US 11402326

I'll search for authoritative information on this patent, including any litigation or CAFC docket activity.

Let me check specifically for litigation and CAFC docket activity involving this patent.

Let me do a final check for any assignment, litigation, or post-grant proceedings specific to this patent.

US Patent 11,402,326 B2 — Analyst Summary

Bibliographic data (per the authoritative full text)

Abstract (as issued)

Systems and methods in which multi-dimensional metric monitoring is used with respect to multi-wavelength scattering for smoke detection. A multi-dimensional metric may dynamically track a slope of a relationship between scattered light of multiple wavelengths being monitored. A multi-dimensional metric monitoring smoke detection algorithm may use multi-dimensional thresholds for initiating a fire alarm and resetting the fire alarm. An optical measuring chamber used for providing the multi-wavelength scattering signals may be configured for wide-scattering-angle signal collection, e.g., using a light trapping sub-chamber having a light-guide diaphragm assembly.

Plain-language overview of the independent claims

The claimed invention pairs two ideas: (a) a "slope of a ratio" metric computed over time from two wavelengths of scattered light, judged against thresholds that have both a direction and a magnitude ("multi-dimensional"); and (b) a specific wide-angle optical chamber geometry that produces clean, angle-independent signal trains.

• Claim 1 (method). Shine two different wavelengths into a sample and read the scattered light from a wide-scattering-angle optical chamber. The chamber must contain two light sources and a photosensor, where the sources sit in association with a light-guide diaphragm that defines a light trapping sub-chamber, the sources are fired in alternately pulsed profiles, and the sensor picks up the two wavelengths separately over time. Then compute a ratio of the two signals, compute a multi-dimensional metric from that ratio over time, compare it to a first multi-dimensional threshold, and decide whether smoke is present from that comparison.
• Claim 6 (system). The apparatus counterpart of claim 1: two light sources, a photosensor, an optical measurement chamber housing them in a wide-scattering-angle configuration, and a light-guide diaphragm defining a light trapping sub-chamber so the photosensor is illuminated only by scattered light (never direct light). A processor runs the same ratio → over-time metric → first-threshold → smoke-presence logic.
• Claim 14 (system). Chamber-centric variant: the chamber has first/second light sources and a photosensor in the wide-angle configuration, plus first and second light-guide plates that together form a light-guide orifice juxtaposed with the photosensor, arranged so the photosensor receives only indirect (scattered) illumination. The processor computes the metric as the slope of the ratio and compares it to a first threshold that is itself a slope predetermined for smoke.
• Claim 16 (method). Same signal path, but the metric is expressly the slope of the ratio over time, the first threshold is a slope predetermined for indicating smoke, and the decision is whether the slope exceeds that threshold slope. (No chamber-geometry limitation is recited.)
• Claim 17 (method). Adds the alarm-clearing branch: in addition to the first (smoke-presence) threshold comparison, compare the metric against a second threshold that is a slope predetermined for indicating smoke abatement, and signal abatement when the slope falls below that second threshold slope.
• Claim 18 (system). Processor-side equivalent of claim 16: ratio value → slope metric → first threshold (a smoke-indicating slope) → smoke if the slope is greater than the threshold.
• Claim 19 (system). Processor-side equivalent of claim 17: adds the second, abatement-slope threshold and the "slope less than abatement threshold" determination.

In substance, the independent claims split into two families: claims that are tied to the wide-angle/light-trapping chamber hardware (1, 6, 14), and claims directed purely to the slope-of-ratio + dual-threshold algorithm (16, 17, 18, 19). Claims 2–5, 7–13, and 15 are dependents adding features such as the 45°–90° scattering-angle range, the two-plate/orifice diaphragm structure, curve-fitting of the ratio, and the dual-threshold logic.

Notable prosecution observation

The granted claim 1 is narrower than the published application's claim 1. In US 2022/0099572 A1, claim 1 was a bare "obtain two signals → compute ratio → compute over-time metric → compare to first threshold" claim, with the wide-angle chamber and alternately-pulsed light-guide-diaphragm structure relegated to dependent claims 2–3. Those limitations were moved into granted independent claim 1. This matters for any freedom-to-operate or invalidity analysis: the enforceability scope now turns on the optical-chamber geometry for claim 1, which is why claims 16–19 (algorithm-only) exist as separate independents.

Uncertainty notes

• No litigation, PTAB, or CAFC activity found. My searches returned no evidence of any district court suit, IPR/PGR, or Court of Appeals for the Federal Circuit docket (2026 or otherwise) involving US 11,402,326. I could not confirm or deny a CAFC 2026 docket from the available results, and I will not assert one exists. Absence of results is not proof of absence — a definitive negative would require checking the USPTO Patent Public Search / PTAB APIs and the CAFC CM/ECF docket directly, which I could not complete.
• I noticed an off-target hit in my searches: a UK Companies House "11402326" entry (a company-incorporation number) and a malleable pipe fitting product code "11402326." These are unrelated to the patent and were disregarded, per the instruction to interpret identifiers literally and not conflate them.
• All bibliographic and claim content above is taken from the authoritative patent text supplied; dates and the "active / 2040-12-18" status are the source's own annotations and are not legal conclusions.
• I did not locate the assignee's recorded reassignment instrument beyond the Google Patents annotation showing a 2020-12-22 recordation to "Hong Kong Applied Science and Technology Research Institute Co., Ltd." with assignors Yu, Chan, Mai, and Shi.

Sources: https://patents.google.com/patent/US11402326/en ; https://patents.justia.com/patent/11402326 ; https://patentimages.storage.googleapis.com/09/13/3f/91668ce2a0c878/US11402326.pdf

I'll search for litigation involving US patent 11402326 across patent litigation databases.

Initial results don't show litigation for this patent. Let me search dedicated litigation databases.

Summary: Litigation Search for U.S. Patent No. 11402326

Result: No litigation involving U.S. Patent No. 11402326 was found.

I searched patent-litigation sources (including Justia dockets/CourtListener RECAP, the Unified Patents litigation portal, RPX Insight, and general web/docket searches) for the exact number 11402326. No district-court, CAFC, or PTAB proceedings were located asserting or challenging this patent.

