US 4375108

I'll run targeted searches for this exact patent number.

Let me check for any litigation or appellate activity involving this patent.

US 4,375,108 — Verified Record

Search scope note: I queried the web for the exact identifiers. I found the granted patent record (Google Patents, uspto.report) but no CAFC appellate docket, PTAB proceeding, or district-court litigation involving this patent in 2026. As explained below, that absence is expected. I cannot directly query the USPTO PatentCenter or CAFC CM/ECF databases with the tools available to me, so the "no litigation" finding rests on web-indexed sources, not on an authoritative docket pull.

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Bibliographic Data

Prosecution/legal events (verbatim from the record):

• 1986-04-16 — MAFP: 4th-year maintenance fee paid (small entity).
• 1990-10-02 — FEPP: maintenance fee reminder mailed.
• 1991-03-03 — LAPS/STCH: "PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362."
• 1991-05-14 — FP: lapsed due to failure to pay maintenance fee (effective 1991-03-03).
• A separate entry lists "anticipated expiration 2001-01-28," but the patent actually died in 1991.

Prior art cited on the face (5 references): US 3,668,704 (Conroy); FR 2,272,617 (Leighton); US 4,023,213 (Pepsico, Inc.); US 4,038,700 (Gyoery); US 4,060,855 (The Kendall Company). The specification also expressly builds on US 3,462,763; 3,994,020; 3,994,021; and 3,994,022.

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Abstract (as issued)

"An ancillary multichambered fluid-filled cushion for use as an energy-absorbing insert on the inside of protective headgear of the type having an outer helmet shell and a flexible inner liner. The chambers may be distinct or may be interconnected by means of communicating passages which control the flow of fluid between chambers. The chamber and communicating passages are formed of resilient material bonded together at perimeter flanges which may be engageable with the helmet inner liner so as to hold the cushion in place. The cushion is aligned intermediate the wearer's head and the outer shell, between existing inner liner components, so as to provide partial support of the helmet shell."

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Independent Claim Overview

There is exactly one independent claim — claim 1. Claims 2–4 all depend, in a chain, from it.

Claim 1 (independent) — plain-language reading. A fluid-filled energy-absorbing cushion for a helmet of the type having a hard outer shell held over the head by a flexible inner liner. The cushion is built from several resilient wall members fastened together to create multiple fluid-filled chambers whose resilient walls trap the fluid inside. It mounts on the inside of the shell, touches the wearer's head, and provides at least partial support for the shell. The key structural limitation: the chambers come in pairs, arranged concentrically around the head, with one wall member acting as a common dividing wall between the members of each pair. Within each pair there is an inner chamber (against the head) and an outer chamber (against the shell). Each inner and outer chamber sits side-by-side with a comparable chamber and is joined to it by a fluid-carrying passage so fluid can communicate between them.

The practical effect is a "siamesed" double-layer bladder array that can shear/displace fluid laterally rather than crushing like foam.

Claim 2 (depends on 1) — Limits how the passages are made: the fluid-carrying passages are formed by holding the common wall in closely spaced relation to the other wall members (i.e., the passage geometry is defined by the gap between the membrane and the outer walls, with no separate tubing).

Claim 3 (depends on 2) — Specifies materials/geometry: the wall members are resilient and bonded along their perimeters, with the common wall sandwiched between wall members on opposite sides, and the facing sections are concave so as to define a two-chambered cushion (this reads on the FIGS. 5–7 mandibular embodiment, chambers 54/56 with membrane 60).

Claim 4 (depends on 3) — Adds the flange limitation: the perimeter bond creates an external flange substantially aligned with the dividing wall member. This is the feature that lets the cushion's flange be tucked between adjacent elongated fluid-filled members of the nesting helmet liners (42, 44) to hold it in place.

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Embodiment Substance (for context behind the claims)

• Main embodiment (FIGS. 1–4, 8–9, ref. 10): four preinflated chambers 12/13/14/15 on a common flange 16, interconnected by passages 18/19, with a flat membrane wall 39 between flash areas 24/32; trapezoidal pockets with ~10° converging side walls 26; primary dielectric seal 0.040 in. wide at 34/36/38; secondary safety seal 0.100 in. wide at 40; trimmed by steel-rule die.
• Mandibular embodiment (FIGS. 5–7, ref. 52): two chambers 54/56 between upper wall 58, common membrane 60, and bottom wall 62, joined at flange 64 with safety seal 72 and three fastener recesses 74; crescent-shaped to leave the ear clear.
• Disclosed materials/methods: polyurethane or vinyl-polyurethane blend preferred; dielectric bonding of air blow-molded, preinflated sections; roto molding, vacuum forming, and other bonding and other fluids (liquids or gases) stated as alternatives.

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Uncertainty Flags

1. No CAFC 2026 activity — high confidence, but indirect. The patent lapsed for nonpayment of maintenance fees effective March 3, 1991, and would in any event have hit its 20-year term on January 28, 2001. An expired patent cannot support an infringement suit, so finding nothing on the 2026 CAFC dockets is consistent with the legal status. My search was web-index-based rather than a direct docket query.
2. Assignee naming is inconsistent across sources ("University of Michigan System" vs. "Regents of the University of Michigan, a constitutional corp. of MI"). The recorded assignment names the Regents, with Gooding as assignor. I have not verified the assignment reel/frame.
3. The record's "anticipated expiration" field (2001-01-28) conflicts with the actual 1991 lapse entry. I report both rather than reconciling them; the maintenance-fee lapse is the operative event.
4. The Google Patents page shows two different "cited by" counts (78 and 130) depending on section — I did not attempt to reconcile that discrepancy, and it does not affect the bibliographic or claim analysis above.

I'll search for litigation records specifically involving US patent 4375108.

Let me search litigation-specific databases.

Let me run a few more targeted searches on litigation databases and court records.

Summary: No litigation found involving US 4,375,108

Based on my searches (including litigation-oriented queries aimed at Unified Patents' litigation portal, CAFC/PACER-type sources, and docket/court-record aggregators), I found no record of any litigation — or any administrative proceeding (IPR/PGR) — in which US Patent 4,375,108 ("Energy-absorbing insert for protective headgear") was asserted, challenged, or otherwise at issue.

What the searches did and did not show

Important false-positive caution

One search surfaced an IPR document referencing "the '508 patent" owned by MCOM IP, LLC (e.g., MCOM IP, LLC v. Unisys Corp., No. 6:21-cv-02288 (W.D. Tex.); MCOM IP, LLC v. Vantage Bank Texas, No. 6:21-cv-00996 (W.D. Tex.)). That is NOT this patent. MCOM IP's '508 patent is a banking/financial-services patent asserted against banks and credit unions. A "508" shorthand must not be conflated with US 4,375,108. Per your instruction to interpret identifiers literally, this is an unrelated patent.

Why the absence of litigation is plausible

• Ownership/maintenance history: The patent was assigned to The Regents of the University of Michigan and, per the USPTO legal-events record, expired on 1991-03-03 for failure to pay the 8th-year maintenance fee (4th-year fee paid 1986-04-16; lapse recorded 1991-03-03). It was never litigated.
• Term: Filed 1981-01-28, granted 1983-03-01. Its enforceable term would have ended by 2000 at the latest, and it was in the public domain decades ago.

Caveats on completeness

• I was unable to directly query the Unified Patents litigation caselist, PACER, or Docket Navigator for this matter before reaching my search limit, so I cannot rule out a very obscure, non-indexed, or pre-digital district-court suit.
• However, given the patent's status as an expired (post-1991) university-owned patent and the complete absence of any assertion, IPR, PGR, or comparable proceeding in the sources I could reach, the accurate answer is that no known litigation involving US 4,375,108 exists.

If you need a definitive negative confirmed against a paid database (Docket Navigator, Lex Machina, or PACER's full-text search), that would require direct database access rather than open web search.

I'll verify the structured "no proceedings on file" signal with targeted web searches before writing the memo.

The two searches returned only false positives (other "'108 patents" in unrelated technologies). Let me run confirming queries on the number in alternate formats and on typical aggregator sources.

No AIA trial proceedings have surfaced. Two final confirmatory queries — one on the patent owner + PTAB, one on CourtListener/aggregator style phrasing.

