US 5809972

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

Search scope and a caveat up front

I searched for the literal identifier US 5,809,972 (and variants "5809972"). I do not have direct API access to USPTO PatentCenter/PAIR or the CAFC docket system — findings below come from web-indexed sources (Google Patents, FreePatentsOnline, Justia Patents, CourtListener/Justia dockets, IPWatchdog). Where I have no authoritative confirmation, I say so explicitly.

Nothing in the search results indicates any 2026 CAFC appeal or 2026 district court docket involving US 5,809,972. Two near-miss identifiers surfaced and should be deliberately excluded:

• "2020 WL 5809972" — a Westlaw case citation (Amos v. Taylor, N.D. Miss. 2020), cited in unrelated discovery orders (e.g., https://storage.courtlistener.com/recap/gov.uscourts.lawd.[189520](/patent/189520)/gov.uscourts.lawd.189520.18.0.pdf). Not a patent.
• The "'972 patent" in Range v. Hyliion, N.D. Cal. No. 3:26-cv-02311 (2026) — part of an e-Trailer/electric-vehicle patent family ('712, '508, '972, '560, '369, '742) having nothing to do with carburetors (https://www.govinfo.gov/content/pkg/USCOURTS-cand-3_26-cv-02311/pdf/USCOURTS-cand-3_26-cv-02311-0.pdf). Different patent; different number.
• Also JP5809972B2 (a Japanese pest-control/communications patent) — a different jurisdiction and document entirely.

A practical reason for the absence of 2026 activity: the patent's anticipated expiration date is 2016-06-21, and its status is listed as "Expired – Lifetime."

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Bibliographic summary — US 5,809,972

Assignment chain (per Google Patents legal events): Barry S. Grant → Branch Banking and Trust Co. (security agreement, eff. 2008-12-23) → High Performance Industries, Inc. (assignment eff. 2011-07-06) → Demon Fuel Systems, Inc. (eff. 2011-12-13) → Holley Performance Products Inc. (merger of Demon Fuel Systems, eff. 2014-04-10), followed by a long series of security interests and releases (Wells Fargo, Wilmington Trust, LBC, Hawthorn, GE Capital, Cerberus, UBS, AEA) through 2021. I have not independently verified each reel/frame; these are as reported on the Google Patents page.

Prior art cited on the face of the patent (5 references): US 3,868,936 (Renault); US 4,204,507 (Bendix); US 4,494,511 (Nippondenso); US 4,354,470 (Honda Giken); US 4,430,275 (Leroy Penrod).

Abstract (verbatim): "Fuel at a regulated pressure passes from a fuel to tank one or more fuel injectors disposed in fuel injector housings formed in mounting blocks that are mounted to the sides of a carburetor center section. Each injector is in fluid communication with a booster venturi ring that is suspended in each carburetor barrel. The injectors intermittently deliver high pressure pulses of fuel to the booster venturi rings which disperse the fuel into the airstream. The high velocity of the airstream passing through the suspended booster venturi ring decreases the pressure of the airstream, resulting in greater atomization of the injected fuel."

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Independent claims in plain language

Claim 1 — the apparatus/system. A carburetor-based fuel injection system with:

1. a carburetor center section with multiple barrels, each barrel forming a venturi passage that has a wall constriction creating a low-pressure zone as air flows through;
2. one throttle valve per barrel, downstream of the constriction;
3. fuel injector mounting blocks, each with at least one injector housing and a mounting surface, where one block is mounted onto each mounting surface of the center section;
4. a fuel injector in each housing; and
5. fuel conduits running through both the mounting blocks and the center section — each conduit runs from one injector, through its block, and through the center section to one venturi passage, so each injector fluidly communicates with one passage.
   The claim closes with a functional statement: the injectors can be used to intermittently and sequentially inject fuel into the venturi passages, with atomization occurring in the low-pressure zones, and the atomized fuel passing into the engine for combustion.

Practical read: the point of novelty is not injection alone, nor a venturi alone, but the physical marriage of the two — a bolt-on injector block feeding fuel through the carburetor's own internal conduit to the barrel's venturi, where the constriction does the atomizing.

Claim 9 — the retrofit/conversion kit. A system for converting a conventional carburetor center section into fuel injection. It recites: mounting blocks with at least one injector housing and a mounting surface configured to engage the center section's mounting surface; a fuel conduit from each housing configured to connect with an existing center-section fuel conduit that runs from the mounting surface to a barrel; a fuel injector in each housing with its nozzle directed into that conduit; sensing means for engine operating conditions; and control means for actuating the injectors in response. Injectors are intermittently and sequentially actuated to inject fuel so the venturi passages atomize it before it enters the engine.

Practical read: this is the "bolt it on in place of the float bowl/metering block" claim, drafted in kit form (note the prospective "configured to"/"adapted to" language), plus the electronic control layer.

Claim 13 — the method of conversion. Steps: (a) provide a conventional center section with barrels/venturi passages, mounting surfaces on opposite sides, and fuel conduits from those surfaces to the barrels; (b) provide at least one mounting block with injector housing(s), a mounting surface, and a conduit from each housing to that surface; (c) mount an injector in each housing, nozzle facing the conduit; (d) mount the block onto the center section so the two fuel conduits communicate; (e) connect the injector to control means for intermittent actuation; and (f) connect the control means to sensing means so timing and duration track engine conditions — with the fuel atomized by the venturi passages before combustion.

Practical read: a step-by-step retrofit method claim covering the removal of float bowls/metering blocks and their replacement by injector blocks, plus the electronic hookup.

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Things worth flagging (accuracy and claim-interpretation notes)

• A drafting oddity in claims 9 and 13: both recite that the injectors "inject fuel and air into the carburetor barrels." Read against the specification — which describes only fuel being injected (at 15–25 psi from a plenum, with air drawn through the venturi) — this appears to be a drafting artifact rather than a genuine air-injection limitation. Any construction dispute would likely require reconciling the claim language with the specification. I am noting this as a textual observation, not a legal conclusion.
• Claim scope differences: claim 1 requires the mounting blocks on "each of said mounting surfaces" of a multi-barrel center section, while claims 9 and 13 use "at least one" block — so the kit/method claims are broader on that point. Claim 2 (dependent) narrows to opposite-side mounting; claim 3 to the perpendicular injector-axis orientation; claims 4–5 to a cylindrical fuel plenum oriented perpendicular to the injector axis; claims 6–7 to the suspended booster venturi ring and its spacing relative to the wall constriction; claim 8 to the sensing/control means.
• Documented numeric detail: the specification states the booster venturi ring outlet is positioned "between twenty and thirty thousandths of one inch upstream" (0.020–0.030 in) of the wall constriction — a specific dimensional teaching that could matter for written-description/support arguments.
• Typos in the source document: "float blows" for "float bowls"; "carburetor converstion system" in claim 12; inconsistent reference-numeral use (e.g., 48 used for both the booster-ring inner surface and the center-section mounting surfaces). These are transcription/reproduction artifacts in the granted text, and I have reproduced them rather than corrected them per your instruction.
• Uncertainty disclosure: I could not confirm from an authoritative USPTO source (PatentCenter/PAIR or the Official Gazette) the maintenance-fee history beyond the fee events listed (4th, 8th with surcharge, and 12th-year payments; a 2006 maintenance-fee reminder), nor could I confirm the absence of a termination of the 2021 security-interest releases. I also found no evidence of PTAB proceedings, reexamination, or CAFC appeals for this patent. If you need litigation-grade confirmation, the authoritative checks are USPTO PatentCenter for the application, the PTAB API for AIA/reexam proceedings, and PACER/CourtListener for district and appellate dockets.

I'll search for litigation involving US patent 5809972 across patent litigation databases.

The initial searches returned noise. Let me target specific litigation databases.

Let me search more targeted litigation databases and the patent's own litigation history.

Findings: Litigation involving U.S. Patent No. 5,809,972

Short answer: I found no evidence of any infringement litigation (district court, CAFC, or ITC) involving U.S. Patent No. 5,809,972. The searches I ran did not surface any case in which this patent was asserted, challenged, or otherwise at issue.

What the patent is (for disambiguation)

U.S. Patent No. 5,809,972, titled "Venturi-assisted fuel injection carburetor system," lists Barry Grant as inventor, claims priority to 1996-06-21, was filed 1997-07-23, and issued 1998-09-22. It is a continuation-in-part of Ser. No. 08/668,219 (now abandoned), which claimed priority to provisional Ser. No. 60/000,149. Google Patents records it as "Expired – Lifetime," with anticipated expiration 2016-06-21. (Source: https://patents.google.com/patent/[US5809972](/patent/US5809972)/en)

What I did find — and what it is not

The record for this patent is dominated by assignments and security interests, not litigation. The Google Patents legal-events/assignment record shows a long chain of:

• Security agreements and releases (Branch Banking and Trust; Wells Fargo; Wilmington Trust; LBC Credit Partners; Hawthorn Finco; GE Capital; Cerberus; UBS; AEA Debt Management).
• Assignments/mergers among Barry S. Grant → High Performance Industries, Inc. → Demon Fuel Systems, Inc. → Holley Performance Products Inc. (merger, 2014).

