US 3423048

I'll run targeted searches for this specific patent number and any CAFC 2026 activity.

I have the authoritative patent text plus search results. Let me do one more targeted check on litigation/CAFC references and the patent family.

US Patent 3,423,048 — Summary

Important search note: A USPTO/CAFC-targeted search for the specific number 3423048 returned no Court of Appeals for the Federal Circuit 2026 docket activity for this patent. Searches of CAFC-adjacent sources produced only unrelated hits bearing the same digit string (e.g., an ACM DOI 10.1145/3423048, a Washington State EPA waste "sequence number 3423048"), which I've excluded as noise. I cannot confirm any litigation, PTAB proceeding, or Federal Circuit appeal involving this patent, and I state that as an absence of evidence rather than a verified negative — I do not have authoritative access to a complete CAFC docket database.

Bibliographic data (from the patent's own front matter, as reproduced on Google Patents)

Abstract (verbatim, as printed)

The abstract states the invention relates to gas-turbine power plants of the kind where an air compressor feeds combustion apparatus whose hot gases drive a first turbine rotor that drives the compressor, then drive at least one further "power turbine rotor" transmitting power to a driven device. The stated object is a plant suited to substantial variation in mechanical power output — e.g., driving helicopter rotors or lift fans, or driving a constant-speed electric generator at constant frequency under varying electrical demand. The core structure recited is an air compressor; combustion apparatus; a first turbine rotor driving the compressor; second and third turbine rotors acted on in series after the first; differential gearing with two input elements driven respectively by the second and third turbine rotors and an output element constituting the power output member; and control means regulating gas flow between the second and third turbine rotors to vary the relationship between their power outputs. (Source: https://patents.google.com/patent/[US3423048A](/patent/US3423048A)/en)

Plain-language overview of the independent claims

There are four claims total, all independent. The specification calls the flow-regulating control means an "adjustable nozzle ring," embodied as an adjustable ring of vanes (item 7) between turbine rotors 4 and 6.

Claim 1 — Helicopter / "compound" aircraft power plant.
A gas-turbine plant for a helicopter containing, in combination: (a) an air compressor feeding combustion apparatus; (b) a first turbine rotor driven by the hot gases and driving that compressor (the gas-generator/"core" spool); (c) second and third turbine rotors in series downstream of the first; (d) differential gearing whose two inputs are driven respectively by the second and third turbine rotors and whose output is the power output member; (e) control means regulating gas flow between the second and third rotors, thereby altering how power is split between them; (f) "additional power transmitting means" taking power directly off one of those two rotors to a driven device; and (g) that device being a fan rotor delivering air to at least one jet-propulsion nozzle — with the differential output driving the helicopter rotor(s). In short: one engine whose free-power section is split so the same hot-gas stream simultaneously turns the main rotor (via the differential) and a propulsive fan (directly), giving a "compound helicopter" configuration. In the illustrated embodiment, turbine rotor 6 drives the fan hub 9/10 in duct 11 feeding cold nozzle 13, while the epicyclic differential (sun 17 on shaft 5, annulus 18 on shaft 3, planets 20) drives output shaft 26 through bevels 23/24/27/28 to the helicopter rotor 26a.

Claim 2 — Dependent on claim 1; zero-fan-speed capability.
Adds that the gas control between the second and third rotor is arranged so the turbine rotor directly connected to the fan rotor can be slowed substantially to zero — i.e., the fan/propulsive side can be shut down while the gas generator continues to run and power the helicopter rotor. (The specification says "reduced to zero if and when desired.") This is the key operational benefit over brake-based prior approaches.

Claim 3 — Air-cushion vehicle power plant.
Same core architecture (compressor / combustor / first turbine driving compressor / second and third turbines in series / two-input differential with power-output element / inter-rotor flow control / additional power transmitting means), but the loads are reassigned: the differential output member drives a first fan that supplies the air cushion, and the additional power transmitting means drives a second (propulsion) fan feeding at least one jet-propulsion nozzle. The specification notes constant output speed is not required in this application.

Claim 4 — Aircraft embodying the power plant.
Again the same core architecture, embodied in an aircraft having a lift fan, a further fan, and at least one propulsion nozzle receiving air from that further fan, wherein the differential output drives the lift fan and the additional power transmitting means drives the further fan (the printed claim text ends "...is arranged to drive air to the further fan," which reads as a drafting/OCR artifact for driving that fan). The specification's corresponding passage describes a ducted lift fan driven by shaft 26 and the fan 10 feeding jet-propulsion nozzles, "not necessarily at a constant speed."

Practical/legal observations

• All four claims are independent and share the same inventive core: series second/third power turbines + differential summing + variable inter-turbine nozzle control for power splitting, with the claims differentiated mainly by application/environment (helicopter, air-cushion vehicle, aircraft with lift fan) and by the zero-fan-speed limitation in claim 2.
• The patent has been expired since at least January 21, 1986, so it is prior art / public-domain subject matter today; it appears in modern search results primarily as a "Similar Documents" and citation reference (e.g., it is cited-by lineage relevant to later compound-helicopter and convertible-engine work such as United Aircraft's US 3,678,690/3,678,691).
• Uncertainty flag: Google Patents labels Bristol Siddeley Engines Ltd as both original and "current" assignee; Bristol Siddeley was absorbed into Rolls-Royce in the 1960s–70s, but I have not verified any recorded assignment chain beyond the front page and therefore do not assert a present-day owner. Likewise, the "Expired – Lifetime" status and the 1986 expiration date are the database's stated assumptions, not an adjudicated legal conclusion.

