US 5269275

I'll search for authoritative information on US 5269275 and check for any litigation references.

Let me check for any litigation or post-issuance proceedings involving this patent number specifically.

US Patent 5,269,275 — Verified Data Sheet

Note on scope: I searched for the literal number 5269275 / 5,269,275 (no auto-correction). Everything below matches the authoritative full text of US5269275. I found no litigation, ITC, or Federal Circuit activity tied to this number — see the caveat at the end.

Bibliographic data

Abstract

A pulse-width-modulated controller for N₂O and enrichment-fuel delivery having (a) a system control logic section that processes signals from throttle-position, engine-speed, and other user-selectable sensors, and (b) a driver section controlling electrically operated injectors or solenoid valves. The driver section opens the injectors only when all sensed parameters are satisfied, and holds them open for a duration set by a pulse-width modulation section. That PWM section receives signals based on present throttle position and engine speed, scales them by user-set N₂O and enrichment-fuel values in a tuning section, and continuously supplies the driver with a pulse whose width is proportional to the proper delivery amount at that instant. The tuning section is also user-settable to a maximum ignition-timing adjustment and feeds an ignition control section that automatically retards timing in proportion to the amount of N₂O/enrichment fuel being delivered.

Independent claims (plain language)

• Claim 1 — Apparatus (broadest controller). An engine-speed sensor and a throttle-position sensor feed a gate that emits a binary "go" signal once a threshold engine speed and throttle position are both reached. Two programmable memories hold the N₂O delivery rate and the enrichment-fuel delivery rate. Two multipliers combine those stored rates with the engine-speed and throttle-position signals to produce a N₂O-amount signal and a fuel-amount signal. A clock signal is compared against each amount signal to generate two pulse outputs whose widths are proportional to the respective amounts. Separate N₂O-injector and enrichment-fuel-injector drivers are gated by both the binary "go" signal and their respective pulse output. Both delivery rates are continuously adjusted with engine speed and throttle position by continuously varying the two pulse widths.

• Claim 7 — Apparatus (alternative, more explicit structure). Restates claim 1 with named elements: first/second sensors, first/second threshold memories, first/second comparators producing binary outputs, an AND gate combining them into a binary control output, third/fourth memories for the two delivery rates, first/second multipliers producing the two amount signals, and N₂O and fuel injector drivers coupled to the control output and the multiplier signals — again requiring continuous adjustment of the pulse widths (and hence delivery) once the thresholds are reached.

• Claim 8 — Method. Steps: (1) pre-select a threshold engine speed and throttle position at which N₂O + enrichment-fuel delivery commences; (2) pre-select an N₂O delivery rate and an enrichment-fuel delivery rate; (3) monitor engine speed and throttle position; (4) continuously adjust the pre-selected rates according to engine speed and throttle position by continuously varying the N₂O and fuel injection pulse widths; and (5) continuously deliver N₂O and fuel at the adjusted rates once the thresholds are reached.

Dependent claims (for completeness)

• Claim 2: adds ignition-timing control means coupled to the N₂O multiplier output.
• Claim 3: the gate means includes third/fourth programmable memories for the threshold RPM and threshold throttle position.
• Claim 4 / 5: the first / second multiplier is coupled to the sensors through an adder.
• Claim 6: adds a fifth programmable memory storing an initial enrichment-fuel richness value, coupled in via a second adder (the "fuel offset" feature).

Legal status

• Expired – Fee Related (lapsed). Maintenance fees were paid at 4 years (1997) and 8 years (2001); the 12-year window fee was not paid. USPTO records show: maintenance-fee reminder mailed Jun 29, 2005; lapse for failure to pay maintenance fees Dec 14, 2005; patent expired due to nonpayment under 37 CFR 1.362 (recorded Jan 11, 2006). Google Patents lists an anticipated expiration of Nov 2, 2012 (i.e., 20 years from filing), but the patent actually went abandoned in 2005.
• Prior art cited on the face of the patent includes Wheatley US 4,494,488 and US 4,572,140; Norcia et al. US 4,683,843; McMaster US 4,688,522; Vaznaian US 4,798,190; Furrow US 4,840,157; Budde US 4,953,348; Meaney US 5,088,464 and US 5,174,263; Paielli US 5,091,858; plus Accel "Thunder Twin Fuel Injection" materials and Calmap 6.0 instructions.
• The patent is cited by several later nitrous systems, including Meaney/Echlin US 5,444,628, Brunswick US 6,758,198, Competition Cams US 5,967,099, and Wilson US 6,269,805.

Litigation / CAFC 2026 dockets — uncertainty disclosure

I found no Federal Circuit appeal, district-court case, or post-grant proceeding referencing 5,269,275. My web searches for combinations of the patent number with "CAFC," "2026 docket," "litigation," and "lawsuit" returned zero hits for this patent; the only CAFC 2026 result was an unrelated stent case (Board of Regents v. Boston Scientific). I do not have direct query access to PACER, the CAFC docket system, or USPTO Patent Trial & Appeal Board filings, so I cannot affirmatively certify that no such proceeding exists — only that none surfaced. Given the patent lapsed in 2005 and its claims were tied to 1990s analog nitrous controllers, any live 2026 dispute would be unusual. Treat the "no litigation" conclusion as unverified rather than authoritative.

I'll search for litigation involving US patent 5269275.

The first search returned no results, and the second returned only an unrelated Japanese patent (JP5269275B2 — a pachinko/gaming machine patent, a different document entirely). Let me search dedicated litigation databases.

Let me try specific litigation portals and docket databases.

Summary Finding

I found no evidence of any litigation involving US Patent 5,269,275.

I searched for the specific number and related party/vendor terms across litigation-oriented sources, and every hit either returned zero results or resolved to a different document:

Litigation Table

Documented Context for US 5,269,275 (not litigation, but relevant to enforceability)

• Patent: "Pulse width modulated controller for nitrous oxide and fuel delivery"; US 5,269,275 A; App. No. 07/970,395.
• Inventor: David Dahlgren. Original assignee: Individual; 50% undivided interest assigned to David Rook (recorded 1992‑11‑02, effective 1992‑10‑26; Reel/Frame 006302/0044).
• Priority/filing date: 1992‑11‑02; grant date: 1993‑12‑14.
• Terminal status: Maintenance-fee lapse for failure to pay fees under 37 CFR 1.362, effective 2005‑12‑14; status "Expired – Fee Related." Anticipated expiration listed as 2012‑11‑02.
• Consequence: Because the patent lapsed in 2005 and the term in any event would have run to 2012, the patent is expired and unenforceable, which is consistent with (though not proof of) the absence of any recorded infringement litigation — any suit would have had to be filed before expiration.

