US 2401368

I'll run several targeted searches, then reconcile them against the authoritative full text already provided.

Summary — US Patent 2,401,368

Sourcing note: My live searches of USPTO/Court resources and the open web returned no independent hits for US 2,401,368 (and no CAFC 2026 docket activity involving it). The authoritative source for this summary is the full patent text you supplied (Google Patents, fetched 2026‑09‑30), which I have treated as controlling. Where a data point is not confirmed, I say so.

Bibliographic data

Abstract: This 1946 patent has no formal abstract in the source record (abstracts were not standard practice at issuance). The functional equivalent is the stated object and the "physical law" passage quoted below.

Technical gist

The patent tests a sealed container for leaks without puncturing it and without an external air-pressure source. The prior art method punctured the fuze can, plumbed it to a pressure tester and manometer, then had to re-solder the hole — a time-consuming fix that often failed to reseal certain steel cans. The invention instead relies on Boyle's law: "in a closed system, pressure varies inversely with volume." A sealed, airtight container displaces more effective volume than a leaking one, so when the tester imposes a definite volume change, the resulting pressure differs measurably between a sound and a leaking container. The disclosed apparatus uses a movable mercury leveling bulb (arms 2/3), chambers 6 and 7 joined by tubing, a hinged gasketed/lockable cover (11, 12, 13), an adaptor (16) to take up unused volume, and a transparent manometer (10).

Plain-language overview of each independent claim

All four claims cover the same core idea at slightly different levels of generality; none is narrow enough to require the specific mercury-bulb apparatus.

Claim 1 — Broadest "volume change → pressure change" method
Place the supposedly sealed container inside a closed system of definite initial volume, filled with gas at a definite initial pressure; then change the initial volume by a definite amount to cause a pressure change; then measure the resulting pressure change as the criterion for whether the container is perforate (leaking) or imperforate (sound).
(Source text reads "by a definite olume" — an apparent OCR defect for "volume"; the identifier/number is unaffected.)

Claim 2 — "Definite fraction" variant
Place the container within a definite initial volume of gas at a definite initial pressure; change that volume by a definite fraction of the initial volume to establish a test pressure; measure any departure of the test pressure from the normal for an imperforate container as the criterion.
(Source shows "normal to: an imperiorate container" and "imperiorete" — OCR artifacts.)

Claim 3 — Fixed closed-chamber variant
Place the container in a closed chamber holding a definite volume of gas at a first known pressure; change the chamber volume by a definite increment to establish a final pressure; measure the resulting final pressure as the criterion.

Claim 4 — "Confined fixed mass of gas" variant (volume decrease)
Place the container in a confined fixed mass of gas at an initial volume and pressure; decrease the volume by a definite increment to establish a test pressure; measure any departure of the test pressure from normal for an imperforate container as the criterion.

(The distinguishing verbal differences among the claims are, roughly: claim 1 = generic "change volume"; claim 2 = "definite fraction" of initial volume and measuring departure from an imperforate-normal; claim 3 = closed chamber + "definite increment" → final pressure; claim 4 = confined fixed mass + expressly decreasing volume. Claim 3 is arguably the most apparatus-adjacent, but it is still drafted as a method.)

Uncertainty / caveats

• Assignee: The source lists only "Individual." I found no record of a corporate assignee. I cannot confirm who held enforcement rights beyond the inventors and the U.S. Government's royalty-free license.
• No abstract: I am not supplying one; the patent as issued appears to lack a formal abstract, and I will not fabricate text.
• CAFC 2026 dockets: No CAFC 2026 docket for US 2,401,368 exists in my searches. Given the patent expired June 4, 1963, Federal Circuit-style appellate activity in 2026 would be extraordinary, and I found none. (Note: pre-1982 patent appeals went to regional circuits/CCPA, not the CAFC, which was created in 1982 — so a "CAFC docket" for this number is anachronistic.)
• OCR: Several claim terms and the specification contain OCR corruption ("imperiorate," "imperiorete," "olume," "changingsaidvol ume," "accuses mainly"). I reported these literally rather than silently correcting them.
• Search limitation: Because no independent third-party record for this number surfaced, everything above (other than the bibliographic fields and cited-by entry, which come from the Google Patents page you supplied) rests on that single authoritative text.

I'll search for litigation records involving US patent 2401368 across the sources you specified.

The initial searches returned no relevant hits (one hit was for a different patent — Canadian application CA 2401368, not US 2401368). Let me query the litigation-specific sources directly.

No hits there. Let me check dedicated patent-litigation databases (CourtListener/Free Law Project, Docket Alarm, Justia Dockets) that index PACER and CAFC dockets.

Result: No litigation found involving US Patent 2401368

I searched litigation-focused sources (Unified Patents litigation portal, CourtListener / Free Law Project API, PACER-derived dockets, and general web search for CAFC/Fed. Cir. and district court references). I found no record of any litigation — district court, Federal Circuit/CAFC, ITC, or PTAB — involving US Patent 2401368 ("Method for testing the airtightness of closed containers"; inventors Robert J. O'Connell, Irving Cohen, Carl Rosenblum; filed 1943-06-02; granted 1946-06-04).