Sources cited: https://patents.google.com/patent/US3423048A/en (full text, claims, citations, legal-status data); PDF facsimile https://patentimages.storage.googleapis.com/7f/e7/29/ba7e3f653470aa/US3423048.pdf (original printed specification and claims). No USPTO litigation docket or CAFC 2026 filing for this patent number was located.

I'll research litigation involving US patent 3423048 across patent litigation sources.

Let me search more targeted litigation databases.

Let me check litigation-specific databases directly.

Litigation Search: US Patent 3,423,048

Bottom line

No litigation involving US Patent 3,423,048 was found.

I searched for this specific number (and the correctly punctuated form "3,423,048") across general web sources and patent-focused resources, including the Google Patents record for US3423048A, assignee/portfolio aggregators, and litigation-oriented results. I found no case — no plaintiff, no defendant, no docket entry, no CAFC appeal, no PTAB proceeding — naming US 3,423,048 as an asserted, challenged, or otherwise adjudicated patent.

Result table

Important false-positive warning

One search returned a hit mentioning "the '342 patent" — FloodBreak v. AMI (D. Conn.), a flood-barrier case involving a reasonable-royalty/Georgia-Pacific damages opinion. That is a different patent entirely. It is a shorthand reference to an unrelated later patent whose number happens to end in "342" (FloodBreak's patent, filed in a 2018 complaint). It must not be attributed to US 3,423,048. I flag this because casual keyword matching on "342" produces exactly this kind of misidentification, and the user's instruction to return results only for this precise number is well taken.

Why the absence of litigation is unsurprising

Several independent facts make litigation on this patent highly unlikely to exist:

• Term: US 3,423,048 issued January 21, 1969 (filed Nov. 18, 1966), with an anticipated expiration of January 21, 1986 (17-year term from grant under the pre-URAA regime). The patent has therefore been expired for roughly 40 years, and its enforcement window closed before most modern litigation databases had meaningful coverage.
• Ownership: Assigned originally to Bristol Siddeley Engines Limited (UK). Bristol Siddeley was absorbed into Rolls-Royce in 1966, so any hypothetical enforcement would have been by Rolls-Royce — and no such suit appears of record.
• Database coverage: The requested sources (Unified Patents Portal caselist, Docket Navigator, PACER, CAFC dockets) have substantive coverage concentrated in the ~1990s–2020s for digital records, with sparse pre-1990 coverage. A patent that expired in 1986 would rarely if ever surface there.

Caveats on my confidence

I want to be transparent about scope limitations rather than overstate certainty:

• I was able to run only a limited number of searches before hitting tool limits, so I could not exhaustively query every source the request named (e.g., a full docket-level sweep of the Unified Patents Portal caselist and PACER). No-site I reached returned a positive hit.
• Accordingly, my conclusion is: no known litigation was found in the sources searched, stated with high confidence as to the public digital record, but not characterized as a certified negative. Pre-1986 litigation records are incompletely digitized, so an old, unindexed 1970s–80s suit cannot be conclusively ruled out from web-searchable sources alone. A definitive negative would require a manual PACER/paper-records search for the 1969–1986 window.

If you'd like, I can attempt additional targeted queries (e.g., specific district-court dockets for Rolls-Royce/Bristol Siddeley as defendant, or a CAFC opinion-name search), but based on what is available, there is no litigation to report for US 3,423,048.

I'll verify the canonical "no PTAB activity" signal with targeted web searches before writing up.

Both queries returned empty result sets. Let me try a few differently-framed queries to avoid over-relying on a single search formulation.

The searches surfaced only unrelated PTAB matters (GE v. UTC '605 patent; Unified Patents caselists). Let me run two more targeted checks — one on PTAB E2E/CourtListener, one on the patent number with "IPR" formatting variants.

PTAB practice note — where the record actually stands

Canonical data check: The structured "PTAB proceedings on file" block for this patent returns an empty set — the USPTO Open Data Portal shows no AIA trial proceedings for US 3,423,048. My web verification (five queries: patent number + IPR/PTAB, patent number + PGR, the patent title plus "IPR challenge petition," and a Unified Patents caselist query) returned no proceeding naming this patent. Every hit was noise: GE v. UTC on the '605 patent (IPRs 2016-00531 / -00533), unrelated Unified Patents caselists, and the recurring ACM DOI 10.1145/3423048.

Proceedings overview

Total AIA trial proceedings on file: 0. Breakdown by status: 0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denials. I cannot give a defendant the usual "the patent is hardened" or "claim 1 is dead" framing, because neither has happened — and more importantly, it doesn't matter: US 3,423,048 expired 1986-01-21, so there is no live claim capable of being asserted or of being IPR'd in the first place. The absence of PTAB activity is not a defensive victory; it is a consequence of the patent being four decades past its enforceable term.

Correction to a possible cross-reference confusion. One Board appeal surfaced in my searches — Appeal 2018-007729, Application 14/789,036 — discussing a "Shohet" patent describing a "convertible composite engine" with three coaxial turbines (turbine 38 driving compressor 34, turbine 44 driving fan 16, turbine 46 as a shaft-horsepower free turbine driving a helicopter rotor). That is not a PTAB proceeding on US 3,423,048. Shohet is United Aircraft's US 3,678,690 lineage — a later patent that cites US 3,423,048 (it appears in the "Cited By" list on the Google Patents record). It is prosecution/examiner citation material in an unrelated application, and it must not be attributed to this patent. It is, however, useful prior-art archaeology: it confirms this patent sits in the citation chain of the convertible/compound engine art.

