US 1557244

I'll run targeted searches for this patent number and any litigation references.

Now let me check for any litigation or CAFC references.

Search scope and literal-number discipline

I searched for the number 1557244 exactly as given. Results surface three unrelated documents sharing that numeral, which I am not conflating with the US patent requested:

• EP1557244A2 — "A machine tool provided with a manipulator device" (EPO, priority 2000-06-30, published 2005-07-27). Unrelated subject matter.
• ARE 1557244 — a Brazilian Supreme Court (STF) Recurso Extraordinário com Agravo, Município de Campo Grande v. Ludmila Conceição Monteiro Ronda Mise, final as of 2025-09-16. A judicial docket number, not a patent.
• US1557244A — the requested item, "Rotary toothbrush."

I found no CAFC docket (2024–2026 term) or any federal litigation naming U.S. Patent No. 1,557,244. That is expected: the patent's term expired in 1942, so it has not been assertable in modern litigation. Anyone reporting a 2026 CAFC appeal on this number is likely referring to one of the unrelated identifiers above.

Bibliographic summary — US1557244A

Abstract: This patent predates the U.S. statutory abstract requirement (mandatory practice only after the 1952 Act). There is no formal abstract. The closest thing is the opening statement of the specification:

"This invention relates to an improved tooth brush and has specific reference to a device of this class wherein the brush is rotatably mounted to be rotated during the cleaning operation for more effectively removing matter from the crevises between the teeth which cannot be removed with the common type of brush."

The passage returned under Google's "Definitions" heading is machine-extracted from the description, not an applicant-supplied abstract; I flag that so it is not mistaken for one.

Figures (per the specification)

• Fig. 1 — side elevation, part broken away and in section.
• Fig. 2 — enlarged cross-section on line 2–2 of Fig. 1, showing the channel and rack in the handle's underside.
• Fig. 3 — longitudinal section. (The original text says "taken on the line 3-3 of Figure 3" — an internal inconsistency in the printed patent, presumably meant "3-3 of Figure 1." I quote it as printed rather than silently correcting it.)

The single independent claim, in plain language

The claim is a single unitary (independent) apparatus claim. Paraphrased element by element:

1. A handle in the form of a flat bar — the driver is a straight, flat, elongate bar that the user reciprocates by hand.
2. A channel in the underside at the outer end — the bar's outer (working) end carries an open channel on its underside.
3. A toothed rack — the inner surface of one wall of that channel is serrated, forming a longitudinally extending toothed rack integral with the handle.
4. Rotary cleaning elements with toothed pinion heads — each brush/cleaner has a head fitted with a toothed pinion; the pinions sit inside the channel, and their teeth mesh with the rack teeth. This is the "positive driving connection" touted in the specification.
5. A metal casing — a metal casing partially surrounds the channeled handle portion and the pinions, holding the parts in operative relation.
6. Longitudinally spaced openings — the casing is pierced with openings spaced along its length, through which the cleaning elements project (i.e., the bristles stick out toward the teeth).

Operative principle: hold the casing (or its optional detachable handle 8) stationary against the teeth in one hand and slide the flat bar back and forth with the other. The rack rides past the pinions, spinning the brushes against the tooth surfaces. The specification notes the detachable handle may be removed to allow deeper insertion for cleaning the lingual/inner tooth faces.

Note the scope captured by the claim is narrower than the disclosed invention: the claim requires the rack to be formed in the handle's underside channel wall and requires a metal casing with spaced openings; the "series of independently rotatable brushes" and the detachable handle are described as preferred/optional features and are not separately claimed.

Prosecution and citation history (contextual)

• The patent is cited as background art in roughly 29–49 later U.S./foreign documents, overwhelmingly modern powered-toothbrush filings by Procter & Gamble, Braun GmbH, Church & Dwight, Gillette, Dental Research Corp., and individual inventors (Clemens, Amit, Stollman, Smith, Denney). Representative citations: DE2736286A1, FR2400338A1, US4156620A, US4827550A, WO1992019177A3/US5186627A, US5274870A, US6338176B1, US6453499B1, and multiple P&G "Complex/Multi-motion toothbrush" families.
• Notably, WO1983002218A1 (Sylvain Nahum) cites "US, A, 1557244 (DOMINGUE) 13 October 1925, see the claim" as an anticipatory-type reference — i.e., this patent functions in the art as an early teaching of rack-and-pinion conversion of handle reciprocation into brush rotation.

Statements of uncertainty

• Assignee: I found no evidence of an assignee; "Individual" on Google Patents is a default label, and the printed patent is silent. Treat "unassigned" as probable but unverified.
• No litigation: I could not locate any district-court or Federal Circuit proceeding involving this patent. Given its 1942 expiry, a 2026 CAFC appeal on it is not plausible; the 1557244 matches I did find are an unrelated EPO machine-tool publication and a Brazilian STF docket.
• Abstract: none exists in the original; do not cite the Google "Definitions" text as an abstract.
• The OCR of the source document is degraded (e.g., "numeral l" = numeral 1; "pinion 4" appears once as "pinion k"), and I have read through those artifacts rather than reproducing them as technical content.

I'll search for litigation records involving US patent 1557244.

Let me run a few more targeted checks against litigation databases.

Let me run a final verification with a different identifier format and against litigation-specific sources.

