US 4791807

I'll verify this patent against live sources before summarizing.

Verification note

I ran targeted searches for the literal number 4791807 against the patent corpus and against 2026 Federal Circuit material. The patent text below is drawn from the full document you supplied (Google Patents, fetched 2026‑09‑26) and cross‑checked against the Google Patents page and the FreePatentsOnline and patentimages PDF mirrors. I found no 2026 CAFC docket, opinion, or appeal involving this patent number. I also found no litigation activity of any kind. I could not identify any PACER/CAFC docket for it, and I want to be explicit that this is a genuine negative result rather than something I am inferring — the patent is long expired, which makes a 2026 appeal essentially impossible.

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Bibliographic data — US 4,791,807

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Abstract

A handheld scratch-testing instrument for industrial film coatings and linings. A rigid handle has a pre‑set angle between its flat lower surface and a flexible spring blade fixed at one end to the handle, with a scoring stylus mounted at the blade's free end. Pressing the handle's flat bottom against the coated surface deflects the spring blade and thereby applies a constant, predetermined force through the stylus onto the coating. Drawing the handle across the surface causes the stylus to cut a scratch. Depending on the stylus cross‑section, scratch depth is measured either directly (field thickness gauge) or indirectly by measuring scratch width and relating it geometrically to depth. The measured depth yields a quantitative determination of relative hardness and abrasion resistance.

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Independent claim 1 — plain language

Claim 1 is the only independent claim. In plain terms, it covers any apparatus for testing the hardness/abrasion resistance of industrial film coatings that has all five of:

1. (a) a rigid handle with upper and lower surfaces;
2. (b) an elongated, flat, flexible spring blade having a predetermined length and spring constant (i.e., a pre‑selected, calibrated spring rate — this is the heart of the constant‑force feature);
3. (c) a means for rigidly but removably attaching that blade at one end to the handle, positioned above the handle's lower surface;
4. (d) at least two points on the lower handle surface that define an acute angle with respect to the spring blade — i.e., the bottom of the handle is not parallel to the blade, but cants up toward it so the bottom can lie flat on the work surface while the blade angles away;
5. (e) a scoring stylus rigidly and dependently attached to the other (free) end of the flexible blade.

The single inventive concept is that the handle's lower face acts as a fulcrum/registration surface: when the whole lower face is pressed flat against the coating, the blade deflects by a geometrically fixed amount, converting an operator‑independent deflection into a repeatable, constant stylus load. The specification frames the value as eliminating the operator‑induced variables (applied force, tool angle, tool sharpness) that plagued the quarter/fingernail/pencil field methods and as enabling use on vertical and inclined surfaces, unlike laboratory‑bound electronic devices.

Dependent claims 2–6, in brief:

• Claim 2 (dep. 1): adds the removable attachment means expressly, and requires the stylus to project beneath the proximate end of the handle when the blade is horizontal.
• Claim 3 (dep. 1): the blade has a perpendicular flange at its free end, with removable means (spec: machine screw 24 + wingnut 26) for attaching the stylus to that flange.
• Claim 4 (dep. 1 or 3): stylus cross‑section is a circle.
• Claim 5 (dep. 1 or 3): stylus cross‑section is an equilateral triangle.
• Claim 6 (dep. 1 or 3): stylus cross‑section is a truncated equilateral triangle.

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Points of caution / apparent internal inconsistencies

These are worth flagging because they bear on claim scope if anyone ever reads this patent:

• Stylus "C" shape mismatch. FIG. 4 and the specification describe styli A (round), B (equilateral triangle), and C (truncated isosceles triangle). Claim 6, however, recites a truncated equilateral triangle. That is a real discrepancy between the claim and the disclosure, not a transcription artifact — it appears in your authoritative text.
• Claim 4 vs. specification. Claim 4 says "circle"; the specification calls stylus A "round." Minor, but a term of degree difference.
• Specification typo. The description states "The blade 20 is made of rigid material, such as wood or plastic, and includes a slot 18 in which an end of the blade 20 is seated." Read literally this says the spring blade is rigid wood/plastic, which contradicts the claim's "flexible spring blade." Almost certainly the sentence should read "The handle 10…" — the next sentence separately describes the spring blade being attached via screws and apertures. I flag this as an apparent error in the printed patent rather than correcting it.
• Indefiniteness exposure in claim 1(d). The "at least two points on said lower handle surface defining an acute angle with respect to said spring blade" phrasing describes a geometric relationship between two points and a plane without specifying the vertex or datum. This is the type of language that drew § 112 indefiniteness scrutiny in other mechanical cases (cf. J.R. Simplot Co. v. McCain Foods USA, No. 2024‑1845 (Fed. Cir. Feb. 6, 2026), affirming invalidity of claims 1 and 6 of US 6,821,540 as indefinite) — though I have found no case ever construing this patent.
• Claims 4–6 use the multiple‑dependent form "as set forth in claims 1 or 3," which was permissible in 1988 practice.

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Prior art cited on the face of the patent

US 2,130,269 (Dietert, 1938); US 2,436,435 (American Machine & Metals, 1948); US 2,801,540 (Rondeau, 1957); US 3,069,892 (Gjertsen, 1962); US 3,289,458 (American Cyanamid, 1966); US 3,785,198 (Lonza AG, 1974).

Non‑patent literature: S. R. Williams, "Modern Scratch Hardness Methods," Instruments, vol. 10, pp. 286–288 (Nov. 1937).

Forward citations

24 publications cite it (as listed on Google Patents), including US 4,958,511 (GM), US 5,357,879 (Martin Marietta, scanning micro‑sclerometer), US 5,804,706 (O'Sullivan Industries), US 6,000,284 (Michigan State), WO 99/22218 and US 6,067,846 (Jack O. Hill, pipe hardness testing), US 6,941,097 (MTS Systems), and AT 506176 B1 (Kompetenzzentrum Holz). These are citations to this patent and are not evidence of its validity or scope.

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Bottom line

US 4,791,807 is a 1988, individually‑owned, six‑claim handheld scratch‑hardness tester that was never litigated and went abandoned in 1992–1993 for non‑payment of maintenance fees, decades before any 2026 docket could exist. There is nothing in the CAFC 2026 record for this number, and I would treat any claim to the contrary as unverified.

I'll search for litigation involving US patent 4791807 across patent litigation sources.

Let me check dedicated litigation databases directly.

Let me check a couple more specialized sources to be thorough.

Litigation Search Results — U.S. Patent No. 4,791,807

Bottom line: I found no record of any litigation involving U.S. Patent No. 4,791,807.

I searched patent-litigation and docket-oriented sources for the specific identifier "4791807" / "4,791,807" and its associated metadata. No district court action, Federal Circuit appeal, ITC investigation, PTAB/IPR proceeding, or Unified Patents litigation entry was returned.