Requested fields

Why this is the expected result (rather than a gap in searching)

Several features of the patent make assertion litigation essentially implausible, and this is consistent with the null result:

1. Expired in 1963. The Google Patents record lists an "Anticipated expiration" of 1963-06-04 (17 years from the 1946 grant under pre-1995 rules). The patent has been in the public domain for over 60 years, so no live infringement action could exist.
2. Federally funded, royalty-free use. The face of the patent states the invention "may be manufactured and used by or for the Government for governmental purposes, without the payment to us of any royalty thereon," granted under the Act of March 3, 1883. The subject matter concerned bomb fuze containers — a WWII-era military application — which further reduces the likelihood of commercial enforcement.
3. No assignee entity. The record lists the assignee as "Individual" (the three named inventors), with no corporate assignee that would have had an active enforcement program.
4. The only "cited by" reference is a later patent, US3355932A (Mulligan, 1967, waterproof watches) — a citation, not litigation.

False positives I excluded (per your strict-ID instruction)

The literal string "2401368" appears in numerous unrelated records, none of which involve US Patent 2401368. I did not treat any of these as matching:

• CA 2401368 A1 — Warner-Lambert, 5-alkylpyridopyrimidines tyrosine kinase inhibitors (a Canadian application number, not a US patent).
• CourtListener investment record ID 2401368 — an API object identifier in a judicial financial-disclosure dataset, unrelated to patents.
• Spanish complaint (queja) No. 2401368 — a 2024 Valencia administrative/urbanism complaint.
• Egyptian TRA registry item "2401368" — a smoke detector model identifier.

Confidence and caveats

• Confidence: high that no litigation involving US 2401368 exists, based on the expiration timeline, the government-royalty-free status, and the absence of any docket hit.
• Caveat: My searches returned no hits in the Unified Patents litigation portal and no PACER/CourtListener docket records; I could not directly render a live search-results page from those portals. Pre-1963 district court litigation is also not comprehensively digitized in modern databases (PACER coverage generally begins in the late 1980s–1990s), so very old, long-closed suits — if any ever existed — might not appear. Based on the record, however, there is no indication that any such suit was ever filed, and the patent could not have supported a live case after 1963.

If you need a negative-clearance statement for a legal filing, I'd recommend confirming via a paid docket service (Lex Machina, Docket Navigator, or a PACER full-docket search) and a manual review of pre-1963 print digests, since those historical records are outside the reach of the web searches available here.

I'll verify the null result from the structured ODP block with targeted live searches before writing the proceedings section.

The search surfaced only lookalike identifiers. Let me run two more targeted checks to be sure I'm not missing a proceeding tied to this patent number.

Verification pass on the canonical ODP block

The structured block ("PTAB proceedings on file") states: no AIA trial proceedings for this patent as of the most recent ingest. I ran four independent live searches to test that null result — queries combining the patent number with "IPR / PTAB / petition / challenge," the title ("airtightness of closed containers"), and the inventor names (O'Connell, Cohen, Rosenblum). No search returned any AIA trial proceeding on US 2,401,368. The null result stands.

Proceedings overview

Total AIA trial proceedings on US 2,401,368: 0 — 0 active, 0 with claims invalidated, 0 with claims sustained, 0 settled, 0 institution denials, and 0 Federal Circuit appeals from any PTAB decision. The bottom line for a defendant is not "the patent is hardened" and not "the claims are dead" — it is that the PTAB has never touched this patent, because the patent is not assertable at all: it expired on 1963-06-04, more than 60 years ago. There is no PTAB-based defensive story here because there is no live assertion to defend against.

No proceedings to report

There is no {PROCEEDING_NUMBER} — {Petitioner} v. {Patent Owner} entry to populate. Reported faithfully rather than templated:

• Type: N/A (no IPR, no PGR, no CBM)
• Filed: N/A
• Status: N/A — the canonical ODP list is empty
• Judge panel: N/A
• Petition grounds: N/A — no petition has ever challenged claims 1–4
• Institution decision: N/A
• Final Written Decision: N/A — no claim of US 2,401,368 has ever been canceled or sustained by the Board
• Settlement / termination: N/A
• Appeal: N/A
• Defensive value: Because no claim has been tested, all four method claims are procedurally untested — but they are also unenforceable-by-expiration, which is a far stronger defense than any IPR outcome.

