US 2661416

I'll verify the patent details across the sources you named before summarizing.

The verification search surfaced important noise (FR2661416A1, CA2661416, CN2661416Y — all unrelated). Let me check the litigation/docket angle specifically.

Verification results (search performed)

Explicit uncertainty (per your instructions): I found no CAFC 2026 docket entry, no district court filing, and no PTAB proceeding involving U.S. Patent 2,661,416. I cannot confirm the absence of any historical litigation with high confidence, but given the anticipated expiration date recorded as 1970-12-01, live 2026 litigation would be highly improbable.

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Summary of US Patent 2,661,416

Source of record: https://patents.google.com/patent/[US2661416](/patent/US2661416)/en

Priority caveat: Google Patents records the Austrian priority as the placeholder string "AT2661416X", which appears to be Google's internal identifier rather than a genuine Austrian application number. I could not verify the actual Austrian serial from authoritative sources.

Abstract

No formal abstract appears in the granted text — 1953-era US patents were not required to carry one. The Google Patents page renders a "Definitions" block (machine-derived from the specification) in that position; it should not be treated as an as-filed abstract. The nearest as-filed statement of scope is the "objects" passage and claim 1.

Plain-language overview of the claims

Claim 1 — Weld head (structural).
At least two plate-shaped electrode holders sit side by side in a common plane. On their mutually facing edges are projections that stick out beyond the plane of the plates. The projections from the two holders intermesh like gear teeth along the welding line, with an insulating gap left between adjacent projections of different polarity. Those projections themselves are the weld electrodes.

Claim 2 — Weld head with twin (double-length) electrodes.
Same intermeshing-plate arrangement, but the projections are of two lengths: normal-length projections plus projections of twice the length, arranged in alignment on the facing edges. The long projections each act as a twin electrode serving two adjacent double-spot welding stretches — i.e., they let one electrode participate in two neighbouring weld pairs simultaneously.

Claim 3 — Welding appliance (system-level, independent).
Combines the weld head with its power source: an annular-core transformer whose casing is split into two halves and serves as the secondary conductor. Two plate-shaped electrode holders, side by side in a common plane, are each mechanically and electrically connected to one half of the split casing and insulated from the other half. The holders are bolted to butt faces of the casing and span the insulating gap between the halves, each holder being insulated from the opposite half by the shape of its underside. At least one pair of integral electrodes per holder projects from the common plane and intermeshes gear-teeth-fashion along the welding line, with an insulating gap between them. This is the claim that captures the "no cumbersome leads / no conduction-loss secondary leads" advantage stated in the objects.

Claim 4 — Dependent on claim 3.
Specifies that the underside of each plate-shaped holder is stepped, so it attaches to the butt face of its own half of the transformer casing while leaving an insulating gap between the portion overhanging the other half and that half's butt face.

Contextual notes from the specification

• The embodiment details a four-electrode head (Fig. 1–4): holder 4a carries outer electrodes 5a/6a; holder 4b carries middle electrodes 7b/8b combined as a double electrode.
• Electrode cross-section may be "roof-shaped" (Figs. 1–2); a plastic insulating cover plate with a slot may cap the head.
• For wire-grid welding, longitudinal wires run perpendicular to the welding stretches and transverse wires run parallel to them; pivoted, highly conductive (copper) pressure punches bridge each double-spot stretch, acting as a current shunt/bridge to reduce losses in the transverse wires.
• Exchangeability: heads of equal width with identical screw-hole disposition can be swapped to change from four spots to six spots across the head width (Figs. 6a/6b), and multiple heads may be arrayed side by side with separate current sources to extend the weld row beyond one head's width.

Prior art cited on the face of the patent (6 references)

US1103041A (Fulda, "Multiweld secondary"); US1581868A (Reed, electric welding machine); US1878760A (Hume Steel Ltd, metallic netting/mesh manufacture); US1996901A (Northrop Corp, welding apparatus); US2033616A (Fassler, welding machine); US2588062A (Northwestern Steel & Wire Co, electrode arrangement for fence welding machines).

Cited by (1): US2827546A (Fruengel, method/device for cooling electric resistance welding machines).

OCR/transcription caveats

The fetched full text is OCR-derived and contains garbled tokens (e.g., "electrode holders ea and 4b" for 4a/4b; "01 difierent polarity" for "of different polarity"; "artificial plastics" partially mangled). I have not "corrected" these in a way that changes any claim scope; where a claim term was ambiguous in the OCR, I relied on the parallel recitation in the specification and the cleaner claim-3/claim-4 text.

I'll search for litigation involving US patent 2661416. Let me run several targeted searches.

The first two searches returned unrelated results. Let me try more targeted patent-litigation sources.

Summary of Search Results

I searched for litigation involving US Patent 2,661,416 ("Welding head for simultaneously effecting a series of spot welds according to the double spot method," Kuno Eisenburger, assignee EVG Entwicklungs und Verwertungs GmbH, granted Dec. 1, 1953; Austrian priority Jan. 18, 1951).

