Telephone call charge meter - has ratchet and pawl actuator with solenoid having selected geometry to extend useful life

摘要

The geometry and location of the moving parts in a ratchet wheel mechanism used in telephone call charge counters, are selected to provide max. operational life. The counter wheel (8) with number around the periphery is moved incrementally by a pawl (6) operating on a ratchet wheel (7). The pawl is pinned (14) to a pivotted armature (3) that has a contact pin (11). A solenoid coil (8) provides the contracting force against the action of a spring (5). The contact pin is selected to lie on a radius (12) that is equal to the radius (13) fixing the pawl centre from the contact. This minimises impact of the contact against the solenoid.