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
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
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
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
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
1937 - The large
Hamburg statute: Altona becomes a quarter of Hamburg. The firm address
changes from Dennert & Pape, Altona to Dennert & Pape, Hamburg
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
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
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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International Slide Rule Museum