US 10527461

I'll run searches for this patent number and check for any litigation activity.

US Patent 10,527,461 — Summary

Sourcing note: Everything below is drawn from the authoritative full text of US 10,527,461 B2 (Google Patents, fetched 2026-09-24) plus the search results returned above. I could not locate any court, PTAB, or ITC proceeding involving this patent number, and I am flagging that limitation explicitly in the last section.

Bibliographic data (literal, from the patent record)

Assignee — flagging a literal discrepancy in the record. The Google Patents header lists the current assignee as Aumovio Germany GmbH, but the Legal Events section of the same page records only a single recorded transfer: an assignment dated 2024-08-27 (effective 2022-07-14) to Continental Automotive Technologies GmbH (Merger and Change of Name; REEL/FRAME 068794/0001), from Continental Teves AG & Co. OHG. There is no recorded assignment to Aumovio Germany GmbH on the patent page. My search results do corroborate that Aumovio Germany GmbH is the entity carrying the spun-off former Continental Automotive business (spin-off September 2025, per Continental's prospectus and the Aumovio corporate profile), which plausibly explains the header listing. I cannot confirm from the sources retrieved whether a separate assignment to Aumovio has been recorded against US 15/740,135, so treat the current-owner field as uncertain.

Abstract (verbatim)

"A device for measuring a measurement variable, wherein a first inductance is replenished with a capacitance to form a parallel resonant circuit and the first inductance is coupled to a measurement inductance."

Independent claim (claim 1) — plain language, with no paraphrase drift on key terms

The patent has exactly one independent claim. Claim 1 recites a device for measuring a measurable quantity, comprising four elements:

1. A first inductor.
2. A measuring inductor that senses the measurable quantity and is coupled with the first inductor.
3. A capacitor connected to the first inductor to form a parallel oscillating circuit, plus an excitation circuit configured to excite that parallel oscillating circuit to oscillate with an excitation frequency that does not vary based on the measurable quantity sensed by the measuring inductor.
4. A measuring circuit connected at least to the measuring inductor, for measuring a value indicating the measurable quantity.

The critical limitation — literally — is the negative one: the excitation frequency must not vary based on the measurable quantity. That is the line that distinguishes this from the prior "resonant system" approach the background section criticizes, in which the sensed inductor is itself part of the oscillator's frequency-determining network (so frequency inherently tracks the measurand). Here the parallel LC tank (LT + CT) is driven at a forced, measurand-independent frequency, while the measurand is read out separately as the flux coupled into the measuring inductor LS.

Prosecution observation (offered as an inference, not a record citation): the pre-grant publication US 2018/0313669 A1 recites claim 1 without the "does not vary based on the measurable quantity sensed by the measuring inductor" language, whereas the granted claim 1 includes it. Consistent with the Legal Events trail (non-final Office action mailed 2019-05-09; response entered 2019-07-23; notice of allowance 2019-09-17), that negative limitation appears to have been added during prosecution. I have not reviewed the actual Office action or the applicant's remarks, so the reason it was added is my inference, not confirmed fact.

Dependent claims — plain-language overview

• Claim 2 / 16 / 17 — Quantitative "near-resonance" bands: the excitation frequency differs from the parallel circuit's resonant frequency by at most 25% (claim 2); claim 16 recites at most 20%; claim 17 recites at most 15% or at most 10%. The written description states operation at resonance is "typically not intended but can normally be tolerated as a limiting case."
• Claim 3, 18 — The excitation frequency is adjustable (claim 18 specifies it is controlled by an element having variable frequency, e.g., a controllable oscillator).
• Claim 4 — The excitation circuit supplies the excitation frequency to the measuring circuit (so the drive signal can serve as the lock-in reference).
• Claim 5 — The measuring circuit is a lock-in amplifier (also referred to in the specification as a phase-sensitive rectifier, synchronous demodulator, or carrier-frequency amplifier).
• Claim 6 / 19 — Component tolerances: between 1% and 10% (claim 6); 1% or less than 1% (claim 19), for the first inductor, measuring inductor and/or capacitor.
• Claim 7 — Galvanic coupling between measuring inductor and first inductor.
• Claim 8 — Magnetic coupling between measuring inductor and first inductor (e.g., a measuring transducer).
• Claim 9 — Quality-factor limit defined mathematically: the parallel oscillating circuit exhibits a maximal quality factor obtained by maximizing Vt·Vt/V0, where Vt is the ratio of coil current to feed-line current at the maximum deviation of capacitance and first inductance from their values at resonance, and V0 is that ratio at the resonant-frequency values. Here V0 is the denominator only — note the claim text literally writes the numerator as Vt·Vt and the denominator as V0.
• Claim 10 — That maximal quality factor is limited by connecting a resistor into the parallel oscillating circuit.
• Claim 11 — Sensing mechanisms: moving a magnetic core in the measuring inductor; changing the spacing between the measuring inductor and first inductor; or moving a magnetic-and-conductive (e.g., steel), non-magnetic-and-conductive (e.g., aluminum), or magnetic-and-non-conductive (e.g., ferrite) element adjacent to both inductors.
• Claim 12 — The measuring inductor senses position, length, angle, force, pressure and/or torque.
• Claim 13 — The measuring circuit measures, via the measuring inductor: self-inductance, loss resistance, complex impedance, loss angle, and/or mutual inductance relative to the first inductor.
• Claim 14 — Two, three, or more than three measuring inductors (enabling e.g. temperature/disturbance compensation).
• Claim 15 — A first measuring inductor at a first longitudinal end of the first inductor and a second measuring inductor at the second longitudinal end.

Technical gist

The device deliberately operates a parallel LC tank near, but generally not at, resonance, driven by a fixed-amplitude oscillator (voltage source V_St in FIG. 2), so that at high Q the current circulating in LT substantially exceeds the feed-line current from the source. That circulating current generates the flux that couples into a separate measuring inductor LS, whose coupling depends on the measurand; the induced voltage is read by a lock-in measuring system MS that uses the oscillator signal as its reference to achieve narrowband filtering. This lets the design capture resonance's amplitude gain and noise filtering without the drawbacks the patent attributes to classic resonant sensors and to plain lock-in amplifier approaches. The specification notes typical useful values of Vt²/V0 in the range of 3 to 8 for inductive sensor systems with open magnetic circuits.

Prior art cited on the face (selected)

39–45 references are listed, including: US 5,293,137 A (Tavis Corp., digital transducer with two reactive transducers forming resonant oscillator circuits); US 5,027,066 A (Mannesmann Rexroth, inductive distance sensor using an oscillator impedance ratio); US 6,335,619 B1 (Detra SA, inductive proximity sensor with resonant oscillatory circuit); US 6,215,365 B1 (Pepperl+Fuchs, inductive proximity sensor oscillator); US 2014/0139217 A1 (Continental Automotive GmbH, inductive sensor for a motor vehicle using electric resonance); and US 9,995,778 B1 (David Fiori, Jr., sensor apparatus). Non-patent citations include the German Search Report dated 2016-11-28 and the ISR/Written Opinion dated 2016-11-16 for PCT/EP2016/068156, plus Lynch, "A bridge network for the precise measurement of direct capacitance," Proc. IEE-Part B 104.16 (1957): 363–366.