Important caveat: These filings are recorded under the USPTO assignment (reel/frame) system — i.e., due diligence, financing, and corporate transactions. They are not litigation and should not be reported as such. The current assignee of record is listed as Holley Performance Products Inc.

Sources searched and their results

False-positive "5809972" matches that are NOT this patent (flagging so they aren't mistaken for litigation):

• 2020 WL 5809972 — a Westlaw citation to Amos v. Taylor, No. 4:20-cv-7 (N.D. Miss.), a prison-conditions/civil-rights discovery case. Unrelated.
• JP5809972B2 — a Japanese patent for a pest-exclusion communication device. Unrelated.
• CN201811297499.1 / CN109601629A and a Lithuanian registry notice "5809972" — unrelated non-US filings.
• '580 patents in UCC/ITC/CAFC documents (e.g., Modine's U.S. Pat. No. 4,998,580; Woodway's '580) — these are different patents that happen to be nicknamed "'580."

Limitations on this answer (stated explicitly)

I want to be candid about coverage, because absence of evidence is not proof of absence:

1. I could not directly query the databases you named. The Unified Patents litigation portal (portal.unifiedpatents.com), PACER, and the CAFC docket were not accessible to me via the searches performed — the search engine returned general web results rather than docket records from those systems. I therefore cannot claim to have exhaustively searched them.
2. No litigation was found in the sources I could reach, including Google Patents' legal-events record, FreePatentsOnline, and Justia's patent page.
3. Because the patent expired in 2016, any infringement suit would necessarily have been filed well before then (subject to the 6-year § 286 damages look-back), so a "no litigation" result is plausible but should be verified against a complete docket database.

Recommendation

To confirm definitively, this should be run directly against:

• PACER / CourtListener RECAP (party names to try: Barry Grant, High Performance Industries, Demon Fuel Systems, Holley Performance Products, plus "5,809,972" and "'972 patent").
• Unified Patents litigation portal and MaxVal / Lex Machina / Docket Navigator patent-docket datasets.
• CAFC opinion search and ITC (Section 337) investigations.

Based on the available evidence, my conclusion is: no known litigation involving U.S. Patent No. 5,809,972. I could not verify this with 100% certainty because I was unable to query PACER, the CAFC docket, or the Unified Patents portal directly, and I am flagging that limitation rather than overstating the result.

I'll verify the structured data against web sources before reporting.

Let me run a few more targeted searches to be thorough on docket databases.

One more round to check reexaminations and litigation that might have spawned PTAB filings.

Proceedings overview

Total AIA trial proceedings on US 5,809,972: 0. The USPTO Open Data Portal returns no IPR, PGR, CBM, or derivation proceeding for this patent, and my independent web searches (docket aggregators, PTAB decision text, litigation reporting) surfaced none either — so the breakdown is 0 active / 0 claims invalidated / 0 claims sustained / 0 settled / 0 institution denials. The defensive bottom line is not "the patent has survived IPRs and is hardened" — it is the opposite and stronger: the '972 patent has never been tested at the PTAB and, more importantly, it is expired or long past the damages window, so a demand letter citing claims 1–13 is asserting an unenforceable-late (and likely dead) right rather than a hardened one. The absence of PTAB activity is best explained by expiry, not by the patent's strength.

Important corollary: because the patent has zero PTAB history, there is no IPR-driven claim cancellation to lean on and no § 315(e)(2) estoppel record to mine. A defendant's best defenses here are temporal (expiry / § 286), not PTAB-based.

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Proceedings on file

None. There is no proceeding to report for any of the following, and I am not going to manufacture numbers to fill the template:

• No Inter Partes Review (IPR20xx-xxxxx) — none filed, none instituted, no FWD, no appeal.
• No Post-Grant Review — and none possible: the '972 patent has an effective filing date of 1996-06-21 / provisional 1995-06-22, well before the AIA's 2013-03-16 FITF cutoff, so it is not PGR-eligible. 35 U.S.C. § 321(c).
• No Covered Business Method review — the claims are directed to a mechanical carburetor/fuel-injection apparatus (IPC F02M 71/00), not to a "financial product or service," so CBM eligibility never attached. AIA § 18(d)(1).
• No derivation proceeding, and no ex parte reexamination certificate referenced anywhere in the file history or patent record (I found no evidence of one; I cannot rule out a previously-filed, never-certified request).

Where I looked (so you can reproduce or extend the check):

• USPTO Open Data Portal / PTAB structured data supplied in the prompt — no proceedings.
• Google Patents legal-events and "Cited By" tables for US5809972A — the "Cited By" family lists 40+ later patents that cite the '972 as background art (mostly Holley/MSD/QFT throttle-body patents), but none of those is a PTAB challenge to the '972 itself. https://patents.google.com/patent/US5809972A/en
• FreePatentsOnline full text and claim set. https://www.freepatentsonline.com/[5809972](/patent/5809972).html
• Web searches across PTAB decision text, Docket Alarm, RPX Insight, Justia and CourtListener for "5809972" / "5,809,972" as an asserted or challenged patent. Every "580" hit was a different patent (e.g., 4,998,580 Modine condenser; 9,039,580 Woodway treadmill; 10,619,580 Ethanol Boosting Systems) or an unrelated string match (a Amos v. … Westlaw cite, 2020 WL 5809972). None is US 5,809,972.
• CourtListener full-text: https://www.courtlistener.com/?q=%225809972%22

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Strategic summary

Claim status: 1–13 all UNTESTED, and all expired. No claim of US 5,809,972 has been canceled, narrowed, or confirmed in any AIA trial — because none was ever filed. The claim set stands as issued: independent claims 1 (system), 9 (carburetor conversion kit), and 13 (method of converting), with dependents 2–8 and 10–12. For a defendant, this means there is no FWD to cite and no cancellation to point at. The relevant "narrowing" is temporal, not adjudicative: Google Patents reports the patent as Expired – Lifetime with an anticipated expiration of 2016-06-21 (20 years from the 1996-06-21 priority application), and the recorded maintenance-fee history in the file shows the last FPAY (12-year fee) on 2010-03-19 with no subsequent 16-year payment recorded. Two consequences follow, and I flag the second as factually uncertain: (a) even on the most generous reading, infringement damages are limited to the six years preceding suit under 35 U.S.C. § 286, so a 2026 assertion reaches at most conduct after ~2020 — and if the patent did in fact lapse for non-payment of the 16-year fee around 2014, there is no recovery window at all; (b) the precise lapse date should be confirmed directly against the USPTO Patent Center fee record and via a PTAB E2E / Patent Center "Maintenance Fees" pull and, if needed, a PTO Customer Number / Fee Record request. Do not take the Google "anticipated expiration" label as an adjudicated lapse date.

Estoppel landscape: empty, therefore open. With no IPR/PGR/CBM FWD, § 315(e)(2) and § 325(e)(2) estoppel never attached to anyone — no petitioner, RPI, or privy is barred from anything. That cuts both ways: you are not estopped, but you also get no benefit from an earlier challenger's work product. Note the flip side for the patent owner: there is no defensive record here to point to at all. The only real prior-art/validity fights are the five references the examiner considered — US 3,868,936 (Renault), US 4,204,507 (Bendix), US 4,354,470 (Honda), US 4,434,275 (Penrod), and US 4,494,511 (Nippondenso) — all pre-1985 fuel-injection/carburetor art. Whether those are the best art against claims 1, 9, and 13 is untested, and if the patent were live, the most productive attack is almost certainly § 112 on claims 9 and 13, which require injecting "fuel and air into the carburetor barrels" while the specification describes injecting fuel only (into the booster venturi ring) — a plausible written-description/claim-support problem that an IPR could not reach (IPR is limited to §§ 102/103 on patents and printed publications) but that a district court or an ex parte reexam-adjacent challenge could.

Pattern signals: none — no petitioner, no aggregator, no PO appeal. There is no repeat petitioner, no Unified Patents or other defensive-aggregator filing, and no Federal Circuit appeal, because there is no PTAB case. The nearest litigation context I can confirm is corporate, not PTAB: Barry Grant's other carburetor patent US 6,286,817 was the subject of Holley Performance Products, Inc. v. Barry Grant, Inc. (N.D. Ill. 2004) (DJ action dismissed for lack of a justiciable controversy; parallel infringement suit filed in N.D. Ga.), and Holley and Quick Fuel litigated antitrust claims in Holley Performance Products, Inc. v. Quick Fuel Technology (W.D. Ky. 1:07-cv-00185). Neither case asserted or invalidated the '972 patent, and I am not suggesting otherwise. The '972 ownership chain is real and documented, though: Barry Grant → High Performance Industries, Inc. (2011) → Demon Fuel Systems, Inc. (2011) → merged into Holley Performance Products, Inc. (2014-04-10, REEL/FRAME 032826/0413). So the entity that would assert it today is Holley — a sophisticated, well-counseled owner that has filed its own IPRs and throttle-body patents in this space. That Holley never leveraged the '972 in an ITC or district-court campaign, and that no competitor ever bothered to IPR it, is itself a data point: the patent was not commercially potent enough to provoke a challenge.

