US 5186051

I'll search for authoritative information on this patent, including any litigation dockets.

Let me run a few more targeted searches to check for any litigation or CAFC activity.

Summary of US 5,186,051

Below is a consolidation of the authoritative full text you supplied (Google Patents rendering of US5186051A) plus my targeted searches. Note the searches did not surface any CAFC 2026 docket, district-court case, or PTAB proceeding involving this patent (see "Litigation check" below).

Bibliographic data

Abstract (verbatim)

A device for measuring a flowing air quantity is proposed which comprises a sensor element which is exposed to the flowing air, is constructed in thick-film technology and contains a heating film resistor (R_H), which is arranged on an insulating substrate (10) and through which current flows, and a sensor film resistor (R_S) which is likewise arranged on the insulating substrate (10), serves to sense the temperature of the heating film resistor (R_H) and is a component of a bridge circuit. The heating film resistor (R_H) and the sensor film resistor (R_S), separated from one another by an intermediate film (13) which is a good conductor of heat but is electrically insulating, are accommodated in a bubble (11) which is made of ceramic material, in particular of glass ceramic, and is arched on the insulating substrate (10). The thin diaphragm (14) made of a ceramic material ensures effective thermal uncoupling of the film resistors (R_H, R_S) from the insulating substrate (10). Short response times are thereby achieved.

Plain-language overview of the independent claim

There is exactly one independent claim (claim 1); claims 2–8 all depend on it (claim 5 also depends on claim 1, and claims 6–8 depend on claim 5).

Claim 1 — A hot-film air-flow sensor that avoids the slow, heat-leaking substrate of the prior art by mounting the sensing resistors on a raised ceramic "bubble" diaphragm:

• a substrate that is electrically insulating;
• a bubble of ceramic material formed on the substrate, whose top is an arched membrane/diaphragm with a substrate-facing side and a substrate-remote side;
• a film system on the substrate-remote side of that membrane, so it is thermally uncoupled from the substrate;
• that film system contains (a) a heating film resistor that heats above ambient when current passes, (b) a sensor film resistor that senses the heater's temperature, and (c) between them a thermally conductive but electrically insulating intermediate film that thermally couples the two resistors while insulating them from each other; and
• bridge-circuit evaluation means connected to the sensor resistor to measure its temperature (and hence the heater's temperature via their thermal coupling).

The dependent claims add: the intermediate film is glass (claim 2); sensor resistor between membrane and heater (claim 3) or heater between membrane and sensor resistor (claim 4); a further sensor film resistor R_T for sensing air temperature, mounted on a second arched ceramic bubble on the same substrate (claim 5); membrane reinforced by glass infusion (claim 6); a protective film over the resistor stack and/or R_T (claim 7); and an intermediate glass film between the membrane and the resistor stack, or between the further membrane and R_T (claim 8).

Technical context (from the specification)

• The problem: in the closest prior art (SAE Technical Paper 880,650, pp. 105–109), the heater and sensor resistors sit on opposite faces of a plain substrate. Minimum substrate thickness plus lateral heat spreading makes thermal coupling slow and the temperature reading inaccurate/sluggish.
• The Bosch solution leverages the assignee's earlier glass-ceramic "bubble" diaphragm art — cited as U.S. Pat. No. 4,382,247 (Stecher et al./Bosch), a thick-film pressure cell.
• Fabrication is a thick-film process: print a platform paste (dry/fire in air), print a carbon-paste film (fire in N₂ to retain carbon), print a ceramic thick-film paste over it and fire in N₂ then air — the carbon burns out and the film arches into a diaphragm, later strengthened with glass. Then print the glass film, the platinum sensor resistor R_S, the glass intermediate film 13, the platinum-resinate heater R_H, and the protective film 15.
• Application example (FIG. 5): sensing intake air drawn through a motor-vehicle suction pipe, with the sensor element in the pipe and the electronics in an external housing.

Litigation / CAFC check (as requested)

• No CAFC 2026 docket, district-court case, IPR/PGR, or Federal Circuit appeal involving US 5,186,051 was found. The patent has been expired since 1997, which is consistent with there being no live enforcement activity.
• Caveat on false positives: my searches on the bare number "5186051" returned unrelated hits that are not this patent — e.g., JP 特許第5186051号 (a Japanese gaming-machine patent, KPE Corp.) and Brazilian appellate case no. 5186051-24.2019.4.03.9999 (an INSS benefits appeal). These are coincidental numeric matches and were excluded.

Uncertainty / verification limits

• I was not able to hit the USPTO Patent Center/Patent Public Search API or a CAFC docket system directly; the bibliographic and full-text data above come from the authoritative Google Patents rendering you provided plus corroborating mirrors (FreePatentsOnline, PatentLeaderboard). A direct USPTO/Patent Center and PACER check would be needed to state definitively that no unpublished or very recent 2026 filing exists.
• Inventor name spelling follows the source literally ("Gunther" Stecher, "Richard Muehlheim", "Botho Ziegenbein"); the assignment record renders them "STECHER, GUNTHER; HECHT, HANS; BERGFRIED, DIETRICH; AND OTHERS."
• Two "expiration" dates appear in the record (anticipated expiration 2010-02-16 vs. lapse effective 1997-02-19). Per the legal-events data, the patent actually lapsed in 1997 for non-payment of maintenance fees; the 2010 date is the statutory 20-year end-of-term marker.

Sources: provided Google Patents text (https://patents.google.com/patent/US5186051/en); FreePatentsOnline (https://FreePatentsOnline.com/5186051.html); PatentLeaderboard inventor listing (https://www.patentleaderboard.com/robert-bosch-gmbh/dietrich-bergfried/[1196570](/patent/1196570)).

I'll run targeted searches on litigation databases and court portals for this specific patent number.

Let me try more targeted litigation-database searches.

No litigation surfaced. Let me try docket-specific and patent-litigation aggregator searches.

Litigation search: US Patent 5,186,051

Bottom line: No litigation involving US 5,186,051 was found. Neither the patent-litigation aggregators I could reach, nor general court/docket-oriented searching, surfaced any case — district court, Court of Federal Claims, ITC Section 337, PTAB (IPR/PGR/CBM), or Federal Circuit — in which US 5,186,051 was asserted or challenged.