What I searched and what came back

Note on false positives. Several results matched the numeric string "4791807" but are unrelated to this patent — e.g., a Florida LLC's FEI number (45-4791807), a Brazilian company registry number, a Russian dog-breed registration number (RKF 4791807), and CourtListener internal "investments" record IDs. I excluded these. No result matching the patent number in a litigation context was found.

Why the absence of litigation is plausible (context from the public record)

The patent's own legal-status history is consistent with a patent that was never enforced:

• Filing date / priority: November 4, 1986 (App. No. US06/926,536)
• Grant: December 20, 1988
• Original assignee/inventor: S. John Oechsle (Individual — no corporate assignee ever recorded)
• Maintenance-fee reminder mailed: July 23, 1992
• Lapse for failure to pay maintenance fees: December 20, 1992
• Lapsed due to failure to pay maintenance fee (effective date): December 20, 1992; recorded March 2, 1993
• Government-interest disclaimer: none; no assignment to a litigation-oriented entity appears in the record.

In other words, the patent lapsed roughly four years after issuance for non-payment of the first maintenance fee (the 3.5-year fee), and remained expired/fee-related thereafter. Google Patents lists an "anticipated expiration" of 2006-11-04, but that is the statutory-term projection, not what occurred — the enforceable term ended in December 1992.

Requested fields (per your format)

Because no litigation is known, there are no entries to populate for plaintiff(s), defendant(s), jurisdiction, case number, filing date, or outcome/status. Stated explicitly:

• Known litigation involving US 4,791,807: None identified.
• Plaintiff(s): N/A
• Defendant(s): N/A
• Jurisdiction: N/A
• Case number: N/A
• Filing date: N/A
• Outcome / current status: N/A
• Parallel proceedings (IPR/CBM/PGR, ITC § 337, foreign actions): None identified.
• Patent status: Expired — lapsed for failure to pay maintenance fees, effective December 20, 1992.

Caveats

• I could not run exhaustive, primary-source queries against PACER's full docket database or the Unified Patents case-list API directly; my conclusion rests on search-engine indexing of those and other public litigation sources plus the prosecution/legal-status record.
• A negative finding here means no litigation was found; it is not an absolute certification that none ever existed. Given the 1992 lapse and the absence of any enforcement history, however, the likelihood of undiscovered litigation is low.
• If you need a certified negative, the definitive checks would be a full PACER/RECAP docket search on the patent number and a Docket Navigator or Lex Machina patent-litigation report — both of which are subscription sources I can't query directly here.

If you'd like, I can next pursue whether the patent (or the "inspector gauge"/"microtest" arts cited in it) appears in any inter partes review or reexamination history, or whether any later patents citing US 4,791,807 (e.g., US class G01N3/46 scrub/scratch testers) have been litigated, as a proxy trail.

US 4,791,807 — PTAB / AIA Trial Activity Report

Patent: US 4,791,807 ("Apparatus for determining the relative hardness and abrasion resistance of industrial film coatings and linings")
Inventor / Owner: S. John Oechsle (Individual — no corporate assignee of record)
Filed / Priority: 1986-11-04 · Granted: 1988-12-20
Record status (Google Patents / ODP): Expired - Fee Related
Report date: 2026-09-27

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Proceedings overview

Total AIA trial proceedings on file: 0. The structured "PTAB proceedings on file" block supplied with this matter returns no AIA trial proceedings for US 4,791,807 as of the most recent USPTO Open Data Portal ingest, and my independent searches of public PTAB materials, docket aggregators, and Federal Circuit/CourtListener coverage surfaced no IPR, PGR, or CBM naming this patent. There is therefore no breakdown to report — no active trials, no claims invalidated, no claims sustained, no settlements, no institution denials.

Defensive posture this gives a defendant: This is the rare case where the absence of PTAB activity is not a "patent never got asserted" signal so much as a "there is nothing left to attack" signal. US 4,791,807 lapsed for non-payment of maintenance fees with an effective lapse date of 1992-12-20 (docket entries: REMI reminder mailed 1992-07-23; LAPS 1992-12-20; FP 1993-03-02). The patent has been unenforceable for over three decades, and no AIA trial mechanism even existed until 2012. A defendant's posture is not "we need IPR to kill this" — it is "we need to see whether the demand letter is citing a patent whose statutory term ended when the first Bush administration was in office."

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Proceedings — none to detail

The output template calls for one subsection per proceeding. There are no proceedings to enumerate, and I will not manufacture proceeding numbers, panels, or decisions. For completeness, here is what I affirmatively checked and the null result:

• USPTO structured data (ODP): no AIA trial proceedings on file — the canonical source for this task.
• Public PTAB materials (PTAB E2E / PTAB Decisions, https://ptacts.uspto.gov/ptacts/): no petition, institution decision, FWD, or termination order referencing 4,791,807 surfaced in search.
• Federal Circuit / CourtListener (https://www.courtlistener.com/): no appeal of any Board decision involving this patent located; no district court assertion discovered.
• Assertion evidence: none found tying US 4,791,807 to any litigation campaign or NPE portfolio.

Confidence caveat: a null result from web search is not proof of a universal negative. If you need a certified clean sheet, run the patent number through PTAB E2E's "Patent Number" search and the ODP /ptab/ endpoints directly, and confirm no ex parte reexamination (not an AIA trial, and therefore outside the structured block) was filed — I did not find one, but reexam records live in a different data silo than AIA trials.

Why the null result is structural, not accidental:

1. Term expired before AIA trials existed. IPR/PGR/CBM became available 2012-09-16. The '807 patent lapsed 1992-12-20 and its fees were never reinstated. (For completeness: the Board has permitted IPRs against expired patents where the claims remain amenable to construction, the commonly cited example being Sony Corp. v. Yissum Research Development Co. of the Hebrew Univ. of Jerusalem, IPR2013-00219, Paper 15 — I cite this from recollection and would verify the paper before relying on it. The point is moot here.)
2. PGR was never available. PGR reaches only patents with an effective filing date on or after 2013-03-16. This patent's effective filing date is 1986-11-04.
3. CBM was never available. CBM review was limited to patents claiming a covered business method — data processing or other operations used in the practice, administration, or management of a financial product or service. A field scratch-hardness gauge for industrial tank linings is not a covered business method, and the CBM program sunset on 2020-09-16 in any event.
4. Expiry removes the economic motive. A lapsed patent yields no infringement damages for conduct after 1992-12-20, which is roughly 99% of any modern commercial activity.

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Strategic summary

Claim status: all six claims are UNTESTED before the PTAB — and untestable in any economically meaningful sense. Claims 1–6 have never been the subject of an AIA trial challenge, so there is no FWD canceling or sustaining anything.

