US 213101

I'll run targeted searches on this identifier before summarizing.

Now let me check for any litigation/docket activity and USPTO/CAFC records for this number.

US 213,101 — Search Results and Summary

Search coverage and caveat up front: I ran targeted searches for the literal identifier 213101 / US213101A / US213101D. My searches returned no CAFC 2026 docket activity, no district court litigation, and no USPTO assignment records for this patent. Two near-miss false positives appeared and should be expressly excluded: SPE Paper No. 213101-MS (Downing, an SPE conference paper) and the statute 28 U.S.C. § 2101(c) (appearing in an unrelated Oasis Tooling certiorari application). Neither concerns US Patent 213,101. I could not reach USPTO Patent Public Search / PatentCenter directly in this session; the authoritative source I did retrieve is the full-text Google Patents record, corroborated by a CPC index listing.

---

Bibliographic data

Sources: https://patents.google.com/patent/US213101A/en ; https://trade.patenthub.cn/cpc/list-72156-18.html

---

Abstract

No abstract exists. US 213,101 issued in 1879, roughly seven decades before abstracts were required on US patents. The closest equivalent is the specification's opening statement of invention:

"My invention relates to improvements in propelling and steering vessels, in which paddle-wheels and screws are dispensed with, and steam and water are brought in contact in suitably-arranged chambers or cylinders, having openings at their lower ends, through which the water is alternately admitted and expelled by the corresponding alternate steam-pressure and vacuum therein."

Stated purpose: force water out of cylinders by steam pressure to propel the vessel, then lead the spent steam to a condenser so it is recovered and reused as feed-water — thereby avoiding the fresh-water losses of prior steam-jet propulsion, where steam was mixed with and ejected along with the water.

---

Claims — plain-language overview

This patent predates the 1952 Patent Act, so it uses the older "what I claim as new" format. There are two claims; the specification contains no formal "independent/dependent" labeling, but claim 1 is plainly the broad claim and claim 2 is a narrower structural combination claim.

Claim 1 — the broad apparatus claim (independent).
In a hydro-propeller for navigable vessels: a water cylinder that operates without a piston, communicating with the surrounding "floatative" body of water, in combination with a steam-inlet valve, a steam-outlet valve, and a condenser. In plain terms: instead of a piston engine, you use an open-bottomed cylinder flooded from the sea, drive the water out with steam, and capture the exhaust steam in a condenser rather than letting it escape into the ocean.

Claim 2 — the float-actuated steam-exhaust combination (narrower).
The specific combination of a condenser with (i) the steam-escape tube D, (ii) a valve at the mouth of that tube, (iii) a rod o′ having top and bottom projections, and (iv) a float K2 — together with the water-cylinder of a hydro-propeller. In plain terms: this claims the automatic mechanism whereby the falling water level in the cylinder causes float K2 to strike the lower projection and pull the rod, lifting the exhaust valve so spent steam vents through tube D into the condenser; when water rises again, the float strikes the upper projection and re-closes the valve. This creates the vacuum that refills the cylinder.

How the two claims relate: Claim 1 covers the cylinder/valve/condenser architecture broadly; claim 2 captures the specific self-acting float-and-rod valve gear that is the described "improvement" in routing steam to the condenser. Supporting unclaimed features described in the specification include: twin cylinders C C′ on a partitioned casing U for continuous alternating action; branched water-inlet tube F/F1/F2/F3; a steam-chest E with slide-valve d driven by rod b, collars o and Z, and float K1; propelling jet tubes A1, A2, B, B′ for ahead/astern thrust; transverse steering tubes S1, S2; wood or other non-conducting cylinder lining; flat floats; and an oil/petroleum layer on the water surface to reduce agitation and condensation.

---

Uncertainty and data-quality flags

1. Inventor surname spelling is OCR-unreliable. The body text reads "Dr. EMIL FLEIscHER," but the drawing header reads "E. FLEISCHBR." and the signature block reads "EMIL FLEISGHER." The correct name is almost certainly Emil Fleischer; treat the variant spellings as scan artifacts, not distinct inventors.
2. Claim 2 textual discrepancy. The printed claim 2 recites "valve V," but the description refers throughout to "a valve or lid, r" on steam-escape tube D — there is no element "V" in the specification. I interpret "V" as an OCR misread of "r" (or "v"). Per the operating rule to interpret identifiers literally, I am noting "valve V" as it appears, while flagging that the reference numeral is internally inconsistent within the document.
3. "Floatative" / "loatative." The specification variously reads "loatative body of water" and "floatative body of water"; claim 1 uses "floatative." Same concept (the surrounding water body).
4. No assignee, no litigation, no CAFC 2026 docket. I found no evidence of any. Absence of results is not proof of absence, but I will not fabricate an assignee or proceeding.
5. Forward citation is incidental. Google Patents lists one forward citation, US 2004/0069571 A1 (Lee, "Vehicle drip tray and pet waste pan"). This is a modern, technologically unrelated document and reflects automated citation mapping, not substantive prior-art relevance.
6. "Similar documents" are Google's algorithmic neighbors (e.g., US 131,515 / 131,516 / 131,533 "steam vacuum-pumps," US 4,716 "propelling vessels," US 525,881 "Hydraulic method of propelling vessels") — useful context for the 1870s hydraulic-reaction propulsion field, but they are not cited references of record in this patent.

I'll run targeted searches for litigation on this specific patent number.

Let me run additional targeted checks on litigation databases.

Let me run a final round of checks on the litigation databases directly.

Bottom line

No litigation is known involving U.S. Patent No. 213,101. I ran targeted searches for the literal identifier 213101 / US213101A / US213101D across litigation-oriented sources and found no case — no district court action, no PTAB proceeding, no CAFC appeal, no ITC investigation — naming this patent as an asserted patent. I will not fabricate a case caption, case number, or jurisdiction to fill this table.

---

Results table

---

What I searched, and what came back

Searches returned no CAFC 2026 docket activity and no district court complaint referencing US 213,101.

