US 127451

I'll search for this patent number and check both USPTO records and any 2026 CAFC activity.

Let me try more targeted queries, including the CAFC docket angle.

Summary — US 127,451

Important threshold finding: My web searches (Google Patents, USPTO-hosted document repositories, PTAB/PTAB-style document sources, and general web) did not return any CAFC 2026 docket entry, litigation, or IPR/PGR proceeding involving patent 127451. One query returned zero results; others returned unrelated patents (e.g., US 129,400 to Johns; US 123,765 to Blake; US 5,185 to Benjamin S. Benson — a different Benson, 1847). The reason is structural, not evidentiary: per the record below, US 127,451 expired June 4, 1889, roughly 137 years before the 2026 docket period, so it cannot be the subject of a live 2026 CAFC appeal or district court infringement suit. I could not query the CAFC docket system directly (no API access), so I flag this as "no results found, and none expected" rather than a verified negative.

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Bibliographic data (from the authoritative full text supplied)

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Plain-language overview of the claims

All four claims are combination claims in the 1872 style; none refers back to another claim, so on the face of the document all four stand alone (there is no modern independent/dependent hierarchy, and no "wherein" clauses).

Claim 1 — Valve + detachable exhaust-port subassembly.
Covers the steam-valve "e e" together with a detachable exhaust-port "f f," arranged so that both parts can be conveniently ground/machined into steam-tight joints against (a) the top of the cylinder and (b) the plate "g g." In plain terms: make the valve and the exhaust-port as separate, removable pieces so each can be manufactured and refinished to a tight fit rather than as one integral, hard-to-service part.

Claim 2 — Steam-balanced valve in combination.
Covers the valve "e e" combined with the exhaust-port "f f" and plate "g g," where the valve is arranged to be held tight by steam pressure on the sealing faces but relieved of the excessive pressure that ordinary slide-valves carry on their backs. In plain terms: a valve that seals well because steam presses it onto its seat, yet is not so heavily loaded that it becomes stiff or erratic in operation — better sealing without the usual friction penalty.

Claim 3 — Porting architecture of the valve.
Covers the valve "e e," having passages (shown as "k k" in the description), in combination with the passages in plate "g g" (letter "j"), the central passage running through exhaust-port "f f," and the cylinder ports. In plain terms: the internal routing of steam and exhaust through the valve body and the plate, so the same valve alternately connects each cylinder port to live steam and to the exhaust.

Claim 4 — Adjustable beveled plate + screws.
Covers the combination of a beveled-edged plate "g g" with screws "h h," bearing at the center of the bevels, so the plate can be adjusted to take up manufacturing imperfections in the valve "e e," exhaust-port "f f," or plate "g g." In plain terms: a self-aligning, screw-adjusted mounting plate that lets the assembly be trued up in service instead of requiring remachining.

Stated objects (the "definitions" paragraph, which functions as the abstract substitute): first, a steam valve and piston sufficiently packed by steam pressure to prevent leakage yet sufficiently relieved of ordinary slide-valve pressure to run easily and act certainly; second, to make that valve simple, accessible, easily repaired, and accurately adjustable.

Operation described for Fig. I (not itself claimed): with piston A at the left end of its stroke, linkage B-C shifts the supplemental valve "d," admitting steam through port "m" to one side ("o") of chamber "o o" while exhausting the other side through passage "n," a cavity in valve "d," and passage "l" to main exhaust "J," forcing the chambered valve "e e" to the right, connecting a cylinder port to exhaust "J" and opening another port to the steam-chest, thereby reversing the engine.

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Uncertainty flags

1. Filing date is genuinely unavailable from the material I can cite. The specification is dated June 4, 1872 (the grant date); no separate application date or application number appears. I will not fabricate one.
2. Assignee: no assignment is recorded on the face of the patent. I did not retrieve a USPTO Assignment-database record, so an unrecorded or later assignment cannot be ruled out — but nothing in the record indicates one.
3. Reference characters are OCR-degraded in the available text and I have not auto-corrected them in quoting. Notable garbles: "valve 0 e"/"6 6"/"e 0" for valve "e e"; "9 9"/"9 g"/"g g" for plate "g g"; "0 0" for chamber "o o"; "supplemental valve (1" for valve "d"; "passages 70 and It"/"In" for the "k" passages; "port 13" and "ports 6 i"/"t t"" for cylinder ports. Claim 3 as printed reads "ports t t"," which is almost certainly "t t′," but I report it literally.
4. No abstract exists to summarize; the "definitions" passage is the closest substitute and is quoted as such above.
5. Prior-art adjacency, not identity: Google Patents lists similar documents such as US109167 (1870), US45820 (1865), US129726 (1872), US261485 (1882). These are related steam-valve art, not the same patent, and I have not treated them as such.

Bottom line: US 127,451 is an 1872, four-claim mechanical patent to Benson & Avery of Warren, Massachusetts, on a steam-balanced, easily-serviced reciprocating valve and detachable exhaust-port for direct-acting steam engines. It expired in 1889 and has no 2026 CAFC or USPTO proceedings associated with it that I could locate.

I'll search for litigation involving US patent 127451.

Initial searches returned unrelated results (PCT publication numbers and unrelated litigation). Let me search more specifically.

Let me try a few more targeted sources before concluding.

Litigation Search Report — U.S. Patent No. 127,451

Bottom line

No litigation involving U.S. Patent No. 127,451 was located in any of the searched sources. I found no district court case, no CAFC appeal, no ITC investigation, no PTAB proceeding, and no docketed dispute of any kind asserting or challenging this patent.

What the patent is (for scoping the search correctly)

US127451A, "Improvement in direct-acting steam-engines," issued June 4, 1872, to Hezekiah A. Benson and William Avery of Warren, Mass. Claim 1 is directed to "the valve 0 e and detachable exhaust-port f f, so that they may both easily and practically make steam-joints with plate 9 g and top of cylinder"; claims 2–4 cover the chambered valve in combination with the exhaust-port/plate, the passages 70 k, and the beveled-edged plate 9 g with adjusting screws h h. It is mechanical steam-engine valve art, classified under F15B11/00, F15B11/15 and F04B9/10.

Critically, the Google Patents record shows legal status "Expired – Lifetime," with an anticipated expiration of June 4, 1889. By that date the patent term had run; it could not have been asserted in any modern proceeding.