Confidence and Limitations (stated explicitly, as required)

• High confidence: No litigation is indexed for US 5,269,275 in the sources I could reach. The patent has been expired since 2005/2012.
• Not verified: I could not directly query PACER, the Federal Circuit docket, or run the Unified Patents Portal caselist filtered to patents=5269275 on a rendered page; those require interactive access. My conclusion rests on the web-search results above, which returned no docket entries.
• Do not confuse: The only numeric match returned was JP 5269275 B2 (Japanese gaming-machine patent, applicant Kabushiki Kaisha Sanyo Bussan, filed 2000‑12‑28), which is a different patent and must not be treated as US 5,269,275.
• Recommendation: If a litigation-negative clearance opinion is needed, this should be confirmed by direct PACER/RECAP (CourtListener) docket searches on the plaintiff/assignee names (Dahlgren, Rook, and any commercializer of the technology) and by a Lex Machina / Docket Navigator full-text docket search, since district court dockets from the 1990s–2000s are not fully indexed by general web search.

Proceedings overview

Total AIA trial proceedings on file: 0. The structured "PTAB proceedings on file" block — the canonical list from the USPTO Open Data Portal — returns no IPR, PGR, or CBM for US 5,269,275, and my independent web searches surfaced no PTAB trial involving this patent, no Federal Circuit appeal docketed from any such trial, and no defensive-aggregator (Unified Patents / RPX / AST) filing campaign against it. The breakdown by status is therefore 0 active / 0 claims invalidated by PTAB / 0 claims sustained in a trial / 0 settled / 0 institution denials. The bottom-line defensive posture is not the usual "the patent is hardened by surviving IPRs" or "claims 1–5 are canceled" — it is stronger than either: this patent has been expired for roughly two decades and is very likely unassertable for damages, so there is nothing for a defendant to invalidate at the PTAB and nothing meaningful for a plaintiff to recover.

Two independent reasons, both drawn from the record I was given:

1. Maintenance-fee lapse. The Legal Events table shows 2005-12-14 — LAPS — Lapse for failure to pay maintenance fees, followed by 2006-01-11 — STCH — PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362, with effective date 2005-12-14. Google Patents carries the status verbatim as "Expired - Fee Related." The 8-year maintenance fee was paid on 2001-06-13; the 12-year window lapsed in 2005. Because no maintenance fee was paid, the patent ceased to be enforceable well before the AIA trial regime existed (IPR/PGR/CBM became available 2012-09-16), which is itself a complete explanation for the absence of any PTAB filing.
2. Term expiration. Anticipated expiration is listed as 2012-11-02 (20 years from the 1992-11-02 filing date). Even if the fee lapse above is treated conservatively, the statutory term ended in 2012.

Caveat on the two reasons: the fee lapse is the operative one, but I am reporting it as the ODP record states it. If a petition to accept an unintentionally delayed maintenance fee had ever been granted, the record would show an intervening payment and I found none. I did not independently verify the maintenance-fee status in USPTO Patent Center's fee history — that is the one record I would confirm before relying on this in a litigation posture statement (see "Recommended next steps").

No proceedings to report

There are no entries for this proceeding-detail section, and I will not manufacture any. For completeness, so that a reader does not mistake search noise for a real hit:

• The only PTAB results my searches returned for "526" patents were for U.S. Patent No. 7,171,526 (Micron Technology, Inc. v. North Star Innovations, Inc., IPR2018-01005) — an unrelated semiconductor memory patent. The trailing digits "7,526" and "526" in search results are not a match to 5,269,275, whose number is seven digits in the form 5,269,275.
• A separate result referencing a "526 patent" in a Unified Patents/SynKloud Storage litigation is likewise unrelated (a different patent and a different technology).

I found no petitioner, no judge panel, no institution decision, no final written decision, no settlement, and no CAFC appeal to describe for US 5,269,275. Any such fields would be an invention, and I am not filling them in.

Strategic summary

Claim status: all 8 claims UNTESTED at the PTAB — and all 8 now unenforceable-through-expiration. Claims 1–8 of US 5,269,275 (independent claims 1, 7, and 8; dependent claims 2–6) were never challenged in an AIA trial. This is not a case of a patent surviving an attack; it is a case of a patent that never drew one, because its commercial and enforcement life ended (2005-12-14 fee lapse under 37 CFR 1.362; statutory term 2012-11-02) before AIA trials were available on 2012-09-16. There is no surviving-claims list to give you, because nothing was canceled and nothing was confirmed. The full claim set exists on paper exactly as it issued on 1993-12-14.

Estoppel landscape: § 315(e)(2) is irrelevant here. Because no IPR, PGR, or CBM was ever instituted, no petitioner is burdened by IPR estoppel, and conversely no defendant gets the benefit of a claim already canceled. Practically, this means an IPR-based defense strategy is unavailable for a reason more fundamental than estoppel: an expired patent is a poor candidate for AIA trial review, and a party facing a letter citing this patent has no need for PTAB relief. The relevant defenses are Article III/enforceability and damages-based, not PTAB-based:

• Damages lookback (35 U.S.C. § 286). A six-year limitations period runs backward from the date a complaint is filed. With the patent expired on 2005-12-14 (or at the outside, term-expired 2012-11-02), any complaint filed after roughly 2011-12-14 reaches a period in which the patent likely had already lapsed, and any complaint filed today reaches nothing at all.
• No injunctive relief. A patent that has expired cannot support a permanent injunction against ongoing conduct; all that could theoretically remain would be pre-expiration past damages, which are time-barred as above.
• Ownership note for standing/chains of title. The assignment record lists ROOK, DAVID receiving an undivided 50% from inventor DAHLGREN, DAVID, effective 1992-10-26 (recorded 1992-11-02, Reel/Frame 006302/0044). The current assignee listed is "Individual." Any assertion today would require proof that the two co-owners (or their successors) are joined — a threshold that cuts against a lone asserting party.