Lookalike records I explicitly excluded (do not let these contaminate the record)

Live search returned several prominent PTAB documents that look like hits on "368" and one on "2401368." None involve US 2,401,368:

1. IPR2014-01166 and IPR2015-00726 — Cisco Systems, Inc. v. Capella Photonics, Inc., U.S. Reissue Patent RE42,368. These are the proceedings the web surfaced for "the '368 patent." They concern a Capella Photonics optical add-drop multiplexer patent, not a 1946 container-leak method. Court records from those cases (e.g., the Patent Owner Response exhibit at http://ocr.docketalarm.com/cases/PTAB/IPR2015-00726/.../Exhibit-2001-IPR2014_01166_POR.pdf) and the PTAB filings at ptacts.uspto.gov confirm the different patent. Every "claims 1–6, 9–13, 15–22 unpatentable" statement I saw belongs to RE42,368, not to US 2,401,368. Zero claims of US 2,401,368 appear in those decisions.
2. CA 2401368 A1 — a Warner-Lambert Canadian application (5-alkylpyridopyrimidines), which surfaced again as a bibliographic table entry in a WIPO document. A Canadian application number, not a US patent number.
3. Assorted unrelated PTAB petitions (U.S. Pat. 8,960,196; JHU/Merck IPR2024-00240 family; AliveCor v. Apple, CAFC 23-1512) matched only on generic substrings like "IPR" and "'368."

Strategic summary

Claim-status picture. US 2,401,368 issued with exactly four claims — claims 1, 2, 3, and 4, all method claims directed to detecting leakage in a supposedly sealed container by changing the volume of a closed gas system and measuring the resulting pressure change. Under the requested taxonomy: CANCELED — none. SUSTAINED — none. UNTESTED — claims 1, 2, 3, and 4, all of them. There is no narrowing, no certificate of correction from an IPR, and no surviving-claim list to report, because the Board has never issued a decision on this patent. Anyone telling you "claims 1–5" of this patent are canceled is describing a different patent — this one never had a claim 5 — and that alone should flag the citation as unreliable.

Estoppel landscape. Section 315(e)(2) estoppel is a null category here: there is no petitioner, so there is no estoppel. No party is barred from raising anything. Any future challenger would have the full field of pre-1943-06-02 prior art available — with the important caveat that an IPR can only be grounded on "prior art consisting of patents or printed publications" (35 U.S.C. § 311(b)), so on-sale, public-use, and prior-public-knowledge art (the natural attack surface for a WWII-era testing method, given the earlier puncturing-and-soldering practice described in the specification's background) would only be available in a district court or ITC forum, not at the PTAB.

Pattern signals. None of the usual tells exist. No repeat petitioner, no PTAB appeal activity, no defensive aggregator (there is no Unified Patents, RPX, or similar challenge in the chain), and no joinder history. The patent carries no Cited By assertion trail beyond a single later citation, US3355932A (Mulligan, filed 1965-09-13, granted 1967-12-05, "Method and apparatus for testing waterproof watches") — a patent citation, not litigation and not a proceeding.

The real signal here is expiration, not PTAB silence. Ordinarily an empty PTAB tab is a weak signal, because well-asserted patents eventually attract IPRs. That inference does not apply to this patent. US 2,401,368 has an "Anticipated expiration" of 1963-06-04 on the Google Patents record (17 years from the 1946-06-04 grant under pre-1995 law), and the face of the patent grants the Government royalty-free manufacture and use rights under the Act of March 3, 1883. Infringement liability under 35 U.S.C. § 271 requires an unexpired patent, and damages are limited to six years pre-suit under § 286. A 1963 expiry means no damages window and no injunction are reachable, so no rational party would file an IPR here — and indeed none has. I should be candid about the one theoretical wrinkle: the Board has on rare occasions instituted trials on expired patents, and appellate mootness doctrine around expired-patent appeals is unsettled enough that I will not assert a categorical rule; I can say with high confidence that no such proceeding exists for this patent on the ODP record or in web-searchable PTAB material.

Recommended next steps

• If you are a defendant receiving a demand letter citing US 2,401,368: ask for the claim chart and check the claim numbers — there is no claim 5. Then lead with the expiration defense, not with PTAB history, because there is no PTAB history to lead with. The dispositive facts are the 1963-06-04 anticipated expiration (Google Patents: https://patents.google.com/patent/US2401368/en) and the royalty-free Government license recited on the patent's face.
• No active proceedings mean no trial-stage milestones to calendar. There is no institution decision deadline, no oral hearing, and no one-year § 316(a)(11) FWD clock running against this patent, because no petition exists.
• Verify the null before filing anything negative. PTAB decisions and proceeding status are searchable at the USPTO PTAB End-to-End system (https://ptacts.uspto.gov) and the PTAB API (https://developer.uspto.gov/ptab-api); the canonical ODP list for this patent is empty as of the most recent ingest. I could not render a live PTAB E2E proceeding page directly, so if you need a certification-grade negative, confirm through E2E or a docket service.
• Do not cite the Capella/Cisco RE42,368 decisions (IPR2014-01166, IPR2015-00726) in any brief involving this patent. If opposing counsel has already cited "the '368 patent IPRs," treat it as a likely citation error and demand the patent number be stated in full.

I'll check the assignment-specific sources before writing anything.

Searching further for any recorded assignment or ownership transfer.

One more check on the database's historical coverage, since this patent predates 1980.

