Electrical counting mechanism

摘要

An electrical counting device with a rotary counter, a rotary drive assembly having a driven rotor with a verge for indexing the counter in stepwise fashion and a coaxial drive rotor in frictional engagement with the driven rotor, a coil torsion spring biasing the drive rotor in one angular direction and a tension wire conductor extending angularly about a drum of the drive rotor and connected to be heated and thereby lengthened with an electrical current to index the counter a first one-half count with the torsion spring and a remaining one-half count with the tension wire upon subsequent cooling and contraction thereof.