No proceeding-by-proceeding sections can be populated

The requested per-proceeding template (### {PROCEEDING_NUMBER} — {Petitioner} v. {Patent Owner}, with type, filing date, panel, grounds, institution decision, FWD, settlement, appeal) has no entries. I am not going to invent proceeding numbers, panels, or dispositions to fill it.

Two category notes so the empty set is properly bounded:

• AIA trials (IPR/PGR/CBM): none. Structurally expected — the AIA trial regime only accepts petitions filed on or after 2012-09-16, and by then this patent had been expired for ~26 years. PGR and CBM are unavailable on their face (PGR requires a post-2012 patent; CBM requires a covered business-method claim — not a turbine power plant).
• Non-AIA administrative validity challenges (ex parte reexamination, inter partes reexamination, interference): not found, but I cannot certify a negative. These are not AIA trials, are not in the PTAB proceedings datastream, and pre-1990 records are incompletely digitized. I flag this as evidence not located rather than a verified absence. Given the patent's 1966 filing, an interference is essentially impossible (interferences apply to copending applications/patents in the same family window), and no reexamination request of record has surfaced.

Strategic summary

Claim status: all four claims UNTESTED — and all four expired. Claims 1 and 2 (helicopter/"compound" plant; zero-fan-speed capability), claim 3 (air-cushion vehicle), and claim 4 (aircraft with lift fan) have never been through an AIA trial, never been cancelled, never been confirmed. No Final Written Decision has ever quoted a claim number from this patent. There is no "surviving claim" list to hand a defendant, because there is no enforceable claim at all: the front-page legal status is Expired – Lifetime, anticipated expiration 1986-01-21 (17 years from the 1969-01-21 grant, pre-URAA). Any present-day demand letter citing claims 1–4 of this patent is facially meritless on term grounds alone, before you ever reach validity.

Estoppel landscape: none, in either direction. Because no FWD under 35 U.S.C. § 318(a) has issued and no petitioner has been through a trial on this patent, § 315(e)(2) estoppel does not attach to anyone. There are no barred parties, no privity chains, and no "raised or reasonably could have raised" grounds foreclosed. Practically this is academic — a defendant has no need for an IPR-based invalidity escape hatch when the patent has been public-domain prior art since 1986. The far more useful posture for a defendant or licensee is not PTAB estoppel but § 102 prior-art status: the printed specification, the two examiner-cited references (US 2,937,495, Power Jets Res & Dev, 1960-05-24; US 3,038,307, Saurer AG, 1962-06-12), and the 15–17 "cited by" documents are all free to use defensively.

Pattern signals: uninformative — and that is the signal. No petitioner has filed once, let alone repeatedly. No patent owner has appealed an FWD, because there is no FWD. There is no defensive aggregator (Unified Patents, RPX, Askeladden) in the chain; the Unified caselist query returned only unrelated matters. Normally I would read total PTAB silence as under-assertion. Here it is over-determined: the patent expired in 1986, so there was never an economic window in which a competitor needed to invalidate it at the Board.

Recommended next steps

1. If you hold a demand letter citing this patent: do not build an IPR strategy. There is nothing to IPR. Ascertain whether the letter is actually directed at this patent or at a later patent in the family/lineage — a common point of confusion given that US 3,678,690 / 3,678,691 (United Aircraft) and US 3,493,696 (Rolls Royce) show up in the Cited By list. The mismatch is where the real error usually lies.
2. Anchor any response on expiration, not invalidity. Cite the Google Patents legal-status field for US3423048A ("Expired – Lifetime"; anticipated expiration 1986-01-21) — https://patents.google.com/patent/US3423048A/en — and the grant date 1969-01-21. Note that this status field is the database's stated assumption, not an adjudicated conclusion; if you need a certified term determination, order the USPTO PatentCenter file wrapper and any maintenance-fee/expiration record.
3. Do not represent to a court or opposing counsel that PTAB has invalidated anything here. My searches hit a maximum-steps limit on the final CAFC/CourtListener query, and my conclusion rests on the canonical empty ODP block plus four verified searches. Stated precisely: no AIA trial proceeding on US 3,423,048 was found in the USPTO Open Data Portal or in web searchable sources, with the caveat that pre-1986 administrative and litigation records are incompletely digitized. That is a well-supported negative for the AIA-trial question, not a certified negative for all administrative history.
4. If you actually need a Federal Circuit angle, look one hop downstream: the appeals and IPRs involving patents that cite this one (e.g., the GE/UTC '605-patent line, and Board Appeal 2018-007729 discussing Shohet's three-turbine convertible engine) are where modern PTAB practice in this technology class lives — not on the '048 patent itself.

Sources: Google Patents US3423048A (claims, citations, legal status) — https://patents.google.com/patent/US3423048A/en; PDF facsimile — https://patentimages.storage.googleapis.com/7f/e7/29/ba7e3f653470aa/US3423048.pdf; USPTO PTAB appeal document discussing the Shohet reference (Appeal 2018-007729, App. 14/789,036) — https://e-foia.uspto.gov/Foia/RetrievePdf?system=BPAI&flNm=fd2018007729-02-12-2020-0. No PTAB E2E / P-TACTS / CourtListener record for proceeding numbers naming US 3,423,048 exists to link, because no such proceeding was found.

I'll research the assignment/ownership chain for this patent before writing up. Let me run targeted searches.

Let me probe for actual assignment-center records and inventor/assignee history.

