Invalidity dossier
US 421760
Added 9/21/2026, 4:02:10 AM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview: US 4,217,760 — "Oil Vaporizer and Burner"
Patentee: Ephraim Ralph, of Duluth, Minnesota (county of St. Louis). No assignee is identified.
Dates: Application filed March 8, 1889 (Serial No. 802,492); Letters Patent dated and published February 18, 1890. Google Patents lists a prior-art date of 1890-02-18 and an anticipated expiration of 1907-02-18, with legal status "Expired – Lifetime."
Purpose: To provide a burner that converts hydrocarbon fluids—crude petroleum, oil, gasoline, or benzine—into gas for heating stoves, furnaces, or boilers, and for generating steam in stoves and fireplaces "wherever heat is necessary."
Plain-language scope: A retort (shell or chamber "A," preferably flat-oval) receives hydrocarbon through a supply-pipe "P" containing a plug "S." A very small-diameter feed-regulator and safety supply-tube "E" passes through the plug; its size both minimizes back-pressure/pulsation from the generated gas and prevents flame from traveling back to the reservoir. Inside the retort, a dry-gas cylinder "D" is inserted downward through a screw-threaded top opening. Its upper end is closed, its lower open end rests on the retort bottom, its sides are perforated, and it encloses the vapor outlet—a small opening "I" at the center of the bottom. The cylinder separates "dry and complete gas" from the hydrocarbon being injected. Gas exits through "I," strikes an object placed below (brick, block, or pan), and the flame expands up and around the retort, heating the retort and feed-pipe. A stop-cock in the supply-pipe regulates fuel feed.
The single claim covers the combination of an oil-supply pipe with an oil-vaporizing retort (having a vapor outlet, a supply-opening, and a top opening) and a cylinder extending through the top opening—upper end closed, lower open end on the retort bottom, side openings—and enclosing the vapor outlet.
Not established by this excerpt: the drawing's specific geometry and proportions; the stop-cock's structure (claimed only as a combination element); any assignee, licensee, or ownership transfer; litigation or validity history; and the content of the cited or similar documents. Source: https://patents.google.com/patent/[US421760](/patent/US421760)/en
Generated 10/1/2026, 10:02:37 PM
Cases on file (0)
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Litigation summary
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Proceedings on file (0)
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No PTAB proceedings on file. This patent has not been challenged via IPR, PGR, or CBM. The absence is itself a signal — well-asserted patents eventually attract IPRs. The LLM analysis below may surface filings the ODP feed hasn’t indexed yet.
PTAB challenges
AIA trial proceedings at the USPTO Patent Trial and Appeal Board — IPR, PGR, and CBM. Petitioners, judge panels, claim-level invalidation outcomes from Final Written Decisions, and Federal Circuit appeals. The single most important defensive datapoint after litigation history.
Assignment history
Inventors, original assignee, and the chain of ownership recorded with the USPTO — including the correspondent attorney who recorded each assignment, since shell-LLC chains often share one repeat-player attorney even when the entity names look unrelated. Surfaces NPE / patent-troll patterns: shell-entity transfers, known asserters in the chain, repeat correspondent fingerprints, pre-litigation assignments, and bankruptcy fire-sales.
Prior art
Earlier patents, publications, and products that may anticipate or render the claims unpatentable.
Obviousness
Combinations of prior art that suggest the claimed invention would have been obvious under 35 U.S.C. § 103.
Extensions
Patent term adjustments, term extensions, continuations, divisionals, family members, and expiration dates.
Derivative works
Defensive disclosure: derivative variations of each claim designed to render future incremental improvements obvious or non-novel.