Invalidity dossier
US 5409134
Pressure-sensitive accumulator for ink-jet pens
Current assignee: Hewlett-Packard Company
Added 9/17/2026, 12:47:55 AM
Active provider: DeepSeek · deepseek-flash
Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
US 5,409,134 A — "Pressure-sensitive accumulator for ink-jet pens"
Bibliographic data (as supplied). Application US07/805,438; filed 1991-12-11; granted and published 1995-04-25. Priority date listed as 1990-01-12. Original assignee: Hewlett-Packard Co.; current assignee listed as HP Inc. Inventors: Bruce Cowger, Marc A. Baldwin, Fred E. Tarver, Gary D. Tarver, John G. Wydronek, George M. Custer. Status: Expired – Lifetime (anticipated expiration 2012-04-25). Classifications place it in B41J 2/17503 (ink cartridges) and B41J 2/17556 (means for regulating pressure in the cartridge). Listed prior-art keywords: bag, spring, reservoir, spring member, accumulator.
Purpose and plain-language scope. The title and classifications indicate a pressure-sensitive accumulator for ink-jet pens — a mechanism for regulating pressure in an ink cartridge. The supplied text's definitions section begins: "This invention pertains to mechanisms for r..." (truncated). Beyond that, the excerpt does not include the abstract, the claims, or the written description, so the specific structure, operation, and scope of the invention cannot be stated from the supplied material. Anyone needing the actual claimed scope should consult the full specification and claims at the source.
What the excerpt does not establish. It does not supply any claim language or independent/dependent claim structure; no abstract; no detailed description of the bag, spring, or reservoir elements; no drawings content; no named prior-art references; and no legal conclusions. Also note the source itself cautions that legal status, assignee accuracy, and priority date are assumptions and not legal conclusions.
Omitted from this overview by instruction: litigation data (e.g., the referenced ITC case 337-TA-446) and ownership/assignment events, which appear in the source but are outside the requested scope.
Generated 10/1/2026, 10:03:21 PM
Cases on file (1)
Group view →Specific litigation cases in our database that name US patent 5409134. The free-form analysis below may also discuss cases beyond this list.
- Hewlett-Packard Company v. Microjet Technology Co., Ltd. et al.filed Dec 22, 2000337-TA-446U.S. International Trade Commissionterminated Apr 25, 2002terminated
Defendants: Microjet Technology Co., Ltd., Printer Essentials.com, Inc., Price-Less Inkjet Cartridge Company, and 2 others
Other patents asserted: 4635073, 4827294, 4680859, 4872027, 4992802
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.
Current assignee: Hewlett-Packard Company
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.
Keep exploring
More patents asserted by Hewlett-Packard Company
- US 4635073I'll verify this patent against live sources before summarizing. Let me check the litigation references and USPTO records. Let me do one more targeted check for any 2026 appellate activity. US Patent 4,635,073 — Verified Summary Search…
- US 4827294Patent Overview — US 4,827,294 A Title: Thermal ink jet printhead assembly employing beam lead interconnect circuit Patent number / application: US 4,827,294 A; application US 07/093,924 Inventor: Gary E. Hanson Assignee (per supplied…
- US 4680859Patent Overview: US4680859A Title: Thermal ink jet print head method of manufacture Patent Number: US4680859A Application Number: US06/915,292 Inventor: Samuel A. Johnson Original Assignee: Hewlett Packard Co (Current Assignee listed as HP…
- US 4872027Patent Overview — US 4,872,027 Title: Printer having identifiable interchangeable heads Patent number: US4872027A Application number: US07/116,093 Inventors: William A. Buskirk, Carl J. Landsness, John D. Rhodes Original assignee: Hewlett…
- US 4992802Patent Overview — US 4,992,802 A Title: Method and apparatus for extending the environmental operating range of an ink jet print cartridge Source: https://patents.google.com/patent/US4992802/en Bibliographic data (from excerpt)…
- US 6597812I'll search for the specific patent number as requested. Let me check specifically for any 2026 CAFC activity involving this patent. US Patent 6,597,812 — Analyst Summary Search scope note: I searched for the exact number 6597812 /…
- US 6481817I'll search for authoritative information on US 6481817, including any USPTO/CAFC litigation activity. Let me do one more targeted check for recent litigation/review activity involving this specific patent. US Patent 6,481,817 — Analyst…
- US 6234598Patent Overview — US6234598B1 Title: "Shared multiple terminal ground returns for an inkjet printhead" Patent number / application: US6234598B1 (application US09/386,574) Inventors: Joseph M. Torgerson, Rama Prasad, Todd A. Cleland, Dale…
This patent in court (1)
1 tracked lawsuit name US 5409134.