US 341497

I'll run targeted searches on the USPTO and CAFC dockets for this exact number before summarizing.

Verification note on sources

Two caveats before the summary, per your strict-no-autocorrection rule:

• No USPTO PatentCenter or CAFC hit was returned. My searches for "341497," "341,497," and for a 2026 Federal Circuit docket containing that number produced no PTAB, district-court, or CAFC records for this patent. The "341497" queries instead surfaced unrelated modern documents that merely contain the digit string (e.g., the A61K 31/497 chemical subclass, US 5,723,497, US 3,417,497-style numbers). Those are not this patent and should not be conflated with it.
• The authoritative record I do have is the full text of US 341,497 itself (Google Patents, fetched 2026-09-24), which is reproduced in my instructions. Everything below is grounded in that document. Where the OCR is corrupt, I flag it rather than silently fixing it.

Bibliographic data for US 341,497

Abstract

There is none. US 341,497 issued in 1886, well before abstracts were required on US patents. The functional equivalent of an abstract is the statement of invention (reproduced verbatim from the OCR, minor artifacts retained):

"This invention has for its object to prevent unnecessary loss of heat from the firing of the kilns for revivifying charcoal or analogous substances and permit the utilization of such heat (which at present is allowed to escape) for the purpose of assisting in drying the contents of the drier. The invention consists in surrounding the cooler-pipes of a kiln of this character with an apron, which confines the radiating heat from such pipes, and which forms in effect the hot-air chamber from which the heat may be carried to other places to be utilized. The invention also consists in connecting the hot-air space thus formed by a suitable channel with a chamber in which the charcoal is preliminarily dried."

Plain-language overview — the invention as a whole

Kilns that revivify bone-black ("char") discharge hot product through downward-projecting cooler-pipes (E), which radiate large amounts of heat to the atmosphere. Newhall & Colwell enclose those cooler-pipes with a skirt-like apron (G) that is closed at the top and open at the bottom, creating a hot-air plenum. That captured heat is then routed by a duct (H) into a preliminary drier (A) for the char, and the moist exhaust from the drier is blown back into the kiln's ash-pit (D) to improve combustion — a heat-recovery loop masquerading as a bone-black drier.

Independent claims — plain language

Claims 1–8 are each written in "The combination of …" form without back-reference to a preceding claim, so each stands on its own (claims 2–8 nonetheless recite the physical elements of claim 1 plus additions). Claim 10 is a process claim. Claim 9 is an apparatus claim directed to the drier alone.

1. Claim 1 — A kiln with its downward-projecting cooler-pipes, plus an apron surrounding those pipes that forms a hot-air chamber open at the bottom, closed at the top.
2. Claim 2 — Everything in claim 1, plus the hot-air duct (H) carrying air from the apron chamber to the drier (A), plus a sieve (b) in the drier that distributes/equalizes the incoming hot air.
3. Claim 3 — Claim 1's structure plus the duct (H) and an air-propelling fan (J).
4. Claim 4 — Claim 1's structure plus duct (H), fan (J), and a pipe (L) running from the fan back to the kiln's ash-pit (returning the moisture-laden heated air for more complete combustion).
5. Claim 5 — Claim 1's structure plus duct (H), discharge pipe (I), fan (J), and a bypass pipe (M) from duct H to pipe I, letting air go around the drier rather than through it.
6. Claim 6 — The drier (A) with inlet duct (H), outlet pipe (I), fan (J), branch pipe (M), and dampers (d, c) arranged so that part of the air is drawn through the drier and part past it.
7. Claim 7 — Duct (H) combined with a set of differential-length pickup pipes (f, g, h) of different lengths inside the apron chamber, so the duct draws air from near and far regions of the chamber rather than only the region nearest the duct. (The specification adds that each pipe should have its own damper — OCR renders these as "f If".)
8. Claim 8 — The apron (G) around the cooler-pipes (E), provided with a damper or door (i) in its upper part — for drawing off heated air to heat the building. (The specification allows for more than one such door.)
9. Claim 9 — In the drier (A), inclined shelves (m) along the outer walls, aligned with the shorter series of smoke-flues (a, n) that pass through the drier, providing additional heated-air passages beneath them that would otherwise choke with solid masses of char.
10. Claim 10 — Process claim: the herein-described process of preliminarily drying the char by conveying into it heated air taken from around the coolers of a kiln.

Related and cited material

• US 158,166 (December 29, 1874) — expressly incorporated by reference as the type of preliminary drier (A) shown; the patent states it improves on that drier by adding the inclined shelves of claim 9.
• US 343,666 (June 15, 1886), "Apparatus for drying bone-black in sugar-refineries," appears among the listed similar documents — a close contemporary in the same field.
• Fig. 3 discloses a three-kiln series sharing a single fan (J), with pipes (I, I) feeding a common pipe and pipes (L, L) feeding the several ash-pits.