What the patent is

• Patent: US 11402326 B2 — "Systems and methods for multi-wavelength scattering based smoke detection using multi-dimensional metric monitoring"
• Assignee/Owner: Hong Kong Applied Science and Technology Research Institute Co., Ltd. (ASTRI)
• Appl. No.: US 17/033,584; Priority/Filing: 2020-09-25; Granted: 2022-08-02; Adjusted expiration: 2040-12-18 (status: Active)
• Inventors: Zhinan Yu, Chun Chung Chan, Jiangquan Mai, Fangyi Shi
• Related family members: WO2022061980A1 (PCT/CN2020/120693) and CN112384784B (CN202080002439.1A)

Cases

None. For each requested field:

• Plaintiff(s): N/A
• Defendant(s): N/A
• Jurisdiction: N/A
• Case number: N/A
• Filing date: N/A
• Outcome/status: N/A — no litigation identified

Important caveats about search hits

Several search results contained the string "11402326," but none relate to this patent and should not be mistaken for litigation against it:

1. A Ninth Circuit docket number/filing entry (Biederman v. Powell, No. 19-35581) — the "11402326" is a PACER docket-entry stamp, not the patent.
2. A Ukrainian civil court decision (case 2-7458, document no. 11402326) — unrelated pension case.
3. UK Companies House incorporation numbers (e.g., 11402326) — unrelated corporate registrations.
4. A pipe-fittings catalog part number (11402326) — unrelated.
5. The Google Patents citations page listing US11402326B2 among "cited by/related" documents — a bibliographic citation, not a lawsuit.

Confidence and limitations

• I have high confidence that no publicly indexed litigation currently exists for this specific patent, based on the databases searched.
• However, I cannot guarantee exhaustiveness: sealed complaints, very recent filings not yet indexed, ITC Section 337 investigations, foreign proceedings (e.g., in China involving the CN family member), or state-court actions could exist but would not be captured in the sources above. Non-U.S. litigation, if any, would not appear in PACER/CAFC.
• This is an informational search, not a legal opinion or a formal clearance/infringement analysis.

If you want, I can recommend a targeted Docket Navigator or Lex Machina query using the patent number, assignee names (ASTRI / Hong Kong Applied Science and Technology Research Institute), and the inventor names to confirm the null result against paywalled dockets.

I'll verify the structured ODP data against live sources before finalizing.

Initial searches returned noise. Let me run more targeted queries against PTAB dockets and CourtListener.

Proceedings overview

One AIA trial proceeding count: 0. The structured "PTAB proceedings on file" block — sourced from the USPTO Open Data Portal API — returns no IPR, PGR, or CBM proceedings for US 11,402,326 as of the most recent ingest, and my independent web searches (Google Patents/Justia patent pages, PTAB docket aggregators, CourtListener, and general queries tying the patent number and assignee to IPR/PGR activity) surfaced no older or unindexed proceeding to flag. Breakdown by status is therefore: active 0 / claims invalidated 0 / claims sustained 0 / settled 0 / institution denied 0. The bottom-line defensive posture: the patent is un-challenged at the PTAB — it has neither been hardened by surviving an IPR nor softened by having claims canceled. A defendant gets no free kill from the PTAB; any invalidity case must be built from scratch.

Proceedings

None to report. There is no proceeding number, petitioner, panel, institution decision, Final Written Decision, settlement, or appeal to describe, because no AIA trial has been instituted against US 11,402,326. I will not invent a proceeding number or populate the template fields with speculative content.

Verification trail (what I checked, and what it did not show)

• Structured ODP block (canonical): explicitly states no AIA trial proceedings on file.
• Google Patents page for US11402326B2 (https://patents.google.com/patent/US11402326/en): shows prosecution/assignment events only (2020-09-25 filing; 2020-12-22 reassignment to Hong Kong Applied Science and Technology Research Institute Co., Ltd.; 2022-08-02 grant; status Active, adjusted expiration 2040-12-18). No "PTAB" or litigation event entries.
• Web searches for "11402326" IPR, "US 11,402,326" PTAB, and Hong Kong Applied Science ASTRI smoke detector patent IPR returned only patent-family/publication pages (e.g., https://patents.justia.com/patent/20220099572) and unrelated hits. No IPR/PGR docket, no FWD, no CAFC appeal.
• Note on family: the patent has a PCT (WO2022061980A1) and a Chinese counterpart (CN112384784B, "Smoke detection system and method using multi-dimensional indicator monitoring based on multi-wavelength scattering"). Foreign counterparts are not AIA trials and do not appear in the ODP PTAB list; I found no invalidation action there either, but I did not exhaustively search CNIPA proceedings.

Strategic summary

Claim status of US 11,402,326. Because no IPR or PGR was ever filed and no certificate has issued, all 19 granted claims remain in force, unchanged: claims 1–5 (methods), 6–13 (systems), 14–15 (systems), 16–17 (methods), and 18–19 (systems). Independent claims are 1, 6, 14, 16, and 18; they have not been canceled, narrowed, or disclaimed by any AIA proceeding. Nothing is "dead," so a demand letter citing claim 1 (or its system counterparts, claims 6/14/18 and the method variants 16/17) rests on live claims. The only narrowing that exists in the record is prosecution-history narrowing — notably, the granted claim 1 folded in the "wide-scattering-angle signal collection / light-guide diaphragm / light trapping sub-chamber / alternately pulsed profiles" limitations that appeared as dependent claim 3 in the published application US20220099572A1 (compare https://patents.justia.com/patent/20220099572). That is a real prosecution-history estoppel / claim-construction lever for a defendant, but it is not a PTAB invalidation and does not cancel anything.

Estoppel landscape. There is no § 315(e)(2) estoppel against anyone, because no petitioner exists. No third party is barred by a PTAB FWD from raising art in district court, and no IPR has been finally written off, so there are no "already-raised-or-reasonably-could-have-raised" grounds that are foreclosed. Conversely, this cuts both ways: nothing prevents a defendant or a competitor from being the first to file an IPR — but also nothing has been road-tested, so the strongest art (including the pre-AIA references the patent itself cites: US 8,890,700B2, US 9,541,501B2, US 9,685,058B2, CN104392577A) has not been run through an institution decision. Those references are the natural starting kit for a § 103 combination against the "slope of Blue-to-IR ratio + multi-dimensional threshold" limitations, but they were distinguished on the face of the specification and no panel has yet opined on them. A § 101 challenge to the ratio/slope-computing claims is also untested terrain.

Pattern signals. No repeat-petitioner pattern exists (no petitioners at all). No defensive aggregator (Unified Patents, RPX, etc.) appears anywhere in the chain — I found no evidence of such a filing, and the absence of any proceeding is consistent with the patent never having been asserted in a campaign that would attract an aggregator. The patent owner (ASTRI, a Hong Kong R&D institute) has not pursued any PTAB appeal, since there is no adverse PTAB decision to appeal. The patent is ~4 years old (granted 2022-08-02), with a pre-grant priority date of 2020-09-25.

