US 171924

I'll verify what I can against live sources before summarizing.

Identification and scope check

I searched for the literal identifier 171924 and for US171924A / US171924D. No results were returned for this patent from USPTO PatentCenter, USPTO Assignment, or any Court of Appeals for the Federal Circuit docket. The only "171924" hits my searches returned were WO 2014/171924 (PCT/US2013/036744, building-access control) and WO 2017/171924 (PCT/US2016/054426, RRC connection resumption), plus a Brazilian Supreme Court habeas corpus HC 171924. Those are different documents and I am not conflating them with US 171,924. Everything below is taken from the authoritative full text I was given, at https://patents.google.com/patent/[US171924](/patent/US171924)/en (fetched 2026‑09‑29).

One caveat up front: no CAFC 2026 docketing of this patent is possible or plausible. This is an 1876 patent that expired in 1893, and the Federal Circuit was not created until 1982. If a 2026 filing somewhere bears "171924," it is not this patent.

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Bibliographic summary — US 171,924

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Abstract

There is no abstract. Abstracts were not part of US patent practice in 1876, and Google Patents displays none. The nearest equivalent is the statement of invention in the specification:

"My invention relates to broilers for cooking-stoves, &c.; and it consists in forming the broiler with pan-sides, and a flange or projection upon its under surface, for sustaining it in position, and adapting it for use with an enlarged inclined feed-opening or similar opening of the stove, whereby a neat, compact, and convenient device for broiling meats, &c., is obtained."

Stated problem: conventional broilers were flat castings with shallow gutters, used either inclined in front of the grate or horizontally over stove openings, which caused loss of meat juices and soiling of the stove from flying heated fat, plus smoke. The invention's object is to overcome those objections.

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Independent claim — plain-language overview

This patent has exactly one claim, and it is therefore the sole independent claim (it is printed unnumbered). Verbatim:

"The covered broiler F, having the raised sides and ends f f, a suitable drip-gutter, f, and a projection or flange, g, the whole adapted for use with the inclined feed-opening of a cook-stove, substantially as specified."

In plain language, the claim covers a combination of four elements:

1. A covered broiler (F) — a broiling pan that includes a cover (element E in the description) to keep smoke and burning-fat spatter from escaping. The cover is a positive claim element, not optional.
2. Raised, pan-like sides and ends (f f…) — the broiler body is built with upturned walls, rather than being a flat casting, so juices and fat are contained instead of running onto the stove.
3. A drip-gutter (f) — a longitudinal gutter/channel that collects and drains the meat juices; in the description the guttered bottom bars terminate in this "usual longitudinal drip-gutter."
4. An under-surface flange or projection (g) — a lip on the bottom of the broiler that hooks or catches on the stove's inclined feed-opening so the broiler stays put on that slanted surface.

The final clause ("the whole adapted for use with the inclined feed-opening of a cook-stove") ties the assembly to the stove's enlarged, angled feed door (described as face plate placed at an angle so as to receive reflected heat from the rear fire-chamber wall, preferably closed by folding doors c c). Because the claim is drafted as a combination, all of these elements together define the protected subject matter; a plain flat broiler, or a broiler without the cover or without the retaining flange, would not read on the claim on its face.

Stated advantages in the specification: the meat is exposed to reflected heat yet is removed from the line of draft, protected from products of combustion, and any smoke formed in the closed broiler must pass down into the stove and out with the combustion products.

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Uncertainties and caveats

• Assignee: I have no authoritative assignment record. "None stated" reflects only the face of the patent, which names no assignee.
• Reference characters: The text is OCR-degraded in places. The specification refers to sides/ends "f f f¹ f" and bottom bars "f f," while the claim recites "raised sides and ends f f"; the gutter letter is rendered inconsistently. The character-to-part mapping should not be read too literally. Other OCR artifacts: "8210." = "&c."; "IsAAo DE HA EN" = Isaac De Haven; "feed-openin g" = feed-opening.
• No CAFC or litigation record found for this patent, and as noted, a 2026 CAFC docket entry for it is not plausible. I cannot confirm the absence of 19th-century infringement litigation from the sources available here.
• Related art listed by the database (not part of the patent itself) includes, among others, US137278A and US211550A ("broiler attachments for stoves and ranges"), US173994A ("attachments for cooking-stoves"), and US119066A.

I'll search for litigation involving US patent 171924.

Initial searches returned only unrelated patents. Let me search litigation-specific databases for the exact patent number.

Litigation Search Report — US Patent No. 171,924

Patent identification (literal): US 171,924 A, titled "Improvement in Broilers," inventor Isaac De Haven, of Pittsburg, Allegheny County, Pennsylvania. Application filed September 4, 1875; patent granted/published January 11, 1876. Per the Google Patents record, legal status is "Expired – Lifetime," with an anticipated expiration date of January 11, 1893 (17-year term under the law then in force). Classification: A47J37/06 (roasters; grills; sandwich grills).

Result: No litigation known

I found no litigation involving US Patent 171,924. This is the determination I am prepared to stand behind, subject to the limitations noted below.

Basis for the determination

1. The patent has been expired for over 130 years. US 171,924 issued January 11, 1876 and, per the patent record itself, its term ended January 11, 1893. An expired patent cannot be asserted for infringement (35 U.S.C. § 271 reaches only unauthorized acts "during the term of the patent"). Any infringement suit would have had to be filed and prosecuted before 1893.

2. Searches for the specific number returned no case. Targeted searches for the exact identifier ("US171924," "US 171,924," "171924 patent litigation," "171924 patent infringement lawsuit," and inventor-based searches) surfaced only unrelated matters — never this patent. Examples of the false-positive matches I discarded (they are not US 171,924):

   • OV Loop, Inc. v. Mastercard (S.D.N.Y., No. 23-cv-1773-CS) — asserts U.S. Patent No. 10,032,171 ("the '171 Patent"), a mobile-payment authentication patent. Different number.
   • HTC v. Advanced Audio Devices (PTAB IPR, "the '171 patent") — consumer audio device patent, U.S. App. No. 12/855,510 family. Different number.
   • WO 2014/171924 A1 (PCT/US2013/036744) — building-access-control application. This is a PCT publication number, not US 171,924.
   • Samsung v. WiLUS (IPR2025-01110) — U.S. Patent No. 11,716,171. Different number.
   • Royal Philips N.V. v. Quectel et al. (D. Del., "case 1710," patents 7,944,935 and 7,831,271) — case number coincidence only.

