the volume in the heat transfer pipe can be reduced and the refrigerant amount of flammable R290 can be reduced. Thus, the safety … increases." Reducing internal circuit volume to reduce flammable charge is a market/regulatory-driven design incentive, exactly the kind of articulated reason that supports obviousness.

5.4 Internal heat exchanger type (claim 6)

• US 2005/0039897 A1 (Ken Muto, "Internal heat exchanger") and US 2012/0199326 A1 (Visteon, "Internal heat exchanger") — cited by examiner; both are directed to internal heat exchangers, supplying the double-pipe and/or plate configurations that claim 6 recites as alternatives.
• Lennox US 2015/0276271 independently states the counterflow HX "may be a plate or coaxial tube" — a direct teaching of claim 6's alternatives.
• FR 2916835 A1 (Valeo) — an evaporator and an internal exchanger "in the form of a unitary module" — supports the physical placement of the internal HX together with the second HX in the load-side unit (1.5).

5.5 Sensors + controller (claim 5)

• US 2016/0223239 A1: superheat sensor 240 downstream of the LSHX, controller controlling the metering device — verified.
• US 2016/0131115 A1 (Kim, "Controlling method of air conditioner") and US 2009/0013700 A1 (Unezaki) — control methods using sensed temperatures/refrigerant amount.
• JP 2009-299909 A (Hitachi, refrigeration cycle device) and JP 2012-132578 A (Panasonic) — control of refrigeration cycles.
• Note: claim 5's third sensor location ("between the internal heat exchanger and the flow switching device") corresponds to Trane's sensor downstream of the LSHX on the vapor line, and the claim's functional requirement (run evaporator operation based on sensed temperatures) is a conventional control-function recitation.

5.6 Claim 7 (two-phase evaporator outlet + superheated suction inlet)

Claim 7 is a statement of the intended result of the §3/§4 combination. The specification states it as the mechanism, and Trane's disclosed subcooling/superheat operation achieves it. A claim to the recognized, inherent operating condition produced by the combined structure is vulnerable under MPEP § 2144.04 / In re Hallman-type reasoning (a recitation of the result of a known structure does not confer patentability). Note, however, the specification also states the transitory condition should be verified by sensors — which cuts both ways.

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6. Proposed ground of rejection (primary combination)

Claim 1 is obvious over US 2016/0223239 A1 in view of US 2015/0276271 A1, further in view of JP 2001-227822 A and/or US 2010/0326095 A1/US 2013/0325732 A1.

Element-by-element:

Motivation (KSR-compliant, not TSM-dependent):

1. Same field, same problem: both Trane and Lennox are reversible HVAC heat pumps with a cycle enhancement that is beneficial in only one flow direction; Trane explicitly identifies the efficiency penalty in the reverse mode and offers bypassing as the solution.
2. Known function: check valves as automatic, mode-responsive flow directors are ubiquitous in reversing circuits (Trane, Lennox, US 5,987,907, US 2017/0299241). Using two check valves to shunt a component out of the loop is the predictable use of a known element.
3. Regulatory/market pressure: GWP-driven refrigerant transition (expressly in the '758 specification's Background) plus flammable-charge limits (JP 2001-227822; Unnezaki '700) motivate both the SLHX placement in the interior unit and charge-reduction measures such as microchannel HX.
4. Reasonable expectation of success / predictable results: the asserted benefits (compressor suction superheat, reduced two-phase pressure loss in the gas extension pipe, charge reduction) are the standard, documented effects of a suction-line/liquid-line internal heat exchanger. Nothing in the combination requires a change in the principle of operation of any element.

Dependent claims:

• Claim 2 — flammable refrigerant: inherent in Arkema/Mexichem compositions and JP 2001-227822's R290 (and stated in the '758 Background as the reason for charge limits).
• Claim 3 — flat multiway tube + fin: US 2018/0112897 A1 (verified), alone or with US 2017/0343288 A1; motivation supplied by charge/volume reduction with a flammable refrigerant.
• Claim 4 — expansion mechanism between internal HX and second HX inlet: weakest link in this record. None of the cited references was verified to disclose this specific upstream-throttle placement. Candidate leads to develop: JP 2001-227822 A, JP 2003-194432 A (Matsushita), JP 2009-250592 A (Daikin), JP 5991989 B2 / US 2014/0290292 A1 (Mitsubishi), and US 10,401,047 B2 / US 9,612,047 B2 (Mitsubishi internal-HX + bypass circuits appearing in the same technical family). A separate search for "subcooler with upstream expansion valve / two-stage expansion internal heat exchanger" art is required before asserting this ground. I cannot presently assert claim 4's obviousness with confidence.
• Claim 5 — three sensors + controller: Trane '239 (superheat sensor downstream of LSHX; controller modulating metering device) in view of Unnezaki '700 / US 2016/0131115 A1. Note the possibility that the third sensor position is argued as a mere duplication of known sensor placements (MPEP § 2144.04 — arrangement of known elements).
• Claim 6 — double-pipe or plate: Muto '897, Visteon '326, Lennox '271 ("plate or coaxial tube").
• Claim 7 — two-phase outlet / superheated suction: result of the Trane '239 combination; recited as a condition, not a structure.

