Invalidity dossier
US 945540
Door-latch.
Current assignee: James L Howard & Co
Added 9/23/2026, 4:59:20 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 — US945540A, "Door-Latch"
Bibliographic data (from the source): US Patent 945,540; inventor Frank E. Howard of Hartford, Connecticut; assignee James L. Howard & Company, a Connecticut corporation. Application filed March 10, 1906 (Serial No. 305,235); patent granted and published January 4, 1910; anticipated expiration January 4, 1927; legal status listed as "Expired – Lifetime." Classifications include E05C3/30 (spring-controlled pivoted hook bolts) and Y10T292/093 (cam operating means).
Purpose. The invention improves latch mechanism for sliding doors, of the class shown in U.S. Patent 720,349 (Feb. 10, 1903, to C. P. and F. E. Howard). Two stated aims: (1) carry all mechanism on two side plates rather than in a separate mortised lock frame, easing alignment when fitting to a door; and (2) avoid a direct sight-through opening in the door, preventing passage of air, cinders, and dust — especially in railway cars, where such latches were extensively used.
Plain-language scope. The latch (15), tumbler (18), spindle (2), and swinging loop handles (36, 37) operate substantially like the earlier patent, but the latch and tumbler are pivotally supported on the inner side of one door plate (19), preferably in an appurtenant casing (20) with lock cover (21). A coiled spring (23) or screen (25) is fastened to the side plates on the undersides of the elongated openings (47), extending slightly beyond them to block direct sight. The coupling rod (26) has a crooked or offset portion (27) arching over the screen, its aligned ends (28) passing through the slotted openings into the handles to couple them. The rod is preferably detachable; uncovered slot portions are covered by enlarged handle shoulders (30) when closed. A mortise variant (Fig. 5, extension 11) fully masks the opening. Slot ends serve as abutments for pushing the door. The connecting means may be used with other than swinging handles.
Source: https://patents.google.com/patent/[US945540](/patent/US945540)/en
Not established by the excerpt: the full specification, drawings, or claims (no claim language is supplied); the omitted portions of the description; and any facts about litigation, ownership transfers, validity, or prior art beyond the two patents named.
Generated 10/1/2026, 9:43:57 PM
Cases on file (0)
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Litigation summary
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Proceedings on file (0)
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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
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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.