Method of activating an electromagnetic positioning means and apparatus for carrying out the method

Method of activating an electromagnetic positioning means of the kind comprising a positioning member having an armature affixed thereto, electromagnets for driving the armature between first and second terminal positions, spring means for biasing the armature into a rest position between the first and second terminal positions, and means for energizing the elctromagnets to drive the armature to the terminal positions, the armature together with the positioning member and the spring means constituting an oscillatory system having a predetermined resonant frequency, wherein the method comprises the steps of:

• a. alternatingly energizing the electromagnets at a frequency substantially equal to the resonant frequency of the system for a time sufficiently long to activate the positioning means by swinging the armature in oscillating steps toward the first and second terminal positions;
• b. maintaining the energizing frequency of the electromagnets during the initial oscillations greater than the resonant frequency of the system;
• c. continuously reducing the energizing frequency to zero after the armature has reached a terminal position;
• and
• d. thereafter maintaining one of the electromagnets in an energized state.