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7. Offset: why the examiner may properly have allowed — and the strongest non-obviousness arguments

This is important context and I do not want to overstate the challenger's case.

1. The examiner had these references and still allowed. The record shows US 2016/0223239 A1 and US 2015/0276271 A1 appear in the "Citations (27)" list marked as examiner-cited; the U.S. prosecution sequence was a non-final action (2021-09-14) → one response (2021-12-26) → allowance (2022-01-06). A single-round allowance over references of this closeness suggests the examiner read the references as not teaching the specific 1.7 structure — plausibly because both Trane and Lennox disclose "removal/bypass" in generic terms (check valves, solenoid valves, "any suitable configuration") and via a line-shunting topology, whereas claim 1 recites a bypass pipe connecting the second heat exchanger's own inlet and outlet, a first check valve on that bypass pipe, and a second check valve "at an inlet of the internal heat exchanger." A challenger must show that this specific two-check-valve arrangement, not merely the result of bypassing, would have been obvious.

2. Two internal inconsistencies in claim 1 are real vulnerabilities for whoever relies on it (these were also flagged in the earlier sections and are worth repeating because they cut against a clean obviousness mapping):

   • Limitation 1.7(a) recites a bypass pipe "connecting the refrigerant inlet and the refrigerant outlet of the second heat exchanger." Read literally, that shorts the second heat exchanger itself — not merely the internal heat exchanger — which is inconsistent with the specification's Embodiment 3 (bypass pipe 121 connects the second-heat-exchanger liquid port 11 to the first extension pipe 507, i.e., it bypasses the internal heat exchanger's first passage 100a).
   • Limitation 1.7(c) places the second check valve "at an inlet of the internal heat exchanger," whereas the specification places check valve 123 "between an outlet of the first passage 100a of the internal heat exchanger 100 and the second-heat-exchanger liquid port 11."

   The practical effect is that both the obviousness analysis and any infringement analysis must first resolve what the bypass pipe actually connects. If the bypass is construed (as the specification requires) as bypassing only the internal HX, the Trane/Lennox combination maps more cleanly; if read literally as connecting the second HX's own two ports, the claim recites something the specification does not support and which the prior art would not suggest for that (performance-destroying) purpose.

3. Objective indicia: I found no evidence in this record of secondary considerations (unexpected results, long-felt need, industry praise, copying, licensing) with a nexus to claim 1. The specification's asserted benefits are the expected consequences of the known internal-HX arrangement, which weakens any non-obviousness argument under KSR. Conversely, the near-simultaneous filing of the two Bmil Technologies publications (US 12,313,318 B2; US 12,313,319 B2) citing this patent does not evidence secondary considerations.

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8. What I could not verify (be explicit about this)

• I did not retrieve the full text of JP 2001-227822 A, JP 2003-194432 A, JP 2009-250592 A, JP 2009-299909 A, JP 2011-043279 A, JP 2012-132578 A, JP 5991989 B2, US 2010/0326095 A1, US 2013/0325732 A1, US 2009/0013700 A1, US 2005/0039897 A1, US 2012/0199326 A1, US 2007/0245760-family or the Family Cites Families items (JP 3407441 B2, JP 2001-248922 A, JP 2008-008523 A, JP 2008-121980 A, JP 5627417 B2, DE 102011118761 A1, JP 6323489 B2, FR 3043759 B1). Claims 1 and 4–5 cannot be finally resolved without reading at least JP 2001-227822 A, JP 2009-250592 A, JP 5991989 B2, and US 2009/0013700 A1 in full.
• The only references I verified with descriptive text are US 2016/0223239 A1, US 2015/0276271 A1, US 2018/0112897 A1, US 5,987,907 A, and US 2017/0299241 A1, plus the family members US 10,041,710 B2 and US 11,054,192 that appeared incidentally in search results (not part of the citation list).
• The three non-patent citations on the record (EP extended search report 2021-03-05; ISR 2018-06-19; JP office action 2021-07-06) are prosecution documents, not prior art. The EP/JP office actions may contain the examiner's own obviousness reasoning for the EP 3779326 B1 and JP family members and are the single most useful next source for a ready-made §103 analysis.

Bottom line: There is a strong, articulable KSR-compliant ground against claims 1, 2, 3, 6, and 7 and a workable ground against claim 5, built on US 2016/0223239 A1 + US 2015/0276271 A1 + JP 2001-227822 A / Arkema '095 / Mexichem '732 and (for claim 3) US 2018/0112897 A1. Claim 4 is not established on this record and requires additional prior-art development. Any rejection of claim 1 must confront (i) the examiner's single-round allowance over the very same Trane and Lennox references, and (ii) the literal wording of the bypass-pipe and second-check-valve limitations, which is internally inconsistent with the specification and must be construed before a clean element mapping can be completed.