Recommended next steps

• If you are a defendant: treat this as a blank slate. Do not expect a prior IPR to carry your invalidity case — there is none, and no estoppel helps or hurts you. Because a first-filed IPR is available and no panel has construed the claims, a § 102/§ 103 petition built on the art the patent itself distinguishes (US 8,890,700B2; US 9,541,501B2; US 9,685,058B2; CN104392577A, plus any blue/NIR dual-wavelength scattering art) is the highest-leverage move, and filing it first also avoids being the second petitioner facing § 315(e)(2)/§ 325(e)(2) estoppel. The grant-stage narrowing of the "wide-scattering-angle light-guide diaphragm / light trapping sub-chamber / alternately pulsed profiles" limitations (granted claim 1 vs. published claim 3) is your best non-art, prosecution-history argument, particularly for the 45°–90° collection configuration recited in claims 7/14. Also mine the short product lifetime and the Alice/§ 101 angle on the "compute a ratio, fit a slope, compare to a threshold" method claims.
• If you are the patent owner: the patent is intact and un-assailed, which is a clean enforcement position — but note that assertion is usually the trigger for an IPR. Expect the first serious defendant to petition. The claim set is defensible on its face (numerical thresholds, 45°–90° scattering range, specific diaphragm structure), but the broadest method claim 1 recites a computing/ comparing algorithm that invites a § 101 attack.
• Trial-stage milestones: not applicable — there is no pending proceeding, so there is no institution-decision deadline, no oral hearing date, and no statutory one-year FWD due date to track. If a petition is filed, the § 314(b) institution deadline is three months from the patent owner's preliminary response, and the § 316(a)(11) FWD deadline is one year from institution.
• The absence is itself a signal. No PTAB activity on a 2022-granted patent means it has likely not been widely asserted. That is favorable for a defendant facing a first assertion, because you can be the first to frame the invalidity record rather than fight an established FWD — but it also means you cannot lean on any prior panel's claim constructions.

Confidence note: I have high confidence in the "zero proceedings" conclusion given the canonical ODP block plus negative results across Google Patents, Justia, CourtListener, and PTAB docket aggregators. If a brand-new petition was filed within the last few weeks, it may not yet be reflected in either the ODP ingest or search indices; if you need belt-and-suspenders confirmation, search PTAB E2E (https://ptacts.uspto.gov) and the PTAB docket by patent number directly, as I could not retrieve a live E2E docket page from these sources.

I'll research the assignment record for US 11,402,326 across USPTO Assignment Center, Google Patents legal events, and NPE databases.

I found the primary assignment record. Let me verify there are no additional recordings and check for any subsequent transfers or NPE activity.

Let me do a final confirmation search for any subsequent assignment or NPE-related recording.

Assignment Record — US Patent 11,402,326 B2

Owner/chain reconstruction. I retrieved the actual recorded assignment instrument (cover sheet + assignment document) for this patent from the USPTO's assignment repository, rather than relying on aggregator summaries. There is exactly one recorded assignment in the entire chain of title. No post-issuance transfers appear.

Primary record located: http://legacy-assignments.uspto.gov/assignments/assignment-pat-054730-0726.pdf (EPAS ID PAT6464991). Verification entry point: https://assignmentcenter.uspto.gov/ (search patent 11402326).

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Inventors

All four named inventors are ASTRI personnel, all with Hong Kong residential addresses recited in the assignment instrument itself:

Basis for "employer = ASTRI": the assignment instrument carries the ASTRI docket HKAP.P0146US/100113690 and the project/group tag "(Q0727IoTSEN)" (IoT Sensing), and all four assignors conveyed their entire right, title and interest to ASTRI. This is the classic employer-takes-title pattern for a research institute.

Unusual patterns: None evident. Notably un-unusual for a fire-sale precursor: all four inventors executed their assignments on the same date (2020-10-29, per cover sheet) and none is recorded as having separately assigned or disclaimed. There is no evidence that any inventor departed ASTRI within 12 months of filing — I cannot confirm or deny departures from the available records, and I will not infer them. ASTRI has high researcher turnover as a matter of general practice, but no record supports a departure finding here.

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Original assignee

Hong Kong Applied Science and Technology Research Institute Co., Ltd. ("ASTRI") — the entity named on the issued patent and still the current assignee per Google Patents legal events.

• Primary line of business: Government-funded applied R&D and technology transfer. Founded 2000 by the Hong Kong SAR Government; Hong Kong's largest public R&D centre. Patents are, in ASTRI's own framing, "the product" — it licenses/transfers IP to industry rather than manufacturing consumer goods. Portfolio exceeds ~1,500 patents (post-2025 merger with the Nano and Advanced Materials Institute).
• Does it ship a product embodying the claims? No. ASTRI is an R&D/licensing institute; it does not itself market smoke detectors. Its models include ITF platform projects (ASTRI owns all IP, industry partners take non-exclusive licences), contract research, and spin-offs (partner/investor acquires the technology and takes over commercialization). No ASTRI-branded smoke-detector product was identified.
• Current status: Operating (not acquired, dissolved, or in bankruptcy). As of 2025 it was slated to merge with NAMI under an ITC cost-saving plan; that is a supervisory merger of government R&D bodies, not an asset sale or insolvency event.

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Assignment timeline

One assignment only (reel 054730, frame 0726):

• 2020-10-29 (executed) / recorded 2020-12-22 — Reel 054730/0726
  • Conveyance: Assignment ("NEW ASSIGNMENT"; instrument titled "ASSIGNMENT BY INVENTORS" — full right, title and interest, including all divisions/continuations/reissues and foreign counterparts)
  • Assignors: Zhinan Yu; Chun Chung Chan; Jiangquan Mai; Fangyi Shi (all executing 2020-10-29 per cover sheet)
  • Assignee: HONG KONG APPLIED SCIENCE AND TECHNOLOGY RESEARCH INSTITUTE CO., LTD., 5/F, Photonics Center, 2 Science Park East Avenue, Hong Kong Science Park, Shatin, New Territories, Hong Kong
  • Correspondent: R. Ross Viguet, Norton Rose Fulbright US LLP, 2200 Ross Avenue, Suite 3600, Dallas, Texas 75201; email doipdocket@nortonrosefulbright.com; fax (214) 855-8200; docket HKAP.P0146US/100113690. Submitted/executed by Viguet 2020-12-22.
    • Recurrence flag: No recurrence — this correspondent appears on the sole link of this chain. Norton Rose Fulbright is a large general-practice firm doing prosecution work for operating companies and institutions; a single appearance is not an NPE tell under the stated rule.
  • Context: Initial inventor-to-employer assignment — standard employment/prosecution chain perfecting ASTRI's title ~1 month after filing and ~2 months before publication. Not a fire-sale, securitization, or transfer-to-asserter.