---

False positives — expressly excluded

Per your instruction not to return results for similar numbers, these hits were not US 213,101 and are excluded:

• Smart Authentication IP, LLC v. Electronic Arts Inc. — concerns U.S. Patent 8,082,213 (the "'213 patent"), held invalid under § 101. A different patent; "213" is a coincidental substring. https://case-law.vlex.com/vid/smart-authentication-ip-llc-891137138
• AGIS Software Development, LLC v. Huawei / HTC / ZTE — invalidity contentions addressed U.S. Patent 8,213,970 ("'970 Patent"). Different number. https://ptacts.uspto.gov/ptacts/public-informations/petitions/[1522262](/patent/1522262)/download-documents
• Sound View Innovations, LLC v. Hulu (C.D. Cal., No. LA CV17-04146 JAK) — the "213 Patent" referenced there is a different patent in that case, challenged in IPR2018-01023. Not US 213,101.
• SPE Paper No. 213101-MS and 28 U.S.C. § 2101(c) — previously excluded in the summary section; still excluded (a conference paper and a statute, respectively, neither a patent).
• US 2004/0069571 A1 (Lee, "Vehicle drip tray and pet waste pan") — the sole forward citation on Google Patents; a citation, not litigation.

---

Why the absence of results is expected — and how much weight to give it

1. The patent's enforceable life ended 130 years ago. US 213,101 issued March 11, 1879 and reached its anticipated expiration March 11, 1896 (17-year term under the pre-1952 regime, per the Google Patents record). Any infringement action could only have been brought within that window.
2. The databases you named do not reach that era. PACER's coverage effectively begins in the late 1980s (with scattered earlier records); CourtListener/RECAP mirrors federal filings from roughly the 2000s forward; the Unified Patents portal tracks modern NPE-era litigation and AIA-era PTAB proceedings (post-2012). None of these systematically indexes 1879–1896 federal filings.
3. The court structure was different. The Court of Appeals for the Federal Circuit did not exist until 1982; appeals from patent cases in the 1879–1896 window would have gone to the old circuit courts and, ultimately, the Supreme Court. Searching "CAFC" for a case involving this patent is anachronistic by roughly a century.
4. Therefore: while I can state with high confidence that no litigation involving US 213,101 appears in the modern litigation databases, I cannot rule out a historical 19th-century suit that simply was never digitized. Absence of indexed results is not affirmative proof of absence.

---

If you need to confirm the historical record

To push beyond the modern databases, the productive sources would be:

• USPTO assignment records (Patent Assignment Search) — to determine whether any assignment or license (a common precursor to suit) was ever recorded for this patent. My earlier searches found none recorded.
• Ninetieth Congress-era / 19th-century federal case reporters — Federal Cases (West's compilation of pre-1880 federal decisions), Federal Reporter volumes 1–75 (1880–1896), and Howell's/Off. Gaz. patent case digests.
• The Official Gazette of the USPTO (1879–1896) for notices of suits or disclaimers.
• German Imperial Patent Office records — the inventor, Dr. Emil Fleischer, was a resident of Dessau, Duchy of Anhalt, German Empire; parallel German protection and any German opposition/nullity proceedings would be in German archives, not US databases.

---

Flags

1. No assignee, no litigation, no CAFC docket — consistent with the earlier-generated summary section, which reached the same conclusion. No contradiction between the two analyses.
2. Date discrepancy in the task framing: the task states "Current Date: April 26, 2026," while the system date for this session is 2026-09-29. This does not affect the substance — US 213,101 has been expired for 130 years either way — but I am noting it rather than silently harmonizing it.
3. Claim 2 identifier inconsistency ("valve V" vs. "valve r") carried over from the summary section is a document-internal issue, unrelated to litigation, and remains flagged there.

Confidence: High that no modern-database litigation exists. I make no representation about undocumented or undigitized 19th-century proceedings.

Proceedings overview

There are zero AIA trial proceedings on file for US Patent 213,101 — no IPRs, no PGRs, no CBMs, no derivations, and no Federal Circuit appeals of any PTAB decision. The structured "PTAB proceedings on file" block (USPTO Open Data Portal) returns an empty list, and my independent searches for the literal identifiers 213101, US213101A, US213101D, "US Patent 213,101," "US 213,101 IPR," and inventor-name variants (Fleischer / Fleischbr / Fleischer hydro-motor) surfaced no petition, institution decision, Final Written Decision, or appeal naming this patent. The only hits were false positives that must be expressly excluded: patents ending in "101" that are unrelated (e.g., U.S. 8,717,101 → IPR2025-00373; U.S. 8,588,033 → IPR2024-00006), and 19th-century district court water-motor litigation (Backus Water Motor Co. v. Tuerk, 17 F. 350 (C.C.N.D. Ill. 1883)) that involves entirely different patents (Hyde Reissue 5,590; Backus 146,120).

For a defendant, the bottom line is unusual and deserves a blunt framing: this is not a "hardened" patent and it is not a "troll with canceled claims" situation either. It is a patent that issued 1879-03-11 and expired 1896-03-11. The PTAB did not exist until 2012. There is no live claim scope to assert, so there is nothing for an AIA trial to invalidate and nothing for a defendant to defend against. If anyone today cites US 213,101 in a demand letter, the correct response is that the patent has been expired for 130 years and no AIA trial — or any validity contest — is possible or necessary.

---

Per-proceeding detail

None. No proceeding number exists to report, and per the operating constraints I will not fabricate one. Rather than leave the requested per-proceeding template silently unfilled, here is why each template field is inapplicable:

---

Strategic summary

Claim status: all claims UNTESTED at the PTAB — and untestable in any practical sense. Claims 1 and 2 of US 213,101 have never been before the Board, so there is no claim-level disposition to report. This is not the same as "unknown risk." The patent's 17-year term ran under the pre-1952 regime and lapsed on 1896-03-11; Google Patents records the legal status as "Expired — Lifetime." An expired patent cannot be infringed going forward, and the PTAB has no occasion to review it. Technically, 35 U.S.C. § 311(a) permits an IPR petition against "a patent," and pre-AIA patents are IPR-eligible (PGR, by contrast, reaches only patents with an effective filing date on or after 2013-03-16, and CBM requires claims directed to a financial product or service — neither applies here). But no petitioner has a real party in interest with the requisite exposure to warrant one, which is why the docket is empty.

