US 3423489

I'll ground this in the authoritative patent text provided, and run a couple of searches to check for any litigation/docket trail.

Sourcing note

My authoritative source here is the patent document itself (Google Patents full text, fetched 2026‑09‑30): https://patents.google.com/patent/[US3423489](/patent/US3423489)/en. Two caveats up front:

1. I could not search the USPTO PatentCenter or the CAFC docket system directly — my only tool is a general web search. Searches for "3423489" / "'489 patent" + litigation returned nothing involving this patent (hits for a "’489 patent" in connection with Idenix/sofosbuvir are a different patent number and must not be conflated with US 3,423,489). I therefore have no authoritative CAFC 2026 docket information, and I would not expect any: the record shows "Anticipated expiration 1986‑01‑21" and "Expired – Lifetime," so an appeal implicating this patent in 2026 is essentially implausible.
2. Date conflict: your prompt says April 26, 2026; the environment/system date is 2026‑09‑30. I have not reconciled these; flagging per the "don't auto-correct" rule.

Bibliographic summary — US 3,423,489

Prior art expressly discussed: US 2,799,897 (Jansen, July 23, 1957); US 2,911,672 (Van Erven Dorens); US 3,015,128 (Somerville, Jan. 2, 1962).

Abstract

The fetched document as given to me does not contain a separately labeled "Abstract" field, so I will not invent one. The de facto abstract is the "Briefly summarized" paragraph of the description:

"…the present invention involves forming a concentric biliquid column having an inner core of liquid to be encapsulated and an outer tube of hardenable liquid encapsulating material which is caused to travel as a stream in a trajectory path for a time sufficient to allow the column to constrict due to natural forces, i.e. cohesive forces, surface tension and the like, first into a string of capsules and then ultimately into individual droplets or capsules in which the encapsulating material completely encloses the encapsulated liquid. The encapsulating material is congealed sufficiently upon separation of the stream into individual capsules to withstand impact upon falling. … It is much preferred to direct the biliquid column or stream to travel through a gaseous medium… rather than into a liquid medium."

If you need the official abstract text as printed on the face of the patent, I'd need the USPTO/Espacenet PDF — I can't confirm it verbatim from what I have.

Plain-language overview of the independent claims

The patent has three‑and‑a‑part independent claims. Claims 2–9 depend from claim 1; claims 11–12 depend from claim 10. Caveat: the document text I was given truncates in the middle of claim 12 (description copy) and again in the middle of the third independent claim (claims listing). So I can describe claim 1 and claim 10 with high confidence, and the third independent claim only partially.

Claim 1 — the core process (broadest claim).
Make a biliquid column: a tube of capsule‑shell‑forming material wrapped around a core of the liquid to be encapsulated. Send that column along a trajectory that has a horizontal component (i.e., a free‑flight/parabolic path, not just a straight drop into a bath) and let it fly long enough that natural forces alone (surface tension/cohesion) pinch the column into spheroids, each shell spheroid enclosing a core. Then harden the shell material into solid shells that encapsulate the fill. The point of the "horizontal component" is that the break‑up is driven by the liquid's own physics rather than by a bath, pulses, or a nozzle geometry — and the capsules must harden in flight enough to survive landing.

Claim 10 — the gaseous‑atmosphere variant.
Same idea as claim 1, but expressly requiring the trajectory to be in a gaseous atmosphere and requiring the column to constrict into individual spheroids (rather than merely "spheroids"), each of which completely encloses a fill core, hardened into solid spheroidal shells. This claim is the clean "drop‑in‑air, no hardening bath" statement of the invention. It is the claim the specification's FIGURE 1/3/air‑trajectory teaching is built around, and dependents 11 (shells are spherical) and 12 (column formed by discharging a fill‑material stream as a jet into the encapsulating material) narrow it.

Third independent claim — the parameterized "small capsule" method (claim 13 by position).
Text as it appears (truncated in my source):

"A method for encapsulating liquids in capsules having diameters of from about 10 to 4000 microns comprising providing a hardenable liquid encapsulating material; discharging a jet of fill liquid to be encapsulated from an orifice having a diameter between about 5 and 1500 microns under pressure at a velocity greater than about 1 m./sec. into said encapsulating material, thereby forming a column of enclosing liquid encapsulating material concentrically surrounding said fill liquid, the dimensionless Reynolds number, [text ends]"

So it is the numerically bounded claim: capsule size range (10–4000 µm), orifice size range (5–1500 µm), minimum jet velocity (≈1 m/sec, the stated minimum to form a useful jet), and a Reynolds‑number limitation (the specification requires Re below about 4000, preferably below 2000, for laminar breakup).

Claims 13–15 in full, and the exact independent claim count, cannot be verified from the text I hold — the transcription stops mid‑claim. Note also that the machine‑generated claim paraphrase in the Google Patents "Definitions/claims" index is abridged and reworded (it even preserves a misspelling, "sufiicient," from the OCR); the authoritative claim language is the description's "What is claimed is:" block. If a claim‑by‑claim chart matters for your purpose, pull the granted‑patent PDF or the USPTO image file rather than any auto‑extracted text.

Substantive highlights worth knowing (all directly from the specification)

• No liquid hardening bath required. Hardening occurs in flight, either by ambient gas cooling or — preferred for capsules above ~300 µm — by internal cooling (a fill liquid substantially cooler than the molten shell), which the patent says gives denser, less stress‑cracked, lower‑permeability shells for crystallizable shell materials such as waxes (those showing >10% volume shrinkage on congealing).
• Chemistry is broad: waxes, fats, proteins, carbohydrates, gelatin/agar, low polymers, low‑melting metals/alloys, fusible inorganic salts (e.g., magnesium nitrate hexahydrate), glasses, naphthalene, sulfur, paradichlorobenzene. Fills include water and aqueous solutions, organic liquids, and liquid metals such as mercury.
• Rate claims: 30,000–120,000 capsules per orifice per minute; 26 worked Examples, including Example XXIV (wax shells, reported 0.20%/day diffusional loss, ~241‑day half‑life) and Example XXVI (the FIGURE 2 two‑impinging‑jets variant).
• Claim 9 covers connected strings of capsules (FIGURE 4), with the adhesive‑line application described as a separate utility.
• Surfactant addition is taught to lower fill/shell interfacial tension (preferably <60 dynes/cm; below 10 dynes/cm for aqueous fills in organic shells), and immersion depth of the orifice is the FIGURE 1 knob for shell thickness.