Pattern signals. No petitioner has filed anything, let alone multiple petitions. The patent owner has never appealed a PTAB decision (there was none) and never litigated to an appellate decision that I could find. There is no defensive aggregator in the chain — Unified Patents, RPX, and similar entities show no filings against this patent, which is consistent with its expired status and its niche (1992-vintage analog nitrous-oxide enrichment controllers for carbureted race engines). The mark-and-say "individual assignee" structure plus the 50/50 split with the inventor's assignee is the profile of a small-practitioner patent, not a monetization campaign, and there is no evidence of one.

Recommended next steps

1. Treat the patent as non-threatening and say so plainly. There is no PTAB activity to leverage, so an IPR-based defense is off the table — but so is the assertion itself. If you receive a demand citing US 5,269,275, respond that the patent expired for nonpayment of maintenance fees on 2005-12-14 (37 CFR 1.362) and that its statutory term ended 2012-11-02, and demand the sender identify (a) the date the accused conduct began, (b) why it falls within the six-year window of § 286, and (c) the chain of title from Dahlgren and Rook.
2. Verify the fee-lapse fact in Patent Center before you put it in a brief. Search USPTO Patent Center for application 07/970,395 and pull the fee/payment history and maintenance-events tabs. The ODP-derived "Expired - Fee Related" status and the 2005-12-14 lapse entry are strong, but the fee history is the primary record I was not able to inspect directly. Also confirm there is no petition to accept an unintentionally delayed maintenance fee and no ex parte reexamination or reissue on file — those are not AIA trials and would not appear in the structured PTAB feed, so the ODP block's silence does not rule them out. Check them in Patent Center, not in the trial feed.
3. Confirm the absence in PTAB E2E yourself. Run a party search and a patent-number search in PTAB E2E and the PTAB Decisions database for patent number 5,269,275. My finding of zero proceedings rests on (i) the structured ODP block and (ii) negative web searches; a direct E2E query is the authoritative confirmation and takes about a minute.
4. If any litigation ever does appear, docket it through CourtListener/PACER immediately. I found no Federal Circuit appeal and no district court docket asserting this patent. If one surfaces, the same maintenance-lapse and § 286 arguments are your first-line defense, and the CAFC would be the venue for any appeal (there being no PTAB FWD to appeal from).

Bottom line: No AIA trial proceeding has ever been filed on US 5,269,275. There is no FWD to link to and no disposition to quote, because none exists. The absence is the signal — and here it is compounded by a 2005 maintenance-fee lapse and a 2012 term expiration, which together mean a defendant today should be asking why the patent is being asserted at all, rather than preparing a PTAB petition.

I'll verify the assignment record against live sources before writing anything.

Let me verify the co-assignee and check for any enforcement activity.

Inventors

David Dahlgren — sole named inventor; address of record 2 Ashby St., Mystic, Conn. 06355.

• Employer at time of filing (determinable): self-employed. Dahlgren operated Engine Management Systems (EMS), a one-man engineering/prototyping business in Mystic, CT, per his 2021 obituary in The Day: "Engine Management Systems, his own business… EMS was a one-man factory and prototype house combined." Earlier in his career he ran Moroso's NASCAR engine shop. He was not an employee of any corporate assignee at filing — consistent with the patent's "Original Assignee: Individual" listing.
• Unusual-pattern check: the classic red flag (all inventors leaving the original assignee within 12 months of filing) does not apply — there was no corporate assignee to leave. The relevant event is the inverse: Dahlgren transferred a 50% undivided interest to a private individual seven days before the application was filed (executed 1992-10-26; filed 1992-11-02). That is a pre-filing equity split with a co-investor, not an inventor-departure pattern.
• Post-filing history: no further recorded transfer of Dahlgren's retained 50% for the remaining life of the patent. Dahlgren died 2020-12-30; because the patent had already lapsed in 2005, no enforceable rights passed to his estate.
• Namesake hazard (flagged, not resolved): PatentLeaderboard shows a "David Dahlgren" with 7 patents spanning Flowco Production Solutions, Volvo Car, Wayne Fueling Systems and an unaffiliated set. I could not verify whether that is the same person or an aggregated same-name inventor. Do not conflate that portfolio with this patent.

Original assignee

Individual co-owners — David Rook (Hempstead, N.Y.) and David Dahlgren (Mystic, Conn.), each holding an undivided 50% (Google Patents "Original Assignee: Individual"; FreePatentsOnline and Justia both list "Assignees: David Rook (Hempstead, NY), David Dahlgren (Mystic, CT)").

• Why not an operating company: the invention was not filed by a corporation. It was the product of Dahlgren's own shop. The obituary independently corroborates that EMS was a real, functioning business — it says Dahlgren "holds a patent for a pulse width modulated controller for nitrous oxide and fuel delivery" and credits EMS builds with two class wins at the Rolex 24 at Daytona and 13+ Bonneville/Australia land-speed records.
• Did it ship a product embodying the claims? Likely yes, in low volume and undocumented — the spec describes a buildable analog control using off-the-shelf parts (NE 566 timer, Motorola 3484S4-2 injector drivers, National Semiconductor components) and the obituary describes EMS as a bespoke builder of engine-management systems. However, I found no product literature, catalog, part number, or commercial sales record for an EMS-branded PWM nitrous controller. Treat "shipped a product" as plausible but unverified.
• Primary line of business (Rook): not determinable. No corporate entity, no product, no other patents surfaced for David Rook as assignee. I found a Justia inventor page for "David W. Rook," but I could not confirm it is the same individual.
• Current status: both natural persons. Dahlgren deceased (2020-12-30). The patent itself expired 2005-12-14 for nonpayment of maintenance fees, so ownership is now moot — there is no enforceable right to own.

Assignment timeline

There is exactly one recorded assignment in the USPTO chain, plus the standard fee/expiry events. This is a finding in itself: Google Patents' legal events for US 5,269,275 contain a single AS (Assignment) record and no subsequent Assignment, Security Agreement, Merger, Change of Name, License, or Release entry.

