Mechanical drum counter with reset facility - has heart shaped cam on each drum engaged by reset lever striker

摘要

The mechanical drum counter with reset facility consists of a number of wheels set on a common shaft (2), each drum bearing numerals on its outer rim (10) and representing one decade. Rotation through one revolution moves the neighbouring next highest decade drum on one digit. One side of each drum carries a heart-shaped cam (31) and integral pawl (24) at the end of a flexible finger extending from the outer face of the cam. The pawl normally engages with pins on the next highest decade drum to produce a 36 deg. shift per revolution when the pawl strikes a dog (29) on the reset mechanism (32). When the spring-loaded reset lever is pushed inwards, reset fingers (33) one per drum-engage with the heart cam to reset the drum to zero. At the same time, the dog also moves out of the path so that the drum can rotate freely.