Litigation Search Results — US Patent No. 1,557,244

Finding: No litigation is known involving US Patent No. 1,557,244.

I searched litigation-oriented sources (Unified Patents litigation portal, PACER-derived/Thomson Reuters court document repositories, PTAB/PTACTS records, and general web searches keyed to the exact number in several formats: 1557244, US1557244, US 1,557,244, and "1,557,244"). No case — plaintiff, defendant, jurisdiction, case number, or filing date — matched this patent. I will not fabricate entries to fill the requested table, so no table is provided.

What the searches returned (all false positives)

Every apparent "hit" was a different identifier that merely shares the digit string:

Context and caveats

• Life of the patent: Filed 1924-07-03 (Appl. No. 724,044), granted 1925-10-13, and per Google Patents the legal status is "Expired – Lifetime" with anticipated expiration 1942-10-13. The patent has therefore been unenforceable for over 80 years and cannot support a live infringement action.
• Assignee: Individual (inventor Nazaire T. Domingue, Waterbury, Connecticut). There is no corporate assignee on record that would appear as a modern patent plaintiff.
• Google Patents' litigation data: The patent's page lists 29 "Cited By" references (mostly Procter & Gamble and Church & Dwight toothbrush patents) but shows no litigation section and no "Cited By" examiner citations under a litigation heading — consistent with no asserted-case record.
• Scope of my search: I could not corroborate against a paywalled full-text litigation database (e.g., Docket Navigator, Lex Machina) or pre-digital case law before roughly the mid-20th century. It is possible in principle that an infringement or validity suit was filed between 1925 and 1942 that is not digitized and would not surface in these searches. I flag this as an unresolved limitation rather than asserting a definitive negative for that period.
• Per your instruction, I have interpreted the identifier literally and did not substitute any similar patent number.

Recommendation

If you need a defensible negative for diligence purposes, the pre-1942 window should be checked against a historical case-law index (e.g., the Decennial Digest / West's Federal Practice Digest covering 1925–1942, and the Federal Reporter/F.2d for the Second Circuit and D. Conn., where the inventor resided). Absent that check, I can confirm only that no litigation appears in any modern, searchable source.

I'll verify the structured block's negative finding against public PTAB sources before writing this up.

Let me check the PTAB E2E / PTAB decisions sources directly, and confirm the legal-status angle.

Proceedings overview

Total AIA trial proceedings on US 1,557,244: zero. The USPTO Open Data Portal (ODP) structured block returns no AIA trial proceedings for this patent as of the most recent ingest, and my independent web checks against PTAB sources (PTAB E2E / PTACTS, PTAB Final Written Decision texts, and general searches keyed to 1557244, US1557244, 1,557,244, and Domingue) surfaced no IPR, PGR, or CBM involving this patent — so there is no breakdown by status to report (active: 0 / claims invalidated: 0 / claims sustained: 0 / settled: 0 / institution denied: 0).

The defensive posture this gives a defendant is not the "patent has survived two IPRs and is hardened" posture, and it is not the "claims are canceled, the demand letter is baseless" posture either. It is a simpler and much stronger one: the patent cannot be asserted at all. US 1,557,244 issued 1925-10-13 and, per its own record, expired 1942-10-13 — status "Expired – Lifetime." There is no live claim scope to defend against, so the absence of PTAB activity is not evidence of a hardened patent; it reflects that no rational challenger would spend a § 311 petition on a patent that has been unenforceable for over eight decades. Anyone sending a demand letter citing "US 1,557,244" for a modern rotary toothbrush is relying on an expired patent, and the correct response is to refuse to engage on validity grounds and to say so directly.

No per-proceeding sections are included, because there are no proceedings to describe. I will not manufacture proceeding numbers, panels, or holdings to fill the template.

Strategic summary

Claim status — CANCELED vs. SUSTAINED vs. UNTESTED. There is nothing to tabulate: no claim of this patent has ever been tested in an AIA trial. The patent carries one claim (the specification refers to "the adjoined claim," singular — a single unitary apparatus claim covering the flat-bar handle, the underside channel with a serrated rack wall, the pinion-headed rotary cleaning elements, and the metal casing with longitudinally spaced openings). That claim stands exactly as issued, having never been narrowed, canceled, or confirmed by the Board. Under 35 U.S.C. § 318(b) no certificate has issued and none can issue absent a trial. Its legal effect today is nil because the term ran out in 1942.

Estoppel landscape — § 315(e)(2). There is no estoppel, because § 315(e)(2) estoppel only attaches to a petitioner who obtains a final written decision. With no petitioner, no FWD, and no privity chain, no prior-art ground is foreclosed to anyone. In principle, IPR remains formally available: 35 U.S.C. § 311 permits a petition on "a patent," and the AIA's transitional provisions do not exclude pre-AIA patents, so a 1925 patent is not categorically outside the Board's jurisdiction. But there are two decisive practical bars: (i) PGR is unavailable (requires an application filed on or after 2013-03-16) and CBM is unavailable (requires a financial-product/service patent, 35 U.S.C. § 18(d)(1)); and (ii) a challenge to an expired patent yields no commercially useful relief — you cannot clear a right that no longer exists, and the Board has no power to revive or cancel an already-lapsed term. There is no useful PTAB play here.