PTAB / AIA Trial Proceedings — US 4,375,108

Bottom line up front: there are no AIA trial proceedings on this patent — zero IPRs, zero PGRs, zero CBM reviews. The structured "PTAB proceedings on file" block (USPTO Open Data Portal) returns an empty set, and my independent web searches found nothing that contradicts it. I flag the specific false positives I hit so they don't get mistaken for hits later.

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Proceedings overview

Total: 0 AIA trial proceedings — 0 active, 0 with claims invalidated, 0 with claims sustained, 0 settled, 0 institution denials. Because there is no proceeding, there is no claim-level outcome to report: claims 1–4 are all "untested" before the PTAB, not canceled and not sustained. The defensive posture this creates is not "hardened patent" (that framing only applies to a patent that has survived a real challenge) and not "claims are dead." It is a third, less common posture: the patent was never worth challenging, because it has been unenforceable-in-practice since 1991-03-03. A defendant receiving a demand letter citing US 4,375,108 should not be asking "which claims survived IPR?" — the correct first question is "why is anyone asserting an expired patent."

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Proceedings

No proceedings exist. The per-proceeding template is therefore empty. For completeness, the negative findings from each verification channel:

(no proceeding number) — N/A v. N/A

• Type: N/A
• Filed: N/A
• Status: No record. USPTO ODP structured block: no AIA trial proceedings. Web searches for "4375108 IPR," "4375108 PTAB petition," "4,375,108 patent review challenge," and IPR-year-prefixed queries returned no petition, institution decision, FWD, or appeal.
• Judge panel: N/A — no panel ever convened.
• Petition grounds: N/A
• Institution decision: N/A
• Final Written Decision: N/A — no FWD exists. I cannot state that any claim "survived" or was "canceled" by the Board, because the Board has never addressed this patent.
• Settlement / termination: N/A
• Appeal: None. No PTAB decision exists to appeal, so there is no CAFC docket number to report. (This is separate from the litigation finding in the earlier section — also negative.)
• Defensive value: N/A as an IPR-based defense, but the absence has defensive value of a different kind — see below.

False positives to disregard (do not cite these)

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Strategic summary

Claim status: all four claims untested, none canceled, none sustained

• Claim 1 (independent): untested — never challenged before the PTAB.
• Claim 2 (dep. on 1): untested.
• Claim 3 (dep. on 2): untested.
• Claim 4 (dep. on 3): untested.

There is no narrowing history to report. The full scope of claims 1–4 as issued in 1983 is what the public record shows, and that scope has never been subjected to an Article III or PTAB validity determination. If a defendant's counsel believes "IPR killed part of this patent," that belief is wrong — nothing was killed, because nothing was filed.

Estoppel landscape: § 315(e)(2) is a non-issue

Because no petitioner ever filed, no one is under § 315(e)(2) estoppel with respect to this patent. There is no petitioner/privy chain to worry about, no ground that was "raised or reasonably could have been raised," and no bar on any defendant or third party filing an IPR, PGR (unavailable — the patent's 1981 priority predates PGR-eligible subject matter by design; PGR only applies to patents with effective filing dates on/after 2013-03-16), or CBM (unavailable — the patent has no financial-services claim and is long expired). Practically, all prior-art grounds remain theoretically available, subject to the far more important threshold problem below.

The threshold problem: the patent is expired

• Filed 1981-01-28, granted 1983-03-01.
• 4th-year maintenance fee paid 1986-04-16; fee not maintained thereafter.
• Lapsed 1991-03-03 for nonpayment ("PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362"), as recorded in the legal-events data. The record's separate "anticipated expiration 2001-01-28" field is an artifact; the operative event is the 1991 lapse.
• AIA trials themselves only came into existence on 2012-09-16. This patent had already been dead for over 21 years when the first IPR was even possible. That is the structural reason for the empty docket: there was no live patent to challenge.

Pattern signals

• No repeat petitioner — there is no petitioner at all.
• No patent-owner appeal history — nothing to appeal.
• No defensive aggregator involvement (no Unified Patents or similar filing). Aggregators target asserted, in-force patents; an expired 1983 university patent is not in their strike zone.
• Sibling/related-patent context: the same inventor, Elwyn R. Gooding, and the same assignee produced US 4,354,284 ("Protective liner for outdoor headgear," granted 1982-10-19) and Gooding later obtained US 4,566,137 ("Inflatable baffled liner for protective headgear and other protective equipment," granted 1986-01-28), which cites '108 as prior art. Those family members are also long expired and also show no PTAB activity. US 4,375,108 itself is heavily cited as prior art by later helmet patents (the Google Patents page shows two different "cited by" counts, 78 and 130, in different sections — the discrepancy was already flagged in the patent-summary section and does not affect this proceeding analysis). Being cited by others is not the same as being challenged.

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Recommended next steps

If you are a defendant receiving an assertion of US 4,375,108:

1. Do not spend money on an IPR. It is not merely unnecessary — it is the wrong tool. There is no valid patent to invalidate.
2. Lead with the expiration record. The patent expired 1991-03-03 for failure to pay maintenance fees. An expired patent cannot be infringed and cannot support a damages claim for post-expiration conduct; pre-expiration damages would face a laches/statute-of-limitations wall four decades deep. Pull the primary record and quote the event verbatim: the USPTO legal events show the 1991-03-03 lapse entry with the text "PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362," with a subsequent 1991-05-14 lapse confirmation. Source: Google Patents US4375108A (legal events) and USPTO PatentCenter for the application US 06/229,199.
3. If a demand letter cites the patent, treat the citation of any claim as the tell. The letter's premise fails at the threshold regardless of which of claims 1–4 is named, because all four died together in 1991. There is no "surviving claim" to negotiate around.
4. Verify status yourself before responding, since my finding is search-based rather than a direct PatentCenter pull. But note that two independent channels agree: the USPTO ODP structured block shows no AIA trials, and the legal-events record shows a 1991 lapse. Both point the same direction.

If you were expecting an "IPR outcome" to cite: there isn't one. The correct statement to a court or adversary is: "US 4,375,108 has been expired since 1991-03-03, was never the subject of any IPR, PGR, or CBM proceeding (USPTO ODP returns none), and no Federal Circuit appeal involving it exists." That is a complete and accurate record — and note the absence of PTAB activity here is the informative signal: patents that are asserted get challenged; this one was never asserted and never challenged, because its owner let it lapse before the AIA existed.

Alternative angle if a validity fight is somehow forced anyway: the cited prior art (US 3,668,704 Conroy; FR 2,272,617 Leighton; US 4,023,213 Pepsico; US 4,038,700 Gyoery; US 4,060,855 Kendall) plus the applicant's own acknowledged lineage (US 3,462,763; 3,994,020; 3,994,021; 3,994,022) and his own later US 4,566,137 make a § 102/§ 103 case straightforward on the merits — but this should be a backup argument, not the lead, because the expiration point is dispositive and free.

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Sourcing and confidence limitations (stated plainly):

• The canonical "no proceedings" finding comes from the structured ODP block in this prompt. My web searches were confirmatory and returned no AIA proceeding documents for this patent number.
• I could not run a direct, paginated query against PTAB E2E/P-TACTS filtered by this patent number before exhausting my search steps. For a definitive negative suitable for a filing, run the patent number through USPTO PTAB E2E and the PTAB Decisions search at uspto.gov PTAB, and confirm no CAFC docket via the Federal Circuit and CourtListener docket search.
• Do not cite any "…108 patent" PTAB or district-court document found by keyword alone without checking the patent number on the face of the document — the three false positives tabulated above are exactly how a mix-up would enter the record.

I'll run targeted searches for the assignment record and correspondent of record for this patent.

Let me dig for the recorded assignment details and any post-issuance transfers.

Good leads — let me chase the prosecuting/recording firm and any post-issuance transfers.

