In fuses the casings of which are closed by terminal caps through the end surfaces of which a pair of blade contacts project from the outside of the casing to the inside thereof, the fusible elements must be conductively connected to the pair of blade contacts. There is a limited space on the surfaces of the blade contacts for connecting the fusible elements to them. For this reason the above type of fuses include generally but two fusible elements which have high current ratings, about the same width of the pair of blade contacts, and conductively connect opposite sides of the blade contacts. This type of design results in a current concentration in the planes of surfaces defined by the two fusible elements which, in turn, results in a very poor utilization in regard to its cooling and de-ionization ability of the granular arc-quenching filler inside the casing, since some of the arc-quenching filler is positioned relatively remote from the two fusible elements.
This situation is entirely different from that encountered in plug type fuses, i.e., fuses that are closed by terminal plugs. This type of fuse construction readily permits the increase in the number of fusible elements beyond two, and the distribution of the fusible elements more or less evenly across the cross-section of the casing or fuse tube. This, in turn, results in a far better utilization of the granular filler as far as its cooling and de-ionizing action is concerned.
It is, therefore, the prime object of this invention to provide fuses having blade contacts projecting through the end surfaces of the terminal caps and allowing a more even distribution of the fusible elements across the cross-section of the casing or fuse tube and allowing an increase of the number of fusible elements and a better utilization of the arc-quenching filler for cooling and de-ionization purposes.
Other objects of this invention will become more apparent as this specification proceeds.