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Recommended next steps

If you are a defendant receiving a demand letter citing US 5,809,972:

1. Lead with expiry and § 286, not validity. Google Patents lists the patent as "Expired – Lifetime" with anticipated expiration 2016-06-21 (https://patents.google.com/patent/US5809972A/en). Confirm the exact lapse date against USPTO Patent Center (fee history) and, if you need a clean date, order the Patent Status/Fee Record. If the 16-year fee was never paid after the recorded 2010-03-19 12-year payment, the patent lapsed years before any actionable conduct, and there is nothing to infringe.
2. Then walk the § 286 six-year window. Even if the patent ran its full term, any recovery is capped at six years pre-suit, which in 2026 excludes essentially all pre-2020 conduct. For an aftermarket carburetor/EFI product with a normal product lifespan, that is likely fatal to the claim.
3. There is no PTAB shortcut and no PTAB risk. You cannot point to a canceled claim (none exists), and you also cannot be met with an adverse FWD (none exists). If the patent were somehow still live, the correct vehicle would be an IPR on §§ 102/103 over the examiner-cited art plus contemporaneous carburetor/EFI references, paired with a § 112 written-description attack on "inject fuel and air" in claims 9 and 13 in district court — but note the Board will apply Phillips construction (not BRI) to an expired patent, and instituting a trial on an expired patent purely for a retrospective damages theory is a poor use of the estoppel you would incur.
4. No due dates to track. There is no institution deadline, no oral hearing, no 1-year statutory FWD clock, and no CAFC docket — because no proceeding exists. Do not let anyone tell you otherwise.

If you are advising the patent owner (Holley): the honest read is that this patent has been off the board for roughly a decade, no PTAB or reexam record was ever built for it, and its only realistic value now is as portfolio lineage/background art for the later Holley and MSD throttle-body families it is cited by. Before any assertion, verify the fee record and expiry date — asserting an expired or lapsed patent invites a § 285 fee motion.

Confidence and limits: I am highly confident there are no AIA trial proceedings on US 5,809,972 — the ODP structured data is empty and my searches found no counter-evidence. I have not verified the precise maintenance-fee lapse date, and I did not have direct PTAB E2E or Patent Center query access; the 2014-lapse possibility above is an inference from the last recorded FPAY event (12-year fee, 2010-03-19) plus the absence of a 16-year event, not a confirmed fact. Treat the 2016-06-21 figure as the patent's nominal/anticipated expiration and confirm the fee status before relying on it in a filing.

I'll search for specifics on the assignment record, correspondents, and entity status before reconstructing the chain.

Now let me try to surface the recorded correspondents (attorneys) for these reel/frame entries.

Let me make one more attempt at correspondent data and confirm the corporate/bankruptcy status of the assignors.

Inventors

Barry Grant — sole named inventor on US 5,809,972 (Espacenet lists inventor "GRANT BARRY [US]"; Google Patents lists a single inventor). Employer at time of filing: Barry Grant, Inc. (d/b/a BG Fuel Systems / Demon Carburetion), Dahlonega, Georgia — a company Grant founded and owned.

Unusual pattern (present, and material): the patent was never assigned to Grant's operating company. Google Patents records the original assignee as "Individual" and Espacenet records the applicant as "GRANT" — i.e., Barry S. Grant held the '97 application and the issued patent personally. This is the opposite of the usual "all inventors assign to employer at filing" pattern. Because the patent sat outside the operating company, it did not pass through the Barry Grant, Inc. bankruptcy estate by operation of the estate's own title — it later moved by a separate, personal assignment from Grant (Reel 026565/0001), keyed to the July 6, 2011 asset auction (see below).

Continuity note: the application is a continuation-in-part of Ser. No. 08/668,219 (filed 1996-06-21, now abandoned), which claimed priority to provisional Ser. No. 60/000,149 (filed 1995-06-22) — so the effective 20-year term runs to 2016-06-21, which matches the "Anticipated expiration" entry in the record. No 16-year maintenance-fee entry appears in the Google Patents legal events; the last fee paid was the 12-year fee (2010-03-19).

Original assignee

Barry S. Grant, an individual (Google Patents: "Original Assignee — Individual"; Espacenet: applicant "GRANT").

• Did they ship a product embodying the claims? Direct evidence: no. Barry Grant personally shipped nothing. The operating business that bore Grant's name — Barry Grant, Inc. / BG Fuel Systems / Demon Carburetion — commercially shipped carburetors (Demon, Road Demon, Mighty Demon, Demon 98, etc.). The '972 claims, by contrast, describe a fuel-injection conversion (injector mounting blocks replacing float bowls/metering blocks, feeding booster venturi rings). I found no evidence that BG/Demon ever shipped an injection product practicing the '972 claims, and the prior litigation section already found no assertion activity. Treat product-embodiment as unclear.
• Primary line of business: aftermarket high-performance carburetion and fuel-system components.
• Current status: dissolved after bankruptcy. Barry Grant, Inc. filed Chapter 11 on 2009-10-13, never filed a plan, ceased operations 2011-02-18, was converted to Chapter 7 at a 2011-02-22 hearing, and its operating assets were sold at public auction to High Performance Industries, Inc. on 2011-07-06 (source: https://www.hotrod.com/news/more-on-the-barry-grant-bankruptcy-saga). The '972 patent itself was held personally by Grant and assigned to High Performance Industries on that same auction date.
• Current assignee of record: Holley Performance Products Inc. (Bowling Green, KY) — an operating company; Google Patents lists it as current assignee, and it is the surviving entity from the 2014 merger with Demon Fuel Systems. Holley is a public company (Holley Inc.), which is relevant because its debt financings are the source of most of the "noise" in this record.

Assignment timeline

The Assignment Center does have records for this patent. Below is the complete chain as reflected in the Google Patents legal-events/assignment record (the authoritative text provided), reorganized into conveyances vs. security/release filings.

Correspondent limitation (stated plainly): the Google Patents legal-events feed that is the authoritative source here does not expose the 37 CFR 3.73 correspondent/attorney field, and my searches did not surface the recorded correspondents for these reel/frame entries. I therefore cannot report correspondent names for any link in this chain, and NPE signal #3 (repeat correspondent) is assessed as unclear rather than guessed. I did not treat a TTAB trademark correspondent for a Holley-related party ("James R Menker, Holley & Menker PA," appearing in a trademark opposition file) as an assignment correspondent — those are different record classes and I am not conflating them.

A. Title transfers (the actual ownership chain)

• 2011-07-06 (executed) / recorded 2011-07-08 — Reel 026565/0001

  • Conveyance: Assignment of Assignors Interest
  • Assignor: Grant, Barry S. (individual)
  • Assignee: High Performance Industries, Inc. (Kentucky)
  • Correspondent: not available in the source record (see limitation above)
  • Context: Bankruptcy fire-sale — executed on the exact date (2011-07-06) of the public auction of Barry Grant, Inc.'s operating assets to Holley's then-parent, High Performance Industries. This is where the patent left the inventor personally and entered the Holley corporate family.

• 2011-12-13 (executed) / recorded 2011-12-13 — Reel 027371/0471

  • Conveyance: Assignment of Assignors Interest
  • Assignor: High Performance Industries, Inc.
  • Assignee: Demon Fuel Systems, Inc. (Kentucky)
  • Correspondent: not available
  • Context: Internal reorganization — the '972 asset moved out of the acquisition vehicle into the Demon-branded operating subsidiary. (Executed/recorded same day = housekeeping, not negotiation.)

• 2014-04-10 (executed) / recorded 2014-05-06 — Reel 032826/0413

  • Conveyance: Merger
  • Assignor: Demon Fuel Systems, Inc.
  • Assignee: Holley Performance Products Inc. (Kentucky)
  • Correspondent: not available
  • Context: Internal reorg / merger — Demon Fuel Systems absorbed into Holley, which is the current assignee of record. Title has not moved since.

B. Securitization encumbering the '972 patent (no change of title)

These are not ownership transfers and must not be reported as such — they are liens and lien releases. They move in parallel with Holley's private-equity/leveraged financings.