Uncertainties I am not going to paper over: (a) no litigation/CAFC docket record for this number was retrievable, and none is expected given the 1986 expiration; (b) the abstract field is absent from my source; (c) claims after 12 are truncated; (d) some example data are visibly corrupted by OCR (e.g., "3.5-1105mm," "1.2104 mm," half‑numbers where a ± range is intended), so I would not rely on those figures without the PDF.

I'll search the litigation databases for this specific patent number.

Let me check the specialized litigation databases directly.

Let me check Docket Alarm, CourtListener, and Justia specifically.

Litigation Search — U.S. Patent 3,423,489

Bottom line: No litigation involving U.S. Patent 3,423,489 is known. I found zero cases — no district court action, no ITC investigation, no CAFC appeal, no PTAB proceeding, no reexamination.

Retrieval limitation (stated up front, per the "don't fabricate" rule)

My only research tool is a general web search. I could not query the Unified Patents litigation caselist (https://portal.unifiedpatents.com/litigation/caselist), PACER, the CAFC docket, Docket Alarm's case database, or CourtListener's RECAP index as interactive databases — a direct hit query on docketalarm.com "3,423,489" and on CourtListener returned only the platforms' own marketing/document-wrapper pages, not case records. So my negative finding rests on targeted queries across litigation-reporting surfaces, not on a complete docket sweep. I flag that honestly rather than claiming a universal negative.

What the searches did return

Every query for the literal number produced only non-litigation results, and every litigation hit was a different patent with "489" as its trailing digits. Interpreting identifiers literally, none of these is US 3,423,489:

I also re-confirmed via search that no complaint, ITC investigation, or appellate opinion names Arens, Sweeny, or Minnesota Mining and Manufacturing in connection with this encapsulation patent.

Why the null result is the correct answer, not a research gap

This is not a case where absence of evidence is weak evidence of absence. Three independent structural facts make litigation on this patent essentially impossible, and each is verifiable on the face of the document:

1. Expired 1986‑01‑21. The Google Patents record shows "Anticipated expiration 1986‑01‑21" and status "Expired – Lifetime" (https://patents.google.com/patent/US3423489/en). A 17‑year pre‑URAA term running from the 1969‑01‑21 grant. An expired patent cannot support an infringement claim, so no case could have been filed after that date — and none was filed before it on any record I could reach.
2. Damages window closed long ago. Even for pre‑expiry conduct, 35 U.S.C. § 286's six‑year lookback has been exhausted for over three decades.
3. Pre‑AIA patent. Filed 1966‑11‑01, so IPR is the only AIA vehicle even theoretically available (§ 311 reaches "a patent"), and no IPR exists — a result I independently verified in the PTAB section already on the record for this analysis.

Requested table — as populated as the evidence allows

I will not populate a case number or filing date, because doing so would require inventing one.

Cross-reference / contradiction check against the earlier sections

This section is consistent with the previously generated "PTAB challenges" and "Assignment history" sections — all three independently conclude no proceedings exist. One flag, repeated from the earlier work so it is not lost: the prompt's stated date is April 26, 2026, while the environment date is 2026‑09‑30. I have not reconciled that discrepancy and am not treating it as an error.

I also incorporate the standing warning from the PTAB and assignment sections: if anyone asserts "the '489 patent" against you, the probability is overwhelming that they mean a different patent — most likely US 7,978,489 (MyPAQ), US 11,037,489 (Alexander), or US 7,121,489 (Allied), all of which are or have been in active litigation, or the 3M abrasive-article '489 patent from the Kinik ITC action, Inv. No. 337‑TA‑449. Misreading the number is itself a signal about the sender's diligence.

Verification note. The negative finding above reflects searches run on 2026‑09‑30 against litigation-reporting surfaces (search-engine-indexed PTAB filings, district court complaints, Federal Circuit opinions, and litigation-press coverage). It is a strong negative, but it is not a certified PACER/CAFC docket clearance. For a formal clearance opinion, the confirming searches are: PACER Case Locator "Patent Number" search restricted to 3,423,489; the CAFC docket by party (Arens / Sweeny / Minnesota Mining and Manufacturing); and Unified Patents' litigation caselist filtered on the patent number.

I'll verify the structured data with targeted searches before reporting.

Let me run a couple more targeted checks for any AIA trial or post-issuance challenge tied to this specific patent.

PTAB Proceedings Report — U.S. Patent 3,423,489

"Encapsulation process" — Arens & Sweeny, assignors to Minnesota Mining and Manufacturing Co. (3M). Filed 1966-11-01, granted 1969-01-21, expired 1986-01-21. Source: https://patents.google.com/patent/[US3423489](/patent/US3423489)/en

Proceedings overview

Zero AIA trial proceedings (IPR, PGR, or CBM) have ever been filed against U.S. Patent 3,423,489. The structured "PTAB proceedings on file" block from the USPTO Open Data Portal returns none, and independent searching found no petition, institution decision, Final Written Decision, or Federal Circuit appeal naming this patent or its inventors (Arens / Sweeny) as patent owner — so there is no breakdown by status to report (0 active / 0 invalidated / 0 sustained / 0 settled / 0 institution-denied). The bottom-line defensive posture is stronger than any IPR outcome could deliver: the patent expired by operation of law on 1986-01-21, roughly 26 years before the AIA IPR regime existed, so no defendant faces a live infringement claim — a demand letter citing 3,423,489 is facially baseless, not merely vulnerable.

Per-proceeding detail

None — verified negative

There is no {PROCEEDING_NUMBER} to populate, and I will not invent one. For completeness, the fields the template asks for map to "not applicable" as follows:

• Type: n/a — no IPR, PGR, or CBM docket exists for this patent.
• Filed: n/a.
• Status: n/a. (The only status on file is the patent's own: "Expired – Lifetime," anticipated expiration 1986-01-21.)
• Judge panel: n/a — no APJ panel has ever touched this patent.
• Petition grounds: n/a.
• Institution decision: n/a.
• Final Written Decision: n/a.
• Settlement / termination: n/a.
• Appeal: n/a — no FWD exists to appeal. The Federal Circuit has never decided a validity appeal on this patent.
• Defensive value: Total. Any infringement theory premised on 3,423,489 fails at the term, not at the merits.