• 1992-10-26 (executed) / recorded 1992-11-02 — Reel 006302/0044
  • Conveyance: Assignment
  • Assignor: David Dahlgren
  • Assignee: David Rook, Hempstead, New York
  • Correspondent: Not retrieved. This is the one field I could not obtain. The USPTO Assignment Center correspondent-of-record for Reel 006302/0044 did not surface in any indexed source I could reach, and I will not guess at a name. For disclosure completeness: the prosecuting law firm of record on the patent is Galgano & Belkin (per FreePatentsOnline/Justia "Law Firm" field). That is the attorney who prosecuted the application — it is not confirmation of who filed the assignment record, and the two roles are frequently different. Because the chain contains only one link, the "repeat correspondent" test is structurally inapplicable regardless.
  • Context: pre-filing co-ownership split — the inventor conveyed half his equity to a private co-venturer seven days before filing.
  • Text of record: "ASSIGNS AN UNDIVIDED FIFTY PERCENT (50%) TO THE ASSIGNEE; ASSIGNOR: DAHLGREN, DAVID; REEL/FRAME: 006302/0044," effective date 19921026.

Subsequent legal events (non-assignment, for completeness):

• 1997-06-03 — FPAY, 4-year maintenance fee paid
• 2001-06-13 — FPAY, 8-year maintenance fee paid
• 2004-12-09 — FEPP, small-entity status / payor number assigned
• 2005-06-29 — REMI, maintenance fee reminder mailed
• 2005-12-14 — LAPS, lapse for failure to pay maintenance fees
• 2006-01-11 — STCH, patent expired due to nonpayment under 37 CFR 1.362
• 2006-02-07 — FP, lapsed

Note the divergence flagged in the earlier section: Google Patents lists an anticipated expiration of 2012-11-02 (20 years from filing), but the patent actually went abandoned in 2005. There was never a 12-year fee window payment — the patent died at the 12-year mark.

No post-issuance assignments exist. There is no chain to reconstruct beyond the single 1992 link. Any party asserting ownership today would be asserting a right that lapsed two decades ago.

Timeline diagram

timeline
    title Ownership of US 5269275
    1992 : Dahlgren files application
         : Half interest assigned to David Rook
    1993 : Patent issued to Rook and Dahlgren
    1997 : Year 4 maintenance fee paid
    2001 : Year 8 maintenance fee paid
    2005 : Lapsed for unpaid maintenance fee
    2006 : Patent formally expired
    2020 : Inventor Dahlgren dies

NPE / troll-pattern signals

1. Shell-entity transfer — not present. No transfer to any LLC or corporate entity appears anywhere in the record. The sole assignment (Reel 006302/0044, 1992-11-02) moved a 50% undivided interest from one natural person to another natural person. There is no "IP / Patents / Licensing / Holdings / Ventures" suffix, no registered-agent address, and no Delaware or Texas single-member LLC anywhere in the chain.

2. Known asserter in the chain — not present. Neither David Dahlgren nor David Rook matches any entry on the named NPE lists (Acacia, Marathon Patent Group, Intellectual Ventures, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation Corp, Spangenberg entities), and no entity surfaced as a high-frequency plaintiff by RPX or Unified Patents is connected to Reel 006302/0044. My searches for a known asserter tied to this patent returned nothing.

3. Repeat correspondent across the chain — not present (and structurally untestable). With a single recorded assignment, there is no chain across which a correspondent could recur. Unclear on the specific identity: I could not retrieve the Assignment Center correspondent field for Reel 006302/0044, so I cannot name the filing attorney. I decline to substitute the prosecution firm of record (Galgano & Belkin) for the assignment correspondent — those are different roles.

4. Cascading transfers — not present. One transfer, executed 1992-10-26, recorded 1992-11-02, and nothing for the following 30 years. There is no sequence of LLC-to-LLC hops, no shared correspondent address, no common-principal pattern, and no transfers inside any 24-month window beyond the single 1992 event.

5. Pre-litigation transfer — not present. No infringement suit naming US 5,269,275 was found. The 1992 assignment predates any conceivable suit by ~30 years and was executed pre-filing, which is a co-investment structure rather than a standing/venue arrangement. Caveat: my docket-specific search was truncated before completion, so this is a negative result from partial coverage, not a certified absence of litigation.

6. Bankruptcy fire-sale — not present. Neither the inventor nor the co-assignee was a corporate debtor; no Chapter 7/11 proceeding connects to this patent, and there was no patent sale in any bankruptcy proceeding.

7. Privateering — not present. There is no operating company in the chain capable of "privateering" — the patent was held by two private individuals from filing. No SEC filing (10-K/8-K) references this patent or either assignee, because neither is a public company.

8. Defensive aggregator — not present. The chain does not terminate at RPX, AST, LOT Network, Unified Patents, or OIN. It terminates at two natural persons and then at expiry.

Aggregate: zero of eight signals present. This is a textbook individual-inventor patent, not an NPE vehicle.

Verdict

Insufficient data — which, per the rubric, is the correct call when the record contains only the original assignment.

The entire recorded chain is a single entry: David Dahlgren to David Rook, 50% undivided, executed 1992-10-26 and recorded 1992-11-02 at Reel 006302/0044. That is a pre-filing equity split between two private individuals, not a transfer to an assertion vehicle — there is no LLC, no corporate assignee, no subsequent conveyance, no correspondent recurrence, and no litigation. The patent lapsed for nonpayment of maintenance fees on 2005-12-14 and expired under 37 CFR 1.362 on 2006-01-11, so it has been unenforceable for roughly two decades and cannot support any 2026 assertion campaign regardless of who nominally holds it.

Two explicit uncertainty disclosures:

1. The correspondent of record on Reel 006302/0044 was not retrieved and is reported as unknown rather than inferred.
2. My search specifically targeting infringement complaints citing 5,269,275 was cut off before completion, and I lack direct PACER / PTAB / CAFC query access. The "no litigation" finding is therefore unverified, though it is consistent with a patent that expired in 2005.

Verification link: https://assignmentcenter.uspto.gov/ (search patent number 5269275) — indexed mirror at https://assignment.uspto.gov/patent/index.html — Google Patents legal events: https://patents.google.com/patent/US5269275/en

I'll verify the specifics of each cited reference before building the § 102 anticipation analysis.

Now let me verify the electronic engine-management references, which are the most likely § 102 candidates.

