Contact structure for an electric circuit interrupter

Claim 1

IN AN ELECTRIC CIRCUIT INTERRUPTER, A PAIR OF COACTING BUTT CONTACTS RELATIVELY MOVABLE FROM A POSITION OF ENGAGEMENT TO A POSITION OF DISENGAGEMENT TO ESTABLISH A CIRCUITINTERRUPTING ARC THEREBETWEEN, AT LEAST ONE OF SAID CONTACTS BEING A CUP-SHAPED MEMBER COMPRISING A BODY PORTION AND A FLANGE PROJECTING LATERALLY FROM SAID BODY PORTION TOWARD SAID OTHER CONTACT, SAID FLANGE TERMINATING AT ITS FREE END IN A GENERALLY ANNULAR CONTACT-MAKING SURFACE EXTENDING ABOUT THE PERIPHERY OF SAID CUP-SHAPED MEMBER AND FACING SAID OTHER CONTACT, SAID OTHER CONTACT HAVING A CONTACT-MAKING SURFACE GENERALLY ALIGNED WITH THE CONTACTMAKING SURFACE OF SAID FIRST CONTACT AND BUTTING THEREAGAINST WHEN SAID CONTACTS ARE ENGAGED, SAID CONTACT-MAKING SURFACES PARTING LAST DURING A CIRCUIT-INTERRUPTING OPERATION TO INITIATE SAID ARC BETWEEN SAID CONTACT-MAKING SURFACES, MEANS FOR PRODUCING ARC-MOTION IN A CIRCUMFERENTIAL DIRECTION ALONG SAID CONTACT-MAKING SURFACES COMPRISING A PLURALITY OF SLOTS IN SAID FLANGE EXTENDING THROUGH THE ENTIRE RADIAL THICKNESS OF THE FLANGE, EACH OF SAID SLOTS INTERSECTING SAID CONTACT-MAKING SURFACE AND EXTENDING FROM SAID CONTACT-MAKING SURFACE TOWARD SAID BODY PORTION VIA A PATH DISPOSED AT AN ACUTE ANGLE TO SAID CONTACTMAKING SURFACE.