Invalidity dossier
US 6550261
Low temperature storage cabinet
Current assignee: Hoshizaki Electric Co Ltd
Added 9/23/2026, 10:23:11 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 6550261 B1
Title: Low temperature storage cabinet
Assignee/Applicant: Hoshizaki Electric Co Ltd (original assignee; assignment recorded to HOSHIZAKIDENKI KABUSHIKI KAISHA, inventors Shima, Suyama, and Hara)
Key dates: Priority 1999-05-20 (JP11140689A); filed 2001-11-29; granted/published 2003-04-22; expired 2021-11-29 ("Expired - Lifetime")
Purpose: The patent addresses a low temperature storage cabinet (refrigerator, freezer, or refrigerator/freezer) for storing foodstuffs, beverages, and similar articles. It aims to reduce electric power consumption caused by a heater embedded in the cabinet's opening frame structure to prevent dewfall. The text notes that activating the dewfall-prevention heater during compressor operation increases the cooling load through heat generation, causing frequent compressor operation and wasted electricity.
Plain-language scope: The cabinet has a heater embedded in the opening frame structure (to prevent dewfall where the door contacts the cabinet body) and a compressor controlled according to inside cabinet temperature. According to the description, the heater is activated synchronously with compressor operation and, during compressor stoppage, is activated according to outside humidity or inside cabinet temperature. The cabinet may include an inside temperature sensor, an outside humidity sensor, an outside temperature sensor, and/or a surface temperature sensor, with control means (a microcomputer and driving circuits) to control heater activation. In one described approach, a dewfall temperature is calculated from outside temperature and humidity, and the heater is activated when the frame surface temperature is at or below that dewfall temperature, and deactivated when higher. Drawings and time charts illustrate several control methods and heater activation-rate circuits.
What the excerpt does not establish: It does not provide the full claim set (claims are referenced but not reproduced), the complete description, or the exact wording of claim limitations. It does not establish prosecution history, the full prior-art analysis, or the specific content of the cited Japanese publications. Litigation, ownership transfers beyond the recorded assignment, and validity are not addressed per instruction.
Generated 10/1/2026, 9:33:27 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
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.