No litigation involving US Patent 2,661,416 was found.

I could not identify any case — no plaintiff, defendant, jurisdiction, case number, or filing date — in which this patent was asserted or challenged. Searches of modern patent-litigation aggregators (Unified Patents Portal, CourtListener/RECAP) and general web sources returned only unrelated hits (e.g., a "CVE 2661416" Chilean corporate notice, a different patent family, and various "266" patents such as the DMF v. Elco '266 patent, which is a different, unrelated patent). None concerned US 2,661,416.

Important Caveats on Why This Is Likely a True Negative

I want to be explicit rather than imply a comprehensive negative:

1. The patent is long expired. The record shows the anticipated expiration date as December 1, 1970 (17 years from the 1953 grant). Any enforcement litigation would therefore have been filed roughly between 1953 and 1970.

2. Pre-digital-era cases are poorly covered. CourtListener/RECAP and the Unified Patents Portal predominantly cover federal litigation from the 2000s onward (and RECAP largely from 2000s–present). A 1950s–60s district-court infringement suit — especially one that settled, was un-reported, or involved a foreign (Austrian) patentee — would generally not appear in these databases even if it existed. I cannot rule out an un-digitized 1950s–60s case based on the searches performed.

3. The search tools available did not include a direct case-list query against the Unified Patents litigation caselist via API, PACER, or the Federal Circuit docket for this specific number — I relied on keyword web searches, which are not exhaustive for historical records.

Recommendation

If a definitive, exhaustive answer is required, it would need to be confirmed by:

• Docket Navigator / Lex Machina historical coverage (best commercial source for pre-1990s patent cases),
• Direct PACER queries for the 1950s–60s, and
• Manual review of the patent's USPTO file history / assignment records (which can reference related litigation and license disputes).

Based on the information available and the searches conducted, there is no known litigation involving US Patent 2,661,416. I state this with the caveat that the absence is likely due to the patent's age and the limited historical coverage of the databases searched, rather than a positive confirmation that no such suit ever existed.

I'll verify the structured data with a couple of targeted searches before writing.

PTAB / AIA Trial Landscape — US 2,661,416

Proceedings overview

There are zero AIA trial proceedings on file for US 2,661,416 — no IPRs, no PGRs, no CBMs. The USPTO Open Data Portal structured block reports no AIA trial proceedings, and targeted web searches surfaced no PTAB or Federal Circuit activity for this patent number. The breakdown by status is therefore: active 0 / claims invalidated 0 / claims sustained 0 / settled 0 / institution denied 0 (no filings at all).

The bottom line for a defendant is not the IPR-flavored "hardened" or "invalidated" posture the prompt anticipates — it is more fundamental: US 2,661,416 issued 1953-12-01, was filed 1952-01-07 on a 1951-01-18 Austrian priority, and its term expired 1970-12-01 per the Google Patents legal-status record ("Anticipated expiration"). A 1953 patent with a 1970 expiration is long dead as an enforceable right, and the absence of any AIA trial is explained by that, not by the patent having withstood attack. If a demand letter or infringement contention cites US 2,661,416, the threshold response is a standing/expiration objection, not an invalidity theory.

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For each proceeding

None exist. Because the instruction is explicit — "Do not invent proceeding numbers" — I am not populating the per-proceeding template with placeholders or fabricated trial numbers. There is no IPR20XX-#####, no petitioner, no panel, no Final Written Decision, and no appeal to report here. Any AIA trial number you may see associated with a "welding head" or "double spot method" patent belongs to a different patent (e.g., modern wire-welding and mesh-welding patents such as those asserted in the PTAB filings surfaced in search, which concern unrelated patents like U.S. 8,747,116 and 9,293,057 and are not this patent).

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Strategic summary

Claim status: all four claims are UNTESTED at the PTAB — but untested because the patent is expired, not because it is unimpeachable. Claims 1 and 2 are the apparatus claims (plate-shaped electrode holders with gear-teeth-meshing projections serving as weld electrodes; claim 2 adds twin/ double-length projections acting as a twin electrode for two adjacent double-spot stretches). Claims 3 and 4 are the appliance claims tying the holders to a split-casing annular-core transformer secondary (claim 4 reciting the stepped underside). No claim has been canceled, confirmed, or construed by the Board, because the Board has never had a petition. Do not tell anyone that claims 1–4 were invalidated — they were not. Likewise, do not represent that the patent "survived" any challenge.

Estoppel landscape: § 315(e)(2) is a non-issue because there has been no IPR, PGR, or CBM. No petitioner exists to be estopped, and no privity chain bars anyone. If a defendant were somehow facing an assertion of this patent (it cannot lawfully be asserted now given the 1970 expiration), the entire prior-art universe would remain available — including the six references cited on the face of the patent (US 1,103,041 Fulda; US 1,581,868 Reed; US 1,878,760 Hume Steel; US 1,996,901 Northrop; US 2,033,616 Fassler; US 2,588,062 Northwestern Steel & Wire) and post-issuance art from the intervening 55+ years of wire-mesh and resistance-welding development. No estoppel, no § 325(d) discretion problem from prior Board findings, no IPR record to work from or against.

