On 8 June 1886, Lawrence Wilson Swem (1856-1917), a jeweler of West Liberty, Muscatine, Iowa, patented a simple keyboard adding machine (US patent 343506), somewhat similar to the earlier adder of Marshall Cram from 1877 and very similar to the later adding machine Centigrpah of Arthur Shattuck from 1886 and 1891.
Like other machines of this kind (so called single-column adders), the device of Swem was intended to add a single digit at a time, i.e. the unit column is entered first, then the tens, the hundreds, the thousands, and so on, certainly rather cumbersome task (as every partial sum had to be recorded on paper and the sum eventually performed), which greatly limits the usefulness of such devices.
Let’s examine the internal mechanism and operation of the adding machine of Swem, using the patent drawing (see the lower image).
The numbers, entered by the keyboard, are transferred to the ratchet-wheel (B) by means of the rock-shaft (A). The wheel (B) is turning is turning freely or loosely thereon, and is provided with a specific number of teeth, ordinarily one hundred. This wheel can be rotated only in one direction, which is secured by a radial arm (C), a pawl-arm (D), retaining-pawl (F), and a spring (B’).
Secured to the ratchet-wheel (B), so as to turn with it, is a disk (G), having a series of numbers (from 1 to 99) on its periphery. The number entered on the disk (G) can be ascertained by means of a suitable indicator (G’).
The carry mechanism is implemented by means of a cam (H), mounted on the one side of the disk (G), on which rests one end of the an arm (I), the other being pivotally supported on a post (K), erected on the base (E). The post (K) has on top an extension (L), which supports a ratchet-wheel (M), with a specific number of teeth, say 14, and a plate (N), with an orifice (O), through which may successively be seen numbers on the said ratchet-wheel (M), corresponding in position to the teeth thereon. When the disk (G) has revolved once, the cam (H) will raise the arm (I) till it has reached the apex of the said cam will carry the pawl (R) from one tooth of the wheel (M) to another.
Thus it is evident that if there are 99 numbers on the disk (G) and 14 on the wheel (M), any number from 1 to 1500 may be indicated, and addition of amounts till the said sum is reached easily and rapidly accomplished without mental labor.
Biography of Lawrence Swem
Lawrence Wilson Swem was born in Iowa on 24 April 1856, to Ezra B. Swem (14 Apr 1815-17 Nov 1871) and Phoebe (Phebe) H. Swem (nee Gregg) (11 Jan 1819-17 Jan 1887). The family had nine children, but it seems only six of them survived to adulthood: Amanda Jane (1842-1921), Mary (1848-1869), Lawrence Wilson (24 Apr 1856-28 Sep 1917), Edward Lawrence (23 Oct 1838-4 May 1918), James Madson (30 Mar 1845-10 May 1909), and William Carroll (7 Apr 1861-1 Apr 1931).
Lawrence Swem married on 28 June 1877, to Elva Ora Swem (nee McFadden) (18 Jan 1859-14 Dec 1922). They had two children: Roy J. Swem ( 9 Aug 1878-2 Oct 1934), and Gay Lawrence (18 May 1881-23 Sep 1959).
Lawrence Wilson Swem spend most of his life in West Liberty, a small town in Muscatine County, Iowa, United States, working as a jeweller and mechanic.
Besides the above-mentioned patent for adding machine, Lawrence Swem was a holder of six more patents for various devices like: lamp extinguisher (patents US201570), hydraulic air pump (US556220), gas making apparatus (US595979), mold for castings (US981033), ring expanding press (US1154893), and hydrocarbon burner (US1216248).
Lawrence Wilson Swem died on 28 September 1917, and was buried in Oakridge cemetery, West Liberty.