On 24 April 1860, David R. Nelson of Jackson, Ohio, patented (US patent №28006) a keyboard machine for adding numbers, one of the early calculators of that type, after the machines of James White, Luigi Torchi, and Jean-Baptiste Schwilgué in Europe, and the key adders of his compatriots Dubois D. Parmelee, Orlando Lane Castle, Thomas Hill, and Leonard Nutz.
The calculator of Nelson (see the lower patent drawing) was a simple single-column adder (column adders can have two or more result digits, but you can only add into the rightmost digit, and then generally only with the integers one through nine) with one output dial. The numbers are entered with five finger keys (marked with B) hinged at b to box A. Each key is provided with a spring a used to return it against the stop board C after depression.
D is a ratchet wheel journaled in the box A and stop board C, and carrying on the upper end of its spindle an index or pointer c, adapted to move over the face of the dial E). The teeth on the periphery of the wheel D are equal in number to the divisions or units on the dial E so that a rotation of the wheel to the extent of a given number of teeth carries the finger of the dial over the same number of divisions or units on the dial.
J, J, are springs provided with friction pads i made to press on the face of the wheel D to prevent its being carried by momentum to a farther extent of rotation than that given it by the lever and pawl F, G. The pressure of the said springs is adjustable by a set screw j. The check pawl I may, if preferred be dispensed with, the friction pads i serving to prevent the retrograde motion of the wheel D.
The index c is constructed with a spring socket so that it may turn with the spindle of the wheel D, yet be free to be set by hand independently of wheel D to any desired position on the dial.
Almost nothing is known about the inventor of this keyboard calculator—David R. Nelson.
He was born in 1835 in Jackson, a small town in Ohio, as the third child of John Nelson (1805-1885) and Mary Polly Nelson, nee McBride (1801-1880). David had an elder brother—Absolom F. Nelson (1830-1920), and a sister—Mary Ann Nelson-Hastings (1832-1874).
The father of David—John Nelson (born 1805 in Virginia, died 16 Feb 1885 in Jackson) was known as “Landlord Nelson”) and was a pioneer settler of Jackson, Ohio. He was a prominent local businessman—a merchant, who kept a store, and owned and conducted “Nelson’s Hotel”, one of the very early taverns, so most probably the young David devised his calculator to assist his father’s business. The mother of David—Mary Polly McBride (born in Vanceburg, Kentucky, on 5 April 1801, died 27 May 1880 in Jackson) was a daughter of John McBride of Ireland and Mary Mitchell of Scioto County, Ohio. Mary Polly married John Nelson on 17 December 1829, and their first child Absolom was born in Sep 1830. Later they had four more children, but two of them died in infancy.
David R. Nelson died on 5 April 1890, in Jackson, Ohio.