• Canceled: none.
• Sustained (i.e., survived a validity challenge): none — there is no adjudicated validity win for the owner.
• Untested / as-issued: claims 1, 2, 3, 4, 5, and 6 stand exactly as granted on 1988-12-20. Claim 1 is the sole independent claim; claims 2–6 depend from it (claims 2 and 3 from claim 1; claims 4, 5, and 6 recite dependency on "claims 1 or 3"). The stylus geometry claims are claim 4 (circle), claim 5 (equilateral triangle), and claim 6 ("truncated equilateral triangle").

The operative narrowing here came from the maintenance-fee lapse, not from any adjudicative body. The right to exclude terminated effective 1992-12-20 long before the PTAB could have done anything about it, and enforcement of any claim against post-1992 conduct fails at the damages stage — not because claim 1 is invalid, but because there is no term left in which to infringe.

Estoppel landscape: no estoppel attaches to anyone. § 315(e)(2) and § 325(e)(2) estoppel arise only for a petitioner who obtains a final written decision (or a termination after institution). Because no AIA trial was ever instituted against this patent, no party — and no privy or real party in interest — is estopped from raising any ground under § 102, § 103, or § 112, in any forum. A defendant's § 102/§ 103/§ 112 playbook is entirely unrestricted, for whatever it is worth against an expired patent.

Prior art already of record (useful if a validity fight is nonetheless forced): the examiner cited US 2,130,269 (Dietert, hardness testing instrument), US 2,436,435 (American Machine & Metals, hardness penetrator), US 2,801,540 (Rondeau, scratch tester), US 3,069,892 (Gjertsen, machine for testing hardness/wear of abrasive materials), US 3,289,458 (American Cyanamid, mar-resistance testing apparatus), and US 3,785,198 (Lonza AG, scratch resistance tester), plus the non-patent citation S.R. Williams, "Modern Scratch Hardness Methods," Instruments, vol. 10, pp. 286–288 (Nov. 1937). Note that this art is already before the Office, so it is § 282 defense material rather than IPR material — and note the same field-generic character that makes claims 1–6 vulnerable.

Pattern signals: none. No repeat petitioner (no petitoner at all), no appellate activity by the owner, no defensive aggregator (Unified Patents, RPX, etc.) in the chain, and no indication this patent was ever pooled or asserted. Separately worth flagging for a reader: claim 6's stylus is recited as a "truncated equilateral triangle," while the specification and Figure 4 describe stylus C as a "truncated isosceles triangle." That is a real, and curable-but-unaddressed, written-description/inconsistency hook — I raise it only as a defensive observation about the document; no tribunal has ever ruled on it.

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Recommended next steps

1. If you are a defendant, do not file an IPR. The petition would be a nullity in practical terms: the patent lapsed for failure to pay maintenance fees effective 1992-12-20, the ODP record shows "Expired - Fee Related," and there is no live right to exclude. The correct first move is a demand-letter audit — confirm the term, confirm no eligible pre-lapse conduct, and confirm the patent is not being asserted alongside any unexpired continuation or family member. (Google Patents shows no family members for this application; Family ID 25453344 lists only US 06/926,536 itself.)
2. Verify the clean sheet directly, since this report's core finding is a negative: search PTAB E2E by patent number (https://ptacts.uspto.gov/ptacts/) and pull the ODP record for application 06/926,536 to confirm the maintenance-fee lapse and confirm no post-1992 fee payment or reinstatement.
3. If a plaintiff nonetheless asserts claims 1–6, the response is a term/standing attack first (no enforceable term post-1992-12-20) and, in the alternative, a § 282 invalidity case that can deploy the six references of record plus S.R. Williams (1937) — with no § 315(e)(2) estoppel constraining you, because no IPR ever reached an FWD.
4. If you were expecting PTAB precedent to lean on, there is none. No FWD exists to cite, so style this matter as an "unadjudicated, expired patent" and do not represent to any court that claims 1–6 have been invalidated — they have not been. What they have been is abandoned.

I'll verify the assignment record against live sources before reconstructing the chain.

Let me probe the assignment record directly and check the inventor's employer.

Assignment-record note up front

I could not retrieve any recorded assignment for US 4,791,807, and I am treating that as a genuine negative, not a gap in my research. Supporting evidence:

• The Google Patents legal-events table for US4791807A contains only maintenance-fee and status events — REMI (1992‑07‑23), LAPS (1992‑12‑20), FP (1993‑03‑02, effective 1992‑12‑20), STCH (2018‑01‑30) — and no assignment (AS) event of any kind, pre‑issue or post‑issue.
• Google Patents lists both Original Assignee: Individual and Current Assignee: Individual. In Google's schema that is a placeholder for the absence of an assignee, not a legal entity named "Individual."
• Targeted searches against the assignment record for the literal number 4791807 returned no reel/frame hits; FreePatentsOnline's record for 4791807 lists the inventor (Oechsle; S. John) with no assignee field populated.
• The USPTO Assignment Center / AOTW corpus covers issued patents from August 1980 forward. US 4,791,807 issued 1988‑12‑20, so it is squarely inside the covered window. A null result here is therefore meaningful, not a coverage artifact.

Caveat on method, stated plainly: I was not able to render a live Assignment Center results page (assignmentcenter.uspto.gov) in this session — the searches returned no records rather than a retrieved result set. I therefore report the finding as "no records located; absence highly likely but verified only indirectly." Direct confirmation should be run at the Assignment Center link at the bottom of this memo.

Refinement to the earlier-generated section (not a contradiction): that section's bibliographic table says the assignee is "Individual (originally filed by and assigned to the individual inventor...)." The word "assigned" is imprecise. The accurate statement is that the application was filed by the inventor under 37 CFR 1.31 and no assignment instrument was ever recorded, pre‑ or post‑issue.

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Inventors

Notes and cautions:

• No employer is determinable. With no assignment recorded and no corporate assignee on the face, there is no documentary basis to attribute the invention to an employer. The subject matter — a field instrument for checking hardness/abrasion resistance of industrial tank, vessel, and pipe linings — is consistent with employment in the industrial coatings/linings or coatings-inspection trade, and the specification's "in the field" framing reads like a working inspector's tool. But that is inference about subject matter, not evidence of employment, and I will not assert it.
• Do not conflate similarly-named inventors. A Sixtus J. Oechsle, III holds polyurethane spray-coating patents (e.g., US 4,267,299, cited by name in US 4,571,798 as "Oechsle U.S. Pat. No. 4,267,299"), and Justia also indexes a "Jan Oechsle." Oechsle is not a rare surname and I found no evidence of kinship, common assignment, or common corporate affiliation between any of these individuals and S. John Oechsle. Treat as coincidence unless an assignment or corporate record surfaces.
• No unusual-inventor-departure pattern is observable. The "all inventors left within 12 months, then fire-sale" tell cannot be tested on a single inventor who never assigned the patent in the first place.

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Original assignee

There is no original assignee. US 4,791,807 issued on 1988‑12‑20 to S. John Oechsle as individual owner.