Why an AIA trial on this patent is structurally implausible (not just absent)

Look-alike dockets — do not confuse these with 3,423,489

Searches for "the '489 patent" surface a lot of unrelated patents. None of the following is US 3,423,489:

• The 3M abrasive-article '489 patent litigated at the ITC in Inv. No. 337-TA-449 and appealed in Kinik Co. v. Int'l Trade Comm'n, 362 F.3d 1359 (Fed. Cir. 2004) (claim construction on "mixture" / liquid-binder volume) — https://www.courtlistener.com/opinion/[785650](/patent/785650)/kinik-company-v-international-trade-commission-and-minnesota-mining-and/. Sole common attribute: same assignee (3M) and a similar last-three-digits shorthand.
• The MyPAQ power-plug '489 patent challenged in an IPR against Samsung Electronics (W.D. Tex. parallel litigation; the petition states "This is the first petition challenging the '489 Patent").
• The Sonos/Google media-content '489 patent at issue in N.D. Cal. Case No. 3:20-cv-03845-EMC.
• Various others ending in "489" (e.g., 8,897,489; 9,934,489-family; 4,510,489).

I could not confirm the full patent numbers for the MyPAQ and Sonos patents from the excerpts retrieved, so I am not asserting them.

Strategic summary

Claim status on 3,423,489: 15 claims issued; 15 UNTESTED and 15 EXPIRED. No claim was ever canceled, narrowed, or amended — by PTAB or (so far as the record shows) by reexamination. The claim set comprises 15 claims per the patent front page; the OCR of the claim text available runs from claim 1 through claim 12/13 and is truncated thereafter, so I will not characterize the independent/dependent structure beyond what is legible (claims 1, 10, and the final method claim are the independent claims visible in the text). Because term expired 1986-01-21, "canceled vs. sustained" is an academic distinction: every claim is unenforceable as a matter of term, and no PTAB outcome could make the patent more or less dead.

Estoppel landscape. Statutory estoppel under 35 U.S.C. § 315(e)(2) attaches only to a petitioner that obtained an instituted IPR — and since no IPR was ever instituted, no estoppel exists against anyone. A defendant today may raise any § 102, § 103, § 112, or § 101 ground in any forum, unencumbered. More to the point, the constraint on a defendant is not estoppel but mootness: a patent whose term ended in 1986 cannot support prospective injunctive relief and supports only damages for acts more than six years stale, i.e., none. The conversation a demand letter presumes — "what prior art is left to me?" — never starts.

Pattern signals: none. There is no repeat petitioner, no serial-IPR family, no defensive aggregator (Unified Patents, RPX, OpenSky, etc.) in the chain, and no aggressive patent-owner appellate strategy — because none of these was legally or commercially possible in the patent's lifetime. What does exist is a rich post-expiry citation life: examiners have applied 3,423,489 as an X-category reference against later applications — for example, in the WO2011051033A3 search report, US 3,423,489 A (1969-01-21) is cited against claims 1–12 of that application, and Google Patents' own prior-art keyword map for this document is dominated by "capsules / fill / shell / liquid / temperature." That is the real strategic significance of this patent today: it is a defensive weapon (a § 102(b) printed publication from 1969), not an offensive one.

Recommended next steps

If you are a defendant and someone has asserted 3,423,489 against you:

• There is no Final Written Decision to link to, because there is no PTAB proceeding. The dispositive fact is the expiry date on the face of the patent: "1986-01-21 — Anticipated expiration" (https://patents.google.com/patent/US3423489/en). 17-year pre-URAA term from the 1969-01-21 grant. Term cannot be revived, and the six-year damages recovery window of 35 U.S.C. § 286 has been closed since 1992.
• Preserve the assertion letter. A demand premised on a patent expired for ~40 years is a candidate for a declaratory-judgment action of non-infringement/non-liability and, in egregious cases, Rule 11 or state-law unfair-competition exposure. Identify the actual patent being asserted — the odds are high that the sender conflated 3,423,489 with a later "489" patent (see the look-alike list above), which is itself a Rule 11 point if the sender cannot read the numbers correctly.
• Do not spend money on an IPR. There is no live claim to invalidate and no estoppel benefit to be gained.

If someone is citing 3,423,489 as prior art against your own application or patent:

• The reference is a § 102(b) printed publication as of 1969 and is fully fair game. It is also strong § 103 ammunition — a pre-AIA reference with an explicit biliquid-column teaching, Reynolds-number and orifice-diameter parameters (claims 1, 10, and the jet-velocity claim at 1 m/sec), and 26 worked examples.
• Further, if your patent is the one under attack, note that its own family is small: BE705960, CH475002, DE1586198B2, GB1200200, NL158070B, SE337802 (per the Google Patents family listing), which narrows the art-unit search.

If you expected active proceedings: there are none to monitor — no institution-deadline, oral-hearing, or one-year statutory FWD clock is running. That absence is itself the signal here: this patent predates the AIA by a generation and reached the end of its term before the first IPR petition was ever filed (2012-09-16). Patents that are actively asserted attract IPRs; this one could never have attracted one. Treat any representation that it is a live, enforceable right as a red flag about the sender.

Verification caveat. The ODP ingest is the canonical negative; my searches (queries targeting "3,423,489" and "US3423489" against IPR/PGR/CBM terms and against the inventor names) surfaced no contrary proceeding as of 2026-09-30. I cannot prove a universal negative, but given a 1986 expiry, the prior probability of an unindexed filing is effectively zero.

I'll start by gathering what I can verify about this patent's ownership record before writing anything.

Let me dig further into whether any assignment was recorded against this specific patent.

Retrieval status (read this first)

I was not able to reach the Assignment Center database. https://assignmentcenter.uspto.gov/ is a JavaScript application that does not expose record content to text-fetch tools, and every query I ran against the patent number returned no USPTO assignment record for US 3,423,489. What I can retrieve is consistent:

• The Google Patents legal-events panel for this patent contains no assignment or reassignment entry at all. Its events are: 1966-11-01 application filed by Minnesota Mining and Manufacturing Co.; 1966-11-01 priority to US591326A; 1966-11-01 priority to NL6714317A; various 1967 foreign filings; 1969-01-21 granted; 1969-01-21 publication; 1986-01-21 anticipated expiration; status "Expired – Lifetime." Source: https://patents.google.com/patent/US3423489/en (Legal Events).
• The front matter of the printed patent names the assignee directly in the assignee clause rather than through a printed reel/frame: "Robert P. Arens, North St. Paul, and Norman P. Sweeny, North Oaks, Minn., assignors to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware."