• 2008-12-23 / recorded 2009-01-28 — Reel 022162/0214 — Security Agreement — Assignor Grant, Barry S. → Assignee Branch Banking and Trust Company (Georgia). Context: securitization — Grant pledged the patent personally, roughly 10 months before his company's Chapter 11. This is the security interest that underpinned the later bankruptcy sale.
• 2011-12-28 / recorded 2012-01-04 — Reel 027480/0708 — Security Agreement — Demon Fuel Systems, Inc. → Wells Fargo Capital Finance, Inc. (California).
• 2011-12-28 / recorded 2012-01-06 — Reel 027490/0852 — Security Agreement — Demon Fuel Systems, Inc. → Wilmington Trust, National Association (Minnesota).
• 2012-06-07 / recorded 2012-06-08 — Reel 028342/0295 — Security Agreement — Demon Fuel Systems, Inc. → LBC Credit Partners II, L.P., as Agent (Pennsylvania).
• 2012-06-08 / recorded 2012-06-16 — Reel 028388/0916 — Termination and Release of Security Interest (of Reel 027490/0852) — Wilmington Trust NA (successor-by-merger to Wilmington Trust FSB) releasing Holley Performance Products, Inc., Demon Fuel Systems, Inc., Sniper Motorsports, Inc.
• 2012-06-07 / recorded 2012-06-29 — Reel 028487/0941 — Security Agreement — Demon Fuel Systems, Inc. → Hawthorn Finco, LLC (New York).
• 2013-10-24 / recorded 2013-10-25 — Reel 031496/0062 — Security Agreement — Holley Performance Products Inc., Demon Fuel Systems, Inc., QFT Holdings, Inc. and others → General Electric Capital Corporation, as Agent.
• 2013-10-24 / recorded 2013-10-30 — Reel 031513/0841 — Release by Secured Party — LBC Credit Partners II, L.P. → Demon Fuel Systems, Inc.
• 2013-10-24 / recorded 2013-10-30 — Reel 031512/0872 — Release by Secured Party — Hawthorn Finco, LLC → Demon Fuel Systems, Inc.
• 2013-10-24 / recorded 2013-10-30 — Reel 031508/0928 — Release by Secured Party — Wells Fargo Bank, N.A., as Agent → Demon Fuel Systems, Inc.
• 2015-09-22 / recorded 2015-09-22 — Reel 036664/0148 — Patent Security Agreement — Holley Performance Products Inc., QFT Holdings, Inc., Holley Performance Systems, Inc. and others → Cerberus Business Finance, LLC, as Collateral Agent.
• 2015-09-22 / recorded 2015-09-24 — Reel 036686/0964 — Release of Security Interest — General Electric Capital Corporation → Demon Fuel Systems, Inc., Holley Performance Systems, Inc., QFT Holdings, Inc., Holley Performance Products Inc.
• 2018-10-26 / recorded 2018-11-05 — Reel 047419/0953 — Release by Secured Party — Cerberus Business Finance, LLC → MSD LLC, Holley Performance Systems, Inc., QFT Holdings, Inc., ACCEL Performance Group LLC, Powerteq LLC, Holley Performance Products Inc.
• 2018-10-26 / recorded 2018-11-06 — Reel 047429/0343 — Security Interest — Flowmaster, Inc., APR, LLC, ACCEL Performance Group LLC and others → UBS AG, Stamford Branch, as Collateral Agent (Connecticut).
• 2018-10-26 / recorded 2018-11-18 — Reel 048147/0510 — Security Interest — same grantor group → AEA Debt Management LP, Second Lien Collateral Agent (Connecticut).
• 2018-10-26 / recorded 2018-11-18 — Reel 048475/0125 — Corrective Assignment (delete patent numbers previously recorded at Reel 047429/0343; confirms the UBS first-lien security interest).
• 2021-11-18 / recorded 2021-11-24 — Reel 058944/0279 — Release by Secured Party — AEA Debt Management LP (Second Lien Collateral Agent) → High Performance Industries, Inc., Holley Performance Systems, Inc., Holley Performance Products Inc., Racepak LLC, Powerteq LLC, MSD LLC, ACCEL Performance Group LLC, APR LLC, Flowmaster, Inc.
• 2021-11-18 / recorded 2021-11-24 — Reel 058948/0926 — Release by Secured Party — UBS AG, Stamford Branch (First Lien Collateral Agent) → same released parties.

Maintenance-fee records (2002, 2006 with late surcharge, 2010) confirm the family kept the patent alive and paying fees until natural expiry.

Timeline diagram

timeline
    title Ownership of US 5809972
    1996 : Priority filing by Barry S Grant
    1998 : Patent granted to Barry S Grant
    2009 : Personal security interest to BB and T
    2011 : Assigned to High Performance Industries
         : Reassigned to Demon Fuel Systems
         : Auction sale completed 6 July
    2012 : Lender security interests recorded
    2014 : Demon merged into Holley
    2015 : Cerberus collateral security interest
    2016 : Patent term expires
    2018 : UBS first lien security interest
         : AEA second lien security interest
    2021 : All security interests released

NPE / troll-pattern signals

1. Shell-entity transfer — Not present. No link in the title chain has an "IP / Patents / Licensing / Holdings / Ventures" suffix. The post-2011 assignees are High Performance Industries, Inc. (Reel 026565/0001), Demon Fuel Systems, Inc. (Reel 027371/0471) and Holley Performance Products Inc. (Reel 032826/0413) — all branded aftermarket-parts operating entities. QFT Holdings, Inc. appears only as a co-grantor of security interests (Reels 031496/0062, 036664/0148, 047419/0953), never as a title holder of '972. No single-purpose Delaware/Texas LLC with a registered-agent address appears anywhere in the chain.

2. Known asserter in the chain — Not present. No assignee matches Acacia, Marathon, Intellectual Ventures, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation Corp, or any Spangenberg entity. The chain terminates at Holley, an operating OEM/aftermarket supplier. Corroborated by the prior litigation section's finding of no known suits.

3. Repeat correspondent across the chain — Unclear (cannot assess). The reel/frame entries above are verifiable, but the correspondent field is not exposed in the Google Patents legal-events data and did not surface in search. Because the signal requires recurrence evidence and I have none, I decline to score it. Verifying this requires pulling each of the reels directly from Assignment Center.

4. Cascading transfers — Pattern mechanically present, but benign context. Two title transfers occurred inside ~5 months (2011-07-06 Reel 026565/0001 and 2011-12-13 Reel 027371/0471). However, both assignees are the same corporate family — HPI was the acquisition vehicle and Demon was its branded subsidiary — and the cause is documented as a court-supervised asset auction, not an attempt to obscure ownership. Same-state (Kentucky) entities, same corporate group. Scored not present as an NPE signal.

5. Pre-litigation transfer — Not present. Per the prior litigation section, no infringement suit naming '972 was found, so there is no suit date against which to measure a 6-month window. The 2011–2014 transfers predate expiry by 2–5 years and are bankruptcy/reorg-driven, not assertion-driven.

6. Bankruptcy fire-sale — Present. Barry Grant, Inc. → Chapter 11 (2009-10-13) → Chapter 7 (ordered 2011-02-22) → assets sold at public auction to High Performance Industries on 2011-07-06 (https://www.hotrod.com/news/more-on-the-barry-grant-bankruptcy-saga). The corresponding patent assignment, Reel 026565/0001, executed 2011-07-06, matches the auction date exactly. The personal security interest at Reel 022162/0214 is the mechanism by which the asset was reachable by the secured creditor, and the Chapter 7 trustee "abandoned those assets to Barry Grant's secured creditor," who then sold the secured loans to HPI. This is a genuine distress-transfer signal — but the buyer is an operating competitor, not an NPE.

7. Privateering — Not present / unclear. HPI (Holley's parent) acquired a competitor's assets in bankruptcy. There is no evidence of a Holley→NPE transfer, no license-back arrangement, and no asserted campaign surfaced in SEC filings or third-party (Patent Progress / EFF) coverage in the prior section. Absent that evidence, this must not be inferred.

8. Defensive aggregator (anti-NPE) — Not present. The chain does not terminate at RPX, AST, LOT Network, Unified Patents, or OIN. It terminates at Holley Performance Products Inc.

Verdict

Operating-company assertion — with an explicit caveat on the "assertion" element.

Justification: the title chain is a short, fully operating-company chain — Reel 026565/0001 (2011-07-06, Barry S. Grant → High Performance Industries), Reel 027371/0471 (2011-12-13, HPI → Demon Fuel Systems), and Reel 032826/0413 (2014-04-10, Demon → Holley Performance Products Inc., merger) — with every other reel/frame entry being a security agreement or release (Reels 022162/0214, 027480/0708, 027490/0852, 028342/0295, 028487/0941, 031496/0062, 036664/0148, 047429/0343, 048147/0510, 048475/0125 and their corresponding releases at 028388/0916, 031508/0928, 031512/0872, 031513/0841, 036686/0964, 047419/0953, 058944/0279, 058948/0926). No shell LLC, no known NPE, no defensive aggregator, and no pre-litigation transfer appears anywhere.

Important caveat, flagged rather than glossed: the "assertion" half of that label is not supported — the prior section found no suit asserting '972, and the patent expired 2016-06-21, making a future assertion impossible (subject to the § 286 look-back). This taxonomy has no clean "operating-company-owned, non-asserted" bucket; if forced to choose among the four, operating-company ownership is the accurate characterization and I am not importing an assertion that the record does not show. The one substantive adverse finding is the bankruptcy fire-sale (Reel 026565/0001, matching the 2011-07-06 auction), which is a distress signal but points to an operating-company buyer, not an NPE.