Prior-Art Analysis — US 5,269,275

Verification step (performed first): I searched the literal number 5269275 / 5,269,275 with no auto-correction and confirmed against the authoritative full text at https://patents.google.com/patent/US5269275/en. The only numeric near-match that surfaces in searches is JP 5269275 B2 (a Japanese gaming-machine registration) — a different document that must not be used here, consistent with the prior Litigation section.

Scope note: All ten U.S. patent references appear as "Cited by examiner" on the face of US 5,269,275, i.e., they were before the examiner during prosecution. The three non-patent citations were also of record.

1. Critical date framework

Filing/priority date: 2 Nov 1992. Pre-AIA §§ 102(a)/(b)/102(e) therefore break down as:

Two of the cited references issue after the '275 filing date and can therefore only be § 102(e) art: US 5,174,263 (issued 29 Dec 1992) and, marginally, the '464/'858 pair.

2. Quick-reference table

3. Reference-by-reference

1. US 4,494,488 — Wheatley, "Fuel charging system for high performance vehicles"

• Assignee: Ram Automotive Company. Filed 23 May 1984; issued 22 Jan 1985.
• Description: N₂O supply cylinder held at ~900 psi, pressurized by a nitrogen blanket via pressure regulator/adapter; liquid N₂O and fuel delivered through separate spray bars, each gated by a solenoid valve actuated by a driver push-button in the cockpit.
• Claims potentially anticipated: None. It discloses only the environment (N₂O + enrichment-fuel plumbing, solenoid gating). It has no engine-speed sensor, no throttle-position sensor, no gate, no programmable memory, no multiplier, no clock, no comparator, and no variable pulse width — every element (c)–(j) of claim 1 is absent, and there is no "continuously adjusted" rate as required by claims 1, 7, and 8. Relevant only to the claim preamble.
• Source: https://patents.google.com/patent/[US4494488A](/patent/US4494488A)/en

2. US 4,572,140 — Wheatley, "Nitrous oxide precooler"

• Assignee: Ram Automotive Company. Filed 9 Oct 1984; issued 25 Feb 1986.
• Description: A hose jacket forms a cooling chamber around the N₂O delivery conduit; a purge solenoid injects vaporized N₂O into the chamber to keep the charge liquid before the delivery solenoid fires.
• Claims potentially anticipated: None. Purely hydraulic/thermal; no electronic control, no sensing, no pulse-width modulation.
• Source: https://www.sumobrain.com/patents/us/Nitrous-oxide-precooler/[4572140](/patent/4572140).html

3. US 4,683,843 — Norcia, Wheatley & Norcia, "Nitrous oxide fuel injection safety system"

• Assignee: Ram Automotive Company. Filed 13 Aug 1986; issued 4 Aug 1987.
• Description: N₂O supply line to a spray bar with a normally-open vent valve + one-way check valve; a relay energizes N₂O, fuel, and vent solenoids only if a fuel-pressure switch and an oil-pressure switch are both closed (oil pressure standing in for ~2000 RPM minimum).
• Claims potentially anticipated: None. This is the closest cited art on the "threshold + gating" concept of claim 1 element (c)/claim 3 — but it (i) uses pressure switches, not programmable memory storing a threshold value; (ii) has no throttle-position input at all; and (iii) produces only on/off solenoid energization, with no pulse-width modulation and no continuously varied rate. A § 103 combination reference, not a § 102 reference.
• Source: http://patentimages.storage.googleapis.com/72/ef/2a/7ba05d7d6aa6a4/US4683843.pdf

4. US 4,688,522 — McMaster, "Fluid power transfer device and fuel system therefor"

• Filed 15 Jul 1985; issued 25 Aug 1987.
• Description: Fluid-power transfer hardware for a fuel system (pressure-transfer mechanism for a pressurized fluid supply).
• Claims potentially anticipated: None. Mechanical/fluid-handling art with no electronic control, sensing, memory, or pulse-width generation.
• Confidence caveat: I did not retrieve the full text of this reference; the characterization above rests on the title, classification, and the '275 specification's own use of it. Treat as lower-confidence than references 1–3, 6, 7 and 9, which I verified directly.

5. US 4,798,190 — Nitrous Oxide Systems, Inc., "Nozzle"

• Filed 30 May 1986; issued 17 Jan 1989.
• Description: Nozzle geometry for introducing N₂O into an intake airstream.
• Claims potentially anticipated: None. Hardware-only; no electronics whatever.
• Confidence caveat: as with #4, characterized from the face-of-patent citation and title; not independently re-verified.

6. US 4,840,157 — Furrow, "Engine speed control circuit for drag racing"

• Filed 20 May 1988; issued 20 Jun 1989.
• Description: A crystal-referenced clock (4060 fourteen-stage ripple counter + 4013 D flip-flop) producing a 100 Hz square wave, feeding first and second down-counters, with a starting circuit that synchronizes operation to the launch and temporarily drives a speed-adjustment assembly or a solenoid energizing assembly for a precisely controlled period.
• Claims potentially anticipated: None in full, but this is the only cited reference that structurally supplies claim 1's "clock means generating a pulse of predetermined frequency" — notably the same building-block family (counter/timer square-wave generator) the '275 specification uses for clocks 702/704 ("NE 566" timer). Furrow's output modulates elapsed race time, not N₂O/fuel delivery proportional to RPM × TPS, so it cannot anticipate claims 1, 7, or 8; it is § 103 material on the clock element.
• Source: https://patents.google.com/patent/[US4840157A](/patent/US4840157A)/en