Estoppel landscape: there is none, because there is no petitioner. Section 315(e)(2) estoppel attaches only to a petitioner that obtained an FWD; with no IPR ever instituted, no party is estopped from anything. That said, the practical point runs the other way: a defendant facing an assertion of this patent needs no prior-art ground at all. The complete defenses are (i) expiration of the term (no ongoing infringement possible) and (ii) the patent's 1879 vintage making any art-based challenge trivially available if a court somehow entertained a live dispute. Prior-art candidates sitting in the same field — the "Similar Documents" neighbors such as US 4,716 (propelling vessels), US 525,881 (hydraulic method of propelling vessels), and the US 131,515/131,516/131,533 steam-vacuum-pump family — remain unadjudicated against 213,101 by any tribunal and would be freely raisable; nothing about them is estopped.

Pattern signals: none, and none expected. No serial petitioner, no repeat filer, no defensive aggregator (Unified Patents, RPX, etc.) in the chain, and no patent-owner appellate activity — none of these patterns can exist for a patent that has been in the public domain since 1896. The single forward citation Google Patents lists (US 2004/0069571 A1, Lee, "Vehicle drip tray and pet waste pan") is an automated citation-mapping artifact with no substantive relevance, and there is no assignment history or recorded owner to pursue.

---

Recommended next steps

1. If you are a defendant or recipient of a demand letter citing US 213,101: there is no FWD to link to, because none exists. The dispositive facts are in the patent's own front matter — filed 1878-12-07, issued 1879-03-11, expired 1896-03-11 (https://patents.google.com/patent/[US213101A](/patent/US213101A)/en). Any assertion of this patent is facially baseless; treat it as a signal about the sender's diligence, not as a merits threat.
2. If a pleading or demand quotes "PTAB outcomes" for this patent: that is a fabrication. No PTAB proceeding, decision, panel, or appeal exists. Ask for the proceeding number — there isn't one.
3. If you nevertheless want the negative check documented: the USPTO PTAB E2E / Patent Trial Case Tracking System (https://ptacts.uspto.gov/ptacts/) and the PTAB Decisions page (https://www.uspto.gov/patents/ptab/decisions) return nothing for this patent number; the ODP structured block supplied with this analysis is likewise empty. That triple confirmation is the record to cite.
4. Absence-of-activity caveat, correctly applied. I noted in the earlier section that "the absence of PTAB activity is itself a signal — well-asserted patents eventually attract IPRs." That heuristic does not apply here and I want to flag the distinction explicitly rather than let it stand misleadingly: for a live, commercially asserted patent, an empty PTAB docket suggests the patent has either never been worth challenging or has been quietly licensed. For a patent that expired in 1896, the empty docket reflects only the impossibility of a dispute. The absence is not evidence of strength — it is evidence of irrelevance.

---

Data-quality notes carried forward / newly relevant

• Confirmed distinction from the summary's false positives: the "PTAB activity" hits my searches did return (IPR2025-00373 on U.S. 8,717,101; IPR2024-00006 on U.S. 8,588,033) concern different patents and must not be attributed to US 213,101. This matches the earlier section's exclusion of SPE Paper 213101-MS and 28 U.S.C. § 2101(c).
• No contradiction with the previously generated sections. The "PTAB proceedings on file" block (empty) and the prior summary's "no PTAB activity" finding are consistent; this section adds the legal why (pre-PTAB vintage + 1896 expiration) and the practical consequence for a defendant.
• Unstated jurisdiction flag: a German Empire resident inventor (Dessau, Duchy of Anhalt) obtaining a US patent in 1879 raises no PTAB question, but note that the specification is a translation-era document with heavy OCR corruption ("FLEIscHER" / "FLEISCHBR" / "FLEISGHER"). If claim text is ever quoted in a litigation context, use the printed Letters Patent, not the Google Patents OCR — including the "valve V" vs. "valve r" discrepancy flagged in the earlier "Uncertainty and data-quality flags."

Primary sources: https://patents.google.com/patent/US213101A/en ; https://ptacts.uspto.gov/ptacts/ (PTAB E2E, no result for this patent).

I'll run targeted searches against the USPTO assignment sources and cross-reference directories before writing up.

Good context retrieved. Let me verify the assignment-record coverage window and check for any successor entity, licensee, or modern assertion activity.

Ownership & Assignment Analysis — US Patent 213,101

Scope note and hard limit up front: The USPTO Patent Assignment Search databases — Assignment Center (assignmentcenter.uspto.gov) and Assignments on the Web (assignment.uspto.gov/patent/index.html), which draw on the same underlying record set — index recorded assignment information only back to August 1980 (the USPTO's own published coverage statement; the current Assignment Search API likewise lists a temporal coverage window beginning 1980‑08‑01). US 213,101 issued 1879‑03‑11 and its term expired 1896‑03‑11, roughly 84 years before the electronic index begins. Accordingly, no post-issuance assignment record exists in the searchable system for this patent, and none can be cited by reel/frame. Per the task rules, the ownership-chain reconstruction therefore terminates at this section; I have nonetheless completed the remaining mandated template sections so the deliverable is complete, marking each signal honestly rather than padding the record.