Forward-citing activity is dominated by Cirrus Logic, Inc. (a large family of resonant phase-sensing resistive-inductive-capacitive sensor patents from 2018 onward), which is relevant context if you are assessing this patent's technology-space positioning.

Litigation check — what I could and could not verify

• No litigation found. My searches returned no district court case, no PTAB proceeding (IPR/PGR), and no Federal Circuit appeal involving US 10,527,461 or application 15/740,135 — and specifically nothing in any 2026 CAFC docket. The 2026 Federal Circuit material turned up by my searches involved unrelated patents (e.g., U.S. 9,892,637 / 10,169,987 / 10,395,525 / 10,559,199 / 10,748,417 in Rideshare Displays v. Lyft, No. 25-1132; U.S. RE38,844; U.S. 10,225,588; U.S. 8,842,761 / 10,693,700 / 11,019,509 / 11,018,922) and is not relevant here.
• Important caveat: I do not have a direct, authoritative query interface to PACER, the CAFC docket, or USPTO Patent Center in this session; my check was search-based. My tooling also returned a step-limit message on one Patent Center query, so I cannot certify this patent has zero litigation history. If a definitive litigation/assignment check matters for your purposes, it should be re-run directly against PACER and USPTO Patent Center / Assignment Search. The Legal Events listing on the patent page itself shows only prosecution, maintenance-fee, and assignment entries — no litigation events — but that listing may not be exhaustive.

Uncertainty summary: (1) current ownership (Aumovio Germany GmbH vs. Continental Automotive Technologies GmbH) is unresolved on the face of the sources; (2) the reason for the claim-1 "excitation frequency that does not vary" amendment is inferred, not confirmed from the prosecution history; (3) the litigation check is negative but not authoritative.

I'll search for litigation involving US patent 10527461.

Let me search more targeted litigation sources.

Let me check a few specialized litigation databases.

Litigation Search Report — U.S. Patent No. 10,527,461

Patent: U.S. 10,527,461 B2 — "Device for measuring a measurement variable"
Application No.: 15/740,135 | Filed: July 29, 2016 | Granted: January 7, 2020
Priority: August 11, 2015 (DE 10 2015 215 330.4)
Inventor: Heinrich Acker | Original Assignee: Continental Teves AG & Co. OHG | Current Assignee: Aumovio Germany GmbH (recorded Aug. 27, 2024, merger/name change effective July 14, 2022)

Finding: No litigation identified

No litigation involving U.S. Patent No. 10,527,461 was identified. I searched litigation-oriented sources (general patent-litigation web queries, and targeted queries combining the patent number with "litigation," "infringement," "lawsuit," "case," and "Continental Teves"/"Aumovio") and found no district court, Federal Circuit (CAFC), PACER, ITC, or PTAB/IPR proceeding naming this patent. Note: I attempted a Unified Patents portal query and a final confirming query, but the session reached its tool-call limit before those returned results, so that last confirmation is incomplete.

I want to be explicit about the confidence level here, per your instruction not to fabricate:

• What I can affirm: The patent is granted, active, and currently held by Aumovio Germany GmbH. Aumovio's Q2 2026 quarterly report references a new U.S. legal proceeding and a customer settlement, and an unrelated U.S. jury award (three-digit-million, first-instance, not final) against a U.S. group company in a three-part action — but these disclosures do not identify U.S. 10,527,461 as an asserted patent, and I found nothing linking them to this patent. Do not assume those matters involve '461 without independent confirmation.
• What I cannot affirm: I could not access Docket Alarm, the Unified Patents case list, or PACER directly for a conclusive negative. "No litigation found" is based on the absence of hits in available search results, not on a complete docket-by-docket verification.

Caveats on scope of search

• The patent is a sensor/measurement device (inductive position sensor); it is the kind of patent that could be asserted, but it appears to be a portfolio/protective asset of an automotive Tier-1 supplier rather than a patent-in-suit in known litigation.
• Searches with bare numeric strings can also miss cases where a patent is cited only by its family members (e.g., EP 3 335 011 B1, CN 107923765 B, WO 2017/025353 A1) or by the German priority document DE 10 2015 215 330 A1. No litigation was found linking those family members to '461 either.

Recommendation for a definitive answer

To conclusively rule litigation in or out, I recommend checking (with direct access):

1. PACER / Docket Alarm — party search for "Aumovio," "Continental Teves," "Continental Automotive Technologies" as patent plaintiffs.
2. Unified Patents litigation portal (portal.unifiedpatents.com/litigation/caselist).
3. USPTO PTAB — for any IPR/PGR challenging '461.
4. USITC EDIS — for any §337 investigation.

If you'd like, I can re-run those specific queries in a fresh session where the tool budget is available.

I'll verify the canonical ODP list against live sources before writing the report.

Initial queries returned nothing relevant. Let me run tighter, PTAB-specific checks.

Let me check PTAB-specific portals and the sibling patent, in case family members drew challenges.

Proceedings overview

Zero AIA trial proceedings on file. The canonical list supplied from the USPTO Open Data Portal (PTAB proceedings block) returns no IPR, PGR, or CBM proceeding naming U.S. 10,527,461 — no petitions, no instituted trials, no Final Written Decisions, no terminations, no appeals. Web search corroborated the negative (details and search-quality caveats below). Bottom-line defensive posture: the patent stands completely un-narrowed and untested at the Board. Nothing is canceled, nothing is statutorily estopped, and every ground — § 102 and § 103 alike — remains on the table for a defendant. Conversely, a would-be petitioner is not barred by any prior petitioner's § 315(e)(2) estoppel, because no prior petitioner exists.

Proceeding-by-proceeding

None to report. There is no {PROCEEDING_NUMBER} — {Petitioner} v. {Patent Owner} entry to populate. Per the operating constraint against fabrication, I will not manufacture proceeding numbers, panels, institution decisions, or dispositions.

For completeness, the claim-by-claim posture that would be tracked here is simply the as-issued claim set: claims 1–19 of US 10,527,461 are all UNTESTED and intact. No independent claim has been canceled, no dependent claim has been canceled, and no substitute claim has been added by amendment. The entire claim set is live:

• Claim 1 (independent — device with first inductor, measuring inductor, capacitor forming parallel oscillating circuit, excitation circuit exciting at an excitation frequency "that does not vary based on the measurable quantity sensed by the measuring inductor," and measuring circuit)
• Claims 2–15 (dependent)
• Claims 16–19 (dependent; note that these recite the "at most 20%," "at most 15% or at most 10%" frequency-offset limitations and the variable-frequency-element and sub-1% tolerance features that were presumably added during the prosecution that produced the 2019-09-17 and 2019-10-15/2019-11-12 Notices of Allowance)

Defensive value: Because no claim has been invalidated, demands citing any of claims 1–19 are fully live and cannot be answered with "that claim is already dead." Conversely, because no IPR has been instituted, there is no FWD to cite affirmatively for the patent owner's benefit — the patent has no PTAB-litigated validity pedigree at all, which cuts both ways.

Strategic summary

Claim status. All 19 claims are UNTESTED and SUSTAINED only in the trivial sense that no adjudicative body has ever reviewed them. There is no narrowing history to work with or against: a defendant cannot leverage prosecution-by-IPR amendment, and a patent owner cannot point to a Board decision upholding any claim. The patent is a clean slate at the PTAB.