What I searched and what came back

No entry on the Unified Patents litigation portal, no Docket Alarm / Justia / CourtListener docket, and no reported decision naming this patent number was located.

Why this is the expected result

The absence of litigation is consistent with the prosecution/legal-events record already established in the prior section:

• The patent issued 1993-02-16 and lapsed for failure to pay maintenance fees effective 1997-02-19 (maintenance-fee reminder 1996-09-24; lapse 1997-02-16). It has been unenforceable/unexpired-by-lapse for over 25 years.
• A patent that died in 1997 would have had only a ~4-year enforceable window, and no matching case appears in that window or after.

Requested case table

Caveats and verification limits

1. Date inconsistency to flag: the task header says "Current Date: April 26, 2026," while the system context states today is 2026-09-28. I note this rather than silently reconciling it; it does not change the substantive result (the patent lapsed in 1997 either way).
2. No direct portal access: I could not query the Unified Patents portal, PACER, the CAFC docket system, or USPTO Patent Center/PTAB APIs directly. My conclusion rests on web-search coverage of those sources. A definitive "no litigation ever" statement would require a direct PACER/CAFC docket query and a Patent Public Search/PTAB proceeding check.
3. Numeric-match trap: the number "5186051" collides with at least two unrelated identifiers (JP Patent No. 5186051 — KPE Corp. gaming machine; and Lithuanian registry notice 5186051). Per the strict rule, I have not auto-corrected these; they are excluded because they are not US 5,186,051.
4. Prior-section consistency: this finding agrees with the earlier "Litigation / CAFC check" in the patent summary (no CAFC 2026 docket, district-court case, or PTAB proceeding). No contradiction found.

If you want a belt-and-suspenders confirmation, the remaining checks would be: (a) PACER docket search for "5,186,051" across all districts; (b) CAFC docket search; (c) USPTO Patent Center / PTAB API for any IPR/PGR tied to application 07/656,097. None are reachable from my current tooling.

I'll verify against public sources before writing up.

Proceedings overview

Zero AIA trial proceedings are on file for US 5,186,051. The structured "PTAB proceedings on file" block — the canonical list sourced from the USPTO Open Data Portal — returns no IPR, PGR, or CBM involving this patent, and no proceeding is recorded as active, instituted, settled, denied, or decided. Independent web verification (Google Patents PTAB/litigation sections, PTAB petition documents, CourtListener, and general docket queries) surfaced nothing to the contrary. Defensive posture: the patent is not "hardened" by surviving IPRs — it is simply un-challenged at the Board, because it lapsed for non-payment of maintenance fees effective 1997-02-19 and left no commercially meaningful enforcement target.

Why zero is the expected number here — three independent reasons

1. The patent died in 1997. The legal-events record in the authoritative Google Patents text shows a maintenance-fee reminder mailed 1996-09-24, "Lapse for failure to pay maintenance fees" on 1997-02-16, and "Lapsed due to failure to pay maintenance fee," effective 1997-02-19, under the status "PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362." There is a separate "anticipated expiration" marker of 2010-02-16, which is the statutory 20-year end-of-term date, not the operative death of the patent. A 1997 lapse removes the motive: the AIA trial regime only began on 2012-09-16, fifteen years after the patent stopped being enforceable, so any IPR would have been a pure academic exercise.
2. The AIA regime postdates the patent's entire enforceable life. IPR/PGR/CBM were created by the America Invents Act (2011), with CBM available from 2012-09-16 and IPR from 2012-09-16 as well. US 5,186,051 issued 1993-02-16 and lapsed in 1997. There was no window in which the patent was both in force and subject to AIA trials. (Note: the Board does have jurisdiction over expired patents in some circumstances — see, e.g., the panel discussion in IPR2023-00590, Paper 10, Apple v. Gesture Tech. Partners, addressing expiration and Article III jurisdiction — but that jurisdictions question is moot where no petition was ever filed.)
3. No assertion means no petitioner. AIA trials are overwhelmingly filed by accused infringers. With no known district-court assertion of this patent (the earlier litigation section of this analysis found none), there was no party with the standing-in-fact motivation to file. Defensive aggregators such as Unified Patents typically target patents being asserted in the wild; this one never was.

No proceedings to report

Because the canonical list is empty, there are no {PROCEEDING_NUMBER} — {Petitioner} v. {Patent Owner} entries to write. I will not manufacture proceeding numbers, panel rosters, institution dates, or final written decisions for a docket that does not exist. Specifically, and for the record:

• No petitioner, no filing date, no institution decision, no FWD, no settlement, no appeal exists for this patent at the Board.
• No Federal Circuit appeal arising from a PTAB proceeding on this patent exists; CourtListener returned no hit for US 5,186,051.
• Any claim-level outcome table (canceled vs. sustained) would be empty — all eight claims (claim 1 independent; claims 2–8 dependent) stand as issued and un-amended at the Office. They stand, however, only as an expired historical document.

False positives excluded (numeric matches — NOT this patent)

Strategic summary

Claim status. There is nothing to reconcile: no claim of US 5,186,051 has been canceled, narrowed, disclaimed, reexamined, or amended by the Board, because no AIA trial and no ex parte reexamination of this patent appears in the record. Claim 1 and its seven dependents are "untested, as issued." That is a distinct status from "sustained" — the Board has never passed on their patentability, and any suggestion that they "survived" an IPR would be a fabrication. The dependents add: glass intermediate film (claim 2); sensor resistor between membrane and heater (claim 3); heater between membrane and sensor resistor (claim 4); a second arched ceramic bubble carrying the reference-temperature film resistor R_T (claim 5); membrane reinforced by glass infusion (claim 6); a protective film over the resistor stack and/or R_T (claim 7); and an intermediate glass film between the membrane and the resistor stack (claim 8).

Estoppel landscape. There is no § 315(e)(2) estoppel on this patent, and there cannot be. Estoppel attaches only to a petitioner that obtained a final written decision; with zero proceedings, no entity is estopped, no ground is foreclosed, and no art is reserved. The practical consequence runs the other way: because no IPR was ever filed, the entire universe of § 102/§ 103 art — including art that a would-be petitioner might have been estopped from raising in a second bite — remains theoretically available to a litigant. That theoretical availability is worthless in practice, because the patent expired in 1997 and cannot underpin an infringement claim for any post-1997 conduct. Damages would be confined to pre-1997 infringement, now barred by the six-year recovery limit of 35 U.S.C. § 286 and by laches-type defenses.

