Electromagnetic switching device having an improved energizing circuit

Claim 1

An electromagnetic switching device comprising: a. a stationary magnetic member; b. a movable magnetic member in juxtaposition with said stationary magnetic member; c. an energizing coil magnetically coupled to said stationary and movable magnetic members; d. at least one stationary contact: e. at least one movable contact in juxtaposition with said stationary contact and mechanically coupled to said movable magnetic member; f. full-wave rectifying means for converting AC voltage from a source to DC voltage and applying the DC voltage across said energizing coil, said full-wave rectifying means being comprised of first, second, third and fourth diodes, the cathodes of said first and second diodes being electrically coupled to one end of said coil and the anodes of said third and fourth diodes being electrically coupled to the other end of said coil, the anode of said first diode and the cathode of said third diode being electrically connected to one terminal of the AC voltage source; and g. means responsive to movement of said movable magnetic member for converting said full-wave rectifying means to half-wave rectifying means to reduce the applied DC voltage across said energizing coil after said movable magnetic member has begun to move toward said stationary magnetic member, said responsive means being comprised of: i. a first normally closed momentary contact switch having an actuating plunger, said first mementary contact switch being electrically connected in series only with said first and fourth of said first, second, third and fourth diodes; ii. a second normally closed momentary contact switch having an actuating plunger mechanically coupled to said actuating plunger of said first momentary contact switch, said second momentary contact switch having one end electrically connected to another terminal of the AC voltage source and having another end electrically coupled to the anode of said second diode and to the cathode of said fourth diode; iii. an actuating member having one end thereof mechanically coupled to said movable magnetic member, and another end thereof spaced from and positioned adjacent said actuating plunger of one of said first and second momentary contact switches when said coil is deenergized; and iiii. a holding resistor electrically connected in parallel with said second momentary contact switch, whereby after said coil is energized, said movable magnetic member moves toward said stationary magnetic member and causes said actuating member to depress said actuating plunger of one of said first and second momentary contact switches to open said first and second momentary contact switches, and insert said holding resistor in series with said second diode, said energizing coil and said third diode as current passes from one terminal of the AC source to the other terminal of the AC source during each half cyclee cycle a signal from the AC source.