Corroborating cross-reference: the assignment record is consistent with the prior litigation section — no pre-litigation assignment, no NPE in the chain, and the current assignee of record (Holley Performance Products Inc.) is the same entity identified there.

Verification links:

• USPTO Assignment Center: https://assignmentcenter.uspto.gov/ (search patent number 5809972)
• Legacy Assignment Search: https://assignment.uspto.gov/patent/index.html
• Google Patents legal events: https://patents.google.com/patent/US5809972/en

Open item to close out: pull the 21 reel/frame entries above in Assignment Center to capture the correspondent of record for each — specifically whether a single firm recorded both the 2011 Grant→HPI assignment and the 2011 HPI→Demon transfer, and whether the same firm recorded the 2012–2015 lender liens. That is the only signal in this analysis still unresolved.

I'll research each examiner-cited reference for US 5,809,972 to characterize them accurately.

Prior Art Analysis — U.S. Patent No. 5,809,972

"Venturi-assisted fuel injection carburetor system" | Inventor: Barry Grant | App. No. 08/899,342 | Filed 1997-07-23 | Priority 1996-06-21 | Granted 1998-09-22 | Status: Expired – Lifetime (anticipated expiration 2016-06-21)
Source of record: https://patents.google.com/patent/US5809972/en

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0. Framing (read this first — it changes how you should read §102 below)

1. The five "patent citations" on the face of US 5,809,972 are all examiner-cited references (each carries the * = "Cited by examiner" flag in the Google Patents table; none is flagged as third-party). They are the prior art of record considered during prosecution — the correct starting set for "most relevant prior art."
2. Governing law is pre-AIA §102 (application filed 1997-07-23, before the AIA's 2013-03-16 change). The relevant anticipation provisions are pre-AIA §102(a) and §102(b).
3. Every one of the five references is §102(b) art and effectively bulletproof as prior art: the latest publication among them is 1985-01-22 (US 4,494,511), and the '972 patent's earliest possible priority date is 1995-06-22 (provisional 60/000,149) — a gap of more than ten years. Each was also patented/published long before the applicant's invention, so each is §102(a) art as well.
4. Priority chain to keep straight: '972 is a continuation-in-part of Ser. No. 08/668,219 (filed 1996-06-21, now abandoned), which claimed priority to provisional 60/000,149 (filed 1995-06-22). This matters only if any claim was not supported in the parent; for the five references here it is irrelevant, since all predate even the provisional.
5. Caveat up front: These five references individually disclose subsets of the '972 claims. Based on the full texts I retrieved, none appears to disclose every element of independent claim 1, 9, or 13 in a single reference, so a clean §102 anticipation of the independent claims is unlikely. Their real bite is (a) against specific dependent-claim elements and (b) as §103 obviousness combinations — especially Penrod (block-for-bowl conversion architecture) + Bendix (throttle-body electronic injection). I flag this rather than overstate an anticipation conclusion, and I cannot give a legal opinion.

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1. The five examiner-cited references — full citations

Presented in priority-date order, exactly as listed on the '972 face (Google Patents "Patent Citations (5)", all marked *cited by examiner):

Additional filing-date detail:

• US 3,868,936 — U.S. app. 235,154 filed 1972-03-16; inventor Jean-Pierre Rivere (per PatentHub listing).
• US 4,204,507 — U.S. app. 05/778,638 filed 1977-03-17; inventors Gary L. Casey and Granville Hurlong, Jr.
• US 4,494,511 — Ser. No. 09,360 filed 1979-02-05 (through a chain of Rule 60 continuations of abandoned apps. 244,911 and 9,360).
• US 4,354,470 — U.S. app. 165,369 filed 1980-07-02; inventors Kiyoshi Miyaki, Akihiro Yamato, Hidenobu Nagase, Kazuo Otsuka.
• US 4,430,275 — filed 1982-08-13.

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2. Reference-by-reference analysis

2.1 US 3,868,936 A — Renault — "Fuel injection systems" (pub. 1975-03-04)

Full citation: U.S. Patent 3,868,936, "Fuel injection systems," Regie Nationale des Usines Renault, priority 1971-03-19, published 1975-03-04.

Description (from the documents): Per-cylinder indirect fuel injection into the intake pipe. A main venturi ("tuyere") 1 in the intake pipe 2, with an auxiliary venturi / "double diffuser" 3 just upstream whose outlet is level with the neck of the main venturi. A fuel injector 4 injects into an injection passage 5 and sprays through a spout 6 located at the neck of the auxiliary venturi 3. A butterfly valve 7 sits downstream of the main venturi. A second injector 8 downstream of the butterfly handles idle/low load. The specification expressly contemplates multiple stepped tuyeres fed by injectors through feed ducts to each tuyere neck, and states a key benefit: injecting at the tuyere neck where gas speed is maximum yields best atomization, permitting low-pressure electromagnetic injectors. Radial/diametrically opposed orifices deliver fuel at the neck.

§102 relevance to '972:

• Claim 6 / claim 7 (booster venturi ring with fuel outlet near the wall constriction): This is the strongest mapping. Renault discloses a suspended auxiliary (booster) venturi whose outlet is level with the neck of the main venturi, fed by an injector via a conduit, so fuel is ejected at the zone of highest velocity/lowest pressure. Substantially the venturi-assisted atomization mechanism of claim 6 and the "outlet positioned adjacent the wall constriction" placement of claim 7.
• Claim 1: Discloses the sub-elements of a venturi passage with a constriction (1b) and a fuel conduit from an injector to that venturi (1g, partially), plus fuel atomization by the venturi low-pressure zone (1h). It does not disclose a multi-barrel carburetor center section with side mounting surfaces, side-mounted injector mounting blocks, or injectors seated in housings in those blocks (1a, 1c, 1e, 1f). Renault's structure is an intake-pipe/port configuration, not a carburetor center section.
• Net: Does not anticipate claim 1 as a whole; directly relevant to dependent claims 6–7 and as §103 art for the venturi-atomization concept.

2.2 US 4,204,507 A — Bendix — "Fuel electric fuel injection valve" (pub. 1980-05-27)

Full citation: U.S. Patent 4,204,507, "Fuel electric fuel injection valve," The Bendix Corporation, filed 1977-03-17, published 1980-05-27.

Description: A single-point (throttle-body) fuel injection system. A throttle body has first and second air intake throats corresponding to two intake-manifold planes; a throttle plate controls air flow in each throat. A fuel-accumulating bowl integrally formed with the throttle body is closed by a diaphragm/cover; a pair of injectors inside the bowl inject pulsed portions of fuel through a sonic nozzle into each throat. Injection is timed to crankshaft position (e.g., 15° BTDC) to enhance cylinder-to-cylinder distribution. A pressure regulator (sharing the bowl diaphragm) controls fuel pressure. The pulses are governed by an electronic control unit (an ECU II-1 / ECU-II-1A derivative) in response to sensed engine conditions. The specification explicitly frames the invention as combining the good features of carburetors and multipoint EFI while avoiding "wall wetting," and repeatedly discusses the throat/venturi airflow.

§102 relevance to '972:

• Claim 1: Closest "electronic carburetor" art of the five. Discloses plural barrels/throats (1a‑like), throttle valves in each (1d), a plurality of fuel injectors (1f), fuel introduced into the air intake throat (1g‑like), and intermittent, timed (sequential) injection into the airstream (1h). It does not disclose (i) a carburetor center section with mounting surfaces on its sides carrying side-mounted injector mounting blocks, (ii) injectors seated in housings formed in such blocks, or (iii) conduits running from an injector, through its mounting block, and through the center section to the venturi. Bendix's injectors live inside the integrally-formed bowl, and the throats are not described as carburetor-style venturi walls with a wall constriction in the claim-1 sense.
• Claim 8 (sensing means + control means): Strongly relevant — Bendix discloses an ECU responsive to sensed engine conditions pulsing the injectors. This element is squarely met.
• Net: Does not anticipate claim 1 outright (fails the mounting-block-on-side-surface and through-center-section-conduit elements), but it is the key §103 reference for the "electronically controlled injectors pulsing fuel into a multi-throat air body" half of the invention, and it reads on claim 8.

2.3 US 4,494,511 A — Nippondenso — "Fuel injection system for internal combustion engines" (pub. 1985-01-22)

Full citation: U.S. Patent 4,494,511, "Fuel injection system for internal combustion engines," Nippondenso Co., Ltd., priority 1978-02-14, published 1985-01-22.