Sources searched and what they returned

Required caveats (why "no results" is not the same as "no litigation ever existed")

1. Index coverage is the limiting factor, not the patent. The databases I searched (Unified Patents Portal, CourtListener/RECAP, PACER-derived corpora, CAFC opinions) systematically cover roughly the late-20th century forward. Federal equity and patent suits from the 1870s–1880s are, with rare exceptions, not digitized and not docket-retrievable. A suit on this patent, if it occurred, would in all likelihood leave no trace in these tools. I therefore cannot represent that no suit was ever filed — only that none is discoverable in the sources instructed.
2. Termination of term forecloses modern fit. With expiration on June 4, 1889, no post-1889 plaintiff or defendant can exist. There is no possibility of an AIA-era IPR, CBM, PGR, or a modern district court or ITC action.
3. Number-collision risk is real and I applied the strict rule. I explicitly discarded results for similar-but-different identifiers — WO 2008/127451, WO 2015/127451, 337-TA-1276, Case 24-1285, IPR2020-01258, and § 315/Section 337 statutory cites — rather than treating them as matches. I did not auto-correct any identifier.
4. No family/litigation data. The Google Patents family record (ID=2196871) lists a single application/publication (US127451A or US127451D) with no related litigation, no assignments, and no post-issuance proceedings.

Conclusion

Known litigation involving U.S. Patent No. 127,451: none identified. To the extent the question seeks modern enforcement activity, the answer is a definitive no — the patent expired June 4, 1889. To the extent it seeks contemporaneous 19th-century enforcement, the honest answer is that I found no evidence, but the absence is attributable to the non-existence of digitized records for that era rather than to affirmative proof that no suit was ever brought. A definitive answer on 19th-century enforcement would require manual review of the pre-1900 federal equity dockets for the District of Massachusetts and the old Circuit Court for Massachusetts, which are not accessible through the requested sources.

If you want, I can draft a follow-up research plan identifying the specific archival indexes (e.g., the National Archives Boston regional holdings and the published Federal Cases reporter volumes) that would be needed to close the 1870s–1880s gap.

PTAB / AIA Trial Activity — US 127,451 A

Short answer: there is no PTAB activity on this patent. Zero AIA trial proceedings. None can be, and none ever could have been. The structured "PTAB proceedings on file" block is the canonical source and it returns an empty set; my two independent web searches (PTAB/E2E dockets, decisions, and general commentary) surfaced nothing — no IPR, no PGR, no CBM, no pre-AIA inter partes reexamination, no Federal Circuit appeal. I flag no unindexed proceedings, because none appear to exist.

Proceedings overview

Total proceedings on US 127,451: 0 (active: 0 / claims invalidated in an AIA trial: 0 / claims sustained in an AIA trial: 0 / settled: 0 / institution denied: 0). The bottom line for a defendant is not "the patent is hardened" — it is that the patent expired on 1889-06-04, 123 years before the AIA created IPR/PGR/CBM on 2012-09-16, and 93 years before any Board (BPAI, 1984) existed to conduct a contested post-issuance trial. There is no PTAB estoppel on either side, and there is also no enforceable claim to attack: the patent's own record status is "Expired – Lifetime," with an anticipated expiration of 1889-06-04. Any demand letter citing US 127,451 is not a PTAB problem — it is a demand letter citing a 19th-century patent that has been dead since Grover Cleveland's first term.

No proceeding — this is the complete list

There is no proceeding narrative to give you, and I will not manufacture one. For the record, here is what does exist in the file:

• Publication: US127451A, "Improvement in direct-acting steam-engines."
• Inventors / patent owners of record: Hezekiah A. Benson and William Avery, of Warren, Massachusetts.
• Granted: 1872-06-04. Anticipated expiration: 1889-06-04. Legal status: Expired – Lifetime.
• Family applications: 1 (Google's family view lists the application as "US127451D," which is that source's internal document identifier for the same 1872 filing — not a separate patent or a second proceeding).
• Claims: four, all apparatus claims directed to a steam-valve (e e) and a detachable exhaust-port (f f) cooperating with plate g g, screws h h, and passages k k/j (claim text as printed is OCR-degraded — e.g., "what we claim isl." for "…is: 1." — so claim language should be verified against the printed original before quoting).
• Post-issuance events: none beyond the administrative grant/expiration entries. No reexamination (ex parte reexam did not exist until 1981, ninety-two years after expiration; inter partes reexam not until 1999), no interference, no appeal.

Why the zero is structural, not coincidental. AIA trials are creature-of-statute proceedings available only for patents "in force." Even setting that aside, an IPR requires that someone care enough about a live claim to spend six figures attacking it. The patent's last possible day of infringement was 1889-06-04. The Google Patents "Similar Documents" list (US261485A, US109167A, US45820A, etc.) is not a PTAB record and not prior art cited in any instituted trial — it is an algorithmic similarity list, and I would not cite it as evidence of anything.

Strategic summary

Claim status: all four claims are UNTESTED at the PTAB, and all four are expired. There is no cancellation certificate, no narrowed substitute claim, no surviving-claim set. From a defensive posture this is maximally simple: the patent has never been adjudicated in an AIA forum, so there is no PTAB estoppel barring any ground against it, but there is likewise no PTAB kill shot to point to. If the question is "which claims survived IPR," the honest answer is "the question is inapposite — nothing was reviewed, and the entire right lapsed in 1889." Where an expired patent's claims were nonetheless subject to a live IPR (that happens where damages for pre-expiration conduct are still in dispute), the Board applies Phillips-style construction rather than BRI — but that scenario requires an underlying live controversy, and the 35 U.S.C. § 286 six-year damages lookback would reach back only to roughly 2020, i.e., 131 years after this patent expired.

Estoppel landscape — none. No petitioner exists, so 35 U.S.C. § 315(e)(2) estops no one. That cuts both ways: there is no waiver protecting a would-be infringer and no waiver protecting the patent owner. The only real constraint on anyone asserting US 127,451 is the patent term itself, plus the ordinary defenses available against any asserting party (laches/§ 286 damages cap, standing, and the plain fact that practicing a steam engine in 2026 cannot infringe a patent that lapsed in 1889).

Pattern signals — none to read. No repeat petitioner, no serial IPR filer, no defensive aggregator (Unified Patents, RPX, Open Invention Network) in the chain, no patent-owner push for PTAB appeals. The absence is not the "well-asserted patents eventually attract IPRs" signal here. The absence is because the asset is a historical artifact of the pre-1952 patent system, not a live right.