Pattern signals: none. There is no repeat petitioner, no defensive aggregator (no Unified Patents, RPX, etc.) in the chain, no PTAB appeal history, and no district-court-then-PTAB "parallel track." The only forward citation in the record is US 2,827,546 (Fruengel, assigned out to a cooling method for resistance welding machines), which is a citation, not a challenge. The current listed assignee is EVG Entwicklungs- und Verwertungs GmbH (Austria), which is the same entity that filed the 1952 application — a continuity of ownership consistent with a legacy corporate portfolio rather than an active assertion campaign.

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Recommended next steps

1. If you are a defendant receiving a demand citing US 2,661,416: the patent's term expired 1970-12-01. Check whether the letter is a misfire (wrong patent number), a portfolio-rhetoric bluff, or part of a bundle. If any suit has actually been filed on this number, the first responsive filing is a Rule 12(b)(6) motion premised on expiration/lack of enforceable term, not an IPR. There is no FWD to link to because none exists — cite the Google Patents legal-status entry at https://patents.google.com/patent/US2661416/en showing "Anticipated expiration 1970-12-01, Expired – Lifetime."

2. If you need to characterize the patent's substance (e.g., in a freedom-to-operate clearance for a modern mesh-welding line), treat 2,661,416 as public-domain prior art, not as a live right. Claims 1–4 are usable as § 102/§ 103 art against later patents, and the specification's disclosure (split-casing annular-core transformer secondary with plate electrode holders intermeshing gear-teeth-fashion along the welding line) is a useful § 102(b) reference for any post-1953 mesh-welding claim.

3. If you were expecting a PTAB record and found none: the absence here is explained, and it is not the "well-asserted patents eventually attract IPRs" signal. This patent predates the AIA by roughly six decades; its enforceable life ended before the Federal Circuit existed. Confirm against PTAB E2E (https://ptab.uspto.gov) with the patent number and against CourtListener (https://www.courtlistener.com) for any CAFC docket — my search found no appellate activity on this number.

4. Verify before relying: the ODP structured block is your canonical source for "no AIA proceedings," and I confirmed it via web search, but I found no affirmative negative statement from the USPTO itself — only absence of results. If the stakes are high, run the patent number directly through PTAB E2E and the USPTO Patent Center assignment/legal-status record before taking a position in a filing.

I'll research the assignment record for US 2661416 across the USPTO Assignment Center, Google Patents legal events, and corporate records for the original assignee.

Good context on the assignee. Now let me check the specific assignment records and any litigation/NPE activity linked to EVG.

Assignment & Ownership Analysis — US Patent 2,661,416

Critical database limitation up front: The USPTO Assignment Center (Assignments on the Web / AOTW) only contains assignment records submitted since August 1980 (per Finnegan's Prosecution First guidance and USPTO practice). US 2,661,416 issued 1953-12-01 and its term expired 1970-12-01 — a decade before the electronic assignment database began. Therefore, any pre-1980 assignment of this patent is invisible to the Assignment Center and cannot be reconstructed from it. This is a coverage gap, not a finding that no assignment occurred. I state this explicitly because the task's premise (that the Assignment Center will surface reels/frames for this patent) does not hold for a patent of this vintage.

I also cross-checked the Google Patents legal-events record supplied in the authoritative full text: it lists only Application filed (1952-01-07), Application granted (1953-12-01), Publication (1953-12-01), and Anticipated expiration (1970-12-01). There is no AS (Assignment) legal event of the kind that appears for newer EVG patents (e.g., US 18/692,085, US 5,447,110, which do show AS — ASSIGNMENT OF ASSIGNORS INTEREST entries with reels such as 006814/0190). The absence of any AS event on this record is consistent with an assignment executed and recorded long before 1980.

Inventors

• Kuno Eisenburger — sole named inventor. At the time of filing (Austrian priority 1951-01-18; US filing 1952-01-07) he was associated with, and an assignor to, EVG Entwicklungs- und Verwertungs-Gesellschaft m.b.H. of Graz, Austria — the firm he co-founded. A German-language biographical source (siebenbuerger.de) records that Eisenburger was a prolific Austrian engineer and that "nach dem Weltkrieg waren es Schweißmaschinen für jede Art von Stahlgittern, die eine mit ihm in Graz gegründete Firma erzeugt" (after the war, welding machines for every kind of steel grid were produced by a firm founded with him in Graz) — i.e., EVG.

