US 7162374

I'll search for authoritative information on this specific patent number, including any 2026 litigation activity.

Let me run additional targeted searches for litigation/docket activity and the USPTO record.

US Patent 7,162,374 — Analyst Summary

Source of record: Google Patents full text, https://patents.google.com/patent/[US7162374](/patent/US7162374)/en (fetched 2026-09-30). All identifiers below are reproduced literally as they appear; nothing has been auto-corrected.

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1. Bibliographic data

Caution on one data point: The cover page records the priority as "2002-11-07 … Priority claimed from DE10251891A" while the specification's Cross-Reference section expressly claims priority to two German applications — DE 102 46 747.1 (Oct. 7, 2002) and DE 102 51 891.2 (Nov. 7, 2002) — plus PCT/EP2003/009560. I report both exactly as they appear rather than reconciling them.

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2. Abstract (verbatim)

"A device for determining flow parameters, particularly the temperature and flow speed and changes therein, in a fluid flow for monitoring and a fire recognition or oxygen measuring device provided with such a device are provided. A slow or sudden blockage, crack or break in a pipe system of an aspirative fire recognition device is recognized by a measurement technique, whereby an air flow sensor, operated with a constant excess temperature, is combined with a regulation algorithm, running in a microprocessor, for monitoring pipe system fluid flow or flow resistance. The required resistance of the air flow sensor can thus be calculated by an exact sensor calibration curve and a precise control loop formed. The measured values recorded by the air flow sensor are extremely reliable, such that changes in condition for the flow parameters provide information about the state of the pipe system or the intake system."

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3. Plain-language overview of the independent claims

The patent has 7 claims total; claims 1, 5, 6 and 7 are independent, and claims 2–4 depend from claim 1.

Claim 1 — The core device

A device for measuring flow parameters (temperature, flow velocity, flow resistance and its changes) in a monitored fluid stream, particularly in smoke/gas intake detectors. It has three parts:

• a thermoelectric air flow (air stream) sensor operated in constant-temperature mode;
• a thermoelectric temperature sensor; and
• a regulation circuit that sets a predetermined excess temperature at the air flow sensor, where "excess temperature" is defined in the claim as the difference between the sensor's temperature and the temperature of the fluid being monitored.

The distinguishing features are that (a) the regulation circuit, implemented in a microprocessor, contains a regulation algorithm that operates the air flow sensor at a constant excess temperature (so the sensor's working point does not drift as the fluid temperature changes), and (b) the microprocessor also contains an evaluation algorithm for monitoring fluid flow or flow resistance in the pipe system, which recognizes "nongradual" (i.e., sudden, step-like) fluid flow changes that are not attributable to disruptive ambient influences (such as air pressure or ambient temperature drift). In plain terms: keep the sensor at a fixed temperature above ambient, measure the electrical power needed to do so, and use the electronics to distinguish a genuine sudden event (blockage, break, crack, vandalism of an intake opening) from slow environmental drift.

Claim 2 — (dependent on claim 1) Calculation of flow parameters

The evaluation algorithm is further configured to compute flow parameters from the electric heating power of the air flow sensor — specifically mass stream, flow velocity, volume stream, flow resistance of an intake pipe system, and fluid temperature. (This tracks the specification's equations (1)–(5), including the King-type relation Q = [A + B·(ρ·V)^(1/n)]·(ΔT − T) and P = I²·R.)

Claim 3 — (dependent on claim 1) Density compensation

The evaluation algorithm includes compensation for a temperature-dependent and/or pressure-dependent density change of the fluid flow, so that the measured power is not corrupted by density variation (optionally using an absolute air-pressure sensor and a stored correction-factor table).

Claim 4 — (dependent on claim 1) Memory of starting values

The microprocessor contains a memory for storing starting values of the flow parameters, which the evaluation algorithm uses to compute status changes (i.e., long-term drift, gradients) in those parameters against a baseline captured at start-up.

Claim 5 — Assembly with the detector in the pipe system

An assembly of: (a) a pipe system for taking air samples from a target space; (b) a detector receiving those samples; and (c) the flow-parameter determination device of claim 1's type disposed in the pipe system (thermoelectric air flow sensor + microprocessor with the constant-excess-temperature regulation algorithm and the nongradual-flow-change evaluation algorithm). In effect, the same inventive core recited in an aspirating (aspirative) fire/gas detection installation context.

Claim 6 — Assembly with sensor in the center of the air entry channel

Same assembly structure as claim 5, but the detector has an air entry channel with a center, and the flow sensor is disposed in the center of that air entry channel. Purpose per the specification: central placement brings the electrical components into one unit and improves measurement consistency.

Claim 7 — Assembly with sensor in a narrowed cross-section

Same assembly structure as claim 5, but the detector's air entry channel has a portion narrowed in cross-section, and the flow sensor sits in that narrowed portion, so the local flow velocity (and hence sensor dynamics/sensitivity) is increased to resolve very small flow changes.

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4. Litigation / docket check — and explicit uncertainty

• I searched for the patent number in connection with CAFC 2026 dockets and infringement/litigation reporting and found no Federal Circuit appeal, district court case, or PTAB proceeding involving US 7,162,374.
• I cannot confirm this as an authoritative negative. My searches did not return a docket-level database hit either way, and I have no access to a live PACER/Docket Alarm query result for this number. Treat "no litigation found" as absence of evidence in the sources I could reach, not as a verified clearance.
• What the record does show: the patent lapsed on 2019-01-09 for failure to pay maintenance fees and is flagged Expired – Fee Related, with anticipated expiration 2023-08-28. A lapsed patent is generally not a live infringement vehicle as of 2026.
• Forward citations of note (third-party references to this patent) include US 9,134,716 B2 (Siemens Schweiz AG, "Detection of blockages and interruptions with an aspirating smoke detector (ASD)") and US 11,609,144 B2 (Carrier Corporation, "Detection of leakage in an aspirating fire detection system"), showing this disclosure remains cited in the aspirating-detection art. Wagner's own later filings EP 4,530,611 A1 / WO 2025/068,492 A1 ("Particle detection unit with integrated air flow sensor…") cite the family.

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5. Bottom line

US 7,162,374 (Burkhardt / Wagner Alarm- und Sicherungssysteme, now Wagner Group GmbH) claims a microprocessor-regulated constant-excess-temperature air-flow sensor system — rather than the prior-art Wheatstone-bridge constant-absolute-temperature anemometer of FIG. 1 — paired with an evaluation algorithm that distinguishes sudden, non-environmental flow changes to detect blockages, cracks or breaks in the intake pipe system of an aspirative smoke/gas detector or oxygen-measurement device. Claims 5–7 wrap the same core into an aspirating-detector assembly, with claim 6 adding center-of-channel sensor placement and claim 7 adding sensor placement in a narrowed channel cross-section. The patent is expired and I found no 2026 CAFC or litigation activity, though that negative is not authoritatively verified.

I'll run targeted searches across patent-litigation sources for this specific number.

The initial broad searches returned unrelated hits (e.g., a '374 patent in tire-pressure cases, a Lithuanian registry notice numbered 7162374, PTAB cases for other patents). Let me run more precise, source-directed queries.

Answer: No litigation involving US Patent 7,162,374 is known

I searched for litigation specifically on US Patent 7,162,374 (US App. 10/530,386; Burkhardt; Wagner Alarm- und Sicherungssysteme GmbH → Wagner Group GmbH). I found no district court case, ITC Section 337 investigation, PTAB proceeding, or CAFC appeal asserting or challenging this patent. Because there is no case to report, the requested per-case fields (plaintiff, defendant, jurisdiction, case number, filing date, status) cannot be populated — there is no litigation to list.

Date discrepancy flagged: the task header states "Current Date: April 26, 2026," while the system/environment date and the patent-fetch timestamp are 2026-09-30. I have not reconciled these; treat the findings below as applying to both dates (nothing in the intervening five months changes the analysis, since the patent lapsed in 2019).

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1. Searches run and what they returned

The last three queries returned without usable results because I exhausted my search budget. I therefore cannot claim an exhaustive search. The three that did complete produced zero references to this patent in any litigation context.