Recommended next steps

• If you are a defendant being accused of infringing US 127,451, the dispositive point is not a PTAB outcome — it is expiration and status. Pull the record from USPTO PatentCenter and the Google Patents record for US127451A, which show "Expired – Lifetime" with an anticipated expiration of 1889-06-04. Request the plaintiff's damages theory and demand they identify post-2020 (or any) accused conduct and the live claim they assert; there is no FWD disposition to quote because no FWD exists.
• If you are evaluating IPR as a defense strategy: it is not available in any meaningful sense here, and no fee is worth paying. There is no institution decision to schedule, no one-year trial clock running, no oral hearing upcoming, and no FWD due date — because there is no trial.
• If you are litigating and someone tells you this patent "survived IPRs" or "was invalidated in IPR," that statement is false. The correct record is: no PTAB proceedings on file as of the most recent ODP ingest (2026-10-01). I would treat any contrary representation as a red flag about the asserting party's diligence.
• Where to verify for yourself: USPTO PTAB E2E and the PTAB Decisions page (searches for "127451" return nothing); CourtListener has no Federal Circuit appeal to show, as the Federal Circuit did not exist until 1982 — ninety-three years after expiration.

Constraint note: I have not invented any proceeding number, panel, ground, or disposition. Every identifier above is taken verbatim from the structured PTAB-on-file block and the patent record cited in your prompt.

I'll verify whether any assignment records exist for this patent before drafting.

Data-quality preamble (read before using any of this)

Three identifier traps verified before analysis:

1. US 127,451 (the patent) is not US application 09/127,451. The latter is a 1998 application that issued as US 6,125,147 ("Method and apparatus for reducing breathing artifacts in compressed video"), a completely unrelated modern patent that appears in keyword searches for "127451." Any assignment record surfaced for that serial number belongs to a different chain.
2. "US127451D" is not a real application number or reel/frame. It is a Google Patents placeholder shown in the "Application number" field for pre-1980 grants where no serial is in the digital record. Family ID=2196871 is likewise a Google artifact. Neither is an assignment identifier.
3. Assignment Center coverage. Per USPTO's own documentation, the searchable assignment database contains recorded assignment information back to August 1980 only ("This searchable database contains all recorded Patent Assignment information back to August 1980"). US 127451 issued in 1872 and expired in 1889 — 91 years before the electronic database begins.

Inventors

The specification names no corporate entity. No employment relationship, shop name, or manufacturing affiliation appears anywhere on the face of the patent or in the printed description. I searched for "Hezekiah A. Benson," "Benson & Avery," and combinations with Warren, Massachusetts and steam engines, and returned no results — I could not identify an employer, partnership, or operating business for either inventor, and I am not going to infer one from the surname or the town. This is a genuine gap, not a negative finding.

Pattern note: the "inventors depart within 12 months" tell is inapplicable. There is no employer to depart from — both men are named as individual grantees.

Original assignee

None. The patent grants directly to Hezekiah A. Benson and William Avery as individuals; there is no assignee named on the face of US 127451. This is routine for the period — the 1836 Act as amended permitted, but did not require, recordation of an assignment before grant, and most 1872 mechanical patents issued to individuals, with any manufacturing rights conveyed later by private contract.

• Product embodying the claims: The patent is a direct-acting steam engine with a chambered main valve (e e) operating in a chamber o o against a detachable exhaust port f f, with a beveled adjustment plate g g and screws h h. Whether a commercial engine was built to this design cannot be established from the patent record. The claim set (four claims, all directed to the valve/exhaust-port/adjusting-plate combination) reads as a shop-floor improvement to a specific engine, which is consistent with a small manufacturer — but that is inference, not evidence, and I am not recording it as a finding.
• Primary line of business: Undetermined.
• Current status: Not applicable in any conventional sense. The patent term ran 17 years from grant and expired 1889-06-04, as reflected in Google Patents legal events ("1889-06-04 — Anticipated expiration"). No successor entity to Benson or Avery has been identified.

Assignment timeline

The USPTO Assignment Center has no records for US 127451. I confirmed this is a coverage-window limitation, not a search failure: the Assignment Center database begins August 1980, and this patent expired June 4, 1889.

The only ownership events of record are the two on the patent face and in Google Patents legal events:

• 1872-06-04 (grant) — no reel/frame; USPTO grant record
  • Conveyance: Original grant to inventors (not an assignment)
  • Assignor: n/a
  • Assignee: Hezekiah A. Benson and William Avery, Warren, Massachusetts (individuals)
  • Correspondent: none recorded
  • Context: Original issuance to individual inventors
• 1889-06-04 — no reel/frame; USPTO legal-status record
  • Conveyance: Statutory expiration (not an assignment)
  • Assignor: n/a
  • Assignee: n/a
  • Correspondent: none recorded
  • Context: Patent term ends; no further enforcement or transfer is legally possible

Per your instruction, I stop the assignment section here. One warning for anyone continuing the search manually: any pre-1980 assignment of this patent, if one was ever executed, would exist only as the original recorded instrument on USPTO Assignment Division microfilm or among the Patent Office's historical records at the National Archives, retrievable by a manual title-abstract order — it cannot be pulled from assignmentcenter.uspto.gov or assignment.uspto.gov, and a zero-result search there does not prove no assignment existed.

Timeline diagram

timeline
    title Ownership of US 127451
    1872 : Issued to Benson and Avery
         : No assignee named on patent
    1889 : Patent term expires at 17 years
    1980 : Electronic assignment records begin
         : No records exist for this patent

NPE / troll-pattern signals

Every signal is assessed against a record that contains zero recorded post-issuance assignments. Most are therefore "not present" in the sense of no evidence, which is different from evidence of absence — I flag that distinction below rather than overstating it.

1. Shell-entity transfer — not present. No operating assignee exists to transfer from, and no LLC, "IP Holdings," or licensing entity appears anywhere in the record. There is no reel/frame to cite because there is no recorded conveyance.

2. Known asserter in the chain — not present. No assignee of any kind is recorded after 1872. No match against Acacia, Marathon, Intellectual Ventures, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, or any Spangenberg entity — there is no assignee to match.

3. Repeat correspondent across the chain — not present. No correspondent of record exists; the single "assignment" event is a statutory grant, which is not recorded with a correspondent at all. No attorney appears on this patent's chain.

4. Cascading transfers — not present. Zero transfers, so zero chained transfers, in any window.

5. Pre-litigation transfer — not present. No assignment and no infringement litigation naming US 127451 was found in any search. Claims 1–4 expired in 1889 and cannot support a cause of action.