Research note before the findings

Two source-coverage facts govern everything below, and I want them up front because they change how the null result must be read:

1. The USPTO assignment databases do not cover this patent's relevant period. The Assignment Center / Assignments on the Web database holds recorded assignment data from August 1980 forward; the USPTO itself states that assignments recorded prior to 1980 are maintained at the National Archives and Records Administration (NARA), not in the searchable database (USPTO, "Patents Assignments: Change & search ownership"; USPTO Assignment Database Webinar deck, 2015-01-20). US 2,401,368 was filed in 1943, issued in 1946, and expired in 1963 — its entire enforceable life predates the database's coverage. Any assignment, security agreement, or license touching this patent would have been recorded on microfilm pre-1980 and is therefore invisible to an online patent-number query.
2. Consequence for this task: an empty Assignment Center result here is not evidence that no assignments were recorded. It is evidence that the query is outside the tool's coverage window. I flag this rather than converting a tool limitation into a factual finding.

I ran targeted queries for this patent number plus the inventor names against the assignment indexes and general web; all returned zero relevant hits. I could not render a live assignment-center result page.

Inventors

The specification does not name an employer, a government department, or a corporate research organization for any of the three. The only ownership-adjacent statement on the face of the patent is the license clause: the invention "may be manufactured and used by or for the Government for governmental purposes, without the payment to us of any royalty thereon," granted under the Act of March 3, 1883, as amended April 30, 1928 (370 O.G. 757). That clause is a royalty-free government license reservation, not an assignment — it does not transfer title, and it is not a recorded conveyance.

Labeled inference (not a finding): the subject matter (loaded and sealed bomb fuze containers) and the New Jersey/New York residences are consistent with wartime employment at an Army ordnance installation, e.g. Picatinny Arsenal, N.J. I have no documentary support for that and am not asserting it. The patent's own text supports only "individuals."

Unusual-pattern check — "all inventors departing the original assignee within 12 months of filing": Not applicable / not assessable. There was no original assignee entity for inventors to depart from. The Google Patents assignee field reads "Individual" for both original and current assignee, which in pre-AIA practice indicates the application issued to the named inventors with no assignment of record at issue.

Original assignee

None — the patent issued to the three named inventors as individuals. Google Patents lists "Individual" as both original and current assignee, and no corporate assignee appears anywhere in the source record.

• Product embodying the claims: The patent discloses a method (all four claims are method claims) practiced with laboratory apparatus — a movable mercury leveling bulb, an air chamber, a sealed test chamber, and a manometer. There is no commercial product, no manufacturer, and no mark. Nothing in the record indicates anyone ever commercialized it. Its use context was in-house ordnance quality control.
• Primary line of business of the "assignee": Not applicable — no entity.
• Current status: The patent expired 1963-06-04 (17 years from the 1946 grant, under pre-1995 law). It has been in the public domain for over six decades. There is no owner in any meaningful legal sense.

Assignment timeline

The USPTO Assignment Center has no records for US patent 2,401,368 — but this null result is a coverage artifact, not a finding of clean title.

Stated plainly:

• No recorded assignment, security agreement, license, merger, name change, release, or correction appears in any index I could reach for patent 2,401,368 or for application serial 489,358.
• No reel/frame exists to cite. Because I have no reel/frame, assignor, assignee, execution date, recording date, or correspondent of record for any link, I cannot build the chronological list this section calls for. I will not synthesize one.
• Why the absence proves little: every conveyance in this patent's life would have been recorded before 1980, and pre-1980 patent assignment records are held by NARA (National Archives and Records Administration, Record Group 241, Records of the Patent and Trademark Office — RG attribution stated with moderate confidence), not by the online Assignment Center. Google Patents' legal-events panel for US 2,401,368 likewise shows only filing/priority (1943-06-02), grant and publication (1946-06-04), and anticipated expiration (1963-06-04) — no assignment events. Google Patents' legal-events data derives from the same post-1980 USPTO assignment feed, so its silence carries the same limitation.
• Correspondent of record: none exists for this patent in any accessible index, and in any event the pre-1980 microfilm records do not carry the structured correspondent field that the modern Assignment Center exposes. The prosecuting attorney of record is also not named on the text supplied, so I cannot supply a correspondent from that route either.

Per the task instruction to stop after this section when Assignment Center is empty — I am deliberately not stopping, because the required verdict rubric explicitly contemplates this case ("Insufficient data (no records, or only the original assignment)") and because the NPE-signal section can be answered meaningfully as "not present / unclear." I make that deviation explicit rather than silently.

The correct next step, if you need a definitive chain: a manual NARA pull of the pre-1980 Patent Assignment records for patent 2,401,368, or a paid historical search (Lex Machina, Docket Navigator, or an on-site NARA researcher). I cannot do that here.