Pattern signals. None of the usual signatures are present. No repeat petitioner (there is no petitioner). No Patent Owner appeals — CourtListener and the Federal Circuit docket show no appeal of any Board decision involving this patent, and none is possible where there was no Board decision. No defensive aggregator (Unified Patents or similar) appears anywhere in the chain; Unified's name surfaced in my searches only in connection with unrelated '244-numbered modern patents and generic § 325(d) precedent citations. The only "activity" on this patent in the public record is forward citation: roughly 29–49 later documents cite it as background art, overwhelmingly modern powered-toothbrush filings by Procter & Gamble, Braun, Church & Dwight, Gillette, and Dental Research Corp. That is citation traffic, not adversarial traffic — it tells you the art regards this patent as an early teaching of rack-and-pinion conversion of handle reciprocation into brush rotation (see WO1983002218A1, citing "US, A, 1557244 (DOMINGUE) 13 October 1925, see the claim"), not that anyone is litigating it.

Recommended next steps

1. If you are a defendant receiving an assertion on US 1,557,244, stop litigating validity and attack the right to assert. The patent expired 1942-10-13. A demand letter citing it is facially deficient; the defensible response is a refusal-to-license letter citing the expiry, plus a preservation letter to the Federal Trade Commission or state Attorney General if the demand is part of a pattern.
2. Do not spend money on a PTAB petition. No IPR/PGR/CBM exists or is worth filing. PGR and CBM are jurisdictionally unavailable (pre-2013 filing; non-financial patent); IPR is technically available under § 311 but futile. There is no active trial stage to track, no institution-decision deadline, no oral hearing, and no 1-year § 316(a)(11) FWD due date to calendar.
3. Verify the identifier before you act. The digit string 1557244 has produced documented false positives in this analysis, and a defendant may be dealing with one of them rather than with this patent:
   • EP 1 557 244 A2 — "A machine tool provided with a manipulator device" (EPO, WO 0202281 family, PCT/EP2001/…, filed 2001-06-23, published 2005-07-27). Unrelated field. (EPO PISE record)
   • Brazilian STF, ARE 1.557.244 — Município de Campo Grande v. Ludmila Conceição Monteiro Ronda Mise, a public-competition (concurso público) appointment case, distributed to Min. Gilmar Mendes 2025-06-27, res judicata 2025-09-16. A docket number, not a patent, and a litigation matter — not a PTAB matter.
   • CVE 1557244, Diario Oficial de Chile (2019-03-07) — a corporate-formation notice. Not a patent.
   • 2018 WL 1557244 — a Westlaw citation (S.D. Ohio). Not a patent, not a PTAB trial.
   • Various '244 patents (e.g., IPR2025-00420 concerning U.S. 6,899,244; the '631 IPR referenced in PACT v. Intel; the '244 patent in the Natera/CareDX dispute) — different patents whose numbers merely end in "244."
4. If the demand letter in fact cites a live modern patent number that resembles this one, re-run this analysis on that number. The correct answer will look completely different, and I would need the actual number to produce it.

Citation pins for verification:

• Google Patents record (source of the structured data): https://patents.google.com/patent/US1557244/en — shows status "Expired – Lifetime," anticipated expiration 1942-10-13, and no litigation section.
• USPTO PTAB E2E / PTACTS (search portal): https://ptacts.uspto.gov/ptabweb/ — no proceedings found.
• USPTO PTAB Final Written Decisions: https://www.uspto.gov/patents/ptab/decisions — no decision cites this patent as the subject patent.
• CourtListener: https://www.courtlistener.com/ — no Federal Circuit appeal involving this patent.

Unresolved limitation I am flagging rather than papering over: AIA trials only became available 2012-09-16. A hypothetical pre-2012 "IPR" is a legal impossibility (the proceeding did not exist), so my negative for the 1925–1942 window is structural rather than evidentiary. My negative for 2012–present rests on the ODP structured block plus public-source searches; I could not independently query a paywalled PTAB analytics platform (e.g., Docket Navigator, Lex Machina) to double-confirm. I found nothing to suggest a proceeding exists, and the patent's 1942 expiry makes one economically inexplicable.

I'll reconstruct the assignment record. Let me query the USPTO Assignment Center and cross-reference sources.

Research note on source coverage (read first — it governs everything below)

I could not execute a live query against the Assignment Center interface in this session, but the governing fact about the source is documented and decisive:

"This searchable database contains all recorded Patent Assignment information back to August 1980." — USPTO, Assignment Database webinar deck, uspto.gov

US 1,557,244 was filed 1924-07-03 and issued 1925-10-13, with anticipated expiration 1942-10-13 ("Expired – Lifetime," Google Patents). Any assignment of this patent would have been executed and recorded in 1925–1942 — i.e., decades before the online Assignment Center's coverage begins. The Assignment Center is therefore structurally incapable of returning a record for this patent, even if one existed on paper. Pre-1980 assignment records live at the USPTO Public Search Facility and the National Archives (NARA), not in the online database.

Consequence: any "no results, therefore unassigned" conclusion from Assignment Center alone is a coverage artifact, not a title finding. I flag this rather than presenting a database blank as evidence of an unencumbered chain.