6. Bankruptcy fire-sale — not present. No corporate assignee ever existed to file Chapter 7 or 11. The Bankruptcy Code postdates this patent by 107 years.

7. Privateering — not present. Requires an operating-company assignor and an NPE proxy. Neither exists here.

8. Defensive aggregator — not present. The chain does not terminate at RPX, AST, LOT Network, Unified Patents, or OIN. It terminates at statutory expiration.

Framework caveat: the entire NPE apparatus you asked me to test presumes a live or recently-live patent with a transferable interest. US 127451 has had no enforceable rights for 137 years. The signals are not merely absent — they are structurally inapplicable, and "not present" here should be read as no applicable record, not as diligence cleared it.

Verdict

Insufficient data.

Justification: the USPTO Assignment Center contains zero records for US 127451, which is expected given that its searchable coverage begins August 1980 and this patent issued 1872-06-04 and expired 1889-06-04 per Google Patents legal events ("1889-06-04 — Anticipated expiration"). No reel/frame exists to cite in any direction — no shell transfer, no known asserter, no repeat correspondent, no defensive-aggregator termination — so there is no evidentiary basis for any NPE call. Note also that no post-1889 assertion is legally possible, making the NPE question moot: any demand letter or suit citing US 127451 as an unexpired right would itself be the anomaly worth investigating, not the assignment chain.

Verify the negative at the USPTO Assignment Center: https://assignmentcenter.uspto.gov/ (search patent number 127451; expect zero post-1880 hits, and screen out the unrelated application 09/127,451 / US 6,125,147).

I'll research this patent and its prior art landscape.

Scope note and an important finding on "citations"

I searched for US 127,451 specifically (Benson & Avery, "Improvement in Direct-Acting Steam-Engines," Warren, Mass., patented June 4, 1872; expired by anticipated expiration June 4, 1889). Two methodological points must be stated up front, because they materially affect the answer you asked for:

1. US 127,451 has no patent citations of record. The authoritative Google Patents record for this patent (a reproduction of which is in my working text) contains only a "Similar Documents" block — an algorithmic similarity list — plus a "Family/Publications" block. There is no "References Cited," "Citations," "Cited By," or "Patent Citations" section. This is entirely expected: applicant/examiner citation practice on U.S. patent faces did not exist in 1872. So I cannot give you a list of formal citations, and I will not fabricate one. What I can do — and do below — is analyze the actual prior-art landscape of record for this patent, i.e., the "Similar Documents" set, and classify each by whether it can legally be prior art against a June 4, 1872 patent.

2. Applicable law is not 35 U.S.C. § 102. US 127,451 issued under the Patent Act of July 8, 1870 (16 Stat. 198), which predates both the 1952 Act (which created §§ 102/103/112 in their modern form) and, obviously, the AIA. The controlling novelty standard was § 24 of the 1870 Act (patentee must be the original and first inventor; prior patents, printed publications, and public use or sale bar patentability). I apply the modern § 102 framing you requested as an analytical lens, but flag that it is anachronistic for a patent of this vintage — as is any § 103 obviousness analysis.

Identifier caveats (strict, per instructions): The OCR of this record is degraded. The literal strings printed in the record include "valve 6 e," "valve '0 6," "valve e 0," "plate 9 9," "exhaust-port f f," "ports 6 i," "ports t t"," "passages 70 and It," and "supplemental valve (1." The patent's own claim text renders the valve as "e e"/"0 e," the plate as "g g"/"9 g," and the exhaust-port as "f f." I do not silently normalize these; I quote them as they appear and note where a character is likely a scan artifact. Also, a search for "127451" returns a false positive — JP 2018138019-A/127451 (a GenBank patent-sequence record, "Polycomb-Associated Non-Coding RNAs," Ohsumi et al.) — a different jurisdiction and unrelated art, which I exclude, as you instructed.

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The "Similar Documents" set for US 127,451, classified by prior-art eligibility

The critical date for prior art against this patent is June 4, 1872 (its grant date; absent an earlier filing date visible in the record, the grant date is the operative reference point). Only references publishing before that date can anticipate claims 1–4.

Bottom line: only four of the twenty-five "Similar Documents" are legally available as prior art against US 127,451. The other twenty-one are post-dated and are relevant only as forward art (i.e., US 127,451 is prior art against them).

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The four pre-critical-date references — detail and § 102 analysis

1. US 109,167 — Herman F. Ambos, Columbus, Ohio — "Improvement in steam-engines" — patented Nov. 15, 1870

Sources: https://patents.google.com/patent/[US109167](/patent/US109167) ; https://patentimages.storage.googleapis.com/b0/4f/46/88ce17257ecb89/US109167.pdf

Description. A direct-acting steam engine for working pumps. Ambos places a ported cylinder E between two piston-heads on the piston rod, fitted to work endwise and steam-tight in the main cylinder A; a cylindrical endwise-movable valve F with two peripheral chambers works around cylinder E and bears steam-tight against the inner surface of cylinder A. Ports c c and c' c' in the shoulders of cylinder E register alternately with steamways e and f. The specification states expressly that "all the mechanism for alternately cutting off steam from opposite ends of the main cylinder is contained within the shell of this cylinder, and between the two piston-heads," and that the cutting off/letting on of steam is "effected by the direct action of the piston-heads upon a ported endwise-moving box or slide-valve."

§ 102 relevance.

• Claim 2 (valve "so arranged as to work with sufficient steam-pressure to insure tight joints, yet relieved of the excessive pressure incident to ordinary slide-valves") — Ambos's valve F is described as working "steam-tight" against the cylinder bore and as snug but loose around cylinder E, which is conceptually adjacent to the balanced/pressure-loaded valve idea. This is the strongest point of contact. However, Ambos achieves tightness by a nested concentric arrangement (valve around a ported cylinder inside the main bore), not by a detachable exhaust-port f f co-planar with a plate g g. It does not disclose the claimed sub-combination, so it is an obviousness-type reference rather than a clean § 102 anticipation.
• Claims 1, 3, 4 — No disclosure of the beveled-edged adjustable plate g g with bearing screws h h (claim 4), nor of the reciprocating chambered slide valve e e having internal passages k k cooperating with plate passages j and a through-passage in the exhaust-port (claim 3). Ambos's valve is a cylinder-shaped valve, not a chambered box slide valve.
• Confidence: moderate that US 109,167 is the single most relevant prior-art reference in the set; low that it anticipates any individual claim as drafted.

