Fuse structure

A fuse having a rated current for protecting electric or electronic circuitry comprising:

• a body having a blow chamber;
• a fusible element contained within the body and extending through the blow chamber, and a contact disposed on the body and electrically connected to the fusible element for making an electrical connection between the fuse and the circuitry;
• the blow chamber effectively thermally insulating a portion of the fusible element therein so that thermal energy in said fusible element portion can increase within the blow chamber for causing the element to open when an elevated current is applied to the element;
• the blow chamber retaining a pressure created therewithin by vaporization of a portion of the element sufficiently to cause an arc produced by fusion of the element to extinguish;
• means for dissipating thermal energy located on portions of the fusible element without the blow chamber for preventing the fusible element from opening without the blow chamber before opening within the blow chamber;
• the body comprising a plurality of joined body portions having opposing surfaces;
• a blow chamber portion disposed in each body portion for forming the blow chamber;
• confronting walls being disposed around the blow chamber portions extending from said surfaces;
• the fusible element being sandwiched between the walls when the body portions are joined;
• and the body portions being joined with sufficient strength for allowing the fuse to fail gracefully at the pressure created within the blow chamber by fusion of the element at a predetermined voltage and an elevated current.

A fuse having a rated current for protecting electric or electronic circuitry comprising:

• a body containing a fusible element;
• means for defining a hot spot on the fusible element located within the body;
• said means for defining a hot spot having a relatively low thermal conductivity as compared with a thermal conductivity of the body for inhibiting thermal energy transfer from said hot spot to said body;
• the body encapsulating the hot spot and the element;
• a contact disposed on the body thermally conductively connected to the element and electrically connected to the element for making an electrical connection between the fuse and the circuitry;
• and means for sufficiently sealing said hot spot so that a pressure created by vaporization of a portion of the element within the hot spot can cause an arc initiated by fusion of the element to extinguish.

A fuse having a rated current, for protecting electric or electronic circuitry, the fuse comprising:

• a body and a fusible element within said body;
• a contact disposed on the body and electrically connected to the fusible element for electrically connecting the fuse to the circuitry;
• the body including means for providing said body with structural strength sufficient for maintaining structural integrity of the body for retaining a pressure, sufficient for causing an arc, initiated by a predetermined voltage, to extinguish, the pressure being created within the body by vaporization of a portion of the fusible element at the predetermined voltage and an elevated current;
• and means for limiting a rate of thermal energy dissipation from the fusible element to a rate providing for opening of the fusible element within a predetermined time period at a predetermined elevated current being disposed at a location along the fusible element within the body.