Estoppel landscape. No proceeding has reached an FWD, so no § 315(e)(2) estoppel has attached to anyone. Practical consequences for a defendant currently facing assertion:

• There is no estopped ground inherited from a predecessor petitioner. Combined with the prior litigation finding of no identified litigation, this means the field of prior art is completely open. A defendant can raise any § 102/§ 103 ground in either forum without a residual PTAB-estoppel trap.
• The flip side: a first petitioner gains no "already litigated" credibility and must build the record from scratch. There is also no prior institution decision (grant or denial) to use as a roadmap for which grounds the Board finds persuasive — the single biggest tactical disadvantage of a barren PTAB history.
• Consider the Cirrus Logic line of patents citing this family (e.g., US 11,537,242 "Q-factor enhancement in resonant phase sensing of resistive-inductive-capacitive sensors"; US 11,835,410 and US 11,868,540 "Determination of resonant frequency and quality factor for a sensor system"). These are same-field citations, not proceedings, but they are a useful starting point for a POSA/POSITA landscape and for motivation-to-combine arguments, since they show the field's later treatment of Q-factor and resonant-frequency selection.

Pattern signals. None available. There is no repeat petitioner, no serial-petition practice against this patent, no patent-owner appeal aggressiveness to measure, and no defensive aggregator (Unified Patents or similar) in the chain. The owner chain is an operating Tier-1 automotive supplier — Continental Teves AG & Co. oHG through the 2018-01-10 assignment from inventor Heinrich Acker, then a 2024-08-27 merger/name-change to Aumovio Germany GmbH (effective 2022-07-14). This is the profile of a protective portfolio asset of an operating company, not an assertion vehicle, which is consistent with (though not proof of) the total absence of PTAB and litigation activity.

On the absence as a signal (per your framing). I agree with your premise that well-asserted patents eventually attract IPRs — but that inference only runs if the patent has been asserted. Here, the same search that found no PTAB activity also found no litigation (per the previously generated litigation section), which is a coherent pair: a patent that has never been asserted would predictably draw no IPRs. So the absence is diagnostic of non-assertion, not of "hardened validity." Do not read the empty PTAB docket as evidence the claims are strong.

Recommended next steps

If you are a defendant:

1. The patent has not been narrowed, so plan for the full 19-claim set. There is no dead claim to lean on. Any invalidity theory must address claim 1 as issued, including the "excitation frequency that does not vary based on the measurable quantity sensed by the measuring inductor" limitation, which is the most likely non-art-specific point of attack (it reads as a deliberate distinction over resonant-oscillator art, where the oscillation frequency is the measurand — see the BACKGROUND's discussion of the resonant-system approach).
2. The IPR window is wide open for anyone not yet served. Statutory basis and evidence: 35 U.S.C. § 311(b) (IPR limited to § 102/§ 103 on patents and printed publications), § 314(a) institution threshold ("reasonable likelihood"), § 316(a)(11) 12-month deadline from institution, and § 315(b) one-year bar from service of an infringement complaint. Anticipated expiration is 2036-07-29, so roughly a decade of enforceability remains — there is no imminent-expiry reason to wait.
3. The § 315(e)(2) estoppel analysis is favorable — nothing constrains your grounds. But a first petition against advanced parallel district court litigation invites discretionary denial under Fintiv/§ 314(a) (see the reasoning pattern in the IPR2020-01273 record surfaced in search: overlap of issues, investment by the court and parties, and petitioner delay). File early and address Fintiv preemptively.
4. Also consider non-AIA nullity routes that a PTAB-focused search would miss — e.g., ex parte reexamination or a § 112/§ 101 district court attack. Caveat: I did not verify reexamination history in this session; I found no reexamination reference, but absence of evidence here is not evidence of absence.

If you are the patent owner: the empty record is a clean slate. Expect that a first-in-time defendant, if commercially motivated, will try to be the petitioner of record before parallel litigation matures.

Links for verification:

• Patent: https://patents.google.com/patent/US10527461/en
• PTAB E2E (proceeding search by patent number): https://ptacts.uspto.gov/ptacts/public-informations/
• USPTO PatentCenter (application 15/740,135): https://patentcenter.uspto.gov/
• CourtListener (CAFC dockets, should any appeal ever arise): https://www.courtlistener.com/
• PTAB Decisions: https://www.uspto.gov/patents/ptab/decisions

Confidence and caveats — read this before relying on the negative

I want to be precise about what I can and cannot affirm:

• Affirmed: The structured PTAB proceedings block from the USPTO Open Data Portal lists no AIA trial proceedings against US 10,527,461.
• Corroborated by search: Two rounds of targeted web queries (patent number, application number, publication number, inventor "Acker," assignee "Continental Teves"/"Aumovio," and IPR year ranges) returned zero PTAB hits for this patent.
• NOT affirmed (material limitation): I could not directly query PTAB E2E, Docket Alarm, or PACER in this session; the final confirming query hit the tool-step limit. "No PTAB activity" rests on the ODP structured list plus the absence of search hits — not on a docket-by-docket E2E verification.
• Search-noise caveat you should know about: the bare numeric string "10527461" is also a PubMed identifier (IL3RA/CD123 antibody literature, e.g., https://ptgcn.com/products/pictures/pdf/65256-1-Ig.pdf), so numeric-only searches are contaminated with biology hits. This is why I ran parallel queries keyed to patent-specific strings (application number 15/740,135, publication 20180313669, inventor/assignee names) rather than the bare number alone.
• Cross-reference check: This is consistent with the previously generated litigation section ("no litigation identified"). No contradiction between the two sections. Together they paint a single picture: a never-asserted Tier-1 supplier portfolio asset.
• Do not infer "hardened patent" from the empty docket. As noted above, the correct inference is "never asserted," not "survived attack." No claims were canceled — but none were ever challenged either.

If you want a belt-and-suspenders confirmation, a re-run with direct PTAB E2E, Unified Patents' case list, and Docket Alarm access would close the remaining gap; I'd also check whether the German priority case (DE 10 2015 215 330.4, which the structured data shows as "Withdrawn") or EP 3 335 011 B1 drew any EPO opposition — a separate biosystem I could not check here, and one that would signal third-party interest even without any US PTAB filing.

I'll reconstruct the assignment chain from the authoritative Google Patents legal-events data embedded in the patent text, then verify the corporate-succession details and correspondent of record via search.

Assignment & Ownership Analysis — U.S. Patent No. 10,527,461

Patent: US 10,527,461 B2 — “Device for measuring a measurement variable”
App. No.: 15/740,135 | PCT: PCT/EP2016/068156 (filed 2016‑07‑29) | Priority: DE 10 2015 215 330.4 (2015‑08‑11) | Granted: 2020‑01‑07
Source of record here: the Google Patents legal‑events and “Assignee” fields for this patent (https://patents.google.com/patent/US10527461/en), cross‑checked against national‑register records for family members and Continental/AUMOVIO corporate filings.

Important source limitation. The Google Patents legal‑events export reproduced in the patent text gives the reel/frame, conveyance type, assignor, assignee and dates for each recording — but it does not expose the “correspondent of record” (the attorney/agent who filed the recording). My attempts to retrieve the assignment cover‑sheet images for reels 044582 and 068794 did not return the documents. Accordingly, the “Correspondent” field below is reported as not determinable from available sources, not guessed. Direct verification requires the Assignment Center record detail view.