Uncertainty flags

• Title discrepancy: "And augustus" (indexed) vs. "BONE-BLACK DRIER" (specification and drawing sheets). I have not auto-corrected the indexed title, but the drawing-sheet and specification headings are unambiguous.
• OCR damage affects inventor surname spelling ("COLWELL" vs. "OOLXVELL"/"OOLWELL"), claim numbering (the sixth claim is rendered "(5."), and reference characters (damper "c"/"6"; pipe dampers "f If"). Treat these letters as OCR variants, not distinct elements.
• No assignee exists to report — I found none, and I will not infer one.
• No litigation or PTAB/CAFC activity exists to report. A patent that expired May 11, 1903 cannot appear on a 2026 Federal Circuit docket, and my searches returned nothing for it. I could not retrieve a PatentCenter record directly (the queries returned unrelated modern filings), so the Google Patents full text supplied above is the operative source of record.

I'll search for litigation records involving this patent number.

Let me run additional targeted searches.

Let me try a few more searches, including historical case reporters and CourtListener.

Result: No litigation found involving U.S. Patent No. 341,497

I ran targeted searches for litigation keyed specifically to the number 341497 / 341,497. I found no case — historic or modern — in which U.S. Patent No. 341,497 was asserted, challenged, or otherwise at issue. I am not able to tell you plaintiff, defendant, jurisdiction, case number, or filing date, because no such record surfaced.

Identification of the patent searched

Before stating the negative result, it is important to fix exactly which document is at issue, because searches for "341497" return many unrelated hits and the strict no-auto-correction rule matters here:

The patent is directed to an apron (G) surrounding the cooler-pipes (E) of a revivifying kiln to capture radiant heat, and a duct (H) carrying that heated air into a preliminary bone-black/charcoal drier (A), with fan (J), dampers (d, c, i), differential pipes (f g h), branch pipe (M), and inclined drier shelves (m m). Claims 1–10 cover those combinations plus a process claim (claim 10) for preliminarily drying char with heated air from around the kiln coolers. I describe this only to establish that I searched for the right patent.

What the searches returned — and why none of it is this patent

Every hit I retrieved had to be discarded because it concerned a different patent or a different identifier:

• PacSec3, LLC v. Forescout Technologies, Inc. / PacSec3, LLC v. Splunk, Inc. (E.D. Tex., Nos. 2:22-cv-00055 and 2:22-cv-00056) and IPR2022-01230 — these concern U.S. Patent No. 7,523,497, a network-security patent. Numerically similar, legally unrelated. Not returned as a match.
• SE341497B — a Swedish patent publication (filed 1968), concerning pipe-wall tapping fittings. Different authority, different number series.
• T-1754-96 (2001 FCT 895) — a Canadian Federal Court digest where "341497" is merely a pagination item number in the Federal Courts Reports index, not a patent.
• Brazilian appellate process 2011.61.09.011237-3 (ApelRemNec 341497) — a tax case; "341497" is a court docket index number.
• Various bone-button dyeing and expansion-bolt cases (e.g., Heaton-Button, Imperial Chemical Mfg. Co. v. Stein, Diamond Expansion Bolt/Newhall counterclaims) — these involve genuinely 19th/early-20th-century patents and a Newhall, but not this patent number.

The Unified Patents litigation portal domain returned only generic unrelated material (case lists for other patents); no entry for patent 341,497.

Why a negative result is expected here

1. The patent has been expired for over 120 years. Google Patents records the anticipated expiration as 1903-05-11 (17 years from the 1886 grant, the term then in force). Infringement liability ended with the term, so there is no modern exposure and no basis for a contemporary suit.
2. The pre-digital gap. Unified Patents' portal, Docket Navigator, CourtListener, and PACER are the tools the task pointed to. Their coverage of district-court dockets is essentially the modern electronic era. Any suit on an 1886 patent would have been brought in 1886–1903 and, if reported at all, would appear in printed reporters (Federal Reporter volumes ~20–120, Blatchford, Banning & Arden, etc.) rather than in an electronic docket. I searched for such reporters by inventor name and patent number and found nothing tying them to this patent.
3. No PTAB/IPR possible. Inter partes review (and its predecessors) did not exist during the patent's life; a PTAB-style challenge to this patent is legally impossible.

Honest limitations

• I do not have a direct, credentialed query interface to PACER or to the CAFC docket; my results come from web searches over the sources you named and the open web. A definitive negative would require a full-text search of the historic Federal Reporter and Decisions of the Commissioner of Patents for 1886–1903, which I could not perform here.
• I found no evidence of litigation, but I cannot prove the absolute absence of an unreported 19th-century equity suit.

Conclusion: No litigation is known involving U.S. Patent No. 341,497. I will not provide plaintiff/defendant/jurisdiction/case-number fields, because supplying them from the "497" hits discussed above would be a misidentification of a different patent.

I'll verify the structured data against public sources before writing this up.

Proceedings overview

Total AIA trial proceedings on file for US 341,497: zero (0) — no active proceedings, no claims invalidated, no claims sustained, no settlements, no institution denials, and no Federal Circuit appeals. The structured "PTAB proceedings on file" block is dispositive here: the USPTO Open Data Portal returns no AIA trial proceedings for this patent as of the most recent ingest, and my independent web searches surfaced no IPR, PGR, or CBM referencing patent number 341,497 or its title/parties (Newhall & Colwell, "Bone-Black Drier"). The defensive posture this gives an accused infringer is not "hardened patent" and not "canceled claims" — it is something more basic: this patent is a 19th-century patent that expired on 1903-05-11, so there is no live monopoly to attack and no PTAB estoppel to inherit. Anyone receiving a demand letter citing US 341,497 is not facing a patent problem; they are facing a fraud or scam problem.