Inventors

• Sole named inventor; the patent is signed "NAZAIRE T. DOMINGUE" with no co-inventors, and Google Patents' inventor field lists him alone ("Nazaire T Domingue").
• Employer: undeterminable from any source I found. Waterbury, Connecticut in 1924 was a brass-goods and clock-manufacturing center (Scovill Manufacturing, Chase Brass & Copper, Waterbury Clock Co.). The claimed structure — a flat metal bar with a machined rack, pinions, and a metal casing — is consistent with a metalworking-trades background, and the "Individual" assignee designation means the patent was not filed on behalf of an employer. I am explicitly labeling the Waterbury-industry link as contextual inference, not a finding. No corporate entity, no shop name, and no employment record for Domingue surfaced in the searches run.
• Unusual-pattern screen (all inventors departing within 12 months of filing): not applicable and not observed. A single individual inventor with no corporate assignee has no "departure from the original assignee" event to track. There is no evidence of an employer-attribution dispute or of a co-inventor split.

Original assignee

• On the face of the patent: no assignee. The printed front matter names no assignee — the document reads "NAZAIRE T. DOMINGUE, OF WATERBURY, CONNECTICUT," full stop.
• Google Patents lists Original Assignee: Individual and Current Assignee: Individual. As noted in the earlier bibliographic section, "Individual" is a default label meaning "no assignee of record," not the name of an entity. I concur that this reflects an unassigned patent but state it as an inference.
• Product embodying the claims: none found. This is a 1925 hand-driven reciprocating-brush device with no identified commercial manufacture, no brand, and no product literature. No evidence of shipping product.
• Primary line of business: N/A. An unassigned individual inventor has no line of business to characterize. There is no corporate assignee whose business could be described.
• Current status: N/A for an entity. The patent itself: rights expired 1942-10-13; 83 years out of term. No successor-in-interest to an unassigned patent other than the inventor's own heirs, and no record of any heir ever recording anything.

⚠️ Contradiction check: the earlier "Prosecution and citation history" section correctly labeled the 29–49 documents under Google Patents' "Cited By" heading as forward citations by later filers (P&G, Braun, Church & Dwight, Gillette, Clemens, Amit, Stollman, Smith, Denney). Those are art citations, not assignments. Nothing in that set transfers title, and none of those companies ever held rights in US 1,557,244. I restate this because a naive ownership read of a "Cited By" table is exactly how a fan-out portfolio is misattributed.

Assignment timeline

The USPTO Assignment Center has no records for US Patent No. 1,557,244 — and, per the coverage note above, it could not have any, because the database begins in August 1980 while this patent's entire enforceable life ended in 1942.

Per the output instructions, I stop the formal section here. What follows is the honest completion of the remaining requested fields given that finding, rather than a padded fabrication.

No reel/frame, no conveyance type, no correspondent, and no execution or recording date exists to report. I will not invent a reel/frame pair, and I will not name a correspondent — the correspondent field is only meaningful where a recordation exists, and none does.

Verification paths

• Assignment Center (modern): https://assignmentcenter.uspto.gov/
• Legacy Assignment Search (Aug 1980 → present): https://assignment.uspto.gov/patent/index.html
• For the 1925–1942 window, the only defensible sources are NARA (Record Group 241, Patent Assignment records) and the USPTO Public Search Facility's paper records — neither is online.

Timeline diagram

Only documented events are shown. No ownership transfer is diagrammed because none is documented. (Google Patents "legal events" for this patent are limited to the filing/grant/expiration entries below.)

timeline
    title Ownership of US 1557244
    1924 : Application filed by Nazaire T Domingue
         : Serial No 724044
    1925 : Patent issued to Domingue as individual
         : No assignee named on the patent
    1942 : Patent term expired
         : No recorded transfer in chain

NPE / troll-pattern signals

Every signal is assessed against the evidence available. Because the chain is a single unassigned inventor from 1924 with a term that ended in 1942, most signals are structurally inapplicable; I mark them accordingly rather than scoring them as affirmative findings.

1. Shell-entity transfer — Not present. No assignment records exist at all, so there is no "IP / Licensing / Holdings / Ventures" entity, no single-purpose LLC, and no registered-agent address anywhere in the chain. The prior summary's "Assignee: Individual" is a default label, not a shell.
2. Known asserter in the chain — Not present. Neither the inventor nor any entity appears on RPX, Unified Patents, or any public high-frequency-plaintiff directory. None of Acacia, Marathon, IV, IPNav, Wi-LAN/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation Corp, or any Spangenberg entity is connected to this patent in any source I found. The modern companies that cite it (P&G, Braun, Church & Dwight, Gillette) are forward citers, not assignees.
3. Repeat correspondent across the chain — Unclear / not applicable. There is no correspondent of record on any reel because there is no recordation. I have no attorney name to report and will not supply one.
4. Cascading transfers — Not present. Zero transfers, therefore no chained-LLC sequence in under 24 months and no shared correspondent address to test.
5. Pre-litigation transfer — Not present. No transfer, and no infringement suit — confirmed in the earlier Litigation section, which found no modern searchable case and flagged the pre-1942 window as un-digitized. With expiry in 1942 there is no live action this chain could have been arranged to support.
6. Bankruptcy fire-sale — Not present. The assignee is an unassigned individual, not a Chapter 7/11 debtor; no Kodak/Nortel/Polaroid-style sale event exists for this asset.
7. Privateering — Not present. No operating company ever held rights, so there is no corporate patent-holder transferring to an NPE to assert on its behalf. No SEC 10-K/8-K disclosure could name this patent as an asserted asset.
8. Defensive aggregator (anti-NPE) — Not present. The chain does not terminate at RPX, AST, LOT Network, Unified Patents, or OIN. This is not the inverse "neutralized" case either — the patent simply lapsed on its own 17-year term in 1942 with title never leaving the inventor.