No further recorded assignments. Google Patents legal events show only the single "AS / Assignment" entry dated 2020-12-22 and no later owner changes. There is no security agreement, no change-of-name, no corrective assignment, and no transfer to any third party.

(Minor record discrepancy to note, not resolve: the repository header reads REEL 054730 FRAME 0726, while an OCR fragment of the same PDF references frame "0727," and one signature-line OCR reads "Oct 24, 2020" against cover-sheet execution dates of 2020-10-29. Treated as OCR/frame-index noise; the cover sheet dates are controlling.)

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Timeline diagram

timeline
    title Ownership of US 11402326
    2020 : Application filed 25 Sep
         : Inventors assign to ASTRI 29 Oct
         : Assignment recorded 22 Dec
    2022 : Patent granted 2 Aug

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NPE / troll-pattern signals

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Verdict

Insufficient data — the chain consists only of the original inventor-to-employer assignment (reel 054730/0726, executed 2020-10-29, recorded 2020-12-22), with no subsequent recordings.

No NPE/troll-pattern signal is present on any of the eight criteria: the assignee is ASTRI, a Hong Kong government-funded applied-R&D institute whose business model is technology transfer and licensing, not assertion; there is no shell LLC, no known asserter, no cascading transfer, no pre-litigation transfer, no bankruptcy sale, no privateering, and no defensive-aggregator termination. On the available record the patent has never left the hands of its original, non-asserting institutional owner.

Caveats: The Assignment Center/PEDS live interfaces were not directly queryable in this session; the findings rest on the recorded instrument PDF and Google Patents legal events, which agree. Sealed, very recent, or non-U.S. recordings (including any Chinese-family action on CN 112384784 B) would not appear in these sources and are not captured here. This is an informational ownership reconstruction, not a legal opinion.

Verification link: https://assignmentcenter.uspto.gov/ (search "11402326"); direct record: http://legacy-assignments.uspto.gov/assignments/assignment-pat-054730-0726.pdf

I'll research the prior-art citations for US 11,402,326 using the USPTO and patent databases.

The Google Patents page for US11402326B2 lists its examiner citations. Let me verify the details of each reference.

I've gathered the citation data. I hit a step limit before completing every Xtralis detail, so I flag where a reference description is partial.

Prior-Art Analysis — US 11,402,326 B2

Source of the citation list: the Google Patents front-page "Citations" table for US11402326B2 (https://patents.google.com/patent/US11402326/en), cross-checked against the specification's own Background section. Note a distinction that matters for the analysis:

• Group A — Examiner/front-page citations (6): the references Google Patents lists under "Citations (6)."
• Group B — Applicant/specification-cited references (4): the references the spec expressly names and incorporates by reference; these are not in the Google Patents citation table but are prior art the patentee itself identified.
• Group C — "Family Cites Families" (9): sibling-family art, largely duplicative; not primary references.

A threshold point applies to the whole exercise: on the issued claim set, none of these references appears to anticipate any claim under § 102 on its own. Every independent claim (1, 6, 14) recites wide-scattering-angle collection in a chamber with a light-guide diaphragm defining a light-trapping sub-chamber and alternately-pulsed sources; and every independent claim (1, 6, 14, 16–19) recites computing a metric from the ratio over time (i.e., the slope) compared against a multi-dimensional threshold. The art below discloses two-wavelength scattering, ratio formation, and static thresholds — not the time-derived slope metric. So the realistic attack is § 103 (obviousness), and I say so at each entry rather than overclaiming § 102.

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Group A — Front-page / examiner citations

A1. US 5,576,697 A — Hochiki Kabushiki Kaisha (Nagashima & Aizawa)

• Title: "Fire alarm system"
• Dates: JP priority 1993-04-30 (JP 5-103369); US App. 08/229,613 filed 1994-04-19; granted 1996-11-19.
• Disclosure: Scattered-light fire alarm with first/second light-emitting devices lit alternately and one or two photodetectors. Detects the parallel- and perpendicular-polarized components of scattered light relative to the scattering plane, computes the ratio of the two amounts, and compares that ratio to a preset reference value to classify smoke type. Expressly notes a scattering angle range of 60°–140°, preferably 90° (claim 6/7).
• Relevant claim mapping:
  • The alternately-pulsed two-source aspect and the "ratio → compare to reference" architecture touch the general framework of claims 1, 6, 18.
  • § 102: No. It is a polarization ratio of one wavelength, not a ratio of two wavelengths, and it has no over-time slope metric and no light-trapping wide-angle chamber geometry. § 103 reference only (general state of the art for alternately-pulsed two-source scattered-light detection).

A2. US 7,239,387 B2 — Novar GmbH (Politze)

• Title: "Fire detection method and fire detector therefor"
• Dates: DE priority 2002-10-07; US filed 2003-08-26; granted 2007-07-03 (family: DE 10246756, EP 1408469 B1).
• Disclosure: Two wavelengths — one IR (~880 nm) and one blue/UV (~475/370 nm) — emitted from different directions into a measuring volume; forward and backward scattered radiation of each wavelength measured separately; ratios of the weighted forward/backward intensities are formed, compared with stored values, combined, and evaluated to produce an alarm. Explicitly uses the ratio to suppress false alarms from water vapor and other deceptions. Sources pulsed (pulse/pause ~1:20,000).
• Relevant claim mapping:
  • Substantively overlaps the "two wavelengths (blue + IR) → ratio → threshold → alarm/nuisance discrimination" concept in claims 1, 6, 14, 16, 18, and the nuisance-suppression purpose of the two-threshold scheme (claims 4/5, 17, 19).
  • § 102: No single claim. It measures forward vs. backward scattering geometry ratios and uses stored static values, not a slope-over-time multi-dimensional metric; no light-trapping sub-chamber. Strong § 103 reference — arguably the closest single art to the ratio/threshold core.

A3. US 2011/0058167 A1 — Xtralis Technologies Ltd.

• Title: "Particle detection"
• Dates: priority 2007-11-15; published 2011-03-10.
• Disclosure (partial — details not fully retrieved): Multi-wavelength scattered-light particle/smoke detection (aspirating-type family). This is the same Xtralis "particle detection" line that uses multiple wavelengths and scattering measurements to discriminate particle types.
• Relevant claim mapping: Background art for multi-wavelength scattered-light particle discrimination (claims 1, 6). § 103 reference; I could not retrieve the exact passage needed to assert any § 102 mapping, and I will not fabricate one.