Proceedings

There are no proceedings to itemize. Per the task constraints, I will not invent proceeding numbers, panels, or outcomes. What I can document is why the count is zero, which is itself the substantive answer:

No AIA proceeding — nothing on file (US 341,497 / US341497A)

• Type: N/A — no Inter Partes Review, Post-Grant Review, or Covered Business Method review has ever been filed.
• Filed: N/A. Note the antecedent timeline: US 341,497 has an application filing date of 1886-03-09 (Serial No. 198,534), was granted 1886-05-11, and shows an anticipated expiration of 1903-05-11 on the face of its Google Patents record (US341497A). AIA trials did not exist until the Leahy–Smith America Invents Act, with IPR available for petitions filed on or after 2012-09-16 — 109 years after this patent lapsed.
• Status: The structured data says "Expired - Lifetime" with "Anticipated expiration" on 1903-05-11. Plain English: the 17-year term under the then-governing statute ran out over twelve decades ago. There is no enforceable claim scope to review.
• Judge panel: N/A — no panel was ever assigned. There is no APJ name to report, and I will not supply one.
• Petition grounds: N/A — no petition was filed. (For completeness on statutory eligibility: PGR is unavailable by definition, as PGR reaches only patents with effective filing dates on or after 2013-03-16; CBM is unavailable on subject matter, since a bone-black drying and kiln waste-heat recovery apparatus is not a "financial product or service" under AIA § 18(d). Only IPR under 35 U.S.C. § 311 would even be formally conceivable, and § 311(a) permits a petition on any patent — including an expired one — but a review of a patent that lapsed in 1903 would be a pure waste of fees.)
• Institution decision: N/A — no decision issued.
• Final Written Decision: N/A — none exists. No claims of US 341,497 have been canceled by the PTAB, and none have been sustained by the PTAB. Its claims 1–10 (including independent claim 1 directed to the kiln B / cooler-pipes E / apron G combination, and claim 10, a process claim to preliminarily drying char with heated air from around the kiln coolers) were never adjudicated in any AIA trial. Do not let anyone tell you otherwise.
• Settlement / termination: N/A.
• Appeal: N/A — nothing to appeal to the Federal Circuit; no CAFC docket exists for this patent. (CourtListener docket search returns no CAFC or district case keyed to this patent.)
• Defensive value: If an assertion cites claims 1–10 of US 341,497, the correct response is not an IPR petition — it is a letter noting the patent expired 1903-05-11, plus a referral to your state attorney general or the USPTO for a probable invention-promotion scam. Filing an IPR would be spending six figures to invalidate a patent that has been in the public domain since the Theodore Roosevelt administration.

Strategic summary

Canceled vs. sustained vs. untested. Every claim of US 341,497 is untested before the PTAB, but that framing flatters the patent. Claims 1 through 10 were never challenged because there was no economic reason to challenge them: the patent's term ran from 1886-05-11 to 1903-05-11, and the "Legal status" field confirms Expired - Lifetime. There are no surviving claims in any enforceable sense. The claim set is worth reading only as technical history — claim 1 covers the combination of the kiln B, its downwardly projecting cooler-pipes E, and the apron G forming a bottom-open, top-closed hot-air chamber; claim 7 covers the differential pipes f, g, h inside the apron chamber to draw from the far end of the chamber rather than only the near end; claim 10 is a process claim for preliminarily drying char using air heated around kiln coolers. Those are useful teaching references today, not live rights.

Estoppel landscape. Because no IPR, PGR, or CBM was ever instituted, 35 U.S.C. § 315(e)(2) estoppel attaches to no one. There is no petitioner, no privy, and no real party in interest carrying a ground that "was raised or reasonably could have been raised." That sounds like it favors a defendant by removing a constraint — and it does, trivially — but it is irrelevant in practice: no defendant needs prior art to defeat a patent that expired in 1903. Collateral consequence worth noting: with no estoppel and no live claims, the entire public domain remains available to any modern defendant, including US 341,497's own specification, published 1886-05-11, which is a fully citable printed publication for § 102(a)(1) purposes against later-filed claims. The specification's disclosure of recovering radiant heat from revivifying-kiln cooler pipes into an apron chamber, ducting it to a drier via a sieve, and returning moist exhaust to the ash-pit to improve combustion, is genuinely useful invalidating art against modern waste-heat-recovery and kiln-drying claims. The patent's highest present-day value is as a prior-art exhibit, not as an asserted right.

Pattern signals. None of the usual PTAB patterns are present — no serial petitioner, no aggressive patent-owner appeal practice, no defensive aggregator (Unified Patents, RPX, Open Invention Network) in the chain. There is no litigation history to trace. The IPR landscape for this patent is simply empty, and the reason is chronological: the PTAB's AIA jurisdiction began 109 years after this patent lapsed. One caveat on my confidence: pre-AIA BPAI interference and reexamination records are not fully indexed in modern AIA-trial tools, so I cannot rule out some 19th- or early-20th-century interference or later reexamination appearing in paper-only archives. But no AIA trial proceeding could exist for this patent, and none does. I claim no knowledge of any such proceeding beyond that.

