ca 1913 Bunzel-Denton Arithmometer Prototype
Rare arithmometer Bunzel 7, model baby - carriage with 7 sliders and dual display. Almost certainly the only known copy and probably a prototype with a shifted crank created by Bunzel. Serial 8080 dimensions 23 x 32 x7 cm Weight 9.5 kg
The machine seems to encapsulate a patent filed by Bunzel on May 25, 1914, for enabling the position of the crank to be shifted from its normal position standing upright on the deck to one where it is horizontal on a side of the machine.
In particular, the patent (for original text and drawing see also below) notes that there are now in existence Thomas type arithmometer and Odhner type pin wheel calculators. Thomas machines have their crank standing up on the deck, whilst the pinwheel’s invariably have their crank on the side. This patent proposes a system in which the crank can be placed either on the deck, or on the side, according to the “taste” of the owner.
Drawing of proposed crank mechanism from patent (see also below)
This machine appears to be a prototype of this proposed mechanism, and here the crank has been placed in front. Achieving this was certainly not a job for amateurs. In the prototype the new mechanism set up is perfectly performed and it seems highly likely this amendment was done by workshops of Bunzel. All the pieces seem original, coming from the same time (even the wear). The arithmometer also has been provided with an ingenious tilt system which ensures that when the machine is inclined, the crank is perfectly horizontal.
Repositioned Crank
Model number on case
Mechanism of the prototype Bunzel
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