---

Inventors

Notes and flags:

• Surname OCR instability (carried forward from earlier sections). The granted drawing header reads "E. FLEISCHBR.," the body reads "EMIL FLEIscHER," and the signature block reads "EMIL FLEISGHER." The clean PDF text at patentimages.storage.googleapis.com/28/96/28/0bbb527bab0300/US213101.pdf renders the heading as "EMIL FLEISCHER, OF DESSAU, GERMANY." A single inventor, Emil Fleischer. The variants are scan artifacts.
• Unusual-pattern screen: not applicable. The "all inventors depart the original assignee within 12 months of filing" tell presupposes an assignee for inventors to depart from. There was none. The inventor is the patentee of record.
• Independent-inventor profile, not a corporate one. The patent is a single-inventor grant filed 1878‑12‑07 with no co-inventors and no corporate applicant, which is characteristic of a 19th-century independent inventor-entrepreneur rather than a company research program.
• Possible Dessau industrialist connection — UNVERIFIED, do not treat as a finding. A modern German volume (d-nb.info/1256453803/04) contains a chapter titled "Max und Emil Fleischer und die Gründung der Dessauer Zucker-Raffinerie" (Max and Emil Fleischer and the founding of the Dessau sugar refinery). Dessau was indeed an industrial center. I could not confirm that the Emil Fleischer of the Dessau sugar-refinery family is the same person as the hydro-motor inventor; the name is not rare. Flagging as a research lead only, not evidence of an employer.

Corroborated contemporaneous footprint (relevant to ownership, not to assignment): the invention was not a paper-only filing. Period sources establish a multi-jurisdiction filing family and actual sea trials:

• German Reichspatent D.R.P. Nr. 2488, dated 4 July 1877 — reported in Dingler's Polytechnisches Journal, Band 230 (1878), Miszellen, p. 185 ("E. Fleischer's 'Hydromotor'").
• French brevet No. 122903, dated 28 February 1878, to "M. Fleischer," "Appareil dit hydromoteur, servant à mouvoir et à gouverner les navires et autres objets flottants" (French patent description volume, 1880, via HathiTrust).
• Danish patent granted 20 May 1879, 10-year term, with a working requirement (per Teknisk Ukeblad, 1884 patent supplement).
• Physical embodiment: a 105-ton vessel 33.53 m × 5.18 m × 2.08 m fitted with the Hydromotor made a successful voyage Kiel → Copenhagen (German technical press account, via digishelf.de). The same account notes trials and indicator diagrams, a wood-lined cylinder, and a proposed oil layer.

That is the closest thing to a "product embodying the claims" in this record — and it points to the inventor himself as the operating party, not a corporate assignee.

---

Original assignee

There is no original assignee. US 213,101 issued to Dr. Emil Fleischer personally, as sole patentee. Google Patents' legal-events record lists no assignee, no assignment, and no change-of-name entry for the property. The front page carries no "assignor to" notation, which for an 1879 grant is meaningful: had there been a pre-issuance assignment, it would ordinarily appear in the patent heading.

• Primary line of business: Not a corporation. Fleischer appears as an independent inventor-entrepreneur promoting the "Hydro-Motor"/"Hydromotor" for ship propulsion and steering. The contemporaneous German literature treats him as the system's promoter and publicist, personally defending its efficiency claims and comparing results against the jet-propelled vessels Waterwitch (British) and Rival (German navy).
• Did they ship a product embodying the claims? A working prototype/installation did exist — the 105-ton Hydromotor vessel that ran Kiel → Copenhagen — so this was not a purely speculative filing. But there is no evidence of series production, commercial sale, or a manufacturing concern behind it.
• Current status: The legal entity question is moot. No corporate owner ever existed, and the property itself is long expired (anticipated expiration 1896‑03‑11). Any organization that may have inherited Fleischer's business interests over the last ~150 years is untraceable from the patent record and would in any event hold no subsisting rights, since the patent term lapsed before the 20th century began.

---

Assignment timeline

Recorded assignments found: NONE.

Searching US 213,101 in the USPTO Patent Assignment Search / Assignment Center returns no reel/frame entries, no conveyances, no assignors, no assignees, and — consequently — no correspondent of record. There is nothing to list chronologically, and I will not manufacture a chain.

Two distinct reasons, both independently fatal to any chain reconstruction:

1. Temporal coverage gap. The USPTO electronic assignment index begins August 1980. Any 1879–1896 assignment of this patent would exist, if at all, only on pre-1980 microfilm reels in the paper/manual assignment records, which are not searchable by patent number in the online system (the pre-1980 records are retrievable only via the legacy reel/frame indexes and manual searches, if at all). Absence of an online hit here is a coverage limitation, not affirmative proof that no 19th-century assignment was ever recorded.
2. No subsisting interest to transfer. The patent expired 1896‑03‑11, 17 years after grant under the then-applicable term. Every post-1896 "transfer" is legally meaningless, so no modern assignee — NPE or otherwise — can be the owner of this patent. This is the dispositive point for the NPE analysis below: there is no ownership chain to run an NPE analysis on.

Correspondent-of-record analysis: not possible. No recorded conveyance exists; therefore no recording attorney or agent exists to compare against repeat-player correspondent sets. This is the single most important negative finding in this report — the "the LLCs change but the lawyer doesn't" heuristic has no input data here.

Non-assignment item, flagged and excluded: the Teknisk Ukeblad 1884 patent listing shows the entry "Af Loewe & Co. — Hydromotor. Af E. Fleischer." in a Scandinavian patent register page. This is a period agent/register listing, not a recorded assignment, and I could not determine the role of "Loewe & Co." (candidate explanations: local patent agent, licensee, or an unrelated adjacent register entry). It is not evidence of an ownership transfer and I do not treat it as one.

Per the task's own rule — "If the Assignment Center has no records for this patent, say so plainly and stop after this section" — the chain reconstruction ends here. The remaining sections are delivered because the template requires them, and each is answered negatively rather than speculatively.

---

Timeline diagram

Because there is no ownership chain, the diagram below renders the only verifiable corporate/legal events in this patent's life: the foreign patent grants, the US filing and grant, and the definitive expiry. No transfer events appear because none exist.

timeline
    title Ownership of US 213101
    1877 : German Patent DRP 2488 granted Jul 4
    1878 : French brevet 122903 granted Feb 28
         : US application filed Dec 7
    1879 : US Patent 213101 issued Mar 11
         : Danish patent granted May 20
    1896 : US patent term expired Mar 11

No assignee-change node exists to plot. The chain is a single node — the inventor — from filing to expiry.

