Invalidity dossier
US 5877794
Method for supplying ink to an ink jet recording device
Current assignee: Fujifilm Business Innovation Corp
Added 9/23/2026, 10:29:50 PM
Active provider: DeepSeek · deepseek-flash
Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 5,877,794 A
Title: Method for supplying ink to an ink jet recording device
Assignee: Fuji Xerox Co., Ltd. (original assignee)
Inventor: Jun Takagi
Key dates (as listed): Priority date 1993-03-09; application US 08/712,269 filed 1996-09-11; granted/publication date 1999-03-02; anticipated expiration 2014-03-09. Legal status listed as "Expired – Fee Related."
Purpose: The invention addresses problems in known ink supply devices. Prior absorbers of sponge or felt retained only about 40–60% of tank capacity, limiting ink utilization and hindering miniaturization; increased negative pressure could interrupt ink supply to the head, risking ejection without ink and allowing air bubbles to enter backward, causing image defects. Capillary-tube designs (cited in the text as Japanese Patent Unexamined National Publication No. Sho 59-500,609 and Japanese Patent Unexamined Publication No. Hei 1-148,559) required bending, could clog from dust or dried ink, and gave unstable negative pressure.
Plain-language scope: The ink tank has two parts. A sealed main ink chamber of fixed internal volume holds ink and connects at its lower portion to the ink jet head via a communicating passage. An auxiliary ink chamber connects to the main chamber's lower space through an open communicating passage, has an air communicating port at its top, and is packed with a porous member. Ink passes through the porous member's capillary portions to admit air bubbles into the main chamber, keeping its negative-pressure space substantially constant for stable ink supply. The porous member also lets ink temporarily escape from the main chamber when environmental changes raise pressure, preventing leakage from the head. Both chambers hold ink, improving accommodation efficiency. The porous member may be fiber bundles, felt-like fibrous material, or open-cell sponge; the head may be integral with or detachable from the tank.
Not established by this excerpt: The full claim set and their exact wording; the complete specification and any omitted description; drawing details referenced (FIGS. 1–8); prosecution history; whether the cited Japanese publications actually qualify as prior art; and current ownership or enforceability.
Generated 10/1/2026, 9:33:19 PM
Cases on file (0)
Specific litigation cases in our database that name US patent 5877794. The free-form analysis below may also discuss cases beyond this list.
No cases on file mention this patent. Upload a CSV or add a case manually in Admin → Manage litigation cases.
Litigation summary
Past and pending lawsuits — plaintiffs, defendants, jurisdictions, outcomes, and notable rulings.
Proceedings on file (0)
All PTAB activity →AIA trial proceedings (IPR / PGR / CBM) filed at the USPTO Patent Trial and Appeal Board against this patent. Sourced from the USPTO Open Data Portal and refreshed every six hours; each proceeding number deep-links to the PTAB E2E docket.
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.