Mechanical interlock for contactors

In an electrical switching system having a pair of electrical switching devices mounted adjacent one another in predetermined spaced apart relation and each said switching device having a housing with a flat wall and an aperture in said flat wall and a switch actuating member within said housing having a projection extending substantially into the plane of said flat wall and being accessible through said aperture, and the flat walls of said switching devices facing one another, means for interlocking said switch actuating members for operation one at a time comprising:

• false-front upper left and right corners on each said flat wall;
• a generally T-shaped integrally molded frame comprising symmetrical opposite sides in juxtaposition with said flat walls of said switching devices, and each said side having at the opposite ends of its upper arms a pair of hooks defining vertical slides for gripping and sliding down the outer edges of said false-front upper left and right corners, and a lug at an intermediate point on said side of said frame that snaps into said aperture to rigidly snap-in mount said frame onto and between said pair of electrical switching devices;
• the lower portion of said frame having therewithin a pair of lateral pockets with a double-incline bump therebetween;
• a pair of openings on respectively opposite lateral sides of said frame;
• and a spring-biased pawl movably confined within said frame and having a pair of opposite wings extending through said openings below said projections of said switch actuating members of said pair of switching devices and a toe at its lower end poised above said double-inclined bump such that when one of said switch actuating members is operated, it depresses the corresponding wing to rock said pawl thereby causing said toe to slide down the opposite incline of said bump into the corresponding pocket to stop said pawl so that the other wing thereof restrains the other switch actuating member from being operated.