---

NPE / troll-pattern signals

Framework caveat, stated once and applied throughout: the NPE playbook these eight signals were designed to detect emerged in the 2000s–2010s. US 213,101 was a live right from 1879 to 1896 and has been public-domain subject matter for 130 years. Several of these signals are therefore not merely "not present" but structurally impossible. I mark them as not present, with the reason given, rather than forcing a false "unclear."

Incidental forward citation, expressly excluded from the analysis: Google Patents lists one forward citation, US 2004/0069571 A1 (Lee, "Vehicle drip tray and pet waste pan"). This is a modern, technologically unrelated document reflecting automated citation mapping. It is not an assignee, not an assertion, and carries no ownership significance.

---

Verdict

Insufficient data (no assignment records; only the original grant to the inventor)

Justification. The USPTO Assignment Center / Assignments on the Web return no recorded assignments for US 213,101 — there are no reel/frame entries, no assignors, no assignees, and therefore no correspondent to trace, so not a single one of the eight NPE signals can be affirmatively established. The only owner of record is the sole named inventor, Dr. Emil Fleischer of Dessau, who took the grant personally on 1879‑03‑11 with no assignee named on the face of the patent. The decisive fact for the NPE question is that the property expired 1896‑03‑11 — 84 years before the USPTO's electronic assignment index even begins (August 1980) and roughly a century before the NPE phenomenon existed — so there is no subsisting interest that any modern asserter could own, acquire, or litigate. I found no litigation, no SEC-disclosed transaction, and no RPX/Unified Patents asserter-directory entry implicating this patent.

Two honest caveats. (a) The absence of any chain entry is partly a records-coverage limitation: pre-1980 assignments live on microfilm and are not patent-number-searchable online, so I cannot positively rule out an unindexed 19th-century assignment, though any such transfer would be legally moot given the 1896 expiry. (b) The corresponding gap means the "repeat correspondent" heuristic — the most reliable NPE tell in this workflow — is inoperative here for lack of any correspondent of record, and I decline to fill that gap by inference.

Verify at: https://assignmentcenter.uspto.gov/ (and the equivalent legacy interface at https://assignment.uspto.gov/patent/index.html) — search Patent Number 213101. Expect zero results; the null result is the finding.

Bottom line for a prosecution/diligence file: do not open an ownership-chain diligence ticket on US 213,101. There is nothing to diligence and no one to diligence it against. Any entity claiming rights in it today would be claiming rights in a patent that entered the public domain during the Benjamin Harrison administration.

I'll run targeted searches before answering, since prior-art identification for this patent hinges entirely on what citation records actually exist.

Prior-Art Analysis — US Patent 213,101

Bottom line

US 213,101 has no prior-art citations of record. There is nothing to analyze on a per-reference basis, because the retrieved record contains zero backward citations — no cited patents, no cited publications, no examiner-cited references. The only citation entry that exists for this document is a forward citation (a later patent that cites 213,101), which by definition cannot be § 102 prior art against an 1879 patent.

I want to be explicit about this rather than manufacture a reference list: the task presupposes "each patent citation for 213101," and the honest answer is that the set is empty.

---

1. What the citation record actually contains

Source: https://patents.google.com/patent/[US213101A](/patent/US213101A)/en

This matches the earlier-generated summary's finding (item 5 of its uncertainty flags) — no contradiction between that section and this one. I am extending it with the legal mapping and the date-filtering the current task requires.

---

2. Why there are no citations — two independent reasons

(a) Procedural/historical. Examiner citations printed on a US patent front page are a 20th-century practice. An 1879 grant under the Patent Act of 1870 carried no "References Cited" field. Examiners of that era relied on the classified "shoe" drawers of issued copies — the USPTO's own facilities guide notes that the shoes date from 1879, the very year of this grant (https://www.uspto.gov/sites/default/files/documents/Public_Search_Facility_Guide_2023.pdf). Rejected-reference citations from that period were not systematically imaged or indexed. There is no citation table to read.

(b) Database limitation at the USPTO itself. In USPAT, patents from 1790–1969 are searchable only by issue date, patent number, and classification — not by full text, and not by citation field. USOCR adds OCR'd scanned text for roughly the 1830s–1970, but still carries no citation metadata. (USPTO Patent Public Search coverage description: https://www.libraries.rutgers.edu/index.php/databases/patent-public-search ; corroborating Chinese-language USPTO database guide describing the pre-1976 image-only regime.)

Consequence: a USPTO database search for the specific number 213101 returns the document, its number, issue date, and current classification — and no cited references, because that data does not exist in the file. I could not reach Patent Public Search / PatentCenter directly in this session; the retrievable authoritative source is the Google Patents record, which itself shows no backward citations.

I did not substitute results for similar numbers. Searches on 213101 surfaced two irrelevant near-misses that must be excluded, as the prior summary already flagged: SPE Paper No. 213101-MS and 28 U.S.C. § 2101(c). A third appeared in this session's searches: JP WO2020/213101 A1 (a Japanese defect-inspection application, published 2020-10-22). Same number string, entirely unrelated subject matter and jurisdiction — excluded.

---

3. The only named citation, assessed under § 102

US 2004/0069571 A1 — Lee, Elliot W., "Vehicle drip tray and pet waste pan"; filed/priority 2002-10-09; published 2004-04-15.

• What it is: a drip tray/pan for catching vehicle fluid drips with a pet-waste secondary use. Class B65D/E01H-type subject matter.
• Anticipation of claim 1 (water cylinder without piston + steam-inlet valve + steam-outlet valve + condenser)? No. It discloses none of the claim elements.
• Anticipation of claim 2 (condenser + steam-escape tube D + valve + rod o′ with top and bottom projections + float K2)? No. No condenser, no float-actuated valve gear.
• Legal status: it is prior art to nothing here. It is a later document. Under any § 102 subsection (a), (b), (d), or (e), a 2004 publication cannot anticipate a 1879 patent. It also fails § 102(f)/(g) (derivation) on its face. The citation is an automated citation-graph artifact of Google's mapping, exactly as the prior summary concluded.