Pattern notes (for completeness, not NPE signals): Eisenburger appears as an inventor/assignor on a cluster of contemporaneous EVG welding patents, e.g. US 2,678,367 and US 2,900,830 (the latter listing "Kuno Eisenburger, Wels, Upper-Austria, and Josef Ritter, Graz, Styria, Austria, assignors to EVG"). His listed residence shifts from Graz to Wels between 1951 and 1959 — a relocation, not a departure from the assignee. There is no evidence of inventors leaving the original assignee within 12 months of filing; the inventors remained EVG assignors for years. This is the opposite of a pre-fire-sale exodus.

Original assignee

EVG Entwicklungs- und Verwertungs-Gesellschaft m.b.H. (also styled "EVG Entwicklungs- u. Verwertungs-Gesellschaft m.b.H."), Graz, Austria (headquarters now at Gustinus-Ambrosi-Straße 1-3, 8074 Raaba-Grambach, near Graz; Austrian Firmenbuch FN 56324 f).

• Line of business: mechanical engineering — design and manufacture of wire-mesh welding lines, grid/grating welding machines, reinforcing-steel processing machines, and turnkey mesh plants. Founded 1949; today a self-described world market leader with 500–600+ employees, subsidiaries including EVG Inc. (New York) and EVG OOO (Moscow).
• Did they ship a product embodying the claims? Yes. EVG's core business is the wire-grid resistance-welding machine; this patent's weld head (multiple electrodes as gear-tooth intermeshing projections on plate holders, fed by a split annular-core transformer secondary) is directly in EVG's product line. The patent's own specification frames the weld head for "the welding of grids or netting of wire."
• Current status: Operating. EVG remains an independent, active Austrian manufacturer and continues to file US patent applications (e.g., pending US 18/692,085 "Welding device for wire meshes," 2022). It has not been acquired, dissolved, or placed in bankruptcy, and shows no indication of ever being a portfolio seller.

Assignment timeline

The USPTO Assignment Center has no retrievable records for US 2,661,416, and none are reconstructed here.

Reason, stated plainly:

1. The AOTW database only covers recordings made from August 1980 forward; this patent's ownership events predate that window.
2. The Google Patents legal-events record shows no AS assignment entries for this patent.
3. Google Patents lists the Current Assignee as EVG Entwicklungs und Verwertungs GmbH — identical to the Original Assignee — which is consistent with the patent never having left EVG.

Accordingly, I cannot provide reel/frame numbers, conveyance types, execution/recording dates, or correspondents of record for this patent, and I will not fabricate them. No correspondent attorney or recording firm can be identified for this chain; the "repeat correspondent" signal is therefore untestable.

Timeline diagram

timeline
    title Ownership of US 2661416
    1949 : EVG founded in Graz Austria
    1951 : Austrian priority application filed
    1952 : US application filed by EVG
    1953 : Patent US 2661416 granted to EVG
    1970 : Patent expires with no recorded transfers

NPE / troll-pattern signals

Assessed against the available record. Because the assignment database is blank for this vintage, most signals are not present on the evidence rather than positively disproven.

1. Shell-entity transfer — Not present. No assignment to any IP/Patents/Licensing/Holdings entity is recorded; the current assignee remains the original operating manufacturer, EVG.
2. Known asserter in the chain — Not present. EVG does not appear on any RPX / Unified Patents / IPNav / Acacia / Marathon / IV asserter list. No NPE name is associated with this patent number. (Cross-referencing the earlier litigation section: no assertion suit naming this patent was found either.)
3. Repeat correspondent across the chain — Unclear / not testable. No correspondent-of-record data exists in the retrievable record because no post-1980 recordings exist for this patent.
4. Cascading transfers — Not present. No chained LLC-to-LLC transfers; no recorded transfers of any kind in the electronic era.
5. Pre-litigation transfer — Not present. No litigation and therefore no transfer timed to precede one.
6. Bankruptcy fire-sale — Not present. EVG has operated continuously since 1949 and is currently active; there is no Chapter 7/11 event and no patent sale in proceedings.
7. Privateering — Not present. EVG did not transfer to an NPE for assertion against competitors; EVG remains the owner and itself practices the technology.
8. Defensive aggregator (anti-NPE) — Not present. The chain does not terminate at RPX, AST, LOT, Unified Patents, or OIN; there is no evidence the patent was acquired for defensive neutralization either.

Verdict

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

Justification: The USPTO Assignment Center returns no assignment records for US 2,661,416, and the Google Patents legal-events record shows only the original filing/grant/expiration with no AS entries, listing EVG Entwicklungs und Verwertungs GmbH as both original and current assignee. Because the AOTW database starts in August 1980 and this patent expired 1970-12-01, the absence of records is a database-coverage artifact rather than positive proof of no transfer — so a definitive ownership-chain conclusion is not supportable. On the evidence that does exist, every NPE/troll signal is not present: the assignee is a long-standing, still-operating Austrian machinery manufacturer that practices the patented weld-head technology in its own products.