Description: An electrically controlled fuel injection system in which an electromagnetic valve (injector) is disposed upstream of the throttle valve in the intake pipe so that a group of cylinders is fed from it. A pressure regulator regulates fuel pressure in proportion to intake pressure downstream of the throttle valve; fuel quantity is set by injection opening interval τ, computed from engine speed N and intake air amount Qa. The control circuit (Fig. 2) uses an air-flow meter, crank-angle/pulse detector, oxygen sensor, and coolant-temperature detector to compute and trim injection duration. The stated object is low-cost, precise metering with a reduced number of injectors; the invention is about the metering/control economics, not about venturi atomization or carburetor conversion.

§102 relevance to '972:

• Claim 8 (sensing means for engine operating conditions + control means actuating injectors): Directly relevant — discloses ECU sensing air flow, engine speed, exhaust oxygen, and coolant temperature, and modulating injector open-time. This is essentially the claim-8 control scheme.
• Claims 1/9/13: No carburetor center section, no barrels/venturi wall constrictions, no side mounting blocks, no conversion of a carburetor. Not anticipatory of any independent claim.
• Net: §103 art for the electronic control/metering features, chiefly claim 8. It corroborates that the "sense conditions → pulse the injector" layer of '972 was old and well known by the late 1970s.

2.4 US 4,354,470 A — Honda Giken Kogyo — "Fuel supply apparatus in internal combustion engine" (pub. 1982-10-19)

Full citation: U.S. Patent 4,354,470, "Fuel supply apparatus in internal combustion engine," Honda Giken Kogyo Kabushiki Kaisha, priority 1979-07-06, published 1982-10-19.

Description: An intake passage is provided with a venturi having at least one fuel-discharge opening in its throat. The discharge opening communicates with a "mixture-producing source" — a perforated bleed tube 10 (many circumferential/axial bleed holes 9) surrounded by an annular space fed with external air through a secondary air port 11 — into which a fuel injection nozzle 8 injects. Injected fuel mixes with external air in the bleed tube, and the fuel-air mixture is drawn into the venturi throat through the discharge opening(s), where it is further atomized by the intake air. A pair of discharge openings is preferably arranged opposite one another so the mixture streams impinge for better atomization; openings may be angled 0–45° downstream. The nozzle need only be a metering valve, so a low-pressure pump suffices.

§102 relevance to '972:

• Claim 1 (core atomization mechanism): Honda discloses a fuel injector feeding fuel, via a passage, into a venturi throat, where the fuel is atomized by the venturi/air-stream — reading on 1(b), a conduit from the injector to the venturi (1g‑like), and 1(h)'s "atomized by the zone of low pressure / passed into the engine for combustion." This is the closest match among the five to the functional heart of claim 1 (injector + venturi-assisted atomization).
• Differences from '972: Honda uses a bleed tube/air-mixing chamber (mixing fuel with external air before the venturi), a single venturi rather than a multi-barrel carburetor center section, and no side-mounted injector mounting blocks replacing float bowls. The injector is not mounted in a block bolted to the center section's side, and there is no conversion architecture. It therefore does not anticipate claims 1, 9, or 13 as a whole.
• Net: Strong §103 reference for the venturi-atomization element and, depending on claim construction, relevant to the atomization language of claim 1 and to claims 6–7's fuel-into-venturi concept.

2.5 US 4,430,275 A — Penrod — "Dual bowl metering block for alcohol and/or nitro-methane burning carburetor and method of conversion" (pub. 1984-02-07)

Full citation: U.S. Patent 4,430,275, "Dual bowl metering block for alcohol and/or nitro-methane burning carburetor and method of conversion," Leroy Penrod, filed 1982-08-13, published 1984-02-07.

Description: A conversion device: a carburetor metering block adapted to attach to a conventional (Holley two-barrel) carburetor and replace the removable fuel bowl and standard metering block, the replacement block being adapted to accept a plurality of individual fuel bowls (more flow for alcohol/nitro-methane). The block attaches through bolt holes 18 aligned with the points of attachment of the original metering block. Each fuel circuit supplies a separate venturi within the carburetor throat — i.e., each barrel of the carburetor is supplied by its own fuel bowl — via replaceable main jets (22/24) and fixed auxiliary jets (26/28). The specification notes more than one such block can replace both primary and secondary metering blocks of a four-barrel carburetor. It claims the block per se and the conversion method.

§102 relevance to '972:

• Claims 9 and 13 (conversion system / conversion method): This is the most on-point reference for the architectural concept at the center of the '972 conversion claims: a block with a mounting face that bolts to a conventional carburetor center section in place of the factory float bowl/metering block, with internal fuel conduits that route to a center-section conduit leading to each barrel/venturi. Penrod discloses the "remove the fuel bowl and metering block → attach a replacement block that feeds each barrel separately" mechanism that '972's claims 9 and 13 describe. The block-for-bowl mounting-surface concept is disclosed.
• But it is not injector-based: Penrod's block meters liquid fuel through fixed/replaceable jets from float bowls; there are no fuel injectors, no injector housings, and no electronic sensing/control means. Because independent claims 9 and 13 each require fuel injectors in housings plus sensing/control means, Penrod does not anticipate claims 9 or 13 as a whole. It anticipates only the sub-combination (block-replaces-bowl conversion) and is a §103 reference that, combined with Bendix (US 4,204,507) and/or Nippondenso (US 4,494,511), would support an obviousness rejection of the conversion claims.
• Net: The most dangerous of the five for the conversion claims, but only in combination; not a standalone §102 reference for any independent claim.

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3. Claim-by-claim §102 / §103 matrix

Legend: A = reference alone discloses the element (potential §102 hit); P = partial / reads on the element with construction; — = element not disclosed; §103 = useful in an obviousness combination. (An independent claim is anticipated under §102 only if every element is met by a single reference — none below meets that bar.)

Reading the matrix: The examiner's five references collectively map onto nearly every element of '972, but across references, not within any one. That is the signature of an obviousness rejection built by combination rather than a §102 anticipation — most plausibly Penrod (§9/§13 conversion architecture) + Bendix (§1 injector/TBI + §8 ECU), with Nippondenso as corroboration of the sensing/control layer and Renault/Honda supporting the venturi-atomization elements.

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4. What the prior art does not cover (the apparent novel core of '972)

Pulling the five references together, none discloses the specific combination that the '972 claims are built around:

• Injector mounting blocks bolted onto the side mounting surfaces of a conventional multi-barrel carburetor center section, in place of the factory float bowls and metering blocks (claims 1e, 9, 13).
• A fuel conduit running from an injector, through its mounting block, and through the carburetor center section, reusing the existing booster-venturi fuel-supply-tube passage to reach each barrel's venturi (claim 1g bound to claim 6).
• Injectors seated in housings in those side blocks with the nozzle aimed at the through-block conduit, with a fuel plenum formed in the block (claims 1f, 4, 5).

That bolt-on-block-replacing-the-float-bowl architecture — the "convert a conventional carburetor to EFI with little modification" premise stated throughout the '972 specification — is not found in any of the five, which is consistent with its having survived prosecution. The closest single reference to that architecture is Penrod (US 4,430,275), which supplies the block-for-bowl concept but not the injectors; the closest to the functional result (injector + venturi atomization) is Renault (US 3,868,936) and Honda (US 4,354,470); and the closest to the electronics is Bendix (US 4,204,507) and Nippondenso (US 4,494,511).

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5. Important notes, limitations, and things NOT to confuse with prior art

• Do not treat the "Cited By" list as prior art to '972. The 40–68 later documents (e.g., US 6,120,007; US 6,290,215; the long Holley/MSD/Demon-family chain, US 9,482,198; US 11,391,255; etc.) all post-date '972. They are forward citations relevant to the validity/scope of those later patents, not prior art against '972. Only the five examiner-cited references analyzed above are prior art of record.
• The Google Patents legal-events record for '972 is assignments/security interests, not litigation (e.g., Grant → High Performance Industries → Demon Fuel Systems → Holley Performance Products, plus bank/lender liens). This was covered in the earlier litigation section and is not prior art; I note it only so the assignment chain isn't mistaken for a citation or challenge.
• Verification status: I retrieved the full text/abstracts of all five references (Renault via FreePatentsOnline and the USPTO-hosted PDF; Bendix, Nippondenso, Honda, and Penrod via Google Patents / Justia / patenthub listings). The citations, dates, and assignees above are taken from those documents and the '972 face. I did not have direct access to a USPTO PatentCenter image for every reference, and I have not performed a full element-by-element reading of every drawing figure; the §102/§103 mappings above are based on the retrieved specifications and are analytical, not legal conclusions.
• No auto-correction of identifiers: US 3,868,936 / US 4,204,507 / US 4,494,511 / US 4,354,470 / US 4,430,275 are reported exactly as they appear in the '972 record and as verified in the sources cited. Note these are frequently confused with look-alike numbers (e.g., US 4,392,151 Nippondenso; US 4,832,988; US 5,329,905 Honda) — those are different patents and are not citations of '972.

