On 24 July 1877, one O. Berndt of Nienburg, Germany, got a patentschrift (see German patent №81) for addirmaschine (adding machine) with an interesting construction. The keyboard adding machine of Berndt is one of the earliest developments of this type in Germany, and even though it never acquired any practical importance, it deserves our attention, because of its well-designed construction and the implementation of a unique operation principle—numeric keypad combined with automatic decade function.
The so-called decade function of this adding machine is a special feature. It has the effect that with the first keystroke the units, the second the tens, etc. can be added to a number. A counter shows how many decades of a number have already been entered. After entering the whole number, the operator can reset the decade function by pressing a key and then entering the next number.
The mechanics of the machine (see the lower patent drawing) consists of:
– Keypad with eleven keys
– Counter
– Drive mechanism between keys and counter
– Transfer of tens of the counter
– Automatic decade function
The device has eleven keys, ten of which serve for setting up the digits of the addends, and one for adding the set number to the result. In addition, the machine is first set to zero, which lowers the eleventh key (upper left key) to the bottom. The key for the first digit from the right is pushed (to enter the units digit) and this action raises the eleventh key by a small increment; then the second (tens) digit is set, which again raises the eleventh key, and so on. The eleventh key is raised ever higher as more digits are entered. After the total value has been set (maximum ten digits), the eleventh key is pressed down to add the set value to the ten-positional result mechanism. The second and subsequent amounts are added in the same manner. The machine is not provided with a zero setting, and the individual numeral drums must be successively adjusted to zero by the depression of the corresponding digital keys. There is no indication of an overflow of the result mechanism either.
Biography of O. Berndt
We are not sure who was the inventor of this adding machine. In fact, there was a very good German mechanical engineer from this time with the same name—Otto Berndt, but there are no records of whether he created such a device or even if he was in Nienburg in 1877. This man was Karl Ernst August Otto Berndt (born 29 Jan 1857 in Neuruppin, a small town in Brandenburg–died 9 Feb 1940 in Darmstadt).
Otto Berndt was the son of the leather merchant and engineer Ernst Berndt and his wife Wilhelmine Berndt, née Kufahl. From 1875 to 1881 he studied mechanical engineering at the Technical University Berlin-Charlottenburg. In 1881 he passed the first state examination and was appointed government building supervisor, the second state examination followed in 1884. From 1885 to 1887 Berndt was employed as a government builder (assessor in the public building administration) at the main railway workshop in Halberstadt. From 1887 to 1892 he worked in the mechanical engineering office of the Royal Railway Directorate in Magdeburg.
In 1892, Berndt was appointed as full professor for general mechanical engineering and mechanical technology at the Technical University of Darmstadt. His concern was to conduct research in addition to teaching. He expanded the fields of machine tools and power machines, steam boilers, and machine elements established before his appointment to include a chair for water power machines and later a chair for paper production. Berndt remained at the University of Darmstadt upon his retirement in 1927, serving as professor, dean, and rector for many years.