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2. Hits examined and rejected as false positives (do not repeat these as this patent)

These appeared in results and are not US 7,162,374:

• U.S. Patent No. 5,463,374 — tire-pressure monitoring / RKE licenses, Signal IP, Inc. v. American Honda Motor Co., Signal IP v. Mazda, C.D. Cal. Nos. LA CV14-02454 JAK, LA CV14-02962 JAK, LA CV14-03109 JAK, LA CV14-03111 JAK, SA CV14-00491 JAK. Different patent, different art.
• U.S. Patent No. 10,251,374 — referenced in an answer/amended-complaint (Meridian, Count 6, indirect infringement). Same last three digits, entirely different patent.
• "Winet Labs LLC v. Apple Inc." and the SiRF v. ITC, 601 F.3d 1319 discussion — refer to some other '374 patent, not this one.
• "Pranešimo Nr. 7162374" — a Lithuanian companies-registry (registrucentras.lt) filing notice number, not a patent.
• "7162374 VALERIA IANK E FREITAS" — a Brazilian JUCISRS registration listing, not a patent.
• Various Unified Patents PTAB exhibits (IPR2019-00635, IPR2020-01201, IPR2020-01338, etc.) — these list other patent numbers; none lists 7,162,374.

I am flagging these explicitly so that no one downstream mistakes a similar-numbered matter for litigation on this patent.

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3. Why a negative is plausible here (context, not proof)

The bibliographic record in the patent text is consistent with a patent that was never litigated:

• Expired – Fee Related. Per the Google Patents legal events, the patent lapsed 2019-02-11 for failure to pay maintenance fees, effective 2019-01-09 (37 CFR 1.362), with "Anticipated expiration 2023-08-28." A patent that lapsed seven-plus years ago is an unlikely vehicle for a live 2026 infringement suit.
• No PTAB trial found. Post-grant challenges to this patent would appear in the PTAB/CASELIST-type sources; nothing surfaced.
• The family (EP 1549916 A1, JP 2006-502392 A, AU 2003258682, WO 2004/034001 A1) shows no enforcement activity in the results either.
• Forward-citation activity is technical, not adversarial. US 9,134,716 B2 (Siemens Schweiz, aspirating smoke detector blockage detection) and US 11,609,144 B2 (Carrier, aspirating fire-detection leakage) cite this patent as prior art — i.e., it is being cited by others, not asserted by its owner. Wagner's own later EP 4,530,611 A1 / WO 2025/068,492 A1 filings also cite the family.

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4. Verification limits — stated plainly

As a matter of professional candor, I must be precise about what "no litigation known" means here:

1. I could not query PACER, the Federal Circuit docket, or the Unified Patents litigation caselist directly. The Unified Patents CASELIST and Docket Alarm are gated/subscription resources; my web searches surfaced only their public excerpts, none matching this patent.
2. My search budget was exhausted, so three intended queries did not complete (§1).
3. Searches were limited to indexed public web content. A docket is not required to be indexed, and settled or dismissed cases can leave thin public traces.
4. Accordingly: "No litigation found" = absence of evidence in the sources I could reach, not a verified negative. It is not a freedom-to-operate clearance and should not be relied on as one.

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5. Recommended next steps to convert this into a verified negative

• Direct query of PACER (D.D.C., D.N.J., E.D. Tex., and Wagner's likely fora) and the Court of Appeals for the Federal Circuit docket by patent number.
• Docket Alarm / Lex Machina / Unified Patents CASELIST patent-profile lookup for 7,162,374.
• USPTO Patent Trial and Appeal Board and USPTO Patent Center / Assignment records for any post-grant or reissue activity.
• ITC EDIS search for Section 337 complaints naming the family (aspirating smoke/gas detection).
• Wagner Group GmbH corporate/enforcement history, given the 2012 merger chain (Wagner Alarm- und Sicherungssysteme → Wagner Deutschland → Wagner Group).

Bottom line: Based on the sources I could reach, there is no known litigation involving US 7,162,374, and the patent's lapse in 2019 makes ongoing enforcement unlikely — but this is an unverified negative, and I recommend a direct PACER/PTAB/CASELIST lookup before relying on it.

I'll verify the canonical "no proceedings" block against live sources before finalizing.

Proceedings overview

Total AIA trial proceedings on file for US 7,162,374: zero (0). The canonical structured block in this prompt — sourced from the USPTO Open Data Portal — returns no IPR, PGR, or CBM proceeding, and no post-grant review is docketed against this patent. The breakdown is therefore: 0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denials. Bottom-line defensive posture: claims 1–7 of US 7,162,374 are entirely untested at the PTAB. There is no FWD to hand a court, no cancellation to fall back on, and — critically — no § 315(e)(2) estoppel binding anyone. Any defendant facing assertion today stands where the first challenger has always stood: the entire claim set is presumptively valid under § 282 and must be attacked from scratch, but the path is also unobstructed, because no petitioner has burned any ground.

One structural point drives the whole analysis: the patent lapsed on 2019-01-09 for nonpayment of maintenance fees (37 CFR 1.362), flagged "Expired – Fee Related," with an anticipated expiration of 2023-08-28. A lapsed patent does not stop an AIA petition — the Board has entertained IPRs on expired patents — but it does collapse the economic motive to file one. That is very likely why this docket is empty, and it is a more plausible explanation than "the claims are so strong nobody bothered."

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No proceedings to report

Per the operating constraints, I will not invent proceeding numbers. There is nothing to list in the per-proceeding format, and I decline to manufacture entries.

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Strategic summary

Claim status: all seven claims UNTESTED. No claim of US 7,162,374 has ever been canceled, confirmed, or even construed by the Board. Independent claim 1 (the microprocessor-implemented constant-excess-temperature regulation algorithm plus the evaluation algorithm "recognizing nongradual fluid flow changes not based on disruptive ambient influences"), dependent claims 2–4, and independent assembly claims 5, 6, and 7 each remain exactly as issued on 2007-01-09. For a defendant, that means the prior-summary's "hardened / survived IPRs" framing does not apply — but neither does the "claims are dead, stop writing demand letters" framing. The patent's defensive picture is neutral-and-stale: untested at the PTAB and unenforceable-in-fact because it lapsed.

Estoppel landscape: empty, in both directions. Because no petition was ever filed, § 315(e)(2) estoppel binds no one. A defendant contemplating an IPR is free to choose any ground — § 102 or § 103, on any combination of references — with no risk that a prior petitioner's institution decision or FWD narrows the field. Equally, the patent owner cannot point to any Board finding in its favor to raise the cost of challenge. The prior-art field is fully open: the prosecution-cited references (DE 3810240 A1; US 4,846,133; US 4,946,555; US 5,339,687 / DE 69011099 T2; CH 683800 A5; DE 4407209 A1; US 2001/0025526 A1; DE 19605638 C1 (Wagner Alarm Sicherung); DE 19924400 C1 (Securiton AG); US 6,450,024 B1) were never tested in a contested forum, and neither was the foreign search-report art (JPS 5965720, JPS 6134422, JP 2756256 B2, JP 3312712 B2, JP 3356990 B2, etc.) that appears in the family-cites list. Any of these could still be paired and asserted in a fresh petition.

Pattern signals: none. No repeat petitioner, because there is no petitioner at all. No defensive aggregator — I found no Unified Patents, RPX, or other aggregator involvement in this patent (searches returned only Unified's unrelated patent-portal page for a Wagner scattered-light detector, AU-2019290965-A1, not this patent). No patent-owner appeal activity, because there has been no adverse Board decision to appeal. The only litigation-adjacent signal in the record is forward citation: US 9,134,716 B2 (Siemens Schweiz AG, "Detection of blockages and interruptions with an aspirating smoke detector (ASD)") and US 11,609,144 B2 (Carrier Corporation, "Detection of leakage in an aspirating fire detection system"), plus Wagner's own later filings EP 4,530,611 A1 and WO 2025/068,492 A1 ("Particle detection unit with integrated air flow sensor…"). That tells you the technology is live and commercially relevant; it says nothing about the validity of these particular claims.

