Four-stroke engine
Otto files the first British patent application for his four-stroke gas engine
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Original prompt & settings (JSON) ↗The famous 17 May date belongs to a British application filed through a London attorney — not to Otto's German patent.
British application No. 2081
Nicolaus August Otto filed British application No. 2081 for his improved gas-motor engine on 17 May 1876. It was the first filing in an international patent campaign, not a German or U.S. one.
Otto worked through the British patent attorney Charles Denton Abel. The application opened with a provisional specification and was sealed with its final specification on 1 August 1876, for a fourteen-year term.
Four strokes, two revolutions
The protected engine spread intake, compression, ignition and expansion, and exhaust across four piston strokes — which takes two full turns of the crankshaft.
Otto had built a working engine that compressed and burned its charge in one cylinder at Deutz that year, and he and Gasmotoren-Fabrik Deutz moved to protect it before publication and international commercialisation.
Built at Deutz, described earlier in France
Applications followed in Germany on 5 June, France on 9 June, Spain on 27 June and the United States on 13 July, with the versions disclosing differing amounts of technical detail. German Imperial Patent No. 532 dates from 1877.
The filing established a patent claim rather than undisputed priority for the four-stroke concept. Alphonse Beau de Rochas had described the cycle theoretically in an 1862 French patent but apparently did not build an engine, and that prior publication later helped invalidate major German claims.
Sources
Researched 23 Aug 2026 4 sources 2 audit passes, 1 issue open
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Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →
What the sources leave uncertain
- May 17 is specifically the British filing date. The German application was filed June 5, 1876; German Imperial Patent No. 532 dates from 1877.
- The British records can be described either as Otto applying through Abel or as letters patent granted to Abel as Otto's agent, reflecting contemporary British filing practice—not a different inventor.
- The filing establishes a patent claim, not undisputed priority for the four-stroke concept. Beau de Rochas had described the cycle theoretically in 1862, and that prior publication later helped invalidate major German claims.