Pattern signals. None to read. There is no repeat petitioner, no patent-owner appeal campaign, and no defensive aggregator in the chain. Robert Bosch GmbH's protection strategy for this technology family ran through prosecution and related filings — notably the family members DE 4012081 A1 ("Method and arrangement for measuring air amounts"), DE 4307512 A1 and DE 4307513 A1 ("Measuring element"), plus EP 0430979 B1, JP H04500269 A, KR 900702336 A and WO 1990002317 A1 — rather than through PTAB or court enforcement. The patent's citation neighborhood (US 4,382,247 Stecher et al./Bosch; EP 0 271 660 A2 Bosch; US 4,837,176 VDO; US 4,777,820 Bosch) is technical prior art, not litigation or PTAB history.

Recommended next steps

• If you are a defendant facing a demand letter citing US 5,186,051: the strongest point is not an IPR or a PTAB outcome — it is expiration. The patent lapsed for non-payment of maintenance fees effective 1997-02-19 (Google Patents legal events, code LAPS/FP, https://patents.google.com/patent/US5186051/en). Demand the asserted claims' post-1997 damages theory with particularity; there cannot be one. Cite the legal-events record directly.
• Do not commission an IPR. An AIA petition would be available in principle (the Board will entertain expired patents — IPR2023-00590, Paper 10, https://ptacts.uspto.gov/ptacts/public-informations/petitions/[1553612](/patent/1553612)/), but it would cost a full petition budget to invalidate claims that a 1997 lapse already rendered unenforceable. If you want an Office-side knockout for a defensive-cleanliness reason, note that ex parte reexamination is available for up to six years after lapse or expiration — that window is long shut here.
• No trial-stage milestones exist to track. There is no institution decision deadline, no oral hearing date, and no statutory one-year FWD due date, because there is no trial. If someone tells you otherwise, ask them for the proceeding number — none exists.
• If you need the definitive negative on paper: the absence flows from the canonical ODP-sourced "PTAB proceedings on file" block (empty) plus my corroborating searches. A belt-and-suspenders confirmation would be a direct USPTO PTAB E2E / Patent Trial and Appeal Board End-to-End search on the patent number and a CourtListener docket query for US 5,186,051 — resources I could not query via API here, so I state the negative with high, but not absolute, confidence for any unpublished or very recent filing.

Cross-reference notes for the assembled report

• Date contradiction (flagging, per instruction): the earlier litigation section states "The task states the current date as April 26, 2026," whereas this task states 2026-09-28. The source text was fetched 2026-09-26. None of these dates change any conclusion, since the patent lapsed in 1997.
• Prior-art citation discrepancy (flagging): the earlier Patent-summary section renders the closest prior art as "SAE Technical Paper 880,650, pp. 105–109." The authoritative full text supplied in this prompt says "SAE Technical Paper Series 880,560, pages 105-109." The full text governs; the "880,650" rendering appears to be an error in the earlier section.
• Status discrepancy carried forward, not resolved: the record contains both an "anticipated expiration" of 2010-02-16 and a lapse effective 1997-02-19. Per the legal-events data, 1997 is the operative date; the 2010 date is the statutory 20-year marker. This is the single most important fact for a defendant and should be stated consistently throughout the report.

I'll verify the assignment record against USPTO Assignment Center mirrors and cross-check the reel/frame cited in the legal-events data.

Let me try to pull the actual recorded assignment document and check for any post-issuance recordings.

Let me attempt to retrieve the actual recorded assignment document image from the USPTO legacy assignment archive.

Assignment & Ownership Chain — US 5,186,051

Verification note up front: assignmentcenter.uspto.gov and assignment.uspto.gov are JavaScript applications that could not be queried directly from this environment. The assignment data below is taken from the USPTO-derived legal-events record carried in the authoritative Google Patents text you supplied, which cites the reel/frame, execution dates, and parties for the sole recorded conveyance. Where I could not retrieve a field (notably the correspondent of record for reel 005772/0403), I say so rather than guess. This is a single-link chain, so the depth of analysis the task envisions (repeat correspondents, cascading LLCs) does not exist here.

Inventors

• Employer evidence. All five are listed as inventors on a patent whose original assignee is Robert Bosch GmbH, and the only recorded conveyance is an "ASSIGNMENT OF INTEREST" from these five inventors to Robert Bosch GmbH (reel 005772/0403). That is the record support for Bosch as the acquiring employer. Individual employment agreements are not in the patent record, so for four of the five I cannot show the employment relationship independently of the assignment itself.
• Lineage signal (benign, not a red flag). Inventor Gunther Stecher is the same-named inventor of US 4,382,247 ("Pressure sensor," assigned to Robert Bosch GmbH), which this patent cites as its enabling thick-film "bubble" diaphragm art. This is a same-employer, same-technology repeat inventor — the opposite of the "inventors flee the assignee" pattern.
• Departure pattern: not present. There is no record of any inventor executing a second assignment (e.g., an individual quitclaim to a third party, an inventor-held shell, or a reissue-driven assignee change). Because the chain has exactly one link, the "all inventors depart within 12 months" precursor to a portfolio fire-sale cannot be observed — and the absence of any inventor-side filing over a 35-year record is inconsistent with it.
• Name-spelling variance (flagged, not corrected). Google's inventor field renders "Dietrich Bergfried"; the assignment record as reproduced in the legal events renders "BERGFRIED, DIETRICH." Same person, transcription variance. Per the operating rules I have not auto-corrected either rendering. Similarly "Gunther" (no umlaut) and "Muehlheim" as transcribed.

Original assignee

Robert Bosch GmbH — Postfach 30 02 20, D-70442 Stuttgart, Federal Republic of Germany (address as recorded on Bosch assignment cover sheets of this era).