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Recommended next steps

• If you are a defendant being asserted against, lead with status, not invalidity. The patent expired for failure to pay maintenance fees effective 2019-01-09 and Google Patents records Google's legal-status flag as Expired – Fee Related with anticipated expiration 2023-08-28 (source: https://patents.google.com/patent/US7162374/en, "Legal Events": LAPS event 2019-02-11, description "PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362"). Demand damages/royalty demands based on post-2019-01-09 conduct are defective on their face, and there is no possibility of an injunction. Note that a lapsed patent can in principle be revived for unintentional lapse under 35 U.S.C. § 41(c) / 37 CFR 1.378, so verify current fee status with the USPTO Patent Center before relying on lapse alone.
• No PTAB decision to link. There is no FWD and no institution decision for this patent, so I cannot "link explicitly to the FWD and quote the disposition" — nothing exists to quote. The absence is confirmed against the USPTO Open Data Portal block in this prompt.
• If you nevertheless want a PTAB track, confirm the window first. For an unexpired patent, the § 315(b) one-year clock runs from service of a complaint alleging infringement; check whether any complaint has been served, because it starts the clock. For this patent, weigh whether an IPR is worth filing at all given the expired term — the practical answer is usually no. Realistic verification steps: query the PTAB E2E / P-TACTS case search (https://ptacts.uspto.gov/ptabweb/) and the USPTO PTAB API (https://developer.uspto.gov/ptab-api/) directly for application 10/530,386 and patent 7,162,374; and search CourtListener (https://www.courtlistener.com/) for the patent number to confirm no CAFC appeal referencing it exists.
• Watch the live family instead. Wagner's current-generation filings — EP 4,530,611 A1 and WO 2025/068,492 A1, both priority-dated 2023-09-28 — are the commercially operative continuation of this subject matter. Freedom-to-operate analysis aimed at 2026 products should be directed there, not at this 2002-priority patent.

Caveat on completeness: the negative above reflects (a) the canonical zero-count block provided in this prompt and (b) live searches that surfaced no IPR/PGR/CBM or appeal involving US 7,162,374. I did not obtain a direct, docket-level database hit from PTAB E2E or PACER. Treat "no PTAB activity" as well-supported but not independently docket-verified; a direct E2E query is the confirming step and is cheap to run.

I'll verify the assignment chain and check for any records or litigation I might have missed.

Ownership & Assignment Analysis — US 7,162,374 B2

Patent: US 7,162,374 B2 · App. 10/530,386 · Device for the determination of flow parameters for a fluid and method for operating such a device
Verification portals: USPTO Assignment Center · Assignment Search index
Evidence base for this section: the legal-events record reproduced in the authoritative full text supplied above (which carries reel/frame identifiers for all three recordings), plus corroborating corporate sources cited inline.

Scope note / limitation, stated up front. Google Patents' legal-events feed reproduces each assignment's reel/frame, conveyance, assignor, assignee and effective date, but it does not expose the correspondent of record (the attorney or firm that filed the recording). I attempted to retrieve the underlying USPTO Assignment Center abstracts for reels 016532/0585, 027970/0293 and 028003/0388; my searches returned no matching abstracts, and I did not obtain a live Assignment Center query result. I therefore report the correspondent field as not retrieved rather than guessing it. Nothing below is inferred from entity naming alone.

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Inventors

Unusual-pattern check: nothing anomalous.

• There is no inventor fragmentation — a single inventor, so no co-inventor scatter across competing later assignees.
• No evidence of inventor departure. The only recorded act by Burkhardt on this record is a routine assignment of the entire interest to the original assignee (reel 016532/0585, executed 2005-03-11). That is the normal employee-inventor → employer conveyance, not a divestiture. There is no recorded release, nunc pro tunc re-assignment back to him, or later personal assignment out.
• Timing is ordinary, not fire-sale-precursor. The inventor→company assignment was executed 2005-03-11 and recorded 2005-05-09 — i.e. roughly 18 months after the 2003-08-28 US/PCT filing and while prosecution was pending. A fire-sale tell would be the opposite: an operating assignee shedding rights, or all inventors departing within 12 months of filing. Neither appears here.

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Original assignee

Entity named on the issued patent (original assignee): Wagner Alarm- und Sicherungssysteme GmbH, Germany.

Primary line of business. Technical fire-protection and fire-prevention systems — the aspirating ("aspirative") smoke detection line marketed as TITANUS®, the oxygen-reduction active fire-prevention line OxyReduct®, extinguishing systems FirExting®, and the VisuLAN® hazard-management platform. The company describes itself as a German family business founded in 1976, active in fire protection for ~40 years, with ~700 patents and ~500 employees (revenue ~EUR 85 M in FY 2015/2016). See Wagner Group corporate materials: https://www.wagnergroup.com/fileadmin/user_upload/documents/Press/WAGNER_auf_der_Security_2016_-_Pressevorbericht.pdf and https://www.wagnergroup.com/fileadmin/user_upload/documents/Press/Pressemitteilung_WAGNER_Gremienarbeit.pdf

Did they ship a product embodying the claims? Yes — strongly evidenced. The invention is an air-flow/flow-resistance monitoring arrangement inside the intake detector of an aspirating smoke/gas detection system (specification FIGS. 3, 4a, 4b), and Wagner's own product literature advertises "Luftstromüberwachung PIPE-GUARD" (air-flow monitoring) among the feature set of the TITANUS® aspirating detectors: https://www.wagnergroup.com/fileadmin/user_upload/documents/Press/WAGNER_auf_der_Security_2016_-_Pressevorbericht.pdf Wagner also holds VdS/CE conformity certification (EN 54-20) for the TITANUS MICRO-SENS® / RACK-SENS® aspirating detector series, placed on the market by WAGNER Group GmbH, Schleswigstraße 1–5, DE 30853 Langenhagen — a real manufacturing/HQ address, not a registered-agent mail drop: https://aguilera.es/documentacion/Detecci%c3%b3n%20Aspiraci%c3%b3n/Manuales/aetr-manual-en.pdf

Current status: Operating. The asset is held by Wagner Group GmbH (Langenhagen, Germany), reached via an internal merger and a name change — see the timeline below. Wagner Group is an active, ongoing concern that is still filing (its own later EP 4 530 611 A1 / WO 2025/068 492 A1, "Particle detection unit with integrated air flow sensor…", claim priority to 2023-09-28 and cite this family) and still litigating/opposing in its own name (see NPE signal 7 below). No bankruptcy, no receivership, no dissolution appears anywhere in the record.

The patent itself, however, is dead. Google Patents records a lapse for nonpayment of maintenance fees on 2019-02-11 (effective 2019-01-09, 37 CFR 1.362), status Expired – Fee Related, with anticipated expiration 2023-08-28. Wagner chose to stop paying — the rational move for an owner practicing the technology internally — rather than the patent being seized or sold off.

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Assignment timeline

Three recordings exist. All three move the patent along one corporate family tree; none transfers it outside the Wagner organization. The chain is short, fully internal, and terminates at an operating company.

1. Executed 2005-03-11 / recorded 2005-05-09 — Reel 016532/0585 (per the supplied Google Patents legal-events record: "ASSIGNMENT OF ASSIGNORS INTEREST; ASSIGNOR: BURKHARDT, LUTZ; REEL/FRAME: 016532/0585", effective date 20050311)

• Conveyance: Assignment (of inventors' interest)
• Assignor: Burkhardt, Lutz (the sole inventor)
• Assignee: Wagner Alarm- und Sicherungssysteme GmbH, Germany
• Correspondent: Not retrieved. The record I could access does not expose the correspondent field, and a targeted search on the reel number returned no abstract. Flagging the method here so the tell is not lost: if a correspondent does appear on 016532/0585, the relevant question is whether that same attorney/firm recurs on the 2012 Wagner recordings or on recordings for unrelated patents.
• Context: Routine employee-inventor → employer conveyance; secures title in the original assignee during pendency. Not a sale, not a securitization.

2. Effective 2008-01-02 / recorded 2012-04-02 — Reel 027970/0293 (record: "MERGER; ASSIGNOR: WAGNER ALARM-UND SCHERUNGSSYSTEME GMBH; REEL/FRAME: 027970/0293")

• Conveyance: Merger
• Assignor: WAGNER ALARM-UND SCHERUNGSSYSTEME GMBH — reproduced literally as the record spells it; note the recorded spelling "Scherungssysteme", which differs from "Sicherungssysteme" as used elsewhere. Per the operating rules I am not auto-correcting this; it is almost certainly a transcription variant of the same company, but the literal string is what the record shows.
• Assignee: Wagner Deutschland GmbH, Germany
• Correspondent: Not retrieved (same limitation as above).
• Context: Internal reorganization — a German-law merger of the original operating entity into an intermediate holding/operating company (Wagner Deutschland GmbH). Note the ~4.25-year gap between the 2008-01-02 effective date and the 2012-04-02 recording date; this is a bulk re-recording of a corporate transaction, not a negotiated transfer of this patent.

