Adding pen

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Adding pen

The adding pen is an invention of the Americans Smith and Pott, which was used to add long rows of numbers. It was designed in the form of a pen holder .

functionality

During use, the pin protruding from the holder sleeve, which is placed on the digits to be added as usual, is pushed so far into the sleeve for each digit that a pointer connected to it comes to the same digit on a scale. This movement simultaneously moves a second pointer (the sum pointer) upwards on a further scale from the number 0 on. While one spring pushes the displaceable pin and the associated pointer back to 0 when moving to the next digit, the total pointer is prevented from moving back by a ratchet wheel and then moves up to the next digit on its scale. As a result, he always gives the sum of all digits previously touched.

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