Origin of modern calculating machines

by J. A. V. Turck

The lateral positions of the projectable gear teeth correspond to the spacing of the type-wheels, and an intermediate gear G, meshing with each type, or register wheel, is loosely mounted on the shaft H, interposed between the said wheels and the actuating drum E, so that when the drum is revolved by the crank provided for that purpose, the gear teeth protruding from the drum will engage the intermediate gears G, and turn them and their type or register wheels as many of their ten points of rotation as have been set up in their respective orders of the setting devices of the drum.

Revolving the drum in one direction adds, while revolving it in the opposite direction subtracts, and repeated revolutions in either direction give respectively the multiple forms of addition or subtraction which result in either multiplication or division, as the case may be.

The actuating drum E, is provided with means by which it may be shifted to the left to furnish means for multiplying by more than one factor and to simplify the process of division.

The means for the carry of the tens consist of a series of teeth i, formed by the bent end of a pivoted spring-pressed lever arm which is pivoted to the inside of the actuating drum with the tooth protruding through a slot in the drum, so arranged as to allow motion of the tooth in a direction parallel to the drum axis.

From Drawings of Pottin Patent No. 312,014

Normally these teeth are held in a position to escape engagement with the intermediate gears G, but provision is made for camming the teeth i, to the left into the path of an intermediate gear of one order as the type or register wheel of the lower order passes from 9 to 0.

The parts which perform this function are the cam m, located on the left side of each wheel, the plunger M, which operates in the fixed shaft H, and which has a T-shaped head that, when projected into the path of the carrying teeth i, serve to cam them sidewise and bring about the engagement referred to, which results in the higher type or numeral wheel being stepped forward one space.

The cam-lugs j on the drum serve to engage and push back the T heads of the cam plungers M, after they have brought about the one-step movement of the higher wheel.