Recommended next steps

1. If you hold a demand letter citing US 341,497, treat it as a scam artifact. There is no FWD to link to and no disposition to quote, because no IPR was ever filed — that is the point. Cite the Google Patents record showing Publication date 1886-05-11 and Anticipated expiration 1903-05-11 with status Expired - Lifetime (US341497A), and note that the 17-year term ended 122 years ago. A demand predicated on this patent is not a colorable infringement claim.
2. Do not file an IPR. There is no active proceeding to track and no trial-stage milestone to calendar (no institution decision deadline, no oral hearing date, no one-year § 316(a)(11) FWD due date). Even though § 311(a) technically permits a petition against an expired patent, an IPR here would burn fees with zero defensive payoff and cannot produce a stay or estoppel benefit that matters.
3. Repurpose the patent as prior art. Pull the full specification and figures from the USPTO PatentCenter record or Google Patents and docket it as an 1886-05-11 printed publication for any modern case involving kiln waste-heat recovery, apron-type hot-air chambers, sieve-equalized duct discharge into a drier, or exhaust recycling to an ash-pit. Also check the patent's own cited parent, US Patent No. 158,166 (December 29, 1874) — the drier design this specification improves upon with inclined shelves m m along the outer walls — as a companion reference.
4. State plainly that no PTAB activity exists. The absence here is not the ordinary "well-asserted patents eventually attract IPRs" signal; it is an artifact of a patent that predates the agency's review authority by a century. If someone presents this patent as a live right, the mismatch between the assertion and the 1903 expiration date is the finding worth reporting to the USPTO's Office of Enrollment and Discipline or your state AG.

I'll verify whether any assignment records exist for this patent before writing anything up.

Verification performed before writing

• Google Patents legal events for US 341,497 (from the authoritative text supplied): the only events are 1886-05-11 Application granted, 1886-05-11 Publication of US341497A, and 1903-05-11 Anticipated expiration. There is no assignment, reassignment, or change-of-name event of any kind. (Family ID 2410580 lists one application, US341497D — that is a Google Patents internal document ID for this same filing, not a separate legal entity or transfer.)
• USPTO Assignment Center / Patent Assignment Search returned no records for patent 341497. Note the structural caveat before drawing conclusions from that: USPTO's online assignment indexes are populated mainly from the 1980s onward (with only patchy pre-1980 image coverage). For an 1886 patent, an empty result is the expected result and is not evidence that no transfers ever occurred. Historic ownership for a patent this old can only be established from the printed U.S. Patent Assignment Abstracts volumes or the original patent-office assignment liber records, which are not online-searchable by patent number.

Inventors

• Both names appear on the face of the specification: "GEORGE M. NEVVHALL, OF PHILADELPHIA, PENNSYLVANIA, AND AUGUSTUS NV. COLVELL, OF NE\V YORK, N. Y." The Google Patents OCR mangling ("NEVVHALL", "COLVELL", "OOLWELL", "WVe") is a scan artifact; the correct spellings are Newhall and Colwell, and the repeated "And augustus" in the title field is an OCR truncation of the two-inventor header, not part of the title. The true title is "Bone-Black Drier."
• Filing to grant was 63 days (filed March 9, 1886, Serial No. 198,534, "No model"; granted May 11, 1886). Fast even for the era, and consistent with a small, uncomplicated mechanical case.
• Pattern note — no departure signal is assessable. The prompt's "all inventors departing the original assignee within 12 months" heuristic requires an original corporate assignee and a personnel record. Neither exists here: this patent issued unassigned, and no employment relationship is recited anywhere in the document. Two inventors in two different cities (Philadelphia and New York) is consistent with a joint consulting/engineering arrangement, but that is an inference from geography, not a documented fact, and I state it as such.

Original assignee

There is none. US 341,497 issued on its face to the two named inventors personally — the heading reads "GEORGE M. NEWHALL … AND AUGUSTUS W. COLWELL," with no assignee line, and the specification contains no assignment recital. Under 1886 practice this means title vested in Newhall and Colwell as tenants in common.

• Product embodying the claims: The patent is directed to hardware, and it explicitly contemplates being built and run. The claims recite a kiln with downwardly projecting cooler pipes, an apron forming a bottom-open/top-closed hot-air chamber around those pipes, a hot-air duct to a preliminary drier, a suction fan, and associated dampers (claims 1–9), plus a process claim for preliminarily drying char using heat drawn from around a kiln's coolers (claim 10). Whether either inventor ever commercialized a unit is not determinable from the patent or any source I can reach.
• Primary line of business: Unknown for both individuals. The technical context is bone-black (animal-char) revivification, which in this period was overwhelmingly a sugar-refining operation — the specification's own datum point is the drier of Letters Patent No. 158,166 (December 29, 1874), and a near-contemporaneous, similarly titled case, US 343,666, "Apparatus for drying bone-black in sugar-refineries" (June 15, 1886), appears in Google Patents' "Similar Documents" list. That establishes the field, not the inventors' employer.
• Current status: Not applicable in the corporate sense. Any operating business the inventors may have been affiliated with in 1886 has, 140 years later, either dissolved, been absorbed, or is untraceable through the sources available. I found no bankruptcy, acquisition, or dissolution record for a Newhall/Colwell entity. The patent itself is Expired – Lifetime, with anticipated expiration recorded as 1903-05-11 (seventeen years from grant).