Verification links:

• USPTO Assignment Center (search by patent number): https://assignmentcenter.uspto.gov/
• USPTO legacy Assignment Search (AOTW, same underlying records, post-Aug-1980): https://assignment.uspto.gov/patent/index.html
• Google Patents record (legal events, original/current assignee): https://patents.google.com/patent/US2661416/en

Caveat: A definitive pre-1980 chain would require manual review of the paper assignment records (pre-1980 reels held by the USPTO Assignment Recordation Branch) and the patent's file history — sources not reachable through the online Assignment Center for a patent of this era.

I'll research the patent and each of its cited references. Let me run the searches.

Let me research each cited reference individually.

Prior-Art Analysis — US Patent 2,661,416

Important method note up front: My verification workflow was cut short (search-step limit) partway through retrieving the full text of the six cited references. Below I separate (A) what is verified from the authoritative patent record (the Google Patents/ USPTO bibliographic data reproduced in the source text you provided), from (B) my reasoned, clearly-labeled preliminary relevance assessment, which is based on the references' titles, dates, assignees and the technical field, not on a full-text/claim-by-claim reading of each reference. I did not want to fabricate claim language I could not retrieve.

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1. Confirmation of the target patent (specific number 2,661,416)

From the authoritative record (source: patents.google.com/patent/US2661416/en):

Note a recurring identifier-confusion hazard: the application number is US 265,344 and the patent number is 2,661,416. Those are distinct. Any search returning a "265344" document is the same family — the application — not a different patent.

Statutory caveat: this patent expired 1970-12-01. It cannot be infringed today, so "anticipation" here is a historical/validity question only.

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2. The cited references (verbatim from the patent's "Citations (6)" list)

All six were listed as "Cited by examiner" (i.e., cited during prosecution — the strongest signal of relevance). The dates below are exactly as listed in the record; for these pre-1930 patents the "priority date" column is effectively the filing date.

Forward citation (not prior art): US2827546A (Fruengel, filed 1954-12-13, published 1958-03-18, "Method and device for cooling electric resistance welding machines") cites 2,661,416. This is a later document and cannot be § 102 art against 2,661,416; it is only relevant to show the field continued, and possibly as § 103 background if ever needed.

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3. The claims to be measured against the art (verbatim subject matter)

• Claim 1 — Weld head: ≥2 plate-shaped electrode holders side by side in a common plane; projections on the facing edges that project beyond the plane of the plates and intermesh gear-teeth fashion along the welding line, with an insulating gap between adjacent projections; the projections serve as the weld electrodes.
• Claim 2 — As claim 1, plus projections of predetermined length and projections of twice that length in alignment, each double-length projection serving as a twin electrode for two adjacent double-spot stretches.
• Claim 3 — Welding appliance: annular-core transformer whose split casing serves as the secondary conductor; two plate-shaped holders, each electrically + mechanically connected to one half of the split casing and insulated from the other half; holders attached to the butt faces and extending across the insulating gap; each holder insulated from the opposite half by the shape of its underside; ≥1 pair of integral electrodes intermeshing gear-teeth fashion with an insulating gap.
• Claim 4 — As claim 3, where the underside of each plate-shaped holder is stepped to attach to its own half's butt face while leaving an insulating gap over the other half's butt face.

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4. Preliminary relevance / potential § 102 anticipation assessment

Because the distinctive limitation of the invention is the "intermeshing gear-teeth projections that project beyond the plane of plate-shaped holders" (claims 1 and 2) and the split-transformer-casing-as-secondary with plate holders spanning the gap (claims 3 and 4), the references sort roughly as follows. These are hypotheses to be confirmed against full text; I was unable to complete that full-text pull.

Most likely relevant (multi-electrode mesh/fence welding):

• US2588062A — Northwestern Steel & Wire, "Electrode arrangement for fence welding machines" (pub. 1952-03-04).

  • Why: same assignee class of art (wire fence/mesh welding), and it is the closest in time (published ~10 months before this patent issued, filed 1948). An "electrode arrangement" for welding many wires simultaneously is exactly the environment of claims 1–2.
  • Potential § 102 target: claims 1 and 2 — if its electrode arrangement shows side-by-side holders with interleaved/intermeshing electrode projections separated by an insulating gap. This is the single best candidate for the primary reference; it is also the natural § 103 combination base.

• US1878760A — Hume Steel Ltd, mesh/netting manufacture (pub. 1932-09-20).

  • Why: expressly directed to welding metallic meshing/netting/fabric — the commercial use stated in the specification (longitudinal + transverse wires). Likely discloses multiple cooperating electrodes acting on crossed wires.
  • Potential § 102 target: claim 1 (multiple electrodes in one head welding a series of crossings), and background for claims 2–3.

Relevant to the current-source / secondary-conductor limitations (claims 3–4):

• US1103041A — Edward Fulda, "Multiweld secondary" (pub. 1914-07-14).

  • Why: the title itself addresses a "multiweld secondary" — i.e., a transformer secondary arranged to feed multiple weld points. This is the most on-point reference for the "several pairs of electrodes supplied by a common source in parallel" objective and for the secondary-conductor aspect of claim 3.
  • Potential § 102 target: claim 3 (to the extent it discloses a single secondary serving multiple electrode pairs). If it shows a split secondary / split casing, it becomes directly material to claims 3–4.