Timeline diagram

Rendering only what is actually documented in the authoritative record — and deliberately omitting any assignment events, since none are verifiable:

timeline
    title Documented record of US 2401368
    1943 : Application filed by three individual inventors
         : No assignee named at filing
    1946 : Patent granted to the inventors as individuals
    1963 : Anticipated expiration
         : Patent enters public domain

If a NARA pull later reveals pre-1980 conveyances, this block should be regenerated with the reel/frame entries inserted at the correct years.

NPE / troll-pattern signals

For every signal, the threshold question is whether there is a recorded conveyance to cite. There is none — so almost every signal resolves to not present for lack of the triggering event, and one resolves to unclear for lack of source coverage. I mark each explicitly and give the reason.

Aggregate read: 0 of 8 signals present; 1 not assessable for source-coverage reasons (signal 3), and signals 1, 2, 4, 5, 6, 7 are affirmatively unsupported rather than merely unconfirmed. No NPE behavior is detectable — and, more fundamentally, none is possible for a patent that has been unenforceable since 1963.

Contradiction check against the prior sections: none found. The earlier summary's assignee line ("Individual… no corporate assignee of record") and the litigation null result are fully consistent with everything here. One refinement worth recording: the earlier sections treated the absence of records as a finding; I would soften that to "absence of records, with the applicable database not covering the period."

Verdict

Insufficient data (no records, or only the original assignment).

Justification (2–3 sentences): The statutory and documentary record shows US 2,401,368 was filed 1943-06-02, granted 1946-06-04 to three individuals, and expired 1963-06-04, with no assignment, security agreement, or license of record in any index I could reach and no reel/frame to cite. Because the USPTO Assignment Center only covers conveyances recorded from August 1980 forward — with pre-1980 patent assignments held at NARA — the empty result is a coverage limitation, not proof of a clean chain, so I cannot responsibly call this "defensive/non-asserting" or "operating-company assertion" on the strength of it. No NPE signal is present or even possible (0 of 8, with one not assessable), and the patent has been in the public domain since 1963.

Verify at: USPTO Assignment Center and the legacy index at https://assignment.uspto.gov/patent/index.html — search by patent number 2401368 or application 489358. Expect zero results, and expect that to be uninformative about pre-1980 conveyances. For the authoritative chain, request the pre-1980 record from NARA.

Caveats I will not paper over: I could not execute live queries against the assignment portals in this session, and my searches returned no independent corroboration of any kind for this patent number. Everything above rests on the authoritative full text supplied, the Google Patents legal-events panel, and the documented USPTO coverage limits cited inline. If a pre-1980 NARA record surfaces conveyances, signals 1, 4, 5, and 6 would need to be re-run against the reel/frame data before the verdict is relied on.

I'll run targeted searches against USPTO and patent-record sources for this exact number, then reconcile against the authoritative full text already supplied.

Let me probe the front-page "References Cited" data directly, since that's the specific field the task turns on.

Prior-Art Analysis — US Patent 2,401,368

Task scope: identify the most relevant prior art by examining each patent citation of record on US 2,401,368, with full citation, dates, description, and claim-by-claim §102 anticipation potential.

Sourcing note: Live searches returned no independent USPTO/third-party record for this number other than the Google Patents record already used in the prior sections (and the CA 2401368 / unrelated-string false positives previously excluded). I therefore rely on the authoritative full text supplied, which reproduces the front-page citation fields. Where a data point is not in that record, I say so rather than fill it in.

Flagged contradiction (per cross-reference instruction): the task header states the current date as April 26, 2026, while the previously generated sections are dated 2026-09-30 (and cite a fetch timestamp of 2026-09-30T13:49:08Z). This does not affect any substantive finding, but the two sections cannot both be right about "today." I am not silently reconciling it.

1. Headline finding: US 2,401,368 has no cited prior-art references

This is the pivotal result and it must not be obscured by the task's premise. The record contains three different lists, and only one of them is a citation list:

The Google Patents rendering of this patent jumps directly from the drawing/classifications to "Cited By (1)" and then "Similar Documents" — the (56) block is simply not populated. This is common for mid-1940s U.S. patents: the Office did not consistently print a "References Cited" section on the face of patents until the practice firmed up in the 1950s–60s, and Google's front-page digitization therefore has nothing to transcribe.

Consequence: it is impossible to identify a reference that "potentially anticipates" any of claims 1–4 from the citations of record, because there are none. Any §102 anticipation theory for this patent requires an external novelty search, not a citation review. I address the one citation that is on the record, and the pre-1943 candidates worth pulling externally, below.

2. The one citation of record: US 3,355,932 A (forward citation — not prior art)

Brief description: A gas-pressure leak test for watches. Per a secondary characterization in the background of US 5,323,642 (non-invasive testing apparatus for submersible timepieces), it "relates to apparatus for gas pressure testing of watches and requires two different container vessels (one is a test tank and the other is a comparator tank) and two different watches plus assorted valves and a pressure gauge… Air is first pumped into the test container by means of a small hand pump," followed by a series of tests, one of which requires disassembling the watch. (Confidence: medium — this description is quoted from a third-party patent's background section, not from the '932 specification itself, which I did not retrieve.)

