Rudolf Diesel patents the Diesel engine at the German Patent Office in Berlin

Background. Rudolf Diesel, a German engineer, developed the compression-ignition engine concept over several years. He published his theoretical framework in 1893, initially proposing a cycle that he later corrected to a constant pressure cycle. His work relied on mechanical compression to raise air temperature sufficiently for fuel ignition, distinguishing his engine from other internal combustion designs of the era.

Patent Process. Between 1894 and 1895, Diesel filed patents and addenda in various countries for his engine. The first patents were issued in Spain, France and Belgium in December 1894, and in Germany (No. 86,633) in 1895; only the year is attested for the German grant. Separately, on 30 March 1895, Diesel applied for patent RP 86633 for a starting process with compressed air, a filing distinct from the engine patent issuance. His 1895 patent application described the cycle he had adopted.

Technical Context. The engine's operation depends on the elevated temperature of air in the cylinder caused by mechanical compression. Diesel's 1895 patent application described the specific cycle he adopted after abandoning his original theory. This technical foundation justified the patent grant, as the compression-ignition method was central to the engine's efficiency and distinct from prior designs.