3. Effective 2008-02-05 / recorded 2012-04-06 — Reel 028003/0388 (record: "CHANGE OF NAME; ASSIGNOR: WAGNER DEUTSCHLAND GMBH; REEL/FRAME: 028003/0388")

• Conveyance: Change of Name
• Assignor: Wagner Deutschland GmbH
• Assignee: Wagner Group GmbH, Germany
• Correspondent: Not retrieved (same limitation).
• Context: Change of name only — no change in beneficial ownership; this is the same corporate person renamed to the group brand. It is the terminal link in the chain, and the assignee named there remains the current owner (matching Google Patents' "Current Assignee: Wagner Group GmbH").

If the Assignment Center shows no further records for this patent after reel 028003/0388, that is itself the finding: the patent never left the Wagner organization, and no later assignment exists to any licensing entity. (Because I could not open a live Assignment Center query — see the scope note — I report "no further records appear in the authoritative full text supplied" rather than asserting a verified negative. The USPTO record should be re-queried directly at https://assignmentcenter.uspto.gov/ before this is relied on.)

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Timeline diagram

timeline
    title Ownership of US 7162374
    2002 : German priority filings by Wagner
    2003 : PCT and US application filed
    2005 : Inventor Burkhardt assigns to Wagner
    2007 : US 7162374 B2 issued
    2008 : Merger into Wagner Deutschland
         : Group renamed Wagner Group GmbH
    2012 : Both 2008 events recorded at USPTO
    2019 : Lapsed for unpaid maintenance fees

(Note on the diagram: the 2008 merger and name-change events were executed in Jan/Feb 2008 but only recorded at the USPTO in April 2012 — the diagram places them at 2008, their execution year, consistent with the reel entries above.)

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NPE / troll-pattern signals

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Verdict

Operating-company assertion.

The complete recorded chain is three intra-family links — Burkhardt → Wagner Alarm- und Sicherungssysteme GmbH (reel 016532/0585, executed 2005-03-11), then merger into Wagner Deutschland GmbH (reel 027970/0293, effective 2008-01-02), then name change to Wagner Group GmbH (reel 028003/0388, effective 2008-02-05) — with no transfer to any third party, no licensing entity, and no aggregator at any point, so every one of the eight NPE signals is not present (only signal 3, repeat correspondent, is unclear solely because the correspondent field was not retrievable). The owner is a German family operating business that ships certified aspirating smoke detectors practicing the claims (TITANUS® with PIPE-GUARD air-flow monitoring, EN 54-20/VdS certified) and enforces its rights directly against competitors — EPO oppositions against Carrier (2025-09-29) and Honeywell (2025-07-03) and the FX Prevent litigation on sibling EP 1 062 005 — which is the definition of operating-company rather than NPE behavior. Caveat for accuracy: I found no US assertion of this particular patent, and the patent has been Expired – Fee Related since 2019-01-09 (anticipated expiration 2023-08-28), so the verdict describes the character of the owner and its enforcement posture, not a live US assertion of US 7,162,374.

Verify at: https://assignmentcenter.uspto.gov/ (search by patent number 7162374 or application 10/530,386) — specifically, pull the abstracts for reels 016532/0585, 027970/0293 and 028003/0388 to fill the one gap I could not close, the correspondent of record on each.

I'll verify the USPTO record and pull details on each cited reference.

Key finding — the search surfaced a closely related Wagner/Burkhardt reference (DE 196 05 637) not in my earlier summary. Let me pull details on the cited references.

Prior-Art Analysis — US 7,162,374 B2

A note on sourcing before I begin. You asked me to search the USPTO database for patent number 7162374 specifically. In this session my searches returned the record via Google Patents (full text), Justia Patents, FreePatentsOnline and EPO publication-server documents, not a direct USPTO PatentCenter/Patent Full-Text (PatFT) page. The bibliographic data below is taken from the patent's own front page as reproduced on Google Patents (source of record: https://patents.google.com/patent/US7162374/en), which is the same data USPTO publishes. Do not treat any of my "no anticipation" or "anticipates" statements as a legal conclusion — they are technical-analyst assessments.

Also flagging a minor inconsistency in the assignment: the current task states the date is April 26, 2026, whereas the fetched record and prior-section header are dated 2026-09-30. It does not affect the analysis, but I note it rather than silently reconciling it.

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1. Confirmed bibliographic identity (no auto-correction applied)

Legal framework for the §102 tags below. This is a pre-AIA case (filed 2003-08-28). Because the U.S. filing date is 2003-08-28, the §102(b) critical date is 2002-08-28 (one year before U.S. filing; foreign priority does not move this date). US 6,450,024 B1 published 2002-09-17 — after that critical date — so it can only be §102(e) art (U.S. patent, applied for 2001-03-07). Everything else on the front page published before 2002-08-28 and is §102(b) art.

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2. The 11 patent citations on the front page

The page presents two overlapping lists ("Citations (9)" and "Patent Citations (11)"). The union of 11 references is below. Note the internal inconsistency: the 9-item list omits US4846133A and DE69011099T2, which appear in the 11-item list. I reproduce all 11 rather than picking one list.

Framing point that governs every entry

Claim 1's characterizing features are two:

• (a) a microprocessor regulation algorithm holding a constant excess temperature ΔT at a thermoelectric air-flow sensor (ΔT defined as sensor temp − fluid temp), i.e. constant temperature difference, not the prior-art constant absolute temperature; and
• (b) an evaluation algorithm for monitoring fluid flow or flow resistance in the pipe system that recognizes "nongradual" fluid-flow changes not based on disruptive ambient influences.

Claims 5–7 each incorporate the claim-1 device into an aspirating-detector assembly. Therefore no reference can anticipate claims 5, 6 or 7 unless it anticipates claim 1 and adds the pipe system/detector. Each entry is assessed against that bar.

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2.1 DE 38 10 240 A1 — Mitsubishi Electric Corp

• Citation: DE 38 10 240 A1, "FUEL CONTROL DEVICE," Mitsubishi Electric Corp.
• Priority/filing: 1987-04-09 · Published: 1989-02-23
• Type: §102(b) (published >1 yr before U.S. filing)
• Description: Engine fuel-control art. A hot-wire/hot-film air-flow signal is used for fuel metering; typically includes intake-air temperature compensation for the flow sensor.
• §102 assessment: Discloses the generic thermal (hot-wire) flow-measurement element only. Discloses neither the microprocessor constant-excess-temperature regulation nor pipe-monitoring/nongradual-change recognition. Does not anticipate any of claims 1–7. Possible §103 background for the "thermoelectric air flow sensor" element.

2.2 US 4,846,133 A — Mitsubishi Denki Kabushiki Kaisha

• Citation: US 4,846,133 A, "Fuel control apparatus," Mitsubishi Denki K.K.
• Priority/filing: 1987-04-09 · Published: 1989-07-11
• Type: §102(b)
• Description: U.S. counterpart of the DE 38 10 240 A1 family — fuel control using a thermal air-flow meter.
• §102 assessment: Same as 2.1. No anticipation of any claim; background art only.

2.3 US 4,946,555 A — Canadian Liquid Air Ltd. / Air Liquide Canada

• Citation: US 4,946,555 A, "Apparatus and method for measuring vent gas flow rates and parameters in pulp and paper processing."
• Priority/filing: 1989-01-19 · Published: 1990-08-07
• Type: §102(b). (Flagged with an examiner-citation asterisk on the Google Patents list.)
• Description: Industrial thermal measurement of vent/process gas flow rate and gas parameters; a thermally-based flow measurement with correction for gas conditions.
• §102 assessment: Industrial process gas flow, no aspirating-detector pipe system and no constant-excess-temperature microprocessor regulation. Does not anticipate claims 1–7. Only marginal relevance to the §103 backdrop for claim 3 (temperature/pressure-dependent density compensation).

2.4 US 5,339,687 A — Endress & Hauser Limited

• Citation: US 5,339,687 A, "Flowmeter," Endress & Hauser Limited.
• Priority/filing: 1989-02-18 · Published: 1994-08-23 (grant)
• Type: §102(b)
• Description: A flowmeter (thermal/flow-sensing) of the Endress & Hauser line.
• §102 assessment: No anticipation of claims 1–7. Generic flowmeter art.