   Consistent with the instruction to interpret alphanumeric identifiers literally, none of these involve US 171,924.

3. No PTAB or post-grant activity. AIA post-grant proceedings (IPR/PGR/CBM) are unavailable for this patent both because they did not exist until 2012 and because they apply only to unexpired patents. No such proceeding exists.

Limitations on this conclusion (stated candidly)

• I was not able to directly load the Unified Patents litigation portal case list (portal.unifiedpatents.com/litigation/caselist), PACER, or a CourtListener docket specific to this patent during this session. Those databases also have essentially complete coverage only of the modern electronic-records era — in any event, the Unified Patents portal indexes post-AIA assertions of live patents.
• A pre-1893 infringement action, if one ever existed, would survive only in 19th-century court records (e.g., old Federal Circuit/regional reporters or the "Commissioner of Patents" annual reports), which are not indexed in the sources available here. I have no evidence that any such case exists, but I cannot affirmatively rule out an unrecorded 1876–1893 proceeding from these searches.

Practical note

For a doctrine-of-equivalents-era patent of this vintage, "litigation" as the term is used in modern patent practice (district court infringement actions, ITC § 337 investigations, PTAB proceedings, CAFC appeals) does not exist for US 171,924. Its significance today is as prior art / historical background in the field of stove-and-broiler cookware, not as an asserted patent — which is consistent with how the family data shows only the single 1876 US application (family ID 2241331) and no continuation or reissue activity.

Bottom line: No known litigation involves US Patent 171,924; the patent expired in 1893 and any suit would have had to predate that.

I'll verify the "no proceedings" default against live sources before writing this up.

Proceedings overview

Zero AIA trial proceedings exist on US 171,924. Per the structured "PTAB proceedings on file" block (USPTO Open Data Portal), the canonical list is empty — 0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denials — and my independent web searches for the exact identifier returned no petition, institution decision, Final Written Decision, or appeal bearing this patent. The defensive posture this gives a defendant is not "the patent has survived two IPRs and is hardened" and not "claims 1–5 have been canceled." It is the third category the framework doesn't have a slot for: there is no PTAB track record because there is nothing to defend against — US 171,924 issued 1876‑01‑11 and, per the patent record itself, its term ended 1893‑01‑11. Any demand letter citing this patent has a § 271 problem long before it has an IPR problem.

No proceedings to enumerate

There are no proceeding numbers to report. I am deliberately not listing candidates, because every "171924" hit I found was a different document (see False positives below), and the instruction not to invent proceeding numbers is absolute.

Why the number is zero — and which AIA vehicles are even theoretically open

This matters because "no IPRs were filed" is only reassuring if IPRs could have been filed and nobody bothered. Here the vehicle availability is asymmetric:

• IPR (35 U.S.C. §§ 311–319) — theoretically available, factually never used. Under AIA § 6(c)(2)(A), IPR "shall apply to any patent issued before, on, or after" 2012‑09‑16, so an 1876 patent is not categorically exempt. More importantly, the Federal Circuit has now confirmed the Board's jurisdiction over expired patents: Gesture v. Unified Patents, 127 F.4th 368, 368–69 (Fed. Cir. 2025) ("the [PTAB] has jurisdiction over [inter partes review proceedings] concerning expired patents"), discussed in the government's brief in Gesture v. Unified Patents, No. 24‑1281 (U.S.), https://www.supremecourt.gov/DocketPDF/24/24-1281/[378013](/patent/378013)/20250926131534717_250933a%20BIO%20for%20efiling.pdf. Nobody has ever filed one against US 171,924, which is unsurprising: expiration in 1893 means there is no accused product, no § 315(b) one-year clock, and no commercial reason to spend post-grant fees.
• PGR (§§ 321–329) — unavailable. PGR reaches only patents subject to the first‑inventor‑to‑file provisions. An 1876 patent is a pre‑AIA patent; no PGR can be filed.
• CBM (§ 18) — unavailable twice over. The transitional program sunset on 2020‑09‑20, and a cast-iron broiler pan does not claim "a financial product or service."
• Ex parte reexamination — available but not a PTAB proceeding. Reexamination has always applied to expired patents (amendment is simply barred for them). If someone genuinely needed a formal PTO certificate canceling the claim — e.g., to neutralize the patent as a cited reference artifact — reexam, not IPR, is the correct forum. It is outside the scope of this report.

False positives I screened out (none involve US 171,924)

Consistent with interpreting identifiers literally, these are not this patent and are not PTAB proceedings on it:

• HTC v. Advanced Audio Devices — the "'171 patent" from application 12/855,510, a consumer digital-audio patent; the snippet is from the Board's motion-to-amend analysis in an unrelated IPR (https://ptacts.uspto.gov/ptacts/public-informations/petitions/[1459342](/patent/1459342)/download-documents). Different patent.
• WO 2014/171924 A1 (PCT/US2013/036744) — building access control (https://patentimages.storage.googleapis.com/a1/b6/a5/fd2e4e2aecfcd9/WO2014171924A1.pdf). A PCT publication number.
• Gesture / Apple / LG / Google / Unified Patents IPRs on the '431, '079, and '949 patents — cited here only for the legal proposition about expired-patent jurisdiction, never as proceedings on 171,924.
• IPR2025‑00826 / ‑00806 / ‑00969 (Google v. patent owner re the '517 patent) — surfaced only because the snippet discusses expired patents; different patent entirely.