Plain statement: I found no evidence of any post-issuance assignment for US 3,423,489 in any source I could retrieve. The only ownership transfer of record in the retrievable record is the original inventor→3M assignment implied by the patent's own assignee clause and confirmed by the "Original Assignee: Minnesota Mining and Manufacturing Co." field. You should treat the reel/frame for that original assignment as unverified — I will not invent one. Pre-1970s 3M assignment reels exist but I could not confirm the specific frame from the sources available to me, and no retrieved document (including the Reel 009596/0391 Dow/3M cross-license cover sheet, which lists 29 unrelated 3M patents and does not include 3,423,489) ties a frame to this patent.

Per your instruction, the assignment timeline below therefore terminates at the original assignment. I have continued into the remaining sections in abbreviated, explicitly-contingent form so the NPE analysis is on the record — but every signal below is scored against a chain of length one.

Inventors

Both resided in Twin Cities suburbs adjacent to 3M Center, and both are named as "assignors to Minnesota Mining and Manufacturing Company," i.e. they assigned to an employer, not to a purchaser. This is an ordinary corporate-employee-inventor pair, not a founder-inventor pair.

Departure pattern — not present, at least for Arens. The tell you asked about (inventors leaving within 12 months of filing, preceding a fire sale) is affirmatively contradicted for Arens: he is the named inventor on a much later 3M-owned application claiming a 1992-04-10 US priority (US 867,139), published as AU-B-35264/93 / AU 664244B2, applicant Minnesota Mining and Manufacturing Company, "Article Capable of Displaying Defined Images," and that document cites an earlier Arens patent, US 4,877,253. That is a ~26-year continued filing relationship with the same assignee. Source: https://patentimages.storage.googleapis.com/5b/4e/a1/0c7aacdb3ce1b9/AU664244B2.pdf

For Sweeny I found no evidence either way about his tenure. Unclear, not a finding.

Original assignee

Minnesota Mining and Manufacturing Company (Delaware corporation), St. Paul, Minnesota — the entity named on the issued patent and listed by Google Patents as both Original Assignee and Current Assignee ("3M Co").

• Primary line of business: diversified industrial manufacturer (adhesives, abrasives, tapes, coatings, retroreflective sheeting, microreplication, health care). It is an operating company in the ordinary sense, and the patent's own worked examples point at 3M commercial lines: Example I capsules are stated to be "useful in preparing pressure activatable self-marking devices such as sheet materials," and Example XXV's gelatin capsules are described as edible with pressure- or solution-releasable contents. The Arens 1992 AU 664244 continuation of that subject matter (imageable/markable sheet articles) is further evidence 3M kept building in this space. I have not verified a specific branded 3M product that reads on claims 1, 10 or 12, and I am not going to assert one.
• Current status: operating. Corporate name changed from "Minnesota Mining and Manufacturing Company" to "3M Company"; 3M's in-house IP holder is 3M Innovative Properties Company (3M Center, St. Paul, MN 55133-3427). Neither is in bankruptcy; there was no Kodak/Nortel-style event here. 3M did pursue patent litigation in the 2000s (e.g. the ITC Section 337 action against Kinik, Inv. No. 337-TA-449), but that case concerned a different 3M patent also abbreviated as "the '489 patent" — an abrasive-article patent. Do not conflate it with US 3,423,489; no source I retrieved ties this patent to that or any other suit.

Assignment timeline

No assignment record for US 3,423,489 was retrievable. The only ownership link evidenced anywhere is the original inventor→assignee assignment implicit in the patent's assignee clause (executed on or before the 1966-11-01 filing date; not granted a front-page reel/frame in the sources I could reach).

For completeness, two 3M-entity-level recordings exist in the public record and are the documents that would have carried this patent if it were included. I flag them strictly as unverified against this patent — I am not recording them as this patent's chain of title:

• The 2502/0547 document is independently attested in multiple USPTO TSDR/TTAB Assignment Abstracts of Title (e.g. https://ttabvue.uspto.gov/ttabvue/ttabvue-91289899-OPP-1.pdf, https://ttabvue.uspto.gov/ttabvue/ttabvue-92058474-CAN-1.pdf). Those abstracts are for trademarks, so they prove the document exists and prove its correspondent, but they do not prove it was recorded against US 3,423,489.
• The 010558/0421 recording is attested for US 6,223,401 via INPADOC legal status. It reflects 3M's 1999 mass movement of patents into its in-house IP subsidiary — an internal reorganization, not a third-party sale. Again, not confirmed for this patent, and note this patent's 17-year term had already expired in 1986, so it is a poor candidate for inclusion in a 1999 consolidation of live assets.
• Correspondent note: James F. Voegeli appears as 3M's Assistant Chief Intellectual Property Counsel / Office of Intellectual Property Counsel correspondent in 3M recordings in the 1998–2002 window (compare the Dow/3M Reel 009596/0391 cover sheet signed by H. Sanders Gwin of Dow and the 1999 Gantrez-era 3M filings). He is 3M's own in-house attorney — the opposite of the anonymous repeat-player outside counsel pattern that signals an NPE recording operation.

If you need the actual reel/frame for this patent, the reliable path is the Assignment Center "Patent Number" search at https://assignmentcenter.uspto.gov/ (mirror: https://assignment.uspto.gov/patent/index.html), then cross-check the Google Patents Legal Events tab at https://patents.google.com/patent/US3423489/en#legalEvents.

Timeline diagram

timeline
    title Ownership of US 3423489
    1966 : Filed by Arens and Sweeny
         : Assigned to Minnesota Mining and Mfg
    1969 : Patent issued Jan 21
    1986 : Patent term expires Jan 21
    1999 : 3M IP unit transfer unconfirmed here
    2002 : 3M name change unconfirmed here

NPE / troll-pattern signals

Contingent on the findings above — i.e. a chain of length one terminating at 3M.

1. Shell-entity transfer — not present. No assignment to any entity with an "IP / Patents / Licensing / Holdings / Ventures" suffix, no registered-agent address, no single-purpose LLC appears anywhere in the retrievable record for this patent. The only 3M-side entities involved (3M Company, 3M Innovative Properties Company) are the operating company and its wholly-owned in-house IP holder at 3M Center, St. Paul — a corporate address, not a registered-agent service.

2. Known asserter in the chain — not present. No assignee in the chain matches Acacia, Marathon, Intellectual Ventures, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation Corp, or any Spangenberg entity. Original and current assignee is 3M throughout.

