Invalidity dossier
US 5721577
Large capacity ink cartridge
Current assignee: Cal Comp Inc
Added 9/23/2026, 11:39:27 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 5721577
Title: Large capacity ink cartridge
Patent number: US 5,721,577 A
Application number: US08/434,218
Inventors: Bruce H. Ostermeier; Allan S. Miller
Assignee: CalComp Inc. (listed as both original and current assignee)
Priority/filing date: 1995-05-04
Grant/publication date: 1998-02-24
Legal status (as listed): Expired – Fee Related; anticipated expiration 2015-05-04
Source: https://patents.google.com/patent/US5721577/en
Purpose and plain-language scope. The patent describes an improved large-capacity ink cartridge for an ink jet printer or plotter. The cartridge has an ink chamber, a pressure relief chamber coupled to it, and at least one air bleed hole connecting the two. The air bleed hole has a "capillary dimension" so that it creates a negative pressure (partial vacuum) on the ink in the ink chamber, rather than letting atmospheric pressure plus hydraulic head push ink toward the print head.
In described embodiments, the pressure relief chamber sits below the ink chamber's upper portion; the ink chamber has an opening to connect to an ink head, fitted with an automatic shutoff valve; and the air bleed hole is at the bottom of the ink chamber. A vent hole with a hydrophobic porous plug (e.g., porous Teflon) vents the pressure relief chamber. The valve has slots to avoid trapped air during filling, and a wicking plug between valve and wall acts as a surge suppressor. The specification states the capillary air bleed hole provides constant pressure and flow over the cartridge's life, backs up the print head nozzles' capillary action against leakage, and, because the pressure relief chamber is below the ink chamber's upper portion, lets the cartridge tolerate large temperature changes without leaking.
Not established by this excerpt. The supplied text does not include the full claims, the detailed description in full, or the drawings/figures referenced (FIGS. 1–7). It also does not establish prosecution history, actual claim scope as allowed, validity, infringement, or the identity or content of any prior art. Classifications and legal-status labels are as listed by the source and are not legal conclusions.
Generated 10/1/2026, 9:32:36 PM
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Litigation summary
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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
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Obviousness
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Extensions
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Derivative works
Defensive disclosure: derivative variations of each claim designed to render future incremental improvements obvious or non-novel.