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Strategic summary

Claim status: 100% UNTESTED, and it does not matter. US 171,924 has exactly one claim, printed unnumbered in the original — the covered broiler F with raised sides and ends, a drip-gutter, and an under-surface flange g adapted to the stove's inclined feed-opening. It has never been construed by the Board, never been the subject of an institution decision, and never been canceled or confirmed in an AIA trial. In district-court shorthand it would be called "claim 1," but no adjudicative body has ever used that label, so no cancellation certificate exists to point at. Nothing is dead by PTAB action; everything is dead by operation of law — the term ran out 1893‑01‑11, 17 years from grant under the statute then in force.

Estoppel landscape: there is none, and the silence cuts in the defendant's favor. § 315(e)(2) estoppel and § 325(e)(2) estoppel are petitioner-specific — they bar a petitioner and its privies after a final written decision. With no petitioner, no privies, and no FWD, no PTAB estoppel attaches to anyone. Every § 102/§ 103 ground, and every prior-art reference in the field (including the database's "similar documents" set — US137278A, US211550A, US173994A, US119066A), remains unburdened by estoppel. The practical consequence is narrow: this matters only if the patent were somehow asserted, and it cannot be.

Pattern signals: absent, not concealed. No repeat petitioner (there is no first petitioner), no patent-owner appeal activity (no decision to appeal), no defensive aggregator involvement (Unified Patents appears in my results only in the Gesture chain, on other patents), and no family activity — the Google Patents family (ID 2241331) contains a single US application with no continuation, reissue, or reexamination. The absence of IPRs here is not the usual "well-asserted patents eventually attract IPRs" signal; it is the signal of a patent that has not been economically live since the Grover Cleveland administration. Under the USPTO's current institution framework — Director-controlled institution under the 2025‑10‑16 Squires memorandum — a hypothetical petition on a 143-year-expired cooking implement would be discretionary-denied on about six independent grounds, if it were ever filed.

Flagged contradiction with the earlier-generated sections. The prior "Litigation summary" section justified the absence of post-grant activity by saying AIA proceedings "are unavailable for this patent both because they did not exist until 2012 and because they apply only to unexpired patents." The first reason is right; the second is wrong as a matter of current law and should be corrected. IPR applies to any patent issued before, on, or after 2012‑09‑16, and the Federal Circuit in Gesture (127 F.4th 368) squarely rejected the argument that expiration strips the Board of jurisdiction — see the government's brief at No. 24‑1281, https://www.supremecourt.gov/DocketPDF/24/24-1281/378013/20250926131534717_250933a%20BIO%20for%20efiling.pdf. Expired patents are IPR-eligible; US 171,924 simply never had one filed. The earlier section's conclusion (no PTAB activity) is correct; its stated reason overstated the bar. The "no litigation" and "no PTAB" findings otherwise dovetail and I found nothing contradicting them.

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Recommended next steps

• If you are a defendant and a demand letter or complaint cites US 171,924: do not build an IPR strategy. There is no FWD to link to, because there is no proceeding — and the dispositive point needs no PTAB authority at all: the patent expired 1893‑01‑11, so no act can infringe it under 35 U.S.C. § 271, which reaches only acts "during the term of the patent." Respond with the expiration date from the face of the patent (https://patents.google.com/patent/[US171924](/patent/US171924)/en) and, if useful, the Board's expired-patent jurisprudence only to foreclose the "we'll revive it" argument. I will not quote a disposition that does not exist.
• If you need the claim formally dead rather than merely expired: no PTAB vehicle fits (IPR possible in theory, pointless in practice; PGR and CBM categorically unavailable). File an ex parte reexamination request instead — reexam reaches expired patents, with amendment barred for them. Verify current fees and the fee-reduction schedule at the USPTO fee page before filing.
• If you are monitoring rather than defending: there are no trial-stage milestones to track — no institution-decision deadline, no oral hearing, no statutory 1‑year FWD due date, because the 1‑year clock in § 316(a)(11) starts at institution and no institution exists. Set a watch on the PTAB E2E docket (https://ptab.uspto.gov) and the Decisions database (https://developer.uspto.gov/ptab-web/#/search/decisions) only if you want a dated negative record; the ODP structured pull in this prompt is already that record as of the latest ingest.
• Plainly stated: no PTAB activity exists on US Patent 171,924. That absence is a factual finding, not an inference — the patent's 1893 expiration makes it the expected result, and no proceeding number, panel, ground, or settlement should be attributed to this patent from any source.

Sources checked: Google Patents record for US171924A (https://patents.google.com/patent/US171924/en, fetched 2026‑09‑29); USPTO ODP "PTAB proceedings on file" block (canonical, empty); web searches for "171924" + PTAB/IPR/petition/patent litigation; PTAB petition documents at ptacts.uspto.gov (unrelated patents); Gesture v. Unified Patents materials at the Supreme Court docket for No. 24‑1281. Not directly loaded: PTAB E2E case list and CourtListener docket search (both linked above for independent verification); their coverage of 19th-century subject matter is in any event nil.

I'll attempt to verify the assignment record against live sources before writing.

Assignment and Ownership Report — US Patent 171,924 ("Improvement in Broilers")

Source check performed this session. I attempted the USPTO Patent Assignment Center (https://assignmentcenter.uspto.gov/, mirrored by the legacy https://assignment.uspto.gov/patent/index.html) for the literal identifiers 171924, US171924A, and US171924D, plus text searches on the title and inventor. Every query returned zero assignment records. No reels, no frames, no conveyance types, no correspondents to report. Nothing below invents one.

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Inventors

Named witnesses on the specification are W. N. Paxton and James I. Kay — witnesses, not inventors. There is a single inventor and no joint-inventor situation.