3. Repeat correspondent across the chain — not present. There is only one correspondent visible anywhere near this chain, James F. Voegeli of 3M's own Office of Intellectual Property Counsel (Reel 2502/0547), and he is the assignee's in-house counsel, not an outside filer. A single appearance by an in-house attorney is explicitly not the signal you described. No outside recording firm recurs.

4. Cascading transfers — not present. Zero consecutive transfers, let alone multiple chained LLCs within 24 months. The 1999 and 2002 recordings (both unconfirmed for this patent) are 3M→3M reorganizations 33–36 years after issuance.

5. Pre-litigation transfer — not present / moot. No infringement suit naming US 3,423,489 was found, and the patent expired 1986-01-21 (Google Patents: "Anticipated expiration 1986-01-21," status "Expired – Lifetime"). An expired patent cannot ground an infringement claim, so no pre-litigation transfer could have had any purpose.

6. Bankruptcy fire-sale — not present. 3M never filed Chapter 7/11. No Kodak/Nortel/Polaroid-style sale proceeding touches this patent.

7. Privateering — not present. No transfer out of 3M to an NPE asserting on 3M's behalf. 3M is a large, litigious-in-its-own-name operating company that has asserted its own patents directly (e.g. the Kinik ITC action), not through proxies.

8. Defensive aggregator — not present. Chain does not terminate at RPX, AST, LOT Network, Unified Patents, or OIN. (In practice the patent is equally neutralized — by expiry rather than by acquisition.)

Verdict

Insufficient data — no post-issuance assignment records are retrievable for this patent, only the original assignment to Minnesota Mining and Manufacturing Company.

Justification: the Google Patents legal-events record for US 3,423,489 contains no assignment entry of any kind, and the only ownership evidence available is the original inventor→3M assignment reflected in the patent's own assignee clause ("assignors to Minnesota Mining and Manufacturing Company," front page) and the "Original Assignee / Current Assignee: 3M" fields. Even the two 3M-entity-level recordings that exist in the public record — Reel 2502/0547 (Minnesota Mining and Manufacturing Company → 3M Company, merger/change of name, executed 2002-04-08, recorded 2002-04-30, correspondent James F. Voegeli) and Reel 010558/0421 (→ 3M Innovative Properties Company, effective 1999-09-15) — are unverified against this particular patent, and both are internal corporate reorganizations rather than transfers to an asserter. Note also that this patent's term expired 1986-01-21, so it has been unenforceable for roughly four decades and carries no NPE value regardless of the record; the correct plain reading, once you confirm the record at the Assignment Center, is likely "original assignee 3M retained ownership; no NPE activity."

Verify at: https://assignmentcenter.uspto.gov/ (patent-number search) and https://patents.google.com/patent/US3423489/en#legalEvents.

I'll research this systematically. Let me start with searches for the patent and its citations.

Let me dig into the citation lists for this patent specifically.

1. Verification of the number (interpreted literally, no auto-correction)

I confirmed the record for the literal identifier US3423489A / US 3,423,489 and no similar number:

Source: the Google Patents record for US3423489 (https://patents.google.com/patent/US3423489/en) and the granted specification PDF (patentimages…US3423489.pdf). Note on methodology: I could not open a USPTO API response directly in this session; the record above was cross-checked against the Google Patents front page and the printed specification, which is the same document USPTO PatentCenter and Global Dossier serve.

Because the application was filed 1 Nov 1966, it is governed by pre‑AIA 35 U.S.C. § 102. Any reference that "issued/patented" more than one year before 1 Nov 1966 (i.e., before 1 Nov 1965) is a statutory § 102(b) bar; references earlier than the invention date fall under § 102(a).

2. The patent citations of US 3,423,489

Important scoping caveat first. Only those references that pre-date 1 Nov 1966 can be prior art against this patent. The only patent citations I could verify for US 3,423,489 are the three U.S. patents expressly discussed in its "Background" section:

US 2,799,897 (Jansen), US 2,911,672 (Van Erven Dorens), and US 3,015,128 (Somerville).

The retrieved version of the Google Patents page did not render the official "Patent Citations" table, so I cannot certify that this is the complete list of record. If you need the definitive citation list (including any foreign search-report documents such as BE705960 or GB1200200), it should be pulled from the "Patent Citations"/"Similar Documents" tabs of the US3423489 record and from USPTO PatentCenter / Global Dossier for application 591,326. I flag this rather than guess.

Reference A — US 2,799,897 (Jansen)

• Full citation: US 2,799,897 A, "Method for producing seamless filled capsules," inventor Jansen. Issued July 23, 1957 (date given verbatim in the 3,423,489 specification). Filing date not verified in the records I retrieved.
• Brief description: Concentric encapsulating nozzle(s); filler and encapsulating composition are delivered under only hydrostatic head or a few ounces of pressure and drop from the nozzle as a composite drop that severs itself and assumes a true spherical shape without a heat after‑treatment. Encapsulating composition viscosity preferably not in excess of 1500 centipoises; the forming capsules are supported on a cooling liquid bath. Jansen expressly criticizes the earlier Merrill et al. practice (about 40 p.s.i. and high‑viscosity gelatin requiring an after‑treatment).
• § 102 status: § 102(a)/(b) — issued before 1 Nov 1965.
• Potential § 102 anticipation: None of claims 1–15, as literally written. Jansen discloses a core‑in‑shell composite drop and shell congealing, but no "biliquid column … directed in a trajectory having a horizontal component" (claim 1), no "trajectory in a gaseous atmosphere" (claim 10), and no jet at > 1 m/s with orifice 5–1500 µm / Reynolds < 4000 (claim 12). Jansen teaches away from the claimed high‑velocity jet (he avoids substantial pressure).
• Realistic role: § 103 secondary reference. It supplies the "concentric core/shell" and capillary‑breakup background and, notably, the gellable‑colloid shell element of claim 5 (gelatin) and the general "hardening into solid shells" step.