Verdict

Insufficient data — no records, and no ownership transfer beyond the original (non-)assignment.

The Assignment Center returns nothing for US 1,557,244, and the source's August-1980 coverage floor means a null result is expected rather than probative: the patent's entire 1925–1942 enforceability window predates the online database, so no reel/frame, correspondent, or conveyance type can be cited. The only ownership datum is the face of the patent itself, which names Nazaire T. Domingue of Waterbury, Connecticut as inventor with no assignee ("Individual" being Google's default label), and Google Patents records anticipated expiration 1942-10-13. With no recorded transfer, no asserted suit, and no living term, no NPE signal can be marked present — a "high" or "moderate" NPE call here would require me to fabricate reel/frame entries, which I will not do.

Verify at: https://assignmentcenter.uspto.gov/ (modern records, Aug 1980→present) and https://assignment.uspto.gov/patent/index.html. For a diligence-grade negative on the 1925–1942 chain, the paper record at NARA (RG 241) must be pulled — the online Assignment Center cannot produce one.

I'll search for the patent and its citation records, then verify each candidate reference individually.

Threshold finding: the citation record for US 1,557,244

I hit the tool-step limit before I could verify every candidate reference individually, so I will be explicit below about what is verified versus what is title/date metadata only.

The most important finding is structural: US 1,557,244 has no prior-art citations of record.

The authoritative text I fetched (the Google Patents reproduction of the USPTO record) contains no "(56) References Cited" / "Cited" section. What it contains is:

A 1924-filed, 1925-granted patent was not subject to any duty of disclosure, and pre-1952 patents do not carry an IDS/prior-art listing on their face. So the honest answer to "look at each patent citation for 1557244" is: there are no backward citations to analyze. Analyzing the forward citations as if they were prior art would be a category error — every one of them postdates the 1924-07-03 filing and therefore cannot anticipate under any version of § 102.

I also did not obtain a separately hosted USPTO record (Patent Public Search / PatentCenter page) in this session; my searches returned Google Patents mirrors of the USPTO document plus third-party search reports. I treat the fetched full text as authoritative, consistent with your source instruction.

Correction to my earlier section (flagged as required)

My prior "Prosecution and citation history" section stated that WO1983002218A1 (Nahum) cites US 1,557,244 "as an anticipatory-type reference." That was wrong, and I am correcting it. The actual PCT search report in WO1983002218A1 lists it as:

A US, A, 1557244 (DOMINGUE) 13 October 1925, see the claim;

Category "A" means the ISA classified it as "documents defining the general state of the art which are not considered to be of particular relevance" — not X (novelty-destroying) or Y (inventive-step-destroying). The same report lists US 2172624 (ROMANI), 1939 and US 2059035 (ROTHSCHILD), 1936 the same way. So Domingue is background art to Nahum, not an anticipation reference. I flag this contradiction between my two sections.

Additional literal-number false positive found

The fetched results also surfaced FR 3039601 B1, whose "N° d'enregistrement national : 1557244" is a French national registration number, not this patent. Consistent with the strict no-auto-correct rule, I record it and exclude it. Likewise, EP 1 557 244 A2 is confirmed as the unrelated machine-tool application — EP1724054A1's family table lists "EP 1557244 A2" as a family member of IT TO20000657, consistent with my earlier bibliographic findings.

The claim that has to be anticipated

There is exactly one claim (the specification says "the adjoined claim," singular). All § 102 analysis collapses to Claim 1, which requires every one of:

1. handle in the form of a flat bar;
2. a channel in the bar's underside at its outer end;
3. the inner surface of one wall serrated into a longitudinally extending toothed rack (rack integral with the handle);
4. rotary cleaning elements with toothed-pinion heads seated within the channel, pinion teeth meshing with the rack;
5. a metal casing partially surrounding the channeled handle portion and the pinions;
6. longitudinally spaced openings in the casing through which the cleaning elements extend.

Anticipation requires all six. A reference that shows rotatable brushes but no rack-and-pinion (i.e., no positive mechanical drive from a reciprocating bar) cannot anticipate, because element 4 is the point of novelty the applicant himself emphasized ("positive driving connection").

Table A — Forward citations ("Cited By"): NOT § 102 prior art

Listed only so the record is complete and so the distinction is documented. All postdate 1925-10-13 and therefore cannot be prior art to a 1924-07-03 filing.

Conclusion for Table A: zero references in this group can anticipate Claim 1 under § 102 (any subsection) — each is decades later in time.

Table B — "Similar Documents" dated BEFORE 1924-07-03: the only § 102 candidates

These are Google's similarity list, not citations. Their dates are the only reason any of them can even be considered. Dates marked ✔ were verified against the full document text in this session; the rest are the dates printed on Google's similarity list and were not independently verified for disclosure content.

Conclusion for Table B: none of the three fully verified pre-1924 references discloses a rack-and-pinion drive, a channeled flat-bar handle, or a metal casing with spaced openings. Claim 1 is not anticipated by the verified art.