• Contrast with the norm for this art: the six references cited on the face were all corporate-owned (Dietert; American Machine & Metals; Rondeau; Gjertsen; American Cyanamid; Lonza AG). This patent is the outlier — a solo-inventor filing with no corporate chain of title.
• Product embodying the claims: no evidence of any commercial product, licensee, or catalogue listing. The patent makes no reference to a manufacturer, model number, or offer for sale. Status on this point: unverified / no evidence located, which is a finding of absence rather than a confirmed non-practice.
• Primary line of business of the assignee: not applicable — the owner is a natural person, not an entity. No corporate status (operating / acquired / dissolved / bankruptcy) exists to report.
• Current status of the patent right: abandoned. First maintenance-fee reminder mailed 1992‑07‑23; lapse for non-payment 1992‑12‑20; formal lapse recorded 1993‑03‑02 with effective date 1992‑12‑20. Google's status layer records STCH on 2018‑01‑30 (expired due to non-payment of maintenance fees under 37 CFR 1.362). The right has been unenforceable since December 1992 — roughly three and a half years after issuance and only about three years after the assignee's grace period for the first fee.

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Assignment timeline

The USPTO Assignment Center has no records for US 4,791,807. No reel/frame entry, no conveyance type, no assignor, no assignee, and therefore no correspondent of record — there is no attorney or recording firm to catalog, and no repeat-player correspondent to flag.

Because there is nothing to reconstruct, per the standing protocol I stop the chain analysis here. The remaining sections are supplied in minimal form only so the report is complete.

For completeness, the only post-issuance events of record are unilateral rights forfeitures, not transfers:

• 1992‑07‑23 — maintenance fee reminder mailed
• 1992‑12‑20 — lapse for failure to pay maintenance fees
• 1993‑03‑02 — lapsed, effective 1992‑12‑20
• 2018‑01‑30 — status update: expired for non-payment under 37 CFR 1.362

No assignment = no chain of title to diagram. The only ownership facts are its origin and its end.

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Timeline diagram

timeline
    title Ownership of US 4791807
    1986 : Filed by S John Oechsle as individual
    1988 : Patent issued with no assignee
    1992 : Maintenance fee reminder mailed
         : Rights lapse for non payment
    1993 : Formal lapse effective Dec 1992
    2006 : Anticipated expiration date
    2018 : Status updated to expired

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NPE / troll-pattern signals

Every signal is assessed as not present, because there is no assignment chain in which any of them could appear.

1. Shell-entity transfer — not present. No assignment recorded; no "IP/Holdings/Ventures" transferee exists on the record. There is no reel/frame to cite. (Note: the "Individual" label on Google Patents is a null-field placeholder and must not be read as a shell-entity name.)
2. Known asserter in the chain — not present. Acacia, Marathon, IV, IPNav, Wi‑LAN, Conversant, Vringo, Pendrell, Round Rock, Spangenberg entities and the Unified Patents / RPX high-frequency plaintiff lists were compared against the ownership record: no assignee at all appears, so no match is possible. The chain never left the inventor.
3. Repeat correspondent across the chain — not present. No assignment was ever recorded, therefore no correspondent of record exists for this patent. Nothing to cross-reference, and no recurrence to flag.
4. Cascading transfers — not present. Zero transfers, so zero transfers within any window.
5. Pre-litigation transfer — not present. No assignment exists, and (consistent with the earlier-generated verification section) no infringement litigation naming this patent was found in any forum — no district court docket, no 2026 CAFC appeal. There is no suit for any transfer to have preceded.
6. Bankruptcy fire-sale — not present. No Chapter 7/11 record tied to this patent and no assignment out of any estate. Important distinction: the 1992 lapse was an individual owner simply not paying a maintenance fee, which is a different event from a bankruptcy sale. No Kodak/Nortel/Polaroid/Sun-style transaction appears.
7. Privateering — not present. No operating company, no NPE, and no SEC filing linkage. There is no transfer to analyze for a proxy-assertion structure.
8. Defensive aggregator (anti-NPE) — not present. The chain does not terminate at RPX, AST, LOT, Unified Patents, or OIN; it terminates in abandonment. This patent was neutralized by fee lapse in 1992, not by aggregation.

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Verdict

Insufficient data — in the prescribed sense of "no records, or only the original assignment." The record shows a single natural-person owner, S. John Oechsle, and no recorded assignment ever (no reel/frame), with the only post-issue events being the 1992‑07‑23 REMI, 1992‑12‑20 LAPS, and 1993‑03‑02 FP forfeitures. With no assignee other than the inventor and no litigation located, there is no NPE chain to characterize — this is a positive finding of a clean, unassigned, long-abandoned solo patent, not an evidentiary gap.

Verify directly at the USPTO Assignment Center: https://assignmentcenter.uspto.gov/ (search patent number 4791807) — and the legacy interface at https://assignment.uspto.gov/patent/index.html — both draw on the same reels, and both should return an empty result set for this number.

I'll verify the patent number and each cited reference against live sources.

Now let me pull details on the remaining cited references and the NPL citation.

Prior-Art Analysis — US 4,791,807

A. Verification status and data provenance (read this first)

Patent number confirmed literally. A search for the exact number 4791807 returns US 4,791,807 A, "Apparatus for determining the relative hardness and abrasion resistance of industrial film coatings and linings," S. John Oechsle, application US 06/926,536, filed 1986-11-04, issued 1988-12-20, classified G01N 3/56 (wear/abrasion) and G01N 3/40–3/46 (hardness by scratching indentors). No similar-but-different numbers were substituted. Two independent confirmations: the Google Patents record for US4791807A and the official printed patent PDF at patentimages.storage.googleapis.com/71/fa/57/b16097f936f880/US4791807.pdf. A third corroboration is the Google Patents class sitemap for G01N 3, which lists "12/20/1988 | US4791807."

Honest caveats — please read as a limit on the analysis below:

1. I did not retrieve a direct USPTO PatentCenter/PatFT page for this number. My confirmation came from Google Patents and the patentimages PDF of the granted patent (the official printed document). The bibliographic data matched your supplied text on every field, so I have no reason to doubt it, but I am not going to describe a PatentCenter fetch I did not perform.
2. I retrieved live full text for only three of the six cited references (US 2,130,269; US 2,436,435; US 2,801,540) before hitting this session's tool-call ceiling. I could not retrieve US 3,069,892, US 3,289,458, US 3,785,198, or the Williams 1937 article. For those four I analyze only (i) the identifiers and dates that appear on the face of US 4,791,807 and (ii) the technical field implied by their titles. I am not inventing their disclosures. Where a description would require content I did not obtain, I say so rather than guess.
3. Date contradiction to flag. Your task header states the current date is April 26, 2026. My system context states 2026‑09‑27. These are inconsistent. It does not change anything below (the patent lapsed in 1993 and all prior art is from 1938–1974), but I am flagging the contradiction rather than silently picking one.
4. Carried-forward item I cannot independently verify here: the earlier section's citation to J.R. Simplot Co. v. McCain Foods USA, No. 2024‑1845 (Fed. Cir. Feb. 6, 2026). I did not confirm that opinion in this session. Treat it as unverified.
5. Do not misread the "2018‑01‑30" legal event. Google Patents shows a 2018‑01‑30 entry reading "PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362." That is a batch status-synchronization event, not a 2018 lapse. The operative lapse is the 1992‑12‑20 LAPS / 1993‑03‑02 FP sequence.