Assignment timeline

The USPTO Assignment Center has no records for US patent 341,497, and Google Patents reports no legal events other than the 1886 grant, the 1886 publication, and the 1903 expiration.

There are therefore no recorded assignments to list, and — critically — no reel/frame numbers, no conveyance types, no assignors, no assignees, and no correspondents of record exist to report. I will not supply placeholder reel/frame data, because inventing an assignment record for a 140-year-old patent would be indistinguishable from fabricating one.

Two honest qualifications, stated so this finding is not over-read:

1. This is the expected result, not a distinctive finding. USPTO's electronic assignment index does not reach back to 1886. An absence of hits establishes only that nothing has been indexed, not that Newhall and Colwell (or their heirs, estates, or any successor business) never transferred title.
2. The chain that matters for your NPE analysis cannot exist here. Every one of the eight signals below requires a modern corporate ownership record, a litigation docket, or a repeat-player correspondent. All three are temporally impossible for a patent that expired in 1903. There is no litigation over an expired 1886 patent, no asserter directory entry, and no security agreement, merger, or change of name that could be filed.

Pursuant to the stated instruction to stop after this section when the Assignment Center shows no records, I am not running the NPE signal grid or the Mermaid timeline — populating either would require exactly the fabricated reel/frame entries the constraints forbid. For completeness of the record: applying the verdict taxonomy mechanically, this patent falls under Insufficient data, resting solely on the original grant to two individual inventors with no indexed post-issuance activity.

Verification link: https://assignment.uspto.gov/patent/index.html (search 341497; also https://patents.google.com/patent/[US341497](/patent/US341497)/en → "Legal Events").

I'll start by pulling the authoritative records for US 341,497 and its cited/related references.

Let me verify the specification-cited reference and check whether Google Patents lists any examiner citations for this 1886 patent.

Prior-Art Analysis — US 341,497 (Bone-Black Drier)

Headline finding, stated plainly

US 341,497 has no patent-citation list. I searched for one; there is none to report, and that is a historical fact about the document, not a gap in my search. Patents issued in 1886 were not printed with "References Cited" on their face — that practice did not begin at the USPTO until the mid-20th century. Google Patents' page for this patent accordingly shows no "Patent Citations" section at all; the only lists it renders are (a) a "Similar Documents" block, which is an algorithmic similarity list generated by Google and is not an examiner citation list, and (b) "Prior art keywords" (drier, apron, air, pipes, duct), which is also algorithmic.

So the honest deliverable is:

1. The one reference the specification itself citations-by-name: US 158,166.
2. The algorithmic "Similar Documents" list, presented as candidates, clearly labeled as not citations, with a §102 screen on each based on its date.
3. A date screen that separates documents that could be §102 prior art from those that legally cannot be (later-issued art).

Nothing I found — and nothing in the patent's own record — discloses an apron surrounding kiln cooler-pipes forming a top-closed, bottom-open hot-air chamber. That is the structural core of claim 1.

1. Citation of record inside US 341,497: US 158,166

Brief description (from how 341,497 uses it): A preliminary bone-black/charcoal drier of the general class into which the patentees' duct (H) delivers heated air; its walls bear smoke-flues (a, n) and, in the 341,497 improvement, receive inclined shelves (m m) aligned with the shorter flue series.

§102 assessment: Does not anticipate any claim of US 341,497.

• Claims 1–8 all require the kiln (B) with downward-projecting cooler-pipes (E) plus the apron (G). US 158,166 is a drier, not a kiln-cooler assembly, so it cannot meet the claim-1 backbone that every one of claims 2–8 incorporates.
• Claim 9 ("In the drier A, the inclined shelves m, placed along the outer walls") is the claim most often mis-mapped to US 158,166 — but the patentee's own words foreclose it: the shelves are what 341,497 added to the 158,166 construction. A reference cannot anticipate an element the patentee identifies as the improvement over it. No anticipation.
• Claim 10 (process) requires "heated air from around the coolers of a kiln." US 158,166 discloses no kiln coolers. No anticipation.

Its correct role is background/§102(a) "described in a printed publication" art for the drier environment recited in the preamble of claims 2 and 9 — i.e., it establishes that the drier half of the combination was old, which is presumably why the patentees confined novelty to the apron-and-duct loop and the inclined shelves.

Identifier-collision warning (flagged, not corrected): A search for "US158166" surfaces US 2,231,231, whose application serial number is 158,166 (rendered "US158166A / US15816637A" in Google's metadata). That is an application-number coincidence in a 1937 filing — not the 1874 Letters Patent. Do not conflate them. Likewise, do not conflate this patent with US 3,417,497-style numbers, A61K 31/497, or US 5,723,497; those are unrelated modern documents that merely share digit strings.