• US1581868A — Reed, "Electric welding machine" (pub. 1926-04-20). General resistance-welding machine; probable art on welding-machine construction/electrode mounting. Candidate against claim 1 only if it discloses plural intermeshing electrodes; otherwise § 103 background.

• US1996901A — Northrop Corp, "Welding apparatus" (pub. 1935-04-09). Multi-spot welding apparatus art. Candidate against claims 1–2 if it shows plural electrode holders in a common plane; needs full-text confirmation.

• US2033616A — Peter W. Fassler, "Welding machine" (pub. 1936-03-10). General welding-machine art; weakest of the six on its face. Most likely § 103 background (electrode holders / pressure arrangement) rather than § 102.

Ranking: (1) US2588062A, (2) US1878760A, (3) US1103041A, (4) US1996901A, (5) US1581868A, (6) US2033616A.

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5. What I could and could not verify (honesty statement)

• Verified: the bibliographic data of all six cited references and of 2,661,416, as reproduced from the patent record; the fact that all six were examiner citations; claim numbering/structure (4 claims) and their subject matter.
• Not verified: the actual disclosure text and claims of the six references. My targeted search for US1103041A returned no results, and my attempts to pull the others were interrupted at the step limit. Accordingly, the § 102 mappings above are preliminary relevance hypotheses and must be confirmed against each reference's full text before being relied on. Under § 102 a reference anticipates only if it discloses every element of the claim (e.g., for claims 1–2, specifically the projections that project beyond the plate plane and intermesh gear-teeth fashion); a title-level match is not sufficient.
• Not auto-corrected: I treated "2661416" strictly as US 2,661,416 and did not substitute any similar number. Application 265,344 is treated as the same family (the application, not a separate patent), not as a citation.

To complete this reliably, the next step is a full-text retrieval of US2588062A and US1103041A first (Google Patents PDF or USPTO Patent Public Search / PatentCenter, which also carries the prosecution file history where the examiner's reasons of allowance or rejection for these six citations would be recorded), then US1878760A, US1996901A, US1581868A and US2033616A.

I'll ground the obviousness analysis by pulling details on each prior-art reference, then build the combination analysis.

Let me pull specifics on the remaining cited references, especially the Fulda "Multiweld secondary," Reed, Fassler, and Northwestern Steel & Wire references.

Obviousness Analysis — US 2,661,416 under 35 U.S.C. § 103

Building on: the Patent summary (claims 1–4 breakdown, prior-art list) and Litigation summary already generated. This section does not repeat those; it applies them.

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0. Two threshold flags before the merits

(a) Which § 103 standard governs. The application was filed 7 January 1952 and the patent issued 1 December 1953. The Patent Act of 1952's § 103 took effect 1 January 1953. A modern (2026) obviousness challenge to a patent that issued in 1953 is legally academic — the patent expired on the anticipated expiration date of 1 December 1970 and is long unenforceable. For a hypothetical validity analysis, the honest answer is that two different standards yield two different answers:

• Modern KSR/Graham frame (what your question asks for): the claims are, in my assessment, likely invalid — the asserted contribution is an arrangement of admittedly known elements.
• Contemporaneous 1953 frame: at issuance, the governing standard was the strict "invention" test of Cuno Engineering Corp. v. Automatic Devices Corp. (1941) ("flash of creative genius") and Great Atlantic & Pacific Tea Co. v. Supermarket Equipment Corp. (1950). Under that standard a compact, commercially successful combination of known elements stood a materially better chance of being sustained. I flag this because the answer changes with the era, and a good-faith § 103 opinion must say so rather than pick one silently.

(b) Admission against interest in the specification. The specification repeatedly characterizes key features as "known per se" or as belonging to an "aforesaid older proposal." Specifically:

• The double-spot method itself: "The invention relates to … the double spot method wherein both electrodes are arranged on the same side …" — treated as prior, not invented here.
• The alternating-polarity/intermeshed layout: "…it is convenient to make the arrangement of the electrodes in accordance with the aforesaid older proposal in such a manner, that pairs of adjacent inner electrodes … have the same polarity…"
• Pressure punches bridging the stretches are used "in a manner known per se."
• Extending the weld row beyond the head width "can be attained in a known manner by arranging several weld heads side by side with separate sources of welding current."

Under MPEP 2129 / Atofina v. Great Lakes Chem. Corp., an applicant's own characterization of subject matter as known prior art is usable against the claims. These statements shrink the claimed contribution to: (i) making the intermeshed projections integral plate teeth, (ii) doubling the length of some teeth, and (iii) bolting the toothed plates onto the two halves of a split-casing transformer. That framing drives everything below.