A4. US 2011/0221889 A1 — Xtralis Technologies Ltd.

• Title: "Particle detection"
• Dates: priority 2008-06-10; published 2011-09-15.
• Disclosure: Companion Xtralis filing in the same "Particle detection" family as A3 (multi-wavelength scattering / particle classification).
• Relevant claim mapping: Same as A3 — § 103 background for multi-wavelength particle discrimination; no § 102 mapping asserted given I could not retrieve the specific disclosure passages.

A5. US 2013/0135607 A1 — Apparatebau Gauting GmbH (Wedler et al.)

• Title: "Scattered radiation fire detector and method for the automatic detection of a fire situation"
• Dates: priority 2011-11-25; US App. 13/684,786 filed 2012-11-26; published 2013-05-30; granted as US 9,036,150 B2 (2015-05-19).
• Disclosure: Two first radiation sources of a first wavelength and a second source of a longer second wavelength, plus a scattered-radiation sensor, all aimed at a common scattering-volume center. The sensor unit computes scattered-radiation intensity quotients Q₁=I₁(λ₁,fwd)/I₂(λ₂,fwd), Q₂, Q₃ and uses them for the fire decision, including modifying a threshold to reject non-fire aerosols (dust, spray, cigarette smoke). First wavelength ~470–525 nm (blue/green), second ~940 nm (IR); scattering angles ~60°/120°.
• Relevant claim mapping:
  • Directly parallels the "compute a value based on a ratio of the first and second scattered light signals … compare to a threshold" core of claims 1, 6, 16, 18, and the nuisance (non-fire) classification purpose underlying the two-threshold scheme (claims 4/5, 17, 19).
  • § 102: No claim as issued. Its quotients are of instantaneous scattered intensities compared to fixed/stored values or a modified threshold — it does not derive the metric from the ratio over time (no slope) and has no multi-dimensional slope threshold; also no light-guide diaphragm/light-trapping sub-chamber. Very strong § 103 reference for claims 1, 6, 16, 18 (alone or with A1/A2).

A6. US 2015/0228171 A1 — Siemens Schweiz AG

• Title: "Smoke alarm according to the scattered light principle having a two-color light-emitting diode with different sizes of LED chips"
• Dates: priority 2014-02-13; published 2015-08-13.
• Disclosure: Scattered-light smoke alarm using a two-color LED (two emission wavelengths realized as different-size LED chips in one package) with a photosensor — i.e., a compact two-wavelength scattering source.
• Relevant claim mapping: Hardware/background art for the two-different-wavelength light sources recited in claims 1, 6, 14, 18, 19. § 103 reference (source configuration); no § 102 mapping — it addresses a two-color emitter, not the ratio-slope metric or chamber geometry.

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Group B — Applicant/specification-cited references

These four are named in the patent's Background (each "the disclosure of which is incorporated herein by reference") as the art the invention improves upon — and they are the most targeted to the ratio-threshold concept the patent distinguishes.

B1. US 8,890,700 B2

• Description (per the patent's own characterization): "uses a ratio between the signals from the two wavelengths with respect to a static threshold to determine the presence of particles having a size indicative of smoke."
• Mapping: Closest prior art to the ratio-of-two-wavelengths element of claims 1, 6, 16, 18. § 102: No — it uses a static (single-dimensional) threshold, which is precisely the deficiency the '326 patent claims to remedy via the multi-dimensional/slope metric. Its § 102 relevance is confined to the ratio computation, not the claimed metric; § 103 reference.

B2. CN 104392577 A

• Description: "uses an algorithm and a metric based on signals from two wavelengths of scattered light with respect to a static threshold."
• Mapping: Same as B1 — ratio/metric + static threshold core of claims 1/16/18. § 103 reference; not § 102 (static threshold, no slope metric).

B3. US 9,541,501 B2

• Description: "uses two different wavelength light sources disposed to provide narrow scattering angle signal collection to determine the presence of particles having a size indicative of smoke."
• Mapping: Relevant to the two-wavelength sources and — importantly — it is the narrow-angle counterexample the '326 patent distinguishes from its claimed wide-angle (45°–90°) collection (claims 1, 6, 7, 14). § 103 reference; helps frame the wide-angle-chamber limitation but does not anticipate it.

B4. US 9,685,058 B2

• Description: "uses two different wavelength light sources disposed to provide narrow scattering angle signal collection to obtain a metric incorporating signals from two wavelengths … used with respect to static thresholds."
• Mapping: Closest of Group B to the full ratio-plus-metric architecture, but again with static thresholds and narrow-angle collection. § 103 reference for claims 1, 6, 16, 18; not § 102.

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Group C — "Family Cites Families" (9), for completeness

GB 9417484 D0 (Hochiki, light-scattering smoke sensor); JP H1123458 A (Nittan, smoke sensor + monitoring system); CA 2339170 A1 (GSBS Development, light scattering smoke detectors); GB 2397122 B (Appleby, fire detector with low false alarm rate); US 7,692,773 B2 (Luminex, LED-based measurement systems); CN 100394456 C (Novar, fire-identification method); JP 4652716 B2 (Nittan, smoke detector); US 7,802,901 B2 (Cree, LED multi-chip lighting units); DE 502008003347 D1. These are sibling/related-family and peripheral (e.g., LED packaging, general low-false-alarm detectors). They reinforce the general state of the art but are not close § 102/§ 103 art for the metric or chamber claims.

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Bottom-line § 102 / § 103 assessment

No single reference in the citation list anticipates any independent claim under § 102, because none discloses (i) deriving the metric from the ratio over time (the slope) and (ii) comparing it to a multi-dimensional threshold — the two features on which every independent claim turns — and the chamber-family claims (1, 6, 14) additionally require the wide-angle light-guide-diaphragm/light-trapping geometry that none of these shows. The strongest invalidity theories are § 103 combinations, most plausibly a primary reference teaching the two-wavelength ratio (e.g., US 7,239,387 or US 8,890,700) combined with art showing nuisance/threshold discrimination (US 2013/0135607) or wide-angle collection.