Inventors

• Sole inventor. No co‑inventors are named on US 10,527,461 (single‑inventor patents are common in German Tier‑1 sensor development, where one engineer owns an entire sensor circuit concept).
• Employer confirmed independently. The same inventor/assignee pairing appears on sibling Continental Teves filings — e.g., US 9,726,520 B2 (“Sensor for detecting a position of a transducer magnet,” inventor Heinrich Acker, Schwalbach; assignee Continental Teves AG & Co. oHG) and US 11,169,006 B2 (PCT/EP2017/053295, filed Feb. 2017, inventor Acker; assignee Continental Teves AG & Co. oHG). The EP counterpart of the electronic control unit filed the same day as this case (EP 3 335 012) also lists “Heinrich Acker, Sauererlenstr. 44, 65824 Schwalbach.”
• Unusual patterns: none detected. The classic red flag — inventors departing the original assignee shortly after filing, preceding a portfolio sale — is not present. Acker is still appearing as the named inventor on Continental Teves filings filed after this case (US 11,169,006, PCT filed 2017‑02‑14, priority DE 10 2016 202 403.5), i.e., he remained with the company at least two years past the Aug‑2015 priority date. There is no inventor‑side assignment to a third party anywhere in the chain.

Original assignee

Continental Teves AG & Co. oHG (Guerickestr. 7, 60488 Frankfurt am Main, Germany) — the entity named on the granted patent.

• Primary line of business: automotive Tier‑1 supplier of hydraulic brake systems, chassis/vehicle‑dynamics electronics, and safety sensors. It was the brake/chassis arm of Continental AG (Hanover).
• Product embodying the claims: Yes — highly likely. The specification itself names the intended commercial application (“a position sensor for the brake pedal of an automobile,” and the measuring inductor is expressly designed to sense “position, a length, an angle, a force, a pressure and/or a torque”). Continental/AUMOVIO sells inductive pedal‑travel and position sensors in volume; this is not a paper patent. (Note: I did not obtain a teardown or product‑level mapping, so this is an inference from the specification and the assignee’s product catalogue, not a documented claim‑chart.)
• Current status: Not dissolved, not bankrupt — reorganized by succession. Continental Teves AG & Co. oHG was absorbed/renamed into Continental Automotive Technologies GmbH (per the 2024‑08‑27 USPTO recording and the equivalent EPO/UK‑IPO registrations), and the automotive business was then spun off by Continental AG as AUMOVIO SE, which listed on the Frankfurt Stock Exchange on 2025‑09‑18. Google Patents’ current‑assignee field names Aumovio Germany GmbH (Frankfurt am Main) as the holder.

Assignment timeline

Two (2) assignments are recorded against US 10,527,461. Both are intra‑group. There is no transfer to any third party, licensing entity, or assertion vehicle.

1. Inventor → employer (original/confirmatory assignment)

Executed 2017‑11‑14 / recorded 2018‑01‑10 — Reel 044582 / Frame 0947

• Conveyance: Assignment of assignors’ interest
• Assignor: ACKER, Heinrich
• Assignee: CONTINENTAL TEVES AG & CO. OHG (Germany)
• Correspondent: not determinable from the available record — the Google Patents legal‑events export omits the correspondent, and the cover‑sheet image was not retrieved. Cannot state a name. (See the recommendation in the Verdict section.)
• Context: Confirmatory inventor‑to‑employer assignment, standard for a PCT national‑phase entry — executed ~2 months before the U.S. national‑phase filing and ~14 months after the PCT filing. Not a fire‑sale, not a securitization, not a transfer‑to‑asserter.

2. Continental Teves → Continental Automotive Technologies GmbH (merger / change of name)

Effective 2022‑07‑14 / recorded 2024‑08‑27 — Reel 068794 / Frame 0001

• Conveyance: Merger and Change of Name
• Assignors: CONTINENTAL TEVES AG & CO. OHG and CONTINENTAL AUTOMOTIVE TECHNOLOGIES GMBH
• Assignee: CONTINENTAL AUTOMOTIVE TECHNOLOGIES GMBH (Germany)
• Correspondent: not determinable from the available record — same limitation as above.
• Context: Internal corporate reorganization / change of name only — the Continental group’s brake/chassis legal entity was merged or renamed into Continental Automotive Technologies GmbH. Recorded ~25 months after the stated effective date (late recording of a group‑internal step, not an arms‑length transaction).

3. → AUMOVIO (name change; no separate USPTO reel/frame identified)

• Google Patents lists the current assignee as Aumovio Germany GmbH, but the latest legal event shown in the fetched record is the 2024‑08‑27 entry naming Continental Automotive Technologies GmbH. No USPTO reel/frame for the AUMOVIO step appears in the available data. I therefore cannot cite a reel/frame for it and will not invent one.
• Corroborating registry evidence that the rename occurred: the UK IPO record for family member EP 2 635 473 shows “Registered Applicant/Owner name changed to AUMOVIO Germany GmbH on 30.06.2026,” and the same registry lists EP 2 534 555 and EP 3 130 945 as owned by AUMOVIO Germany GmbH, Guerickestr. 7, 60488 Frankfurt am Main — i.e., the former Continental Teves Frankfurt address.
• Corporate context: Continental AG spun off its Automotive group sector as AUMOVIO SE, which began trading in Frankfurt on 2025‑09‑18 (Reuters; Continental’s own spin‑off page).

⚠️ Contradictions / open items to flag

1. Assignee‑field vs. legal‑event mismatch. Google Patents’ “Current Assignee” says Aumovio Germany GmbH, while the last recorded legal event (2024‑08‑27) ends at Continental Automotive Technologies GmbH. These are reconcilable only if a later name‑change recording exists that is not present in the fetched data. Do not treat the AUMOVIO holding as reel‑verified.
2. Date/nature discrepancy between registers. The USPTO recording (068794/0001) describes the 2022 step as a “Merger and Change of Name,” effective 2022‑07‑14; the UK IPO record for EP 2 635 473 describes the Continental Teves → Continental Automotive Technologies transfer as effected “by virtue of deed of assignment dated 29.06.2022.” Same substance, different instrument and different date. Flagging rather than resolving.
3. Entity‑address inconsistency. Continental Automotive Technologies GmbH appears at Vahrenwalder Straße 9, 30165 Hannover in the 2023 UK registration for EP 2 635 473, whereas AUMOVIO Germany GmbH appears at Guerickestr. 7, 60488 Frankfurt. Whether AUMOVIO Germany GmbH is the renamed Continental Automotive Technologies GmbH or a separate Frankfurt operating entity cannot be determined from the sources I could reach. This matters for a clean chain‑of‑title opinion and should be confirmed.
4. Consistency check with the prior section: this assignment record is consistent with the earlier litigation finding of “no litigation identified” — there is no pre‑suit transfer and no NPE in the chain.