• Named on the issued patent? Yes. Original assignee and current assignee are both Robert Bosch GmbH; no intervening conveyance is recorded.
• Product embodying the claims? The specification itself is the evidence that Bosch commercialized this: FIG. 5 describes the sensor element (20) mounted in the intake suction pipe (19) of a motor vehicle with the evaluation electronics in an external housing (21) — i.e., a hot-film air-mass meter for engine load sensing, a Bosch production line (the HLM/HLM-series air-mass meters). The patent is a manufacturing-process patent (thick-film bubble on a ceramic substrate), and the claimed device is the production sensor element itself.
• Primary line of business: diversified automotive/mobility supplier (Bosch Mobility), industrial technology, consumer goods, energy/building technology; also one of the world's largest automotive-sensor suppliers.
• Current status: Operating. Bosch is a privately held GmbH whose majority shareholder is Robert Bosch Stiftung GmbH (a charitable foundation); it is not publicly traded, has not been acquired, and has no bankruptcy filing in its history. Securitization or 8-K/10-K evidence does not exist for it in the way it would for a listed US operating company — there is no SEC reporting obligation to cross-check.

Assignment timeline

Chronological list of every recorded assignment (there is exactly one conveyance; the fee-payment events are listed separately below because they are not ownership transfers):

• 1991-02-05 to 1991-02-11 (executed) / recorded 1991-02-27 — Reel 005772/0403
  • Conveyance: Assignment ("ASSIGNMENT OF INTEREST")
  • Assignor: Stecher, Gunther; Hecht, Hans; Bergfried, Dietrich; and others (Ziegenbein, Botho; Muehlheim, Richard) — all five named inventors
  • Assignee: ROBERT BOSCH GMBH (D-70442 Stuttgart, Germany)
  • Correspondent: Not determinable. The legal-events rendering of this record does not expose a correspondent/attorney field, and I could not retrieve the scanned reel 005772/0403 document itself. I therefore cannot state who filed it, and I decline to infer a firm from the Bosch pattern. (For calibration only, and not evidence for this reel: the one Bosch assignment I could independently corroborate is Kenyon & Kenyon, Richard L. Mayer, Reg. No. 22,490, One Broadway, New York, NY 10004, as correspondent on reel 015926/0145 recorded 2004-10-29 — a different Bosch patent, ~13 years later. That does not establish anything about 005772/0403.)
  • Context: Ordinary inventor-to-employer assignment, executed in the days immediately preceding Bosch's US national-stage entry. The application US 07/656,097 was filed 1991-02-27 — the same date as recording — which is the standard sequencing when a PCT case (PCT/DE1989/000524, filed 1989-08-09) enters the US national phase and the inventors' rights are formally conveyed as the US file is opened.

Non-conveyance events in the record (listed to prevent misreading them as assignments):

Post-issuance assignment record: none. There is no recorded change of name, merger, security agreement, license, release, or correction for this patent, and no assignment away from Bosch. The chain terminates at the original assignee.

Timeline diagram

timeline
    title Ownership of US 5186051
    1988 : Priority filing DE 3829194
    1989 : PCT application filed
    1991 : Inventors assign to Robert Bosch GmbH
         : US national stage filed
    1993 : Patent issued
    1996 : Maintenance fee reminder
    1997 : Lapsed for nonpayment

NPE / troll-pattern signals

Adjacent note — family treatment, not an NPE signal. Bosch let the family lapse unevenly: DE 3829194 A1 (1988) is not_active / withdrawn; WO 1990002317 A1 (1989) ceased; EP 0430979 B1 expired – lifetime; KR 900702336 A abandoned; JP H04500269 A (JP 1508447 A) still shows pending/active in the source record; US 5,186,051 expired – fee related. Bosch also continued the technology in-house via DE 4012081 A1 (1990-04-14, "Method and arrangement for measuring air amounts") and DE 4307512 A1 / DE 4307513 A1 (1993-03-10, "Measuring element") — i.e., Bosch protected the platform through its own follow-on filings, the classic operating-company pattern, rather than by transferring anything.

Verdict

Insufficient data — in the rubric's specific sense of "only the original assignment."

The entire ownership record of US 5,186,051 is a single inventor-to-employer assignment executed 1991-02-05 to 1991-02-11 and recorded 1991-02-27 at reel 005772/0403, conveying the five inventors' rights to Robert Bosch GmbH, which remains the owner of record. No subsequent conveyance, security interest, change of name, merger, or license is recorded, so there is nothing in the chain to evaluate for NPE behavior; all eight troll-pattern signals come back negative or not-applicable on the evidence available, and the one field that would matter for signal #3 — the correspondent for reel 005772/0403 — could not be retrieved. The patent lapsed for non-payment of maintenance fees effective 1997-02-19 (reminder mailed 1996-09-24), four years into term, which is why the patent has no enforcement history at all.

To verify directly: run the patent number on the USPTO Assignment Center — https://assignmentcenter.uspto.gov/ (alternate index: https://assignment.uspto.gov/patent/index.html) — and pull the scanned document at reel/frame 005772/0403 to read the correspondent of record; that is the single open field in this report.

I'll verify the prior-art citations against USPTO/public records and gather the details needed for a § 102 analysis.

Now let me verify the remaining cited references individually.

Let me verify the SAE paper reference and the EPO search report for the family member, plus the stacked-resistor prior art.

Prior-Art Analysis — US 5,186,051 (Robert Bosch GmbH)

0. Sourcing note (read first)

I was not able to query the USPTO Patent Public Search / Patent Center API directly from my tooling. The citation data below is taken from the USPTO front-page "References Cited" data as mirrored in the authoritative Google Patents rendering supplied in this task (https://patents.google.com/patent/US5186051/en), cross-checked against EPO Global Patent Index, EPO publication-server search reports, SAE Mobilus, and patent mirrors (FreePatentsOnline, Justia, searchlight.law). Treat the reference list as reliable; treat my characterizations of each reference as verified against the quoted text where I cite it.

Important internal inconsistency in the source record (flagged, not reconciled): the Google Patents rendering shows two different citation lists for this patent:

The 4-document list is the one I use below, because it also appears under the heading "Patent Citations (4)" alongside the "Cited By" tables. Asterisks in the source mark "cited by examiner"; US4777820A carries no asterisk, i.e. it appears to have been cited by a party other than the examiner (applicant/third party). That distinction is preserved below.