Employer determination — evidence and its limits. The patent itself names no employer. The following independent sources point to the same firm:

• A trademark registration by De Haven & Co. (Limited), business location Pittsburgh, PA, for the "Cinderella" brand of cooking and heating stoves and ranges, dated March 1, 1887 (Library of Congress, https://www.loc.gov/item/2020708058/; also indexed in the Digest of Trade-marks, "Stoves and Ranges. De Haven & Co., Pittsburgh, Pa. Climax").
• The Stove Index lists "D. De Haven & Sons."
• A secondary collector's description states David DeHaven (b. 1812, d. 1887) founded the stove business in the mid-1800s and turned it over to his son Isaac DeHaven, the firm going out of business in the late 1800s (WorthPoint auction listing — weak, non-authoritative source, cited only as corroboration).

Assessment: same surname, same city, same trade, and a documented father-to-son succession makes it highly likely that Isaac De Haven filed this patent as a principal of the family stove concern. I am flagging that as probable but not documented at the level of certainty I would want — I have no incorporation record, partnership filing, or assignment deed tying Isaac De Haven to D. De Haven & Sons specifically. There is no competent evidence of an inventor departing an assignee within 12 months of filing, because there is no assignee and no employment agreement on the record.

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Original assignee

None. The patent issued January 11, 1876 in the sole name of Isaac De Haven; no assignee is printed on the face of the patent and none appears in the Google Patents record (family ID 2241331, a single US application with no continuations, divisionals, or reissues). Pre-1880 US practice permitted issuance directly to an inventor without a recorded assignment, and that is what happened here.

• Entity on the patent: Isaac De Haven, individually. Effectively, the "original assignee" is the inventor personally.
• Product embodying the claims: No direct evidence found. The likely operating vehicle was the family stove firm (De Haven & Co. / D. De Haven & Sons) of Pittsburgh, a manufacturer of cooking and heating stoves and ranges — the exact product category this broiler attaches to. I found no advertisement, catalog, or specimen showing a broiler made to this claim, so "shipped a product embodying the claims" is unverified as to this specific patent.
• Primary line of business: cast-iron stove and range manufacturing, Pittsburgh, Pennsylvania.
• Current status: Dissolved / out of business in the late 1800s (secondary-source narrative only). No successor entity identified, no bankruptcy filing found, no acquisition found. Note the city was spelled "Pittsburg" until the dropped-H was formalized in 1891 — the patent's spelling is authentic to its 1875 filing date, not an OCR error.

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Assignment timeline

The USPTO Assignment Center has no records for US Patent 171,924. I therefore report no chronological assignment list, because there is nothing to list.

Two structural reasons, stated precisely so this is not mistaken for a gap in my searching:

1. Database coverage window. The Assignment Center's searchable index covers recorded patent assignment information from August 1980 to the present. US 171,924 issued in 1876 and its term ended in 1893 — roughly nine decades before the online index begins. A pre-1980 conveyance, if one were ever recorded, would exist only in the historical/microfilm assignment records at the USPTO Public Search Facility, which are not exposed as reel/frame data in the online search I can query. I could not verify whether any pre-1980 record exists, and I will not assert either way.
2. Termination in 1893. The Google Patents legal-events record shows "Expired – Lifetime" with an anticipated expiration of 1893-01-11. There is no live property to convey.

The Google Patents legal-events panel shows only three entries — 1876-01-11 Application granted, 1876-01-11 Publication of US171924A, and 1893-01-11 Anticipated expiration — and no assignment events of any kind. Note also that the identifier "US171924D" (and "US171924DA") appearing in the family data is a Google Patents document/application ID, not an assignment reel or an assignee — do not read it as a conveyance.

Per the stopping rule for this task ("if the Assignment Center has no records, say so plainly and stop"), the analysis would normally end here. I am continuing only because the required output order enumerates the remaining sections; every remaining section is moot, and I mark it as such rather than pad it with speculation.

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Timeline diagram

timeline
    title Ownership of US 171924
    1875 : Application filed by Isaac De Haven
         : No assignee recorded
    1876 : Patent issued in inventors own name
    1887 : De Haven and Co trademark registered
    1893 : Patent term expired

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NPE / troll-pattern signals

None of these signals can be evaluated against a reel/frame, because no reel/frame exists. I am marking each on the record actually available.

1. Shell-entity transfer — not present. No assignment of any kind is recorded, and no "IP / Holdings / Licensing / Ventures" entity appears anywhere in the family data or legal events. The chain is a single individual.
2. Known asserter in the chain — not present. No assignee exists to compare against the Acacia / Marathon / IV / IPNav / Wi-LAN / Conversant / Vringo / Pendrell / Innovatio / MPHJ / Lumen View / Round Rock / Spangenberg lists. All of those entities either did not exist or were not in the assertion business in 1876–1893, and none appears here.
3. Repeat correspondent across the chain — not applicable / no data. Zero recorded assignments means zero recorded correspondents of record. I have no attorney name to test for recurrence against Unified Patents, RPX, or Patent Progress asserter lists. (The two names on the specification, W. N. Paxton and James I. Kay, are witnesses, not recording correspondents, and are not a basis for an NPE finding.)
4. Cascading transfers — not present. No transfers at all, cascading or otherwise.
5. Pre-litigation transfer — not present. No assignment and no infringement suit (see the litigation section of this analysis: none found, and none possible after 1893). Nothing to time within six months of a complaint.
6. Bankruptcy fire-sale — not present / unclear. No bankruptcy filing, docket, or Section 363 sale involving Isaac De Haven or a De Haven stove entity was found. The narrative evidence is that the firm simply went out of business, which is distinct from a bankruptcy sale — but that narrative rests on a single non-authoritative collector's listing, so I flag the manner of the firm's wind-down as unclear while the existence of a fire-sale is not present on the record.
7. Privateering — not present. Requires an operating company transferring to an NPE that asserts on its behalf. No such transfer, no such asserter.
8. Defensive aggregator — not present. The chain does not terminate at RPX, AST, LOT, Unified Patents, or OIN. It terminates at statutory expiration in 1893, which is a different kind of neutralization (the patent lapsed; it was not acquired and shelved).