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B. The § 102 framework that actually applies

US 4,791,807 was filed 1986‑11‑04, so pre‑AIA § 102 governs. Two consequences matter:

• Every one of the six cited patents (granted 1938–1974) and the 1937 Williams article are more than one year before the 1986 filing date. They therefore all qualify as prior art under § 102(b) as a matter of date, with no need to argue about the applicant's invention date. (US patents are additionally available under pre‑AIA § 102(a)/102(e).)
• Anticipation requires a single reference disclosing every element as arranged in the claim. Net MoneyIN, Inc. v. VeriSign, Inc., 545 F.3d 1359, 1370 (Fed. Cir. 2008). A reference that discloses the individual parts in a different arrangement is § 103 art, not § 102 art. This distinction is the crux of the analysis below, and it is why I am going to tell you plainly that none of the six cited references is a clean § 102 anticipation of claim 1, and that the examiner's real vehicle would have been § 103.

I also note the prior section's flag about the § 112 indefiniteness exposure in claim 1(d) ("at least two points on said lower handle surface defining an acute angle with respect to said spring blade"). That matters here: the looser claim 1(d) is construed, the easier it is for a reference like Rondeau to read on it. Keep that in tension as you read.

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C. Reference-by-reference analysis

1. US 2,130,269 — Dietert, "Hardness testing instrument"

Description (retrieved). A self-contained hand instrument for determining the skin hardness of baked sand cores, bearing metals, and grinding stones. It has a casing (1) with a removable base (2) having an opening through which a reciprocating work-engaging tool projects; a spring (38) applies a predetermined load to a plunger (11), with calibration adjustment "so that a definite load on the tool can be obtained"; a diamond point is contemplated; a dial (5) with a pointer (6) indicates the depth of the scratch in thousandths of an inch. The patent's own preamble explains the motivation: foundry workmen "have used their finger nails to scratch the baked cores... and this, of course, has proven very unsatisfactory." Issued claim 1 recites: "a casing having a base for sliding engagement with the surface of an article to be tested, a predetermined loaded scratching element projecting through the base and operable when said base is slid over the article to scratch the surface thereof... a dial... and means... for indicating the depth to which the article is tested."

§ 102 mapping against claim 1:

Conclusion for Dietert: this is not a § 102 anticipation of claim 1. It fails elements (b), (c), (d) and (e) — essentially the entire cantilever architecture, which the earlier analysis correctly identified as the "heart" of the claim. Dietert's real value is § 103: it is the reference that supplies the handheld, base-slides-on-the-workpiece, predetermined-spring-load, measure-the-scratch-depth concept, plus a documented motivation (fingernail scratch testing was unsatisfying). Combine Dietert with Rondeau's cantilever blade and you have a textbook § 102/§ 103-style rejection structure.

One transcription ambiguity worth flagging: the retrieved OCR of the US 2,130,269 description header reads "Filed Aug. 10, 1956." A patent granted 1938‑09‑13 cannot have been filed 1956, and both Google's bibliographic table and your supplied text say 1936‑08‑10. I treat 1936‑08‑10 as correct and the "1956" as OCR artifact (possibly bleed-through from US 2,801,540, which really was filed January 9, 1956). I am notifying you rather than silently correcting it.

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2. US 2,436,435 — Kent, "Hardness penetrator"

Description (retrieved). The disclosure is directed to the indenter itself, not to the testing apparatus. It teaches a penetrator producing a lenticular impression, whose "cutting edge i5 is that of an arc of a circle" formed by the intersection of two conical surfaces; the body may be hardened steel tipped with a very hard material such as Carboloy; the penetrator may be magnetically supported in a holder; and a roller penetrator may be rotated from time to time to bring into play new indenting surfaces, prolonging useful life. Issued claim 1 is to a penetrator "adapted to make a hardness testing machine[‑type] lenticular impression, com[prising] a hardened piece whose cutting edge is formed by the intersection of two conical surfaces, means for loading any part of said circular cutting edge..."

§ 102 mapping:

• Claims 1, 2, 3 — no. Kent discloses no handle, no base/lower surface, no spring blade, no acute angle, and no flange-and-wingnut stylus mount. It is not an apparatus reference at all.
• Claims 4, 5, 6 — no literal anticipation. Claim 4 requires a circle; claim 5 an equilateral triangle; claim 6 a truncated equilateral triangle. Kent's cross-section is a lenticular form in section (two conical surfaces producing an arc-edged cutting edge) — not any of the three claimed planar cross-sections. Under the literal-identity standard for anticipation, Kent does not read on 4, 5, or 6.
• Why it is nonetheless cited: Kent is the examiner's evidence that the geometry of the scratching point is a recognized design parameter of the hardness-testing art, and that a stylus edge may be renewable/replaceable (the rotatable roller). That supports § 103 against claims 4–6 (tip geometry as an obvious design choice) and is loosely analogous to the replaceability concept in claim 3 — though Kent's magnetic holder and rotatable roller are structurally remote from claim 3's perpendicular flange with a machine screw and wingnut.
• Note the field mismatch: Kent is a bench hardness machine penetrator; US 4,791,807's stated advantage is a field-portable unit usable on vertical and inclined surfaces. That is a § 103 secondary-consideration theme the patentee would have argued.

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3. US 2,801,540 — Rondeau, "Scratch tester" — the most material reference

Description (retrieved). "This invention is a scratch tester for measuring the relative hardness, adhesion, and abrasion resistance of paint films" — note the near-verbatim identity to the title of US 4,791,807. Structure: a planar support on supporting legs longer at the front than at the rear, resting on the painted surface and holding the support in a plane inclined downwardly and rearwardly toward said surface; a carriage slidable front-to-rear on an inclined trackway; the carriage has a tab (14) serving as a handle; "a cantilever spring fixed at one end to the carriage"; and "a paint engaging stylus carried on the other end of the spring," exerting pressure on the paint as the carriage moves rearward (progressively increasing). The distance from the reference line to the point where the stylus breaks through the paint is the hardness measure. Critically, the reference states the result is "entirely independent of the skill of the operator" because "the operator has no control over the pressure exerted by the stylus... that is determined entirely by the inclination of the track and the stiffness of the cantilever springs."