Contradiction with the previously generated section: the earlier summary states the closest prior art is "SAE Technical Paper 880,650, pp. 105–109." The authoritative full text says 880,560, and my verification confirms SAE 880560 ("Hot-Film Air Mass Meter — A Low-Cost Approach to Intake Air Measurement," R. Sauer, Robert Bosch GmbH; SAE SP-737, 29 Feb 1988, pp. 105–109). The "880,650" figure in the prior section is an error and should be corrected to 880,560.

1. § 102 date framework for this patent

Consequence: a reference is § 102(b) art only if published before 1988-08-09; it is § 102(a) art if published before 1988-08-29; it is § 102(e) art if it is a US patent/grant published application whose US filing date precedes 1988-08-29.

2. The four cited references — full citations

Non-patent literature cited in the specification (the admitted closest prior art):

3. Reference-by-reference analysis

3.1 US 4,382,247 A — Pressure sensor (Bosch) — § 102(b)

Disclosure (verified from the patent text): an insulating substrate (1) of 96% Al₂O₃ ceramic; a glass-ceramic membrane (2) screen-printed over a carbon-black/organic filler (3), sintered in nitrogen, then fired in an oxidizing atmosphere so the filler burns out and the membrane arches/bulges away from the substrate; the membrane is then reinforced by additional printing steps and an amorphous glass layer (6) closes the chamber; on the free-standing membrane are applied, by thick-film printing, conductive tracks and resistors R1, R2 covered by a glaze/glass coating, plus further glass/ceramic layers. The disclosure expressly contemplates "additional printing steps and firing steps … in order to reinforce and strengthen the membrane."

Element mapping to claim 1:

Which claim(s) it potentially anticipates under § 102: None as a whole. It is a structural reference — it anticipates only isolated structural sub-features that appear in dependent claims, and even then never in combination with claim 1's heater/sensor/intermediate-film stack. Closest dependent-claim overlap: claim 6 (membrane reinforced by infusion of glass), claim 7 (protective film), claim 8 (glass film between membrane and overlying film), and the "bubble/membrane" concept of claims 1 and 5. Because claims 6–8 depend on claim 5 → claim 1, the missing heater/sensor/intermediate-film/bridge elements defeat anticipation of every claim.

Real significance: this is a § 103 reference. It is Bosch's own acknowledged source for the thick-film glass-ceramic "bubble" — the specification itself cites it for exactly that. Combined with a stacked-resistor flow sensor (US 4,777,820 or US 4,831,876), it supplies the only element claim 1 adds over the flow-sensor art.

3.2 US 4,831,876 A — Measurement probe (VDO Adolf Schindling AG) — § 102(e)

Disclosure (verified): a probe for measuring the mass of flowing fluid, particularly intake air of an internal-combustion engine; at least one temperature-dependent resistor in the fluid path forming part of a bridge circuit; resistors (2, 4, 5) are layers with meander-shaped current paths; the probe is controlled so the resistors sit at a temperature dependent on (but higher than) the fluid temperature. Critically for this case, the reference states: "a thermal contact is made possible between the first and the third resistors in the manner that a part of the layers of the first and third resistors (2, 4) overlap, an electric insulating layer being provided between the two layers." A fourth resistor (1) in the fluid path takes on the fluid temperature (the R_T-analogue).

Element mapping to claim 1:

Which claim(s) it potentially anticipates under § 102: None as a whole. It discloses every element of claim 1 except the ceramic bubble/arched membrane — i.e. the sole point of novelty. It is therefore the best § 102(e) reference for a "claim 1 minus the bubble" argument, but it cannot anticipate claim 1, and because dependent claims 2–8 all incorporate the bubble limitation, it cannot anticipate any of them either. Its independent significance is § 103: VDO already taught the overlapping-resistor/insulating-interlayer/bridge combination for intake-air mass measurement as of 1987.

3.3 EP 0 271 660 A2 — Device for determining the mass flow of a flowing medium (Bosch) — § 102(b)

Disclosure (verified from the EPO publication): substrate (20) as carrier; a layer-like measuring resistor (R_H) and a likewise layer-like heating resistor (R_S) whose heating output is regulated so that R_H holds a constant temperature, the heating output being the measure of mass flow; bridge circuit; the area of R_S is larger than R_H and extends toward the substrate fastening to prevent heat outflow from the measuring resistor; R_H and R_S sit on a lip (33) separated by a slit (25) to reduce heat conduction to the substrate holder; protective layer (44) over the resistors; an additional temperature-dependent resistor on a separate substrate for medium-temperature compensation.

Family note — do not double-count: EP 0 271 660 A2 and US 4,777,820 A are members of the same family, sharing DE 3638138 (priority 1986-11-08). The EPO Global Patent Index entry for EP0271660A3 explicitly records "orig: US4777820A". They are one disclosure, cited twice; they are not two independent references.

Element mapping to claim 1: identical to §3.4 below — heater + sensor + bridge + protective layer + deliberate thermal-uncoupling-from-substrate means are all present; the ceramic arched bubble/membrane is absent.

Which claim(s) it potentially anticipates under § 102: None as a whole (same reasoning as §3.4). Note that as § 102(b) art (published 1988-06-22, before the 1988-08-09 critical date) it is a statutory bar that cannot be sworn behind or antedated by the DE priority date.

3.4 US 4,777,820 A — Apparatus for determining the flow rate of a flowing medium (Bosch) — § 102(e)

Disclosure (verified): the US counterpart of DE 3638138 / EP0271660. Substrate (20) carrier; film measuring resistor (R_H) and film heating resistor (R_S); heating output regulated so the measuring resistor has constant temperature; resistance bridge (R₂, R_K, R₃, R_S) whose imbalance drives the heating current, the heating power being the flow-rate measure; thermally insulating slits (25) cut into the substrate to block heat flow between resistors and to the substrate fastening; the measuring resistor placed remote from the leading edge to reduce soiling; protective layer (44) over the resistor films. Its background section expressly describes the prior art of US 4,399,697 (Kohama et al.), in which "the first film acts as a heating resistor and is secured directly on the substrate and the second film is embodied as a temperature-dependent measuring resistor and rests on the first film, with an electrically insulating film located between them," and states that this insulating film "is so thin that good heat transmission from the heating resistor to the measuring resistor is possible." Claim 24 of US 4,777,820 itself covers the two resistors on the same flat side, the measuring resistor underlaid by the heating resistor.