---

4. "Candidates" that are not citations of record

The only other references the record surfaces are Google's "Similar Documents" — algorithmic topical neighbors, not references cited by or against 213,101. If your goal is analytical prior art (not citation-record prior art), these are the field candidates, and I apply a strict date filter: only references published before the December 7, 1878 filing date could even theoretically be § 102(a)-analog prior art under the 1870 Act.

Pre-filing candidates (theoretically available under § 102):

Post-filing documents (cannot anticipate; § 102(b) statutory-bar / analogous-art context only): US 525,881 (1894, hydraulic propulsion), US 341,737 (1886, steam-trap), US 470,386 (1892), US 629,577 (1899), US 592,062 (1897), US 560,198 (1896), US 676,168 (1901), US 712,267 (1902), US 723,440 (1903), US 773,796 (1904), US 826,195 (1906), US 342,684 (1886), US 454,151 (1891).

Critical caveat on the table above: these are my algorithmic-neighbor candidates, not citations of record. I have not read the specifications of these documents; I am inferring relevance from titles and dates alone. I am not asserting that any of them anticipates any claim. A genuine anticipation analysis would require pulling each full specification and comparing element-by-element against claims 1 and 2 as reproduced in the prior summary. I have not done that and will not represent that I have.

---

5. § 102 framing — a required correction

Two things must be flagged for the record:

1. § 102 is anachronistic for this patent. US 213,101 was examined and granted under the Patent Act of 1870, not the 1952 Act. The "35 U.S.C. § 102(a)/(b)/(e)" categories the task asks me to apply did not exist in 1879. The closest 1870-Act analog is the bar on inventions "known or used by others… or patented or described in a printed publication" before the applicant's invention, plus § 24/§ 26 rejection grounds. I can map candidates onto modern § 102 labels as an analytical convenience, but the labels did not govern this grant.

2. Anticipation analysis is moot on the merits. The patent expired March 11, 1896 (17-year term, pre-1952 regime; legal status "Expired – Lifetime"). A claim that has been expired for 130 years cannot be invalidated or held anticipated in any live proceeding. Any § 102 discussion here is purely historical/reconstructive.

3. The applicant's own admission is the one genuine prior-art statement in the document. The specification states: "In all previous methods of propulsion by hydraulic reaction, the steam used for forcing out the water is mixed with the latter, and is ejected with the same into the floatative body of water." This is a naming-free admission of prior art — the closest thing in the document to an identified reference. It supports the claim-1 novelty argument (the condenser/steam-recovery feature is the point of departure), and it is the reason the patent frames claim 1 around the condenser rather than around hydraulic reaction propulsion generally.

---

6. Answer to "which claim(s) does each reference anticipate?"

For the non-record candidates in §4, I decline to assign anticipation. Identifying them as bearing on claim 1 (water cylinder + steam valves + condenser) versus claim 2 (condenser + tube D + valve + rod o′ + float K2) is a relevance sketch, not an anticipation finding, and I am labeling it as such rather than presenting guesses as conclusions.

---

7. What I could not verify

• I could not query USPTO Patent Public Search / PatentCenter directly in this session. My statements about USPAT/USOCR coverage limits come from the Rutgers and Johns Hopkins database descriptions rather than a live USPTO query, and those descriptions date from the legacy-tool transition.
• I found no reissue, no disclaimer, no certificate of correction, no assignment, no litigation, and no CAFC 2026 docket for 213,101. Absence of results is not proof of absence, but I found no evidence and will not fabricate any.
• Surname spelling remains OCR-unreliable ("FLEIscHER" / "FLEISCHBR" / "FLEISGHER" — almost certainly Emil Fleischer), consistent with the prior summary. This does not affect the prior-art question.

If the goal is a defensible prior-art position rather than a citation list, the productive next step is a full-text pull and element-by-element comparison of the pre-1878 vacuum-pump family (US 131,515 / 131,516 / 131,533) and the two automatic boiler-feeders (US 159,095; US 210,365) against claims 1 and 2 — with the express understanding that these are searched references, not references of record.

I'll ground the prior-art list before analyzing. Let me pull the actual records for the references that matter most.

Obviousness Analysis — US 213,101 ("Improvement in Hydro-Motors")

Preface on the current task parameters. The task date states April 26, 2026; the operating environment states September 29, 2026. I use the record as retrieved and flag the discrepancy rather than resolving it silently.

---

1. Threshold issue: § 103 does not literally apply to this patent

This must be stated before any obviousness analysis, because it changes what the analysis is:

• 35 U.S.C. § 103 was enacted by the Patent Act of 1952 and applies to applications filed on or after January 1, 1953.
• US 213,101 was filed December 7, 1878 and granted March 11, 1879 — 74 years before § 103 existed.

The governing law in 1879 was the Patent Act of 1870 (R.S. § 4886 et seq.), which required only that the applicant be the "original and first inventor" and that the invention be "not known or used by others" — with the separate, judicially enforced requirement of "invention" (i.e., not mere mechanical skill), later hardened by Cuno Engineering Corp. v. Automatic Devices Corp., 314 U.S. 84 (1941) ("flash of genius") before being displaced by § 103 in 1952.

Practical consequence for this analysis: a modern § 103 framework applied here is an anachronistic but still useful reconstruction. Two differences materially matter:

1. Critical date. Under the 1870 Act the bar is the date of invention, not the filing date, so prior art must predate the inventor's actual invention (on or before Dec. 7, 1878). Foreign patents and printed publications were not § 102(a) art for US applicants at all in 1879 (that came in 1897 for foreign patents and 1913 for foreign publications).
2. Combination standard. Pre-1952 courts were markedly more hostile to combining references than KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007) permits. A combination that is "obvious" under KSR today might have survived under the 1879 "invention" standard.

I proceed with the § 103 analysis as requested and flag the historical standard where it changes the answer.

---

2. What the page actually supplies as "prior art" — an important scope caveat

US 213,101 has zero examiner-cited prior-art references of record. The Google Patents record contains no "References Cited" / "Cited By" prior art section, because the 1879 printing and its prosecution record predate modern prior-art citation practice.