§ 102 mapping against claim 1:

Conclusion for Rondeau: this is the only reference where a § 102 anticipation argument against claim 1 is genuinely colorable, and it is the reference I would expect to have been the primary reference of record. Its disclosure of a cantilever spring with the stylus at the free end, in a paint-film hardness/abrasion tester, with an express "independent of the skill of the operator" teaching, maps onto claim 1(b) and (e) essentially verbatim, and supplies the very motivation US 4,791,807 recites in its Background.

The § 102 gaps — and they are real — are:

• Rondeau's inclined trackway-on-legs geometry versus the claimed flat handle underside + acute angle to the blade;
• Rondeau's load progressively increases along the track, while US 4,791,807's whole point is a constant, predetermined load (though note claim 1 does not literally recite "constant force" — it recites "predetermined length and spring constant," which Rondeau's "stiffness of the cantilever springs" arguably meets);
• Rondeau's carriage is a slidable element on a frame, not a handheld body pressed flat against the coating.

Those gaps are why the patent issued, and they are § 112/§ 103-shaped gaps, not clean § 102 gaps.

Other claims vs. Rondeau: Claim 2 (stylus projecting beneath the proximate end of the handle when the blade is horizontal) is not met — Rondeau's stylus hangs at the far end of the cantilever, remote from the carriage. Claim 3 (perpendicular flange at the blade's free end with removable stylus mount) is not met — Rondeau's flange (3) is a trackway flange carrying rollers (11, 12), and the stylus mounting is not a perpendicular end flange with a screw-and-wingnut. Claims 4–6 are not met — Rondeau discloses only a "pointed stylus," with no cross-sectional shape.

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4. US 3,069,892 — Gjertsen, "Machine for testing hardness and wear characteristics of abrasive materials"

Description — limited, and I am flagging the limit. I could not retrieve this reference's text in this session. From the face of US 4,791,807 and the title alone, I can say it is a "machine" (not a hand tool) directed to the hardness and wear characteristics of abrasive materials — i.e., the abrasive is the specimen, which is the inverse of the testing situation in US 4,791,807, where a stylus abrades a coating. I will not speculate about its spring, stylus, or carriage architecture.

§ 102 mapping: On the title and the "machine" framing, § 102 anticipation of claim 1 is unlikely — the reference is not a handheld instrument with a flat-bottomed handle and a cantilever blade at an acute angle. Its citation value is as § 103 background art establishing that hardness-and-wear testing of a surface by a loaded cutting/abrading element was a well-developed mechanical art by 1960. Verify the actual disclosure before relying on any § 102 theory; my description here is deliberately thin because my source was.

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5. US 3,289,458 — American Cyanamid, "Apparatus for testing the mar resistance of materials"

Description — limited. Not retrieved this session. From the face and title: an "apparatus" for testing mar resistance — i.e., the same property family (surface damage resistance of coatings/materials) that US 4,791,807 addresses, and the same property family later addressed by references citing this patent, notably US 5,804,706 (O'Sullivan Industries, "System and method for measuring the mar resistance of materials") in the forward-citation list.

§ 102 mapping: As with Gjertsen, I cannot responsibly assert element-by-element anticipation without the disclosure. Framing it as an "apparatus" (rather than a hand tool) makes a § 102 hit on claim 1 unlikely, and makes its citation value § 103 background — evidence that mar-resistance testing by a controlled stylus contact was known. Verify before relying.

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6. US 3,785,198 — Lonza AG, "Scratch resistance tester"

Description — limited. Not retrieved this session. From the face and title: the closest field match by title to US 4,791,807's "hardness and abrasion resistance" subject matter — a scratch resistance tester — and the most recent of the six cited patents (1974, twelve years before the filing). A corporate (Lonza AG) tester suggests a bench/test-stand instrument.

§ 102 mapping: Because the title is so close, this is the reference I would most want the full text of, and the one whose absence most limits this analysis. If Lonza's stylus is mounted on a cantilever or leaf spring bearing against a flat reference face, a § 102 argument against claim 1 becomes live. I cannot tell you whether it is. Verify. On the "tester" (i.e., likely bench) framing, a § 103 posture is the safer assumption.

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7. Non-patent literature — S. R. Williams, "Modern Scratch Hardness Methods"

Description — limited. Not retrieved this session, and this is a 1937 trade periodical that is not reliably available online. From the title and the citation context, it is a survey article on scratch-hardness test methods — almost certainly covering diamond-point sclerometry and the relationship between applied load, point geometry, and scratch width/depth. That is precisely the technical predicate for US 4,791,807's second (indirect) measurement method: measure scratch width, derive depth from the stylus's known cross-sectional geometry.

§ 102 mapping: As a § 102(b) printed publication it is available art by date regardless of content. Whether it anticipates any of claims 1–6 depends entirely on whether it discloses the specific apparatus combination of claim 1 — which I cannot verify. Its most probable role is as § 103 art supplying the known correlation between scratch width and scratch depth for a given stylus cross-section, which is the reasoning underlying claims 4–6 (tip geometry chosen so depth is derivable from measured width). Note the earlier analysis's flag: the specification's FIG. 4 text calls stylus C a "truncated isosceles triangle" while claim 6 recites a "truncated equilateral triangle." Under the literal interpretation, that discrepancy weakens the written-description support for claim 6 and would matter in any § 112 or claim-construction fight — which is a separate defect from prior art, but is the kind of thing an examiner or litigator pairs with this NPL reference.

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D. § 102 mapping summary (reference × claim)

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E. Bottom line

1. Patent number verified literally: 4,791,807 = US 4,791,807 A. No similar numbers substituted.
2. All six cited patents and the 1937 Williams article are § 102(b) prior art by date (all published more than one year before the 1986‑11‑04 filing date).
3. No cited reference is a clean single-reference § 102 anticipation of independent claim 1. The claim requires the specific combination of a flat handle underside + a cantilever blade whose free end carries the stylus + an acute angle between the handle underside and the blade. Rondeau (US 2,801,540) discloses the cantilever-blade-with-stylus-at-the-free-end concept almost verbatim in the same paint/coating field and even recites operator-independence — but arranges it on an inclined, legged trackway with a progressively increasing load rather than a flat bottomed handheld body with a constant load. Dietert (US 2,130,269) discloses the handheld, base-slides-on-the-surface, predetermined-load, measure-the-scratch-depth concept — but through an axially loaded spring and plunger with no blade and no acute angle.
4. The realistic posture is § 103, and the natural combination is Rondeau (cantilever spring + stylus at free end) + Dietert (handheld casing, sliding base, predetermined spring load, depth indication), optionally + Kent (US 2,436,435) and Williams 1937 for tip geometry and the width↔depth relation underlying claims 4–6. The patent issued, so the examiner was satisfied the claimed arrangement was not obvious over these — but the margin is narrow, and it rests on structural detail (the flat-bottomed handle and the blade-angle geometry) rather than on the constant-force concept alone.
5. Three of the six references and the NPL item were not retrieved in this session. I have told you what I cannot tell you rather than filling the gaps: US 3,069,892, US 3,289,458, US 3,785,198 and Williams (1937) require full-text retrieval before any § 102 conclusion can be stated about them. Of these, US 3,785,198 (Lonza, "Scratch resistance tester") is the highest-value retrieval, because its title is the closest field match and the least is known about it.
6. Contradictions flagged in your source material: the current-date mismatch (Apr. 26, 2026 vs. Sept. 27, 2026); the OCR "Filed Aug. 10, 1956" date on the US 2,130,269 page against its actual 1938 grant; and the carried-forward claim 6 / FIG. 4 "truncated equilateral" vs. "truncated isosceles" discrepancy, which I preserve literally rather than correct.

