Invalidity dossier
US 6315398
Thermal ink jet heater design
Current assignee: Xerox Corp
Added 9/23/2026, 10:15:10 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 6,315,398 B1
Title: Thermal ink jet heater design
Patent number / application: US 6,315,398 B1; application US 07/963,969
Assignee: Xerox Corp (original and current assignee as listed)
Key dates:
- Priority / filing date: 1992-10-21
- Publication (grant) date: 2001-11-13
- Anticipated expiration: 2018-11-13
- Status: Expired – Fee Related
Inventors: Cathie J. Burke; Narayan V. Desphande; William G. Hawkins; Dale R. Ims; Michael P. O'Horo; Gary A. Kneezel; Thomas A. Tellier; Ivan Rezanka
Purpose (per the text): The invention is directed to ink jet printing systems, and in particular to drop-on-demand ink jet printing systems having printheads with heater elements. The background explains that ink jet systems divide into continuous-stream and drop-on-demand types; in drop-on-demand, a droplet is expelled from an orifice directly to a position on a recording medium in accordance with digital data signals, and no droplet is formed unless one is to be placed on the medium, so no ink recovery, charging, or deflection is required.
Plain-language scope (per the text): The disclosed subject matter concerns thermal ink jet heater (resistive element) design and layer structure within bubble jet print heads, classified for printhead nozzle production, resistive elements, and layer structure. Prior-art keywords listed are: ink, resistive layer, wall, pit, insulative film.
Source: https://patents.google.com/patent/US6315398/en
What the excerpt does not establish:
- The full text of the claims, and therefore the precise legal scope of the invention, including specific layer materials, thicknesses, or dimensions.
- The detailed description, drawings, and any working examples or embodiments.
- The specific prior-art references relied upon or overcome.
- The full discussion of technical problems addressed beyond the general background on drop-on-demand versus continuous ink jet.
Consistent with the instruction, no litigation, ownership-transfer, validity, or prior-art analysis has been undertaken; the reassignment entries in the source are noted only as they appear and are not legal conclusions.
Generated 10/1/2026, 9:33:39 PM
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Litigation summary
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Proceedings on file (0)
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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
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.