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Confidence & limitations

• Group A citations and their dates are taken from the Google Patents front page for US11402326B2; Group B descriptions are the patent's own characterizations (I did not independently verify each reference's full text within my step budget).
• I was unable to fully retrieve the disclosure of the two Xtralis references (A3, A4) and therefore do not assert specific § 102/§ 103 mappings for them beyond noting they are multi-wavelength particle-detection art. Do not treat "partial" descriptions as complete.
• I could not retrieve the actual USPTO Information Disclosure Statement / examiner citation list (PTO-892 / form SB/08) directly; the grouping above is derived from Google Patents and the specification. A definitive § 102/§ 103 mapping would require the prosecution file wrapper (PatentCenter) to see which references the examiner actually applied and how.
• This is technical prior-art analysis, not a legal opinion on validity or infringement.

I'll research the prior art references cited in this patent and check for additional prior art before building the obviousness analysis.

Good, I'm getting useful detail. Let me dig into the two remaining cited references and look for the patent's own prior-art/citation listing.

Obviousness Analysis — US 11,402,326 B2 under 35 U.S.C. § 103

Note on build-on: I do not repeat the bibliographic, abstract, claim-tree, prosecution, or litigation material already generated above. This section takes that claim taxonomy as given (hardware-family independents 1 / 6 / 14; algorithm-only independents 16 / 17 / 18 / 19; dependents 2–5, 7–13, 15) and works the § 103 question.

Note on tool limits: My prior-art retrieval stopped partway through the allotted steps (the last three queries returned a step-limit message). Where I could not independently open a reference, I say so explicitly and rely on the authoritative patent text's own characterization of it — flagged inline. I do not assert text I did not actually see.

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1. The four references identified in the patent's Prior Art section

The patent's Background (§ "Prior Art") names exactly four references, with their disclosures characterized as follows (patent text, authoritative):

Sources: patent text at https://patents.google.com/patent/US11402326/en ; CN 104392577 A at https://patents.google.com/patent/CN104392577A/en .

⚠️ Discrepancy flag (per instructions I flag rather than paper over): I could not independently retrieve the specification text of US 8,890,700 B2 or US 9,685,058 B2 before the step limit, so for those two I am relying on the patent's own summary. That is admissions-by-the-applicant framing, which is ordinarily usable against the applicant, but it is second-hand.

⚠️ Second flag — internal tension in the patent's own characterization. The patent calls US 9,541,501 B2 a narrow-angle reference. The pre-grant publication that appears to correspond to it (US 2016/0153905 A1, "Scattered-light smoke detector having a two-color LED…", inventors Allemann/Schmid/Walker, matching the patent-listing data for US 14/955,101 → US 9,541,501 B2 at https://www.patenthub.cn/cpc/list-[168617](/patent/168617)-18.html ) discloses a forward scattered-light arrangement with a scattered-light angle of 20°–90°, in particular 30°–70°, and alternating pulsing of the two LED chips with a single photosensor, plus an intermediate diaphragm mechanism comprising a diaphragm aperture arranged "so that a large part of the light emitted by the two LED chips passes through the diaphragm aperture in a range of between 50% and 85%" (see https://patentimages.storage.googleapis.com/07/ab/9c/98ff8ad1a4e721/US20160153905A1.pdf ). I treat the correspondence as a strong but unconfirmed inference; the Allemann/Schmid/Walker two-color-LED family is a well-populated one, and I cannot exclude that the publication belongs to a sibling rather than to the '501 patent itself.

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2. Person of ordinary skill in the art (POSITA)

For purposes of the Graham factors, the POSITA here is a designer of photoelectric fire-detection products: a bachelor's degree in electrical, optical, or applied-physics engineering (or equivalent), plus roughly 2–5 years of experience with LED/photodiode optical chambers and embedded alarm-signal processing — or a master's degree with less experience. That person is familiar with (a) Mie/Rayleigh scattering and the fact that short wavelengths scatter more strongly off sub-micron smoke than off multi-micron nuisance aerosols; (b) two-color ("blue/IR") smoke discrimination as a commercial standard; (c) pulsed LED drive and synchronous photodiode sampling; and (d) ordinary time-series techniques (moving averages, exponential smoothing, regression, derivative/rate-of-change estimation) as applied to alarm signals. None of this is in dispute from the specification.

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3. Element-by-element mapping of independent claim 1 (the most constrained independent)

Claim 1 is the most hardware-heavy independent, and therefore the hardest to invalidate. Mapping:

Consequence: Claim 1 is not a close call on nine of ten limitations. It reduces to (i) wide-angle chamber + light-trapping diaphragm geometry and (ii) the slope-of-ratio metric. Both are addressed below.

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4. The three combinations a challenger would run

4.1 Combination A — "Two-color ratio engine + alternating-pulse chamber + rate-of-change logic"

References: US 8,890,700 B2 (or CN 104392577 A / US 9,685,058 B2) + US 9,541,501 B2 (≈ US 2016/0153905 A1) + US 2018/0149590 A1.

What the combination yields: every limitation of claims 16 and 18 verbatim, and every limitation of claims 1 and 6 but for the chamber-geometry limitation.

Motivation to combine (KSR / MPEP 2143 rationales):

1. Same field, same problem, same solution type. All three are photoelectric smoke detectors using two-wavelength scattering to reject steam/cooking aerosols. The Background itself concedes the entire field was addressing this ("The foregoing smoke detector configurations, although generally effective at detecting smoke, are prone to false alarms…"). A POSITA optimizing a two-color detector would as a matter of course consult the two-color LED/optical-chamber art and the two-color algorithm art.
2. Complementary, not overlapping, teachings. The '501/'905 reference supplies the hardware that produces clean, temporally separated two-color samples (alternating pulses, one photodiode, diaphragm aperture). The '700/'577 references supply the algorithm that consumes exactly those samples (ratio → threshold). Combining a known signal-generation front end with a known signal-processing back end is the paradigm case of "combining prior art elements according to known methods to yield predictable results" (MPEP 2143.01).
3. The substitution of a static ratio threshold by a trend/slope metric is a known technique applied to a known device. The Erdtmann family (US 2018/0149590 A1; US 2018/0059008 A1; US 2015/0346086 A1) teaches comparing rate of increase / rate of change of the scattered-light signal against a threshold, explicitly for the purpose of decreasing activation time and separating flaming fires from nuisances — precisely the two deficiencies the '326 patent attributes to the cited static-threshold art ("prone to false alarms… long resetting times after a fire extinguished"). That is KSR's "use of a known technique to improve similar devices in the same way." See https://www.freepatentsonline.com/y2018/0149590.html and https://www.patentsencyclopedia.com/app/20180059008 .
4. Articulated reason to prefer the trend over the static value. The patent's own FIG. 3B narrative supplies it: a static ratio threshold must be set high, so nuisance curves 302/303 eventually cross it (false alarm) while a genuine fire is only caught late. A rate-of-change threshold inverts both errors. Any POSITA viewing those two curves would reach for the derivative.

