Invalidity dossier
US 4500895
Disposable ink jet head
Current assignee: HP Inc
Added 9/24/2026, 2:14:57 AM
Active provider: DeepSeek · deepseek-flash
Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview: US4500895A — "Disposable Ink Jet Head"
Bibliographic data (from supplied source): US Patent 4,500,895 A; application US06/490,754; filed 1983-05-02; published/granted 1985-02-19; original assignee Hewlett-Packard Co. (current assignee listed as HP Inc); inventors Roy T. Buck, Frank L. Cloutier, R. Ernst Erni, Robert N. Low, and F. Duncan Terry. Legal status listed as expired — lifetime (anticipated expiration 2003-05-02). Foreign filings noted include DE, EP, JP, KR, SG, and HK.
Purpose: Prior ink jet heads were "expensive and complex," requiring continuous multi-year use, refillable ink supplies, accessible maintenance parts, and user handling of fluid couplings — exposing hands and clothing to ink. The invention addresses this by providing a head simple and inexpensive enough to be disposable.
Plain-language scope: The head is self-contained in a single unit containing a sealed ink reservoir, ink, thermal thin-film jetting resistors, thin-film electrical runs and pads, fluid interconnection, and jetting orifices. A glass or ceramic substrate carries the resistors and conductors, with a jet feed hole through it. An orifice plate (glass, ceramic, or metal such as nickel) attaches to the substrate and has 1–3 milinch drop expulsion holes plus capillary grooves; it also protects the resistors. The substrate mounts in a molded plastic backing plate having alignment pins, a capillary feed groove, and a fill hole. An elastic hollow ink reservoir (silicone rubber, or a two-piece plastic/resilient shell shaped "in the general shape of a sewing thimble") supplies back pressure so ink exits only when resistors are energized. A molded outer housing protects the reservoir and includes an air-pressure equalization vent. The hydraulic system is sealed except for the expulsion holes; the user replaces the head via a simple mechanical and low-voltage electrical connection.
Not established by the excerpt: The claims, the full description and figures, prosecution history, and prior-art analysis are omitted or truncated ("[Excerpt only]"), so the exact claim scope and any legal conclusions cannot be determined here.
Source: https://patents.google.com/patent/[US4500895](/patent/US4500895)/en
Generated 10/1/2026, 9:30:48 PM
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Litigation summary
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PTAB challenges
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Assignment history
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Prior art
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Obviousness
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Extensions
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Derivative works
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