2.5 DE 690 11 099 T2 — Endress & Hauser Ltd., Manchester

• Citation: DE 690 11 099 T2, "FLOWMETER," Endress & Hauser Ltd., Manchester.
• Priority/filing: 1989-02-18 · Published: 1994-12-01
• Type: §102(b)
• Description: German translation of the EP member of the same US 5,339,687 A family (item 2.4). It appears in the 11-item list but not the 9-item list.
• §102 assessment: Duplicate family member of 2.4 — same conclusion: no anticipation of any claim.

2.6 CH 683 800 A5 — Cossonay Meteorology Systems S

• Citation: CH 683 800 A5, "An apparatus for measuring physical properties of fluids."
• Priority/filing: 1990-11-13 · Published: 1994-05-13
• Type: §102(b)
• Description: Swiss instrument for measuring physical properties of fluids (meteorological/flow-parameter instrumentation).
• §102 assessment: No anticipation of claims 1–7. General fluid-property measurement.

2.7 DE 44 07 209 A1 — Robert Bosch GmbH

• Citation: DE 44 07 209 A1, "Device for measuring the mass of a flowing medium," Robert Bosch GmbH.
• Priority/filing: 1994-03-04 · Published: 1995-09-07
• Type: §102(b)
• Description: Bosch hot-film/hot-wire air-mass meter for a flowing medium (engine intake air), with temperature-correction circuitry.
• §102 assessment: Highly relevant to the thermoelectric sensor concept, but it is a mass-flow meter, not a pipe-integrity monitor, and it does not disclose microprocessor constant excess-temperature regulation. Does not anticipate any claim; a potential §103 reference for the sensor element.

2.8 US 2001/0025526 A1 — Klaus Reymann

• Citation: US 2001/0025526 A1, "Device for measuring the mass of a flowing medium," Klaus Reymann.
• Priority/filing: 1994-03-04 · Published: 2001-10-04
• Type: §102(b); also potentially §102(e) as a U.S. publication with an early effective date.
• Description: U.S. publication in the same Bosch mass-flow family as DE 44 07 209 A1 (item 2.7).
• §102 assessment: Same as 2.7 — no anticipation of claims 1–7.

2.9 DE 196 05 638 C1 — Wagner Alarm- und Sicherungssysteme (applicant's own family)

• Citation: DE 196 05 638 C1, "Fire detection method for room or equipment housing," Wagner Alarm Sicherung.
• Priority/filing: 1996-02-15 · Published: 1997-06-12 · (WO 97/30427; EP 0 880 765 A1)
• Type: §102(b)
• Description: Aspirating fire detection in which room/equipment air is continuously drawn via a suction line with suction openings to a detector for a fire characteristic value. This is the only cited reference from the aspirating-fire-detection field and from the same assignee.
• §102 assessment: Establishes the aspirating-detector environment recited in claims 5–7, but discloses no thermoelectric constant-excess-temperature sensor and no nongradual-flow-change evaluation algorithm. Does not anticipate any claim. Its role is to supply the claim-5/6/7 preamble context — and note that the airflow-monitoring sibling of this document (see §4) is the genuinely relevant Wagner prior art, not this one.

2.10 DE 199 24 400 C1 — Securiton AG

• Citation: DE 199 24 400 C1, "Fire detectors and fire detection methods," Securiton AG. (EP counterpart EP 1 056 062 A2.)
• Priority/filing: 1999-05-27 · Published: 2001-01-25
• Type: §102(b)
• Description: In an aspirating fire detector, the volume flow to the detector is measured indirectly from the fan motor's electrical power consumption and rotational speed (quotient formation), then compared with upper/lower volume-flow limits to detect clogging of entry openings or interruption/breakage of the flow channel. The EP text expressly discusses that volume flow depends on mass flow and density, which in turn depend on air pressure and temperature, and criticises the earlier DE 44 28 694 C2 for needing an airflow + air-pressure + temperature sensor (i.e., it is squarely in the "density compensation" conversation).
• §102 assessment: The most relevant cited reference to the aspirating-detector claims and the density-compensation concept. It discloses the aspirating detector (claims 5–7 preamble), volume-flow monitoring to detect blockages/breaks (the purpose of claim 1(b)), and the temperature/pressure/density dependence that motivates claim 3. However, it measures flow via fan motor power/speed, not a thermoelectric air flow sensor operated in constant temperature mode with microprocessor-regulated constant excess temperature ΔT. Because claims 5–7 all incorporate the claim-1 device, DE 199 24 400 C1 cannot anticipate claims 5, 6 or 7, and it does not anticipate claim 1. Its real force is as a §103 combination reference, especially against claims 3 and 5/6/7.

2.11 US 6,450,024 B1 — Delta M Corporation ⭐ closest cited reference

• Citation: US 6,450,024 B1, "Flow sensing device," Delta M Corporation.
• Priority/filing: 2001-03-07 · Granted/published: 2002-09-17
• Type: §102(e) only (post-dates the 2002-08-28 §102(b) critical date; it is a U.S. patent granted on an application filed 2001-03-07, i.e., before applicant's invention).
• Description (from the published disclosure): Two RTD sensors in the fluid; constant current sources; an analog-to-digital converter digitizes sensor voltages; "a microprocessor calculates the value of the heated sensor resistance, R_H, required to maintain a constant ratio between the first and second sensor resistances (R_H/R_C)"; the microprocessor then commands more/less heating current; "the apparatus maintains a constant difference between a temperature of the sensing means and the fluid temperature during calibration and the same difference is maintained during operation"; mass flow rate is proportional to the current needed to hold the ratio constant; the microprocessor calibrates and outputs the mass flow rate.
• §102 assessment:
  • Claim 1 — potential anticipation, arguable. US 6,450,024 discloses a microprocessor that holds a constant temperature difference between a heated thermoresistive sensor and a reference sensor (i.e., exactly the "constant excess temperature ΔT" element (a)), with AD conversion and a feedback loop. If ΔT (sensor temp − fluid temp) and "constant R_H/R_C" are treated as equivalent, then element (a) reads on this reference. But element (b) — an evaluation algorithm that recognizes nongradual flow changes not based on disruptive ambient influences to monitor pipe-system flow/flow resistance — is absent (it is a mass-flow meter with no pipe-integrity function). On a strict, all-elements reading, claim 1 is not anticipated; on a broad reading of "evaluation algorithm for monitoring fluid flow," it is the single best anticipation candidate among the cited art.
  • Claim 2 — possible anticipation if element (b) is read broadly: it computes mass flow from heating current/power.
  • Claim 3 — not anticipated (no explicit temperature/pressure density-change compensation algorithm for a duct).
  • Claim 4 — not anticipated (no stored starting values used to compute status changes of a pipe system).
  • Claims 5, 6, 7 — not anticipated (no pipe system, no aspirating detector, no centre/narrowed air-entry-channel sensor placement).
  • Net: Strongest cited §102(e) reference and the natural §103 primary reference for claims 1–2.

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3. Non-patent citation

• "English translation of International Search Report" (1 item). This is not prior art; it is the translated ISA search report for the PCT case, whose cited documents are the §102 references analysed above. It carries no independent §102 weight.

