Electro:magnetically activated alarm bell - has armature which operates against return spring strip to maximise alarm power output

摘要

An electro-magnet actuated alarm bell is designed to provide maximum response sensitivity coupled with maximum output power. the alarm bell (G) striker (K) has a rigidly coupled cross member (A) that is pivoted onto the electromagnet body. Two coils (5) are used to produce a magnetic field through two pole pieces (SK), with the field completed by a permanent magnet (P). - A performed spring (F) locates around the cross-member with clearance (b) in the rest position. When the coils are differentially energised the cross member presses aginst the spring which provides return action after the alarm bell has been struck. this increases the impact power for a given coil size.