Element mapping to claim 1:

Which claim(s) it potentially anticipates under § 102: None as a whole. It is the closest patent reference and defeats any reading of claim 1 that ignores the bubble/membrane limitation, but the arched ceramic bubble is missing. Dependent claims 2–8 all carry claim 1's bubble through, so none is anticipated.

3.5 NPL-1 — SAE 880560 (Sauer/Bosch) — § 102(b), the admitted prior art

Disclosure: the specification itself characterizes this as the "generic category" prior art: "the heating film resistor is arranged on one side of the insulating substrate and the sensor film resistor serving to sense the temperature of the heating film resistor is arranged on the other side of the insulating substrate, opposite the heating film resistor, these two resistors being applied in a planar form to the flat surface of the insulating substrate." The '051 patent derives its entire stated problem from this document (insufficient thermal coupling; lateral heat spreading → inaccurate, sluggish sensing). Corroborated by contemporaneous Bosch HFM-2 product literature describing a ceramic substrate carrying thick-film resistors R_s, R_H, R_S, R_1 with R_H holding platinum resistor R_S at constant temperature above ambient, evaluated in a bridge.

Which claim(s) it potentially anticipates under § 102: None. It lacks the ceramic bubble/arched membrane and the intermediate heat-conducting/insulating film. It is § 102(b) art as to the bridge/heater/sensor-on-substrate elements only, and is the natural starting point for the § 103 obviousness analysis (which the '051 specification effectively concedes).

4. Bottom-line answer

No single reference of record anticipates any claim of US 5,186,051 under 35 U.S.C. § 102.

The claimed combination is not derivable from any one reference because claim 1 requires the arched ceramic bubble with the film system on its substrate-remote side, and none of the cited art — including the two Bosch flow-sensor documents — has a bubble. The prior art instead attacks substrate heat loss by slits and lips cut into the substrate (US 4,777,820 / EP 0 271 660) or not at all (SAE 880560). That structural difference is the whole inventive step.

Where the references actually matter (a § 103 case, not § 102):

• US 4,382,247 is the express, applicant-admitted source of the thick-film glass-ceramic bubble on an insulating substrate — supplying claim 1's missing element (and the subject matter of claims 6 and 8).
• US 4,777,820 / EP 0 271 660 supply heater film resistor + sensor film resistor + bridge evaluation + protective layer, and expressly acknowledge stacked-film teaching with an insulating interlayer via US 4,399,697 (Kohama et al.), published 1983-08-23 (also § 102(b) art).
• US 4,831,876 independently supplies the overlapping-resistor/insulating-interlayer/bridge combination specifically for intake-air mass measurement, and an R_T-analogue fluid-temperature resistor.
  A combination of US 4,382,247 with either flow-sensor document is the realistic validity challenge; none of them alone is an anticipation.

5. Caveats and flags

1. Corrected figure: the earlier section's "SAE Technical Paper 880,650" is wrong; the authoritative text and SAE Mobilus both give 880560 (Sauer, pp. 105–109). Use 880560.
2. Family duplication: US 4,777,820 A and EP 0 271 660 A2 are the same disclosure (DE 3638138 family). They must not be counted as two independent references in any obviousness combination.
3. "By another" for § 102(e): the Bosch references (US 4,777,820 / EP 0 271 660) have a different inventive entity (Hecht, Kienzle, Kleinhans, Kuhn, Wocher) from US 5,186,051 (Stecher, Hecht, Bergfried, Ziegenbein, Muehlheim), so § 102(e) is satisfied notwithstanding the common assignee. "Hecht" appears on both — a common-assignee/co-inventor overlap worth noting if § 103 is asserted.
4. Source-list inconsistency (flagged, not resolved): the Google Patents page shows both a 3-document and a 4-document citation list; US 4,777,820 A appears only in the 4-document list and without an examiner asterisk. A verbatim USPTO front-page ("References Cited") pull would settle whether US 4,777,820 A is examiner-cited or applicant/third-party-cited.
5. Not verified directly. I could not reach USPTO Patent Public Search/Patent Center, PACER, or the EPO Register APIs. The analysis rests on the authoritative Google Patents rendering plus corroborating EPO/SAE mirrors.
6. Optional derived references (NOT citations of US 5,186,051 — listed only as context): US 4,399,697 (Kohama et al., pub. 1983-08-23, § 102(b)) and US 4,816,200 (Stecher, Spitzenberger, Müller, Bosch — "Method of making an electrical thick-film, free-standing, self-supporting structure," which itself cross-references US 4,382,247; issue date not independently confirmed in this session) are the substantive teachings that would likely be reached in an obviousness combination. I flag them as unverified rather than asserting their exact bibliographic data.

I'll ground the obviousness analysis in the actual cited references before writing.

Let me verify two specific points — the acknowledged closest prior art (SAE paper) and the stacked heater/insulator/sensor reference.

Obviousness Analysis — US 5,186,051 under 35 U.S.C. § 103

Status note (flagging, per instruction): this task header says "Current Date: April 26, 2026," while the session context says 2026-09-28 and the authoritative full text was fetched 2026-09-26. The contradiction was already flagged in the litigation and PTAB sections; it changes nothing here. Also carried forward: the earlier Patent-summary section renders the acknowledged closest prior art as "SAE Technical Paper 880,650, pp. 105–109," but the authoritative full text says "SAE Technical Paper Series 880,560, pages 105-109." The full text governs, and I use 880,560 throughout (see Verification limits).

Practical stake (stated once, not repeated): the patent lapsed for non-payment of maintenance fees effective 1997-02-19, so this is a validity audit of an expired document, not a live invalidity defense. That does not change the legal test; it only removes the commercial consequence.

1. Governing law and the critical date

The application is US 07/656,097, a national-stage filing (PCT/DE1989/000524) filed 1989-08-09, claiming DE 38 29 194 priority of 1988-08-29. The America Invents Act does not apply. Pre-AIA § 103(a) governs, with Graham v. John Deere and KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007) supplying the framework.

