In 1881 Peter C. Forrester from San Francisco, patented (see US patent Nr. 249606) a keyboard adding machine (see the nearby patent drawing).
The adding device of Forrester has a framework with an upright portion and a keyboard resembling somewhat an upright-piano. It has dial-plates and indicators adapted to be moved by clock mechanism and an escapement, an oscillating plate (marked with M), with a groove m for releasing said escapement, in combination with the means for oscillating said plate, consisting of the pinion l, segment K, crank I, upright rod G, crank F, rocking shaft D, with its pins d, and removable keys B, with their adjusted lifters b.
The device has a motor-spring, adapted to be wound up as a clock. The shaft on which it is carries the large gear X, from which motion is transmitted through appropriate gears to the dial or escapement-shaft S and to the shaft which operates the dial-finger Z of the dial-plate recording tens.
In short columns of numbers the device is not as useful as in long ones. When the latter have to be added the time taken in turning the dials after each row is not noticeable.
Biography of Peter Forrester
Peter C. Forrester was born in Detroit, Michigan, in 1858, to Peter C. Forrester and Mary White. He lived in several western US states like Nevada, California, and Washington. Peter C. Forrester was a prolific inventor and businessman, the author of many (at least 10) US patents for various inventions like: method of mining coal (US patent 473734), scroll former (US543233), tool for binding metal strips (US543234), drill (US628404), filtering apparatus (US284495), and others.
On 25 July 1900, Peter Forrester married to Bessie Lynette Toner (1872-1925) from Detroit, Michigan.
Peter C. Forrester died on 5 July 1952, in Tacoma, Washington, at the age of 94.