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1. Level of ordinary skill in the art (PHOSITA)

A designer/engineer with roughly 3–5 years' experience in resistance spot-welding equipment, specifically multi-point mesh, fence, and grid welding machinery, familiar with: split-casing/toroidal welding transformers and their secondaries; electrode holders and pressure-actuating (hydraulic/pivoted) systems; shunt-current behavior in grid welding; and the double-spot (same-side electrode) method. The references themselves establish that this level of skill included knowledge of series current paths through multiple electrodes, insulation gaps between opposite-polarity electrodes, and minimization of secondary-lead impedance (see US1996901A discussion below).

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2. The prior art as established by the record

From the "Prior Art" section of the page, the six face-cited references and one cited-by reference:

Grounding I was able to verify this session. I retrieved the claim text of US1996901A (Northrop), which is decisive for the motivation analysis:

• Claim 1: "a pair of insulated electrodes connected to said source and mounted to contact the same side of a unitary work sheet to be welded, a pair of connected electrodes mounted to contact the other side…"
• Claim 3: "…means for connecting certain adjacent electrodes apart from said sheet, and means insulating the connected electrodes from other electrodes on the same side of the work to form a series path for the welding current through said electrodes repeatedly threading the work."
• Specification: "one of the objects of this invention is to provide a machine wherein the lengths of secondary leads is reduced to a minimum"; and a further object is "the reduction of the charge thus imposed against the work by forming a plurality of welds at the same time"; electrodes are described as "highly conductive bodies" (copper).

Explicit uncertainty: I could not retrieve the full specifications of US1103041 (Fulda), US1581868 (Reed), US1878760 (Hume), US2033616 (Fassler), or US2588062 (Northwestern) in this session. Statements below about what those references show are therefore flagged as (i) what the examiner's citation and title support, and (ii) what a PHOSITA would infer. Where a firm conclusion depends on the unretrieved disclosure, I say so. US2588062 in particular governs the strength of the claim-1 challenge and should be read in full before relying on this opinion.

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3. Claim 1 — the structural weld head

Claim 1 elements (as recited):

Mapping:

• 1a, 1b, 1c, 1f — A plate holder with edge projections that are themselves the electrodes is a comb/rack-shaped electrode bar. Given that the specification admits the electrodes are "made in one piece with the holder" as an expedient to avoid conduction loss, and given US1996901 teaches electrodes as "highly conductive bodies" integral with self-aligning mounts and yokes, integral-plate electrode holders are squarely within the skill level. US2588062 (electrode arrangement for fence welding machines) is the natural primary reference for a row of holders along a fence-welding line.
• 1d, 1e — The intermeshing gear-tooth layout with an insulating gap between opposite-polarity neighbors is the essence of alternating-polarity multi-spot welding. Two independent supports: (i) US1996901's express teaching of "insulating the connected electrodes from other electrodes on the same side of the work" to define a series path; and (ii) the applicant's own admission that alternating/intermeshing disposition follows the "aforesaid older proposal."

Motivation to combine (KSR rationales (a), (c), (f)):

1. Same field / same problem. All references are directed to making multiple resistance spot welds simultaneously in mesh, fence, or sheet work — the field of endeavor and the problem addressed are identical.
2. Interdigitation solves a recognized design constraint. Packing N electrodes of alternating polarity into the minimum weld-line pitch requires interleaving. Gear-tooth intermeshing is the predictable mechanical way to do it, and it simultaneously provides the required insulating gap in the inter-tooth space.
3. Predictable result, no new function. Each element (plate holder, projection, gap, electrode) performs exactly its known function; the combination is an arrangement of known parts, not a new mode of operation — the classic ground of § 103.

Assessment: Claim 1 is likely obvious over US2588062 in view of US1996901 (and, for the mesh context, US1878760). Strength of this conclusion is moderate and hinges on the unretrieved full text of US2588062; if US2588062 discloses only non-intermeshing tandem electrodes, the combination still works but requires more reliance on US1996901's insulation/series-path teaching.

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4. Claim 2 — twin (double-length) electrodes

Added limitation: projections of a predetermined length plus projections of twice length, aligned on facing edges, each long projection serving as a twin electrode for two adjacent double-spot stretches.

Why this is obvious:

1. The specification supplies the motivation itself. The patent explains that in an alternating-polarity head "the outer electrodes would have one adjacent opposite electrode only, and would accordingly carry a weaker welding current," and that the long/twin electrode arrangement is adopted "in order to supply all points of weld with the same current intensity." Equalizing current distribution among electrodes is a recognized, pre-existing objective of the art — cf. US1996901, whose entire thrust is equalized pressure and current distribution among opposed electrode pairs via equalizing yokes and common hydraulic supply.
2. Altering electrode contact length to change current density is a routine design variable — a PHOSITA adjusting electrode geometry to equalize current is doing ordinary optimization, not invention (KSR: "a court must ask whether the improvement is more than the predictable use of prior art elements according to their established functions"; and the "obvious to try" / "design choice" rationales).
3. Result is fully predictable: a double-length tooth bridging two adjacent stretches is the geometric sum of two known single electrodes and performs the known bridging function the (admittedly known) pressure punches already performed for the current path.

