Calculators of Louis Troncet

After the slide adders of Claude Perrault, Caze and Kummer, in 1889, the frenchman Louis Troncet, a teacher and Director of a school, created his version of this type of calculator, which he called the Arithmographe. Troncet's invention became so popular that the term “Troncet-type” is often used to refer to this class of device. The device was in production almost 30 years. Millions of devices of this type were sold. It was on the market until the 1970s.

Louis Troncet was a holder of four french patents: No 123135 from 1878, No 133106 from 1879, No 171473 from 1885 and No 197579 from 1889 (never published as fees were not paid). The first patent(from 1878) was for a slide adder with dials, called Numerateur, which never was put in production (see the lower patent drawing of the device).

The patent drawing of the Numerateur of Troncet

The next three patents are for different versions of the Arithmographe (see the patent drawing of the third version from 1889).

The patent drawing of the third Arithmographe of Troncet

Namely the third version of the Arithmographe (see the lower photo) featured so clever and reliable construction, that became a market hit in the end of 19th and the beginning of 20th century.

The Arithmographe of Troncet

The Arithmographe is with dimensions 10 x 13,6 x 0,5 cm. A good description of the workings of the device can be seen in the manual (see the lower image) from a very popular in the US analog of the Arithmographe, the Baby Calculator.

The manual Baby

Troncet manufactured and sold also another calculating device, so called Totalisateur (dial adder) (see the lower photo), which was a circular adding device. It however didn't became a market hit, in contrast with the Arithmographe.

The Totalisateur of Troncet