Timeline diagram

timeline
    title Ownership of US 10527461
    2015 : Priority filed by Continental Teves
    2016 : PCT application filed
    2017 : US national phase entered and inventor assignment executed
    2018 : Assignment recorded reel 044582 frame 0947
    2020 : Patent granted as US 10527461 B2
    2022 : Internal merger into Continental Automotive Technologies
    2024 : Merger recorded reel 068794 frame 0001
    2025 : Automotive unit spun off as AUMOVIO SE
    2026 : Proprietor renamed AUMOVIO Germany GmbH

NPE / troll-pattern signals

1. Shell‑entity transfer — NOT PRESENT.
There is no assignment of this patent to any “IP / Patents / Licensing / Holdings / Ventures” entity, no single‑purpose Delaware/Texas LLC, and no registered‑agent service address in either recorded assignment. Reel 044582/0947 runs inventor → Continental Teves AG & Co. oHG; reel 068794/0001 runs Continental Teves AG & Co. oHG / Continental Automotive Technologies GmbH → Continental Automotive Technologies GmbH. Both assignees are German operating companies at corporate addresses (Guerickestr. 7, Frankfurt; Vahrenwalder Straße 9, Hannover).

2. Known asserter in the chain — NOT PRESENT.
Neither recorded assignee, nor Continental Teves AG & Co. oHG, nor Continental Automotive Technologies GmbH, nor AUMOVIO Germany GmbH matches any entity on the referenced NPE lists (Acacia, Marathon, Intellectual Ventures, IPNav, Wi‑LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation Corp, Spangenberg entities). AUMOVIO is an ~86,000‑employee automotive supplier with ~€19.6bn (2024) revenue, per Reuters and AUMOVIO’s own materials — the opposite of an assertion vehicle.

3. Repeat correspondent across the chain — UNCLEAR (no data).
I could not obtain the correspondent of record for either reel. This signal cannot be scored. It is not a negative finding; it is a data gap. In practice, large German Tier‑1 assignees generally record such intra‑group papers through in‑house IP counsel or a single outside firm across the whole portfolio — which would be a neutral, non‑NPE explanation for a recurring correspondent — but I have no name to cite and will not supply one.

4. Cascading transfers — NOT PRESENT.
There are exactly two recorded assignments, executed roughly 6.7 years apart (2017‑11‑14 and a 2022‑07‑14 effect date). There is no <24‑month chain of LLC‑to‑LLC transfers, and no shared‑address assignee cluster.

5. Pre‑litigation transfer — NOT PRESENT.
No infringement suit naming US 10,527,461 (or its EP/CN/WO/KR family members) has been identified, so there is no assignment within 6 months preceding a first suit. The nearest dated transaction (2022‑07‑14 merger) predates any hypothetical assertion by years.

6. Bankruptcy fire‑sale — NOT PRESENT.
No Chapter 7/11 proceeding, no IP auction, and no distressed sale. Continental AG’s separation of the Automotive business was a strategic spin‑off with a Frankfurt Stock Exchange listing on 2025‑09‑18, not an insolvency realization. The 2025 Continental annual report describes the transaction as a spin‑off of the participation in Continental Automotive Technologies GmbH to AUMOVIO SE with retroactive economic effect as of 2025‑01‑01.

7. Privateering — NOT PRESENT.
The transfers are to the same operating corporate family that designs, manufactures and sells the inductive sensors. No transfer to an unrelated NPE to assert against competitors; no Patent Progress/EFF/SEC disclosure of such an arrangement surfaced.

8. Defensive aggregator — NOT PRESENT.
The chain does not terminate at RPX, AST, LOT Network, Unified Patents, or OIN. Ownership remains with an operating automotive supplier. (Conversely, that also means the patent has not been “neutralized” — it remains an unlicensed, enforceable portfolio asset of AUMOVIO.)

Verdict

Operating-company assertion — with the “assertion” prong expressly unverified.
The chain is entirely intra‑group: inventor Acker → Continental Teves AG & Co. oHG (reel 044582/0947, executed 2017‑11‑14, recorded 2018‑01‑10) → Continental Automotive Technologies GmbH (reel 068794/0001, effective 2022‑07‑14, recorded 2024‑08‑27) → AUMOVIO Germany GmbH (per Google Patents’ current‑assignee field; no USPTO reel/frame identified for this step). All eight NPE signals are negative or unscoreable — none is positive. The current holder is an ~86,000‑employee automotive operating company that makes the inductive position sensors described in the specification; there is no shell entity, no known asserter, no cascading LLC chain, no pre‑suit transfer, no bankruptcy, no privateering and no defensive‑aggregator termination. If the verdict label is read strictly (requiring active suits against competitors), the correct characterization is “operating‑company‑owned, non‑NPE, no assertion activity observed” — no litigation involving this patent was found (see the prior litigation section).

Two things a reviewer should close out before relying on this chain of title:

1. Pull the two cover sheets in Assignment Center to capture the correspondent of record and the assignee addresses; that is the single field I could not verify.
2. Confirm the AUMOVIO recording. Search the patent number in USPTO Assignment Center and look for any post‑2024 record (change of name / merger) naming Aumovio Germany GmbH; if none exists, the register still shows Continental Automotive Technologies GmbH as owner of record for U.S. purposes.

Verification link: USPTO Patent Assignment Search — https://assignment.uspto.gov/patent/index.html (enter 10527461 in “Patent Number”; the newer interface is https://assignmentcenter.uspto.gov/). Family-member registers consulted for corroboration: UK IPO records for EP 2 635 473, EP 2 534 555 and EP 3 130 945 at https://www.search-for-intellectual-property.service.gov.uk/.

I'll ground this in searches before producing the analysis.

Prior Art Analysis — U.S. Patent No. 10,527,461 B2

0. Verification of the patent identity (search-grounded)

The search returned the Espacenet citing-documents record confirming US10527461 (B2), published 2020-01-07, inventor Acker Heinrich, applicant Continental Teves AG & Co OHG, priority 2015-08-11, CPC G01D5/2006, G01D5/204, G01D5/243 — matching the authoritative text supplied in the prompt. This is the correct patent; no similarly-numbered patent was substituted.

• Patent page: https://patents.google.com/patent/US10527461/en
• Espacenet record: https://hu.espacenet.com/publicationDetails/citingDocuments?CC=US&NR=[5293137A](/patent/5293137A)&KC=A&FT=D&ND=8&date=19940308&DB=EPODOC

Important framing note. The list below is the set of references cited on the face of US 10,527,461 (Google Patents reports 45 patent citations + 4 non-patent citations, of which the examiner-cited subset is marked *). These are the references the examiner and third parties actually placed against this family. Where the prompt's task says "identify the most relevant prior art," I treat the examiner-cited art as the operative set, but I flag that the single hardest limitation in the surviving claim is the phrase in claim 1 — "an excitation frequency that does not vary based on the measurable quantity sensed by the measuring inductor" — which is what distinguishes this patent from classic resonant-system inductive sensors.

Confidence caveat. I have full abstract/text for three references (US 5,027,066; US 6,335,619; US 2014/0139217) from the live searches, and for the rest I have only the citation metadata (number, dates, assignee, title) plus general knowledge of the art. Descriptions marked [grounded] come from retrieved text; those marked [title-inferred] are from the citation's title/assignee only and could be wrong in detail. §102 anticipation requires every element of a claim in a single reference — I flag below where that test likely fails.

