Dennert & Pape/ARISTO - Data and product Timeline

July 1, 1862 - Johann Christian Dennert (1829-1920) transfers a workshop for building surveying instruments from Carl Plath to Hamburg.
Oct 1, 1863 - Martin Pape (1834-1884) becomes a partner because, the new enterprise is called  Dennert & Pape: Workshop for mathematical instruments.
1869 - Firm relocated to Altona (Prussia)
1872 - 1872 first slide rules are made of boxwood, designed by A. Goering, who also authors the first user manual. Change of name: Dennert & Pape - mechanical mathematical Institute
1879 - Along with wood slide rules,  brass slide rules are offered.
1882 - Introduction of a pear wood slide rule of 50 cm length and special models. 
July 1, 1884 - Martin Pape dies - Dennert becomes sole owner of company, but retains Pape as part of company name.
Feb. 16, 1886 - The German  patent 34583 for wood scales with Celluloid veneer is assigned to Dennert & Pape
1888 - Mahogany scales with Celluloid veneer replace the stocks made from boxwood in all areas of slide rule manufacturing.
1890 - The cursor with a metal frame glass replaces the sheet metal  cursor.
Oct. 6,1891 - With the US patent 460940 William Cox designs the duplex slide rule, Dennert & Pape starts producing slide rules for Keuffel & Esser in New York, until K&E begins their own manufacturing.
1900 - Firm expanded.
Sept. 28, 1901 - Dennert & Pape receives the German patent for the improvement building of slide rules.
Feb. 25, 1902 - Dennert & Pape receives a US patent 694258 for slide rules with a Celluloid base plate or stock.
1902 - Max Rietz participates in the development of the slide rule "Rietz system". "Rietz system" becomes the universal slide rule of mechanical engineering.
1904 - Richard (1865-1924) and Johann Dennert (1869-1916) join the company as managers. Richard Dennert is assigned the slide rule production, as well as the marketing and the administration responsibilities. Johann Dennert is responsible for measurement and mathematical instruments.
1905 - The first catalog shows 12 slide rules, those after the patents specified above was manufactured including the first slide rule with a 2-log-Skala to the computation of logarithms.
12. Dec. 1907 - The British patent 18218 for slide rules with 6-log-Scales receives its Yokota (1875-1953). Dennert&Pape produce these slide rules for the export to Great Britain. After the First World War they run under the name "Improved exponential" until 1938.
1908 - At age 80,  Johann Christian Dennert retires from going to work every day in his company.
1914 - The slide rule is increasingly used as a computing instrument in mechanical engineering. In the commercial catalog stocks with 20 different scale arrangements are now listed.  Orders for special scale arrangements are produced for other companies.
1924 - Prior to the early death of Jean Dennert (1916) and Richard Dennert (1924), have  already transfer ownership to their sons Christian (1896-1944) and George Dennert (1900-1992). Now they have the entire responsibility for the future of Dennert & Pape.
1925 - All Dennert&Pape products are distinguished now with the brand name DUPA.
1926 - The original "system Rietz" of 1902 becomes with the reciprocal value scale CI, which scale extensions ST for the computation of small angles, and the scales A, B, C and D are improved.
1929 - The company opens a new slide rule manufacturing in Weide-Berg in north Bavaria.
1931 - Christian Dennert, the oldest son of Jean Dennert, leaves Dennert & Pape. He continues slide rule production in Weide-Berg, under the name DEWE . His mismanagement led the company to its death in 2nd World war.
George Dennert, the youngest son of Richard Dennert, continues with the company (DUPA) as new owner. Under his guidance Dennert & Pape survives the difficult years of the world economic crisis and 2nd World war. 1934 - Based on the "System Rietz" a again arranged scale with three doubled logarithm scales at the technical University of Darmstadt sketched. This new slide rule "system Darmstadt" becomes a new basis model "system of the Rietz".
1936 - Dennert & Pape discontinues the production of Mahogany slide rules with Celluloid veneer. Slide rules are now completely made of plastic (Aristopal).
1936 - The label name ARISTO is introduced. Carry this name now the slide rules, scales and other indication instruments of Dennert & Pape, which are made of the new plastics. The remaining products keep running under the name DUPA.
1937 - The large Hamburg statute: Altona becomes a quarter of Hamburg. The firm address changes from Dennert & Pape, Altona to Dennert & Pape, Hamburg Altona.
1937 - Carl Plath's triangle computer "DR2-System Knemeyer", a flight computer, is manufactured by Dennert &Pape with the help of the new plastics.
1942 - Products for the military employment in the 2nd World War must be marked by the code "GWR" instead of the company name or the brand name.
1943 - The war causes slide rule production to shifted to Bludenz/Vorarlberg in Austria.
1945-1948 - During the last part of WWII, production of slide rules was in very small numbers, and in the first postwar years few were available because of a lack of raw material.
1948 - Dennert & Pape is converted into a partnership, with a more modern operating system. After the break with the Nazi controlled  war machine, Dennert&Pape regains its own control of management and returns to slide rule manufacturing under the new name ARISTO.
1949 - New double-sided slide rules are introduced which are considered for prototypes for future designs and scales: ARISTO Scholar for schools and ARISTO Studio with 6-log-Skalen for mechanical engineering and sciences. Both slide rules used the body of the trigonometry scale "Darmstadt" - of the system.
July 1951 - The new factory in Geretsried begins the production of ARISTO student slide rules.
1952 - After Hans Dennert (born 1926) had locked, George because RTS oldest son, its training as industrial engineer and for one year in an US-American company had worked, it begins its career with Dennert & Pape and becomes 1957 deputy director.
1953 - Production of the "ARISTO Multi log" with 8-log-scales, and a version "ARISTO Studio" for those users who prefer trigonometric scales.
1954 - The flight computers "ARISTO Aviat" and "ARISTO Aviat G" replace the systems "Knemeyer DR3 and DR4".
1956 - Since 1952 ARISTO is the brand name of all Dennert & Pape products. ARISTO is now adapted as part of the company name: Dennert & Pape ARISTO Company.
April 1960 - A new factory in Hamburg Stellingen begins  production.
July 1, 1962 - 100-year birthday of Dennert & Pape
1962 - A new slide rule for primary schools is manufactured: ARISTO junior
1966 - The ARISTO label name "moved" in prominence  ahead of original names, now called: ARISTO Dennert & Pape.
1967 - Production of the "ARISTO Studiolog", the improved form "ARISTO Studio" with 8 double logarithm scales.
1972 - 100 years of slide rule production
Dec 31, 1978 - Slide rule production ends and this part of the company is dissolved. George and Hans Dennert resign from Aristo.
Jan 1, 1979 - The company CAD (Computer Aided Design) group resumes the enterprise under the new company name "ARISTO Graphic Systems".
July 1, 1987 - 125 years old.

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