⚠️ Method note up front (read before the sections)

I attempted to reach USPTO Assignment Center records for US 3,423,048 via the Assignment Search portal and general indexing, and I could not retrieve any reel/frame-level assignment record. I therefore have no reel numbers, no frame numbers, no correspondent-of-record names, and no execution/recording dates from the Assignment Center to report. Per the task instructions ("Don't fabricate assignments"), I am reporting that gap explicitly rather than filling it with plausible-looking but invented reel/frame data.

What follows is what I can ground: the face-of-patent assignment language, the corporate-succession history of the assignee, and an assessment of the NPE signal checklist against that evidence. Where I could not verify something, I say so.

Also flagging a contradiction with the earlier-generated summary (as instructed): the prior section noted Google Patents lists Bristol Siddeley Engines Ltd as both original and current assignee, and correctly hedged it. My research shows that hedge was warranted — BSEL was absorbed into Rolls-Royce in October 1966, six weeks before this application was filed. So the "current assignee" field on Google Patents is almost certainly a stale bibliographic field carried over from the pre-issue assignment record, not a statement of present-day ownership. I treat it as unreliable.

Inventors

Pattern observations:

• No unusual inventor-departure pattern is inferable, and I would caution against inferring one. The standard "all inventors left within 12 months → portfolio fire-sale" tell cannot be tested here: I found no post-1966 employment records for either man, and the assignee's ownership changed via a share purchase, not an asset sale (see below), so any departure would have no bearing on title.
• The employer at filing is a legal wrinkle, not a red flag. The patent describes the inventors as "assignors to Bristol Siddeley Engines Limited... a company of Great Britain." BSEL's own corporate parent had already changed: Rolls-Royce Limited's acquisition of Bristol Siddeley is reported as completed 7 October 1966, roughly six weeks before the 18 November 1966 US filing date. The NYT reported the agreed merger terms on 27 August 1966. So at filing the inventors were employees of a just-acquired, wholly-owned Rolls-Royce subsidiary.
• Both named inventors are individuals with no other US patent record I could surface in the searches run. I could not confirm either inventor's subsequent career or whether they remained with Rolls-Royce. That is an explicit gap, not a negative finding.

Original assignee

Bristol Siddeley Engines Limited (BSEL) — London, England, a company of Great Britain.

Critical ownership nuance: the 1966 Rolls-Royce/BSEL transaction was a share purchase. A share purchase transfers title to the company, not title to the company's individual patents — the patents stay inside the acquired subsidiary. This is why the absence of a "merger" or "assignment" recording for this patent in US records is entirely expected and is not evidence of a missing link.

Separately, beware a related but inapplicable precedent: in June 1972, Rolls-Royce (1972) Ltd sold "all patents, specifications, drawings, catalogues and the name" of Armstrong Siddeley Motors Ltd to the Armstrong Siddeley Owners Club Ltd. That dealt with the Armstrong Siddeley car business's IP. Do not read that as transferring this patent. US 3,423,048 issued to and was prosecuted under Bristol Siddeley Engines Limited as assignee, and I found nothing tying it to the 1972 ASOC transaction.

Assignment timeline

USPTO Assignment Center returned no records I could retrieve for this patent. No reel/frame entries, no conveyance types, no correspondent of record.

The only assignment-type fact I can state is from the face of the printed patent, which recites: "George Frederick Clarke... and Derek Aubrey Roberts... assignors to Bristol Siddeley Engines Limited, London, England, a company of Great Britain." That is the standard formulation for a pre-issue assignment executed by the inventors in favour of the corporate employer, recorded at or before issue. I cannot supply the reel/frame, execution date, or recording date for it.

Finding: the chain appears to consist of the original inventor→corporate-employer assignment, and nothing else recorded post-issuance. If the Assignment Center shows any later entry (e.g., a change-of-name for BSEL, or an internal Rolls-Royce reorganisation), I did not capture it and it should be independently verified at https://assignment.uspto.gov/patent/index.html (search by patent number 3423048) or https://assignmentcenter.uspto.gov/.

Because I could not obtain a single verified reel/frame, I am not going to reproduce the multi-entry timeline format with invented fields. The honest rendering is a corporate-event timeline, not a recorded-assignment timeline.

Timeline diagram

timeline
    title Ownership of US 3423048
    1959 : Bristol Siddeley formed by merger
    1961 : BSEL buys de Havilland Engine and Blackburn Engines
    1966 : Rolls-Royce agrees takeover terms in August
         : Rolls-Royce completes BSEL purchase in October
         : Application filed in November by BSEL
    1969 : Patent issues as US 3423048
    1971 : Rolls-Royce Ltd enters receivership
    1986 : Patent term expires
    2026 : No post-issuance assignments retrieved

NPE / troll-pattern signals

Every signal below is scored against verified evidence only. Because I could not retrieve a single Assignment Center reel/frame, I have no correspondent names to test signals 3 and 4 against — which materially limits the analysis and is stated plainly.

Verdict

Insufficient data — no post-issuance assignment records were retrieved, so the chain consists of the original pre-issue inventor→employer assignment plus corporate succession that never had to be recorded at USPTO.

The justification: the patent issued 21 January 1969 to Bristol Siddeley Engines Limited, whose ownership passed to Rolls-Royce Limited on 7 October 1966 via a share purchase — a transaction that transfers the company but not the company's individual patents, and therefore generates no Assignment Center record. With no later assignee, no correspondent of record, and no litigation found, there is no basis for any NPE characterisation. The only affirmative ownership finding I can defend is that US 3,423,048 has been public domain since its anticipated 1986-01-21 expiration, with its residual corporate provenance inside what is today Rolls-Royce plc.

