Impulse stepping digital counter unit mechanism - with very cheap stepping arm requiring no adjustment or additional parts

摘要

The mechanism achieves accurate counting with a simple non-adjustable arm. This is achieved by ensuring that the stepping arm will always return to behind the next tooth of the number-wheel after an impulse. Two mechanisms for achieving these aims are described. The number-wheel is injection moulded, with the sawtooth ratchet-wheel near the central axis, and a curved surface slot inside the periphery. The stepping arm of bronze lies on a tooth on the ratchet wheel and has a boss on one side projecting into the slot. The curves are formed so that when the arm returns the boss comes in contact with the curve for one tooth and is guided behind the next tooth. The second mechanism has bosses on the number-wheel, and a cam on the side of the stepping arm tip which guides it behind the next tooth.