Invalidity dossier
US 7257336
Developing device, image forming device equipped therewith, and developing density adjusting method
Current assignee: Sharp Corp
Added 9/23/2026, 5:18:41 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview: US 7,257,336 B2
Title: Developing device, image forming device equipped therewith, and developing density adjusting method
Assignee: Sharp Corp (original assignee also Sharp Corp; assigned to Sharp Kabushiki Kaisha on filing)
Key dates: Priority date 2004-01-14; filing date 2005-01-13; publication of US20050152708A1 on 2005-07-14; granted 2007-08-14. Legal status listed as Expired – Lifetime, with adjusted expiration 2025-04-08.
Inventors: Masayasu Narimatsu, Masakatsu Hayashi, Hiroshi Kawamoto, Makoto Uehara, Jitsuo Masuda.
Purpose (from the supplied excerpt): The invention concerns a developing device that develops an electrostatic latent image on an image carrier (e.g., a photoreceptor drum) using toner, an image forming device incorporating it, and a method of adjusting developing density. The excerpt explains that developed image density fluctuates due to various factors, so density must be adjusted to keep image quality constant. A typical adjustment develops a "criterial patch image" (test image) on the photoreceptor drum, transfer belt, or similar, detects its density, and performs γ correction based on the difference from a predetermined reference density using a conversion table prepared from experimental data. The table converts patch image density to a correction amount for developing bias, grid voltage, and the like.
Plain-language scope (per the excerpt): For two-component developer, carriers remain in the developer tank while only toner is consumed and replenished. To maintain quality, toner concentration must be kept appropriate; generally the developer's magnetic permeability is measured as a toner-concentration index, and when the detection signal exceeds a supply-judgment reference value, toner is supplied. The excerpt also mentions Japanese Laid-Open Patent Publication No. 190993/1999 (Tokukaihei 11-190933, published 1999-07-13) describing developing-density adjusting means involving a charging-apparatus output correction amount (grid correction amount).
Not established by this excerpt: The full claim language, the complete description, the specific novel features distinguishing the invention, and the details of the referenced Japanese publication (the excerpt is truncated mid-sentence). No litigation, ownership-transfer, validity, or prior-art analysis is drawn.
Generated 10/1/2026, 9:43:40 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
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Derivative works
Defensive disclosure: derivative variations of each claim designed to render future incremental improvements obvious or non-novel.