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4. ⭐ Critical finding: the closest reference is not on the U.S. citation list

My searches surfaced a Wagner/Burkhardt document that is absent from the US 7,162,374 front page but is, on subject matter, the most on-point prior art for the pipe-monitoring half of the invention:

DE 196 05 637 / WO 97/30426 A1 — "Verfahren zur Luftstromüberwachung in einer Branderkennungsvorrichtung sowie Branderkennungsvorrichtung zur Durchführung des Verfahrens" (Method of monitoring air flow in a fire-detection device, and fire-detection device for carrying out the method)

• Inventors: Bastian Bernhard, Burkhardt Lutz, Lewonig Horst — note Lutz Burkhardt is the sole named inventor of US 7,162,374
• Applicant: Wagner Alarm- und Sicherungssysteme GmbH
• Priority: 1996-02-15 · WO published: 1997-08-21 · Type: §102(b)
• Disclosure: An aspirating fire-detection device with two air-flow sensors (3, 4) monitoring the mass flow in two intake-pipe systems. A differential signal from the two sensors is zeroed at commissioning ("bei der Inbetriebnahme … auf Null abgeglichen"), and flow monitoring is evaluated on the adjusted differential signal — preferably also on an adjusted summation signal — via an evaluation circuit with upper and lower thresholds and a display unit that signals a malfunction. The stated object is expressly to "eliminate as far as possible the influence of environmental parameters, in this case in particular variations in air pressure, on the air-flow monitoring."
• §102 assessment: This maps remarkably closely onto claim 1's distinguishing element (b) and onto claim 4:
  • "monitoring … flow … in the pipe system" — disclosed;
  • "changes not based on disruptive ambient influences" (air-pressure fluctuations) — that is the document's stated raison d'être and its differential-zeroing mechanism;
  • "starting values … stored … used for calculating status changes" (claim 4) — the zeroing at commissioning is exactly a stored baseline.
  • But it discloses two air-flow sensors with a differential/summation evaluation, not a thermoelectric air flow sensor operated in constant-temperature mode with microprocessor-regulated constant excess temperature ΔT. So it does not anticipate claim 1 or claims 5–7, nor claims 2–3. It is, however, a very strong §102(b)/§103 secondary reference against the "nongradual changes / ambient-influence rejection" limitation and against claim 4, and it strongly reinforces an obviousness attack on claim 1(b).

Also worth flagging (public-use / §102(a)–(b) art, dates unverified): Wagner's commercial TITANUS® / PIPE•GUARD aspirating smoke-detector literature states that the air-flow monitoring is "temperature-compensated and can be adjusted dependent on the air pressure," that sensitivity is "adjustable up to monitoring a single hole," and that "accurate detection of single blocked air sampling points possible to indicate sabotage of the pipe system." These are the commercial claims of the patent's own specification (including the "cardboard box in front of an intake opening / vandalism" scenario in the description). I could not date these brochures in this session, so I cannot fix them to before the 2002-08-28 critical date — treat this as a lead for §102(a)/(b) prior-public-use investigation, not a conclusion.

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5. Family ("Family Cites Families," 13 items) — these are JP-prosecution citations

These 13 are Japanese references cited against the JP family member JP 2006-502392 A, not against the U.S. case. They are reproduced literally; several have no assignee name given, only the applicant name in characters.

§102 assessment (JP set): All published before 2002-08-28 and are therefore §102(b) art as printed publications. The two with the most conceptual proximity to the invention are JPH 06-229800 A (thermal mass-flow sensor with an abnormality-diagnosis function) and JP 3312712 B2 (threshold-setting for high-sensitivity smoke detectors, i.e., the alarm-threshold design question). Neither discloses the microprocessor constant-excess-temperature regulation of claim 1, and neither is an aspirating pipe-integrity monitor, so none anticipates claims 1–7. Note also that JP 3487776 B2 (2004-01-19) post-dates the U.S. filing and can only be relevant to the JP case, not to the validity of the U.S. claims.

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6. Consolidated §102 verdict table (the 11 cited references)

Bottom line on the cited art: No reference on the US 7,162,374 front page discloses all elements of any independent claim as arranged. The two strongest are US 6,450,024 B1 (constant-difference temperature maintained by a microprocessor — attacks claim 1(a) and claim 2) and DE 199 24 400 C1 (aspirating-detector volume-flow monitoring via fan power, with explicit air-pressure/temperature density discussion — attacks claim 3 and the claims 5–7 context). Neither reaches claim 1(b) or claims 5–7 in full.

The reference the citation list under-uses is the applicant's own DE 196 05 637 / WO 97/30426 A1 (Burkhardt et al., 1997), which directly targets the "reject ambient (air-pressure) influences in pipe airflow monitoring using a zeroed baseline" idea — i.e., the substance of claim 1(b) and claim 4 — but with two flow sensors and no constant-excess-temperature thermoelectric element. Combined with US 6,450,024 B1, that pair is the most credible §103 combination against claim 1 as issued.

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7. Explicit uncertainties (do not treat as verified negatives)

1. I could not open a live USPTO PatentCenter/PatFT record in this session; the bibliographic data is from Google Patents' reproduction of the printed front page. Where the front page itself is internally inconsistent (9-item vs. 11-item citation lists; the priority-field vs. specification priority discrepancy noted in my earlier section), I have reported both rather than reconciling them.
2. Publication-type classification is mine. A "T2" (DE 690 11 099 T2) is a translation document; I have treated it as a printed publication of the same family as US 5,339,687 A, but the exact family relationship was inferred, not confirmed from the register.
3. I did not retrieve the actual PCT/EP2003/009560 ISA search report (the case's own non-patent citation is only its English translation). The category codes (X/Y/A) that would show which references the examiner considered most material against which claim are not available to me and would be the single most useful next document to pull.
4. DES 199 24 400 C1 content is characterised from its EP counterpart EP 1 056 062 A2; I did not read the DE C1 text itself.
5. The PIPE•GUARD/TITANUS public-use lead is undated in my sources and must not be cited as §102 art without a verified publication date.
6. No litigation/validity challenge to US 7,162,374 was located, consistent with the earlier section — but that remains an unverified negative, and the patent is expired (lapsed 2019-01-09), so §102 analysis here is of historical/defensive value rather than live-enforcement value.

Forward-citation context (not prior art): the disclosure is still cited by US 9,134,716 B2 (Siemens Schweiz, blockages/interruptions in an aspirating smoke detector) and US 11,609,144 B2 (Carrier, leakage in an aspirating fire-detection system), and Wagner's own later EP 4,530,611 A1 / WO 2025/068,492 A1 cite the family.

I'll ground this obviousness analysis with targeted searches on the key cited references before mapping them to the claims.

Strong results. Now the remaining core references — the Bosch/Reymann mass-flow sensor, the Endress+Hauser flowmeter, and the Japanese thermal-flow/diagnostic art.

Obviousness Analysis — US 7,162,374 B2 under 35 U.S.C. § 103

Scope note. This builds on the earlier sections (bibliographic data, claim map, litigation/PTAB status). It does not repeat them. Two things carried forward as operative: (a) all seven claims are untested and the patent lapsed 2019-01-09 (37 CFR 1.362), so any § 103 analysis here is retrospective/hypothetical; (b) the previously flagged date contradiction (task header "April 26, 2026" vs. environment/fetch date 2026-09-30) persists and does not affect the substantive analysis.

Reference-set note. The task directs me to the Prior Art section of the Google Patents page (https://patents.google.com/patent/US7162374/en). That section contains: 11 "Patent Citations," 13 "Family Cites Families" (foreign search-report art), and 1 non-patent citation ("English translation of International Search Report"). I verified disclosure content for several references by direct document review (URLs below) and mark the rest as title-only / unverified. I do not assert specific disclosures for references I could not open.

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1. The invention reduced to § 103 elements

Claim 1 is the gate. Stripping the preamble to intent-of-use language, the limitations are:

Claims 2–4 add (2) computing mass stream/velocity/volume stream/flow resistance/fluid temperature from heating power; (3) temperature- and/or pressure-dependent density compensation; (4) memory of starting values used to compute status changes. Claims 5–7 re-wrap A–E as assemblies (pipe system + detector), adding (6) sensor at the center of the air entry channel and (7) sensor in a narrowed cross-section of that channel.

The specification's own "peak temperature" cleaning step (up to 500 °C, fan off) is described at length but appears in no claim. It is therefore irrelevant to validity and I address it only in passing below.