Reference B — US 2,911,672 (Van Erven Dorens) — most relevant prior art

• Full citation: US 2,911,672 A, "Process and apparatus for the manufacture of seamless filled capsules," inventor Van Erven Dorens. The 3,423,489 specification cites it as "U.S. Patent 2,911,672, to Van Erven Dorens" (no date given). Issue date not verified in the records I retrieved; the number falls in the 2.9‑million series, consistent with a 1959 issue date — treat that year as unconfirmed.
• Brief description: A concentric nozzle extrudes a composite coherent jet consisting of a core of filler material and a jacket of encapsulating material (i.e., a concentric biliquid column) downwardly directly into a cooling bath. A hollow ring with an annular slit concentric with the jet intermittently extrudes cooling liquid under hydraulic pressure; the resulting vibration creates initial constrictions in the jet, after which "the jet on its way through the cooling liquid constricts itself further … and ultimately breaks into separate composite drops," which become substantially spherical and are cooled until the shell congeals. Gelatin viscosity preferred 400–1000 cps; filler loads of 10–500 mg.
• § 102 status: § 102(a)/(b), assuming pre‑1 Nov 1965 issue (consistent with the specification's framing as prior art).
• Potential § 102 anticipation — this is the closest reference, but each independent claim still fails at least one limitation:
  • Claim 1 — discloses the biliquid column (core + outer tube), constriction into spheroids, and hardening into solid shells. Not anticipated only because the trajectory is downward into a liquid bath, so the claimed "trajectory having a horizontal component" is absent.
  • Claim 10 — discloses constriction into individual spheroids of encapsulating material and hardening. Not anticipated because the trajectory is through a liquid cooling bath, not "in a gaseous atmosphere."
  • Claims 2, 3, 11 — the "hardening by freezing / spherical shell" concepts are closely met (claim 2: molten normally‑solid shell hardened by freezing; claim 11: spherical shells), but both depend on claim 10/1 and therefore fail on the same trajectory limitation.
  • Claim 12 — not anticipated: no orifice‑diameter (5–1500 µm), velocity (> 1 m/s) or Reynolds‑number (< 4000) teaching.
  • Claims 4–9, 13–15 — no disclosure of wax, glass, metal, aqueous fill, or interconnected‑strand collection.
• Realistic role: The primary § 103 reference against claims 1, 2, 3, 10 and 11.

Reference C — US 3,015,128 (Somerville)

• Full citation: US 3,015,128 A, inventor Somerville. Issued January 2, 1962 (date given verbatim in the 3,423,489 specification). Title not verified in the records I retrieved.
• Brief description: A circularly shaped curtain of encapsulating liquid flows over a circular wall pierced with orifices around its circumference; the fill material is dropped onto a rotating distributor plate in the middle of the curtain, and centrifugal force drives droplets through the wall orifices, which are covered by the falling curtain, so the droplets pick up a coating. The coated droplets spherize by surface tension and are hardened by air drying or equivalent. The specification notes its drawbacks: complex equipment, difficult process control/uniformity, and a likelihood of air entrainment in the capsules.
• § 102 status: § 102(a)/(b) — issued before 1 Nov 1965.
• Potential § 102 anticipation: None. Somerville does not form a biliquid column at all — discrete droplets impinge a curtain — so there is no "outer tube … and a core … constrict[ing] along its length into spheroids" (claims 1, 10, 12).
• Realistic role: § 103 secondary reference. Its spraying/air‑hardening step ("air drying") is the closest teaching to the gaseous‑atmosphere trajectory and airborne hardening recited in claim 10 (and to claim 1's hardening step).

3. Forward citations (documents citing US 3,423,489) — not prior art

For completeness and to avoid confusion with the request: the documents below are ones that cite 3,423,489 (i.e., it is prior art to them). They post‑date 21 Jan 1969 and therefore cannot anticipate any claim of 3,423,489:

• US 4,218,409 — "Encapsulating method," Eastman Kodak Company (freepatentsonline.com/4218409.html).
• US 5,246,636 — "Process for making microcapsules and apparatus therefor," issued Sept. 21, 1993 (justia.com/patent/5246636).
• WO 2011/051033 A3 search report — lists "US 3,423,489 A (Arens) 21.01.1969" as an X‑category citation spanning its own claims 1–12, i.e., 3,423,489 is treated there as anticipating that later disclosure.
• JP 6825025 B2 (tobacco scent capsule manufacturing), KR 102039468 B1, and EP 1414956 B1 (paragraph [0063]) also list US3423489A in their citation tables.

This pattern — 3,423,489 being used as X‑category art against later biliquid‑column filings — is itself the best indicator of where its true novelty lies: the free‑flight constriction of a biliquid column in a gaseous trajectory, not the core/shell idea itself.

4. Bottom line

1. Most relevant prior art: US 2,911,672 (Van Erven Dorens) — it is the only cited reference that forms a concentric composite biliquid stream, relies on constriction and natural forces to break it into individual spheroids, and hardens the shell into solid capsules. It fails claim 1 (no horizontal trajectory component) and claim 10 (liquid bath rather than gaseous atmosphere), so it anticipates nothing literally but is the strongest § 103 reference.
2. US 2,799,897 (Jansen) — concentric‑nozzle, gravity‑fed drops onto a cooling bath; § 103 background, no § 102 anticipation of any of claims 1–15.
3. US 3,015,128 (Somerville) — rotating‑plate/falling‑curtain, not a biliquid column; § 103 secondary reference for the air‑hardening element; no § 102 anticipation.
4. Claim 12 in particular appears unanticipated by all three, because its numeric limitations (orifice 5–1500 µm, fill velocity > 1 m/s, Re < 4000) have no counterpart in the cited art.
5. Caveats I will not paper over: (a) I could not render the official "Patent Citations" table for US3423489, so additional cited references may exist and should be confirmed via USPTO PatentCenter/Global Dossier; (b) the filing date of US 2,799,897 and the issue date of US 2,911,672 were not verifiable from the records retrieved — I have not fabricated them; and (c) this is a technical prior‑art assessment, not a legal conclusion on patentability or validity.

I'll ground this analysis in the prior art identified on the patent page, then verify the references.

Let me gather the specific disclosures of the Jansen and Van Erven Dorens references, plus related cited art.

Obviousness Analysis — US 3,423,489 ("Encapsulation process")

Patent: US 3,423,489 A — Arens & Sweeny, assignors to Minnesota Mining and Manufacturing Co. (3M). Filed 1966‑11‑01, granted 1969‑01‑21, expired 1986‑01‑21 (per the page: https://patents.google.com/patent/US3423489/en).
Legal standard applied: Pre‑AIA 35 U.S.C. § 103(a) (Graham v. John Deere factors), assessed as of the 1966 priority/filing date. Because the patent is long expired, this is a retrospective validity study, not a live challenge.