Assessment: Claim 2 is likely obvious over the claim-1 combination in view of the current-equalization teaching of US1996901 (with US2588062 supplying the multi-electrode fence-welding row). The claim reads as a design choice to equalize current, recited without any unexpected result.

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5. Claim 3 — the welding appliance (independent, system level)

Claim 3 elements:

Mapping and motivation — this is the claim most exposed to § 103:

• 3a — A split-casing toroidal (annular-core) transformer whose casing is the secondary was a known resistance-welding power-source topology; US1103041 (Fulda, "Multiweld secondary") is cited precisely for a secondary supplying multiple weld points, and the specification of US 2,661,416 introduces this transformer as an assumption ("it is assumed that an annular core transformer having a casing serving as a secondary conductor is used"). That is an admission that the power source is not the inventive contribution.
• 3c, 3d, 3e — Mounting the electrode holders directly onto the two halves of the split secondary casing, spanning the gap and insulated from the opposite half, is the structural consequence of the admitted objective: eliminating secondary leads. That objective is expressly stated in the prior art — US1996901: "one of the objects of this invention is to provide a machine wherein the lengths of secondary leads is reduced to a minimum," and its specification explains that "the potential drop in these conductors, both resistive and reactive, forms a large portion of the total impedance in the welding circuit" and that conductors "should preferably be as short as it is possible to make them."

Motivation to combine: The problem (secondary-lead impedance and connected-load waste at the very high currents of spot welding) and the solution direction (bring the secondary conductor to, or make it integral with, the electrode holders) are taught by US1996901; US1103041/Fulda supplies the multi-weld secondary; and the split-casing-as-secondary transformer is a known building block. Combining them to bolt toothed plate holders directly onto the two secondary halves is the predictable mechanical realization of a stated goal, with no change in the function of any element. This is the strongest single-reference-plus-rationale case in the patent.

Assessment: Claim 3 is likely obvious over US1103041 in view of US1996901 (with US1581868/Reed and US2033616/Fassler corroborating multi-electrode machine arrangements).

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6. Claim 4 — stepped underside (dependent on claim 3)

Added limitation: the underside of each holder is stepped, so it attaches to its own half's butt face while leaving an insulating gap between the overhanging portion and the other half's butt face.

Why this is obvious: Claim 3 already requires insulation of each holder from the opposite half. Claim 4 merely recites one specific geometry — a step/rabbet — for achieving a clearance/creepage gap that claim 3 already mandates, and the specification itself calls it a "suitable shape of its underside." Where the only difference from the prior art is a change in shape that does not change the operation or result, the claim is obvious as a matter of routine engineering (In re Kuhle; Gardner v. TEC). The step performs no function beyond the insulation already required by claim 3.

Assessment: Claim 4 is likely obvious as an obvious mechanical expedient in view of the claim-3 combination, and independently as a design choice (spacer, rebate, counterbore, or step are interchangeable known ways to maintain an insulating gap).

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7. Secondary considerations — and why they don't rescue the claims on this record

• Commercial success of EVG mesh welders is plausible but unproven here, and to be probative must be tied by nexus to the claimed features rather than to the double-spot method (admitted prior art) or to market factors.
• Long-felt need for reduced secondary losses cannot carry the claims because US1996901 (1935) already identifies and addresses that need — a "known" need that the art had already begun to solve.
• "Simplicity and compactness" (the stated objects) are advantages of degree, not unexpected results, and are precisely what a combination of known compact elements predictably yields.
• The applicant's own statements that the intermeshed alternation comes from the "aforesaid older proposal" and that several cooperating features are "known per se" affirmatively undercut any argument that the arrangement produced an unexpected or synergistic result.

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8. Bottom-line combination table

Overall assessment (explicitly conditional): Under a modern KSR/Graham § 103 analysis, claims 1–4 appear invalid as obvious. Under the contemporaneous 1953 standard (Cuno/A&P Tea), the same claims could plausibly have been sustained as a compact and useful combination — which is consistent with the patent having issued. Because the patent has been expired since the recorded anticipated expiration date of 1 December 1970, this analysis has no live enforcement consequence.

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9. Limitations of this analysis (stated rather than glossed over)

1. Unverified reference contents. I retrieved the claim/description text of US1996901A but not the full texts of US1103041, US1581868, US1878760, US2033616, or US2588062. My characterizations of those are based on their titles/assignees as recorded in the Prior Art section plus art-level inference, and are flagged as such.
2. US2827546 (Fruengel) post-dates the 7-Jan-1952 filing and is therefore not available as § 103 prior art; I have not used it as such.
3. US2588062 is decisive for the strength of the claim-1 challenge and should be read in full (claims and drawings) before this opinion is relied upon.
4. No prosecution-history/intrinsic-evidence review was performed here; the file wrapper would show whether the examiner relied on any of the above references under § 103, and on which claims, at allowance.