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2. The prior art, clustered

Cluster A — Thermal flow sensing with microprocessor-regulated ΔT (teaches A, B, C, D; claims 2, 3, 4)

• US 6,450,024 B1, Flow sensing device, Delta M Corporation, filed 2001-03-07, issued 2002-09-17 (https://patents.google.com/patent/[US6450024B1](/patent/US6450024B1)/en; PDF: patentimages…/US6450024.pdf). Verified. A heated RTD plus a reference RTD ("a first sensor… resistance which is a substantially linear function of a fluid temperature"; second sensor likewise); A/D conversion of both sensor voltages; a microprocessor that "calculates the value of the heated sensor resistance, R_H required to maintain a constant ratio between the first and second sensor resistances (R_H/R_C)"; a D/A converter driving the heated-sensor current source up/down; the process "repeated periodically under any fluid flow conditions." Critically, the reference states the apparatus "maintains a constant difference between a temperature of the sensing means and the fluid temperature during calibration and the same difference is maintained during operation," and that "the fluid ambient temperature is also calculated from the reference sensor resistance." Mass flow "is proportional to the amount of current (I_H) required to maintain the ratio"; "calibration information is stored in the microprocessor memory"; and during measurement the flow equation is "solved by the microprocessors in real time, using stored stem loss data and thermophysical properties for the measured temperatures."
• DE 440 7209 A1 / C2 and its US counterpart US 2001/0025526 A1 (Bosch; Reymann et al.) — Device for measuring the mass of a flowing medium. Verified (https://patents.google.com/patent/US20010025526#1 and https://patents.google.com/patent/DE4407209C2). Hot-film temperature-dependent resistors on a ceramic substrate, "electrically connected… to an electronic evaluation circuit… which contains, for example, a bridge-like resistance measuring circuit." Directly useful for claims 6–7: the measuring part "is divided symmetrically by the mid-axis, for example approximately in the middle of the intake conduit, so that the medium can flow against a temperature-sensitive measuring element… if possible without any disturbing marginal influences from the wall," and the medium is routed through a measuring duct within the part.
• US 4,946,555 (Canadian Liquid Air), US 5,339,687 / DE 690 110 99 T2 (Endress & Hauser, Flowmeter), CH 683 800 A5 (Cossonay Meteorology Systems, An apparatus for measuring physical properties of fluids — I confirmed only that it is a heat-loss anemometric sensor family, cf. the related US 5,247,156), DE 38 10 240 A1 / US 4,846,133 (Mitsubishi, fuel control), and the Japanese search-report art JPS 6134422 A, JP 3356990 B2, JP 3356990/JPH 08-20292 B2 (Hitachi), JPS 5965720 A (Yamatake Honeywell, "Microflowmeter"), JPH 09-218066 A (Murata, "Flow rate sensor") — title-only here. These are thermal-anemometry references of record; I do not rely on any specific disclosure from them.

Cluster B — Flow monitoring and diagnosis in aspirating fire detectors (teaches E, claim 4, and the claims 5–7 context)

• DE 199 24 400 C1, Securiton AG, 1999-05-27, published 2001-01-25 — Brandmelder und Verfahren zur Branddetektion. Verified via its EP publication, EP 1 056 062 A2/A3 (http://data.epo.org/publication-server/rest/v1.2/patents/EP1056062NWA2/document.pdf). An aspirating detector that continuously draws air samples from a monitored location via a flow channel to a measuring chamber; the volume flow is determined indirectly from the fan motor's electrical power consumption and rotational speed, a quotient forms a volume-flow measurement value, and that value is compared with at least one predetermined volume-flow limit.
• Its acknowledged background, DE 44 28 694 C2 (described in EP 1 056 062 A2 at ¶¶[0002]–[0005]) — the closest thing in this record to claim 3. The prior detector measured volume flow and compared it to a window defined by an upper and a lower limit, activating an optical display/relay output "after expiry of a delay time," to detect clogging of the intake openings (dust) and interruption of the flow channel (mechanical damage or accidental disassembly). And because "der Volumenstrom der dem Branddetektor zugeführten Luft von dem Massenstrom und der Dichte der Luft abhängig ist, und diese wiederum eine Funktion des Luftdrucks und der Temperatur ist," it had an air-flow sensor, an air-pressure sensor and a temperature sensor. That is density compensation, recited verbatim.
• DE 196 05 638 C1, Wagner Alarm- und Sicherungssysteme, 1996-02-15, published 1997-06-12 — Fire detection method for room or equipment housing. Verified via DE 196 05 638 C5 (patentimages…/DE19605638C5.pdf): continuous supply of room or equipment-cooling-air samples to a detector through at least one supply line having a number of intake openings, and "eine Auswerteeinheit, die mit dem Detektor elektrisch verbunden ist, [die] nach vorgegebenen Kriterien ein Signal ab[gibt]" — i.e., an evaluation unit applying predetermined criteria to the detector output. This is Wagner's own prior aspirating platform, and it supplies the "smoke and gas intake detectors" environment of the claim.
• JP 3,312,712 B2 (Hochiki, "Optimal threshold setting method for high-sensitivity smoke detector") and JP 2,756,256 B2 (Nohmi Bosai, "Storage type fire alarm"), JP 3,487,776 B2 (Hochiki, "Information display system for fire detection equipment") — title-only. Titles indicate threshold/threshold-setting and stored-data evaluation teachings, directly pertinent to claim 4 and to limitation E's environmental-discrimination problem.
• JP H06-229 800 A (Hitachi Metals, "Mass flow sensor with abnormality diagnosis function and abnormality diagnosis method") — title-only. On its face, a thermal mass-flow sensor with a built-in abnormality diagnosis function — i.e., evaluating the flow signal to diagnose a fault rather than merely report flow.
• Supplementary (not in the page's citation list; located via search): WO 97/30426 A1, Verfahren zur Luftstromüberwachung in einer Branderkennungsvorrichtung (PCT/EP97/00681) — two air-flow sensors in two intake pipe systems, a differential signal that "is adjusted to bring it to zero when the fire-detection device is started", and an evaluation circuit "with a lower and an upper threshold value" that displays a malfunction — expressly "to eliminate as far as possible the influence of environmental parameters, in this case in particular variations in air pressure." I flag this as outside the cited set; the applicant identity was not stated in the excerpt I retrieved.

Cluster C — Hot-wire burn-off (unclaimed, noted for completeness)

A 1983 hot-wire mass-air-flow patent, US 4,370,887, teaches deliberately driving the bridge to overheat the temperature-dependent resistor so that "deposits on the surface… burn off" (quoted in the search hit). Located via search; not in this patent's citation list. Relevant only if a claim to the cleaning step existed — it does not.

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3. Claim 1 — the combination and the motivation

Proposed ground: US 6,450,024 B1 in view of DE 199 24 400 C1 (and DE 44 28 694 C2 as acknowledged therein) and DE 196 05 638 C1 (optionally with JP H06-229 800 A).

Why a POSITA would have combined them (KSR/Graham factors).

1. Same field and same problem. Both clusters address the flow of air through a conduit, and Cluster B exists precisely because an aspirating detector is only as good as its intake air path. Securiton's own framing of the problem — accurate detection of clogging and of duct interruption, without an expensive high-accuracy pressure sensor or added flow resistance — is a direct design incentive to substitute a better flow-measurement front end. Delta M is exactly that: a drift-free, temperature-compensated, microprocessor-calibrated thermal front end that removes the fluid-temperature dependence that otherwise corrupts the flow reading. The patent's own background concedes that sensors "are dependent on the temperature of the fluid stream and on the air pressure… and are therefore unsuitable for continuous use, without equalization." Delta M is the equalization.
2. Predictable combination of known elements. Replacing an analog servo-bridge constant-temperature controller (admitted art, FIG. 1) with a microprocessor executing a stored-characteristic regulation algorithm is the routine digitization of a known control loop, and Delta M had already done it in the same measurement modality. The result — a working point that does not shift with fluid temperature — is the predictable consequence of holding ΔT constant, not an unexpected discovery.
3. A recognized, solvable signal-discrimination problem with known tools. The differentiation of a genuine step event from slow ambient drift is ordinary signal processing (rate-of-change/high-pass discrimination, baseline subtraction, threshold windows with delays), and the field already used threshold windows, delay times, and start-up zeroing (WO 97/30426) precisely to strip out air-pressure effects. The patent's own specification supplies the operative insight and thereby an admission of what was known or at least readily knowable: "changes resulting from disruptive ambient influences (air pressure, temperature) generally proceed more slowly than a pipe break." Under In re Boesch / In re Nomiya-type reasoning, an applicant's own characterization of the prior art and of the ordinary skill level is usable evidence in the § 103 analysis.
4. Articulated, concrete motivation. One need not rely on generic "obvious to try." Securiton states the deficiency (cost/complexity of pressure compensation; need to detect blockage and break) and the patent states the same deficiency; the combination of Cluster A and Cluster B closes it without changing the principle of operation of either reference.

Contrary teaching? None identified. Delta M's constant resistance ratio R_H/R_C could be argued to differ from a constant absolute excess temperature, but Delta M itself recites a maintained constant temperature difference and a real-time fluid-temperature computation, so that distinction collapses on the reference's own words.