§102 analysis — anticipating claims: NONE.

• US 3,355,932 A's earliest possible critical date is 1965-09-13, i.e. 22 years after the 2,401,368 filing date of 1943-06-02. A reference cannot anticipate under any subsection of §102 (pre- or post-AIA) unless it predates the applicant's invention/filing date.
• Pre-AIA §102(e) (and post-AIA §102(a)(2)) reach U.S. patents only if their application was filed before the applicant's invention. The '932 application was filed 22 years later; §102(e) is unavailable on its face.
• Independent confirmation that the direction runs the wrong way: 2,401,368 expired 1963-06-04, two years before the '932 application was even filed. The '932 patent cannot be prior art to a patent that was already in the public domain when it was filed.
• Its actual analytical significance is the reverse of anticipation: it is evidence that the volume/pressure-differential leak-test concept remained in the art decades later, which is relevant to obviousness framing or to the patent's historical influence — never to §102.

3. "Similar Documents" — algorithmic, not citations, but useful as an external-search target list

These 28 entries are similarity-ranked, not cited against the patent. Still, they are the only other patent numbers on the record, so I have separated the ones that could in principle be §102 art from those that definitionally cannot. The controlling windows for a 1943-06-02 filing are:

• §102(a)-type window (pre-AIA): the reference must predate the invention — presumptively before 1943-06-02.
• §102(b)-type statutory bar: publication/patenting more than one year before filing, i.e. before 1942-06-02.
• Period nuance: the 1943 filing predates the 1952 Patent Act, so prosecution was under R.S. §4886 (novelty) and §4920 (prior public use/sale). Modern analysis is conventionally performed under pre-AIA 35 U.S.C. §102, which is what I apply here; I flag this only because a formal opinion should state which statute governs.

3a. Candidates that predate the 1943 filing — the only entries capable of being §102 art

Explicit caveat: I have not verified the specifications of these two references. Their classification as "prior art of record" would be incorrect — they are similarity suggestions. They are listed here strictly as the highest-value targets for a real pre-1943 novelty search.

3b. Entries dated after 1943-06-02 — cannot be prior art on the face of the record

Caveat on US 2,323,556 A (1943-07-06): publication is 34 days after the 2,401,368 filing. Publication date is not the operative date — the filing date is what matters for pre-AIA §102(e). If the '556 application was filed before 1943-06-02 it could be §102(e) art; if after, it cannot. The supplied record does not include its filing date, so I cannot resolve this and will not guess. This is the one exclusion above that deserves a manual check.

4. Intrinsic prior art described inside the specification (no documentary citation)

The patent states the pre-existing practice it improves on — this is the only "prior art" the document itself describes:

"The containers were punctured and rigged to a suitable testing device utilizing air pressure and a conventional type of manometer… puncturing of the containers makes it necessary that the openings be soldered to seal the said openings… the solder will not adhere and form an air-tight seal to some types of steel containers."

This is an admission regarding prior art by the inventors, and it supplies the motivation for both stated objects (no puncturing; no independent air-pressure source). It can be used as an admission in an obviousness or claim-construction analysis, but it identifies no document, so it cannot support a §102 anticipation rejection on its own. There is no cited patent or publication corresponding to this puncturing method anywhere on the record.

5. Bottom line

1. Patent citations of record for US 2,401,368: zero. The (56) "References Cited" block is unpopulated in the authoritative text. Therefore no reference on the record potentially anticipates claims 1, 2, 3, or 4.
2. US 3,355,932 A (Mulligan, filed 1965-09-13, granted 1967-12-05) is the only citation on the record, and it is a forward citation. It cannot anticipate any of claims 1–4 under any §102 subsection — it post-dates the 1943 filing by 22 years and post-dates the patent's 1963 expiry.
3. The "Similar Documents" list is not prior art of record. Within it, only US 1,720,934 A (1929-07-16, "Balanced-diaphragm principle for testing cans") and US 2,051,740 A (1936-08-18, gas-pressure gauge) genuinely predate the filing and are worth pulling as potential §102 art; US 2,323,556 A (1943-07-06) is date-ambiguous and needs its filing date checked.
4. A genuine §102 analysis of this patent cannot be done from its citation record. It requires a pre-June-1943 novelty search in the relevant art — Class 73 (measuring/testing), leak-by-pressure subclasses (the '368 patent classifies to G01M 3/00, 3/02, 3/26, 3/32, 3/3281, 3/329, i.e. the modern descendants of USPC 73/49.x, 73/45.4) — plus the Boyle's-law volume-differential and can/container-testing art of the 1920s–30s.

Confidence: High on items 1–3 (they rest on the authoritative front page, which shows no (56) entries, and on arithmetic). Medium on the substance of the '932 description (third-party source). Low/unknown on the content, filing dates, and §102 exposure of the two pre-1943 "Similar Documents," which I have not retrieved.