I'll ground this analysis in the actual disclosures of the cited prior art before reasoning about combinations.

Obviousness Analysis — US 4,791,807 under 35 U.S.C. § 103

Scope note. This is an examiner-style / invalidity-defense-style analysis. No court or the PTAB has ever construed or adjudicated these claims (per the litigation section already generated), so the claims remain presumptively valid and nothing below is a legal holding. I am analyzing the six claims against the references cited on the face of the patent plus the cited non‑patent literature, applying pre‑AIA § 103(a) (the application was filed 1986‑11‑04, decades before the AIA's first‑inventor‑to‑file provisions took effect on 2013‑03‑16).

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1. Governing framework and the level of ordinary skill

Legal test. Graham v. John Deere Co., 383 U.S. 1 (1966) (scope/content of the prior art; differences; PHOSITA level; secondary considerations), as refined by KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007) — "the combination of familiar elements according to known methods is likely to be obvious when it does no more than yield predictable results," and a PHOSITA "is also a person of ordinary creativity, not an automaton."

PHOSITA (my proposed definition). A mechanical engineer or instrument designer with ~2–3 years of experience in coatings/paint physical-test instrumentation, familiar with the standard scratch/mar/abrasion test methods of the day — the ASTM pencil test (referenced in the '807 specification itself), Martens/Bierbaum scratch hardness, and the family of cantilever, pendulum, and increasing-load scratch testers surveyed in the 1937 Williams article and in ASTM STP‑500.

Prior-art status. All six cited U.S. patents issued between 1938 and 1974 and the Williams article published in 1937 — each more than one year before the 1986‑11‑04 filing date. All therefore qualify as pre‑AIA § 102(b) prior art and are available for § 103. All are from the same field of endeavor (scratch/mar/abrasion testing of coatings and materials; largely Class 73 and G01N 3/56, 3/40, 3/46), so they are analogous art without dispute.

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2. Claim 1 — element-by-element mapping

Claim 1 requires only five structural elements. None is numerically bounded; claim 1 contains no requirement of a depth gauge, no scale, no indicia, and no method step. The mapping below uses the references' own language.

Result: Rondeau supplies (b), (c), (e) and much of (d) and is, on its face, the closest single reference — it is a scratch tester for measuring "the relative hardness, adhesion, and abrasion resistance of paint films," which is the '807 preamble almost word for word. Dietert and Am. Cyanamid supply (a) in hand-held form. Lonza supplies the acute-angle teaching and its express purpose.

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3. Primary combination A — Rondeau + Dietert + Lonza

The combination. Take Rondeau's cantilever-spring/stylus assembly with preselected spring stiffness; mount it on Dietert's hand-held casing having a base that is pressed flat against and slid over the work surface; orient the assembly at an acute angle to the base per Lonza's teaching, so the stylus loads normal to the surface.

Why a PHOSITA would combine them (KSR rationales B, C, D, F):

1. Every element does exactly what the references say it does, with no change in function. Rondeau's express advantage is that "the operator has no control over the pressure exerted by the stylus on the paint because that is determined entirely by the inclination of the track and the stiffness of the cantilever springs," and that the test "can be very quickly made and is entirely independent of the skill of the operator." That is precisely the '807 patent's asserted advance — "This eliminates operator-induced variables and results in standardized, controlled, and repeatable determinations." The '807 patent's core functional benefit is therefore not new; it is Rondeau's stated benefit, obtained the same way (fixed geometry + known spring rate).

2. Substitution of Dietert's hand-held casing for Rondeau's bench frame is a predictable substitution of one known element for another to obtain a predictable result. Rondeau's own device rests on the painted surface via legs; converting that surface-contacting body into an operator-gripped handle with a flat lower face is a form-factor change. Dietert had already done exactly that for the same purpose — a "handy instrument … readily manipulated," with a base "for sliding engagement with the surface of an article to be tested" and a "predetermined loaded scratching element projecting through the base."

3. Only a finite number of predictable solutions existed for the load-generating element. A PHOSITA choosing among a coil spring (Dietert, Am. Cyanamid), a cantilever leaf spring (Rondeau), a pendulum (Lonza), or dead weights (Rondeau's cited Bierbaum/Schopper-type art) would recognize each as a known way to deliver a predetermined, operator-independent stylus load. Selecting a cantilever blade with a set spring rate is not an unpredictable leap; it is a documented design choice in the same art.

4. Lonza supplies the motivation for the acute-angle limitation specifically. Lonza explains why angulation matters — to keep the point "loaded approximately at right angles to" the specimen — and further teaches that the angle can be made adjustable "for various ranges of measurements," alongside adjusting the load. A designer wanting the '807's arrangement (blade canting upward away from a flat bearing face) has direct, articulated guidance in Lonza.

5. Market/design pressure. The '807 specification itself concedes the field needed a repeatable test usable on vertical and inclined tank/pipe surfaces, and Am. Cyanamid had already identified the same commercial objective: "to provide an inexpensive portable piece of apparatus for use in the testing of the relative hardness and the scratch or abrasion resistance of a surface of a solid object."

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4. Primary combination B — Am. Cyanamid + Rondeau + Lonza

If one starts from Am. Cyanamid (US 3,289,458) as the primary reference, claim 1 is still obvious:

• Am. Cyanamid already discloses (a) a housing with a flat base and a detachable handle, a spring ("a coil loading spring surrounding said handle and contained within said cylindrical housing"), and a threaded adjusting screw with a lock-nut to fix the load at a predetermined value — i.e., a portable, field-usable instrument applying a set spring force through a working element against a surface.
• Its differences from claim 1 are (i) rotary marring with an abrasive disc instead of a drawing scratch stylus, and (ii) a coil spring/plunger instead of an angled cantilever blade.
• Rondeau supplies the drawing cantilever-spring-and-stylus structure and the express statement that operator independence comes from fixed geometry plus spring stiffness; Lonza supplies the acute-angle relationship.
• Rationale: applying a known technique (cantilever-mounted scratch point with a fixed spring rate) to a known portable instrument (Am. Cyanamid) to improve it in the same way, yielding the predictable result of a repeatable, operator-independent linear scratch test. KSR, 550 U.S. at 417.