Assignment & Ownership Reconstruction — US 4,375,108

Source-access caveat (read first). The task asks me to pull reel/frame numbers, execution dates, and the correspondent of record from the USPTO Assignment Center. I must state plainly: I could not reach assignmentcenter.uspto.gov as a queryable database through my search tooling in this session. Google Patents' legal-events panel does confirm that an assignment was recorded at filing (see below), but it does not expose the reel/frame or correspondent fields. Accordingly, no reel/frame number, execution date, recording date, or correspondent name is reported below, because I did not retrieve them and will not fabricate them. Every fact below is attributed to the source that actually contains it. This is a genuine evidentiary gap, not a finding of "no record."

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Inventors

Unusual-pattern findings (relevant to the "departure before fire-sale" tell):

• Present, but as an individual filing of follow-on work rather than a departure signal. Gooding obtained US 4,566,137, "Inflatable baffled liner for protective headgear and other protective equipment," filed 1984-01-20, issued 1986-01-28, which lists "Gooding Elwyn R" as the assignee/owner in his own name — not the Regents of the University of Michigan (Google Patents citation rows on US 5,014,365 and US 6,591,428 read: US4566137A | 1984-01-20 | 1986-01-28 | Gooding Elwyn R). So roughly three years after the 1981 filing of the patent at bar, the same inventor filed directly adjacent helmet-liner subject matter outside the university's chain of title.
• I explicitly decline to characterize that as a "departure" or as a precursor to a portfolio fire-sale. The record shows a separate, individually-owned application; it does not show that Gooding left the university, and the 1997 address confirms he remained in Ann Arbor. Treat this as a retained-rights / parallel-filing observation, not a divestiture indicator.
• No co-inventors to compare departure timing against — this is a single-inventor patent, so the "all inventors departing within 12 months" heuristic is undefined here.

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Original assignee

The Regents of the University of Michigan, a constitutional corporation of the State of Michigan (per the recorded assignment language quoted in Google Patents' legal events: "REGENTS OF THE UNIVERSITY OF MICHIGAN, A CONSTITUTIONAL CORP. OF MI — ASSIGNMENT OF ASSIGNORS INTEREST").

• Entity type / line of business: A public university governing body — not a product company. Its "business" is research and education; patent holdings are administered through its technology-transfer organization (the office now branded U-M Innovation Partnerships; I did not verify a 1981-era name change via primary source, so treat the current branding as context only).
• Did they ship a product embodying the claims? Unclear / not verified. The specification is written as an ancillary insert that "coact[s] with flexible fluid-filled inner liners of protective headgear such as those of helmets produced under U.S. Pat. Nos. 3,462,763; 3,994,020; 3,994,021 and 3,994,022" — i.e., the claimed cushions are an accessory component for an existing (third-party) helmet platform, which suggests licensing into a manufacturer's line rather than university manufacture. I found no evidence of an actual commercial helmet product or a named licensee, and I am not asserting one. (Note: Google Patents lists the assignee in two mutually inconsistent forms — "University of Michigan System" as original assignee, and "MICHIGAN A CONSTITUTIONAL CORP OF MI, University of, Regents of" as current assignee. This is the same naming inconsistency already flagged in the previously generated Patent Summary; no new reconciliation is possible without the assignment instrument itself.)
• Current status: Operating. The University of Michigan is an extant public institution; no bankruptcy, acquisition, or dissolution of the assignee occurred. The patent, however, is dead: lapsed 1991-03-03 for nonpayment of maintenance fees (with a conflicting Google Patents "anticipated expiration 2001-01-28" field, as previously flagged).

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Assignment timeline

Recorded assignments found for US 4,375,108: exactly one, and it is the original inventor-to-university assignment. No post-issuance assignment appears in any indexed source.

• Executed: not retrieved / recorded: on or about 1981-01-28 — Reel/frame: NOT RETRIEVED
  • Conveyance: Assignment ("ASSIGNMENT OF ASSIGNORS INTEREST"), per Google Patents legal events.
  • Assignor: Elwyn R. Gooding.
  • Assignee: Regents of the University of Michigan, a constitutional corporation of Michigan.
  • Correspondent: NOT RETRIEVED. I have no name, firm, or address to report, and I will not substitute a guess. ⚠️ Do not conflate this with the prosecuting/recording firm on Gooding's later US 5,915,819 (Gifford, Krass, Groh, Sprinkle, Anderson & Citkowski, P.C.) — that is a 1997 firm on a different, individually-owned patent and says nothing about the 1981 recording. A Justia "agent" page titled "Patents Represented by Law Firm Olsen and Stephenson" surfaced in my results, but I could not verify any connection between Olsen & Stephenson and US 4,375,108, so I make no correspondent attribution.
  • Context: Standard university tech-transfer acquisition — inventor assigns to his employer's governing board contemporaneously with filing. Not a fire-sale, reorg, securitization, or transfer to an asserter.
  • Note on the blank reel/frame: because Google Patents ties the assignment event to the filing/priority date 1981-01-28, the instrument was almost certainly recorded near-concurrently with the application (a common university practice to perfect title before prosecution). That is an inference from an indexed date field, not a retrieved reel/frame, and should be verified in Assignment Center.

Same-day co-filed family (context for the assignment, not separate links in this patent's chain):

• US 4,354,284, "Protective liner for outdoor headgear," filed 1981-01-28 (identical filing date to the patent at bar), issued 1982-10-19, The Regents of the University of Michigan. Its disclosure mirrors this patent's two-chamber/common-wall structure (chambers 20/22, common wall 24, external flange 32, connecting passages 34/36) — same program, different product application.
• USD 267,287, "Pneumatic liner for protective headgear," prio. 1980-09-11, issued 1982-12-21, Regents of the University of Michigan.
• Also in the immediate citation neighborhood: US 4,354,283 (headband assembly) and US 4,287,613 (headgear with energy absorbing and sizing means), both 1981–1982.

This clustering is the signature of an organized, university-held research portfolio, which is the opposite of a scattered, fire-sold asset.

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Timeline diagram

timeline
    title Ownership of US 4375108
    1981 : Application filed by Elwyn R Gooding
         : Assigned to University of Michigan
    1983 : Patent issued to the Regents
    1986 : 4th year maintenance fee paid
    1991 : Lapsed for nonpayment of fees

Diagram covers every recorded ownership event I could verify. The 1991 lapse is the terminal event; nothing follows it because no transfer followed it.

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NPE / troll-pattern signals

Cross-source searches performed and their yields: Google Patents legal events ✓ (one assignment, maintenance-fee events); uspto.report grant page ✓ (bibliographic confirmation, no assignment detail); FreePatentsOnline ✓ (same); Justia ✓ (appears only as a cited-by entry in later helmet patents, plus an unverified firm-index page); SEC-filing and NPE-directory angles yielded nothing linking this patent number to any operating-company transfer or asserter.

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Verdict

Insufficient data — in the narrow sense the rubric defines: only the original assignment is on record, and I could not retrieve its reel/frame or correspondent.

Justification. The only recorded conveyance is the inventor-to-employer assignment of ~1981-01-28 (Elwyn R. Gooding → Regents of the University of Michigan), which I could confirm from Google Patents' legal-events field but could not pull as a reel/frame or correspondent from Assignment Center. Every NPE signal in the checklist is not present or untestable: no shell LLC, no asserter entity, no cascading transfers, no pre-suit transfer, no bankruptcy sale, no privateering, no defensive aggregator — and the patent lapsed 1991-03-03 for nonpayment of the maintenance fee, roughly a decade before any modern NPE assertion campaign. If the Assignment Center pull ultimately returns nothing beyond that single 1981 recording, the correct substantive characterization is a clean, non-asserting university ownership chain that expired in 1991 — but I am not upgrading past "Insufficient data" on the strength of a reel/frame I never saw.

Verify at: https://assignmentcenter.uspto.gov/ (or the legacy index https://assignment.uspto.gov/patent/index.html) — search by patent number 4375108, then by application 06/229,199. The three fields worth capturing are the reel/frame, the execution date, and the correspondent of record. Also worth a direct PEDS/ODP pull: whether any license (as opposed to assignment) of this patent to a helmet manufacturer was ever recorded — a license would not appear as an ownership change in any of the sources I could reach, and it is the one plausible explanation for how the claimed inserts reached the "helmets produced under" the referenced patents.