Two unverified but promising leads I found (worth a follow-up search)

A secondary source (a Zenodo-hosted 1920 patent-grant listing) shows two pre-1924 patents titled "Rotary toothbrush":

• US 1,341,916 — "Rotary toothbrush," Basil W. Leach (Golconda, Nev.)
• US 1,351,159 — "Rotary toothbrush," William N. and R. L. Cavileer (Ray, Ariz.)

Both carry 1920-era grant numbers (pre-dating the 1924-07-03 filing by roughly four years and thus squarely within the § 102 window). I have not verified their claim scope, exact dates, or drawings — I have only the title and named inventors from a list of issued patents. These are the strongest follow-up candidates for real anticipation art and should be pulled and read in full.

Table C — "Similar Documents" dated AFTER 1924-07-03: NOT § 102 prior art

Special caveat on US 1,500,722 A (1924-07-08): its issue date is 5 days after Domingue's filing, but a U.S. patent issued in July 1924 was normally filed 1–3 years earlier, so its filing date could well precede 1924-07-03. Under pre-1952 law (R.S. § 4886), a U.S. patent barred novelty only if it was "patented" before the applicant's invention — the modern § 102(e) "filed-before" treatment of pending applications did not exist. Absent evidence of Domingue's actual invention date, a reference issued 5 days after his filing is not safely citable as § 102 art, and I have not verified its filing date or disclosure. Flagged as unresolved.

Overall § 102 conclusion

No reference in the available record anticipates the sole claim of US 1,557,244 under 35 U.S.C. § 102. The claim's distinguishing element — the handle-integral toothed rack in the underside channel driving toothed pinion heads of independently rotatable brushes, enclosed by a perforated metal casing — is not shown by any of the three pre-1924 references I could read in full (Gardner '042, Cosens '966, Buckley '789).

Statements of uncertainty (explicit)

1. I could not verify eleven of the twelve pre-1924 "Similar Documents." Their descriptions above are inferences from titles, not from read disclosures. I have not asserted anticipation for any of them.
2. US 1,341,916 and US 1,351,159 ("Rotary toothbrush," 1920) are the most promising untested prior art and were identified only through a secondary index; verify against the primary documents.
3. Statutory framework: the controlling law is the pre-1952 Act (R.S. § 4886), whose novelty bars ran from the applicant's invention date, not the filing date. Because Domingue's invention date is unknown and no evidence of record establishes it, I used the 1924-07-03 filing date as the operative cut-off — the most conservative and defensible bright line. The precise application of the pre-1952 two-year clause to printed publications is a doctrinal point I flag for verification rather than assert.
4. OCR degradation in the source (e.g., "pinion k" for pinion 4; "numeral l" for numeral 1; "Heinrich Ixhers" for an 1893 inventor's surname) is read through, not reproduced as technical content.
5. No litigation: consistent with my prior section, the 1942 expiry means no modern § 102 challenge could exist; the anticipation analysis above is therefore an academic/validity-study exercise, not a live-controversy one.

I'll pull content on the pre-1924 references from the "Similar Documents" list, since those are the only candidates that can qualify as prior art against a July 3, 1924 filing date.

Strong pre-1924 hits so far (Albers US1326900, Cavileer US1351159, Cruikshank US1481891). Let me probe for the mechanical motion-conversion teachings specifically.

Preliminary framework — two caveats before the §103 analysis

1. §103 is anachronistic for this patent. US 1,557,244 was filed 1924‑07‑03 and granted 1925‑10‑13. 35 U.S.C. § 103 did not exist until the 1952 Act; the governing standard in 1924–25 was the judicially created "invention" requirement of Hotchkiss v. Greenwood, 52 U.S. (11 How.) 248 (1851), i.e., whether the variation required more ingenuity than that of the ordinary mechanic skilled in the art. I am therefore performing the requested §103 analysis retrospectively/hypothetically. Substantively the two tests converge closely for a mechanical case like this, and I flag the substitution rather than silently treating §103 as the law of 1925.

2. The "Prior Art" listings on the Google Patents page are not a prior-art determination. The page supplies (a) a "Cited By" list of ~29–49 documents and (b) a machine-generated "Similar Documents" list. Nearly every "Cited By" item post-dates the patent by 50–80 years (Clemens US4156620, P&G "Multi-motion toothbrush" families, Braun, Gillette, the 2006 Denney application, etc.). These are forward citations; they can no more invalidate US 1,557,244 than a 2020 patent can invalidate a 1925 one. The "Similar Documents" list is likewise a similarity ranking, not a legal screening. I therefore build the analysis below only from items whose reference date precedes the critical date.

Critical date: filing 1924‑07‑03 (Appl. No. 724,044). I note that under the pre‑1952 statute (R.S. 4886) a patent granted more than two years before filing was a statutory bar regardless of the applicant's date of invention, and any patent granted before the applicant's invention date was anticipatory. All references relied on below issued ≥ 4 years before filing, so none is escapable by swearing behind.

Sorting the listed art by date — what is actually available

Note the significance of the ❌ rows: the art was crowded. Rotary toothbrushes under that exact title appear repeatedly (US1351159, US1481891, US1561062 "Rotary toothbrush," plus "Rotary toothbrush, Basil W. Leach" listed in a contemporaneous dental-journal patent digest). Density of independent filings on the same narrow concept is itself a KSR-type signal that the concept was within ordinary skill.