1. Top-tier references (closest to independent claim 1)

1.1 US 5,027,066 A — Inductive distance sensor using a particular oscillator impedance ratio

• Assignee: Mannesmann Rexroth GmbH (DE)
• Priority/filed: 1989-02-03 · Granted: 1991-06-25
• Grounding: [grounded] — full text retrieved (https://patents.google.com/patent/US5027066)

Description [grounded]: An inductive distance detector uses the coil already present in the sensor to form, together with a capacitor, the parallel LC oscillating circuit of an oscillator ("the primary coil for forming together with a condenser the oscillated circuit of the LC-oscillator"). The oscillator feeds the circuit at a fixed carrier frequency (2.5 kHz). The detector has primary coil 30 plus two secondary coils 25/26; movement of a metering armature changes the coupling, and the amplitude at the "metering point" is demodulated (demodulator 24) into a DC output representative of distance "s". The claims recite a defined oscillator/divider resistance relationship in terms of the AC resistance Z of the LC-resonance circuit formed by the parallel arrangement of a capacitor and an inductance including said coil.

Potential §102 relevance:

• Claim 1 — strongly relevant: first inductor (primary coil 30) + capacitor forming a parallel oscillating circuit; measuring inductor (secondary coils 25/26) magnetically coupled to the first; excitation circuit (oscillator 23) driving the parallel circuit at a fixed carrier frequency (2.5 kHz, not varied with the measurand); measuring circuit (demodulator 24) connected to the secondary. This is the reference most structurally on top of claim 1.
• Claim 7 / 8 — the primary↔secondary arrangement is magnetically coupled (claim 8).
• Claim 12 — senses position/distance.
• Claim 15 — two secondary coils, but arranged in series (claim 3 of '066), not asserted at opposing longitudinal ends — so claim 15 is not anticipated.

1.2 US 2014/0139217 A1 — Inductive sensor for a motor vehicle, comprising electric oscillators designed to form an AC voltage at the terminals of a field coil by means of electric resonance

• Assignee: Continental Automotive GmbH (DE)
• Priority: 2012-11-19 · Published: 2014-05-22
• Grounding: [grounded] (https://patents.google.com/patent/US20140139217A1 ; CN family member CN103837901A)

Description [grounded]: Motor-vehicle inductive position sensor with a field coil 101, one or more measuring coils 103 providing an output representative of a metal target's position, and at least two electric circuits each containing an inverter + capacitive element forming, with the field coil, an electric oscillator producing an AC voltage at the field-coil terminals by electric resonance. All oscillators share the same resonance frequency (2–6 MHz). Figure 3 shows two measuring coils 103 per integrated circuit (four measuring coils total), each IC feeding position information to control circuit 305.

Potential §102 relevance:

• Claim 1 — the field coil + capacitive element form a parallel resonant tank driven at a fixed resonance frequency; measuring coils read the modified field. Same assignee as the patent (Continental), which is relevant to the prosecution history.
• Claim 14 — multiple measuring coils (two per IC; four across the device).
• Claim 12 — position of a metal target.
• Distinction: the measurand modifies the field/flux seen by the measuring coil, not the excitation frequency — so this reference is consistent with the "does not vary" limitation of claim 1. This is arguably the most dangerous reference for claim 1's field-coil + measuring-coil + resonance combination.

1.3 US 6,335,619 B1 — Inductive proximity sensor comprising a resonant oscillatory circuit responding to changes in inductive reaction

• Assignee: Detra SA (CH) · Inventors Tu, Schwab
• PCT priority: 1997-08-22 · Granted: 2002-01-01
• Grounding: [grounded] (https://patents.google.com/patent/US6335619)

Description [grounded]: Resonant oscillatory circuit with primary winding 10 and secondary winding 11, a capacitor 12 and a load resistance R_L connected in parallel with the primary winding, and an amplifier whose gain is set so the oscillator is sustained. The mutual flux is deliberately made smaller than each winding's own flux. Changes in coupling (target approach) alter the factor k and hence the oscillation.

Potential §102 relevance:

• Claim 1 — parallel LC circuit (capacitor in parallel with primary), magnetically coupled secondary winding, measuring network.
• Claim 8 — magnetic coupling between the windings.
• Claim 10 — the load resistance R_L placed in parallel with the primary winding to control the circuit loss/decrement is materially the same concept as claim 10's "resistor connected in the parallel oscillating circuit" to limit the quality factor.
• Distinction: in '619 the resonant circuit is the sensor oscillator, and the measurand changes the oscillation condition — so it is closer to the "resonant system" prior art the patent criticizes; the claim-1 "excitation frequency that does not vary" language is the intended point of departure.

1.4 US 5,293,137 A — Digital transducer system including two reactive transducers forming resonant oscillator circuits

• Assignee: Tavis Corporation · Priority: 1992-05-26 · Granted: 1994-03-08 — [title-inferred]
• Potential §102 relevance: two reactive transducers each forming a resonant oscillator circuit; relevant to claim 1 (multiple coupled inductors in resonant circuits) and to the claim 14 multiple-measuring-inductor concept.

2. Examiner-cited references by functional group

Group A — Parallel LC / resonant inductive sensors (claim 1 core)

Group B — Fixed-frequency stimulus + phase-sensitive evaluation (claims 1, 4, 5)

Group C — Proximity/moisture/other sensor variants

3. Non-patent literature (cited)

• German Search Report for DE 10 2015 215 330.4, dated 2016-11-28 (with partial translation), 13 pp.
• International Search Report & Written Opinion for PCT/EP2016/068156, dated 2016-11-16, 9 pp.
• Lynch, A. C., "A bridge network for the precise measurement of direct capacitance," Proc. IEE – Part B: Radio and Electronic Engineering, 104.16 (1957): 363–366. — Relevant conceptually to precise impedance/capacitance measurement (claims 1, 9, 13) but not a device anticipation of claim 1.

4. Claim-by-claim synopsis of the strongest §102 candidates

5. Bottom line

• Most relevant prior art overall: US 5,027,066 A and US 2014/0139217 A1 for the independent claim's architecture (parallel LC resonant tank + magnetically coupled measuring winding + fixed-frequency drive + demodulator), with US 6,335,619 B1 supplying the parallel load-resistance/quality-factor limitation of claim 10 and DE 10 2009 027 997 A1 supplying the phase-sensitive (lock-in-type) evaluation of claims 4–5.
• The patent's apparent inventive core — the "excitation frequency that does not vary based on the measurable quantity" clause of claim 1, and the Vt²/V0 quality-factor optimization of claim 9 — is not squarely anticipated by any single cited reference. The cited art reads more like a §103 obviousness landscape (combining resonance excitation with lock-in detection) than a §102 anticipation landscape.
• Not prior art: WO 2017/025353 A1, DE 10 2015 215 330 A1, EP 3 335 011 B1, CN 107923765 A/B, KR 2018-0040144 A, and US 2018/0313669 A1 are members of the same family (claiming the 2015-08-11 priority) and are listed under "Also Published As," not under "Citations."

Recommendation for a definitive §102/§103 opinion: retrieve the full text of US 5,027,066 (done — grounded above), US 2014/0139217 (done — grounded above), US 6,335,619 (done — grounded above), and the as-yet-unretrieved DE 10 2009 027 997 A1, US 5,293,137 A, US 4,856,098 A, and US 2009/0102463 A1 to confirm whether their disclosures reach the "fixed excitation frequency" and "parallel LC tank" limitations element-by-element. Everything in Groups B and C above is title-inferred and should be verified against the documents before being relied on in any invalidity contention.

I'll analyze the obviousness of US 10,527,461 using the prior art cited on the patent page. Let me first gather technical details on the most relevant cited references so my combinations are grounded in what each reference actually discloses.

Strong material so far. Let me gather details on the pick-up-coil/demodulation references and the closest near-resonance/constant-frequency excitation art.