7. US 4,955,348 — Budde, "Fuel injection conversion system for V-twin motorcycle engines"

• Filed 8 Nov 1989; issued 11 Sep 1990. Listed on the '275 face as "William A. Budde." (Note the Google Patents front matter for '275 renders the assignee as "William A. Budde" — the correct assignee/inventor name is Budde.)
• Description: EFI conversion for carbureted V-twin motorcycles. Claim 1 recites, inter alia, an electronic sensing means deriving engine timing from the ignition system, a throttle potentiometer for sensing the position of the throttle and producing an electronic signal in response thereto, a status sensing means (air/engine temperature + intake vacuum), and a control unit electronically integrating the electronic signals from the throttle potentiometer, the electronic sensing means, and the status sensing means to generate signals that operate the fuel injectors "at the proper time and for the calculated duration" — i.e., pulse-width-controlled injection computed from throttle position and engine speed. It also includes manually adjustable idle mixture controls and a high-speed mixture control.
• Claims potentially anticipated:
  • Claim 1: No — lacks N₂O entirely, lacks the two-rate programmable memories, lacks N₂O/fuel comparator pulse outputs from a common clock. But it supplies engine-speed sensing + throttle-position sensing + duration-computed injection.
  • Claim 7: No — same gaps (no N₂O, no first/second threshold memories, no AND gate of two threshold comparators).
  • Claim 8: Closest of all cited art, but still not anticipatory: every step of claim 8 expressly requires nitrous oxide threshold, nitrous oxide delivery rate, and a nitrous oxide injection pulsewidth. Budde is a fuel-only (gasoline) system; it therefore cannot anticipate claim 8 as written.
  • Claim 6: Budde's manually adjustable idle mixture control is the functional analogue of the claimed "fifth programmable memory means for storing a value proportional to initial enrichment fuel richness" — but it is a manual control, not a memory, and there is no "second adder."
• Litigation flag (see § 5 below): this reference — not the '275 patent — is the one with a substantial court record.
• Source: https://patents.google.com/patent/US4955348

8. US 5,088,464 — Echlin, Inc., "Motorcycle engine management system"

• Filed 24 Jun 1991; issued 18 Feb 1992. § 102(e) art as of 24 Jun 1991; also potentially § 102(a) if applicant's invention post-dates 18 Feb 1992 (unlikely).
• Description: Microprocessor-based engine management for motorcycles — sensor inputs processed to schedule injector/ignition events. Filed as a counterpart to the '263 application (same filing date).
• Claims potentially anticipated: None demonstrated at the level of specificity required. As an engine-management system it is relevant to the general architecture of claim 1 (sensor inputs → electronic control → actuators) and is best treated as § 103 background art, most naturally combinable with Paielli '858.
• Confidence caveat: I could not retrieve the full '464 claim set; the characterization is inferential from the title, assignee, filing pair, and its citation role. Flagged as not independently verified at the claim level.

9. US 5,091,858 — Paielli, "Electronic control of engine fuel delivery"

• Assignee: Digital Fuel Injection (Farmington Hills, MI). Filed 26 Oct 1989 as a CIP of Ser. No. 07/296,218 filed 9 Jan 1989; issued 25 Feb 1992.
• Description: Electronic engine control with memory-stored look-up tables of injector pulse-width control parameters addressable as a function of engine speed and air-manifold pressure; an electronic controller addresses the table and energizes the injector "for a time duration that varies as a function of said first parameter"; the tables are externally reprogrammable in real time without interrupting engine operation.
• Claims potentially anticipated:
  • Claim 1 — most serious § 102 candidate in the set, but still not anticipatory. Paielli maps to: "second programmable memory means for storing a value corresponding to rate of enrichment fuel delivery" (the pulse-width look-up table), "multiplier means ... generating a signal proportional to amount of [fuel] to be delivered" (table weight × sensor signal), and an injector energized for a duration proportional to that amount (the comparator/pulse-width function, albeit implemented digitally). It fails element (b) in that the second addressed axis is manifold pressure, not throttle position, and it wholly lacks any nitrous oxide delivery rate, N₂O multiplier, N₂O comparator, or N₂O driver. Verdict: not anticipatory; high-value § 103 art.
  • Claim 7: No — no AND-gated pair of threshold comparators, no first/second threshold memories, no N₂O channel.
  • Claim 8: No — the method steps expressly recite nitrous oxide.
  • Claims 4/5 (adder coupling): Paielli's table-addressing is not an "adder" coupling the sensors to the multiplier; no anticipation.
• Sources: http://www.everypatent.com/comp/pat5091858.html ; https://portal.unifiedpatents.com/patents/patent/US-[5091858](/patent/5091858)-A

10. US 5,174,263 — Echlin, Inc., "Motorcycle engine management system"

• Filed 24 Jun 1991; issued 29 Dec 1992 — i.e., issued 15 days after the '275 patent's filing date.
• § 102 status — important: it is not available under § 102(a) or § 102(b) (its publication post-dates the critical date). It can only be prior art under § 102(e), as of its 24 Jun 1991 filing date, on the theory that it is a U.S. patent granted on an application filed by another before the applicant's invention. Its citation on the '275 face is therefore best explained as the examiner using a co-pending application.
• Description: The companion application to '464; motorcycle engine-management (sensor-driven injector/ignition scheduling).
• Claims potentially anticipated: None demonstrated. Same reasoning and same confidence caveat as #8 — § 103 background art only.

Non-patent citations (of record)

4. Claim-mapping matrix — does any single reference § 102-anticipate a claim?

Bottom line: no cited reference anticipates any claim of US 5,269,275 under § 102.

The reason is structural and applies uniformly: every independent claim (1, 7, 8) expressly requires a nitrous oxide delivery rate, a nitrous oxide pulse width, and a nitrous oxide injector driver, adjusted continuously against both engine speed and throttle position. The reference set splits cleanly into:

• N₂O-side art (1, 2, 3, 5) — discloses N₂O + enrichment fuel hardware and, in Norcia's case, pressure-switch gating, but no electronic rate control, no memory, no multipliers, no PWM.
• Electronic-control art (7, 8, 9, 10) — discloses speed/TPS sensing, look-up-table or computed injection duration, and injectors energized for calculated durations, but no nitrous oxide channel whatsoever.
• Clock/timer art (6) — supplies a building block (a square-wave clock) but not the delivery-control combination.

5. Where the real invalidity risk lies (§ 103, not § 102)

The references that matter for an obviousness challenge to claims 1, 7, and 8 are:

1. Paielli US 5,091,858 (primary) — reprogrammable pulse-width look-up tables addressed by speed and pressure; injector energized for a duration varying with the parameter. Supplies the "programmable memory + proportional pulse width" core.
2. Budde US 4,955,348 (primary, and the strongest on TPS) — throttle potentiometer and engine-speed sensing integrated by a control unit to fire injectors for a calculated duration; manually adjustable idle/high-speed mixture controls.
3. Norcia US 4,683,843 (secondary) — N₂O + fuel delivery gated on threshold engine-speed (oil-pressure proxy) and fuel-pressure conditions; also supplies the safety-shut-off concept the '275 specification lists in its AUX inputs.
4. Furrow US 4,840,157 (secondary) — square-wave clock and counters for timed solenoid energization.
5. Echlin US 5,088,464 / 5,174,263 (secondary) — motorcycle engine-management architectures.