Because the effective filing date is 1988-08-29, the art set divides as follows:

• § 102(b) art — publicly available before 1987-08-29. This captures US 4,382,247.
• § 102(a)/(e) art — published/patented before the effective filing date, but within one year of it; or US patents/printed publications with an earlier effective US filing date. This captures EP 0 271 660 A2 (published 1988-06-22), US 4,777,820 (granted 1988-10-18 on a 1987-10-13 US filing), US 4,831,876 (granted 1989-05-23 on a 1986-03-03 DE priority), and SAE 880,560.

All are available for use in a § 103 combination regardless of whether they also qualify under § 102(b).

2. The reference set actually cited on the face of the '051 patent

Per the "Prior Art" section of this page, the four references of record are:

Two further references matter even though they are not on the '051 face:

• US 4,399,697 (Kohama et al.) — cited inside EP 0 271 660 B1's description: "Aus der US-A-43 99 697 ist bereits eine Vorrichtung … bekannt," namely a heating resistor film secured directly on a carrier with a temperature-dependent measuring resistor film resting on it "unter Zwischenlage einer Isolierschicht" (with an interposed insulating layer), where "the insulating film separating the heating resistor and the measuring resistor is so thin that good heat transmission from the heating resistor to the measuring resistor is possible." The reference's own stated object is to make the heater "closer to the temperature dependent resistive wire, thereby improving the response of the flow measurement," and it covers the heater film with "insulating material such as glass or resin."
• JP-A-57-93 212 — cited as an "X" reference in the EP'660 search report: heater resistor layer and measuring resistor layer on one flat side of an un-slit substrate, with an insulating layer between them.

3. The single-reference question: is there anticipation?

No. No one reference discloses every limitation of claim 1:

• SAE 880,560 / US 4,777,820 / US 4,831,876 / US 4,399,697 all disclose the resistor pair, the intermediate insulating film, and bridge evaluation — but on a solid flat substrate, not on an arched ceramic bubble.
• US 4,382,247 discloses the arched ceramic bubble with thick-film resistors on its free-standing membrane — but only a single resistance layer (or a pair of side-by-side strain-sensing resistors R1, R2 for a pressure sensor), with no heater/sensor pair separated by a thermally conductive, electrically insulating intermediate film, and no bridge evaluation of a thermally coupled heater/sensor pair.
• US 4,816,200 (Stecher/Spitzenberger/Müller, continu. of the '247 application) discloses free-standing thick-film structures usable to "sense pressures, temperatures, or gas flow" and thick-film resistors "for use in a bridge circuit," but again no stacked heater/sensor film system inside a bubble. Availability caveat: its 1989-03-28 issue date postdates the 1988-08-29 critical date; it is usable only if its § 102(e) date traces to the 1980 parent filing (Ser. No. 181,839). I therefore use it only as corroboration and rest the rejection on US 4,382,247, which is § 102(b) art on its face.

Conclusion: the case is a § 103 case built on two or three references, and it is strong.

4. Combination A (primary): SAE 880,560 / US 4,777,820 + US 4,382,247

4.1 Claim chart for claim 1

Every limitation is met. The only element absent from each individual reference is the combination of the stacked film system with the bubble membrane.

4.2 Motivation to combine

1. Same field, same problem, same art. Both references are thick-film sensing elements for automotive engine control, and both attack the identical defect: heat conducted away through the substrate. US 4,777,820 states the defect outright ("unwanted heat transmission … slows the starting up process … and also makes for a slow response"), and US 4,399,697 states that "part of the heat is taken by the support, thus causing a flow measurement error corresponding to the heat loss." The '051 specification states the same problem in the same words. A POSITA seeking a faster air-mass meter had every reason to look for a lower-thermal-mass resistor support.
2. The secondary reference is the assignee's own, and it invites the combination. US 4,382,247 is Bosch art, and US 4,816,200 (its sibling) says the structure "can also be utilized to sense pressures, temperatures, or gas flow." Bosch's own document therefore tells the artisan that the bubble platform is a flow-sensor platform.
3. KSR rationales, each independently sufficient:
   • Known technique applied to a known device to yield a predictable result. Screen-printing a free-standing ceramic membrane over a sacrificial filler was a known thick-film technique (US 4,382,247 claims and specification).
   • Simple substitution of one known element for another. Replacing the solid substrate of SAE 880,560 as the resistor support with a thin ceramic membrane already used for exactly that purpose (printing and firing resistors on it) is substitution of a known element to obtain the known benefit of reduced thermal mass.
   • "Obvious to try" over a finite, identified set. The art recognized exactly three ways to cut substrate heat loss — reduce substrate thickness (SAE 880,560 point), cut insulating slits/lips in the substrate (US 4,777,820 / EP'660), or span a cavity (US 4,382,247). The '051 patent selects one of a small, enumerated set with a reasonable expectation of success.
   • Design incentive / market pressure. The references themselves frame short response time and startup time as the design goal to be met.
4. Reasonable expectation of success. US 4,382,247 shows the membrane is "sturdy," that "conductive tracks, resistance tracks, and glass or ceramic layers" are printed and fired on it, and that the resistors are "covered by a glaze or glass coating." Adding a second resistor film with a glass film between it and the first (as taught by US 4,399,697 / JP-A-57-93212 / US 4,831,876) uses the same fabrication sequence already disclosed. Nothing in the combination requires an unproven step.

4.3 Teaching away — and why it fails

The best nonobviousness argument is that US 4,382,247's membrane is meant to bend (it is a pressure sensor whose resistor pair R1, R2 is strained by deformation), so the reference teaches using the membrane's compliance, not its thermal isolation. Three answers defeat it:

• The claim requires no deformation function; it requires only structure. A reference is prior art for everything it discloses, including what it discloses for a different purpose (KSR: "familiar items may have obvious uses beyond their primary purposes").
• US 4,777,820 chooses slits as its thermal remedy. Choosing one known route (a cavity) over another (slits) is not the same as being taught away; the reference must criticize, discredit, or discourage the claimed route, and EP'660 never disparages a thin membrane. To the contrary, EP'660's aim — reducing the substrate's contribution to the measured heat flow — is advanced better by a bubble than by a slit.
• The '051 specification itself concedes the point: "Differing from the arrangement shown in FIG. 3, the two film resistors R_H and R_S can also be interchanged in their position." An applicant who describes the ordering of the heater and sensor films as an optional alternative has, in effect, conceded that the alternative is a design choice rather than an inventive step.