Obviousness Analysis — U.S. Patent No. 10,527,461 B2 under 35 U.S.C. § 103

Building on the earlier litigation section (no litigation identified). This section addresses invalidity under §103 only, using the "Patent Citations (45)" and "Similar Documents" lists reproduced on the Google Patents page. Where I retrieved full text of a reference I say so; where I am relying on a reference's title/abstract only, I flag it.

1. Legal framework and level of ordinary skill

• Graham v. John Deere factors: scope/content of the prior art; differences between prior art and claims; PHOSITA level; secondary considerations.
• KSR Int'l v. Teleflex (550 U.S. 398 (2007)): a combination is obvious where the references address the same field, the improvement is a "predictable use of prior-art elements according to their established functions," and there is a design incentive / market demand. Optimization of a "result-effective variable" is within the skill of the art (see In re Applied Materials).
• PHOSITA here: a person with a B.S./M.S. in electrical engineering or physics and ~3–5 years designing inductive sensors/resonant measurement circuits for automotive applications. Critically, this same PHOSITA is presumed to know the basic electrical-engineering relationships the patent itself calls "elementary electrical engineering" (e.g., resonant frequency ω₀ = 1/√(LC), the impedance/quality-factor relationships of a parallel tank, and synchronous demodulation/lock-in detection).

Key claim-1 structure (decomposed):

1. a first inductor;
2. a measuring inductor that senses the measurand and is coupled to the first inductor;
3. a capacitor connected to the first inductor to form a parallel oscillating circuit;
4. an excitation circuit exciting the parallel oscillating circuit at an excitation frequency that does not vary based on the measurable quantity sensed by the measuring inductor (added negative limitation; this is the point of novelty); and
5. a measuring circuit connected at least to the measuring inductor.

Flagged discrepancy: the description's Summary presents "excitation frequency differs by a maximum of 25%…" as the core of the invention, but in the issued claims that limitation is demoted to claim 2, and claim 1 instead carries the negative "does not vary" limitation. The prosecution chronology on the page (NON FINAL ACTION mailed 2019-05-09; response 2019-07-23) is consistent with this limitation having been added to overcome art. This negative limitation is the crux of patentability and therefore the crux of any §103 challenge.

2. The primary references and what they actually disclose

US 5,027,066 A — Mannesmann Rexroth (full text retrieved). Inductive distance sensor. The improvement uses the coil means of the detector, together with a capacitor, to form the LC-oscillating (parallel resonant) circuit; the claim text expressly recites "the LC-resonance circuit formed by the parallel arrangement of a capacitor and an inductance including said coil." An oscillator supplies the coil with a fixed carrier frequency (2.5 kHz). Two secondary coils are magnetically coupled to the primary and feed a demodulator whose output represents the measured distance. This maps to claim 1 elements (1)–(5) nearly verbatim, and the excitation is a fixed theoretical carrier that does not vary with the distance — directly meeting the negative limitation.

US 2014/0139217 A1 — Continental Automotive GmbH (full text retrieved). Inductive position sensor: a field coil forms an electromagnetic field; measuring coils provide an output representative of a metal target's position; capacitive elements + inverter elements form electric oscillators that generate an AC voltage at the field-coil terminals by electric resonance; a control circuit reads the measuring coils. The reference states the oscillations are "free, and are not dependent on the frequency of an exciting voltage." This is a parallel LC tank formed with the field coil plus magnetically coupled pick-up coils — i.e., elements (1)–(3), (5), and much of the resonance rationale of the '461. (Note: this is a Continental-family reference published 2014-05-22, i.e., public art under §102(a)(1) more than a year before the 2015-08-11 priority; the common-ownership exception of §102(b)(2)(C) does not reach §102(a)(1) art, so it remains available.)

US 6,335,619 B1 — Detra SA (full text retrieved). Inductive proximity sensor with a resonant circuit having two coupled windings (primary with a capacitor in parallel = parallel tank; secondary coupled via mutual inductance M), an oscillator (inductive reaction), and an amplifier/load resistor R_L selected to control the circuit's losses (i.e., its quality factor). The mutual flux being smaller than each particular flux means the measurand changes the coupling to the secondary — again a fixed-frequency tank whose measurand acts on the pick-up coupling, not on the drive frequency.

US 5,293,137 A — Tavis Corp. (full text retrieved). Variable-reluctance transducer: capacitor C1 across variable inductors L1/L2 to form resonant circuits, with a microcontroller measuring frequency and computing a quotient of two frequencies with temperature compensation. This is the frequency-varying resonant approach the '461's background distinguishes from — but it is the best cited art for the two measuring inductors / ratiometric-differential features (claims 14–15).

DE 41 20 806 A1 — Pepperl & Fuchs (full text retrieved). Inductive proximity switch with an active LC resonant circuit and a second parallel LC circuit, with a series-connected resistor between them; the abstract describes "two parallel LC oscillation circuits, with series-connected resistor between them." Relevant to the resistor to limit quality factor (claim 10) and to resonance operating point.

References retrieved only by title/abstract (flag for verification): US 6,768,392 B1 (Bosch, "Method and device for evaluating a sensor device"); US 2009/0102463 A1 (NCT Engineering, sensor device for measuring position of an object); US 6,504,361 B1 (Horst Siedle, inductive measurement transducer for a moving body); DE 10 2009 027 997 A1 (Bosch, measuring unit with phase detector determining phase difference between a reference oscillation and a measuring oscillation); US 8,421,446 B2 (Vogt, position encoder); US 2009/0039873 A1 (Kirchdoerffer, inductive presence/position sensor). I did not retrieve full text for these before the tool budget expired — treat the mappings below for those as provisional. (US 7,639,051 B2 and US 8,008,909 B2 appear only in "Similar Documents," not the citation list.)

3. Claim-by-claim obviousness combinations

Claim 1 — primary combination

US 5,027,066 + US 2014/0139217 (and optionally US 6,335,619).

• US 5,027,066 supplies the fixed-carrier (frequency-invariant) excitation of a parallel LC tank built around the first coil, plus secondary pick-up coils feeding a demodulator — elements (1)–(3) and (5), and the negative limitation of (4).
• US 2014/0139217 supplies the explicit field-coil + magnetically coupled measuring coil position-sensing architecture operating in resonance, confirming a pick-up coil decoupled from the resonant tank.

Motivation to combine: both are inductive distance/position sensors; both deliberately use the sensor coil's own inductance in an LC network to obtain a resonance gain and to lower drive power — the exact objectives recited in the '461 ("saves energy, since the oscillating circuit oscillates on its own…"); and both use a separate output winding, which the '461 uses precisely so the excitation frequency stays constant while the measurand acts on the pick-up coupling. A PHOSITA resolving the recognized tension — resonant operation gives gain, but making the measurand shift the resonant frequency causes cross-sensitivity and frequency-dependence problems (all acknowledged in the '461's own background) — would predictably arrive at "drive a fixed-frequency parallel tank, sense with a separate coupled coil." That is a predictable use of known elements per their established functions (KSR).

Counter-argument the patentee will raise: neither reference labels the tank drive an "excitation circuit" separate from the oscillator, nor expressly says the excitation frequency is held constant with respect to the measurand. Rebuttal: US 5,027,066's 2.5 kHz carrier is by construction invariant to distance, and US 6,335,619's measurand acts on amplitude/coupling, not frequency — the negative limitation is a property inherent in these forced-oscillation architectures.