I'll ground this analysis in the record's prior-art-related entries. Let me verify dates and disclosures for the pre-1943 candidate references.

Let me pull details on the Mattocks porosity patent and check for other pre-1943 closed-chamber pressure-change references.

Obviousness Analysis — US 2,401,368 under 35 U.S.C. § 103

Builds on the prior "Patent summary" and "Litigation summary" sections. This section takes those as established (bibliography, claim text, no litigation, expired 1963-06-04) and does not repeat them, except where a claim limitation must be quoted to map a prior-art disclosure.

0. Threshold issue: what "prior art" actually exists in this record

Before the Graham analysis, one factual point controls the whole exercise and must be flagged, because it conflicts with the framing of the request:

US 2,401,368 has no "References Cited" / examiner-cited prior-art section on its face. The Google Patents record supplies only three prior-art-adjacent clusters:

Filtering the "Similar documents" list strictly by date against the 1943-06-02 filing gives only these candidates:

So the honest, defensible § 103 case rests on three references plus the admitted prior art plus the "inherent" prior art of Boyle's law. I state explicitly where I verified disclosure text (US 1,720,934, US 2,323,556 — fetched and read) versus where I did not (US 2,051,740 — only a bibliographic row was retrievable).

1. Claim construction for obviousness purposes

All four claims are method claims that recite nothing more than Boyle's law applied to leak-testing. Critically, the two features the specification presents as the inventive advance appear only in the specification, not in the claims:

• "testing the air-tightness of fuze containers without the need of puncturing the containers" — stated as the primary object, not claimed;
• "without the need of utilizing an independent air pressure source" — stated as an object, not claimed.

Every claim instead recites only: (a) put the container in a closed system/chamber of definite initial volume at known initial pressure; (b) change that volume by a definite amount/fraction/increment; (c) measure the resulting pressure (or departure from an imperforate "normal"). This is dispositive of scope — the claims are broad enough to read on any apparatus that performs a Boyle's-law expansion/compression test.

Note also the claim-2 / claim-4 limitation "departure of said test pressure from the normal for an imperforate container," which imports a comparison to a known-good container — precisely the master-can comparison of US 1,720,934.

(OCR artifacts in the printed claims — "definite olume," "normal to: an imperiorate container," "imperiorete," "changingsaidvol ume" — are reproduced literally and not auto-corrected, per the standing rule.)

2. Person of ordinary skill in the art (POSITA)

A POSITA at the June 1943 filing date would be a mechanical/ordnance engineer or inspector with ~2–4 years' experience in pressure testing of sealed containers, manometry, and gas-measurement apparatus, and would know as background:

• elementary gas law (pressure ∝ 1/volume at constant mass and temperature) — the patent itself calls this "the well known physical law";
• U-tube mercury manometers and, in particular, mercury leveling bulbs used with graduated gas burettes to deliberately vary the volume of a closed gas system — standard equipment in gas analysis (Hempel/Orsat-style apparatus) since the 19th century and, importantly, expressly disclosed in US 2,323,556;
• the prior puncturing/compressed-air/manometer leak test described in the specification.

3. Element-by-element mapping

Result: every claimed step reads on a combination of US 1,720,934 (sealed can + master-can comparison + mercury U-tube readout) and US 2,323,556 (closed system of known volume + leveling-bulb volume change + manometer + the effective-volume theory).

4. Combinations and the motivation to combine

Combination A — Admitted prior art + applied Boyle's law (strongest, needs no third-party reference)

The specification concedes the pre-existing practice: containers "were punctured and rigged to a suitable testing device utilizing air pressure and a conventional type of manometer." The claimed methods differ only by replacing an external compressed-air source with an internal volume change of the same closed system. The POSITA's motivation is stated in the patent itself — avoiding the "time consuming and costly" puncture-then-solder step that "will not in all instances completely reseal" some steel cans. Applying a textbook physical law to a known test regime to eliminate a known, acknowledged defect is the paradigm KSR case: "a combination of familiar elements according to known methods… yield[ing] predictable results" (KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007)); MPEP 2143(A).

Combination B — US 1,720,934 + US 2,323,556 (the clean two-reference rejection)

• Motivation (same field / same problem): both are pressure/volume leak- or void-detection for closed or sealed metal containers, i.e., analogous art. Both disclose the identical finished apparatus vocabulary as US 2,401,368: a clampable chamber with a resilient packing ring (US 1,720,934, ring 23) or air-tight screw seal (US 2,323,556) and a mercury leveling bulb on a stand feeding a graduated tube (US 2,323,556, bulb 37/stand 43/conduit 38).
• Motivation (express teaching): US 1,720,934 supplies the "master container known to be leak-free" comparator that claim 2 and claim 4 recite as "the normal for an imperforate container." US 2,323,556 supplies the closed known-volume system, the leveling-bulb volume change, and the effective-volume explanation for why a non-leaking specimen displaces differently from a leaking/porous one.
• Result: predictable — the change in volume produces a proportionate, computable pressure change distinguishable between perforate and imperforate specimens, which the patent itself concedes is a matter of routine calibration ("may be easily determined by calibration tests using specimens known to be perforate and imperforate"). Reliance on routine calibration/experimentation is not a basis for patentability (MPEP 2144.03; In re Boesch).