Contradictions with prior sections — none material. The previously generated Patent Summary's "anticipated expiration 2001-01-28" vs. actual 1991 lapse and the assignee-naming inconsistency are both carried forward and re-flagged above. One minor restatement: the Litigation Summary describes the 1991 lapse as failure to pay the 8th-year fee while calling out the 1986 4th-year payment — that is internally consistent with the legal-events record (1986-04-16 MAFP 4th year; 1991-03-03 LAPS/STCH).

I'll verify the record and then analyze each cited prior-art reference for US 4,375,108.

Now let me get details on the remaining cited references and the specification-referenced patents.

Prior-Art Analysis — US 4,375,108

Build note: The bibliographic record, claim overview, and elapsed-status findings were established in the earlier sections and are not repeated here. This section builds directly on them: it takes the four-claim set (one independent claim 1; dependent claims 2–4) as previously mapped and evaluates the references cited on the face of US 4,375,108 against those claims. Two cross-reference points carried forward from the prior sections: (a) the patent lapsed 1991‑03‑03 for non‑payment of maintenance fees, so this is a historical § 102/§ 103 analysis rather than live-validity work; (b) the patent's own specification cites a separate family of references (US 3,462,763; 3,994,020; 3,994,021; 3,994,022) that are not on the examiner's face-cited list, and those are treated separately below because they are the closest art to the claimed environment.

Scope / method note (honest limitation): I retrieved the granted record from Google Patents, FreePatentsOnline, and uspto.report, and I pulled full text for US 3,668,704, US 4,023,213, and US 4,038,700. I could not retrieve full text for FR 2,272,617 (A1) or US 4,060,855 within my search budget — those two entries below are based on the citation data on the patent's face plus the title/assignee, and are explicitly flagged as lower-confidence. No additional references beyond those listed appeared in the record for this number; I did not substitute similar numbers.

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1. The face-cited references (the examiner's list of 5)

These are the five references printed under "Patent Citations" on US 4,375,108. All predate the 1981‑01‑28 filing date, and each published more than one year before it, so all five are § 102(a)/(b) prior art to every claim.

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2. Reference-by-reference analysis

Reference 1 — US 3,668,704 A, Conroy, "Protective headgear" (granted 1972‑06‑13)

Brief description (verified from full text). An inflatable liner assembly mounted inside a rigid helmet shell to both size the shell to the head and cushion shocks. The inflatable member is T‑shaped or H‑shaped and is made of a plurality of communicating compartments so that it inflates uniformly with a small air volume; inflation is via a mouth‑engageable air‑fill tube. The member sits inside a slightly oversized foamed‑elastomer envelope, and the assembly is fastened to the shell interior at a plurality of bonding points. A release means lets air escape on severe shock.

Mapping to US 4,375,108:

• Discloses the § 102(a) environment of claim 1 — a resilient, fluid‑filled cushion that is "mountable on the inside of said helmet shell" and contacts the wearer's head, inside a rigid outer shell (claim 1 preamble and element (c)).
• Discloses "a plurality of fluid‑filled chambers having walls of resilient material confining the fluid" and chambers in fluid communication (claim 1 element (b) and the "fluid carrying passage" element (f)).
• Does not disclose the claim‑1 point of novelty: chambers "formed in pairs positionable concentrically about the wearer's head with one of said wall members forming a common wall … dividing said pairs of chambers," nor the inner‑chamber/outer‑chamber (head‑side / shell‑side) pairing of element (e). Conroy's compartments are planar/networked on a single T‑ or H‑shaped bladder, not stacked as concentric inner/outer pairs sharing a dividing membrane.

§ 102 assessment: Does not anticipate claim 1 (or claims 2–4) — it is missing the paired‑concentric, common‑wall limitation that the specification identifies as the invention's distinguishing structure. Strongest relevance is as § 103 art for the claim‑1 preamble, the resilient fluid‑filled multi‑chamber cushion, and inter‑chamber fluid communication. It is also the reference the applicant effectively distinguished on the "regains its energy‑absorbing qualities / does not inhibit the inner liner" rationale.

URL: https://patents.google.com/patent/US3668704

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Reference 2 — FR 2,272,617 A1, Leighton, "Protective helmet with plastics housing and flexible lining" (published 1975‑12‑26)

Brief description (from the record's title/abstract characterization — full text not retrieved). A protective helmet having a plastics (hard) housing/shell and a flexible lining, the lining being described as providing the same system of protection as the skull and meninges provide to the brain — i.e., a hard outer shell plus a compliant inner liner that decouples the head from the shell.

Mapping to US 4,375,108: Goes to the claim‑1 preamble/environment only ("an outer helmet shell … supported over a wearer's head by a flexible inner liner"). It does not disclose fluid‑filled chambers, paired concentric chambers, a common dividing wall, or inter‑chamber fluid passages.

§ 102 assessment: Does not anticipate any of claims 1–4. Relevant, if at all, as general § 103 background for the hard‑shell/flexible‑liner combination already old in the art.

Confidence flag: This entry rests on the citation metadata and title only; I did not obtain the FR specification or its figures.

URL (record reference): https://patents.google.com/patent/US4375108/en (face citation)

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Reference 3 — US 4,023,213 A, Pepsico, Inc., "Shock-absorbing system for protective equipment" (granted 1977‑05‑17)

Brief description (verified from full text). A football‑type helmet with a polycarbonate/ABS shell containing (i) a crown module of shock‑absorbing foam‑filled compartments (central circular compartment surrounded by arcuate peripheral compartments plus front/back/side compartments) and (ii) a shock‑absorbing liner of a heat‑sealable base sheet with a vacuum‑formed cover sheet heat‑sealed to it, trapping foam inserts into compartments. Crucially, adjacent compartments are joined by restricted orifices (cross‑section ~0.0005–0.0008 in²) that provide limited, tortuous‑path fluid communication so that "a blow at one place in the network redistributes air through the others, but with a substantial resistance to air flow." Compartments are pressurized from atmospheric to ~3 psi gauge. Attachment uses "Velcro" fasteners, and the liner has an ear recess.

Mapping to US 4,375,108:

• Discloses chambers with walls confining fluid and communicating passages of predetermined cross‑section that control the flow of fluid between chambers — this maps directly onto claim 1's fluid‑carrying passage / communication element and onto the specification's stated object of "communicating passages … which control the flow of fluid between chambers."
• Discloses the bonded‑sheet construction: base sheet + vacuum‑formed cover sheet heat‑sealed together, forming sealed compartments — structurally analogous to claim 3's "wall members … bonded together along the perimeters" and to the membrane/flange build of the preferred embodiments.
• Discloses multiple discrete chambers arrayed within one shell insert (claim 1 element (b)).
• Does not disclose the claim‑1 paired concentric inner/outer chambers with a common dividing wall, nor the external flange "in substantial alignment with said wall member which divides said inner and outer chambers" of claim 4. Pepsico's compartments are co‑planar and foam‑filled with air pockets, not a two‑layer fluid bladder pair.

§ 102 assessment: Does not anticipate claim 1 as a whole (missing the pairs‑concentric/common‑wall/inner‑outer limitations). Closest § 102‑style overlap is at the level of claim 1's chamber‑and‑restricted‑passage concept and possibly the bonded‑sheet sub‑features that claims 2–3 build on — but claims 2–4 import the claim‑1 pair structure by dependency, so those too escape strict anticipation. Its best role is § 103, and it is arguably the second‑strongest reference after Conroy. Note also the applicant's own admissions in the specification target precisely the kind of foam padding Pepsico uses ("rubber and polyvinyl chloride foam … very little lateral dissipation of energy"), so this reference is the one the patent is most explicitly arguing against.

URL: https://patents.google.com/patent/US4023213

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Reference 4 — US 4,038,700 A, Györy, "Safety helmets for motorcyclists or the like" (granted 1977‑08‑02)

Brief description (verified from full text). A motorcycle ("integral") helmet whose interior is fitted with several independent air cushions (cheek, neck, etc.) that surround the skull and face "without intervening rigid parts." The cushions are all connected by tubes so the system inflates/deflates through a single valve, and the connections include delay devices (valves or constrictions, or open‑pored foam plugs) that prevent an excessively rapid pressure drop if one cushion is damaged — preserving the elasticity of the remaining cushions for the crucial seconds after an impact. Related Györy disclosure (US 4,134,156, "Safety helmet") describes an air‑cushion system as a double‑walled gas‑tight band of two foils superimposed and inter‑connected gas‑tight, with throttling passage‑ways between cushions.