2. US 45,820 — "Improvement in valves for steam-engines" — issued Jan 10, 1865

Sources: conventional USPTO/Google-Patents record; cross-listing at https://trade.patenthub.cn/cpc/list-[138861](/patent/138861)-10.html (which classifies US 45,820 under the group "valves mounted in or on the piston or piston rod").

Description. I was able to confirm the number, date, title, and its CPC-family placement, but I was not able to retrieve the full specification, drawings, or inventor name within this session. I will not characterize its disclosure beyond what is verified.

§ 102 relevance (limited). Based on title and classification alone, this is a valve-gear/valve-structure reference in the same art as claim 2 of US 127,451. Its classification placement (valves mounted in or on the piston or piston rod) suggests a valve carried by the reciprocating member — a different architecture from the Benson & Avery arrangement, in which the chambered valve e e is a separate member driven by the main piston through B C (the piston rod and its connection to supplemental valve d). I cannot presently assign anticipation to any of claims 1–4. Treat as a candidate § 102(a) reference requiring retrieval of the full text before any conclusion.

3. US 121,018 — "Improvement in rotary steam-valves" — issued Nov 14, 1871

Source: date and title from the patent record; specification text not retrieved in this session.

Description. By title and date, a rotary steam valve — i.e., a valve whose motion is angular/oscillatory — patented roughly seven months before US 127,451.

§ 102 relevance. The Benson & Avery invention is, on its face, expressly a reciprocating chambered slide valve ("Its bottom sides operate the ports… thus producing a reciprocating motion to the main piston"; Fig. III is a "top view of chambered valve with exhaust-port"). A rotary valve is a structurally distinct species. Unless the rotary-valve disclosure happens to describe a chambered valve cooperating with a detachable port and an adjustable plate — which the title does not suggest — it is unlikely to anticipate claims 1–4. I flag this as an untested assumption; the specification should be pulled before relying on it. Confidence of non-anticipation: moderate, on title alone.

4. US 105,986 — "Improvement in valves for steam-engines" — issued Aug 2, 1870

Source: date/title from the patent record; specification text not retrieved in this session (my search step budget was exhausted on this item).

Description / § 102 relevance. Title and date place it squarely in the valve art ~22 months before the critical date, making it a legitimate § 102(a) candidate for claim 2 in particular. I am not able to characterize its disclosure and therefore make no anticipation finding. I explicitly decline to guess. This is the reference I would retrieve first in any follow-up analysis.

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Supplementary prior art not in the "Similar Documents" list (recommended, flagged as non-citation)

Because the "Similar Documents" list is algorithmic rather than a citation record, it likely omits the most legally significant art in this field. Based on the sources retrieved, these are the references a competent searcher would actually cite against claims 1–3:

• US 4,8902 — J. Wesley Carhart, Cohoes, N.Y., "Improvement in valves for steam-engines," July 25, 1865 (https://patents.google.com/patent/US48902A/en). Discloses a valve "so arranged that it is balanced in any pressure to which it may be exposed, and that it is kept in its seat by the action of the steam itself in such a manner that it will work free and easy under the heaviest pressure… and yet be perfectly steam-tight," with a bearing surface below the abutment to balance upward pressure, a lip, and a chamber in the large end of the valve "for the purpose of keeping the valve in its seat by means of steam admitted to said chamber." This is the closest textual match I found to claim 2's stated object (packed by steam pressure to prevent leakage, yet relieved of excessive pressure). If any single reference threatens claim 2, it is this one — and it is not in the "Similar Documents" list. This is my most significant finding.
• US 51,393 — John Rowrotham, "Balanced Slide Valve," Dec. 5, 1865 (reported in the Annual Report of the Commissioner of Patents, 1865). A slide valve with the exhaust opening through it, plus spring-held strips mating with the steam-chest cover to form a steam-tight joint while accommodating inaccuracy between valve seat and chest cover — relevant background to claims 1 and 4 (steam-joint formation and accommodation of construction imperfection).
• Worthington direct-acting steam pump, US 13,370 (July 31, 1855) and Worthington duplex US 24,838 (July 19, 1859); King direct-acting pump valve gear, US 107,504 (Sept. 20, 1870); Sewell & Cameron US 42,694 (May 10, 1864) — all described in U.S. National Museum Bulletin 173 (https://repository.si.edu/bitstream/handle/[10088/10218](https://assignmentcenter.uspto.gov/search/patent/reelFrameDetail?reelFrame=10088-10218)/1/USNMB_1731939_unit.pdf). These establish the well-developed state of direct-acting steam-engine valve gear before 1872 and are the natural § 103/obviousness-type backdrop for claims 1–3.

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Claim-by-claim § 102 summary

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Explicit limitations of this analysis

• No formal citation record exists for US 127,451; the "Similar Documents" list is a similarity heuristic, not a citation set, and it demonstrably omits highly relevant art (US 4,8902; US 51,393; Worthington art).
• Three of the four eligible references (US 45,820, US 121,018, US 105,986) were not read in full in this session. Any anticipation conclusion as to them is an open question, not a finding.
• The § 102/§ 103 framework is anachronistic for a patent granted under the Act of 1870. The substantive question in 1872 was whether Benson & Avery were the original and first inventors; contemporary practice contained no doctrine of obviousness as codified in 1952.
• OCR degradation means characters in the claims (e.g., 6 e, 0 e, 9 9, 6 i, 70/It) are unreliable; I have preserved them literally and offered probable readings only where the specification's own parallel language supports it.
• I did not locate any foreign counterpart, interference, or litigation involving US 127,451; the record shows only a single-member family (US 127,451A / US 127,451D, family ID 2196871) and Expired–Lifetime status.

I'll ground this analysis in the actual content of the references listed on the patent page. Let me pull the pre-1872 documents (the only ones that can legally serve as prior art against a June 4, 1872 patent) and check the date of each listing.

Let me pull the two remaining pre-1872 references (US45820A and US121018A) to ground the analysis.

Obviousness Analysis — US 127,451 (Benson & Avery, "Improvement in Direct-Acting Steam-Engines")

Source of record: https://patents.google.com/patent/[US127451](/patent/US127451)/en — grant date June 4, 1872; listed expiration June 4, 1889; legal status "Expired – Lifetime"; family ID 2196871 (application US127451D / publication US127451A).

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1. Threshold framing (read this before the analysis)

Three caveats materially affect how a §103 analysis can be run on this document.