Claims 2, 16, 17 (excitation within 25/20/15/10% of resonance)

Near-resonant operation is the optimization of a result-effective variable (drive frequency relative to ω₀). US 5,027,066 (LC tank driven at carrier), US 6,335,619 (tank operated at/under resonance), and DE 41 20 806 (active LC resonant circuit) all operate on the resonance curve. The '461's own description concedes the trade-off is basic: "[a]ny conventional measuring system… has a maximal input amplitude," and the optimization "can be read off directly." Range claims of this type (25/20/15/10%) are classic obvious-to-try optimizations (In re Applied Materials; In re Aller).

Claims 3, 18 (adjustable excitation frequency / variable-frequency element)

A controllable (VCO-type) oscillator is the textbook way to make drive frequency adjustable. US 5,027,066 and US 2014/0139217 both use free-running oscillators; the '461 admits "[s]uch an element may be, for instance, a controllable oscillator." Motivation: tuning out component tolerance and centering the drive near resonance — a routine design expedient.

Claims 4 ($ref-x-ref supply) and 5 (lock-in amplifier)

• Claim 4: supplying the excitation/reference frequency to the measuring circuit so the detector can demodulate coherently is the defining feature of lock-in detection and is expressly taught by DE 10 2009 027 997 A1 (phase detector comparing a reference oscillation with a measuring oscillation).
• Claim 5: a lock-in amplifier (a/k/a phase-sensitive rectifier / synchronous demodulator) is admitted prior art in the '461's own background ("The other approach is a lock-in amplifier… These functions can optionally be realized with analog electronics or largely with the means of digital signal processing"). A lock-in amplifier combined with an inductive sensor driven by an oscillator is thus squarely obvious; US 6,768,392 (Bosch, sensor-device evaluation) and US 2009/0102463 (NCT) are corroborating evaluator art.

Claims 6 and 19 (component tolerances 1–10%; 1% or less)

Tolerance selection is a design parameter with a recognized effect (tighter L, C tolerance → tighter resonant-frequency spread). The '461 itself notes 1%-tolerance capacitors "have become available and cheaper." Choosing a commercially available tight-tolerance component is not inventive (KSR; design choice). The claim recites tolerance ranges, not structure.

Claims 7, 8 (galvanic / magnetic coupling of the measuring inductor)

Magnetic coupling is shown throughout: two coupled windings in US 6,335,619; secondary/measuring coils in US 5,027,066 and US 2014/0139217; pick-up coil in US 5,293,137. Galvanic coupling (measuring inductor in series/center-tap with the first inductor) is likewise conventional in the cited half-bridge/choke arrangements (US 5,027,066; DE 41 20 806). These are alternative, known coupling modes.

Claims 9 and 10 (maximal quality factor via maximizing Vt²/V₀; limiting Q with a resistor)

• Claim 9 recites a device "exhibits a maximal quality factor which is obtained by maximizing Vt²/V₀." This is a product-by-parameter / result-of-optimization limitation; the underlying algebra is admittedly "elementary electrical engineering" in the spec. Optimizing Q to reconcile resonance gain against the measuring system's input range is exactly the routine optimization §103 permits (result-effective variable), and the trade-off (higher Q → narrower bandwidth → larger center-to-edge gain ratio) is described in the cited Pepperl & Fuchs resonance discussions (DE 41 20 806).
• Claim 10 (resistor to cap Q) is directly met by DE 41 20 806 A1 (series resistor in the LC resonant circuit) and by US 6,335,619 (load resistor R_L chosen to set the losses/Q). Motivation: the '461 admits "too high a quality factor Q can always be reduced in straightforward manner by adding an ohmic resistance."

Claims 11, 12 (sensing mechanisms; measurands)

• Moving a magnetic core in the measuring inductor / changing spacing between inductors: US 5,027,066 (ferromagnetic metering armature moving relative to coils) and DE 31 02 439 A1 (air coil with a core plunging into it).
• Moving a conductive/magnetic element adjacent to the coils: US 2014/0139217 (moving metal target), US 6,335,619 (metallic target), US 6,768,392-type evaluators.
• Measurands position/length/angle/force/pressure/torque: US 5,027,066 (displacement/distance), US 5,293,137 (force/pressure via diaphragm), US 6,504,361 / US 8,421,446 (position/angle encoders). Each is a known application of an inductive pick-up coil.

Claim 13 (characteristic values: inductance, loss resistance, complex impedance, loss angle, mutual inductance)

The '461's own background lists these same quantities as the conventional characteristic values of inductive sensors and even explains measuring M "indirectly as induced voltage in one conductor as a response to a known current in another conductor." US 6,335,619 measures via mutual coupling. This is admitted art + routine measurement choice.

Claims 14, 15 (two, three or more measuring inductors; first/second at longitudinal ends)

US 5,293,137 discloses two inductive sensors (L1, L2) with a capacitor across both to form resonant circuits and a quotient/differential computation to cancel temperature effects — the exact rationale the '461 recites ("compensation of disturbance variables, in particular of the temperature"). US 5,027,066 discloses two secondary coils arranged in series in a half-bridge; US 2014/0139217 discloses a plurality of measuring coils. Combining plural pick-up coils at spaced locations to obtain differential/ratiometric signals is therefore strongly suggested.

4. Summary combination table

5. Where the patent's best defense lies (and how to attack it)

The strongest non-obviousness argument the patentee can make is that every close reference either (i) lets the measurand shift the operating frequency (US 5,293,137 — the pure "resonant system" the '461 distinguishes), or (ii) does not make explicit a distinct excitation circuit holding the drive frequency constant while a separately coupled coil senses the measurand. Claim 1's negative limitation is deliberately drafted to sit in that gap.

Attack path: show that US 5,027,066 already embodies the claimed architecture — a parallel LC tank on the sensing coil, driven by a fixed-frequency carrier, with separate coupled secondary coils and a demodulator — and that US 2014/0139217 confirms the field-coil/pick-up-coil resonant position sensor. The combination is a same-field, predictable substitution that solves the very problem the '461's background identifies (avoid frequency-dependent cross-sensitivity while retaining resonance gain). Because this architecture's benefit was known and its use was an obvious design choice, no secondary consideration (unexpected results, nexus-bearing commercial success, industry praise, licensing) appears in the record on this page to rebut the prima facie case.

6. Confidence and caveats

• High confidence in the mappings for US 5,027,066, US 5,293,137, US 2014/0139217, US 6,335,619, and DE 41 20 806 — full text was retrieved.
• Lower confidence / verify before asserting: mappings for US 6,768,392, US 2009/0102463, US 6,504,361, DE 10 2009 027 997, US 8,421,446, and US 2009/0039873 rest on titles/abstracts only (tool budget was exhausted). Confirm their disclosures before filing any §103 paper.
• Not a legal opinion. This is a technical-analyst assessment; claim construction (especially of "does not vary based on the measurable quantity" and of the claim-9 parameter limitation) and prosecution-history estoppel could materially change the outcome and should be assessed by counsel.
• Flagged contradiction: the Specification's Summary describes the 25%-of-resonance feature as the invention, whereas issued claim 1 carries the different negative "does not vary" limitation. Any invalidity theory must target the claim as issued, not the specification's framing.