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A sprocket wheel is a gear wheel with adjustable number of teeth. It serves particularly as drive for mechanical calculating machines. Sprossenradmaschinen are called in Europe also Odhner or Brunsviga machines. The central element of these machines is a wheel with an adjustable number of teeth (rungs).
From the hand of Gottfried William Leibniz (1646-1716) originates first admitted draft a sprocket wheel. It is assumed that it considered this sprocket wheel beside the late Staffelwalze than drive for its calculating machines, used by it. With its sprocket wheel draft a tooth had to be raised, which raised all its predecessors with. An appropriate rigging device and the sprocket wheel body are missing on the design. The Italian astronomer and mathematics professor Giovanni Poleni (1683-1761) built a wooden calculating machine with weight drive, which he described 1709 in "Miscellanea" on page 27. The sprocket wheel sketched by it functioned with nine folding rungs. A first, yet satisfyingly not working calculating machine model showed Poleni that its drive principle was suited. A second machine, more carefully worked and from harder wood built, succeeded to it according to desire. In addition that the machine could process maximally three-figure numbers, as well as large and unmanageable was, the number of revolutions of the is to be noticed was strongly braked the decimal carry to have unsatisfactorily functioned is. It is recapitulatory, like Bischoff writes, "an imperfect and useless tool" been. However the publication of the construction and function mode of the Poleni machine may have served later technical designers of Sprossenradmaschinen than suggestion.
The Schwabe Antonius brown (1686-1728) developed 1727 a Sprossenradmaschine, which is today in the possession technical museum for industry and trade Vienna. The fundamental idea for the development of a Sprossenradmaschine could have brown from Poleni, whose machine in Theatrum was described arithmetico - geometricum by Jacob Leupold 1727, a publication, which probably knew brown. Beside this Sprossenradmaschine brown built also still one place segment calculating machine from the years 1841 and 1848 comes for two round Sprossenradmaschinen French physician of the Didier Roth, which is today in the possession of the Paris national of the Techniques. It received an English patent for this invention in the year 1843. Although the machines are to have been unreliable, the used sprocket wheels had developed. Further work of Roth is a classification of calculating machines from the year 1843 and a small, oblong adding machine named "Additionneur" from the year 1841, which was served by means of an adjusting pin. A further Sprossenradmaschine comes from the Englishman David Isaac Wertheimber, which was patented in the year 1843. Late sprocket wheel used by Odhner is very similar Wertheimbers construction. Both adjust the rungs with the help of a curve slot. Over a realization Wertheimbers machine is not anything well-known. The American franc Stephen Baldwin (1838-1925) sent on 5 October 1872 a complete description and designs of one of him developed Sprossenradmaschine to the American patent office, in order to protect its rights at this invention. On 8 September 1873 this calculating machine or an advancement was announced to the patent, which was given to it on 2 February 1875 with the No. 159,244. As follows from the illustration, the rungs are stored and with a semicircular tension ring from the sprocket wheel body are pressed in its construction springily. Similarly as with the later Odhner calculating machines also with Baldwin the decimal carry with the sprocket wheel is realized. In its Patentzeichnungen also a printing element for these machines is contained. Up to the year 1874 ten this "Baldwin Calculators" were manufactured: Although for a series production conceives, never larger numbers of items were produced. Its machine is to have been susceptible to mechanical errors too expensively and.
Baldwin busy itself also with other calculating machine constructions. Like that the Monroe calculating machine, an editing keyboard relay roller machine, developed by it, was a commercial success.
In the following the sprocket wheel principle of the Odhner machines is described:
Nine rungs are stored into radially in-milled slots in a sprocket wheel body. Opposite the sprocket wheel body a curve slot is brought in into the swivelling tension ring, which holds the rungs in their position. If the tension ring is turned in the clockwise direction, then the rungs push themselves successively outward. A scale attached on the housing of the calculating machine it is in such a way divided that the number of shifted out rungs is equal to the adjusted number. Now if the entire sprocket wheel is turned by the operating handle, reach zero to nine rungs into a transmission gear wheel.
A characteristic of the sprocket wheel construction of the Odhner calculating machines is that also the decimal carry with it is realized: Additionally to the nine rungs are still two springily with springs stored decimal rungs at the sprocket wheel, which can be pressed by the decimal preparation lever into the processing level.
While in the process of the 19-ten of century four-species machines with relay roller drive can be developed obviously more simply to ready for the market ones, machines with sprocket wheel on the European market the supremacy take over at the beginning of the 20-ten of century.
These can be manufactured economically, have compact outer mass and are maintenance-poor also under rough conditions. Individual model rows are produced in some 10,000 pieces. For the end of the history of the development of mechanical calculating machines these must compete with the first electronic computers. Here the Staffelwalze has the advantage that this is moveable via engine strength fast. With sprocket wheels the variable number of teeth provides for a changing emphasis, which would be to be adjusted only mechanically.
The last Sprossenradmaschinen are inexpensive claimant devices by hand, like the shown Brunsviga 13 RM. This was produced into the 60's-years of the 20-ten of century in Spain.
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