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Verdict

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

Justification: The USPTO Assignment Center returned zero records for 171924 / US171924A / US171924D, and the Google Patents legal-events panel contains only grant, publication, and 1893 expiration entries — no assignment events. There is no reel/frame, assignor, assignee, conveyance type, or correspondent of record to analyze, and the underlying index does not reach back to the 1876–1893 window in which any such record would have been created. The patent was issued to and apparently held by a single individual, Isaac De Haven of Pittsburgh, who was in the stove-manufacturing business; the absence of recorded transfers is consistent with him retaining the patent personally until it expired in 1893, but that is an inference from silence and is not proof of continuous individual ownership. No NPE or troll-pattern signal is supported — every signal above is either not present or unevaluable for want of a recorded transfer.

Verify at: https://assignmentcenter.uspto.gov/ (search by patent number 171924; legacy portal https://assignment.uspto.gov/patent/index.html). For any pre-1980 record, the USPTO Public Search Facility's historical assignment collection — not the online index — is the only place it could exist.

I'll search for the specific patent number and its citation data.

Let me check the Google Patents citation sections and USPTO records directly.

Let me verify whether Google Patents/USPTO lists any cited references, and check the pre-1876 broiler art.

Prior-Art Search Report — US Patent No. 171,924

(Literal identifier: 171,924. Everything below concerns only that document. Where a search returned a different number, I say so and exclude it.)

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1. USPTO / database search for the number "171924"

Searching the literal identifier 171924 in the USPTO-linked record (via Google Patents, which mirrors the USPTO front-page data at https://patents.google.com/patent/[US171924](/patent/US171924)/en, fetched 2026‑09‑29) returns one US document:

Numbers I explicitly did not treat as this patent (per the literal-interpretation rule): IN171924B (Indian patent, poultry incubators, 1988 priority — a different jurisdiction and subject matter) and WO 2014/171924 A1 (PCT/US2013/036744, building access control). Neither is US 171,924.

Small date note / potential inconsistency to flag: the task header states "Current Date: April 26, 2026," while the authoritative fetched record is timestamped 2026‑09‑29 (as were the earlier-generated sections of this analysis). This does not affect any conclusion — the patent has been expired since 1893 either way — but I flag it because the instruction was to build on, not silently overwrite, the prior sections.

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2. Citation status of US 171,924 — the direct answer to "look at each patent citation"

US 171,924 lists no patent citations. There is no "References Cited," "Citations," or "Cited By" section in the document, in the Google Patents record, or in the USPTO-derived front page. This is expected, not an omission in my search:

• US patents issued in 1876 were not printed with a front-page "References Cited" list. That practice, and the examiner-citation data that populates modern "Citations" fields, post-dates this patent by roughly a century (the modern front-page citation format begins with the 1976-era patents).
• Accordingly, there is no list of cited U.S. patent documents to enumerate for this patent. Any patent list attributed to US 171,924's citations would be fabricated.

Important distinction — "Similar Documents" is not a citation list. The Google Patents page for US171924A shows a separate "Similar Documents" block (~25 entries). That is a computed similarity/landscape list generated by Google, not references cited by the applicant or examiner. I use it below only as a lead-generation tool, clearly labeled as such.

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3. Most relevant prior art (candidate references)

Because the patent cites nothing, the useful output is: (a) the prior-art admissions inside the specification itself, and (b) the earliest-dated potentially anticipatory references found in the databases. The sole claim is a combination claim — all of {covered broiler F; raised pan sides/ends f; drip-gutter f; under-surface flange/projection g; adapted to the inclined feed-opening of a cook-stove} must be present in a single reference to anticipate under § 102.

3A. Prior-art admissions in the specification (self-identified prior art)

These are statements in the patent describing what was already known — usable as applicant admissions:

3B. Dated candidate references (from the Similar Documents landscape, screened by date)

Only references published before De Haven's September 4, 1875 filing can anticipate under § 102. Those are the only ones analyzed as anticipatory. (Statutory note: in 1875 the governing law was the Patent Act of 1870, not the 1952 Act; I map to the concepts of 35 U.S.C. § 102(a)/(b) as requested.)

Pre-filing references — potential § 102 prior art:

Post-filing references (cannot anticipate; listed because the database surfaces them — useful only as hindsight/context, or as § 102(e)-type art if their filing dates precede De Haven's):

• US 173,994 A — "Improvement in attachments for cooking-stoves," published 1876‑02‑22 — about six weeks after US 171,924 issued. Its publication cannot anticipate; its filing date is unverified here, so I do not assert it as prior art.
• US 211,550 A — "Improvement in broiler attachments for stoves, ranges," 1879‑01‑21 — same title family as US 137,278 but later; cannot be prior art to US 171,924.
• US 189,557 A (1877‑04‑17, "Improvement in stoves"), US 191,035 A (1877‑05‑22, "Improvement in bakers"), US 199,446 A (1878‑01‑22), US 213,499 A (1879‑03‑25, "Improvement in ranges"), US 225,234 A (1880‑03‑09), US 278,267 A (1883‑05‑22), US 356,260 A (1887‑01‑18, "Attachment for cooking stoves"), US 413,689 A (1889‑10‑29), US 457,433 A (1891‑08‑11), US 638,134 A (1899‑11‑28), US 716,501 A (1902‑12‑23, "Portable stove"), US 747,814 A (1903‑12‑22, "Portable stove"), US 762,588 A (1904‑06‑14, "Stove"), US 991,676 A (1911‑05‑09, "Cooking-stove"), US 1,052,239 A (1913‑02‑04, "Cook stove or range"), US 1,176,720 A (1916‑03‑21, "Broiler-plate"), US 1,250,861 A (1917‑12‑18, "Barbecue-stove"), US 1,869,392 A (1932‑08‑02, title garbled in the OCR). All post-date US 171,924 and cannot anticipate its claim.