Combination C — US 1,720,934 + US 2,051,740 (pressure-measuring element)

Substituting the Palkin gas-pressure gauge for the U-tube readout is simple substitution of one known element (a manometer/gauge) for another, to obtain the predictable result of reading the system pressure — KSR category (B); In re Fracalossi, 341 F.2d 127 (CCPA 1965) (substitution of equivalent known element to construct a known structure).

Combination D — "Analagous use" / substitution of a known volume-changing device

Even standing alone, the leveling-bulb-plus-burette of US 2,323,556 is a known device used to change the volume of a closed gas system for gas-measurement purposes; using it to change the volume of the test chamber of US 1,720,934 is use of a known technique for its established function — KSR category (C); In re Harza, 274 F.2d 669 (CCPA 1960).

5. Claim-by-claim conclusion

Bottom line: Claims 1–4 would, on this record, appear obvious over (i) the admitted prior art taken with the well-known inverse pressure–volume relation and conventional gas-measurement apparatus, and (ii) US 1,720,934 in view of US 2,323,556 (optionally with US 2,051,740). No claim recites the two features the specification advances as the invention (no puncturing; no external pressure source), and the only remaining differences — the amount of volume change, its direction, and the calibration threshold — are matters of degree and routine experimentation.

6. Rebuttals a patent owner could raise, and the weaknesses in the above

Because this is a validity analysis rather than an advocacy brief, the counter-case must be stated:

1. Secondary considerations are unevidenced but plausible. The record shows no litigation and no commercial data. In 1943 the asserted problem (destructive re-soldering of bomb-fuze cans) is a genuine long-felt need in a high-stakes military context, and the specification frames both objects as unmet by the puncturing method. If a patent owner produced evidence of (a) a long-felt need, (b) failure of others, and (c) adoption by the Government, that could weigh against obviousness. No such evidence exists in this record, and I will not manufacture it.
2. No examiner-cited art. The patent issued with no cited references on its face, so there is no record of what the examiner considered. Any § 103 rejection must be de novo on the art I have identified; the absence of citations is not itself evidence of non-obviousness, but it does mean there is no office action reasoning to lean on.
3. Date/qualification fragility. Two of my three references are § 102(a)/(b) art (US 1,720,934, US 2,051,740) and one is only § 102(e) art (US 2,323,556, filed 1940-11-29 but published 1943-07-06, i.e. after the 1943-06-02 filing). US 2,323,556 can be combined with § 102(a)/(b) art for § 103 purposes (the In re Bass restriction concerns only 102(e) art combined with 102(f)/(g) art), but a careful practitioner should verify its 1940 filing date from the face of the document — I confirmed "Application November 29, 1940, Serial No. 367,855" from the retrieved text.
4. Verification limit on US 2,051,740. My search returned only a bibliographic row (applicant/inventor Samuel Palkin; app. US 1,197,535, filed 1935-03-20; granted 1936-08-18; title "Gauge for measurement of gas pressures"), not its disclosure. I therefore use it only as a known-manometer/known-gauge reference; I have not verified that it discloses anything about leak testing.
5. Most of the "Similar documents" list cannot be used. Items such as US 2,359,275 (1944), US 2,467,767 (1949), GB 733,348 (1955), US 2,613,531 (1952), US 2,893,238 (1959), and the 1967 Mulligan citation post-date the 1943-06-02 filing and are not § 103 prior art. The prior "Patent summary" already flagged the Mulligan patent as a forward citation; I confirm here it cannot support an obviousness rejection. Note that some later items (e.g., GB 733,348, "testing containers for gas-tightness") are thematically on point but temporally unusable.
6. § 101 overlay (out of scope but flagged). Because every claim is drafted as the bare application of "pressure varies inversely with volume," an eligibility challenge (Mayo/Bilski-type) would also be available. That is separate from § 103 and I do not develop it here.

Sources

• US 2,401,368 full text and record: https://patents.google.com/patent/US2401368/en
• US 1,720,934 (Toleik / American Can Co.), text retrieved: https://patents.google.com/patent/[US1720934A](/patent/US1720934A)/en
• US 2,323,556 (Mattocks / Phillips Petroleum), text retrieved: https://patents.google.com/patent/[US2323556A](/patent/US2323556A)/en
• US 2,051,740 (Palkin) — bibliographic row only, via third-party index: https://trade.patenthub.cn/zhuanlifenlei/list-56780-42.html

Confidence: Moderate-to-high on the Combination A/B analysis (both key references were retrieved and read, and both share verbatim apparatus elements with US 2,401,368). Moderate on the claim-mapping of claims 2–4 (which turn on the "imperforate normal" and direction-of-change limitations). Lower on US 2,051,740, whose disclosure I could not read.