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6. Bottom line

• The most relevant prior art to US 5,809,972 is its five examiner-cited references: US 3,868,936 (Renault), US 4,204,507 (Bendix), US 4,494,511 (Nippondenso), US 4,354,470 (Honda Giken Kogyo), and US 4,430,275 (Penrod), all published 1975–1985 and all qualifying as pre-AIA §102(b) art.
• Likely single-reference §102 hits, if any, are limited to dependent-claim elements: Renault (US 3,868,936) against the suspended-booster-venturi/fuel-at-the-constriction concepts of claims 6–7, and Bendix (US 4,204,507) / Nippondenso (US 4,494,511) against the engine-sensing/control element of claim 8.
• No single reference appears to anticipate independent claims 1, 9, or 13. The realistic validity challenge is a §103 combination, led by Penrod (conversion-block-for-bowl architecture) + Bendix (throttle-body electronic injection + ECU), supported by Honda/Renault (venturi atomization) and Nippondenso (sensor/control metering).
• The apparent point of novelty: side-mounted, injector-bearing blocks that replace a conventional carburetor's float bowls/metering blocks and deliver injected fuel through the center section into each barrel's existing booster venturi, under sequential electronic control.

If you want, I can extend this to the parent application US 08/668,219 (abandoned) and provisional 60/000,149 to see whether the examiner considered the same five references there, and can run the five references' own forward-citation trees to surface any additional art that a challenger could raise.

I'll ground the obviousness analysis in the actual prior-art references of record before drawing § 103 conclusions.

(Note: the preamble states today's date as 2026-09-27 while this task states 2026-04-26 — I'm flagging the discrepancy and proceeding with the task's framing; it does not affect the analysis, which turns on a 1996–1997 priority date.)

The Bendix reference (US 4,204,507) is a single-point throttle-body injection system — highly material. Let me pull the remaining references.

Let me examine the remaining references and the earlier "similar documents" that predate the 1996 priority date.

Obviousness Analysis — U.S. Patent No. 5,809,972 under 35 U.S.C. § 103

Bottom line up front: Claims 1, 6, 7, 8, 9, and 13 are, in my assessment, vulnerable to a strong § 103(a) challenge built from the five references already of record — principally Penrod (US 4,430,275) for the bolt-on, side-mounted block that replaces the carburetor's metering block/float bowl and feeds each barrel's venturi, combined with Bendix (US 4,204,507) for per-throat electronic fuel injection in a carburetor-style throttle body, and Renault (US 3,868,936) for injecting into a venturi throat / suspended booster-venturi geometry. Claims 2–5, 10–12 fall on design-choice and common-rail plenum reasoning. The patent's own background section supplies the motivation to combine, which is unusually damaging.

Caveat on scope: I retrieved and verified the full text or substantial specification text of all five references of record. I did not retrieve the specification of any reference in the "Similar Documents" list, so I do not rely on those for specific disclosures — I flag them only as likely-better art that should be pulled. I also flag below why the "Cited By" references cannot be used as prior art here.

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1. Governing framework

Statute. The application was filed 1997-07-23 with a priority date of 1996-06-21 (CIP of 08/668,219, filed 1996-06-21; provisional 60/000,149, filed 1995-06-22). Because the application was filed before March 16, 2013, pre-AIA 35 U.S.C. § 103(a) governs (AIA § 3(n)(1)). All five references of record issued between 1975 and 1985 — more than one year before even the 1995 provisional — so each is § 102(b) prior art regardless of which priority date ultimately attaches to any given claim.

Standard. Graham v. John Deere Co., 383 U.S. 1 (1966) (scope/content of prior art; differences; PHOSITA level; secondary considerations), as qualified by KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007) — the claimed combination need not be taught or suggested in a single reference; a combination of known elements according to known methods yielding predictable results is obvious, and "if a technique has been used to improve one device, and a person of ordinary skill in the art would recognize that it would improve similar devices in the same way, using the technique is obvious." MPEP §§ 2141–2144.04 supply the exemplary rationales invoked below.

Level of ordinary skill (PHOSITA). As of June 1996: a mechanical/automotive engineer (B.S.M.E. or equivalent) with roughly 2–5 years' experience in fuel/air induction for spark-ignition engines — familiar with (i) modular Holley-style carburetors having removable fuel bowls and metering blocks bolted to the sides of a center section, and (ii) electronically controlled fuel injection using solenoid injectors pulse-width-controlled by an ECU from MAP/TPS/RPM inputs.

Analogous art. All five references are in the same field of endeavor and address the same problem (metering and atomizing fuel for a spark-ignition engine). They are presumptively combinable. Corroborating detail: the '972 patent is classified in F02M 71/00 — "Combinations of carburettors and low-pressure fuel-injection apparatus," and in Y10S 261/82 — "Upper end injectors." The claimed subject matter is, by the Office's own classification scheme, a combination of two known technologies.

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2. The references of record — verified content

Why the "Cited By" references are not prior art (important). The 40–68 "Cited By" documents (e.g., US 6,120,007; US 6,290,215 Pinsker; US 6,467,465 Lorts; US 9,485,198 / US 11,391,255 Fuel Injection Technology; US 10,294,902 Holley) all published after 1996. Under pre-AIA § 102(b) their publication dates are too late; under § 102(e) their earliest US filing (1996-02-13 for US 6,120,007) is after Grant's invention date (≤ 1995-06-22), and US 6,120,007 is in any event Grant's own work, not "by another." Do not cite them as art. They are useful only as evidence of the commercial trajectory.

Supplementary art worth adding (pre-1996, so § 102(b)-eligible): the "Similar Documents" list contains several on-point references I did not retrieve and therefore do not rely on — notably US 3,826,234 (Fuel injection apparatus in an I.C.E.), US 4,200,073 (Electronic throttle body fuel injection system), US 4,250,842 (Electronic injection carburetor), US 4,555,037 (uniform fuel distribution to a multi-cylinder engine), US 5,069,186 (fuel injection assembly for I.C.E.), and CA 1,274,130. For the "sequentially" limitation, US 3,751,231 (Nippondenso) expressly discloses "means for sequentially distributing the pulse signal … to solenoid operated fuel injection valves associated with individual cylinders … in a predetermined order."

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3. Element-by-element mapping of independent claim 1

Difference over the art: the '972 patent's asserted novelty is architectural — packaging the injectors in removable side-mounting blocks that replace the OEM float bowl/metering block, and routing injected fuel through the carburetor's own internal passages to each barrel's venturi. That is precisely Penrod's bolt-on replacement block, with Bendix's per-throat injector substituted for the bowl/jet hardware, on a Renault/Honda venturi that does the atomizing.

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4. The primary combination and the motivation to combine

Combination A (the core): Penrod '275 + Bendix '507 + Renault '936, optionally + Honda '470 and Nippondenso '511

Rationales (MPEP 2143 / KSR):

1. Combining prior-art elements according to known methods, yielding predictable results. Each element does exactly what it is known to do: Penrod's block distributes fuel to each barrel's venturi from a side-mounted, OEM-replacement block; Bendix's ECU-pulsed injector meters fuel precisely into a throat; Renault's tuyère neck atomizes. The result — better metering plus better atomization — is the arithmetic sum of the known benefits, not a new mechanism.

2. The motivation is stated in the prior art itself, and in the patent's own background. Bendix's specification is the clearest: the disclosed system is "calculated to combine the desirable features of both the carburetor and multipoint fuel injection systems while eliminating the problem areas of both." The '972 background says the very same thing: "it can be appreciated that a fuel system combining the high atomization of a carburetor and the precise fuel metering of fuel injectors would be desirable." A statement of the object in the patent's own background is an admission of the motivation and forecloses any "no suggestion to combine" argument.

3. Use of a known technique to improve a similar device (KSR). Penrod teaches the how of swapping the carburetor's fuel-metering hardware for a bolt-on block that feeds each venturi. Bendix teaches that a single pulsed injector per throat is a superior metering device for a carburetor-style throttle body. Substituting the injector for the bowl/jet in Penrod's block is the "simple substitution of one known element for another to obtain its predictable benefits" (MPEP 2144.04).

4. Explicit design incentive in Penrod. Penrod states the block is usable with "any carburetor that can be converted to the detachable metering block concept" — an express invitation to apply the side-mounting, per-barrel-passage architecture to other metering hardware.

5. Renault supplies the placement and geometry. Renault injects into the tuyère neck, with the auxiliary (booster) tuyère outlet level with the main venturi neck, and states the atomization benefit explicitly. No more than routine engineering is required to route the Penrod/Bendix injector output to that same neck.

Combination B (independent, for claim 1): Bendix '507 + Penrod '275 alone

If Bendix's throttle-body system is treated as the "carburetor center section" (it has throats, throttle plates, a fuel bowl, and fine atomization at the throat), then adding Penrod's side-mounted, bolt-on injector blocks containing the injectors — with conduits through the blocks into the body's existing passages — yields every element of claim 1. Motivation: converting an existing throttle body/carburetor by bolt-on hardware, which Penrod expressly teaches.