3C. Bottom line on anticipation

• No single reference in the available record discloses every element of the sole claim — specifically, none of the pre-1875 references shows a flange/projection on the under surface (g) of a covered pan-broiler sized and shaped to retain it on an inclined feed-opening, which is the point of novelty the specification stresses ("a flange or projection, g, which serves to retain the broiler in position when used upon the inclined feed-opening").
• Therefore my determination is: no § 102 anticipation established on the record available. The closest references — US 119,066 (covered/enclosed detachable broiler U, hung on bracket B/hooks Q) and US 137,278 (broiler attachment for stoves and ranges) — are § 103-type references whose combination with the admitted conventional drain-gutter broiler would be the realistic invalidity theory, not clean anticipation. US 111,963 supplies the "enclosed, smoke-free broiling" teaching.
• The claim is also unusually narrow/brittle for a different reason worth noting for completeness: it recites the "covered broiler" while the specification calls the cover (E) something "usually employed," and it ties the whole combination to "the inclined feed-opening of a cook-stove" — so its scope depends heavily on the stove structure, not just the broiler.

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4. Caveats (stated explicitly, per the "do not fabricate" rule)

1. There is no citation list for this patent. Any enumeration of "citations for US 171,924" would be invented. What I have provided is (a) the specification's own prior-art admissions and (b) dated candidate references drawn from the database's similarity list.
2. I retrieved full text for US 119,066 and US 111,963 only. For US 137,278, US 211,550, US 173,994, US 108,240, and US 113,556 I have only the title and publication date from the Google Patents record — I could not open their specifications within this session, so my element-by-element comparison for those is provisional. In particular, whether US 137,278 discloses the under-surface retaining flange g is unverified.
3. Filing dates vs. publication dates. For the 1870s references, anticipation turns on what was patented or described before De Haven's invention/filing, not on issue date alone. I have publication dates for all; filing dates for the pre-1875 references are unverified. This matters most for US 173,994 A (issued 1876‑02‑22, i.e., after US 171,924), which I therefore do not classify as prior art.
4. No litigation, no PTAB, no CAFC record exists for this patent (consistent with the earlier-generated section); it is expired art, relevant today as historical background in the stove/broiler-cookware field, not as an asserted patent.

I'll ground this analysis by pulling the actual content of the pre-1875 references from the "Similar Documents" list, since §103 requires me to know what each reference actually discloses.

Two searches surfaced highly material references that are not on the page's "Similar Documents" list. Let me pin down US137278A (the closest-listed reference) and check the others.

Obviousness analysis — US 171,924 under 35 U.S.C. § 103

Threshold caveat (must be stated before any § 103 analysis)

Section 103 did not exist when this patent issued. US 171,924 was granted January 11, 1876, 76 years before the Patent Act of 1952 created § 103. In 1876 the patentability standard was the "invention" requirement of Hotchkiss v. Greenwood, 52 U.S. (11 How.) 248 (1851). I am running the modern § 103/KSR framework below because that is what the task asks for, but the historical standard should be applied to any real-world conclusion about this patent's validity. I flag this rather than silently applying a statute that post-dates the document by three-quarters of a century.

Second threshold issue: the page's "Similar Documents" list is not a prior-art list

Google Patents displays no "References Cited" or examiner-cited prior-art table for US 171,924 — only a "Prior art keywords" block (broiler; broilers; stove; improvement; feed) and a "Similar Documents" list, which is a text-similarity ranking, not art cited by an examiner or by the applicant. Of the 25 documents on that list, only six pre-date the September 4, 1875 filing date and are therefore even eligible as prior art:

Everything in the bottom row is disqualified. Using a 1917 or 1932 broiler patent against a September 1875 application would be a legal error, and I will not do it, even though the database groups them with the patent.

Claim element breakdown

The single claim (quoted and parsed in the previously generated claim section above) requires the conjunctive combination of: (1) a covered broiler F; (2) raised, pan-like sides and ends; (3) a drip-gutter; (4) an under-surface projection/flange g; and (5) adaptation for use with the stove's inclined feed-opening. I rely on that earlier parse and will not restate it.

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Graham factor 1–2: scope/content of the art and the level of ordinary skill

PHOSITA (1875): a stove-foundry patternmaker or cast-iron stoveware designer of ordinary mechanical skill — conversant with cook-stove casing, fire-box and hearth openings, ash-pan arrangements, and the ordinary flat cast gridiron/broiler with a gutter. Nothing in the claim requires anything beyond this skill level; every element is a cast-or-stamped sheet-metal mechanical part.

Scope and content — what the searchable art actually discloses:

US 115,984 (David E. Roe, "Improvement in Broilers," June 13, 1871) — https://patentimages.storage.googleapis.com/19/66/71/e43ac80dda0a09/[US115984](/patent/US115984).pdf

"The lower edge of the frame A is turned inward and upward, so as to form a channel or groove, D, around the lower part of the broiler ... to catch and hold the juice or gravy which runs from the meat. At the inner side of the groove D the metal of the frame is turned downward and projects below the bottom corner a of the groove to form a flange, E, which enters the hole of the stove, and serves as a guide in placing the broiler in position."

Roe also inclines the bars ("the radial bars F incline downward toward the rim ... the juice or gravy ... drip[s] into the channel or groove D") and expressly states: "It will be understood that any suitable cover may be used with the broiler, when desired." Claim 2 is "[t]he combination, with the frame A and channel or groove D, of the downwardly-projecting flange E."

This reference alone discloses elements (2), (3) and (4) of De Haven's claim, plus an express invitation to add element (1).

US 147,790 (Anna Price, "Improvement in Gridirons"/Meat-Broilers, filed Sept. 15, 1873, granted Feb. 24, 1874) — https://patentimages.storage.googleapis.com/f6/b9/3d/63dc3c2f75d750/[US147790](/patent/US147790).pdf

"C is a cover, which fits tightly upon the frame B. ... The bars of the gridiron being grooved in the ordinary manner, the slant toward the doors carries the grease forward into the fire of the stove, feeding the fire and avoiding the smoke. ... by the draft being forced underneath the broiler, the smoke and gases are carried off up the chimney, and no unpleasant flavor is communicated to the meat."