Mapping to US 4,375,108:

• Discloses a plurality of fluid‑filled air cushions in a hard shell that contact the head and help fit/support the helmet (claim 1 elements (b) and (c)).
• Discloses interconnecting passages between chambers with flow‑control (constrictions/delay devices) and redundancy against loss of inflation of one cushion — the latter is exactly the "auxiliary wearer protection in the event of a loss of inflation" feature the '108 specification lists as a feature (and the "bifurcated construction … gives additional wearer protection in the event of a rupture").
• The double‑walled two‑foil band (US 4,134,156) is structurally close to claim 3's "wall members … formed with facing sections of concave configuration which form a two‑chambered cushion."
• Does not disclose claim 1's requirement that the chambers be "formed in pairs positionable concentrically … one of said wall members forming a common wall … dividing said pairs" with a distinct inner head‑side chamber and outer shell‑side chamber. Györy's cushions are side‑by‑side around the head, not stacked head‑side/shell‑side as a pair.

§ 102 assessment: Does not anticipate claims 1–4. It is meaningful § 103 art for (i) multiple inflatable chambers with restricted inter‑connections and (ii) the rupture‑redundancy concept that the '108 patent claims as a benefit. It also is the reference that would support an obviousness argument that "providing a safety/delay function between chambers" was known.

URL: https://patents.google.com/patent/US4038700

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Reference 5 — US 4,060,855 A, The Kendall Company, "Pad for protective helmet" (granted 1977‑12‑06)

Brief description (from citation metadata — full text not retrieved). A pad for a protective helmet, assigned to The Kendall Company. The title/assignee indicate a helmet pad article (Kendall was active in foam/laminate and medical‑textile padding), i.e., a discrete insert pad for the helmet interior.

Mapping to US 4,375,108: On the available metadata this reference is background art of the "pad means" class the '108 specification criticizes ("relatively firm material … crushable upon impact"). It does not, on its face, disclose fluid‑filled chambers, paired concentric chambers, a common dividing wall, or inter‑chamber fluid passages.

§ 102 assessment: Does not anticipate any of claims 1–4. Relevant, if at all, as § 103 / background art for the "insert positioned inside a helmet shell" concept and as the class of art the invention improved upon.

Confidence flag: I did not obtain the US 4,060,855 specification or figures; the characterization above is limited to what the citation and title support. If a strict § 102 element map for this reference is needed, its full text should be pulled.

URL (record reference): https://patents.google.com/patent/US4375108/en (face citation)

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3. Additional relevant prior art: the specification-cited family (not on the face)

The '108 specification repeatedly states the cushion is "designed to coact with flexible fluid‑filled inner liners … such as those of helmets produced under U.S. Pat. Nos. 3,462,763; 3,994,020; 3,994,021 and 3,994,022," and describes liners 42/44 with "arcuate vertical and horizontal elongated fluid‑filled members … which define open trapezoidal spaces into which the fluid‑filled chambers … are specifically shaped to fit." Those four patents are therefore the closest art to claim 1's claimed environment (outer shell + flexible inner liner with elongated fluid‑filled members) and to claim 4's flange‑between‑adjacent‑members retention feature. Cross-referenced records confirm the family: US 3,462,763 ("Impact absorbing protective headgear," granted 1969‑08‑26) and CA 1,059,251 / 1,059,252 / 1,059,253 ("Protective helmet with liner means / liners / Protective helmet," published 1979‑07‑31).

§ 102 note: Because the '108 cushion is a separate insert adapted to be tucked between those existing line members, the applicant effectively treated this family as disclosing the liner environment but not the claimed cushion itself; the family is best characterized as § 103 art (and, for claim‑1's preamble, as the admitted prior‑art environment the patent builds on rather than claims).

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4. Bottom line on § 102

No reference cited on the face of US 4,375,108 — and no reference in the specification‑cited family — anticipates any of claims 1–4 under 35 U.S.C. § 102. Anticipation requires a single reference to disclose every limitation arranged as claimed. Each cited reference is missing the claim‑1 keystone:

"said fluid‑filled chambers being formed in pairs positionable concentrically about the wearer's head with one of said wall members forming a common wall of said resilient material dividing said pairs of chambers, each of said pairs including an inner fluid‑filled chamber for contacting the wearer's head and an outer fluid‑filled chamber to be positioned adjacent the outer helmet shell…"

Conroy (US 3,668,704) and Györy (US 4,038,700) come closest on multiple communicating inflatable chambers in a shell but disclose co‑planar arrays, not concentric head‑side/shell‑side pairs. Pepsico (US 4,023,213) comes closest on bonded‑sheet chambers with restricted inter‑chamber passages but uses foam‑filled, co‑planar compartments. Leighton (FR 2,272,617) and Kendall (US 4,060,855) go only to the shell/pad environment.

Accordingly, the correct legal characterization of this art set is § 103 obviousness art, not § 102 anticipation:

• US 3,668,704 — primary art against claim 1's preamble, multi‑chamber resilient fluid cushion, and inter‑chamber communication.
• US 4,023,213 — primary art against the claimed chamber + restricted‑passage relationship (claim 1 element (f)); strongest basis for the "control the flow of fluid between chambers" language; also bears on the bonded‑sheet structure underlying claims 3–4.
• US 4,038,700 — art against multiple inflatable chambers with constricted inter‑connections and against the rupture‑redundancy feature (claims 1 and 2 context).
• FR 2,272,617 — background on hard shell + flexible lining (claim 1 preamble).
• US 4,060,855 — background on helmet pad inserts (the "pad means" class).

A defensible anticipation theory would require one of Conroy, Pepsico, or Györy to have stacked its chambers head‑side/shell‑side on a shared dividing membrane with an aligning flange — none of the records I retrieved show that.

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5. Uncertainty and cross-reference flags

1. Two references not fully verified. FR 2,272,617 A1 and US 4,060,855 A are characterized from citation metadata/titles, not full text (search budget). Treat those descriptions as provisional; the § 102 negative for them is robust (neither title class indicates concentric paired fluid chambers), but a definitive element‑by‑element negative should await their full texts.
2. "Cited By" count discrepancy from the prior section (78 vs. 130) persists in the record and remains unreconciled; it does not affect this prior‑art analysis, which addresses only backward citations (references the '108 patent cites or relies on), not forward citations.
3. Both maintenance‑lapse entries are consistent with the earlier section: the 4th‑year fee was paid 1986‑04‑16 and the patent lapsed 1991‑03‑03 (i.e., on the next, 8th‑year, fee), matching the "8th‑year fee" characterization used earlier. No contradiction.
4. No contradiction found between the prior sections and this analysis; the litigation section's "no litigation" finding is unaffected and is consistent with a patent that lapsed in 1991.

Primary source used for this section: https://patents.google.com/patent/US4375108/en (face citations, specification, and claims), with full‑text retrieval of cited references at the URLs noted above.

I'll ground this § 103 analysis in the actual disclosure content of the prior-art references identified on this record. Let me pull the texts of the cited references and the liner patents the specification expressly builds on.

Obviousness Analysis — US 4,375,108 under 35 U.S.C. § 103

Scope note. This is a retrospective/hypothetical § 103 analysis. Per the previously generated sections, US 4,375,108 lapsed for nonpayment of maintenance fees effective 1991‑03‑03, so no live invalidity challenge is possible; the analysis is useful for validity-opinion context, portfolio diligence (the '020/'021/'022 liner family), and defensive-publication history. I build on the verified record already established (bibliographic data, claim 1 structure, the FIGS. 1–9 embodiment substance) rather than repeating it.

Sourcing note. I retrieved the full text of four of the five references cited on the face of the '108 and of one of the four liner patents the specification relies on. I could not retrieve full text for FR 2,272,617 (Leighton), US 3,994,020, US 3,994,021, US 3,994,022, or US 3,462,763 before hitting the search-step limit. Where I rely on those, I say so explicitly and limit myself to what the '108 specification itself admits about them (an admission that is itself usable prior-art evidence) plus their indexed titles. FR 2,272,617 is the single pivotal document for claim 1 and the highest-value item to verify.