Verify directly at: https://assignment.uspto.gov/patent/index.html (search patent number 3423048) and https://assignmentcenter.uspto.gov/. A definitive reel/frame-level negative would require that portal (or a manual pre-1986 paper-records pull), which I could not complete within this session.

Sources consulted: Google Patents US3423048A record and PDF facsimile (face-of-patent assignment recital, claims, legal-status data); TheFreeDictionary/Bristol Siddeley corporate history; New York Times, "Merger Detailed by Rolls-Royce," 27 Aug 1966; Rolls-Royce corporate-history accounts confirming completion of the BSEL acquisition on 7 October 1966; GoodIP assignee page for Bristol Siddeley Engines Ltd (confirming US3423048A as a BSEL filing). No USPTO Assignment Center reel/frame data was successfully retrieved.

USPTO database search for the exact number 3423048

Result: the search resolved cleanly to a single record — no near-miss or similar-number substitutions are reported below.

This is the same document analyzed in the sections above, so I do not repeat its bibliographic or claim content. The examiner-cited prior art of record consists of two U.S. patents only, listed on the front page as:

• "5/1960 Perry 60‑226" → US 2,937,495
• "6/1962 Oprecht 60/39.16" → US 3,038,307

Both are the subjects of the reference-by-reference §102 analysis below. (Note: I treat only these two as patent citations to the patent. The 15–17 "Cited By" documents are later publications and therefore are not §102 prior art against US 3,423,048; they are lineage/obviousness context only. Separately, the Google Patents page lists several Procter & Gamble absorbent-article patents under "Cited By" — these are plainly a database artifact and must not be treated as technical prior art.)

Statutory framework

US 3,423,048 was filed 1966‑11‑18 and granted 1969‑01‑21, so it is governed by the pre‑AIA §102. For a reference to anticipate a claim under §102, it must disclose every limitation of that claim, arranged as in the claim (the "single-reference, all-elements" rule). Both cited references issued more than one year before the 1966 filing date (1960 and 1962 respectively), so each qualifies as a §102(b) statutory bar, and each also qualifies under §102(a) as "patented … before the invention thereof." Anticipation versus obviousness is therefore a live distinction I keep explicit throughout.

Reference 1 — US 2,937,495 A

Full citation: US 2,937,495 A, Gas turbine plant, Sydney William Henry Perry (Cove, Farnborough, England), assignor to Power Jets (Research and Development) Limited, London, England. 7 claims; U.S. Cl. 60‑356.
Filing date: February 25, 1957 (Ser. No. 642,183).
Foreign priority: Great Britain, February 27, 1956.
Publication/grant date: May 24, 1960. Anticipated expiration May 24, 1977 ("Expired – Lifetime," per the database).
Source: https://patents.google.com/patent/[US2937495A](/patent/US2937495A)/en

Brief description. A ducted-fan gas-turbine jet-propulsion power plant. A compressor and a coaxial, axially-spaced turbine assembly are provided, in which:

• a first turbine rotor is drivingly connected to the compressor rotor through a shaft that passes through the combustion system;
• two further turbine rotors are mounted one upstream and one downstream of the first rotor and are rotatable mechanically independently of it;
• each of those two further rotors carries a row of ducted-fan rotor blades mounted on the tips of its turbine blades (tip-mounted fan rings);
• the upstream/downstream rotors may be arranged to contra-rotate relative to the first rotor; in one form they are drivingly interconnected, in another they are mechanically independent;
• notably, the turbine blade rows are in direct guide-blade relationship, and "no stationary turbine nozzle vanes or intermediate stator blades are provided" — the upstream blades act as inlet guide vanes for the intermediate rotor, and the intermediate blades for the downstream rotor. The turbine exhausts as a propulsive jet through a second annular exhaust duct.

Relation to the claims of US 3,423,048 — potential §102(a)/(b) effect.

Anticipation vs. obviousness. US 2,937,495 is best characterized as highly material art for §103, and as anticipatory of the bare sub-combination (compressor + first turbine + two further series turbine rotors carrying fans) if a claim were drawn only to that sub-combination. Against the issued claims, it is a §102–insufficient but §103-relevant reference, because the differential-gearing and inter-rotor flow-control elements — the heart of the invention per the specification — are simply not there (indeed the reference's explicit teaching away from stationary nozzle vanes between rotor rows cuts against a §103 combination built on it).

Reference 2 — US 3,038,307 A

Full citation: US 3,038,307 A, Counter-rotating turbine wheels and auxiliary bucket wheel control device, inventor Oprecht; assignee Saurer AG (Adolph Saurer A.G.), Arbon, Switzerland. U.S. Cl. 60/39.16 (front-page citation form "6/1962 Oprecht 60/39.16").
Filing date: February 25, 1958.
Publication/grant date: June 12, 1962.
Source: https://patents.google.com/patent/US3038307 (record and full text; the corresponding front-page entry appears as "Counter-rotating turbine wheels and auxiliary bucket wheel control device").

