Single revolution clutches, particularly for franking machines

摘要

A single revolution clutch in a reduction gear in a franking machine is designed to avoid fraudulent operation and double cycling and for economical production by arranging a worm to drive a split worm wheel having a gap in each arcuate row of teeth respectively on the first and second worm wheel parts. Before operation, the worm rotates in the gaps. On release by a detent of a shoulder a spring brings a tooth into mesh with the worm which rotates the first worm wheel part until a lost-motion connection is engaged bringing the second worm wheel part into mesh with the worm to drive an output shaft. The detent is released by an electrical pulse then guided by a cam track to engage the shoulder arresting the first worm wheel part while the second part continues so as to stress the spring and return to the initial position with respect to the first part.