Claim: "the combination of the grooved bars A of a gridiron, slanting toward and projecting into the fire-box of a cooking-stove, with the frame B and cover C." This is a covered, framed, grooved-bar broiler seated over a stove opening, slanted toward the fire, whose stated purpose is grease management and smoke abatement — i.e., elements (1), (2), (3) and the entire functional object De Haven asserts.

US 120,528 (Charles Noble, "Improvement in Gridirons," Oct. 31, 1871) — https://patentimages.storage.googleapis.com/b9/20/d7/33807ab895d8c3/[US120528](/patent/US120528).pdf

"[T]he gridiron being provided with a non-perforated cover and fitting closely to the hearth-plate prevents the smoke and gases from the embers from rising upward and deteriorating the flavor of the meat."

Claim: "The hearth-plate A, covering the opening in the base-plate of a stove, perforated near its edge, and having an opening, a, to which is fitted the covered gridiron B." A covered broiler fitted to an opening in a stove plate for smoke control.

US 119,066A (John Van, "Improvement in Portable Cooking-Ranges," Sept. 19, 1871) — https://patents.google.com/patent/[US119066A](/patent/US119066A)/en
Discloses a third part of the invention as "a peculiar form and adaptation of detachable broiler," including a broiling chamber formed as a box (U) with "a pipe, 2, leading from the rear upper part of the box U through the apertures 19 into the chimney 3, [which] serves to conduct off all fumes arising from the operation of the broiling-chamber," and a supporting bracket R for the detachable broiler. A covered broiler chamber whose fumes are deliberately routed back into the stove's exhaust path.

US 23,963 (Van & Barringer, "Improvement in Stoves," May 10, 1859) — https://patentimages.storage.googleapis.com/c0/73/2e/3896401175f1d6/US23963.pdf
A hinged stove door that drops to form a hearth for roasting/broiling, with "b is a broiler, which may be used while the door h is closed by opening the register g to allow the smoke to pass within the stove." Smoke from a broiler deliberately passed into the stove.

US 113,086 (found by search; docket number series 113,xxx indicates ~March 1871 — date not verified in this session) — https://patentimages.storage.googleapis.com/94/ae/a5/37da0932c5834b/[US113086](/patent/US113086).pdf. Its specification contains an admission of what was old:

"[T]his receding front F to the fire-box has been previously made in some form or other, and also an opening through the same for the purpose of feeding the fire with coal, for broiling and for other purposes ..."

That is a direct, in-art acknowledgment that an inclined stove front with an opening used both for firing and for broiling pre-dated De Haven.

US 132,167 (Marshall & Marshall, "Improvement in Broilers," Oct. 15, 1872) — https://patentimages.storage.googleapis.com/e0/07/59/5daeb3eea0994d/[US132167](/patent/US132167).pdf. Broiling "by means of reflected heat," with adjustable legs to set incline, and "the lower reflector being inclined toward the rear the gravy is conducted away from the fire." Relevant to De Haven's asserted "reflected heat" and grease-away-from-fire advantages.

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The three strongest § 103 combinations

Combination A — Roe (US 115,984) + Van (US 119,066A) [+ Price (US 147,790) for the cover]

Motivation to combine: (i) same field and same problem — Roe, Van and Price are all broilers/gridirons for cook-stoves, and all three address grease containment, spatter and smoke; (ii) express suggestion in the art — Roe itself states the cover is usable "when desired," which is a direct teaching to add the very element De Haven claims; (iii) Price expressly teaches that a close-fitting cover "carries off" the smoke and keeps it out of the meat's flavor, supplying the reason to add the cover; (iv) reasonable expectation of success — the combination is a mechanical aggregation of a gutter, a flange, a rimmed pan and a lid, with no unpredictable interaction. KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398, 417 (2007) ("if a technique has been used to improve one device, and a person of ordinary skill in the art would recognize that it would improve similar devices in the same way, using the technique is obvious").

Combination B — Combination A + an inclined-front stove opening reference (US 113,086 and/or US 23,963)

• US 113,086 supplies an express in-art admission that a receding/inclined stove front with an opening used for feeding and broiling was old.
• US 23,963 supplies a stove whose front door opens to a slanted/level hearth for broiling and whose broiler smoke is directed "within the stove."

Motivation: De Haven's only asserted point of novelty over the flat-gutter broiler he himself describes is placement on the stove's inclined feed-opening. Once the inclined, multi-purpose front opening is conceded to be old (it is, on the face of US 113,086), seating a flanged broiler on it is a choice of position, and the flange of Roe '984 is expressly a "guide in placing the broiler in position." Where the prior art teaches a projection for locating a broiler in an opening, using that same projection to locate it on an inclined opening is the predictable use of a known element for its known function (MPEP 2144.03; KSR, 550 U.S. at 417). No reference teaches away.

Combination C — Noble (US 120,528) + Roe (US 115,984)

Noble claims a covered gridiron fitted to an opening in a stove plate specifically to stop smoke; Roe claims frame + gravy channel + flange entering the stove hole. Substituting Roe's flanged, guttered, pan-framed broiler body for Noble's gridiron in Noble's stove-plate opening is a straight substitution of one known broiler body for another in the same opening, with the same smoke-control function. Motivation: both are classified in the same broiler/gridiron stove art, both solve the same smoke-and-grease problem, and the substitution of parts in a stove opening is the most routine of foundry-level engineering acts.

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KSR "design choice / mere change of position" overlay

De Haven's own specification supplies the strongest § 103 factor against the claim. It concedes the starting art ("broilers are, in general, flat castings having shallow gutters or depressions to drain off the meat-juices") and states the object as "to overcome the objections and annoyances specified" — smoke and flying fat. It then identifies the novelty as the combination with an inclined opening whose face plate "is placed at an angle, so as to receive the reflected heat from the rear wall."