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4. Claims 2–4

• Claim 2 (compute mass stream, flow velocity, volume stream, flow resistance, fluid temperature from heating power). Delta M computes mass flow from I_H, derives fluid temperature from the reference RDT, and stores calibration constants and property lookup tables in microprocessor memory; King's law and P = I²R are the admitted framework of FIG. 1 and equations (1)–(2). Flow resistance follows from the measured volume stream by the specification's own equation (5) once cross-section and coefficients are known; Securiton demonstrates that a constriction in the entry path changes the measured flow at a given fan setting — i.e., that flow resistance is the diagnostic quantity of interest. Strong.
• Claim 3 (temperature- and/or pressure-dependent density compensation). Directly disclosed: DE 44 28 694 C2 includes air-flow, air-pressure and temperature sensors because volume flow depends on mass flow and density, and those depend on pressure and temperature; Securiton's improvement exists to avoid the pressure sensor. Delta M supplies temperature-linked property tables plus an ambient-temperature computation. Motivation: density is a known nuisance variable with an exact governing relation (ideal gas). Strong — this is the best-supported dependent claim.
• Claim 4 (memory of starting values used to compute status changes). Delta M stores calibration information and real-time constants in microprocessor memory; DE 44 28 694 C2 and WO 97/30426 adjust/zero the measurement at commissioning and compare thereafter to limits; aspirating-detector practice generally (Hochiki JP 3,312,712 B2, title) uses stored thresholds and drift compensation. Motivation: a baseline is required for any long-term drift or gradient measurement. Strong.

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5. Claims 5–7 (assemblies)

• Claim 5. Pipe system + detector + the claim-1 device: taught essentially directly by DE 196 05 638 C1 (aspirating supply line with intake openings → detector → evaluation unit) and DE 199 24 400 C1 (fan, flow channel, measuring chamber, volume-flow monitoring with limits, blockage/break detection), with the flow-measuring device supplied by Cluster A. The only question is whether the claim-1 device is "disposed in the pipe system"; the specification places it in the intake detector's air entry channel, i.e., in the intake path. Strong.
• Claim 6 (sensor at the center of the air entry channel). This is the most elegantly met limitation in the entire set, and it comes from a reference of record that the examiner cited for unrelated reasons: US 2001/0025526 A1 (Bosch/Reymann) places the measuring part approximately in the middle of the intake conduit so that flow impinges on the temperature-sensitive element "if possible without any disturbing marginal influences from the wall." That is the exact motivation — avoidance of wall boundary-layer/thermal effects and improved repeatability — that supports central placement in claim 6. Strong.
• Claim 7 (sensor in a narrowed cross-section of the channel). Positioning a thermal sensor in a constriction to raise local velocity, signal magnitude and time response is elementary fluid mechanics and standard anemometry practice; Bosch's measuring duct is itself a restricted bypass passage within the conduit. The patent's stated benefit — increased velocity → increased dynamics → detection of "extremely slight changes" — is a predictable result of a result-effective variable (geometry) that a POSITA would have optimized as a matter of routine design. Strong, on the weaker "obvious to try / optimization of a known parameter" footing rather than on an explicit teaching.

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6. Counterarguments a patent owner would raise — and how they fare

1. "No single reference discloses the whole combination." Correct but legally immaterial under § 103; the ground is a combination, with articulated motivation (§ 3 above).
2. "The references are from different fields (industrial mass flow vs. fire detection)." Weak. KSR endorses combining elements from the same field of endeavor and from analogous fields; both are thermal measurement of airflow in a duct, and Securiton's problem statement supplies the link.
3. "Constant ratio ≠ constant excess temperature." Weak, as shown: Delta M recites the constant temperature difference in terms.
4. "The 'nongradual… not based on disruptive ambient influences' discrimination is not taught." This is the patent owner's best argument and the honest soft spot in the ground. It is a negative, result-oriented limitation. The art teaches limit/window comparison with delay times and start-up zeroing, plus density compensation; it does not, in the excerpts I verified, expressly teach classifying a change as sudden as the trigger. Expect the petitioner to argue (i) the limitation is functional and the cited art inherently distinguishes step events from the slow pressure/temperature drift it exists to reject, and (ii) the specification's own explanation ("ambient influences… proceed more slowly than a pipe break") establishes the technique as conventional knowledge. Success will turn on whether the tribunal requires an explicit teaching of a rate-of-change test or accepts reasonable expectation from ordinary signal-processing practice.
5. Secondary considerations. None is supported on this record: no evidence of unexpected results, no licensing or commercial-success nexus tied to the claimed features, and the patent lapsed unasserted in 2019. Long-felt need can be argued (maintenance-free aspirating flow monitoring), but the need was being addressed concurrently by others (Securiton's own improvement program; Siemens' later US 9,134,716 B2; Carrier's later US 11,609,144 B2), which cuts against the patent as the source of the solution. I found no objective indicia evidence in the material available to me; that is a limitation of my record, not a finding that none exists.

Procedural flag for an IPR track. US 6,450,024 B1 is flagged on the page as examiner-cited (asterisk in the "Patent Citations" table, per Google's convention, together with US 4,946,555). A ground resting principally on Delta M therefore invites § 325(d) discretionary denial. The cleaner petition would (a) lead with a reference the examiner did not substantively consider — e.g., DE 44 28 694 C2 or WO 97/30426 (neither appears in the citation list) — or JP H06-229 800 A (title-only here), and (b) use Delta M for the constant-ΔT microprocessor front end with an explicit § 325(d) traverse explaining why the examiner did not appreciate the constant-ΔT-plus-diagnostic combination.

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7. Bottom line

• Claim 1: strong § 103 case via US 6,450,024 B1 + DE 199 24 400 C1 (with DE 44 28 694 C2) + DE 196 05 638 C1. The only genuinely contestable limitation is the "nongradual / not based on ambient influences" discrimination, and the specification's own admissions substantially supply the missing motivation.
• Claims 2, 3, 4: strong. Claim 3 in particular (density compensation) is nearly verbatim in the Securiton-acknowledged prior detector; claim 4 has both Delta M's stored calibration constants and the fire art's start-up zeroing/baseline practice.
• Claim 5: strong (aspirating assembly art is directly on point). Claims 6 and 7: strong, claim 6 via Bosch's express central-placement-beyond-wall-effects teaching and claim 7 via routine optimization of channel geometry.
• Overall: were this patent alive and asserted, I would assess claims 1–7 as vulnerable to a well-constructed § 103 challenge, with the softest point being the sudden-vs.-slow discrimination language. Because the patent expired for nonpayment effective 2019-01-09, this analysis is useful for defensive/responsive purposes (e.g., rebutting a royalty demand improperly extending past lapse) rather than for offensive filing.

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8. Explicit confidence and verification limits

Verified by direct document review: US 6,450,024 B1; US 2001/0025526 A1 / DE 440 7209 C2; DE 199 24 400 C1 via EP 1 056 062 A2/A3 (including its description of DE 44 28 694 C2); DE 196 05 638 C1 via DE 196 05 638 C5; and the Wagner aspirating family documents surfaced in the same searches.

Title-only / disclosure NOT verified here (I therefore did not rely on any specific disclosure): US 4,946,555; US 5,339,687 / DE 690 110 99 T2; CH 683 800 A5; DE 38 10 240 A1 and US 4,846,133; JP 2,756,256 B2; JP 3,312,712 B2; JP 3,356,990 B2; JP 3,487,776 B2; JP H06-229 800 A; JP H09-218 066 A; JP H08-202 92 B2; JP 2549713 Y2; JP 2965297 B2; JPS 59-65720 A; JPS 61-34422 A; JPS 61-95213 A; JPS 61-137017 A.

Not in the page's Prior Art section but located via search and flagged as such: WO 97/30426 A1; US 4,370,887 (burn-off). I did not confirm the applicant/assignee of WO 97/30426 from the excerpt retrieved.

Not reviewed: the prosecution file wrapper, any examiner's statement of reasons for allowance, and the EPO/JP/AU counterpart prosecution. If the examiner expressly relied on US 6,450,024 B1 to allow the claims (e.g., on the constant-ratio vs. constant-absolute-ΔT point), that reasoning should be read before finalizing the ground; I could not retrieve it. Also note § 112 issues (e.g., claim 1's "the pipe system" lacks antecedent basis, and the spec's disclosure of the discrimination algorithm is thin) are outside § 103 and, for the negative-limitation argument above, cut both ways.