2. The "Similar Documents" list — candidates, NOT citations

The full text I hold lists 25 documents under "Similar Documents." None of these is a citation of record against US 341,497. I screen each by date, because under any version of §102 a reference must predate the relevant date (here, filing March 9, 1886; invention date presumably earlier in 1886 or late 1885).

2a. Documents that pre-date the March 9, 1886 filing — the only ones capable of being §102 prior art

Net: not one pre-1886 item in this list discloses a kiln (B) + downward-projecting cooler-pipes (E) + apron (G) forming a top-closed, bottom-open hot-air chamber. Claim 1 is not anticipated by any listed document.

2b. Documents that post-date US 341,497 — legally incapable of §102 anticipation

These are listed for completeness and to prevent mis-citation. Each issued after May 11, 1886 and therefore cannot be §102(a)/(b) or §102(e) art against this patent (pre-AIA or otherwise):

Special flag on US 343,666 ("Apparatus for drying bone-black in sugar-refineries," 1886-06-15): it is the thematically closest document in the whole list to US 341,497 — same material (bone-black), same industry (sugar refineries), same function (drying) — and its issue date falls just five weeks after 341,497 issued. Because its grant post-dates 341,497's grant, only its filing date could make it §102(e) art, and I could not retrieve US 343,666's filing date or full text within this session. I therefore cannot state whether it anticipates claims 2, 9, or 10, and I will not guess. This is the single highest-value follow-up lookup.

3. Closely related art found outside the citation list (pre- and post-date), for context

These surfaced in searches of the bone-black revivification field and are the documents a modern examiner would have cited had the practice existed:

The US 592,547 and US 708,898 examples are worth stating explicitly: they show that the "draw hot air off the cooling-pipes to dry the char" concept became standard practice after 341,497 — which is consistent with (though not proof of) the Newhall/Colwell patent being the origin point, and which is why they cannot be cited against it.

4. Claim-by-claim anticipation matrix

5. Legal framework caveat (important for how you use the §102 column)

The claim asks for anticipation "under 35 U.S.C. § 102." US 341,497 issued May 11, 1886, sixty-six years before the Patent Act of 1952 created §102. The governing novelty statute at grant was Rev. Stat. § 4886 ("not known or used by others in this country, and not patented or described in any printed publication in this or any foreign country" before the applicant's invention). The §102 column above is therefore an explicitly anachronistic retrofit — useful for comparative analysis, but it is not the law that applied to this patent. The practical consequences:

• Nearly all of the coverage in §102(a)/(b)/(e) collapses into the Rev. Stat. § 4886 "printed publication" and "prior patent" bars.
• §102(e) (patents as of their filing date) and §102(f)/(g) have no meaningful 19th-century analogue; my treatment of US 343,666 and US 339,874 above leans on §102(e), which is a modern construct.
• The patent's anticipated expiration (recorded as 1903-05-11) means no infringement or validity exposure has existed for over 120 years.

6. What I could not determine — stated rather than filled in

• No USPTO PatentCenter citation record was retrievable. My USPTO-directed searches for the literal ID produced no record; the queries returned unrelated modern filings. The operative source remains the Google Patents full text supplied in my instructions (fetched 2026-09-24).
• I could not retrieve the full text or filing date of US 158,166 (Dec. 29, 1874). My §102 assessment of it rests on the admissions in 341,497 (that the drier is 158,166's type, and that the inclined shelves are the patentees' addition). This is sound for the anticipation question but is not a substitute for reading the reference.
• I could not retrieve the specification of US 343,666 (June 15, 1886). Its issue date alone disqualifies it from §102(a)/(b), but its filing date is unknown to me and it is the most thematically relevant document in the list. This is the top priority for any follow-up.
• Incomplete OCR degrades the titles/inventors of US 228,464, US 267,813, US 308,291, and US 368,298 to single surnames or fragments ("kitts," "Brock," "tomkins," "mcdonald"). I have not guessed their contents.
• No assignee and no litigation/PTAB record exist for this patent (consistent with the earlier sections of this analysis).

Bottom line: US 341,497 carries one named reference (US 158,166) and no citation list. Against the claim set as a whole, the closest actual prior art is US 27,462 (Mitchell, 1860) — same field, same cooler-below-kiln geometry, same "dry the char before revivification" objective, but lacking the apron and the heated-air-conveyance loop. On the record available to me, no reference anticipates any of claims 1–10.

I'll ground the prior-art analysis with targeted searches on the references listed on the page before building the §103 combinations.

Prior-art mapping requires the disclosures behind the numbers listed on the page. Let me pull the key ones.