Brief description. A gas-turbine power plant for vehicles, of the kind having two turbines — one turbine driving the compressor, while the other, mechanically separated from the first, "handles the remaining drop and yields the effective power." The disclosure contemplates giving at least part of the power turbine oppositely oriented (counter-rotating) bucket rings, and adds an "addition gear … in the form of a single-step planetary gear, the effective power being taken off the satellite [planet] carrier." In the illustrated embodiment (Figs. 1–2):

• the power-turbine wheels 1 and 2 are respectively connected by shafts 10 and 11 to the sun wheel 7 and to the outer gear rim 5 of a planetary gear;
• planet pinions 6 mesh between rim 5 and sun 7, their shafts being joined by the satellite (planet) carrier 8, which carries the driven output shaft 9;
• brakes B and B′ on the two shafts are selectively applied for forward/reverse drive and for vehicle braking;
• Figs. 3–4 add a stationary bucket ring 16 interposed between turbine wheels 1 and 2 (or in front of them), fitted with vanes 17 "susceptible of rotary displacement during operation." The reference states that this rotary displacement of the guide blades 17 "renders possible an additional variation, i.e., an increase or a reduction, in the rate of power input and the rate of flow in the bucket rings 3 and 4," and that the auxiliary equipment "renders possible the variation, over a wide range, of the admission" to the bucket rings.

Relation to the claims of US 3,423,048 — potential §102(a)/(b) effect. This is the closer and more dangerous reference, and it maps onto the core of the invention almost element-for-element:

Claim-by-claim:

Anticipation vs. obviousness. US 3,038,307 is the reference the examiner almost certainly cited for the combination of a series second/third turbine pair with a planetary differential and variable inter-turbine guide vanes. Its antipication reach is the sub-combination, not the four issued claims (each of which is bound to an aircraft/vehicle environment and an "additional power transmitting means" to a distinct fan). Its principal legal significance to US 3,423,048 is therefore as §102(b)/§103 prior art for the gear-and-nozzle core, and as the disclosure that most constrains any broad reading of claim 1's structural elements (a) through (e).

Consolidated mapping: citations → claims of US 3,423,048

Net answer to "which claim(s) it potentially anticipates":

• US 2,937,495 — does not anticipate any of claims 1–4 as issued; potential §102 relevance is limited to the "plural series free-turbine rotors, each driving a fan" sub-combination, which is not itself a claim.
• US 3,038,307 — does not anticipate any of claims 1–4 as issued; it comes closest to claim 1 (and to the structural cores of claims 3 and 4), disclosing the series-rotor + differential + inter-rotor nozzle-control combination, but is missing the recited environment and the "additional power transmitting means," so its true role is §103 obviousness against the core, plus §102 against any broader reading of the structural limitations.

Caveats and flags

1. Do not conflate anticipation with obviousness. My statement that neither reference anticipates the issued claims is a limitation-by-limitation conclusion under the all-elements rule, not a claim that these references are weak art. US 3,038,307 in particular is strong §103 material for the differential/nozzle core, and a combination of US 3,038,307 with the fan-driving teaching of US 2,937,495 could bear on the "additional power transmitting means + fan" aspect of claim 1 — though the specification's emphasis on nozzle control overriding the reference's brake-based approach is a genuine distinction (compare the "brakes" criticism recited against the later Gist patent in United Aircraft's US 3,678,690, which cites this family's lineage).
2. "Cited By" is not prior art. US 3,493,696 (Rolls Royce), US 3,498,057 (Turbokonsult), US 3,678,690/3,678,691 (United Aircraft) and the rest post-date the 1966 filing and therefore cannot anticipate under §102; I list them nowhere as §102 art. The Procter & Gamble "Cited By" entries on the Google Patents page are a data artifact.
3. Full-text confirmation limited. I verified the claims and description of US 2,937,495 and the key passages of US 3,038,307 from the patent records quoted above; I hit tool limits before pulling the complete claim set of US 3,038,307, so my description of it rests on its quoted abstract/description passages (planetary gearing, counter-rotating wheels, rotary-displaceable guide vanes 16/17, brakes B/B′) rather than a claim-by-claim reading of that reference. That does not change the anticipation conclusion, which turns on the reference's disclosure, not its own claim wording.
4. Legal status ("Expired – Lifetime," 1977/1986 expirations) is the database's stated assumption, not an adjudicated conclusion; US 3,423,048 has been expired since at least 1986 and is public-domain/prior art today.
5. This continues to disclose no litigation naming US 3,423,048, consistent with the earlier section (I flag it here only for continuity, not as new content).

I'll analyze obviousness using the prior art identified on the patent's page. Let me first verify the content of the two cited prior-art references.

Obviousness Analysis Under 35 U.S.C. § 103 — US Patent 3,423,048

Building on the claim summary and prior-art identification already established in the patent summary section, this analysis treats the two examiner-cited references — US 2,937,495 (Perry / Power Jets) and US 3,038,307 (Oprecht / Saurer) — as the operative prior-art set, since those are the references that appear on the patent's own Prior Art / "References Cited" section.

1. Legal framework and the person of ordinary skill

Standard. Under § 103, a claim is obvious if the differences between the claimed subject matter and the prior art are such that the subject matter as a whole would have been obvious at the time of invention to a person having ordinary skill in the art ("PHOSITA"). The Graham v. John Deere factors govern: (1) scope and content of the prior art; (2) differences between the prior art and the claims; (3) the PHOSITA's level of skill; and (4) secondary considerations. KSR Int'l v. Teleflex supplements this by permitting the motivation to combine to be supplied by "the nature of the problem to be solved," "common sense," and "market demand," and by recognizing that combining known elements with predictable results is obvious.

PHOSITA here. A person with a mechanical/aeronautical engineering degree and roughly 3–5 years of experience in gas-turbine engine design — specifically free-power-turbine ("power turbine") architectures, turbine nozzle/vane control, and epicyclic gear trains. This person would know the state of duplex/triplex turbine layouts, ducted-fan tip drives, and differential summing of two turbine outputs. The patent itself confirms this baseline: it repeatedly treats the "conventional combustion turbine assembly," the fixed nozzle ring "D," and automatic fuel control "known per se" as givens (see the specification's description of rotor 1 and the fuel-control paragraph).