Reasonably-expected-to-succeed: Yes. Nothing in the combination is unpredictable; the patent concedes as much by describing its "multi-dimensional metric" arithmetic in a single sentence (slope of R over time).

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4.2 Why the "multi-dimensional metric" and "multi-dimensional threshold" language does not save the claims

The specification defines the metric as SlopeR, "having both orientation and magnitude dimensions," and the thresholds TR1/TR2 as establishing an orientation (positive vs. negative slope) and a magnitude. That is simply a signed rate-of-change and a signed rate-of-change limit.

• A rate-of-change comparison to a threshold (Erdtmann) inherently has a sign and a magnitude; art need not use the applicant's coined "multi-dimensional" label. In re Bond, 910 F.2d 831 (Fed. Cir. 1990) — a patentee cannot avoid prior art by giving a known thing a new name.
• The claimed numeric limits are results-effective optimizations, not inventive selections: TR1 "may be set to a value (e.g., 10/(100 s))" between two empirically observed gradient limits (20/(100 s) fire, 4/(100 s) nuisance); TR2 "can be 0/(100 s) to −4/(100 s)… set to a value (e.g., −2/(100 s))." Selecting an operating point within an empirically observed window, expressly for the purpose of straddling it, is routine optimization (In re Applied Materials, 692 F.3d 1289 (Fed. Cir. 2012)).
• The smoothing/fitting of claims 3 and 11 is admitted conventional: "segmented cubic spline fitting," "Savitzky-Golay filter, Kernel smoother, etc." for "fitting measured data into smooth curves." Erdtmann teaches both line fitting (slope) and smoothing/filtering. § 103 is met when the applicant admits the technique is known.

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4.3 Combination B — "Add the wide-angle / light-trapping chamber"

References: Combination A + US 4,181,439 (Cerberus, "Smoke detector with a conical ring-shaped radiation region") and/or US 4,547,675, with US 2008/0246623 / JP 4010455 B2 for angle-dependent collection.

What the addition supplies (claim 1's remaining limitation; cl. 7's 45°–90°; cl. 8/14's two-plate + orifice geometry):

• US 4,181,439 discloses exactly the architecture claimed: a radiation source focused into a ring-shaped region, a receiver "along the cone axis" that is "practically not impinged by direct radiation… however receives from the substantially cone-shaped zone radiation which is forwardly scattered"; screening diaphragms to prevent residual direct radiation from reaching the receiver; and — key — a "rotationally symmetrical plastic body" with ring-shaped shoulders acting in the same manner as the screening diaphragms, ring-shaped scattered-light entry surfaces, and funnel-shaped tapering reflection surfaces that "collect the scattered radiation in a large spatial angular range." Source: https://companyprofiles.justatic.com/patent/[4181439](/patent/4181439) . That is a light-guide diaphragm defining a light-trapping/scattering sub-chamber with a collection orifice juxtaposed to the photosensor, arranged so the photosensor sees only indirect (scattered) light.
• US 4,547,675 teaches two transmitters of different wavelengths, alternating emission (cl. 37–38), and an evaluation circuit forming an output signal from radiation that has passed through the measuring path — plus collimating optics and reflectors at the measuring path.
• US 2008/0246623 / JP 4010455 B2 show that two light-emitting elements at different scattering angles (with different wavelengths) were a routine design axis, and that collection geometry is a tunable parameter in this art.

Motivation to combine:

1. The problem was known and the fix was the conventional one. The '326 patent itself states the defect of prior chambers: narrow-angle collection "often results in low throughput and convoluted angle dependence for nuisances (large particles), causing invalid data points and unreliable calculations." Collecting over a broad angular band to raise throughput and average out angular dependence is the textbook remedy, and Cerberus expressly claims the benefit ("it is possible to have a single radiation receiver detect the radiation emitted from a larger scattering region or range… hence… increased sensitivity").
2. The motivation is created by the chosen metric. Once the metric is a slope of the ratio, the algorithm needs a consecutive, low-noise data stream — the patent says so ("collection of consecutive data points with sufficient signal and eliminated angle dependence to facilitate multi-dimensional metric monitoring"). Cerberus's wide-capture geometry supplies precisely that. This is an articulated, not hindsight, motivation: the algorithm requirement precedes and drives the optics choice.
3. Claimed 45°–90° is nested inside the art's disclosed ranges. US 2016/0153905 A1 (Allemann et al.) discloses forward-scatter at 20°–90°, in particular 30°–70°; the '326 claim 7 range 45°–90° overlaps the broader disclosed range and overlaps the narrower preferred range over 45°–70°. Optimizing a working range inside a disclosed range is routine (ClearValue v. Pearl River Polymers, 668 F.3d 1340 (Fed. Cir. 2012) — obviousness where claimed range overlaps prior-art range).
4. Diode-lens/diaphragm geometry in a molded chamber is a design choice. The two-plate + orifice structure of claims 8/14 is one of a small number of predictable ways to shield a photodiode from direct LED light — a function the Siemens diaphragm-aperture art (US 9,541,501; US 9,569,946 B2, "diaphragm mechanism… to avoid direct LED light on the photo sensor") already performs. See https://patentimages.storage.googleapis.com/a2/cf/65/68c3e56f01de07/US9569946.pdf .

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4.4 Combination C — "Abatement / reset threshold"

Applies to claims 4, 5, 12, 13, 15, 17, 19. Add the dual-threshold teaching of the Erdtmann family to Combination A.

• US 2015/0346086 A1 / US 2015/0103346 A1 disclose comparing the (corrected) two-wavelength ratio to a first threshold (smoke particles present when ratio > threshold) and to a second threshold ("determine the presence of nuisance particles by comparing the ratio… to a second threshold… nuisance particles being determined to be present when the ratio… is smaller than the second threshold"), and expressly contemplate the second threshold being lower than the first. Sources: https://www.freepatentsonline.com/y2015/0346086.html ; https://www.freepatentsonline.com/y2015/0103346.html . Dual, signed thresholds on a two-wavelength metric are therefore squarely taught.
• Resetting an alarm when the condition abates is inherent to the art, and the '326 patent claims nothing more than applying the second threshold to the slope rather than to the ratio.
• Necessary consequence of Combination A. Once smoke is declared on a positive-slope crossing, clearing it on the opposite-signed crossing (SlopeR < TR2, TR2 negative) is the only sensible complementary test; without it the alarm could never clear, and the specification gives no other mechanism. "[A] disclosure… that a result is the necessary consequence of the steps performed" supplies the limitation (In re Kao, 639 F.3d 1057 (Fed. Cir. 2011)).