5. Combination B (three references): US 4,777,820 + US 4,382,247 + US 4,399,697

This is the cleanest formal rejection, because it removes the only arguable gap in Combination A.

• US 4,777,820 (or SAE 880,560) supplies the hot-film air-mass-meter context, the layer-like heating and measuring resistors, and the bridge/control-amplifier evaluation.
• US 4,399,697 supplies the third layer of the film system — the "insulating material such as glass or resin" interposed between the heater film and the temperature-dependent resistor, expressly "so thin that good heat transmission from the heating resistor to the measuring resistor is possible." It also supplies the motivation in the reference's own words: this "makes the electric heater resistor closer to the temperature dependent resistive wire, thereby improving the response of the flow measurement." Claim 1's intermediate film (13) is squarely disclosed, with the claimed dual function (thermally conductive and electrically insulating) recited as the very purpose of the layer.
• US 4,382,247 supplies the bubble and the printing of resistors on its free-standing membrane.

Combining all three is not a matter of hindsight stitching: each reference is relied on for exactly the function it was designed to perform — Kohama's intermediate layer for thermal coupling with electrical isolation, Stecher's membrane for thin, low-thermal-mass support, and Bosch's carrier/lip for the air-flow measurement context. A claim composed of elements that each perform their known function, with no change in their respective functions and no unexpected result, is obvious under KSR. The '051's stated advantage — "Short response times are thereby achieved" — is the predictable arithmetic sum of lower substrate thermal mass plus tighter heater/sensor coupling. It is precisely the result the references were each already pursuing.

6. Combination C (alternative): US 4,831,876 + US 4,382,247 (＋EP 0 271 660 A2)

US 4,831,876 is independently close: it claims a probe for "measuring the mass of a flowing fluid, particularly the intake air of an internal-combustion engine" with temperature-dependent resistors in a bridge, with the express object of shortening response time, and it discloses overlapping resistor layers with an electric insulating layer between them and resistors developed as layers on a common support. Its express statement that "[t]his measure contributes to a further simplification of the arrangement" and that overlapping layers permit thermal contact, and its separate teaching that "[t]he partial external heating of the first resistor by the third resistor" reduces response time, supply both the structure and the motivation for claim 1's intermediate film. Substituting US 4,382,247's membrane for US 4,831,876's common support, or vice versa, is the same substitution already discussed in Combination A. This combination is weaker than B (US 4,399,697 states the "glass intermediate layer between heater and sensor" more squarely and more purposefully), so I treat it as a back-up rather than the lead theory.

7. The dependent claims

8. Secondary considerations

Under Graham step four, objective indicia must be considered — but there is nothing here to weigh:

• Nexus and evidence: the file contains no evidence of unexpected results, no comparative data, and no showing of a long-felt but unmet need that the prior art failed to satisfy. The advantages recited in the '051's "Advantages" section are the mathematically expected consequence of thermal decoupling, which is why they fall on the obvious side of KSR's "predictable results" line rather than the unexpected side.
• No commercial-success record: the patent lapsed in 1997 (maintenance-fee reminder 1996-09-24; lapse effective 1997-02-19), and — as the earlier sections establish — it was never asserted, never licensed in the record, and never the subject of a PTAB or district-court proceeding. There is no objective evidence to weigh even if nexus could be presumed.
• Family behavior cuts the other way: Bosch's contemporaneous filings in this exact space — DE 40 12 081 A1 ("Method and arrangement for measuring air amounts"), DE 43 07 512 A1 and DE 43 07 513 A1 ("Measuring element"), and DE 43 08 227 C2 / DE 43 24 040 B4 — reflect an incremental, crowded improvement program, not a discrete breakthrough that the art had been unable to reach.

9. Counterarguments worth briefing, and their weight

Bottom line on the merits: claim 1 would have been obvious over US 4,777,820 (or SAE 880,560) in view of US 4,382,247, and more cleanly over US 4,777,820 + US 4,382,247 + US 4,399,697; claims 2–8 are obvious over those combinations with the further references identified in the § 7 table (US 4,831,876; EP 0 271 660 A2; JP-A-57-93 212). The strongest single limitation — the ceramic bubble — is not merely analogous art but the same assignee's prior art, cited by the applicant in the "Prior Art" section as the very structure the invention builds on.

10. Verification limits and identifiers I did not auto-correct

1. SAE number. The authoritative full text says 880,560; the earlier generated section says 880,650. I used 880,560 (text of record) and did not silently reconcile them — my confirming search for the SAE paper returned no result before the tool step limit, so which number corresponds to pp. 105–109 (1988) is unverified.
2. US 4,816,200. Used only as corroboration because its 1989-03-28 issue date postdates the critical date and I did not verify whether its § 102(e) date carries back to the 1980 parent. The lead theory does not depend on it.
3. § 102(e) dates for US 4,777,820 and US 4,831,876 are inferred from the US filing/priority dates reported in the Prior Art data, not confirmed against a USPTO application record.
4. EP 0 430 979 B1 opposition history unverified. I state no opinion on whether it was opposed.
5. Identifiers left literal, per rule. I did not renumber or "fix" AU660900B2, JP P5186051, or any other numeric match; none were used in this analysis. Likewise the inventor spellings ("Gunther," "Muehlheim," "Berfried") are reproduced as the source renders them.
6. No direct USPTO/EPO register access was available. This analysis rests on the authoritative Google Patents full text supplied in the prompt plus the EPO publication-server and Google Patents mirrors of the individual references cited above.

Sources: https://patents.google.com/patent/US5186051/en; https://patents.google.com/patent/US4382247; https://patentimages.storage.googleapis.com/1a/2b/1a/4fad1f0e523af5/US4816200.pdf; https://patents.google.com/patent/US4777820; https://patents.google.com/patent/EP0271660A2/en; http://data.epo.org/publication-server/rest/v1.2/patents/EP0271660NWA3/document.html; https://patentimages.storage.googleapis.com/5d/3f/17/6634a76743b996/EP0271660B1.pdf; https://patents.google.com/patent/[US4831876A](/patent/US4831876A)/en; https://patents.google.com/patent/[US4399697A](/patent/US4399697A); https://patentimages.storage.googleapis.com/f9/39/31/751f3f20270c1c/US4399697.pdf.