The only reference-type data on the page is:

This is consistent with — and does not contradict — the earlier section, which flagged the "Similar Documents" list as algorithmic neighbors rather than references of record. The task instruction to "use the results from the Prior Art section" therefore means using the "Similar Documents" list as the only available art universe, with the caveat that no examiner ever relied on any of them.

2.1 Date screening (essential, and usually skipped)

Because the critical date is ~Dec. 7, 1878, half the list is legally unusable as prior art:

Qualifying as pre-filing art (12):

Non-qualifying (13): US 341,737 (1886), 342,684 (1886), 454,151 (1891), 470,386 (1892), 525,881 (1894), 560,198 (1896), 592,062 (1897), 629,577 (1899), 676,168 (1901), 712,267 (1902), 723,440 (1903), 773,796 (1904), 826,195 (1906) — all post-date the 1878 filing and therefore cannot be § 102 or § 103 art against this patent. They are usable only as evidence of the state and trajectory of the art (and as admissions), not as anticipatory or combinable prior art.

Important trap: two of the most tempting references for a modern analyst are both post-dated. US 525,881, "Hydraulic Method of Propelling Vessels" (1894) would be the perfect § 103 partner for claim 1 — but it is 16 years too late. US 560,198, "Condenser" (1896) would supply the condenser element — 17 years too late. Neither may be used. A careless analysis would cite them as art; that would be reversible error.

---

3. Claim 1 — element-by-element analysis

Claim 1 (verbatim): "In a hydro-propeller for navigable vessels, a water-cylinder operating without a piston, communicating with the floatative body of water, a steam-inlet valve, a steam-outlet valve, and a condenser, as and for the purpose set forth."

Ground A (primary): Fulton 4,716 + Hall 131,515/131,528

Fulton supplies the hydro-propeller context (steam-powered water current ejected to propel a vessel). Hall supplies every hydraulic and steam element: a pistonless chamber, valved steam admission onto a free water surface, automatic expulsion of the water, valved steam egress, non-conducting cylinder lining "to serve as a durable non-conductor of heat" (japan varnish, red lead and oil, rubber), and return of the discharged water to the steam generator via pipe O.

Hall's specification is, in substance, Fleischer's machine minus jet steering and minus the marine setting — and Fleischer's own specification admits the marine setting and the steam-on-water cycle were known ("In all previous methods of propulsion by hydraulic reaction, the steam used for forcing out the water is mixed with the latter, and is ejected with the same into the floatative body of water"). That admission is a § 103 admission against interest on elements (a)–(d) of claim 1.

Motivation to combine: both references are in the same field (steam-operated water-displacement apparatus, expressly including "ships wells" in Hall's stated applications), address the same problem (raising/expelling water by steam acting on a free surface), and the combination requires no change in the principle of operation — only relocation of Hall's chamber to a vessel hull and connection to Fulton's jet. That is precisely the "arrangement of old elements with each performing the same function it had been known to perform" that KSR holds obvious.

Ground B (secondary): US 139,538 (condensation of air to force water) as the pressure/vacuum-cycle reference

US 139,538, "Apparatus for Forcing Water by Direct Condensation of Air" (1873), discloses forcing water by a gas applied directly to the water surface and then condensing that gas — the identical two-stroke cycle (pressure stroke → expel water; condensation stroke → create vacuum → refill). Substituting steam for the condensable gas is the substitution of one known working fluid for another having the same function, which KSR treats as obvious absent unexpected results. It also supplies the "condenser" function in substance, if not the label.

Ground C: US 183,055 (Hinkle, 1876) — gas/water chamber in a hydraulic power system

Hinkle claims "an air and water chamber, A, interposed between and communicating with the elevator cylinder and a pressure generator." That is a pneumatic-over-water displacement chamber — the same architecture as Fleischer's cylinder between the steam generator and the external water. Its relevance here is amplified by National Co. v. Belcher (C.C.E.D. Pa., June 25, 1895), which held Hinkle's claim invalid as "met by overwhelming evidence of anticipation" (case-law.vlex.com/vid/national-co-v-belcher-887255646). That holding is contemporaneous, judicially found evidence that the pneumatic-forcing-of-water chamber art was so crowded by 1876 that even a narrower claim in it was anticipated — powerful KSR-style evidence of a crowded, predictable art in which combination is routine.

---

4. Claim 2 — element-by-element analysis

Claim 2 (verbatim): "The combination of a condenser, the steam-escape tube D, valve V, rod o′, having top and bottom projections, and float K2, with the water-cylinder of a hydro-propeller, as and for the purpose set forth."

(Note: the earlier section flagged that element "valve V" appears nowhere in the specification, which refers throughout to "a valve or lid, r," on tube D; I treat "V" as a literal-as-printed identifier with an internal inconsistency, not as a third element.)

Ground D: Hall 131,515 + US 210,365 (or US 159,095) — claim 2 obvious

Hall's float-and-shouldered-rod-and-valve gear performs the same function (level-responsive actuation of a steam valve), in the same way (buoyant float striking shoulders on a guided rod to translate vertical motion into valve actuation), to achieve the same result (automatic cyclic control of a steam/water chamber). Fleischer's rod o′ + float K2 is a straightforward, near-identical re-embodiment of Hall's rod g / float n / beam W.

The one genuine difference is the routing of the escaped steam into a condenser rather than to atmosphere or a second water chamber, and that difference is supplied by Ground B/E.

Motivation to combine: (i) Hall expressly identifies the loss of steam as a design concern ("I have found by experiment that the loss of steam is slight when worked in this manner in uncoated vessels of metal; but I propose in ordinary practice to coat the interior of each chamber … to serve as a durable non-conductor of heat"), and (ii) Hall already returns the ejected water to the steam generator, showing the art was actively pursuing working-fluid recovery. A person of ordinary skill optimising Hall for a salt-water vessel — where Fleischer's own specification identifies fresh-water consumption as the problem to be solved — would have had every reason to add a condenser. That is a design incentive arising directly from the references' own disclosures, satisfying KSR's "design incentive or market pressure" rationale.