(a) The statute did not exist. US 127,451 issued in 1872, eighty years before 35 U.S.C. §103 was enacted (July 19, 1952). The substantive standard in force at grant was the Act of July 8, 1870 and the judicially developed "invention" requirement of Hotchkiss v. Greenwood, 52 U.S. (11 How.) 248 (1850) — i.e., whether the difference from the prior art would have been obvious to "the ordinary mechanic." A §103 analysis of this patent is therefore a retrospective, hypothetical exercise, not an assertion about law actually applied to the patentee. Nothing here should be read as a validity holding; the patent is long expired and unenforceable.

(b) The "Similar Documents" list is machine-generated. Google Patents' similarity list is a CPC/text-similarity artifact, not a legally curated prior-art set. Critically, the modern CPC classes assigned to this 1872 patent — F15B11/00, F15B11/08, F15B11/15 (servomotor systems) and F04B9/00, F04B9/08, F04B9/10 (fluid-driven piston pumps) — did not exist as such in 1872 and are back-classification only. They must not be used to reason about the field of the invention or analogous art for a 1872 PHOSITA.

(c) 21 of the 25 listed references are legally unusable. With a critical date of June 4, 1872, only references predating that date can be §102/§103 art. Applying the page's own printed dates:

So the page's Prior Art section supplies a four-reference usable universe: US45820A, US105986A, US109167A, US121018A. The remaining 21 — including every "balanced slide-valve," "steam-actuated valve," and "direct-acting pumping-engine" entry, which are the most on-point titles — post-date the patent and cannot be combined. They are usable, at most, as background evidence of what the art regarded as routine in the following decades, which is not a permissible §103 use.

Verification disclosure. I was able to retrieve and read the full text of US109167A (Ambos) in two independent copies (https://patents.google.com/patent/[US109167](/patent/US109167) and https://patentimages.storage.googleapis.com/b0/4f/46/88ce17257ecb89/US109167.pdf). I was not able to retrieve the specifications of US45820A, US105986A, or US121018A; searches returned only bibliographic hits (e.g., a Chinese CPC index confirming US45820A / US45820D, 1865-01-10, "Improvement in valves for steam-engines": https://trade.patenthub.cn/cpc/list-[138861](/patent/138861)-10.html#1). I therefore cannot and do not assert what those three references disclose. Any combination resting on them is flagged below as unverified.

To avoid resting the analysis on unread documents, I supplement the page's list with contemporaneous, pre-June-4-1872 art that I did verify, explicitly labeled as coming from outside the page's Similar Documents list. If the task instruction is read to confine me strictly to the page's list, then the analysis reduces to the US109167A-based combinations in §5, and the remaining claims are analyzed against the general level of skill.

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2. The claim set as construed

The claims appear under the page's "Definitions" heading and are reproduced verbatim in the specification. OCR corruption must be flagged rather than silently corrected: the printed claim text reads "valve e 0" (elsewhere "valve 6 e"), "plate 9 9," "70 and It," "chamber 0 0," and "ports t t"." Consistent with the descriptive text ("valve e e," "plate g g," "chamber o o," "exhaust-port f f," "port m," "exhaust-passage j"), the reference letters are e e (chambered/valve shuttle), f f (detachable exhaust-port block), g g (adjusting plate), o o (chambered space), j / j (passages in plate g g), m, n, t t′ (ports), h h (adjusting screws), d (supplemental valve), k (passages in valve e e). I analyze on that basis and flag the uncertainty.

Construction notes that bear on obviousness. Claims 1 and 4 close with "constructed substantially as shown and described" and claim 2 is drawn to a result ("sufficient steam-pressure to insure tight joints, yet relieved of the excessive pressure..."). Claims of this form are coextensive with the disclosed structure and the disclosed function. Under the Act of July 8, 1870, §26, the applicant was required to "particularly point out and distinctly claim" the invention; claims 1 and 2 push hard against that requirement. Two practical consequences: (i) a §103 attack on claims 1–2 is really an attack on whether the disclosed structure is an obvious aggregation, and (ii) the broad functional language makes it comparatively easy to read the same function out of a prior-art valve that achieves the identical result by a different mechanism — the classic "result vs. means" problem.

PHOSITA (1872): a steam-engine valve designer/mechanician of ordinary skill, with several years' shop experience in slide, balanced and rotary/oscillating valve design, exhaust and cut-off porting, and the standard practice of grinding a valve and its seat to a steam-tight joint; familiar with the then-current literature on valve friction, wear, and steam-tightness.

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3. The technical problem the claims address

The specification itself frames the problem and thereby supplies much of the motivation-to-combine evidence: the inventors state their objects as (i) a steam valve "sufficiently packed by steam pressure to prevent leakage, yet sufficiently relieved from the pressure incident to ordinary slide-valves to insure ease in running and certainty in action," and (ii) simplicity, accessibility, easy repair, and accurate adjustment. That is a stated design objective, and where the prior art addresses the same objective, motivation to combine is supplied largely by the applicant's own admission.

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4. Element-by-element mapping

Claim 1 — valve e e + detachable exhaust-port f f, both making steam-joints with a plate and the cylinder top

• US109167A (Ambos, 1870-11-15) — verified. Discloses a ported cylinder E and a cylindrical endwise-movable valve F with "two chambers, g g′, formed into its periphery," where "the ends of this valve are smoothly dressed, so that when it is in contact with either one of the said shoulders it will tightly close the angular ports c c therein," and "the circumference of valve F works steam-tight in contact with the inner surface of the cylinder A." Ambos thus discloses the exact functional core of claim 1: a shuttle valve whose dressed ends and circumference are designed to make steam-tight joints against (a) a seating/shoulder surface and (b) a surrounding cylindrical surface — and which is removable/assemblable as a discrete part relative to those surfaces. The "detachable" character in claim 1 is a shop-practice expedient (a part you can lift out, grind, and replace) that Ambos' construction inherently requires.
• US107161 (Caldwell, 1870-09-06) — verified, extra-list. Discloses a "semi-annular block D ... fitted tightly into place, and is permanent," and a semi-annular valve E fitted to slide snugly in the recess C, with a central chamber c′ "at all times in communication with the exhaust-port F." A separately fitted block plus a snugly-fitting sliding valve is the same physical architecture as "valve e e and detachable exhaust-port f f... make steam-joints with plate g g and top of cylinder."
• US51393 (Rowbotham, 1865-12-05), "Balanced Slide Valve," as abstracted in the Annual Report of the Commissioner of Patents for 1865 — verified (https://upload.wikimedia.org/wikipedia/commons/0/0a/Annual_report_of_the_Commissioner_of_Patents_-_U.S._Department_of_Commerce%2C_Patent_Office._Volume_2%2C_1865._%28IA_s607id13664380%29.pdf): a valve "having the exhaust opening through it, so as to leave a passage open to the steam chest cover," in combination with "certain strips adapted to each other, and to the sides of the valve, and to the cover of the steam chest, so as to form a steam-tight joint between the valve and the top thereof," the strips being spring-held and movable "so as to provide for any inaccuracy in the space between the valve seat and the cover of the steam chest," and being "provided with recesses for steam upon all of their bearing surfaces, to prevent undue friction." This is a striking disclosure of a detachable, spring-held, steam-tight joint-forming element cooperating with a valve and a cover plate — claim 1's "detachable" part making steam-joints. It also independently bears on claim 4 (compensation for construction inaccuracy).
• US52556 (Gallatin, 1866-02-13) — verified, extra-list — discloses an oscillating valve "with a flat face, which is ground down upon a corresponding flat seat," i.e., the grinding-to-a-steam-joint practice that claim 1's "make steam-joints" describes.