Two references carry the analysis

Albers, US 1326900 (https://patents.google.com/patent/US1326900; https://www.freepatentsonline.com/[1326900](/patent/1326900).html) is the closest single reference. From its description:

• "two brush heads 7 are preferably employed… the brush heads are arranged in close relation and are carried by shafts 8 and 9."
• "suitable spurs or gear wheels 10 are keyed and mesh with each other."
• "These gear wheels are preferably housed within a casing comprising an outer section 11 and an inner section 12… section 12 having an inwardly extending flange 16 soldered to the interior of wall 14."
• "Shaft 8 extends beyond the exterior of wall 13 and is there provided with a suitable manipulating knob 18."
• "Knob 18 is turned so as to turn the shaft 8, brush 7 and gear wheel 10. Since gear wheel 10 meshes with gear wheel 10', the latter… is accordingly driven… Both brushes as a result will receive whirling motion."
• A pivoted handle 20 is provided on the casing.

Albers therefore teaches, in the toothbrush art and six years before Domingue's filing: (i) a plurality of rotary cleaning elements, (ii) each brush head carrying a toothed gear on its shaft — i.e., functionally a pinion on the brush head, (iii) those gears housed in a casing which maintains them in operative relation, (iv) the casing being metal (soldered construction), and (v) a handle attached to the casing to hold the head stationary. That is Domingue's elements (d) [pinion-on-brush, meshing toothed drive], (e) [metal casing], and the two-handle/two-hand operation of the specification, all squarely met.

Cruikshank, US 1481891 (https://patents.google.com/patent/US1481891A/en; PDF at patentimages.storage.googleapis.com/04/93/84/b60d79709fbcac/US1481891.pdf) supplies the missing kinematic link. Its object is stated in terms nearly identical to Domingue's:

"the object of my invention is to provide a device of this nature in which the brush member is adapted to be revolved against the teeth by manually operated mechanism to brush the same by rotary movements instead of lateral movements… and which device is simple in construction and operation."

Structurally it teaches "a socketed member 1 rotatably mounted in a sleeve 2… connected at its other end to the end of a right and left spirally grooved rod 4 longitudinally movable within a cylindrical sleeve or handle 5, on which rod… are mounted nuts 6 and 7… If therefore the right hand nut is held to the sleeve and the sleeve, that is, the handle 5, moved forward… the rod 4 will rotate." Claim 1 recites "means for detachably connecting the nut to the handle whereby lateral movement of the handle causes rotation of the rod, and a stem removably mounted in the socket… provided at its free end with a rotary brush."

Cruikshank therefore discloses the exact functional principle of Domingue's claim: hold one part stationary, reciprocate the handle longitudinally, and convert that linear reciprocation into rotation of a rotary brush — a "positive driving connection between the handle and… rotatable brushes," to use Domingue's own words. It simply implements the conversion with a screw-thread/nut pair rather than a rack and pinion.

Element-by-element mapping of claim 1

Claim 1 (the sole claim) requires: (a) handle in the form of a flat bar; (b) channel in the bar's underside at its outer end; (c) one channel wall serrated to form a longitudinally extending toothed rack; (d) rotary cleaning elements whose heads include toothed pinions located in the channel, pinion teeth meshing with rack teeth; (e) a metal casing partially surrounding the channeled handle portion and pinions; (f) longitudinally spaced casing openings through which the cleaning elements extend.

The residual novelty is therefore the substitution of one notorious motion-conversion mechanism — the rack and pinion — for another (Cruikshank's screw-and-nut) or for a finger-turned gear train (Albers), and the placement of that rack as a serration on one wall of a channel in the underside of a flat bar.

Combination 1 (primary): Albers + Cruikshank, in view of the common knowledge of rack-and-pinion

Proposed: Albers US 1,326,900 in view of Cruikshank US 1,481,891, further in view of the ordinary mechanical knowledge that a toothed rack meshing with a toothed pinion converts linear reciprocation into rotation.

Motivation to combine, articulated on the KSR factors:

1. Same field, same problem, same solution category. Both references are toothbrushes; both address removal of material from between the teeth; both solve it by rotating the brush rather than scrubbing laterally. Albers and Cruikshank are analogous art to Domingue by any measure (field of endeavor and problem addressed are identical).
2. Predictable result from a known equivalent. The rack and pinion is the canonical equivalent of Cruikshank's screw/nut for translating reciprocation into rotation. Substituting one known mechanism for another known mechanism that performs the same function in the same way to achieve the same result is the paradigm of obviousness. Nothing in Domingue's claim reflects an unexpected result — the specification asserts only "extreme simplicity and durability," which is precisely the motivation to make the substitution, not a surprising consequence of it.
3. Finite, identified, predictable set of solutions. An artisan seeking to (i) eliminate Albers' finger-operated knob and gear train and (ii) eliminate Cruikshank's screw/nut friction and detent button, while retaining "a positive driving connection between the handle and… rotatable brushes" (Domingue's stated feature), has only a handful of known options: rack and pinion, worm, cam, crank, screw. Choosing the simplest is ordinary design choice, not invention.
4. Design incentive supplied by the art itself. Cruikshank's own stated object is "simple in construction and operation"; Albers' knob-and-gear-train requires a separate actuating motion. Combining them yields a device where the same stroke that holds the head in place drives the brushes — a straightforward aggregation of known advantages with no change in principle of operation.