Combination C (for claim 6): Renault '936 is nearly dispositive

Claim 6's "suspended booster venturi ring … attached to a fuel supply tube … in fluid communication with said fuel outlet … and with one of said fuel conduits" reads directly onto Renault's suspended auxiliary tuyère 3 on radial arms, fed by feed passage 5 and groove 14, with radial holes 12 discharging into the tuyère neck. The '972 specification concedes the booster ring and its supply tube are "conventional in the art." Claim 6 adds essentially nothing over the admitted prior art other than the substitution of the block-mounted injector for the float-bowl feed — Combination A again.

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5. Dependent claims 2–8

• Claim 2 (blocks on opposite sides). Penrod: primary and secondary metering blocks on a four-barrel; mounting surfaces of a Holley center section are on opposite sides. Predictable placement. Also, with two barrels' worth of hardware per side, mounting on opposite sides is the only packaging option.
• Claim 3 (injector axis perpendicular to the barrel axis). Design choice as a matter of packaging. An injector housed in a block bolted to the side of a center section must necessarily have its axis transverse to the barrel axis; the '972 spec states exactly this and offers no criticality. Under KSR/MPEP 2144.04, mere orientation of a known component is not patentably distinct absent a showing of a result-effective variable. Renault's radial feed passage 5 and Honda's radial openings 19 are transverse injection geometries.
• Claim 4 (fuel plenum in the block in fluid communication with each injector). This is a common-rail/manifold bore. Pressure-regulated supply to multiple injectors is standard: Bendix's fuel bowl; Nippondenso's pressure regulator 8 feeding the electromagnetic valve; Renault's pressure-fed injector. Drilling one supply bore through a block to feed two injectors is a predictable expedient (MPEP 2144.04). The '972 spec admits the plenum is nothing more than "a cylindrical bore … provided with openings."
• Claim 5 (plenum as a cylindrical bore perpendicular to the injector axes). A predictable variation of claim 4 — the natural geometry when injectors are housed side-by-side in a block and a single supply bore is gun-drilled across them (MPEP 2144.04). No unexpected result is asserted.
• Claim 6. See Combination C above.
• Claim 7 (booster outlet opening "positioned adjacent said wall constriction"). Renault expressly places the auxiliary tuyère outlet "level with the neck of said main Venturi." Note that claim 7 recites adjacency, not the 0.020–0.030 in. numeric range from the specification (compare §"things worth flagging" in the prior summary). If a patentee tried to import that range into claim 7, it would face a written-description/support problem — the claim does not recite it. And optimizing a spacing (a result-effective variable) by routine experimentation is obvious under MPEP 2144.05.
• Claim 8 (sensing means + control means). Nippondenso '511 discloses the complete loop — air-flow meter, crank-angle detector, oxygen sensor, coolant-temperature sensor, and an electronic circuit generating the injector opening interval from intake pressure and Q_a/N. Bendix '507 discloses pulsed-injector control by an electronic control unit. The '972 specification itself calls the ECU approach conventional ("a computer which senses the manifold absolute pressure, the throttle position, and the engine rpm"). Claim 8 is obvious over Nippondenso alone or Nippondenso + Bendix. (Nippondenso is common ownership-neutral, different field actors, and was cited of record — no § 102(c)/103(c) complication.)

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6. Claims 9–12 — the conversion-kit claims

Claim 9 adds to the Claim 1 architecture: (i) block "configured to connect" with the center section's existing conduit, (ii) the injector nozzle "directed toward" that conduit, and (iii) sensing means + control means.

• (i) and (ii): Penrod '275 is a direct hit. Its block attaches to the carburetor at the same relative position as the original metering block, its bolt holes "aligned with the points of attachment on the original metering block," and it delivers fuel (via jets/circuits that "diagonally intersect within the metering block") to each venturi. Penrod's stated object is an "inexpensive, yet reliable way of converting a conventional … carburetor." Substituting an injector-nozzle outlet for the jet outlet in that block is a predictable substitution.
• (iii): Bendix '507 (pulsed electronic control) + Nippondenso '511 (sensing/control means). See Claim 8.
• "adapted to"/"configured to" language: these are capability limitations. A prior-art kit that can be so connected meets them; no different analysis applies.

⚠️ Drafting oddity that helps the challenger. Claims 9 and 13 recite that the injectors "inject fuel and air into the carburetor barrels." Read literally (as the operating rules require), that limitation is met directly by Honda '470, whose "mixture producing source 7" deliberately mixes injected fuel with external air and discharges the fuel-air mixture into the venturi through openings 19 — where the venturi atomizes it. So the apparent error does not save claims 9/13; if anything, Honda '470 or Honda + Penrod renders them obvious (and could support a § 102(b) anticipation argument as to that limitation). If instead the limitation is construed in light of the specification (fuel only), Combination A applies unchanged because Honda is not needed for the "fuel and air" element. Either way claims 9–13 are exposed.

Claims 10–12 are the claim-3/4/5 limitations in kit form; the same design-choice and common-rail reasoning applies.

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7. Claim 13 — the method claim

Steps: (a) provide a conventional center section with barrels/venturi passages, opposite-side mounting surfaces, and existing fuel conduits from those surfaces to the barrels; (b) provide a mounting block with housing, mounting surface, and a conduit to that surface; (c) mount an injector with its nozzle toward the conduit; (d) mount the block so the two conduits communicate; (e) connect the injector to control means; (f) connect control means to sensing means.

• (a) is the admitted prior art carburetor (the '972 specification relies on it).
• (b)–(d) are Penrod's disclosed method of conversion — the patent's title literally includes "and method of conversion," and its block replaces the OEM metering block, bolt-hole-aligned, with fuel circuits to each venturi.
• (e)–(f) are Bendix '507 (electronic pulsing) and Nippondenso '511 (sensing means / electronic control circuit).

A method claim is obvious if the prior art discloses the steps or the obvious variants thereof. Each step here is either admitted prior art or expressly disclosed in Penrod, Bendix, or Nippondenso. Claim 13 also carries the "fuel and air" oddity addressed above.

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8. Anticipated patent-owner rebuttals and why they likely fail

Secondary considerations. None are established on this record. The patented technology was clearly commercialized (the assignment chain shows Barry Grant → High Performance Industries → Demon Fuel Systems → Holley, 2011–2014), but there is no evidence of a nexus between that commercial activity and the claimed combination, no long-felt-need evidence, and no unexpected-results data. Absent such evidence, secondary considerations do not overcome the prima facie case.

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9. Residual uncertainties and verification flags

1. ⚠️ US 4,204,507 title vs. content. The title of record is "Fuel electric fuel injection valve," but the full text returned by Google Patents for US4204507A describes a single-point throttle-body fuel-management system (multiple throats, one injector per throat, fuel bowl, electronic pulsing, fine atomization). These may be two different Bendix documents. Before relying on the Bendix mapping in a formal opinion, pull the actual US 4,204,507 PDF and confirm which disclosure it contains. If US4204507 turns out to be directed only to an injector valve body, then Bendix supplies the injector/control element but not the throttle-body "center section" element — in which case Bendix + Penrod + Renault still reads on claim 1 using Renault for the venturi/throttle structure, so the conclusion is unchanged. It only matters which reference carries the "throttle body" element.
2. I did not retrieve the specifications of US 3,826,234, US 4,200,073, US 4,250,842 ("Electronic injection carburetor"), US 4,555,037, US 5,069,186, US 5,117,794, or the two Canadian patents in the "Similar Documents" list. Several appear to be more squarely on point than the art that was actually cited. A complete invalidity search should pull these — the presence of "Electronic injection carburetor" (US 4,250,842) and "Electronic throttle body fuel injection system" (US 4,200,073) in the similar documents list suggests the examiner may not have applied the closest art.
3. I could not confirm the examiner's grounds of allowance, the prosecution history, or any reexamination/PTAB record (consistent with the earlier sections' finding of no IPR/PGR/reexam). The prosecution history could contain applicant arguments or a Rule 132 declaration that bear on the § 103 analysis; obtain it from USPTO PatentCenter.
4. Practical stake is low. The patent is Expired – Lifetime (anticipated expiration 2016-06-21). Absent litigation, this analysis matters chiefly for defensive posture, for opinions on the descendants in the "Cited By" family (Holley/MSD/Fuel Injection Technology EFI throttle bodies), and for any priority/derivation questions.
5. The date discrepancy between the preamble (2026-09-27) and this task (2026-04-26) is noted but immaterial: everything here turns on the 1995–1997 priority dates and 1975–1985 reference dates.

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10. Conclusion

Bottom line: the '972 patent claims the bolting-together of two commercially mature technologies — a modular, side-mounted Holley-style fuel-metering block and an electronically pulsed injector — on a venturi barrel where the venturi does what venturis have always done. Every element is disclosed in art that issued between 1975 and 1985, one reference (Bendix) recites the motivation in words, and the patent's own background concedes the desirability of the combination. The strongest invalidity theory is Penrod + Bendix + Renault, with Nippondenso for the electronics and Honda for the fuel-air atomization and low-pressure-injector teachings.