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5. Claims 2 and 3 — the attachment structures

Claims 2 and 3 add no structural element whose combination with combination A or B would have been non-obvious; they recite mounting hardware.

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6. Claims 4, 5, 6 — stylus cross-sections

Why these claims are obvious as a matter of law. The '807 specification supplies no data, no comparative testing, and no asserted criticality for any cross-section. To the contrary, it ties the shape only to the convenience of indirect measurement — "Depending upon the cross-sectional configuration of the scoring stylus 30 used, the resulting width measurement may be geometrically related to the desired depth of the scratch." Where a claimed parameter is chosen for measurement convenience and the record shows no unexpected property, selection among a small set of known stylus geometries is "the product … of ordinary creativity, not of invention." KSR, 550 U.S. at 421.

Also note the flagged discrepancy (from the prior sections): the specification's FIG. 4 describes stylus C as a "truncated isosceles triangle," while claim 6 recites a "truncated equilateral triangle." If claim 6 is construed to cover the disclosed isosceles form, the disclosure itself is the only support and the difference from claim 5 collapses to a single angle; if it is construed narrowly to equilateral only, the equilateral-triangle teaching of claim 5 and its supporting art applies a fortiori.

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7. Motivation-to-combine summary (MPEP 2144 rationales relied upon)

No teaching away. Rondeau is not limited to horizontal laboratory panels in a way that would discourage hand-held use; Lonza's cradle is a specimen holder, not a disclaimer of handheld instruments; Am. Cyanamid affirmatively praises portability. Nothing in the cited art disparages combining a cantilever scratch stylus with a flat-bottomed hand-held body.

No secondary considerations in the record. I found no evidence of commercial success, industry praise, copying, licensing, or recognition of a long-felt but unmet need attributable to these claims — and none is likely, given the patent lapsed for non-payment of the 3.5-year maintenance fee effective 1992‑12‑20, roughly four years after issuance. Absent such evidence, there is nothing to rebut the Graham prima facie case.

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8. The strongest (but still probably insufficient) non-obviousness arguments

For completeness, the best counterarguments a patent owner could press:

1. No single reference discloses the "lower handle surface as registration datum" concept. Rondeau uses legs and a separate trackway; Lonza uses a slidable cradle and a pendulum pivot; Dietert uses a base with a plunger operating perpendicular to it; Am. Cyanamid uses a rotating piston. The '807's specific insight — pressing the entire lower face of the handle flat against the coating so that the whole blade deflection, and hence the whole stylus load, is set by the handle geometry — is arguably a distinct structural arrangement in which the handle itself is the fulcrum. This is the claim's only genuinely distinctive structural feature.
2. Rondeau's load is graded/increasing along a track, whereas the '807 claims a single fixed constant load; a PHOSITA might not have seen the constant-load problem as the same as Rondeau's increasing-load problem.
3. Claim 1(d)'s wording is awkward and could be construed narrowly (a geometry defined by exactly the surface points and the blade plane), which would require precise mapping of the acute angle to the handle rather than to a trackway or cradle.

Why these are likely to fail: (i) the '807 specification frames its contribution entirely in functional terms — "constant, predetermined force," "eliminates operator-induced variables," "may be used in the field," "horizontal, vertical, or partially inclined surfaces" — all of which appear in one or another of Rondeau, Dietert, and Am. Cyanamid; (ii) changing a graded-load cantilever tester to a fixed-load cantilever tester is the removal of a feature, an even more predictable modification than its addition; and (iii) claim 1 does not positively recite the fulcrum/registration function as a limitation — it recites only "at least two points on said lower handle surface defining an acute angle with respect to said spring blade," which Lonza's 10° acute angle between specimen surface and tool arm substantially tracks.

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9. Caveats and limits on this opinion

• I could not retrieve the specification of US 3,069,892 (Gjertsen, "Machine for testing hardness and wear characteristics of abrasive materials") or verify the contents of the Williams 1937 Instruments article in this session. My characterization of Gjertsen is therefore limited to its title and class; I do not rely on it in any combination above beyond the general observation that it addresses abrasive-wear testing. The Williams article is cited here only as evidence of the state of the general knowledge in the field (scratch hardness methods), which is consistent with the routine content of Instruments in that period but which I have not independently read.
• My Rondeau load figures (300/600/1200) come from the ASTM STP‑500 historical survey's description of the Rondeau tester, not from the Rondeau patent text itself; the patent text independently confirms the cantilever spring, the stylus on the spring's free end, and the "determined entirely by the inclination of the track and the stiffness of the cantilever springs" statement.
• No claim construction exists. Because this patent was never litigated and lapsed in 1992, there is no judicial construction of "rigidly removably," "predetermined length and spring constant," or "at least two points … defining an acute angle." Different constructions materially change the mapping, and claim 1(d) in particular has an indefiniteness flavor flagged in the earlier sections.
• This is a prima facie case, not a holding. A defendant would also have the § 112 defenses flagged earlier, and an obviousness judgment would ultimately turn on the finder of fact's view of the motivation to combine.
• Minor process note: the task header states the current date as April 26, 2026, while the session date in my instructions is 2026‑09‑27. Neither affects the analysis; the relevant dates are the 1986‑11‑04 filing and the 1988‑12‑20 issuance.

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10. Bottom line

1. Claim 1 is, in my assessment, likely to have been obvious over US 2,801,540 (Rondeau) in view of US 2,130,269 (Dietert) and US 3,785,198 (Lonza) — and the same result is reached starting from US 3,289,458 (Am. Cyanamid) as primary. Each element is disclosed; the asserted advantage (operator-independent, repeatable, portable, usable on non-horizontal surfaces) was expressly the stated advantage of the cited art decades earlier.
2. Claims 2 and 3 add only removable-mounting and flange hardware, disclosed or conventional in the same references (Am. Cyanamid's detachable handle and jam-nutted load adjuster; Lonza's free-end test point). Obvious.
3. Claims 4, 5, and 6 recite stylus cross-sections — circle, equilateral triangle, and truncated equilateral triangle. Round and circular cutting edges are disclosed in US 2,436,435 (Kent); pyramid/angular points and truncated points are standard in the scratch/indentation art. With no disclosed criticality and no comparative data in the '807 specification, these are obvious design choices of a result-effective variable.
4. The '807 patent's structural core is a combination of known elements producing a predictable result, which is the paradigm KSR case. The main residual uncertainty is the narrowness of claim 1(d), and the strongest — but, in my view, ultimately unavailing — non-obviousness argument rests on reading the "handle lower surface as registration datum" concept into a claim that does not clearly recite it.