Time lag dual element fuse having means for precluding arc initiation adjacent terminals

Claim 1

IN AN ELECTRIC TIME-LAG FUSE HAVING A PREDETERMINED MINIMUM FUSING CURRENT AND INCLUDING A TUBULAR CASING OF INSULATING MATTERIAL, A PAIR OF TERMINAL ELEMENTS CLOSING THE ENDS OF SAID CASING, A RIBBON FUSE LINK OF A METAL HAVING A RELATIVELY HIGH FUSING POINT INSIDE SAID CASING CONDUCTIVELY INTERCONNECTING SAID PAIR OF TERMINAL ELEMENTS AND DEFINING A PLURALITY OF SERIALLY RELATED POINTS OF REDUCED CROSS-SECTIONAL AREA, A LINK-SEVERING OVERLAY OF A METAL HAVING A RELATIVELY LOW FUSING POINT SUPPORTED ON SAID LINK AT THE CENTER REGION THEREOF, A PULVERULENT ARCQUENCHING FILLER INSIDE SAID CASING SURROUNDING SAID LINK AND SAID OVERLAY, SAID FUSE BEING MADE OF SUCH MATERIALS AND HAVING SUCH PROPERTIES THAT IT HAS A TRANSFER CURRENT CAUSING, WHEN EXCEEDED, A SHIFT OF THE POINT OF INITIAL BREAK FORMATION FROM SAID OVERLAY TO ONE AXIALLY OUTER OF SAID PLURALITY OF SERIALLY RELATED POINTS OF REDUCED CROSS-SECTIONAL AREA, THE NOVEL FEATURE CONSISTING IN A HOLLOW RECEPTACLE OF INSULATING MATERIAL EMBEDDED IN SAID BODY OF ARC-QUENCHING FILLER MOUNTED ON SAID FUSE LINK AND LIMITED TO THE CENTER REGION THEREOF, SAID RECEPTACLE DEFINING A VOID SURROUNDING SAID OVERLAY AND LIMITING HEAT DISSIPATION THEREFROM TO SAID ARC-QUENCHING FILLER, THE SIZE AND MASS OF SAID RECEPTACLES BEING SUFFINCIENTLY SMALL OF PRECLUDE BY VIRTUE OF THE PRESENCE THEREOF ANY CHANGE OF SAID PREDETERMINED MINIMUM FUSING CURRENT.