Otis Carter Formby King (1876–1944) was an electrical engineer
in London who invented and produced a cylindrical
slide rule
A slide rule is a hand-operated mechanical calculator consisting of slidable rulers for conducting mathematical operations such as multiplication, division, exponents, roots, logarithms, and trigonometry. It is one of the simplest analog ...
with helical scales, primarily for business uses initially. The product was named Otis King's Patent Calculator, and was manufactured and sold by Carbic Ltd. in London from about 1922 to about 1972.
With a
log-scale decade length of 66 inches, the Otis King calculator should be about a full digit more accurate than a 6-inch pocket slide rule. But due to inaccuracies in tic-mark placement, some portions of its scales will read off by more than they should. For example, a reading of 4.630 might represent an answer of 4.632, or almost one part in 2000 error, when it should be accurate to one part in 6000 (66"/6000 = 0.011" estimated interpolation accuracy).
The
Geniac brand cylindrical slide rule sold by Oliver Garfield Company in New York was initially a relabelled Otis King; Garfield later made his own, probably unauthorized version of the Otis King (around 1959). The UK patents covering the mechanical device(s) would have expired in about 1941–1942 (i.e. 20 years after filing of the patent) but copyright in the drawings – which would arguably include the spiral scale layout – would typically only expire 70 years after the author's death.
Patents
* UK patent GB 207,762 (1922
* UK patent GB 183,723 (1921
* UK patent GB 207,856 (1922
* US patent US 1,645,009 (1923
* Canadian patent CA 24198
* Canadian patent CA 24107
* French patent FR56998
* French patent FR57661
* German patent DE 41881
See also
*
Bygrave slide rule
*
Fuller's cylindrical slide rule
External links
Dick Lyon's Otis King pages
References
{{DEFAULTSORT:King, Otis
1876 births
1944 deaths
English inventors
Mechanical calculators
Logarithms
English inventions
Analog computers