Electro-magnetic relay with first and second spring biasing means

摘要

A high sensitivity electromagnetic relay has a moving armature held against two pole pieces of a magnetic circuit by means of a permanent magnet. The armature is subject to the action of two return springs which tend to draw the armature off the pole pieces. A first, non-adjustable spring provides the main antagonistic torque while an adjustable spring which is a separate component part from the main spring is used for fine adjustment of the force acting against the permanent magnet. The amount of current flowing through a coil which is required to trip the relay can then be adjusted finely.