ELECTROMAGNETIC PRINT HAMMER

摘要

An electro-magnetic print hammer comprises a single magnetic hammer element in which an impact mass is coupled to a pivotted armature by flexible stem. The hammer-stem has (N+1/2) periods of oscillation at its resonant frequency during the free flight time of the hammer mass. A permanent magnet with a strong magnetic force which decays rapidly with distance holds the hammer element fixed upon motion of the armature until the armature torque exceeds the magnet holding force to cause the hammer mass to break loose with a snap action. Stop means prevents armature impacts with the operating pole piece of a stator core. The visco-elasticity of the armature stop matches the rebound characteristics of the print medium when impacted by the hammer mass.