1. The prior art actually on the page

The US 3,423,489 page does not contain a "Patent Citations" table. What it contains is:

• A "Prior art keywords" field (fill, capsules, liquid, shell, temperature) — these are Google's indexing terms, not references, and carry no evidentiary weight.
• An auto‑generated "Definitions" block — likewise not a legal disclosure.
• The specification's own background section, which expressly identifies and discusses three references. These are the operative "prior art section of this page":

The spec also names, second‑hand through the Somerville discussion, Merrill et al. US 2,275,154 and Raley US 2,766,478 (vertical concentric tubes forming an annular orifice; film + filler mass falls into a hardening bath). See https://patents.google.com/patent/US3015128A.

⚠️ One further document surfaced in searching — US 2,932,061 (concentric filler/shell conduits whose combined stream "disintegrates into separate drops" under natural or artificial forces, then is carried through a spirally wound cooling conduit). It is not listed on the US 3,423,489 page, so I am not treating it as prior art "of record" here; it is noted only because it is highly material if it is in fact a Van Erven Dorens‑family document. I could not confirm its inventor/assignee within this session and will not assert it.

2. What the claims require (as reproduced on the page)

Note on scope. Claim 1 is the broadest claim and is not limited to (a) a gaseous atmosphere, (b) jet‑dragging of shell material through a bath, or (c) any size/velocity/Reynolds range. Claim 10 adds only the gaseous atmosphere. Only claim 12 (and its dependents) captures the commercially distinguishing embodiment (Figures 1 & 3 — the fill jet pulling a shell of molten wax upward out of a bath). This asymmetry drives the analysis below.

3. Reference‑by‑reference disclosure mapping

3.1 Van Erven Dorens, US 2,911,672 — the closest reference

From the page text at https://patents.google.com/patent/US2911672A/en:

• "the combined stream of encapsulating material and of filler material extrudes from the nozzle 4 as a composite coherent jet, consisting of a core of filler material and a jacket of encapsulating material" → reads directly on claim 1's "biliquid column comprising an outer tube of capsule shell forming material and a core of fill material."
• "natural forces as e.g. [surface tension] … the jet on its way … constricts itself further in the places of the initial constrictions and ultimately breaks into separate composite drops, consisting of a core of filler material and a shell of encapsulating material. … these drops assume a substantially spherical shape and are cooled to a temperature at which the shell material congeals so that seamless filled capsules result." → reads on claim 1's "constrict along its length into spheroids" + "hardening," and on claims 2 and 11.
• It uses a pulsating ring of cooling liquid to seed the constrictions.

What it lacks: free‑flight (horizontal‑component) trajectory; gaseous atmosphere; jet‑type formation; the size/Re/velocity ranges.

3.2 Jansen, US 2,799,897 — the sphericity/air‑extrusion reference

From the PDF and page (https://patents.google.com/patent/US2799897A/en; https://patentimages.storage.googleapis.com/ef/04/0e/a1442d91fdf739/US2799897.pdf):

• Claim 2: "extruding the heated capsule shell‑forming material … through a capsule‑forming orifice into air at substantially room temperature to form a semi‑congealed, droplet‑shaped capsule shell, while simultaneously introducing liquid filler material into said capsule shell until the semi‑congealed capsule severs from the orifice to form a semi‑congealed spherical capsule, dropping the capsule into a liquid cooling medium…" → discloses airborne travel of a two‑phase capsule and surface‑tension spheronization before the hardening bath.
• Viscosity window 300–1500 cps; extrusion under a 50–500 mm hydrostatic head; teaching that low viscosity/low pressure is what permits true sphericity "without … an after treatment such as heating," and that high pressure/high viscosity produces "capsules of non‑uniform shape and irregular wall thickness" with "substantial tails."
• Teaches that a liquid cooling medium is required to support and congeal the capsule.

What it lacks: the biliquid column/jet constriction mechanism (Jansen drops discrete capsules from an orifice rather than subdividing a column); the horizontal free‑flight trajectory; jet formation.

3.3 Somerville, US 3,015,128 — the free‑flight / air‑hardening / throughput reference

From https://patents.google.com/patent/US3015128A:

• Centrifugal apparatus that casts the wet capsules outwardly through air ("sling them outwardly") into a hardening bath — i.e., a trajectory with a horizontal component in a gaseous atmosphere.
• "The coated droplets assume a spherical shape due to surface tension, and can be hardened by air drying or by other means" (as characterized in the US 3,423,489 specification).
• Expressly teaches high rate of formation and relatively small capsule size as the objects of the invention: "the centrifugal encapsulating nozzle is capable of producing relatively small sized individual capsules of filler material at a relatively high rate of formation," with a further stated object of an "even higher rate of formation."

What it lacks: a pre‑formed biliquid column; shell‑material hardening by congealing while airborne (it hardens in a bath); absence of air entrainment.

4. Combinations that would have rendered the claims obvious

Combination 1 (strongest): Van Erven Dorens + Jansen

Where the claims read on the combination: every element of claim 1 except the horizontal free‑flight trajectory.

• Biliquid column, constriction under natural forces, spheroid formation, congealing shell = Van Erven Dorens, verbatim.
• Molten normally‑solid organic/wax/colloid/metal shells and freezing‑type hardening (claims 2–7) = Van Erven Dorens (gelatin shell, congealed in cooling liquid) and Jansen (liquefiable normally solid shell, viscosity 300–1500 cps).
• Spherical shells (claim 11) = both.
• Aqueous fill (claim 8) = Jansen's "any liquid filler"; Van Erven Dorens's oil fill.

Motivation to combine (why a PHOSITA would do it):

1. Same field, same problem, same mechanism. Both are seamless‑capsule processes in which a shell‑forming material and a fill are brought into a concentric two‑phase relationship and subdivided by surface tension. KSR‑style "familiar elements according to known methods" applies squarely.
2. A recognized, articulated deficiency in the primary reference. The US 3,423,489 specification itself states the rate limitation of the Dorens approach: "the speed at which the composite stream travels is limited by resistance of the cooling bath to flow therethrough… and by practical limitations on the velocity at which the cooling liquid may be pumped to carry away the capsules from the forming zone before they are sufficiently hardened so as not to adhere to one another on contact" (https://patents.google.com/patent/US3423489/en). That is exactly the problem Jansen's "extrude into air" step is designed to avoid — Jansen's whole point is that the shell must be free to spheronize without hydrodynamic support, and the bath is only a terminal cooling step.
3. A predictable result. Removing a liquid drag medium from a forming stream and letting the stream travel in air is a mechanical substitution with an expected effect (less drag → higher throughput), and the spheronizing force (surface tension) is unchanged. There is no teaching away in either reference; Jansen's low‑viscosity/low‑pressure teaching (300–1500 cps) is compatible with Van Erven Dorens's preferred 400–1000 cps shell range — the ranges overlap almost exactly, which is itself evidence that the two disclosures are directed to the same design space.
4. Reasonable expectation of success. Van Erven Dorens already describes the jet self‑constricting "under natural forces" independently of the pulsating ring; a PHOSITA would appreciate that the pulsation only seeds constrictions and is not essential to subdivision. Jansen supplies the congealing‑on‑severing behavior.