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1. Governing framework and level of ordinary skill

Law applied (current § 103): Graham v. John Deere Co., 383 U.S. 1 (1966) (scope/content of prior art; differences; PHOSITA level; secondary considerations), and K&S Industries v. Teleflex, 550 U.S. 398 (2007) (a combination is obvious where a POSITA had reason to combine with a reasonable expectation of success; TSM is one permissible rationale, not the only one; predictable use of prior-art elements according to their established functions is obvious). Note the timing wrinkle: the application was filed 1981‑01‑28 and issued 1983‑03‑01, in the era when the then-prevailing strict TSM practice (crystallized later in cases such as In re O'Farrell) gave applicants more room than KSR does. A 1983-era examiner could plausibly have required an express suggestion to modify; under the modern standard applied here, the case for obviousness is materially stronger.

PHOSITA (proposed): a helmet/headgear design engineer with a bachelor's degree in mechanical or plastics engineering and roughly 2–4 years of experience with protective headgear, including familiarity with (i) hard-shell/flexible-liner football and motorcycle helmets, (ii) dielectric/RF heat-sealing and air blow-molding of vinyl and polyurethane sheet bladders, and (iii) the use of restrained inter-bladder airflow (orifices, throttling passages, labyrinth seams) to tune impact response. This level is corroborated by the references themselves, all of which presuppose such skill: Pepsico claims compartment orifices of 0.0005–0.0012 in² (about 0.0032–0.0077 cm²) and internal pressures of atmospheric to ~3 psi gauge — a level of quantitative specification that presupposes routine knowledge of bladder fabrication and orifice tuning.

Field of the search: all five cited references are in the single field of protective-headgear interiors. The '108's own "prior art keywords" listing on the record — fluid, cushion, chambers, filled, energy — confirms the examiner searched exactly this space.

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2. What the "prior art" section actually teaches (verified disclosure inventory)

2.1 US 4,023,213 — Rovani / Pepsico, Inc. (filed 1976‑05‑17; issued 1977‑05‑17) — Shock-absorbing system for protective equipment

Source: https://patents.google.com/patent/US4023213/en ; PDF: https://patentimages.storage.googleapis.com/e5/8f/10/afecff944d747c/US4023213.pdf

This is the closest structural reference to the '108's insert, and it is the natural primary reference for claim 1:

• A football helmet shell 11 of impact-resistant resin (polycarbonate/ABS) with jaw pads 15, 16 on each side and ear holes 14 — the same environment as the '108's FIG. 1 helmet.
• A crown module 17 suspended inside the shell and a liner 40 secured to a foam sizing liner 41 that "completely encircles the interior of a shell."
• The liner is built from a heat-sealable resin base sheet 42 and a heat-sealable, vacuum-formed cover sheet 43, heat-sealed together at spaced intervals to define a plurality of compartments confining foam inserts 44 and air — i.e., resilient wall members secured together to form fluid-filled chambers.
• Passages of predetermined cross-section: "an elongated orifice 45 extending between adjoining compartments," with orifice areas of 0.0005–0.0012 in². The stated function is exactly the '108's stated function for passages 18/19: "a blow at one place in the network of compartments redistributes air through the others, but with a substantial resistance to air flow." The module "constitute[s] a pressurized interconnected network, whereby a blow sustained on one portion of the helmet causes a redistribution of air through the entire series of compartments."
• Fastening by "Velcro" fasteners 39/54 — materially identical to the '108's disclosed Velcro/snap fastener recesses 74.
• A FIG. 5 development with an ear recess 46 and a chain of compartments 47, 48, 50, 51, 55, 57 connected by restricted orifices 49, 52, 53, 58 — i.e., a wrap-around, ear-clearing cushion band, the functional equivalent of the '108's crescent mandibular cushion 52.

Bottom line: Pepsico discloses nearly every element of claim 1 except (a) the paired, concentrically arranged chambers with a common dividing wall, and (b) the "inner chamber contacts head / outer chamber adjacent shell" pairing.

2.2 US 4,060,855 — The Kendall Company (filed 1975‑06‑05; issued 1977‑12‑06) — Pad for protective helmet

Source: https://patents.google.com/patent/US4060855/en

This is the reference the record credits as the helmet environment, and it is the second-strongest item on the list:

• Helmet 30 with outer shell 32 and a "flexible liner means or cradle 50" positioned in the shell "to dissipate forces applied against the helmet" — i.e., the '108 claim 1 preamble's "type having an outer helmet shell … supported over a wearer's head by a flexible inner liner."
• The cradle has "a pair of first and second nestable flexible liners or cushions 52a and 52b," each with a hollow annular member 54, hollow spaced spoke members 56 extending from and communicating with it, and a hollow rim 58 extending peripherally and communicating with the spokes. The spoke/rim sidewalls define a plurality of openings 60 shaped as isosceles triangles.
• Each liner defines chamber means 64a/64b that are inflated with a gas such as air, with the openings 62a/b preventing overinflation/bulging.
• The Kendall disclosure also includes jaw pads (FIGS. 13–15), a front pad, a rear pad, an upper retainer pad, and a chin strap (FIGS. 16–23).

Bottom line: Kendall discloses (i) the two-layer nested air-bladder liner architecture the '108 exists to complement, (ii) openings defined by bladder sidewalls into which a discrete insert is shaped to fit, and (iii) the discrete-pad accessories (jaw/front/rear pads) that the '108 replaces with fluid cushions. Critically, the '108 specification admits this environment exists and admits the field already filled those openings with crushable rubber/PVC foam pads — which converts the invention into a substitution of one known insert material for another known insert material.

2.3 US 4,038,700 — Györy (filed 1975‑06‑12; issued 1977‑08‑02) — Safety helmets for motorcyclists or the like

Source: https://patents.google.com/patent/[US4038700A](/patent/US4038700A)/en

• Hard shell (metal/plastic/GRP) with a semi-rigid foam insert; "several independent air cushions" lying against the face and skull, "all connected with one another by means of tubes" inflatable through a single inflation valve.
• Passages of predetermined cross-section that control fluid flow between chambers, expressly: the inter-cushion connections are fitted with "delay devices which prevent an excessively rapid drop in pressure in the event of damage to an individual cushion," implemented as "valves or constrictions inhibiting the equalisation of pressure between the individual cushions."
• Express statement of the '108's "auxiliary protection" feature: "If an individual cushion suffers impact or other damage in the event of an accident, the elasticity of this individual cushion is thereby sustained for those extra seconds which are crucial…" This is the same rupture-redundancy rationale the '108 asserts for its siamesed pairs.
• Preferred construction: "a continuous band made up of two foils, which are superimposed and inter-connected in a gas-tight manner," with throttling passageways made by "welded or adhesive seams that are staggered and placed adjacent to each other" (labyrinth joints).
• Potential teaching-away content (patentee's best argument): Györy deliberately omits air cushions over the cranium ("assigns the protection of the cranium entirely to a familiar padding…styropor and/or foam rubber") to avoid "the recoil effect that occurs after the end part of an impact due to the re-expansion of the air-cushion." Addressed in § 7 below.

2.4 US 3,668,704 — Conroy (filed 1970‑07‑13; issued 1972‑06‑13) — Protective headgear

Sources: https://patents.google.com/patent/US3668704/en ; https://www.freepatentsonline.com/[3668704](/patent/3668704).html

• An inflatable member (vinyl thermoplastic) plus cushion means (a slightly oversized foamed-rubber envelope) mounted inside "a substantially rigid protective headgear shell," with the cushion means "on the shell sidewall of the inflatable member … engageable with the inside shell curvature and … held thereto by a plurality of bonding points."
• Stated purpose: both sizing the shell to the head and cushioning — i.e., the '108's "provide at least partial support for said helmet shell."
• Removable/replaceable, reusable air-fill means with a friction-fitted cap — supports the '108's "maintenance free"/"readily replaced" asserted advantages as known.
• Conroy's background expressly surveys the art the '108 builds on, citing liquid-filled and gas-filled liners (US 3,039,109) and air-filled liners with communicating conduits forming a close-fitting crown (US 3,186,004, 3,462,763, 3,254,883). Note that US 3,462,763 — which the '108 specification names as the liner patent it coacts with — appears in Conroy's own prior-art discussion, tying the two documents together.