Assessment: Claim 1 reads on Ambos alone for the valve/joint function and on Rowbotham for the detachable, spring-seated joint-forming element. The remaining "novelty" of claim 1 is the naming of a removable part and the statement of a shop goal (grindable, replaceable seats) — which, per Hotchkiss and later KSR, is the work of an ordinary mechanic, not invention.

Claim 2 — steam-packed tight yet relieved of ordinary slide-valve pressure

This is the heart of the patent, and the pre-1872 art is dense and explicit. Every reference below is verified, and each states the identical dual objective:

• US52556 (Gallatin, 1866-02-13) — https://patentimages.storage.googleapis.com/7a/9c/c9/7fe4f638cf83b3/US52556.pdf. "In order to counteract the upward pressure of the steam or other fluid on the valve, a secondary piston is applied, the area of which is equal, or nearly so, to the combined areas of the cavities in the valve... If steam is admitted to the upper part of the small cylinder the piston is depressed, and the valve is held down on its seat with a pressure which is always in proportion to the upward pressure of the steam on said valve. ... By this arrangement, the valve is prevented from jumping off from its seat, and a valve is obtained which is easily kept tight, which can be made cheap, and which absorbs but little power in its operation." That sentence is a complete anticipation of claim 2's function: packed by steam pressure to prevent leakage, yet not over-loaded, so it runs easily.
• US48902 (Carhart, 1865-07-25) — https://patents.google.com/patent/US48902A/en. Object: to arrange the valve "so that it is balanced in any pressure to which it may be exposed, and that it is kept in its seat by the action of the steam itself in such a manner that it will work free and easy under the heaviest pressure to which it may be exposed, and yet be perfectly steam-tight." The reference further claims "a chamber in the large end of the valve for the purpose of keeping the valve in its seat by means of steam admitted to said chamber" — structurally identical in function to the patent's chambered arrangement in chamber o o.
• US85105 (Lawson, 1868-12-22) — https://patentimages.storage.googleapis.com/c7/6f/5d/cbab3f83e4c333/US85105.pdf. A "covering or false chest" over the slide valve with through-ports, giving "constant communication... a perfect equality of pressure... The advantages I claim... are the reduction of the area of the valve, consequently diminishing friction, and, as a constant communication of steam is kept up all through the several passages, thus keeping the valve, as it were, in equilibrium... requiring but little exertion to cause it to reciprocate."
• US51393 (Rowbotham, 1865) — spring strips with steam recesses "to prevent undue friction," forming a steam-tight joint to the chest cover (see above).
• US54959 (Richards, 1866-05-22) and US50389 (Rogers) sit in the same line of development (balanced/counterbalanced valves), per the Smithsonian's Catalog of the Mechanical Collections (https://repository.si.edu/bitstream/handle/[10088/10218](https://assignmentcenter.uspto.gov/search/patent/reelFrameDetail?reelFrame=10088-10218)/1/USNMB_1731939_unit.pdf).

Assessment: Claim 2, read functionally, is anticipated in function by US52556 and US48902, and is obvious in any event over US85105 or US51393. Because claim 2 recites a result ("sufficient steam-pressure to insure tight joints, yet relieved of the excessive pressure...") without confining it to the patentee's particular means, the case for obviousness is strong; the only serious defense would be to read the claim narrowly to its disclosed chamber-o-o/supplemental-valve-d structure, at which point the claim is close to the disclosed embodiment and equally close to US48902's "chamber in the large end of the valve."

Claim 3 — valve e e with passages k k, plus passages j in plate g g, the passage through port f f, and ports t t′

• US109167A (Ambos, 1870-11-15) — verified. Discloses a valve F with two peripheral chambers g, g′ cooperating with a ported cylinder E whose "two ports e e are at certain times caused to register alternately with the extremities of the steamway f, and the two ports e′ e′... alternately with the extremities of the steamway e," with cross-over steamways "for the escape of exhaust-steam from opposite ends of the cylinder," and all the porting contained within the cylinder shell. This is the same invention as claim 3 — a shuttling chambered valve whose passages alternately connect each cylinder end to steam and to exhaust. If anything, Ambos is more integrated (valve inside the cylinder) than the patent's plate-mounted arrangement.
• US107161 (Caldwell, 1870-09-06) — verified. Valve with three open-ended chambers, "the central one, c′, of which is at all times in communication with the exhaust-port F, and alternately with the ports or side pipes G G′... The end chambers, e′ e″, are always in communication with the supply-pipe H... and alternately with the ports G G′." Functionally identical porting scheme; also discloses small steam-apertures (ports e‴, J J′, K K′, M M′, N N′, O, P) for operating the valve automatically at each end of the stroke — the piston-actuated pilot function performed in the patent by supplemental valve d and ports m, n, t t′.
• US107504 (King, 1870-09-20), direct-acting pump valve gear — verified via the Smithsonian catalog: a direct-connected steam pump with valves operated by an arm on the piston rod, using a spring-actuated slide to "rapidly change the valve position as the pistons near the end of their strokes." This is the direct-acting (tappet/pilot-operated, non-eccentric) class into which US 127,451 falls.
• US121018A (rotary steam-valves, 1871-11-14) — on the page's list and date-eligible, but content not verified; I will not speculate as to its disclosure.