Every asserted functional benefit was already separately known:

• Reflected heat + inclined broiling → Marshall '167;
• Gravy carried away from the fire → Marshall '167; Price '790;
• Covered broiler over a stove opening to stop smoke rising to the meat → Noble '528; Price '790;
• Broiler smoke routed back into the stove/flue → Van '066; Van & Barringer '963;
• Flange on a broiler's underside entering the stove opening to position it → Roe '984 (both the flange and its locating function).

MPEP 2144.04 (mere rearrangement of parts / change of position) and In re Japikse, 181 F.2d 1019 (CCPA 1950), are directly applicable to element (5): relocating a known broiler from the horizontal stove hole to the slanted feed door, with no new coaction, is a change in position. De Haven would argue the opposite — that the new position yields new coaction: the meat is "removed from the line of draft," "protected from the products of combustion," and "any smoke formed in the closed broiler must, of necessity, pass down into the stove." That is the strongest non-obviousness argument in the record. Its weakness is that Van '066 and Van & Barringer '963 already achieved the "smoke passes into the stove" result, and Noble '528 and Price '790 already achieved the "smoke prevented from reaching the meat" result — so the asserted coaction is the sum of results separately obtained in the art, not an unexpected new one.

Contemporaneous judicial evidence of the obviousness climate

Two 19th-century decisions in the same art corroborate the analysis (they are evidence of the state of the art, not prior art):

• Bridge v. Excelsior Mfg. Co., 4 F. Cas. 94 (C.C.E.D. Pa. 1879) — https://law.resource.org/pub/us/case/reporter/F.Cas/0004.f.cas/0004.f.cas.0094.pdf — "the cam being old, the use of a swinging door as a lever being old, and the shelf being old, it might be a question whether there was a sufficient degree of invention in bringing these old elements to bear on the hinged shelf." Directly on point for a claim that combines old stove elements.
• Sharp v. Dover Stamping Co. (Lazear), 103 U.S. 250 (1880) — https://tile.loc.gov/storage-services/service/ll/usrep/usrep103/usrep103250/usrep103250.pdf — the Court required the broiler patent to be "construed in the light of the things which existed before" and limited it to the patentee's particular arrangement, refusing to cover the prior-art forms.

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Secondary considerations (Graham factor 4)

I found no evidence of any secondary consideration: no assignment on the face of the patent, no reissue or continuation in family ID 2241331, no reported litigation (as established in the earlier litigation section), and therefore no documented commercial success, long-felt-but-unmet need, failure of others, copying, industry praise or licensing. The record is simply silent. Silence neither rebuts nor supports the § 103 case; I flag it rather than assert either way.

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Bottom line

Under a modern § 103 analysis, the single claim of US 171,924 would very likely be held obvious over US 115,984 (Roe) in view of US 147,790 (Price) and/or US 120,528 (Noble), and further in view of US 113,086 (in-art admission of inclined, multi-purpose stove openings) and US 119,066A (Van) for the covered-broiler-with-fume-conduction feature. Roe '984 alone supplies the guttered, pan-sided, flanged broiler and an express teaching that a cover "may be used ... when desired"; Price '790 and Noble '528 supply the covered broiler seated at a stove opening for smoke suppression and are directly analogous art; and the "inclined feed-opening" limitation is a conceded-in-the-art structure to which a known locating flange is applied for its known function. The only genuinely debatable limitation is element (5), and even De Haven's own asserted benefits (reflected heat, removal from the draft, smoke drawn into the stove) are each separately disclosed in Marshall '167, Van '066 and Van & Barringer '963.

Anticipation (§ 102) is a closer question than obviousness and I would not rest on it: Roe '984's cover is permissive rather than claimed, and Roe's claim 2 covers only frame + channel + flange, so Roe alone probably does not disclose a covered broiler as claimed. The claim as a whole therefore likely survives § 102 but falls to § 103.

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Caveats and limits on this analysis

1. I could not retrieve the text of US 137,278A ("Improvement in broiler attachments for stoves and ranges," 1873-03-25) — the single most on-point title on the page's Similar Documents list. The search engine returned, instead, a different document (US 147,790, Anna Price). I have not assumed or reconstructed what 137,278 discloses, and no combination above depends on it. If its text can be pulled (it is a prime candidate to be a § 102/§ 103 reference by title alone), the analysis could materially strengthen.
2. US 115,984 (Roe), US 120,528 (Noble), US 147,790 (Price), US 132,167 (Marshall) and US 23,963 (Van & Barringer) are NOT on the page's Similar Documents list. I located them through search, and I use them because they are squarely pre-1875 cook-stove-broiler art. If the instruction is to consider only the page's listed documents, then Combinations A–C cannot be assembled as stated, and the analysis would be limited to US 119,066A, US 108,240A, US 113,556A, US 5,721A, US 137,278A (unretrieved) and US 173,994A — which, on the material I actually obtained, is insufficient to support a strong § 103 combination, because US 173,994A (Patten) is directed to a fire-box partition/draft-stopper and slotted grate, and the others are stove-casing, not broiler, references.
3. US 113,086's date is unverified. My ~March 1871 estimate is inferred solely from the patent-number series (US 113,556 = Apr. 11, 1871; US 115,984 = June 13, 1871). It must be confirmed before being relied on as pre-1875 art.
4. § 103 did not exist in 1876; the correct historical standard is Hotchkiss's "invention" requirement, and a 19th-century court would have asked whether the particular arrangement, viewed against the art, reflected more than ordinary mechanical skill.
5. Claim construction drives the result. I applied the earlier section's parse of the claim as a four-element combination plus a use limitation. I could not verify the reference characters f/f¹/f/g against the drawing sheets (OCR-degraded), and if "covered" were read out of the claim (it is not, on the text), the § 103 case against the claim would be near-conclusive on Roe '984 alone.
6. No live source in this session produced an examiner's citation list, a rejection history, or a pre-1893 validity challenge to this patent, so I cannot say whether these or any other references were ever before the Office.