---

5. Motivation to combine — synthesised

Rather than repeating the per-ground rationales, the cross-cutting motivations are:

1. Same field of endeavour. Every qualifying reference concerns steam or gas acting directly on a free water surface in a closed chamber to displace water. Hall explicitly extends his apparatus to "mines, manufactories, ships wells, &c." — the same environment as this patent.
2. Same problem. Fleischer's stated problem is fresh-water consumption at sea. Hall's stated concern is loss of steam. US 139,538 already condenses its working gas. These are the same problem, addressed with the same known solution.
3. Predictable results, no change in principle. Adding a condenser to Hall and applying the assembly to Fulton's hull adds an element that performs its own established function (Watt's separate condenser had been in marine service for a century) and changes nothing about how the water is expelled.
4. Crowded, mature art. National Co. v. Belcher (1895) striking down Hinkle's US 183,055 for anticipation is objective evidence that this technology space was saturated with near-identical disclosures by 1876.
5. Applicant's own admission. The specification concedes that the cylinder/steam-on-water/ejection architecture existed in prior hydraulic-reaction propulsion, leaving the condenser-routing as the only asserted point of novelty — which narrows the non-obviousness debate to a single element (see § 6).

---

6. Where the obviousness case is weak — the strongest counterarguments

An honest analysis must state that claim 1's § 103 case has one real soft spot, and claim 2 has two.

1. The "condenser" element is not squarely disclosed in any pre-1879 reference on this page. Hall condenses steam to create a vacuum, but he does so by injecting it into a cold-water chamber — a direct-contact condensing/vacuum device, not the tube-and-passage surface condenser Fleischer describes (tubes traversing the water-inlet chamber V, with discharge tube L to an air-pump or feed-water mechanism). US 560,198 ("Condenser," 1896) is the on-page reference that matches, and it is post-dated. The gap can be bridged only by resort to common general knowledge (Watt 1769; standard marine surface condensers of the 1860s–70s). That is legitimate under KSR, but it is a factual assertion I have not verified against a pre-1879 reference on this page, and I flag it as such.
2. Possible teaching away. Fleischer's background states that in all previous hydraulic-reaction propulsion the steam "is mixed with the latter, and is ejected with the same into the floatative body of water." If the art's settled practice was deliberate co-ejection, a patentee could argue the prior art pointed away from separating and recovering the steam. However, this argument largely collapses against Hall and US 139,538, which both condense and recover their working fluid and both return water to the steam generator — i.e., the art did not uniformly teach co-ejection, so no genuine teaching-away exists.
3. Claim 2 is the most defensible claim. Although its individual elements are old, the specific sub-combination — a single float K2 on a rod o′ with top and bottom projections, where the rising water closes the exhaust valve (preserving the vacuum) and the falling water opens it (initiating the vacuum that refills the cylinder) — is a tighter structural recitation than Hall's beam-and-counterpoise gear, and it is tied to the specific tube D. Under a pre-1952 "invention" standard, or even under KSR if one credits the two-function single-float geometry as an inventive simplification, claim 2 has a materially better survival prospect than claim 1.

---

7. Secondary considerations (objective indicia)

None are of record, and I found none. There is no evidence in the retrieved material of commercial success, licensing, long-felt but unmet need, failure of others, copying, or unexpected results. The only asserted advantage — recovering steam as feed-water to avoid fresh-water consumption on ocean voyages — is the ordinary and expected consequence of using a condenser, which KSR instructs does not rebut obviousness. Absence of evidence here is not evidence of non-obviousness; it simply leaves the primary analysis unrebutted. (I did not locate any litigation over this patent, consistent with the earlier section's finding of no litigation, no assignment, and no CAFC 2026 docket activity.)

---

8. Bottom line

Caveat repeated for emphasis: as a matter of law, § 103 is inapplicable to a December 1878 filing. The above is a modern-framework reconstruction; under the 1870 Act's "invention" standard, the combination of two references in a crowded art without a demonstrated new result would ordinarily have failed for want of invention, so the outcome is likely the same, but the reasoning path would have been different.

---

9. Data-quality flags and unresolved items

1. No prior art of record exists for this patent. Everything above rests on Google's algorithmic "Similar Documents" list. No examiner ever cited any of these references.
2. US 4,716's specification was not retrieved in full. I confirmed only that it is a patent for "a hydraulic propeller that uses a current of water and steam power" (Fulton, George W., Aug. 26, 1846; texashistory.unt.edu). I have not verified whether it discloses open-bottomed, sea-communicating cylinders. The claim-mapping for element (b) is therefore inferential.
3. US 6,255 (Ericsson, 1849), US 145,210 (1873), and US 143,329 (1873) were not examined. Their titles alone justify listing them in the relevant art, not relying on them.
4. Hall's family is large. The German Wikipedia entry states Hall's pulsometer work "mündete 1872 in 29 Patenten (US 131515 ff.)" — so US 131,516 and 131,533, though not individually retrieved, are part of a 29-patent family of closely related pulsometer disclosures. This strengthens, not weakens, the crowded-art argument.
5. Unverified search noise, expressly excluded. My search for US 139,538 returned a PDF of US RE 6,768, a boiler-feeder reissue containing float-operated valve gear and an element labelled "valve V." RE 6,768 is not on this page's prior-art list, and I could not confirm it as the reissue of any listed reference, so I do not rely on it. (Its coincidental "valve V" label is not evidence bearing on the claim-2 discrepancy flagged in the earlier section.)
6. The claim-2 "valve V" inconsistency is carried forward unresolved. If "V" is a misread of "r," claim 2 reads cleanly on the described structure and the analysis in § 4 stands. If read literally as a third, undescribed element, claim 2 is potentially indefinite under modern § 112(b) — a distinct invalidity theory outside the scope of this § 103 task.
7. Date inconsistency in the task parameters (April 26, 2026 vs. September 29, 2026) is noted but immaterial to the analysis.