A proposed § 103 combination (Paielli or Budde in view of Norcia, optionally with Furrow) is the realistic attack vector: it supplies the electronic PWM rate control, the TPS/RPM sensing, the threshold gating, and the N₂O/fuel plumbing — leaving as the non-trivial residue the linking of N₂O rate and enrichment-fuel rate through separate multipliers and separate comparators from a common clock so the two pulse widths are continuously and simultaneously adjusted, plus (claim 2) ignition retard proportional to N₂O amount. Those are the features that carried the '275 patent over the cited art.

6. Cross-reference flags against the previously generated sections

I was asked to flag contradictions explicitly:

1. No contradiction on the patent itself. The record verified here matches the earlier Data Sheet exactly: App. 07/970,395, filed 2 Nov 1992, issued 14 Dec 1993, inventor Dahlgren, 50% assigned to Rook, lapsed for non-payment of maintenance fees effective 14 Dec 2005. The "no litigation against US 5,269,275" conclusion stands.
2. Nuance that should be added to the Litigation section. The earlier section concluded there was no litigation "in the neighborhood." That needs qualification: the prior art cited on the face of '275 includes US 4,955,348 (Budde), which was litigated extensively through the Federal Circuit — Budde v. Harley-Davidson, Inc., 250 F.3d 1369 (Fed. Cir. 2001) and 116 F. App'x 270 (Fed. Cir. 2004) (N.D. Cal. No. C-98-20447-JF), over an EFI conversion system for V-twin motorcycles. So while the '275 patent has no docket, the technical field it sits in does. Sources: https://www.courtlistener.com/opinion/[773385](/patent/773385)/william-a-budde-v-harley-davidson-inc-and-harley-davidson-motor/ ; https://storage.courtlistener.com/harvard_pdf/[8458346](/patent/8458346).pdf
3. Minor naming/assignee correction. The earlier summary attributes the Budde reference generically; the '275 front matter and Google Patents associate US 4,955,348 with William A. Budde. No conflict with the earlier text, just a precision point.
4. Date-convention note. This task header states "Current Date: April 26, 2026," while the session date is 2026-09-17. Neither affects the analysis, which turns entirely on the 2 Nov 1992 filing date and the pre-1993 reference dates.

7. Confidence and limitations (stated explicitly)

• High confidence: The ten U.S. references, their filing/issue dates, jurisdictions, and § 102 categories; the descriptions of US 4,494,488, 4,572,140, 4,683,843, 4,840,157, 4,955,348, and 5,091,858, all of which I verified against full text or complete claim sets.
• Lower confidence / not independently verified at claim level: US 4,688,522 (McMaster), US 4,798,190 (Nitrous Oxide Systems nozzle), US 5,088,464 and US 5,174,263 (Echlin). These are characterized from the face-of-patent citation list, titles, classifications, and (for the Echlin pair) their shared 24 Jun 1991 filing date. An examiner-grade analysis should pull the full specifications of these four before issuing a formal opinion; my conclusion that none anticipates is robust for the N₂O-side hardware references (they contain no electronics at all), but should be re-checked for the Echlin pair.
• Uncertainty on the Accel/Calmap non-patent citations: the brochure and Calmap 6.0 instructions are undated on their face, so no § 102 date can be established without extrinsic evidence (catalog dates, copyright records, distributor affidavits). The 1991 Owner's Manual is the only non-patent item with a usable year.
• Legal caveat: the § 102(a)/(e) analyses depend on Dahlgren's actual date of invention, which is not of record here. I have used the 2 Nov 1992 filing date as the presumed constructive date of invention, which is the correct default but is rebuttable.

I'll ground this analysis by pulling the actual prior-art references cited on the face of US 5,269,275 before applying § 103.

Critical finding: Meaney's US 5,088,464 (cited on the face of the patent) already discloses a nitrous solenoid with automatic fuel enrichment and spark retard. Let me verify that reference family and the remaining cited art.

Preliminary compliance notes

Two integrity items before the analysis:

1. Date conflict (flagging, per rules): this task header says "Current Date: April 26, 2026," while my operating context states 2026‑09‑17. I use the task header for framing but flag the inconsistency rather than silently reconcile it.
2. Contradiction with the earlier bibliographic section (flagging): the prior Bibliographic Data Sheet listed "Primary Examiner E. Rollins Cross; Assistant Examiner Erick Solis." FreePatentsOnline's front‑page transcription of US 5,269,275 lists "Primary Examiner: SOLIS, ERICK R." with no Cross. Those cannot both be right; the examiner attribution in the earlier section should be treated as unverified. (freepatentsonline.com/5269275.html)
3. Scope caveat: the patent lapsed 2005‑12‑14 for non‑payment (37 CFR 1.362), so no live IPR/PGR can reach it. This § 103 analysis is therefore retrospective — it matters for understanding the scope that was granted, for reading the surviving Echlin/Meaney family, and for any later‑art clearance work that maps the '275 as a family member.

§ 103 Analysis — US 5,269,275 (Dahlgren)

1. Framework and PHOSITA

Governing law: pre‑AIA § 103 (filed 1992‑11‑02). Critical date for § 102(b) statutory bars: 1992‑11‑02 minus one year = 1991‑11‑02. References filed before 1992‑11‑02 but issued after are still available under § 102(e).

PHOSITA: a person with a BS in electrical or mechanical engineering (or equivalent hands‑on racing‑electronics experience) plus ~2–4 years designing or calibrating aftermarket electronic engine‑management systems; familiar with stock analog timers/comparators (the '275 itself names the NE566 timer, and Furrow uses a 4060 ripple counter + 4013 flip‑flop), Motorola injector drivers, and with commercial EFI/nitrous tuning practice (Haltech F3, Accel "Thunder Twin," Calmap, NOS, Jacobs NMM).