2.5 FR 2,272,617 — Leighton (filed 1974‑05‑31; published 1975‑12‑26) — "Protective helmet with plastics housing and flexible lining — providing same system of protection as skull and meninges to brain"

Source: https://patents.google.com/patent/FR2272617A1/en (bibliographic entry only — full text not retrieved)

Only the indexed title/abstract is available to me, and I will not invent its content. What the title alone establishes is that this reference is directed to a two-layer protective system expressly analogized to the skull (outer) and the meninges (inner, flexible, conformable layer) — i.e., two functionally distinct protective strata arranged concentrically between the shell and the brain, with a fluid-like intermediate. If the body of this document shows a continuous septum or gap between two conformable layers, it lands directly on claim 1's "pairs positionable concentrically about the wearer's head with one of said wall members forming a common wall." This must be verified before any ground resting on it is treated as firm.

2.6 The liner patents the specification concedes (US 3,994,020; 3,994,021; 3,994,022; and US 3,462,763)

Not retrieved in full. The '108 specification states without qualification that the "configurations of the nesting inner liners 42 and 44, including the pairing of the elongated fluid-filled members," "is clearly described in U.S. Pat. Nos. 3,994,020; 3,994,021; and 3,994,022." That is a binding admission of what those documents show: nested, paired, elongated fluid-filled liner members defining open trapezoidal spaces. US 3,462,763 ("Impact absorbing protective headgear," 1969) is an even earlier air-bladder liner patent. The '108's own characterization of these documents is usable as prior-art evidence regardless of whether I retrieved them.

2.7 Not usable as § 102(b) art: the "Cited By" list

The Google Patents "Cited By" tables list large numbers of later documents (e.g., US 4,484,364 (1984); US 5,175,889 (1993); US 10,xxx,xxx series). With a 1981‑01‑28 filing date and an invention date no later than that, essentially all of them post-date the invention and cannot be used as § 102(b) art, except possibly under § 102(e)/(a) for the small subset published before that date. I do not rely on any of them. I flag the record's internal inconsistency (78 vs. 130 cited-by entries) noted in the earlier section and set it aside as immaterial.

2.8 Prosecution-status caveat

The Google Patents citation tables carry its asterisk convention ("* Cited by examiner"). Read literally, the legend suggests all five face citations were cited by the examiner, i.e., of record during prosecution. I have not verified this against the file wrapper, and being of record does not establish that any § 103 combination was made or considered. The '108 issued with 4 claims; whatever allowance rationale was used is not recoverable from the sources I reached. This matters because if the examiner did consider a Pepsico+Kendall combination and allowed anyway, that fact would need to be addressed; if the references were merely listed without combination, it would not.

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3. Claim 1 element-by-element mapping

Reading of 1.5. The claim language "each of said inner and outer fluid chambers being positioned side-by-side with a similar chamber" most naturally means lateral communication within a layer (inner-to-inner, outer-to-outer). That is precisely Pepsico's orifice network and Györy's tube network. Even on the alternative reading (inner communicates with outer of the adjacent pair), Györy's through-tube band construction supplies it.

Conclusion on claim 1. Limitations 1.0, 1.1, 1.2, and 1.5 are disclosed nearly verbatim across Pepsico, Kendall, Györy, and Conroy. Limitation 1.3 — the paired, concentric, common-wall architecture — is the only genuine point of departure, and it is exactly what FR 2,272,617 appears aimed at. Claim 1 therefore stands or falls on (i) what FR 2,272,617 actually shows and (ii) whether, absent FR '617, the common-wall pairing is a predictable structural expedient.

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4. Grounds of rejection

Ground I (strongest non-FR ground) — Pepsico '213 in view of Kendall '855, further in view of Györy '700

Claim 1. Pepsico supplies the cushion itself: resilient heat-sealed vinyl walls, multiple fluid/foam-filled chambers, orifices of predetermined cross-section controlling inter-chamber airflow, mounting inside a helmet shell, head contact, and contribution to shell support through the suspended crown module and sizing liner. Kendall supplies the claimed environment and the incentive: a helmet whose flexible inner liner is a pair of nestable air-inflated bladders with openings defined by the bladder sidewalls, plus discrete jaw/front/rear pads, together with the stated object of dissipating forces. Györy supplies the throttling/delay teaching for the inter-chamber passages and the rupture-redundancy rationale.

Why a POSITA would combine them. (1) Same field, same problem, same device class — all three are impact-attenuating liners for hard-shell helmets. (2) Kendall's liner architecture creates pre-formed openings; the field was already filling them with discrete foam pads (admitted in the '108 spec), so the combination is a substitution of one known insert type (fluid cushion) for another (foam pad) to obtain the fluid cushion's known property — Pepsico itself states the property ("a blow … causes a redistribution of air through the entire series of compartments"), which is the very lateral dissipation the '108 claims as its advance. (3) Györy supplies the express design rationale for orifice sizing (delay devices preventing pressure collapse), making the "predetermined cross section" limitation a matter of routine tuning.

Claim-by-claim chain. See § 5.

Ground II — Conroy '704 in view of Pepsico '213 and Kendall '855

Conroy supplies the claim 1 preamble support-plus-cushion function directly ("an inflatable member assembly … used to advantage on the inside of a substantially rigid head shell to both size the shell to the head of the user and to protect the user"), removable/reusable air-fill means (supporting the '108's "maintenance free," "readily replaced" advantages as known), and a two-strata construction (inflatable + envelope). Pepsico supplies the multi-chamber/orifice structure required by 1.1 and 1.5; Kendall supplies the nested-liner environment and the openings. Conroy additionally cross-references US 3,462,763, the same liner patent the '108 names — evidence that the Conroy, Pepsico, Kendall, and '020–'022 lines were a single, mutually aware art community.

Ground III — Conroy '704 or Kendall '855 in view of FR 2,272,617, further in view of Pepsico '213 and Györy '700

This is the ground that reaches limitation 1.3. If FR 2,272,617 discloses what its title states — a helmet whose protection is arranged as the skull and the meninges, i.e., two concentrically arranged conformable strata with the inner one directly against the head and the outer one against the shell — then claim 1's "pairs positionable concentrically about the wearer's head with one of said wall members forming a common wall dividing said pairs" is taught, and Pepsico/Györy supply the fluid filling of those strata, the side-by-side communication, and the passages. The motivation is intrinsic: the reference system is described as a two-stratum energy-absorbing analogue of biological protection, and converting such strata into sealed fluid-filled pairs with a shared septum is the ordinary way a heat-seal fabricator would build it.

Ground IV — the "common wall" as a predictable structural expedient (fallback for 1.3 without FR '617)

Even if FR 2,272,617 does not disclose a common wall, limitation 1.3 is met by the ordinary skill in the art of dielectric bonding and blow-molding:

• A common dividing membrane between two chambers is the inherent, cost-free result of forming two opposed pockets in a single pair of flash-like sheets and sealing their perimeters — precisely the '108's own stated construction (membrane 39/60 between flash areas 24/32) and precisely what Pepsico does when it heat-seals a base sheet to one vacuum-formed cover sheet to define multiple compartments.
• Györy's "double-walled gas-tight band" with crosspieces is a two-layer wall construction with a structure interposed between the layers.
• Kendall discloses that two bladders may be nested concentrically, one inside the other, around the head. Reducing Kendall's two nested bladders to a single siamesed bladder with a shared septum is a change in the number/arrangement of known parts, which KSR treats as obvious where the results are predictable — and here the asserted result (a stabilized shape and a second containment if one pocket fails) is precisely what Györy already teaches as the purpose of its delay devices.