Obviousness Analysis — U.S. Patent No. 341,497 ("Bone-Black Drier")

1. Threshold: what statute am I applying, and to what?

35 U.S.C. § 103 did not exist when this patent was granted. US 341,497 issued May 11, 1886 (Google Patents); § 103 was enacted in the Patent Act of 1952. Treating the number and date literally, as instructed, the nonobviousness question in 1886 would actually have been decided under the judge-made "invention" requirement of Hotchkiss v. Greenwood, 52 U.S. (11 How.) 248 (1850), which § 103 later codified. I run the requested § 103 analysis below, but every conclusion should be read as a retrospective, hypothetical § 103 application to a patent that expired May 11, 1903 — with two period-specific glosses that matter and that modern § 103 practice would not supply:

• The "aggregation" doctrine. 19th-century courts routinely held that juxtaposing old elements, each performing its own function without a new cooperative result, was not invention at all. This cuts against claims 2–8, which are largely juxtapositions of known elements.
• No secondary-considerations infrastructure. Long-felt-need/commercial-success evidence (the Graham/KSR toolkit) would have to be reconstructed from 1880s sugar-refinery practice; I found corroborating state-of-the-art evidence (see § 2) but no evidence of record bearing on the patentee's commercial success.

Level of ordinary skill (PHOSITA): a sugar-refinery char-house engineer or mechanical draftsman circa 1885, familiar with revivifying kilns (retorts, cooler tubes beneath the kiln floor, ash-pits), with the waste-heat-recovery literature of the 1860s–80s and with ordinary sheet-metal ducting, dampers and fans. The art was mature: the literature of the period describes bone-black kilns supplied from an integral preliminary drier traversed by the kiln's combustion gases ("the black reaches the tubes in a dry state, as it previously passes through the drier f, a chamber traversed by a large number of metallic tubes, through which travel all the combustion-gases" — Sugar Growing and Refining, Blaize kiln, Google Books PDF).

Caveat on the page's own metadata. Google Patents labels the field "Prior art date: 1886-05-11" and lists "Prior art keywords: drier, apron, air, pipes, duct." Both are artifacts: 1886-05-11 is the issue date, not a prior-art date, and the keyword list is extracted from US 341,497's own specification. Neither may be used as a reference disclosure.

2. Which references on the page are actually available as prior art

The page's "Similar Documents" list mixes pre- and post-1886 documents. Only documents publicly available before the March 9, 1886 filing — or US patents whose applications were filed before the applicant's invention, the then-equivalent of § 102(e) — qualify.

Flag re: the earlier Litigation/Prior-Art section. That section described US 343,666 as "a close contemporary in the same field." That framing should be corrected for § 103 purposes: a June 15, 1886 grant is ten weeks after US 341,497's March 9, 1886 filing and is therefore not prior art absent an earlier application date, which I could not verify.

3. Claim-by-claim element mapping and combinations

Combination A — Claim 1 (kiln + cooler-pipes + closed-top/open-bottom apron)

• Primary: US 27,462 A (kiln B with ash-pit D and downward sheet-metal coolers F below the retort floor).
• Secondary: US 339,874 (casing R enclosing a heat source, capturing the rising heated air for a drying use) and US 172,608 (case E/H/J inclosing flues whose heat "is ordinarily lost," to be recovered).
• Motivation: twofold and explicit in the art — (i) US 27,462 itself states "economy in fuel" as an object; (ii) the 1880s drying literature treated radiated flue/pipe heat as wasted and recoverable by simple enclosure (US 172,608, US 339,874). A skirt around downward coolers is the minimal mechanical step: it is a hood over a known hot surface, open below so char can still discharge.
• Assessment: obvious. Almost certainly also an aggregation under the era's doctrine.

Combination B — Claim 2 (adds duct H + sieve b)

• Primary: Combination A. Secondary: US 339,874 (perforated wall h distributing heated air into the material; duct/flue system L/M/N/S conveying heated air to the drying zone) and US 172,608 (admitting heated air "between the layers" at multiple heights, via slot I/m openings).
• Motivation: to distribute heat uniformly through a packed bed; a foraminous plate as an air-diffuser is a staple expedient, and US 339,874 shows the same function performed by a perforated surface.
• Assessment: obvious. The sieve adds no cooperative result beyond uniform distribution.

Combination C — Claim 3 (adds fan J)

• Primary: Combination B. Secondary: US 339,874's suction-fan T.
• Motivation: a suction fan is the acknowledged means of forcing air through a resistance-laden bed; US 339,874 uses precisely a suction fan on the downstream side of the material. The patent's own spec concedes "fans are not always needed" and that natural draft suffices — which, if anything, weakens any argument that the fan element is inventive.
• Assessment: obvious.

Combination D — Claim 4 (adds pipe L from fan to ash-pit, returning moisture-laden air)

• Primary: Combination C. Secondary: US 27,462 (ash-pit D as the kiln's air inlet; "economy in fuel" object) plus ordinary furnace practice of preheating combustion air.
• Motivation: once heated air has been used for drying, its residual heat is still valuable; the kiln's ash-pit is the natural combustion-air intake, so returning the stream there recovers residual heat rather than venting it. Note the claim's own premise is improved combustion despite the moisture load — and moisture in combustion air is an engineering trade-off a PHOSITA can evaluate.
• Assessment: obvious as a combination, though this is the claim whose operability premise (moist air improving combustion) is most assailable on a different ground — enablement/utility, not § 103 — and I flag that as unresolved without furnace-test evidence.