2. Scope and content of the prior art

The single most important fact for this analysis: the applicants' own Background admits that the only deficiency attributed to NMM is that "the NMM system does not, however, account for throttle position as a factor." Everything else the '275 claims as its contribution — preset start RPM, ramp to 100%, coordinated fuel enrichment, proportional spark retard — is admitted to be in the prior art.

3. Claim 1 element‑by‑element mapping (Combination A: Meaney '281 + Meaney '464 + Paielli '858, with Furrow)

Conclusion — Combination A: claim 1 would have been obvious, and my honest read is that claims 1, 3, 7 and 8 are arguably anticipated by Meaney '281 taken alone (its flowchart is a literal AND of enable ∧ TPS‑min ∧ RPM‑min, followed by simultaneous NOS + fuel + spark adjustment; its claim 32 method mirrors claim 8 of the '275). At minimum they are obvious.

4. Motivation to combine (this is where the case collapses)

1. Express cross‑reference in the art itself. Meaney '281 states: "Reference is made to the subject matter of U.S. Pat. No. 5,091,858 by Perry M. Paielli … The current invention is a nitrous oxide delivery system which may use the type of electronic control unit described in the Paielli application." That is a printed, express teaching to combine the two references — the strongest form of motivation evidence. And Paielli '858 is itself cited on the face of the '275.
2. Same field, same problem, same assignee. '464, '263 and '281 are all Echlin/Meaney nitrous‑plus‑fuel systems; the '275's field is identical. KSR/In re Kahn: same‑field combinability is presumed where the references address the same problem.
3. The references solve the very problem the '275 identifies. The '275's stated aim is continuous, tractable N₂O metering rather than a fixed shot. '281's stated aim is that the user not suffer "loss of control of the vehicle due to the sudden increase in power," achieved by threshold‑gated, ramped, traction‑responsive N₂O delivery. Identical problem → motivation.
4. Design need / market pressure. Both the admitted NOS and NMM systems were commercially ramping N₂O; Haltech and Calmap were shipping user‑programmable fuel/spark maps. A POSITA seeking to implement the admitted NMM ramp with proportional fuel and spark had every reason to use the then‑standard PWM pulse‑width architecture (Paielli tables, '281 PWM valves, Furrow clocked solenoids) rather than invent it.
5. All implementations used off‑the‑shelf parts. The '275 itself says all parts are available from National Semiconductor or Motorola — i.e., substituting an NE566/op‑amp/comparator analog PWM engine for the microprocessor implementations of Paielli/'281 is a predictable substitution of known technology for its known function (KSR).

5. Claim‑by‑claim § 103 conclusion

6. Secondary considerations (no saving evidence)

• No unexpected results. Each benefit recited in the '275's Summary (gradual/predictable power increase, traction‑sensitive modulation, linked N₂O/fuel ratio, automatic retard) was an already‑announced goal of '281 ('"without harming the engine or power train, or causing a loss of control of the vehicle due to the sudden increase in power"') and of the admitted NOS ramp and NMM. Absent a nexus to a specific unexpected result, this factors against patentability.
• No long‑felt‑but‑unsolved need. The "fixed shot" problem the '275 frames was already being solved in the market by NMM/NOS ramping and by Echlin's systems on the '275's own filing date.
• No evidence of copying, licensing, praise, or commercial success in the record — and the patent lapsed for non‑payment of the 12‑year fee in 2005, which is at least consistent with limited commercial significance of the claimed architecture itself.
• Failure of others: none shown; the Echlin family had already attained the result.

7. The patentee's best (likely unavailing) rebuttals

1. "The references are digital/table‑lookup; claim 1 requires multiplier + clock + comparator." Paielli reads a value out of a table addressed by speed and load — arguably not a literal "multiplication" of a stored rate by two sensor signals. This is the '275's strongest structural point and probably why it issued over the Echlin art of record. Counter: (i) claim 1's "clock means … comparator means" reads on any PWM generator and the spec concedes the NE566 is a stock part; (ii) '281 claim 9 expressly claims PWM‑valve duty‑cycle control; (iii) the physical relationship (N₂O/fuel demand scales with RPM × throttle) makes a multiplication the natural implementation; KSR at 418 ("predictable use of prior art elements according to their established functions").
2. "Teach‑away." Wheatley deliberately delivers N₂O at "a relatively constant and sustained rate" (via a nitrogen blanket), which can be argued to steer away from a variable‑rate PWM scheme; Norcia and the '275's Background both warn that metering is hard and over‑injection is hazardous. Counter: a disclosure that a particular parameter (supply pressure) should be held constant is not a teaching away from varying delivery rate; and '281 (same field, later‑filed but 1991 priority) affirmatively embraces controlled ramping. This argument is unlikely to carry.
3. "Art not considered." Ironically this cuts against the patentee: Meaney '281 could not have been considered — it issued 1994‑02‑15, two months after the '275 granted, and pre‑2000 applications were not published at 18 months. It is nonetheless § 102(e) prior art as of 1991‑02‑27. The '275's allowance therefore rests on a record that was missing the closest Echlin nitrous‑control disclosure.

8. Bottom line

Under Graham/KSR, all eight claims of US 5,269,275 would have been obvious under § 103, with claims 1, 3, 7 and 8 arguably anticipated under § 102(e) by Meaney US 5,287,281 alone, and certainly invalid over the combination of 5,287,281 + Meaney 5,088,464/5,174,263 + Paielli 5,091,858, optionally with Furrow 4,840,157 and Norcia 4,683,843. The motivation is not merely inferable — it is written into the prior art, because 5,287,281 expressly directs the reader to Paielli 5,091,858, a reference that appears on the face of the '275.

Confidence and limitations: High confidence on the claim mappings for '281, '464, '263 and '858 (I retrieved and read their disclosures/claims directly). Not verified: Vaznaian '190, McMaster '688,522, Budde '953,348, and the three NPL items (Accel brochure/manual, Calmap 6.0) — I retrieved bibliographic data only, so I have not relied on them for any limitation. I also did not attempt to establish Dahlgren's actual reduction‑to‑practice date, which could theoretically antedate the '281 filing date of 1991‑02‑27 and remove it (though not '464, '263, Paielli, Furrow or Norcia) from the prior art. That date is not in the record I reviewed.