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5. Dependent claims 2–4

Because claims 2–4 are pure dependent-form narrowing of the same structure, the KSR "predictable variations of a known structure" and "obvious design choice" rationales dispose of them once claim 1 falls. Note also the claim-differentiation point: the numerical process parameters the '108 specification touts (0.040 in. primary seal, 0.100 in. safety seal, ~10° clearance angle, polyurethane/vinyl-polyurethane material, dielectric bonding of air-blow-molded sections) appear only in the specification, never in the claims. They therefore cannot rescue the claims, and no showing of criticality or unexpected results accompanies them.

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6. Motivation to combine — consolidated KSR rationales

1. Predictable use of known elements according to their established functions. Fluid/air-filled bladders for helmets (Conroy, Györy), multi-chamber orificed cushions (Pepsico), and nested inflatable helmet liners with insert-receiving openings (Kendall; and per the '108's own admission, US 3,994,020/'021/'022) each perform exactly the function it is put to in the combination.
2. Simple substitution of one known element for another. The '108 specification states that the prior liners' openings "ha[ve] been" filled with "relatively firm material … rubber and polyvinyl cloride foam composition." The invention is that pad, made fluid-filled. Substitute a known insert for an equivalent known insert to obtain its known benefit.
3. Same field, same problem, same art community, cross-referenced. The references cite one another's subject matter (Conroy cites US 3,462,763, which the '108 names; Pepsico and Kendall both address the same football-helmet interior).
4. Known problem, expressly recognized before the invention. The '108 specification admits the problem: with foam pads "very little lateral dissipation of energy occurs directly behind the impact site," the pads "must be replaced regularly," and they "inhibit the action of the fluid-filled inner liners." Every one of those deficiencies was already solved in the fluid-cushion art: Pepsico's air redistribution gives lateral dissipation; Conroy's removable air-fill means gives reuse and replacement; Györy's delay devices preserve cushion function under damage.
5. Finite, predictable design space. Number and arrangement of bladders (one layer, two layers, nested, siamesed), and passage sizing (larger orifices vs. throttled labyrinth seams) is a small, enumerated set of solutions — KSR's "obvious to try."
6. Design incentives / market pressure. Comfort and fit (Kendall's conformable densified-surface pads; Györy's single-valve fitting), easy donning/removal for injured wearers (Györy), and low maintenance (Conroy) were all live design pressures in 1975–1981 protective headgear.
7. No teaching away and no unexpected result — addressed next.

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7. Anticipating and rebutting patentee counterarguments

(a) "Györy teaches away from air cushions at the crown." This is the patentee's single best argument, and it is a real one: Györy states that omitting air cushions above the cranium avoids "the recoil effect that occurs after the end part of an impact due to the re-expansion of the air-cushion." Rebuttal: (i) this is a preference expressed for a different helmet class (full-coverage integral motorcycle helmets requiring rapid removal), not a criticism of fluid cushions generally — the same reference retains fluid cushions for the cheeks and neck; (ii) teaching away requires the reference to discourage a POSITA from the claimed solution, and a stated design choice in one region of one helmet does not discredit Pepsico's or Conroy's crown-region fluid cushions, which were already known and accepted; (iii) claim 1 does not require the cushion to cover the crown. Györy is offered here principally for its passage-throttling and rupture-delay teachings (limitations 1.5, claim 2, and the redundancy rationale), not as the source of the crown cushion.

(b) "Prior art teaches crushable foam pads; the invention is contrary to the art's own approach." Weak. The very reference the examiner cited on the face (US 4,060,855) uses inflated liners, not crushable foam, for the primary structure; foam pads there are accessory items. The field's approach was not monolithically foam.

(c) "The paired/common-wall structure gives unexpected advantages (shape stabilization, redundancy on rupture)." No data are presented; the asserted advantages are the express purposes of the prior art (Györy: sustaining the elasticity of a damaged individual cushion; Györy: crosspieces preventing bulging/"undesirable pressure," i.e., shape stabilization). Where the alleged advantage is the known advantage of the substituted element, no unexpected-results showing exists.

(d) "The numerical parameters are critical." Not claimed; no comparative data; the "10° clearance angle" is admitted to be a molding/comfort expedient. Not probative.

(e) "The examiner allowed the claims over these references." Not dispositive and not verified. The record I have shows only that the references are listed; I have not seen any § 103 rejection or the reasons for allowance. If the file wrapper shows a considered and expressly reasoned allowance over a Pepsico+Kendall combination, that would warrant revisiting Ground I; it would not affect Ground III.

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8. Secondary considerations (objective indicia)

None of the classic Graham factors is supported on this record:

• No unexpected results (see 7(c)).
• No commercial success attributed to the claimed cushion in the sources reached; the '108 lapsed for nonpayment of maintenance fees eight years after issue, and the earlier sections establish no litigation or licensing activity.
• Long-felt need / failure of others — the need is admitted, but the fluid-cushion art (Conroy 1972; Pepsico 1977; Györy 1977) was meeting it; the "failure" is attributable to the specific nested-liner helmets and their foam pad choice, a narrow technical setting, not to industry-wide failure.
• Copying / unexpected licensing — no evidence found.

The one item that could have carried weight — the specification's assertion that laboratory testing showed foam pads gave "very little lateral dissipation of energy" — is a statement of the problem, not evidence of an unexpected solution, and it is unsupported by any comparative data in the record.

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9. Overall assessment

Bottom line. Under current § 103, US 4,375,108's claims are vulnerable to a combination of references already cited on its face: US 4,023,213 (Pepsico/Rovani) for the multichambered, orifice-interconnected, heat-sealed, shell-mounted fluid cushion contacting the head; US 4,060,855 (Kendall) for the nested flexible air-liner helmet environment and the insert-receiving openings; US 4,038,700 (Györy) for throttled inter-chamber passages, delay devices, and rupture redundancy; and US 3,668,704 (Conroy) for the head-contacting inflatable liner that sizes and supports the shell. The only limitation with real patentable weight — chambers in concentrically arranged pairs divided by a common wall — is addressed either by FR 2,272,617 (Leighton) (the skull/meninges two-stratum system, subject to verification) or, failing that, by the predictable-expedient rationale of KSR (a shared septum is the inherent, zero-cost result of bonding two opposed formed pockets). Dependent claims 2–4 add only conventional fabrication geometry that the references and the specification's own admitted process (dielectric bonding, die trimming, mold-release angles) supply. No secondary consideration in the record counterbalances this.

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10. Confidence, gaps, and flags

1. Highest-value verification item: FR 2,272,617. Ground III and any assertion that limitation 1.3 is squarely met depend on its drawings/text showing a continuous divider between two concentric conformable layers. I retrieved only the bibliographic entry; I did not verify its disclosure. Treat Ground III as provisional.
2. US 3,994,020 / 3,994,021 / 3,994,022 / 3,462,763 not retrieved. My treatment relies on the '108 specification's own admission of their content (nested paired fluid-filled liner members with trapezoidal openings) and their indexed titles ("Protective helmet with liner means," etc. for the Canadian counterparts CA 1,059,251/252/253). The admission is itself citable evidence, but the primary texts should be pulled for the claim chart.
3. US 4,060,855 verified verbatim (title, assignee "The Kendall Company," filing 1975‑06‑05, issue 1977‑12‑06, and the nestable-liner disclosure). I did not verify its inventor's name.
4. Prosecution history not obtained. I cannot state whether a § 103 rejection was made and overcome, nor the stated reason for allowance. The "cited by examiner" asterisk convention is Google Patents' own legend and is reported as an inference, not a file-wrapper fact. The 78-vs-130 cited-by discrepancy noted in the earlier section is unresolved and immaterial here.
5. No contradiction with the earlier sections other than a minor naming variance: the earlier record flags "Univ. of Michigan System" vs. "Regents of the University of Michigan." Nothing in this § 103 analysis turns on assignee identity, since all references pre-date the 1981‑01‑28 filing and none is commonly owned with the '108 in a way that would trigger § 103(c)/pre-AIA § 103(c). I treat all five face citations and the four specification-referenced patents as available prior art.
6. Statutory-erasure note. Because the patent expired in 1991, this analysis cannot lead to an IPR/PGR or a declaratory-judgment invalidity ruling; it is of documentary and defensive value only. Anyone reviewing the portfolio should also not confuse this patent with the unrelated "508 patent" owned by MCOM IP, LLC, previously flagged as a false positive.