Conclusion for Combination 1: Claims 1, 2, 3, 4, 5, 6, 7, 8, 11 (and 9, with the wax/rapid‑solidification embodiments of Van Erven Dorens) are, in my assessment, reasonably likely to be held obvious over Van Erven Dorens in view of Jansen.

Combination 2: Van Erven Dorens + Somerville (directed at claim 10)

Claim 10's added limitation is that the column is "directed in a trajectory in a gaseous atmosphere." Somerville teaches precisely that: capsules are flung through air and hardened by contact with air. Motivation: Somerville expressly frames its invention as an improvement in rate of formation of small capsules, and it identifies the gravity/concentric‑tube devices (Merrill, Raley — the same genus as Van Erven Dorens) as deficient in "capsule size and rate of production." A PHOSITA seeking to raise throughput of the Van Erven Dorens process would look to Somerville's airborne casting.

Caveat: Somerville's capsules are a film of shell material wrapped around a discrete droplet in flight — not a pre‑formed biliquid column that subdivides. So Combination 2 is weaker standing alone for claim 10 and is best presented as Van Erven Dorens + Jansen + Somerville (Jansen supplying the biliquid/co‑extrusion structure and airborne extrusion, Somerville supplying the free‑flight‑in‑gas + air‑hardening + high‑throughput teaching). That three‑way combination maps cleanly onto claim 10.

Combination 3: Jansen + Somerville (secondary; supports claims 10 and the 9‑style "hardened while airborne" concept)

Both teach hardening without a supporting bath — Jansen by dropping a semi‑congealed, already‑spherical capsule through air into a bath, Somerville by air‑drying. Combined, they teach the concept of airborne congealing that claim 10 recites. This combination is weaker against claim 1 (neither discloses column constriction) but is a useful secondary showing for the "gaseous atmosphere" element.

Combination 4: Any of the above + the artisan's own knowledge (claim 12's numeric ranges)

Claim 12's limitations are almost entirely numerical: orifice 5–1500 µm, fill jet ≥1 m/s, capsules 10–4000 µm, plus (in the truncated text and in claims 13–15) a Reynolds number ceiling. Under In re Aller / KSR, reciting a range that is the inherent result of the disclosed process or that is obtained by routine experimentation does not create patentability, absent a showing of criticality. Here the specification asserts criticality — "the velocity … must be at least about 1 meter per second in order to form a jet" and "the Reynolds number … should be below about 4000, and more preferably below 2000" — but those are art‑recognized fluid‑mechanics thresholds (laminar‑to‑turbulent transition at Re ≈ 2000–4000 for pipe flow; the Poiseuille relationship is characterized in the spec as "well‑known"). To the extent claims 13–15 simply recite "below about 4000" / "below about 2000," those are the textbook transition values and are vulnerable as routine optimization of a known parameter.

The element that resists this combination is the claim 12 requirement that the fill jet be discharged into the encapsulating material so that the jet drags a concentric shell with it (spec: "frictional forces between the fast moving jet of fill liquid and the encapsulating liquid… the fill liquid stream to drag along with it a concentric shell"). None of Jansen, Van Erven Dorens, or Somerville discloses or suggests this — all three positively supply shell material through a dedicated shell conduit/orifice, and Jansen in particular cautions that high‑velocity/high‑pressure operation is to be avoided because it produces "capsules with substantial tails … non‑uniform shape and irregular wall thickness." That is an affirmative teaching that cuts against the jet‑drag embodiment, and it is the best non‑obviousness argument available on this record.

5. Summary judgment table

6. Rebuttal evidence a patent owner could raise (and how strong it is)

The specification asserts several results-based arguments that would function as secondary considerations if timely raised:

1. Independence from surface tension. Spec: "it is possible to encapsulate low surface tension liquids within high surface tension liquids" — while the FIGURE 2 embodiment requires the higher surface‑tension liquid to form the core. Strength: moderate — it is a genuine functional difference, but it is asserted only for the Figures 1/3 (jet‑drag) embodiments, not for claim 1 generally.
2. No air entrainment, contrasted explicitly against Somerville. Strength: moderate, and directly probative, because the patent frames it as an advantage over one of the very references a challenger must combine.
3. Internally‑cooled, dense, low‑stress shells with superior barrier properties (spec: "shells hardened or congealed by internal cooling have a dense, more impermeable structure characterized by a low rate of vapor diffusion along crystal boundaries"; Example XXIV: 0.20%/day diffusional loss, 241‑day half‑life). Strength: potentially strong — this is the closest thing to an unexpected result, but it is recited in no claim and therefore supports nothing beyond the jet‑drag embodiment.
4. Absence of any liquid hardening bath. Strength: weak — Jansen and Somerville already teach airborne/air‑drying hardening.

7. Confidence and caveats

• High confidence in the disclosures of US 2,911,672, US 2,799,897, and US 3,015,128 as quoted above; all quotations are from the patent pages/PDFs cited inline.
• Claims 12–15 are only partially reproduced on the page — the claim text breaks off mid‑sentence at "the dimensionless Reynolds number," and claims 13–15 are absent entirely. My characterization of those claims as numerical‑range dependents is an inference from the specification and should be verified against the granted patent copy before being relied on.
• I did not have access to a file‑history "References Cited" list for US 3,423,489, nor to any "Similar Documents" list. If the examiner cited additional art (e.g., US 2,932,061, which appeared in search but is not on this page), the obviousness case — particularly against claim 12 — could be materially stronger. I flag US 2,932,061 as unverified and expressly do not rely on it here.
• The foreign members of the family shown on the page (NL 158070 B, BE 705960 D, FR 1542184 A, DE 1586198 B2, CH 475002 A, SE 337802 B, GB 1200200 A) are counterparts, not prior art, and are not usable in a § 103 combination against this patent.