Assessment: Claim 3's porting is squarely within the verified disclosure of US109167A, and largely within US107161.

Claim 4 — beveled-edged plate g g + screws h h for adjustment

• US51393 (Rowbotham, 1865) — spring-held strips "to provide for any inaccuracy in the space between the valve seat and the cover of the steam chest": the identical purpose (compensating for construction imperfection) by an equivalent (spring vs. screw) expedient.
• US118764 (Wheelock) — semi-rotary balanced valve in which a screw-threaded valve shaft carries a check-nut and set-nut "so that... the valve will advance into its chamber when sufficiently worn to require it," and by which "a practically steam-tight joint may be formed." (Date not confirmed from my retrieval; cited for the principle of screw-adjustment of a valve to its seat, not for date-based reliance.)
• The claim's own mechanism — a plate whose beveled upper ends receive screws bearing at the center of the bevels, giving "sufficient freedom of motion in the plate" to self-align — is a textbook self-aligning/leveling bearing (a screw with a beveled or spherical seat). This is elementary mechanical expedient, and under the 1872 "ordinary mechanic" test (Hotchkiss) and under KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007) ("a court must ask whether the improvement is more than the predictable use of prior art elements according to their established functions"), the substitution of a screw-adjusted beveled bearing for a spring-compensated strip is a predictable, results-identical substitution.

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5. The combinations and the motivation to combine

The following are the combinations I would actually plead. All "Combination" primary references are verified, date-eligible, and in the same field of endeavor (steam-engine valves and direct-acting engines).

Combination A — For claims 1, 2, 3

US109167A (Ambos) in view of US52556 (Gallatin) and US51393 (Rowbotham).

• US109167A supplies the chambered shuttling valve, the valve chest for it, the steam-tight joints at the valve ends and circumference (claim 1), and the alternating steam/exhaust porting to the cylinder ends (claim 3), in a direct-acting pump engine.
• US52556 / US48902 supply the steam-pressure-packed-but-relieved valve in which hold-down pressure is proportional to the valve's own cavity area (claim 2).
• US51393 supplies the spring-held, detachable strips forming a steam-tight joint between valve and chest cover while accommodating "any inaccuracy" (claims 1 & 4).

Motivation: (i) All three address the same, expressly recognized problem — Ambos' engine and the patent's engine are both piston-driven, valved steam pumps; Gallatin's stated goal is verbatim the patent's stated goal ("easily kept tight... absorbs but little power"); Rowbotham's stated goal is accommodating the very imperfections that claim 1's "detachable... make steam-joints" and claim 4's adjustment plate exist to accommodate. (ii) The references are complementary, not overlapping: Ambos teaches the porting and the reciprocation, the balance references teach how to relieve the valve without losing steam-tightness. (iii) The patent's own preamble concedes the objective set, which supplies the "reason the skilled artisan would have made the combination" (KSR). (iv) The result is a mere aggregation of separately known functions — each element performing exactly the function it was known to perform — the paradigm of predictable combination.

Combination B — For claims 1, 2, 4

US48902 (Carhart) or US85105 (Lawson) in view of US51393 (Rowbotham).

• Carhart gives the balanced valve "kept in its seat by the action of the steam itself," with an end chamber admitting steam to hold it to its seat — the patent's steam-packed/relieved valve, including the chambered hold-down structure.
• Lawson gives the enclosing "false chest" with through-ports establishing pressure equilibrium, "reducing the area of the valve" and "diminishing friction," and explicitly teaches that its "improvement can be easily adapted to existing steam-cylinders, since it requires but little change in the details" — an express motivation to apply the balancing expedient to existing engines, which is precisely the setting (a direct-acting engine with a valve chest) in which the patent's valve operates.
• Rowbotham supplies the detachable steam-tight joint-forming strips (claim 1) and the compensation for construction inaccuracy (claim 4).

Combination C — For claim 3 (alternative)

US107161 (Caldwell) in view of US109167A (Ambos) or in view of US107504 (King).
Caldwell's three-chamber oscillating valve with a permanently exhaust-connected central chamber and alternately connected side ports, plus its small piston-actuated apertures for automatic reversal at stroke ends, meets claim 3's porting and the "compelling reversal of the engine" function recited in the specification. King's direct-acting pump gear supplies the piston-actuated, non-eccentric actuation.

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6. Rebuttal: what would the patent owner argue, and how does it fare?

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7. Bottom line

• Only 4 of the 25 references in this page's Prior Art section (US45820A, US105986A, US109167A, US121018A) are legally available as pre-June-4-1872 art. The most on-point titles in the list — US162714A (balanced and cut-off valves, 1875), US200242A (balanced slide-valves, 1878), US261485A and US471882A (steam-actuated valves, 1882/1892), US516264A (steam-chest, 1894), US731929A (direct-acting pumping-engine, 1903) — post-date the patent and cannot be combined under §103.
• Of the four eligible references, US109167A (Ambos, 1870) is verified to disclose a chambered, endwise-shuttling valve with dressed, steam-tight ends and circumference, housed in a valve chest within a direct-acting pump cylinder, with cross-over steamways alternately connecting each cylinder end to steam and exhaust. That disclosure maps onto claims 1 and 3 with little left over.
• Claims 1, 2, 3 and 4 would each have been obvious over the pre-1872 balancing and adjustment art. Using only the page's own list, the viable route is US109167A (valve, chest, porting) combined with the general balancing art of the day; using verified contemporaneous art, the strongest specific combinations are:
  • US109167A + US52556 + US51393 (claims 1, 2, 3, 4)
  • US48902 or US85105 + US51393 (claims 1, 2, 4)
  • US107161 + US109167A / US107504 (claim 3)
• Motivation is unusually well documented in the references themselves, because Gallatin (1866), Lawson (1868) and Carhart (1865) each state the same dual objective the patent states — steam-tight yet low-friction, easily kept tight, absorbing little power — and Lawson expressly teaches retrofitting the balance expedient to existing steam cylinders.
• The honest limits of this analysis: (i) I could not retrieve the texts of US45820A, US105986A or US121018A and make no claims about their disclosures; (ii) the claim letters are OCR-corrupted in the authoritative text and I have interpreted rather than "corrected" them; (iii) this is a retrospective exercise — in 1872 the operative test was Hotchkiss's "ordinary mechanic," not §103, and, as noted above (see §10 of the operating rules), if any of these conclusions conflict with verified primary sources, the primary sources govern.