Claim chart under this combination: (d) and (e) from Albers; the reciprocation-to-rotation drive from Cruikshank; (a)–(c) and (f) as obvious design/expedient details of housing that drive — putting a rack in the underside channel of a bar handle and perforating the casing where the brushes emerge are the routine shop-work of the ordinary mechanic.

Combination 2 (reinforcing): Albers + Cruikshank + Cavileer

Cavileer, US 1,351,159 (1920‑08‑31; filed 1917‑03‑27) — https://patentimages.storage.googleapis.com/a7/49/a6/8349b5f8f85895/US1351159.pdf — teaches a "rotary tooth brush" in which "the handle portion thereof is provided with a shaft on which the brush body is mounted for free rotary movement," an L‑shaped resilient backing, and an expressly stated purpose of "remove[ing] particles of foreign matter accumulating between the crevices of the teeth" — the ipsissimis verbis purpose recited in Domingue's specification. Cavileer supplies (i) the free-rotary brush/shaft mounting and (ii) the spaced-opening/backing structure (element f), and reinforces that the crevice-cleaning objective was well known. Cosens & Peden, US 1,369,966 (1921‑03‑01; https://patents.google.com/patent/US1369966) is cumulative: it teaches cleaning "by alternate up and down rotary movements of the brush instead of lateral movements, as is the most common, and inefficient, practice" — i.e., the art had already recognized the rotary-motion insight in the specification's background paragraph.

Combination 3 (alternative, single‑reference pathway for elements a–c)

If a pre‑1924 toothbrush or brush reference expressly discloses a rack-and-pinion drive (I could not verify the disclosures of US 1,137,916, US 1,007,090, US 827,965, US 1,425,923, US 1,475,789, or US 1,487,075 — see caveats), then Albers + that reference is a cleaner two-reference case, and if the reference is a toothbrush, a §102 anticipation argument opens as well.

Anticipated counter-arguments and why they likely fail

• "Independently rotatable" plurality. Albers' brushes are coupled through meshing gears. Domingue's plural pinions all mesh with a single common rack. Arguable distinction — but the claim's language ("rotary cleaning elements embodying head[s] including toothed pinions") does not itself require kinematic independence, and meshing several pinions off one common rack instead of off each other is an obvious alternative arrangement with no new result.
• No express disclosure of a "flat bar" handle with an underside channel. This is a shape/assembly choice. A bar handle with a channel on its underside is the natural way to carry and enclose a rack, and nothing in the claim reflects any functional consequence of flatness beyond packaging.
• Secondary considerations. The record shows no evidence of commercial success, licensing, copying, long‑felt but unsolved need, or failure of others. The closest thing to a preamble in the specification — "extreme simplicity and durability" — is aspirational, and the crowded contemporaneous art (multiple "Rotary toothbrush" patents in 1920–1925) undercuts any "failure of others" theory. Under KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), unsupported assertions of a "new design" do not rebut a prima facie obviousness case.

What I could not verify — stated explicitly

1. I did not obtain the full text or claims of US 1,137,916, US 1,007,090, US 827,965, US 1,425,923, US 1,475,789, US 1,487,075, or US 490,831. They appear only as titles/dates in the "Similar Documents" list. Any of them could contain an express rack-and-pinion teaching, which would strengthen (or convert to anticipation) the analysis above. This is the single largest gap.
2. I have not verified whether any pre‑1924 patent expressly recites a rack and pinion in combination with a toothbrush. My combination therefore relies on the rack and pinion as common mechanical knowledge rather than on a located printed reference. That is legally permissible (and was permissible in 1925 as well), but it is a weaker evidentiary posture than a documentary reference.
3. The Cruikshank timing caveat. US 1,481,891 issued 1924‑01‑29, ~5 months before Domingue's filing. Under the pre‑1952 statute its only reference date is its grant date, so it is prior art only if Domingue's date of invention falls after 1924‑01‑29. The presumptive invention date is the filing date, but an applicant could theoretically have antedated it. Because of this, I rest the primary case on Albers (1920) + common knowledge of rack-and-pinion, with Cruikshank as corroboration of the toothbrush art's specific familiarity with reciprocation-to-rotation drives rather than as an indispensable reference. (Note that Albers' own application, filed 1918‑02‑01, was not published before grant, so it too has only its 1920 grant date as its reference date — still >4 years pre‑filing and safe.)
4. I did not locate the printed text of US 1,341,916 ("Rotary toothbrush", Basil W. Leach), which appears in a contemporaneous dental-journal patent digest. If its content is on point, it is further §102 art.
5. Litigation posture is unchanged from the earlier section: no case, and none plausible after 1942. The Nahum reference (WO 1983/002218 A1) that cites "US, A, 1557244 (DOMINGUE)… see the claim" is forward evidence of how the art reads this patent — as the basic rack-and-pinion reciprocating-handle teaching — not independent art against it.

Bottom line: On the art actually identified, claim 1 would in my assessment have been obvious under the Hotchkiss "invention" standard as contemporaneously applied, and would be obvious under §103 today, on Albers US 1,326,900 in view of Cruikshank US 1,481,891 and the common knowledge of rack-and-pinion motion conversion, optionally reinforced by Cavileer US 1,351,159. The only feature not located verbatim in the toothbrush art is the serrated channel wall forming the rack — a mechanical expedient within the ordinary skill of a 1924 mechanic. That conclusion is contingent on the unverified references in caveat 1.