2. What each reference discloses

US 2,937,495 A — Power Jets Res. & Dev. Ltd. ("Perry"), "Gas turbine plant" (1960)

This is a ducted-fan gas-turbine power plant with three turbine rotors in an axial series:

• "a compressor and a turbine assembly coaxial therewith and axially spaced therefrom, the turbine assembly including a first rotor in driving connection with the compressor rotor ... and two further rotors mounted one upstream and the other downstream of the first rotor and rotatable mechanically independently thereof."
• "each of said two further rotors carrying a row of ducted fan rotor blades mounted on the tips of the turbine rotor blades."
• The turbine "discharges a propulsive jet stream of exhaust gases through a second annular exhaust" (i.e., a rear jet nozzle), while the fan flow discharges through a separate ducted-fan flow path.
• Contra-rotation is contemplated; the blades of one rotor "act as inlet guide vanes for" the next.
• Notably, the two further rotors 5 and 7 are locked to one another by "circumferentially interengaging driving dogs 37 affording a driving connection whereby the two turbine rotors 5, 7 are constrained to rotate at the same speed."

What it teaches: the core spool (compressor + combustor + first turbine) followed by second and third free-turbine rotors in series, AND "additional power transmitting means" in the claim's sense — power taken directly off a free rotor (here via tip-mounted fan blades) to a fan rotor delivering air to at least one jet-propulsion nozzle. It does not teach a differential gearset, and it does not teach an adjustable inter-turbine nozzle (it expressly states "no stationary turbine nozzle vanes or intermediate stator blades are provided"). Its rotors are also locked together, so it teaches away from an independently variable split between them.

US 3,038,307 A — Saurer AG ("Oprecht"), "Counter-rotating turbine wheels and auxiliary bucket wheel control device" (1962)

This reference supplies the two elements missing from Power Jets:

• Differential/planetary gearing: "the addition gear preferably ... in the form of a single step planetary gear, the effective power being taken off the satellite carrier." Concretely: sun wheel 7 on shaft 10 (turbine wheel 1), outer gear rim 5 on shaft 11 (turbine wheel 2), planet pinions 6 on satellite carrier 8 driving the output shaft 9. Two turbine-driven inputs sum to one output member — the precise mechanics recited in the claim's "differential gearing comprising two input elements ... and an output element which constitutes a power output member."
• Adjustable inter-turbine flow control: "FIG. 3 shows the turbine wheels 1 and 2, and interposed therebetween the stationary bucket ring 16 provided with buckets or vanes 17 which are susceptible of rotary displacement during operation." And: "the rotary displacement of the guide blades 17 on the stationary ring 16 renders possible an additional variation, i.e., an increase or a reduction, in the rate of power input and the rate of flow in the bucket rings 3 and 4." That is the claim's "control means arranged to regulate the gas flow between the second and third turbine rotors and thereby vary the relationship between the power outputs of these two turbine rotors."
• Selective disablement of a turbine rotor: brakes B and B′ allow one turbine wheel to be held stationary while the other drives the output through the planetary — supporting claim 2's reduction of one rotor's speed "substantially to zero."

What it teaches: the differential-summing architecture plus a variable nozzle ring between two turbines to shift the power split — the exact "control" concept the specification calls the "adjustable nozzle ring."

3. Mapping to the independent claims

Claim 1 (helicopter compound power plant):

Every element of claim 1 appears across the two references, with the only gap being the express substitution of a helicopter rotor for Power Jets' propulsive-jet output — a use already conventional and repeatedly disclosed in the same art (the "Similar Documents" list includes US 3,483,696 / GB 1,120,658, "Power plant for a helicopter," Rolls-Royce).

Claims 3 (air-cushion vehicle) and 4 (aircraft with lift fan) recite the same core architecture with the loads reassigned to a cushion/lift fan plus a second propulsive fan. These are pure changes of intended use/environment; the specification itself frames them as applications (shaft 26 driving a cushion fan or lift fan; fan 10 feeding propulsion nozzles; "unnecessary ... to be maintained at constant speed"). Under KSR, adapting a known power-plant architecture to a new but analogous vehicle application is obvious where the result is predictable.

4. Motivation to combine (the KSR rationales)

1. Same field / analogous art. Both references are gas-turbine power plants, both classify in the same area (the patent's own CPC is F02C 7/36 — power transmission arrangements between turbine shafts / to the power user, i.e., exactly the subject matter of both references).
2. The references address the same problem from complementary sides. Power Jets solves "how do I drive a propulsive fan from a free turbine"; Saurer solves "how do I combine two turbine outputs into one controllable power output and vary their split." A compound-helicopter designer needs both simultaneously: a main-rotor output and a propulsive fan. Combining them is the logical assembly of two known solutions to a two-part requirement.
3. Predictable, known mechanical results. Planetary differential summation of two inputs is a textbook function; a variable nozzle ring between turbines to shift flow/power is expressly described in Saurer. Combining them yields no unexpected result — each component performs its own known function.
4. "Obvious to try." With Saurer teaching an adjustable ring "interposed between" two turbine wheels purely to vary power split, and Power Jets teaching direct (tip) fan drive off a free rotor, arranging Power Jets' two series free rotors to feed a Saurer-type differential — and sketching a fan off one of them — is a finite, predictable design variation, not an inventive leap.
5. Claim 2 is a mere statement of an enabled capability. Saurer already teaches (a) variable nozzle control affecting "rate of power input ... in the bucket rings," and (b) brakes that bring a turbine wheel to a standstill. Slowing the fan-driving turbine "substantially to zero" is therefore an expected operational mode of the combined system, not a new invention.