Combination E — Claim 5 and Claim 6 (bypass pipe M and dampers d, c: part through, part past the drier)

• Primary: Combination D. Secondary: US 27,462's flue damper i "so that either or both flues at each side of the chamber may be used as desired" (a verified, pre-1886 teaching of a damper used to apportion a hot gas stream among paths).
• Motivation: when drier demand is less than plenum supply, or when char is already dry enough, the surplus must still be routed to the ash-pit rather than lost; a parallel bypass with proportioning dampers is the standard way to apportion a gas stream. The spec frames it purely as regulation ("draw part of the air through the drier and part of the air past the drier").
• Assessment: obvious. Reference characters d, c in the patent versus i in US 27,462 is a coincidence of lettering, not of disclosure; I note it only because the coincidence invites mis-citation.

Combination F — Claim 7 (differential-length pickup pipes f, g, h, each with a damper)

• Primary: Combination B. Secondary candidates: any pre-1886 multi-inlet ducting; I did not verify a specific reference teaching staged takeoffs of unequal length within a single plenum.
• Motivation: ordinary fluid-mechanics reasoning — a single takeoff starves the far end of a plenum by pressure-drop asymmetry; multiple takeoffs of graded length equalize collection. The spec's own justification is exactly this ("prevent the duct H from taking the heated air from only that part of the apron-chamber G which is nearest the duct").
• Assessment: the most defensible claim, but still weak. Under modern § 103 (KSR, "design incentives... predictable variations," "a finite number of identified, predictable solutions") this is optimization by routine engineering; under Hotchkiss it is mechanical skill. Absent evidence that earlier workers tried and failed to even out plenum draw, I cannot call it nonobvious with confidence.

Combination G — Claim 8 (apron with damper/door i in its upper part, for building heat)

• Primary: Combination A. Secondary: US 27,462's damper i; general waste-heat space-heating practice.
• Motivation: winter space heating of the char house is an independent, obvious use for a captured hot-air body; a door/damper in the upper, hottest stratum is the natural tap. The spec itself presents this as an optional convenience ("Should any part of the heated air... be desired for the purpose of heating the building").
• Assessment: obvious. An optional, admitted-alternative use recited in a claim is classically vulnerable.

Combination H — Claim 9 (inclined shelves m m along the drier's outer walls, in line with the short smoke-flues a n)

• Primary: US 158,166 (the drier of record A). Secondary: US 350,170's inclined plates m above retorts, whose heated undersides "effect a partial drying of the bone-black upon the upper surface of said plates" — but that reference is dated after the filing and is usable only as evidence of the art's trajectory, not as § 102/§ 103 art. Pre-1886 grain/fruit driers with partitions, valves and baffles (US 172,608's cases and slots; US 56,708's division of the grain space) supply only generic "deflect and distribute" teachings.
• Motivation: prevent packing/choking of material against a heat-exchange surface and open extra air passages — a recognized drying-art problem.
• Assessment: genuinely arguable in the patentee's favor. This is the one apparatus claim whose specific placement (aligned with the shorter flue series, on the outer walls) is a structural coordination not squarely shown in a pre-1886 reference I could verify. I would not predict invalidity on the record available to me.

Claim 10 — Process claim (preliminarily drying char with heated air from around the kiln coolers)

• Primary: US 27,462 — which already discloses drying spent bone-black in association with the kiln, expressly by evaporation, i.e., by heat, adjacent to the cooler tubes F.
• Motivation/assessment: if US 27,462's drying is driven by heat from the kiln/cooler region, claim 10 is close to anticipated; if its drying is merely ambient-air evaporation-and-draining, then claim 10 is at best an obvious use of a known heat source for its known purpose (drying char before firing), particularly given that the era's kilns were already fed from preliminary driers. I could not resolve which on the excerpt retrieved, and I flag that as the single most fact-dependent question in this analysis.

4. Net assessment

Bottom line: on the references actually available as of March 9, 1886, a PHOSITA had (a) a kiln of exactly this type with cooler tubes and an ash-pit, (b) an express fuel-economy and char-drying objective, (c) a drying-art practice of enclosing hot flues to recover heat "ordinarily lost" and delivering it into the material bed at multiple heights, and (d) perforated distributors, dampers and suction fans as staples — for exactly the reasons recited in US 341,497's own statement of invention. Claims 1–8 and 10 would very likely have been held obvious (or unpatentable as mere aggregations) under the 1886 "invention" standard. Claim 9 is the only element I would defend on this record.

5. Caveats I will not paper over

• I did not retrieve the underlying disclosures of US 158,166, US 156,568, US 172,740, USRE7,713, US 209,589, US 228,464, US 255,769, US 267,813, US 283,673, or US 308,291; those entries are reasoned from title and date only. My searches reached the step limit before covering them.
• US 27,462 A's exact grant date was not re-verified in this pass; I treat it as pre-1886 US art, which is consistent with its place in the low-number series and with the "coolers F" / "damper i" disclosure retrieved.
• US 350,170's and US 343,666's application dates are unknown to me; if either was filed before March 9, 1886, it becomes available and materially strengthens the attack on claim 9. That is the highest-value verification still outstanding.
• No litigation, PTAB, or CAFC record exists for this patent (consistent with the earlier Litigation section); this analysis is therefore purely notional — there is no validity judgment to appeal to, and the patent expired 1903-05-11.