Under Combination C, claims 17 and 19 — whose whole added content is "second threshold = a slope predetermined for indicating smoke abatement; abatement when slope < that threshold" — collapse into a straightforward substitution of metric (slope for value) in a taught dual-threshold scheme.

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5. Per-claim obviousness bottom line

Overall: The portfolio's § 103 exposure is concentrated in the algorithm-only independents (16–19), which is exactly the point noted earlier — the applicant deliberately moved the chamber limitations into granted claim 1 (narrowing it relative to published claim 1 of US 2022/0099572 A1) while carving out algorithm-only independents. That drafting choice buys enforceability breadth at the cost of obviousness exposure on the narrow claims. The hardware-backed claims 1/6/14 are substantially stronger, and their validity would likely turn on the wide-angle/light-trapping chamber limitation.

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6. The best non-obviousness rebuttals, and why each is weak

6.1 "The art teaches away from wide-angle collection because narrow angles encode particle size."

This is the applicant's strongest argument. The named references US 9,541,501 B2 and US 9,685,058 B2 are characterized as narrow-angle; narrow-angle collection is used precisely because the angular scattering function is size-discriminative, and averaging over 45°–90° can smear that information. Counterpoints: (a) the '326 patent never claims a required angular resolution, only a range, and 45°–90° nests inside the 20°–90° range the Allemann publication itself discloses; (b) Cerberus affirmatively teaches the benefit of wide angular capture; (c) nothing cited states that wide collection is inoperative or inferior — a teaching away requires more than a preference (In re Fulton, 391 F.3d 1195 (Fed. Cir. 2004)); (d) the two-wavelength ratio metric is itself size-discriminative independent of collection angle, blunting the premise. Expectation: this argument likely fails, but it is where a validity fight would concentrate for claims 1/6/14.

6.2 "Criticality of the specific thresholds (TR1 = 10/(100 s), TR2 = −2/(100 s))."

Weak. The specification frames these as values inside empirically observed gradient windows for stated device gain conditions; no unexpected result or criticality is demonstrated, and the ranges are expressly described as adjustable to environment and user preference. That is a hallmark of routine optimization, not of a § 103 rebuttal.

6.3 "No additional sensors needed / fewer components."

An advantage flowing from omitting an element (the added CO/temp/humidity sensors described in the Background) is generally given little weight; deleting a component and its function is prima facie obvious unless the deletion yields an unexpected result (In re Nuvasive, 842 F.3d 1376 (Fed. Cir. 2016) discusses the standard for negative limitations). The record shows no unexpected result.

6.4 Secondary considerations (Graham factor 4).

I found no evidence in the record before me of unexpected results, commercial success, long-felt but unmet need, failure of others, copying, or industry praise tied to this patent. The stated "industry standards beginning to require nuisance rejection" cuts toward motivation in the art, not toward non-obviousness. Absence of evidence is not proof of absence — licensing/Nexis records and the assignee's product literature would need to be checked — but on the current record this factor is neutral-to-negative for the patentee.

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7. Confidence, and what would change the conclusion

High confidence: Claim 1's nine non-geometric limitations are individually and collectively taught by the cited art; alternating pulsing with a single photosensor and a diaphragm aperture is expressly disclosed in the Siemens two-color-LED family; dual signed thresholds on a two-wavelength metric are expressly disclosed in the Erdtmann family; rate-of-change/slope-over-time against a threshold, and line fitting to obtain a slope, are expressly disclosed in Erdtmann; wide-angle collection with light-shielding diaphragms and a scattering sub-chamber is expressly disclosed in Cerberus US 4,181,439. The KSR/MPEP 2143 motivations are articulable without hindsight because the patent's own Background states the problems (false alarms, slow reset) that the secondary references solve.

Material uncertainties I will not paper over:

1. I did not open the specifications of US 8,890,700 B2 or US 9,685,058 B2; their treatment here rests on the patent's own summary.
2. The identification of US 2016/0153905 A1 as the pre-grant publication of US 9,541,501 B2 is an inference from matching title/inventors/application number; if it is a sibling application, the "alternately pulsed profiles" and "diaphragm aperture" teachings still exist somewhere in that Siemens family, but I would not attribute them to the '501 patent without confirmation.
3. I have not verified whether any single reference is an anticipatory § 102 art for claims 16/18; a § 102 attack on those claims should be run directly against the Erdtmann family, whose full specifications I only saw in part.
4. No litigation, PTAB, or CAFC activity was found for this patent (per the earlier sections above); consequently there is no court record of claim construction that would alter the "multi-dimensional" construction argued in § 4.2.

Recommended confirmatory steps for a formal opinion: (i) pull the full facsimiles of US 8,890,700 B2 and US 9,685,058 B2 from USPTO Patent Public Search and confirm the static-threshold and narrow-angle characterizations; (ii) confirm the US 2016/0153905 A1 ↔ US 9,541,501 B2 lineage via the patent's own "Related U.S. Application Data"; (iii) run a § 102 chart of Erdtmann US 2018/0149590 A1 and US 2018/0059008 A1 against claims 16 and 18; and (iv) run an infringement/freedom-to-operate screen against the same two Erdtmann applications, since they are both the best § 103 art and the most likely blocking art in the opposite direction.

Sources: https://patents.google.com/patent/US11402326/en ; https://patents.google.com/patent/CN104392577A/en ; https://patentimages.storage.googleapis.com/07/ab/9c/98ff8ad1a4e721/US20160153905A1.pdf ; https://patentimages.storage.googleapis.com/a2/cf/65/68c3e56f01de07/US9569946.pdf ; http://data.epo.org/pise-server/rest/collections/lgpi/EP0877345B1.pdf ; https://www.freepatentsonline.com/y2015/0346086.html ; https://www.freepatentsonline.com/y2015/0103346.html ; https://www.freepatentsonline.com/y2018/0149590.html ; https://www.patentsencyclopedia.com/app/20180059008 ; https://companyprofiles.justatic.com/patent/4181439 ; https://patentimages.storage.googleapis.com/b1/11/41/b738045e0e5699/US4547675.pdf ; https://www.freepatentsonline.com/y2008/0246623.html ; https://patents.google.com/patent/JP4010455B2/en ; https://patents.google.com/patent/CN109601019B/en ; https://www.patenthub.cn/cpc/list-168617-18.html