5. The patentee's best non-obviousness arguments (and why they may fail)

To be balanced, the strongest arguments against obviousness are:

• Neither reference discloses the simultaneity of both loads. Power Jets takes power only to fans (and locks rotors 5/7 together, foreclosing a variable split); Saurer takes power only to a single vehicle output shaft (with no fan, no duct, no aircraft, no tip-mounted blades). The claims require one of the second/third rotors to drive the differential output and also have power taken directly off a rotor to a fan. Neither reference suggests this "split-use" of a single free-turbine stage.
• Power Jets arguably teaches away by locking its two free rotors to identical speed via driving dogs 37 — the opposite of the independently variable relationship the claims require.
• Saurer's architecture may not be "second and third rotors in series after the first." Its text describes a two-turbine layout ("one ... driving the compressor while the other ... handles the remaining drop"); whether wheels 1 and 2 are both downstream of a compressor-driving rotor in series is not unambiguous from the snippet reviewed. A claim limitation ("second and third turbine rotors acted upon in series by the hot gases after they have acted upon the first turbine rotor") may therefore lack clean anticipation from Saurer alone.
• No explicit motivation in either reference to produce a compound helicopter combining a main rotor and a propulsive fan; that specific objective is supplied by the patent.

Rebuttal: Under KSR, the motivation need not be in the references themselves; it may come from the problem to be solved. The "compound helicopter" objective (a known aircraft category) directly supplies the reason to couple Power Jets' fan-drive to a Saurer-style controllable output. And the "series" limitation is squarely met by Power Jets' three-rotor series arrangement, so the combination of the two references supplies all elements — Power Jets for the three-rotor series + direct fan drive, Saurer for the differential and the inter-turbine variable nozzle.

6. Conclusion

Claim 1 would likely be held obvious over US 2,937,495 in view of US 3,038,307: Power Jets supplies a gas generator plus second/third free-turbine rotors in series with direct tip-driven ducted fans discharging to a propulsion nozzle; Saurer supplies the two-input planetary differential summing the two free turbines into one output member and the adjustable inter-turbine bucket/vane ring that varies the power split between them; and driving a helicopter rotor from the free-power output is conventional. The combination is a predictable aggregation of known elements in the same field (F02C 7/36), satisfying § 103 under KSR.

Claim 2 is obvious: Saurer's variable ring varies flow/power input to the bucket rings, and Saurer's brakes already stop a turbine wheel — so slowing the fan-driving rotor substantially to zero is an expected capability.

Claims 3 and 4 are obvious as well: they recite the identical core architecture (all elements already supplied by the two-reference combination) applied to air-cushion and lift-fan aircraft, with the loads reassigned — a predictable change of intended use, which the specification itself presents as mere applications.

Strongest residual non-obviousness hook: the specific simultaneous split — differential output to a main/lift rotor while a fan is driven directly off one of the two contributing free turbines. That dual-load architecture is not expressly shown in either reference, and a patentee would press that point. It is the only leverage substantial enough to argue, and it turns entirely on whether the fact-finder accepts that combining the two references would naturally yield that arrangement.

7. Confidence and caveats

• High confidence: both cited references exist with the content above, and the examiner relied on exactly these two (front page: "5/1960 Perry 60-226" = US 2,937,495; "6/1962 Oprecht 60-39.16" = US 3,038,307). The claim-element mapping and the differential + adjustable-ring teachings of Saurer are well grounded in the reference text.
• Flagged uncertainty — Saurer's turbine count: I reviewed Google Patents excerpts, not the full Saurer specification/figures. The exact topology (whether the two wheels 1/2 are both downstream power turbines in series, versus one driving the compressor) is ambiguous in the snippet, so my reliance on Saurer for the "second and third rotors in series" limitation is partial — that limitation is more cleanly supplied by Power Jets. This does not change the overall combination result (the two references are combined, not relied on individually), but it matters if anyone attempts a single-reference § 102/§ 103 attack using Saurer alone.
• Supplementary art not relied upon: the "Cited By" and "Similar Documents" lists include US 3,498,057 (Turbokonsult AB), whose stated priority date (1966-10-13) predates US 3,423,048's filing (1966-11-18) and would therefore be a candidate pre-AIA § 102(e) reference to the general architecture, plus US 2,583,872 (planetary gearing between compressor, turbine, and power consumer), US 2,702,985 (power take-off from rotatable guide blading), and US 3,483,696 / GB 1,120,658 (helicopter power plant). I note these qualitatively as reinforcing the obviousness picture but have not verified their full disclosures, so I do not rest the analysis on them.
• This is a technical validity/obviousness assessment, not a legal opinion; claim construction and secondary-considerations evidence could alter the outcome in litigation.

Sources: https://patents.google.com/patent/[US3423048A](/patent/US3423048A)/en (claims, citations, classification); https://patents.google.com/patent/[US2937495A](/patent/US2937495A)/en (Power Jets ducted-fan plant); https://patents.google.com/patent/US3038307 (Saurer counter-rotating turbine wheels / adjustable bucket ring). No CAFC 2026 or other litigation activity was located for this patent (as set out in the prior litigation section), consistent with its 1986 expiration.